Directing photocatalytic pathway to exceedingly high antibacterial activity in water by functionalizing holey ultrathin nanosheets of graphitic carbon nitride

Insight on the optimized electronic structure of carbon nitride on ultrafast water treatment via photocatalytic activation of ferrate

Ferrate (Fe(VI)) is a widely used water purifier and is easily affected by external factors. Given that the actual water environment conditions are complicated, this study designed an oxygen-doped carbon nitride (CNO) with rich electron sites to explore whether direct electron transfer promotes the degradation efficiency of Fe(VI) for pollutants under visible light. For comparison, we also prepared phosphorus-doped carbon nitride (CNP), which has electron-deficient sites and indirect electron transfer. In the CNO/Fe(VI)/light system, not only more high-valent iron and reactive oxygen species were generated, but also the pollutant degradation rate, reaction kinetics, and electron yield were significantly better than those of the CNP and CN systems, verifying the superiority of direct electron transfer. In addition, CNO showed excellent performance in both actual solar photocatalysis and continuous flow experiments. Therefore, the photocatalysis/direct electron transfer mechanism proposed provides an innovative strategy for improving the application potential of Fe(VI) in the field of pollution control and its industrialization application.

A Review on Photocatalytic Hydrogen Peroxide Production from Oxygen: Material Design, Mechanisms, and Applications

Hydrogen peroxide (H2O2) finds extensive applications in various industries, particularly in the environmental field. The photocatalytic production of H2O2 through the oxygen reduction reaction (ORR) or the water oxidation reaction (WOR) offers a promising approach. However, several challenges hinder effective on-site production, such as the rapid electron-hole pair recombination, inefficient visible light utilization, and limited selectivity in H2O2 formation. Thus, developing efficient photocatalysts to overcome these challenges is crucial. This review comprehensively outlines the development of photocatalysts and their modification techniques. It also summarizes and compares the H2O2 yield and apparent quantum yield among various photocatalysts with and without the use of organic sacrificial reagents. Density functional theory (DFT) calculations propose the band structure of photocatalysts and the mechanisms underlying oxygen reduction to H2O2. Finally, this review explores the potential environmental applications of photocatalytically produced H2O2. This review guides the design and optimization of photocatalysts, facilitating the continued advancement and application of photocatalysts in environmental contexts.

Bismuth-based photocatalysts for pollutant degradation and bacterial disinfection in sewage system: Classification, modification and mechanism

The discharge of polluted water poses a great threat to human health. Therefore, the development of effective sewage treatment technology is a key to achieve sustainable health development of society. Recent research showed that light-driven bismuth-based nanomaterials provided a promising chance for treating sewage system owing to their adjustable electronic features, excellent physical and chemical properties, abundant storage and environmental safety. However, the detailed overview and systematic understanding of the development of highly efficient bismuth-based photocatalysts is still unsatisfactory. In this review, we summarized the classification of bismuth-based photocatalysts, and the relationship between the structural design and the change of optical performance is illustrated. Importantly, the reliable modification strategies for improving photocatalytic capability are emphasized. Finally, the challenges and future development directions of light-driven bismuth-based nanoplatforms in wastewater treatment applications are discussed, hoping to provide an effective guidance for exploring the photocatalytic wastewater treatment process.

Graphitic Carbon Nitride Confers Bacterial Tolerance to Antibiotics in Wastewater Relating to ATP Depletion

Graphitic carbon nitride (C3N4) is a kind of visible light-responsive photocatalyst that has been of great interest in wastewater treatment. However, its environmental impact and biological effect remains to be elucidated. This study investigated the effect of C3N4 nanosheets on bacterial abundance and antibiotic tolerance in wastewater. Interestingly, as compared to the wastewater containing the antibiotic ofloxacin alone, the wastewater containing both ofloxacin and C3N4 had much higher numbers of total living bacteria, but lower levels of the ofloxacin-resistant bacteria and the ofloxacin-resistant gene qnrS. The model bacterium Staphylococcus aureus was then used to explore the mechanism of C3N4-induced antibiotic tolerance. The nanosheets neither adsorbed the antibiotic nor promoted drug efflux, uncovering that drug adsorption and efflux were not involved in antibiotic tolerance. Further investigations revealed that the nanosheets, like arsenate and menadione, drastically reduced ATP levels and induced the production of reactive oxygen species for enhanced antibiotic tolerance. This study revealed an antibiotic-tolerating mechanism associated with C3N4-induced ATP depletion, and shed a light on the effect of photocatalysts on microbial ecology during their application in wastewater treatment.

