Microwave-assisted one-step rapid synthesis of ternary Ag/Ag2S/g-C3N4 heterojunction photocatalysts for improved visible-light induced photodegradation of organic pollutant

Construction of Ag/CdZnS QDs nanocomposite for enhanced visible light photoinactivation of Staphylococcus aureus

With increasing use of antibiotics, the development of antibiotic-resistant pathogens poses a serious threat to human health and the environment. Photocatalytic inactivation of these harmful pathogens is one of the novel and non-antibiotic treatments. The study fabricated Ag NPs decorated CdZnS QDs via a facile and biological co-precipitation method using L. camara plant extract as a green alternative to treat the toxic chemicals. The fabricated Ag/CdZnS QDs (NCs) were prepared for the efficient treatment of antibiotic-resistant pathogens as they raise a major global concern. The fabricated NCs were characterized with various characterization techniques to verify its physicochemical properties. The fabricated NCs have shown excellent photo-sterilization performance of 97 % against S. aureus. The excellent activity was attributed to the decoration of Ag NPs on CdZnS QDs as it helped in shortening band gap, improved visible light absorption ability, increased active sites, and boosted photogenerated electron/hole pairs stability. Radical trapping experiment and ESR analysis indicated the involvement of •OH and h+ in the photoinactivation of bacteria. The photo sterilization reaction of NCs was carried out under different environmental conditions, including light and dark conditions and different pH conditions. The experiment was carried out in sewage-treated water in order to test the real-time application, and the fabricated NCs achieved excellent 95.9 % photo-inactivation of S. aureus cells in sewage treated water and the Chemical Oxygen Demand (COD) of the system was increased after photo inactivation treatment. The fabricated NCs have also shown excellent reusable efficiency of 95% after six runs and the photostability and anti-corrosive nature of NCs were confirmed. The study provides an insight for the employment of photocatalysis for the sterilization of pathogens in real time aquatic environment across the globe.

Ag2S Nanoparticles Supported on 3D Flower-Shaped Bi2WO6 Enhanced Visible Light Catalytic Degradation of Tetracycline

A three-dimensional flower-shaped Bi2WO6 has been prepared by a hydrothermal procedure without the addition of an auxiliary agent and under neutral conditions with ultrapure water serving as solvent, and the Ag2S-Bi2WO6 composite with weight ratios of 5, 10, and 15% was prepared by a hydrothermal method. The crystallinity, morphology, mode of binding, and optical properties of the Ag2S-Bi2WO6 composite were characterized, the results of which showed that the composite had excellent dispersion, crystallinity, and purity. The composite with a weight ratio of 10% had the best photocatalytic performance, and the degradation rate of tetracycline reached 95.51% within 120 min, an increase of 27.35% over Bi2WO6. In experiments, some focus was given to the effect of the initial solution pH and the concentrations of humic acid and inorganic anions on the degradation efficiency. Based on free radical capture experiments and the semiconductor theory, the main active substances and mechanisms in the optical catalytic reaction process were studied, and speculation was given concerning the degradation pathway for the target pollutants. This study has conceived novel methods for the development of dual semiconductor systems consisting of a Ag NP composite and in doing so has provided new approaches for the development and photocatalysis for water pollution control.

AgBr nanoparticle surface modified SnO2 enhanced visible light catalytic performance: characterization, mechanism and kinetics study

In this study, a simple hydrothermal procedure and in situ precipitation method were used to prepare SnO2-AgBr composites, where the molar ratios of SnO2 and AgBr were 1 : 1, 1 : 2 and 2 : 1. Characterization results showed that the composites had excellent dispersion, crystallinity, and purity. A photocatalytic degradation experiment and first-order kinetic model indicate that SnO2-AgBr (1 : 1) had the best photocatalytic performance, and the degradation rates of 30 mg L-1 simulated MO and MG wastewater reached 96.71% and 93.36%, respectively, in 150 min, which were 3.5 times those of SnO2. The degradation rate of MO and MG increases with the dosage. Humic acid inhibited the degradation of MG, while a low concentration of humic acid promoted the degradation of MO, and the composite has good stability with pH. A free radical trapping experiment shows that ·OH and ·O2- were the main active substances, and h+ was the secondary one. According to the results of the characterization and photocatalysis experiments, a Z-scheme mechanism for the SnO2-AgBr composite was proposed, and the degradation pathway of target pollutants was speculated upon. This study has conceived novel methods for the development of a mature Z-scheme mechanism and in doing so has provided new approaches for the development of photocatalysis for water pollution control.

