Visible light driven CuBi2O4/Bi2MoO6 p-n heterojunction with enhanced photocatalytic inactivation of E. coli and mechanism insight

Interconnected Periodic Macroporous NaNbO3 for High-Efficiency Solar-Driven Photocatalytic Hydrogen Evolution

Highly ordered periodic macroporous structures have been extensively utilized to significantly enhance the photocatalytic activity. However, constructing 3D interconnected ordered porous ternary nanostructures with highly crystalline frameworks remains a formidable challenge. Here, we introduce the design and fabrication of 3D interconnected periodic macroporous NaNbO3 (PM NaNbO3) to effectively increase the density of surface-active sites and optimize the photogenerated carrier-transfer efficiency. By incorporating Pt as a cocatalyst, PM NaNbO3 exhibits an exceptional photocatalytic hydrogen generation rate of 10.04 mmol h-1 g-1, which is approximately six and five times higher than those of calcined NaNbO3 (C-NaNbO3) and hydrothermal NaNbO3 (H-NaNbO3), respectively. This outstanding performance can be attributed to the synergistic effects arising from its well-interconnected pore architecture, large surface area, enhanced light absorption capability, and improved charge carrier separation and transport efficiency. The findings presented in this study demonstrate an innovative approach toward designing hierarchically periodic macroporous materials for solar-driven hydrogen production.

Recent progress on bismuth-based light-triggered antibacterial nanocomposites: Synthesis, characterization, optical properties and bactericidal applications

Bacterial infections pose a seriously threat to the safety of the environment and human health. In particular, the emergence of drug-resistant pathogens as a result of antibiotic abuse and high trauma risk has rendered conventional therapeutic techniques insufficient for treating infections by these so-called "superbugs". Therefore, there is an urgent need to develop highly efficient and environmentally-friendly antimicrobial agents. Bismuth-based nanomaterials with unique structures and physicochemical characteristics have attracted considerable attention as promising antimicrobial candidates, with many demonstratingoutstanding antibacterial effects upon being triggered by broad-spectrum light. These nanomaterials have also exhibited satisfactory energy band gaps and electronic density distribution with improved photonic properties for extensive and comprehensive applications after being modified through various engineering methods. This review summarizes the latest research progress made on bismuth-based nanomaterials with different morphologies, structures and compositions as well as the different methods used for their synthesis to meet their rapidly increasing demand, especially for antibacterial applications. Moreover, the future prospects and challenges regarding the application of these nanomaterials are discussed. The aim of this review is to stimulate interest in the development and experimental transformation of novel bismuth-based nanomaterials to expand the arsenal of effective antimicrobials.

Construction of a g-C3N4/Bi(OH)3 Heterojunction for the Enhancement of Visible Light Photocatalytic Antibacterial Activity

Photocatalytic technology has been recently conducted to remove microbial contamination due to its unique features of nontoxic by-products, low cost, negligible microbial resistance and broad-spectrum elimination capacity. Herein, a novel two dimensional (2D) g-C3N4/Bi(OH)3 (CNB) heterojunction was fabricated byincorporating Bi(OH)3 (BOH) nanoparticles with g-C3N4 (CN) nanosheets. This CNB heterojunction exhibited high photocatalytic antibacterial efficiency (99.3%) against Escherichia coli (E. coli) under visible light irradiation, which was 4.3 and 3.4 times that of BOH (23.0%) and CN (28.0%), respectively. The increase in specific surface area, ultra-thin layered structure, construction of a heterojunction and enhancement of visible light absorption were conducive to facilitating the separation and transfer of photoinduced charge carriers. Live/dead cell staining, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) assays and scanning electron microscopy (SEM) have been implemented to investigate the damage to the cell membrane and the leakage of the intracellular protein in the photocatalytic antibacterial process. The e-, h+ and O2•- were the active species involved in this process. This study proposed an appropriate photocatalyst for efficient treatment of bacterial contamination.

Enhanced Antibacterial and Wound Healing Using a Metal-Organic Cluster Inspired by Artificial Photosynthesis

Bacterial infection poses a constant threat to human health. It is crucial to develop cost-effective and multifunctional solutions to combat bacteria. In this study, inspiration has been taken from artificial photosynthesis and a hydrogel containing a photocatalytic metal-organic cluster (MOC) has been creatively formulated for wound healing and antibacterial purposes. Complete photocatalytic cycles have been achieved by combining the oxidative Ti-center and the reductive Cu-center, in which reactive oxygen species (1 O2 and ·OH) have been generated. The MOC has the capability to eliminate Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) at a concentration of 40 µg mL-1 . In addition, the hydrogel formulation (H-MOC) has been applied to wounds infected with S. aureus, resulting in improved healing efficiency. This work presents an innovative approach to utilizing photocatalytic biomaterials as non-antibiotic medications.

Prism-like integrated Bi2WO6 with Ag-CuBi2O4 on carbon nanotubes (CNTs) as an efficient and robust S-scheme interfacial charge transfer photocatalyst for the removal of organic pollutants from wastewater

