Low Recombination Rate Research Articles

High-recombining genomic regions affect demography inference based on ancestral recombination graphs.

Multiple methods of demography inference are based on the ancestral recombination graph. This powerful approach uses observed mutations to model local genealogies changing along chromosomes by historical recombination events. However, inference of underlying genealogies is difficult in regions with high recombination rate relative to mutation rate due to the lack of mutations representing genealogies. Despite the prevalence of high-recombining genomic regions in some organisms, such as birds, its impact on demography inference based on ancestral recombination graphs has not been well studied. Here, we use population genomic simulations to investigate the impact of high-recombining regions on demography inference based on ancestral recombination graphs. We demonstrate that inference of effective population size and the time of population split events is systematically affected when high-recombining regions cover wide breadths of the chromosomes. Excluding high-recombining genomic regions can practically mitigate this impact, and population genomic inference of recombination maps is informative in defining such regions, yet the estimated values of local recombination rate may not be utilized for this decision. Finally, we confirm the relevance of our findings in empirical analysis by contrasting demography inferences applied for a bird species, the Eurasian blackcap (Sylvia atricapilla), using different parts of the genome with high and low recombination rates. Our results suggest that demography inference methods based on ancestral recombination graphs should be carried out with caution when applied in species whose genomes contain long stretches of high-recombining regions.

Comprehensive investigation of electronic and optical features in two-dimensional MoS2/WS2-SnO2 van der Waals heterostructures

First-principles calculations have been employed here to investigate the optical and electrical properties of experimentally synthesized Mo(W)S2-SnO2 vdW heterostructures [J. Phys. Chem. C 2020, 124, 1, 647–652, Chem. Phys. 2019, 525, 110398]. Rigorous dynamical stability assessments confirm structural robustness, evident in phonon dispersion and AIMD simulations at 500 K. The interfacial binding energy values reflect the stability of our simulated heterostructures. With intrinsic type-II band alignment and direct band gaps of 1.21[Formula: see text]eV (MoS2-SnO[Formula: see text] and 1.003[Formula: see text]eV (WS2-SnO[Formula: see text], these heterostructures emerge as promising candidates for high-efficiency optical devices. Higher static dielectric constants in comparison with numerous heterostructures signify low charge carrier recombination rates, enhancing practical appeal. Optical analyses reveal substantial visible and ultraviolet (UV) spectrum absorption, while MoS2-SnO2 and WS2-SnO2 heterostructures exhibit photoelectric conversion efficiencies of 15.08% and 13.65%. A thorough examination of optical characteristics provides a comprehensive understanding of positioning Mo(W)S2-SnO2 vdW heterostructures for advanced optoelectronic devices.

Size and Crystallinity‐Dependent Photocatalytic Performance of MIL‐53(Fe) and MIL‐53(Fe)/g‐C3N4 Composite

ABSTRACTMIL‐53(Fe) is a novel photocatalytic material that has been developed over the past decade; however, significant efforts are still required to fully optimize its photocatalytic performance in order to meet the requirements of practical applications. In this paper, we investigated the effects of size and crystallinity on the photocatalytic performance of MIL‐53(Fe) and its composites x‐MIL‐53(Fe)/g‐C3N4 (x‐MIL‐Fe/CN). During the hydrothermal synthesis process, the control over particle size was achieved by adjusting the amount of acetic acid (HAc). Ball milling was utilized to manipulate both the size and crystallinity of MIL‐53(Fe). Photocatalytic experiments demonstrated that MIL‐53(Fe) and 15‐MIL‐Fe/CN, characterized by the smallest particle sizes and great crystallinity, exhibited the highest photocatalytic activity. This enhancement in photocatalytic activity can be attributed to the reduced band gap and lower recombination rate of photogenerated carriers. Notably, the hydrogen evolution rate for 15‐MIL‐Fe/CN reached up to 4950 μmol·g−1·h−1, but MIL‐53(Fe) achieved a 98% degradation of methyl orange within 60 min.

Design of long‐wavelength infrared InAs/InAsSb type‐II superlattice avalanche photodetector with stepped grading layer

AbstractWeak response in long‐wavelength infrared (LWIR) detection has long been a perennial concern, significantly limiting the reliability of applications. Avalanche photodetectors (APDs) offer excellent responsivity but are plagued by high dark current during the multiplication process. Here, we propose a high‐performance type‐II superlattices (T2SLs) LWIR APD to address these issues. The low Auger recombination rate of the InAs/InAsSb T2SLs absorption layer is exploited to reduce the dark current initially. AlAsSb with a low k value is employed as the multiplication layer to suppress device noise while maintaining sufficient gain. To facilitate carrier transport, the conduction band discontinuity is optimized by inserting an InAs/AlSb T2SLs stepped grading layer between the absorption and multiplication layers. As a result, the device exhibits excellent photoresponse at 8.4 μm at 100 K and maintains a low dark current density of 5.48 × 10−2 A/cm2. Specifically, it achieves a maximum gain of 366, a responsivity of 650 A/W, and a quantum efficiency of 26.28% under breakdown voltage. This design offers a promising solution for the advancement of LWIR detection.

