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One of the most challenging problems in nanomaterials research is their accurate characterization, which is fundamental for the efficient use of these technologically promising materials. Absolute absorption, quantum efficiency, thermal diffusivity, and the elastic constants are important parameters for photonic applications. Although the conventional absorption or emission techniques can provide the absorption coefficient, the determination of the absolute absorption is not a trivial measurement due to the presence of scattered light. On the contrary Photoacoustic (PAS) and Photothermal Spectroscopy are very sensitive techniques, immune to scattered or reflected light, and easy to be used to measure the absolute absorption in many different wavelength ranges.

Photoacoustic Spectroscopy (PAS) and Photothermal deflection Spectroscopy (PDS) are excellent techniques for studying the optical absorption spectra of opaque and highly light-scattering substances such as nanomaterials. In this paper we review recent advances in the methodology of PAS and its novel applications. In particular we discuss the performance of PAS to detect circular dichroism of intrinsic chiral materials [1] as well as extrinsic pseudo-chiral metasurfaces [2], showing how the selective absorption of circularly polarized light depend on the orientation of the metasurface. We also applied PAS in the VIS/IR range to measure the resonant absorption peaks related to the guided modes of GaAs-based NW on Si [3–5].

Photoacoustic and Photothermal Spectroscopy are excellent techniques for studying the optical absorption spectra of opaque and highly light-scattering substances such as nanomaterials. In this paper we review recent advances in the methodology and its novel applications at the nanoscopic scale.

Design of durable solar CO2 conversion devices requires a mechanistic understanding of molecular-level reactions at the electrode-electrolyte interface that lead to interfacial degradation.[1] This interface often incorporates such features as a porous and rough surface to maximize active area and enhance catalytic performance. However, this roughness may introduce local water pool inclusions, whose size may have an unforeseen, detrimental impact on device durability due to their local pH being very different from the bulk pH. It is well-recognized that for water pools containing less than molecules, the solution pH cannot be defined in the conventional sense because the pools are too small to support stable water ion concentrations near neutral pH. Rather, the water ion concentrations fluctuate to very high values for short periods of time. To better understand pH in small pools, we combine theoretical calculations using QM/MD and stochastic simulations [3]. We combined Ab initio MD and the accurate RexPoN force field [2] simulation to quantify the thermodynamic free energy to create water ion pairs through the reaction as a function of the water pool size. The free energies are used to calculate the equilibrium constants for this reaction and the ion pair generation and recombination rate constants. The rate constants are then used as inputs to the stochastic simulations to gain insights into ion pair generation frequency and lifetime statistics over extended periods of time (hours). Proton and hydroxide diffusion are also incorporated in the stochastic simulation to understand how far water ions may travel from where they are generated. The results show that the combination of Grotthuss and vehicular diffusion mechanisms for H3O+ and OH- can lead to unequal distributions at an adjacent interface. We will discuss how the stochastic generation and recombination of water ions influences buffer chemistry and dissolved CO2 chemistry. Reference [1] S. Nitopi, E. Bertheussen, S.B. Scott, X. Liu, A.K. Engstfeld, S. Horch, B. Seger, I.E.L. Stephens, K. Chan, C. Hahn, J.K. Nørskov, T.F. Jaramillo, I. Chorkendorff, Progress and Perspectives of Electrochemical CO2 Reduction on Copper in Aqueous Electrolyte, Chem. Rev. 119 (2019) 7610–7672. https://doi.org/10.1021/acs.chemrev.8b00705. [2] S. Naserifar, W.A. Goddard, The quantum mechanics-based polarizable force field for water simulations, J. Chem. Phys. 149 (2018). https://doi.org/10.1063/1.5042658. [3] W.D. Hinsberg, F.A. Houle, Kinetiscope, (n.d.). http://www.hinsberg.net/kinetiscope.

