Photoluminescent, self-cleaning titanium oxide nanocomposites with multifunctional properties

Abstract

Photoluminescent and self-cleaning properties of an Eu³⁺ doped titania–silica–lanthanum phosphate nanocomposite (Eu-TSL) prepared by an aqueous sol–gel process and films fabricated on glass substrates by dip coating are investigated in the present work. These nanocomposites containing Eu³⁺ as dopants exhibit red luminescence upon visible light excitation, after heat treatment at 400 °C. For an excitation wavelength of 465 nm, the PL spectra of Eu-TSL show intense peaks at 613 nm (⁵D₀–⁷F₂), characteristic of Eu³⁺ ions. This red emission has a life time of ∼0.5 ms. 1 mol% Eu added TSL shows ∼96% methylene blue dye degradation after two hours UV light exposure which is attributed to the presence of anatase phase, optimum crystallite size (5.7 nm) and enhanced specific surface area (147 m² g⁻¹). Eu-TSL was found to be five times more efficient in decolourization of methylene blue than Eu-TiO₂ from the reported literature. Eu-TSL retains all the major properties including photoactivity, transparency (∼97%) and low wettability (∼80°). In addition, red emission could be integrated at very low europium doping levels (1 mol%). Even though europium doping on titania is reported widely, a multifunctional luminescent and self-cleaning composition based on Eu-TSL synthesized by an aqueous sol–gel route is reported for the first time.