Rational Design of Pyrene and Thienyltriazine-Based Conjugated Microporous Polymers for High-Performance Energy Storage and Visible-Light Photocatalytic Hydrogen Evolution from Water

Conjugated microporous polymers (CMPs) have found extensive applications in various fields, such as optoelectronics, CO2 capture, and catalysis. However, their potential in electrochemical supercapacitors as energy storage and H2 production systems remains relatively unexplored. This limited exploration can be attributed to certain challenges, including issues related to structural and electrochemical stability, as well as the relatively modest specific capacitance. Additionally, many of the CMPs discovered thus far have exhibited lower energy densities, further contributing to this underexplored aspect of their utility. In this study, we prepared two different CMPs [TPET-TTh and PyT-TTh CMPs] containing thienyltriazine units (TTh) for the redox mechanism and constructed electrodes for supercapacitor applications. The synthesized TPET-TTh and PyT-TTh CMPs displayed exceptionally high specific surface areas of 545 and 528 m² g⁻¹, respectively. Furthermore, their pore sizes were very similar, centered at approximately 0.39 and 0.36 nm, respectively. To evaluate their electrochemical properties, the TTh-CMPs were examined using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD). The resulting CV curves exhibited rectangular shapes, indicative of the characteristic behavior of electric double-layer capacitors, across a range of potential and scan rates. These TPET-TTh and PyT-TTh CMPs delivered nominal specific capacitances of 74 and 76 F g−1 at 0.5 A g−1, respectively. In addition, they exhibited outstanding capacity retentions of 95.2 and 97.30 % even after 2000 cycles [analyzed at 10 A g−1]. The TTh-CMPs also exhibited excellent light-capture capabilities. The PyT-TTh CMP has faster charge separation and lower charge recombination rates than TPET-TTh CMP. This results in a higher hydrogen evolution rate from the water decomposition reaction. The H2 production rate of PyT-TTh CMP could be as high as 18,533 μmol g−1 h−1, which is approximately 4-fold that of TPET-TTh CMP. This study offers a strategy for the design of TTh-containing CMPs that exhibit exceptional energy storage application and photocatalytic efficiency for H2 evolution. Figure 1

Piezoelectric effect promotes photoelectrochemical properties of 2D-3D ZnIn2S4/β-CdS strongly coupled interface

In the process of photoelectrochemical (PEC) hydrodecomposition, it is important to design photoelectrode materials with low cost, high charge separation efficiency and low charge recombination rate. Herein, 2D-3D strongly coupled ZnIn2S4/β-CdS nanocomposites were prepared by a two-step hydrothermal method. Meanwhile, the piezoelectric polarization was used to induce its generation of built-in electric field, which suppressed the secondary compounding of photogenerated charge carriers caused by the interfacial structural defects of the semiconductor heterojunction. The results show that ZnIn2S4/β-CdS has better photoelectrochemical decomposition ability of water under ultrasound, and its photocurrent density increases with the increase of ultrasound frequency, reaching a maximum value of 0.46 mA·cm−2 at 1.23 VRHE, which is 3.5 times higher than that before ultrasound. In addition, by comparing the significant increase of photocurrent conversion efficiency under the applied bias voltage before and after ultrasound, it can be concluded that the enhanced catalytic activity of ZnIn2S4/β-CdS is attributed to the efficient coupling effect between ZnIn2S4 and β-CdS under ultrasound conditions. This coupling effect enables the fast electron transfer at the interface between ZnIn2S4 and β-CdS. Consequently, this strongly coupled nanocomposite will provide inspiration for further construction of nanocomposites for photocatalytic decomposition of water.

Luminescence Patterns on Multimillimeter Single-Crystal MAPbBr3 Microplatelets via Thermal Ablation Effects.

