Electrode processes at gas vertical bar salt vertical bar Pd nanoparticle vertical bar glassy carbon electrode contacts: salt effects on the oxidation of formic acid vapor and the oxidation of hydrogen

The electrochemical oxidation of formic acid to CO2 is facile at nano-palladium catalysts. In conventional electrochemical systems this process is conducted in aqueous phase and the resulting formation of poorly soluble CO2 gas can limit the kinetics. Here, an alternative electrochemical system with the gas phase in closer contact to the palladium nanoparticle catalyst is investigated based on a glassy carbon electrode and a solid salt electrolyte. It is demonstrated that the reaction zone of salt (here (NH 4)2SO4 is most effective), palladium nanoparticle catalyst, and gas phase, is where the electrochemical oxidation process occurs. The effects of the type of salt, the partial pressure of formic acid, and the gas flow rate are investigated. Preliminary data for the oxidation of hydrogen gas at the saltpalladiumelectrode contact are reported. A significant salt effect on the palladium catalysed reactions is observed and potential future applications of "salt cells" in sensing are discussed. © 2011 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique

Electrode processes at gassaltPd nanoparticleglassy carbon electrode contacts: Salt effects on the oxidation of formic acid vapor and the oxidation of hydrogen

The electrochemical oxidation of formic acid to CO2 is facile at nano-palladium catalysts. In conventional electrochemical systems this process is conducted in aqueous phase and the resulting formation of poorly soluble CO2 gas can limit the kinetics. Here, an alternative electrochemical system with the gas phase in closer contact to the palladium nanoparticle catalyst is investigated based on a glassy carbon electrode and a solid salt electrolyte. It is demonstrated that the reaction zone of salt (here (NH 4)2SO4 is most effective), palladium nanoparticle catalyst, and gas phase, is where the electrochemical oxidation process occurs. The effects of the type of salt, the partial pressure of formic acid, and the gas flow rate are investigated. Preliminary data for the oxidation of hydrogen gas at the saltpalladiumelectrode contact are reported. A significant salt effect on the palladium catalysed reactions is observed and potential future applications of "salt cells" in sensing are discussed. © 2011 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique

Catalyst-free synthesis of sodium amide nanoparticles encapsulated in silica gel

Crystalline sodium amide nanoparticles encapsulated in an amorphous silica framework were formed by ammoniation of a precursor material, silica gel loaded with metallic sodium, under mild conditions and without catalysis. This ammoniation was performed in situ on TOSCA beamline at ISIS, RAL, using anhydrous gaseous ammonia. The resulting material exhibits no pyrophoricity and much reduced air- and moisture-sensitivity compared to the bulk amide. The nanoparticles formed will offer a greatly increased surface area for chemical reactions where amide is currently used as an important ingredient for industrial applications. We anticipate that this method of sodium amide production will have a diversity of applications. © 2013 Elsevier B.V. All rights reserved

"Hydrothermal wrapping" with poly(4-vinylpyridine) introduces functionality: pH-sensitive core-shell carbon nanomaterials

Negatively charged carbon nanoparticles (surface-phenylsulfonated) are "wrapped" in a poly(4-vinylpyridine) cationomer and hydrothermally converted into a pH-responsive core-shell nano-composite. With a "thin shell" this nano-material (ca. 20-40 nm diameter) is water-insoluble but readily dispersed into ethanol and deposited onto electrodes. Zeta-potential measurements suggest a point of zero charge (PZC) at ca. pH 4.5 with negative functional groups dominating in the more alkaline range and positive functional groups dominating in the acidic range. XPS data suggest carboxylate and pyridinium-like functional groups. This is further confirmed in voltammetric measurements for adsorbed cations (methylene blue) and adsorbed anions (indigo carmine). The specific capacitance reaches a maximum of 13 F g-1 at the PZC explained here tentatively by a "shell charging" effect within the nanoparticle shell. This journal is © The Royal Society of Chemistry

Crystal growth of Cu2ZnSnS4 solar cell absorber by chemical vapor transport with I2

Single crystals of Cu2ZnSnS4 have been produced within sealed quartz ampoules via the chemical vapour transport technique using I2 as the transporting agent. The effects of temperature gradient and I2 load on the crystal habit and composition are considered. Crystals have been analyzed with XRD, SEM, and TEM for compositional and structural uniformities at both microscopic and nanoscopic levels. The synthesized crystals have suitable (I2-load dependent) properties and are useful for further solar absorber structural and physical characterizations. A new chemical vapour transport method based on longitudinally isothermal treatments is attempted. Based on a proposed simplistic mechanism of crystal growth, conditions for crystal enlargement with the new method are envisaged

Hydrothermal conversion of one-photon-fluorescent poly(4-vinylpyridine) into two-photon-fluorescent carbon nanodots.

A novel two-photon-fluorescent N,O-heteroatom-rich carbon nanomaterial has been synthesized and characterized. The new carbon nanoparticles were produced by hydrothermal conversion from a one-photon-fluorescent poly(4-vinylpyridine) precursor (P4VP). The carbonized particles (cP4VP dots) with nonuniform particle diameter (ranging from sub-6 to 20 nm with some aggregates up to 200 nm) exhibit strong fluorescence properties in different solvents and have also been investigated for applications in cell culture media. The cP4VP dots retain their intrinsic fluorescence in a cellular environment and exhibit an average excited-state lifetime of 2.0 ± 0.9 ns in the cell. The cP4VP dots enter HeLa cells and do not cause significant damage to outer cell membranes. They provide one-photon or two-photon fluorescent synthetic scaffolds for imaging applications and/or drug delivery