Enhanced photocatalytic activities of polypyrrole sensitized zinc ferrite/graphitic carbon nitride n-n heterojunction towards ciprofloxacin degradation, hydrogen evolution and antibacterial studies

2H-SnS2 assembled with petaloid 1T@2H-MoS2 nanosheet heterostructures for room temperature NO2 gas sensing

In this study, we explored the gas-sensing capabilities of MoS2 petaloid nanosheets in the metallic 1T phase with the commonly investigated semiconducting 2H phase. By synthesizing SnS2 nanoparticles and MoS2 petaloid nanosheets through a hydrothermal method, we achieve notable sensing performance for NO2 gas at room temperature (27 °C). This investigation represents a novel study, and to the best of our knowledge no, prior similar investigations have been reported in the literature for 1T@2HMoS2/SnS2 heterostructures for room temperature NO2 gas sensing. The formed heterostructure between SnS2 nanoparticles and petaloid MoS2 nanosheets exhibits synergistic effects, offering highly active sites for NO2 gas adsorption, consequently enhancing sensor response. Our sensor demonstrated a remarkable sensing response (R a/R g = 7.49) towards 1 ppm of NO2, rapid response time of 54 s, baseline recovery in 345 s, good selectivity and long-term stability, underscoring its potential for practical gas-sensing applications.

Facile fabrication of B-rGO/ZnFe2O4 p-n heterojunction-based S-scheme exciton engineering for photocatalytic Cr(vi) reduction: kinetics, influencing parameters and detailed mechanism

The fabrication of p-n heterostructures was found to be an effective strategy to stimulate the interfacial exciton shipment and photocatalytic reactions. Herein, we report a p-n junction synthesized by combining p-type boron-doped reduced graphene oxide (B-rGO) with an n-type ZnFe2O4 semiconducting material for Cr(vi) reduction under LED light irradiation. The band structures of ZnFe2O4 and B-rGO were evaluated using UV-vis spectroscopy, Mott-Schottky (M-S) plots and photocurrent studies. The results indicated that ZnFe2O4 and B-rGO exhibit a conventional type-II charge transfer, and the Fermi-level (E F) of ZnFe2O4 was found to be much lower than that of the B-rGO material. Based on these investigations, an S-scheme charge-migration pathway was suggested and demonstrated by the photocatalytic activity and nitroblue tetrazolium (NBT) chloride experiments. The optimal 2 wt% B-rGO/ZnFe2O4 heterojunction exhibits the highest photocatalytic performance, i.e. 84% of Cr(vi) reduction in 90 min under 20 W LED light irradiation with a rate constant of 0.0207 min-1, which was 4.6- and 2.15-fold greater than that of ZnFe2O4 (ZnF) and B-rGO, respectively. The intimate interfacial contact, excellent photon-harvesting properties, effective exciton segregation and availability of active electrons are some factors responsible for enhanced photocatalytic Cr(vi) reduction. In order to fulfill the demand of applied waste-water management, the influences of various photocatalyst amounts, pH values and co-exiting ions on photocatalytic activities were evaluated. Finally, this work provides a way to fabricate S-scheme-based p-n-heterostructures for photocatalytic wastewater treatment.

Removal of sulfonylurea herbicides with g-C3N4-based photocatalysts: A review

The accumulation of agricultural chemicals in the environment has become a global concern, of which sulfonylurea herbicides (SUHs) constitute a significant category. Solar-driven photocatalysis is favored for removing organic pollutants due to its high efficiency and environmental friendliness. Graphite carbon nitride (g-C3N4)-based materials with superior catalytic activities and physicochemical stabilities are promising photocatalysts. This review describes the g-C3N4-based materials and their uses in the photocatalytic degradation of SUHs or other organic pollutants with similar structures. First, the fundamentals of g-C3N4-based materials and photocatalytic SUHs degradation are discussed to provide an in-depth understanding of the mechanism for the photocatalytic activity. The ability of different g-C3N4-based materials to photocatalytically degrade SUH-like structures is then discussed and summarized based on different modification strategies (morphology modulation, elemental doping, defect engineering, and heterojunction formations). Meanwhile, the effects of different environmental factors on the photocatalytic performance of g-C3N4-based materials are described. Finally, the major challenges and opportunities of g-C3N4-based materials for the photocatalytic degradation of SUHs are proposed. It is hoped that this review will show the feasibility of photocatalytic degradation of SUHs with g-C3N4-based materials.

