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 O-2 molecules.