Transport and optical properties of SiO2–polypyrrole nanocomposites

Conducting polypyrrole-wide band gap semiconducting silica (SiO2) nanocomposites are prepared by polymerizing pyrrole in the presence of colloidal silicon oxide sol. The nanocomposites are characterized by Fourier transform infrared spectrometer and scanning electron microscope. Three dimensional variable range hopping conduction process is involved in electric conduction. The current density ( J ) satisfies the power law, J ∝ V m , with 1 < m < 2 at voltage V > 0.5 V . Optical absorption spectra reveal that the π – π ∗ transition of polypyrrole shifts from 3.9 eV to 4.58 eV with increase of silica concentration.