Synthesis and characterization of nitrogen-doped TiO2 nanoparticles prepared by sol–gel method

The N-doped TiO2 has been synthesized by sol–gel method, using titanium isopropoxide, isopropanol and an aqueous solution of ammonia with ratio 2:1:10. The concentrations used for the NH3 aqueous solution were 3, 7, 10 and 15 %. The samples have been analysed by X-ray diffraction, electron microscopy (SEM and TEM) thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), micro-Raman spectroscopy and diffuse reflectivity. TEM, SEM, DSC and TGA showed that the morphology is influenced by the presence of N3− ions but not by the concentration of the solution. Instead reflectance gave us a relation between values of the energy gap and the concentration of N3− ions: the gap between valence and conduction band lowers as the concentration of NH3 in the starting solution increases. From these results we can say that the properties of the material have been tuned by doping with nitrogen ions because the particles absorb more light in the visible range, and this is important for photovoltaic and photocatalytic applications.