High-throughput experimentation for photocatalytic water purification in practical environments

High-throughput screening instrument was developed for photocatalytic water purification, enabling the simultaneous testing of 132 photocatalytic reactions under uniform visible light irradiation, temperature control, and stirring. The instrument was used to investigate the effects of different catalysts (TiO2, ZnO, α-Fe2O3) and environmental waters (seawater, urban wastewater, and industrial wastewater) on dye degradation. It was observed environmental ions, particularly carbonate and phosphate ions, significantly reduced catalyst activity by inhibiting the adsorption of dye molecules. To develop effective catalysts for dye degradation in industrial wastewater, 15 types of noble metal nanoparticles (NPs) were supported on photocatalysts. The study found that noble metal NPs with high work functions and oxidation resistance, such as Au and Pt, exhibited higher activity even in the industrial wastewater, likely converting environmental ions into active species. These findings, based on 432 test results, demonstrate the effectiveness of the developed high-throughput screening instrument for optimizing photocatalytic water purification.

Aloe vera-derived graphene-coupled phenosafranin photocatalyst for generation and regeneration of ammonia and NADH by mimicking natural photosynthetic route

Aloe vera-derived graphene (ADG) coupled system photocatalyst, mimicking natural photosynthesis, is one of the most promising ways for converting solar energy into ammonia (NH3 ) and nicotinamide adenine dinucleotide (NADH) that have been widely used to make the numerous chemicals such as fertilizer and fuel. In this study, we report the synthesis of the aloe vera-derived graphene-coupled phenosafranin (ADGCP) acting as a highly efficient photocatalyst for the generation of NH3 and regeneration of NADH from nitrogen (N2 ) and oxidized form of nicotinamide adenine dinucleotide (NAD+ ). The results show a benchmark instance for mimicking natural photosynthesis activity as well as the practical applications for the solar-driven selective formation of NH3 and the regeneration of NADH by using the newly designed photocatalyst.

Research status and prospect of nano silver (Ag)-modified photocatalytic materials for degradation of organic pollutants

Nano silver (Ag) was metallic Ag monomers with particle size to the nanoscale. Photocatalyst was a kind of semiconductor material with photocatalytic function. Loading precious metal Ag onto semiconductor surfaces by microwave, laser-induced, solvent-thermal and hydrothermal methods could capture photogenerated electrons, reduced the compounding rate of holes and photogenerated electrons during the photocatalytic process, thereby improving the electron transfer efficiency of photocatalysis and enhancing the absorption of visible light by silver nanoparticles through the plasma resonance effect. The highly reactive free radicals produced by photocatalysts were used in the organic degradation process to degrade organic matter into inorganic matter and was a faster, more efficient and less polluting method of pollutant degradation, which has attracted a lot of attention from researchers. This review discussed the modification of various types of photocatalysts by nano Ag through different methods. The photocatalytic degradation of dyes, antibiotics and persistent organic pollutants by different modified composites was also analyzed. This review covered the several ways and means in which nano Ag has modified diverse photocatalytic materials as well as the photocatalytic degradation of dyes, antibiotics and persistent organic pollutants. This review identified the drawbacks of the existing nano Ag-modified photocatalytic materials, including their low yield and lack of recyclability, and it also offered suggestions for potential future directions for their improvement. The purpose of this review was to further research on the technology of nano Ag-modified photocatalytic materials and to encourage the creation of new modified photocatalytic nanomaterials for the treatment of organic pollutant degradation.

Fabrication of Ru loaded MgB2 with guar gum hybrid for photocatalytic degradation of crystal violet

Today, dyes/pigment-based materials are confronting a serious issue in harming marine ecology. Annihilate these serious water pollutants using photoactive 2D nanohybrid catalysts showed promising comparativeness over available photocatalysts. In the present work, a facile route to decorate Ruthenium (Ru) on 2D MgB2 flower-like nanostructures was developed via ecofriendly guar gum biopolymer substantial template (MgB2/GG@Ru NFS) and its photocatalytic performance was reported. Synthesis of MgB2@Ru, MgB2/GG@Ru NFS and commercial MgB2, was studied by FTIR, XRD, FE-SEM, EDX, AFM, TEM, UV-vis spectra, and XPS analysis. From the results, the MgB2/GG@Ru NFS exhibited a superior photocatalytic performance (99.7 %) than its precursors MgB2@Ru (79.7 %), and MgB2 (53.7 %), with the degradation efficiency of the crystal violet (CV) within 100 min under visible light irradiation. The proposed photo-catalyst MgB2/GG@Ru NFS showed negligible loss of photocatalytic activity even after five successive cycles, revealing its reusability and enhanced stability due to the network structure. The photocatalytic mechanism for MgB2/GG@Ru NFS was evaluated by trapping experiment of active species, verifying that superoxide (O2-) and electron (e-) contributed significant role in the dye degradation.

