Functional materials for environmental sensors and energy systems

Resume : Due to ever-increasing industrial activities, agriculture and urban waste waters, toxic heavy metals (HMs) such as mercury, cadmium and lead are released in environment. These substances can cause detrimental effects on the ecosystem and human health. In this regard, it is very important to develop portable and fast sensors for monitoring HMs. Graphene having extremely low electronic noises, high signal-to-noise ratio and large surface area is considered as an ideal candidate for chemical sensors. Recent success in epitaxial growth of high-quality and large-scale graphene layers by thermal decomposition of silicon carbide (SiC) has attracted special attention because of a possibility to use an unintentionally formed Gr/SiC junction as a sensing platform. Here we propose a new sensing mechanism driven by a fast change of intrinsic graphene properties and, as a consequence, barrier height of Gr/SiC junction due to charge transfer between graphene with incoming adsorbates such as Cd2+, Hg2+ and Pb2+. Such an interaction leads to modification of electrical properties of Gr/SiC junctions. Thus, we measured and analyzed the shift of the capacitance-voltage (C-V) curves and current-voltage (I-V) characteristics of the Gr/SiC devices, in which detection of heavy metals is enabled. The detailed carrier transport mechanisms occurring at two-dimensional (2D) graphene/ three -dimensional (3D) SiC interface under the influence of the HMs is comprehensively studied and discussed.

Resume : This is a overview of the COST Action TD1105 EuNetAir - European Network on New Sensing Technologies for Air-Pollution Control and Environmental Sustainability - funded in the COST framework. The objective of the Concerted Action (2012-16) (www.cost.eunetair.it) is to develop new sensing technologies for Air Quality Control at multidisciplinary scale by coordinated research on nanomaterials, sensor-systems, air-quality modelling and standardised methods to support environmental sustainability with special focus on SMEs. This international Networking, coordinated by ENEA (Italy), includes over 120 institutions and over 200 international experts from 31 COST Countries (Austria, Belgium, Bulgaria, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Israel, Italy, Latvia, Luxembourg, The Former Yugoslav Republic of Macedonia, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovenia, Spain, Sweden, Switzerland, Turkey, United Kingdom) and 7 Non-COST Countries (Australia, Canada, China, Morocco, Russia, Ukraine, USA) to create a S&T critical mass in the environmental issues. This COST Action [1-4] focuses on a new detection paradigm based on sensing technologies at low cost for Air Quality Control and set up an interdisciplinary top-level network to define innovative approaches in sensor nanomaterials, gas sensors, devices, wireless sensor-systems, distributed computing, methods, models, standards and protocols for environmental sustainability within the European Research Area. [1] M. Penza et al., Procedia Engineering, 2015, 120, 476-479 [2] M. Penza et al., Procedia Engineering, 2014, 87, 1370-1377 [3] M. Penza et al., Proceedings IEEE SENSORS 2014, 1-7. DOI: 10.1109/ICSENS.2014.6984918 [4] M. Penza et al., AMA Science, Open Access. DOI: 10.5162/4EuNetAir2015/01

Resume : A chemical sensor consists of a physical transducer i.e., a transducer of physical quantities into convenient output signals, and a chemically selective layer so that measurable output signals can be produced in response to chemical stimuli. It is often the physical transducer that imposes both fundamental and practical limitations on the performances achievable with chemical sensors. As a result, implementation of a transduction principle or innovative transducer design is always a significant milestone in the area of chemical sensors. New effects discovered at the nanoscale allow new perspectives on chemical sensor transduction. Miniaturization of a sensor down to a single nanostructure unit is not only a useful test for the fundamental limit of detection, but, most importantly, represents a promising approach towards real-time detection of single binding events, which is a key issue for future research in chemistry, biology and medicine. For commercial success, major advances in sensor technology are required in terms of simple structure, lower cost, selectivity, durability, and reliability. The most suitable sensors of these types are based on semiconductors that do not undergo irreversible chemical reactions forming stable oxides upon exposure to air at high temperature. Metal oxide gas sensors offer better stability and sensitivity as compared to other organic materials like polymers. The fundamental sensing mechanism is based on atmosphere changes closed to the active material, which leads to variations in the electrical or optical properties. Application of metal oxides as chemical sensors exploiting novel architectures for environmental monitoring will be reviewed as well as other application like food safety by a novel Electronic Nose

Resume : Gas sensors are of high importance for many applications ranging from indoor air quality monitoring and personal safety systems to outdoor environmental monitoring. The employment of metal oxide nanowires is a very powerful strategy to push the performance of gas sensing devices. Nanowire integration with standard CMOS technology, however, remains a major challenge. We present electronic gas sensor devices based on different types of metal oxide nanowires, such as CuO and ZnO nanowires, which are directly synthesized on CMOS fabricated microhotplate (µhp) chips by a thermal oxidation process. Other types, such as SnO2 and WO3 nanowires, are transferred to the µhp chips by a special process technology. The fabrication procedure results in multi-nanowire devices, where many nanowires in parallel are employed as gas sensing components. The µhp chips are fabricated in standard 0.35µm CMOS technology and are designed for Through-Silicon-Via technology to enable 3D-integration to a smart System-in-Package. We will present gas sensor measurements toward different target gases such as CO, CO2, and a specific HC-mix both in dry as well as in humid synthetic air. The presented technologies can be used in a CMOS backend process and enable the fabrication of CMOS integrated metal oxide nanowire gas sensing devices. Such CMOS integrated nanowire arrays are highly promising candidates for realizing smart multi-parameter sensing devices for the consumer market. This work was done within the project “MSP - Multi Sensor Platform for Smart Building Management” (FP7-ICT-2013-10 Collaborative Project, No. 611887).

Resume : The unique properties of shape controlled ZnO particles as gas-sensors have been largely reported. However, a clear assessment of their sensing mechanism is still an open challenge. Aiming to contribute in facing with this issue, we compared the sensing behavior of morphology-controlled ZnO crystals with specific exposed surfaces to that of ZnO (ZnO®) particles with uneven shape. Besides an expected higher electrical response for shape controlled crystals exposing (0001) high-energy surfaces, we observed significant differences in the reactivity of their VO• paramagnetic species. In fact, the ESR spectra of ZnO® revealed that these defects increase upon interaction with CO while decrease under oxidation treatments. In shape controlled crystals an opposite trend has instead been observed. From these outcomes, we have proposed morphology-dependent sensing mechanisms. While in ZnO® irregular nanoparticles the sensing is associated to an oxygen vacancy mechanism, in shape controlled crystals it seems only indirectly involve the oxygen defects. This corroborates the idea, considered valuable in many studies, that the sensing properties of ZnO particles with predominant (0001) surfaces rely on an oxygen ionosorption mechanism. We believe that these findings and the adopted approach may positively contribute to the debate still existing between the so called “oxygen vacancy” and “ionosorption” models in the interpretation of sensing of semiconductor metal-oxides.

Resume : Pressure sensitive paints (PSPs) are effective, non-intrusive tools used to map the O2 flow on complex surfaces through simple optical detection. Their functioning mechanism relies on the photoluminescence (PL) quenching experienced by suitable chromophores exposed to O2. Quantitative O2 detection, however, requires sophisticated calibration protocols to correct for experimental geometry and temperature. Ratiometric PSPs (rPSPs) can overcome this limits exploiting the different sensitivity to O2 of coexisting emissive states. To date, all reported rPSPs are based on mixtures of organic chromophores or dye-functionalized nanocrystals (NCs), which suffer from phase segregation, energy transfer and different temperature sensitivities of the emitters. Here, we report the first example of rPSPs based on a single type of emitter, namely CdSe NCs coated with ultra-thick CdS shells exhibiting dual-color PL arising from simultaneous radiative recombination of core- and shell-localized excitons. Since red-emitting core excitons are separated from the environment by the shell, they are unaffected by O2 that instead severely quenches the green shell PL1. As a result, upon lowering the O2 pressure from 1 to 10-3 bar, the green PL undergoes >300% increase, whereas the core PL remains largely unvaried, with the total emission color changing from red to yellow to green. This result confirms their suitability for a disruptive advancement in the field of rPSPs. 1 NanoLett 2014, 14, (7), 3855.

Resume : Fiber-optic sensors (FOS) based on porous silica films that operate in reflectance mode are very suitable to detect volatile organic compounds (VOCs). These sensors combine the advantages of the optical fiber with the flexibility of the sol-gel process to obtain silica films with controlled porous texture and surface chemistry. We report experimental results on the effect of temperature (15 – 50 ºC) on the response of FOS that use films of phenyl-silica xerogels as the sensing elements. The sols were prepared by the sol-gel process at pH 10 with mixtures of Phenyltriethoxysilane (PhTEOS) and Tetraethylorthosilane (TEOS) in 30:70, 40:60, and 50:50 molar percentages. Films were affixed to the end of the optical fiber by the dip-coating technique. The measuring system works under volumetric static conditions. FTIR and 29Si-NMR spectroscopies confirmed the presence of Si-C bonds and that the phenyl group was incorporated into the xerogels. The response decreased with temperature, which can be attributed to the decrease in the adsorption of VOCs. At a given temperature, experimental data agreed with a model based on adsorption of VOCs molecules on the film that, in turn, changes the refractive index of the external medium. Applying the Clausius-Clapeyron equation to the experimental data at different temperatures provided the molar enthalpy of adsorption, which for n-hexane varied from 11 to 36 kJ mol-1.

Resume : We present a new concept for gas sensing with an optical read out. Hydrogen measurements based on a tungsten oxide inverse opal with contactless signal detection were investigated. This approach allows us to quantify hydrogen under harsh conditions. The chosen material design leads to the optical properties, which allow the optical read out of a known gas reaction between tungsten oxide and hydrogen. The sensor setup is based on photonic crystals, which were synthesized in an easy way using a casting method. The reflectance spectrum of such crystals is mainly defined by the periodicity of the two materials it consists of and their refractive indices. During the gas reaction the refractive index of the tungsten oxide changes and so the reflectance spectrum of the crystal is manipulated. This allows us to use the shift of the reflectance maximum as a sensor signal with contactless optical read out. Besides measurements we also present a model and simulations of how the sensing mechanism might work.

Resume : The aim of this work is to present a review on the conductivity and gas sensing mechanism nanocomposites of TiO2 – SnO2 as compared with solid solutions and microcrystalline thin films. Mixed-oxide system of TiO2-SnO2 is believed to be an efficient active material for gas sensing resistors with improved selectivity. Chung et al [1] were the first to report on stable CH4 and CO sensors of this type in 1992. It has been suggested [1] that the improved gas sensing performance relies on the Schottky barrier formation at grain boundaries of well-developed SnO2 grains embedded in the finely dispersed TiO2 amorphous matrix. Since then, numerous papers appeared [2-4] among which our own contributions [5-8] dealing with different forms of TiO2-SnO2 system. We have studied gas sensing and catalytic behavior of microcrystalline ceramics, thin films and quite recently the nanomaterials. The motivation for these investigations relies in the unresolved problem whether the simple mixture of constituents or the solid solution demonstrates better sensing properties. This work presents a survey of the research carried out for TiO2-SnO2 materials in order to compare their properties in the case of composites and solid solutions. References [1] Chung WY, Lee DD, Sohn BK. Effects of added TiO2 on the characteristics of SnO2-based thick film gas sensors, Thin Solid Films 1992;221:304-309. [2] Dusastre V, Williams DE. Gas-sensitive resistor properties of the solid solution series Tix(Sn1-ySby)1-xO2 (0

Resume : The emergence of nanocarbonaceous materials has enabled a real advance on the development of new functional materials especially in the field of chemical sensors. If their aromatic nature and the modulation of their surface chemistry make possible their functionalization by covalent or non-covalent bonding of functional groups, the high specific surface area of nanocarbons ensure the distribution of sensing molecules onto a large surface. Thus, a large number of actives sites can interact with the target analytes, leading to sensing devices with higher sensitivity, lower detection level and high resolution. Such performances are key factors for sensors devoted to environmental monitoring. Original hybrid materials have been developed based on the non-covalent functionalization of nanocarbons by indigo or metallophthalocyanine organic molecules. The non-covalent functionalization of nanocarbons have been emphasized by SEM, TEM, XRD and TGA characterizations. The interactions of aromatic hydrocarbons on phthalocyanine/nanocarbons materials have been exploited for the development of QCM-based sensors devoted to benzene, toluene and xylene detection à room temperature. Complementary, the irreversible chemisorption of ozone on indigo/nanocarbons hybrid material led to the achievement of selective filters with high durability. Associated to phthalocyanine chemoresistor into a sensor-system, such filter enable the selective measurement of nitrogen dioxide at ppb level in air.

