Structural, optical, and electrical characteristics of anatase titanium dioxide tailored by doping of nitrogen and copper ions

Abstract

Pure anatase TiO2 nanoparticles and its mono–doped and co–doped derivatives [i.e. (TiN0.007O1.993); (Ti0.998Cu0.002O2); (Ti0.998Cu0.002N0.007O1.993)] were prepared by sol–gel auto–combustion technique. Further, the effects of copper (Cu) and nitrogen (N) dopants have been investigated on structural, optical and dielectric properties of nanostructured TiO2 using X–ray diffraction (XRD), Raman spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy and dielectric spectroscopy measurement respectively. The Rietveld refinement analysis of XRD data and Raman spectra revealed that all the synthesized samples have pure anatase phase having tetragonal structure with space group of I41/amd. The pure anatase phase of doped samples illustrate the substitution of Cu ions at Ti4+ sites and N ions at O2− sites in the TiO2 host lattice. The crystallite size of TiO2 and its derivatives has been observed in the range of 11–14 nm. The band gap of TiO2 reduced from 3.2 to 1.9 eV with mono–doping and co–doping of the N and Cu in TiO2 lattice as confirmed by UV–Vis spectroscopy. This red–shift might be occur due to the possible formation of N–2p and Cu–3d localized levels (mono–doping case), and the creation of isolated intermediate states (co–doping case). The dielectric spectroscopy was carried out to investigate the electrical properties in details and explained in terms of structural and intrinsic ionic behaviour of different dopants. The detected band gap energies in N/Cu mono–doped and co–doped anatase TiO2 fall within the visible spectrum, rendering them suitable for harnessing solar energy in photocatalysis and photovoltaic applications.