Construction of Ag-TiO2 Hierarchical Micro-/Nanostructures on a Ti Plate for Photocatalysts via Femtosecond Laser Hybrid Technology

Titanium dioxide photocatalysts can break down pollutants using natural light. They possess notable light stability, chemical stability, and catalytic effects, thus leading to extensive research worldwide. However, the limited light absorption range of titanium dioxide and their inefficiencies in generating and transporting photogenerated carriers hinder the enhancement of their photocatalytic performance. In this study, we employ a femtosecond laser composite processing method to create an Ag-TiO2 nanoplate composite catalyst. This method doubles the catalytic efficiency compared with the structure processed solely with the femtosecond laser. The resulting Ag-TiO2 nanoplate composite catalysts show significant promise for addressing environmental and energy challenges, including the photodegradation of organic pollutants.

Graphitic carbon nitride (g-C3N4)-assisted materials for the detection and remediation of hazardous gases and VOCs

Graphitic carbon nitride (g-C3N4)-based materials are attracting attention for their unique properties, such as low-cost, chemical stability, facile synthesis, adjustable electronic structure, and optical properties. These facilitate the use of g-C3N4 to design better photocatalytic and sensing materials. Environmental pollution by hazardous gases and volatile organic compounds (VOCs) can be monitored and controlled using eco-friendly g-C3N4- photocatalysts. Firstly, this review introduces the structure, optical and electronic properties of C3N4 and C3N4 assisted materials, followed by various synthesis strategies. In continuation, binary and ternary nanocomposites of C3N4 with metal oxides, sulfides, noble metals, and graphene are elaborated. g-C3N4/metal oxide composites exhibited better charge separation that leads to enhancement in photocatalytic properties. g-C3N4/noble metal composites possess higher photocatalytic activities due to the surface plasmon effects of metals. Ternary composites by the presence of dual heterojunctions improve properties of g-C3N4 for enhanced photocatalytic application. In the later part, we have summarised the application of g-C3N4 and its assisted materials for sensing toxic gases and VOCs and decontaminating NOx and VOCs by photocatalysis. Composites of g-C3N4 with metal and metal oxide give comparatively better results. This review is expected to bring a new sketch for developing g-C3N4-based photocatalysts and sensors with practical applications.

Recent Trends in Plasmon-Assisted Photocatalytic CO2 Reduction

Direct photocatalytic reduction of CO₂ has become an highly active field of research. It is thus of utmost importance to maintain an overview of the various materials used to sustain this process, find common trends, and, in this way, eventually improve the current conversions and selectivities. In particular, CO₂ photoreduction using plasmonic photocatalysts under solar light has gained tremendous attention, and a wide variety of materials has been developed to reduce CO₂ towards more practical gases or liquid fuels (CH₄ , CO, CH₃ OH/CH₃ CH₂ OH) in this manner. This Review therefore aims at providing insights in current developments of photocatalysts consisting of only plasmonic nanoparticles and semiconductor materials. By classifying recent studies based on product selectivity, this Review aims to unravel common trends that can provide effective information on ways to improve the photoreduction yield or possible means to shift the selectivity towards desired products, thus generating new ideas for the way forward.

Photocatalytic degradation of methylene blue at nanostructured ZnO thin films

The photocatalytic degradation of the wastewater dye pollutant methylene blue (MB) at ZnO nanostructured porous thin films, deposited by direct current reactive magnetron sputtering on Si substrates, was studied. It was observed that over 4 photocatalytic cycles (0.3 mg · l^-1MB solution, 540 minUV irradiation), the rate constantkof MB degradation decreased by ∼50%, varying in the range (1.54 ÷ 0.78) · 10^-9(mol·l^-1·min^-1). For a deeper analysis of the photodegradation mechanism, detailed information on the nanostructured ZnO surface morphology and local surface and subsurface chemistry (nonstoichiometry) were obtained by using scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) as complementary analytical methods. The SEM studies revealed that at the surface of the nanostructured ZnO thin films a coral reef structure containing polycrystalline coral dendrites is present, and that, after the photocatalytic experiments, the sizes of individual crystallites increased, varying in the range 43 ÷ 76 nm for the longer axis, and in the range 28 ÷ 58 nm for the shorter axis. In turn, the XPS studies showed a slight non-stoichiometry, mainly defined by the relative [O]/[Zn] concentration of ca. 1.4, whereas [C]/[Zn] was ca. 1.2, both before and after the photocatalytic experiments. This phenomenon was directly related to the presence of superficial ZnO lattice oxygen atoms that can participate in the oxidation of the adsorbed MB molecules, as well as to the presence of surface hydroxyl groups acting as hole-acceptors to produce OH· radicals, which can be responsible for the generation of superoxide ions. In addition, after experiments, the XPS measurements revealed the presence of carboxyl and carbonyl functional groups, ascribable to the oxidation by-products formed during the photodegradation of MB.

