Self-cleaning and spectral attributes of erbium doped sodium-zinc-tellurite glass: Role of titania nanoparticles

Abstract

Highly transparent and durable self-cleaning materials became demanding for diverse applications. To attain such goals, glass system with composition (69 - x)TeO2-20ZnO-10Na2O-1Er2O3-(x)TiO2, where x = 0.0, 0.1, 0.2, 0.3 and 0.4 mol% were synthesized using the conventional melt quenching method and characterized. For the first time, the influence of embedded TiO2 (Titania) nanoparticles (TNPs) concentration variation on the self-cleaning and spectral properties was examined to establish their correlation. TEM micrograph revealed the nucleation of spherical TNPs (average size ˜ 14 nm) inside the amorphous matrix. Reduction in the optical band gap energy (from 3.08–3.03 eV) and water contact angle (from 68o to 43o) both were evidenced with the increase in TNPs contents, wherein the later one (reduced contact angle or enhanced wettability) was attributed to the enhanced hydrophilicity of the glass samples. Conversely, a slight increase in the methylene blue (MB) degradation rate with the increase of TNPs contents up to 0.2 mol% indeed indicated an improved photocatalytic activity of the synthesized glass. The absorption spectra exhibited ten significant bands of Er3 + ions in the wavelength range of 407 to 1532 nm. The emergent three prominent photoluminescence (PL) emission bands of the glass sample (with 0.2 mol% of TNPs) positioned at 535 nm, 555 nm and 670 nm were enhanced by a factor of 6.77, 4.56 and 2.00, respectively. Surface plasmon resonance (SPR) band of the embedded TNPs inside the glass was detected around 581 nm. Furthermore, Raman band of the glass (containing 0.4 mol% of TNPs) centred at 845 cm- 1 displayed an intensity enhancement by a factor of 3.58 times, which was ascribed to the TNPs localized SPR field mediated effect. It is established that the measured enhanced hydrophilicity (self-cleanliness) and improved spectral features of the present glass composition was steered by the TNPs surface plasmon assisted effects.