Optical, structural and fluorescence microscopic studies on reduced form of polyaniline: The leucoemeraldine base

Electrochemically deposited thin films of emeraldine salt (ES) on indium-tin-oxide (ITO) glass plate and [111] silicon crystal were treated chemically with a phenyl hydrazine (PNH) solution in order to obtain a leucoemeraldine base (LB) form of polyaniline (PANI). The NMP-treated PANI films were washed using different organic solvents. ES, LB and air-oxidized LB films were examined using UV-visible, optical microscopy, X-ray diffraction and fluorescence microscopic techniques. The obtained results showed a direct correlation in the optical, structural and fluorescence behaviour of the LB form of PANI. An X-ray diffraction study revealed the partial crystallinity in the ES, whereas the LB and the air-oxidized LB showed amorphous structures. The first evidence of high fluorescence microscopic behaviour in the LB form of PANI has been observed. The gradual decrease in fluorescence signal as a function of time for the LB film has been interpreted as being due to the diffusion phenomenon in relation to the contact of the complex of the phenyl ring with O2 molecules.