Preparation, characterization, and photocatalytic performance of a PVDF/cellulose membrane modified with nano Fe3O4 for removal of methylene blue using RSM under visible light

In this work, a polymeric membrane-based polyvinylidene fluoride coated with cellulose and loaded with iron oxide nanoparticles (PVDF/cellulose/Fe3O4) was synthesized and was characterized using FESEM, XRD, AFM, and contact angle measurements. The activity and modification of the PVDF/cellulose/Fe3O4 membrane under visible light for the removal of methylene blue were studied using the central composite design. The effect of influential variables such as pH, methylene blue concentration, amount of Fe3O4 in the membrane, and irradiation time on MB removal was investigated. Analysis of variance was used to determine the significance of experimental factors and their interactions. About 72.5% methylene blue removal using the PVDF/cellulose/Fe3O4 membrane under visible light was achieved at optimum conditions of a pH of 9, methylene blue concentration of 600 mg L-1, Fe3O4 amount of 0.03 g, and irradiation time of 117 min. Finally, results confirmed that the proposed membrane has good performance for methylene blue removal under visible light.

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.

Heterogeneous porous biochar-supported nano NiFe2O4 for efficient removal of hazardous antibiotic from pharmaceutical wastewater

Due to the dual issues of antibiotic resistance and bioaccumulation toxicity, antibiotics are ubiquitously present in aquatic environments, and this is causing serious concern. Herein, novel nickel ferrite (NiFe2O4) nanoparticles were successfully loaded onto activated biochar (BC) derived from banana peel (BP) to obtain magnetic nanocomposite (BC-NiFe2O4) as an effective biosorbent for the ciprofloxacin antibiotic (CIP) elimination from pharmaceutical effluent. A facile co-precipitation approach was utilized to construct the heterogeneous BC-NiFe2O4. The synthesized materials were systematically characterized using techniques such as XRD, FE-SEM, EDX, HR-TEM, BET, FTIR, and XPS. In addition, the magnetic measurements indicated the ferromagnetic behavior of the BC-NiFe2O4 sample. The influencing factors (i.e., pH, contact time, initial concentration, dose of adsorbent, ions interference, and solution temperature) of the adsorption process were also well studied. The adsorption capacity of the BC-NiFe2O4 heterostructure was 68.79 mg g-1 compared to the BC sample (35.71 mg g-1), confirming that the loading of magnetically NiFe2O4 nanoparticles onto the surface of porous biochar enhanced its stability and adsorption performance for CIP removal, wherein the metal-antibiotic complex has a significant effect for the removal of CIP. Moreover, the Langmuir adsorption isotherm and the pseudo-second-order model displayed a good fit for the experimental data. The values of △H° and △G° revealed that the adsorption process was endothermic and spontaneous. The coordination affinities, π-π stacking, and H-bonding interactions play a more critical role in the adsorption mechanism that confirmed by FTIR and XPS analysis. To study the stability of BC-NiFe2O4 nanocomposites, desorption and recycling studies were investigated. The results revealed that after three cycles, no significant loss in removal efficiency was detected, reflecting the stability and reusability of the prepared BC-NiFe2O4 nanocomposite.

Investigation of the Photocatalytic Activity of Electrospun and Surface-Modified PAN/α-FeOOH Nanofibers for the Degradation of Hazardous Azo Dyes

Decoration of α-FeOOH nanorods over PAN nanofibers was performed using the electrospinning technique. The as-designed decorated nanofibers were characterized using various techniques such as wide-angle powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectrophotometry (UV-vis), thermogravimetry analysis (TGA), N2 adsorption-desorption isotherm (BET), and X-ray photoelectron spectrometry (XPS). α-FeOOH NRs were decorated uniformly over PAN fibers, as observed from its morphological investigation, which shows novelty. 1D α-FeOOH nanorods with PAN nanofibers have not been studied for photocatalytic characteristics. No literature mentions that α-FeOOH nanorods coated in PAN NFs act as photocatalysts to degrade hazardous azo dyes. α-FeOOH nanorods on PAN NFs inhibit aggregation and increase dye binding, boosting photocatalytic performance. PAN/α-FeOOH NFs have a maximal specific surface area with a reduced bandgap than α-FeOOH NRs. PAN/α-FeOOH nanofibers showed excellent photocatalytic activity for the degradation of Trypan blue (TB) (120 min, 99.7%) and Eriochrome black T (EBT) dyes (160 min, 97.6%), respectively, under solar light irradiation. PAN/α-FeOOH NFs have the potential to be used in the degradation of azo dyes and the treatment of wastewater due to their low energy requirements and versatility.

Facile fabrication of carboxymethylcellulose/ZnO/g-C3N4 containing nutmeg extract with photocatalytic performance for infected wound healing

New topical antibacterial agents are required to inhibit and development of bacteria and also promoting the wound healing process. This study was evaluating the healing effect of Myristica fragrans extract coated with carboxymethyl cellulose, zinc oxide and graphite carbon nitride (CMC/ZnO/g-C3N4/MyR) by photocatalytic process on the healing process of full-thickness infectious excision wounds in mice. Nanosheets were prepared and physicochemical properties were evaluated. Safety, in vitro release, antibacterial activities under in vitro and in vivo condition, wound contraction, histopathological properties and the protein expressions of tumor necrosis factor-α (TNF-α), collagen 1A (COL1A) and CD31 were also evaluated. Physicochemical properties confirmed their successful synthesis. Nanosheets exhibited antibacterial activity under in vitro and in vivo conditions. The formulations containing CMC/ZnO/g-C3N4/MyR, significantly (P < 0.05) competed with standard ointment of mupirocin for accelerating the wound healing process due to their effects on bacterial count and the expression of TNF-α and also accelerating the proliferative phase. This structure can be used as a safe structure in combination with other agents for accelerating the wound healing process following future clinical studies.

