Hybrid composites incorporating low dimension materials for sensors and clean energy applications

Resume : We demonstrate that poly(vinylidene fluoride) (PVDF)-based percolative composites using two-dimensional (2D) MXene nanosheets as fillers exhibit significantly enhanced dielectric permittivity. The poly(vinylidene fluoride-trifluoro-ethylene-chlorofluoroehylene) (P[VDF-TrFE-CFE]) polymer embedded with 2D Ti3C2Tx nanosheets reaches a dielectric permittivity as high as 105 near the percolation limit of about 15.0 wt % MXene loading, which surpasses all previously reported composites made of carbon-based fillers in the same polymer. Up to 10 wt % MXene loading, the dielectric loss of the MXene/P(VDF-TrFE-CFE) composite indicates only an approximately fivefold increase (from 0.06 to 0.35), while the dielectric constant increased by 25 times over the same composition range. Furthermore, the ratio of permittivity to loss factor of the MXene-polymer composite is superior to that of all previously reported fillers in this same polymer. The dielectric constant enhancement effect is demonstrated to exist in other polymers as well when loaded with MXene. We show that the dielectric constant enhancement is largely due to the charge accumulation caused by the formation of microscopic dipoles at the surfaces between the MXene sheets and the polymer matrix under external applied electric field.

Resume : Hybrid materials consisting of inorganic nanostructures embedded in conducting polymer matrices have emerged as promising systems for room temperature thermoelectric applications. They are attractive due to their intrinsic low thermal conductivities, the ability to engineer interfaces for energy filtering effects and phonon scattering, and their ability to take advantage of high-throughput and solution processable manufacturing. Most hybrid materials reported in the literature have been p-type, owing to difficulties in n-type doping of conducting polymers in conjunction with the nature of the applied nanocrystals. This has resulted in a strong drive to develop new n-type materials, since both are necessary for module development. Here we explore our recent developments in the synthesis of chalcogenide nanowires encapsulated in PEDOT:PSS that are used as templates for the synthesis of Ag2-xE (where E=Te, Se) via topotactic chemical transformation processes. This synthetic method allows us to engineer the composition of our hybrids, whereby we are able to directly influence the thermoelectric properties, including the production of both p-type and n-type materials from the same parent material. We utilize XRD, TEM, XPS, and UPS to detail the development of our materials with changing stoichiometry and relate this to their thermoelectric performance. Ultimately, we aim to develop an understanding of how to use solution-based synthesis to influence thermoelectric device properties.

Resume : Graphene on noble-metal nanostructures constitutes an attractive nanocomposite with possible applications in sensors or energy conversion. Gold nanoparticles (NPs) were prepared on SiO2 substrate by local annealing of gold thin films using focused laser beam. CVD-grown graphene was transferred onto the prepared NPs. Subsequent Raman-spectroscopy measurements were performed on the samples using different laser powers. We used higher laser intensity (6 mW) to locally anneal the hybrid material. Low laser powers (0.6 mW) were used to characterize the doping and the strain formed in the same areas both before and after local heating. As a control experiment, graphene was transferred onto clean SiO2 substrate as well. While we found that higher intensity laser irradiation increased gradually the doping and the defect concentration in SiO2-supported graphene, the same irradiation procedure did not induce such irreversible effects in the graphene supported by Au NPs. Moreover, the laser irradiation induced dynamic hydrostatic strain in the graphene on Au NPs, which turned out to be completely reversible. These results point out the role of the substrate in the resistance of graphene against laser irradiation, and can have implications in the development of graphene/plasmonic nanoparticle based high temperature sensors. The paper was published in NANOSCALE 10, 13417 (2018).

Resume : An effect of a destruction of organic molecules under the laser excitation at the analysis by surface enhanced Raman scattering (SERS) spectroscopy is well-known drawback of this ultrasensitive technique. Here to overcome such a limitation, we protected analyte molecules adsorbed on the SERS-active substrates with graphene-containing films. Different plasmonic materials for the SERS-spectroscopy based on sculpted semiconducting templates and nanostructures of coinage metals were fabricated by electrochemical and electroless techniques. Graphene was grown on a copper foil by the chemical vapor deposition and transferred to the SERS-active substrates coated with analyte molecules at submolar concentrations. We found that protection with carbon nanostructure composed of 1-4 layers of graphene prevents organic molecules' burning while the SERS-analysis. This provides detection of organic compounds including but not limited to dyes, peptides and proteins adsorbed from the solutions at the concentrations lower than femtomolar. Simulations of the electric and thermal fields’ distributions and strength revealed that this protective effect is caused by decrease of the heating temperature by 10 Celsius degrees caused by laser if the film of 4 graphene layers is used.

Resume : In order to functionalize 2D materials, their physico-chemical properties can be modified and tuned via diverse methods: coupling to the substrate, vacancies, adsorbed species (clusters and molecules), substitutional impurities (via precursors during growth) and intercalation (atomic and molecular). However, in the cases of incorporation of substitutional and intercalated elements the challenge is the poor control over the concentration and form of incorporation. An alternative approach is to incorporate the foreign species by implanting low-energy ions, precisely tuning the amount of implanted ions and their kinetic energy. Here, we demonstrate the integration of foreign elements in graphene using the state-of-the-art technique of ultra-low energy ion implantation. Our scanning tunneling microscopy and x-ray photoelectron spectroscopy experiments show the formation of nanobubbles for implanted noble gases (Ar and Ne), and various forms of incorporation for implanted transition metals (Mn). We are able to control the density of the nanobubbles with the ion mass, implantation energy and fluence. Moreover, we have identified the energy range for Mn incorporation with minimum damage to graphene for substitutional and intercalation purposes.

Resume : The novel hybrid structures involving single molecule magnets (SMMs) grafted to two-dimensional nano-materials (such as graphene) constitute a tunable array of magnetic nano-objects that could lead to novel spin-based technologies and attracted research activities of experimental groups. Here, we report extensive theoretical studies of: (i) the stability of such hybrid structures, (ii) the nature of interactions between the localized spin in SMM and 2D material to which the molecule is grafted, and (iii) possibility of tuning the magnetization of SMMs with external electric field. The studies are based on ab initio calculations in the framework of density functional theory (DFT) and density functional tight-binding method (DFTB). In both cases we pay particular attention to the proper description of the van der Waals dispersive forces and magnetism. In particular, we consider TM-Phthalocyanines (with TM = V, Cr, Mn, Fe, Ni) and two SMMs with tetrahedrally coordinated TM (Fe or Cr) bound to two doubly deprotonated 1,2 -bis(methanesulfonamido) benzene ligands, both grafted to the graphene monolayer. We address also the important issue how the adhesion and magnetic properties of SMMs are influenced by (i) structural defects in graphene (such as vacancies, 5-7 defects, N-dopants), and/or (ii) intentional functionalization of graphene with simple amines, hydrocarbons, and OH groups. Acknowledgement: This research has been supported by the NCN grant OPUS (UMO-2016/23/B/ST3/03567).

Resume : We report Layer-by-Layer (LbL) self-assembly of pillared two-dimensional (2D) multilayers, from water, onto a wide range of substrates. This LbL method uses a small molecule, tris(2-aminoethyl) amine (TAEA), in combination with a colloidal dispersion of a 2D material, Ti3C2Tx MXene, to LbL self-assemble (MXene/TAEA)n multilayers, where n denotes the number of bilayers. Assembly with TAEA is fundamentally different from assembly with polymers and results in highly ordered pillared (MXene/TAEA)n multilayer where the TAEA expands the interlayer spacing of MXene layers by only around 1 Å and reinforces the interconnection between MXene flakes. The TAEA-pillared MXene multilayers show higher electronic conductivity of 7.3 × 104 S m-1 compared with other MXene multilayers fabricated by LbL self-assembly techniques. These multilayers are also shown to be resistant to mechanical deformation. Importantly, the MXene/TAEA multilayers could be used as electrodes for flexible all-solid-state supercapacitors delivering a high volumetric capacitance of 583 F cm-3 and an integrated high energy density of 3.0 Wh L-1 corresponding to a power density of 4400 W L-1. This strategy enables large-scale fabrication of highly conductive pillared MXene multilayers, and potentially fabrication of other types of 2D heterostructures on various substrates.

Resume : Abstract for EMRS 2019 My research focuses on multi-functional covellite(CuS) 2D fin-like structures that are prepared via RF magnetron sputtering. These fins are self-assembled due to plasma heating during the deposition process thus achieving a polycrystalline nature.[1] Due to copper vacancies in the crystal structure[2-4], CuS is a degenerate semiconductor and a plasmonic resonance in the iR region. Its unique properties has lead to its multi-functionality from p-type solar absorber[5, 6], photodetector[7], carbon dioxide reduction[8] and photothermal biomedical applications[9]. The copper sulfide family(Cu2-xS) have also been shown to exhibit resistive memory(ReRAM) in composite layered devices (eg.Cu/Cu2-xS, Cu2-xS/CuS)[10, 11]. In a letter published in Applied Physics Letter[1], I fabricated a ReRAM device from fin-like CuS on n-Si substrate with a writing speed in 20us with low switching voltages of 1V to -3V. Moreover, the difference of resistance from ON to OFF state was around 2 orders of magnitude. The fin-CuS circumvents the need to prepare complicated composite devices to achieve a ReRAM behaviour, as per previous literature on CuS ReRAM devices. Additionally, I managed to fabricate fin-like Cu2S through co-sputtering allowing me to control the stoichiometry of copper sulfide. This knowledge has also been extended the fin-like silver copper sulfide which exhibits a unique semiconductor to conductor behaviour upon illumination, ideal for photodetector applications. In recent years, CuS is gaining much attraction in the field of photothermal vaporisation of water[12]. A relatively new field in renewable energy, photothermal vaporisation utilises light-to-heat behaviour of certain materials, in addition a porous thermal insulating layer in order to trap heat on the surface of the water to provide localised heating leading to increase vaporisation efficiency. Due to copper sulfides’ plasmonic resonance in the near-iR region, vaporisation efficiencies of 60-90% have been reported. Fin-like CuS shows promising results with excellent light-trapping and light-to-heat behavior with efficiency of around 80%. Reference 1. Ng, Z.Q.C., et al., Self-assembled 2D finned covellite (CuS) for resistive RAM. 2018. 113(6): p. 063102. 2. Roy, P. and S.K. Srivastava, Nanostructured copper sulfides: synthesis, properties and applications. CrystEngComm, 2015. 17(41): p. 7801-7815. 3. Guillén, C. and J. Herrero, Nanocrystalline copper sulfide and copper selenide thin films with p-type metallic behavior. Journal of Materials Science, 2017. 52(24): p. 13886-13896. 4. Sun, S., et al., Diversified copper sulfide (Cu2-xS) micro-/nanostructures: a comprehensive review on synthesis, modifications and applications. Nanoscale, 2017. 9(32): p. 11357-11404. 5. Chopra, K.L. and S.R. Das, Cu2S Based Solar Cells, in Thin Film Solar Cells. 1983, Springer US: Boston, MA. p. 349-390. 6. Sebastian, S., et al., PVD of copper sulfide (Cu 2 S) for PIN-structured solar cells. Journal of Physics D: Applied Physics, 2013. 46(49): p. 495112. 7. Zhan, Z., et al., Photoresponse of multi-walled carbon nanotube–copper sulfide (MWNT–CuS) hybrid nanostructures. Physical Chemistry Chemical Physics, 2011. 13(45): p. 20471-20475. 8. Manzi, A., et al., Light-Induced Cation Exchange for Copper Sulfide Based CO2 Reduction. Journal of the American Chemical Society, 2015. 137(44): p. 14007-14010. 9. Marin, R., et al., Highly Efficient Copper Sulfide-Based Near-Infrared Photothermal Agents: Exploring the Limits of Macroscopic Heat Conversion. 2018. 14(49): p. 1803282. 10. Congiu, M., et al., Printable ReRAM devices based on the non-stoichiometric junction CuS/Cu2-xS. Electronics Letters, 2016. 52(22): p. 1871-1873. 11. Yi, J., et al. Research on switching property of an oxide/copper sulfide hybrid memory. in 2008 9th Annual Non-Volatile Memory Technology Symposium (NVMTS). 2008. 12. Tao, F., et al., Copper Sulfide-Based Plasmonic Photothermal Membrane for High-Efficiency Solar Vapor Generation. ACS Applied Materials & Interfaces, 2018. 10(41): p. 35154-35163.

Resume : The interest in understanding the interaction between graphene and adatoms or admolecules spans a wide range of research fields. Since the properties of the graphene-adsorbate system strongly depend on the adsorption configuration, it is important to not only understand these effects from a theoretical point of view, but also to be able to probe them experimentally. We present and extensive study of the interaction between graphene and adatoms (Hg, Cd, In and Ag), using a combination of density functional theory (DFT) calculations and perturbed angular correlation (PAC) spectroscopy. The electric field gradient (EFG) can be calculated using DFT for each atomic configuration and measured using PAC. We find the EFG to be sensitive to the local atomic configuration, distinguishing isolated from cluster configurations, and for some cases, varying significantly with small variations in adatom position (at the sub-Å scale). Based on these calculations, we discuss how the EFG can be used as an experimental observable providing insight on the local atomic configuration and bonding stability of adatoms and admolecules on graphene. In particular, we studied the adsorption of Hg on graphene, using PAC spectroscopy at the ISOLDE facility at CERN (using 199mHg as probe). With the support of DFT calculations, we were able to identify Hg adsorbed in the form of HgO2 molecules. Hg is adsorbed with much higher binding energies in molecular form (exceeding 1 eV) than as isolated adatom (below 0.2 meV), with oxygen playing a crucial role. This work constitutes a proof-of-principle for the use of hyperfine techniques to study the interaction between graphene and adsorbed atoms and molecules, at the atomic scale.