Resume : Cost effective and quick detection of hydrogen gas at room temperature has always remained a challenge. This study reports the hydrogen gas sensing characterstics of hybrid nanostructure using single walled carbon nanohorn (SWCNHs) fabricated by simple chemical method. The sensing response of hybrid nanostructure is due to their change in electronic nature structure on the exposure of H2 gas and this are important for understanding the effect of gas adsorption on their electronic conduction. In addition, the sensor fabrication involves simply drop-casting treatment at room temperature in normal condition. The repeatability and low recovery time in N2 atmosphere of this sensor are the main advantages for the detection of low concentration ( 2%) of H2 gas at the room temperature conditions.

Resume : Mesoporous nitrogen rich carbon (MNC) material has been prepared as a highly sensitive and conveniently usable probe for electrochemical determination of heavy metal ions including Pb (II), Cd (II) and Cu (II). Spontaneous adsorbability of MNC material has been utilized for eliminating the requirement of pre-concentration step, essentially involved in determination of metal ions. Square wave stripping voltammetry (SWSV) studies implied the superior electrocatalytic activity of MNC modified GCE (MNC/GCE) towards determination of Pb (II) and Cd (II). The linear calibration curves range from 0.01 µM-100 µM and 0.01 µM-70 µM for simultaneous determination of Cd(II) and Pb(II) with an excellent sensitivity of 18.46 μA μM-1 cm-2 and 87.71 μA μM-1 cm-2 respectively. The limit of detection (LOD) for simultaneous determination of Pb (II) and Cd (II) was calculated out to be 0.0005 μM and 0.001 μM (3σ method) which suggests the potential efficacy of MNC towards continuous monitoring of Pb (II) and Cd (II) in natural water resources without requirement of time-consuming pre-concentration step.

Resume : As member of the wide family of carbon materials, the carbon nanotubes (CNTs) offer remarkable properties [1] which are closely related to their narrow structure and surface chemistry. For gas sensors where matrices of higher surface area are potentially appealing, carbon nanotubes are good candidates to fulfil efficient gas sensors requirement. Additionally, they present electronic and optical properties combined with their suitability for different deposition techniques, and this enables them to be associated to different transduction modes (resistive, electrochemical, mass and optical). These features as well as their versatile surface chemistry make them ideal for developing novel and efficient gas sensors. However, CNTs need to be chemically or physically modified to overcome their lack of solubility and selectivity of detection. To this aim, surface functionalization (covalent and non-covalent) is an excellent option which improved simultaneously the solubility and the selectivity depending on the functional groups attached to the surface. In this context, we have developed sensitive materials based on functionalized CNTs for application devoted to air pollutants monitoring. The prepared sensing materials are characterized by standard techniques (UV-Vis spectroscopy, TGA, TEM, Raman analysis) and sensor responses were established by means of resistive and QCM (Quartz Crystal Microbalance) transducers. References: [1] D.M. Guldi, et. al., Chem. Rev. 2010, 110, 6768.

Resume : The preparation and characterization of MWCNTs-based chemiresistors, functionalized with Au and Pd NPs, to improve the sub-ppm detection of gaseous pollutants, compared to pristine ones, is reported. An electrophoretic process was proposed to deposit, directly on the outer MWCNTs sidewalls, electrochemically-preformed Au or Pd NPs with controlled size.[1,2] Different deposition times were used to tune the metal content on MWCNTs, as revealed by chemical and morphological analyses. The gas sensing properties of pristine and doped MWCNTs were evaluated at different operating temperatures (100-200°C) towards various concentrations of gaseous pollutants (e.g. NO2, H2S), and related to the metal used in the doping, and to its loading. Metal-doped MWCNTs sensors exhibited a very high gas sensitivity, fast response, reversibility, good repeatability, and sub-ppm range detection limit, with the MWCNTs sensing properties controlled by the type and loading of used catalyst. Specifically, Au-decorated MWCNTs with the lowest Au content revealed the highest sensitivity towards NO2 at 150°C;[1,2] instead, MWCNTs with the highest Pd loading showed the highest NO2 sensitivity at 100°C. Finally, on the basis of the gas sensing performance of prepared hybrid gas sensors, sensing mechanisms have been proposed, evaluating the effect of their chemical composition. [1] E. Dilonardo et al., Sens. Act. B 2016, 223, 417–428. [2] E. Dilonardo et al., J. Sens. Sens. Syst. 2014, 3, 1–8.

Resume : Oxygen electrochemistry plays a crucial role in the deployment and large scale adoption of fuel cell (FC) technologies. Some of the most promising FCs in terms of potential to mitigate emissions, rely on the use of Pt-group metals (PGM) as electroctalysts, where most of the metal load is necessary to improve the rate at which the sluggish oxygen reduction reaction (ORR) takes place at the cathode. PGM cost and scarcity have been identified in fact as primary obstacles to large scale applications of FCs; thus, there is great interest in the discovery and optimization of ORR electrocatalysts that do not rely on PGM. N-doped carbons, often in combination with low cost metals, have been shown to display electrocatalytic activity in ORR. In this presentation we will discuss studies of ORR activity of nanostructured N-doped carbons in the absence and in the presence of non-precious metals in their structure. First, we report on the template-free synthesis via ultrasonic spray pyrolysis of Fe- and N-doped porous carbon microspheres. Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Focused Ion Beam (FIB) milling were used to understand microsphere structure, whereas X-ray Diffraction (XRD) and Photoelectron Spectroscopy (XPS) were used to investigate bulk and surface chemistry. Microspheres were found to display ORR activity in acidic solution; results suggests that direct formation of H2O is the preferred ORR mechanism. Second, we discuss studies of ORR activity in alkaline solution of graphene-like nanostructured carbon with tailored edge-plane density. Interestingly, these materials offer a versatile platform for mechanistic studies of structural and chemical motifs that result in ORR activity in nanocarbons.

Resume : 2D materials offer a unique platform for sensing with extremely high sensitivity, since even minimal chemical interaction causes noticeable changes in electrical conductivity, which can be used as sensor readout. However, the sensitivity has to be complemented with selectivity, and, for many applications, improved response- and recovery times. This has been addressed, for example, by combining graphene (for sensitivity) with metal/oxide nanoparticles (for selectivity). On the other hand, functionalization or modification of the graphene often results in poor reproducibility. Here, we investigate the gas sensing performance of epitaxial graphene on Silicon Carbide (SiC) decorated with nanostructured metallic layers as well as metal-oxide nanoparticles deposited using scalable thin-film deposition techniques, like hollow-cathode pulsed plasma sputtering. Under certain modification conditions the electronic properties of the surface remain those of graphene, while surface chemistry can be tuned to improve sensitivity, selectivity and speed of response to gases relevant for air quality monitoring and control, such as nitrogen dioxide, benzene, and formaldehyde. The presentation will also include results on other monolayer gas sensing layers like iron oxide on top of platinum and 2D metals on SiC, which offer additional possibilities like operation at high temperature and in harsh conditions, while maintaining all the promises of 2D materials as extremely sensitive transducers.

Resume : Graphene as 2D material can be fully exposed to environment and hence provides an ideal platform for chemical sensing. However, in order to achieve the sensitivity and selectivity required by environmental sensors, additional adsorption centres have to be created at its surface e.g. by controlled formation of defects, dopants or clusters. In the present work, we demonstrate the functionalization of single layer graphene by pulsed laser deposition (PLD) and its impact on the sensitivity to main pollutant gases. PLD can be used as a precise tailoring tool for this purpose as typically only ~1/100th of a monolayer is deposited by a single laser pulse. The dependence of gas sensitivity and response speed from the composition and amount of deposited material as well as from its average ‘landing energy’ on graphene was studied. Different target materials were used for functionalizing graphene: metals (Ag, Pd, Ru, Au), oxides (ZrO2, SnO2, TiO2, NiO), nitride (TiN). Average thickness of deposited material was varied between 0.01 to 20 monolayers. The surface morphology of deposited materials and defectiveness of graphene were studied. Performance benchmarking with commercial semiconductor NO2 sensors showed that the sensitivity of our graphene-based sensors was in the practical range and such figures of merit as the sensitivity divided by long-term drift or by cross-sensitivity to humidity were superior in case of graphene based sensors.

Resume : Growing awareness about impact of pollution for human health, development of industry, and growing use of nanomaterials, has increased the need for monitoring of air quality. Nano size dust and ash particles can pose serious health issues. Moreover, certain technologies such as microelectronics and pharmacology require dust free environments. Several Particulate Matter (PM) sensors have already been developed, however there is a need to detect smaller particles and smaller concentrations as well as increasing the portability of the devices and shorten the time of analysis. In this paper, laser shaped thick-film interdigitated electrodes are used for capacitive sensing of nanoparticles at high frequencies. The sensors have been manufactured in Low Temperature Co-fired Ceramic, which is a well-established packaging technology offering many advantages such as cost-effectiveness resistance to high temperatures and harsh environments. Different designs were tested and sensitivity test was performed for chosen designs. Sensors were exposed to two different nanoparticles, 40 nm CuO and 8-11 nm carbon black using ink-jet printing as a method to provide controlled amount of nanoparticles on selected area. The sensor signals were measured at 1 GHz to 10 GHz providing clear responses for both nanoparticles compared to reference signal without particles. Thus, high frequency based detection of nanoparticles with thick-film IDE structure appears promising for nanoparticle detection.

Resume : Actual hydrogen (H2) sensors require high sensitivity, autonomous operation and easy integration in fuel cell technologies for stationary and portable power. This article presents the design process of an innovative Surface Acoustic Wave hydrogen sensor based on a Palladium-Platinum (PdPt) catalytic material developed in a previous research. Among the advantages of this sensor there are wireless data accessibility without the need of any power supply. Under H2 exposure, the nanostructured PdPt catalyst exhibits repeatable and reversible exothermal response, such that its temperature is correlated with H2 concentration (2°C in 4000 ppm of H2). The sensing is carried out by a SAW transducer which transforms the PdPt temperature variations derived from the catalytic reaction into an electrical signal relative to the H2 concentration. Our design process allows to develop an optimal sensor system including the electrical and mechanical structure, for high sensitivity applications.

Resume : Hybrid organic-inorganic molecular species can be very appealing for the development of novel nanodevices for sensing and energy conversion. Divacant polyoxometalates (POM) are robust and molecular polyanionic metal-oxides that can be conveniently exploited as inorganic platforms for anchoring two organic pendants in a tweezer-type arrangement. In particular, the use of organic chromophores as pendants enables the use of spectrophotometric and spectrofluorimetric techniques to highlight recognition phenomena of metal ions and organic molecules, involving an interplay of the two domains. Recent results obtained with different hybrid POMs, including complexes bis-functionalized with pyrene or dansyl moieties will be presented, demonstrating the possibility to use these nano-sized hybrids for sensing applications (with metal ions) and for the preparation of ordered materials (upon interaction with carbon nanostructures).

Resume : Acetone, the most commonly used solvent in research and industry, is highly volatile and hazardous to human health and living organisms. Exposure to high concentrations of acetone vapor may cause headache, allergy, fatigue, and even narcosis. Acetone contained in the human breath is an indicator of blood glucose levels. Hence sensitive detection and quantification of acetone is essential. In this study, acetone sensors based on ZnO:Au and ZnO:Pd compounds were developed. Zinc oxide thin films were grown by pulsed laser deposition (PLD) and nanopatricles of gold or palladium were subsequently laser-deposited on the surface of the ZnO films. The ZnO:Au and ZnO:Pd films were tested as acetone sensors. We find that the presence of the Au or Pd nanoparticles improves the detection of acetone. As the quantity of metallic nanoparticles on the ZnO surface increases, the operating temperature, for which small concentrations of acetone are detected, decreases. The operating temperature of the sensors was 155 – 200 0C, which leads to lower power consumption and increased operating safety, compared to other metal oxide acetone sensors which operate at higher temperatures. The response time of the sensors decreased for thicker ZnO films. The ZnO:Pd compound performed better as an acetone sensor.