Utilization of ZnFe2O4-Polyaniline (PANI), ZnFe2O4-Polystyrene (PST), and ZnFe2O4-Polypyrrole (PPy) nanocomposites for removal of Red X-GRL and Direct Sky Blue dyes from wastewater: Equilibrium, kinetic and thermodynamic studies

In this study, ZnFe2O4-Polyaniline (PANI), ZnFe2O4-Polystyrene (PST), and ZnFe2O4-Polypyrrole (Ppy) nanocomposites were synthesized by the adsorption method and characterized by field emission scanning electron microscopy and Fourier transform infrared spectrometer. Batch adsorption experiments were conducted for removing two types of hazardous dyes Red X-GRL and Direct Sky Blue 51 from an aqueous solution and the effect of pH, adsorbent dosage, contact time, and initial concentration of dyes were investigated. Meanwhile, kinetic, isotherm, and thermodynamic parameters were also determined. The electrolyte and surfactant effect was also tested for the prepared nanocomposites. To test the reusability desorption study was also conducted.

Noble metal-free doped graphitic carbon nitride (g-C3N4) for efficient photodegradation of antibiotics: progress, limitations, and future directions

Graphitic carbon nitride (g-C₃N₄) is well recognised as one of the most promising materials for photocatalytic activities such as environmental remediation via organic pollution elimination. New methods of nanoscale structure design introduce tunable electrical characteristics and broaden their use as visible light-induced photocatalysts. This paper summarises the most recent developments in the design of g-C₃N₄ with element doping. Various methods of introducing metal and nonmetal elements into g-C₃N₄ have been investigated in order to simultaneously tune the material's textural and electronic properties to improve its response to the entire visible light range, facilitate charge separation, and extend charge carrier lifetime. The degradation of antibiotics is one of the application domains of such doped g-C₃N₄. We expect that this research will provide fresh insights into clear design methods for efficient photocatalysts that will solve environmental challenges in a sustainable manner. Finally, the problems and potential associated with g-C₃N₄-based nanomaterials are discussed. This review is expected to encourage the ongoing development of g-C₃N₄-based materials for greater efficiency in photocatalytic antibiotic degradation.

Degradation of ciprofloxacin by a constitutive g-C3N4/BiOCl heterojunction under a persulfate system

Ciprofloxacin (CIP) is a third-generation quinolone antimicrobial with broad-spectrum antimicrobial activity, and is not fully metabolized in the human body, resulting in more than 70% of CIP being excreted into water as a prodrug. In this study, g-C₃N₄/BiOCl heterojunction structure composites were prepared to study the degradation effect of ciprofloxacin (CIP) under photocatalytic conditions. The results showed that CIP at 10 mg L^-1 was best degraded after 90 min at 0.3 g L^-1 g-C₃N₄/BiOCl-2, pH of 5.8 and PS dosing of 1 mM. The quenching experiments and electron spin resonance spectroscopy (ESR) confirmed that ˙OH, ˙SO₄ ^- and h⁺ played a major role. After the photocatalytic degradation of this reaction system, the biological toxicity of CIP was effectively controlled. This material is stable and the CIP removal rate remained above 80% after four cycles of experiments.

Chlorophyll sensitized and salicylic acid functionalized TiO2 nanoparticles as a stable and efficient catalyst for the photocatalytic degradation of ciprofloxacin with visible light

Developing efficient and stable visible light active photocatalyst has significant environmental applications. Though dye sensitization of TiO₂ nanoparticles with natural chlorophyll pigments can potentially impart visible light activity, their long-term stability is a major concern. We investigated the functionalization of TiO₂ with salicylic acid, and subsequent sensitization with chlorophylls to improve the catalyst stability for the photocatalytic degradation of Ciprofloxacin (CPX) under visible light. A significant improvement in the degradation efficiency and catalyst stability was observed for five reuse cycles. Further, an optimum CPX degradation of ∼75% was achieved with 0.75 g L^-1 catalyst dosage of 0.1 chl/0.1 SA-TiO₂, initial pH of 6, and 10 ppm of initial CPX for a visible light exposure of 2 h. The degradation followed the pseudo-second-order kinetics. In addition, the ciprofloxacin degradation was reduced in the wastewater matrix system due to the presence of other scavenging species such as chlorides, sulphates, and alkalinity. Significant reduction in the toxicity of degradation compounds after the photocatalytic degradation was observed in comparison to parent CPX. Further, the degradation pathway and plausible mechanism of degradation of CPX were also proposed.

