Sequentially photocatalytic degradation of mussel-inspired polydopamine: From nanoscale disassembly to effective mineralization

Mussel-inspired polydopamine (PDA) coating has been utilized extensively as versatile deposition strategies that can functionalize surfaces of virtually all substrates. However, the strong adhesion, stability and intermolecular interaction of PDA make it inefficient in certain applications. Herein, a green and efficient photocatalytic method was reported to remove adhesion and degrade PDA by using TiO2-H2O2 as photocatalyst. The photodegradation process of the PDA spheres was first undergone nanoscale disassembly to form soluble PDA oligomers or well-dispersed nanoparticles. Most of the disassembled PDA can be photodegraded and finally mineralized to CO2 and H2O. Various PDA coated templates and PDA hollow structures can be photodegraded by this strategy. Such process provides a practical strategy for constructing the patterned and gradient surfaces by the "top-down" method under the control of light scope and intensity. This sequential degradation strategy is beneficial to achieve the decomposition of highly crosslinked polymers.

From Plastic Waste to Green Hydrogen and Valuable Chemicals Using Sunlight and Water

Over 79 % of 6.3 billion tonnes of plastics produced from 1950 to 2015 have been disposed in landfills or found their way to the oceans, where they will reside for up to hundreds of years before being decomposed bringing upon significant dangers to our health and ecosystems. Plastic photoreforming offers an appealing alternative by using solar energy and water to transform plastic waste into value-added chemical commodities, while simultaneously producing green hydrogen via the hydrogen evolution reaction. This review aims to provide an overview of the underlying principles of emerging plastic photoreforming technologies, highlight the challenges associated with experimental protocols and performance assessments, discuss recent global breakthroughs on the photoreforming of plastics, and propose perspectives for future research. A critical assessment of current plastic photoreforming studies shows a lack of standardised conditions, hindering comparison amongst photocatalyst performance. Guidelines to establish a more accurate evaluation of materials and systems are proposed, with the aim to facilitate the translation of promising fundamental discovery in photocatalysts design.

A g-C3N4/rGO/Cs3Bi2Br9 mediated Z-scheme heterojunction for enhanced photocatalytic CO2 reduction

Photocatalytic CO2 reduction plays a crucial role in advancing solar fuels, and enhancing the efficiency of the chosen photocatalysts is essential for sustainable energy production. This study demonstrates advancements in the performance of g-C3N4 as a photocatalyst achieved through surface modifications such as exfoliation to increase surface area and surface oxidation for improved charge separation. We also introduce reduced graphene oxide (rGO) in various ratios to both bulk and exfoliated g-C3N4, which effectively mitigates charge recombination and establishes an optimal ratio for enhanced efficiency. g-C3N4/rGO serves to fabricate a hybrid organic/inorganic heterojunction with Cs3Bi2Br9, resulting in a g-C3N4/rGO/Cs3Bi2Br9 composite. This leads to a remarkable increase in photocatalytic conversion of CO2 and H2O to CO, H2 and CH4 at rates of 54.3 (±2.0) μmole- g-1 h-1, surpassing that of pure Cs3Bi2Br9 (11.2 ± 0.4 μmole- g-1 h-1) and bulk g-C3N4 (5.5 ± 0.5 μmole- g-1 h-1). The experimentally determined energy diagram indicates that rGO acts as a solid redox mediator between g-C3N4 and Cs3Bi2Br9 in a Z-scheme heterojunction configuration, ensuring that the semiconductor (Cs3Bi2Br9) with the shallowest conduction band drives the reduction and the one with the deepest valence band (g-C3N4) drives the oxidation. The successful formation of this high-performance heterojunction underscores the potential of the developed composite as a photocatalyst for CO2 reduction, offering promising prospects for advancing the field of solar fuels and achieving sustainable energy goals.

Tailoring ZnS nanostructures through precipitation-cum-hydrothermal synthesis for enhanced wastewater purification and antibacterial treatment

This study presents a novel blend of synthesis techniques for shape-controlled ZnS nanoparticles. Zinc sulfide (ZnS) nanoparticles with distinct morphologies cauliflower-like microstructures (∼4.5 μm) and uniform nanospheres (200-700 nm) were synthesized through an innovative blend of precipitation and hydrothermal techniques. Capping with polyvinylpyrrolidone (PVP) significantly decreased crystallite size (3.93 nm-2.36 nm), modulated the band gap (3.57 eV-3.71 eV), and dramatically influenced morphology, highlighting the novelty of shape-controlled synthesis and its impact on optoelectronic and functional properties. X-ray diffraction confirmed crystallinity and revealed the size-controlling influence of PVP. UV-vis spectroscopy suggested potential tuning of optical properties due to band gap widening upon PVP capping. Field-emission scanning electron microscopy (FESEM) unveiled distinct morphologies: cauliflower-like microstructures for ZnS and uniform nanospheres (200-700 nm) for PVP-ZnS. Both structures were composed of smaller spherical nanoparticles, demonstrating the role of PVP in promoting controlled growth and preventing agglomeration. High-resolution transmission electron microscope (HRTEM) images depicted that the majority of nanoparticles maintain a spherical shape, though slight deviations from perfect sphericity can be discerned. Fourier-transform infrared (FTIR) spectroscopy confirmed that successful PVP encapsulation is crucial for shaping nanospheres and minimizing aggregation through steric hindrance. Photocatalytic activity evaluation using methylene blue (MB) dye degradation revealed significantly faster degradation by PVP-ZnS under ultraviolet (UV) irradiation (within 60 min as compared to 120 min for ZnS), showcasing its superior performance. This improvement can be attributed to the smaller size, higher surface area, and potentially optimized band gap of PVP-ZnS. Additionally, PVP-ZnS exhibited promising antibacterial activity against S. aureus and P. aeruginosa, with increased activity at higher nanoparticle concentrations.

Direct Z-scheme system of UiO-66 cubes wrapped with Zn0.5Cd0.5S nanoparticles for photocatalytic hydrogen generation synchronized with organic pollutant degradation

Optimized fabrication of Z-scheme photocatalyst based on MOF materials offers sustainable energy generation and environmental improvement due to their attractive properties. The Z-scheme heterojunctions consisting of UiO-66 cubes covered with Zn0.5Cd0.5S nanoparticles were fabricated by a facile solvothermal method. Thanks to the Z-scheme carrier transport under simulated sunlight irradiation, UiO-66@Zn0.5Cd0.5S exhibited enhanced photocatalytic performance of H2 generation synchronized with organic pollutant degradation in fluoroquinolone antibiotic wastewater. Synergistically, the highest comprehensive performance was obtained in ciprofloxacin solution. The H2 yield reached 224 μmol∙ g-1∙ h-1 and simultaneously the removal efficiency was up to 83.6 %. The degradation pathways revealed that the process of piperazine ring cleavage and decarboxylation also generates H protons, further promoting the production of H2. Therefore, the effective spatial separation and transfer of the photoinduced carriers are attributed to the good band structure, large specific surface area, and cooperative reduction and oxidation reactions of UiO-66@Zn0.5Cd0.5S, resulting in significant photocatalytic activity. The toxicity assessment of antibiotics and intermediate products during the photocatalytic reaction also verifies the reduction of environmental risk. This study highlights a promising way to expand the application of the MOFs-based photocatalyst in clean energy conversion coupling with water remediation.

g-C3N4@CuO electrostatic self-assembly toward Ralstonia solanacearum: Insights from cytomembrane and motility disruption

BACKGROUND

Ralstonia solanacearum, a notorious and refractory bacterial plant pathogen, threatens multiple vegetable crops and causes significant economic loss in agriculture. Long-term use of traditional medicines not only increases the problem of drug resistance, but also causes great environmental pollution. Therefore, there is an urgent need to develop new agents with high efficacy and low toxicity.