Photocatalytic hybrid carbon nanotubes (CNTs)-mediated Ag-CuBi2O4/Bi2WO6 photocatalyst was fabricated using a hydrothermal technique to effectively eliminate organic pollutants from wastewater. The as-prepared samples were characterized via Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction patterns (XRD), high-resolution transmission electron microscope (HR-TEM), UV-vis Diffuse Reflectance spectrum (UV-Vis DRS), and photoluminescence (PL) studies. The photocatalytic performance of fabricated pristine and hybrid composites was examined by photo-degradation of toxic dye viz. Rhodamine B (RhB) under visible light. Photo-degradation results revealed that the fabricated Ag-CuBi2O4/CNTs/Bi2WO6 semiconductor photocatalyst followed pseudo-first-order kinetics and displayed a higher photocatalytic rate, which was found to be approximately 3.33 and 2.35 times higher than the pristine CuBi2O4 and Bi2WO6 semiconductor photocatalyst, respectively. Re-cyclic results demonstrated that the formed composite owns excellent stability, even after five consecutive cycles. As per the matched Fermi level of CNTs in between Ag-CuBi2O4 and Bi2WO6, carbon nanotubes severed as electron transfer-bridge, Ag doping on CuBi2O4 surface successfully increased photon absorption all across CuBi2O4 surface. Also, it hindered the assimilation of photoinduced electron-hole pairs. The increased photocatalytic efficiency is contributed to the uniform dispersion of photo-generated electron-hole pairs via the construction of an S-scheme system. ROS trapping and ESR experiments suggested that (∙OH) and (O2-∙) were the main radical species for enhanced photo-degradation of RhB dye. The current investigation, from our perspective, highlights the new insights for the fabrication of practical CNTs-mediated S-scheme-based semiconductor photocatalyst for the resolution of environmental issues based on practical considerations.

Antibacterial Activity and the Mechanism of the Z-Scheme Bi2MoO6/Bi5O7I Heterojunction under Visible Light

Z-scheme Bi2MoO6/Bi5O7I heterojunction was constructed by an in situ solvothermal method, which was composed of Bi2MoO6 nanosheets growing on the surface of Bi5O7I microrods. The antibacterial activities under illumination towards Escherichia coli (E. coli) were investigated. The Bi2MoO6/Bi5O7I composites exhibited more outstanding antibacterial performance than pure Bi2MoO6 and Bi5O7I, and the E. coli (108 cfu/mL) was completely inactivated by BM/BI-3 under 90 min irradiation. Additionally, the experiment of adding scavengers revealed that h+, •O2- and •OH played an important role in the E. coli inactivation process. The E. coli cell membrane was damaged by the oxidation of h+, •O2- and •OH, and the intracellular components (K+, DNA) subsequently released, which ultimately triggered the apoptosis of the E. coli cell. The enhanced antibacterial performance of Bi2MoO6/Bi5O7I heterojunction is due to the formation of Z-scheme heterojunction with the effective charge transfer via the well-contacted interface of Bi2MoO6 and Bi5O7I. This study provides useful guidance on how to construct Bi5O7I-based heterojunction for water disinfection with abundant solar energy.

Fabrication of multiphase MoSe2 modified BiOCl nanosheets for efficient piezo-photoelectric hydrogen evolution and antibiotic degradation

Efficient spatial charge separation plays a crucial role in improving the photocatalytic performance. Therefore, 1T/2H MoSe2/BiOCl (1T/2H MS/BOC) and 2H MoSe2/BiOCl (2H MS/BOC) piezo-photocatalysts are synthesized. By combining piezoelectric catalysis and photocatalysis, a highly active piezo-photocatalytic process is realized. The optimal 1T/2H MS/BOC piezo-photocatalyst displays superior diclofenac (DCF) degradation and hydrogen (H2) evolution activity under the combined action of ultrasound and light. In particular, the DCF degradation kinetic constant (k) of optimal 0.5% 1T/2H MS/BOC under the synergistic effect of ultrasound and light is 0.057 min-1, which is 8.1 and 6.3 times higher than those of BiOCl (0.007 min-1) and 0.5% 2H MS/BOC (0.009 min-1). Moreover, the H2 evolution rate of 0.5% 1T/2H MS/BOC is 122.5 μmol g-1 h-1, which is also higher than those of BiOCl (45.8 μmol g-1 h-1) and 2H MS/BOC (49.5 μmol g-1 h-1). The dramatic improvement in the DCF degradation and H2 evolution piezo-photocatalytic performance of 1T/2H MS/BOC catalysts is ascribed to the built-in polarization electric field and abundance of active sites of 1T/2H MS/BOC as well as the advantageous band structure between BiOCl and 1T/2H MoSe2. Additionally, three probable degradation pathways of DCF were put forward from the results of liquid chromatography-mass spectrometry (LCMS) and density functional theory (DFT) calculations. This study provides the design strategy of high efficiency piezo-photocatalysts in environmental purification and energy-generation fields based on phase and band structure engineering.

Peroxymonosulfate-based photocatalytic oxidation of tetracycline by Fe2(MoO4)3/Cd0.5Ni0.5S heterostructure; DFT simulation

The current research is meant to develop novel semiconductor photocatalysts, for the decomposition of tetracycline (TC) as a model organic contaminant in the aquatic environment. The fabrication of Fe₂(MoO₄)₃/Cd_0.5Ni_0.5S (FMO/CNS) composite has proven to be an effective method for improving the sustainability and photocatalytic activity of Cd_0.5Ni_0.5S (CNS). Under visible light irradiation, FMO/CNS nanocomposite demonstrated significant PMS activation which led to 1.36 and 1.81 times TC removal efficiency as compared to immaculate Fe₂(MoO₄)₃(FMO) and CNS. FMO/CNS composite potentially promotes the segregation of electron-hole pairs (e^--h⁺) and exemplifies amazing photocatalytic performance for TC degradation. Its significant photocatalytic activity is due to its unique structure, which includes tiny pores on the surface that confine the PMS molecule to the interface. The FMO/CNS composite has significantly greater piezocatalytic activity than pure FMO and CNS, demonstrating the synergistic effect of FMO and CNS. In the degradation of TC, holes and key reactive radicals (^•O₂^-/^•OH/SO₄^-•) played a major role. Computational studies (DFT) estimates, including the determination of intermediates, confirmed that the hydroxyl addition and C-N cleavage pathways were responsible for TC degradation. As a result, this work delivers a new approach to developing novel photocatalysts with high photocatalytic activity for the abatement of organic contaminants in water.

