Physicochemical Effects of Proton Implantation Doping on Transparent Nanoscale Thin Films of Polyaniline Emeraldine Base Covalently Fabricated on Organosilanized Surfaces

Physicochemical effects of proton implantation doping on transparent nanoscale thin films of non-conductive polyaniline emeraldine base covalently fabricated on organosilanized surfaces were investigated in this study. Resistance measurement using the Au-electrode array coated with an initially non-conductive thin film of polyaniline emeraldine base showed that proton irradiation could first induce a drastic effect to decrease the resistance of polyaniline emeraldine base and then continue to act as a doping process to further exponentially reduce the resistance to yield a relatively stable conductive state for the proton-irradiated PANI EB. Analysis of experimental results obtained by X-ray photoelectron spectroscopy and Raman spectroscopy also revealed that (i) the proportion of bonding structures characterized as protonated amine/imine groups related to electrical conduction for polyaniline was increased after proton irradiation, (ii) nitro groups were introduced to the polymer by the applied proton beam propagating through the ambient air and (iii) crosslinking could be induced by proton irradiation through the formation of phenazine-like structures between polymer chains. With crosslinking and nitration, the proton-irradiated polyaniline exhibited electrical conductivity similar to that of polyaniline derivatives with N-alkylaniline and nitroaniline as co-monomer units in the polymer chains.