Graphene oxide-CdS composite with high photocatalytic degradation and disinfection activities under visible light irradiation

Nanomaterial-Enhanced Hybrid Disinfection: A Solution to Combat Multidrug-Resistant Bacteria and Antibiotic Resistance Genes in Wastewater

This review explores the potential of nanomaterial-enhanced hybrid disinfection methods as effective strategies for addressing the growing challenge of multidrug-resistant (MDR) bacteria and antibiotic resistance genes (ARGs) in wastewater treatment. By integrating hybrid nanocomposites and nanomaterials, natural biocides such as terpenes, and ultrasonication, this approach significantly enhances disinfection efficiency compared to conventional methods. The review highlights the mechanisms through which hybrid nanocomposites and nanomaterials generate reactive oxygen species (ROS) under blue LED irradiation, effectively disrupting MDR bacteria while improving the efficacy of natural biocides through synergistic interactions. Additionally, the review examines critical operational parameters-such as light intensity, catalyst dosage, and ultrasonication power-that optimize treatment outcomes and ensure the reusability of hybrid nanocomposites and other nanomaterials without significant loss of photocatalytic activity. Furthermore, this hybrid method shows promise in degrading ARGs, thereby addressing both microbial and genetic pollution. Overall, this review underscores the need for innovative wastewater treatment solutions that are efficient, sustainable, and scalable, contributing to the global fight against antimicrobial resistance.

One-pot synthesis of g-C3N4/N-doped CeO2 nanocomposites and their potential visible light-driven photocatalytic degradation of methylene blue dye

In the pursuit of efficient photocatalytic materials for environmental applications, a new series of g-C3N4/N-doped CeO2 nanocomposites (g-C3N4/N-CeO2 NCs) was synthesized using a straightforward dispersion method. These nanocomposites were systematically characterized to understand their structural, optical, and chemical properties. The photocatalytic performance of g-C3N4/N-CeO2 NCs was evaluated by investigating their ability to degrade methylene blue (MB) dye, a model organic pollutant. The results demonstrate that the integration of g-C3N4 with N-doped CeO2 NCs reduces the optical energy gap compared to pristine N-doped CeO2, leading to enhanced photocatalytic efficiency. It is benefited from the existence of g-C3N4/N-CeO2 NCs not only in promoting the charge separation and inhibits the fast charge recombination but also in improving photocatalytic oxidation performance. Hence, this study highlights the potential of g-C3N4/N-CeO2 NCs as promising candidates for various photocatalytic applications, contributing to the advancement of sustainable environmental remediation technologies.

Innovative enhancement of electron tunneling synergy in carbon-doped Ta2O5CuO photocatalyst with nematic liquid crystal for safe drinking water

This study focuses on enhancing the photocatalytic properties of carbon-doped Ta2O5CuO (C-Ta2O5CuO) nanocomposites for drinking water purification. The nanocomposites were fabricated by depositing C-Ta2O5CuO onto Nematic Liquid Crystal Polaroid (NLCP) obtained from a discarded laptop monitor, employing the sputter deposition method. The X-ray diffraction (XRD) and High-resolution transmission electron microscopy (HRTEM) determined the nanocomposite thin films' crystallinity and structural properties. The EDX and XPS analyses confirmed the elemental composition and reality of the Cu-incorporated Ta2O5 nanocomposites, respectively. The combination of electron tunneling enhancement provided by the NLCP and graphitic carbon led to exceptional photocatalytic performance. This was particularly evident in the efficient degradation of P-Rosaniline Hydrochloride (PRH) dye in an aqueous medium. C-Ta2O5CuO catalytic activities were estimated at various dye concentrations, repeatability, reusability with time, and kinetics. Coating's stability and long-term activity in photocatalysis reactions were also tested. Additionally, Cu present in the C-Ta2O5CuO and ˙OH radicals exhibited remarkable bactericidal activity. They displayed significant antibacterial efficacy against both gram-positive Escherichia coli (E. coli) and gram-negative Staphylococcus aureus (S. aureus) bacteria. These findings have significant implications for the development of advanced materials with potent photocatalytic and antibacterial properties, holding promise for improving drinking water quality and addressing environmental and health challenges.

Catalyzing Artificial Photosynthesis with TiO2 Heterostructures and Hybrids: Emerging Trends in a Classical yet Contemporary Photocatalyst

Titanium dioxide (TiO2) stands out as a versatile transition-metal oxide with applications ranging from energy conversion/storage and environmental remediation to sensors and optoelectronics. While extensively researched for these emerging applications, TiO2 has also achieved commercial success in various fields including paints, inks, pharmaceuticals, food additives, and advanced medicine. Thanks to the tunability of their structural, morphological, optical, and electronic characteristics, TiO2 nanomaterials are among the most researched engineering materials. Besides these inherent advantages, the low cost, low toxicity, and biocompatibility of TiO2 nanomaterials position them as a sustainable choice of functional materials for energy conversion. Although TiO2 is a classical photocatalyst well-known for its structural stability and high surface activity, TiO2-based photocatalysis is still an active area of research particularly in the context of catalyzing artificial photosynthesis. This review provides a comprehensive overview of the latest developments and emerging trends in TiO2 heterostructures and hybrids for artificial photosynthesis. It begins by discussing the common synthesis methods for TiO2 nanomaterials, including hydrothermal synthesis and sol-gel synthesis. It then delves into TiO2 nanomaterials and their photocatalytic mechanisms, highlighting the key advancements that have been made in recent years. The strategies to enhance the photocatalytic efficiency of TiO2, including surface modification, doping modulation, heterojunction construction, and synergy of composite materials, with a specific emphasis on their applications in artificial photosynthesis, are discussed. TiO2-based heterostructures and hybrids present exciting opportunities for catalyzing solar fuel production, organic degradation, and CO2 reduction via artificial photosynthesis. This review offers an overview of the latest trends and advancements, while also highlighting the ongoing challenges and prospects for future developments in this classical yet rapidly evolving field.