Low-cost and resource-efficient monolithic photocatalyst with enhanced solar light utilization for the photocatalytic treatment of organic wastewater

Developing low-cost, well-performing, and resource-efficient photocatalysts with enhanced solar light utilization can contribute to the practicability of photocatalytic techniques in organic wastewater treatment. This study fabricated and characterized a novel sunlight-driven BiOBr- and acetylene black (AB)-loaded monolithic photocatalyst. The fly ash-based geopolymer acts as photocatalyst support that can also provide adsorption sites and semiconductor metal oxide (Fe₂O₃). A conductive network in the geopolymer structure formed by AB can promote the separation of e^--h⁺ pairs generated by active sites (BiOBr and Fe₂O₃). Moreover, the photothermal effect induced by AB can assist the photocatalytic reaction at the microinterface of the photocatalyst. This photocatalyst was suspended on the surface of an aqueous solution for sufficient contact with oxygen from the air and is thus beneficial for producing ¹O₂ and ·OH as the main active species. Within 30 min, it exhibited higher photothermal-photocatalytic activity with 96% removal efficiency of the target pollutant methylene blue (MB), which occurred at an initial concentration of 20 mg L^-1. The demethylation and hydroxylation process induced by the active species constituted the primary degradation pathway for MB by Bi/AB/MFGP. Overall, this study provides a valuable reference for developing economical, effective, and practical photocatalysts and applying geopolymers in photocatalysis.

A Comprehensive Review on Graphitic Carbon Nitride for Carbon Dioxide Photoreduction

Inspired by natural photosynthesis, harnessing the wide range of natural solar energy and utilizing appropriate semiconductor-based catalysts to convert carbon dioxide into beneficial energy species, for example, CO, CH₄ , HCOOH, and CH₃ COH have been shown to be a sustainable and more environmentally friendly approach. Graphitic carbon nitride (g-C₃ N₄ ) has been regarded as a highly effective photocatalyst for the CO₂ reduction reaction, owing to its cost-effectiveness, high thermal and chemical stability, visible light absorption capability, and low toxicity. However, weaker electrical conductivity, fast recombination rate, smaller visible light absorption window, and reduced surface area make this catalytic material unsuitable for commercial photocatalytic applications. Therefore, certain procedures, including elemental doping, structural modulation, functional group adjustment of g-C₃ N₄ , the addition of metal complex motif, and others, may be used to improve its photocatalytic activity towards effective CO₂ reduction. This review has investigated the scientific community's perspectives on synthetic pathways and material optimization approaches used to increase the selectivity and efficiency of the g-C₃ N₄ -based hybrid structures, as well as their benefits and drawbacks on photocatalytic CO₂ reduction. Finally, the review concludes a comparative discussion and presents a promising picture of the future scope of the improvements.

Enhanced photocatalytic activity of nano-silica/copper plasmon by aminofunctional silane for dye pollutant degradation

The synthesis of silica gel nanostructures and loading it with copper specie via a hydrothermal process were performed. The sample is treated with an amino-functional reagent 3-aminopropyl triethoxysilane (APTES). The products were characterized by X-ray diffraction (XRD), FT-IR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), TGA/DSC measurements, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the nanostructures were studied for degradation of methylene blue dye (as a classic dye contaminant) in aqueous solution utilizing visible light source. The results displayed that the sample treated with APTES is much more effective in photocatalytic degradation of methylene blue. This modified catalyst could eliminate methylene blue dye (50 mL, 18 µg mL^-1) within 60 min under visible light. The degradation efficiency was increased by shortening the degradation time to 30 min in the alkaline medium. The pseudo-first-order model well describes the kinetics of the reaction.

Hotspots in action: near-infrared light mediated photoelectrochemical oxygen evolution on high index faceted plasmonic gold nanoarchitectures

Photo-induced electrochemical water splitting is a fascinating approach to overcome the present energy demands as well as environmental issues. To this end, near-infrared (NIR) photocatalysts stand out as promising candidates (where 53% of the solar light is NIR light) to solve the present energy crisis but the lack of NIR-activated photocatalysts has remained a great challenge for decades. Herein, for the first time, we report the synthesis of high-index faceted plasmonic Au nano-branched 12 tip nanostars, which can absorb the whole spectral region of electromagnetic radiation (UV-vis-NIR), for efficient water splitting. Moreover, the plasmonic hot spots on the Au 12 tip nanostars significantly promote the photoelectrochemical oxygen evolution reaction (OER) under NIR light (915 nm) with long-term stability. Remarkably, the Au 12 tip nanostars exhibit 250-fold enhancement of activity under 915 nm laser irradiation and 6.5-fold enhancement of activity under 532 nm laser irradiation, as compared to the Au NPs. Furthermore, the Finite-Difference Time-Domain (FDTD) study confirmed that the significant photoelectrochemical (PEC) enhancement in the NIR light region could be attributed to the hot-electron injection/plasmonic hot spot mechanism upon localized surface plasmonic resonance (LSPR) excitation. Overall, we anticipate that the present work would help to develop new NIR photoelectrocatalysts for meeting future energy demands.

