Novel insights into the properties of AgBiO3 photocatalyst and its application in immobilized state for 4-nitrophenol degradation and bacteria inactivation

Construction of TiO2/CuPc Heterojunctions for the Efficient Photocatalytic Reduction of CO2 with Water

Utilizing solar energy for photocatalytic CO2 reduction is an attractive research field because of its convenience, safety, and practicality. The selection of an appropriate photocatalyst is the key to achieve efficient CO2 reduction. Herein, we report the synthesis of TiO2/CuPc heterojunctions by compositing CuPc with TiO2 microspheres via a hydroxyl-induced self-assembly process. The experimental investigations demonstrated that the optimal TiO2/0.5CuPc photocatalyst exhibited a significantly enhanced CO2 photoreduction rate up to 32.4 μmol·g-1·h-1 under 300 W xenon lamp irradiation, which was 3.7 times that of the TiO2 microspheres alone. The results of photoelectrochemical experiments indicated that the construction of the heterojunctions by introducing CuPc effectively promoted the separation and transport of photogenerated carriers, thus enhancing the catalytic effect of the photocatalyst.

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

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

Design of TiO2/Ag3BiO3 n-n heterojunction for enhanced degradation of tetracycline hydrochloride under visible-light irradiation

Pharmaceutical residual contaminants in aquatic ecosystems have caused severe risks to human health. Affordable, eco-friendly and effective photocatalysts to deal with these pollutants has become a hot topic in the scientific community. In this research, Ag₃BiO₃ nanoparticles were embedded on TiO₂ to form n-n heterojunction through a facile hydrothermal method. According to scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR), brunauer emmett teller (BET), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), photoluminescence (PL), X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS) tests, the successful construction of TiO₂/Ag₃BiO₃ heterojunction is proved. TiO₂/Ag₃BiO₃ heterojunctions were employed as photocatalysts to remove tetracycline hydrochloride (TCH) under visible light irradiation in aqueous solution. Optimum TCH photodegradation efficiency was observed for TiO₂/Ag₃BiO₃ (10%), 15.4 times superior to that of TiO₂. The enhanced TCH photodegradation efficiency of TiO₂/Ag₃BiO₃ results from improved light absorption capacity and the reduction of recombination of photogenerated charge carriers via generation of n-n heterojunctions. The mechanism of increasing the photodegradation efficiency of TCH was determined by employing reactive species quenching experiments. TiO₂/Ag₃BiO₃ (10%) also exhibited an acceptable stability.

Er3+/Sm3+ co-doped Bi2O2CO3 in photocatalytic water treatment: Immobilization, acute toxicity, sterilization, and catalytic oxidation activity

Defect construction and rare earth doping are the linchpins to completing the target of partial electronic regulation. In Er³⁺/Sm³⁺ co-doping Bi₂O₂CO₃, rare earth doping resulted in the exposure of {001} crystal plane in Bi₂O₂CO₃ and cause surface defects and electron traps, achieving wide light response capability and fast carrier separation. Furthermore, a potential TC degradation route was acknowledged derived from LC-MS. Then, the median lethal concentration LC50 (96 h) is 80 ppm, probing the 2E2SBOC photocatalyst has low toxicity in actual wastewater. Combining with immobilization technology, not only does it have little impact on the organisms in the wastewater, but it is easy to recycle after degradation. In terms of new water disinfection technology, bacterial experiments in natural waters proved that 2E2SBOC has a potential disinfection system, which promotes the exposure of more active sites during degradation. This effective project offers a novel perspective for the development and application of rare-earth-doped photocatalysts.