Polystyrene microplastics enhance oxidative dissolution but suppress the aquatic acute toxicity of a commercial cadmium yellow pigment under simulated irradiation

Commercial cadmium yellow (CdS) pigment widely coexist with microplastics (MPs) in surface water, thus it is important to understand how MPs affect CdS pigment stability and toxicity under irradiation. Herein, the dissolution of CdS pigment (krelease = 0.118 h-1) under irradiation was visibly increased to 0.144 h-1 by polystyrene (PS) MPs, due to reactive species generation such as 1O2, •OH and 3PS* , while O2•- was unimportant to this process. The O2, humic acid, photoaging status of PS MPs could promote PS MPs-related CdS pigment dissolution rate by modifying reactive species generation. However, the CO32-, PO43- and alkaline condition significantly decreased the dissolution rate to 0.091, 0.053 and 0.094 h-1, respectively, through modifying free Cd2+ stability. Comparably, PS MPs-related CdS pigment dissolution was relatively slow in natural water samples (krelease = 0.075 h-1). PS MPs at environmental concentration can also promote CdS pigment dissolution and Cd2+ release, but suppress acute toxicity of CdS pigment to zebrafish larvae as increasing 10 h survival from 65% to 85% by adsorbing the Cd2+ and decreasing Cd2+ bioavailability. This study emphasized the environmental risks and human safety of CdS pigment should be carefully evaluated in the presence of PS MPs in aquatic environments.

Stable and Highly Efficient Photocatalysis with Two-Dimensional Organic-Inorganic Hybrid Perovskites

Two-dimensional organic-inorganic hybrid perovskites (OIHPs) have excellent photoelectric properties, such as high charge mobility and a high optical absorption coefficient, which have attracted enormous attention in the field of optoelectronic devices and photochemistry. However, the stability of 2D OIHPs in solution is deficient. In particular, the lack of stability in polar solutions hinders their application in photochemistry. In this work, (iso-BA)2PbI4 was used as a model to explore the three possibilities of the stable existence of a 2D perovskite in aqueous solution. And two of these systems that stabilize the presence of (iso-BA)2PbI4 were further investigated through electrochemical testing. Moreover, (iso-BA)2PbI4 2D hybrid perovskites exhibited an outstanding degradation rate. The chiral perovskite (R/S-MBA)2PbI4 is able to degrade a 30 mg/L methyl orange solution completely within 5 min, making it one of the fastest catalysts for this particular organic reaction. Further, based on the electron spin resonance test, a degradation mechanism by the halide perovskite was proposed. Based on the great catalytic performance as well as good reusability and stability, (R/S-MBA)2PbI4 perovskites are expected to be a new generation of catalysts, making a great impact on the application of asymmetrically catalyzed photoreactions.

In-situ preparation of mossy tile-like ZnIn2S4/Cu2MoS4 S-scheme heterojunction for efficient photocatalytic H2 evolution under visible light

The reasonable design and fabrication of heterojunction could regulate the photocatalytic performance to some extent, yet it is still a great challenge to construct the S-scheme heterostructure with the stable as well as tight interface on the surface of semiconductor photocatalysts. Herein, the ZnIn2S4/Cu2MoS4 (ZIS/CMS) S-scheme heterostructure was fabricated by in-situ assembling ZIS nanosheets on the CMS plates, obtaining a mossy tile-like morphology. Owing to the compact interface resulting from in-situ growth, this unique architecture efficiently facilitated the separation and transfer of light-induced charges, guaranteed the larger interface area, and enriched the active sites for photocatalytic redox reactions. After adjusting the mass ratio of CMS in ZIS/CMS, S-scheme heterostructure exhibited the remarkable performance with an optimal H2 producing rate up to 1298 μmol·h-1 g-1, about 13.8 times than that of pristine ZIS. The mechanism and driving force of charge transfer and separation in S-scheme heterostructure photocatalysts were explained and discussed. This investigation will provide new insight into design and construction of S-scheme heterojunction photocatalysts for H2 evolution.

Preparation of a high-efficiency low-toxicity CdS/C60 bactericide and investigation of the mechanism

Photocatalysis is considered as a promising technology to solve bacterial contamination, but the development of efficient photocatalysts with a strong generalizable light response remains a challenge. CdS has a suitable energy gap and good response to visible light, but the photogenerated carrier separation efficiency is low, and the photo-corrosion phenomenon leads to the significant release of Cd²⁺. In this paper, the CdS/C₆₀ composite photocatalyst bactericide is synthesized via a simple one-step hydrothermal method. Testing via EIS, I-t, PL, and TRPL show that the C₆₀ in the composite improves the hole-electron separation efficiency of CdS, resulting in a better photocatalytic performance. The complete inactivation of S. aureus and E. coli can be achieved within 40 min and 120 min, respectively, by dispersing 100 μg mL^-1 of CdS/C₆₀-2 in a diluted bacterial solution under simulated visible-light irradiation. Combined with ESR, SEM, fluorescence staining, DNA gel electrophoresis and ICP technology, it is believed that the high inactivation of bacteria is attributed to the ROS produced during the photocatalytic process, which destroy the integrity of the bacterial cell membrane and further destroy the DNA inside the bacteria, thus causing bacterial inactivation, rather than the inactivation being caused by Cd²⁺ toxicity.

