An investigation of the role of samarium on the sol stability, particle growth, optical, and photocatalytic performance of TiO2

In this work, we provide a new investigation on the effect of Sm³⁺ doping on the sol–gel mixture and stabilization of TiO₂ sol. Sm³⁺ dopant was initially dissolved in dilute ethanol solvent to form Sm-ethanol solvation shells. After hydrolysis, the effect of Sm-modified solvent on the growth and aggregation of TiO₂ primary particles was put in evidence. ¹H-NMR spectrum of Sm–TiO₂ sol shows signals broadening of nBuOH and ethanol molecules without splitting effect, indicating that the two alcohols are located in solvation shells surrounding the Sm³⁺ cations. The stabilization of TiO₂ colloidal sol is induced by the bound Sm³⁺-solvate species to Ti-oxo-alkoxy polymers, inhibiting the growth of TiO₂ particles. In the absence of Sm³⁺ dopant, the TiO₂ colloidal sol shows a high resolution ¹H-NMR spectrum with splitting of ¹H signals of ethanol and free nBuOH. SEM analysis of TiO₂ consists of monodisperse spherical particles, whereas Sm–TiO₂ shows a massive monolith with small particle size. These effects were correlated with TG/DTA and XRD results showing that Sm³⁺ dopant induces a more complex and prolonged thermal decomposition, decreasing the crystallization degree of TiO₂ anatase. The effect of Sm³⁺ doping on UV-absorption region, adsorption capacity, and photocatalytic activity of TiO₂ nanoparticles was also investigated.