Preparation, Characterization, and Photocatalytic Performance of Ag/BiOBr0.85I0.15 Nanocomposites

In the present paper, a series of Ag/BiOBr_0.85I_0.15 composite nanoparticles with different silver loading were prepared by a combined solvothermal and photocatalytic reduction method. The composite samples have been characterized by XRD, XPS, SEM, EDX, TEM, UV-Vis, and N₂ adsorption/desorption techniques. The characterization results showed that BiOBr_0.85I_0.15 composite nanoparticles have a tetragonal phase structure. Silver nanoparticles are uniformly distributed on the BiOBr_0.85I_0.15, which results in surface plasmon resonance absorption, effectively increasing the visible light absorption ability of BiOBr_0.85I_0.15. The photocatalytic activity of the samples was evaluated by photocatalytic degradation of ammonia nitrogen in circulating aquaculture water under simulated sunlight irradiation. The effect of the Ag loading amount on the photocatalytic degradation of ammonia nitrogen was investigated. Silver loading of 1% (molar ratio) can effectively improve the degradation capacity of the catalyst for ammonia nitrogen in water. The recycling experiments show that 1%Ag/BiOBr_0.85I_0.15 has good photocatalytic stability. ESR characterization and oxidation species scavenging experimental results suggest that h⁺, ¹O₂, and ·O_2^- are the main oxidizing species in the photocatalytic system.

Application of perovskite oxides and their composites for degrading organic pollutants from wastewater using advanced oxidation processes: Review of the recent progress

In the recent years, perovskite oxides are gaining an increasing amount of attention owing to their unique traits such as tunable electronic structures, flexible composition, and eco-friendly properties. In contrast, their catalytic performance is not satisfactory, which hinders real wastewater remediation. To overcome this shortcoming, various strategies are developed to design new perovskite oxide-based materials to enhance their catalytic activities in advanced oxidation process (AOPs). This review article is to provide overview of basic principle and different methods of AOPs, while the strategies to design novel perovskite oxide-based composites for enhancing the catalytic activities in AOPs have been highlighted. Moreover, the recent progress of their synthesis and applications in wastewater remediation (pertaining to the period 2016-2022) was described, and the related mechanisms were thoroughly discussed. This review article helps scientists to have a clear outlook on the selection and design of new effective perovskite oxide-based materials for the application of AOPs. At the end of the review, perspective on the challenges and future research directions are discussed.

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

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

Hierarchical porous zeolitic imidazolate frameworks (ZIF-8) and ZnO@N-doped carbon for selective adsorption and photocatalytic degradation of organic pollutants

Removing organic contaminants such as dyes from water is essential to purify wastewater. Herein, zeolitic imidazolate framework-8 (ZIF-8) and ZnO@N-doped C are reported as effective adsorbents and photocatalysts for the adsorption and degradation of organic dyes. The materials showed effective and selective adsorption toward anionic dyes such as methyl blue (MeB) dye in the presence of fluorescein (FLU) dye. The adsorption capacities of ZnO@N-doped C for MeB and FLU dyes are 900 mg g⁻¹ and 100 mg g⁻¹, respectively. According to UV-Vis diffuse reflectance spectroscopy (DRS) data, ZnO@N-doped C has a lower bandgap (2.07 eV) than ZIF-8 (4.34 eV) and ZnO (3.12 eV). Thus, ZnO@N-doped C serves as an effective photocatalyst for the degradation of both dyes under UV exposure. The degradation efficiency capacity of the dye (50 mg L⁻¹) is >90% using 200 mg L⁻¹ of the photocatalyst. The mechanism of adsorption and photocatalysis is investigated. The photodegradation pathway of the dye involved the generation of oxidative hydroxy radicals (OH˙), which can degrade the dyes. The degradation products of FLU were recorded using mass spectrometry.

Removing organic contaminants such as dyes from water is essential to purify wastewater.