Ultrafast extraction of uranium from seawater using photosensitized biohybrid system with bioinspired cascaded strategy

The highly effective utilization of uranium resources in global seawater is a viable method to satisfy the rising demands for fueling nuclear energy industry. Herein, inspired by the multi-mechanisms of the marine bacteria for uranium immobilization, CdS nanoparticles are deposited on the cell of marine bacterial strain Bacillus velezensis UUS-1 to create a photosensitized biohybrid system UUS-1/CdS. This system achieves high uranium extraction efficiency using a cascaded strategy, where the bacterial cells guarantee high extraction selectivity and the photosensitive CdS nanoparticles realize cascading photoreduction of high soluble U(VI) to low soluble U(IV) to enhance extraction capacity. As one of the fastest-acting adsorbents in natural seawater, a high extraction capacity for uranium of 7.03 mg g^-1 is achieved with an ultrafast extraction speed of 4.69 mg g^-1 d^-1. The cascaded strategy promisingly improves uranium extraction performance and pioneers a new direction for the design of adsorbents to extract uranium from seawater.

Graphene oxide-incorporated silver-based photocatalysts for enhanced degradation of organic toxins: a review

Environmental contamination and scarcity of energy have been deepening over the last few decades. Heterogeneous photocatalysis plays a prominent role in environmental remediation. The failure of earlier metal oxide systems like pure TiO₂ and ZnO as stable visible-light photocatalysts demanded more stable catalysts with high photodegradation efficiency. Silver-based semiconductor materials gained popularity as visible-light-responsive photocatalysts with a narrow bandgap. But their large-scale usage in natural water bodies for organic contaminant removal is minimal. The factors like self-photocorrosion and their slight solubility in water have prevented the commercial use. Various efforts have been made to improve their photocatalytic activity. This review focuses on those studies in which silver-based semiconductor materials are integrated with carbonaceous graphene oxide (GO) and reduced graphene oxide (RGO). The decoration of Ag-based semiconductor components on graphene oxide having high-surface area results in binary composites with enhanced visible-light photocatalytic activity and stability. It is found that the introduction of new efficient materials further increases the effectiveness of the system. So binary and ternary composites of GO and Ag-based materials are reviewed in this paper.

Multipollutant Abatement through Visible Photocatalytic System

Water pollution damages the aquatic environment due to the presence of organic contaminants, which in turn is distressing to the ecosystem. Photocatalytic activity is a greener and promising method to degrade these organic contaminants. In this research, we present the degradation of diverse water pollutants through zinc/iron oxide nanoparticles serving as photocatalysts. The photocatalyst was studied for its efficiency to photodegrade congo red, brilliant green and para nitro phenol. Moreover, it also presented an antibacterial activity against the bacterium E. coli. Photocatalyst was characterized via X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy, and fourier-transform infrared spectroscopy. Tauc plot was used to measure the optical band gap (1.84 eV). The effect of various parameters such as catalyst dose, contact time, dye dose/concentration and pH were also investigated to determine the optimum point of maximum degradation through response surface methodology. A face-centered composite design was used, and a quadratic model was followed by congo red, brilliant green dyes and para nitrophenol. The maximum photodegradation efficiencies were 99%, 94.3%, and 78.5% for congo red, brilliant green and phenol, respectively. Quantum yield for congo red, brilliant green and para-nitrophenol were 9.62 × 10−8, 1.17 × 10−7 and 4.11 × 10−7 molecules/photons, while the reaction rates were 27.1 µmolg−1h−1, 29.61 µmolg−1h−1 and 231 µmolg−1h−1, respectively.

Plasmonic and bi-piezoelectric enhanced photocatalysis using PVDF/ZnO/Au nanobrush

The photocatalytic degradation, as an environmental-friendly technology, has great significance for cost-effective and efficient catalysis processes, wherein piezo-photocatalysis can significantly increase the catalytic degradation rate using both solar and mechanical energy. Here, a ternary heterostructure PVDF/ZnO/Au (PZA) nanobrush photocatalyst with high piezo-photocatalytic efficiency was presented via low-temperature hydrothermal and chemical reduction methods. Under both solar and mechanical energy, the current response and degradation rate of the as-synthesized PZA nanobrush all increase significantly compared with that under solar alone and under mechanical energy alone, and the excellent recyclability is investigated. It is found that the PZA nanobrush with ultrasonic-assisted piezo-photocatalysis completely degrade MO of 20 mg/L in 60 min, which exhibits greater enhancement of photocatalytic activity than with stirring-assisted piezo-photocatalysis due to higher power. The high piezo-photocatalytic activity of PZA nanobrush is attributed to the surface plasmon resonance (SPR) coupling of Au and built-in electric field originating from the ZnO and PVDF, which can increase the absorption of visible light, promote the charge transfer and separation of photogenerated electrons/holes. This work introduces the SPR and bipiezotronic effect to improve plasmonic photocatalysis with PZA heterostructures, which offers a new solution in green technologies to design high-performance catalysts for the environmental remediation.

