Photocatalytic activity of SnO2-TiO2 composite nanoparticles modified with PVP

Dana Toloman; Ovidiu Pana; Maria Stefan; Adriana Popa; Cristian Leostean; Sergiu Macavei; Dan Silipas; Ioana Perhaita; Mihaela Diana Lazar; Lucian Barbu-Tudoran

doi:10.1016/j.jcis.2019.02.026

Photocatalytic activity of SnO₂-TiO₂ composite nanoparticles modified with PVP

J Colloid Interface Sci. 2019 Apr 15:542:296-307. doi: 10.1016/j.jcis.2019.02.026. Epub 2019 Feb 7.

Affiliations

¹ National Institute for R &D of Isotopic and Molecular Technology, 67 - 103 Donat St., 400293 Cluj-Napoca, Romania.
² National Institute for R &D of Isotopic and Molecular Technology, 67 - 103 Donat St., 400293 Cluj-Napoca, Romania. Electronic address: ovidiu.pana@itim-cj.ro.
³ Raluca Lipan Institute for Research in Chemistry, "Babes-Bolyai" University, 30 Fantanele St., 400294 Cluj-Napoca, Romania.

PMID: 30763897
DOI: 10.1016/j.jcis.2019.02.026

Abstract

Interface modified SnO₂-TiO₂ composite nanoparticles were produced in two stages: first SnO₂ nanoparticles were prepared by chemical precipitation in the presence of polyvinylpyrrolidone (PVP) and thermally treated at 500 °C then TiO₂ was deposited on top of modified SnO₂ and followed by a final annealing. As a consequence SnO₂-TiO₂ composite nanoparticles get crystallized while PVP is decomposed into monomer units and other attached smaller molecular fragments. TGA coupled with FT-IR spectroscopy confirmed the presence of monomers and other moieties as a result of PVP thermal fragmentation. The crystalline phases and composition of the two oxides were evidenced by X-ray diffraction, HRTEM and XPS. It was found that specific surface area of the composites increases with the increase in the initial amount of PVP. Also, the oxidation potential of the TiO₂ shell, as determined by UV photoelectron spectroscopy (UPS), significantly decreases as the PVP quantity increase and further modifies the band alignment between SnO₂ and TiO₂ components. Additionally, both XPS and UPS spectra as well as EPR investigations indicate the presence of many localized states inside the band gap of TiO₂. With a moderate PVP content the combined effects of band alignment, gap localized states and porosity make possible an increased number of reactive oxygen species (ROS) generation thus increasing photocatalytic activity against RhB dye solution under visible irradiation. The photocatalytic mechanism was elucidated based on the identification of radical species involved and in accordance with energy bands alignment, gap states, and porosity. Besides water purification by photocatalysis, SnO₂-TiO_2, as ROS generating heterostructures may be used in applications like antibacterial and antitumoral, deodorizing, air purifying, self-cleaning, gas sensing, as well as in hydrogen production.

Keywords: Composite; Interface; Nanoparticles; Photocatalysis; SnO(2); TiO(2).