Nanoparticles: advances in synthesis, characterization, theoretical modelling and applications

Resume : Ceria (CeO2) is a fundamentally interesting and industrially relevant catalyst. However, it remains a very challenging material for TEM observations, as it reduces strongly and spontaneously under the electron beam in high vacuum. In this presentation, I will highlight how controlling the nature of the atmosphere within an aberration-corrected environmental TEM (ETEM) is an efficient and powerful way to control the redox state of ceria, while providing numerous opportunities to study a wide range of physical and chemical phenomena at the atomic scale. For instance, the atomic mobility at {100} surfaces is strongly affected by the nature of the surrounding gas, and could be used to indirectly indicate the adsorption/desorption of gaseous species. This work also demonstrates the direct visualization of adsorbed oxygen or CO2 molecules at {100} surfaces. The nature of the contrasts is evaluated from high resolution TEM (HRTEM) simulations, which reproduce semi-quantitatively the experimental images. Directly visualizing the projected atomic structure of the top surface of ceria through HRTEM imaging is a great opportunity to investigate the current capabilities of the ETEM to validate atomistic models of adsorbed molecules at surfaces. This work highlights the potential of the ETEM at high spatial resolution to directly image adsorbed molecules, and thereby better understand the surface coverage and the nature of adsorption sites predicted by atomistic calculations.

Resume : We report a new multi-scale procedure based on the recently developed Stochastic Kinetic Mean Field (SKMF) approach, combined with the Phase Field model (PFM) and CALPHAD database, to study the nucleation-growth-coarsening process in the Ag-Cu alloy. The SKMF approach reproduces the nucleation and early growth of copper precipitates in the silver matrix, and the PFM then simulates the coarsening of the microstructure. To ensure the consistency of the procedure, the length and time scales of SKMF and PFM are connected by matching the interface profiles and growth velocity of an isolated growing precipitate as simulated by both methods. Moreover, the free energy used in the PFM is derived from the interaction energies used in SKMF. Two different implementations of the procedure are proposed. First, the post-nucleation microstructure as provided by SKMF is used as the initial condition for subsequent PFM simulations. Second, only the particle size distribution and particle density are transferred to PFM, thereby giving access to bigger systems.

Resume : For revealing internal atomic processes in bimetallic nanoparticles, individual hemispherical Ag-Cu alloy particles were grown by direct current (DC) magnetron sputtering. Phase separation of particles was found to be size- and composition-dependent. Particles smaller than 5 nm in diameter remained as a solid solution of the components for all tested compositions (15-80 at.% Ag). At 15 and 30 at.% Ag compositions phase separation was observed only for particles above 5 nm in diameter. The solubility curve is asymmetric in Ag-Cu, which means that the excess free energy function cannot be described by a second order polynomial of the composition (non-regular solution), that is the interaction energy is composition dependent. In this work we apply the Cahn-Hilliard theory and a 3D atomistic kinetic model, the Stochastic Kinetic Mean Field (SKMF), what we further developed purposefully so it can use the Redlich-Kister polinomials from CALPHAD calculations. We demonstrated that the gradient energy coefficient - composition function can be calculated from the interaction energy. We also showed that when the interaction energy is composition dependent this necessarily means that the gradient energy coefficient is also composition dependent.

Resume : New innovations are transforming the Transmission Electron Microscope (TEM) from a simple high-resolution image acquisition tool into a nanoscale materials research and development laboratory. Researchers can now better understand material behavior by analyzing samples in real-world gas or liquid environments, at high temperature and with ultra-low noise electrochemical and electrical biasing techniques. With the new in situ tools from Protochips, materials research occurs in highly controlled environments at high resolution without sacrificing the analytical capabilities of the TEM such as EDS. Applications for these tools include heterogeneous catalyst reactions, imaging of living cells, nanostructure nucleation and growth, battery and fuel cell materials, high temperature nanoparticle behavior, soft materials, and semiconductor devices. In this presentation we show the most recent results using the Protochips Atmosphere™ gas cell, the Protochips Poseidon™ Select flowing liquid and electrochemistry cell, and the Protochips Fusion™ heating and electrical biasing system. Sample preparation methods using Focused Ion Beam techniques were developed to address the different challenges emerging from in situ heating and biasing experiments. A full Clarity software suite allows for the control of experiments, data recording and analysis as well the as the seamless integration of in-situ data into TEM camera software.

Resume : The properties of nanoparticles are known to critically depend on their local chemistry but characterizing three-dimensional (3D) elemental segregation at the nanometer scale is highly challenging. Scanning transmission electron microscope (STEM) tomographic imaging is one of the few techniques able to measure local chemistry for inorganic nanoparticles but conventional methodologies often fail due to the high electron dose imparted. Here, we demonstrate realization of a new spectroscopic single particle reconstruction approach built on the ?single particle? method developed by structural biologists [1]. We apply this technique to the imaging of PtNi nanocatalysts and find new evidence of a complex inhomogeneous alloying with a Pt-rich core, a Ni-rich hollow octahedral intermediate shell and a Pt-rich rhombic dodecahedral skeleton framework with less Pt at ?100? vertices. The ability to gain evidence of local surface enrichment that varies with the crystallographic orientation of facets and vertices is expected to provide significant insight toward the development of nanoparticles for sensing, medical imaging, and catalysis. We also discuss recent advances in elemental characterisation of nanoparticles in liquids and gases using engineered graphene liquid cells [2] and in situ holders optimised for X-ray spectroscopy in situ. [1] Wang et al, Nano Lett., 2019, 19 (2), pp 732?738 DOI: 10.1021/acs.nanolett.8b03768 [2] Nano Lett., 2018, 18 (2), pp 1168?1174 DOI: 10.1021/acs.nanolett.7b04713

Resume : Compared to bulk silicon, silicon nanocrystals (Si-ncs) show strong optical and electrical properties due to quantum confinement, making them suitable for a plenty of applications in optoelectronic. As in bulk silicon, a fine control of impurity doping allow to tune Si-ncs based devices for a specific use. Si-ncs can be synthesized from the decomposition of silicon supersaturated SiO2 film. In such host material, the properties of doped Si-ncs are determined by the effective location of impurities (in the core of Si-ncs, at the Si/SiO2 interface or in the surrounding matrix). If some studies have been carried out on theoretical structural description, only a few relate experimental results. In this work, a deep structural analysis of n (P, As) and p (B) doping of Si-ncs embedded in SiO2 elaborated using different elaboration process has been performed using Atom Probe Tomography. It allowed us to perform 3D mapping of these materials at the atomic scale to investigate the location of impurities and the Si clustering characteristics (size distribution, composition ?). We showed that n-type impurities are, in each cases, efficiently introduced in the core of every single Si-ncs allowing a high doping of Si-ncs. However, the comparison between As and P doping revealed a strong influence of the dopant nature on the Si-ncs growth. P-type doping seems much more complicated. In fact, B remain in majority in the matrix, but some Si-ncs still contain a low level of impurities.

Resume : Electron tomography is a 3D characterization technique that has greatly contributed to the understanding of materials at the nanometer level. Recently, the technique has been extended to spectroscopic signals such as electron energy loss spectroscopy (EELS) and X-ray energy dispersive spectroscopy (EDX), bringing valuable 3D information about the structure and chemistry of the nanomaterials. Using conventional spectral processing and reconstruction algorithms, these modes require: 1) long acquisition times, and hence electron doses, to acquire high signal-to-noise ratio spectra; and 2) a large number of spectrum images to faithfully reconstruct the structure in 3D. To avoid damaging the sample during the tomographic acquisition, it is necessary to explore advanced machine learning methods and reconstruction algorithms. Several decomposition methods have been successfully applied to EELS and EDX analysis, either for denoising or for dimensionality reduction. In parallel, recent advances in reconstruction algorithms, in particular the development of compressed sensing approaches, have allowed reliable 3D information to be extracted from heavily sub-sampled datasets. In this talk, we will present recent advances in both fields, and apply them to EELS and EDX tomography of various nanostructures.

Resume : It is well known that nanosizing significantly affects the physical properties of the matter. This is mainly explained by the fact that at the nanoscale the ratio between surface and bulk atoms is very high leading to a large atomic population at the surface with modified properties. Thus, the surface energy in the thermodynamic description cannot be longer ignored. For metal-hydride systems, the hydrogen solubility, the kinetics and the enthalpy of hydride formation can be modified by decreasing the particle size. Moreover, the surface reaction kinetics are enhanced and the reaction paths involving atomic diffusion within the particles are reduced, which allow very fast reaction rates. Accordingly, nanosizing gives the possibility to tailor both thermodynamic and kinetics properties. In this work, the interaction of hydrogen with Pd, Rh nanoparticles and Pd-Rh nanoalloys stabilized on different supports will be addressed as function of nanoparticle size from tens down to 1 nm. In contrast with bulk metal, Pd nanoparticles with 1 nm average size form solid solutions with hydrogen at standard conditions. The case of Rh is also interesting since bulk metal does not form a hydride phase at standard conditions, whereas Rh nanoparticles with sizes below 2 nm absorb hydrogen forming a hydride phase. Finally, the interaction of Pd and Rh nanoparticles with hydrogen has important consequences on the catalytic performances in several reactions involving hydrogen.

Resume : Silver catalysts are industrially used amongst others to produce formaldehyde from methanol, and for the epoxidation of ethylene to ethylene oxide [1]. Moreover, silver has promising catalytic properties for the selective hydrogenation of ?,?-unsaturated aldehydes [2]. Supported silver catalysts are generally synthesized using precipitation or impregnation routes. In this work, we explore melt infiltration as an alternative technique: we heat a physical mixture of silver nitrate and a porous support above the melting point of silver nitrate, which then enters the pores as a result of capillary forces. This strategy allows high metal loadings and eliminates the need for a solvent [3], but challenges arise regarding control over the silver particle size and distribution. The narrow pore size distribution of the chosen ordered mesoporous silica support, SBA-15, allowed us to follow the infiltration process of the silver nitrate in situ, and study its subsequent decomposition to form metallic silver. By varying the decomposition conditions (temperature and atmosphere), we attained either silver nanowires or small spherical silver particles inside the mesopores of the SBA-15. We show the synthesis of either supported silver nanowires or spherical particles, and their application in the hydrogenation of cinnamaldehyde. 1. M. O. Ozbek, I. Onal, R. A. van Santen, J. Catal., 284, 230?235 (2011) 2. P. Claus, H. Hofmeister, J. Phys. Chem. B, 103, 2766-2775 (1999) 3. P. E. de Jongh, T. M. Eggenhuisen, Adv. Mater., 25, 6672?6690 (2013)

Resume : In this study, we present the conversion of metallic Ni nanoparticles into NiF2 through fluorination under pure molecular fluorine F2. For such purpose, Ni nanoparticles of median diameter of 50 nm were purchased and fluorinated at temperatures ranged in between room temperature and 450°C. It was then possible to get different proportions of NiF2 shell onto Ni core. The structure of Ni-doped NiF2 was investigated by X-ray diffraction (XRD) and Pair Distribution Function (PDF) and the texture by transmission electron microscopy (MET) and magnetic force microscopy (MFM). The proportion of NiF2 and Ni phases and the fluorination mechanisms change depending the fluorination temperature, then it appears possible to tune the stoichiometry of the material by the control of this parameter. Structural data obtained by XRD and PDF, but also TEM pictures, show first the progressive formation of a thin and continuous NiF2 shell until 250°C, the initial spherical shape is preserved but only a third of Ni can be converted into NiF2. Increasing the fluorination temperature leads to damages into the shell and affects the spherical shape. Finally, at the highest temperature, the total conversion of Ni into NiF2 can then be obtained and agglomerated NiF2 nanoparticles are obtained. The properties of such materials depend strongly of the Ni/NiF2 composition but also of its nanostructuration and the interfaces. So, in this presentation, we will present how the electronic, optical and magnetic properties can be adjusted by a judicious choice of the synthesis parameter set (among them the fluorination temperature) and we will underline the advantages of syntheses by gas-solid fluorination. Some applications as lithium batteries, magnetism will be discussed.