Graphene-derived antibacterial nanocomposites for water disinfection: Current and future perspectives

Antimicrobial nanomaterials provide numerous opportunities for the synthesis of next-generation sustainable water disinfectants. Using the keywords graphene and water disinfection and graphene antibacterial activity, a detailed search of the Scopus database yielded 198 and 1433 studies on using graphene for water disinfection applications and graphene antibacterial activity in the last ten years, respectively. Graphene family nanomaterials (GFNs) have emerged as effective antibacterial agents. The current innovations in graphene-, graphene oxide (GO)-, reduced graphene oxide (rGO)-, and graphene quantum dot (GQD)-based nanocomposites for water disinfection, including their functionalization with semiconductor photocatalysts and metal and metal oxide nanoparticles, have been thoroughly discussed in this review. Furthermore, their novel application in the fabrication of 3D porous hydrogels, thin films, and membranes has been emphasized. The physicochemical and structural properties affecting their antibacterial efficiency, such as sheet size, layer number, shape, edges, smoothness/roughness, arrangement mode, aggregation, dispersibility, and surface functionalization have been highlighted. The various mechanisms involved in GFN antibacterial action have been reviewed, including the mechanisms of membrane stress, ROS-dependent and -independent oxidative stress, cell wrapping/trapping, charge transfer, and interaction with cellular components. For safe applications, the potential biosafety and biocompatibility of GFNs in aquatic environments are emphasized. Finally, the current limitations and future perspectives are discussed. This review may provide ideas for developing efficient and practical solutions using graphene-, GO-, rGO-, and GQD-based nanocomposites in water disinfection by rationally employing their unique properties.

Recent progress of silver-containing photocatalysts for water disinfection under visible light irradiation: A review

Photocatalysis has emerged as an environmentally friendly approach for microbial disinfection. The development of visible-light-driven (VLD) photocatalysts for water pollution remediation is imperative, considering that visible light constitutes a substantial fraction of the solar spectrum. The modification of photocatalysts by Ag/AgX (X = Cl, Br, I) deposition can be used to improve photocatalytic efficiencies. This is achieved by preventing photogenerated electron-hole pairs recombination through electron trapping mechanisms. With the introduction of silver NPs, visible light absorption can also be increased through its SPR enhancement. Silver also possesses excellent antimicrobial properties. Consequently, a novel class of Ag/AgX-containing hybrid materials has recently emerged as a promising candidate for water disinfection. This review summarizes the latest advances in the synthesis of Ag/AgX-containing photocatalysts using various synthetic methods. The microbial disinfection efficiencies of the as-prepared materials, the main reactive oxygen species and disinfection mechanisms are also reviewed in detail. Finally, some areas that need to be improved are discussed along with new insights as perspectives for future developments in this field.

Sunlight-promoted photodegradation of Congo red by cadmium-sulfide decorated graphene aerogel

Herein, a simpler-viable methodology for the surface decoration of pear fruit derived graphene aerogel (GA) via cadmium sulfide (CdS) has been presented. GA can be easily synthesized from bio-mass, which provide an economic advantage. Surface decoration via CdS imparts photocatalytic activities in functionalized graphene aerogels (f-GA). CdS-f-GA is being explored here as a photocatalyst for the degradation of a toxic azo dye named Congo red in the presence of sunlight. The rate and mechanism associated with photodegradation were analyzed by performing kinetics and radical trap-based quenching experiments. Nuclear magnetic resonance and fourier transform infrared spectroscopy analyses of the control and photodegraded products were performed to ensure the degradation of the organic framework of Congo red. Additionally, the real-life applicability of CdS-f-GA was also analyzed by degrading the dye in different types of industrial samples (via the method of external spiking), which can advance its practical relevance.

Review elucidating graphene derivatives (GO/rGO) supported metal sulfides based hybrid nanocomposites for efficient photocatalytic dye degradation

Photocatalysis by utilizing semiconductors for the removal of toxic pollutants has gained tremendous interest for remediation purposes. The organic pollutants usually include; pesticides, dyes and other phenolic compounds. An imperative restraint associated with the photocatalytic effectiveness of the catalyst is the rapid recombination of the light generated electrons and holes. The particle agglomeration and electron-hole recombination hinders the rate of pollutant removal. For decades, researchers have used metal-sulfides efficiently for photocatalytic dye degradation. The recent use of hybrid nanomaterials with the combination of graphene derivatives such as graphene oxide and reduced graphene oxide (GO/rGO)-metal sulfide has gained interest. These composites have displayed an impressive upsurge in the photocatalytic activity of materials. The current review describes the various researches on dye photodegradation by employing (GO/rGO)-metal sulfide, exhibiting a boosted potential for photocatalytic dye degradation. A comprehensive study on (CuS, ZnS and CdS)–GO/rGO hybrid composites have been discussed in detail for effective photocatalytic dye degradation in this review. Astonishingly improved dye degradation rates were observed in all these studies employing such hybrid composites. The several studies described in the review highlighted the varying degradation rates based on diverse research parameters and efficacy of graphene derivatives for enhancement of photocatalytic activity.