Resume : Hybrid composites, fabricated by the synergistic combination of graphene and metal nanoparticles (NPs), are considered promising candidates for the design and production of innovative and functional sensing, energy production/storage, electronics, catalytic devices. The physico-chemical response of such devices is dictated by the properties arising from the combination of the properties of both components. In particular, charge transfer effects between graphene and NPs are at the basis of several devices operation. Here we present an approach to fabricate graphene-metal NPs hybrid composites and we provide some experimental results related to the metal/graphene charge transfer effects. Ligand free laser produced metal nanoparticles (Au, Pd, Pt, AuPd, PtPd) are properly mixed to graphene layers to fabricate graphene-supported two-dimensional arrays. The amount of the Raman 2D signal shift and some current-voltage curves obtained by Conductive Atomic Force Microscopy (C-AFM) demonstrate that the chemical composition of the metal nanoparticles drives the charge transfer phenomena. A combined analysis of these results allow us to draw a general framework for the interpretation of charge transfer mechanisms in graphene-NPs hybrids.

Resume : In recent years, due to the increasing interest in long-term human space missions, much attention has been given to the dangerous effects of space radiation and to find sensitive and light-weight materials for radiation damage detection. Here, the fabrication and properties of UV-sensitive functional coatings containing graphene/DNA interfaces are presented. Graphene nanoplatelets (GNP) acting as signal transducer and UV-sensitive DNA strands are assembled by sonication-driven non-covalent assembly and embedded in a polymer matrix for enhanced adhesion on space-grade materials and structures. DNA macromolecules are efficient solubilizing agents for the highly hydrophobic carbon nanoparticles, ensuring a good stability of the GNP dispersions without altering their electrical and chemical properties. Surface analytical techniques, SEM imaging and electrical impedance spectroscopy are used to investigate the effects of UV irradiation on the properties and morphology of the sensor coatings. We show that these graphene-based coatings can be used to detect the effects of UV radiation exposure in real time through changes of the surface electrical properties. Possible applications include monitoring the damage induced by solar UV radiation, especially the most energetic UV-C band, which adversely affects the performance of spacecraft components and the life of biological systems in space.

Resume : Thermoelectric (TE) devices, which harvest electrical energy directly from temperature gradients, are an emerging technology due to their potential applications for next generation power generators. As the concept of practical and wearable thermoelectric generator (TEG) begins to surface, requirements such as flexibility, being lightweight and mass producibility have become important. Herein, we have rationally designed a bracelet-type TEG structure where the CNT ink is printed directly on a flexible cable and the device is operated in the out-of-plane direction of heat source. In order to fabricate the CNT ink, the polymer binders, poly(acrylic acid) and poly(ethylenimine), were used as a p- and n-type dopant, respectively. The optimized doping levels for p- and n-type CNT inks were both achieved at dopant levels of 10 wt%, corresponding to the power factor of 129 and 135 μWm-1K-2, respectively. The flexible TEG based on 60 pairs of n- and p-doped CNT ink printed onto a cable shows the maximum power output of 0.2 and 1.95 μW at temperature differences of 10 and 30 K, respectively, which is one of the highest output powers for flexible TEGs based on CNT inks. In addition, the mechanical durability of the TEG shows rare change of the circuit resistance after 3500 bending cycles.

Resume : Gas sensors play an increasingly important role in our modern society, particularly for industrial production and public security. Specially, AlGaN/GaN heterostructures have some advantages in the application of gas sensing. A high electron sheet carrier concentration and high electron mobility can be easily obtained without intentional doping and the two-dimensional electron gas (2DEG) is located near the surface and very sensitive to the change of the atmospheric gases. Therefore, there are great demands on achieving the AlGaN/GaN high electron mobility transistor (HEMT) based hydrogen gas sensors for detection of high sensitivity and short response time. In this work, a simple and convenient method for the formation of Pt nanoparticulate films as a sensing material by controlling deposition rates is demonstrated to realize AlGaN/GaN high electron mobility transistor (HEMT) based high-sensitivity hydrogen gas sensors. The Pt nanoparticulate films produced at low deposition rate (Sample 1: 0.3 Å/s) exhibit a smooth surface and uniformly sized Pt grains while the films produced at high deposition rate (Sample 2: 1.5 Å/s) consist of bigger Pt grains and more coalesced grains on the surface. The deposition rate has a distinct effect on the surface morphology. Maximum current change percentage for sample 1 was 2.1 × 103 % at VGS of – 4.3 V while that for sample 2 was 4.4 × 103 % at VGS of – 4.5 V. The sample 2 has twice larger current response to hydrogen gas than the sample 1, which results from large increase in channel conduction induced by huge catalytic surface area of Pt nanoparticulate films. This technique offers an alternative method for the facile deposition of a sensing material, potentially useful in various applications such as gas, chemical and biological sensors.

Resume : Dealloying is a broad method to fabricate nanoporous gold (NPG) by etching gold/silver alloy in nitric acid. Here we reported the fabrication of controllable ultrafine NPG film with pore sizes about 5 nm by a simple modified dealloying method. The mechanism of this new synthesis method was also discussed. SEM and TEM results show the surface structures of the as prepared NPG film. The NPG film with ultrafine pore sizes exhibit improved surface enhanced Raman scattering (SERS) sensitivity. While we focused here on alloy films, this convenient, low-cost and scalable method in this study are generally applicable to other metallic structures like metal wires for improving their performance in many applications.

Resume : Organic-inorganic luminescent hybrid materials (HM) based on PbF2 inorganic matrices are promising for OLED application. One of the main task when synthesizing the above HM is preservation of a major content of organic molecules from destruction both at the melting synthesis technique and at coprecipitation from aqueous solutions of HF which is used as a fluorinating agent. In the present research we developed the soft synthesis technique of HM by the substitution of HF to ammonium bifluoride. As organic constituents we used highly efficient phosphors: beta-diketone complexes of Eu, 8-hydroxyquinoline complexes with metals I, II and III group of the Periodic Table. The effect of organic molecules or molecular fragments on size and morphology of obtained PbF2 nanoparticles, luminescence properties of HM both directly after precipitation, drying, and after calcination of powders were analyzed. The soft synthesis resulted in a capture of phosphor molecules by precipitating of PbF2 nanocrystallites. The proceeding of the exchange reaction between a metal-organic complex and a matrix during the heat treatment of precipitated powders resulted to the formation of Pb-complexes of different coordination. By this way we have achieved controlled changes in HM photoluminescence parameters. This research was financially supported by the grant 17.1.18.0026.01 (10.4702.2017/BC).

Resume : Nanocomposites represent an interesting class of materials because their applications are of multidisciplinary importance. Interactions at the interface of heterostructures, are leading to superior performance and sometimes to synergistic interactions. Graphene-based materials are among the most intriguing materials for researchers in recent times due to their exotic properties which find applications in various domains right from sensors to textiles, pharmaceuticals, intelligent coatings and biomedical applications. When such materials are incorporated in polymer matrices to form either composites or doped-polymers or simply carbon-reinforced-polymers, their applications broadens. Novel polyvinylidene difluoride and graphene/titanim dioxide nanocrystals (graphene/TiO2/PVDF) based composite nano and micro fibers were fabricated by electrospinning. The effect of composing the nanomaterials in the polymeric matrix was studied using SEM, XRD and Raman spectroscopy. Structural, morphologic and electrical properties of the engineered nano and micro fibers proved the successful integration of both graphene and TiO2 nanopowder with the polymeric matrix in novel materials with enhanced functionality that are promising candidates for various applications.

Resume : Graphene oxide (GO) has become a promising 2D material in many areas, such as gas separation, seawater desalination, antibacterial materials and so on due to its abundant oxygen-containing functional groups, excellent dispersibility in various solvents, and is easy to scale-up. The graphene oxide membrane (GOM), a laminar and channel-rich structure assembled by stacked GO nanosheets, served as a kind of precise and ultrafast separation materials has attracted widespread attention in membrane separation field. GOM/conical nanopore structure is obtained by spin-coating GO solutions on PET conical nanopore which possesses ion rectification property and the corresponding ion transport properties are carried out. Comparing to pure PET conical nanopore, the existence of GOM not only enhances the cation conductance but also makes the maximum ion rectification ratio increasing from 4.6 to 238.0 in KCl solution. Assisting COMSOL simulation method, it is proved that the GOM can act as cation source to improve the ion selectivity and rectification effect of GOM/conical nanopore system. Finally, the chemical stability of GOM/conical nanopore is also investigated and the results reveal that the GOM/conical nanopore can perform the ion rectification behavior in a wider pH range than pure conical nanopore. The presented results demonstrate the great potential applications of GOM/conical nanopore system in ionic logic circuits and sensor systems.

Resume : Charge density wave (CDW) materials are characterized by periodic modulation of electron charge density. CDW are also coupled to a periodic lattice distortion (PLD) which results in periodic modulation of atomic positions [1]. CDW materials can be also be intercalated with metal ions, and organic molecules which takes place within the van-der-Waals gap [2]. The intercalation process can result in large changes to the atomic structure, electronic and magnetic structure of the host structure [1, 2]. We have investigated the changes in the atomic and electronic structure of 1T-TaS2 due to intercalation with Triethylenediamine (C6H12N2) [3]. We show that the intercalation process leads to strong modifications in the atomic, electronic, and the CDW structure of 1T-TaS2. This is characterized by a structural transformation from the octahedrally coordinated 1T-TaS2 phase to the trigonal-prismatic 4H-TaS2 phase [3]. Structural phase transformation with the intercalation is also reflected in the valence electron energy loss spectra (VEELS). In this energy region the VEELS spectra of 1T-TaS2 is characterized by a strong peak between 2-2.5 eV. This peak is shifted to 3.5-4 eV in both 2H-TaS2 and intercalated 1T-TaS2. We discuss the nature and origin of changes in the VEELS spectra and the relationship to the structural transformation observed during the intercalation process. 1 J. Wilson, F. D. Salvo, and S. Mahajan, Adv. Phys. 24, 117 (1975). 2R. H. Friend, and A. D. Yoffe, Adv. Phys. 36, 1 (1987). 3 P.M Williams, C. Scruby, W. B. Clark, and G. S. Parry, J.Phys. Colloq. 37, C4-139(1976)

Resume : Low-dimensional nanomaterials such as carbon nanotubes (CNT), semiconductor nanowires, graphene and graphene-like two-dimensional transition metal dichalcogenides (TMDs) have been spotlighted for studying the bio-interaction and biosystem because of their small size comparable to the biomolecules and inert properties to the chemicals. Especially, molybdenum disulfide (MoS2) is one of the most typical TMDs and due to its high sensitivity in sensing the biomolecule with low level of noise, MoS2 provides a potential for ultrasensitive bioelectronic applications. In this study, we made the fundamental bioelectronics platform using the MoS2-lipid bilayer hybrid structure with surface engineering. Firstly, we synthesized the film of MoS2 with chemical vapor deposition (CVD) methods. We demonstrated the lipid bilayer formation on the MoS2 film with the microfluidic channels and characterized the physical properties of the lipid hybrid structure using fluorescence imaging and fluorescence recovery after photobleaching (FRAP) test. We created MoS2-lipid bilayer hybrid structure and characterized the device performances. We also showed the MoS2-lipid hybrid structure incorporated with the proton channels in various pH environments. This hybrid platform will offer the biomimetic environment for utilizing the functionalities of the various membrane proteins as well as biological signal sensing applications.

Resume : ScF3 nanoparticles doped with trivalent ytterbium(Yb3+) and erbium(Er3+) are prepared by a modified thermal-decomposition(hot-injection) method using trifluoroacetate precursors in oleic acid (OA), oleylamine (OM) and 1-octadecene (ODE). Under the irradiation of near-infrared light, the ScF3 nanoparticles emit visible upconverted luminescence light. Taking surface defects into consideration, to minimize its quenching effects, the nanoparticles are coated with an inert shell. Especially, ScF3 is a peculiar material with negative thermal expansion (NTE) and a varying lattice parameter under different temperature conditions promising as a good candidate for thermometer which the temperature ranging from 75K to 353K. Herein, we report a novel up-conversion luminescence-based thermometer by using ScF3: Yb/Er nanoparticles with biological application potential.