Design of novel p-n heterojunction ZnBi2O4-ZnS photocatalysts with impressive photocatalytic and antibacterial activities under visible light

Heterojunction structures have attracted considerable attention for enhancing electron migration across interfaces. In this report, ZnBi₂O₄-ZnS(12%) heterojunction photocatalysts was found to be capable of degrading over 94% of indigo carmine in a 15 mg/L solution within 90 min of visible light irradiation at a catalytic dose of 1.0 g/L and pH 4. Furthermore, more than 82% of the total organic carbon (TOC) was removed, confirming the almost complete mineralization of the indigo carmine by ZnBi₂O₄-ZnS(12%). Moreover, the photocatalyst exhibited high stability and retained its photocatalytic activity up to the 5th cycle of operation without photocorrosion. The dramatic enhancement in the visible-light photocatalytic performance of the ZnBi₂O₄-ZnS heterojunctions over pristine ZnBi₂O₄ and ZnS was due to the formation of a superior heterojunction between the n-type semiconductor, ZnS, and the p-type semiconductor, ZnBi₂O₄. This heterojunction facilitated the separation and transfer of the photoinduced electron at the interfaces of the two semiconductors. Furthermore, the ZnBi₂O₄-ZnS(12%) exhibited an inhibition zone of 15 mm against fecal Escherichia coli (ATCC 8739), with a minimum inhibitory concentration (MIC) of 150 μg/mL. These results demonstrated that the novel ZnBi₂O₄-ZnS p-n-type heterojunction is a promising visible-light active photo-catalyst for the degradation of organic pollutants and inhibition of fecal E. coli.

Ultra-Fast Construction of Novel S-Scheme CuBi2O4/CuO Heterojunction for Selectively Photocatalytic CO2 Conversion to CO

Herein, step-scheme (S-scheme) CuBi2O4/CuO (CBO/CuO) composite films were successfully synthesized on glass substrates by the ultra-fast spraying-calcination method. The photocatalytic activities of the obtained materials for CO2 reduction in the presence of H2O vapor were evaluated under visible light irradiation (λ > 400 nm). Benefiting from the construction of S-scheme heterojunction, the CO, CH4 and O2 yields of the optimal CBO/CuO composite reached 1599.1, 5.1 and 682.2 μmol/m2 after irradiation for 9 h, and the selectivity of the CO product was notably enhanced from below 18.5% to above 98.5% compared with those of the bare samples. In the sixth cycling experiment, the yields of main products decreased by less than 15%, and a high CO selectivity was still kept. The enhanced photocatalytic performance of CO2 reduction was attributed to the efficient separation of photogenerated charge carriers. Based on the photocatalytic activity, band structure and in situ-XPS results, the S-scheme charge transfer mechanism was conformed. The study provides an insight into the design of S-scheme photocatalysts for selective CO2 conversion.

Antimicrobial Effectiveness of Innovative Photocatalysts: A Review

Waterborne pathogens represent one of the most widespread environmental concerns. Conventional disinfection methods, including chlorination and UV, pose several operational and environmental problems; namely, formation of potentially hazardous disinfection by-products (DBPs) and high energy consumption. Therefore, there is high demand for effective, low-cost disinfection treatments. Among advanced oxidation processes, the photocatalytic process, a form of green technology, is becoming increasingly attractive. A systematic review was carried out on the synthesis, characterization, toxicity, and antimicrobial performance of innovative engineered photocatalysts. In recent decades, various engineered photocatalysts have been developed to overcome the limits of conventional photocatalysts using different synthesis methods, and these are discussed together with the main parameters influencing the process behaviors. The potential environmental risks of engineered photocatalysts are also addressed, considering the toxicity effects presented in the literature.

Effective photodegradation of rhodamine B and levofloxacin over CQDs modified BiOCl and BiOBr composite: Mechanism and toxicity assessment

In this contribution, carbon quantum dots (CQDs) modified 3D-flower like BiOX (X = Cl, Br, I) photocatalyst were successfully prepared via a facile mechanical compounding method. The crystal structure, surface composition, morphologies, optical properties and photocatalytic activities were investigated in detail. The photocatalytic activity of the as-obtained photocatalyst were evaluated by degradation of rhodamine B (RhB) and Levofloxacin (LEV) under near IR-UV-vis light irradiation, the CQDs/BiOX composite displayed enhanced photocatalytic activity as compared with individual BiOX materials. The CQDs/BiOX composite had the outstanding light harvesting and electron transfer ability because of the ordered ultrathin nanosheet structure of the BiOX, the formation of metal Bi under photoinduction, and the synergistic effects between CQDs and pure BiOX. Antibacterial activity and effects on Rye seeds growth of the LEV degradation intermediate were also researched. Reactive-species-trapping experiments exhibited that h⁺ and O₂^- were the active reactive species during photodegradation process. This work provided an effective and simple strategy for designing QDs modified Bi-rich oxyhalides in organic pollutant containing wastewater treatment.