Promising Graphene-Based Nanomaterials and Their Biomedical Applications and Potential Risks: A Comprehensive Review

Graphene-based nanomaterials (GBNs) have been the subject of research focus in the scientific community because of their excellent physical, chemical, electrical, mechanical, thermal, and optical properties. Several studies have been conducted on GBNs, and they have provided a detailed review and summary of various applications. However, comprehensive comments on biomedical applications and potential risks and strategies to reduce toxicity are limited. In this review, we systematically summarized the following aspects of GBNs in order to fill the gaps: (1) the history, synthesis methods, structural characteristics, and surface modification; (2) the latest advances in biomedical applications (including drug/gene delivery, biosensors, bioimaging, tissue engineering, phototherapy, and antibacterial activity); and (3) biocompatibility, potential risks (toxicity in vivo/vitro and effects on human health and the environment), and strategies to reduce toxicity. Moreover, we have analyzed the challenges to be overcome in order to enhance application of GBNs in the biomedical field.

Au-SnO2-CdS ternary nanoheterojunction composite for enhanced visible light-induced photodegradation of imidacloprid

Herein, we have developed a novel synthetic strategy for the fabrication of Au-SnO₂-CdS ternary nano-heterojunction catalyst and its utility towards LED light derived photocatalytic degradation of imidacloprid has been evaluated. The synthesized ternary nanocomposite was characterized using sophisticated analytical techniques to evaluate the catalyst's morphological, structural and surface chemical properties. The photocatalytic activity of the ternary catalyst towards the degradation of imidacloprid was evaluated under LED irradiation. Approximately 95% of the degradation efficiency was achieved with a pseudo-first-order reaction rate of 15.6 × 10^-3 min^-1. The degradation efficiency of Au-SnO₂-CdS nano-catalyst was found to be ~1.2, 1.4 and 2.1 times to that of the pristine Au, CdS and SnO₂ nanomaterials under similar experimental conditions. The effect of variation of parameters like contact time, initial pollutant concentration and pH on degradation efficiency has also been investigated. Moreover, the identification of various degradation products and reactive intermediates were made with high-performance liquid chromatography and electron spin resonance techniques.

Transition metal dichalcogenide (TMDs) electrodes for supercapacitors: a comprehensive review

As globally, the main focus of the researchers is to develop novel electrode materials that exhibit high energy and power density for efficient performance energy storage devices. This review covers the up-to-date progress achieved in transition metal dichalcogenides (TMDs) (e.g. MoS₂, WS₂, MoSe_2,and WSe₂) as electrode material for supercapacitors (SCs). The TMDs have remarkable properties like large surface area, high electrical conductivity with variable oxidation states. These properties enable the TMDs as the most promising candidates to store electrical energy via hybrid charge storage mechanisms. Consequently, this review article provides a detailed study of TMDs structure, properties, and evolution. The characteristics technique and electrochemical performances of all the efficient TMDs are highlighted meticulously. In brief, the present review article shines a light on the structural and electrochemical properties of TMD electrodes. Furthermore, the latest fabricated TMDs based symmetric/asymmetric SCs have also been reported.

Ce2O3/BiVO4 Embedded in rGO as Photocatalyst for the Degradation of Methyl Orange under Visible Light Irradiation

A p–n heterojunction semiconductor structure composed of Ce3O4 and BiVO4 has been synthesized and then incorporated into reduced graphene oxide (rGO) by the hydrothermal method. The ternary composites were characterized by X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron diffraction spectroscopy (EDS), and UV–vis spectroscopy. The efficiency of the composites as photocatalysts was determined by studying the oxidative degradation of methyl orange in aqueous solution under visible light irradiation. The effect of parameters such as pH, catalyst loading, and concentration of the dye solution was examined in order to determine their influence on the photocatalytic activity of the composites. The composite incorporated into reduced graphene oxide presented the highest percentage (above 90%) in 2 h time, attributed to the effect of the increased surface area. The process of the enhanced photocatalytic activity has been discussed based on the energy band positions of the nanoparticles within the composite.

Fabrication of novel magnetic CuS/Fe3O4/GO nanocomposite for organic pollutant degradation under visible light irradiation

The magnetic nanocomposites composed of copper sulphide, iron oxide, and graphene oxide (CuS/Fe₃O₄/GO) were synthesized through a facile sol-gel combined with hydrothermal techniques for photodegradation of methylene blue (MB) as a model organic pollutant. The as-prepared samples were characterized by powder X-ray diffraction (XRD), vibrating sample magnetometer (VSM), differential reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray analysis (EDX) and results confirmed successful synthesis of magnetic nanocomposite. Presence of Fe₃O₄ and GO in nanocomposite induced a synergistic effect in CuS performance as CS₈₈F₆G₆ (i.e. 88% CuS, 6% Fe₃O₄, and 6% GO). The photocatalytic degradation efficiency of MB reached up to 90.3% after exposure to visible light irradiation for 80 min. The composite nanosheets are photostable, reusable, and magnetically recoverable, revealing potential application in removal of organic pollutants.

