The use of gold nanoparticles as biological probes requires the improvement of colloidal stability. Dihydrolipoic acid (DHLA), a dithiol obtained by the reduction of thioctic acid, appears therefore very attractive for the stabilization and the further functionalization of gold nanoparticles because DHLA is characterized by a carboxylic acid group and two thiol functions. The ionizable carboxylic acid groups ensure, for pH > or = 8, the water solubility of DHLA-capped gold (Au@DHLA) nanoparticles, prepared by the Brust protocol, and the stability of the resulting colloid by electrostatic repulsions. Moreover almost all DHLA, adsorbed onto gold, adopts a conformation allowing their immobilization by both sulfur ends. It is proved by sulfur K-edge X-ray absorption near edge structure spectroscopy, which appears as an appropriate tool for determining the chemical form of sulfur atoms present in the organic monolayer. Such a grafting renders the DHLA monolayers more resistant to displacement by dithiothreitol than mercaptoundecanoic acid monolayers. The presence of DHLA on gold particles allows their functionalization by the electroluminescent luminol through amine coupling reactions assisted by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. As a luminol-functionalized particle is nine times as bright as a single luminol molecule, the use of the particles as a biological probe with a lower threshold of detection is envisaged.

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Electrochemical properties of low temperature (LT) crystallized LiCoO, are investigated. LT LiCoO, was obtained by a precipitation process in aqueous solution and a final heat-treatment at 400°C in air. Potentiometric, voltammetric, and ac impedance experiments are performed as well as x-ray diffraction measurements on electrochemically delithiated compounds. LT LiCoO2 shows electrochemical and structural properties quite different from that exhibited by the high temperature (lIT) LiCoO,. The main differences appear in terms of practical voltage, reversibility, Li transport in oxide, and structural changes as Li is deintercalated. This work clearly proves the 3D character of LT LiCoO2 (spinel-like structure). In spite of a lower working potential and a satisfactory capacity (zx = 0.5), the LT LiCoO, is highly reactive toward the electrolyte and is characterized by a slower Li transport than in layered HT LiCoO,.

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Dihydrolipoic acid (DHLA) capped gold nanoparticles (Au@DHLA) are characterized in solid and liquid states by sulfur K-edge XANES spectroscopy; it clearly shows that DHLA is anchored to gold thanks to both sulfur ends.