Metallisation of gel surfaces under ambient conditions.

A room temperature method to coat a non-conducting gel phase with a metal is described, which uses galvanic displacement. Electrolytes are dissolved in the gel phase to allow metal deposition from an immiscible liquid electrolyte solution. Conformal deposition was achieved by imprinting the gel, followed by galvanic displacement of gold.

Inhibited and enhanced nucleation of gold nanoparticles at the water|1,2-dichloroethane interface.

The deposition of gold at the interface between immiscible electrolyte solutions has been investigated using reduction of tetrachloroaurate or tetrabromoaurate in 1,2-dichloroethane, with aqueous phase hexacyanoferrate as reducing agent. In a clean environment without defects present at the interface, the Au(III) complex was reduced to the Au(I) complex, but no solid phase formation could be observed. A deposition process could only be observed through the addition of artificial nucleation sites in the form of palladium nanoparticles at the interface. This process could be associated with the reduction of the Au(I) halide complex to metallic gold, by determining the gold reduction potentials in 1,2-dichloroethane. XANES measurements indicate that tetrachloroaurate ion transfers intact into the organic phase, with the central Au atom retaining its oxidation state of +3 and the overall anion remaining charged at -1.

Transport of neutral and ionic solutes: the gel/electrode and gel/electrolyte interfaces.

Transport through a polysaccharide gel phase has been investigated voltammetrically using both redox voltammetry at a gel covered electrode and ion transfer voltammetry across the gel/liquid interface (Gel/L). The apparent diffusion coefficients, D(app), of a range of neutral and ionic electroactive species have been determined in both uncharged and anionic polysaccharide media, agar, and kappa-carrageenan, respectively. It is shown that the diffusion of electroactive species in agar gel occurs at a rate similar to that of diffusion in aqueous solution for a range of redox couples. In the kappa-carrageenan medium, by contrast, the diffusion coefficient obtained for cationic solutes was found to be approximately an order of magnitude lower than the value in aqueous solution. The difference in D(app) is attributed to two independent processes: electrostatic interactions between the charge of the sulfonate groups of the kappa-carrageenan gel and the charge of the solute, as well a change in hydration of the solute molecules.