RESULTS

In this study, we have synthesized and characterized graphitic carbon nitride incorporated copper oxide composite (g-C3N4@CuO), which showed higher antimicrobial effect than graphitic carbon nitride nanosheets (g-C3N4 nanosheets) and copper oxide nanoparticles (CuONPs). Ralstonia solanacearum exposed to g-C3N4@CuO exhibited higher levels of oxygen toxicity, cell membrane damage, DNA damage, motility disruption and even cell death compared to g-C3N4 nanosheets and CuONPs. In addition, g-C3N4@CuO was more effective in the control of tobacco bacterial wilt than g-C3N4 nanosheets and CuONPs.

CONCLUSION

Thus, this study provides a new perspective on g-C3N4@CuO control of bacterial diseases in crops, and the mechanism is related to the destruction of cell membrane damage and motility disruption. © 2024 Society of Chemical Industry.

In-situ and wavelength-dependent photocatalytic strain evolution of a single Au nanoparticle on a TiO2 film

Photocatalysis is a promising technique due to its capacity to efficiently harvest solar energy and its potential to address the global energy crisis. However, the structure-activity relationships of photocatalyst during wavelength-dependent photocatalytic reactions remains largely unexplored because it is difficult to measure under operating conditions. Here we show the photocatalytic strain evolution of a single Au nanoparticle (AuNP) supported on a TiO2 film by combining three-dimensional (3D) Bragg coherent X-ray diffraction imaging with an external light source. The wavelength-dependent generation of reactive oxygen species (ROS) has significant effects on the structural deformation of the AuNP, leading to its strain evolution. Density functional theory (DFT) calculations are employed to rationalize the induced strain caused by the adsorption of ROS on the AuNP surface. These observations provide insights of how the photocatalytic activity impacts on the structural deformation of AuNP, contributing to the general understanding of the atomic-level catalytic adsorption process.

TiO2-based photocatalysts from type-II to S-scheme heterojunction and their applications

Photocatalysis is a promising sustainable technology to remove organic pollution and convert solar energy into chemical energy. Titanium dioxide has drawn extensive attention in this field owing to its high activity under UV light, good chemical stability, large availability, low price and low toxicity. However, the poor quantum efficiency derived from fast electron/hole recombination, the limited utilization of sunlight, and a weak reducing ability still hinder its practical application. Among the modification strategies of TiO2 to enhance its performance, the construction of heterojunctions with other semiconductors is a powerful and versatile way to maximise the separation of photogenerated charge carriers and steer their transport toward enhanced efficiency and selectivity. Here, the research progress and current status of TiO2 modification are reviewed, focusing on heterojunctions. A rapid evolution of the understanding of the different charge transfer mechanisms is witnessed from traditional type II to the recently conceptualised S-scheme. Particular attention is paid to different synthetic approaches and interface engineering methods designed to improve and control the interfacial charge transfer, and several cases of TiO2 heterostructures with metal oxides, metal sulfides and carbon nitride are discussed. The application hotspots of TiO2-based photocatalysts are summarized, including hydrogen generation by water splitting, solar fuel production by CO2 conversion, and the degradation of organic water pollutants. Hints about less studied and emerging processes are also provided. Finally, the main issues and challenges related to the sustainability and scalability of photocatalytic technologies in view of their commercialization are highlighted, outlining future directions of development.

S-Scheme Boron Phosphide/MoS2 Heterostructure with Excellent Light Conversion Ability for Solar Cells and Water Splitting Photocatalysts

Monolayer molybdenum disulfide (MoS2) with a suitable direct band gap and strong optical absorption is very attractive for utilization in solar cells and photocatalytic water splitting. Nevertheless, the broader utilization of MoS2 is impeded by its low carrier mobility and limited responsiveness to infrared light. To overcome these challenges, we constructed a variety of stackings for the boron phosphide (BP)/MoS2 van der Waals heterostructure (vdWH), all of which display S-scheme band alignments except for the AC' stacking. The constituent BP monolayer has superior carrier mobility and strong infrared and visible light response, which makes up for the shortcomings of MoS2. The study revealed that the AB stacking exhibits a remarkable power conversion efficiency of 22.27%, indicating its significant application prospect in solar cells. Additionally, the AB stacking also exhibits a promising application prospect in photocatalytic water splitting due to its suitable band structure, S-scheme band alignment, strong optical adsorption characteristic, high solar-to-hydrogen efficiency, and robust built-in electric field. Meanwhile, applying uniaxial tensile strains along the x-axis direction is more beneficial for photocatalytic water splitting. Hence, the AB-stacked BP/MoS2 vdWH shows significant potential for use in both solar cells and photocatalytic water splitting. This work paves the way for exploring the application of S-scheme heterostructures in solar energy conversion systems.

Commonly Existing Hole-Capturer Organics Adsorption-Induced Recombination over Metal/Semiconductor Perimeters: A Possible Important Factor Affecting Photocatalytic Efficiencies

Photocatalysis is a physiochemical effect arising from the relaxation of photoinduced electrons from the conduction band to the valence band. Controlling the electron relaxation to occur through photocatalytic pathways and prohibiting other relaxations is the main scientific thought for photocatalytic studies. It is needed to know the parallel relaxation pathways that can compete with photocatalytic reactions. By means of in situ photoconductances (PCs) and photoinduced absorptions (PAs), the current research studied the photoinduced electron relaxations of the Au/TiO2 in different atmospheres and at different temperatures. The PC and PA relaxations became different and fast when methanol, ethanol, isopropanol, and acetone were introduced; they also tend to decrease as temperature increases, while that of the undecorated TiO2 in all atmospheres and the Au/TiO2 in pure N2 increased. The results indicated that the organic adsorptions over the Au/TO2 perimeters change the relaxation pathway, and a hole-capturing organics adsorption-induced recombination over the Au/TiO2 perimeter was proposed to explain the relaxations. We found that this relaxation also exists for Ag/TiO2, Pt/TiO2, and Au/ZnO, so it is a commonly existing physical course for the metal/semiconductor (M/S) materials. The effect of the organics and M/S structures on the relaxation was discussed, and the relationship with photocatalytic reactions was also analyzed. Our finding means that blocking this relaxation pathway is an effective way to increase photocatalytic activities, which might open a door for highly active photocatalyst developments.

The enhanced photocatalytic performance of CPAA doping with different concentrations of Titanium oxide nanocomposite against MB dyes under simulated sunlight irradiations

The pure conjugated polyarylene azomethine (CPAA) and its nanocomposites (CPAA-TiO2) with different concentrations of TiO2 nanoparticles were successfully prepared by in-situ technique and analyzed by different advanced techniques. XRD has confirmed the structural properties and crystallinity of (CPAA) and nanocomposites. The SEM clearly shows that the (CPAA) is uniform and homogeneous, with tightly connected aggregate layers in shape. However, the amount of TiO2 in the nanocomposites greatly affects their morphology, revealing structural differences and indicating a reaction between (CPAA) and TiO2, especially at a higher concentration of 5% TiO2. A new composite of (CPAA) was introduced and the photocatalytic effect for MB was studied. The removal efficiency of (pure-CPAA) over MB dye under simulated sunlight was 62%. However, (CPAA-TiO2 1%) destroyed 90% of MB dyes. It was discovered that the low band gap of (CPAA-TiO2 1% (2.84 eV)) accelerates high electron-hole recombination, increasing photocatalytic activity.