International audience

Precise x-ray diffraction measurements using high-energy x rays of synchrotron radiation and systematic Raman scattering measurements were carried out for ${\mathrm{Ge}}_{x}{\mathrm{S}}_{100\ensuremath{-}x}$ $(10\ensuremath{\leqslant}x\ensuremath{\leqslant}40)$ network glasses. The structural models of the network glasses were proposed based on the results. In the stoichiometric composition ${\mathrm{Ge}}_{33}{\mathrm{S}}_{67}$, ${\mathrm{GeS}}_{4}$ tetrahedral units are connected forming either corner-sharing or edge-sharing structures. In the S-rich glasses, S atoms are inserted between two neighboring ${\mathrm{GeS}}_{4}$ tetrahedra, resulting in a flexible floppy network. In a much more S-rich region, some ${\mathrm{S}}_{8}$ ring molecules are isolated from the network, and assemble to form a crystal in nanoscopic scale. In this respect, ${\mathrm{Ge}}_{10}{\mathrm{S}}_{90}$ samples are regarded as crystallized glasses. In the Ge-rich region, the ${\mathrm{GeS}}_{4}$ tetrahedra are connected with bridging Ge atoms. The connection makes a new rigid network. The bridging Ge-S bond is weaker than the intratetrahedron bond, and this leads to drastic changes in the optical properties.

International audience; We present a review of the structural properties of LiFePO4. Depending on the mode of preparation, different impurities can poison this material. These impurities are identified and a quantitative estimate of their concentrations is deduced from the combination of X-ray diffraction analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and magnetic measurements. An optimized preparation provides samples with carbon-coated particles free of any impurity phase, insuring structural stability and electrochemical performance that justify the use of this material as a cathode element a new generation of lithium secondary batteries.

Domain switching characteristics of lead zirconate titanate ceramics with and without poling under compressive loading are investigated using electron backscatter diffraction. For loading in the poling direction, the switching strain is stronger than that for loading perpendicular to the poling direction. There is strong domain switching when the domain ( c -axis of the tetragonal structure) is orientated close to the loading direction. A large number of domains are switched between 85.4° and 90.0°, with many crossing the loading axis. Each grain consists of domains with three different patterns; i.e., with c -axis orientated in three directions in each grain. The patterns remain unchanged even with domain switching and strong deformation. However, the ratios among the patterns depend on compressive stress. Under stress, one or two specific domain modes are switched to about 90°, although others are not switched as much. These domain switching characteristics are related to the poling and loading directions. 90° domain switching model is proposed on the basis of twin deformation model. Due to the aspect ratio of c / a = 1.014 (tetragonal structure), the angle of the switching is less than 90° (89.2°). This angle is corresponding to the switching angle obtained by an electron backscatter diffraction analysis (Ave. 88.9°).

This paper deals with information processing in biomolecule-based biomimetic systems (i.e., artificial systems in which a biomolecule is involved, and whose purpose is to mimic biological functions). Several approaches are presented, based on structures ranging from the macroscopic to the nanoscopic scale. The first part is devoted to the biosensing function: the basic principle, the possible transducers, the main applications. The second part presents integrated information on processing functions in macroscopic structures: active transport, biological clocks, mathematical operations, information storage and control functions. In the third part, the evolution of this field toward the nanoscopic scale is described, with the presentation of some methods of creating nanoscopic structures (adsorbed and chemically bound monolayers, black lipid membrane (BLM) and Langmuir-Blodgett techniques), and their application in the field of biosensors. Finally, new trends in information processing by nanoscopic systems are discussed.