Multivalent Effect of Defect Engineered Ag2S/g-C3N4 3D Porous Floating Catalyst with Enhanced Contaminant Removal Efficiency

Chlorophenols, as a major environmental pollutant, enter water systems through industrial wastewater, agricultural runoff and chemical spills, and they are stable, persistent under natural conditions, and highly hazardous to water resources. The objective of this article is to prepare Ag2S-modified C3N4 three-dimensional network photocatalyst by calcination method to use photocatalysis as an efficient, safe, and environmentally friendly method to degrade chlorophenols. Ag2S/C3N4 has an excellent visible light absorption range, low band gap, effective separation of photogenerated charges, and active free radicals production, all of which make for the enhancement of photocatalytic degradation performance of the Ag2S/C3N4 system. Under the light irradiation (λ ≥ 420 nm), the photocatalytic degradation efficiency of 2,4,6-Trichlorophenol reach 95% within 150 min, and the stable photocatalytic degradation activity can still be maintained under different pH water environment and four degradation cycles. When Ag2S is loaded on ACNs, more photogenerated electrons are generated and subsequent reactions produce highly reactive groups such as •O2- and •OH that will originally be able to continuously attack TCP molecules to degrade pollutants. Therefore, this study shows that the photocatalyst provides a novel research approach for realizing the application in the field of pollutant degradation.

Efficient detection for Nitrofurazone based on novel Ag2S QDs/g-C3N4 fluorescent probe

In the paper, a novel fluorescent probe based on Ag₂S QDs/g-C₃N₄ composite was synthesized by loading Ag₂S quantum dots (Ag₂S QDs) on the surface of g-C₃N₄ through in-situ synthesis method and developed to detect Nitrofurazone (NFZ) sensitively. The results showed that the linear detection range of Ag₂S QDs/g-C₃N₄ to NFZ was 0-30 μM, with a low detection limit of 0.054 μM. The results of time-fluorescence-resolved spectroscopy and UV-vis absorption spectroscopy exhibited that the possible detection mechanism of Ag₂S QDs/g-C₃N₄ to NFZ was proposed to be Internal Filtration Effect (IFE). Moreover, Multiwfn wavefunction analysis was employed to uncover the possible interaction between the Ag₂S QDs/g-C₃N₄ and NFZ, thereby further revealing the fluorescence detection mechanism from the scale of atoms. Combining experiments and theoretical calculations, we proposed the sensing mechanism of the formation of non-fluorescent ground state complex linked by hydrogen bonds. This work indicated that the Ag₂S QDs/g-C₃N₄ composite processed the ability to detect NFZ efficiently and sensitively.

Recent Advances in g-C3 N4 -Based Photocatalysts for Pollutant Degradation and Bacterial Disinfection: Design Strategies, Mechanisms, and Applications

Emerging photocatalytic technology promises to provide an effective solution to the global energy crisis and environmental pollution. Graphite carbon nitride (g-C₃ N₄ ) has gained extensive attention in the scientific community due to its excellent physical and chemical properties, attractive electronic band structure, and low cost. In this paper, research progress in design strategies for g-C₃ N₄ -based photocatalysts in the past five years is reviewed from the perspectives of nanostructure construction, element doping, and heterostructure construction. To clarify the relationship between application requirements and structural design, variations in the morphology, electronic energy band structure, light absorption capacity, as well as interfacial charge transfer caused by various modification strategies are discussed in detail. The recent applications of g-C₃ N₄ -based photocatalysts for pollutant degradation and bacterial disinfection are reviewed, as well as the antimicrobial activity and degradation mechanisms. Finally, current challenges and future development directions for the practical application of g-C₃ N₄ -based photocatalysts are tentatively discussed.

CdS/Ag2S/g-C3N4 ternary composites with superior photocatalytic performance for hydrogen evolution under visible light irradiation

CdS/Ag2S/g-C3N4 ternary composites as photocatalysts with different amounts of Ag2S were successfully synthesized through a simple chemical deposition method. These photocatalysts were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) mapping and X-ray photoelectron spectroscopy (XPS) to obtain the information of the structure and composition. Compared with the pure samples and binary composites, CdS/Ag2S/g-C3N4 ternary composites showed enhanced hydrogen production activities, and the maximum hydrogen production rate of CdS/Ag2S(2%)/CN is about 1020.54 μmol g-1 h-1 in Na2S-Na2SO3 solution. Based on the photoluminescence and electrochemical results, the improved photocatalytic activity could be attributed not only to the synergic effect of ternary components in the composite, but also to the introduction of Ag2S that provided abundant active sites for H2 production. A possible mechanism was investigated in detail.