The Zn Vacancy-Mediated De-Accumulation Based Process for Hydrogen Production Performance Promotion of 1D Zn─Cd─S Nanorods

Due to their anisotropy, 1D semiconductor nanorod-based materials have attracted much attention in the process of hydrogen production by solar energy. Nevertheless, the rational design of 1D heterojunction materials and the modulation of photo-generated electron-hole transfer paths remain a challenge. Herein, a ZnxCd1-xS@ZnS/MoS2 core-shell nanorod heterojunction is precisely constructed via in situ growth of discontinuous ZnS shell and MoS2 NCs on the Zn─Cd─S nanorods. Among them, the Zn vacancy in the ZnS shell builds the defect level, and the nanoroelded MoS2 builds the electron transport site. The optimized photocatalyst shows significant photocatalytic activity without Platinum as an auxiliary catalyst, mainly due to the new interfacial charge transfer channel constructed by the shell vacancy level, the vertical separation and the de-accumulation process of photo-generated electrons and photo-generated holes. At the same time, spectral analysis, and density functional theory (DFT) calculations fully prove that shortening difference of speed between the photogenerated electron and hole movement process is another key factor to enhance the photocatalytic performance. This study provides a new path for the kinetic design of enhanced carrier density by shortening the carrier retention time of 1D heterojunction photocatalysts with improved photocatalytic performance.

Interactive impacts of photoaged micro(nano)plastics and co-occurring chemicals in the environment

In the environment, sunlight or ultraviolet (UV) radiation is considered to be the primary cause of plastic aging, leading to their fragmentation into particles, including micro(nano)plastics (MNPs). Photoaged MNPs possess diverse interactive properties and ecotoxicological implications substantially different from those of pristine plastic particles. This review aims to highlight the mechanisms and implications of UV-induced photoaging of MNPs, with an emphasis on various UV sources and their interactions with co-occurring organic and inorganic chemicals, as well as the associated ecological and health impacts and factors affecting those interactions. Compared to UV-B, UV-A and UV-C were more widely used in laboratory studies for MNP degradation. Photoaged MNPs act as vectors for the transportation of organic pollutants, organic matter, and inorganic chemicals in the environment. Literature showed that photoaged MNPs exhibit a higher sorption capacity for PPCPs, PAHs, PBDEs, pesticides, humic acid, fulvic acid, heavy metals, and metallic nanoparticles than pristine MNPs, potentially causing significant changes in associated ecological and health impacts. Combined exposure to photoaged MNPs and organic and inorganic pollutants significantly altered mortality rate, decreased growth rate, histological alterations, neurological impairments, reproductive toxicity, induced oxidative stress, thyroid disruption, hepatotoxicity, and genotoxicity in vivo, both in aquatic and terrestrial organisms. Limited studies were reported in vitro and found decreased cellular growth and survival, induced oxidative stress, and compromised the permeability and integrity of the cell membrane. In addition, several environmental factors (temperature, organic matter, ionic strength, time, and pH), MNP properties (polymer types, sizes, surface area, shapes, colour, and concentration), and chemical properties (pollutant type, concentration, and physiochemical properties) can influence the photoaging of MNPs and associated impacts. Lastly, the research gaps and prospects of MNP photoaging and associated implications were also summarized. Future research should focus on the photoaging of MNPs under environmentally relevant conditions, exploiting the polydisperse characteristics of environmental plastics, to make this process more realistic for mitigating plastic pollution.

Non-Enzymatic Glucose Sensors Composed of Polyaniline Nanofibers with High Electrochemical Performance

The measurement of glucose concentration is a fundamental daily care for diabetes patients, and therefore, its detection with accuracy is of prime importance in the field of health care. In this study, the fabrication of an electrochemical sensor for glucose sensing was successfully designed. The electrode material was fabricated using polyaniline and systematically characterized using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and UV-visible spectroscopy. The polyaniline nanofiber-modified electrode showed excellent detection ability for glucose with a linear range of 10 μM to 1 mM and a detection limit of 10.6 μM. The stability of the same electrode was tested for 7 days. The electrode shows high sensitivity for glucose detection in the presence of interferences. The polyaniline-modified electrode does not affect the presence of interferences and has a low detection limit. It is also cost-effective and does not require complex sample preparation steps. This makes it a potential tool for glucose detection in pharmacy and medical diagnostics.

Unveiling Dynamic Structure and Bond Evolutions in BiOIO3 Photocatalysts during CO2 Reduction

We have established a correlation between photocatalytic activity and dynamic structure/bond evolutions of BiOIO3-based photocatalysts during CO2 reduction by combining operando X-ray diffraction with photoelectron spectroscopy. More specifically, the selective photo-deposition of PtOx species on BiOIO3 (010) facets could effectively promote the electron enrichment on Bi active sites of (100) facets for facilitating the adsorption/activation of CO2 molecules, leading to the formation of Bi sites with high oxidation state and the shrink of crystalline structures. With introducing light irradiation to drive CO2 reduction, the Bi active sites with high oxidation states transformed into normal Bi3+ state, accompanying with the expansion of crystalline structures. Owing to the dynamic structure, bond, and chemical-state evolutions, a significant improvement of photocatalytic activity for CO evolution has been achieved on PtOx-BiOIO3 (195.0 μmol g-1 ⋅ h-1), much higher than the pristine (61.9 μmol g-1 ⋅ h-1) as well as metal-Pt decorated BiOIO3 (70.3 μmol g-1 ⋅ h-1) samples. This work provides new insights to correlate the intrinsically dynamic structure/bond evolutions with CO2 reduction activity, which may help to guide future photocatalyst design.

Charge Transport Approaches in Photocatalytic Supramolecular Systems Composing of Semiconductor and Molecular Metal Complex for CO2 Reduction

The design of photocatalytic supramolecular systems composing of semiconductors and molecular metal complexes for CO2 reduction has attracted increasing attention. The supramolecular system combines the structural merits of semiconductors and metal complexes, where the semiconductor harvests light and undertakes the oxidative site, while the metal complex provides activity for CO2 reduction. The intermolecular charge transfer plays crucial role in ensuring photocatalytic performance. Here, we review the progress of photocatalytic supramolecular systems in reduction of CO2 and highlight the interfacial charge transfer pathways, as well as their state-of-the-art characterization methods. The remaining challenges and prospects for further design of supramolecular photocatalysts are also presented.

Enhanced photocatalytic degradation of Rhodamine B using gold nanoparticles decorated on BaTiO3 with surface plasmon resonance enhancement

This study focused on synthesizing and applying gold nanoparticle (Au NP) decorated barium titanate (BaTiO3) nanoparticles for photocatalytic purposes. BaTiO3 NPs were synthesized using a facile hydrothermal method. Various techniques were employed to characterize the structure and morphological characteristics of the prepared materials. The photocatalytic degradation of Rhodamine B over the Au NPs-modified BaTiO3 photocatalysts was studied. Trapping experiments were conducted using different scavengers to elucidate the degradation mechanism and the involvement of photogenerated species. The incorporation of an appropriate amount of Au NPs into the composites resulted in a significant improvement in photocatalytic activity, attributed to the combined effect of Schottky junction at the interface and the surface plasmon resonance of Au NPs.

Nanostructurally Engineering Covalent Organic Frameworks for Boosting CO2 Photoreduction

Herein, a series of imine-linked covalent organic frameworks (COFs) are developed with advanced ordered mesoporous hollow spherical nanomorphology and ultra-large mesopores (4.6 nm in size), named OMHS-COF-M (M = H, Co, and Ni). The ordered mesoporous hollow spherical nanomorphology is revealed to be formed via an Ostwald ripening mechanism based on a one-step self-templated strategy. Encouraged by its unique structural features and outstanding photoelectrical property, the OMHS-COF-Co material is applied as the photocatalyst for CO2-to-CO reduction. Remarkably, it delivers an impressive CO production rate as high as 15 874 µmol g-1 h-1, a large selectivity of 92.4%, and a preeminent cycling stability. From in/ex situ experiments and density functional theory (DFT) calculations, the excellent CO2 photoreduction performance is ascribed to the desirable cooperation of unique ordered mesoporous hollow spherical host and abundant isolated Co active sites, enhancing CO2 activation, and improving electron transfer kinetics as well as reducing the energy barriers for intermediates *COOH generation and CO desorption.

