Vapor phase secondary doping of polyaniline (emeraldine salt) thin films with o-chlorophenol investigated by UV-VIS-NIR: Effects of primary dopants, substrate surfaces, and pre-treatments of organic vapors

In this study, the effects of incorporated primary dopants, pre-treatments of organic vapors, and wettability of substrate surfaces on the vapor phase secondary doping of a series of polyaniline (emeraldine salt) thin films with o-chlorophenol were investigated by UV-VIS-NIR. The response of each of these thin films upon vapor phase secondary doping by o-chlorophenol was analyzed by comparing the change in the NIR intensity of obtained spectra before and after the secondary doping. The results showed that the types of primary dopants and pre-treatments of organic vapors, but not the wettability of the substrate surfaces, could significantly affect the responses of polyaniline thin films to secondary doping. Although HCSA (camphorsulfonic acid)-doped polyaniline thin films responded to secondary doping by o-chlorophenol, no response to vapor phase secondary doping was observed when HCl-doped polyaniline thin films were exposed to o-chlorophenol. Pre-treatments of in situ deposited HCSA-doped polyaniline thin films by organic vapors (CHCl3 or NMP; N-methyl-2-pyrrolidinone) showed that these HCSA-doped polyaniline thin films responded to only NMP vapor. It is also interesting to find that the combined effect of the treatments with CHCl3 vapor followed by o-chlorophenol vapor on in situ deposited HCSA-doped polyaniline thin films was almost equivalent to that of the treatments with NMP vapor followed by o-chlorophenol vapor, even though the respective treatment by CHCl3 or NMP vapor alone had a different effect on in situ deposited HCSA-doped polyaniline thin films.