Resume : Titania (TiO2) nanoparticles can be applied as photo-catalyst, as a protection from UV irradiation in sunscreen, or as the hard component in hybrid materials. The reactivity of titania nanoparticles and the mechanical properties of hybrid materials is influenced by the particle shape to a large extend. During aqueous and non-aqueous synthesis the shape can be controlled adjusting the concentration of the different components in the solution, namely hydrohalic acids, carboxylic acids, and amines. Fluoric acid, for example, is known to stabilize platelet shaped particles, whereas amines stabilize a rod-like shape. From the theoretical point of view the stabilization mechanism of fluoride is well understood. The influence of amines, halides other than fluoride, and carboxylic acids on the particle shape, however, is less studied and not understood so far. Here, results from DFT calculations on the adsorption of these components at the dominant titania surfaces are presented. The space of possible adsorption configurations is sampled exhaustively to find the most stable structures. The nanoparticle shape at different thermodynamic conditions is predicted using the Wulff construction. For the hydrohalic and carboxylic acids theoretical and experimental particle shapes agree very well, but except for fluoride only bi-pyramidal particles are observed. On the other hand, the results for the amines show that the explanation of rod shaped particles is not that simple.

Resume : Solar and wind based energy supply will increase by more than one decade by the year 2040, which lays foundation for the hydrogen economy concept where hydrogen serves as an energy carrier. Hydrogen utilization requires, however, introduction of efficient, durable and economically feasible electrochemical conversion of electrical energy into hydrogen bond energy. Electrochemical water splitting can meet these expectations if its key components, electrocatalysts, can be improved. Today scarce platinum group metals (PGMs) are utilized to electrocatalyze the hydrogen evolution reaction. In addition to PGM availability and cost issues, these electrocatalysts suffer from inadequate durability because of the altering operation conditions. Single-walled carbon nanotubes (SWNTs) have several beneficial properties needed for electrochemical applications: high conductivity, good chemical and electrochemical durability and appropriate properties for fabricating 3D electrodes. Here, the unique morphology of SWNTs contributes to achieve material with ultra-low loadings Pt nanowires (PtNW). The high activity and excellent durability is attributed to favorable PtNW interaction with the SWNTs as well as exposed PtNW edge-sites which adsorb hydrogen optimally and help to alleviate repulsive interactions on the nanowire surface. In addition, the metallic nature of Pt, morphological effects and enhanced surface wetting contribute positively to the performance.

Resume : CuOx/CeO2 catalysts are active in the preferential CO oxidation (CO-PROX) and water gas shift (WGS) reactions. For the first we found that their selectivity to get CO2, not H2O, improves if CuOx lies on CeO2 nanocubes (NCs) exposing (001) faces, instead of lying on ceria nanospheres (NSs). DFT calculations show a stronger CuOx-CeO2 interaction on (001) faces, stabilizing Cu cations against reduction. This explains the better selectivity as Cu(0) is known to be the phase activating H2. Operando DRIFTS shows that if Cu lies on NCs Cu+ carbonyls remain to higher temperature than on NSs or nanorods (NRs), correlating with the high selectivity. Synchrotron XPS data show that heating in dry O2 spreads CuO on NCs (a wetting effect) but not on NSs. XAFS data in same conditions show, for samples with same Cu surface load, more distinct next-nearest neighbours around Cu on the NC sample, agreeing also with the stronger interaction predicted by DFT. Finally, NEXAFS data show that under CO the NC-supported sample resists reduction better than the NS-supported sample, agreeing with the DFT predictions. XPS data in these experiments show also for CuOx on NSs Cu(2p) peaks at unusual positions; DFT models suggest this may be due to Cu+ with higher O coordination at the CuOx-CeO2 interface. We started also studies on CeO2 shape effects in Ni/CeO2 catalysts used in ethanol steam reforming, observing again differences in selectivity towards several products depending on the nanoceria particle shape.

Resume : Nanoparticles of Au supported on TiO2 have various applications in photocatalysis, plasmonics and photovoltaics. These supported materials are commonly synthesized using liquid-based techniques such as sol-gel and deposition-precipitation. These methods, while being low-cost, result in a high level of impurities and formation of Au particles with inhomogeneous size and composition. Here we present a vapor-based approach via atomic layer deposition (ALD) for controlled deposition of Au nanoparticles on TiO2. We also use the designed structures for photocatalytic degradation of pollutants. We perform a low temperature thermal ALD process using Trimethylphosphino-trimethylgold (III) and two oxidizers (ozone and water) in a fluidized bed reactor under atmospheric pressure condition. We show the effects of Au precursor saturation and oxidizing reactants on controlling the nucleation, particle size distribution and composition of the Au nanoparticles. We also investigated the effects of Au loading and particle size on the photocatalytic activity of Au/TiO2 nanoparticles. Our studies suggest that the oxidizers have an opposite effect on Au particle size distribution. A threefold enhancement in the photocatalytic activity of TiO2 is achieved when Au/TiO2 nanoparticles are used for degrading pollutants. This all vapor process provides a highly controlled and efficient method for producing Au/TiO2 particulates that meet the criteria for various applications.

Resume : Silver nanoparticles (AgNPs) have been attracting an increasing interest in the development of electrochemical sensors due to their high electrical conductivity and ability to the enhance the electron transfer between the sensor and the electrode. In this work we present a novel ionically-imprinted thin sensor film based on tannic acid, TA, and Ag NPs, which was tailor-designed for voltammetric tracing of aluminum ions, Al(III), in biological fluid. In the first stage, AgNPs were presynthesized via direct reduction of Ag(I) by TA resulting in tannic acid-stabilized AgNPs of size ranging between 2 and 10 nm, as observed by dynamic light scattering and transmission electron microscopy. In the following step, the Al(III) ions were added to the mixture to complex the TA molecules adsorbed on AgNPs and an anodic potential was applied to self-assemble the (TA@AgNPs) ? Al (III) complexes into a thin film on the surface of ITO electrode. The Al(III) ions imprinted on the surface of the film, were then chemically removed from the film, as monitored by cyclic voltammetry and X-ray photoelectron spectroscopy, creating vacancies ready to bind the Al(III) ions present in the analyzed fluid. The obtained film was employed for sensing of Al3 present in bovine serum. A correlation between the current value of TA-Al(III) CV peak and the concentration of Al(III) in the range corresponding to aluminum levels for a healthy individual, from 0 to 6 µg/L, was obtained. Incorporation of AgNPs resulted in an improved sensitivity of the film by three orders in magnitude in the measured Al(III) concentration.

Resume : The deposition of transition-metal nanoparticles on various oxide materials is a topic of interest due to its optical, plasmonic, and catalytical properties. The size and distribution density influence these properties. Thus, it is important to be able to form metal clusters of desired characteristics. In this work, magnetron sputtering technique is suggested to use due to the ability to control deposition parameters easily. TiO2 thin films of 200 nm thickness were deposited on room temperature (20 ºC) SiO2 substrates from two Ti targets using reactive magnetron sputtering technique. Subsequently, thin films (5 nm and 10 nm) of copper, magnesium, and nickel were formed on TiO2 thin films and Si substrates in Ar environment using the magnetron sputtering method. After deposition, metal/TiO2 thin films and metal/Si were annealed at 300 ºC, 350 ºC, 400 ºC, 450 ºC, and 500 ºC temperatures in N2 atmosphere for 1.5 h to form nanoclusters. The distribution of nanoclusters was investigated by scanning electron microscope. Different distribution of nanoclusters was observed depending on substrate type, annealing temperature, and thickness of the metal thin film. The higher density of metal nanoclusters was obtained on Si substrates due to the lower surface energy of Si in comparison to TiO2 thin films. Funding: This project has received funding from European Social Fund (project No 09.3.3-LMT-K-712-01-0162) under grant agreement with the Research Council of Lithuania (LMTLT).

Resume : ZnO nanoparticles were synthesized using sol-gel method. The influence of the annealing temperature on the structural, morphological and optical properties of ZnO nanoparticles is studied. The properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), Uv-Vis spectroscopy and EDS. XRD analysis demonstrates that the crystallinity of ZnO is improved with annealing for all growth temperatures selected (45, 55 and 65 °C) as indicated by narrower and more intensified diffraction intensities of the annealed ZnO compared to that of the as prepared particles. The average crystallite sizes of the ZnO particles increased from 29.9 nm to 33.3 nm with annealing indicating the tendency of large grain growth in the nanoparticles due to annealing. SEM micrographs showed that annealed ZnO nanoparticles aggregated and became larger in diameter compared to its as prepared counterparts. The EDS analyses, for as prepared and annealed samples indicate the purity of all the synthesized samples with no peaks other than Zn and O. The photoluminescence peak intensity ratios of ultraviolet to that of visible emission (UVPL/ VisPL) are found to increase on annealing. The UVPL/ VisPL intensities ratio range between 0.9-2.4 for the as prepared samples and 5.0-7.1 for annealed samples. Quenching of visible emission on annealing is known to be responsible for this. The red shift in both the visible and UV emission with increasing particle size due to annealing closely follows the red shift in the band edge emission, indicating that the two complement each other. The average band gap is observed to decrease from 3.25 eV to 3.22 eV with the increase in crystallite sizes occasioned by annealing. Keywords: ZnO; Nanoparticles; Sol-gel; Growth temperature, Structure, Luminescence

Resume : Zinc oxide has been shown to be suitable for many advanced applications such as water purification and solar cells. In this trend, different nanostructures of ZnO were prepared by intercalation of carbon nanotubes inside Zn-Al nanohybrid. This nanohybrid was formed through intercalation of long chain of fatty acid C18 H38 inside Zn-Al layered double hydroxides. X-ray diffraction of the interlayered spacing of Zn-Al LDH increased from 0.75 nm to 2.1 nm after intercalation with CNTs and the organic fatty acid forming CNTs-C18H38-Zn-Al nanohybrid. By treatment of the nanohybrid at high pressure and temperature, different sizes of the doped zinc oxides nanoparticles and zinc aluminum oxides nanocomposites were produced. The doped zinc oxides nanoparticles have symmetrical spherical shape with 10 nm in diameter. Zinc aluminum oxides nanocomposites have large particles with 100 nm in diameter. According to the nano size and structures, the band gap energy of these products changed from 1.8 eV to 3.2 eV to produce effective photocatalysts. Purification of water was achieved through complete decolorization and mineralization of the green pollutants from water after 176 min of irradiation of UV light using the doped zinc oxide. In case of using the nanocomposites, the green dye was completely removed after 355 min. Comparing with the results of the doped zinc oxide which prepared by usual method, these nanomaterials were very effective because water purification was achieved in a shorter time. Finally, the experimental results concluded that nanohybrids have positive impact to create effective nanoparticles for water purification using light. Biography: Adil is Chairman of Physics Department and Chairman of Mathematics and Statistics Department at King Faisal University in Saudi Arabia. Adil received his PhD in 2017 from University of Sheffield, UK from Department of Materials Science and Engineering. Adil's research is a blend of the Chemistry, Physics and Engineering of Inorganic Materials, especially oxides, which focuses on materials with interesting and/or useful electrical properties, especially ionic conductors, mixed ionic/electronic conductors, semiconductors, ferro- and di-electrics.