Doping and defects in carbon nitride cause efficient in situ H2O2 synthesis to allow efficient photocatalytic sterilization

In situ photocatalytic synthesis of H2O2 for disinfection has attracted widespread attention because it is a clean and environmentally friendly sterilization method. Graphitic carbon nitride has been used as a very selective photocatalyst for H2O2 generation but has some limitations (e.g., insufficient light absorption, rapid electron-hole recombination, and slow direct two-electron reduction processes) that prevent efficient H2O2 production. In this study, potassium-doped graphite carbon nitride with nitrogen vacancies (NDKCN) was prepared using a simple method involving a thermal fusion salt and N2 calcination, which possessed an ultrathin nanosheet structure (1.265 nm) providing abundant active sites. Synergistic effects caused by nitrogen vacancies and K+ and I- doping in the NDKCN photocatalyst gave the NDKCN a good ability to absorb light, undergo fast charge transfer, and give a high photoelectric current response. The optimized photocatalytic H2O2 yield of the NDKCN was 780.1 μM·g-1·min-1, which was 10 times the yield of the pristine g-C3N4. Tests involving quenching reactive species, electron spin resonance, and rotating disk electrodes indicated that one-step two-electron direct reduction on the NDKCN caused excellent H2O2 generation performance. The ability to efficiently generate H2O2 in situ gave NDKCN an excellent bactericidal performance, and 7.3 log10 (colony-forming units·mL-1) of Escherichia coli were completely eliminated within 80 min. Scanning electron microscopy images before and after sterilization indicated the changes in bacteria caused by the catalytic activity. The new g-C3N4-based photocatalyst and similar rationally designed photocatalysts with doping and defects offer efficient and simple in situ H2O2 sterilization.

In situ synthesis of graphitic carbon nitride nanosheet/Ti3C2Tx MXene/TiO2 Z-scheme heterojunctions boosting charge transfer for full-spectrum driven photocatalytic sterilization

The development of a full-spectrum responsive photocatalytic germicide with excellent charge separation efficiency to harvest high antimicrobial efficacy is a key goal yet a challenging conundrum. Herein, graphitic carbon nitride nanosheet (PCNS)/Ti3C2Tx MXene/TiO2 (PMT) Z-scheme heterojunctions with robust interface contact were crafted by in situ interfacial engineering. The strong internal electrical field (IEF) from PCNS to TiO2, evinced by the Kelvin Probe Force Microscopy (KPFM) characterization, can obtain high charge separation efficiency with 73.99%, compared to Schottky junction PCNS/Ti3C2Tx (PM, 32.88%) and PCNS (17.70%). The Ti3C2Tx component can not only serve as a transfer pathway to accelerate the recombination of photoexcited electrons of TiO2 and holes of PCNS under the Ultraviolet-visible (UV-vis) light irradiation, but also replenish the photogenic electron concentrations to semiconductors in the near-infrared (NIR) light illumination. Meanwhile, the increased temperature due to the localized surface plasmon resonance (LSPR) can further boost the electronic activity to the generation of reactive oxygen species (ROS). Taken together, the PMT performs a high disinfection efficiency up to 99.40% under full solar spectrum illumination, 3.88 and 9.75 times higher than PCNS and TiO2, respectively, surpassing many reported Z-scheme heterojunctions. This work offers guidance for the design of Z-scheme heterojunction with the implanting of plasmons to secure excellent full-spectrum responsive photocatalytic sterilization performance.