"Magnetic Ni-Zn ferrite anchored on g-C3N4 as nano-photocatalyst for efficient photo-degradation of doxycycline from water"

In the present work, mixed-spinel ferrite anchored onto graphitic carbon nitride (GCN) was synthesized for mineralization of antibiotic pollutant from waste water. A Z-scheme g-C₃N₄/Ni_0.5Zn_0.5Fe₂O₄ nano heterojunction was fabricated by three step procedure: pyrolysis, solution combustion and mechanical grinding followed by annealing. The prepared photocatlyst was tested for degradation of Doxycycline (DC) drug under the natural sun light. Results revealed that the prepared heterojunction has maximum degradation efficiency of 97.10% pollutant in 60 min experiment. The Z-scheme heterojunction between g-C₃N₄ and Ni-Zn ferrite improves the photoinduced charges separation and protection of redox capability and therby increases the photo degradation efficiency. The scavenging experiments suggested that O₂^-● and h⁺ as main active species responsible for degradation of the antibiotic. In addition, the dopant variation can drive the shists in band gap and energy band positiong too which makes then excellent candidates for synthesizing tunable heterostructures with organic semiconductors. The work focusses on designing and developing of saimpler but efficient magnetic heterojunctions with superior redox capability for solar powered waste water treatment.

Interface Engineering of Conjugated Polymer-Based Composites for Photocatalysis

Photocatalysis can create a green way to produce clean energy resources, degrade pollutants and achieve carbon neutrality, making the construction of efficient photocatalysts significant in solving environmental issues. Conjugated polymers (CPs) with adjustable band structures have superior light-absorption capacity and flexible morphology that facilitate contact with other components to form advanced heterojunctions. Interface engineering can strengthen the interfacial contact between the components and further enlarge the interfacial contact area, enhance light absorption, accelerate charge transfer and improve the reusability of the composites. In order to throw some new light on heterojunction interface regulation at a molecular level, herein we summarize CP-based composites with improved photocatalytic performance according to the types of interactions (covalent bonding, hydrogen bonding, electrostatic interactions, π-π stacking, and other polar interactions) between the components and introduce the corresponding interface building methods, identifying techniques. Then the roles of interfaces in different photocatalytic applications are discussed. Finally, we sum up the existing problems in interface engineering of CP-based composites and look forward to the possible solutions.

An overview of nanomaterial-based novel disinfection technologies for harmful microorganisms: Mechanism, synthesis, devices and application

Harmful microorganism (e.g., new coronavirus) based infection is the most important security concern in life sciences and healthcare. This article aims to provide a state-of-the-art review on the development of advanced technology based on nanomaterial disinfection/sterilization techniques (NDST) for the first time including the nanomaterial types, disinfection techniques, bactericidal devices, sterilization products, and application scenarios (i.e., water, air, medical healthcare), with particular brief account of bactericidal behaviors referring to varied systems. In this emerging research area spanning the years from 1998 to 2021, total of ~200 publications selected for the type of review paper and research articles were reviewed. Four typical functional materials (namely type of metal/metal oxides, S-based, C-based, and N-based) with their development progresses in disinfection/sterilization are summarized with a list of synthesis and design. Among them, the widely used silver nanoparticles (AgNPs) are considered as the most effective bacterial agents in the type of nanomaterials at present and has been reported for inactivation of viruses, fungi, protozoa. Some methodologies against (1) disinfection by-products (DBPs) in traditional sterilization, (2) noble metal nanoparticles (NPs) agglomeration and release, (3) toxic metal leaching, (4) solar spectral response broadening, and (5) photogenerated e^-/h⁺ pairs recombination are reviewed and discussed in this field, namely (1) alternative techniques and nanomaterials, (2) supporter anchoring effect, (3) nonmetal functional nanomaterials, (4) element doping, and (5) heterojunction constructing. The feasible strategies in the perspective of NDST are proposed to involve (1) non-noble metal disinfectors, (2) multi-functional nanomaterials, (3) multi-component nanocomposite innovation, and (4) hybrid techniques for disinfection/sterilization system. It is promising to achieve 100% bactericidal efficiency for 10⁸ CFU/mL within a short time of less than 30 min.

Polypyrrole-based nanomaterials: A novel strategy for reducing toxic chemicals and others related to environmental sustainability applications

Aqueous contaminants such as pharmaceuticals, dyes, personal care products, etc., are the common water contaminants that show adverse health effects. Photocatalysis is one of the well-known techniques to treat these water contaminants. Currently, most inorganic photocatalysts show a poor balance between adsorption and photocatalytic activity. In addition, heavy metal pollution and low biosafety are significant concerns in photocatalysis. Thus, environmentally friendly photocatalysts are required to avoid the secondary pollution caused by some inorganic semiconductor-photocatalysts. Organic polymer-based photocatalysts are low-cost, stable, non-toxic, and can utilize visible and NIR light for photocatalysis. In this review, we have discussed polypyrrole as a photocatalyst. Polypyrrole is a conducting organic polymer photocatalyst that is highly stable with high charge mobility and strong binding sites for photocatalytic reactions. Besides these advantages, polypyrrole has limitations, such as high charge recombination due to a small bandgap and poor dispersity. So we have explored the modifications to polypyrrole photocatalysts, such as doping and heterojunctions. Further, we have explained the applications of polypyrrole in photocatalysis as an adsorbent, sensitizer, degradation of pollutants, and energy production. Finally, the future aspects of polypyrrole photocatalysis are also explored to improve the path of future research.