Nanoscale zero-valent iron (Fe) modified by sodium (Na) bentonite (B-nZVI) was prepared to remove copper (II) (Cu2+) and lead (II) (Pb2+) from an aqueous solution. B-nZVI and sodium bentonite were characterised by X-ray diffraction, Lorentz transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). From the XPS spectra, lead (II) was detected on the surface of B-nZVI, indicating that lead (II) was removed by adsorption to B-nZVI. The copper (II) in the solution obtained electrons from B-nZVI and was reduced to copper (0). Sodium bentonite (B-nZVI) showed higher removal efficiencies for lead (II) than copper (II) under various conditions. As the concentration of copper (II) increased from 75 to 200 mg/l at a constant lead (II) concentration of 100 mg/l, the removal efficiency of lead (II) decreased considerably, from 81 to 49%. The removal efficiencies of copper (II) and lead (II) by B-nZVI were close to 100% at pH = 6. The temperature of best removal efficiency for copper (II) and lead (II) was 50°C when the adsorbent dose was 1 g/l, the pH was 5, the concentration of lead (II) was 200 mg/l, the concentration of copper (II) was 100 mg/l and the adsorption time was 4 h. In general, the synthesised B-nZVI exhibits great potential as an excellent material for use in the treatment of waste water that simultaneously contains copper (II) and lead (II).

In this paper a recess gate AlGaN/GaN HEMT on beta gallium oxide (BGO) is designed and analysed using Silvaco ATLAS TCAD software. The DC and RF performance of the device is compared with a schottky gate AlGaN/GaN HEMT on BGO substrate. For optimizing the gate recess depth, three variations with recess depths 6 nm, 12 nm and 20 nm is also simulated. A highest transconductance of 0.4 mS/ µm is observed for recess gate AlGaN/GaN HEMT on BGO substrate with a recess gate depth of 20 nm with a decrease in current density. The radio frequency performance is also highest for the recess gate AlGaN/GaN HEMT with recess gate depth of 20 nm. The device exhibited a maximum oscillation frequency of 2.6 THZ which is highest till reported.

Iron nanoparticles has attracted more attention than other nanomaterials for its small particle size, high magnetism, low toxicity, surface properties and its extensive applications in science. Plant extracts, microorganisms and agricultural waste products are used for the green synthesis of these nanoparticles. Green synthesis uses metabolites obtained from plants and microorganisms as reducing and covering agents. In addition, it provides an advantage over other synthesis methods because it does not contain harsh chemicals, uses non-toxic reagents, is biocompatible and environmentally friendly. In this study, iron-iron oxide (Fe-Fe3O4) nanoparticles (LP- Fe NPs) were synthesized using lemon peel extract and optimum Fe:Lemon peel extract (Fe: LP exract) ratio was determined. Nanoparticles were characterized by X-ray diffractometer (XRD), UV-vis Spectrophotometer and Scanning Electron Microscope (SEM). The UV-vis absorption spectrum of iron nanoparticles showed a peak in the 250-350 nm range. XRD analysis results confirmed that the product is a Fe-Fe3O4 mixture. According to SEM analysis results, the largest particle size according to the 1:2 ratio was recorded as 159 nm. The smallest particle size was recorded as 66.68 nm. It has been observed that the increased lemon peel extract causes agglomeration. As a result, green synthesis of lemon peel, which is agricultural waste; It creates low-cost, environmentally friendly products.

As the Internet of Things (IoT) has become a widespread phenomenon, promising sensor applications at the nanoscale have begun to emerge. One example is imaging via distributed massive nanoscale nodes (NSNs), which can be used to implement “invisible surveillance cameras” by, for example, painting liquids containing nanoscale sensors onto walls. This imaging method requires periodic data transfer from thousands of NSNs to a data collection node (DCN). An essential technique for handling such transfers is the media access control (MAC) protocol. However, existing protocols cannot support periodic transfer from numerous NSNs because of inefficient communication caused by a large amount of headers in the packets. In this article, we introduce an original MAC protocol and discuss its capability in terms of implementing imaging applications. The proposed protocol applies a time-division access (TDA) feature to reduce the amount of headers and a two-layered protocol to enable simultaneous transmission among nodes. Slot assignment is an essential function in TDA and requires communication among nodes. Unlike existing methods, our simple approach enables communication by exploiting the unique features of the focused application. The results of the numerical simulation reveal that the proposed MAC protocol allows for periodic imaging with more than three thousand nodes and produces high-quality images very close to those obtained using ideal communication. These results are achieved by employing an original design framework to determine appropriate key parameters, such as the number of clusters and frame rate.