Resume : Owing to its excellent mechanical and thermal properties as well as optical performance, sapphire (crystalline Al2O3, alpha alumina) is extensively used as window in optical sensors for harsh conditions, for example underwater surveillance in the oil industry. However, under these conditions the sapphire surfaces are continuously exposed to oil and other fouling mixtures, which can lead to contamination of the window surface. Hence, making the surface underwater oleophobic would be highly desirable. We found out that a sapphire surface can change from oleophilic to superoleophobic depending on the crystal miscut, polishing method and initial cleanliness state when submerged in water. Moreover, giving the surface the hydrophilic character improves the underwater oleophobic character. This could be understood in the context of underwater superoleophobic surfaces found in nature that exhibit higher propensity for trapping water. Inspired by the underwater superoleophobic self-cleaning surfaces found in nature such as fish scales, sapphire surfaces could be further developed for maintenance free solutions for permanent underwater installation of optical instrumentation.

Resume : Much attention has been paid to water splitting process by light irradiation because of its potential to obtain clean and high energy from water [1]. Among variety of materials, TiO2 has drawn much attention because of its promising applications in utilization of solar energy such as photocatalysis [2], photovoltaic [2] and photocatalytic water splitting [4]. To improve these properties, the morphologies and macroscopic structures of TiO2have been intensively studied by many authors in the literature [5]. Moreover, the synthesis of porous structures has attracted increasing interest of researchers [6] as their potential applications in the field of catalysis, ion exchange, and adsorption. Various strategies were taken into account regarding this sphere of study. Latex spheres can be used as templates to form ordered macroporous materials [7]. Despite these efforts, the photocatalytic performance of porous TiO2 was restricted by its low visible light absorption and its fast recombination of photo-generated electrons and holes. Therefore to enlarge the photoresponse spectrum, considerable efforts have been made, such as doping with transition and/or noble metals, non-metals, deposition in quantum dots and construction of heterojunctions with other semiconductors. Construction of a heterojunction between porous TiO2 and other semiconductors with a suitable band gap is an effective method to extend the light absorption spectrum and accelerate photogenerated electron-hole separation, thus enhancing the solar-to-hydrogen conversion efficiency [8]. Silver Sulfide (Ag2S) is a binary chalcogenide semiconductor with a narrow band gap well corresponding to the visible spectrum and considerable photostability in aqueous solution under light irradiation. Several methods have been used for the synthesis of various nanostructures of Ag2S such as nanosheet, nanowire and microsphere for solar water splitting. Among these approaches, electrodeposition technique [9] was used for the deposition of Ag2S thin films onto TiO2. Compared with other deposition methods, electrodeposition provide numerous advantages, including, low temperature processing, arbitrary substrate shapes, controllable film thickness, morphology, and potential low capital cost. It is an isothermal process mainly controlled by electrical parameters. In the present work, semiconducting low band gap Ag2S thin films are used to sensitize highly-oriented porous TiO2 thin films. In this context, we will prepare Ag2S coated TiO2 thin films supported on ITO coated glass combining the sol-gel process, spin coating and electrodeposition technique. This work reports the synthesis conditions, the main physic-chemical characterizations of the resulting hetero-junctions, including X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Visible absorption spectroscopy; the photocatalytic activity of Ag2S and heterostructure Ag2S /TiO2 was measured following the degradation of an organic model substrate, methylene blue under visible light. The photoelectrochemical properties of the samples were also studied. References [1] Z. Zou, J. Ye , K. Sayama, H. Arakawa, Direct splitting of water under visible light irradiation with an oxide semiconductor photocatalyst. Nature 7 (2001) 414-625. [2] K. Nakata, T. Ochiai, T. Murakami, A. Fujishima, Photoenergy conversion with TiO2 photocatalysis , Electrochemica Acta 84 (2012) 103-111. [3] X. J. Huang, Y.K. Choi, Chemical sensors based on nanostructured materials. Sensors Actuators B (2007) 122:659. [4] A. Fujishima, k. Honda, Electrochemical photolysis of water at a semiconductor electrode, Nature 238 (1972) 37. [5] W.J. Yang, C.Y. Hsu, Y.W. Liu, R.Q. Hsu, T.W. Lu, C.C. Hu, The structure and photocatalytic activity of TiO2 thin films deposited by dc magnetron sputtering, Superlattices and Microstructures, Volume 52, Issue 6, December 2012, pp.1131-1142 [6] H. Behera, S. Mandal, T. Sahoo, Oblique wave trapping by porous and flexible structures in a two-layer fluid, Phys Fluids, 25 (11), 2013 [7] Zhiqiang Sun, Yunfeng Li, Yanfang Wang, Xin Chen, Junhu Zhang, Kai Zhang, Zifeng Wang, ChunxiaoBao, JianboZeng, Bing Zhao, and Bai Yang, Three-Dimensional Colloidal Crystal-Assisted Lithography for Two-Dimensional Patterned Arrays, Langmuir, 23 (21), 10725 (2007) [8] C. Han, Z. Li, J. Shen, photocatalytic degradation of dodecyl-benzenesulfonate over TiO2-Cu2O under visible irradiation, Journal of Hazardous Materials 168 (2009) 215-219. [9] Ibtissem Ben Assaker, MounirGannouni, Jamila Ben Naceur, Munirah Abdullah Almessiere, AmalLafy Al-Otaibi, TaherGhrib, ShouwenShen, RadhouaneChtourou , Electrodeposited ZnIn2S4 onto TiO2 thin films for semiconductor-sensitized photocatalytic and photoelectrochemical applications, Applied Surface Science, Volume 351, 1 October 2015, pp. 927-934

Resume : Lead-free piezoelectric ceramics are urgently needed to replace the PZT-based materials because of their lead oxide toxicity. Ceramics such as BaTiO3 are promising candidate, however the properties of pure BaTiO3 are still very low (d33= 150; kt= 22%) compared with very hard PZT. One way of improvement is the doping with donor and/or acceptor. Thus, Co, Ca and Nb-doped BaTiO3 ceramics were prepared using conventional solid state reaction. The Co3+/Co2+, substituting as donor, leads to oxygen vacancies in ABO3 perovskite structure but increases the piezoelectric performance (d33 = 210 pC/N and kt= 39%). To balance the structural defects, Co substitution with Nb 5+ acceptor or thermal annealing at 1000°C under O2 atmosphere was studied. It improves the properties with d33= 250pC/N and kt= 45%. Furthermore a study of the ceramic process has been made in order to bring it closer to industrial process. The first purpose was to lower the sintering temperature by using Li2O as sintering aid. Thus, addition of Li2O yields dense ceramics with relative density d= 95–98% and with acceptable piezoelectric properties (d33= 210pC/N, kt= 42%) at 1100°C instead of 1350°C as in BaTiO3 conventional sintering. Moreover, the homogeneity of the material has been studied as well as the homogeneity obtained during the ceramic process in the furnace. The microstructure and the properties have been observed and tests have been carried out on 22 samples at the same time.

Resume : Functional polymer membrane has been highlighted due to its higher functionality in separation processes for liquid and gaseous mixtures and in other important applications of membranes, such as bio-materials, catalysis production. In this study, sputtered Pt film was coated on PTFE membrane surface. The Ti film was inserted for improved adhesion between Pt film and PTFE membrane. Under negative electrical bias, the Pt film coated PTFE membrane showed almost 30% reduction of Cl- ions in NaCl solution. In addition, solution including nitrate ions was also investigated in this study. Selective ion transportation through Pt film coated PTFE membrane under electrical bias will be systemically presented using proposed mechanism and experimental results.

Resume : Physicochemical properties of nanoparticles may depend on their size and shape and are traditionally assessed in ensemble-level experiments, which accordingly may be plagued by averaging effects. These effects can be eliminated in single-nanoparticle experiments. Using plasmonic nanospectroscopy, we present a comprehensive study of hydride formation thermodynamics in individual Pd nanocrystals of different size and shape, and find corresponding enthalpies and entropies to be nearly size- and shape-independent. The hysteresis observed is significantly wider than in bulk, with details depending on the specifics of individual nanoparticles. Generally, the absorption branch of the hysteresis loop is size-dependent in the sub-30 nm regime, whereas desorption is size- and shape-independent. The former is consistent with a coherent phase transition during hydride formation, influenced kinetically by the specifics of nucleation, whereas the latter implies that hydride decomposition either occurs incoherently or via different kinetic pathways. References: 1. Gschneidtner, T. A. et al. A Versatile Self-Assembly Strategy for the Synthesis of Shape-Selected Colloidal Noble Metal Nanoparticle Heterodimers. Langmuir 30, 3041-3050, (2014). 2. Syrenova, S. et al. Hydride formation thermodynamics and hysteresis in individual Pd nanocrystals with different size and shape. Nature Materials 14, 1236-1244, (2015).

Resume : Nickel foam supported CuO@NiCo2O4 nanoforests with mesoporous hierarchical core/shell structure are prepared by combining a facile, scalable, and cost-effective thermal oxidation method with a simple hydrothermal method followed by a calcination procedure. The smart hybridization of CuO nanowires and NiCo2O4 nanosheets into hierarchical core/shell array configuration results in remarkably enhanced electrochemical performances with high specific capacitance, excellent rate capability and good cycle performance compared with pure nickel foam supported NiCo2O4 nanosheets. A high specific capacitance of 1298.8 F g-1 at a current density of 1 A g-1 has been exhibited and excellent rate capability of about 96.3% capacitance retention at 5 A g-1 can be obtained. The CuO@NiCo2O4 based supercapacitor exhibits wonderful long cycle life with only 2.1 % capacitance loss after 2000 cycles and the coulombic efficiency maintains about 100% during the cycling. These excellent electrochemical performances demonstrate that the nickel foam supported hierarchical core/shell CuO@NiCo2O4 nanowire heterostructure array electrodes are highly desirable for application as advanced supercapacitor electrodes.

Resume : The activated microporous carbon derived from almond shell has been successfully prepared through the activation process with KOH (C-2) and HNO3 (C-3). The activation results in microstructures with BET specific surface area of 1363.1 m2 g-1 with KOH treatment. And the content of Nitrogen reaches about 10 % with HNO3 activation. When evaluated as electrodes for supercapacitors, both of these two microporous carbon electrode materials exhibit high specific capacitance, good rate capability and excellent long cycle life. C-2 electrode possesses the specific capacitance as high as 286.1 F g-1 at 1 A g-1 and the retention of capacitance maintains at 84.1 % even at 1 A g-1. Furthermore, the Coulombic efficiency remains at 100% after 10000 cycles. These two methods to prepare the microporous carbon are facile and safety, and easy for mass production. Thus, it can provide a kind of readily available, renewable and cheap raw electrode materials for high performance EDLCs.

Resume : A two steps strategy has been exploited to prepare sulfur impregnated N, P-doped hierarchical porous carbon as cathode for high performance Li-S Batteries. A template-free method for the fabrication of N and P co-doped hierarchical porous carbon (HPC) were firstly used by simply pyrolysis of polyaniline aerogels synthesized in the presence of phytic acid. The resultant carbon show a high specific surface area and good electrical conductivity. For the application in Li-S batteries, sulfur impregnated N, P-doped hierarchical porous carbon hybrid material was produced by homogeneously mixing sulfur with N, P-doped HPC under heat treatment at 155℃. As cathode electrode, these sulfur impregnated N, P-doped HPC hybrid materials show high capacity and highly stable cycling performance, suggesting that the novel cathode have alluring prospect for Li-S batteries.