Resume : In order to optimize the dielectric performance of polymer derived SiCN ceramics (PDCs-SiCN), carbon nanowires (CNW) were deposited in SiCN by catalytic chemical vapor deposition. Microstructure evolutions, dielectric property and electromagnetic (EM) wave absorption capacity of CNW/SiCN were investigated. Results show that carbon nanowires had plentiful defects on their roughened surface and formed hierarchical network in SiCN which benefited the impedance match and generated strong conductivity and polarization loss, enhancing the absorption ability of CNW/SiCN. When CNW accounted for 5.61wt%, minimum reflection coefficient reached -51 dB with EAB of 3.0 GHz at 2.7 mm in thick, showing excellent microwave absorbing performance. The favorable microwave absorption ability could be ascribed to three aspects including enhanced conductivity loss derived from the excellent conductivity of CNW, polarization loss generated by defects, and multiple reflection loss enhanced by hierarchical network. By comparing the variation tendency between defect concentration and electrical conductivity in CNW/SiCN, it is rational to conclude that the conductivity loss dominated the dielectric loss while the polarization loss and repeated multi-reflection simultaneously worked. We have already proceeded to a study regarding the effect of heat-treatment temperature since CNW have the potential to promote the crystallization process of amorphous PDCs thereby improving their dielectric properties.

Resume : Phase composition, structure, morphology, and magnetic properties of La0.6Ag0.2Mn1.2O3-? nanopowder were investigated using XRD, SEM, TEM, and magnetic methods. Magnetic nanoparticles (MNPs) of La0.6Ag0.2Mn1.2O3-? were synthesized using a nitrate pyrolysis method. MNPs have a spherical shape and are single-phase with a rhombohedral R-3c type of perovskite structure distortion. The size distribution function of MNPs is LogNormal Distribution with an average MNP size < d> = 68 ± 2 nm. On the basis of the magnetic properties analysis, average magnetic moment of manganese ? = 4.61 ?B, Curie temperature ?? = 312 ?, saturation magnetization MS = 426.8 emu/cm3, effective anisotropy constant Keff = 7123 erg/cm3, magneto-crystalline anisotropy constant K1 = 2.522?104 erg/cm3 for each MNP, exchange constant A = 3.47?10-7 erg/cm were determined. It was concluded that La0.6Ag0.2Mn1.2O3-? refers to magnetically soft material with magnetic hardness parameter k = 0.022 < < 1. The critical sizes of single-domain state (d ? 40 nm), vortex state (40 ? d ? 67 nm), and multi-domain state (d ? 67 nm) were calculated. In the narrow temperature range ?TC = 4 K near TC, giant magnetocaloric effect was detected. The absence of coercivity above blocking temperature ?? = 301 ? and the large magnetocaloric effect in weak magnetic fields H = 200?500 Oe allow to use La0.6Ag0.2Mn1.2O3-? nanopowder in intelligent hyperthermia control systems with automatic temperature stabilization within 39?43 °? range.

Resume : Metal oxide such as ZnO and TiO2 are widely utilized in chemical sensors and photocatalysts for their redox properties related to the electron-hole pair on the metal oxide surface with analyte species. To enhance these properties, it is necessary to reduce the particle size and increase the active area. Cerium oxide is a good material for this purpose including catalysts, sensors, electrochemistry, batteries and energy storages. This study reports very efficient preparation of monodisperse cerium oxide nanorods through simple hydrothermal synthesis. Our synthetic route of cerium oxide nanorods is highly dependent on the reaction time and found to be 10 minutes for the optimum condition. The cerium oxide nanorods are further converted into nanospheres by the spontaneous assembly of cerium oxide nanoparticles onto nanorods. The TEM result shows that the nanorods are grown with high crystallinity in the < 110> direction. The cerium oxide nanorods show the growth process of the Ostwald ripening phenomenon. The cerium oxide nanorods prove to be very efficient electron mediators for use as excellent photocatalytic materials and highly sensitive chemical sensors. The chemical sensor fabricated on a carbon paper substrate shows a high sensitivity of 1.81 ?A mM-1 cm-2 and a detection limit of 6.4 ?M with a correlation coefficient of 0.950. As a result of comparing the selectivity of methanol and acetone as a chemical sensor, the selectivity of acetone is found to be very high.

Resume : Metal fluorides present many applications in sensors, batteries, actuators or optical devices. Many methods have been developed for synthesis of metal fluorides nanoparticles and their self-assembly. Among them, microemulsion method is exploited for the preparations of metal fluoride nanostructures, like self-assembled YF3 nanoparticles or BaF2 nanoparticles. Here our attention is paid to the synthesis of MnF2/MnF3 and NiF2 nanoparticles. These materials are attracting attention as conversion reaction material for Li ion batteries due to their specific capacities (554 mAh/g for NiF2 and 577 mAh/g for MnF2), and the electrochemical performance of these nanomaterials could be improved by engineering self-assemblies. In addition, the magnetic properties are also interesting, and could be modified by nanostructuration. In this talk, we present the synthesis of hydrated fluoride nanoparticles which self assembles into truncated bipyramidal structures by reverse microemulsion. The self-assemblies of nanoparticles into theses architectures are controlled by varying the reaction time and water to surfactant ratios. Few examples of nanostructuration of MnF2 and NiF2 are given in the literature. An important drawback is the formation of hydrated compounds, and the dehydration of the resulting nanomaterials remains difficult. Here, we come up with a new strategy to synthesize anhydrous fluoride nanoparticles and their self-assemblies. Hydrated materials are transformed to dehydrated ones under F2 and the self-assemblies of nanoparticles are successfully retained. The Electrochemical and magnetic properties of resulting nanomaterials have been studied.

Resume : We investigate the influence of carbon nanotubes (CNT) aligned array on the magnetic properties of ensemble of densely packed Co nanoparticles (NPs) embedded inside CNT. Each CNT contains only one nanosized Co. Such a special structure was formed by catalyst chemical vapor deposition (CCVD) activated by current discharge plasma and hot filament. The Co NPs, previously deposited onto SiO2/Si substrate, acted as a catalyst. By varying the parameters of the CCVD process, we were able to also sputter the substrate instead of CNT growth. Co NPs were used as a mask and the structure of Si-based nanocones with Co NPs on the top of each cone was formed. Exhaustive investigation of the structural, morphology and crystalline properties of Co nanoparticles were performed. The magnetic properties of two kinds of samples, Co on the Si-based nanocones and Co inside CNTs, differ drastically. In the former case, the magnetic anisotropy of thin-film-type has been observed with large magnetic domains. Whereas for the Co-CNT samples ferromagnetic NPs were magnetically isolated. It was established that the magnetic anisotropy of nanosized Co plays more dominant role than the dipole interaction between Co NPs (1). The role of the CNT container in this is investigated. (1) ?Impact of aligned CNT nanotubes array on the magnetostatic isolation of closely packed ferromagnetic nanoparticles.? Danilyuk A.L., Kukharev A.V., Cojocaru C.S., Le Normand F., Prischepa S.L Carbon, 139 (2018) 1104-1116 with SI

Resume : The present study investigated the influence of microstructures on the electrochemical response of Cu-Ni alloys in Sodium Chloride solution. The Cu-Ni alloy thin films were fabricated on silicon substrates by magnetron sputtering. The X-ray diffraction (XRD) analysis and surface characterization with a scanning electron microscope (SEM) revealed that microstructures including preferred orientation of the [111] direction along the surface normal and mean crystallite size were influenced from the deposition pressure and the sputtering power. The electrochemical behaviors of these deposited films were examined by potentiodynamic polarization in 3.5 wt.% Sodium Chloride solution. Potentiodynamic polarization plots demonstrated that the corrosion current densities of deposited films were found to be related to microstructures. It could be explained by the compact morphology of the Cu-Ni alloy thin films affecting the dissolution rate, the access of corrosive species to the film and the passive layers formation on deposited films. This phenomenon which is in the context of microstructures and electrochemical behaviors of metallic alloy of Cu-Ni in chloride media indicates several interesting and fundamental relationships.

Resume : Cu2+, which is readily absorbed in the human body from nature, is essential for human life and health, whereas it can cause neurotoxicity known as Wilson?s disease at higher concentrations. Therefore, the development of convenient detection and removal methods is of importance to monitor and maintain Cu2+ concentrations in environmental waters at lower than limited levels. Recently, we demonstrated that Cu2+ ions are readily adsorbed at the surface of GdVO4:Eu nanoparticles (NPs) in aqueous media and that (trace amounts of) Cu2+ can filter the emitted light to quench the fluorescence of GdVO4:Eu. Because such a filter effect can effectively occur only if the absorption band of the metal ion is complementarily overlapped with the emission bands of GdVO4:Eu, highly selective and sensitive fluorescence quenching can be achieved by the Cu2+ ion adsorption. To improve the efficiency and convenience of Cu2+ removal from environmental waters, a tailoring technique has been developed to construct a recyclable film covered with YVO4:Eu NPs. Thus, the film of Eu3+-doped layered yttrium hydroxide (LYH:Eu) nanosheets was directly grown on the slide glass substrate using the chemical bath deposition technique, where LYH:Eu sheets are preferably oriented perpendicular to the substrate surface. The as-prepared films have the microscale hierarchical surfaces composed of LYH sheets. YVO4:Eu nanoparticles were then tailored at the edge of LYH:Eu nanosheet in an aqueous Na3VO4 solution. This tailoring method can immobilize NPs to keep from aggregating. The luminescence quenching of YVO4:Eu NPs by the filter effect of adsorbed Cu2+ ions was useful for the luminescent ?turn-off? adsorbent film for Cu2+ ions. The tailor-made films in the present work exhibited a high performance and satisfactory practicability and recyclability for detecting and removing Cu2+ ions.

Resume : Polymer gel containing magnetic particles is a stimuli-responsive gel that viscoelastic properties can be controlled by applying magnetic fields. We have fabricated magnetoelastic soft materials with various polymer matrices thus far, and succeeded to fabricate a magnetic hydrogel that demonstrates drastic and reversible changes in dynamic modulus without using strong magnetic fields. The magnetic hydrogel exhibits drastic changes in storage modulus even at high modulus. At zero magnetic field, the storage modulus for magnetic gel is low with an order of ~104 Pa although the gel contains large amount of particles (volume fraction ~0.30), indicating the random dispersion of magnetic particles. Magnetic particles align to the magnetic lines of force and form a chain structure under magnetic fields, resulting in high storage modulus exceeding 4 MPa. In this paper, we present the magnetic response of storage modulus, morphological changes by magnetic fields, and the interaction between carrageenan and magnetic particles. The origin of significant magnetorheological effect for carrageenan magnetic gels is discussed.