Metal-organic framework heterojunctions for photocatalysis

Heterojunctions combining two photocatalysts of staggered conduction and valence band energy levels can increase the photocatalytic efficiency compared to their individual components. This activity enhancement is due to the minimization of undesirable charge recombination by the occurrence of carrier migration through the heterojunction interface with separated electrons and holes on the reducing and oxidizing junction component, respectively. Metal-organic frameworks (MOFs) are currently among the most researched photocatalysts due to their tunable light absorption, facile charge separation, large surface area and porosity. The present review summarizes the current state-of-the-art in MOF-based heterojunctions, providing critical comments on the construction of these heterostructures. Besides including examples showing the better performance of MOF heterojunctions for three important photocatalytic processes, such as hydrogen evolution reaction, CO2 photoreduction and dye decolorization, the focus of this review is on describing synthetic procedures to form heterojunctions with MOFs and on discussing the experimental techniques that provide evidence for the operation of charge migration between the MOF and the other component. Special attention has been paid to the design of rational MOF heterojunctions with small particle size and controlled morphology for an appropriate interfacial contact. The final section summarizes the achievements of the field and provides our views on future developments.

Current trends in textile wastewater treatment-bibliometric review

A bibliometric study using 1992 to 2021 database of the Science Citation Index Expanded was carried out to identify which are the current trends in textile wastewater treatment research. The study aimed to analyze the performance of scholarly scientific communications in terms of yearly publications/citations, total citations, scientific journals, and their categories in the Web of Sciences, top institutions/countries and research trends. The annual publication of scientific articles fluctuated in the first ten years, with a steady decrease for the last twenty years. An analysis of the most common terms used in the authors' keywords, publications' titles, and KeyWords Plus was carried out to predict future trends and current research priorities. Adsorbent nanomaterials would be the future of wastewater treatment for decoloration of the residual dyes in the wastewater. Membranes and electrolysis are important to demineralize textile effluent for reusing wastewater. Modern filtration techniques such as ultrafiltration and nanofiltration are advanced membrane filtration applications.

Small variation induces a big difference: the effect of polymerization kinetics of graphitic carbon nitride on its photocatalytic activity

Graphitic carbon nitride (g-CN) has emerged as a promising visible-light-responsive photocatalyst, and its activity is highly sensitive to synthesis conditions. In this work, we attempt to correlate the photocatalytic activity of g-CN with its production yield, which is kinetically determined by the specific condensation process. Bulk g-CN samples were synthesized by the conventional condensation procedure, but in static air and flowing air, respectively. The one synthesized in static air showed a lower production yield with an increased specific surface area and preferential surface chemical states, corresponding to a significantly improved activity for photocatalytic hydrogen evolution (PHE) and dye degradation. We further synthesized a series of g-CN samples by merely changing the synthetic atmosphere, the ramping rate, and the loading amount of the precursor, and the difference in their PHE performance was found to be as high as 7.05 times. The notable changes in their production yields as well as the photocatalytic activities have been discussed from the point of view of polymerization reaction kinetics, and the self-generated NH3 atmosphere plays a crucial role.

Photoelectrochemical-driven nitrogen reduction to ammonia by a Vo-SnO2/TiO2 composite electrode

N2 molecules with the NN triple bond structure are difficult to cleave under mild conditions to achieve the nitrogen fixation reaction. Photoelectrochemical (PEC) catalysis technology combining the advantages of photocatalysis and electrocatalysis provides the possibility of the nitrogen reduction reaction under ambient conditions. Herein, an SnO2/TiO2 photoelectrode was first fabricated through depositing SnO2 quantum dots on TiO2 nanorod arrays via a simple hydrothermal method. The oxygen vacancy (Vo) content was then induced in SnO2 through annealing SnO2/TiO2 at high temperature under an inert atmosphere. The heterogeneous structure of Vo-SnO2 quantum dots and TiO2 nanorods boosted the separation of photocarriers. The photoelectrons generated by photoexcitation were transferred from the conduction band of TiO2 to the conduction band of Vo-SnO2 and trapped by Vo. Vo activates N2 molecules adsorbed on the catalyst surface, and reacts with H+ in the electrolyte to generate NH3. The nitrogen fixation yield of PEC catalysis and its faradaic efficiency can reach 19.41 μg cm-2 h-1, and 59.6% at -0.2 V bias potential, respectively. The heterogeneous structure of Vo-SnO2/TiO2, introduction of Vo and synergistic effect between light and electricity greatly promotes the PEC nitrogen reduction to NH3.

Metal-organic framework-based S-scheme heterojunction photocatalysts

Photocatalysis is a promising technology to resolve energy and environmental issues, where the design of high-efficiency photocatalysts is the central task. As an emerging family of photocatalysts, semiconducting metal-organic frameworks (MOFs) with remarkable features have demonstrated great potential in various photocatalytic fields. Compared to MOF-based photocatalysts with a single component, construction of S-scheme heterojunctions can render MOFs with enhanced charge separation, redox capacity and solar energy utilization, and thus improved photocatalytic performance. Herein, an overview of the recent advances in the design of MOF-based S-scheme heterojunctions for photocatalytic applications is provided. The basic principle of S-scheme heterojunctions is introduced. Then, three types of MOF-based S-scheme heterojunctions with different compositions are systematically summarized including MOF/non-MOF, MOF-on-MOF and MOF-derived heterojunctions. Afterwards, the enhanced performances of MOF-based S-scheme heterojunctions in hydrogen production, CO2 reduction, C-H functionalization, H2O2 production and wastewater treatment are highlighted. Lastly, the current challenges and future prospects regarding the design and applications of MOF-based S-scheme heterojunctions are discussed to inspire the further development of this emerging field.

Estimating Nonradiative Excited-State Lifetimes in Photoactive Semiconducting Nanostructures

The time evolution of the exciton generated by light adsorption in a photocatalyst is an important feature that can be approached from full nonadiabatic molecular dynamics simulations. Here, a crucial parameter is the nonradiative recombination rate between the hole and the electron that form the exciton. In the present work, we explore the performance of a Fermi's golden rule-based approach on predicting the recombination rate in a set of photoactive titania nanostructures, relying solely on the coupling of the ground and first excited state. In this scheme the analysis of the first excited state is carried out by invoking Kasha's rule thus avoiding computationally expensive nonadiabatic molecular dynamics simulations and resulting in an affordable estimate of the recombination rate. Our results show that, compared to previous ones from nonadiabatic molecular dynamics simulations, semiquantitative recombination rates can be predicted for the smaller titania nanostructures, and qualitative values are obtained from the larger ones. The present scheme is expected to be useful in the field of computational heterogeneous photocatalysis whenever a complex and computationally expensive full nonadiabatic molecular dynamics cannot be carried out.

Chemical conversion of imine- into quinoline-linked covalent organic frameworks for photocatalytic oxidation

Post-synthetic modification is an important strategy for improving and enhancing the properties and functions of covalent organic frameworks (COFs). Two imine-linked COFs are converted into the quinolone-linked COFs by converting the dynamic imine linkages in the COFs into more robust quinolone ring via aza-Diels-Alder cycloaddition reaction. The prepared quinolone-linked COFs not only maintain good crystallinity and porosity, but also possess expanded conjugate planes, enhanced light absorption and excellent stability. The quinolone-linked COFs present remarkable performance of photocatalytic oxidation reactions, including oxidation of phenylboric acids, coupling of benzylamine, and oxidation of thioethers. This work is helpful for preparing organic porous photocatalytic materials with high performance and long life.

