Shape Effect of Zinc-Tin Oxide Nanostructures on Photodegradation of Methylene Blue and Rhodamine B under UV and Visible Light

Abstract

Water pollutants are currently a major concern, demanding for simple processes for water treatment, photocatalysis being one of the most efficient and promising processes. Metal oxide materials are being widely studied for this application, due to their wide band gaps, with nanostructures being particularly interesting because of their high surface-to-volume ratio. In this context, zinc-tin oxide (ZTO) nanostructures are quite appealing owing to the multiplicity of structures and morphologies possible to achieve with low-cost solution-based synthesis and to the lack of critical elements in favor of abundant and nontoxic ones. In this work, three different ZTO nanostructures, namely, ZnSnO 3 nanowires, Zn 2 SnO 4 nanoparticles, and Zn 2 SnO 4 polyhedrons, were studied for the photodegradation of methylene blue and rhodamine B under both UV and visible light irradiation. The nanostructures were synthesized by a low-cost seed-layer-free hydrothermal method at only 200 °C, compatible with direct growth on flexible substrates. ZnSnO 3 nanowires in the powder form, reported as photocatalytic agents for the first time, showed enhanced photocatalytic activity, especially under UV light, degrading both dyes in only 90 min and outperforming Zn 2 SnO 4 nanoparticles and polyhedrons. Photocatalysis under visible light is also demonstrated, with a degradation of >40% of rhodamine B in 12 h. This work shows the feasibility of a simple, low-cost fabrication method and sustainable, nontoxic materials to achieve structures with efficient photocatalytic activity.

Fabrication and Photocatalytic Properties of Zinc Tin Oxide Nanowires Decorated with Silver Nanoparticles

“…According to the tangent of the diagram, the band gaps of ZTO NWs and 3 at% Ag-ZTO NWs were 4.05 and 4.04 eV, which are close to the previously reported value (3.92 eV). The wider band gap for the ZTO NWs may be attributed to their smaller sizes [ 14 ]. The similar absorption edges before and after Ag modification indicate that their bandgap energy difference is negligible [ 22 , 23 ].…”

“…Ternary metals have higher chemical stability as compared to binary metal oxides. ZTO nanostructures have been fabricated for various important applications, including optical sensors [ 6 , 7 ], gas sensors [ 8 , 9 ], dye-sensitized solar cells [ 10 , 11 ] and photocatalysts [ 12 , 13 , 14 ]. In the past few years, different techniques have been applied in synthesizing one-dimensional ZTO nanostructures, including the hydrothermal method [ 15 , 16 ], CVD [ 7 , 17 ] and the template method [ 18 ], among which CVD is the best choice since it is more economical and environmentally friendly [ 19 , 20 ].…”

High UV and Sunlight Photocatalytic Performance of Porous ZnO Nanostructures Synthesized by a Facile and Fast Microwave Hydrothermal Method

“…The RhB •+ cation radicals can also be further decomposed into N-deethylated products by hydrolysis or by reacting with HO 2 • / O 2 •− radicals. The resulting N-deethylated products are responsible for a gradual hypsochromic shift in the absorbance peak since the N-deethylation of RhB is known to be a stepwise process [ 77 , 78 , 127 , 128 ]. This hypsochromic shift in the absorbance peak was not observed in Figure 5 a, suggesting that the degradation of RhB through sunlight photocatalysis by the porous ZnO nanostructures is the predominant degradation route in these experiments.…”

Metal Oxide-Based Photocatalytic Paper: A Green Alternative for Environmental Remediation

“…Several studies reported the use of metal oxide materials in the photocatalytic degradation of organic contaminants/dyes [19,34,37,38,[71][72][73][74]. However, their photocatalytic performance strongly depends on the crystal structure, morphology, elemental composition, crystalline phase, exposed surface facets, intrinsic defects (such as oxygen vacancies), lattice distortions, and doping, among others [75][76][77].…”

“…Moreover, it is largely known that materials' properties are enhanced at the nanoscale level when compared to bulk counterparts [79]. For that reason, the surface-to-volume ratio of metal oxides is highly increased at the nanoscale, and more active sites on their surface are available for organic molecules to interact, leading to higher overall adsorption capacity and enhanced photocatalytic performance in environmental remediation [35,74].…”