The development of facile synthetic methodologies for Er³⁺ doped TiO₂ novel luminescent nanoparticles with controlled and uniform crystalline phase, shape and size is very crucial to manipulating their optical properties and exploring their potential applications in diverse fields. For this reason, various chemical approaches including sol-gel, chemical vapour decomposition, and microwave assisted method  to mention a few have been developed. Among them, this study has been devoted to the sol-gel method due to its unique features such as ease of synthesis, synthesis of high purity nano-sized crystalline powders at low temperatures  and better homogeneity and production of high purity powder. TiO₂ doped with an intention of producing up-converted luminescence has not been fully explored. Structural, morphological, molecular functional groups as well as optical absorption analysis through various techniques have been done. 

Scanning electron microscope showed the morphological change in the structure of Er:TiO₂ as compared to undoped sample. Energy dispersive X-ray spectroscopy (EDX) confirmed the Er doping in the TiO₂ nanoparticles. Both the XRD and TEM analyses confirm that both the pure and Er doped TiO₂ are in pure anatase phase and in nano size range, respectively. From the PL analysis it is found that doping Er³⁺ improves the  luminescence behavior in comparison with the pure TiO₂ nanoparticles. Intense Er³⁺-based emission peaks in the range 520–560 nm were observed for all samples. It was observed that Er-dopant concentration had direct impact on photoluminescence intensity. Upon excitation at 350 nm, two down-conversion contributions at 378 nm and 435 nm attributed to indirect band gap and defect-related emissions, respectively were observed from both pure and Er³⁺ doped TiO₂ nanoparticles. Overall, doping very low concentrations of Er³⁺ greatly alters the structural morphology and directly increases the luminescence behavior of TiO₂ suitable for advanced  photocatalytic applications.

Keywords: TiO₂, Erbium doping, photoluminescence