FeAu mixing for high-temperature control of light scattering at the nanometer scale

Control of the optical properties of a nanoparticle (NP) through its structural changes underlies optical data processing, dynamic coloring, and smart sensing at the nanometer scale. Here, we report on the concept of controlling the light scattering by a NP through mixing of weakly miscible chemical elements (Fe and Au), supporting a thermal-induced phase transformation. The transformation corresponds to the transition from a homogeneous metastable solid solution phase of the (Fe,Au) NP towards an equilibrium biphasic Janus-type NP. We demonstrate that the phase transformation is thermally activated by laser heating up to a threshold of 800 °C (for NPs with a size of hundreds of nm), leading to the associated changes in the light scattering and color of the NP. The results thereby pave the way for the implementation of optical sensors triggered by a high temperature at the nanometer scale via NPs based on metal alloys.

All-inorganic lead halide perovskites for photocatalysis: a review

Nowadays, environmental pollution and the energy crisis are two significant concerns in the world, and photocatalysis is seen as a key solution to these issues. All-inorganic lead halide perovskites have been extensively utilized in photocatalysis and have become one of the most promising materials in recent years. The superior performance of all-inorganic lead halide perovskites distinguish them from other photocatalysts. Since pure lead halide perovskites typically have shortcomings, such as low stability, poor active sites, and ineffective carrier extraction, that restrict their use in photocatalytic reactions, it is crucial to enhance their photocatalytic activity and stability. Huge progress has been made to deal with these critical issues to enhance the effects of all-inorganic lead halide perovskites as efficient photocatalysts in a wide range of applications. In this manuscript, the synthesis methods of all-inorganic lead halide perovskites are discussed, and promising strategies are proposed for superior photocatalytic performance. Moreover, the research progress of photocatalysis applications are summarized; finally, the issues of all-inorganic lead halide perovskite photocatalytic materials at the current state and future research directions are also analyzed and discussed. We hope that this manuscript will provide novel insights to researchers to further promote the research on photocatalysis based on all-inorganic lead halide perovskites.

Photocatalytic ethylene production by oxidative dehydrogenation of ethane with dioxygen on ZnO-supported PdZn intermetallic nanoparticles

The selective oxidative dehydrogenation of ethane (ODHE) is attracting increasing attention as a method for ethylene production. Typically, thermocatalysts operating at high temperatures are needed for C-H activation in ethane. In this study, we describe a low temperature ( < 140 °C) photocatalytic route for ODHE, using O2 as the oxidant. A photocatalyst containing PdZn intermetallic nanoparticles supported on ZnO is prepared, affording an ethylene production rate of 46.4 mmol g-1 h-1 with 92.6% ethylene selectivity under 365 nm irradiation. When we employ a simulated shale gas feed, the photocatalytic ODHE system achieves nearly 20% ethane conversion while maintaining an ethylene selectivity of about 87%. The robust interface between the PdZn intermetallic nanoparticles and ZnO support plays a crucial role in ethane activation through a photo-assisted Mars-van Krevelen mechanism, followed by a rapid lattice oxygen replenishment to complete the reaction cycle. Our findings demonstrate that photocatalytic ODHE is a promising method for alkane-to-alkene conversions under mild conditions.

Emerging environmentally friendly bio-based nanocomposites for the efficient removal of dyes and micropollutants from wastewater by adsorption: a comprehensive review

Water scarcity will worsen due to population growth, urbanization, and climate change. Addressing this issue requires developing energy-efficient and cost-effective water purification technologies. One approach is to use biomass to make bio-based materials (BBMs) with valuable attributes. This aligns with the goal of environmental conservation and waste management. Furthermore, the use of biomass is advantageous because it is readily available, economical, and has minimal secondary environmental impact. Biomass materials are ideal for water purification because they are abundant and contain important functional groups like hydroxyl, carboxyl, and amino groups. Functional groups are important for modifying and absorbing contaminants in water. Single-sourced biomass has limitations such as weak mechanical strength, limited adsorption capacity, and chemical instability. Investing in research and development is crucial for the development of efficient methods to produce BBMs and establish suitable water purification application models. This review covers BBM production, modification, functionalization, and their applications in wastewater treatment. These applications include oil-water separation, membrane filtration, micropollutant removal, and organic pollutant elimination. This review explores the production processes and properties of BBMs from biopolymers, highlighting their potential for water treatment applications. Furthermore, this review discusses the future prospects and challenges of developing BBMs for water treatment and usage. Finally, this review highlights the importance of BBMs in solving water purification challenges and encourages innovative solutions in this field.

Near-Infrared Chiroptical Activity Titanium Dioxide Supraparticles with Circularly Polarized Light Induced Antibacterial Activity

Titanium dioxide (TiO2) has attracted significant attention in the fields of antibacterial activity and pollutant degradation due to its well-known photocatalytic properties. However, the application of TiO2 is significantly limited by its large band gap width, which only allows excitation by ultraviolet light below 400 nm. Here, we propose the use of surface chiral functionalization of TiO2 to tune its band gap width, thus enabling it to be excited by near-infrared-region light (NIR), resulting in the effective separation of electron-hole pairs. By controlling the solvent polarity and forming numerous weak interactions (such as hydrogen bonding) between chiral ligands and TiO2, we successfully prepared chiral TiO2 superparticles (SPs) that exhibited a broad circular dichroism (CD) absorption at 792 nm. Under circularly polarized light (CPL) at 808 nm, the chiral SPs induced the separation of electron-hole pairs in TiO2, thus generating hydroxyl and singlet oxygen radicals. Antibacterial tests under CPL in NIR showed that the chiral TiO2 SPs exhibited excellent antibacterial performance, with inhibition rates of 99.4% and 100% against Gram-positive and Gram-negative bacteria, respectively. Recycling-reuse experiments and biocompatibility evaluation of the material demonstrated that the chiral TiO2 SPs are stable and safe antibacterial materials, thus indicating the potential application of chiral TiO2 SPs in antibacterial aspects of medical implants.

Carbon Dot as Visible-Light Photoredox Catalysts for a Myriad of Organic Transformations

Metal-free catalysts for various organic transformations are of high demand now. In this study, we present a new carbon dot as an efficient metal-free nanophotocatalyst for carrying out a series of organic bond formation reactions. Using a single photocatalyst carbon dot, Csp2-Csp2, Csp2-B, Csp2-S, Csp2-Se, and C-P bond formation reactions were performed with a high yield of the corresponding products. Moreover, Csp2-H activation of the aromatic ring was achieved by merging the carbon dot photocatalyst with a transition metal. Interestingly, these carbon nanodot-based catalysts show good recyclability a few times without any significant loss of catalytic activity. The development of catalytic systems based on carbon dots has its merits vested in the advantageous properties of this nanomaterial, such as a robust chemical nature and cheap cost of preparation. This report demonstrates that a carbon dot indeed holds the potential to replace expensive metal-based catalysts as well as organic dyes in five different photoredox reactions.

Exploring the Remarkably High Photocatalytic Efficiency of Ultra-Thin Porous Graphitic Carbon Nitride Nanosheets

Graphitic carbon nitride (g-C3N4) is a metal-free photocatalyst used for visible-driven hydrogen production, CO2 reduction, and organic pollutant degradation. In addition to the most attractive feature of visible photoactivity, its other benefits include thermal and photochemical stability, cost-effectiveness, and simple and easy-scale-up synthesis. However, its performance is still limited due to its low absorption at longer wavelengths in the visible range, and high charge recombination. In addition, the exfoliated nanosheets easily aggregate, causing the reduction in specific surface area, and thus its photoactivity. Herein, we propose the use of ultra-thin porous g-C3N4 nanosheets to overcome these limitations and improve its photocatalytic performance. Through the optimization of a novel multi-step synthetic protocol, based on an initial thermal treatment, the use of nitric acid (HNO3), and an ultrasonication step, we were able to obtain very thin and well-tuned material that yielded exceptional photodegradation performance of methyl orange (MO) under visible light irradiation, without the need for any co-catalyst. About 96% of MO was degraded in as short as 30 min, achieving a normalized apparent reaction rate constant (k) of 1.1 × 10-2 min-1mg-1. This represents the highest k value ever reported using C3N4-based photocatalysts for MO degradation, based on our thorough literature search. Ultrasonication in acid not only prevents agglomeration of g-C3N4 nanosheets but also tunes pore size distribution and plays a key role in this achievement. We also studied their performance in a photocatalytic hydrogen evolution reaction (HER), achieving a production of 1842 µmol h-1 g-1. Through a profound analysis of all the samples' structure, morphology, and optical properties, we provide physical insight into the improved performance of our optimized porous g-C3N4 sample for both photocatalytic reactions. This research may serve as a guide for improving the photocatalytic activity of porous two-dimensional (2D) semiconductors under visible light irradiation.