Progress in the Preparation and Modification of Zinc Ferrites Used for the Photocatalytic Degradation of Organic Pollutants

Zinc ferrite is a type of photocatalytic material with high physicochemical stability, narrow band gap, high carrier separation efficiency, high porosity, and paramagnetism, which makes it easy to recover. Thus, zinc ferrite is widely used as a photocatalyst in water treatment. In this paper, the preparation principles as well as the advantages and disadvantages of typical methods used to prepare zinc ferrite including hydrothermal, co-precipitation, sol-gel, and other novel methods such as biosynthesis have been summarized. Modification methods such as elemental doping, composite formation, and morphological modification have been highlighted. Using these modification methods, the catalytic activity of zinc ferrite toward the photocatalytic degradation of organic pollutants in water has been enhanced. Biosynthesis is regarded as a promising preparation method that uses biological materials instead of chemical materials to achieve the large-scale preparation of zinc ferrite using low cost, energy efficient, and environmentally friendly processes. Meanwhile, the combination of multiple modification techniques to enhance the photocatalytic performance of zinc ferrite will be an important research trend in the future.

Boosted spatial charge carrier separation of binary ZnFe2O4/S-g-C3N4 heterojunction for visible-light-driven photocatalytic activity and antimicrobial performance

A potential method for removing toxins from contaminated wastewater, especially organic pollutants, is photo-catalysis. Here, a simple technique for producing zinc ferrite nanoparticles (ZnFe2O4 NPS) with varying quantities of sulphur doped graphitic carbon nitride nanocomposites (ZnFe2O4/S-g-C3N4 NCs) has been described. Then, using X-ray diffraction (XRD), TEM, EDX, XPS, photocurrent response, EIS, and Fourier Transform Infrared spectroscopy (FT-IR), the photo-catalytic activity of the produced nanoparticles (NPs) and nanocomposites (NCs) was examined and evaluated. The photo-catalytic activity of ZnFe2O4/S-g-C3N4 NCs was compared to a model pollutant dye, methylene blue, while degradation was evaluated spectrophotometrically (MB). Solar light has been used through irradiation as a source of lighting. The photocatalytic behaviour of the ZnFe2O4/S-g-C3N4 NCs photocatalyst was superior to that of genuine ZnFe2O4 and S-g-C3N4, which was attributed to synergic effects at the ZnFe2O4/S-g-C3N4 interconnection. Antimicrobial activity of ZnFe2O4/S-g-C3N4 against Gram-positive and Gram-negative bacteria under visible light was performed. In addition, these ZnFe2O4/S-g-C3N4 NCs show a lot of promise as an antibacterial agent.

Investigation on visible-light photocatalytic performance and mechanism of zinc peroxide for tetracycline degradation and Escherichia coli inactivation

In this study, zincperoxide (ZnO₂) with broad energy gap was firstly used for visible-light-induced photocatalytic degradation of tetracycline (TC) and inactivation of Escherichia coli (E. coli). A small amount of ZnO₂ (10 mg) could efficiently degrade 100 mL of 50 mg/L TC in a wide pH range (4-12), and the degradation performance was rarely suppressed by common matrix species and natural water sources. Also, 100 mg/L ZnO₂ could inactivate around 7-log E. coli cells within 60 min under visible-light irradiation. Quenching experiments and electron paramagnetic resonance (EPR) results confirmed that superoxide radical (•O₂^-) and singlet oxygen (¹O₂) were the main reactive oxygen species (ROS), which were attributed to the self-sensitization of TC and the photoexcitation of released H₂O₂ under the catalysis of Zn(OH)₂ from the hydrolysis of partial ZnO₂, respectively. The pathways of TC degradation and processes of visible-light-induced TC degradation and E. coli inactivation were proposed and deduced in detail. This work presented the enhanced visible-light photocatalytic activities of ZnO₂ for antibiotic degradation and bacterial inactivation, and provided a deep insight into the mechanisms of visible-light-induced TC degradation andE. coli inactivation over ZnO₂.

