The influence of the electrodeposition parameters on the morphology of organo-transition metal complexes for thin film gas sensor applications

Abstract

This paper describes the electrodeposition of tetrabutylammonium bis(1,3-dithiol-2-thione-4,5-dithiolate) nickelate (Bu 4NNi(dmit) 2) onto platinum, 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. The bulk conductivity of the deposited films was found to be 4×10 −2 S cm −1 irrespective of the heterocycle added. Cyclic voltammetry was carried out using the three electrodes: the gold and platinum electrodes showed similar electrochemical behaviour, with the peaks assigned to the redox properties of the metal-dmit; the SnO 2 electrode did not yield any distinct peaks. It is suggested that this was because the rate of electron transfer to the SnO 2 electrode was the rate-limiting step rather than the rate of diffusion to the electrode surface as in the 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 dichloromethane had a much lower surface area than those deposited from nitrobenzene, and the magnitude of the change in resistance on exposure to sulphur dioxide was a factor of four lower than for the films deposited in nitrobenzene. Studies were also carried out on copper and cobalt 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. © 1997 Elsevier Science S.A.