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We have designed an excellent visible-light-driven and high-performance photocatalyst with a Ag-Cu2O-ZnO nanowire heterostructure in our work by combining the hydrothermal approach with plasma–liquid technology. The structural and morphological characteristics and optical properties of the samples were evaluated using X-ray diffraction, field-emission scanning electron microscopy, and spectrophotometry, respectively. The results show that the Ag nanoparticles are mainly positioned on the Cu2O nanoclusters compared with the ZnO nanowire surface, forming broccoli-like Ag-Cu2O nanoclusters during the Ar gas plasma treatment process in an aqueous solution. The diameter of the Ag/Cu2O nanoclusters ranges from 150 to 180 nm. The Ag-Cu2O-ZnO nanowires exhibited improved photocatalytic performance, decomposing approximately 98% methyl orange dye in 30 min. This is a consequence of the synergistic interactions between the p-n heterojunction formed at the Cu2O-ZnO interfaces and the localized surface plasmon resonance (LSPR) effect of the Ag nanoparticles, which broaden the visible light absorption range and effectively separate the photogenerated charge carriers.

Plasmonic photocatalytic nanocomposites of TiO2 and Au nanoparticles (NPs) have recently attracted the attention of researchers, who aim to improve the photocatalytic activity of potential TiO2 NPs. In this study, we report photocatalytic activity enhancement for a Au/TiO2 nanocomposite prepared by the plasma–liquid interaction method using an atmospheric microplasma apparatus. The enhanced photocatalytic activity of the prepared Au/TiO2 is demonstrated by the degradation of methylene blue (MB) in water under both ultraviolet (UV) and visible light irradiation. The prior treatment of TiO2 with microplasma in a NH3 and H2O2 solution is found to strongly improve the photocatalytic activity of both the treated TiO2 NPs, as well as the synthesized Au/TiO2 nanocomposite.

Green carbon quantum dots (CQDs) were fabricated through microplasma-liquid interactions, involving the treatment of an orange juice solution at atmospheric pressure and room temperature. Morphological analyses of the CQDs revealed a spherical shape with an average size of approximately 2.5 nm. The emission peak at a wavelength of 440 nm was observed for the blue emissive CQDs, with an excitation wavelength of 350 nm. The CQDs exhibited excellent luminescence activity, with emission dependent on the excitation wavelength, shifting towards longer wavelengths. The Raman spectrum of the CQDs displayed two peaks at 1425.3 and 1625.4 cm−1, representing predominantly disorder and graphitic bands. These green-synthesized CQDs possess tunable luminescence and biocompatibility, making them promising candidates for potential applications in biolabelling, antibacterial agents and optoelectronics. [ABSTRACT FROM AUTHOR]

In this work, photocatalytic performance is divulged in the ternary CuO-Ag-ZnO nanowire synthesized via a two-step approach. The decoration of Ag and CuO nanostructures onto the surface of ZnO nanowires was simply carried out by using the plasma electrolytic oxidation method in a short time. The structure, size, morphology, and optical properties of as-prepared samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, and spectrophotometry measurements. The diameters of Ag nanoparticles and ZnO nanoflowers are in the range of 5–20 nm and 20–60 nm, respectively. Within the first 15 min, methyl orange was decolorized 96.3 and 82.8% in the CuO-Ag-ZnO and Ag-ZnO, respectively, and there is only about 46.7% of that decomposed in pure ZnO. The CuO-Ag-ZnO shows a higher rate constant k = 0.2007 min−1 and a lower half-life time t = 6.1 min compared to Ag-ZnO and bare ZnO nanowires. The photo-reusability of the ternary nanostructures was estimated to be much outweighed compared to ZnO nanowires. Interestingly, the synergic incorporation between noble metal–semiconductor or semiconductor–semiconductor in the interfaces of Ag-CuO, Ag-ZnO, and CuO-ZnO expands the visible light absorption range and eliminates the photogenerated electron–hole recombination, resulting in a superior visible-light-driven photocatalyst.