Impact of reaction parameters for photodegradation pharmaceuticals in wastewater over gold/titania photocatalyst synthesized by pyrolysis of NH2-MIL-125(Ti)

The efficient remediation of pharmaceuticals, including wastewater, remains a remarkably challenging issue for water regeneration. Herein, porous Au/TiO₂ synthesized by pyrolysis of NH₂-MIL-125(Ti) was utilized to be an efficient photocatalyst for mineralization of trimethoprim (TMP) and Metronidazole (MNZ) as the parent compound. The effects of different factors, including TMP and MNZ concentrations, light intensity, H₂O₂ concentration, Au/TiO₂ dosage, and pH value of reaction solution on the degradation and mineralization performances during UV and visible light (VIS), were addressed. The porous Au/TiO₂ photocatalyst exhibited superior photocatalytic degradation of TMP and MNZ under UV and VIS illumination. The optimum pH values were 4; the optimum dosage of Au/TiO₂ was 1.5 g/L, H₂O₂ concentration was 9.8 mM, TMP and MNZ concentrations was 10 ppm, and their photodegradation efficiency was 100% after 30 min illumination time and mineralization efficiency 98.2% after 3 h illumination for TMP and MNZ, respectively under UV illumination, however, the photodegradation efficiency was 100% after 50 min illumination and mineralization efficiency 96.3% after 4.5 h illumination time for TMP and MNZ, respectively under VIS illumination. The real wastewater matrix with 10 mg/L of TMP and MNZ were subjected to 60 min of illumination under similar optimum conditions of synthetic solution. The results indicated that photodegradation efficiency was determined to be 100% after 70 min illumination time for removal of both TMP (k = 3.4 × 10^-2 min^-1) and MNZ (k = 2.87 × 10^-2 min^-1). This is ascribed to the incorporation of Au NPs onto TiO_2, reducing the photoinduced electron-hole recombination, thus promoting the photocatalytic performance. The possible mechanism for photodegradation of antibiotics was also discussed. The demonstration of photocatalysis mechanism over Au/TiO₂ photocatalyst can provide some directing in the enhancement of novel photocatalysts based on MOFs doped by noble metal.

Magnetic Metal Oxide-Based Photocatalysts with Integrated Silver for Water Treatment

In this review, the most recent advances in the field of magnetic composite photocatalysts with integrated plasmonic silver (Ag) is presented, with an overview of their synthesis techniques, properties and photocatalytic pollutant removal applications. Magnetic attributes combined with plasmonic properties in these composites result in enhancements for light absorption, charge-pair generation-separation-transfer and photocatalytic efficiency with the additional advantage of their facile magnetic separation from water solutions after treatment, neutralizing the issue of silver’s inherent toxicity. A detailed overview of the currently utilized synthesis methods and techniques for the preparation of magnetic silver-integrated composites is presented. Furthermore, an extended critical review of the most recent pollutant removal applications of these composites via green photocatalysis technology is presented. From this survey, the potential of magnetic composites integrated with plasmonic metals is highlighted for light-induced water treatment and purification. Highlights: (1) Perspective of magnetic properties combined with plasmon metal attributes; (2) Overview of recent methods for magnetic silver-integrated composite synthesis; (3) Critical view of recent applications for photocatalytic pollutant removal.

Enhanced photocatalytic treatment using plasmonic Ag@Ag3PO4/Ag@AgCl nanophotocatalyst for simultaneous degradation of multiple parabens and UV-filters in various aquatic environments under visible light irradiation

In this study, simultaneous photocatalytic degradation of different parabens (methyl-, ethyl-, propyl-, and butyl paraben) and UV filters (benzophenone-3, 4-methylbenzylidene camphor, 2-ethylhexyl 4-(dimethylamino) benzoate, ethylhexyl methoxycinnamate and octocrylene) in water matrices was performed under visible light irradiation using novel double plasmonic Ag^@Ag₃PO₄/Ag^@AgCl nanophotocatalyst, synthesized by an easy and fast photochemical conversion and photo-reduction. It was found that the nanophotocatalyst with appropriate mole ratio of Ag^@Ag₃PO₄/Ag^@AgCl (1:3) showed superior photocatalytic activity than individual plasmonic nanoparticles. This is because there are two simultaneous surface plasmon resonances (SPR) generated by the metallic Ag nanoparticles, in addition to the hetero-junction structure formed at the interface between Ag^@Ag₃PO₄ and Ag^@AgCl. The structures of the synthesized photocatalysts were characterized, and the principal reactive oxygen species in the photocatalytic process were identified via a trapping experiment, confirming superoxide radicals (^∙O₂^-) as the key reactive species of the photocatalytic system. The process of photodegradation of the target pollutants was monitored using an optimized method that incorporated solid-phase extraction in combination with gas chromatography-mass spectrometry. The simultaneous photodegradation process was modeled and optimized using central composite design. The kinetic study revealed that the degradation process over Ag^@Ag₃PO_{4 (30%)}/Ag^@AgCl _(70%) under visible light followed a pseudo-first-order kinetic model. The simultaneous degradation of target compounds was further investigated in sewage treatment plant effluent as well as tap water. It was found that the matrix constituents can reduce the photodegradation efficiency, especially in the case of highly contaminated samples.