Resume : Nanostructures of Copper Hydroxide (Cu(OH)2) and its salts have been of interest in energy storage and gas sensing applications since the past decade due to their catalytic properties. For energy storage, layered metal hydroxide salts are generally used as a thin film for electrode material in Li-ion batteries or as a hybrid electrode in supercapacitors. Moreover, Cu(OH)2 nanowires (NWs) are also studied as ammonia and humidity sensors. For these applications, a high degree of control of the nanostructures morphology is desired in order to enhance the performances, in particular by taking the benefit of the high surface over volume ratio. Among the synthesis methods of Cu(OH)2 thin films or nanostructures, the liquid phase chemical methods are attracting due to their low cost, low thermal budget and the ability for scaling up in mass production. In this work, we show the bottom-up synthesis and shape control of Cu(OH)2 based nanostructures grown in liquid phase, from 1D nanowires to 2D layered nanoplatelets and 3D nanocrystals. The shape control is performed by simply changing the concentration of precursors in the solution and the reaction temperature. The obtained Cu(OH)2 based nanostructures are analyzed using X-ray Diffraction, Atomic Force Microscopy, and Photo Luminescence. They are stable in air, and we demonstrate that they can be easily integrated onto electrode materials by dip coating.

Resume : Transition metal dichalcogenides (TMDs) are emerging 2D materials with potential use for the hydrogen evolution reaction (HER) because they possess the desired binding energy with protons. To date, TMD-based HER catalytic performance is enhanced mostly by chemical modification techniques such as introduction of defects, doping, and phase control. However, structural and morphological control are also important because these may increase the available surface area and control wettability of the material. The receding contact angle on the surface of the catalyst especially affects its performance; a large receding angle generates large gas bubbles, thereby inhibiting the reaction from occurring in the dead spaces of the gas bubbles. In this study, we fabricated hierarchical MoS2 wrinkles with the precise control of the wrinkle dimensions. By changing the hierarchical wrinkle wavelengths, we were able to control the wettability of MoS2, especially the receding contact angle, which is critical for gas detachment during hydrogen evolution. By controlling the degree and direction of the strain induced during shrinking, we tuned the contact angle from 60° to 130° and achieved anisotropic wetting. Notably, the hierarchical MoS2 wrinkles showed a reduced receding contact angle relative to that of a single wrinkle, thereby inducing the faster detachment of gas bubbles and enhancing the hydrogen evolution performance compared with flat MoS2. Hierarchical wrinkles with a controlled receding angle showed an overpotential reduced by 60 mV relative to that of primary wrinkles. Additionally, we demonstrated that our method can be applied to other TMDs such as tungsten disulfide (WS2).  

Resume : We report a simple methodology for growing MoO₃ nanowires doped with ReO₃ nanocrystals by APCVD (Atmospheric Pressure Chemical Vapor Deposition) process. The morphology, size and crystallinity of MoO₃ nanowires doped with ReO₃ can be controlled depending on several experimental conditions such as growth temperature, growth time, and flow rate of carrier gas. The morphology and the crystal structure of the hybrid nanostructures were characterized by Field emission scanning electron microscope (FE-SEM), Energy dispersive spectroscope (EDS), X-ray diffraction (XRD), Raman spectroscope and X-ray photoelectron spectroscopy (XPS). Furthermore, even if MoO₃ is a semiconductor, the doping of ReO₃ having the metallic property could readily enhance the electrical properties of MoO₃ nanostructures. Thus, the electrical conductivity measurements in a single nanowire configuration are carefully performed to investigate its electrical properties for future potential applications.

Resume : Rational design and facile synthesis of hierarchical architectures based on 1-dimensional (1-D) nanostructures are currently of great interest as unique building blocks with novel functions toward the development of advanced nanoscale devices. Extensive efforts have been thus devoted to synthesize a variety of nanoscale heterostructures in which secondary 1-D nanostructures directly grow in a radial direction on a primary 1-D backbone, resulting in higher dimensionality structures and capability of achieving parallel connectivity and interconnection. We demonstrate the growth of highly single crystalline ruthenium oxide (RuO₂) nanorods directly grown on electrospun carbon nanofibers (ECNFs) by combining electrospinning with a simple precipitation and recrystallization method. The recrystallization by thermal annealing process was carefully performed under various temperature conditions between 180℃ and 300℃. Structural characterizations of prepared nanostructures were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD). Single crystalline RuO₂ nanorods on carbon fibers have a rectangular shape with the lateral dimension of 30~50 nm and the length of 100-150 nm long depending on the annealing temperature. Furthermore, the electrochemical property of the hybrid nanostructures of RuO₂-ECNF as supercapacitor electrodes is investigated in an aqueous electrolyte. The CV curves display the symmetric shape with a rapid current response on voltage reversal at each end potential, good electrochemical reversibility and ideal capacitive behavior. The RuO₂-ECNF electrode annealed at 250 ℃ exhibits high capacitance (199 Fg^-1 at 1 mAcm^-2) and enhanced energy and power efficiency (21.5-12.7 Whkg^-1 in the power density range of 400-10.000 Wkg^-1) in a 6 M KOH aqueous electrolyte. This improved electrochemical performance is ascribed to the combinative effect between the double-layer capacitance of ECNF and faradaic capacitance of the RuO₂ nanorods. The structural and capacitive properties of these materials will be reported in detail.

Resume : Over the last few decades, three-dimensional printing has garnered tremendous amounts of attention in various applications by a virtue of the heretofore unachievable capability of forming versatile structures. In particular, exploiting highly functional materials for the active creation of new devices is of paramount importance to herald new possibilities in the area of 3D-printed electronics. In this study, we demonstrate the fabrication of 3D-printed electrical circuitry consisting of embedded electrical components and conformal-printed electrode features on the surfaces of pre-formed 3D polymer and paper structures, through a printing process involving metallic percolative doughs. The structural factors processable with the conductive dough are investigated by comparatively monitoring the 3D printability of percolative doughs with different rheological properties (storage modulus, loss modulus and yield stress). It is also suggested that 3D-printed origami structures are achievable via the formation of 3D-shaped electrodes inside paper structures owing to the intrinsic deformation stability of electrodes printed from the conductive doughs.

Resume : Carbon fiber-reinforced plastics (CFRPs) have received a lot of attention in a variety of industries due to their excellent mechanical, chemical and thermal properties, especially high specific strength. Despite these excellent properties, relatively poor toughness and impact resistance compared to metals or polymers are fatal shortcomings, limiting their use in automotive and aerospace applications. The cause of this disadvantage is due not only to the brittleness of the carbon fiber itself but also to its weak mechanical properties which are not reinforced by the fibers. The delamination of 2D CFRPs is one of the causes for lower mechanical properties, and some methods such as z-pinning, resin toughening, and interface strengthening have been attempted to overcome this problem but cannot be a fundamental solution. Three-dimensional (3D) woven composites have been actively studied to avoid delamination under impact and local buckling under compression in the aerospace industry. In this study, a new manufacturing method of 3D woven preforms was investigated that can produce 3D woven preforms, featuring continuous and rapid production of various 3D structured preform. Then, 3D woven carbon fiber composites were fabricated using epoxy matrix via resin transfer molding process. Tensile, bending and compressive tests were carried out to evaluate the mechanical properties of 3D woven composites, demonstrating that various 3D structures ranging from thin sheet to thick brick types and their composites can be manufactured effectively using the new method.

Resume : Polyurethane (PU) foams are used in a widespread range of applications such as insulators and dielectric materials, but their applicability is limited due to their poor mechanical properties. It seems appealing to modify PUs using nanoparticles. One-dimensional carbon nanotubes (CNTs) and two dimensional graphene nanoplatelets (GNPs) owing to their unique properties can be used as hybrid nanofillers to form well dispersed three-dimensional networks, which can overcome the dispersion problem of single nanofillers. CNTs and GNPs have a self-assembling ability due to the π –π interaction, which could decrease aggregations, resulting in enhancing the contact area between nanofillers and the polymer matrix. Micromechanical modeling and mechanical properties of PU hybrid nanocomposite foams with MWCNTs and GNPs were studied by mean of tensile strength and modified Halpin–Tsai equation. Three types of GNPs with various flake sizes and specific surface areas (SSA) were used to study GNP types dependence on the synergistic effect of MWCNT/GNP hybrid nanofillers. The results exhibit an outstanding synergetic effect between MWCNTs and GNPs with a flake size of 1.5 μm and a higher SSA, which tensile strength of PU was enhanced by 43% as compared to 19% for MWCNTs and 17% for GNPs at 0.25 wt%.

Resume : Nowadays, there is a continuing demand on miniaturization of electronic devices. Thus, there is a need for these high-density-powered microelectronic devices to have efficient heat dissipation. One of the solutions of thermal management is the use of thermal interface material (TIM). The requirements for an efficient thermal interface material are low specific weight, high thermal conductivity, pliable and stable under thermal cycling. This study focused on the effect of sonication in the fabrication of polymer-clay nanocomposites on the properties of material which will be suitable for heat transport in microelectronic devices. Solution intercalation method was employed in the preparation of nanocomposites at 5% by volume filler loading. Organomodified montmorillonite (MMT) were dispersed in the polymer matrix via two methods, manual mixing and high frequency ultrasonication methods. With the aid of ultrasonication, an increase in the d-spacing between MMT platelets was observed based on transmission electron microscopy (TEM) and x-ray diffraction (XRD) results. Elastomeric properties were also observed from stress-strain graphs of compression testing using the universal testing machine (UTM). The modification in the microstructure resulted to the enhancement of the thermal conductivity from 1.00 W/m-K for neat resin to 2.87 W/m-K for the nanocomposite when sonication was applied. This could be due to the heat transferred from chain to chain by rotation and vibration of chains; and the presence of MMT between polymer chains made it faster and easier for these chains to rotate. Results showed that application of high frequency sonication ensures modification of microstructure to a better homogeneity and improved filler dispersion thus resulting to a better thermal conductivity.

Resume : Hybrid polymer composites have attracted significant interest in the field of materials science and engineering over the years. Composite material may have new or enhanced properties compared with their pristine individual components. Graphene is a single atom thick sheet of graphite that is self-assembled through Van der Waals forces and consists of sp2 carbon lattices regarded as 2D material with superior properties and negligible thickness.1 Two dimensional graphene (G) and graphene based materials have attracted tremendous interest in the past decade owing to their superior surface area and show exceptional physical properties such as mechanical strength, good electrical and electrochemical activity.2,3 Pressurised gyration has shown great promise in forming nano- and micro-assemblies such as nanofibres, composite nanofibres and microbubbles and capsules.4,5 This technique offers consistency, reliability and is easy-to scale up.4 In typical pressurised gyration of polymer solution, the centrifugal force and the fluid flow overcomes the withholding surface tension force to initiate instability in a liquid jet that subsequently breaks up into fibres. Finally, the evaporation of the solvent leads to solidification of the fibres formed. In this work, composites fibres based on TPU and phenolic resin polymer matrices with filler graphene nanoplatelets have been prepared using a pressurised gyration process. The process makes use of simultaneous centrifugal force and dynamic fluid flow to jet the fibres before evaporation of the solvents to form the composite fibres. The forming process conditions such as vessel rotating speed, working pressure and the polymer concentration used had a significant effect on fibre diameter. FTIR and Raman spectroscopy analysis confirmed the various bonding characteristics of the hybrid composite fibre structures. Focussed ion beam milling and etching verified the effective incorporation of graphene nanoplatelets into the fibre composites. The well dispersed and strongly adhered graphene in the polymer matrices will contribute to a unique reinforced polymer composite for many applications. Importantly, this approach a promising large scale manufacturing route for graphene reinforced composite fibres at low cost has been developed. Keywords: Graphene; nanoplatelets; Pressure; Gyration; Polymer

Resume : 2-dimensional nanostructures are promising because they can make the ultra-thin applications in the field of photovoltaics, semiconductors, electrodes, sensors, and energy related devices. Graphene is an electrical conducting material, whereas graphene oxide is an electrical insulating material. Both the graphene and the graphene oxide are ultra-thin materials with the thickness of less than few nanometers. In this experiment, we fabricate the planar and vertical heterostructures of graphene/oxidized graphene. First, graphene is grown by chemical vapor deposition process. And then, oxidation of graphene is conducted by potassium permanganate and diluted sulfuric acid solution. The characteristics of oxidized graphene and unoxidized graphene are investigated by optical microscope and Raman spectroscopy. We also evaluate the several properties of oxidized graphene as functions of the oxidation time and oxidant concentration.

Resume : UiO-66(Zr) framework has been widely used for many applications due to its high surface area, and excellent chemical and thermal stability. Conventionally, UiO-66(Zr) has been prepared in autoclave by solvothermal synthesis, which requires a lengthy reaction time (typically 24 h) producing small amount of product. In this work, multi-grams of UiO-66(Zr) was rapidly produced in a continuous tubular reactor under microwave heating. The metal salt and organic linker precursor solutions were continuously introduced into the tubular reactor by a microfluidic syringe pump system. The results showed that UiO-66(Zr) with high yield, porosity and crystalinity was produced within a short reaction time of 10min. Analyses of the UiO-66(Zr) characterstics indicated that residence time, reaction temperature and modulator concentration were affected on the formation of UiO-66(Zr) framework. The UiO-66(Zr) obtained at optimum conditions were tested for gaseous toluene adsorption at various temperatures.

Resume : We describe the formation of porous crystal through the solid‐state reaction of an organic single‐crystal under acid catalyst. The superstructure of 5,5′,5′′‐(1,3,5‐triazine‐2,4,6‐triyl)triisophthalonitrile (TIPN) can be formed by cyclotrimerization of 1,3,5‐tricyanobenzene (TCB) single-crystals. The TIPN superstructure was confirmed by single-crystal X‐ray diffraction and visualized by transmission electron microscopy. The superstructure hexagonally packed 1‐dimensional (1D) channels along the crystal axis. Due to interdigitated nitrile interactions in the crystal lattice, TIPN superstructure has tolerance of electron‐beam and heat (< 500 °C).