Novel sphere-like copper bismuth oxide fabricated via ethylene glycol-introduced solvothermal method with improved adsorptive and photocatalytic performance in sulfamethazine removal

In this research, ethylene glycol-introduced solvothermal method was employed to fabricate a novel sphere-like CuBi₂O₄ material to improve the adsorptive and photocatalytic performance of conventional CuBi₂O₄. A series of characterization has been applied to investigate properties of the obtained CuBi₂O₄ (CBO-EG3). Compared with conventional rod-like CuBi₂O₄ (CBO), the synthesized sphere-like CBO-EG3 exhibited rough surface, larger specific surface area, and more effective separation of photo-generated carriers, which overcome main shortcomings of CuBi₂O₄. The removal efficiency of typical antibiotic sulfamethazine (SMZ) reached almost 100% under the optimal experimental conditions. About 70% of SMZ could be adsorbed in 180-min dark reaction, with residual being photodegraded in 30 min. CBO-EG3 showed much higher photocatalytic efficiency than pure CBO, attributing to its highly effective photo-induced electron and hole separation. Meanwhile, substantial adsorption of pollutant on CBO-EG3 contributed vastly to removal of SMZ, photo-generated electrons and holes inclined to react with adsorbed SMZ directly, and photocatalytic process was mainly led by non-radical reaction. Elimination of SMZ in actual water samples and recycling experiment were also performed to evaluate CBO-EG3's practical application potential. This study delivered a method to promote CuBi₂O₄'s adsorptive and photocatalytic ability, which could expand the application of CuBi₂O₄ in wastewater treatment.

Bi-based photocatalysts for bacterial inactivation in water: Inactivation mechanisms, challenges, and strategies to improve the photocatalytic activity

Bi-based photocatalysts have been considered suitable materials for water disinfection under natural solar light due to their outstanding optical and electronic properties. However, until now, there are not extensive reviews about the development of Bi-based materials and their application in bacterial inactivation in aqueous solutions. For this reason, this work has focused on summarizing the state of the art related to the inactivation of Gram- and Gram + pathogenic bacteria under visible light irradiation using different Bi-based micro and nano structures. In this sense, the photocatalytic bacterial inactivation mechanisms are analyzed, considering several modifications. The factors that can affect the photocatalytic performance of these materials in real conditions and at a large scale (e.g., water characteristics, pH, light intensity, photocatalyst dosage, and bacteria level) have been studied. Furthermore, current alternatives for improving the photocatalytic antibacterial activity and reuse of Bi-based materials (e.g., surface engineering, crystal facet engineering, doping, noble metal coupling, heterojunctions, Z-scheme junctions, coupling with graphene derivatives, magnetic composites, immobilization) have been explored. According to several reports, inactivation rate values higher than 90% can be achieved by using the modified Bi-based micro/nano structures, which become them excellent candidates for photocatalytic water disinfection. However, these innovative photocatalytic materials bring a variety of future difficulties and opportunities in water disinfection.

A potential spoilage bacteria inactivation approach on frozen fish

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US&HVEF technology revealed an inactivation effect on S. putrefaciens.

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US&HVEF technology minimized the thawing damage to frozen fish.

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US&HVEF thawing achieved better quality maintenance of frozen aquatic products.

Frozen products are more susceptible to microbial spoilage during thawing. Therefore, the development of a thawing technology with effective bacteriostasis is still urgent in food science. In this study, red sea bream was used as the research object, S. putrefaciens was incubated on the surface of fish fillets, and ultrasound plus high voltage electric field (US&HVEF) was performed to investigate the antibacterial activity. On this basis, the effect of US&HVEF thawing on the quality characteristics of fillets was further studied. The results indicated that US&HVEF showed a better antibacterial performance toward S. putrefaciens, with the lethality of 96.73%. Furthermore, US&HVEF could minimize thawing loss, preserve fillets texture, stabilize the secondary and tertiary conformation of myofibrillar protein (MFP), and inhibit the MFP aggregation and oxidation. Accordingly, this study shows that food safety also involves spoilage bacteria prevention except for quality and proves that US&HVEF technology has great potential in food thawing.

Enhanced photocatalytic and antibacterial activities of S-scheme SnO2/Red phosphorus photocatalyst under visible light

The construction of wide bandgap semiconductors with heterojunctions is an effective strategy to improve the photocatalytic activity of narrow-bandgap semiconductors, such as red phosphorus (RP). The novel step-scheme (S-scheme) heterojunction can separate photocarriers effectively while retaining the high reduction-oxidation capacity of the catalyst. Herein, a SnO₂/hydrothermally treated RP (SnO₂/HRP) S-scheme heterojunction was constructed and was found to display superior performance in the photocatalytic degradation of pollutants and the disinfection of bacteria. The 5%SnO₂/HRP (mass ration of SnO₂ with 5 wt%) composite had the strongest photocatalytic activity. It could degrade 97.5% of Rhodamine B (RhB) after 12 min of light exposure. The photodegradation rate constant of this composite reached 2.96 × 10^-1 min^-1, which was 4.4 and 59.2 times higher than that of pure HRP and SnO₂, respectively. Furthermore, this S-scheme heterojunction composite exhibited a higher efficient photocatalytic antibacterial rate (99.4%) for Escherichia coli (E. coli) under visible-light irradiation, than pure HRP (66.4%) and SnO₂ (72.9%). Further mechanistic investigations illustrated that the intimate contact between HRP and SnO₂ in the S-scheme system heterojunction could effectively boost carrier transfer and improve the photocatalytic activity of the semiconductor. This investigation provided an efficient recyclable S-scheme heterojunction composite for the photocatalytic degradation of pollutants and bacteria.

