Multifunctional Tb-doped SnO2 based photocatalytic agent for water remediation: Study of defect-related properties

Abstract

A new methodology to obtain Tb-doped SnO2 nanoparticles based on precipitation method followed by hydrothermal treatment was developed. Two series of nanoparticles with various Tb concentrations were fully characterized with large number of methods, including XRD method, FTIR, XPS, and Raman spectroscopy, TEM imaging, SSA estimation, optical transmittance study, luminescence spectroscopy and quantum-chemical calculations.The oriented attachment mechanism of nanoparticle growth is shown to occur under hydrothermal treatment. Computational study of interaction energies of mutually oriented nanoparticles and role of ions in the synthesis media was performed. Study of photoluminescence characteristics of the obtained nanoparticles is provided. The presence of blue and green luminescence is shown. The blue luminescence is related to SnO2 self-luminescence, while the green is related to Tb. Increase of Tb concentration suppress blue self-luminescence of SnO2, and promote green luminescence due to an increase of the energy transfer from crystal host to doping Tb ions.The nanoparticles are shown to possess photocatalytic activity of 97–100% under Vis light irradiation. Using a complex of modern physicochemical methods, a new factor affecting photocatalytic efficiency was revealed – the ratio of vacancies to defects (Vac/Def). A clear dependency of photocatalysis and normalized Vac/Def ratio to interaction energy between pollutant and catalysts surface is explained via quantum-chemical calculations for the first time, and demonstrated on examples of colored solution of organic dye methylene blue and colorless solution of oxytetracycline. Detailed study of the relation between morphological and structural properties of nanoparticles and their photocatalytic properties is provided. High degradations percent are achieved under simple LED light bulb. A concept of a chemical and computational experiments-based route for the development of effective photocatalysts is suggested.