Boosting sluggish photocatalytic hydrogen evolution through piezo-stimulated polarization: a critical review

To address the growing energy demand, remarkable progress has been made in transferring the fossil fuel-based economy to hydrogen-based environmentally friendly photocatalytic technology. However, the sluggish production rate due to the quick charge recombination and slow diffusion process needs careful engineering to achieve the benchmark photocatalytic efficiency. Piezoelectric photocatalysis has emerged as a promising field in recent years due to its improved catalytic performance facilitated by a built-in electric field that promotes the effective separation of excitons when subjected to mechanical stimuli. This review discusses the recent progress in piezo-photocatalytic hydrogen evolution while elaborating on the mechanistic pathway, effect of piezo-polarization and various strategies adopted to improve piezo-photocatalytic activity. Moreover, our review systematically emphasizes the fundamentals of piezoelectricity and piezo-phototronics along with the operational mechanism for designing efficient piezoelectric photocatalysts. Finally, the summary and outlooks provide insight into the existing challenges and outline the future prospects and roadmap for the development of next-generation piezo-photocatalysts towards hydrogen evolution.

gCN-P: a coupled g-C3N4/persulfate system for photocatalytic degradation of organic pollutants under simulated sunlight

A coupled g-C3N4/PDS system, named gCN-P, has been put forward to degrade refractory organic pollutants under simulated sunlight which integrates photocatalysis and PS-AOPs (advanced oxidation of persulfate based on sulfate radicals). The coupled g-C3N4 and PDS showed superior synergistic effect for MO degradation under simulated sunlight. Results showed that almost all MO was removed in the gCN-P system after irradiation for 80 min under simulated sunlight. The degradation rate of gCN-P system was improved by 12.6 and 4.9 times compared to single PDS and g-C3N4 systems, respectively. And only by adding 0.01 g of persulfate into the gCN-P system. The results of quenching experiments and EPR showed that O2-, 1O2 and h+ were main active species for the degradation of MO in the gCN-P system under simulated sunlight. Application of the gCN-P system in tap water samples demonstrated its excellent performance in real-world water environment, and the gCN-P system was employed for removing other new contaminants such as bisphenol A, ciprofloxacin, and paracetamol. The results demonstrated the gCN-P system can effectively remove organic pollutants under sunlight in practices.

Development and Mechanistic Studies of Ternary Nanocomposites for Hydrogen Production from Water Splitting to Yield Sustainable/Green Energy and Environmental Remediation

Photocatalysts lead vitally to water purifications and decarbonise environment each by wastewater treatment and hydrogen (H2) production as a renewable energy source from water-photolysis. This work deals with the photocatalytic degradation of ciprofloxacin (CIP) and H2 production by novel silver-nanoparticle (AgNPs) based ternary-nanocomposites of thiolated reduce-graphene oxide graphitic carbon nitride (AgNPs-S-rGO2%@g-C3N4) material. Herein, the optimised balanced ratio of thiolated reduce-graphene oxide in prepared ternary-nanocomposites played matchlessly to enhance activity by increasing the charge carriers’ movements via slowing down charge-recombination ratios. Reduced graphene oxide (rGO), >2 wt.% or <2 wt.%, rendered H2 production by light-shielding effect. As a result, CIP degradation was enhanced to 95.90% by AgNPs-S-rGO2%@g-C3N4 under the optimised pH(6) and catalyst dosage(25 mg/L) irradiating beneath visible-light (450 nm, 150 watts) for 70 min. The chemical and morphological analysis of AgNPs-S-rGO2%@g-C3N4 surface also supported the possible role of thiolation for this enhancement, assisted by surface plasmon resonance of AgNPs having size < 10 nm. Therefore, AgNPs-S-rGO2%@g-C3N4 has 3772.5 μmolg−1 h−1 H2 production, which is 6.43-fold higher than g-C3N4 having cyclic stability of 96% even after four consecutive cycles. The proposed mechanism for AgNPs-S-rGO2%@g-C3N4 revealed that the photo-excited electrons in the conduction-band of g-C3N4 react with the adhered water moieties to generate H2.

Engineering an oxygen-vacancy-mediated step-scheme charge carrier dynamic coupling WO3−X/ZnFe2O4 heterojunction for robust photo-Fenton-driven levofloxacin detoxification

Schematic representation of the photo-Fenton degradation of levofloxacin under solar-light illumination.

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.

g-C3N4: Properties, Pore Modifications, and Photocatalytic Applications

Graphitic carbon nitride (g-C3N4), as a polymeric semiconductor, is promising for ecological and economical photocatalytic applications because of its suitable electronic structures, together with the low cost, facile preparation, and metal-free feature. By modifying porous g-C3N4, its photoelectric behaviors could be facilitated with transport channels for photogenerated carriers, reactive substances, and abundant active sites for redox reactions, thus further improving photocatalytic performance. There are three types of methods to modify the pore structure of g-C3N4: hard-template method, soft-template method, and template-free method. Among them, the hard-template method may produce uniform and tunable pores, but requires toxic and environmentally hazardous chemicals to remove the template. In comparison, the soft templates could be removed at high temperatures during the preparation process without any additional steps. However, the soft-template method cannot strictly control the size and morphology of the pores, so prepared samples are not as orderly as the hard-template method. The template-free method does not involve any template, and the pore structure can be formed by designing precursors and exfoliation from bulk g-C3N4 (BCN). Without template support, there was no significant improvement in specific surface area (SSA). In this review, we first demonstrate the impact of pore structure on photoelectric performance. We then discuss pore modification methods, emphasizing comparison of their advantages and disadvantages. Each method's changing trend and development direction is also summarized in combination with the commonly used functional modification methods. Furthermore, we introduce the application prospects of porous g-C3N4 in the subsequent studies. Overall, porous g-C3N4 as an excellent photocatalyst has a huge development space in photocatalysis in the future.