Resume : Ordered mesoporous MCM-41 silica is commonly used for the production of functionalized materials, such as adsorbents, catalysts, membranes, and sensors. In this research, we realized β-cyclodextrin(β-CD)-functionalized MCM-41 silica producing by postsynthesis grafting to hexagonally ordered aminopropyl-containing support. Aminopropyl-MCM-41 silica support was prepared by co-condensation of tetraethyl orthosilicate and (3-aminopropyl)triethoxysilane in the presence of cetyltrimethylammonium bromide. Surface grafting of β-CD onto aminopropyl-MCM-41 silica was carried out under mild conditions thought the activating agent (N,N'-carbonyldiimidazole) usage. Characterization of β-CD-MCM-41 silica was performed using XRD, TEM, chemical analysis, and low-temperature adsorption-desorption of nitrogen. Hexagonally ordered pore structure of obtained silica was confirmed by XRD and TEM analyses, where the presence of diffraction peak at 2θ = 2.20 grad. is attributed to the (100) reticular planes, and the long-range array of tubular voids on the TEM images is observed. The estimated content of amino and β-CD groups on the surface of aminopropyl-MCM-41 and β-CD-MCM-41 silicas was 0.74 and 0.28 μmol/m2, respectively. So many unreacted amino groups may indicate that β-CD are mainly grafted at the entrance of the pores, preventing further penetration of oligosaccharide moieties to the inner pore surface with other anchoring sites. The pore size distribution plot (NLDFT model) confirms the complex pore structure of β-CD-MCM-41 silica with two types of mesopores (3.4 and 5.1 nm) as well as textural porosity within the sheet-like particles. β-CD-MCM-41 silica has high surface area (580 m2/g) and large pore volume (0.97 cm3/g).

Resume : Donor-acceptor molecules have received an increasing interest in fields such as: dye-sensitized solar cells, molecular electronics and non-linear optics thanks to their specific spectroscopic and electronic properties, which are related to the intramolecular charge transfer that occurs in these systems. In particular, fullerene derivatives are one of the most widely used electron acceptor unit because of their capacity to accept up to 6 electrons. On the other side, ferrocene, for its remarkable stability and strong electron donor ability, is supposed to be the most suitable counterpart to build an efficient donor-acceptor dyad, as reported in literature, where different fullerene/ferrocene hybrid systems with interesting properties have been proposed. In this work, we address a quantum chemical study on the structural, electronic and optical properties of novel push-pull macromole-cules based on fullerene-ferrocene groups linked by a phenyleneethynylene conjugated bridge, in order to better understand the structure-function relationship and the in-silico design of new donor-acceptor dyad materials for applications in the organic photovoltaic field. Acknowledgement: We thank to Italian Ministry for Instruction University and Research (MIUR, PRIN project no. 2012a4z2ry) and Centro de Investigación en Química Aplicada (CIQA project no. 6236) for financial support.

Resume : The objective of this work is to treat the fly ash produced from a power plant (PP). For this reason the PP was analyzed by many technics such as X-ray fluorescence (XRF), CHN Analyzer, Inductively coupled plasma (ICP), Nitrogen adsorption and desorption isotherms (BET). With these technics the composition, the chemical and physical proprieties of PP are determined. The treatment of PP is carried out into a plasma reactor with transferred arc plasma. To study the volatility of toxic element present in PP during the treatment of fly ash by plasma, a computer code was used. This model is based on the calculation of system composition using the free enthalpy minimization method, coupled with the equation of mass transfer at the reactional interface. The model enables the determination of the effects of various parameters (e.g., temperature, plasma current, and presence of oxygen in the carrier gas) on the toxic element volatility.

Resume : Perovskite cubic BaZrO3 ceramic is prepared by the flash pyrolysis route. Rietveld refinement of XRD pattern of calcined powder at 900 °C, 1100 °C and sintered at 1600 °C describes that a single-phase compound is formed of an Pm-3m cubic crystal structure with a lattice constant a = 4.19352, 4.19370, and 4.19336 Å respectively. The HRTEM image of calcined powder at 1100 °C for 4 h shows nearly spherical in shape and is sub micrometer aggregates of nano-crystallites of 10–50 nm in size. The FESEM image of sintered pellet at 1600 °C for 8 h reveals highly dense nature of BaZrO3. The observed Raman spectrum of BaZrO3 is assigned to have its source in the nanodomains with the symmetry different than cubic one. AC electrical properties reveal four relaxations. An equivalent circuit model with four RC loops in series is used to extract the electrical conductivity of BaZrO3 in 3% humidified O2. The total conductivity of BaZrO3 dense ceramic is found 7.3546  10-5 S-cm-1 at 750 °C in 3% humidified O2. The giant dielectric constant (ε’) of BaZrO3 is attributed to the Maxwell–Wagner polarization mechanism as well as to the thermally activated mechanism of charge carriers. The dielectric measurements were studied by fitting the electrical modulus with the Kohlrausch–Williams–Watts (KWW) function.

Resume : Recently, ultraviolet (UV) thin film photodetectors (PDs) have received much consideration in different field of research due to their applications environmental monitoring, optical communications and large-area displays. Optimization of photodetectors including new morphological aspects is indispensible to improve the thin film photodetector performance. In this context, this paper presents a numerical investigation including new interface grating morphology effects in order to optimize the photodetector performance and design parameters. In the present work, the impact of grating designs on the device behavior is studied using optical and electrical modeling and an optimized design is proposed to improve the UV absorbance of the photodetector. The specific photodetector studied is based on a Si/TiO2 structure, though qualitative findings are applicable to any thin film photodetector application. Si/TiO2 PD with optimized triangular grating exhibits an enhancement over conventional planar PDs. The purpose of this work is to find an optimal diffraction grating structure that would help in obtaining high optical and electrical performances.

Resume : We investigated characteristic of DC sputtered Li-doped Cu2O films to use as p-type layer for p-n heterojunction piezoelectric nanogenerators. The electrical, optical, morphological and structural properties of Li-doped Cu2O films were investigated as a function of Ar/O2 flow ratio during RF sputtering. In addition, microstructure and interfacial structure of the Li-doped Cu2O layer was analyzed by using a high resolution transmission electron microscope in detail. The p-type conductivity of the Li-doped Cu2O films was confirmed by Hall measurement. Furthermore, using the n-ZnO and p-Li:Cu2O layers, the p-n diode was fabricated and electrically characterized to confirm the p-type conductivity of Li:Cu2O layer. Obvious rectifying behavior can be observed in the p-n heterojunction diode, indicating the formation of p-type Li:Cu2O layer on n-ZnO. The semitransparent and flexible Li:Cu2O-ZnO heterojunction piezoelectric nanogenerators demonstrates the output power up to ~67.5 μW and piezoelectric potential screening effect in ZnO layer significantly reduced by existence of p-type Li:Cu2O layer. Based on performance of Li:Cu2O-ZnO heterojunction piezoelectric nanogenerators, we suggested a possible mechanism to explain the effect of p-type Li:Cu2O layer.

Resume : The possibility to improve an efficiency of electrostatic harvesters by usage of polymer/nanostructured carbon (PNC) composites was investigated. In electrostatic harvesters the energy of mechanical oscillations is converted into electrical energy through deformation of dielectric layer between plates of charged capacitor. To increase the change of voltage during the deformation of dielectric layer between capacitor plates, its dielectric permittivity should decrease with tensile deformation. As a candidate for such a dielectric material PNC composite was chosen. Capacitor samples containing PNC dielectric layer were elaborated from 1) SVR-3L natural rubber with added curing ingredients (this is used as a matrix); 2) high structure Degussa™ Printex™ EX-2 carbon black with average particle size 30 nm (filler); 3) two brass electrodes (thickness of each electrode 2 mm). Thickness of the PNC composite layer for each sample is 1mm. The concentration of the filler in the composite layer was chosen to be from 2 up to 8 mass parts per 100 mass parts of rubber. Tensile and compressive deformation measurements conducted on PNC samples showed, that under tensile and compressive deformation dielectric permittivity of composite is changing non monotonically. The decrease of the dielectric permittivity with increasing of the tensile and stretching deformation of the dielectric layer was observed. It was also found, that character of dielectric permittivity change for both - tensile and compressive deformation - is different. The change of dielectric properties observed indicates about complex processes taking place in the PNC dielectric layer.

Resume : Hematite α-Fe2O3 spindle-like particles with controlled aspect ratio were prepared via an environment-friendly and low cost microwave route, without any organic additive. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis were conducted to characterize the structure and the morphology of synthesized particles. Possible oriented-attachment-based formation mechanisms of the particles were discussed. Gas sensing experiments for the detection of ammonia concentrations with hematite sensitive layers were conducted using an original microwave transduction. Its main advantages are the possibility to carry room-temperature measurements even with electrical insulator, and the acquisition of data over a wide range of frequencies. The sensor microwave design involves a conductor-backed coplanar waveguide (CBCPW) on which the hematite sensitive layer is deposited. Hematite deposition was realized via a simple doctor-blade protocol on the most responsive areas, identified by Near-Field Microwave Microscopy (NFMM). A comparative microwave gas sensing study was conducted to evaluate the gas response of these morphologies upon ammonia exposure at room temperature, and revealed that each morphology presents a significantly different behavior upon gas adsorption. This work is part of a general study on the relation between morphology and properties in the hematite case.

Resume : Recently, there has been remarkable accomplishment in the field of stretchable electronics including display panels, radio frequency electronics, light emitting diodes (LEDs), acoustic devices, strain, and pressure sensors. Stretchable devices are required to ensure that no performance deterioration occurs due to body movements when electronics are applied to non-coplanar surfaces such as the human body. In this study, we report on the fabrication of a stretchable polyaniline nanofiber temperature sensor array with an active matrix (AM) consisting of the SWCNT thin film transistors (TFTs). In order to achieve mechanical stability under an externally applied strain, a specially designed soft Ecoflex substrate is used with locally implanted SWCNT TFTs and temperature sensors on stiff poly(ethylene terephthalate) films. Thus, the SWCNT TFTs are protected from the applied strain, and they are electrically connected via embedded interconnections of liquid metal Galinstan. Owing to the embedded Galinstan interconnections, SWCNT TFTs, LED arrays, and temperature sensors maintain their performance under the deformations such as bending and stretching. In addition, the fabricated 5 × 5 AM temperature sensor array can be easily attached to the skin owing to its thin film structure and use of the soft and sticky Ecoflex. The temperature sensor exhibits a high resistance sensitivity of 1.0 %/°C and a response time of 1.8 s in the temperature range from 15 to 45 °C. The integrated temperature sensor array with the SWCNT TFT-based AM backplane on the stretchable substrate gives mechanical stability under biaxial stretching of 30%, and the resultant spatial temperature mapping does not show any mechanical or electrical degradation. This work clearly suggests the high potential application of our stretchable AM temperature sensor array to realize high performance skin attachable electronic skin devices.

Resume : Pollution exposure of people living in urban areas is a health risk as the concentration of toxic compounds and particles is high in these areas. It is known that small particles go through the airways to the lungs and eventually enter the blood circulation. Nowadays nanomaterials are also used more extensively. Therefore, easy to use devices for biosafety evaluation of these materials are very interesting. Cell viability monitoring is one way to characterize biosafety of materials including nanoparticles. Traditionally, this is performed with stain based cytotoxicity evaluation kits. These measurements are expensive, laborious and provides only end-point measurements. Best way to tackle these problems is Lab-on-a-chip (LOC) concept, which integrates various laboratory functions on a miniaturized device. In this work a LOC device with cell viability measuring CMOS chip based on capacitance sensing was built. Healthy cells attach and spread out on the surface of the chip, while dying cells ball-up and this change in capacitance can be measured. The challenge is related to the packaging of this sensor chip. In this work, low temperature co-fired ceramic (LTCC) technology was combined with flip-chip bonding using different epoxy adhesives. Chip packaged in LTCC module was then integrated with printed circuit board, data acquisition and measurement-controlling software. Reliability, biocompatibility and cell viability measurements were successfully performed and will be reported.

Resume : Semi Solid Flow Batteries (SSFB) are batteries in which both positive and negative suspensions, catholyte and anolyte, respectively, are pumped from reservoir tanks to electrochemical cell to release energy. SSFB preserve typical advantages of Redox Flow Batteries (RFB); flexibility in configuration and operation as well as energy and power decoupling, while the use of alkaline redox-active materials and organic solvents maximizes energy density of the system e.g. 309 Whkg-1[1]. LiNi1/3Co1/3Mn1/3O2 (LNCM) based suspensions as catholyte for SSFB have been prepared by magnetic stirring and characterized by galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). The resistance and electrochemical performance of cells (vs. Li/Li+) are affected by the content of superconductive Ketjen Black (KB) in suspensions. In static conditions, a cell with 11.87 and 13.97 % in volume of KB and LNCM based suspension, respectively, delivers high capacity 130 mAhg-1 at 5 mAcm-2 and a coulombic efficiency of 90 % over 10 injections. Impedance analysis show that the high frequency semicircle in Z’ vs Z’’ plots is attributed to a contact resistance and fitted using a parallel combination of a resistor with a Constant Phase element (CPE). In flow conditions, cell potential depends on applied current as well as operation time. The last has been characterized by EIS and discussed in terms of suspension stability over time. [1] Q. Huang and Q. Wang, ChemPlusChem, 2015, 80 (2), 312-322.