Resume : Nitrogen dioxide (NO2) is a gas species that play a vital role in particular industrial, farming, and healthcare sectors. However, there are still significant challenges for NO2 sensing at low detection limits, especially in the presence of other interfering gases. The NO2 selectivity of current gas-sensing technologies is significantly traded-off with their sensitivity and reversibility as well as fabrication and operating costs [1-5]. In this work, we present essential progress for selective and reversible NO2 sensing by demonstrating an economic sensing platform based on the charge transfer between physisorbed NO2 gas molecules and two-dimensional (2D) tin sulfide (SnS) flakes at room temperature. An extraordinary response factor of ~36 is demonstrated to ultralow 150 parts per billion (ppb) NO2 at room temperature, within the physisorption temperature bands for SnS. The device shows high sensitivity and superior selectivity to NO2 at operating temperatures of less than 140o C, which are well below those of chemisorptive and ion conductive NO2 sensors with much more low selectivity [5-8]. The demonstrated 2D SnS based sensing device holds the most significant potential for producing future commercial low-cost, sensitive, and selective NO2 gas sensors.

Resume : Anisotropic synthesis of two-dimensional (2D) monocrystalline Au flakes attracts significant interest due to its importance toward the future development of optical nanocircuitry for high-speed communication and quantum computation applications. In this study, 2D Au microplates were synthesized by seedless aniline assisted polyol reduction with anisotropic control of the polyaniline oxidation states (PAOS) that form in-situ. Three different PAOS were identified by a novel algorithm based on subtraction deconvolution of UV-vis spectra: A (372 nm), B (680 nm), and C (530 nm). Time-dependent UV-Vis Spectra and SEM images of Au nanostructures showed that PAOS controls the 2D flake shape, size, and crystallization parameters. Different growth regimes associated with relevant growth mechanism (protonation, deprotonation and thermal decomposition) were resolved. Specifically, we found that state A is responsible for the nucleation of gold from the AuCl4- solution (region i), state B is responsible for the aggregation of the nucleation sites (region ii), and state C is responsible for the 2D shape of the microplate and for the control of Au monocrystalline flake growth (region iii). We used a time-resolved deconvolution model for the solution-growth of nanomaterials, which accurately describes the charge transitions (intra and inter transitions) and growth regimes by effective permittivity parameter in solutions. In terms of the development of a basic understanding of PAOS, deconvolution, and Au flake formation, our approach and our promising results provide inspiration for anisotropic investigations of other metals and their syntheses with desired properties and monocrystallinity for optoelectronic applications.

Resume : Induced pluripotent stem cells (iPSCs) are typically derived by reprogramming factors, eg. Oct4, Sox2, cMyc and Klf4. However, the genomic integration of the transcription factors may have the risk of mutations being inserted into the target cell?s genome. Recently, clustered regularly interspaced short palindromic repeats associated protein 9 (CRISPR/Cas9) system has been employed to edit genomes. In this work, the molecular imprinting of peptide on chitosan is optimized with various imprinting template or chitosan concentrations. These magnetic peptide-imprinted chitosan nanoparticles (MPIC NPs) are then characterized by dynamic light scattering (DLS), high performance liquid chromatography (HPLC), Brunauer-Emmett-Teller (BET) and superconducting quantum interference device (SQUID) analysis. Finally, mutated clustered regularly interspaced short palindromic repeats associated protein 9 (CRISPR/dCas9) without endonuclease activity is produced by the transfection of plasmid to HEK293T cells. The adsorption of dCas9 protein are monitored by both total protein kits and Cas9 staining. These MPIC NPs are employed to deliver the dCas9 nuclease complexed with a synthetic guide RNA (gRNA) into HEK293T cells to activate their Oct4 gene expression, which are examined by quantitative real-time polymerase chain reaction (qRT-PCR) and staining of Oct4 and Cas9. ACKNOWLEDGEMENTS: We appreciate financial supports from Ministry of Science and Technology of ROC under Contract nos. MOST 106-2221-E-390 -013 -MY3, MOST 106-2314-B-390 -001 -MY2 and MOST 107-2923-M-390 -001 -MY3. REFERENCES: 1. M.-H. Lee, C.-C. Leu, C.-C. Lin, Y.-F. Tseng, H.-Y. Lin* and C.-N. Yang*, Gold-decorated magnetic nanoparticles modified with hairpin-shaped DNA for fluorometric discrimination of single-base mismatch DNA, Microchimica Acta, 186:80 (2019) 2. M.-H. Lee, J. L. Thomas, C.-L. Liao, S. Jurcevic, T. Crnogorac-Jurcevic and H.-Y. Lin*, Epitope Recognition of Peptide-imprinted Polymers for Regenerating Protein 1 (REG1), Separation and Purification Technology, 192, 213-219 (2018) 3. M.-H. Lee, J. L. Thomas, J.-Z. Chen, J.-S. Jan and H.-Y. Lin*, Activation of Tumor Suppressor p53 Gene Expression by Magnetic Thymine-imprinted Chitosan Nanoparticles, Chemical Communications, 52, 2137-2140 (2016) 4. M.-H. Lee, J. L. Thomas, Y.-C. Chen, H.-Y. Wang and H.-Y. Lin*, Hydrolysis of Magnetic Amylase-imprinted Poly(ethylene-co-vinyl alcohol) Composite Nanoparticles, ACS Applied Materials & Interfaces, 4, 916-921 (2012) 5. M.-H. Lee, J. L. Thomas, M.-H. Ho, C. Yuan and H.-Y. Lin*, Synthesis of Magnetic Molecularly Imprinted Poly(ethylene-co-vinyl alcohol) Nanoparticles and Their Uses in the Extraction and Sensing of Target Molecules in Urine, ACS Applied Materials & Interfaces, 2, 1729-1736 (2010)

Resume : Over the last years, luminescence thermometry has emerged as an exciting field of research due to its potential in nanotechnology, biomedicine, photonics and microelectronic applications [1]. We present a simple approach to obtain a luminescence nanothermometer operating in the near infrared (NIR) range (1000-1700 nm) by use of binary mixtures, Ho - Y2O3 + Er - Y2O3 and Ho - Y2O3 + Nd - Y2O3 nanoparticles [2]. The thermometry properties were assessed in terms of emission shape, intensity, excitation wavelength, dynamics, acquisition mode and weight ratio of the binary mixture [3]. The temperature evolution of the emission shape was monitored in the range of 297 - 472?K. For the binary mixture of Ho - Y2O3 + Er - Y2O3 with 3: 1 weight ratio, the maximum relative sensitivity was of 1%K-1 under 536.8 nm excitation [2]. Further, to extend the excitation wavelength from visible range to the first biological window, we assessed the Er, Ho, Yb codoped Y2O3 nanoparticles. For this system, under 905 nm excitation, a maximum relative sensitivity of 1.4-1.5 % K-1 was obtained, among the best values obtained to date for lanthanide based near infrared luminescent thermometers. References: [1] L. Carlos, F. Palacio, Thermometry at the nanoscale: techniques and selected applications, Thermometry Nanoscale Tech. Sel. Appl. 38, 2016, 124-166 [2] D. Avram, C. Colbea, M. Florea, C. Tiseanu, Highly-sensitive near infrared luminescent nanothermometers based on binary mixture. Journal of Alloys and Compounds, 785, 2019, 250-259. [3] D. Avram, C. Tiseanu, Thermometry properties of Er, Yb?Gd2O2S microparticles: dependence on the excitation mode (cw versus pulsed excitation) and excitation wavelength (980 nm versus 1500 nm). Methods and applications in fluorescence, 6(2), 2018, 025004.

Resume : The abnormal accumulation of ?-amyloid (A?) peptide aggregates in the brain is a hallmark of Alzheimer?s disease (AD). Because the self-assembled A? aggregates cause the cell death and brain atrophy by interfering with neuronal communications, numerous efforts to suppress A? aggregation and attenuate A?-induced toxicity have been progressed. Here, we developed novel A? nanosponges that consist of anti-A? single chain variable fragments (scFv) and ultra-large porous silica nanostructures for targeting and eliminating aggregative A? monomers. The presence of the A? nanosponges exhibits notable declines of the A? peptide aggregate through the scFv?s binding affinity to A? peptides. The biocompatible A? nanosponges show the significant enhanced cell viability and mitigation on A? neurotoxicity. After an intracerebral direct injection of A? nanosponges into an AD mouse brain, the brain slices show apparent suppression on A? plaque formations in comparison with the non-treated region. As a result, the A? nanosponges having remarkable therapeutic potentials for A? clearance in vitro and in vivo, are attractive candidates for AD treatments.

Resume : We have prepared various all-organic magnetic soft materials containing a cyclic nitroxide radical moiety as a spin source [1]. In this talk, we report the preparation of all-organic magnetic nanoemulsions composed of the non-ionic surfactant and the hydrophobic nitroxide radical compound [2]. The properties of the nanoemulsions have been investigated by small angle neutron scattering (SANS) and dynamic light scattering (DLS) analyses, EPR spectroscopy, and MRI method. The nanoemulsions showed high colloidal stability, high reduction resistance to ascorbic acid, low cytotoxicity and an enough contrast enhancement in the proton longitudinal relaxation time (T1)-weighted MR images in (-)-PBS in vitro and in vivo. Furthermore, an additional hydrophobic anticancer drug such as Taxol® was simultaneously encapsulated inside the nanoemulsions. We expect that the drug-loaded nanoemulsions can be used as a biocompatible magnetic drug carrier for MRI-visible targeted delivery system. [1] a) Uchida, Y.et al. J. Mater. Chem. 2009, 19, 6877; b) Uchida, Y. et al. J. Am. Chem. Soc. 2010, 132, 9746; c) Takemoto, Y. et al. Soft Matter 2015, 11, 5563 [2] K. Nagura, N. Komatsu, R. Tamura, et al., Chem. Eur. J., 23, 15713 (2017); K. Nagura, N. Komatsu, R. Tamura, et al., Nanotechnology, 30, 224002 (2019); K. Nagura, N. Komatsu, R. Tamura, et al., Pharmaceutics, 11, 42 (2019).

Resume : The electrochemical metallization of non-conductors, including plastics, elastomers, and glass is one of the key processes in electronics and automotive applications. Electroless plating on non-conductors is a chemically complex process and different processing steps are needed for each substrate. However, etching solution and a catalyst such as palladium are commonly used for good adhesion of the metallic layer to the substrate and initiating the electroless plating on non-conductive surfaces. In this work, we report the experimental studies on electroless plating of non-conductors such as silicone rubber, glass and PET films using silica sol-gel catalyst without etching process to reduce environmental pollutant. The results show that silica sol-gel coating layers containing palladium effectively catalyze electroless nickel plating on various substrates and the nickel deposits remained without failure after tape tests.

Resume : Complex hydrides (e.g. LiBH4) are suggested as solid-state electrolytes. LiBH4 shows different polymorphs, the stable phase at room temperature (RT) is orthorhombic and has a low ionic conductivity. However, the hexagonal phase, which is stable at temperatures above 110 °C, has a remarkable high ionic conductivity (~10-3 Scm-1 at 120 °C). A promising approach to enhance the Li-ion conductivity of LiBH4 at RT is the development of new interfaces by ball milling it with oxide nanoparticles. In this work, the effect of adding oxide nanoparticles to LiBH4 by ball milling, on the Li-ion conductivity has been investigated by Electrochemical Impedance Spectroscopy. Firstly, the effect of the mixture composition on Li-ion conductivity in the LiBH4-SiO2 system was analysed. Li-ion conductivity was enhanced for all the composite conductors. The sample containing 20 v/v% of SiO2 showed the highest conductivity (2.2 × 10^-5 S/cm at RT, about tree orders of magnitude higher than LiBH4), and the lowest activation energy. A clear effect of the SiO2 volume fraction was observed, and a tentative explanation for this dependence will be discussed. Different oxides, i.e. CaO, MgO, ZrO2 and TiO2 and Al2O3, were tested and all increased the Li-ion conductivity of the LiBH4 at room temperature, achieving the highest conductivities for the samples containing ZrO2 and MgO (1.3 × 10^-4 S/cm and 1.0 × 10^-4 S/cm, respectively). The reason for the influence of the nature of the oxide is the topic of ongoing investigation. We illustrate that the addition of oxide nanoparticles to LiBH4 offers promising candidates for Li-based solid state electrolytes.