Resume : Wireless power transfer (WPT) gains significant attention since it facilitates a user-convenience when combined with the mobile devices by removing wires and plugs in a power delivery system. This paper presents an innovative way to get around the resistive loss issue associated with the conventional 2D patterning of the power receiving (Rx) coil for WPT module. Instead of having 2D build-up layers with a configuration of Ag coil and NiZn-ferrite (NZF) layer, 3D NiZn-ferrite trench structure having a spiral inductor pattern was first inkjet-printed. A conductive ink was then inkjet-printed into the 3D spiral trench structure to form a high-aspect-ratio 3D spiral inductor coil. To compensate for a possible degradation in the flexibility of the Rx coil due to the increase in the aspect ratio of the coil, the coil was hybridized by alternating layers of Ag and polyimide (PI). Capacitors (CAP) required to tune the WPT resonance frequency were also inkjet-printed and integrated together with the hybrid inductor coil embedded in the 3D trenched ferrite layer. The WPT performance of the flexible Rx module was confirmed by wirelessly receiving power to charge a mobile phone at 6.78 MHz.

Resume : During the last decade, graphene has been stabilized on many single crystal metallic substrates [1]. For several transition metals, the hybridization between the d bands and the graphene π states strongly modifies the electronic structure of the latter. The intercalation of ultrathin layers at the graphene/metal interface is a possible strategy to influence such a hybridization. Metallic films have successfully been intercalated between graphene and the substrate in several cases. Conversely, the intercalation of compounds such as oxides, carbides or nitrates, is more challenging [2]. The presentation will be divided in two parts. In the first one, I show that it is possible to grow an ultra-thin Cr carbide film between graphene and Ni(111), by exploiting the segregation of C atoms from the bulk of the Ni substrate and the intercalation of evaporated metallic Cr at the same time [3]. In the second one, I will discuss how a reactive deposition of Cr in a oxygen atmosphere on the graphene/Ni(111) system leads instead to an ordered and layer-by-layer growth of a Cr2O3 ultrathin overlayer [4]. Graphene, in this case, works as an ideal buffer layer for the growth of high-quality ultrathin oxide layers on a reactive metallic substrate, without oxidation/reduction reactions at the interface. [1] Batzill, M. Surf. Sci. Rep. 67, 83 (2012) [2] Dedkov, Y. et al. Carbon 121, 10 (2017) [3] A. Picone et al., J. Phys. Chem. C, 121, 16803 2017 [4] A. Lodesani et al., ACS Nano (under review)

Resume : In this work, a synthesis method of ZnO nanorods (NRs) will be explained to control their aspect ratio for enhanced optoelectronic properties and realization of a wireless UV sensor application in real time. Due to their interesting optoelectronic and piezoelectric properties, ZnO nanostructures have been employed to provide various applications. However, none of these showed a real wireless smartphone connected UV sensing platform from ZnO NRs. The uniform and reproducible ZnO NRs UV sensors were fabricated and combined with a developed wireless sensing platform. In addition, a flexible UV sensor based on the ZnO nanostructure was suggested. It is difficult to utilize ZnO high sensitivity for flexible electronic devices due to their rigidity. To solve this problem, organic-inorganic hybrid nano composite structure was suggested. However, the organic materials that can be used as the matrix should be porous to maintain the ZnO sensing property. Because the mechanism of ZnO sensor is directly related to the adsorption and desorption of oxygen and water molecules. Therefore, cellulose nanofibers were fabricated to make a porous organic matrix for nano composites. The interfacial interaction between two nanomaterials and mechanical, optoelectronic properties will be discussed. This low dimensional hybrid nano composite sensor is flexible due to the organic porous matrix with high sensitivity. It also shows a multi-sensing properties including UV sensing and humidity sensing. Finally, an optimized and minimized wireless sensor circuitry was fabricated to make a prototype of wearable sensor platform consisting of our developed flexible nano composite sensor.

Resume : Functionalized 2D materials provide an ideal platform for building low-cost chemoresistive sensors. They have, in addition to the high surface-to-volume ratio, two other important advantages: i) the receptor and transducing functions can be easily separated by forming different surface hybrids; ii) technological handling is easier as compared to 1D materials. The receptor function can be tuned by addition of clusters on the surface or by forming layered structures. We have used pulsed laser deposition (PLD) as a functionalization tool for creating highly sensitive graphene-based gas sensors. After deposition of a sub-nanometer oxide layer on the CVD-grown graphene, the gas sensitivity could be increased up to 2 orders of magnitude due to the formation of effective adsorption centers. In addition, the selectivity can be introduced by the selection of the deposited material. For example, TiO2 layer lead to high selectivity towards NO2 or O3 with low (<10%) cross-sensitivity to other tested gases (CO, SO2, NH3, H2S), whereas V2O5 layer lead to a similar result for NH3 gas. However, 100% selectivity was not achievable and therefore electronic nose type approach with differently functionalized and thermally excited sensor elements was developed. The prototype has 4 different sensor elements consisting of graphene hybrids with TiO2, V2O5, In2O3, and Pt. We demonstrate selective detection of NO2, NH3, and O3 gases at low concentrations typical for outdoor air pollution.

Resume : Stretchable and highly-conductive carbon nanotubes (CNT)-Polydimethylsiloxane (PDMS) composite films can be exploited as highly-sensitive strain sensors, shock-absorbent electrical contacts or as flexible energy-storage components. Here, we present a simple, cost-effective, high-yield method to fabricate uniform, highly stretchable, composite CNT-PDMS films with preferred CNT directional orientation (vertically-aligned, (VACNTs, as-deposited) and horizontally-aligned HA-CNTs, rolled)), enabling directional sensing. MWCNTs are deposited on alumina (Al2O3) substrates via photo-thermal chemical vapour deposition (PTCVD) method. PTCVD uses an optical heat as the heat source required for growth, efficiently coupling it with the catalyst, allowing high quality (ID/IG < 0.4), highly dense CNTs with growth rates of up to 500 nm/s. Samples of different MWCNT lengths in both vertical and horizontal orientations are embedded in to PDMS, tested for their electrical and mechanical responses via stretching and compression tests. Firstly, we report gauge factors (GF) of up to 1885.5 with good elastic stretchability (50%) for HACNT-PDMS films and 665.4 GF for VACNT-PDMS with up to 40% elastic stretchability. A linear electromechanical performance (up to 10 % strain) is observed for VACNT-PDMS devices due to stretching direction being perpendicular to the CNT direction, whereas CNT-length dominant electron transfer through recoverable micro-crack formation within the elastomer (for >2% strains), enhancing the GFs resulting in a higher sensitivity for HACNT-PDMS films. Additionally, films are tested under compressive strains and showed GFs as high as 454.3 for VACNT-PDMS films and 234.4 for HACNT-PDMS films at 55% strain with full elastic recovery indicating high directional sensitivity to both stretching and compression. Furthermore, Au-metallising the CNT-PDMS films reveal contact resistances as low as 0.019 Ω/mm2 under compressive strains, demonstrating good power handling capabilities. Finally, electromechanical durability and structural robustness of the films are tested through cyclic compression and stretching tests (> 10,000 cycles) at strain of up to ~75 % with less than 5% degradation in the GF values, which shows that these composite films are very good candidates as wide-range human motion detection and electronic skin applications, as well as conductive shock-absorbing electrical contacts.

Resume : We present a composite material of copper oxide (CuO) nanoparticles inside the one-dimensional pores of nanoporous KIT-6 silica (SiO2). The material is used for the dosimetric detection of hydrogen sulfide gas (H2S) in low ppm concentrations. The system is based on the chemical conversion of CuO to copper sulfide (CuS) at low temperature (160 °C): CuO + H2S -> CuS + H2O. Since CuS is highly conductive ('metallic' CuS), the reaction results in a strong increase of electronic conductivity (measureable). The sensor is, therefore, highly selective to H2S. The reaction is reversible; CuO is regenerated by heating to 350 °C in air (with or without H2S). Long-time stability of our system allows for repeated cycles of measurement and regeneration. This is possible due to the fact that the CuO/CuS nanoparticles are embedded in the nanoporous matrix. Even though severe volume expansion and shrinkage of the particles take place during each cycle, no overall morphological changes in the sensing material occur, which ensures a stable long-term sensing performance. The sensor response is marked by a percolation-type mechanism. Upon exposure to H2S the conductance remains low for a certain induction time during which CuS is gradually formed. Once the percolation threshold is reached, a continuous conduction path forms and the conductance shows a steep increase. The length of the induction period depends on the H2S concentration; hence, measuring this time period allows for assessment of the H2S concentration (after calibration).

Resume : We report results of the development and tests of high-sensitivity, low-frequency magnetic field sensors based on a magnetoelectric (ME) composite consisting of a metglas / bidomain lithium niobate (LN) laminate shaped in form of a tuning fork. An efficient suppression of acoustic and thermal noises in the measurements of AC magnetic fields has been achieved. As a piezoelectric component we used a y+128°-cut LN single crystal. A metglas foil (serving as a magnetostrictive component) was asymmetrically bonded to each tine of the tuning fork. The sensor demonstrated a 6.7 times increase of the sensitivity as compared to a single-plate ME sensor: the magnetic field detection limit was enhanced from 20 pT to 3 pT at a bending resonance frequency of ca. 318 Hz, without any shielding from external noises. The advantages of the ME sensors based on bidomain LN over those based on PZT or PMN-PT are a much higher thermal and chemical stability, non-hysteretic piezoelectric effect, large resistance to creep and ageing effects, lead-free nature and simple and cheap fabrication process. Ultimately, the tuning-fork ME sensors based on bidomain LN single crystals may be used in low frequency, ultra-sensitive and cheap magnetic field sensors for biomedical (magnetocardiography, magnetoencephalography), wearable electronics or space applications. The anisotropic character of the observed magnetolectric effect enables the application of our structures as vector magnetic field sensors.

Resume : Humidity sensors are attracting crescent attention in numerous fields and applications. Nowadays metal oxides and ceramic materials dominate the market of humidity sensors, yet new cheaper and more effecting materials are emerging. In particular graphene oxide (GO) based humidity sensors are promising for their low cost and low temperature operation, however they present critical drawbacks, such as long response and recovery times and poor stability. With the aim of improving the sensing performances, here we report the preparation of a novel humidity sensor based on a layered film of functionalized graphene oxide (fGO). A facile procedure was adopted to chemically functionalize GO with a dangling triethylene glycol and the success of the functionalization was proved by a deep characterization of the material. The fGO was then processed in thin films, and partially reduced via mild thermal treatment. The fGO sensor presented an ultrafast response (25 ms) and recovery in the sub-second range, a high response (up to 30 % change in the resistance), low hysteresis (0.6 %), and excellent repeatability and stability. A comparison was made with an equally processed, not functionalized GO device that showed a 55 % lower sensitivity, longer response and recovery time, high hysteresis (67 %), low reversibility and unstable response. The reasons of the better performance are attributed to the TEG molecules present on the fGO surface, which can at the same time swell with humidity, further increasing the distance between flakes and thus the resistance and release fast the absorbed water molecules, leading to a fast and complete recovery. These fGO sensors are cheap, easily processable and could also be deposed on flexible substrates.

Resume : We report on an original organic heterojunction, built on ITO electrodes and combining a low conducting sublayer (Cu(F16Pc)) and a highly conductive semiconductor (LuPc2). The non-linear I-V characteristics of the devices and impedance spectroscopy demonstrate the existence of energy barriers at the interfaces. Starting from 4 diazonium salts, we showed that the grafting of aromatic moieties could induce an increase of the energy barrier at the interfaces depending on the nature of substituents. Thus, the electrografting of dimethoxybenzene on the electrodes has a strong effect on the electrical properties of the heterojunction, and on the sensitivity to ammonia, in the 1-100 ppm range. Moreover, it allows attaining a LOD of 140 ppb. In addition, the electrodeposition of substituted polyanilines, followed by their covering by LuPc2, led to an original device that can be obtained only by electrochemistry and not by any other solution processing technique. Whereas the aniline and the 2,5-dimethoxyaniline lead to two highly conducting polymers that require a neutralization step before their covering by LuPc2, the poly(2,3,5,6-tetrafluoroaniline) is a poorly conducting material. The obtained double lateral heterojunctions exhibit a particularly interesting response to NH3, at room temperature and in a broad relative humidity range. This work paves the way for the use of substituted polyanilines not only in the field of air quality monitoring but also for health diagnosis by measurement in human breath. Additionally, the electrografting is a versatile and promising method for the fabrication of symmetrical and unsymmetrical heterojunctions that could be used to tune the performances of other conductometric transducers.