Resume : One-dimensional (1D) nanostructures, in particular, semiconducting metal-oxide nanowires have captured considerable attention owing to their remarkable performance as gas sensors, biosensors, solar cells, etc. [1]. ZnO (n-type) features a 3.37 eV band gap, non-toxic,environmentally stable, and, most abundant elements in earth's crust. Moreover, NiO (p-type) possess wide bandgap (3.6–4.0 eV) and is used for electro- chromic devices. In literature these two semiconducting materials has been widely investigated. Further, in nanomaterials based hetrostructures, due to strong heterointeractions between the closely packed interface, their performance is considered as more superior and complex. Herein, we report on the novel preparation and characterization of epitaxial NiO/ZnO heterostructures, consisting of inner NiO NWs [2] and outer ZnO NWs obtained through vapor-phase method. The surface morphology of the nanowires was investigated by using scanning electron microscopy (SEM) while, for structural characterization GI-XRD, the transmission electron microscopy (TEM), and Raman spectroscopy were performed. The diameter of NiO NWs and NiO/ZnO heterostructure was found to be 16-50nm and 80-90nm respectively. The GI-XRD spectra shows that these nanowires have crystalline structures. Further, the TEM study confirms the epitaxial growth of ZnO nanowires on the NiO nanowires. These hetrostructures have potential to be used for gas sensing applications. References: [1] E. Comini et al. 179 (2013) 3. [2] N.kaur et al.120 (2015) 760.

Resume : TiO2 is one of the most intensively investigated compounds in material science due to its essential properties. It is a wide band gap semiconductor having band-edge positions appropriate for solar cell applications and for hydrogen generation by water splitting. It is also known as a non-toxic, environment friendly, corrosion-resistant material. Nano-forms of TiO2 such as nanoparticles, nanorods, nanowires and, in particular nanotubes can be used as photo-electrode in dye sensitized solar cells. Conversion efficiency of solar cells can be significantly improved by using oriented nanorod-like materials on top of transparent conductive oxide. For this purpose we prepared TiO2 nanotube arrays by anodizing titanium thin film deposited on ZnO covered glass substrate. Initial Ti films were prepared by evaporation or magnetron sputtering. Diameter and length of nanotubes were controlled by parameters of anodizatio mainly voltage and etching time. The structural properties of obtained TiO2 nanotubes arrays were estimated upon simultaneous small and wide angle x-ray scattering under grazing incidence geometry. Results will be also correlated by deposition parameters and results obtained by high resolution electron microscopy, scanning electron microsopy and Raman spectroscopy. It will be also discussed possible application in photovoltaic devices.

Resume : Carbon nanotubes (CNTs) exhibit unique physical and chemical properties that are different from other materials due to their extreme aspect offering a number of exciting applications as reinforced plastics, conductive composites, sensors and photonic devices[1]. The CNTs production facilities across the globe have reached of thousands of metric tons. However, concerns have been raised, with most studies agreeing, that CNTs pose a significant potential threat to health and environment. Therefore, development of efficient sensing techniques is needed for their detection. Previously, our group reported on CNTs sensing using newly synthesized Dioxaborne (DOB) dyes [2] and well known cyanine dyes [3]. DOB dye showed promising results towards CNT sensing. The neat dye has monomeric and dimeric forms in water and while interacting with CNT photoluminescence (PL) of the dye is quenched, PL of CNT is red shifted and new PL peaks in the near infra-red range of CNT emission appeared. Present work demonstrates dramatic changes in the properties of DOB with time and its consequence on the mixture of single wall CNTs (CoMoCat, South West NanoTechnologies) and the dye using absorption and PL spectroscopy. The properties of neat DOB dye change with time resulting in reduction of the monomeric and dimeric peaks. The monomeric peak of DOB solution dramatically decreases with few days and a new peak appears due to either aggregation or degradation state of monomeric molecules. The intensity of latter is 80% higher than the former. In the mixture of the dye and CNT, quenching of PL peaks was observed overnight for (6,5) and (7,5) CNT chiralities, whereas PL intensity for the (8,4) chirality was practically unchanged. Thus, we evidence a high selectivity of the dye interaction towards CNT chirality opening up a new way for selective sensing of CNTs. Acknowledgements: The work was supported by NATO SPS project (NUKR.SFPP 984189) and EU FP ‘Horizon-2020’ Marie Skłodowska-Curie Individual Fellowship (FOC4SIP, 654733). References: [1] M. F. L. De Volder Science, 339 , pp. 535-539. (2013) [2] M. Shandura, et al., Sensor Letters, vol. 12, pp. 1361-1367, 2014. [3] P. Lutsyk, et al., " Light: Science & Applications, 5, e16028 2016.

Resume : The dependence of carrier effective mass of GaNxAs1-x, InNxP1-x, InNxAs1-x, and InNxSb1-x alloys on nitrogen content is theoretically investigated using a 10-band k.p model. The electron effective mass m*e at the bottom of conduction band in GaNxAs1-x and InNxP1-x exhibits a gradual increase as a function of N concentration in the range 0-1% and a decrease for x between 1 and 5 %. However, the behavior of m*e in InNxAs1-x and InNxSb1-x shows a strongly decrease in all studied x-range. Our theoretical results are compared with the available data reported in the literature. On the other hand, contrary to heavy-hole effective mass m*hh, the light-hole effective mass m*lh in all studied alloys is significantly affected by nitrogen states which modify the non-parabolicity of the LH band. The modification of the carrier effective mass affects the transport and mobility properties of the III-N-V alloys. Keywords: Diluted III-N-V alloys; 10-band k.p model; carrier effective mass. * Corresponding author: ahmed.rebey@fsm.rnu.tn

Resume : The control the magnitude of magnetic fields generated by different technical devices is an important ecological problem. In the paper for development of magnetic sensors the using acoustoelectronic technology is proposed. In this case the sensor will consists of the acoustic delay line with magnetosensitive film deposited on its surface between interdigital transducers. The variations of magnetic field will lead to changes of magnetic film properties that will cause the changes of acoustic wave parameters. The analysis showed that it is possible to use the thin layers of photoresist (Shipley S1805) with embedded nanoparticles of carbonyl iron as magnetosensitive film. As piezoelectric waveguides were used lithium niobate and quarts plates. The thickness of nanocomposite film produced by using spin coating method was not more 5 micron. The presence of the film does not lead to the significant attenuation of the acoustic waves propagating in delay line. The analysis of the influence of softener (n-methil-pyratidone) which was added into the photoresist on magnetosensitivity of developed films have been carried out. The element analysis, IR spectroscopy, X-ray analysis, XPS-spectroscopy, AFM microscopy of the developed materials have been also carried out. The work is supported by grant Russian Science Foundation #15-19-20046.

Resume : We have theoretically studied optical properties of p-doped GaNAsBi/GaAs Single Quantum Well in order to reach the 1.55µm telecommunication wavelength. The calculation are carried out by solving selfconsistently the band (16×16) Kane Hamiltonien combined with the Poisson equation for the hole charge density. We have investigated the effect of p doping density in the well on the subband energies, potential Fermi level and the confining hole density distribution for specific couple (well width Lw,Bi composition y), with respect of confinement conditions. The increase of doping density blueshifts the fundamental transition. Furthermore, the case of doped barrier has been discussed. Based on these results, potential applications in long wavelength range are proposed.

Resume : As cities grow and become more densely populated, there is a increasing issue of heat management, with buildings expending significant energy resources to maintain comfortable living temperatures. In many parts of the world, this entails the use of both heating and cooling during daylight hours depending on ambient temperatures. Due to the variation in the desired temperature modulation classical solutions can become counter productive in their aim of maintaining comfortable temperatures. To avoid such counter productivity, it is important to employ adaptive intelligent solutions which are able to switch their functionality based on circumstance. Here, we present a model for the design and optimisation of thermochromic smart windows based on the switching properties of vanadium dioxide (VO2) nanoparticles. In recent years vanadium dioxide has generated a broad range of interest due to its heat-mediated transition between a monoclinic distorted-rutile phase and a tetragonal rutile phase, which occurs at a critical temperature tunable via doping with tungsten. The phase transition of vanadium dioxide significantly modulates its optical properties, with the high temperature tetragonal state absorbing considerably more infrared radiation than the lower temperature monoclinic state due to a reduction in band-gap energy. It is such that a window coated with a composite polymer-nanoparticle film may passively vary its transmission of heat based on the ambient temperature, in doing so reducing the variation in temperature from the critical temperature and thus reducing energy usage in temperature management. In comparison to vapour deposited VO2 thin films, VO2 polymer-nanoparticle films may be retrofitted to existing windows and have reduced processing costs. We quantify the smart window performance over the transition between hot and cold state with the two key metrics of this field, transmission modulation of solar irradiance ΔTsol and transmission modulation of solar luminosity ΔTlum; an ideal window design will maximise ΔTsol whilst minimising ΔTlum. The model presented combines both finite-difference-time-domain (FDTD) and Monte Carlo ray-tracing to create a hybrid model capable of modelling both micro- and macroscopic properties of a material composite. Specifically, FDTD can be used to model the optical response of nanoparticles of any geometry not otherwise available with analytical techniques, enabling the design and optimisation of novel nanoparticle geometries with improved modulation of infrared radiation. The results from our FDTD studies are then used in our C++ coded ray-tracer to generate probabilities for absorption, scattering and differential scattering during the transmission of single photons through the window; this process is then repeated many times to build up a macroscopic understanding of the properties of the window. Uniquely, the use of our hybrid model enables us to model both specular and diffuse transmission, from which we can investigate the level of haze resulting from the nanoparticles, a property that is often overlooked but very important in nano-particulate window design.

Resume : A receptor surface based on a hybrid gold nanohole array combined with graphene was prepared and used to detect adenine by Surface Plasmon Resonance (SPR) technique. Surface plasmon resonance depends on the dielectric medium at the vicinity and makes it a quasi-universal detector to a variety of analytes. The label-free nature enables a fast, specific, and sensitive analysis of molecular interactions. However, detection of highly diluted concentrations and small molecules is still challenging. Hybrid plasmon-graphene systems can improve the performance of standard SPR devices. Graphene, a 2-D lattice of sp2-hybridized carbon atoms arranged in a honeycomb structure is an attractive receptor as it omits any bulk phase and therefore allows fast response times. The interplay of the plasmonics of metal nanostructures with graphene photonics modulates and enhances locally the electromagnetic field. Amplification arises from localized surface plasmons at the nanostructures and lead to an increasing capability for sensing. The nanohole arrays, fabricated by nanosphere lithography show enhanced SPR sensitivity in changes of refractive index in close proximity to the surface compared to a film of continuous gold. A deposition of chemically derived graphene oxide enables the binding of planar molecules with aromatic systems via π-stacking. The binding of the model analyte adenine verified the enhanced sensitivity by achieving approximately three times lower limits of detection.

Resume : The interface quality of ZnO and the photoactive polymer blend is of utmost importance in the performance of organic-inorganic hybrid photovoltaic devices. The chemically prepared ZnO electron transporting layer often produces a surface unacceptable for efficient electron extraction and leads to degrade the photovoltaic performance. Herein, we propose a simple technique to enhance the charge collection efficiency of ZnO cathode electrode by thermally evaporated C70 between the ZnO and the photoactive PCDTBT: PC71BM polymer blend. Our investigations show that C70 interlayer efficiently bridges the gaps between ZnO and the polymer blend reducing accumulation of the charges at the interface and thus minimizing the recombination probability. It also plays crucial role in passivating ZnO electrode against traps due to adsorbed chemical species. The inclusion of C70 interlayer into our devices led to a substantial increase in device performance with PCE reaching close to 4%, an increment by a factor of 2 compared to our control devices.