Resume : Gas sensor devices that operate at room temperature (RT) and detect toxic gases are currently more focused in wearable electronics for monitoring the environmental pollution and human health. In this regards, graphene and its derivatives are promising material possessing the prerequisite properties necessary to design advanced sensor devices. Therefore, the present study reports on continuous, strong and flexible graphene oxide (GO) fibers composed of oriented GO sheets that were synthesized by transforming a prealigned liquid crystalline GO solution using a simple wet-spinning assembly. GO fibers were chemically reduced (rGO) for gas sensing. Further, Nitrogen-doped (NrGO) and ZnO-incorporated rGO (ZrGO) fibers were achieved by hydrothermal assisted chemical reduction of GO fibers. A combinatorial ZnO nanoparticles and flower morphology was achieved on the surface of ZrGO fibers. This kind of mixed morphology not only provided more surface-area but also render more catalytic active sites for quicker interactions of the gas molecules, thereby enhancing the gas sensing performance as compared to rGO and NrGO fibers. The fiber sensors were able to detect minimum levels of 1.5 and 8 ppm of NO2 and H2S gas, respectively. Interestingly, the sensing performance of the ZrGO sensor was higher by 8 and 24 fold for NO2 and H2S, respectively, compared to rGO. The sensors exhibited characteristic response patterns for NO2 and H2S, showing excellent selectivity. This work opens a new way for the application of flexible, wearable, robust, lightweight, cheap, and room temperature chemical sensors, that can detect hazardous gases.

Resume : Biofilms are multicellular microbial communities which can develop on any surface, tissue or interface and present a real ecological, industrial and medical challenge. Clinical biofilms are up to 3000 times more resistant to antimicrobial drugs as free-floating bacteria and represent a high risk for patients with implantable devices. The purpose of this study was to develop and characterize the antimicrobial potential of essential oils functionalized silver (Ag)-based core-shell nanoparticles (NPs) and nanocoatings. A Gram positive (Staphylococcus aureus) and a Gram negative (Pseudomonas aeruginosa) monospecific clinical biofilm model was used. AgNPs were functionalized with Eugenia caryophyllata, Eucalyptus globulus and Cinnamomum verum essential oils and thin coatings were obtained by matrix assisted pulsed laser evaporation (MAPLE) technique. Antimicrobial impact of the NPs was established by minimum inhibitory concentration (MIC) assay and antibiofilm activity by a microdilution crystal violet adapted method and viable count. Results revealed that the obtained NPs have low MICs and are highly efficient in both S. aureus and P.aeruginosa planctonic cultures. Regarding biofilms, these nanoparticles have the ability to inhibit biofilms formation when used at MIC/2 doses, but also to inhibit pre-formed biofilms in a microbial strain and NP type dependent manner. E. caryophyllata functionalized AgNPs proved the most significant antibiofilm effect, this being correlated with the significant inhibition of biofilm formation of this nanosystem also on the MAPLE ? obtained thin coating. The antibiofilm effect of the prepared nanocoatings is mantained for at least 72h. This study demonstrates that core-shell NPs containing essential oils represent an efficient and ecological strategy to fight biofilms and these nanosystems may be used to prepare bioactive coatings to avoid device-related infections.

Resume : Semiconductor nanomaterials can also be used in degrading organic pollutants that cause environmental hazard. Photocatalysis is effective in degrading numerous organic substances. Silicon (Si) nanostructures appear to be potentially remarkable photocatalysts and degradation agents because of their extremely large surface areas and small energy gaps, which enable large optical absorption. Fabrication of large area Si nanostructures supported on bulk crystalline silicon for photo-catalytic application utilizing low cost upgraded metallurgical grade Si wafer. Photo-catalytic degradation of organic effluents (dyes) from textile industry is systematically investigated using the Si nanostructures. The reusability of Si based photo-catalyst and methods to increase its recycling lifetime are studied. In this study, porous silicon is formed my electrochemical etching and we use the surface of the porous Silicon as a degrading agent of an organic dye, methylene blue under direct sunlight. This approach represents a simple, low-cost, environmental friendly method for decomposition of organic pollutants. The SEM image revels the structure of formed porous silicon and from the absorption spectra we can infer the degradation of methylene blue is fivefold form the initial position (it decrease from 1.0 to 0.2). The (C0 ? C)/C gives the removal ratio/time/ removal ratio plot gives the significance of the dye degradation.

Resume : Fundamental understanding and precise control of complex nonradiative processes in the nanoscale system find significant interest in recent times due to their importance in various nanophotonics applications. Here we have systematically investigated the mechanism behind photoluminescence (PL) quenching of mercaptosuccinic acid (MSA) capped CdTe QDs in the near field of gold and silver nanoparticles (Au and Ag NPs) by using steady-state and time-resolved photoluminescence (PL) spectroscopy. Resonance coupling between excitonic emission and localized surface plasmon resonance (LSPR) of Au NPs has been tuned by varying the size of QDs. Herein, three differently sized MSA-capped CdTe QDs have been synthesized namely, 2.1 ± 0.7, 3.1 ± 0.4, and 3.9 ± 0.3 nm with emission in green, yellow and red region of the electromagnetic spectrum, respectively. It has been observed that both the luminescence intensity and lifetime of green QDs quench significantly in the near field of 20 nm sized Au NPs. In contrast, the luminescent intensity and lifetime of yellow and red QDs remain unaltered in the presence of Au NPs. Moreover, it has been observed that ligand exchange at the surface of Au NPs with Poly(ethylene glycol) methyl ether thiol (PEG-SH) decreases the quenching efficiency of the green QD-Au NP pair significantly. In addition, the extent of quenching strongly depends on the excitation wavelength. The observed quenching is more efficient at the excitation wavelength close to the LSPR of Au NP. These results have been explained on the basis of a size-dependent nanometal surface energy transfer (NSET) model by incorporating the changes in the complex dielectric function and the absorptivity of the Au NP. On the contrary, irrespective of the sizes of QDs, significant PL quenching has been observed in the presence of 10 nm sized citrate-capped Ag NPs as a consequence of photoinduced electron transfer (PET). The present findings of size and wavelength-dependent long-range nonradiative electromagnetic coupling in hybrid QD-metal NP system can be useful to understand and optimize the performance of various nanophotonic devices.

Resume : Multiple valence oxides, containing rare earth elements, remained of permanent interest in the last years, especially for their capacity to form diverse structures with various compositions showing a wide variety of compositional elemental ratios for each particular type processed under correctly selected sintering conditions. The control of these compositions led to a large number of applications and an enormous body of research, as promoting the composition and peculiar structures as key factors to be tailored to produce precisely the desired properties [1-4]. Our goal was to tailor (based on prediction and reasoning) new materials with perovskite structure based on rare earth by a non-conventional and very modern processing route. An element of originality was that, for the first time were used molecular crystals as precursors for obtaining the REFeO3 , with (RE= Tb, Gd, Ho, Dy) perovskite structures. All morpho-structural and properties investigations were performed compared to similar compounds obtained by classical method (solid state synthesis). A significant improvement in nanoparticles size was observed, decreasing from about 300 nm (classical processing) to about 30-40 nm (molecular crystal precursors). Mossbauer spectra analysis revealed that all investigated samples were magnetically ordered at room temperature.Isomeric shift (IS) values are approximately the same and correspond to Fe3 ions in high spin state. The analysis of hysteresis curves specific to the 4 compounds shows the presence of an antiferromagnetic behavior at low temperatures, which is also maintained at room temperature. These behaviors have been interpreted in terms of a strong magnetic couplings between the two sublattices of the Fe / RE ions. Bibliography 1. Aharony, A. and E. Pytte, 1983, Phys. Rev. 27, 5872. Ali N., M. P., Hill, S. Labroo, and J. E. Greedan, 1989, J.Solid State Chem. 83, 178. 2. Matsuhira, K., C. Sekine, C. Paulsen, and Y. Hinatsu, 2004, J. Magn. Magn. Matter. 272, E981. 3. Gozar A, Logvenov G, Kourkoutis LF, Bollinger AT, Giannuzzi LA, et al. 2008. Nature 455:782?85. 4. Pinna, N., Niederberger, M.: Angew. Chem. Int. Ed. 47, 5292?5304 (2008).

Resume : The investigation of lattice-strain effects in nanoparticles (NPs) is fundamental for the materialization of NP-based nanotechnologies. In the present work, we conduct a comprehensive investigation of lattice strain in crystalline Si NPs, which appears upon oxidation under ambient conditions. Si NPs are currently attracting much interest due to the unique chemical and physical properties of Si at the nanoscale and the environmental inertness, biocompatibility, and high abundance of the silicon element. From monitoring the time evolution of surface oxidation with Raman and infrared spectroscopies, we find a clear correlation between the formation of the surface oxide and appearance of compressive strain in the crystalline core of the Si NPs. This surface-dependent lattice strain increases continuously as the oxidation progresses. By comparing experimental variations of the Raman spectra with theoretical predictions using an improved phonon confinement model [1], we infer that strain is negligible in H-terminated Si NPs with sizes of ~3 nm and that after long-term oxidation the compressive stress induced by the oxide shell is estimated to be 1.2 GPa. These findings link the time-dependent oxidation phenomenon with the experimental observation of compressive strain in Si NPs, clarifying contradicting results found in the literature, and demonstrate a simple route for the deconvolution of confinement and strain effects in low-dimensional structures using Raman spectroscopy. [1] B. Falcão et al., Phys. Rev. B 98, 195406 (2018)

Resume : Nanoparticle-modified structures are common to provide important functionalities for many industrial applications. Under subzero conditions, it is critical to inhibit and delay the interaction between solid objects and ice. Superhydrophobic structures (SHS), including lotus and petal surfaces, are considered potential materials due to the water repellency. Here, hydrophobic silica nanoparticle-modified polyvinylidene fluoride coatings were prepared with tunable wettability. The icephobic performance was evaluated fully with several observation techniques at -10?C. Results show that the icephobic performance of nanoparticle-modified coatings lowers with increasing hydrophobicity. The ice adhesion strength is controlled by mechanical interlocking in the textures and stress concentrator induced by air cushions. The stress concentrator used to reduce ice adhesion is better on the lotus surface than on the petal surface. The lotus and petal surfaces lose their superhydrophobicity in a condensation environment, being less useful for anti-icing due to poor humidity tolerance. Apart from the SHS with excessive mechanical interlocking, the ice adhesion values of all other modified coatings are linearly related to the contact angle hysteresis. Smooth hydrophobic surfaces were found to be better icephobic materials compared to rough surfaces. The intrinsic surface energy of smooth surfaces is significantly linear with the ice adhesion. High freezing delay times were found for smooth low-density polyethylene resin and fluorinated surfaces.