Gold-silver nanoparticles modified electrochemical sensor array for simultaneous determination of chromium(III) and chromium(VI) in wastewater samples

The oxidation state of ions is a crucial aspect that often has been overlooked when determining the toxicity of chromium (Cr) species in environmental samples. In this study, a novel electrochemical sensor array based on gold-silver nanoparticles modified electrodes was developed for simultaneous determination of the two main chromium species (Cr(III) and (VI)). Specifically, the working electrodes of screen-printed carbon electrodes (SPCEs) were modified with silver-gold bimetallic nanoparticles through electrochemical deposition for detection of Cr(VI). The silver-gold bimetallic nanoparticles were further oxidized to form stable silver-gold bimetallic oxide nanoparticles for the detection of Cr(III). The results showed that the addition of silver with a theoretical value of 1% of gold could contribute to the formation and stabilization of oxides on the surface of gold nanoparticles. After characterization, the two kinds of electrodes were integrated as an electrochemical sensor array for selective and sensitive detection of Cr(VI) and Cr(III). The linear range and limit of detection (LOD, identified by three times of signal-to-noise ratio) were found to be 0.05-5 ppm and 0.1 ppb for Cr(VI), and 0.05-1 ppm and 0.1 ppb for Cr(III), respectively. Finally, the electrochemical sensor array was proven for successful detection of Cr(VI) and Cr(III) in tap water, artificial saliva and artificial sweat samples, and monitoring of Cr(VI) and Cr(III) in chromium-containing wastewater treatment process. Combined with a handheld dual-channel electrochemical device, the simultaneous determination of Cr(VI), Cr(III) and total chromium contents can be easily achieved for various samples.

A review of bismuth-based photocatalysts for antibiotic degradation: Insight into the photocatalytic degradation performance, pathways and relevant mechanisms

The intensive production and utilization of antibiotics worldwide has inevitably led to releases of very large amounts of these medicines into the environment, and numerous strategies have recently been developed to eliminate antibiotic pollution. Therefore, bismuth-based photocatalysts have attracted much attention due to their high adsorption of visible light and low production cost. This review summarizes the performance, degradation pathways and relevant mechanisms of typical antibiotics during bismuth-based photocatalytic degradation. First, the band gap and redox ability of the bismuth-based catalysts and modified materials (such as morphology, structure mediation, heterojunction construction and element doping) were compared and evaluated. Second, the performance and potential mechanisms of bismuth oxides, bismuth sulfides, bismuth oxyhalides and bismuth-based metal oxides for antibiotic removal were investigated. Third, we analysed the effect of co-existing interfering substances in a real water matrix on the photocatalytic ability, as well as the coupling processes for degradation enhancement. In the last section, current difficulties and future perspectives on photocatalytic degradation for antibiotic elimination by bismuth-based catalysts are summarized. Generally, modified bismuth-based compounds showed better performance than single-component photocatalysts during photocatalytic degradation for most antibiotics, in which h⁺ played a predominant role among all the related reactive oxygen species. Moreover, the crystal structures and morphologies of bismuth-based catalysts seriously affected their practical efficiencies.

Influence of Ag nanoparticles anchored on protonated g-C3N4-Bi2MoO6 nanocomposites for effective antibiotic and organic pollutant degradation

The development of noble metal-anchored semiconductors for photocatalytic processes is now garnering interest for potential application to toxic pollutants as well as antibiotic degradation. Herein, we report novel Ag@p-g-C₃N₄-Bi₂MoO₆ nanocomposites synthesized by facile hydrothermal and calcination methods with a size of about 50 nm, exhibiting superior photocatalytic activity for charge separation. The resulting nanocomposites were evaluated by various physiochemical techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The charge transfer photogenerated carriers were confirmed by photoluminescence spectra and electrochemical impedance spectroscopy. The anchoring of Ag nanoparticles over p-g-C₃N₄/Bi₂MoO₆ decreased the band gap energy from 2.67 to 2.48 eV, to exhibit an abnormal increase in absorption of light towards the visible light region. The degradation performance of the nanocomposites in terms of antibiotic ciprofloxacin and rhodamine B degradation efficiency was measured 85 and 99.7% respectively. The superoxide radical anion ˙O₂ ^- played a significant role throughout the entire degradation process. Focusing on the probable mechanism based on the desirable results, the present work follows the heterostructure mechanism. Moreover, this work features the feasible applications of Ag@p-g-C₃N₄-Bi₂MoO₆ as a modified photocatalyst in the treatment of both domestic and industrial waste water.