In this work, Plasma-Assisted Rapid Sintering (PARS), a pulsed DC plasma system in a hollow cathode regime, is presented as a novel technology to sinter nanoceramics. Nano-TiO2 powders are used as proof of concept and submitted to thermal treatment using several PARS conditions and sintering schedules. PARS heating process induced solely by the hollow cathode effect is consistent and affordable, providing a homogeneous temperature distribution to the compact. Furthermore, the heating rate and the maximum temperature are easily tunable by the discharge current applied in the plasma source and can go safely from room to maximum temperature in a matter of seconds with heating speed comparable with other reported rapid sintering techniques. Using 1-min of non-isothermal PARS cycles up to 1000 °C, porous nanostructured samples were obtained; reaching 80 % relative density while the grains remained at the nanoscale. Adding dwell times, the relative density was increased up to 96 % using a temperature plateau for up to 10 min, but the TiO2 grains grow intensively when temperatures exceeded 1000 °C. The results indicate that the developed process is a promising new alternative technology for sintering nanoceramics.

This work demonstrates that the introduction of positive lanthanide (Ln) and transition metal (TM) cations into polyoxotungstates (POTs) to stabilize negative oxoboron clusters is a feasible and ge...

Nanoscale ruthenium (Ru)-based materials are promising replacements for existing multilayered Cu interconnects in integrated circuits. However, it is not easy to apply the results of previously reported studies directly to the electrochemical damascene process because the previous studies have mainly focused on thin films by dry deposition. Here, we report the electrical resistivity and microstructure of electrodeposited Ru nanowires. We estimate that the resistivity value of a 10 nm diameter Ru nanowire to be 71.6 μΩ cm after analyzing the resistivity values of individual nanowires with various diameters. Furthermore, we investigate the electrical properties of RuxCo1-x nanowires where x is 0.04–0.99 at.% as possible replacements of the current TaN barrier structures. Over the entire composition range, the resistivity values of alloys are much lower than that of the conventional TaN. Additionally, Ru and Ru-alloy nanowires surrounded by dielectric silica are thermally stable after 450 °C heat treatment. Therefore, the nanoscale Ru and Ru-Co alloys possessing low resistivity values can be candidates for the interconnect and barrier materials, respectively.

The properties of both inorganic and organic materials and the function of biological structures can often only be understood by analyzing them simultaneously on atomic and nanoscopic, if not mesoscopic, scale. Here, the problem arises to render millions to billions of atoms. We propose a method by which it is possible to interactively visualize atomic data, bridging five orders of magnitude in length scale. For this, we propose a simple yet efficient GPU rendering method that enables interactive visualization of biological structures consisting of up to several billions of atoms. To be able to load all atomic data onto the GPU, we exploit the fact that biological structures often consist of recurring molecular substructures. We also exploit that these objects typically are rendered opaquely, so that only a fraction of the atoms is visible. The method is demonstrated on both biological structures as well as atom probe tomography data of an inorganic specimen. We conclude with a discussion about when -during ascension from atomic to mesoscopic scale – level-of-detail representations become necessary. © 2012 Wiley Periodicals, Inc.

A systematic DFT study is performed on (MgO)B, (CaO)n, (SrO)n, and (BaO)n clusters with 6 < n < 50, and which display a cuboid 2X2X2 atomic motif seen in the bulk, rock-salt, configuration. The stability and energy progression of these clusters are used to predict the energies of infinitely long nanorods, or nanowires, slabs, and the bulk global minimum energy. Keywords: Alkaline earth metal oxides, nanoclusters, nanorods, DFT.