Resume : The high transparency of graphene over wide bandwidth of light led to many forms of photodetectors. Graphene has been adopted as transparent electrodes in various solar cells. It has also been transferred onto crystalline-silicon (c-Si) substrates to form Schottky junction photodiodes. Unfortunately, contamination concern makes graphene unwelcome in the front-end processes of standard CMOS technologies, which in turn makes implementing integrated graphene/crystalline-silicon (Gr/c-Si) Schottky junctions impractical. A feasible way to include graphene/silicon photodiodes into CMOS technologies and avoid the contamination problem is to fabricate graphene/amorphous-silicon (Gr/a-Si) junctions during or after the back-end processes. The low-temperature process of depositing a-Si films also has minimal impact on the underlying CMOS devices. Therefore, the Gr/a-Si photodiode is a potentially useful device in the silicon optoelectronic integrated circuits (Si OEICs) with graphene inside. However, the study on the Gr/a-Si photodiode was hardly found in literature. In this work, a Gr/n-type a-Si photodiode integrated on top of a Si NMOSFET was designed and fabricated. In particular, the graphene terminal of the Gr/n-type a-Si photodiode was connected to the poly-Si gate of the NMOSFET via interconnect metal. Similar to the graphene photodiode-oxide-semiconductor field effect transistor (graphene PDOSFET) proposed by the authors before, [1] in which a graphene layer is inserted between the gate oxide and the poly-Si gate of a MOSFET, the composite of the Gr/n-type a-Si photodiode and the NMOSFET is particularly useful in constructing the source followers in the pixels of a CMOS image sensor for detecting high-contrast images. Under illumination, the a-Si of the photodiode absorbs light energy and generates electron-hole pairs. Holes move to the graphene and create an optical voltage, which raises the effective gate potential and thus modulates the channel current of the NMOSFET. The natural logarithmic relation of the optical voltage to the light power allows very wide dynamic range of incident light power without cutting off the function of source follower. And since the Gr/a-Si photodiode does not compete with the transistors in the pixel for occupying chip area, the classical tradeoff between the pixel size and the photodiode fill factor in a pixel can be eliminated. A source follower circuit composed of the Gr/a-Si photodiode integrated with the NMOSFET and a load was devised and tested. Measurements showed that the output voltage of the source follower does vary logarithmically with input light intensity. The successful demonstration of the composite of the Gr/a-Si photodiode and the NMOSFET opens the door of image sensor application for graphene. [1] Klaus Yung-Jane Hsu and Yu-Yang Tsai, “PDOSFET -- A New Field-Effect Transistor Integrated with a Poly-Si/Graphene Photodiode on the Gate Oxide,” Proc. 2016 European-MRS Spring Meeting, Symposium Y, p. Y.16.2., 2016

Resume : Graphene represents a unique sensing platform enabling efficient fluorescence (FL) quenching and graphene-enhanced Raman scattering (GERS). Here, we analyzed micro- and nanoplastics with sizes below 1.5 µm coupled with graphene, this particle range being important due to toxicological reasons. Both reference and filtrated plastic particles from real bottled mineral water were investigated using high-resolution microscopy and spectroscopy techniques. FL intensity measurements performed with different lasers confirmed the decrease of the FL signal originating from micro- and nanoplastics when in intimate contact with graphene. The reduced FL background along with the GERS effect led to pronounced Raman peaks, enabling a detailed chemical characterization of small, thin, and transparent plastic materials (PVC, PE, PS, PP, PET). Moreover, combining GERS with tip enhanced Raman scattering (TERS) increased further the Raman response and spatial resolution down to nanoscale, revealing hybrid plastic, pigment, and additive micro- and nanoparticles in real samples. These results on small-sized plastics interfaced with graphene are supported by similar data obtained on standard aluminium-coated polycarbonate membrane filters. Our approach can be developed toward integrating graphene and other hybrid composites in microfluidics sensing devices to identify and count plastic particles in food.

Resume : Hydrogen (H2) is expected to form a major part of the global energy market as stricter emission regulations come into force. By 2030 the global market for fuel cell vehicles is predicted to grow significantly. However, 95% of global H2 production is still based on the highly CO2-emitting reforming of fossil fuels. Electrolysis is one of the most promising methods to replace steam-reforming. Through electrolysis, intermittent renewable energies such as solar and wind can be used to chemically store energy as low CO2 emission H2. Using H2 from renewable sources rather than fossil fuels would roughly half the lifecycle CO2 emissions from a Toyota Mirai (one third of the lifecycle CO2 emissions of an equivalent gasoline vehicle). Commercial electrolysis is now possible at efficiencies of 70 - 80% using noble metal catalysts, where platinum is typically used as the H2 evolution catalyst. However when future large-scale implementation and the lack of alternative catalysts in the fuel cell sector are considered, there is a strong motivation to find replacement for platinum in water electrolysis devices. Here we present new bio-inspired noble metal-free nanomaterials based on 2D molybdenum sulfide structures incorporating first-row abundant transition metals (M:MoSx) attached to carbon nanotubes (CNT). The electrochemical activity for the hydrogen evolution reaction (HER) was investigated in acidic aqueous electrolyte and the differences between various scalable synthesis methods were shown. M:MoSx.CNT electrocatalysts have an improved HER activity, with significantly reduced overpotential and increased stability compared to the un-modified MoSx. We also investigated the tolerance to oxygen of these materials and we will discuss the opportunity to integrate them into proton exchange membrane (PEM) water electrolysers.

Resume : Hybrid photodetectors make use of excellent photoabsorption of perovskites and high mobility of 2D materials, such as graphene. In the present work, we fabricated a hybrid photodetector using fully inorganic perovskite NCs as photoabsorber and a 2D graphene channel as the transport layer. The hybrid device achieved excellent responsivity and photoconductive gain. Additionally, we examine the photostability of these devices under prolonged light exposure. In our studies, we conclude that the ultrahigh photoconductive gain is achieved due to the carrier trapping within the transport layer, inadvertently causing a band bending in the NCs.

Resume : Tandem III-V solar cells grown on Ge substrates are achieving highest conversion efficiencies. One realistic approach to significantly reduce device costs is to reuse the growth template several times. This practice has already been implemented for Si epitaxy on reusable Si-wafers by generating a porous multi-layer structure which serves as separation layer after growth. In contrast to Si it has been shown that the control of the etching run for Ge is much more complex as (i) bipolar etching is necessary, (ii) the initial current pulse has strong influence on the structure and (iii) constant etching parameters still lead to permanent changes of the etching procedure. In this work we present latest results on the influence of the initial current pulse and the understanding of the etching function over time and layer thickness. The achieved sponge-like and fishbone structures are analyzed by 3D reconstruction using SEM after processing by Focused Ion beam Milling from top to bottom of the porous layer. In each case an exponential decrease in porosity over thickness could be found within the layer. Furthermore we will discuss findings about improving lateral homogeneity of the process on Ge wafers with 4” in diameter which has never been shown so far. This enlargement of process area plays a crucial role for commercialization and will be supported by adapted characterization methods which can analyze very small structures of several tens of nanometers on a whole 4” wafer area.

Resume : Abstract：3D printing technology is applied in the charge of explosive circuit to solve the problems existing in traditional charge technique，such as more defects，low density and poor mechanical properties．To obtain a excellent (2,6-diamino-3,5-dinitropyrazing-1-oxide)LLM-105 explosive ink, the influence rule of LLM-105 solid content，system temperature，LLM-105 particle gradation and functional additives on the rheological properties was investigated by a digital viscometer. Results show that the explosive ink presents non-Newtonian fluid characteristics when the solid content is 72~88% and the apparent viscosity can be described with Ostwald-deWaele model. The apparent viscosity decrases as the particle size increases. When the particle gradation ratio of 20 μm particle size to 4 μm is 6∶1，the apparent viscosity reaches the minimum. Rheological properties of explosive ink will be effectively improved with the addition of surfactant lecithin. With the increasing of lecithin contention，the apparent viscosity of LLM-105 explosive ink will keep up at first and then down. When lecithin contention is 0.1 %，the non-Newtonian index reaches the maximum 0.13. By selecting the LLM-105 explosive ink formulas and adjusting the process parameters, an explosive circuit was successfully prepared using 3D printing technology and results show that 3D printing explosive circuit has more uniform internal structures compared to the traditionally prepared explosive circuit. Key words: Explosive ink; LLM-105; 3D printing; Rheological Property

Resume : Extensive investigations on electrochemical as well as photochemical water splitting has been thus focused to resolve the severe energy crisis and environmental damages nowadays. The important advantage of the water splitting reaction makes it possible to the sustainable production of hydrogen as a promising energy carrier. However, both reactions in the course of the water splitting reaction, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), are kinetically sluggish and then require a high overpotential to take place at a useful rate owing to a stepwise complex four-electron redox process as the thermodynamically uphill reaction. It is necessary for those reactions to use an electrocatalyst lowering down the energy barrier. The finding of an electrocatalyst for OER, which has efficient, stable, abundant, low cost, and environmentally friendly natures, thus plays a crucial role to overcome the bottleneck of the current state of water splitting. We report the effective growth of a unique single phase of spinel cobalt rhodium oxide (Co2RhO4) nanotubes via the electrospinning process combined with the thermal annealing process. In the spinel structure of electrospun Co2RhO4 nanotubes, Co3+ cations and Rh3+ cations randomly occupy the octahedral sites while the remaining half of Co2+ cations occupy the centers of the tetrahedral sites as proven by microscopic and spectroscopic observations. Furthermore, electrospun spinel Co2RhO4 nanotubes exhibit excellent catalytic performances with the least positive onset potential, greatest current density, and low Tafel slope which are even better than those of the commercial Ir/C electrocatalyst for the oxygen evolution reaction (OER) in alkaline solution. As a consequence, this rational engineering of materials with simple and effective strategies could open up a new strategy for developing highly efficient electrocatalysts.

Resume : The high efficient water splitting system should involve the reduction of high overpotential value, which was enhanced the electrocatalytic reaction efficiency of catalysts, during the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. For the high-performance water splitting system, we synthesized Mesoporous Co3N@Amorphous N-doped carbon nanocubes for OER. Mesoporous Co3N@AN-C NCs demonstrate greater OER activity with a remarkably low Tafel plot (72.5 mV dec-1), low overpotential of 280 mV at a current density of 10 mA cm−2, and excellent cycling stability superior to most reported transition-metal nitride particles. Herein, we confirmed that Co4N was synthesized after higher temperature nitridation (650°C). Co4N has higher electrical conductivity than Co3N, but it has lower specific surface area due to aggregation. Therefore, we report a comparison of the Mesoporous CoxN@Amorphous N-doped Carbon Nanocubes based on in-situ nitridation and calcination at various temperature. The morphology of Mesoporous CoxN@AN-C NCs was analyzed by FE-SEM and TEM. The composition was confirmed by XRD and XPS. Also, specific surface area is analyzed by BET. Finally, we analyzed electrochemical properties of Mesoporous CoxN@AN-C NCs.

Resume : A key issue on solid oxide fuel cells (SOFC) is to lower the high operation temperature and improve sluggish kinetics associated with oxygen reduction in the mid-range temperature of ~500 ℃. Here, we report morphologically well-defined Gd0.1Ce0.9O2-δ (GDC) embedded Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) nanofibers via simple electrospinning method to enhance the kinetics and lower the operation temperature. The high surface area and heterogeneous fibrous structure generate a large number of triple phase boundary among the embedded GDC, BSCF fiber and gas. In order to achieve a favorable 1D structure, highly crystalline BSCF particles with ~200 nm size were dispersed in Gd(NO3)3/Ce(NO3)3 based e-spinning solution. During sintering the electrospun green fiber, GDC nanoparticles are synthesized on a BSCF backbone and play an important role on maintaining structural stability. The full cell which employs 2D GDC thin and dense solid electrolyte and 1D cathode shows the maximum power density of 0.65 W/cm2 at 550 ℃ and 1.02 W/cm2 at 600 ℃.

Resume : High performance infrared (IR) photodetectors have been developed over the last few decades for both military and civilian applications such as surveillance, target tracking, mine detection, and medical diagnosis [1−3]. Coventional IR detectors employ a single-band absorber operating in the short-wave IR (SWIR, 1−3 μm), mid-wave IR (MWIR, 3−5 μm), long-wave IR (LWIR, 8−12 μm), and very-long-wave IR (VLWIR, >12 μm) bands. IR focal plane array (FPA) sensors with single-band detector elements have demonstrated high-quality IR imaging [2,3]. However, single-band FPAs are unable to capture the finer details of target and scene images in the presence of clutter and noise or in situations, where the appearance of target and/or background may change [4]. In this work, we investigate the material properties and device performance of InGaAsSb-based barrier IR detectors grown by molecular beam epitaxy (MBE) on n-GaSb substrates. The two IR absorbers, separated by a 100 nm Al0.38Ga0.62Sb barrier, consist of a 2000 nm n-In0.32Ga0.68As0.31Sb0.69 and a 1500 nm n-InAs0.92Sb0.08 alloys with different bandgap energies of ~0.49 eV and ~0.35 eV at 77 K, respectively. The unipolar barrier of AlGaSb blocks the majority carrier (electron) flow, while allowing the minority carrier (hole) flow. This undoped wide bandgap barrier also acts as a surface passivation layer to reduce surface leakage current. Another advantage of the nBn structure is the absence of depletion regions and thus generation-recombination dark current is negligible due to suppressed Shockley-Read-Hall (SRH) recombination. As a result of the elimination of the surface current and the SRH current, our nBn detectors exhibit low dark current densities of ~6.3×10-7 and ~1.0×10-3 A/cm2 under −0.1 V applied voltage at 77 K and 300 K, respectively. The detectors are sensitive only in the SWIR range of 1.5−2.5 μm at a voltage (0 < V < 0.1 V) at 77 K. At a reverse bias (−0.5 < V < −0.25 V), their photoresponse extends to wavelengths of 3.0−3.8 μm (MWIR) at 77 K. Therefore, we have successfully demonstrated voltage tunable two-color nBn detectors with 90% cutoff wavelengths of 2.5 μm and 3.8 μm at 77 K. Our work has made it possible for the InGaAsSb-based nBn detectors to become a promising candidate for fabricating high performance multispectral IR FPA sensors, which yield a much better discrimination of objects and scenes. Renferences [1] A. Rogalski, Prog. Quant. Electron. 27, 59 (2003). [2] Y. Arslan et al., Infrared Phys. Technol. 70, 134 (2015). [3] S. Krishna, J. Phys. D: Appl. Phys. 38, 2142 (2005). [4] A. Haddadi et al., Appl. Phys. Lett. 106, 011104 (2015).