Heterostructured Nanoscale Photocatalysts via Colloidal Chemistry for Pollutant Degradation

With the further acceleration in the industrialization process, organic pollutants and gas pollution in the environment have posed severe threats to human health. It has been a global challenge regarding achieving an efficient solution to pollutant degradation. In such a context, photocatalysts have attracted researchers’ attention for their simplicity, efficiency, cleanliness and low cost. However, the single photocatalyst is facing a research bottleneck owing to its narrow light absorption spectrum and high photocarrier recombination rate. Given that heterojunctions can achieve efficient separation of photogenerated carriers in space, constructing heterostructured photocatalysts has become the most perspective method to improve the performance of photocatalysts. Furthermore, nanoparticles prepared through colloidal chemistry have the characteristics of high dispersion, stability and adsorption, further enhancing the degradation efficiency of heterostructured photocatalysts. This article reviews the primary methods for preparing heterostructured photocatalysts through colloidal chemistry, classifies the heterojunction types by transport routes of photogenerated carriers and summarizes the recent progress of heterostructured photocatalysts in pollutant degradation. To implement environmental remediation, it is crucial to explore economical and efficient photocatalysts for practical applications. It is hoped that this review will stimulate further exploration of colloidal heterostructured photocatalysts for pollutant degradation.

Manganese Cadmium Sulfide Nanoparticles Solid Solution on Cobalt Acid Nickel Nanoflakes: A Robust Photocatalyst for Hydrogen Evolution

Photocatalytic water splitting for hydrogen evolution is one of the most promising methods to mitigate environmental and energy-related issues. In this study, manganese cadmium sulfide (Mn_x Cd_1-x S) solid solution is used to construct a p-n heterostructure with NiCo₂ O₄ through a hydrothermal method. The Mn_0.25 Cd_0.75 S/NiCo₂ O₄ composites are used for photocatalytic hydrogen evolution reaction, and the optimal hydrogen rate with 40 mg of Mn_0.25 Cd_0.75 S/NiCo₂ O₄ 40 mg (MCS/NCO 40) is 61159 μmol g^-1  h^-1 , which is about 16.3 times than that of pure Mn_0.25 Cd_0.75 S. After combining with NiCo₂ O₄ , the light absorption scale, the separation efficiency of photogenerated carriers, and the reaction kinetics are enhanced. Moreover, the band offset of MCS/NCO composites is calculated by the core level alignment method, demonstrating the formation of a p-n heterostructure. The built-in electric field from the p-n heterostructure drives charge transfer and enhances separation efficiency, which results in improved photocatalytic performance.

In-situ construction of step-scheme MoS2/Bi4O5Br2 heterojunction with improved photocatalytic activity of Rhodamine B degradation and disinfection

In this paper, a novel Step-scheme MoS₂/Bi₄O₅Br₂ heterojunction was fabricated through the in-situ mechanical agitation method and the photocatalytic activity of that was examined by the photocatalytic degradation Rhodamine B (RhB) and inactivation of E.coli under visible light irradiation (λ > 420 nm). The Step-scheme MoS₂/Bi₄O₅Br₂ heterojunctions displayed the enhanced photocatalytic ability compared to pure Bi₄O₅Br₂ and MoS₂ and the MoS₂/Bi₄O₅Br₂-3% (MS/BOB-3) heterojunction exhibited the strongest photocatalytic activity which can completely inactivate the 1 × 10⁷ cfu/mL with 180 min and degrade RhB (10 mg/L) with 24 min visible light irradiation, respectively. The photocatalytic mechanism of the MoS₂/Bi₄O₅Br₂ heterojunction is was attributed to the generated active species (h⁺, ·O₂^- and ·OH) which can effectively destroy RhB molecular and cell-membrane of bacterial as demonstrated by multiple techniques such as LC-MS and fluorescence stain. Additionally, characterization results disclosed that the transfer pathway of charge carriers of constructed MoS₂/Bi₄O₅Br₂ heterojunction followed the Step-scheme channel, which not only facilitated the separation and migration of the photo-generated charge carriers, but also improved the light absorption ability of the samples and resulting in the promoted photocatalytic performance of MoS₂/Bi₄O₅Br₂ heterojunction. This work paves a new idea to develop novel bismuth oxyhalide-based photocatalytic system for wastewater purification.

Ultrasonic-Assisted Synthesis of CdS/Microcrystalline Cellulose Nanocomposites With Enhanced Visible-Light-Driven Photocatalytic Degradation of MB and the Corresponding Mechanism Study

A simple and efficient ultrasonic-assisted approach was designed to synthesize CdS/microcrystalline cellulose (MCC) nanocomposite photocatalyst. The obtained products have been characterized by XRD, FE-SEM, TEM, UV-Vis DRS, and nitrogen adsorption isotherms. The results showed that the intimate contact of MCC and CdS is beneficial for enhancing the photocatalytic performance because heterojunction formation can efficiently promote the separation of photogenerated electrons and holes of the nanocomposite photocatalyst. By using 10% MCC coupled CdS, the decoloration rate of methylene blue (MB) in the solution under visible-light was increased nearly 50%. In addition, the reuse experiments confirmed that the CdS/MCC nanocomposite photocatalyst had outstanding cycle performance and durability. Mechanism study demonstrated that hydroxyl radicals, photogenerated holes and superoxide radicals were the active species in the photocatalytic oxidization degradation of MB.