Resume : The properties of nanoparticles (NPs) functionalized with organic molecules are determined by the interaction between the individual NP surface and the molecules. This interaction is complex and represents a considerable characterization challenge. The elucidation of the mechanisms of quenching or enhancement of particular excited states of molecules in functionalized NPs, including plasmon-supporting NPs, ideally requires a combined energy and spatial resolution to resolve all: the fine structure spectra of electronic excitations, surface plasmons and the local structural and chemical variations at the molecular level. STEM is able to provide sub-angstrom spatial resolution using Cs-correction, local chemical identification, if using microscopes equipped with electron energy loss spectrometers or information on chemical bonds, bandgaps and vibrational states if using a new generation of monochromated scopes (less than 20 meV).[1, 2] The high sensitivity of solid organic molecules to ionizing radiation presents a severe practical limitation. In this contribution, I will discuss electron microcopy methods for the study of metal - organic molecule interactions in nanoparticles. These tools can aid the design of NP-based materials for better biodistribution, higher optical yields at relevant wavelengths, sensing selectivity or selective radiosensitizing effects. References: [1] Krivanek, O. L.; Lovejoy, T. C.; Dellby, N.; Aoki, T.; Carpenter, R.; Rez, P.; Soignard, E.; Zhu, J.; Batson, P. E.; Lagos, M. J. Nature 2014, 514, (7521), 209. [2] Krivanek, O. L.; Ursin, J. P.; Bacon, N. J.; Corbin, G. J.; Dellby, N.; Hrncirik, P.; Murfitt, M. F.; Own, C. S.; Szilagyi, Z. S. Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 2009, 367, (1903), 3683-3697.

Resume : The implementation of nanostructured metal oxides and hydroxides into functional and catalytic materials requires knowledge about their growth and stability in changing chemical environments. Tailored metal oxide particle systems with interface properties which are accessible to experimental methods are indispensable model systems in this regard.[1] This presentation deals with examples where structure-property relationships have between established for metal oxide nanocrystals and their transformation behaviour in different water containing environments.[2,3] Particle interface functionalization processes via the gas- or the liquid phase will be compared. Moreover, we learned that adsorbed water originating from the storage of Magnesium oxide nanoparticle powders in air gives rise to significant particle morphology changes at elevated processing temperatures. Under such conditions, protrusions form on (100) terraces in parallel to the formation of step edges and vicinal surfaces which, at lower magnifications, give rise to the appearance of rounded grains which are made up from cubic building blocks. Related local structures can accommodate important new functionalities which are beneficial for sintering and microstructure evolution, on the one hand, or related to catalytic activity, on the other. [1] T. Berger and O. Diwald, ?Defects in Metal Oxide Nanoparticle Powders?, in Defects at Oxide Surfaces, ed. J. Jupille and G. Thornton, Springer International Publishing, ISBN: 978-3-319-14366-8, 2015. [2] G.R. Bourret and O. Diwald, J. Mater. Res. 34, 428-441, 2019. [3] D. Thomele et al. Angew. Chem. Int. Ed. 56, 1407-1410, 2017.

Resume : Titanium dioxide is one of the most commonly used metal oxides in gas sensors both reducing and oxidizing gases. The presence of water molecules is an important factor affecting the electrical properties of TiO2 [1]. Even a small change in relative humidity can cause a significant change in the conductivity of TiO2. 1H-Nuclear Magnetic Resonance (1H-NMR) allows one to investigate the influence of water molecules on TiO2 structure and observe different water fractions bound to the TiO2 surface [2,3]. 1H-NMR measurements of rutile nanopowder were carried out in controlled relative humidity (2-100%) using the Bruker Avance III 300, Bruker Biospin, spectrometer (B0 = 7 T, f = 300 MHz , transmitter power = 400 W; pulse = 2.2 μs; bandwidths 300 kHz). The recorded 1H-NMR spectra were superpositions of one Gaussian component (half-width ~ 30 kHz) coming from protons bound to solid matrix (protons of hydroxyl groups directly bound to TiO2 surface) and since one till four (with the increased hydration level) Lorentzian components coming from mobile protons. The Lorentzian lines differ in half-widths and peak positions of water fractions according to molecular mobility (very tightly, tightly, and loosely, and finally very loosely bound water fraction) and to the magnetic environment. Acknowledgements: National Science Centre, Poland 2016/23/B/ST7/00894 project is acknowledged. [1] Kusior A., Radecka M., Zych Ł. et al. Sens. Actuators, B Chemical 189, 251-259, (2013) [2] Nosaka, A.Y, Fujiwara T., Yagi H., et al. J. Phys. Chem. B, 26, 9121-9125, (2004) [3] Soria J., Sanz J., Sobrados I., et al., J. Phys. Chem. C, 111 ,28, 10590-10596, (2007)

Resume : Methanol is essential to produce chemicals such as acetic acid, alkyl acrylates and various olefins. Over 65 million metric tons of methanol are produced each year by Cu(ZnOx)-catalyzed hydrogenation of CO and CO2. However, fundamentals such as the nature of the active site, the effect of particle size, and the origin of the ZnOx promoter effect are still being debated.[1-3] Recently, a DFT study predicted a strong decrease in activity for particle sizes below 20 nm, due to loss of effectiveness of the ZnOx promotion.[2] Our group was the first to publish experimental results on the dependency of turn-over frequency (TOF) on particle size, showing decreasing activities for particles below 8 nm.[3] Although structure sensitivity was postulated as an underlying cause, the results for unpromoted Cu particles were inconclusive, leaving space for an alternative explanation via the effectiveness of the ZnOx promoter. These previous studies applied employed different supports, mostly metal oxides, to allow variation of the particle size. However, the nature of the support may affect the efficiency of Cu and ZnOx, thus obscuring intrinsic particle size effects. In this study, we utilized carbon as an inert catalyst support to elucidate the particle size effects for both Cu and CuZnOx.

Resume : For a long time Fe?Ni?Co-based alloys with a various combination of different doping components, in which thermoelastic martensite transformations occurs, occupy leading positions in reversible deformation effects. The Fe-Ni-Co-Ti alloy system belongs to the family of new smart ferromagnetic materials exhibiting the shape memory effect and superelasticity. The long-lasting study of the martensite transformation in Fe-Ni-Co-Ti alloys has given the opportunity to find the conditions of its reversibility. When ageing of austenite, the formation of homogeneously distributed coherent with the surrounding matrix spherical nanoparticles occurs. The particles including in austenite retain coherency with the crystal lattice of martensite, that leads to its tetragonality. It makes easier the coherent connection of the austenite and martensite lattices and decreases the level of strains between them that determines the proceeding of thermoelastic martensite transformation. The degree of tetragonality ?/? of such martensite is caused by the superposition of strain fields from coherent nanoparticles within the martensite twin due to the fact that the thickness of martensite twins is much larger than the average distance between the nanoparticles. By means of the proper selection of the alloy composition and their ageing, it has been managed to obtain in the above alloys the thermoelastic transformation with hysteresis from 250 to 20 ?. An increasing the degree of tetragonality ?/? of the crystal lattice ?f martensite results in narrowing hysteresis of martensite transformation. Narrower hysteresis corresponds to the martensite with thinner plates.

Resume : There has been a growing interest in alternative energies, due to the depletion of fossil fuels, and the environmental impact caused by CO2 emissions. As a result, there is an increased focus on various alternative energy sources, such as solar and hydroelectric energy. Solar cells have been used in many application as an eco-friendly and efficient power source. In addition to their own functions of energy conversion, semi-transparent solar cells are considered one of the most promising components in building integrated photovoltaic (BIPV) systems. Semi-transparent Si solar cells, prepared based on mature Si thin-film technology, have drawn much attention as an important semi-transparent solar cell. In order to commercialize the semi-transparent Si solar cells, both improved aesthetics and increased efficiency are required. We have previously reported colored and semi-transparent Ag nanoparticle layers, which resulted in color variation and efficiency improvement of semi-transparent Si solar cells. In this study, we investigate the effect of spin coating parameters on the optical properties of Ag nanoparticle layers, and propose a mechanism to explain the change in reflectance and transmittance with variation in the two independent parameters. The Ag nanoparticle layers were formed by the spin coating of colloid solutions on substrates. The reflectance and transmittance of the nanoparticle layers were measured using an Uv?Vis spectrophotometer. It was confirmed that the saturation of the reflectance and transmittance at high spin speeds is closely related to the liquid thickness dependent on the reciprocals of spin coating variables.

Resume : The coupling of plasmonic metal nanoparticles (NPs) and oxides represents a promising strategy to sensitize wide band gap materials to visible light, and convert solar energy into chemical or electric energy. This possibility is of great relevance for a wide range of applications, like for example sensors, photocatalysts, or photovoltaic devices. The decay of localized surface plasmon resonances (LSPRs) in the metal NPs, occurring on fs time scales, may involve a relevant energy and/or charge transfer to the neighboring oxide and it may lead to modifications of the material properties on much longer time scales, which can be exploited in the applications. An understanding of the mechanisms for plasmonic energy transfer is very relevant for a knowledge-driven optimization of this important class of functional materials. Mass-selected Ag NPs, grown by magnetron sputtering with inert gas aggregation, combined with cerium oxide were chosen as a model system to probe the modifications of the oxide after LSPR excitation. The used physical synthesis method allowed to easily tune the system architecture and to maximize the expected effects. Femtosecond transient absorption spectroscopy was used to probe the dynamics of charge carrier relaxation after the excitation of the LSPRs in the Ag NPs and to evaluate the efficiency of the plasmon-mediated electron transfer from the Ag NPs to the cerium oxide matrix [1]. [1] J. S. Pelli Cresi et al., Nanoscale (2019), doi: 10.1039/C9NR01390C

Resume : Lithium niobate is an excellent nonlinear optical material. One of the recent and very promising applications is the use of LiNbO3 nanoparticles as bioimaging probes to image cells by taking advantage of their Second Harmonic Generation (SHG) properties [1,2]. Such properties, in terms of brightness, depend on the particle size and shape, hence the importance of controlling them. Use of sol-gel precursors (alkoxides) combined with a solvothermal process leads to the synthesis of quite monodispersed single crystalline LiNbO3 nanoparticles with an average size down to 30nm. The variation of some experimental parameters either related to precursors or to solution processing (temperature, solvent, additives) has allowed to change the particle morphology from platelet-like to almost spherical. Particular attention has thus been paid to the understanding of reaction and growth mechanisms. The orientation-averaged SHG response of the synthesized nanoparticles has also been characterized [3]. Finally, Er-doping of these particles has been achieved leading to a simultaneous emission of SHG and upconversion signals after excitation in the near-IR. [1] Staedler, D. ; Magouroux, T. ; Hadji, R. ; Joulaud, C. ; et al. ACS Nano 2012, 6 2542-2549 [2] Slenders, E. ; Bove?, H. ; Urbain, M ; Mugnier, Y. ; et al. J. Phys. Chem. Lett. 2018, 9, 6112?6118 [3] Riporto, J. ; Urbain, M. ; Mugnier, Y. ; Multian, V. ; et al. Opt. Mat. Express 2019, 9, 1955-1966