Resume : We present a stable inkjet printable graphene ink, formulated in isopropyl alcohol via liquid phase exfoliation of chemically pristine graphite with a polymer stabilizer. The rheology and low deposition temperature of the ink allow uniform printing. We use the graphene ink to fabricate counter electrodes (CE) for natural and ruthenium-based dye-sensitized solar cells (DSSCs). The repeatability of the printing process for the CEs is demonstrated through an array of inkjet-printed graphene electrodes, with ~5% standard deviation in the sheet resistance. As photosensitizers, we investigate natural tropical dye extracts from Pennisetum glaucum, Hibiscus sabdariffa and Caesalpinia pulcherrima. Among the three natural dyes, we find extracts from C. pulcherrima exhibit the best performance, with ~0.9% conversion efficiency using a printed graphene CE and a comparable ~1.1% efficiency using a platinum (Pt) CE. When used with N719 dye, the inkjet-printed graphene CE shows a ~3.0% conversion efficiency, compared to ~4.4% obtained using Pt CEs. Our results show that inkjet printable graphene inks, without any chemical functionalization, offers a flexible and scalable fabrication route, with a material cost of only ~2.7% of the equivalent solution processed Pt-based electrodes.

Resume : Waste energy harvesting from ambient environment and biological movements has received considerable attention as an attractive alternative for environmental disorder problems like global warming, depletion of ozone layer, harmful emission of gases, and the energy crisis. Piezoelectric nanogenerators (PENGs) are suitable for powering micro/nanosystems, wireless transmitters, biomedical devices, and wearable electronic devices. Here, we have synthesized Ag decorated ZnSnO3 nanocubes (Ag@ZnSnO3) by a simple solution method and fabricate a lead free nanogenerator to develop an environmentally friendly flexible energy harvester. On periodic finger tapping the fabricated polydimethylsiloxane (PDMS)/Ag@ZnSnO3 based PENG exhibits a recordable open circuit voltage and short circuit current of ∼20.6 V and ~1.2 μA, respectively, at 5 wt % Ag@ZnSnO3 loading, without any electrical poling treatment. The harvested energy can be applicable for driving the liquid crystal display (LCD), light emitting diode (LED), and wrist watch. Also, the fabricated nanogenerator exhibits high mechanical robustness and excellent power generation with outstanding reversibility.

Resume : In this work, we demonstrate a triboelectric nanogenerator (TENG) based on magnetic iron oxide reinforced polyvinylidene fluoride (PVDF) nanocomposite and polyethylene terephthalate (PET) as triboelectric layers which could have potential applications for scavenging biomechanical energy and mechanical vibrations whilst being light weight, transparent, flexible and thin enough to carry along as wearable electronics in powering portable devices. The films were examined for their structural integrity as well as functional analysis. Microscopic analysis shows incorporation of iron oxide particles in the PVDF matrix. Detailed electrical and triboelectric characterization shows that addition of iron oxide to PVDF matrix results in higher power output of the devices than of those containing pure PVDF. TENG output power is found to be sufficient enough to continuously light up 20 light-emitting diodes (LED) connected in series, without the use of capacitor. In addition, the device was also operated in contactless mode using a magnet driven operation, abbreviated as M-TENG which does not have physical contact to the applied mechanical force and hence there was no physical damage to the device. M-TENG has a potential application in shielding against electromagnetic interference (EMI), owing to its magnetic nature.

Resume : The n-type semiconductor gas sensor is widely used for the detection of reducing gas such as CO, H2, and volatile organic compounds (VOCs) gases. In particular, SnO2 is known as a representative semiconductor gas sensing material because it is chemically stable and having high electron mobility. Due to increased environmental concern, there is an increasing demand for semiconductor gas sensors that are selective and responsive towards H2S gas, which is harmful for living being. The H2S is a toxic and malodorous gas produced from coal mine, coal oil gasoline and natural gas manufacturing processes, and wastewater treatment plants. In order to increase the gas sensing response of SnO2 based gas sensor, the addition of noble metals (Pt, Au, Pd) or the structural modification of SnO2 nanoparticles(NPs) is suggested. Out of these noble metals, Au NPs is reported to be a good catalyst for the adsorption and decomposition of H2S gas. Au NPs can facilitate the H2S oxidation by providing a large number of adsorbed oxygen on the surface of SnO2 in Au decorated SnO2 composites. Among various nano-structures, core-shell NPs having Au as core material could be a better sensing material for H2S gas. The core-shell structure can prevent the agglomeration and undesired growth of Au NPs. In this study, Au@SnO2 core-shell NPs has been synthesized by microwave-assisted hydrothermal method. XRD measurements showed the high crystalinity of Au@SnO2 core-shell NPs. The morphology of Au@SnO2 core-shell NPs was examined in FE-SEM and TEM. We also observed the electrical resistance change of Au@SnO2 core-shell NPs according to the content of H2S gas (from 2 ppm to 100 ppm) for investigating sensing response and selectivity behavior.

Resume : Electrolyte-gated OFETs (EGOFETs) have emerged as suitable devices for label-free biosensors, thanks to their impressive sensing performance level [1,2]. However, their operational and environmental stability is highly dependent on organic semiconductor (OS) degradation. In fact, it is reported that such materials are very sensitive to humidity/water [2]. Stability studies are available for devices working with solid-state dielectrics, whereas only a few for EGOFETs [4]. In this work, poly(3-hexylthiophene-2,5-diyl) (P3HT), a p-type OS, was selected as benchmark material to fabricate the channel of EGOFET devices. The implementation of ZnO nanophases [5] was also considered to modify the P3HT channel. Environmental (incubation in water) and operational stability (bias stress) of the as-prepared EGOFETs was evaluated and a possible model for P3HT degradation was proposed. A strategy to preserve device performance and shelf life was also investigated. [1] E. Macchia, K. Manoli, B. Holzer, C. Di Franco, M. Ghittorelli, F. Torricelli, D. Alberga, G.F. Mangiatordi, G. Palazzo, G. Scamarcio, L. Torsi, Nature Communications, 9, 3223 (2018). [2] E. Macchia, A. Tiwari, K. Manoli, B. Holzer, N. Ditaranto, R.A. Picca, N. Cioffi, C. Di Franco, G. Scamarcio, G. Palazzo, L. Torsi, Chemistry of Materials, doi: 10.1021/acs.chemmater.8b04414 (2019). [3] E.K. Lee, M.Y. Lee, C.H. Park, H.R. Lee and J.H. Oh, Adv. Mater. 29, 1703638 (29pp.) (2017). [4] Q. Zhang, F. Leonardi, S. Casalini, I. Temiño, M. Mas-Torrent, Sci. Rep. 6, 39623 (2016). [5] R.A. Picca, K. Manoli, A. Luciano, M.C. Sportelli, G. Palazzo, L. Torsi and N. Cioffi, Sens. Actuators: B. Chemical 274, 210 (2018).

Resume : Semiconducting metal oxides (SMOs) such as SnO2, ZnO, WO3 etc. have been widely investigated for sensing gases such as volatile organic compounds, carbon monoxide, hydrocarbons and other reducing gases. Some (like WO3) show excellent sensing response to nitrogen dioxide as well. However, most SMOs response poorly to carbon dioxide. Current research work portrays investigations of carbon dioxide sensing on thin film sensing elements of various configurations of ZnO (Zinc Oxide) and LFCO (Lanthanum Iron Cobalt Ferrite) where LFCO is a stable perovskite and has been shown to behave differently when in conjunction with ZnO. A single pn junction of ZnO and LFCO show comparatively higher response (31%) to 2500 ppm carbon dioxide (CO2) with respect to pure ZnO (14%) and pure LFCO (9%) as well as lower response time of 150 seconds as compared to the pure materials (ZnO = 300 seconds; LFCO = 500 seconds). The operating temperature for this configuration (225°C) is in between that of ZnO (300°C) and LFCO (200°C). The response (36%) is similar for LFCO – ZnO composite albeit at a higher operating temperature of 300°C and a response time of 300 seconds. The results indicate that it is possible to tune the operating temperature of the carbon dioxide sensor by changing the configurations of the n type (ZnO) and p type (LFCO) thin films without changing the behavior of the sensor with respect to the same concentration of carbon dioxide. Keywords: Zinc oxide, Lanthanum iron cobalt oxide, thin film, composite, carbon dioxide sensing

Resume : The development of freestanding fiber-type chemiresistor, having high integration ability with various portable electronics including smart clothing system, is highly demanding for the next-generation wearable sensing platform. In this work, we present potential suitability of the freestanding reduced graphene oxide (RGO) fiber functionalized with platinum as a sensitive humidity sensor. As a result, nRGO fiber can effectively detect wide humidity levels in the range of 6.1–66.4% relative humidity (RH). A sensitivity of 4.51% at 66.4% RH is achieved. Real-time and portable humidity sensing characteristics are successfully demonstrated toward exhaled breath using Pt-nRGO fiber integrated on a portable sensing module. In addition to humidity sensor, we present ultraporous reduced graphene oxide fiber functionalized with WO3 nanorods (porous WO3 NRs-RGO composite fiber) as a sensitive nitrogen dioxide (NO2) detector. The freestanding porous WO3 RGO fiber shows a notable response ([Rgas-Rair]/Rair × 100 = 6 %) to 1 ppm of NO2.

Resume : Organic-inorganic perovskites such as CH3NH3PbI3 emerged as attractive materials with outstanding potential in applications such as low cost high efficiency solar cells or photodetectors. However, the complex structure of these materials and the difficulty of manipulation hinder their integration into devices. In this work a procedure for rapid prototyping of CH3NH3PbI3 is described. This procedure enables the use of laser-induced forward transfer (LIFT) as a powerful technique for direct writing of organic-inorganic perovskite patterns as a proof of concept for the fabrication of solar cells. A morphological study shows that for a rather large range of laser fluences (150-300 mJ/cm2) it is possible to transfer well defined, regular CH3NH3PbI3 pixels. The structural characterization of the CH3NH3PbI3 pixels by XRD is in good agreement with their morphology, i.e. for laser fluences above 300 mJ/cm2 the transferred CH3NH3PbI3 pixels are damaged (appearance of the pure lead iodide peak). In order to demonstrate LIFT for device (solar cell) fabrication, a multilayer structure (CH3NH3PbI3 (300 nm)/ C60 (30 nm) / BCP bathocuproine (8 nm)) is transferred onto an PEDOT:PSS coated ITO glass slide. A promising open voltage of 0.75 V is measured, which proves LIFT as an alternative method in the future industrial production of micro-solar cells.

Resume : In this work, the perovskite-type oxide LaGaO3 was synthesized by a sol-gel method as novel anode materials for Ni/MH hydrogen batteries, X-ray diffraction (XRD) analysis showed that LaGaO3 perovskite-type oxides are monophasic. They crystallize in the orthorhombic space group Pnma and their electrochemical properties were systematically investigated at different concentrations of the KOH electrolyte (1M, 3M and 7 M) using chronopotentiometry, potentio-dynamicpolarization and chronoamperomertry techniques at 328 K [1] , [2], [3]. After the 20 charge/discharge cycles of the three concentrations, the alloy structure remains perovskite. Like the relationship between the discharge capacity and concentration of electrolyte, the electrochemical kinetic analysis indicates that the exchange current density and the hydrogen diffusion coefficient of the oxide LaGaO3 increase with the rise of the concentration of electrolyte at high temperature [4]. So, the discharge capacity of the oxide LaGaO3 at 328K reaches its maximum value at 220 mAh.g-1 at the third cycle. Thereafter, it decreases to 12mAh g-1 and remains stable at the other 17 cycles[5] [6]. The measurements showed that the electrochemical performance of the LaGaO3 oxide has been greatly influenced by the variation of KOH concentration. Faster activation and highest discharge capacity are achieved at KOH 7M. The kinetic properties of the working electrode have been significantly improved by the elevating the electrolyte concentration.

Resume : Three kinds of AVIMMR intermediates were synthesized by using 1-vinylimidazole with bromoethane, bromopropane and bromobutane respectively by controlling the experimental temperature and reaction time. The optimum reaction conditions were at 120 °C for 24 h, and then by displacement reaction. Br-ion exchange to TFSI-ion produces three AVIMTFSI. The BVIMTFSI with the largest response current, the shortest response time and the lowest resistance was selected by electrochemical test. The VIM was added to the ionic liquid to prepare the blend system. The two ionic liquids were obtained by cyclic voltammetry, chronoamperometry and AC impedance. The best combination is 20% BVIMTFSI 80% VIM. Since the viscosity of the ionic liquid can be reduced by adding the co-solvent, the C5H4F8O co-solvent is mixed in the mixed ionic liquid 20% BVIMTFSI 80%VIM, and the gas sensitivity test of different sweep speeds and different oxygen concentrations is carried out, and the conclusion is that with the sweep speed With the increase of oxygen concentration, the response current increases linearly, which proves that the electrolyte has good oxygen sensitivity and can be applied to the assembly of oxygen sensors.