Graphene-Based Composites as Catalysts for the Degradation of Pharmaceuticals

The incessant release of pharmaceuticals into the aquatic environment continues to be a subject of increasing concern. This is because of the growing demand for potable water sources and the potential health hazards which these pollutants pose to aquatic animals and humans. The inability of conventional water treatment systems to remove these compounds creates the need for new treatment systems in order to deal with these class of compounds. This review focuses on advanced oxidation processes that employ graphene-based composites as catalysts for the degradation of pharmaceuticals. These composites have been identified to possess enhanced catalytic activity due to increased surface area and reduced charge carrier recombination. The techniques employed in synthesizing these composites have been explored and five different advanced oxidation processes-direct degradation process, chemical oxidation process, photocatalysis, electrocatalyis processes and sonocatalytic/sono-photocatalytic processes-have been studied in terms of their enhanced catalytic activity. Finally, a comparative analysis of the processes that employ graphene-based composites was done in terms of process efficiency, reaction rate, mineralization efficiency and time required to achieve 90% degradation.

Potential of the magnetic hollow sphere nanocomposite (graphene oxide-gadolinium oxide) for arsenic removal from real field water and antimicrobial applications

Potential of the magnetic hollow-sphere nanocomposite, graphene oxide-gadolinium oxide (GO-Gd₂O₃) for arsenic (As) removal from real field water with developing a continuous operating system and antimicrobial activity were investigated. The characterization results suggest that the prepared GO-Gd₂O₃ is a hallow sphere wool-like nanocomposite having 50.91 m² g^-1 surface area. The sorption studies revealed that a high adsorption capacity (216.70 mg g^-1) can be achieved using GO-Gd₂O₃ (0.1 g L^-1) at a pH of 6.0, and temperature of 293 K. The main and novel observations from the loading of Gd₂O₃ are that the GO adsorption efficiency, adsorbent separation rate from aqueous solutions, and the stability of the composite have been altered. Thus, the developed material can overcome the separation and stability issues associated with the bare GO, and exhibits an enhanced adsorption capacity toward arsenic was higher or comparable with existing magnetic material. In addition, the developed adsorption method was well applied for real field water samples collected from the mining area of South Korea where the GO-Gd₂O₃ can reduce the quantity of arsenic under the maximum accepted concentration of arsenic considered fit for drinking water stipulated by environmental protection agencies. Furthermore, the GO-Gd₂O₃ nanocomposite shows a high bacterial photocatalytic inactivation and was comparable with other reports.

Shining light on transition metal sulfides: New choices as highly efficient antibacterial agents

Globally, millions of people die of microbial infection-related diseases every year. The more terrible situation is that due to the overuse of antibiotics, especially in developing countries, people are struggling to fight with the bacteria variation. The emergence of super-bacteria will be an intractable environmental and health hazard in the future unless novel bactericidal weapons are mounted. Consequently, it is critical to develop viable antibacterial approaches to sustain the prosperous development of human society. Recent researches indicate that transition metal sulfides (TMSs) represent prominent bactericidal application potential owing to the meritorious antibacterial performance, acceptable biocompatibility, high solar energy utilization efficiency, and excellent photo-to-thermal conversion characteristics, and thus, a comprehensive review on the recent advances in this area would be beneficial for the future development. In this review article, we start with the antibacterial mechanisms of TMSs to provide a preliminary understanding. Thereafter, the state-of-the-art research progresses on the strategies for TMSs materials engineering so as to promote their antibacterial properties are systematically surveyed and summarized, followed by a summary of the practical application scenarios of TMSs-based antibacterial platforms. Finally, based on the thorough survey and analysis, we emphasize the challenges and future development trends in this area.

Graphene: An Antibacterial Agent or a Promoter of Bacterial Proliferation?

Graphene materials (GMs) are being investigated for multiple microbiological applications because of their unique physicochemical characteristics including high electrical conductivity, large specific surface area, and robust mechanical strength. In the last decade, studies on the interaction of GMs with bacterial cells appear conflicting. On one side, GMs have been developed to promote the proliferation of electroactive bacteria on the surface of electrodes in bioelectrochemical systems or to accelerate interspecies electron transfer during anaerobic digestion. On the other side, GMs with antibacterial properties have been synthesized to prevent biofilm formation on membranes for water treatment, on medical equipment, and on tissue engineering scaffolds. In this review, we discuss the mechanisms and factors determining the positive or negative impact of GMs on bacteria. Furthermore, we examine the bacterial growth-promoting and antibacterial applications of GMs and debate their practicability.

Construction of magnetic MgFe2O4/CdS/MoS2 ternary nanocomposite supported on NaY zeolite and highly efficient sonocatalytic degradation of organic pollutants

In this work, the novel magnetically separable NaY zeolite/MgFe₂O₄/CdS nanorods/MoS₂ nanoflowers nanocomposite was successfully synthesized through the ultrasonic-assisted solvothermal approach. FESEM, EDAX, XRD, FTIR, TEM, AFM, VSM, N₂-BET, UV-vis DRS and PL were utilized to identify the as-synthesized nanocomposite. Subsequently, the sonocatalytic activity of this nanocomposite was assessed in the degradation of organic dyes, including methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) from water solutions for the first time. Several analytical parameters like irradiation time, process type, initial MB concentration, H₂O₂ concentration, catalyst dosage, organic dye type, and US power have been systematically investigated to attain the maximum sonocatalytic yield. Regarding the acquired data, the NaY/MgFe₂O₄/CdS NRs/MoS₂ NFs sonocatalyst was incredibly able to completely eliminate the MB via engaging the US/H₂O₂ system. The kinetic evaluates demonstrated the sonodegradation reactions of the MB followed a first-order model. The apparent rate constant (k _app) and half-life time (t _1/2) acquired for the sonodegradation process of MB utilizing the US/H₂O₂/NaY/MgFe₂O₄/CdS NRs/MoS₂ NFs system were measured to be 1.162 min and 0.596 min^-1, respectively. The free ˙OH radicals were also recognized as the main reactive oxygen species in the MB sonodegradation process under US irradiation. In addition, the outcomes of the recyclability study of the NaY/MgFe₂O₄/CdS NRs/MoS₂ NFs sonocatalytic clearly displayed a less than 6% drop of the catalytic activity in up to four sequential runs. Lastly, a plausible mechanism for the sonodegradation reaction of organic dyes was suggested and discussed.