Recent advancements of g-C3N4-based magnetic photocatalysts towards the degradation of organic pollutants: a review

Heterogeneous photocatalysis premised on advanced oxidation processes has witnessed a broad application perspective, including water purification and environmental remediation. In particular, the graphitic carbon nitride (g-C₃N₄), an earth-abundant metal-free conjugated polymer, has acquired extensive application scope and interdisciplinary consideration owing to its outstanding structural and physicochemical properties. However, several issues such as the high recombination rate of the photo-generated electron-hole pairs, smaller specific surface area, and lower electrical conductivity curtail the catalytic efficacy of bulk g-C₃N₄. Another challenging task is separating the catalyst from the reaction medium, limiting their reusability and practical applications. Therefore, several methodologies are adopted strategically to tackle these issues. Attention is being paid, especially to the magnetic nanocomposites (NCs) based catalysts to enhance efficiency and proficient reusability property. This review summarizes the latest progress related to the design and development of magnetic g-C₃N₄-based NCs and their utilization in photocatalytic systems. The usefulness of the semiconductor heterojunctions on the catalytic activity, working mechanism, and degradation of pollutants are discussed in detail. The major challenges and prospects of using magnetic g-C₃N₄-based NCs for photocatalytic applications are highlighted in this report.

ZnFe2O4@WO3-X /Polypyrrole: An Efficient Ternary Photocatalytic System for Energy and Environmental Application

Environmental protection and the necessity of green energy have become fundamental concerns for humankind. However, rapid recombination of photoexcitons in semiconductors often gets in the path of photocatalytic reactions and annoyingly suppresses the photocatalytic activity. In this study, a polypyrrole (PPY)-supported step-scheme (S-scheme) ZnFe₂O₄@WO_3-X (PZFW15) ternary composite was fabricated by a multistep process: hydrothermal and calcination processes, followed by polymerization. During the formation of the heterojunction, the oxygen vacancy (OV) on WO_3-X promotes effective separation and increases the redox power of the photogenerated excitons via the built-in internal electric field of S-scheme pathways between ZnF and WO_3-X. The successful construction of the S-scheme heterojunction was substantiated through X-ray photoelectron spectroscopy, experimental calculations, radical trapping experiment, and liquid electron spin resonance (ESR) characterization, whereas the existence of OVs was well confirmed by EPR and Raman analyses. Meanwhile, the PPY served as a supporter, and the polaron and bipolaron species of PPY acted as electron and hole acceptors, respectively, which further enhances the charge-carrier transmission and separation in the ternary PZFW15 photocatalyst. The designed ternary nanohybrid (PZFW15) displays outstanding gemifloxacin detoxification (95%, 60 min) and hydrogen generation (657 μmol h^-1), i.e., 1.5 and 2.2 times higher than the normal S-scheme ZFW15 heterostructure and pure ZnFe₂O₄ (ZnF), respectively, with an apparent conversion efficiency of 4.92%. The ESR and trapping experiments indicate that the generated ^•OH and ^•O₂ ^- radicals from the PZFW15 photocatalyst are responsible for gemifloxacin degradation. This unique PPY-supported S-scheme heterojunction is also beneficial for the enhanced electron-transfer rate and provides abundant active sites for photocatalytic reactions.

Black titania an emerging photocatalyst: review highlighting the synthesis techniques and photocatalytic activity for hydrogen generation

The TiO₂ semiconductor photocatalyst is in the limelight of sustainable energy research in recent years because of its beneficial properties. However, its wide band-gap and rapid exciton recombination rate makes it a lame horse, and reduces its photocatalytic efficiency. Recently, researchers have developed facile methods for lowering the band-gap, so that it captures a wide range of solar spectrum, but the efficiency is still way behind the target value. After the discovery of black titania (B-TiO₂), the associated drawbacks of white TiO₂ and its modified forms were addressed to a large extent because it not only absorbs photons in a broad spectral range (UV to IR region), but also modifies the structural and morphological features, along with the electronic properties of the material, significantly boosting the catalytic performance. Hence, B-TiO₂ effectively converts solar energy into renewable chemical energy i.e. green fuel H₂ that can ultimately satisfy the energy crisis and environmental pollution. However, the synthesis techniques involved are quite tedious and challenging. Hence, this review summarizes various preparation methods of B-TiO₂ and the involved characterization techniques. It also discusses the different modification strategies adopted to improve the H₂ evolution activity, and hopes that this review acts as a guiding tool for researchers working in this field.

