Role of synthesis of upconversion nanoparticles towards surface modification and photocatalysis

$$\hbox {TiO}₂$$ being a wide band gap semiconducting material cannot use the solar insolation for photocatalysis. An interesting strategy is to dope $$\hbox {TiO}₂$$ with upconverting rare earth materials, which upon infrared (IR) or visible light irradiation can emit ultraviolet light to generate excitons in $$\hbox {TiO}₂$$ for further catalytic reactions. This manuscript reports the incorporation of $$\hbox {Er}₂\hbox {O}₃/\hbox {Yb}₂\hbox {O}₃$$ into $$\hbox {TiO}₂$$ via two synthetic methodologies. One of which yields the co-presence of rare earth oxides and $$\hbox {TiO}₂$$ on the surface, while the other synthetic route yields the rare earth oxides in the core of the $$\hbox {TiO}₂$$ shell. The detailed structural, morphological and optical properties of the laboratory synthesized materials were studied by powder XRD, FE-SEM, STEM, HR-TEM, BET, UV-DRS and PL. The surfaces of the materials did show some difference in their properties depending on their synthesis route, however, the two photon excitation was similar to both the set of materials. The synthesized materials were studied for degradation of rhodamine B dye, and the results suggested that the presence of $$\hbox {Er}₂\hbox {O}₃/\hbox {Yb}₂\hbox {O}₃$$ on the $$\hbox {TiO}₂$$ surface was detrimental for catalytic application, while $$\hbox {TiO}₂$$ exposed on the surface with $$\hbox {Er}₂\hbox {O}₃/\hbox {Yb}₂\hbox {O}₃$$ in the core can be a choice of materials for photocatalytic application.