The polymer/nanoparticle interface of polyaniline (PANI)/TiO2 composite was characterized by using Fourier transform infra-red spectrometer imaging system, Raman (both coupled with optical microscope) and UV-vis spectroscopy. During characterization, as white light from the optical microscope impinges on TiO2, it absorbs supra band-gap photons and electron-hole pairs are produced. On accepting the holes, PANI gets oxidized from emeraldine salt form to its next oxidation state that is pernigraniline salt form, leading to a change in color. In optical micrographs this change in color appears as a halo around each TiO2 particle and defines the extent of the oxidized area of PANI, which helps to characterize the extent of oxidation of PANI at the interface of PANI/TiO2. Further studies revealed that the range and extent of oxidation at the interface in polymer depend on the types of dispersions of TiO2 nanoparticles in PANI matrix. (C) 2016 Elsevier B.V. All rights reserved.