Green approach for the fabrication of a ternary nanocatalyst (Ag-ZnONPs@Cy) for visible light-induced photocatalytic reduction of nitroarenes to aminoarenes

In recent times, the incorporation of metal oxide nanoparticles with organic dyes has piqued the interest of numerous researchers due to their diverse applications under visible light instead of UV radiation. This investigation employed a three-step methodology to fabricate cyanidin-sensitized silver-doped zinc oxide nanoparticles (Ag-ZnO@Cy). Initially, cyanidin dye was extracted from fresh black mulberry fruit, followed by the eco-friendly synthesis of Ag-ZnO nanoparticles (Ag-ZnONPs). The successful integration of the prepared cyanidin dye with Ag-ZnONPs was achieved through a straightforward, environmentally benign, and cost-efficient procedure. The resultant ternary composite underwent comprehensive characterization and confirmation utilizing various techniques, such as SEM, FT-IR, EDX, DRS, elemental mapping, and XRD. The experimental results for Ag-ZnONPs@Cy demonstrated that the nanocrystalline wurtzite exhibited spherical shapes with an average crystal size of 27.42 nm. Moreover, the photocatalytic activity of the synthesized Ag-ZnONPs@Cy was meticulously investigated under blue LED light irradiation. This inquiry encompassed examinations of catalyst amount, regeneration, stability, reusability, and the influence of light source on the hydrogenation of nitroarenes to the corresponding aminoarenes. The findings shed light on the potential of this composite for diverse photocatalytic applications.

Flame doping of indium ions into TiO2 nanorod arrays for enhanced photochemical water oxidation

Indium (In) ions were diffused into a TiO2 (In-TiO2) photoelectrode via a facile and efficient flame doping method resulting in improved photo-induced carrier separation. The dopant concentration was systematically investigated, and a volcano-type relationship between the dopant concentration and photoelectrochemical (PEC) performance was observed. The optimum incident photon-to-current efficiency and photocurrent density of In-TiO2 were 38.6% and 0.70 mA cm-2 at 1.23 V, respectively, 2.1 and 11.2 times the values of pristine TiO2, respectively. In doping resulted in improved charge separation and lower surface adsorption energies for reactant molecules, as evidenced by experimental and computational methods.

Cobalt oxide coupled with graphitic carbon nitride composite heterojunction for efficient Z-scheme photocatalytic environmental pollutants degradation performance

The Co3O4/g-C3N4 Z-scheme composite heterojunction has been effectively built in a facile sonication-assisted hydrothermal manner. The as-synthesized optimal 0.2 M Co3O4/g-C3N4 (GCO2) composite photocatalysts (PCs) revealed admirable degradation efficiency towards methyl orange (MO, 65.1%) and methylene blue (MB, 87.9%) organic pollutant compared with bare g-C3N4 within 210 min under light irradiation. Besides, the features of investigating structural, morphological and optical properties have evidence that the unique decoration effect of Co3O4 nanoparticles (NPs) on the g-C3N4 structure with intimate interface heterojunction of well-matched band structures noticeably facilitates the photo-generated charge transport/separation efficiency, reduces the recombination rates and widens the visible-light fascination which could advantageous to upgrading photocatalytic action with superior redox ability. Especially, the probable Z-scheme photocatalytic mechanism pathway is also elucidated in detail based on the quenching results. Hence, this work delivers a facile and hopeful candidate for contaminated water remediation via visible-light photocatalysis over the efficient g-C3N4-based catalysts.

The Mars-Van Krevelen cycle and non-noble metal Ni jointly promoting Z-scheme charge transfer: a study on the photothermal synergy effect applied in selectively oxidizing aromatic alcohols

Photothermal catalysis is a promising method for selectively oxidizing organic compounds, effectively addressing the energy-intensive and low-selective processes of thermal catalysis, as well as the slow reaction rates of photocatalysis. In this study, a ternary photothermal catalyst, Ni/CeO2/CdS, was synthesized using a simple calcination and solvothermal method. The catalyst demonstrated remarkable improvement in reaction rates and achieved nearly 100% selectivity in converting benzyl alcohol to benzaldehyde through photothermal catalysis at normal pressure. The reaction rates were 5.9 times and 63 times higher than those of CdS and Ni/CeO2 individually. XPS analysis confirmed that the thermal catalysis followed the Mars-Van Krevelen (MVK) mechanism and also proved that photocatalysis facilitated the MVK cycle. Additionally, DFT calculations showed that Ni acted as an electron transfer channel, facilitating efficient Z-scheme charge transfer. The in situ infrared technique was used to dynamically monitor the reaction process and explain the high selectivity of the product. Furthermore, detailed explanations of photocatalysis, thermocatalysis, and photothermal synergistic catalysis were proposed based on the aforementioned characterization and theoretical calculations. This approach establishes a theoretical foundation for the development of efficient photothermal catalysts.

Graphitic Carbon Nitride/Zinc Oxide-Based Z-Scheme and S-Scheme Heterojunction Photocatalysts for the Photodegradation of Organic Pollutants

Graphitic carbon nitride (g-C3N4), a metal-free polymer semiconductor, has been recognized as an attractive photocatalytic material for environmental remediation because of its low band gap, high thermal and photostability, chemical inertness, non-toxicity, low cost, biocompatibility, and optical and electrical efficiency. However, g-C3N4 has been reported to suffer from many difficulties in photocatalytic applications, such as a low specific surface area, inadequate visible-light utilization, and a high charge recombination rate. To overcome these difficulties, the formation of g-C3N4 heterojunctions by coupling with metal oxides has triggered tremendous interest in recent years. In this regard, zinc oxide (ZnO) is being largely explored as a self-driven semiconductor photocatalyst to form heterojunctions with g-C3N4, as ZnO possesses unique and fascinating properties, including high quantum efficiency, high electron mobility, cost-effectiveness, environmental friendliness, and a simple synthetic procedure. The synergistic effect of its properties, such as adsorption and photogenerated charge separation, was found to enhance the photocatalytic activity of heterojunctions. Hence, this review aims to compile the strategies for fabricating g-C3N4/ZnO-based Z-scheme and S-scheme heterojunction photocatalytic systems with enhanced performance and overall stability for the photodegradation of organic pollutants. Furthermore, with reference to the reported system, the photocatalytic mechanism of g-C3N4/ZnO-based heterojunction photocatalysts and their charge-transfer pathways on the interface surface are highlighted.

Visible-light-induced self-propelled nanobots against nanoplastics

The accumulation of plastic debris in aquatic organisms has raised serious concerns about the potential health implications of their incorporation into the food chain. However, conventional water remediation techniques are incapable of effectively removing nanoplastics (NPs) smaller than 200 nm, which can have harmful effect on animal and human health. Herein, we demonstrate the "on-the-fly" capture of NPs through their enlargement (approximately 4,100 times) using self-propelled nanobots composed of a metal-organic framework. Under visible-light irradiation, the iron hexacyanoferrate (FeHCF) nanobot exhibits fuel-free motion by electrostatically adsorbing NPs. This strategy can contribute to reducing plastic pollution in the environment, which is a significant environmental challenge. Light-induced intervalence charge transfer in the FeHCF nanobot lattice induces bipolarity on the nanobot surface, leading to the binding of negatively charged NPs. The local electron density in the lattice then triggers self-propulsion, thereby inducing agglomeration of FeHCF@NP complexes to stabilize their metastable state. The FeHCF nanobot exhibits a maximum removal capacity of 3,060 mg∙g-1 and rate constant of 0.69 min-1, which are higher than those recorded for materials reported in the literature.