Efficient photodegradation of cefixime catalyzed by a direct Z-scheme CQDs-BiOBr/CN composite: Performance, toxicity evaluation and photocatalytic mechanism

Development of low-cost, nontoxic, highly efficient performance photocatalyst for water pollution control engineering is critical for environmental remediation. In this contribution, a direct Z-scheme heterojunction based on C quantum dot (CQDs), bismuth oxybromide (BiOBr) and bulk graphitic carbon nitride (g-C₃N₄, CN) (CQDs-BiOBr/CN composite) with outstanding photocatalytic activity and good reusability is successfully fabricated though a hydrothermal procedure for cefixime antibiotic photodegradation. In particular, the CQDs-BiOBr/CN composite possess the best cefixime degradation effect, the degradation rate is about 92.82% within 120 min. The enhancement photocatalytic activity of CQDs-BiOBr/CN can be ascribed to the improved light-harvest ability, the excellent adsorption performance, the efficient charge transportation and separation capability. A possible degradation pathway of cefixime is proposed base on HPLC-MS. Toxicity experiments demonstrate that the antibiotic activity of cefixime is effectively deactivated after degradation process, and which is no toxic effect for Rye seeds in deionized water. The CQDs-BiOBr/CN also displays the excellent photoactivation activity towards Escherichia coli (E. coli). Reactive-species-trapping experiments show that hydroxyl radical (⋅OH) and superoxide radical (⋅O₂^-) are the active reactive species in the photodegradation process. The CQDs-BiOBr/CN composite demonstrate an effective potential practical application in antibiotic pollutants degradation from wastewater.

Extensive solar light utilizing by ternary C-dots/Cu2O/SrTiO3: Highly enhanced photocatalytic degradation of antibiotics and inactivation of E. coli

Fabrication of a visible-light driven photocatalyst is of great vital for the elimination of antibiotics and microorganism in the wastewater and the construction of sustainable green energy systems. In this work, carbon quantum dots (C-dots) were integrated with Cu₂O/SrTiO₃ p-n heterojunction to optimize the photocatalytic activity. The excellent photocatalytic degradation efficiency of chlortetracycline hydrochloride (CTC·HCl) (92.6% within 90 min) and E. coli inactivation efficiency were observed over C-dots/Cu₂O/SrTiO₃ under visible light irradiation. It is the synergistic effect of p-n heterojunction and modification of C-dots that facilitates the separation and transfer of electron-holes. Meanwhile, the modification of C-dots improves the harvesting of long wavelength solar light of photocatalysts due to its unique up-conversion photoluminescence (UCPL) characteristics. Eventually, the possible photocatalytic degradation path of the catalyst was inferred by LC-MS spectra, and the degradation mechanism was analyzed. This study sheds light on new possibilities for the application of photocatalysts in various light sources and has broad application prospects in water treatment.

Hierarchical Bi2MoO6 microsphere photocatalysts modified with polypyrrole conjugated polymer for efficient decontamination of organic pollutants

To effectively degrade organic pollutants in wastewater, visible-light-driven Bi₂MoO₆/PPy hierarchical heterogeneous photocatalysts were prepared through a solvothermal method and the following in-situ chemical oxidation polymerization. Compared with pristine Bi₂MoO₆ photocatalyst, the composite photocatalysts exhibited dramatically improved photocatalytic activity and photostability towards the degradation of methylene blue dye and tetracycline antibiotic. Bi₂MoO₆/PPy-80 sample achieved the highest photocatalytic degradation rates for methylene blue dye (93.6%) and tetracycline antibiotic (88.3%) under visible light irradiation. These two organic pollutants could be completely degraded into nontoxic small molecules according to in-depth HPLC-MS analysis of degradation products. The transient photocurrent responses, electrochemical impedance spectra, and photoluminescence spectra demonstrated that the introduction of PPy nanoparticles on the surface of Bi₂MoO₆ nanosheets could effectively accelerate the separation of photo-generated electron-hole pairs. Furthermore, a possible synergetic photocatalytic mechanism was put forward based on the electron spin resonance and XPS valence-band spectra. This work indicated that construction of hierarchical composite photocatalysts combining polypyrrole conductive polymer and Bi₂MoO₆ semiconductor in nanoscale is an efficient approach to improve photocatalytic activity for environmental remediation.

One-pot hydrothermal synthesis of CuBi2O4/BiOCl p–n heterojunction with enhanced photocatalytic performance for the degradation of tetracycline hydrochloride under visible light irradiation

The formation of a CuBi2O4/BiOCl p–n heterojunction enhances visible light absorption and promotes the separation of photogenerated electron–hole pairs.

Enhancing the quantum yield of singlet oxygen: photocatalytic degradation of mustard gas simulant 2-chloroethyl ethyl sulfide catalyzed by a hybrid of polyhydroxyl aluminum cations and porphyrin anions

By combining the anionic salt meso-tetra(4-carboxyphenyl)porphyrin (TCPP⁴⁻) and the Keggin polyoxometalate cation cluster [Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺via a simple ion-exchange method, a hybrid (C₄₈H₂₆N₄O₈)[Al₁₃O₄(OH)₂₄(H₂O)₁₂]₂(OH)₁₀·18H₂O (Al₁₃–TCPP) was prepared and thoroughly characterized as a prototype of polyoxometalate–porphyrin hybrids for the photocatalytic degradation of the mustard gas simulant 2-chloroethyl ethyl sulfide (CEES). The experimental results showed that the catalytic degradation rate of CEES in the presence of Al₁₃–TCPP reached 96.16 and 99.01% in 180 and 90 min in methanol and methanol–water solvent mixture (v/v = 1 : 1), respectively. The reaction followed first-order reaction kinetics, and the half-life and kinetic constant in methanol and solvent mixture were 39.8 min, −0.017 min⁻¹ and 14.7 min, −0.047 min⁻¹. Mechanism analysis indicated that under visible light irradiation in air, CEES was degraded through a combination of oxidation and alcoholysis/hydrolysis in methanol and the methanol–water solvent mixture. The superoxide radical (O₂˙⁻) and singlet molecular oxygen (¹O₂) generated by Al₁₃–TCPP selectively oxidized CEES into a non-toxic sulfoxide. The singlet oxygen capture experiments showed that Al₁₃–TCPP (Φ = 0.236) had a higher quantum yield of singlet oxygen generation than H₄TCPP (Φ = 0.135) under visible light irradiation in air. The material Al₁₃–TCPP has good reusability, and the degradation rate of CEES can still reach 98.37% after being recycled five times.

