An Estimate of a Frequency Characterizing the Electrochemical Stability of a Gold Electrode Modified by MHDA Thiol in Different Ways

A theoretical investigation aimed at estimating a characteristic frequency in the medium-low frequency domain in which the impedance response of a given interface measured by electrochemical impedance spectroscopy (EIS) is almost constant, constitutes the basic idea of this work. A theoretical model was subsequently applied to the data resulting from EIS measurements performed on gold electrodes modified by various ways of 16-mercaptohexadecanoic acid (MHDA) thiol functionalization. Analysis of these data revealed a direct relationship between the way the substrate was modified and this characteristic frequency. This work is licensed under a Creative Commons Attribution 4.0 International License

H2 sensing properties of modified silicon nanowires

It has been found that the silicon nanowires modified with noble metals can be used to fabricate an effective H2 gas sensor in the present study. The preparation and surface modification of silicon nanowires (SiNWs) were carried out by chemical methods. The morphology of the silicon nanowires unmodified and modified with nanoparticles of platinum, palladium, silver and gold was investigated using scanning electron microscopy (SEM). The chemical composition of the silicon nanowire layers was studied by secondary ion mass spectroscopy (SIMS) and energy dispersive X-ray analysis (EDX). The structures of type metal/SiNWs/p-Si/Al were fabricated. The electrical characterization (I–V) was performed in primary vacuum and H2 at different concentrations. It was found that the metal type used to modify the SiNWs strongly influenced the I–V characteristics. The response of these structures toward H2 gas was studied as a function of the metal type. Finally, the sensing characteristics and performance of the sensors were investigated

Investigation of Silicon-Based Nanostructure Morphology and Chemical Termination on Laser Desorption Ionization Mass Spectrometry Performance

International audienceWe have evaluated the laser desorption ionization mass spectrometry (LDI-MS) performance of six nanostructured silicon surfaces of different morphologies and chemical functionalizations. The substrates have been synthesized either by metal-assisted etching method or by vapor−liquid−solid (VLS) growth technique. In addition to the commercial nanostructured silicon-based surface (NALDI) target plates, serving as reference, the homemade surfaces have been evaluated in mass spectrometry experiments conducted with peptide solutions mimicking tryptic digests. LDI surfaces synthesized by metal-assisted etching method were the most efficient in terms of signal intensities and number of detected peptides. The surface providing the best LDI-MS performance was composed of two nanostructured layers. Interestingly, we also observed a significant influence of the type of organic coating (hydrocarbon vs fluorocarbon) on peptide ionization discrimination

High performance silicon nanowires/ruthenium nanoparticles micro-supercapacitors

International audienceThe continuous increase of small electronic devices calls for small energy storage components, commonly known as micro-supercapacitors, that can ensure autonomous operation of these devices. In this work, we propose a simple and straightforward method to achieve high energy and power densities of a silicon-based micro-supercapacitor, consisting of silicon nanowires decorated with ruthenium nanoparticles (Ru/Si NWs). The Si NWs are obtained through the common vapor-liquid-solid (VLS) growth mechanism, while a simple electroless process is used to deposit Ru nanoparticles. While silicon nanostructuration allows to increase the surface area, coating with Ru NPs introduces a pseudocapacitance necessary to attain high energy and power densities. The Ru/Si NWs micro-supercapacitor exhibits a specific capacitance of 36.25 mF cm(-2) at a current density of 1 mA cm(-2) in a neutral Na2SO4 electrolyte and a high stability over 25 000 cycles under galvanostatic charge-discharge at 1 mA cm(-2). A solid state supercapacitor is then fabricated with symmetric electrodes separated by a polyvinyl alcohol/sulfuric acid electrolyte. The device displays a specific capacitance of similar to 18 mF cm(-2) at a current density of 1 mA cm(-2) and a specific power density 0.5 mW cm(-2). This solid-state nanowire device also exhibits a good stability over 10 000 galvanostatic charge-discharge cycles

ZnO/Carbon nanowalls shell/core nanostructures as electrodes for supercapacitors

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High performance of 3D silicon nanowires array@CrN for electrochemical capacitors

International audienceSilicon nanowire (SiNWs) arrays were coated with chromium nitride (CrN) for use as super-capacitor electrodes. The CrN layer with different thicknesses were deposited on SiNWs using bipolar magnetron sputtering method. The areal capacitance of the SiNWs-CrN, measured in 0.5 M H2SO4 electrolyte, was as high as 180 mF.cm-2 at a scan rate of 5 mV.s-1 (31.8 mF.cm-2 at 1.6 mA.cm-2) and excellent electrochemical stability with a retention of 92% over 15000 cycles. This work paves the way toward using CrN modified 3D SiNWs arrays in micro-supercapacitors

Achieving on chip micro-supercapacitors based on CrN deposited by bipolar magnetron sputtering at glancing angle

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Silicon nanowire-hydrogenated TiO2 core-shell arrays for stable electrochemical micro-capacitors

International audienceIn this paper, we fabricated silicon nanowire-TiO2 core-shell arrays in a two-step process. First, silicon nanowire arrays (SiNW) were prepared in HF/AgNO3 aqueous solution using metal-assisted chemical etching of bulk silicon. Then, atomic layer deposition (ALD) technique was applied to coat a 20 nm thin shell TiO2 film. The TiO2/SiNW substrates were afterward annealed at 400°C in hydrogen atmosphere for 4 h and tested as electrode materials for electrochemical micro-capacitors. The electrochemical features of the constructed H−TiO2/SiNW electrode were assessed in an aqueous 1 M Na2SO4 electrolyte solution and revealed that the specific capacitance increased six times compared to non-annealed TiO2/SiNW and 20-fold compared to a reference SiNW electrode under the same operating conditions. Importantly, H−TiO2/SiNW also displayed a high stability over 30,000 cycles at 0.1 mA cm−2 with an overall decrease of 19% of the initial capacitance. The hydrogen treatment increased the density of hydroxyl group and enhanced the carrier density on TiO2 surface improving the capacitive properties of H−TiO2/SiNW