Titanium dioxide (TiO2), a non-toxic semiconductor, has garnered extensive interest due to their excellent photocatalytic and self-cleaning properties. Its wide bandgap with rutile phase (3.0 eV), anatase, and brookite phases (3.2 eV) restricts the visible light photocatalytic applications. An effective approach to address this limitation is decorating the brookite-TiO2 surface by metallic gold nanoparticles (Au NPs) leading to the multi-function photocatalyst. Herein, we have successfully prepared TiO2-Au nanocomposites and investigated their photocatalytic activity and self-cleaning behavior. The obtained photocatalysts were prepared by chemical route (sol-gel and hydrothermal methods) and plasma technique. Characterization was analyzed by X-ray diffraction, Raman spectroscopy, scanning, and transmission electron microscopy techniques. TiO2 nanostructures with flower- and rod-like morphology were synthesized by a simple hydrothermal method. The TiO2 rod-like morphology, which contains 24% anatase and 76% brookite phase, favors the TiO2 surface modification and the later reduction of gold precursor to Au NPs under the microplasma–liquid interaction confirming the durability of material. Photocatalytic properties were evaluated through the photodegradation of dyes rhodamine 101 under the simulated visible light irradiation. The TiO2-Au photocatalysts are active under this condition while the pure TiO2 in form of anatase/brookite mixture exhibit high activity under the ultraviolet light. TiO2-Au NPs showed their enhanced the adsorption capacity (42%), followed by the dye decomposition (87%). Self-cleaning behavior was assessed by measuring the contact angle. The results of anti-fogged and self-cleaning properties from the contact angle measurement express highly applicable for the commercial products in sanitation. [ABSTRACT FROM AUTHOR]

To enhance the effectiveness of TiO2 as a photocatalyst, it was believed that the drawbacks of the large bandgap and the rapid electron-hole recombination can be overcome by coupling TiO2 with plasmonic metal nanoparticles. The incorporation of the nanoparticles onto the TiO2 surface requires a suitable procedure to achieve the proper particle adhesion. In this work, we propose a simple, clean, and effective surface activation of TiO2 using plasma enhanced wet chemical surface treatment. Under only 5 min of plasma treatment in a 3% NH3/3% H2O2 solution, gold nanoparticles were found better adhered onto the TiO2 surface. Hence, the methylene blue degradation rate of the Au/TiO2 under sunlight treated was improved by a factor of 3.25 times in comparison to non-treated Au/TiO2 and by 13 times in comparison to the bare rutile TiO2.

A combination of plasmonic nanoparticles (NPs) with semiconductor photocatalysts, called plasmonic photocatalysts, can be a good candidate for highly efficient photocatalysts using broadband solar light because it can greatly enhance overall photocatalytic efficiency by extending the working wavelength range of light from ultraviolet (UV) to visible. In particular, fixation of plasmonic photocatalysts on a floating porous substrate can have additional advantages for their recycling after water treatment. Here, we report on a floating porous plasmonic photocatalyst based on a polydimethylsiloxane (PDMS)-TiO 2 -gold (Au) composite sponge, in which TiO 2 and Au NPs are simultaneously immobilized on the surface of interconnected pores in the PDMS sponge. This can be easily fabricated by a simple sugar-template method with TiO 2 NPs and in situ reduction of Au NPs by the PDMS without extra chemicals. Its ability to decompose the organic pollutant rhodamine B in water was tested under UV and visible light, respectively. The results showed highly enhanced photocatalytic activity under both UV and visible light compared to the PDMS-TiO 2 sponge and the PDMS-Au sponge. Furthermore, its recyclability was also demonstrated for multiple cycles. The simplicity of fabrication and high photocatalytic performance of our PDMS-TiO 2 -Au sponge can be promising in environmental applications to treat water pollution., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)