Maël Penhoat

Highly controlled synthesis of nanometric gold particles by citrate reduction using the short mixing, heating and quenching times achievable in a microfluidic device

Homodispersed 1.8 nm gold nanoparticles were obtained reproducibly in high yields using the classical Turkevich protocol at a high concentration in a continuous flow capillary reactor. The microfluidic reactor made from commercially available items permitted short mixing, heating and quenching times which are the key parameters of this synthesis.

Oxidative Neutralization of Mustard-Gas Simulants in an On-Board Flow Device with In-Line NMR Monitoring

The fast and effective neutralization of the mustard-gas simulant 2-chloroethyl ethyl sulfide (CEES) using a simple and portable continuous flow device is reported. Neutralization takes place through a fully selective sulfoxidation by a stable source of hydrogen peroxide (alcoholic solution of urea-H2 O2 adduct/MeSO3 H freshly prepared). The reaction progress can be monitored with an in-line benchtop NMR spectrometer, allowing a real-time adjustment of reaction conditions. Inherent features of millireactors, that is, perfect control of mixing, heat and reaction time, allowed the neutralization of 25 g of pure CEES within 46 minutes in a 21.5 mL millireactor (tR =3.9 minutes). This device, which relies on affordable and nontoxic reagents, fits into a suitcase, and can be deployed by police/military forces directly on the attack site.

PTFE supported gold nanoparticles as photocatalysts for oxidative esterification of aldehydes

Homogeneous, small gold nanoparticles (d = 1.87 nm) have been prepared by photochemical reduction of HAuCl4 in the presence of Irgacure® 2959 under high power UV irradiation at 365 nm produced by a LED source. These particles have been deposited on PTFE microbeads (d = 200 μm) and evaluated for the catalysis of the oxidative esterification of aldehydes in the presence of H2O2. Under green light (λ ≈ 530 nm) and repeated addition of H2O2, the catalytic system is accelerated and achieves complete conversions in minutes. Furthermore the catalyst can be recycled ten times consecutively without any activity loss by adding a step for AuNP recycling. The mechanism of the reaction follows a zero rate order, and Hammett free energy relationships for substituted benzaldehydes afforded a positive ρ value (ρ = 2.35) demonstrating that the initial hemiacetalisation equilibrium (ρ = 2.31) is the rate determining step. Kinetics data are in agreement with an Eley–Rideal type mechanism and permits proposing a reaction mechanism.

Rapid and facile chemical actinometric protocol for photo-microfluidic systems using azobenzene and NMR spectroscopy

In this study, the photon flux inside a photomicroreactor was determined using chemical actinometry via the photoisomerization of azobenzene at 365 nm. For this purpose, a differential equation, in which the only external data are the tabulated absorption coefficient and the quantum yield of the E isomer, was derived enabling the use of concentrated solutions of azobenzene needed for simple NMR spectroscopy analysis. The developed protocol is shown to be efficient when working using different concentrations, light intensities and solvents.