Nanowires Could Help to Degrade Organic Pollutants with Visible Light

By Hussain AhmedJan 4 2022Reviewed by Megan Craig, M.Sc.

The development of core/shell Ag/SnO₂ nanowires as a novel photocatalytic material for the fast breakdown of organic molecules by light waves is the subject of a recent study published in the journal Catalysts.

Study: Core/Shell Ag/SnO2 Nanowires for Visible Light Photocatalysis. Image Credit: agsandrew/Shutterstock.com

After being coated with a SnO₂ shell, silver nanowires alter their optical characteristics and may be stimulated by visible light. This property of Ag/SnO₂NWs can be used to develop effective and quick photocatalytic degradation systems to eliminate organic contaminants under natural sunlight without the use of any additional radiation devices.

SnO₂: Applications & Limitations

Due to increased environmental contamination and rapid industrial expansion, there has been a surge of attention to developing effective, quick, and broadly applicable photocatalytic systems based on nanoscale materials in the last decade. Semiconductor materials, particularly metal oxides, have been widely explored as photocatalysts due to their unique physio-chemical characteristics.

As a semi-conductive metal oxide with excellent biochemical, physical, and structural stability, as well as excellent performance in the degradation of organic pollutants, SnO₂ is among the most promising materials to be discovered in recent years. However, the inability to use visible light for real-world applications is a significant obstacle to the widespread use of tin oxide (SnO₂).

Due to the high bandgap and the very rapid coupling of photoelectrons and holes, the effective deployment of SnO₂ for industrial applications is severely restricted.

STEM images of (a) core/shell Ag/SnO₂NWs and (b) SnO₂NPs. © Baranowska-Korczyc, A. et al. (2021)

Ag Nanostructures for SnO₂ Applications

Different metallic nanostructures have been used to build a nanocomposite with semiconductors to produce effective carrier segregation under solar light illumination to address these constraints. Using this approach, an electrochemically active biofilm may be made to produce an Ag-SnO₂ hybrid that can be employed as a visual light-driven photocatalyst to break down various organic molecules.

The one-pot hydrothermal process can be used to make an Ag/SnO₂ hybrid that is very efficient in photodegrading phenol. Under light waves, Ag-doped SnO₂ nanostructures altered with turmeric are an effective photocatalyst for the breakdown of rhodamine B.

Ag-SnO₂ nanomaterials can not only be employed as photocatalysts, but they also have excellent antioxidant and antimicrobial capabilities.

(a) The absorbance spectra of AgNWs and the core/shell Ag/SnO₂NWs. (b) Schematic illustration of the photocatalytic mechanism of Ag/SnO₂NWs under visible light irradiation. © Baranowska-Korczyc, A. et al. (2021)

Importance of Silver Nanowires

Although silver nanoparticles of different dimensions can be utilized to make Ag/SnO₂ compounds for catalytic applications, Ag nanowires (AgNWs) have never been exploited for this purpose, despite their numerous benefits.

Strong transparency, good electromagnetic capabilities, excellent electrical efficiency, mechanical stability, nanometric scale, and one-dimensional (1D) shape are all characteristics of AgNWs. Furthermore, in contrast to other silver nanoparticles, the AgNWs' easy separation by filtering or centrifugation allows for simple manufacturing and boosts their usability.

Both nanomaterials' advantageous properties can be combined in the core/shell Ag/SnO₂NWs heterostructure to achieve exceptional catalytic capabilities.

In this study, the researchers offer a novel photocatalytic system based on AgNWs covered with a SnO₂ shell. To explore the photocatalytic degradation mechanism using a new 1-D Ag/SnO₂NWs catalyst, rhodamine B and malachite green were chosen as sample organic dyes and hazardous dyes that are both prevalent in the atmosphere. The deterioration was evaluated by looking at the dye solution's UV absorbance over time.

Research Findings and Conclusion

Under solar light illumination, silver nanowires with a SnO₂ shell can be used as a novel and effective photocatalyst. The quick decomposition process is the result of the combination of benefits of both elements in the core/shell Ag/SnO₂NWs hybrid.

The SPR absorption range of AgNWs after treatment with SnO₂ moves towards the visible range, allowing photons of this frequency to excite electrons in the nanowires.

SnO₂'s photocatalytic efficiency is greatly increased even without UV illumination. The electrical pulses from the metal core are transported to the transition metal shell and grabbed by oxygen molecules, resulting in the generation of radical species that are necessary for organic compound decomposition.

The core/shell metal/semiconductor configuration, which leads to carrier isolation and avoids mixing photoinduced electron-hole pairs, is credited with the Ag/SnO₂NWs system's remarkable photocatalytic performance. For photocatalytic applications, the ease with which an Ag/SnO₂NWs hybrid may be processed using simple separation methods like filtering or centrifugation is highly advantageous.

 (a) The absorbance spectra of malachite green with Ag/SnO₂NWs photocatalyst presence under 450 nm light irradiation. (b) The degradation of malachite green with 2 mg/mL of Ag/SnO₂NWs catalyst (■), with no photocatalyst (▲), with 0.66 mg/mL of SnO₂NPs (▼), 2 mg/mL of SnO₂NPs (◆), and with 2 mg/mL TiO₂ catalyst (★) under 450 nm light irradiation and Ag/SnO₂NWs without irradiation (dark experiment, ●).© Baranowska-Korczyc, A. et al. (2021)

Future Perspective

According to the results, the core/shell of Ag/SnO₂NWs is a highly promising material with great environmental sustainability for constructing future photo electrocatalytic systems for successful remediation operations of diverse organic compounds under direct solar radiation.

Continue reading: Could Nanoparticles Create Sustainable Lighting?

Reference

Baranowska-Korczyc, A. et al. (2021) Core/Shell Ag/SnO₂ Nanowires for Visible Light Photocatalysis. Catalysts, 12(01), 30. Available at: https://www.mdpi.com/2073-4344/12/1/30

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