Engineering of Multifunctional Nanocomposite Membranes for Wastewater Treatment: Oil/Water Separation and Dye Degradation

Multifunctional membrane technology has gained tremendous attention in wastewater treatment, including oil/water separation and photocatalytic activity. In the present study, a multifunctional composite nanofiber membrane is capable of removing dyes and separating oil from wastewater, as well as having antibacterial activity. The composite nanofiber membrane is composed of cellulose acetate (CA) filled with zinc oxide nanoparticles (ZnO NPs) in a polymer matrix and dipped into a solution of titanium dioxide nanoparticles (TiO2 NPs). Membrane characterization was performed using transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and Fourier transform infrared (FTIR), and water contact angle (WCA) studies were utilized to evaluate the introduced membranes. Results showed that membranes have adequate wettability for the separation process and antibacterial activity, which is beneficial for water disinfection from living organisms. A remarkable result of the membranes' analysis was that methylene blue (MB) dye removal occurred through the photocatalysis process with an efficiency of ~20%. Additionally, it exhibits a high separation efficiency of 45% for removing oil from a mixture of oil-water and water flux of 20.7 L.m-2 h-1 after 1 h. The developed membranes have multifunctional properties and are expected to provide numerous merits for treating complex wastewater.

Synthesis and up-to-date applications of 2D microporous g-C3N4 nanomaterials for sustainable development

In recent years, with the development of industrial technology and the increase of people's environmental awareness, the research on sustainable materials and their applications has become a hot topic. Among two-dimensional (2D) materials that have been selected for sustainable research, graphitic phase carbon nitride (g-C3N4) has become a hot research topic because of its many outstanding advantages such as simple preparation, good electrochemical properties, excellent photochemical properties, and better thermal stability. Nevertheless, the inherent limitations of g-C3N4 due to its relatively poor specific surface area, rapid charge recombination, limited light absorption range, and inferior dispersion in aqueous and organic media have limited its practical application. In the review, we summarize and analyze the unique structure of the 2D microporous nanomaterial g-C3N4, its synthesis method, chemical modification method, and the latest application examples in various fields in recent years, highlighting its advantages and shortcomings, with a view to providing ideas for overcoming the difficulties in its application. Furthermore, the pressing challenges faced by g-C3N4 are briefly discussed, as well as an outlook on the application prospects of g-C3N4 materials. It is expected that the review in this paper will provide more theoretical strategies for the future practical application of g-C3N4-based materials, as well as contributing to nanomaterials in sustainable applications.

Nanomaterials for Advanced Photocatalytic Plastic Conversion

As the disposal of waste plastic emerges as a societal problem, photocatalytic waste plastic conversion is attracting significant attention. Ultimately, for a sustainable future, the development of an eco-friendly plastic conversion technology is essential for breaking away from the current plastic use environment. Compared to conventional methods, photocatalysis can be a more environmentally friendly option for waste plastic reprocessing because it uses sunlight as an energy source under ambient temperature and pressure. In addition to this, waste plastics can be upcycled (i.e., converted into useful chemicals or fuels) to enhance their original value via photocatalytic methods. Among various strategies for improving the efficiency of the photocatalytic method, nanomaterials have played a pivotal role in suppressing charge recombination. Hence, in recent years, attempts have been made to introduce nanomaterials/nanostructures into photocatalytic plastic conversion on the basis of advances in material-based studies using simple photocatalysts. In line with this trend, the present review examines the nanomaterials/nanostructures that have been recently developed for photocatalytic plastic conversion and discusses the direction of future development.

Photocatalysis of Metallic Nanoparticles: Interband vs Intraband Induced Mechanisms

Photocatalysis induced by localized surface plasmon resonance of metallic nanoparticles has been studied for more than a decade, but photocatalysis originating from direct interband excitations is still under-explored. The spectral overlap and the coupling of these two optical regimes also complicate the determination of hot carriers' energy states and eventually hinder the accurate assignment of their catalytic role in studied reactions. In this Featured Article, after reviewing previous studies, we suggest classifying the photoexcitation via intra- and interband transitions where the physical states of hot carriers are well-defined. Intraband transitions are featured by creating hot electrons above the Fermi level and suitable for reductive catalytic pathways, whereas interband transitions are featured by generating hot d-band holes below the Fermi level and better for oxidative catalytic pathways. Since the contribution of intra- and interband transitions are different in the spectral regions of localized surface plasmon resonance and direct interband excitations, the wavelength dependence of the photocatalytic activities is very helpful in assigning which transitions and carriers contribute to the observed catalysis.

Renaissance of elemental phosphorus materials: properties, synthesis, and applications in sustainable energy and environment

The polymorphism of phosphorus-based materials has garnered much research interest, and the variable chemical bonding structures give rise to a variety of micro and nanostructures. Among the different types of materials containing phosphorus, elemental phosphorus materials (EPMs) constitute the foundation for the synthesis of related compounds. EPMs are experiencing a renaissance in the post-graphene era, thanks to recent advancements in the scaling-down of black phosphorus, amorphous red phosphorus, violet phosphorus, and fibrous phosphorus and consequently, diverse classes of low-dimensional sheets, ribbons, and dots of EPMs with intriguing properties have been produced. The nanostructured EPMs featuring tunable bandgaps, moderate carrier mobility, and excellent optical absorption have shown great potential in energy conversion, energy storage, and environmental remediation. It is thus important to have a good understanding of the differences and interrelationships among diverse EPMs, their intrinsic physical and chemical properties, the synthesis of specific structures, and the selection of suitable nanostructures of EPMs for particular applications. In this comprehensive review, we aim to provide an in-depth analysis and discussion of the fundamental physicochemical properties, synthesis, and applications of EPMs in the areas of energy conversion, energy storage, and environmental remediation. Our evaluations are based on recent literature on well-established phosphorus allotropes and theoretical predictions of new EPMs. The objective of this review is to enhance our comprehension of the characteristics of EPMs, keep abreast of recent advances, and provide guidance for future research of EPMs in the fields of chemistry and materials science.

Biofunctionalized CdS Quantum Dots: A Case Study on Nanomaterial Toxicity in the Photocatalytic Wastewater Treatment Process