Engineering Atomic Ag1-N6 Sites with Enhanced Performance of Eradication Drug-Resistant Bacteria over Visible-Light-Driven Antibacterial Membrane

Utilizing visible light for water disinfection is a more convenient, safe, and practical alternative to ultraviolet-light sterilization. Herein, we developed silver (Ag) single-atom anchored g-C3N4 (P-CN) nanosheets (Ag1/CN) and then utilized a spin-coating method to fabricate the Ag1/CN-based-membrane for effective antibacterial performance in natural water and domestic wastewater. The incorporated Ag single atom formed a Ag1-N6 motif, which increased the charge density around the N atoms, resulting in a built-in electric field ∼17.2 times stronger than that of pure P-CN and optimizing the dynamics of reactive oxygen species (ROS) production. Additionally, the Ag1-N6 motif inhibited the release of Ag ions, ensuring good biocompatibility. Based on the first-principles calculation, the adsorption energy of O2 on the Ag1/CN (-0.32 eV) was lower than that of P-CN (-0.07 eV), indicating that loaded Ag single atom can lower the energy barrier for O2 activation, generating extra *OH radicals that cooperated with *O2- to effectively neutralize bacteria. As a result, the Ag1/CN powder-catalyst with the concentration of 30 ppm demonstrated a 99.9% antibacterial efficiency against drug-resistant bacteria (Escherichia coli, Staphylococcus aureus, kanamycin-resistant Escherichia coli, and methicillin-resistant Staphylococcus aureus) under visible-light irradiation for 4 h. This efficacy was 24.8 times higher than that of the P-CN powder catalyst. Moreover, the Ag1/CN-based-membrane can maintain a 99.9% bactericidal efficiency for natural water and domestic wastewater treatment using a homemade flow device, demonstrating its potential for water disinfection. Notably, the visible-light-driven antibacterial efficiency of the Ag1/CN catalyst outperformed the majority of the reported g-C3N4-based catalysts/membranes.

Visible light-driven C/O-g-C3N4 activating peroxydisulfate to effectively inactivate antibiotic resistant bacteria and inhibit the transformation of antibiotic resistance genes: Insights on the mechanism

Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) dissemination within water pose a serious threat to public health. Herein, C and O dual-doped g-C3N4 (C/O-g-C3N4) photocatalyst, fabricated via calcination treatment, was utilized to activate peroxydisulfate (PDS) to investigate the disinfection effect on tetracycline-resistant Escherichia coli and the transformation frequency of ARGs. As a result, approximately 7.08 log E. coli were inactivated, and 72.36 % and 53.96 % of antibiotics resistance gene (tetB) and 16 S rRNA were degraded respectively within 80 min. Futhermore, the transformation frequency was reduced to 0.8. Characterization and theoretical results indicated that C and O doping in g-C3N4 might lead to the electronic structure modulation and band gap energy reduction, resulting in the production of more free radicals. The mechanism analysis revealed that C/O-g-C3N4 exhibited a lower adsorption energy and reaction energy barrier for PDS compared to g-C3N4. This was beneficial for the homolysis of O-O bonds, forming SO4•- radicals. The attack of the generated active species led to oxidative stress in cells, resulting in damage to the electron transport chain and inhibition of ATP production. Our findings disclose a valuable insight for inactivating ARB, and provide a prospective strategy for ARGs dissemination in water contamination.

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.

Photocatalytic degradation of multiple-organic-pollutant under visible light by graphene oxide modified composite: degradation pathway, DFT calculation and mechanism

Wastewater containing antibiotics, organic dyes, and waterborne bacteria is a severe threat to human health and the environment. Amoxicillin has a slow metabolism rate in humans. Methylene blue is mutagenic and carcinogenic. In addition, Salmonella causes serious diarrhea. In this study, an effective 2D/2D photocatalyst with excellent elimination of these pollutants was fabricated by combining graphene oxide (GO), Bi2WO6, BiPO4 and Ag species. GO was applied at varying loading contents (0.8, 1.6, 2.4, 3.2 wt%) to improve the properties of the photocatalyst toward the removal of representative pollutants. The chemical structures, morphology, light absorption and charge mobility were investigated by different GO loading samples. The results indicated that when the wt% of GO was 2.4%, the photocatalyst showed excellent photocatalytic properties and removal rates for typical pollutants. Amoxicillin and methylene blue were mineralized into CO2, H2O, and small molecules, while Salmonella was disinfected with excellent photocatalytic efficiency. Furthermore, the possible photodecomposition pathways of amoxicillin and methylene blue were proposed by DFT calculations and intermediates identified by LCMS. The mechanism of the photocatalytic process was investigated by radical trapping experiments, ESR spectroscopy, and Motty-Schottky plots. The free radicals could be produced constantly during the photocatalytic process, leading to mineralization of amoxicillin and methylene blue, and disinfection of Salmonella. In this work, a new perspective on GO modified Bi2WO6 with different loading contents and the degradation pathways of antibiotics and dyes was proposed.