Resume : Harmonic nanoparticles (HNPs) (BaTiO3 [1], KNbO3 [2], LiNbO3 [3] or BiFeO3 [4]) are widely studied as Second Harmonic Generation (SHG) nanoprobes for bio-imaging as they can be excited in the 0.7-1.3 ?m near-infrared range (corresponding to the 1st and 2nd biological transparency windows) thus allowing deep tissue imaging and high-spatial resolution related to the two-photon absorption process. With the booming of nanomedicine, the search for new HNPs with multifunctional properties is of high interest. We present here our work on the development of both luminescent and SHG-active ?-La(IO3)3 nanocrystals doped with Yb3+ and Er3+ [5]. ?-La(IO3)3 is a known noncentrosymmetric compound, which was synthesized at the micron scale by hydrothermal method [6]. It was shown to exhibit non-linear optical properties with a SHG efficiency similar to that of the reference compound, namely lithium iodate (?-LiIO3). In the context of bio-imaging, we developed a microwave-assisted hydrothermal method to synthesize ?-La(IO3)3 nanocrystals with high crystal quality. By controlling various synthesis parameters (temperature, time, stoichiometry ?), well-crystallized undoped and Yb3+,Er3+-doped SHG-active ?-La(IO3)3 nanocrystals of circa 30 nm were obtained, as characterized by TEM. The SHG efficiency was quantitatively assessed from second-harmonic scattering experiments at 1064 nm. It results in relatively high ?d? coefficients measured at 8.2 ± 2.0 pm.V-1 for undoped ?-La(IO3)3, a value comparable to that of the state-of-the-art HNPs. For Yb3+,Er3+-doped nanocrystals excited at 980nm, SHG as well as photoluminescence by up-conversion (UC) were simultaneously observed. As expected, the UC process is enhanced in codoped nanocrystals after excitation of the Yb3+ ions, acting as the sensitizer, and energy transfer to the Er3+ ones. The emission is situated at 525 nm and 546 nm and corresponds to the 2H11/2 ? 4I15/2 and 4S3/2 ? 4I15/2 electronic transitions of Er3+. Because of the non-resonant and resonant nature of the SHG and up-conversion (UC) processes, respectively, the intensity ratio between SHG and UC is readily changed according to the excitation wavelength and a possible competition between each mechanism will be discussed under resonant conditions. [1] Hsieh, C. L.; Grange, R.; Pu, Y.; Psaltis, D. Biomaterials. 2010, 31, 2272-2277 [2] Ladj, R.; Magouroux, T.; Eissa, M.; Dubled, M.; Mugnier, Y.; Le Dantec, R.; Galez, C.; Valour, J. P.; Fessi, H.; Elaissari, A. Colloids Surf. A. 2013, 439, 131-137 [3] Staedler, D.; Magouroux, T.; Hadji, R.; Joulaud, C.; Extermann, J.; Scwung, S.; Passemard, S.; Kasparian, C.; Clarke, G.; Gerrmann, M.; Le Dantec, R.; Mugnier, Y.; Rytz, D.; Ciepielewski, D.; Galez, C.; Gerber-Lemaire, S.; Juillerat-Jeanneret, L.; Bonacina, L.; Wolf, J. P. ACS Nano. 2012, 6, 2542-2549 [4] Staedler, D.; Passemard, S.; Magouroux, T.; Rogov, A.; Maguire, C. M.; Mohamed, B. M.; Schwung, S.; Rytz, D.; Jüstel, T.; Hwu, S.; Mugnier, Y.; Le Dantec, R.; Volkov, Y.; Gerber-Lemaire, S.; Prina-Mello, A.; Bonacine, L.; Wolf, J. P. Nanomedicine. 2015, 11, 815-824 [5] Regny, S.; Riporto, J.; Mugnier, Y.; Le Dantec, R.; Kodjikian, S.; Pairis, S.; Gautier-Luneau, I.; Dantelle, G. Inorg. Chem. 2019, 58, 1647-1656 [6] Taouti, M. B.; Suffren, Y.; Leynaud, O.; Benbertal, D.; Brenier, A.; Gautier-Luneau, I. Inorg. Chem. 2015, 54, 3608-3618

Resume : Si nanocrystals (SiNC) can be relatively efficient light emitters despite their indirect bandgap. Their attributes (e. g. light-emission efficiency) depend heavily on surface passivation. Various schemes were exploited over the years, however, the functionalization with diphenylanthracene (DPA) is quite new in the SiNC field. Here, the DPA molecules function as molecular antennae in order to improve the absorption in the 340 nm - 400 nm range and then transfer the energy to SiNCs, which has a potential benefit in e.g. light-harvesting applications. The DPA-functionalized samples were compared with SiNCs prepared by the same method passivated by dodecene. In order to elucidate the full role of DPA on the SiNCs surface, we employed a range of optical methods such as quantum yield, time-resolved photoluminescence (PL), excitation spectra measurements, etc. We were able to detect a fast (PL decay ~ ns) blue band [1] as well as a slow (PL decay ~ 100 us) red band typical for SiNCs. We found out that the PL of SiNCs passivated by DPA differs markedly compared to the dodecene passivated ones: 1) blue band PL is greatly enhanced, 2) the blue band?s behavior changes with respect to excitation wavelength 3) decays of the red and blue band changes their character. We will discuss the influence of DPA and the underlying energy transfers between NCs and DPA describing the above mentioned results. [1] J. Valenta et al 2008 New J. Phys. 10 073022

Resume : Metal nanoparticles can sustain localized surface plasmon resonances, which are light-driven resonant oscillations of their free electrons. Thanks to their strong spectral dependence on the nanoparticle size, shape, composition, and dielectric environment these resonances can be used as nanoscale probes for a large range of chemical and physical processes. Furthermore, their non-radiative decay into ?hot? charge carriers and heat can be exploited to accelerate and modify chemical reactions at the metal nanoparticle surface. In the present talk, I will show how we use plasmon resonances in noble metal nanoparticles to study hydrogen absorption in individual metal nanocrystals [1-3], probe charge equilibration across metal/semiconductor interfaces [4], and drive the synthesis of hierarchical nanostructures in solution, using both photo-thermal effects and non-thermal processes such as near-field enhancement and hot charge carrier injection [5]. [1] A. Baldi, T. C. Narayan, A.-L. Koh, and J. A. Dionne, Nature Mater. 13, 1143-1148 (2014) [2] T. C. Narayan, A. Baldi, A.-L. Koh, R. Sinclair, and J. A. Dionne, Nature Mater. 15, 768?774 (2016) [3] T. C. Narayan, F. Hayee, A. Baldi, A.-L. Koh, R. Sinclair, and J. A. Dionne, Nature Comm. 8, 14020 (2017) [4] M. Parente, S. Sheikholeslami, G. V. Naik, J. Dionne, and A. Baldi, J. Phys. Chem. C 122, 23631-23638 (2018) [5] R. Kamarudheen, G. W. Castellanos, L. P. J. Kamp, H. J. H. Clercx, and A. Baldi, ACS Nano 12, 8447-8455 (2018)

Resume : Hot-electron chemistry at gold nanoparticle (AuNP) surfaces has received much attention recently because its under-standing provides a basis for plasmonic photocatalysis and photovoltaics. Nonradiative decay of excited surface plas-mons produces energetic hot charge carriers that transfer to adsorbate molecules and induce chemical reactions. Such plasmon-driven reactions, however, have been limited to a few systems, notably the dimerization of 4-aminobenzenethiol to 4,4?-dimercaptoazobenzene. In this work, we explore a new class of plasmon-driven reactions associated with a unimolecular bond-cleavage process. We unveil the mechanism of the decarboxylation reaction of 4-mercaptobenzoic acid and extend the mechanism to account for the ?-cleavage reaction of 4-mercaptobenzyl alcohol. Combining the construction of well-controlled nanogap systems and sensitive Raman spectroscopy with methodical changes of experimental conditions (laser wavelengths, interface materials, pH, ambient gases, etc.), we track the hot charge carriers from the formation to the transfer to reactants, which provides insights into how plasmon excitation eventually leads to the C?C bond cleavage of the molecules in the nanogap.

Resume : Gallium and indium nanoparticles (NPs) have attracted a lot of interest in the last years for biosensing and photonic devices [1,2], since they provide a wide tunability of their localized surface plasmon resonance (LSPR) energy, from the UV to the IR spectral region. Interestingly, these NPs develop a native thin oxide on the surface that preserves the metal from the environment [3]. Furthermore, the thickness of the oxide layer can be increased by thermal processes, tuning the core-shell architecture and modifying the plasmon resonance with the annealing time and temperature [4]. In this work, we use Joule-effect thermal evaporation to produce hybrid structures made of Ga and In NPs on Si substrates. These complex structures of mixed NPs present a spectrally broad plasmonic absorption that can be optically tuned with a wide range of photon energies from UV to IR regions with a full width at half maximum range of ~ 400 to 800 nm. The surface morphology was characterized by means of scanning electron microscopy. The LSPRs were determined by spectroscopic ellipsometry and compared with discrete dipole approximation simulations. These results explore the benefits and limits of hybridization, in new platforms for optical sensing devices. 1. A. García Marín et al., Biosens. Bioelectron. 74, 1069 (2015) 2. Y. Kumamoto et al., ACS Photonics 1, 598 (2014). 3. K.A. Willets et al., Annu. Rev. Phys. Chem. 58, 267 (2007) 4. S. Catalán-Gómez et al., Nanotechnology 29 (2018) 355707)

Resume : In the surface plasmon resonance (SPR) of metal nanoparticles (NPs) the linewidth is determined by radiative and nonradiative damping terms. So far less attention was paid to give an overview of the different semi-empirical scaling factors reported for the radiation damping of spheroidal NPs. In this work we use a local field approach and the kinetic equation method to estimate the linewidth of radiative damping of SPR. As we found the linewidth increases quadratically with the radius of spherical NPs while for nanorods significantly larger radiation damping is found for the transversal than for the longitudinal SPR band. So far this effect induced by shape anisotropy has not been discussed in detail. We also show that the shape of gold nanodiscs can be successfully modelled with prolate spheroids in radiation damping calculations. We also investigate the effect of the underlying substrate. The radiation damping is evaluated for NPs supported on glass, ITO, and Si, i.e., substrates with significantly different refractive indexes. In this case the effect of the anisotropic dielectric environment is taken into account through an effective dielectric constant extracted from the substrate induced mirror charge model. We compare the values resulted by the kinetic equation method to previously reported values of the semi-empirical radiation damping factor and reveal correspondence between these two parameters. In general good agreement is found between calculations and experiments.

Resume : Silicon nanocrystals (SiNCs) in the quantum size range (2-12 nm) can be made as viable light emitters with emission wavelength that can be tuned from the near-infrared (NIR) into the visible by decreasing their size.[1, 2] Silicon nanocrystals, produced by thermal disproportionation of silicon oxide, were co-passivated with dodecene and different organic chromophores, e.g. pyrene,[3] porphyrin,[4] or benzothiadiazole chromophores.[5] Excitation of the organic chromophores results in an efficient energy transfer to the nanocrystal core: this is the working principle of a light harvesting antenna. This approach enabled us to circumvent the drawback of the low molar absorption coefficient of SiNCs. The investigated hybrid material exhibits high quantum yield also in the NIR spectral region with lifetime in the µs range. This research has potential applications in bioimaging, taking advantage of time-gated luminescence microscopy to enhance image resolution and in solar energy conversion, e.g. luminescent solar concentrators, thanks to the apparent large Stokes shift. [1] Y. Yu, G. Fan, A. Fermi, R. Mazzaro, V. Morandi, P. Ceroni, D.-M. Smilgies, B. A Korgel, J. Phys. Chem. C, 2017, 121, 23240 [2] R. Mazzaro, F. Romano, P. Ceroni, PhysChemChemPhys 2017, 19, 26507 [3] M. Locritani, Y. Yu, G. Bergamini, J. K. Molloy, M. Baroncini, B. A. Korgel, P. Ceroni, J. Phys. Chem. Lett. 2014, 5, 3325. [4] A. Fermi, M. Locritani, G. Di Carlo, M. Pizzotti, S. Caramori, Y. Yu, B. A. Korgel, G. Bergamini, P. Ceroni, Faraday Discussion 2015, 185, 481. [5] L. Ravotto, Q. Chen, Y. Ma, S. A. Vinogradov, M. Locritani, G. Bergamini, F. Negri, Y. Yu, B. A. Korgel, P. Ceroni, Chem. 2017, 2, 550.