Resume : In rare-earth (R) - transition metal (TM) intermetallic compounds, the conduction electrons present in the TM experience a local exchange interaction with the R f electrons through a long range RKKY type coupling. This mechanism often leads to the occurrence of complex magnetic phases. The Laves phase compound CeFe2 is an unusual member of the RFe2 family - it has a relatively low Curie temperature (TC ≈ 230 K), an anomalously low lattice constant (7.3 Å), and a reduced magnetic moment (≈ 2.3 μB/f.u.) compared to others, and is on the verge of a magnetic instability [1]. A small but suitable change in electronic structure, caused by doping with certain 3d, 4d, 5d elements or by applying pressure, causes an additional ferromagnetic (FM) to antiferromagnetic (AFM) phase transition at low temperature [2]. In the present work, we investigate the effect of substitutional impurities Cr, Ag and Au in CeFe2. The X-ray Photoelectron Spectroscopy (XPS) measurements establish the mixed valence of Ce in CeFe2 and in the alloys of all compositions. Magnetization measurements on samples with all the impurities and concentrations confirm the presence of a paramagnetic (PM) to ferromagnetic (FM) phase transition at ~ 230 K. Further, the Ag and Au substituted samples are found to retain their FM phase down to 5 K. For Cr impurities, however, there appears a second, possibly FM to antiferromagnetic (AFM), phase transition at a concentration-dependent temperature below 50 K. Strain induced jumps in the magnetization curves and the asymmetric nature of the hysteresis curves are indicative of the FM to AFM phase transition. The Arrott plots for the Cr impurities suggest the second transition to be of the first order. X-ray Absorption Spectroscopy (XAS) is used to investigate d - f hybridizations in these compounds. The hybridization, as determined from the f 0/f 1 peak area ratio, is found to be dependent on Cr concentration and follows the concentration dependence of PM to FM transition temperature. Further, the magnetization results for the Cr doped samples reveal a martensitic nature, which is rarely found in this class of pseudobinary compounds, rendering these to be potential candidates for multifunctional applications. References 1. S. B. Roy and B. R. Coles, J. Phys. F: Met. Phys. 17 (1987) L215. 2. A. Haldar, K. G. Suresh, A. K. Nigam, Phys. Rev. B 78 (2008) 144429.

Resume : To limit the consumption of fossil fuels, hot water production by using photothermal solar receptors is growing in importance. An efficient photothermal receptor have to display a high solar absorptance (α>0.9), in the UV-VIS and near-IR regions (0.5-2µm) with a low thermal emittance (ε<0.1), in the mid-far infrared region (2-20µm) [1-3]. Here we report for the first time the formation of the solar selective CuO layer by the electrophoretic deposition (EPD) of CuO nanoparticles. A tandem absorber-reflector system is formed of CuO thin film and a highly IR reflecting metallic substrate, respectively. CuO suspensions are characterized by Dynamic light scattering (DLS) and Small angle X-Ray diffraction (SAXS) where they show to be stable during the time of the experiment. X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis-NIR spectra and Fourier transform (FTIR) spectra are used to characterize the composition, microstructure and the final optical properties of the films obtained. These CuO tandem systems obtained by EPD exhibits the required optical properties in comparison to traditional processing techniques usually used. [1] Bogaerts WF, Lampert CM. Materials for Photothermal Energy Conversion. Journal of Materials Science. 1983;18:2847-75. [2] Charlot A, Bruguier O, Toquer G, Grandjean A, Deschanels X. Nanocomposites derived from silica and carbon for low temperature photothermal conversion. Thin Solid Films. 2014;553:157-60. [3] Charlot A, Deschanels X, Toquer G. Submicron coating of SiO2 nanoparticles from electrophoretic deposition. Thin Solid Films. 2014;553:148-52.

Resume : The mixed BaMgF4 (BMF) phase has recently attracted great attention due to its interesting multifunctional properties, such as room temperature piezoelectricity and ferroelectricity, transparency (<140 nm) and diamagnetic behavior. These properties offer great potential for application in electronic devices such as sensors, microactuators, infrared detectors, microwave phase filters, energy storage and non-volatile memories In the present study, a comparison between conventional and liquid injection metal-organic chemical vapor deposition (MOCVD) is reported and the relative synthetic routes for the growth of BaMgF4 on Si (001) and single crystalline SrTiO3 (001) substrate have been investigated. For the two used approaches, the volatile, thermally stable -diketonate complexes Ba(hfa)2tetraglyme and Mg(hfa)2(diglyme)2(H2O)2 have been used as single precursors (C-MOCVD) or as solution multimetal source (LI-MOCVD). Structural and chemical characterizations through X-ray diffraction, transmission electron microscopy, energy dispersive X-ray and wavelength dispersive X-ray analyses confirmed the formation of pure, epitaxial BaMgF4 films on SrTiO3 substrates. Piezoresponce Force Microscopy has been used to asses piezoelectric properties. The impact of process parameters on film properties has been addressed, highlighting the strong influence of precursor composition, deposition temperature and oxygen partial pressure on the films composition, microstructure and morphology.

Resume : Owing to their large surface area and tunable pore size, amorphous porous solids such as siliceous, carbonaceous and chalcogenide materials are at the heart of important applications: energy (H2 storage, lithium batteries) and environment (water treatment). Recently, nanoporous chalcogenides (chalcogel) have been demonstrated to be efficient sorbents for environmental remediation from gaseous and water waste media. From a computational point of view, producing glassy surface models capable of mimicking realistically the behavior of a chalcogel and its surface is mandatory in order to understand the structure and adsorption properties of such complex amorphous materials. In this contribution, first-principles and classical atomistic simulations are combined to study the properties of glassy chalcogenide surfaces. Several chemistries will be considered. First-principles molecular dynamics is used to develop a realistic model of these materials with special emphasis on their surface chemistry. A detailed account of the structure of the surface models is given in terms of pair correlation functions, structure factors, chemical order and chemical bonding. The surface properties of these materials will then be assessed by simulating adsorption isotherms of various fluids using classical Monte Carlo simulations. I will show how the realistic details of the surface chemistry drastically affect the adsorption of various gases such as N2, CO2, CH4, H2 and their mixtures.

Resume : Complex multifunctional oxides such as VO2 have attracted a huge R&D interest because of their ultrafast sharp metal insulating transition (MIT) with a significant change in the electrical resistance making them excellent candidates for a variety of next generation novel optoelectronic nanotechnology applications including femtosecond sensors, gas sensors, smart windows for energy-efficient buildings and information storage memories. A series of high quality VO2 thin film nanostructures were successfully grown on both Al2O3 single crystal substrates and RuO2 conducting oxide thin film buffered Al2O3 substrates using a Pulsed Laser Deposition (PLD) system. Conducting mapping of the MIT phase transition in the VO2 thin films at different temperatures using a PFM technique was discussed. Transport measurements of the VO2 epitaxial thin films on Al2O3 substrates as a function of temperature showed a sharp 1st order MIT phase transition with a huge and ultrafast change in the electrical resistance up to 4 orders of magnitude at a transition temperature of 68 +/- 3 C. Moreover, theoretical calculations of the VO2 thin films grown on RuO2 buffered Al2O3 substrates could successfully and perfectly recover the 1st order sharp MIT phase transition with significant change in resistivity as in bulk of the VO2 regardless the conducting oxide thin film underneath it.

Resume : Gas sensors are an important tool in various areas for example in industrial process control, as well as security applications or in research. In this study, a noninvasive gas detection technique, based on the SPR effect with ellipsometric readout (Surface Plasmon Resonance Enhanced Ellipsometry-SPREE), is investigated. The gas sensor consists of a 40 nm SPR-active gold layer and a top-coated 5 nm doped SnOx layer. In the past, it could be shown that, without the top-coating, these type of sensors can detect various gases with sensitivities down to the ppm range (in air). The goal of the present study is to characterize additional top-coating materials (mainly doped SnOx) in dependence of the coating conditions. With the help of the doped-metal oxide, the sensitivity increases by two order of magnitude. Additionally, a selectivity for specific gases (e.g. CO for Fe-doping) is observed which depends on the doping conditions of the coating. Changing the properties of the plasma coating process gives access to a big variety of different layers and enables us to find the best conditions for the determined gas in selectivity and sensitivity. The result of the sputtering progress is analyzed and characterized by using optical methods, mainly spectroscopic ellipsometry (SE), as well as TOF-SIMS, TEM and AFM to find a correlation between the doping concentration, surface structure, the optical properties and the resulting sensing ability.

Resume : Interest in molecular materials has been driven in large part by their various and prosperous applications, especially in the domain of organic electronics, where they offer many advantages as well as alternative approaches. In the present review, we show how the chemical variability of phthalocyanines allowed synthesizing a broad range of hybrid materials. The combination of phthalocyanines or related derivatives with polymers or carbonaceous materials led to efficient chemical sensors. It is shown how the incorporation of macrocyclic molecules in hybrid materials highly modifies the structural and morphological characteristics of the materials. Rugosity, specific surface and porosity being key parameters in the analyte-sensing material interactions, these modifications highly improve the performance of chemical sensors. This is the reason why they are particularly promising materials for the development of new chemical sensors, associated with electrochemical, conductometric or optical transducers. We will show mainly two types of sensing materials, firstly phthalocyanine – grafted carbon nanotubes (CNTs), secondly conducting polymer – phthalocyanine hybrid materials. The combination of phthalocyanines and porphyrins with carbonaceous materials or with polymers in hybrid materials offers the possibility to tune their physical properties, leading to chemical sensors with better performances compared to these prepared from a single component. In addition, these hybrid materials can be deposited, at room temperature, by solution processing.

Resume : Chemical gas sensors based on metal oxides are among the most used devices for the detection of the gas during the environmental, safety and food quality monitoring. ZnO is one of the widely investigated structures for gas sensing due to its high thermal/chemical stability. The sensing mechanism of ZnO chemical sensor is based on the variation of its electrical conductivity in the presence of gases. The studies showed that the ZnO has high sensitivity mainly towards ethanol or acetone. Detection of other gases, such as CH4, NO2, and H2, is of vital interest for wide range of applications. Therefore, the improvement of sensing performance of ZnO for the detection of these toxic, explosive and hazardous gases is remaining as a challenging issue. Graphene and modified graphene were studied for application in gas sensors. The studies showed that the graphene and its oxides might be used as new additives in composite materials for gas sensors. In our work, we report fabrication of a graphene oxide/ZnO composite by coupling graphene oxide (GO) and ZnO nanostructures. We obtained ZnO nanostructures by electrochemical anodization and thermal annealing. Graphite oxide was produced from natural graphite using a modified Hummers method. Aqueous dispersion of GO was prepared by stirring graphite oxide solids in pure water, and then sonicating the resulting mixture for 45 minutes. The fabricated nanocomposites were tested as a sensing material for detection of NO2, H2 and CH4 gases. We found out that the reducing the GO enhanced the nanocomposite conductance and improved the response of composite to all measured gases. The obtained results showed that the fabricated nanocomposite material is promising for development of chemical sensors and electronic noses.

Resume : In regards to its wide use, global ammonia emission in atmosphere increases continuously since the pre-industrial times promoting the formation of particulate matter and affecting flora, fauna and the quality of air and now ammonia is becoming a major pollutant. The main sources of ammonia come from agriculture (fertilizers), animal waste fermentation and industry (refrigeration units…). Ammonia has adverse health effects as respiratory disorder; skin irritation, severe irritation at the ocular level, nausea, headache and an exposition to high concentrations can be fatal. In working places, ammonia concentration is regulated. Moreover ammonia is subject to produce odor nuisances with a negative impact in terms of the quality of life of citizens, safety and economy. In regards to its toxicity, its detection is of great importance for environment. This is why we created new ultra low cost organic electronic gas sensors based on hybrid nanocomposites with metrological performances adaptable to the application. These hybrids based on an intrinsically conducting polymer (polyaniline) and metal oxides (TiO2, SnO2) exhibit synergistic effect due to specific chemical and physical interactions along their interfaces in the composite. Our work was directed on influence estimation of two surface active acids i.e. dodecylbenzenesulfonic acid (DBSA) and lauryl sulfuric acid (LSA) on PANI nanocomposites structure-property relationship and effects of nanoparticles on aniline polymerization kinetics. These effects were used to to optimize the response of the sensors to get linear response in the ppm range or/and to get low detection threshold. The detection threshold can be adapted from ppb to ppm values with response times around one minute. As these sensors are processed in solution, they can be printed on adequate substrates to get miniaturized sensors to create dense sensor networks for environment monitoring.