Sulfone-Modified Covalent Organic Frameworks Enabling Efficient Photocatalytic Hydrogen Peroxide Generation via One-Step Two-Electron O2 Reduction

Photocatalytic oxygen reduction reaction (ORR) offers a promising hydrogen peroxide (H2 O2 ) synthetic strategy, especially the one-step two-electron (2e- ) ORR route holds great potential in achieving highly efficient and selectivity. However, efficient one-step 2e- ORR is rarely harvested and the underlying mechanism for regulating the ORR pathways remains greatly obscure. Here, by loading sulfone units into covalent organic frameworks (FS-COFs), we present an efficient photocatalyst for H2 O2 generation via one-step 2e- ORR from pure water and air. Under visible light irradiation, FS-COFs exert a superb H2 O2 yield of 3904.2 μmol h-1  g-1 , outperforming most reported metal-free catalysts under similar conditions. Experimental and theoretical investigation reveals that the sulfone units accelerate the separation of photoinduced electron-hole (e- -h+ ) pairs, enhance the protonation of COFs, and promote O2 adsorption in the Yeager-type, which jointly alters the reaction process from two-step 2e- ORR to the one-step one, thereby achieving efficient H2 O2 generation with high selectivity.

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.

Dual sulfur defect engineering of Z-scheme heterojunction on Ag-CdS1-x@ZnIn2S4-x hollow core-shell for ultra-efficient selective photocatalytic H2O2 production

Photocatalytic production of hydrogen peroxide (H₂O₂) using sunlight as an energy source, water and molecular oxygen as feedstock is considered as a green and sustainable promising strategy to solve the energy and environmental crisis. Despite significant improvements in photocatalyst design tuning, however, the relatively low photocatalytic H₂O₂ productivity is still far from satisfactory. Herein, we developed a multi-metal composite sulfide (Ag-CdS_1-x@ZnIn₂S_4-x) with double S vacancies and hollow core-shell Z-type heterojunction structure for H₂O₂ generation by a simple hydrothermal method. The unique hollow structure improves the utilization of light source. The existence of Z-type heterojunction promotes the spatial separation of carriers, and the core-shell structure increases the interface area and active sites. Under visible light irradiation, Ag-CdS_1-x@ZnIn₂S_4-x had a high hydrogen peroxide yield of 1183.7 μmol h^-1 g^-1, which was 6 times that of CdS. The electron transfer number (n = 1.53) obtained from the Koutecky-Levuch plot and DFT calculation confirm that the presence of dual disulfide vacancies provides good selectivity of 2e^- O₂ reduction to H₂O₂. This work provides new insights into the regulation of highly selective two-electron photocatalytic H₂O₂ production, and also provides new ideas for the design and development of highly active energy conversion photocatalysts.

Recent Advances in Carbon Nitride-Based S-scheme Photocatalysts for Solar Energy Conversion

Energy shortages are a major challenge to the sustainable development of human society, and photocatalytic solar energy conversion is a potential way to alleviate energy problems. As a two-dimensional organic polymer semiconductor, carbon nitride is considered to be the most promising photocatalyst due to its stable properties, low cost, and suitable band structure. Unfortunately, pristine carbon nitride has low spectral utilization, easy recombination of electron holes, and insufficient hole oxidation ability. The S-scheme strategy has developed in recent years, providing a new perspective for effectively solving the above problems of carbon nitride. Therefore, this review summarizes the latest progress in enhancing the photocatalytic performance of carbon nitride via the S-scheme strategy, including the design principles, preparation methods, characterization techniques, and photocatalytic mechanisms of the carbon nitride-based S-scheme photocatalyst. In addition, the latest research progress of the S-scheme strategy based on carbon nitride in photocatalytic H₂ evolution and CO₂ reduction is also reviewed. Finally, some concluding remarks and perspectives on the challenges and opportunities for exploring advanced nitride-based S-scheme photocatalysts are presented. This review brings the research of carbon nitride-based S-scheme strategy to the forefront and is expected to guide the development of the next-generation carbon nitride-based S-scheme photocatalysts for efficient energy conversion.