A hybrid Al₁₃–TCPP was thoroughly characterized as a prototype of polyoxometalate–porphyrin hybrids for the photocatalytic degradation of the mustard gas simulant 2-chloroethyl ethyl sulfide (CEES).

Integrating the Z-scheme heterojunction and hot electrons injection into a plasmonic-based Zn2In2S5/W18O49 composite induced improved molecular oxygen activation for photocatalytic degradation and antibacterial performance

The semiconductor-based photocatalysts with local surface plasmon resonance (LSPR) effect can extend light response to near-infrared region (NIR), as well as promote charge-carriers transfer, which provide a novel insight into designing light-driven photocatalyst with excellent photocatalytic performance. Here, we designed cost-effective wide-spectrum Zn₂In₂S₅/W₁₈O₄₉ composite with enhanced photocatalytic performance based on a dual-channel charge transfer pathway. Benefiting from the synergistic effect of Z-scheme heterostructure and unique LSPR effect, the interfacial charge-carriers transfer rate and light-absorbing ability of Zn₂In₂S₅/W₁₈O₄₉ were enhanced significantly under visible and NIR (vis-NIR) light irradiation. More reactive oxygen species (ROS) were formed by efficient molecular oxygen activation, which were the critical factors for both Escherichia coli (E. coli) photoinactivation and tetracycline (TC) photodegradation. The enhancement of molecular oxygen activation (MOA) ability was verified via quantitative analyses, which evaluated the amount of ROS through degrading nitrotetrazolium blue chloride (NBT) and p-phthalic acid (TA). By combining theoretical calculations with diverse experimental results, we proposed a credible photocatalytic reaction mechanism for antibiotic degradation and bacteria inactivation. This study develops a new insight into constructing promising photocatalysts with efficient photocatalytic activity in practical wastewater treatment.

Construction of visible light driven silver sulfide/graphitic carbon nitride p-n heterojunction for improving photocatalytic disinfection

Compared with the Z-scheme and type-II heterojunctions, p-n type heterojunctions are more favorable for the migration of photo-induced carriers owing to the advantage of built-in electric fields. In addition, it is still of great significance to understand the carrier migration properties of the p-n heterojunction. Therefore, the development of new p-n heterojunctions and the development of high-efficiency catalysts with effective modulation of light responsiveness and rapid transfer of charge to achieve photocatalytic inactivation have attracted much attention. In this study, we synthesized a Ag₂S/g-C₃N₄ heterojunction via the in situ deposition of Ag₂S onto the g-C₃N₄ substrate. The prepared Ag₂S/g-C₃N₄ composite facilitated photo-generated charge carrier transfer and exhibited outstanding photocatalytic inactivation of bacteria compared to that of a single catalyst under visible light irradiation. In addition, the ACN-2 composites fully deactivated 7 log10 CFU/mL E. coli and 7 log10 CFU/mL S. aureus cells in 90 min under visible light. The quenching experiments confirmed that photo-generated active species (O₂^-, OH, and h⁺) were the major reactive oxygen species that contributed to the inactivation of bacteria. Energy band alignment analysis indicated that a type-II band alignment was formed in the p-n heterostructure, thereby providing strong support for the photocatalytic mechanism. This study not only provides insights into the design of p-n heterostructures, but also presents a promising strategy to enhance the photocatalytic capacities of g-C₃N₄ based materials for pathogen inactivation.

Rational design of n-Bi12TiO20@p-BiOI core-shell heterojunction for boosting photocatalytic NO removal

Bismuth titanate (Bi₁₂TiO₂₀) with unique sillenite structure has been shown to be an excellent photocatalyst for environmental remediation. However, the narrow light-responsive range and rapid recombination of photoinduced electrons-holes limit the photocatalytic performance of Bi₁₂TiO₂₀. To overcome the limitations, a practical and feasibleway is to fabricate heterojunctions by combining Bi₁₂TiO₂₀ with suitable photocatalysts. Here, using a facile chemical precipitation method, a novel and hierarchical core-shell structure of n-Bi₁₂TiO₂₀@p-BiOI (BTO@BiOI) heterojunction was rationally designed and synthesized by loading BiOI nanosheets on BTO nanofibers. The constructed BTO@BiOI composites exhibited significant charge transfer ability due to the synergistic effects of the built-in electric field between BTO and BiOI as well as close interfacial contacts. In addition, the narrow bandgapcharacteristics of the BiOI led to wide light absorption ranges. Therefore, the BTO@BiOI heterojunction exhibited an improved photocatalytic performance under visible light irradiation. The NO removal efficiency of optimal BTO@BiOI was 45.7%, which was significantly higher compared tothat of pure BTO (3.6%) or BiOI (23.1%). Moreover, the cycling experiment revealed that BTO@BiOI composite has a good stability and reusability. The possible mechanism of photocatalytic NO oxidation over BTO@BiOI was investigated in detail.

Direct Z-scheme CuInS2/Bi2MoO6 heterostructure for enhanced photocatalytic degradation of tetracycline under visible light

The construction of direct Z-scheme heterojunctions with high photocatalytic degradation ability is a theme of importance in both environmental and materials sciences, but still retains many unresolved challenges. In this article, we report the construction of Z-scheme CuInS₂/Bi₂MoO₆ heterostructure by in-situ hydrothermal reactions, demonstrating superior photocatalytic activity towards the degradation of tetracycline under visible light, compared to their individual components: that is to say 8 and 2.5 times those of CuInS₂ and Bi₂MoO₆, respectively. The photocatalytic performance of CuInS₂/Bi₂MoO₆ heterostructure is mainly ascribed to the effective charge transfer at the interface through the construction of a direct Z-scheme heterojunction, combined with a ternary sulfide semiconductor absorbing light in the useful region of the solar spectrum. This photocatalyst provides new insights on the fundamental aspects governing the mechanisms responsible for multicomponent photodegradation, while constituting already a promising candidate for practical environmental applications.