Resume : Two dimensional (2D) materials such as atomically thin transition metal oxides and chalcogenides are an excellent platform for sensing applications due to their extraordinary surface area to volume ratio. This morphology allows surface bound analytes to effectively interact with the highly confined and comparatively small number of charge carriers in the 2D system leading to highly sensitive sensing. Analogous to graphene, stratified transition meatal oxides and chalcogenides (TMO&S) can be exfoliated to their unit cell thick fundamental layers with relative ease; however unlike graphene many TMO&S feature a bandgap which can be exploited for the sensing process either via the modulation of photoluminescence arising from a direct bandgap or through the modulation of the electronic structure of the material which can be electronically detected. Furthermore intercalation of multilayer TMO&S with small cations (H+, Li+ etc) has been found to effectively dope the 2D materials, leading to plasmon resonances in the visible spectrum. Surface interaction with an analyte can then further perturbatie the electronic structure of the intercalated 2D material generating an optical signal which can be easily detected. Different sensors based on native and intercalated semiconducting 2D materials will be discussed herein.

Resume : Au nanoparticles have been found to show potentials for various applications such as catalysis, biomedicine, gas sensing, etc. Among the different catalysis applications, Au nanoparticles as artificial enzyme to perform a myriad of oxidation reactions may pose significant implications in both materials science and biomedicine aspects. However, plain, un-modified Au nanoparticles are prone to aggregation during the catalytic reactions, which further hinders their practical use. To address this issue, core-shell structures in which Au nanoparticles are coated with a thin layer of shell material are proposed. For core-shell structures, the core Au particles are protected by the shell material from being aggregated during the reaction period. On the other hand, each of the Au can participate in the catalytic reaction, providing a homogeneous reaction environment to facilitate the catalysis. In this study, Au@Cu2O core-shell nanocrystals have been synthesized and demonstrated remarkable enzyme-mimetic activity toward H2O2 decomposition. The peroxidase-like activity of Au@Cu2O was evaluated by using tetramethylbenzidine (TMB) as the substrate in the presence of H2O2. The oxidation processes of TMB by using Au@Cu2O were analyzed with the typical Michaelis-Menten kinetics model, in which the Michaelis constant (Km) and maximum reaction velocity (Vmax) were obtained and compared. The influence of shell thickness on the activity of the samples were also investigated and realized.

Resume : The energy needed to activate the chemical processes occurring at the surface of solid-state sensor materials is the main source of power consumption of this technology. In this presentation, we will review recent advancements in thermal and optical methods to supply such energy in an efficient way. On the one hand, self-heating in nanostructures is a promising but barely unexploited approach to reduce power consumption under the tens of μW regime. The technical complexity of fabricating suitable devices for such approach has hampered its further development for nearly a decade. Recent results show that efficient self-heating also occurs on larger systems, which are simpler to fabricate. Moreover, new findings about the origin of the unexpected efficiency of these large systems are opening doors for truly engineering self-heated devices easy to implement. On the other hand, optically activated conductometric devices have remained dormant as a scientific curiosity over the years. Most of the past limitations came from the need of UV light sources of relatively high costs. Advancements in LED technology extended the flexibility of the LED technology in the last years, at a much lower cost. In parallel, materials modifications and surface functionalization strategies relaxed the need of UV, making possible the use of other, more efficient and convenient, wavelengths (e.g. visible blue). On top of that, optical activation approaches conductometric operation to the world of optoelectronic, in which further power savings can be achieved (e.g. zero power operation) by using active sensor structures.

Resume : Urban centres will need to monitor air quality using low cost air quality networks and costs are now affordable, but we now must resolve the details: deployment, maintenance, validation and data analysis. Monitoring gases, VOCs and particulates is difficult, but achievable. And air quality networks can be fixed site, car/tram mobile, personal and eventually wearable. Each network has opportunities and problems; calibration, data richness, political issues, personal data security must all be considered. Are the sensors providing good data? As requirements have moved from physical sensor networks (temperature, pressure, strain, light, noise) to chemical sensor networks, the problems of data errors have increased. We will review progress in both North America and Europe on validation of air quality networks.

Resume : We report in this communication on various environmental sensors fabricated on flexible substrates using printing technologies. We have developed a set of sensors working with different principles, capacitive, resistive, colorimetric, and field-effect. These transducers on polymeric or cellulosic substrates were functionalized with various sensing films (polymers and metal-oxides) using printing techniques. Different sensing devices operating at low power or with heating capability for sensing humidity, volatile organic compounds, reducing and oxidizing gases have been produced and evaluated. Formation of arrays has also been investigated and multi-sensor platforms were demonstrated. Performance vs. cost, status and current trends on printed environmental sensors will be discussed. Finally, examples of systems involving these sensors will be described, notably smart RFID labels and smart textiles.

Resume : Three-dimensional networks made up of nanowires or nanotubes are expected to play an important role in the development of next generation of nanostructured devices, as the high degree of wire/tube interconnectivity may be beneficial in a wide range of applications, including chemiresistive sensing. Specifically, we report a novel and reliable method to fabricate highly-sensitive environmental chemiresistive gas sensors based on large-scale interconnected networks of electroconductive polymer nanotubes. The versatile bottom-up strategy allows facile fabrication of centimeter-scale free-standing arrays of interconnected polypyrrole nanotubes (or nanowires) with tunable geometrical dimensions and spatial arrangement. Such networks of elongated nanostructures have great potential to be used in sensing applications, as they provide an extremely large active surface, together with remarkable electrical connectivity and mechanical stability. In particular, the scalable three-dimensional system of polypyrrole nanotubes exhibits an excellent sensitivity toward gaseous ammonia, at gas concentrations as low as 1 ppm. It’s worth pointing out that the entire sensor’s fabrication protocol is exclusively based on simple and low-cost technologies with no sophisticated processing steps, such as lithographic approaches. The as-prepared sensors based on these dense hierarchical nanoarchitectures may be therefore easily integrable for specific and highly-sensitive detection of several gas species.

Resume : The need of fast, sensitive and accurate real time analyses is the driving force for the development of sensor technology. Environmental air quality monitoring is generally executed using complex and expansive instruments, based on laboratory equipment adapted to in-field use. While low-cost devices for real-time monitoring of CO, NOx and O3 are available, aromatic hydrocarbons like benzene, toluene and xylenes (BTX) are generally still monitored with passive samplers and successively off-line analyzed, resulting on data representing averaged exposure levels. In order to provide significant air quality data, reliable quantification of single BTX must be performed. We already reported on a miniaturized system able to reach this goal [1, 2]. Here the results of new efforts aiming to further simplify the system, maintaining the reliability of the data, are presented. A miniaturized system is proposed, composed of a selective supramolecular concentration unit, a MEMS cartridge, filled with the supramolecular cavitand receptor, and a commercial PID as sensor. The issue of achieving at the same time molecular-level selectivity and low-ppb sensitivity for benzene has been solved by disconnecting the recognition element from the detection unit. The recognition event is assigned to a molecular receptor, capable of selectively trapping aromatic vapors at the gas–solid interface. The MEMS cartridge can be heated with a precise control of temperature; the cavitands selectively release species in function of temperature. In this way the MEMS cartridge works as a trap of aromatics compounds at room temperature, and as a GC-like column when heated. [1] Dalcanale E. et al. Chem. Comm. 2007, 2790. [2] Dalcanale E. et al. Sens. Act. B 2009, 141, 322.

Resume : The piezoelectric sensors are known for their high accuracy, low manufacturing cost and high level of miniaturisation. Moreover, GaAs is a crystal with a lot of interesting properties for MEMS applications such as piezoelectric properties, microfabrication opportunities and various possibilities to biofunctionnalize its surface to reach the specificity of molecules grafting. These three points have given us the opportunity to develop a specific GaAs acoustic sensor adapted for detection of molecules in specific media. Using analytical model, we showed that the best performance for electromechanical coupling is obtained in a (100) wafer with an electric field aligned along the <110> direction. The transducer whose active structure is a membrane was obtained using low cost processes of microfabrication and then was connected to PCB to be characterized. The results given here concern the S parameters of the device in wideband frequency (15MHz to 1GHz), microwave microscopy of the electromagnetic field repartition on the sensitive surface. These characterizations constituted preliminary results to optimize the design of electrodes before measurements in gas environment. We have evaluated of the microwave transduction with GaAs in argon flux. The polluant species are toluene and NH3. The interactions between the sensitive material and the gas are demonstrated. The observed variation of the sensor response is clearly due to the variation of the adsorption of gas.

Resume : GaN-capped open gate AlGaN/GaN based HEMTs are used for sensing pH values and ion concentrations in liquids. One example is the monitoring of cell metabolism processes via exchange of potassium ions in a bioreactor. In order to characterize the processes during potassium and water interaction with the HEMT surface, we have investigated their adsorption at n-type GaN(0001) surfaces at 300 K using in-situ photoelectron spectroscopy with focus on adsorbate-substrate charge transfer processes. K adsorption and K & H2O coadsorption initially lead to the saturation of surface dangling bonds accompanied with drastic changes in the interface properties. In all cases, a strong surface dipole forms, lowering the electron emission barrier. Two reaction regimes are identified, which mainly depend on the K coverage. The initial stages are characterized by K ionization and transfer of the 4s electrons towards the substrate inducing an increase of the GaN surface electron density. For higher K coverage, the residual 4s electron density induces the formation of intra-gap states and recovery of surface electron depletion. In case of water interaction, hydroxyl groups are formed including creation of flat band conditions at the GaN surface. The surface band alignment varies between 0.5 eV upward band bending and -0.5 eV downward bending clearly demonstrating that the electron density at the GaN surface can be reversibly tuned by alkali-based adlayers depending on their nature and thickness.

Resume : Selective catalytic reduction of nitrogen oxides (NOx) by NH3 (NH3-SCR) is one of the most promising strategies for the abatement of NOx emissions from diesel engines. To further improve the efficiency of NH3-SCR, it is necessary to get insights into the real-time state of the applied catalysts (mostly zeolite-based) under operational conditions. As revealed in our previous studies by impedance spectroscopy (IS), the proton transport in H-ZSM-5 was supported by stored NH3 as a solvate molecule, which allows H-ZSM-5 zeolites to be used in the sensing of both gas-phase NH3 and NH3-SCR reactions. Here, we performed in situ IS studies on highly comparable zeolites Fe-ZSM-5 and Cu-ZSM-5 (with the Cu or Fe species predominantly in isolated state) as catalysts and sensors simultaneously under SCR-related conditions. While the SCR conversion of stored NH3 on Fe-ZSM-5 can be effectively monitored based on NH3-supported proton transport, the sensing of SCR conversion of stored NH3 on Cu-ZSM-5 was significantly influenced by the formation of intermediates. Simultaneous IS and DRIFTS (diffuse reflection infrared Fourier transform spectroscopy) studies revealed that ammonium ions formed immediately by exposing NH3-saturated Cu-ZSM-5 to NO-containing atmospheres, and subsequently dominated the proton conductivity. Such a correlation of integral electrical response with molecular processes, achieved by our IS-DRIFTS studies, not only clarifies the molecular origin of the NH3-SCR sensing effect, but also provides a new perspective to understand the NH3-SCR mechanism over metal-promoted zeolites.

Resume : Complex nano-architectures of various material combinations (e.g. Si-nanostructures such as wires (NW) and cones (NC), GaN nanostructures, transparent conductive oxides e.g. Al doped ZnO, coinage metal nanoparticles e.g. wires, spheres, graphene and other 2D materials) integrated on Si wafer platforms will be presented to enhance selective optical sensing applications. Among those we show nano-material choices for surface enhanced Raman spectroscopy (SERS) and chemically functionalized resonators such as SiNWs, SiNCs, GaN NWs with distinct resonances for which peak shifts can be determined and quantitatively evaluated based on numerical simulations. We show for selected examples of interest in the area of bio-medical research our nano-material choices, the synthesis options and the viability to serve as signal enhancing SERS substrates. To understand optical signatures with respect to spectral analyte outputs, finite difference time domain (FDTD) simulations are carried out based on which 3D material architectures as signal enhancing substrates will be optimized. Bio-medical targets are from the field of kidney diseases and -injuries as well as bone degradation.