Thermal-Sprayed Photocatalytic Coatings for Biocidal Applications: A Review

There have been ever-growing demands for disinfection of water and air in recent years. Efficient, eco-friendly, and cost-effective methods of disinfection for pathogens are vital to the health of human beings. The photocatalysis route has attracted worldwide attention due to its highly efficient oxidative capabilities and sustainable recycling, which can be used to realize the disinfection purposes without secondary pollution. Though many studies have comprehensively reviewed the work about photocatalytic disinfection, including design and fabrication of photocatalytic coatings, inactivation mechanisms, or practical applications, systematic reviews about the disinfection photocatalysis coatings from fabrication to effort for practical use are still rare. Among different ways of fabricating photocatalytic materials, thermal spray is a versatile surface coating technique and competitive in constructing large-scale functional coatings, which is a most promising way for the future environmental purification, biomedical and life health applications. In this review, we briefly introduced various photocatalytic materials and corresponding inactivation mechanisms for virus, bacteria and fungus. We summarized the thermal-sprayed photocatalysts and their antimicrobial performances. Finally, we discussed the future perspectives of the photocatalytic disinfection coatings for potential applications. This review would shed light on the development and implementation of sustainable disinfection strategies that is applicable for extensive use for controlling pathogens in the near future.

Defected graphene as effective co-catalyst of CdS for enhanced photocatalytic activities

Synthesis of highly efficient photocatalysts for energy and environment catalysis is still a big challenge in the materials field. Cadmium sulfide (CdS) is a promising visible light-driven photocatalyst, which can be composited with co-catalysts to increase its photo-activity and stability. In this study, a kind of graphene material with abundant structure defects (D-rGO) is synthesized by a two-step annealing process with nitrogen-doped rGO (N-rGO) as an intermediate. The high-temperature annealing could remove the doped heteroatoms to form structure defects with five or seven carbon atoms. The D-rGO is then used as co-catalyst for the modification of CdS nanoparticles, and enhanced photocatalytic activities could be obtained. A large hydrogen evolution rate of 102.7 μmol h^-1 g^-1 is achieved, which is also effective for 4-nitrophenol reduction with a rate constant of 0.168 min^-1. The novel CdS/D-rGO composite contains no noble metals and could be used as multi-functional photocatalysts, thus should has great potential in the photocatalysis field.

High selectivity and effectiveness for removal of tetracycline and its related drug resistance in food wastewater through schwertmannite/graphene oxide catalyzed photo-Fenton-like oxidation

Selectively and effectively for removal of tetracycline (TC) and its related antibiotic resistance gene from food wastewater matrix with high-salt and high COD characteristics is highly desirable. In this work, novel schwertmannite/graphene oxide (SCH/GO) nanocomposites were synthesized through a facile oxidation-coprecipitation method. The SCH/GO nanocomposites were characterized by TEM, XRD, BET, PL, DRS, XPS and FTIR. In the presence of 1 mM H₂O₂, the SCH/GO catalyzed Fenton-like oxidation can thoroughly degrade TC under visible light irradiation, even under nature sunlight, whose second-order kinetic rate constant was about 15 times higher than that of pure SCH. SCH/GO was capable of highly selectively capturing and effectively degrading TC in the presence of similar concentration of Cl^-, NO₃^-, SO₄^2- and PO₄^3- with that of food wastewater, even at organic matters concentration of 12.5 times than that of TC. At the same time, the removal of total organic carbon (TOC) and chemical oxygen demand (COD) in aforementioned food wastewater in SCH/GO+H₂O₂+Vis system reached 27.3 % and 34.5 % after 60 min, respectively. The inhibition zone experiments authenticated that the removal of drug resistance of bacteria by TC degradation intermediates can be achieved very well without producing secondary contamination in this system.

Performance optimization of CdS precipitated graphene oxide/polyacrylic acid composite for efficient photodegradation of chlortetracycline

Here a CdS embedded poly acrylic acid (PAA)/graphene oxide (GO) polymeric composite was prepared for the efficient degradation of chlortetracycline (CTC) driven by visible light irradiation. The structure-activity relationship of GO/PAA-CdS was confirmed through the photocatalytic evaluation of a series of samples prepared by varying GO concentration, molar ratio of Cd:S and the amount of crosslinking agent. Through the composition, morphology, photoelectrochemical characterizations and degradation kinetic studies, it could be confirmed that the enhanced photocatalytic activity is attributed to the controlled growth of CdS nanoparticles by polymer net structure and effective electron transfer along GO nanosheets. The photodegradation of CTC was confirmed to be mainly governed by O₂^- and OH radicals generated from GO/PAA-CdS. The degradation intermediates of CTC were confirmed by LC-MS, and possible degradation pathways were proposed based on the prediction of radical attacking sites according to Fukui function values obtained through Density Functional Theory (DFT). Moreover, it was found that the catalytic activity of the photocatalyst was maintained after several cycles confirming the enhanced anti-photocorrosion of GO/PAA-CdS. This research provided an efficient approach by a novel photocatalyst for the removal of CTC from wastewater.

