Annealing effect on structural and optical properties of Metal halides doped polypyrrole

摘要

Polypyrrole (pure) and its metal halide composites have been synthesized by chemical oxidation polymerization technique with ammonium peroxisulphate (oxidant) in aqueous hydrochloric acid medium These pure and doped samples were named as S1(as prepared),S2 (100% Co),S3 (Co Ni 50%),S4 (Ni100%). Further investigation these pure and doped samples were annealed at 200?°C for 4 hrs. The amorphous nature of these annealed and as prepared samples was confirmed by XRD. FTIR spectra & SEM images of all the samples were taken at room temperature, which indicates in significant changes in annealed samples. FTIR spectra give the chemical structure of these samples. Characterization through SEM gives the information of surface morphology, from this it is found that surface of as prepared samples is not smooth but in annealed samples the surface shows fine structure as compared to as prepared samples. The absorption spectra were recorded by USB‐2000 spectrophotometer at room temperature in the wave length range 300-800 nm. From the analysis of absorption spectra, it was observed that energy band gap of samples varies with concentration of dopant, and optical band gap of as prepared samples(S1-S4) was determined to be 2.64, 2.32, 2.57, 2,29 eV, and for annealed samples (A1-A4) values obtained were 2.30, 2.27, 2.36 & 2.16 eV. The variation of band gap with concentration has been explained on the basis of bonding of cobalt and nickel with polypyrrole matrix during their polymerization and effect of annealing.