A Facile Fabrication of ZnFe2O4/Sepiolite Composite with Excellent Photocatalytic Performance on the Removal of Tetracycline Hydrochloride

The excellent photo-response of ZnFe2O4 in the visible light region makes it a promising catalyst, whereas some defects like serious particle agglomeration and easy recombination of photo-generated electron-hole pairs hinder its application. In this work, the ZnFe2O4/sepiolite (ZF-Sep) composites were synthesized using a co-precipitation method. The obtained ZF-Sep composites were characterized by XRD, SEM, TEM, FT-IR, XPS, BET, VSM and DRS. Moreover, the photocatalytic performance was evaluated by the tetracycline hydrochloride removal efficiency under simulated visible light illumination. The results displayed that the ZnFe2O4 with average sizes about 20 nm were highly dispersed on sepiolite nanofibers. All the composites exhibited better photocatalytic performance than pure ZnFe2O4 due to the synergistic effect of the improvement on the agglomeration phenomenon of ZnFe2O4 and the reduction on the recombination rate of photo-generated electrons and holes. The optimum removal efficiency was that of the ZF-Sep-11 composite, which reached 93.6% within 3 h. Besides, the composite exhibited an excellent stability and reusability. Therefore, ZF-Sep composite is a promising catalyst for the treatment of wastewater contained antibiotics.

Highly efficient visible light driven photocatalytic activity of zinc/ferrite: Carbamazepine degradation, mechanism and toxicity assessment

In this present study, spherical shaped zinc ferrite (Zn/Fe₂O₄) was prepared as uniformly sized (65 ± 0.5 nm) nanoparticles with band gap (2.00 eV) in a visible light regime and employed for the photocatalytic degradation of carbamazepine (CBZ). The doping of Zn decreased the band gap (from 2.00 to 1.98 eV) and enhanced the absorption of visible light. Zinc doping also induced effective separation of photogenerated carriers and subsequent charge migration to the surface of the Zn/Fe₂O₄ nanoparticle. On account of the advantages of the material, a high removal efficiency (~ 100%) of CBZ through photocatalytic degradation was achieved. Kinetics of CBZ degradation follows a pseudo first-order with the rate constant 0.0367 min^-1. In-vitro and in-vivo toxicity of the nanoparticles were examined promoting the environmental implications.

Synergistic catalysis of BiOIO3 catalyst for elimination of organic pollutants under simultaneous photo-irradiation and ultrasound-vibration treatment

Development of efficiently catalytic strategy for oxidative purification of organic pollutants is of great significance. Photocatalysis has become one of the most important technologies in the past half a century, but the inefficiency of photocatalysts drastically suppresses its practical application. This work proposes a synergistic photopiezocatalysis of BiOIO₃ under simultaneous photo-irradiation and ultrasound-vibration treatment to degrade various organic pollutants. Different from the high recombination of photo-excited charges in photocatalysis, the ultrasound-induced stress deforms the pyroelectric BiOIO₃ to form a piezoelectric potential that drives photo-/thermo-generated free electrons and holes in catalyst to diffuse along opposite directions. In comparison with the single photocatalysis and piezocatalysis, the photopiezocatalysis possesses a synergistic effect, presenting evidently enhanced catalytic performance for decomposing a variety of organic dyes and a persistent organic pollutant 2,4-DCP. No apparent decrease in activity during successive five runs demonstrates that the photopiezocatalysis of BiOIO₃ has a high stability and reusability. Finally, a plausible photopiezocatalysis mechanism is proposed based on the determination of active species produced on catalyst and intermediates during pollutant degradation. Our findings provide a new insight to promote charge separation and meanwhile develop an efficient synergistic photopiezocatalysis for environment remediation.

Carbon nitride-based photocatalysts for the mitigation of water pollution engendered by pharmaceutical compounds

In recent decades, the destructive impact of active pharmaceutical ingredients (API) present in surface and drinking water on aquatic and terrestrial life forms becomes a major concern of researchers. API like diclofenac (DCF), carbamazepine (CBZ), tetracycline (TC), and sulfamethoxazole (SME) found in water bodies cause antimicrobial resistance and are potent carcinogens and endocrine disruptors. Conventional wastewater treatment methods possess some drawbacks and were found to be insufficient for the effective removal of APIs. Visible light-assisted semiconductor photocatalysis has become an alternative choice for tackling this worse scenario. Graphitic carbon nitride, a metal-free visible light active semiconductor photocatalyst is an emerging hotspot nanomaterial whose practical utility in water purification is widely recognized. This review comes up with an insightful outlook on the panorama of recent progress in the field of g-C₃N₄-assisted photocatalytic systems for the eradication of APIs. In addition, the review summarizes various strategies adopted for the broad-spectrum utilization of visible light and the enhancement of charge separation of pristine g-C₃N₄. The mechanistic pathways followed by different pharmaceuticals during their photocatalytic degradation process were also briefly discussed.