Resume : Scavenging energy from various types of mechanical forces through piezoelectric nanogenerator (PNG) has been a considered great alternative for powering up low-power portable devices and self-powered electronic systems. Here, the ferroelectric and lead-free perovskite zinc titanate (ZTO) nanospheres help to align the molecular –CH2/CF2 dipoles of PVDF, endorsing the nucleation of electroactive γ-phase in the PVDF matrix (γ-PVDF), which is responsible for the generation of piezoelectricity of the PNG without any electrical poling treatment. The fabricated PNG with 2 wt% ZTO loading generates maximum output voltage up to ∼25.7 V and current ∼1.2 μA with a power density of ~ 8.22 μW.cm−2 under cyclic finger imparting with constant pressure (~16.5 KPa). Under finger imparting, the 2.0ZTO/PVDF PNG is capable of lighting up instantaneously 12 red LEDs (connected in series) and 8red LEDs (connected in a parallel) without connecting a capacitor. In addition, the fabricated PNG is successfully exploited to generate electrical power by converting mechanical energy from a wide variety of human activities such as human body movement, walking, and machine vibration and also exhibits outstanding durability for about four weeks without any deterioration in the output performance. This high performance ZTO/PVDF hybrid film paves a new and effective way to fabricate eco-friendly devices, active sensors, and flexible nanogenerators for powering small portable electronic appliances and flexible high energy density capacitors as well.

Resume : A new transparent electrode has widely been researched with numerous applications. In order to respond the recent demand for wearable applications, in particular, suitable for wearable/on-body electronic devices including healthcare sensing and monitoring, novel materials functions are required such as transparency, mechanical reliability under deformation and facile adaptability on topologically structured surfaces. Herein, we report potential application as multifunctional heater of two-dimensional transition metal carbide, called as MXene, first time. Among the classes of various MXene family, Ti3C2Tx, that firstly introduced from Drexel University, exhibits metal-like conductivity (approximately 8,000 S/cm). Also, the existence of majority terminal group (-OH) form the hydrophilic surface, enabled to solution process within water. Therefore, the MXene electric heater can act as the counterpart against GO or reduced GO. We prepared large-area MXene thin-film heater with transparency on the rigid glass substrate by controlling the chemical interaction between MXene and glass. Moreover, the MXene-based heater prepared on the non-rigid substrate (PET) exhibited both physical stability and great heater performance under mechanical deformation. For the practical applications, we simply coated the thin MXene flakes on the surface of PET fibers treated with amino silanization. We prepared MXene threads-based adaptable heaters with diverse shapes through sewing or weaving processes, in which the MXene flakes were strongly adhered on the PET fibers. The flexible, and mechanically adaptable MXene threads heater enabled to the control of body temperature by attaching the heater on the body.

Resume : We present nanomaterials-based force sensors which can be mounted on hand-held surgical tools. Providing information about the force applied on surgical tools enables surgeons to perform surgeries efficiently. Additionally, it can minimize the damage from operations. With the suggested concept of two facing electrodes application, it is easy to control the sensitivity of the sensor by changing the types of applied nanomaterials or controlling the conductivity of each electrode. For instance, the sensitivity can be efficiently enhanced by widening a conductivity gap between applied nanomaterials. Novel approach with crumpled electrodes facing each other offers not only wider working range for applied force measurement but also better sensitivity by taking advantage of gradually changing number of contact points. In contrast with flat electrodes applications, fabricated sensor returns to the original state because the wrinkles provides a restoring force. By integrating four pairs of facing electrodes on hand-held surgical tools, information about the direction of applied force is also available. Suggested system shows the possibility of efficient force measurement and direction awareness for smart surgical tools using nanomaterials-based force sensor.

Resume : Titania nanoparticle-loaded mesoporous silica has been studied as a promising photocatalytic material for the removal of organic pollutants. In this study, we synthesized titania nanoshells deposited on mesoporous silica (SBA-15) by using layer-by-layer (LbL) assembly method. For comparative studies, various amounts of titania were post-impregnated into SBA-15 by sol-gel reactions. The morphologies and photodegradation properties were systematically investigated. Samples prepared by LbL assembly methods show shell-like depositions of titania around mesoporous silicas, while samples prepared by sol-gel reactions present homogeneous dispersions onto mesoporous silicas. Photocatalytic performances on the decomposition of sodium dodecylbenzenesulfonate (SDBS) were examined. The LbL-samples exhibit enhanced photocatalytic performance compared to that of the sol–gel samples. Total degradation amounts were increased over 50% and the apparent first-order rate constant increased by a factor of approximately 2.3-3.7. This work could help in design of titania loaded nanomaterials for various applications such as biosensors, solar cells, and photocatalytic applications.

Resume : In present study ZnO based sensors have been studied in details adopting two different methodologies, doping and nano composite. A study of lower concentration of gallium (0 to 5% wt.) doping in zinc oxide by solid state mechanism for gas sensing characterization have been carried out. On the other hand, Ag nano particles were decorated onto ZnO nanoparticles. Functionalization of ZnO nanoparticles with surface decoration of Ag nanoparticles (5-20 nm) has been achieved by continuous gas phase deposition system. These nanocomposites based chemical sensor performance have been studied for 10 ppm CO gas concentration at 150 ˚C operating temperature. XRD-spectra reveal the phase formation and crystallinity of the samples. FESEM images unveil the morphology and EDAX analysis confirms the wt. percent of Ga in ZnO. Gas sensing characterization at optimized operating temperature and optimized flow rate for NO2, CO, NO, H2 and NH3 gases have been carried out. 2.5 wt. % Ga doped ZnO is found selective and highly sensitive for NO2 gas up to ppb level at moderate operating temperature with stability and repeatability. The Ag loaded ZnO sensor showed selective sensor response towards 10 ppm CO gas with ~ 40 % sensor response in comparison to other air pollutants (10 ppm NO with ~ 11.2% and 10 ppm NO2 with ~20.5%) at 150 °C operating temperature. This current approach enables us to fabricate cost-effective and low-temperature environmental gas sensor with high selectivity for the detection of CO gas. Different mechanisms were found to dominant in case of doping and composite and were studied in detail to explain the change in sensing behavior for both type of sensors. This study provides a way of choosing methodologies used for selecting different kind of gases.

Resume : A flagship application of optical chemical sensors is the real-time monitoring of cell cultures for the biomedical application. The sensors work by the quantification of physical-chemical parameters, e.g. the dissolved oxygen concentration (DO) which is an indicator of formation and cell viability in aqueous media. The principle of most optical chemical sensors studied in the literature is based on variations in the fluorescence signal (intensity or lifetime) when a fluorescent pigment (fluorophore), incorporated in a matrix permeable to gaseous or ionic species and excited to an adequate wavelength (laser, LED), is brought into contact with an analyte, e.g. DO in an aqueous medium. Their integration in the form of miniaturized devices is based on the deposition of a thin layer matrix doped with the fluorophore. While this configuration is perfectly suited to miniaturize devices, it suffers from limitations in terms of detection limit due to the small amount of fluorophores incorporated in the thin-film matrix and to the small fraction of emitted light redirected toward the photodetector. This work aims at proposing a new sensor configuration based on the sol-gel fabrication of fluorophore-doped channel waveguides equipped with diffracting couplers at both ends of the waveguide. In this presentation, we will first describe the operating principle of this sensor and the sol-gel procedure implemented for the fabrication of the selected architecture. We will then present opto-geometric characterizations and modeling as well as fluorescence measurements performed on full-plate thin films, showing the compatibility of the chosen architecture with the objectives. A first proof of concept of light coupling between the waveguide and the diffracting couplers will finally be presented. Acknowledgment: The authors thank the Labex CEMAM Grenoble INP for the award of a thesis grant to M.Bonnel.

Resume : Among various Metal Oxide Semiconductor (MOS) gas sensor materials, ZnO is an n-type semiconductor, which has a band gap of 3.37eV, is recognized as a noticeable sensing material due to its chemical stability, its high electron mobility, and the variation of donor density. Typically, optimal working temperature of ZnO based gas sensors is above 300oC. However, ZnO has a problem in that it has no selectivity for target gases. Recently, as the hydrogen age comes, there is a growing interest in hydrogen gas sensors having selectivity to hydrogen gas. Meanwhile, noble metal nanoparticles (NPs) have been used to improve the sensing properties of gas sensor. Among the various noble metal catalysts, palladium has excellent ability to adsorb hydrogen, so that it can increase the selectivity of the gas sensor to hydrogen gas when used as a catalyst. However, since palladium can be easily oxidized at a high temperature, when it is used as a catalyst of a gas sensor at a high operating temperature, it is oxidized so as to lose its function as a metallic catalyst. Therefore, palladium alloy needs to be considered as a catalyst. On the other hand one of the new strategies for using noble metal NPs in MOS gas sensors is to design core-shell NPs. In the core-shell structure, the shell helps maintain the catalytic properties of the metal core. In this study, Pd-Au alloy nanoparticles were synthesized to prevent oxidation of palladium. Subsequently, Pd-Au@ZnO core-shell NPs were prepared using Au colloid, Zn(NO3)2 and ascorbic acid. To investigate the oxidation behavior of the Pd-Au alloy core, Pd-Au@ZnO core shell nanoparticles were annealed at the range of 100 to 500°C. The synthesis of Pd-Au alloy nanoparticles was confirmed by using XPS and HRTEM, and the oxidation behavior of Pd-Au core was observed using DTA and X-ray diffraction. In addition, the gas sensing tests were performed at operating temperature of 200~500°C for various gases (H2, CO, CH4, C2H6O).

Resume : Electrochemical, non-enzymatic glucose sensors attract huge attention in the field of health monitoring portable devices. The highly selective and sensitive electrode material playing the most important role in construction of such devices can ensure reliable determination of sugar level. Therefore, in this work, we present the glucose sensing platform based on Ti nanodimples filled with Au nanoparticles (NPs). Ti foil was anodized and then chemically etched to produce structured material. Then Au layers (up to 20 nm) were deposited by means of magnetron sputtering and finally electrodes underwent thermal treatment in 450°C. SEM and AFM microscopies confirm configuration of one NP per cavity. Electrochemical performance for different glucose concentrations was investigated in both neutral and alkaline solutions. Selectivity of obtained material was tested in presence of various interfering species, e.g. vitamin C, glycine, uric acid and sodium chloride. The presence of Nafion membrane on the surface of sensor allowed the complete reduction of electrochemical response of above mentioned compounds. Moreover, high sensitivity as well as resistance to multiple measurements and mechanical stress indicate that obtained material exhibits promising properties towards glucose detection and could be regarded as key component of non-invasive glucose sensor. This work has been financed by National Center for Research and Development under the LIDER program (LIDER/2/0003/L-8/16/NCBR/2017).

Resume : Waste heat at high temperature ranges has high potentiality, but most of it is currently dumped into the environment without being used in any reasonable way. Thermoelectric generator is expected to be a useful energy harvester for the waste heat recovery, but there is still much room for improvement to be used in the field. In order to make the thermoelectric generator a commercially-viable technology for waste heat recovery, stable thermal contacts between the thermoelectric generator and the heat source/sink should be guaranteed to maximize the heat flow crossing the thermoelectric materials, leading to maximized output power. For stable thermal contact between the thermoelectric generator and the heat source at high temperature ranges, thermal interface material having both of high thermal conductivity and high-temperature stability is necessary. To meet the requirements, we present a new thermal interface material consist of hybrid fillers based on multi-walled carbon nanotubes coated with silver nanoparticles and silver flakes, and polyimide matrix which has high temperature stability. We are going to show excellent physical properties (printability, high temperature stability, and thermal conductivity) of the thermal interface material and demonstrate their impact on the interface thermal resistance and the thermoelectric power generation characteristics.

Resume : Among two dimensional materials beyond graphene, Molybdenum Disulphide (molybdenite) being in the single layer phase a direct band gap semiconductor, is the prototypical system for optoelectronic applications. Its electronic and optical properties are tuneable as a function of layer number and also by doping. We present here a systematic resonant Raman and photoluminescence (PL) study of few and single layer mechanically exfoliated MOS2. The mechanical exfoliation method is optimised and quantitatively rationalised. We demonstrate that the electronic properties of the single and few layer MoS2 can be tuned by creating sulphur vacancies via thermal induced sulphur desorption. This leads to a controllable engineering of the photoluminescence response and tunes the relative intensity ratio of charged (trions) and neutral excitons. By comparing the PL response of single layer MoS2 with thermally tuned sulphur vacancy concentration with resonant micro-Raman spectra we derive a self consistent picture of the optical and electronic properties of defect engineered MoS2 and propose evidences for the spatial symmetry of the exciton wave function. The effects of thermal annealing are also discussed in relation to post exfoliation layer engineering and of the gas sensing response of the material.