Synthesis, modifications and applications of MILs Metal-organic frameworks for environmental remediation: The cutting-edge review

Ever-increasing anthropogenic activities are radically deteriorating the environment by causing severe pollution. Thus, curtailing the environmental pollution and promotion of sustainable development, are the hot issues confronted by scientists in this modern era. Metal-organic frameworks (MOFs) have been highly recognized as emerging promising materials for environmental remediation due to their versatile structure and extraordinary properties. Among them, MILs (MIL = Matérial Institute of Lavoisier) are the series of MOFs mostly known for their incredible stability, unique tailorable pore structures, and astounding versatile environmental applications. Their exclusive physiochemical properties and multifunctionality make them proficient for a wide range of pollutants removal in the exposure of versatile harsh environments, compared to other MOFs. This piece of research summarizes the state-of-the-art of development of MILs on the broad spectrum, highlighting their specificities, such as synthesis techniques, modifications and applications for environmental remediation. However, MILs wonderful properties and extraordinary applications in multiple fields, their deployment on practical and commercial-scale pollutants remediation is hindered by insufficient scientific research on underlying mechanisms and relationships. Henceforth, this review not only signifies the emerging importance of MILs for environmental applications but also indicates the urgency to maximize the scientific research for exploitation of MOFs on a practical level and promotion of green technologies for environmental remediation.

Recent Advances in Plasmonic Photocatalysis Based on TiO2 and Noble Metal Nanoparticles for Energy Conversion, Environmental Remediation, and Organic Synthesis

Plasmonic photocatalysis has emerged as a prominent and growing field. It enables the efficient use of sunlight as an abundant and renewable energy source to drive a myriad of chemical reactions. For instance, plasmonic photocatalysis in materials comprising TiO₂ and plasmonic nanoparticles (NPs) enables effective charge carrier separation and the tuning of optical response to longer wavelength regions (visible and near infrared). In fact, TiO₂ -based materials and plasmonic effects are at the forefront of heterogeneous photocatalysis, having applications in energy conversion, production of liquid fuels, wastewater treatment, nitrogen fixation, and organic synthesis. This review aims to comprehensively summarize the fundamentals and to provide the guidelines for future work in the field of TiO₂ -based plasmonic photocatalysis comprising the above-mentioned applications. The concepts and state-of-the-art description of important parameters including the formation of Schottky junctions, hot electron generation and transfer, near field electromagnetic enhancement, plasmon resonance energy transfer, scattering, and photothermal heating effects have been covered in this review. Synthetic approaches and the effect of various physicochemical parameters in plasmon-mediated TiO₂ -based materials on performances are discussed. It is envisioned that this review may inspire and provide insights into the rational development of the next generation of TiO₂ -based plasmonic photocatalysts with target performances and enhanced selectivities.

Synthesis and characterization of Ag-AgVO3/Cu2O heterostructure with improved visible-light photocatalytic performance

Heterostructure Ag-AgVO3/Cu2O photocatalyst was prepared by the hydrothermal procedure. The prepared photocatalysts were characterized by different physico-chemical techniques. For Ag-AgVO3/Cu2O composites, AgVO3 shows the monoclinic phase whereas Ag and Cu2O show a cubic phase. SEM images of Ag-AgVO3/Cu2O composites illustrated that the surface of AgVO3 nanorods was covered by Ag and Cu2O nanoparticles. Ultra violet - visible diffuse reflectance spectra revealed that the calculated optical response of Ag-AgVO3/Cu2O composite was found to be 2.24 eV. Additionally, the composite catalyst demonstrated improved photo-efficiency for the decolorization of methylene blue dye compared to that of pristine AgVO3. The better performance of the composite sample can be ascribed to its high charge separation and inhibition in recombination of charges in Ag-AgVO3/Cu2O catalyst Finally, this heterostructure Ag-AgVO3/Cu2O catalyst demonstrated good stability which simply can be recycled a number of times with steadiness; thus, unwraps new possibilities for applications as innovative photocatalyst.

Investigation of simultaneous multiple UV filters degradation efficiency of plasmonic Ag@AgCl photocatalyst in the aquatic environment under sunlight irradiation

UV filters as an important class of emerging organic pollutants are continuously released into and transported between the aquatic environments. So, the removal of these compounds from aquatic environments is of great importance. This study was conducted to evaluate the simultaneous photodegradation of three widely used UV filter compounds (4-methylbenzylidene camphor, 2-ethylhexyl 4-(dimethylamino) benzoate, ethylhexyl methoxycinnamate), in an aqueous environment under sunlight and Ag@AgCl photocatalyst integrated with plasmonic effect. The plasmonic Ag@AgCl nanocomposite was constructed via photochemical conversion and photoreduction. The enhanced photocatalytic performance can be attributed to the surface plasmon resonance effect of the silver nanoparticles and the hybrid effect caused by AgCl. For the monitoring of the target compounds' degradation before and after photodegradation, an optimized method based on membrane-protected micro-solid-phase extraction coupled with gas chromatography-mass spectrometry (GC-MS) was employed. The simultaneous degradation of selected UV filters was also further investigated in contaminated real samples (river water) and the results showed that the matrix constituents could diminish the photocatalytic degradation efficiency.