Crystallographic twins are critical to the properties of numerous materials from magnesium alloys to piezoelectrics. Since the onset of the twin formation is highly sensitive to the triaxial mechanical boundary conditions, non-destructive bulk microscopy techniques are required. Elastic strains can be mapped via X-ray diffraction with a 100-200 nm resolution. However, the interplay of strains with nanotwins cannot be characterized. Here, a method based on dark-field X-ray microscopy to quantify the density of nanotwin variants with twin lamellae of sizes as small as several tens of nanometers in embedded subvolumes (70x200x600 nm3) in millimeter-sized samples is introduced. The methodology is corroborated by correlating the local density of twin variants to the long-ranging strain fields for a high-performance piezoelectric material. The method facilitates direct, in situ mapping and quantification of nanoscale structural changes together with their elastic driving fields, which is the key towards controlling and engineering material's performance at nanometric scales.

Recently in nanophotonics, a rigorous evolution from passive to active metasurfaces has been witnessed. This advancement not only brings forward interesting physical phenomena but also elicits opportunities for practical applications. However, active metasurfaces operating at visible frequencies often exhibit low performance due to design and fabrication restrictions at the nanoscale. In this work, we demonstrate electrochemically controlled metasurfaces with high intensity contrast, fast switching rate, and excellent reversibility at visible frequencies. We use a conducting polymer, polyaniline (PANI), that can be locally conjugated on preselected gold nanorods to actively control the phase profiles of the metasurfaces. The optical responses of the metasurfaces can be in situ monitored and optimized by controlling the PANI growth of subwavelength dimension during the electrochemical process. We showcase electrochemically controlled anomalous transmission and holography with good switching performance. Such electrochemically powered optical metasurfaces lay a solid basis to develop metasurface devices for real-world optical applications.

Hierarchical layered structures, whether in a compact form like nacre or a porous manner like bone, are well known for their combined features of high stiffness, strength, and lightweight, inspiring many man-made materials and structures for high performance applications. The use of nacre/bone like hierarchical structures in polymer nanocomposites can achieve excellent mechanical and functional properties with high filler volume fractions after carefully aligning functional nanofillers, although the fabrication and processing remain a great challenge. In this work, a bio-inspired lightweight nano-cellular epoxy/graphene-Fe3O4 nanocomposite with high nanofiller loading of 75 wt.% was successfully fabricated by combining features from both nacre and bone structures, via a simple compression molding process together with an eco-friendly supercritical CO2 foaming process to achieve robust mechanical strength and excellent electromagnetic interference (EMI) shielding effectiveness (SE) simultaneously. Highly aligned graphene-Fe3O4 nanoplatelets with well controlled nanoscale porous structures (52.6 nm) enabled both low density (1.26 g/cm3) and high specific EMI SE >5200 dB/cm2/g, as well as preserved tensile strength of 67 MPa. This study provides a sustainable route to fabricate nature mimicked structures with high performance and high flexibility for a wide range of applications, from portable electronics to healthcare devices.

Here, all-solid scanning electrochemical cell microscopy (SECCM) is first established by filling polyacrylamide (PAM) into nanocapillaries as a solid electrolyte. A solid PAM nanoball at the tip of a nanocapillary contacts graphene and behaves as an electrochemical cell for simultaneously measuring the morphology and electrochemical activity. Compared with liquid droplet-based SECCM, this solid nanoball is stable and does not leave any electrolyte at the contact regions, which permits accurate and continuous scanning of the surface without any intervals. Accordingly, the resolutions in the lateral (x-y) and vertical (z) directions are improved to ∼10 nm. The complete scanning of the wrinkles on graphene records low currents at the two sidewalls of the wrinkles and a relatively high current at the center of the wrinkles. The heterogeneity in the electrochemical activity of the wrinkle illustrates different electron transfer features on surfaces with varied curvatures, which is hardly observed by the current electrochemical or optical methods. The successful establishment of this high spatial electrochemical microscopy overcomes the current challenges in investigating the electrochemical activity of materials at the nanoscale, which is significant for a better understanding of electron transfer in materials.