Resume : In recent times, graphene oxide (GO) and reduced graphene oxide (rGO) have attracted much attention in the development of nano-composites for sensor and energy related applications. However, inhomogeneities in the structure of GO and rGO have limited the use of these materials in above applications. In this study, Methylene Blue (MB), a cationic dye was used as a simple method to probe the structural changes of GO and rGO during its synthesis. GO was synthesized under different oxidizing times using Improved Hummers method from high crystalline vein- type graphite. These were then thermally reduced at 250 °C to obtain rGO. The adsorption of MB onto GOs and rGOs was characterized using UV-Visible spectroscopic and Fourier transformed infrared (FT-IR) spectroscopic techniques. FT-IR results indicate that MB is adsorbed on GO and rGO in two different orientations, with MB vertically adsorbed on GO through electrostatic interactions, while it is parallelly adsorbed on to the basal plane of rGO through π-π stacking interactions. Further, the results of UV-Visible spectroscopic technique indicate that there are no significant differences in the amount of MB adsorbed on all GOs. However, prominent variations are observed in the amount of MB adsorbed on rGOs, indicating structural differences among the rGOs. These results reveal differences in spatial distribution of oxygen functionalities among the GOs synthesized under different oxidation times. Further the information presented is important in the analysis of surface area using MB on graphene-based nano-composites. Acknowledgement: University of Colombo Grant AP/3/2/2016/CG/29

Resume : In this work, we describe an approach that suppresses recombination, in turn, enhancing the photoresponse via engineering of photon induced electron transfer (PET), reporting one of the highest enhancement till date. Zinc oxide (ZnO) has been widely explored for UV detection despite its large exciton binding energy (60 meV) that can inhibit its photoresponse. ZnO film when coated with carbon nanotubes (CNTs) and nitrogen-doped CNTs (NCNTs) facilitates electron transfer and inhibits recombination, increasing its photocurrent across wavelengths between 275 to 400 nm. This is one of the interesting approaches to enhance the photoresponse of a material. The extent of PET depends on the amount of CNTs/NCNTs. Photocurrent was found to increase 58089 and 36200 % for 254 and 365 nm of wavelength, respectively, when NCNTs were used as the recombination inhibitor on ZnO thin film based MSM device. A photocurrent increase of about 1500% was observed for p-Si/ZnO type device with the deposition of NCNTs. The responsivities of the MSM and p-Si/ZnO devices were found to be 91.3 mA/W and 10.5 A/W, respectively under 365 nm excitation. The same approach was used to enhance photoresponse from a CsBi3I10 film as well, an inorganic lead free halide perovskite. Overall, this work paves the way for an elegant and inexpensive means to hugely enhance photoresponse for large exciton bandgap materials by the simple addition of CNTs/NCNTs.

Resume : Mesoporous oxide films filled with metallic nanoparticles has been widely used to enhance photocatalytic properties by reducing charge recombination, due to a controlled porosity and the presence of light absorbing metallic catalyzers. To study and distinguish these mechanisms, we chose to study nanostructured electrodes made of Ag nanoparticles inside a semi-conductor oxide (TiO2 or Fe2O3) with a control of porosity and particle dispersion as an improved photocatalytic system. We performed electrochemical experiments in a three electrode configuration under various ranges of light irradiation, from UV to visible, to determine the variations of redox potentials and photocurrent and thus getting insights on the photochemical mechanism and material structure influence. A positive shift of 0.2V is observed under visible irradiation, corresponding to a modified reactivity from silver nanoparticles within TiO2 porous matrices. Silver nanoparticles are also modified due to diffusion through the electrolyte and electrochemical Ostwald ripening during photoelectrochemical experiments and have been characterized by electron tomography.

Resume : Our laboratory has developed a new synthetic procedure for generating periodic arrays of metallic nanostructures shaped as hexagonal or triangular nanoplates using a room temperature light-activated growth mode. Such structures have the potential to act as the active components for the detection of biological and chemical analytes using various sensing modalities (e.g., Surface Enhanced Raman Scattering (SERS)). The synthesis is reliant on the formation of Au seeds exhibiting planar defects – without such defects the growth mode is deactivated. Through the engineering of defects, which have been extensively studied using Titan TEM imaging and electron diffraction, such structures have now been produced in high yield. Here, we will describe the techniques used to generate periodic array of seeds, demonstrate their utility in forming substrate-based metallic nanoplates and provide an understanding of the opportunities and challenges that lie ahead. Specifically targeted is the fabrication of such arrays on Si substrates since it can result in technologically relevant substrate-nanostructure electronic interactions such as the injection of the hot electrons generated by plasmonic excitation into the substrate.

Resume : The growing interest in carbon-based materials which represent a wide family due to the manifold allotropic forms (carbon nanotubes (CNTs), graphene, nanodiamond, etc.) is due to their ability to achieve novel properties or to target functional applications (sensors, energy, adsorption etc.) via surface modification. As member of carbon materials family, CNTs and graphene are distinguished material that can be used as matrix able to host functional materials such as metal oxides (MOX) or conducting polymers (CPs) etc. Such an association allows to build functional hybrids materials with excellent properties derived from the combination of the host matrix properties (CNTs or graphene) and the functional materials properties (MOX or CPs). For sensors application, such hybrid materials fabrication is of commensurable importance since it allows to finely tune the functional nanomaterials composition to reach unique sensing performances. Here we will show how the proper functionalization of CNTs or graphene by MOX or CPs has allowed to target specifically pollutants such as H2S or NH3. The role of surface modification to access to sensitive sensors as well as the synthesis and characterization of such functional materials will be presented. Apart from the sensing performances of the hybrids functional materials, the association of the two entities has also enable the elucidation of the interaction mechanisms through understanding the surface reactivity of the nanomaterials.

Resume : With the flourishing development of electronic interactive devices, the perception of smell has shown the potential to combine with multimedia. The controlled release of aroma plays an important role for the integration of olfactory senses into various functional devices. Ti3C2 MXene is a promising material for the controlled release of aroma molecules due to the abundant surface termination groups and metallic nature. The aforementioned properties allow aroma molecules to be adsorbed on the Ti3C2 MXene surface and in situ release by resistive thermal desorption. With the in situ thermal desorption of aroma molecules, it prevents interface issues between the molecule encapsulation materials and the electric heating source. In this work, the Ti3C2 MXene paper can perform the control release of phenethyl alcohol (PA) by applying different levels of voltages and deliver the relative release of PA up to nearly 100%. The Ti3C2 MXene heater shows the temperature ramping to 100oC within 1 second and the stable heating for more than 20 minutes. Moreover, the Ti3C2 MXene shows the air stability for more than 4 months with effective trapping of the PA molecules.

Resume : SERS-active substrates based on gold (Au), silver (Ag) and bimetallic Ag@Au-covered silicon nanowires (SiNWs) were proposed for the detection of the specific metabolite of Pseudomonas aeruginosa bacteria. Pyocyanin (PYO) is currently considered as a biomarker for Pseudomonas infections that is one of the most common pathogens causing respiratory tract infections in immunocompromised patients. In our study Ag@Au SiNWs showed the ability to detect PYO in concentrations down to 1nM in water. Moreover, the measurements on Au@Ag SiNWs were performed for PYO spiked in artificial sputum with final concentrations of 6.25, 12.5, 25, 50, 75, 100 µM. To decrease the influence of the matrix, the substrates were incubated in 5 times with water diluted solutions. The characteristic peak of PYO at 1353 cm -1 could be still distinguished at a concentration of 6.25 µM, which is in the clinically relevant range. The results illustrate the potential of the developed SERS-active substrates to reduce the detection time of bacteria by detecting a metabolite directly from complex matrixes without the need for lengthy extraction protocols and laborious detection schemes. This work was supported by the Russian Science Foundation (Grant № 17-12-01386). S.N.A. also acknowledges Foundation for the Advancement of Theoretical Physics and Mathematics “BASIS”. We gratefully acknowledge the Federal Ministry of Education and Research, Germany (BMBF) for the support of the projects InfectoGnostics (13GW0096F) and EXASENS (13N13856).

Resume : Wearable electronics is attracting much attention that can make our lives more enriching. The most important thing in wearable electronics is conductive fibers. Previous studies have shown that metal fibers have high electrical conductivity but not suitable for use in garments due to poor performance due to corrosion. Therefore, in this study, conductive fibers that can be used for clothing were manufactured using carbon nanotubes (CNTs) instead of conventional metals. After highly purifying CNTs, we produced CNT fibers by wet spinning process. The CNT fibers thus produced here had an excellent electrical conductivity of 30,000 S/cm and a tensile strength of 2 g/den. We introduced insulative fiber layer on the CNT fibers using a braiding process. In addition to excellent electrical conductivity, the conductive fibers developed in this study were flexible enough to be sewn to clothing. For example, we fabricated a 2D capacitive type of textile touch sensor using the developed conductive fibers. Textile touch sensors can be fully integrated into clothings, contributing to wearable electronics that can be applied to many types of smart apparel.

Resume : Sensors and biosensors play a leading role in devices and systems destined for human health and safety. However, most of the existing sensor based systems require complicated electronic structures and high manufacturing costs. Therefore, cheap devices on light, flexible substrates are required. This work deals with the design, fabrication, and characterization of a flexible, wearable, and low cost sensor suited for on-body physiological monitoring based on nanocomposite materials (polymers and graphene) and fabricated by laser-induced forward transfer (LIFT). Conventional LIFT consists of the irradiation, using a pulsed laser, of a thin layer of an absorbing material (the donor) that has been deposited onto a transparent substrate. The layer is irradiated through the substrate and the light-matter interaction which takes place at the interface generates a strong increase of the local pressure. As a result, a small piece of the thin film located above the irradiated area is ejected (as a pixel) from the substrate surface and deposited onto a target substrate (the receiver) arranged in close proximity to the donor substrate. The size of the ejected material is controlled by the size of the incident laser spot. In this work, we printed different polymer:graphene nanocomposites onto flexible substrates (coated with an insulating layer, for ex. Parylene C, which prevents electrical contact with the body fluids). The biosensors fabricated by LIFT are used for the detection of heavy metals in human body fluids. Promising results i.e. high sensitivity and detection limits, i.e. below 100 µg/L were obtained, which proves LIFT as an alternative method for printing nanoscale materials aiming at the fabrication of wearable sensors.

Resume : Nowadays the development of natural biomaterials as promising building polymers for biodegradable, biocompatible and environmentally friendly electronic devices is of great interest. As the common natural polymers, cellulose and its derivative have the potential to be applied in the devices owing to the easy processing, nontoxicity and biodegradability. Here, write-once-read-many-times resistive switching devices based on biodegradable carboxymethyl cellulose-graphene oxide (CMC-GO) nanocomposite are demonstrated for the first time. The hybridization sites formed by the gelation of CMC and GO molecules contribute to the excellent memory behaviors. When compared with devices base on pure GO and CMC, the device with the Al/CMC-GO/Al/SiO2 structure shows brilliant switching characteristics such as high ON/OFF current ratio of ~105, low switching voltage of 2.22 V, excellent stability and durability. What's more, the device shows high flexibility and good resistive switching behaviors even with soft PET substrate (Al/CMC-GO/Al/PET structure). This newly designed cellulose-graphene-based polymer nanocomposites are quite cheap and easy processed for large scale manufacturing of memory devices and can further contribute to future biodegradable data storage applications such as portable stretchable displays, wearable electronics and electronic skins in the coming age of artificial intelligence.

Resume : Because of their atomically-thin structure, high surface to volume ratio, and reduced electric screening, new properties and functionalities are expected to emerge when combining two-dimensional (“2d”) materials with other nanomaterials, including (0-D) nanoparticles, molecules, and (1d) nanowires. These so called Mixed-dimensional Heterostructures (“MH”) are now at the forefront of basic nanoscience and applied nanotechnology [1], providing new sets of possibilities to tailor device functions and explore novel physical properties. We recently found a simple and scalable fabrication route of a new 2D material/ 0D clusters heterostructures, exploiting the self-organized growth over graphene of epitaxial flat core-shell Al-based nanoclusters assemblies. [2] We provide experimental evidence that 2D materials are unique promising alternative to skirt the challenging issue of contacting the nanoparticles one by one with external leads in the sake of developing single electron transport devices. Once implemented into tunnel junctions, our 2D-0D heterostructures demonstrate robust and sharp conductance oscillations resulting from efficient Coulomb blockade mechanisms. Interestingly, these single electron features are preserved on devices with record contact areas of 100 µm² while such transport signatures are usually limited to nanoscale patterned devices in the 100 nm2 range. Finally, the spintronics properties of 2D–0D heterostructures are unveiled [3]. An anisotropic magneto‐Coulomb effect, mediated by spin–orbit coupling within a single ferromagnetic electrode, provides tunable spin‐valve‐like magnetoresistance signatures and controllable magnetic modulation of the device's single‐electron charge states, without need of spin coherent tunnelling transport. These heterostructures pave the way towards scalable nanospintronics device architectures at the crossroads of 2D material physics and spin electronics. Referencies : [1] D. Jariwala, T. J. Marks, and M. C. Hersam, Nature Materials, 16, 170 (2017) [2] F. Godel et al., Advanced Materials, 29, 1604837 (2017) [3] L.D.N. Mouafo et al., Advanced Materials, 30, 1802478 (2018)