THE INFLUENCE OF THE ELECTRODEPOSITION PARAMETERS ON THE MORPHOLOGY OF ORGANO-TRANSITION METAL-COMPLEXES FOR THIN-FILM GAS SENSOR APPLICATIONS

This paper describes the electrodeposition of tetrabutylammonium bis(1 ,3-dithiol-2-thione-4,5-dithiolate) nickelate (Bu4NNi(dmit)(2)) onto p latinum, gold interdigitated and fluoride-doped tin oxide electrodes. The effects of adding pyrrole, thiophene, 3-methylthiophene and furan to the deposition solution on the film morphology were investigated. T he bulk conductivity of the deposited films was found to be 4 x 10(-2) S cm(-1) irrespective of the heterocycle added. Cyclic voltammetry wa s carried out using the three electrodes: the gold and platinum electr odes showed similar electrochemical behaviour, with the peaks assigned to the redox properties of the metal-dmit; the SnO2 electrode did not yield any distinct peaks. It is suggested that this was because the r ate of electron transfer to the SnO2 electrode was the rate-limiting s tep rather than the rate of diffusion to the electrode surface as in t he case of the platinum and gold electrodes. The films deposited onto the interdigitated gold electrodes were exposed to sulphur dioxide and changes in the film resistance were monitored. Films deposited in dic hloromethane had a much lower surface area than those deposited from n itrobenzene, and the magnitude of the change in resistance on exposure to sulphur dioxide was a factor of four tower than for the films depo sited in nitrobenzene. Studies were also carried out on copper and cob alt dmit analogues; the copper-dmit behaved in a similar manner to the nickel-dmit, although the films were of very low conductivity,whereas the cobalt-dmit showed no reversible redox behaviour. (C) 1997 Elsevi er Science S.A.