Plasmonic nano-antimicrobials: properties, mechanisms and applications in microbe inactivation and sensing

Bacterial, viral and fungal infections pose serious threats to human health and well-being. The continuous emergence of acute infectious diseases caused by pathogenic microbes and the rapid development of resistances against conventional antimicrobial drugs necessitates the development of new and effective strategies for the safe elimination of microbes in water, food or on surfaces, as well as for the inactivation of pathogenic microbes in human hosts. The need for new antimicrobials has triggered the development of plasmonic nano-antimicrobials that facilitate both light-dependent and -independent microbe inactivation mechanisms. This review introduces the relevant photophysical mechanisms underlying these plasmonic nano-antimicrobials, and provides an overview of how the photoresponses and materials properties of plasmonic nanostructures can be applied in microbial pathogen inactivation and sensing applications. Through a systematic analysis of the inactivation efficacies of different plasmonic nanostructures, this review outlines the current state-of-the-art in plasmonic nano-antimicrobials and defines the application space for different microbial inactivation strategies. The advantageous optical properties of plasmonic nano-antimicrobials also enhance microbial detection and sensing modalities and thus help to avoid exposure to microbial pathogens. Sensitive and fast plasmonic microbial sensing modalities and their theranostic and targeted therapeutic applications are discussed.

Tetracycline catalytic photodegradation with mesoporous phosphated TiO2: characterization, process optimization and degradation pathway

Concern about the effect of tetracycline (TC) on the ecosystem has been increasing due to its endurance and low decomposition. Photocatalysts have attracted extensive interest as alternatives to other ordinary wastewater treatment methods. A nanosized mesoporous phosphated TiO₂ (P-TiO₂) photocatalyst was fabricated to degrade TC under Xe lamp irradiation. The TC degradation and COD removal rate reached 98.97% and 79.16% within 30 min. Photocatalysts were characterized by SEM, HRTEM, BET, DRS, XRD, XPS and FT-IR techniques. 31 experiments were designed to identify the best conditions for photocatalytic degradation of TC by response surface methodology (RSM) based on a central composite design (CCD). 6 key operating parameters were selected to study their interrelationships by CCD design. Based on the experimental data and ANOVA, the coefficient of determination (R²), the values of “Prob > F” and F-value were determined to be 0.9692, 0.002 and 7.87, respectively, which demonstrated that the model is significant. And the excellent correlation between the predicted and actual values also provided good confidence in the model. To achieve a higher removal rate of TC under appropriate and more economical experimental conditions, the optimum values of P-loading on TiO₂, concentration of P-TiO₂, irradiation time, photo intensity, pH and concentration of TC should be set to 17.45 wt%, 1.00 g L⁻¹, 40.39 min, 5 A, 7, 29.93 mg L⁻¹, respectively, in which the degradation of TC can reach 99.16%. Furthermore, the intermediates of TC verified by GC-MS analysis were mainly chains and rings. A possible pathway of photodegradation was also proposed.

The prepared P-TiO₂ has a perfect degradation effect on TC (99.16%) due to the loading of phosphate. The impact of multiple factors and the best degradation conditions were obtained by RSM. The possible degradation pathways of TC were proposed also.

'Template-free' hierarchical MoS2 foam as a sustainable 'green' scavenger of heavy metals and bacteria in point of use water purification

Molybdenum disulfide (MoS₂), with its unique optical and electrical properties, has been explored for a variety of applications in the recent past. Still, its capabilities in point-of-use heavy metal ion removal remain to be explored. Herein, for the first time using a facile approach, we fabricated three-dimensional (3D) MoS₂ foam from exfoliated single to few-layered MoS₂ sheets for the selective exclusion of heavy metals and stringent bactericidal response. This foam was able to exclude 99.9% of Pb(ii) and 98.7% of As(iii) instantaneously and reduced more than 98% of bacteria E. coli. Moreover, the foam exhibits selective toxicity towards bacterial cells while showing no observable toxicity towards mammalian cells. The foam can be recycled and reused for at least five cycles under accelerated conditions and thus can be used for a promising non-cytotoxic, facile, and environmentally benign process for inline water remediation to remove heavy metal ions from the feed and as a potential antibacterial agent.