Resume : In recent days, there have been increasing attentions toward internet of things (IoT) and one of the emerging research area on IoT is about gas sensors to detect harmful agents that have high potential of causing damages to human body. Especially, volatile organic compounds (VOCs) which are very common in our ordinary life can cause serious damages. Therefore, gas sensors to detect and monitor VOCs have been studied for last decades. Among them, metal oxide semiconductor showed simple operation, cost-effectiveness and fast gas sensing performance with small-scale available, just suitable for IoT application. However, there still remain several challenges like reproducibility for mass production, better selectivity and response time. We present a simple method to solve existing problems through vertically ordered NiO nanorods with Fe deposited in multiple steps by glancing angle deposition. The highly ordered porous structure with multiple p-n junctions of NiO and Fe2O3 formed after annealing at air ambient showed dramatically enhanced response to volatile reducing gases (C2H5OH, C7H8, C6H6, CH3COCH3 and CH3CHO) with fast response time (< 5s) compared with bare NiO nanorods. Interestingly, NiO with Fe2O3 reacted differently to target gases, leading to selective detection. These results are attributed to p-n junctions for response increase (transducer function), effective structure for better gas accessibility (utility factor), and catalytic effect of Fe2O3 (receptor function).

Resume : This is a is a short overview of the European Sensor Systems Cluster (ESSC), that is an EC initiative, launched on November 2014, to maximize impact of the FP7/H2020 research and innovation projects for industrial leadership and key enabling technologies applications. The ESSC cluster has already involved 7 FP7/H2020 projects, European networks and platforms, 13 founder organizations with at least 60 members from more than 15 Countries (January 2016). The European Commission launched a new initiative in the field of Research & Innovation with European Clusters to promote international cooperation, create critical mass in Science & Technology and maximize impact in strategic key sectors for European economic growth with high industrial relevance. The European Sensor Systems Cluster (ESSC) (http://www.cluster-essc.eu) was launched in Brussels on 27 November 2014 under sponsorship of the DG Research and Innovation, Directorate Key Enabling Technologies - Unit Advanced Materials and Nanotechnologies, with Dr. Hans-Hartmann Pedersen (EC Research Programme Officer) as EC Observer. This meeting in Brussels was attended by at least fifteen FP7 and H2020 project coordinators and other representatives from research institutions and SMEs. ESSC is one out of the 19 European Clusters managed/ observed by DG R&I - KET - Unit Advanced Materials & Nanotechnologies. The ESSC [1] will identify technical or non-technical challenges for (bio)chemical sensing and highlight opportunities resulting from nanotechnology, microsystems integration, advanced data evaluation, their systemic integration as well as manufacturing and commercialization based on an application and demand driven approach. ESSC will mobilize a pan-European network, ready to advise, assist and implement national and international measures to strengthen the position of European research and innovation. The ESSC key areas have been identified: Environmental Sustainability, Energy Efficiency, Health Monitoring, Comfort, Industrial Applications. [1] M. Penza et al., AMA Science, Open Access. DOI: 10.5162/4EuNetAir2015/08

Resume : For the last few decades, there have been a great effort to use hydrogen (H2) as an alternative energy instead of fossil fuel due to its renewable, energy efficient and eco-friendly properties. However, intrinsic properties of H2 such as colorless, odorless and tasteless make people hesitate to use the explosive H2 in household or vehicle. Therefore, sensing technology for H2 becomes more important along with increasing demands of safe use of H2 and various sensing techniques has been developed such as electrical, electrochemical, mechanical and optical types of devices. Among these technologies, optical based H2 sensors have attracted more attention from researchers due to its working principle which does not involve the use of electrical components in the sensing area. However, optical H2 sensors that have been developed to date have limitations in their performances such as a sensitivity, response and relaxation time due to intrinsic properties of sensing materials. In this research, we fabricated optical H2 sensors based on a nano-actuator inspired from sensing organs of insects. In order to implement the nano-actuator, first of all, micro/nano-pillar arrays of polyurethane were fabricated using simple molding process. Next, thin palladium (Pd) layer was obliquely deposited onto the only one side of each pillar. Then, the pillars were bent by the residual stress generated in the metal film and the bending angle of the pillars were immediately affected by the H2 concentration due to volume expansion of the Pd layer under H2 exposure. Since optical properties of nano-actuator were also dramatically changed by the change of the bending angles of nano-pillars, the nano-actuator was applied to highly sensitive optical H2 sensor. The biomimetic nano-actuator-based optical H2 sensor shows high sensitivity, fast response time and stable repeatability which are clearly recognizable the naked human eye.

Resume : Development of scalable systems for continuous, in-situ monitoring of water quality remains one of the main challengesforenvironmental research and sustainability. While extensive literature describing new sensing methods and innovative analytical approaches has been published overthe past twenty years, no practical solutionfor affordable integratedanalytical platforms has been proposed. Additionally, the high cost of fabrication of complex fluidic designs and components such as pumps and valves required for these platforms has further restricted the ability to produce an affordable option for end-users outside of government agencies and specialized commercial entities. The development of new materials and device concepts to replace these bulky and expensive components has the potential to generate breakthroughs in the development of cost-effective and reliable monitoring systems. In this paper, the impact of introducing new rapid prototyping techniques and innovative fabrication approaches to the optimization of biomimetic fluidic handling components, specifically light-responsive hydrogel valves fully integrated within microfluidics systems are presented.This provides a low-cost, low-energy and non-contact, scalableapproach to integration of these critical fluid handlingcomponents. The in-situ nature of the valves results in a significant elimination of dead volume in the system, due to the need to site conventional macro valves off-chip. A fully automated prototype LED-triggered platform has been produced to demonstrate various cycles of opening and closing of the polymer-gel valves. This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 604241 Scope:Materials /Hybrid materials: from the laboratory to the market

Resume : The imminent prospect of a hydrogen economy and recent market introduction of hydrogen fuel cell cars demand a development of safe and reliable hydrogen sensors. Hydrogen sensors are also becoming increasingly important in many industrial processes, food industry and in health monitoring. Specifically for fuel cell cars, stringent performance targets have been set by the automotive industries to ensure a safe operation [1]. In this regards optical sensors are beneficial because they provide means for remote readout and are considered safer than electrical sensors as they pose no risk of spark generation. A growing avenue within the field of optical hydrogen sensors is the use nanostructured metal-hydride systems as signal transducer in plasmonic hydrogen sensors [2]. For this application, palladium (Pd) has been the main transducer material since it readily absorbs and releases hydrogen at RT. However, pure Pd exhibits wide hysteresis upon sorption which creates ambiguous readout depending on the sensor’s history. To this end, alloying the hydride-forming metal with another metal (i.e. Pd−Au) has been known to reduce the hysteresis. In this work we present a novel plasmonic optical hydrogen sensor using Pd−Au alloy nanoparticles [3] and its generic fabrication strategy [4]. As the key features of our study, by increasing the Au content in the alloy nanoparticles up to 25 at.%, we find an eight-fold sensitivity increase in the sub-10 mbar pressure range (i.e. the critical pressure range before hydrogen reaches its flammability limit at 40 mbar) compared to a pure Pd, sensor accuracy < 5% throughout the studied 1 mbar−1 bar hydrogen pressure range and, by engineering the sensor nanoparticle size, sub-second sensor response times. Thus we meet or exceed the performance targets set by the automotive industry. Finally we also report a distinct wavelength-independence of the qualitative sensor response to hydrogen pressure. This opens up the possibility to use single-wavelength plasmonic hydrogen sensing, which promises the use of low-cost optical components such as cheap LED light sources and a simple photodiode detector for implementation in real devices. References (1) Boon-Brett, L.; Bousek, J.; Black, G.; Moretto, P.; Castello, P.; Hübert, T.; Banach, U. Identifying Performance Gaps in Hydrogen Safety Sensor Technology for Automotive and Stationary Applications. Int. J. Hydrogen Energy 2010, 35, 373–384. (2) Wadell, C.; Syrenova, S.; Langhammer, C. Plasmonic Hydrogen Sensing with Nanostructured Metal Hydrides. ACS Nano 2014, 8, 11925–11940. (3) Wadell, C.; Nugroho, F. A. A.; Lidström, E.; Iandolo, B.; Wagner, J. B.; Langhammer, C. Hysteresis-Free Nanoplasmonic Pd-Au Alloy Hydrogen Sensors. Nano Lett. 2015, 15, 3563–3570. (4) Nugroho, F. A. A.; Iandolo, B.; Wagner, J. B.; Langhammer, C. Bottom-Up Nanofabrication of Supported Noble Metal Alloy Nanoparticle Arrays for Plasmonics. Submitted. 2015.

Resume : In the last years many groups have focused their research on improving the transport properties of high surface area materials as ideal support for different applications, such as sensors, drug delivery or catalysis. The combination of high surface area with high electrical conductivity is still a challenge, since the chemical approaches to both features are mutually exclusive. In this work, we present a novel and versatile supporting porous material with significant electrical conductivity and high surface area. Our strategy consists of the combination of an insulating porous framework modified on the surface by a transparent conductor oxide to yield excellent surface conductivity, while maintaining the highly porous structure. As a proof of concept we have use this highly porous electrodes to support a coordination polymer of the Prussian blue (PB) family that promotes the water oxidation at neutral pH and ambient conditions.[1] Complete characterization of these electrodes using X-ray Diffraction (XRD), Environmental Scanning Electron Microscopy (ESEM) and electrical characterization of the surface were carried out to determine the penetration and the interaction of the PB with the conductive surface. Correlations with their enhanced electrocatalytic features allowed maximizing current densities and stability.

Resume : The Carbon Capture and Storage (CCS) scheme aims to reduce the amount of CO2 in the atmosphere. One main research direction in CCS is the development of new materials for CO2 capture and detection whose qualities are often assessed by measuring their isosteric heat of adsorption (Qst) using various methods based on gravimetric and volumetric measurement principles. These methods, however, often require precise determination of initial sample weight and/or volume. Therefore it is very appealing to develop an alternative method where such necessities are absent. In the past years, the optical indirect nanoplasmonic sensing (INPS) [1] platform has established itself as a powerful and versatile experimental tool to study functional materials at the nanoscale. Its merits include superior sensitivity down to individual nanoparticles [2], possibility for in situ and in operando experiments under a wide range of conditions, a relatively simple setup and flexibility in terms of the studied sample materials ranging from thin films to nanoparticles, as they can be conveniently deposited on top of the sensors. In this work we demonstrate how INPS can be an attractive alternative to detect and characterize the gas adsorption process in a micro- or mesoporous sorbent material. Specifically, we show how the CO2 isosteric heat of adsorption (Qst) of thin microporous PIM-1 polymer films and of amine-functionalized large-scale commercially available silica nanoparticles can be conveniently obtained without any calibration; as opposed to the conventional methods [3]. Thus, this study provides a generic blueprint for a plasmonic CO2 detection scheme and for efficient optical screening of micro- and mesoporous sorbent materials for CCS or other CO2/gas separation processes in terms of their adsorption energetics and kinetics. References (1) Langhammer, C.; Larsson, E. M.; Kasemo, B.; Zorić, I. Indirect Nanoplasmonic Sensing: Ultrasensitive Experimental Platform for Nanomaterials Science and Optical Nanocalorimetry. Nano Lett. 2010, 10, 3529–3538. (2) Syrenova, S.; Wadell, C.; Nugroho, F. A. A.; Gschneidtner, T. A.; Diaz Fernandez, Y. A.; Nalin, G.; Świtlik, D.; Westerlund, F.; Antosiewicz, T. J.; Zhdanov, V. P.; et al. Hydride Formation Thermodynamics and Hysteresis in Individual Pd Nanocrystals with Different Size and Shape. Nat. Mater. 2015, 14, 1236–1244. (3) Nugroho, F. A. A.; Xu, C.; Hedin, N.; Langhammer, C. UV-Vis and Plasmonic Nano-Spectroscopy of the CO2 Adsorption Energetics in Microporous Polymers. Anal. Chem. 2015, 87, 10161–10165.

Resume : Closing remarks