Cobalt oxide/copper bismuth oxide/samarium vanadate (Co3O4/CuBi2O4/SmVO4) dual Z-scheme heterostructured photocatalyst with high charge-transfer efficiency: Enhanced carbamazepine degradation under visible light irradiation

Herein, a dual Z-scheme heterojunction photocatalyst consisting of Co₃O₄, CuBi₂O₄, and SmVO₄ for carbamazepine (CBZ) degradation was synthesised and characterised by XRD, FTIR, UV-Vis DRS, XPS, FE-SEM, and TEM. The reduction in electron-hole recombination was evaluated by PL, LSV, and EIS analysis. The heterojunction, Co₃O₄/CuBi₂O₄/SmVO₄ (CCBSV) showed enhanced photocatalytic activity of 76.1% ± 3.81 CBZ degradation under visible light irradiation, ascribed to the improved interfacial contact, visible light capturing ability, and enhanced electron-hole separation and transportation through the formation of Z-scheme heterojunction. The formation of dual Z-scheme was confirmed by active radical experiments and XPS analysis that helped to prose the mechanism of degradation. The catalyst showed sustained stability after 4 cycles of reuse. Ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) was employed to identify the degradation by-products of CBZ, and a possible mechanistic degradation pathway was proposed. This study provided an insight into the development of efficient dual Z-scheme heterojunction photocatalyst for remediation of CBZ which can be extended to other organic pollutants.

Recent advances in graphite carbon nitride-based nanocomposites: structure, antibacterial properties and synergies

Bacterial infections and transmission threaten human health and well-being. Graphite carbon nitride (g-C₃N₄), a promising photocatalytic antibacterial nanomaterial, has attracted increasing attention to combat bacterial transmission, due to the outstanding stability, high efficiency and environmental sustainability of this material. However, the antibacterial efficiency of g-C₃N₄ is affected by several factors, including its specific surface area, rapid electron/hole recombination processes and optical absorption properties. To improve the efficiency of the antibacterial properties of g-C₃N₄ and extend its range of applications, various nanocomposites have been prepared and evaluated. In this review, the advances in amplifying the photocatalytic antibacterial efficiency of g-C₃N₄-based nanocomposites is discussed, including different topologies, noble metal decoration, non-noble metal doping and heterojunction construction. The enhancement mechanisms and synergistic effects in g-C₃N₄-based nanocomposites are highlighted. The remaining challenges and future perspectives of antibacterial g-C₃N₄-based nanocomposites are also discussed.

Photo-catalyzed TiO2 inactivates pathogenic viruses by attacking viral genome

Previous observations have been reported that viruses were inactivated using strong irradiation. Here, new evidence was disclosed by studying the effects of nanosized TiO₂ on viral pathogens under a low irradiation condition (0.4 mW/cm² at UVA band) that mimics the field setting. We showed that photo-activated TiO₂ efficiently inhibits hepatitis C virus infection, and weak indoor light with intensity of 0.6 mW/cm² at broad-spectrum wavelength and around 0.15 mW/cm² of UVA band also lead to partial inhibition. Mechanistic studies demonstrated that hydroxyl radicals produced by photo-activated TiO₂ do not destroy virion structure and contents, but attack viral RNA genome, thus inactivating the virus. Furthermore, we showed that photo-activated TiO₂ inactivates a broad range of human viral pathogens, including SARS-CoV-2, a novel coronavirus responsible for the ongoing COVID-19 pandemic. In conclusion, we showed that photo-catalyzed nanosized TiO₂ inactivates pathogenic viruses, paving a way to its field application in control of viral infectious diseases.

Surface dual redox cycles of Mn(III)/Mn(IV) and Cu(I)/Cu(II) for heterogeneous peroxymonosulfate activation to degrade diclofenac: Performance, mechanism and toxicity assessment

Advanced oxidation processes (AOPs) based on heterogeneous catalytic activated peroxymonosulfate (PMS) have been becoming alternatives to conventional wastewater treatment technologies to directly degrade chemical contaminants. To build dual/multi redox cycles of different metal ions may be an effective means for better PMS activation. Herein, this study designed Mn₃O₄/CuBi₂O₄ with dual redox cycles of Mn(III)/Mn(IV) and Cu(I)/Cu(II) to activate PMS for efficiently decomposing and mineralizing diclofenac sodium (DCF). Under optimal reaction conditions, DCF (50 mg/L) was degraded totally within 10 min, and TOC removal rate reached up to 74.3%. The possible mechanism of PMS activation by Mn₃O₄/CuBi₂O₄ was proposed, wherein dual redox cycles of Mn(III)/Mn(IV) and Cu(I)/Cu(II) on Mn₃O₄/CuBi₂O₄ effectively facilitated PMS activation to generate ·O₂^-, ¹O₂, SO₄·^- and ·OH, which was responsible for DCF degradation. Moreover, combined with degraded products detected by high resolution liquid chromatography coupled to mass spectrometry and corresponding toxic assessment results, the possible degradation pathways of DCF were proposed and the relative toxicity of degraded products was evaluated. This work may be useful for developing stronger heterogeneous activators of PMS to construct more efficient AOPs for purifying wastewater.