PVC-SiO2-Ag composite as a powerful biocide and anti-SARS-CoV-2 material

The ongoing COVID-19 pandemic has pushed scientists and technologists to find novel strategies to develop new materials to prevent the transmission, spread, and entry of pathogens into the human body. In this report, the fabrication of polyvinyl chloride (PVC)-SiO₂-Ag composite is presented, in which the percentage of Ag is 0.84% wt. Our findings render that this composite eliminates (> 99.8%) bacteria and fungus (Staphylococcus aureus, Escherichia coli, Penicillium funiculosum) and SARS-CoV-2, by surface contact in 2 h hours and 15 min, respectively. Specific migration analysis shown that the use of the PVC-SiO₂-Ag composite is considered safe and effective for food preservation. This research and innovation front can be considered a breakthrough for the design of biocide materials. Future directions for this exciting and highly significant research field can open the door to the development of new technologies for the fabrication of packaging films to protect consumer products (such as fruits, vegetables, and other foods).

State-of-the-art progress in tracking plasmon-mediated photoredox catalysis

Metal nanocrystals (NCs), particularly for plasmonic metal NCs with specific morphology and size, can strongly interact with ultraviolet-visible or even near-infrared photons to generate energetic charge carriers, localized heating, and electric field enhancement. These unique properties offer a promising opportunity for maneuvering solar-to-chemical energy conversion through different mechanisms. As distinct from previous works, in this review, recent advances of various characterization techniques in probing and monitoring the photophysical/photochemical processes, as well as the reaction mechanisms of plasmon-mediated photoredox catalysis are thoroughly summarized. Understanding how to distinguish and track these reaction mechanisms would furnish basic guidelines to design next-generation photocatalysts for plasmon-enhanced catalysis.

Hot Electrons in TiO2-Noble Metal Nano-Heterojunctions: Fundamental Science and Applications in Photocatalysis

Plasmonic photocatalysis enables innovation by harnessing photonic energy across a broad swathe of the solar spectrum to drive chemical reactions. This review provides a comprehensive summary of the latest developments and issues for advanced research in plasmonic hot electron driven photocatalytic technologies focusing on TiO2-noble metal nanoparticle heterojunctions. In-depth discussions on fundamental hot electron phenomena in plasmonic photocatalysis is the focal point of this review. We summarize hot electron dynamics, elaborate on techniques to probe and measure said phenomena, and provide perspective on potential applications-photocatalytic degradation of organic pollutants, CO2 photoreduction, and photoelectrochemical water splitting-that benefit from this technology. A contentious and hitherto unexplained phenomenon is the wavelength dependence of plasmonic photocatalysis. Many published reports on noble metal-metal oxide nanostructures show action spectra where quantum yields closely follow the absorption corresponding to higher energy interband transitions, while an equal number also show quantum efficiencies that follow the optical response corresponding to the localized surface plasmon resonance (LSPR). We have provided a working hypothesis for the first time to reconcile these contradictory results and explain why photocatalytic action in certain plasmonic systems is mediated by interband transitions and in others by hot electrons produced by the decay of particle plasmons.

Recent advances in g-C3N4 composites within four types of heterojunctions for photocatalytic CO2 reduction

Studies of photocatalytic conversion of CO₂ into hydrocarbon fuels, as a promising solution to alleviate global warming and energy issues, are booming in recent years. Researchers have focused their interest in developing g-C₃N₄ composite photocatalysts with intriguing features of robust light harvesting ability, excellent catalysis, and stable performance. Four types of heterojunctions (type-II, Z-scheme, S-scheme and Schottky) of the g-C₃N₄ composites are widely adopted. This review aims at presenting and comparing the photocatalytic mechanisms, characteristics, and performances of g-C₃N₄ composites concerning these four types of heterojunctions. Besides, perspectives and undergoing efforts for further development of g-C₃N₄ composite photocatalysts are discussed. This review would be helpful for researchers to gain a comprehensive understanding of the progress and future development trends of g-C₃N₄ composite heterojunctions for photocatalytic CO₂ reduction.

Titanium dioxide and graphitic carbon nitride-based nanocomposites and nanofibres for the degradation of organic pollutants in water: a review

The paper reviews graphitic carbon nitride-based nanostructured photocatalytic materials and nanofibres for applications in water purification. Titanium dioxide has shown unique features that continue to attract research and development (R&D) due to its unique properties such as availability, ultraviolet absorptivity, photocatalysis, adsorption of pollutants and solar cell engineering. Graphitic carbon nitride is an attractive photocatalyst due to its non-toxicity characteristics, good visible light absorption and good thermal and chemical stabilities. In water purification, nanofibres are currently noticed due to their distinctive properties of effective separation and sometimes elimination of organic pollutants in water. In this review, synthesis and utility of doped titanium dioxide and carbon nitride with metal nanoparticles and polymeric nanofibres from nanocomposites as effective materials for the degradation of organic contaminations from water are discussed. The history, current trends and future perspectives are highlighted.