Resume : Lanthanum vanadate nanoparticles doped with europium and erbium ions and co-doped with calcium ions were prepared by aqueous nitrate-citrate sol-gel synthesis route taking citric acid as a complexing agent. Phase composition, crystal lattice parameters and microstructure of the synthesized samples were studied by various methods. The XRD analysis has revealed dependence of crystal structure on dopants concentration: monoclinic monazite-type structure for low dopant concentration and tetragonal zircon-type structure for high dopant concentration. The photoluminescence spectra showed narrow lines caused by f-f transitions in the rare earth dopants. Distributions of these lines intensity differ for the samples with different concentrations for both Er3 and Eu3 ions. This effect can be related with different symmetry of the rare earth ions sites in the monoclinic and tetragonal crystal phases. It was shown that crystal structures of the samples also effects on intensity and distribution of the lines intensity in emission spectra. This work has received funding from Ministry of Education and Science of Ukraine and from the EU-H2020 grant No 654360 within the framework of the NFFA-Europe Transnational Access Activity.

Resume : The development of nanotechnologies in the field of medicine has opened up the design of synergic tools where therapeutic and diagnostic features can be combined in a single nanostructure. In this framework, silica nanoparticles (NPs) with a polymeric soft shell and a dye-doped silica hard core (Pluronic-Silica nanoparticles (PluS NPs), patented in 2011 by L.Prodi et al) are versatile nanomaterials, and all the experimental results, so far, are in favours of their benign nature in biomedical applications. The advantages of these NPs include their ease of preparation, inexpensive starting materials and the possibility to functionalize them or to load them with various doping agents especially luminescent species or drugs. However,the solubility of the doping agent(s) imposes constraints on the choice of the reaction system and hence limits the range of molecules that can be included in the NPs.We succeeded in overcoming this problem, improving the current state of the art of the synthetic strategies based on Pluronic F127, by enabling the synthesis in the presence of large amounts of organic solvents We obtained nanoparticles doped with large amounts of water-insoluble silane derivatized metallo-porphyrins developing four different NPs able to act as a chemosensor (nanosensors) for molecular oxygen. Moreover, our synthetic strategy is versatile for many applications allowing the future development of new silica nanosystem also for imaging, drug delivery or catalysis

Resume : Currently silicon nanostructures, besides having high potential for novel micro- and nanoelectronic devices development, are perspective agents for biomedical applications as well [1,2]. In the present work we study the ensembles of nanoparticles fabricated through picosecond laser ablation in distilled water in the course of irradiation of monocrystalline and porous silicon, and silicon micropowders. The size of such particles varies from 2 to 300 nm depending on the type of target used for ablation. Analysis of the produced nanoparticles Raman spectra revealed high level of their crystallinity: more than 88% for all cases. Spectrophotometry measurements of the fabricated silicon nanoparticles revealed relatively high scattering coefficient in the spectral range 400 ? 1000 nm. Optical coherence tomography imaging of the suspensions drops administered on agar gel surfaces indicated high efficiency of the nanoparticles as contrast agents providing contrast up to 30 dB. The reported results demonstrated the perspectives of fabricated nanoparticles suspensions as agents for controlling optical properties in photonics and biomedical applications. The work was financially supported by the Russian Science Foundation (project #19-12-00192). [1] V. Stojanovi?, F. Cunin, J.O. Durand, et al. J. Mater. Chem. B, 4, 7050 (2016). [2] O.I. Ksenofontova, A.V. Vasin, V.V. Egorov, et al. Tech. Phys., 59, 66 (2014).

Resume : ZnO nanoparticles were synthesized by Sol-gel method at different temperatures. The effects of growth temperature on the structure and optical properties of ZnO nanostructures were investigated in detail. Temperature is an important thermodynamic factor that plays a key role in controlling the growth rate of a crystal, the morphology and aspect ratio of ZnO nanostructures. The characterization of the nanoparticles with Scanning Electron Microscopy (SEM) showed that at low temperatures (35 °C and 45ºC) needle like particles were observed. As the growth temperature increases to 75 °C, Spherical particles are formed. The particle size, lattice parameters and crystal structures of the nanoparticles are characterized by X-ray diffraction (XRD). The average crystallite sizes have been found to increase with the increase in growth temperatures from 27.6 nm to 34.2 nm. Results of XRD showed a systematic shift in peak positions towards lower 2? values with the increase in growth temperatures caused by change in lattice parameters. The intensity of the DLE band, as observed, from photoluminescence spectra decreased with the increase in growth temperature. The estimated band gap reduced from 3.31 eV to 3.24 eV with the increase in the growth temperature. Keywords: ZnO; Nanoparticles; Sol-gel; Annealing temperature, Morphology, Luminescence

Resume : The metal phosphorus trichalcogenides (MPX3) are the van der Waals layered materials, which have been widely studied in the bulk form [1]. Since the graphene has been successfully exfoliated, atomically-thin layered materials have captured great attention of the scientific community, due to the wide range of unique properties not observed in th bulk counterparts. The 2D metal phosphorus trichalcogenides are of special note in future magnetic and spintronic device applications. In addition, mixed compositions of metallic cations (M) can result in in enhancement of various properties, e.g. better electrocatalytic performance and water splitting has been previously observed for CoNiPS3 material [2]. Hence, the potential applications of MPX3 could be extended. In this study, we present the results of extensive first principles calculations of the mixed MnxNi1-xPS3 systems. Our studies are based on the ab initio calculations in the framework of the density functional theory (DFT), with the generalized gradient approximation with U correction (GGA U) for the exchange-correlation density functional, and the weak van der Waals forces included, as implemented in the numerical package VASP. The structural, energetic and magnetic properties of MnxNi1-xPS3 monolayers for different metallic compositions x, and different arrangement of spins on the manganese and nickel atoms will be presented. All of the presented results will be compared to NiPS3 and MnPS3 monolayers and theirs bulk counterparts. The research was supported in part by PL-GRID Infrastructure, and computing facilities of the Interdisciplinary Centre of Modelling of the University of Warsaw. The work has been funded by the NCN grant SONATA (no. UMO-2016/23/D/ST3/03446). [1] R. Brec, Solid State lonics 22, 1986, 3. [2] Q. Liang et al., Adv. Funct. Mater. 28, 2018, 1805075.

Resume : The CdS nanoparticles possess a number of unique photocatalytic and optical properties. The application of such nanoparticles can be expanded further by increasing their resistance to agglomeration and oxidation by embedding them into glasses or an amorphous SiO2. The synthesis technique for obtaining of CdS nanoparticles in glass proceeds in two stages: glass melting and secondary heat treatment. However, no comprehensive information on the phase equilibrium and the structure of the interface between the nanoparticles and the glass can be found to date. Therefore, we conduct a theoretical survey for the core@shell CdS@SiO2 nanoparticle system by means of the MD simulations. The study is carried out using an in-house code with the pair potentials. CdS core and SiO2 shell had stoichiometric compositions and diameter of 4 nm and thickness of 2 nm, respectively. The models of CdS core in both the wurtzite and sphalerite phase were considered. Simulations were performed on 0.1 ns time intervals at temperatures from 300 to 1200K. The results show that the CdS sphalerite core may be thermodynamically slightly more stable than the wurtzite core. However, at elevated temperatures, the sphalerite core gets progressively amorphized. According to results, the CdS wurtzite core should crystallize first from the glass matrix under high-temperature conditions. The results are compared with the CdS@TiO2 system. Authors acknowledge the Russian Science Foundation (project ?17-79-20165).

Resume : Most of the applications of semiconductor quantum dots (QDs) are not based on isolated QDs but on a molecular or solid-like assembly of nanocrystals. Therefore, the collective opto-electronic properties of QD materials is influenced by mutual interdot interactions. Moreover, exciton energy transfer and electronic coupling are hampered in colloidal QD aggregates because of the nanoparticle isolation due to the capping ligands that reduce the charge carrier extraction and mobility. Understanding if and how the electronic density of the excitonic states spreads into the ligand shell is essential to understand their photophysics and to engineering ligands promoting interdot excitonic coupling and electronic energy transfer. We address this issue by performing all-atom calculations in models of colloidal QD dimers at the DFT and TD-DFT level of theory. Magic sizes (CdSe)13 and (CdSe)33 QD units are linked by phenyl-dithiocarbamate (PDTC), recently proposed as exciton delocalizing ligand. We show that in the (CdSe)13-PDTC-(CdSe)13 dimer, the formation of interdot delocalized exciton is analogous to the formation of Frenkel exciton in molecular systems but the energy scale of the inter-unit electronic coupling is substantially smaller than those typical of molecular aggregates. In the hetero-dimer (CdSe)13-PDTC-(CdSe)13 excitations are not delocalized but charge transfer states appear at accessible energies. The nature of the coupling is discussed, coulombic contributions are found to dominate even at the smaller surface to surface distance. The validity of the widely used dipole-dipole approximation is critically analyzed.

Resume : Finding novel flexible materials for renewable energy generation is increasing in importance to meet the modern society requirements. Diamond nanoparticles denoted as nanodiamonds (NDs) possess numerous beneficial material properties and are envisioned for a wide range of applications. Blending NDs with organic materials into organic-inorganic composites could provide new beneficial properties for solar cells, in contrast with the well-established but not ideally cost-effective and adaptable silicon photovoltaics. In this work, complexes of polypyrrole (PPy) organic dye covalently grafted to ND surfaces are investigated by atomic scale density functional theory (DFT) computations with a view to their structural and electronic properties. We consider NDs terminated with oxygen, hydroxyl, carboxyl, anhydride, as well as amorphous carbon (a-C:H, a-C:O). Thereby the theoretical model is brought close to real nanodiamonds. We observe spatially separated HOMO and LUMO and favorable energetic level alignment at the ND-PPy interface for the majority of the oxidized NDs. This feature is also retained for NDs with the amorphous surface layer. Excited states are computed by time-dependent DFT (TDDFT) to analyze how the electronic configuration can promote dissociation of excitons, for instance in photovoltaic applications. The computed results thus provide guidance for the synthesis of real ND-PPy composites. We acknowledge financial support from the CVUT student project SGS18/179/OHK4/3T/13 and European Regional Development Fund project CZ.02.1.01/0.0/0.0/15_003/0000464.

Resume : Machine learning methods are efficient tools to develop novel materials for different applications. They are fast, resource efficient, versatile, and low cost. They produce reliable, repeatable results, uncover hidden insights through learning from trends in the data, and are essential synergistic elements of any experimental project, especially those that generate high volumes of multi-dimension data using high throughput experiments. This presentation will provide examples of how these efficient approaches, coupled with a strong understanding of molecular properties and interactions, can generate useful and robust models for ?smart?, self-assembling amphiphiles for targeted drug delivery. This approach also allows the determination of factors that significantly affect the materials properties and therefore allow the design of new materials or optimization of existing materials.