Wavelet-Based Linear-Response Time-Dependent Density-Functional Theory

Linear-response time-dependent (TD) density-functional theory (DFT) has been implemented in the pseudopotential wavelet-based electronic structure program BigDFT and results are compared against those obtained with the all-electron Gaussian-type orbital program deMon2k for the calculation of electronic absorption spectra of N2 using the TD local density approximation (LDA). The two programs give comparable excitation energies and absorption spectra once suitably extensive basis sets are used. Convergence of LDA density orbitals and orbital energies to the basis-set limit is significantly faster for BigDFT than for deMon2k. However the number of virtual orbitals used in TD-DFT calculations is a parameter in BigDFT, while all virtual orbitals are included in TD-DFT calculations in deMon2k. As a reality check, we report the x-ray crystal structure and the measured and calculated absorption spectrum (excitation energies and oscillator strengths) of the small organic molecule N-cyclohexyl-2-(4-methoxyphenyl)imidazo[1,2-a]pyridin-3-amine

Reductive cross-coupling reactions (RCCR) between CN and CO for β-amino alcohol synthesis

International audienc

A Direct and Versatile Access to a,a-Disubstituted 2-Pyrrolidinyl-methanols by SmI2-Mediated Reductive Coupling

International audienceVarious a,a-disubstituted 2-pyrrolidinyl-methanols are efficiently prepared in a single step from ketones using a SmI2-mediated cross-coupling with 1-pyrroline N-oxide. The N-hydroxy-a,a-diphenylprolinol is also easily prepared and resolved

Mass production of silicon nanowires for Lithium-ion battery

International audienceFirst produced by thin film technologies (CVD growth or etching), silicon nanowires (SiNWs) have shown great promises in nanoelectronics, sensors and energy storage. For the latter, high quantities of SiNWs are required. We recently developed a new technology of SiNW synthesis that allows for the preparation of large quantities of SiNWs in bulk in a small, simple reactor within a few hours. Our SiNWs are grown on metal nanoparticles deposited on an unreactive nanopowder of NaCl. After synthesis, the NaCl powder is dissolved in water to recover a dense mat of pure SiNWs. From an air-stable organosilane oil as Si source, about 200mg of SiNWs are obtained in a 100mL steel reactor. NaCl particles play a critical role as a “solid solvent”, keeping catalysts available to reactive gases and apart from each other during growth. Bulk grown SiNWs behave differently from SiH4-fed CVD-grown SiNWs: long and very thin (10nm), very small in diameter, they are strongly hydrophobic and show a low oxygen content even after exposure to air. Lithium-metal batteries made of SiNW-based anodes had a long cycling ability with a stable, high energy capacity (1800mAh/gSi over >100 cycles at 1C) with an initial capacity loss in the first charge-discharge cycles as low as 20%. (poster 13BZD

Organic shell wrapped silicon nanowires as an energy storage material

International audienceSilicon nanowires were first produced by lithography or CVD for electronics, sensing and optical applications. Independently, silicon has emerged as highly promising in lithium-ion battery anodes because of its absorbing 10 times more lithium than the standard carbon anodes. Silicon in battery anodes is submitted to intense mechanical constraints due to lithiation-delithiation, that only very small crystals can handle. Silicon nanowires then appeared as particularly efficient as they can withstand such constraints and maintain battery cycling over several hundreds of cycles. However, silicon nanowires grown as thin films do not fit as material for lithium-ion batteries, neither in terms of mass produced nor in terms of production cost: even a coin cell contains several milligrams of anode material, while silicon nanowires are grown at μg/cm$^2$ by CVD.We recently patented [1] a new technology of silicon nanowire synthesis designed for mass production as a powder. The nanowires are grown in a glass or steel reactor at medium temperature (430°C) from metal nanoparticles deposited on an inert support, and from an air-stable organosilane as the silicon source. Table salt (NaCl) is usually used as a support that can be conveniently removed by washing with water after growth. Growth on salt also avoids handling silicon nanowires as a dry powder, preventing risk of inhaling nanoparticles. The synthesis yields silicon nanowires in gram scale, with a yield of 70-80%. Tests of the pure silicon nanowires in lithium-metal batteries show an excellent capacity retention over 1000 cycles

Mass production of silicon nanowires for Lithium-ion battery

International audienceFirst produced by thin film technologies (CVD growth or etching), silicon nanowires (SiNWs) have shown great promises in nanoelectronics, sensors and energy storage. For the latter, high quantities of SiNWs are required. We recently developed a new technology of SiNW synthesis that allows for the preparation of large quantities of SiNWs in bulk in a small, simple reactor within a few hours. Our SiNWs are grown on metal nanoparticles deposited on an unreactive nanopowder of NaCl. After synthesis, the NaCl powder is dissolved in water to recover a dense mat of pure SiNWs. From an air-stable organosilane oil as Si source, about 200mg of SiNWs are obtained in a 100mL steel reactor. NaCl particles play a critical role as a “solid solvent”, keeping catalysts available to reactive gases and apart from each other during growth. Bulk grown SiNWs behave differently from SiH4-fed CVD-grown SiNWs: long and very thin (10nm), very small in diameter, they are strongly hydrophobic and show a low oxygen content even after exposure to air. Lithium-metal batteries made of SiNW-based anodes had a long cycling ability with a stable, high energy capacity (1800mAh/gSi over >100 cycles at 1C) with an initial capacity loss in the first charge-discharge cycles as low as 20%. (poster 13BZD

An implementation of the nudged elastic band algorithm and application to the reaction mechanism of HGXPRTase from Plasmodium falciparum

International audienc

Synthesis and evaluation of 1-(1H-indol-3-yl)ethanamine derivatives as new antibacterial agents.

International audienceA collection of 3-substituted indole derivatives was prepared using nucleophilic addition of indoles to nitrones. The compounds were then tested for their antibacterial activity against almost thirty bacterial strains representative of common human pathogens. Two types of indolic molecules inhibit the growth of Staphylococcus aureus, including MRSA and VISA strains, with MIC values ranging from 8 to 16 mg/L

Scalable chemical synthesis of doped silicon nanowires for energy applications

A versatile, low-cost and easily scalable synthesis method is presented for producing silicon nanowires (SiNWs) as a pure powder. It applies air-stable diphenylsilane as a Si source and gold nanoparticles as a catalyst and takes place in a sealed reactor at 420 °C (pressure 0.4%. When used in symmetric supercapacitor devices, 1% P-doped SiNWs exhibit an areal capacity of 0.25 mF cm−2 and retention of 80% of the initial capacitance after one million cycles, demonstrating excellent cycling stability of the SiNW electrodes in the presence of organic electrolytes