Optical Characterization of Ultra-Thin Films of Azo-Dye-Doped Polymers Using Ellipsometry and Surface Plasmon Resonance Spectroscopy

The determination of optical constants (i.e., real and imaginary parts of the complex refractive index (nc) and thickness (d)) of ultrathin films is often required in photonics. It may be done by using, for example, surface plasmon resonance (SPR) spectroscopy combined with either profilometry or atomic force microscopy (AFM). SPR yields the optical thickness (i.e., the product of nc and d) of the film, while profilometry and AFM yield its thickness, thereby allowing for the separate determination of nc and d. In this paper, we use SPR and profilometry to determine the complex refractive index of very thin (i.e., 58 nm) films of dye-doped polymers at different dye/polymer concentrations (a feature which constitutes the originality of this work), and we compare the SPR results with those obtained by using spectroscopic ellipsometry measurements performed on the same samples. To determine the optical properties of our film samples by ellipsometry, we used, for the theoretical fits to experimental data, Bruggeman’s effective medium model for the dye/polymer, assumed as a composite material, and the Lorentz model for dye absorption. We found an excellent agreement between the results obtained by SPR and ellipsometry, confirming that SPR is appropriate for measuring the optical properties of very thin coatings at a single light frequency, given that it is simpler in operation and data analysis than spectroscopic ellipsometry.

A rapid green synthesis of Ag/AgCl-NC photocatalyst for environmental applications

The present study focuses on extract-mediated Ag nanoparticles (NPs), AgCl-NPs, and Ag/AgCl nanocomposites (NCs) as photocatalysts along with its antimicrobial and dye degradation activities. The synthesis of these NPs and NCs was performed by using Azadirachta indica plant fruit extract and analyzed using UV-Vis spectroscopy to confirm the synthesis and band gap of these NPs and NCs, X-ray diffraction (XRD) to determine its size and crystalline nature. Fourier transform infrared spectroscopy (FTIR) to discern phytochemicals, responsible for the reduction and capping of the synthesized NCs. Scanning electron microscopy analysis (SEM), transmission electron microscopy analysis (TEM), and energy dispersive X-ray (EDX) spectroscopy analysis were performed to validate the morphology and presence of silver and chloride percentage in the composites. Later, these NPs and NCs were used for their potential role in photocatalytic degradation of methylene blue dye and antibacterial activity against Escherichia coli and Staphylococcus aureus of human pathogen. The prepared Ag/AgCl-NCs exhibited an enhanced photocatalytic and antibacterial activities in comparison with pure Ag and AgCl nanomaterials. However, green-synthesized NPs and NCs played dual roles as a photocatalyst and antibacterial agent in various biomedical and industrial sectors. Moreover, we found that it might be a hot research in many other environmental applications in upcoming days.

Design and application of metal-organic frameworks and derivatives as heterogeneous Fenton-like catalysts for organic wastewater treatment: A review

Advanced oxidation process (AOP), with a high oxidation efficiency, fast reaction speed (relatively no secondary pollution), has become one of the core technologies of industrial wastewater and advanced drinking water treatment. Heterogeneous Fenton-like oxidation process (HFOP) is a kind of AOP, which developed rapidly in recent years in such a way to overcome the disadvantages of traditional Fenton reaction. Metal-organic frameworks (MOFs) and their derivatives become essential heterogeneous catalysts for organics mineralization due to the large specific surface area, abundant active sites, and ease of structural regulation. However, the knowledge gap on the mechanism and the fate of heterogeneous catalyst species during organics degradation activities by MOFs presents considerable impediments, particularly for a wide application and scaling up the process. This work has the potential to provide guidance and ideas for researchers and engineers in the fields of environmental remediation, environmental catalysis and functional materials. This review focuses on clarifying the critical mechanism of •OH production from MOFs and derivatives as well as its action on the organic's degradation process. The recent developments in MOF based HFOP are compared, and more attention is paid for the following aspects in this review: (1) classifies systematically progressive modification methods of MOFs by chemical and physical treatments; (2) analyzes the fate of catalytic species during treating organic wastewater; (3) proposes design ideas and principles for improving the performance of MOFs catalysts; (4) discusses the main factors influencing the catalytic properties and practical application; (5) summarizes the possible research challenges and directions for MOFs and their derivatives as catalysts applied to wastewater treatment in the future.

High-field polarization boosting visible-light photocatalytic H2 evolution of narrow-bandgap semiconducting (1 − x)KNbO3–xBa(Ni1/2Nb1/2)O3−δ ferroelectric ceramics

The photocatalytic H2 evolution of semiconducting KN-based ferroelectrics and its further boosting via a high-field polarization has been studied.