The construction of high efficient visible-light-driven 3D porous g-C3N4/Fe3O4 photocatalyst: A new photo-induced bacterial inactivation material enhanced by cascade photo-Fenton reaction

Photocatalytic disinfection is considered a promising method for eliminating the hazards of pathogenic bacteria. Graphitic carbon nitride (g-C₃N₄) is an ideal photocatalytic bacterial inactivation material for its advantage of tunable band structure, good stability and easy preparation. This work has constructed a novel defective 3D porous g-C₃N₄ by cyanamide carbonation using dendritic mesoporous silica template. The direct loading of Fe₃O₄ nanoparticles provided an excellent pg-C₃N₄-Fe₃O₄ photocatalyst suitable for water disinfection. Compared to pristine g-C₃N₄, the prepared 3D porous defective g-C₃N₄-Fe₃O₄ exhibited the enhanced visible light absorbance as indicated by the band gap decreasing of 0.66 eV, and about 3 and 10 fold increase of photo-induced current response and O₂ adsorption respectively. The pg-C₃N₄-Fe₃O₄ showed excellent visible-light-driven photocatalytic bactericidal activity. It could kill 1 × 10⁷ cfu mL^-1Escherichia coli completely within 1 h under visible-light illumination (100 mW cm^-2) with good reusability, its logarithmic bacterial inactivation efficiency was about 2.5 fold higher than pg-C₃N₄. The enhanced bactericidal performance is mainly ascribed to the Fe₃O₄ involved cascade photo-Fenton reaction.

An innovative S-scheme AgCl/MIL-100(Fe) heterojunction for visible-light-driven degradation of sulfamethazine and mechanism insight

The development of high efficient photocatalysts for antibiotics contamination in water remains a severe challenge. In this study, a novel step-scheme (S-scheme) photocatalytic heterojunction nanocomposites were fabricated from integrating AgCl nanoparticles on the MIL-100(Fe) octahedron surface through facile multi-stage stirring strategy. The S-scheme heterojunction structure in AgCl/MIL-100(Fe) (AM) nanocomposite provided a more rational utilization of electrons (e^-) and holes (h⁺), accelerated the carrier transport at the junction interface, and enhanced the overall photocatalytic performance of nanomaterials. The visible-light-driven photocatalysts were used to degrade sulfamethazine (SMZ) which attained a high removal efficiency (99.9%). The reaction mechanisms of SMZ degradation in the AM photocatalytic system were explored by electron spin resonance (ESR) and active species capture experiments, which superoxide radical (•O₂^-), hydroxyl radical (•OH), and h⁺ performed as major roles. More importantly, the SMZ degradation pathway and toxicity assessment were proposed. There were four main pathways of SMZ degradation, including the processes of oxidation, hydroxylation, denitrification, and desulfonation. The toxicity of the final products in each pathway was lower than that of the parent according to the toxicity evaluation results. Therefore, this work might provide new insights into the environmentally-friendly photocatalytic processes of S-scheme AM nanocomposites for the efficient degradation of antibiotics pollutants.

Preparation of Ni@UiO-66 incorporated polyethersulfone (PES) membrane by magnetic field assisted strategy to improve permeability and photocatalytic self-cleaning ability

Metal-organic frameworks (MOFs) have been considered as promising nanofillers to fabricate mixed matrix membranes for water treatment. However, manipulating distribution of MOFs nanoparticles in the membrane matrix remains a great challenge. In this study, UiO-66 was firstly coated by magnetic Ni via an in-situ reduction reaction, and then incorporated into polyethersulfone (PES) membrane matrix to prepare PES-Ni@UiO-66 membrane. The magnetic Ni allowed to manipulate the distribution of magnetic Ni@UiO-66 in the phase-inversion process by an external magnetic field. The hydrophilic Ni@UiO-66 can be pulled onto membrane surface by the magnetic force, endowing the prepared membrane with rather higher hydrophilicity. The prepared membrane exhibited superior water permeability with a pure water flux of 611.5 ± 19.8 L·m^-2·h^-1 and improved antifouling performance. Moreover, benifiting from photocatalytic activity of the exposed Ni@UiO-66 on membrane surface, the obtained PES-Ni@UiO-66 membrane demonstrated excellent photocatalytic self-cleaning ability with a flux recovery rate (FRR) higher than 95% under UV irradiation. Analyzing by extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory indicated that the improved antifouling performance could be attributed to less attractive or even repulsive interaction between the prepared membrane and pollutants. This work provided valuable guidance for structural regulation and development of high-performance MOFs-based membranes for water treatment.

