Detection of chloroform with a sensor array consisting of electrochemically deposited polythiophenes films: Processes governing the electrical response

Carvalho, E. R.; Correa, A. A.; Consolin Filho, N.; Oliveira, O. N.; Gomes, Henrique L.; Mattoso, L. H. C.; Neto, L. Martin

http://hdl.handle.net/10400.1/6594

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A sensor array made up with electrodeposited polythiophene films onto interdigitated gold electrodes has been used to detect small concentrations of chloroform in water, down to 0.1 mg L-1. An analysis of the impedance data revealed two relaxation processes, one attributed to the polymer coating and associated with the double layer and the other ascribed to the electrolyte. Because these processes depended on the type of polythiophene derivative and on doping, the sensitivity of the electrodes varied. The most sensitive to chloroform was the poly(methyl thiophene) oxidized at 5 mC. Also, doped layers were more sensitive, from which one may infer that a plausible mechanism for detection is the removal of dopant ions by the solvent. Surprisingly, a bare gold metal electrode was more sensitive than some electropolymerized samples, probably because the relaxation processes in the latter were not strongly affected by chloroform.