Valence band spectroscopic study of Co-doped TiO2 nanoparticles using synchrotron based advanced spectroscopic techniques

•Selected area electron diffraction patterns of 400, 600 and 800° C annealed TCO samples showed the rings which correspond to pure anatase, mixed and rutile phases of TiO2.•Valence states of composition elements were confirmed using electron energy loss spectroscopy in STEM mode.•Valence band spectroscopic result of TiO2 NPs indicated that they are mostly made of O-2p derived states.•For TCO samples, Co derived state is also seen.•The observation made on resonant photo-electron spectra indicated that Co 3d ions are strongly hybridized to Ti3+ defective states.