Tunable Optical Absorption on “Zn x Ti x O4-3 y N2 y ” Nanosized Spinel Powders

Using a recently developed sol−gel route to prepare new Ti4+@ZnO nanocolloids, we were able to synthesize, at relatively low temperature (maximum 750 °C) and very short annealing time (1 h) under ammonia gas flow, nanosized colored “Zn1.33Ti1.33O4-3 y N2 y ” oxynitride powders (Zn/Ti = 1) with tunable optical absorption. Above the dissociation temperature of ammonia, the UV−vis spectra are progressively red-shifted with increasing nitriding temperature and the nanosized powder shows a yellowish color at 700 °C under NH3. X-ray diffraction, scanning electron microscopy, X-ray photoemission spectroscopy, oxygen and nitrogen analysis, and UV−vis spectroscopy measurements show that this red shift is directly related to the nitrogen content.