Metal-Free Carbon Quantum Dots Implant Graphitic Carbon Nitride: Enhanced Photocatalytic Dye Wastewater Purification with Simultaneous Hydrogen Production

The use of photocatalysts to purify wastewater and simultaneously convert solar energy into clean hydrogen energy is of considerable significance in environmental science. However, it is still a challenge due to their relatively high costs, low efficiencies, and poor stabilities. In this study, a metal-free carbon quantum dots (CQDs) modified graphitic carbon nitride photocatalyst (CCN) was synthesized by a facile method. The characterization and theoretical calculation results reveal that the incorporation of CQDs into the g-C₃N₄ matrix significantly improves the charge transfer and separation efficiency, exhibits a redshift of absorption edge, narrows the bandgap, and prevents the recombination of photoexcited carriers. The hydrogen production and simultaneous degradation of methylene blue (MB) or rhodamine B (RhB) in simulated wastewaters were further tested. In the simulated wastewater, the CCN catalyst showed enhanced photodegradation efficiency, accompanied with the increased hydrogen evolution rate (1291 µmol·h⁻¹·g⁻¹). The internal electrical field between the g-C₃N₄ and the CQDs is the main reason for the spatial separation of photoexcited electron-hole pairs. Overall, this work could offer a new protocol for the design of highly efficient photocatalysts for dye wastewater purification with simultaneous hydrogen production.

The facile boosting sunlight-driven photocatalytic performance of a metal–organic-framework through coupling with Ag2S nanoparticles

A facile method was successfully developed to tremendously boost sunlight-driven photocatalytic performance of a MOFs material (MIL-53(Fe)) by coupling with silver sulfide (Ag₂S) nanoparticles for the first time.

Facile Preparation of CNT/Ag2S Nanocomposites with Improved Visible and NIR Light Photocatalytic Degradation Activity and Their Catalytic Mechanism

In this work, a series of carbon nanotubes (CNT)/Ag₂S hybrid nanocomposites were successfully prepared by a facile precipitation method. Transmission electron microscope (TEM) observation indicates that Ag₂S nanoparticles with an average particle size of ~25 nm are uniformly anchored on the surface of CNT. The photocatalytic activities of the CNT/Ag₂S nanocomposites were investigated toward the degradation of rhodamine B (RhB) under visible and near-infrared (NIR) light irradiation. It is shown that the nanocomposites exhibit obviously enhanced visible and NIR light photocatalytic activities compared with bare Ag₂S nanoparticles. Moreover, the recycling photocatalytic experiment demonstrates that the CNT/Ag₂S nanocomposites possess excellent photocatalytic stability. The photoelectrochemical and photoluminescence measurements reveal the efficient separation of photogenerated charges in the CNT/Ag₂S nanocomposites. This is the dominant reason behind the improvement of the photocatalytic activity. Based on active species trapping experiments, the possible photocatalytic mechanism of CNT/Ag₂S nanocomposites for dye degradation under visible and NIR light irradiation was proposed.

Recyclable Visible Light-Driven O-g-C3N4/Graphene Oxide/N-Carbon Nanotube Membrane for Efficient Removal of Organic Pollutants

Organic pollutants are harmful to human health, which creates a global need for the development of novel and effective materials for efficiently removing contaminants. Accordingly, an efficient visible light-driven heterostructured membrane combined with oxygen-modified monolayer g-C₃N₄, graphene oxide, and nitrogen-doped carbon nanotubes (CNTs) (O-g-C₃N₄/GO/N-CNT) was successfully fabricated through electrostatic interactions and subsequent vacuum filtration. The results suggested that the O-g-C₃N₄/GO/N-CNT membrane exhibited higher degradation rate than those of O-g-C₃N₄/GO and pure O-g-C₃N₄ under visible light exposure. This enhanced photocatalytic performance was attributed to the introduction of GO and N-CNT, which acted as electronic acceptors for monolayer O-g-C₃N₄ that effectively inhibited recombination of photogenerated electron-hole pairs, thus enhancing visible light photocatalytic activity. Furthermore, the enrichment and degradation rates of O-g-C₃N₄/GO/N-CNT membranes were demonstrated for tetracycline hydrochloride, which were found to be 96.64 and 94.30%, respectively, and no distinct enrichment or catalytic activity reduction was observed when their reusability was measured. These results suggested that these recyclable O-g-C₃N₄/GO/N-CNT membranes provide a new strategy for the highly efficient removal of environmental pollutants.