Plasmonic Photocatalysts for Sunlight-Driven Reduction of CO2 : Details, Developments, and Perspectives

Plasmonic photocatalysis is among the most efficient processes for the photoreduction of CO₂ into valuable fuels. The formation of localized surface plasmon resonance (LSPR), energy transfer, and surface reaction are the significant steps in this process. LSPR plays an essential role in the performance of plasmonic photocatalysts as it promotes an excellent, light absorption over a broad wavelength range while simultaneously facilitating an efficient energy transfer to semiconductors. The LSPR transfers energy to a semiconductor through various mechanisms, which have both advantages and disadvantages. This work points out four critical features for plasmonic photocatalyst design, that is, plasmonic materials, size, shape of plasmonic nanoparticles (PNPs), and the contact between PNPs and semiconductor. Various developed plasmonic photocatalysts, as well as their photocatalytic performance in CO₂ photoreduction, are reviewed and discussed. Finally, perspectives of advanced architectures and structural engineering for plasmonic photocatalyst design are put forward with high expectations to achieve an efficient CO₂ photoreduction shortly.

Recovery of waste gold for the synthesis of gold nanoparticles supported on radially aligned nanorutile: the growth of carbon nanomaterials

Precious and expensive metals are lost each year through the discarding of old jewellery pieces and mine tailings. In this work, small amounts of gold were recovered by digestion with aqua regia from waste tailings. The recovered gold in the form of HAuCl₄ was then used to deposit Au⁰ onto radially aligned nanorutile (RANR) to form a supported catalyst material. The support material, RANR, was synthesized using the hydrothermal technique whereas the deposition of gold was achieved using the deposition–precipitation with urea method at various loadings. Electron microscopy was used to show that the structure of the support is a sphere formed by multiple nanorods aligned in a radial structure. The Au nanoparticles were observed at the tips of the nanorods. It was confirmed by XRD that the support was indeed a rutile phase of TiO₂ and that the Au nanoparticles had a face-centred cubic structure. The various catalysts were then used to synthesize carbon nanomaterials (CNMs) using the chemical vapour deposition technique. A parametric study varying the reaction temperature, duration and carbon source gas flow rate was conducted to study the effects these conditions have on the structural properties of the resulting CNMs. Here, it was found that mainly carbon nanofibers were formed and that the different reaction conditions influenced their graphicity, width, structure and thermal properties.

A hydrothermal method was used to prepare rutile TiO₂ dandelions. A deposition–precipitation method using urea (DPU) was used to load Au metal nanoparticles in calculated weight percentages and the Au/RANR catalysts where used to synthesise CNFs in a CVD reaction.

Ultra-High-Responsivity Vertical Nanowire-based Phototransistor under Standing-Wave Plasmon Mode Interaction Induced by Near-Field Circular OLED

High-responsivity photodevices are strongly desired for various demanding applications, such as optical communications, logic circuits, and sensors. The use of quantum and photon confinement has enabled a true revolution in the development of high-performance devices. Unfortunately, many practical optoelectronic devices exhibit intermediate sizes where resonant enhancement effects seem to be insignificant. Here we design and fabricate an ultra-high-responsivity organic-light-emitting-diode-induced nanowire resonance phototransistor (ONRPT) based on standing-wave resonance in the nanoscale cavity, subjected to a near-field light. Observations of the ONRPT in standing-wave resonance mode indicate a >10⁴ enhancement in the on/off ratio and a six times higher subthreshold slope when compared with the ONRPT in non-resonance mode. The ONRPT, which leads itself to outstanding electrical and favorably stable performance, opens up a plethora of opportunities for high-efficiency energy devices and allows for nanowire applications in the solar cell, piezo-photonic detectors, and optical modulators.

InGaN Nanorods Decorated with Au Nanoparticles for Enhanced Water Splitting Based on Surface Plasmon Resonance Effects

Photoelectrochemical (PEC) water splitting has great application potential in converting solar energy into hydrogen energy. However, what stands in the way of the practical application of this technology is the low conversion efficiency, which can be promoted by optimizing the material structure and device design for surface functionalization. In this work, we deposited gold nanoparticles (Au NPs) with different loading densities on the surface of InGaN nanorod (NR) arrays through a chemical solvent route to obtain a composite PEC water splitting system. Enhanced photocatalytic activity, which can be demonstrated by the surface plasmon resonance (SPR) effect induced by Au NPs, occurred and was further confirmed to be associated with the different loading densities of Au NPs. These discoveries use solar water splitting as a platform and provide ideas for exploring the mechanism of SPR enhancement.

Ultrathin Pd-based nanosheets: syntheses, properties and applications

Two-dimensional (2D) noble metal-based nanosheets (NSs) have received considerable interest in recent years due to their unique properties and widespread applications. Pd-based NSs, as a typical member of 2D noble metal-based NSs, have been most extensively studied. In this review, we first summarize the research progress on the synthesis of Pd-based NSs, including pure Pd NSs, Pd-based alloy NSs, Pd-based core-shell NSs and Pd-based hybrid NSs. The synthetic strategy and growth mechanism are systematically discussed. Then their properties and applications in catalysis, biotherapy, gas sensing and so on are introduced in detail. Finally, the challenges and opportunities towards the rational design and controlled synthesis of Pd-based NSs are proposed.