Fabrication of a magnetic ternary ZnFe2O4/TiO2/RGO Z-scheme system with efficient photocatalytic activity and easy recyclability

A magnetic composite based on TiO2 nanosheets, ZnFe2O4 and reduced graphene oxide (RGO) was synthesized by a one-step hydrothermal synthesis method, which possessed the band structure of a Z-scheme photocatalytic system. The properties and structures of the samples were characterized by XRD, UV-Vis DRS, Raman spectroscopy, SEM, EDS, XPS and PL spectroscopy. Compared with TiO2 nanosheets and the TiO2/RGO composite, the obtained ternary composite with 3 wt% RGO exhibited a significant enhancement in photocatalytic activities, attributed to the efficient charge separation induced by the fabricated Z-scheme system. About 99.7% of p-nitrophenol (p-NP) degraded within 60 min under simulated solar irradiation. Trapping experiments showed that superoxide anions (˙O2 -) and hydroxyl radicals (˙OH) were the main active species in the p-NP photocatalytic degradation. Finally, a possible photocatalytic mechanism of Z-scheme ZnFe2O4/TiO2/RGO was proposed based on the results of trapping experiments and the energy bands of TiO2 and ZnFe2O4.

A Z-scheme ZnIn2S4/Nb2O5 nanocomposite: constructed and used as an efficient bifunctional photocatalyst for H2 evolution and oxidation of 5-hydroxymethylfurfural

A bifunctional Z-scheme ZnIn₂S₄/Nb₂O₅ photocatalyst was fabricated, which can be used both for hydrogen evolution and HMF oxidation.

Enhanced photocatalysis and bacterial inhibition in Nb2O5 via versatile doping with metals (Sr, Y, Zr, and Ag): a critical assessment

Unique optical properties render semiconductor Nb₂O₅ nanoparticles suitable for light harvesting and photocatalytic applications. This study focuses on determining optical properties such as the band gap, conduction band edge, valence band edge and work function of as-prepared solution combustion synthesized Nb₂O₅ nanoparticles with the help of UV-vis Diffuse Reflectance spectroscopy (DRS) and ultraviolet photoelectron spectroscopy (UPS) techniques. Phase purity and the oxidation states of the elements present in the material were confirmed from X-ray diffraction (XRD) patterns and X-ray photoelectron spectra (XPS), respectively. Doping semiconductors with different metal ions impacts the activity of the material, and therefore efforts were made to understand the effect on the photocatalytic performance of Nb₂O₅ due to the incorporation of metal dopants viz. Sr, Y, Zr, and Ag. Lattice parameters were obtained from Rietveld refinement of the XRD patterns. Parameters which are closely related to the photoactivity of the catalysts such as the presence of surface defects, oxygen vacancies, surface area, and charge carrier dynamics were determined from photoluminescence (PL) analysis, Brunauer-Emmett-Teller (BET) surface area measurements and time-resolved fluorescence (TRF) analysis respectively. In addition, the dopant concentrations were optimised for enhanced photocatalytic activity. The doped Nb₂O₅ nanoparticles showed significant activity towards targeted degradation of organic pollutants like 2-chlorophenol (2-CP) and dye contaminants like methylene blue (MB), orange G (OG) and indigo carmine (IC). This strategy yielded a robust response towards inactivation of E. coli and S. aureus as well. Adsorption and photodegradation of MB followed Lagergren's pseudo 1^st order reaction model and the Langmuir Hinshelwood model respectively. Bacterial inactivation and OG, IC and 2-CP photodegradation followed 1^st order kinetics. The reusability of the catalyst for 5 cycles was demonstrated. Finally, a plausible mechanism is proposed based on radical trapping experiments and combined analysis of the characterization techniques.