Accelerated charge transfer of Cd0.5Zn0.5S@ZnS core–shell nano-spheres via decoration of Ni2P and g-C3N4 toward efficient visible-light-driven H2 production

Unique Cd_0.5Zn_0.5S@ZnS-Ni₂P/g-C₃N₄ hybrid nano-spheres demonstrate enhanced photostability, improved light-harvesting and facilitated charge separation toward efficient H₂ evolution from visible-light-driven water-splitting.

A novel n-type CdS nanorods/p-type LaFeO3 heterojunction nanocomposite with enhanced visible-light photocatalytic performance

In this work, a novel n-type CdS nanorods/p-type LaFeO3 (CdS NRs/LFO) nanocomposite was prepared, for the first time, via a facile solvothermal method. The as-prepared n-CdS NRs/p-LFO nanocomposite was characterized by using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), UV-visible diffuse reflection spectroscopy (DRS), vibrating sample magnetometry (VSM), photoluminescence (PL) spectroscopy, and Brunauer-Emmett-Teller (BET) surface area analysis. All data revealed the attachment of the LFO nanoparticle on the surface of CdS NRs. This novel nanocomposite was applied as a novel visible light photocatalyst for the degradation of methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) dyes under visible-light irradiation. Under optimized conditions, the degradation efficiency was 97.5% for MB, 80% for RhB and 85% for MO in the presence of H2O2 and over CdS NRs/LFO nanocomposite. The photocatalytic activity of CdS NRs/LFO was almost 16 and 8 times as high as those of the pristine CdS NRs and pure LFO, respectively. The photocatalytic activity was enhanced mainly due to the high efficiency in separation of electron-hole pairs induced by the remarkable synergistic effects of CdS and LFO semiconductors. After the photocatalytic reaction, the nanocomposite can be easily separated from the reaction solution and reused several times without loss of its photocatalytic activity. Trapping experiments indicated that ·OH radicals were the main reactive species for dye degradation in the present photocatalytic system. On the basis of the experimental results and estimated energy band positions, the mechanism for the enhanced photocatalytic activity was proposed.

Unraveling Photoexcited Charge Transfer Pathway and Process of CdS/Graphene Nanoribbon Composites toward Visible-Light Photocatalytic Hydrogen Evolution

Converting solar energy into chemical fuels is increasingly receiving a great deal of attention. In this work, CdS nanoparticles (NPs) are solvothermally anchored onto graphene nanoribbons (GNRs) that are longitudinally unzipped from multiwalled carbon nanotubes. The as-synthesized CdS/GNR nanocomposites with recyclability present GNR content-dependent activity in visible-light-driven hydrogen evolution from water splitting. In a range of 1-10 wt% GNRs, the CdS/GNR composites with 2 wt% GNRs achieves the greatest hydrogen evolution rate of 1.89 mmol h^-1 g^-1 . The corresponding apparent quantum efficiency is 19.3%, which is ≈3.7 times higher than that of pristine CdS NPs. To elucidate the underlying photocatalytic mechanism, a systematic characterization, including in situ irradiated X-ray photoelectron spectroscopy and Kelvin probe measurements, is performed. In particular, the interfacial charge transfer pathway and process from CdS NPs to GNRs is revealed. This work may open avenues to fabricate GNR-based nanocomposites for solar-to-chemical energy conversion and beyond.

Constructing magnetic and high-efficiency AgI/CuFe2O4 photocatalysts for inactivation of Escherichia coli and Staphylococcus aureus under visible light: Inactivation performance and mechanism analysis

Magnetic materials usually exhibit advanced performance in many areas for their easy separating and recycle ability. In this study, silver iodide/copper ferrite (AgI/CuFe₂O₄) catalysts with excellent magnetic property were successfully synthesized and characterized by a series of techniques. Two typical bacteria Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were applied to estimate the photocatalytic inactivation performance of obtained AgI/CuFe₂O₄ catalysts. Results revealed that the AgI/CuFe₂O₄ (12.5% AgI) composite could absolutely inactivate 3 × 10⁹ CFU/mL E. coli and 2.7 × 10⁸ CFU/mL S. aureus cells severally in 50 min and 40 min under visible light irradiation, which showed a much higher photo-disinfection activity than monomers. Transmission electron microscopy was used to study the biocidal action of this nanocatalyst, the results confirmed that the treated E. coli cells were damaged, the nanocatalyst permeated into cells and resulting in death of cells. Besides, it was found that the destruction of bacterial membrane together with substantial leaked potassium ion (K⁺) which caused by the photo-generated reactive species superoxide radical (O₂^-) and holes (h⁺) could be the direct disinfection principles. For a deep insight into practical applications, the influences of different catalyst concentrations and reaction pH were also taken into discussion in details. The overall results indicated the novel photocatalyst with strong redox capacity and outstanding reusability can be widely employed in bacteria elimination.