Fast synthesis of platinum nanopetals and nanospheres for highly-sensitive non-enzymatic detection of glucose and selective sensing of ions

Novel methods to obtain Pt nanostructured electrodes have raised particular interest due to their high performance in electrochemistry. Several nanostructuration methods proposed in the literature use costly and bulky equipment or are time-consuming due to the numerous steps they involve. Here, Pt nanostructures were produced for the first time by one-step template-free electrodeposition on Pt bare electrodes. The change in size and shape of the nanostructures is proven to be dependent on the deposition parameters and on the ratio between sulphuric acid and chloride-complexes (i.e., hexachloroplatinate or tetrachloroplatinate). To further improve the electrochemical properties of electrodes, depositions of Pt nanostructures on previously synthesised Pt nanostructures are also performed. The electroactive surface areas exhibit a two order of magnitude improvement when Pt nanostructures with the smallest size are used. All the biosensors based on Pt nanostructures and immobilised glucose oxidase display higher sensitivity as compared to bare Pt electrodes. Pt nanostructures retained an excellent electrocatalytic activity towards the direct oxidation of glucose. Finally, the nanodeposits were proven to be an excellent solid contact for ion measurements, significantly improving the time-stability of the potential. The use of these new nanostructured coatings in electrochemical sensors opens new perspectives for multipanel monitoring of human metabolism

The state of absorbed hydrogen in the structure of reduced copper chromite from the vibration spectra

Khassin, Alexander A. Kustova, Galina N. Jobic, Herve Yurieva, Tamara M. Chesalov, Yury A. Filonenko, Georgii A. Plyasova, Lyudmila M. Parmon, Valentin N.The reduction of copper chromite, CuCr2O4, is followed by means of thermogravimetric analysis. The reduced state is studied by means of FT IR spectroscopy, Raman spectroscopy and inelastic neutron scattering. The reduction of copper occurs in two stages: absorption of hydrogen at 250-400 degrees C and dehydration of the reduced state at above 450 degrees C. The measured vibrational spectra prove that a considerable amount of hydrogen is absorbed by the oxide structure with absorbed protons stabilized in OH and HOH-groups (geminal protons). Three groups of vibration bands are observed in the INS spectra, which can be assigned to stretching, bending and libration vibrations. An increase in the reduction temperature of copper chromite results in softening of the stretching and hardening of the bending vibrations, what can be related to the strengthening of hydrogen bonding

Interaction of hydrogen with Cu-Zn mixed oxide model methanol synthesis catalyst

ENERGIE:MATERIAUX+HJOInteraction of hydrogen with model Cu-Zn methanol synthesis catalyst prepared by decomposition of mixed hydroxicarbonate is studied by inelastic neutron scattering, in situ FTIR/MS, and thermal analysis. Reduced (Cu-0.08,Zn-0.92)O mixed oxide accumulates 6H/Cu, mainly as hydride, hydroxyl and formate species. The reduction of copper in the (Cu,Zn)O mixed oxide occurs via a reversible redox interaction with H-2 and absorption of protons as OH--groups with nu =3250 cm(-1) and delta approximate to 1430-1480 cm(-1). Kinetic and thermodynamic parameters of this process are evaluated. The weight loss during the reduction is due to the decomposition of the residual carbonate groups to CO2 via formate intermediates, which occurs in the presence of hydrogen. Exposure of (Cu,Zn)O to air prior to the reduction strongly affects the kinetic parameters of the reduction process. (C) 2013 Elsevier B.V. All rights reserved