Three-phase interface photocatalysis for the enhanced degradation and antibacterial property

Semiconductor photocatalysis, as a means of utilizing stranded renewable solar resources, is now emerging as a viable and promising approach for increasingly severe water pollution. In this work, a high-performance photocatalytic system has been fabricated by immobilizing spiky TiO₂/Au nanohybrids on one side of hydrophobic nanoPE substrate (PE-TiO₂/Au) that forces the enabling of air-liquid-solid triphase photocatalytic interface. Such a triphase system allows efficient oxygen access to the photocatalyst surface, which is feasible for charge separation and reactive oxygen species (ROS) production. Two modes of triphase systems with different gas flow paths were constructed, in which PE-TiO₂/Au was floating on the aqueous solution surface (exposed mode) or immersing in aqueous phase (immersed mode). It is worth mentioning that the exposed PE-TiO₂/Au enables a more efficient oxygen supply, thus leading to a 5.5-fold and 1.8-fold higher reaction kinetics as compared to normal liquid-solid diphase system and immersed PE-TiO₂/Au. Meanwhile, PE-TiO₂/Au also exerts bactericidal effect under visible light irradiation, which effectively inactivates S.aureus (>99.9%) in a lean period of 30 min. The qualities of high lethality rate and short reaction time are endowed to PE-TiO₂/Au due to the co-effect of unique triphase interface microenvironment and elaborate heterojunction of spiky TiO₂/Au nanohybrids. In this paper, we have revealed for the first time that the antibacterial efficiency can be effectively improved by increasing the oxygen supply with the construction of three-phase interface, which represents a promising option in designing highly efficient photocatalytic systems for sewage purification applications.

Synergistic Generation of Radicals by Formic Acid/H2O2/g-C3N4 Nanosheets for Ultra-efficient Oxidative Photodegradation of Rhodamine B

Water pollution is a global challenge endangering people's health. In this work, an ultra-efficient photodegradation system of Rhodamine B (RhB) has been established using a graphitic carbon nitride nanosheet (CNNS) as the semiconductor photocatalyst, from which energy is harvested on both the conduction band and valence band by formic acid and hydrogen peroxide, respectively. The optimized FA/H₂O₂/CNNS system increases the apparent photodegradation rate of RhB by 25 folds, from 0.0198 to 0.4975 min^-1. Through a comprehensive investigation with reactive oxygen species scavengers, electron paramagnetic resonance, high-performance liquid chromatography-mass spectrometry, etc., an oxidative mechanism for RhB photodegradation has been proposed, which combines enhanced charge carrier migration and synergistic generation of multiple radicals. Comparable performance improvements have also been observed for similar systems with different semiconductors, suggesting that such a catalytic system could afford a general approach to enhance semiconductor-catalyzed photodegradation.

Organic Photo-antimicrobials: Principles, Molecule Design, and Applications

The emergence of multi-drug-resistant pathogens threatens the healthcare systems world-wide. Recent advances in phototherapy (PT) approaches mediated by photo-antimicrobials (PAMs) provide new opportunities for the current serious antibiotic resistance. During the PT treatment, reactive oxygen species or heat produced by PAMs would react with the cell membrane, consequently leaking cytoplasm components and effectively eradicating different pathogens like bacteria, fungi, viruses, and even parasites. This Perspective will concentrate on the development of different organic photo-antimicrobials (OPAMs) and their application as practical therapeutic agents into therapy for local infections, wound dressings, and removal of biofilms from medical devices. We also discuss how to design highly efficient OPAMs by modifying the chemical structure or conjugating with a targeting component. Moreover, this Perspective provides a discussion of the general challenges and direction for OPAMs and what further needs to be done. It is hoped that through this overview, OPAMs can prosper and will be more widely used for microbial infections in the future, especially at a time when the global COVID-19 epidemic is getting more serious.