The toxic nature of inorganic nanostructured materials as photocatalysts is often not accounted for in traditional wastewater treatment reactions. Particularly, some inorganic nanomaterials employed as photocatalysts may release secondary pollutants in the form of ionic species that leach out due to photocorrosion. In this context, this work is a proof-of-concept study for exploring the environmental toxicity effect of extremely small-sized nanoparticles (<10 nm) like quantum dots (QDs) that are employed as photocatalysts, and in this study, cadmium sulfide (CdS) QDs are chosen. Typically, CdS is an excellent semiconductor with suitable bandgap and band-edge positions that is attractive for applications in solar cells, photocatalysis, and bioimaging. However, the leaching of toxic cadmium (Cd²⁺) metal ions due to the poor photocorrosion stability of CdS is a matter of serious concern. Therefore, in this report, a cost-effective strategy is devised for biofunctionalizing the active surface of CdS QDs by employing tea leaf extract, which is expected to hinder photocorrosion and prevent the leaching of toxic Cd²⁺ ions. The coating of tea leaf moieties (chlorophyll and polyphenol) over the CdS QDs (referred to hereafter as G-CdS QDs) was confirmed through structural, morphological, and chemical analysis. Moreover, the enhanced visible-light absorption and emission intensity of G-CdS QDs in comparison to that of C-CdS QDs synthesized through a conventional chemical synthesis approach confirmed the presence of chlorophyll/polyphenol coating. Interestingly, the polyphenol/chlorophyll molecules formed a heterojunction with CdS QDs and enabled the G-CdS QDs to exhibit enhanced photocatalytic activity in the degradation of methylene blue dye molecules over C-CdS QDs while effectively preventing photocorrosion as confirmed from cyclic photodegradation studies. Furthermore, detailed toxicity studies were conducted by exposing zebrafish embryos to the as-synthesized CdS QDs for 72 h. Surprisingly, the survival rate of the zebrafish embryos exposed to G-CdS QDs was equal to that of the control, indicating a significant reduction in the leaching of Cd²⁺ ions from G-CdS QDs in comparison to C-CdS QDs. The chemical environment of C-CdS and G-CdS before and after the photocatalysis reaction was examined by X-ray photoelectron spectroscopy. These experimental findings prove that biocompatibility and toxicity could be controlled by simply adding tea leaf extract during the synthesis of nanostructured materials, and revisiting green synthesis techniques can be beneficial. Furthermore, repurposing the discarded tea leaves may not only facilitate the control of toxicity of inorganic nanostructured materials but can also help in enhancing global environmental sustainability.

A Review on Photocatalysis Used For Wastewater Treatment: Dye Degradation

Water pollution is a global issue as a consequence of rapid industrialization and urbanization. Organic compounds which are generated from various industries produce problematic pollutants in water. Recently, metal oxide (TiO2, SnO2, CeO2, ZrO2, WO3, and ZnO)-based semiconductors have been explored as excellent photocatalysts in order to degrade organic pollutants in wastewater. However, their photocatalytic performance is limited due to their high band gap (UV range) and recombination time of photogenerated electron-hole pairs. Strategies for improving the performance of these metal oxides in the fields of photocatalysis are discussed. To improve their photocatalytic activity, researchers have investigated the concept of doping, formation of nanocomposites and core-shell nanostructures of metal oxides. Rare-earth doped metal oxides have the advantage of interacting with functional groups quickly because of the 4f empty orbitals. More precisely, in this review, in-depth procedures for synthesizing rare earth doped metal oxides and nonocomposites, their efficiency towards organic pollutants degradation and sources have been discussed. The major goal of this review article is to propose high-performing, cost-effective combined tactics with prospective benefits for future industrial applications solutions.

Covalent Organic Framework-Semiconductor-Based Heterostructures for Photocatalytic Applications

Photocatalysis is a promising and sustainable technology in the fields of energy conversion/storage and environment purification; however, the utilization of individual component as photocatalyst is generally restricted due to the low catalytic activity deriving from the rapid recombination of photogenerated electrons/holes. Covalent organic framework (COF)-semiconductor-based composite photocatalysts with synergistic effects provide a feasible route to achieve high-performance photocatalytic reactions with more active sites, strong light utilization ability, and high stability. In recent years, significant progress has been made in the rational design and preparation of the COF-semiconductors-based heterostructures for photocatalytic water splitting, carbon dioxide (CO₂ ) reduction, and dye/pollutant degradation. In this Review, the synthetic strategies of COF-semiconductor-based heterostructures are first introduced, which includes the rational design of the morphology, connection modes, and type of heterojunctions. The performance of COF-semiconductor-based heterostructures in different photocatalytic reactions are comprehensively reviewed. The structure-activity relationship and the synergistic effects within the heterostructures are discussed, and the photocatalytic mechanism and the role of COFs during the photocatalytic process are also presented. Finally, an outlook and challenges of realizing COF-semiconductor-based heterostructures with simple synthesis methods, diverse functions, high performance, and well-defined reaction mechanisms are provided.

Electrochemistry of Thin Films and Nanostructured Materials

In the last few decades, the development and use of thin films and nanostructured materials to enhance physical and chemical properties of materials has been common practice in the field of materials science and engineering. The progress which has recently been made in tailoring the unique properties of thin films and nanostructured materials, such as a high surface area to volume ratio, surface charge, structure, anisotropic nature, and tunable functionalities, allow expanding the range of their possible applications from mechanical, structural, and protective coatings to electronics, energy storage systems, sensing, optoelectronics, catalysis, and biomedicine. Recent advances have also focused on the importance of electrochemistry in the fabrication and characterization of functional thin films and nanostructured materials, as well as various systems and devices based on these materials. Both cathodic and anodic processes are being extensively developed in order to elaborate new procedures and possibilities for the synthesis and characterization of thin films and nanostructured materials.

BiVO4 As a Sustainable and Emerging Photocatalyst: Synthesis Methodologies, Engineering Properties, and Its Volatile Organic Compounds Degradation Efficiency

Bismuth vanadate (BiVO₄) is one of the best bismuth-based semiconducting materials because of its narrow band gap energy, good visible light absorption, unique physical and chemical characteristics, and non-toxic nature. In addition, BiVO₄ with different morphologies has been synthesized and exhibited excellent visible light photocatalytic efficiency in the degradation of various organic pollutants, including volatile organic compounds (VOCs). Nevertheless, the commercial scale utilization of BiVO₄ is significantly limited because of the poor separation (faster recombination rate) and transport ability of photogenerated electron-hole pairs. So, engineering/modifications of BiVO₄ materials are performed to enhance their structural, electronic, and morphological properties. Thus, this review article aims to provide a critical overview of advanced oxidation processes (AOPs), various semiconducting nanomaterials, BiVO₄ synthesis methodologies, engineering of BiVO₄ properties through making binary and ternary nanocomposites, and coupling with metals/non-metals and metal nanoparticles and the development of Z-scheme type nanocomposites, etc., and their visible light photocatalytic efficiency in VOCs degradation. In addition, future challenges and the way forward for improving the commercial-scale application of BiVO₄-based semiconducting nanomaterials are also discussed. Thus, we hope that this review is a valuable resource for designing BiVO₄-based nanocomposites with superior visible-light-driven photocatalytic efficiency in VOCs degradation.

Transition metal dichalcogenides nanomaterials based piezocatalytic activity: recent progresses and outlook

Piezoelectric materials have drawn significant attention from researchers in the recent past as the piezo-potential, induced by applied external stress, generates an electric field, which paves the way for the creation and transfer of electrons and holes. After the theoretical prediction of the existence of the piezoelectric effect in transition metal dichalcogenides (TMDCs) semiconductors, intense research efforts have been made by various researchers to demonstrate the effect experimentally. In addition 2D TMDCs exhibit layer-dependent tunable electronic structure, strongly bound excitons, enhanced catalytic activity at their edges, and novel spin/pseudospin degrees of freedom. The edge sites and activated basal planes of 2D TMDCs are shown to be highly active toward catalysis of the hydrogen evolution reaction (HER). However, as compared to electrocatalytic or even photocatalytic performances, TMDC materials exhibit poorer piezocatalytic activity, in general. Therefore, a numbers of research strategies have been made to intensify the piezoelectric effect by synthesizing different types of TMDC nanostructures, by coupling the piezoelectric effect with the photocatalytic effect, by doping with other materials, etc. This review discusses various techniques of synthesis of TMDCs nanostructures and the recent progresses in applications of TMDC nanomaterials in piezocatalysis. In the present article, the piezocatalytic dye degradation performances and HER activity using different TMDCs have been reviewed in detail. Different methods of increasing the piezocatalytic activity of various TMDCs nanostructures have been illustrated. Here, it has also been attempted to systematically summarize and provide an outlook of the charge transfer behaviour and catalytic mechanisms in large varieties of TMDC piezocatalysts and piezo-photocatalysts. In addition, advanced applications of TMDC piezocatalytic materials as piezoelectric nanogenerator, piezocatalytic dye degradation, piezo-phototronic dye degradation and HER studies have been highlighted.