The single crystal distinguishes itself as the most outstanding representative of excellent optoelectronic performance among perovskite semiconductors due to its exceptional charge carrier properties, extraordinary optophysics, precise structural geometries, and superior material stabilities. However, it exhibits mediocre performance in light emission, which can be attributed to its excessive carrier diffusion lengths and extremely low recombination rates. To address this challenge, this study puts forward a controllable high-temperature annealing treatment strategy concentrating on multimillimeter-scale MAPbBr3 micrometer-thick platelet single crystals (MPSCs). Through the utilization of thermal ablation effects to convert the surface monocrystalline lattices into polycrystalline perovskite nanocrystals (PNCs) with a remarkably increased specific surface area, the fluorescence intensity arising from the rapid recombination of free carriers on the PNC surface is enhanced by 320 times compared to the pristine MPSC surface. These PNCs produced through surface annealing, with the characteristic of loose adhesion to surfaces, can be mechanically wiped away and regenerated in situ via reannealing the residual MAPbBr3 MPSCs, guaranteeing high intensity, durability, and standard geometric fluorescence. Moreover, by regulating the surface distributions of thermal ablation effects and carrying out embossing annealing treatment or laser direct writing, we can design and fabricate relatively complex, high-contrast (255×), and clearly resolved fluorescence patterns on MPSC surfaces.

Tuning interfacial charge transfer for efficient photodegradation of tetracycline hydrochloride over Ti3C2/Bi12O17Cl2 Schottky heterojunction and theoretical calculations

In the ecological environment, tetracycline hydrochloride (TCH) is one of the excessive antibiotics from water, which has watched the eye of researchers. Developing a high-performance photocatalyst to address this phenomenon still faces a big challenge. Herein, we describe a straightforward chemical procedure in-situ self-assembly via one-step solvothermal process to create a new two-dimensional/two-dimensional (2D/2D) Ti3C2/Bi12O17Cl2 heterojunction. The heterojunction at the interface with a strong chemical interaction between Ti3C2 and Bi12O17Cl2 is well revealed by the serial characterizations and theoretical calculations. The superior photocatalytic activity of Ti3C2/Bi12O17Cl2 is attributed to its low recombination rate of electrons and holes, photothermal effect, high electron transfer during reactions and high photochemical current. Finally, the photocatalytic mechanism over Ti3C2/Bi12O17Cl2 is also provided. This work provides an intriguing strategy for the construction of superior photocatalysts for pollutant degradation using MXene as co-catalysts.

Enhancing the Light‐Driven Photocatalytic Degradation Activity of ZnO Nanoparticles With the Synergistic Incorporation of Er and Tb Elements

ABSTRACTThe existence of organic pollutants in aqueous media has become a vital issue and a critical threat to human health, where organic toxic dyes represent the major contaminants in wastewater. Over the past few years, photocatalytic techniques have garnered a lot of interest in dye removal from wastewater. In this study, a series of ErxTbxZn1 − 2xO nanophotocatalysts (where x = 0.00, 0.01, 0.03, and 0.05) were synthesized and coded as ZET0, ZET1, ZET2, and ZET3 NPs (nanoparticles). The chemical and physical characteristics of the NPs were investigated using Fourier‐transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy‐dispersive X‐ray (EDX) spectroscopy, and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) techniques. Further examination by performing photocatalytic experiments, ZET1 NPs demonstrated effective Rhodamine B (RhB) dye degradation within 60 min. It was found that the kinetic rate constant values were 0.008, 0.097, 0.050, and 0.040 min−1 for ZET0, ZET1, ZET2, and ZET3 NPs, respectively. Aside from their remarkable photocatalytic degradation efficiency, these ZET1 photocatalysts are highly stable even after five consecutive cycles. In addition, the active species test revealed that the primary oxidation species involved in the photocatalytic process are holes (h+) and hydroxyl radicals (•OH), and a possible photocatalytic mechanism for degrading RhB by ZET1 photocatalysts was tentatively proposed. The enhancement of the photocatalytic degradation efficiency is due to the low recombination rate of photogenerated charge carriers, as well as a strong synergistic impact of Tb, Er, and ZnO components. Thus, the current study could offer a versatile strategy for the design of new and effective nano photocatalysts for wastewater purification in the future.

The Effect of Heat Treatment on the Sol–Gel Preparation of TiO2/ZnO Catalysts and Their Testing in the Photodegradation of Tartrazine

This study aims to synthesize TiO2/ZnO powders and to study the effect of heat treatment on their photocatalytic ability against the Tartrazine anionic dye. The as-obtained powders with the following compositions—90TiO2/10ZnO and 10TiO2/90ZnO (mol%)—were obtained by the sol–gel technique. The prepared gels were annealed at 500 °C and 700 °C and subsequently characterized by XRD, UV–Vis, and SEM methods. The single crystalline phase of TiO2, which has been detected at up to 500 °C is anatase, while for ZnO, it is the hexagonal wurtzite structure. Further increases in the temperature (700 °C) led to the appearance of rutile in the samples. The SEM analysis demonstrated that the binary oxide materials had irregular shaped particles with a tendency to agglomerate. The UV–Vis spectra of the gels exhibited a red shift in the cut-off of the 90TiO2/10ZnO sample compared with pure Ti(IV) butoxide. Photocatalytic tests showed that the investigated samples possessed photocatalytic activity toward Tartrazine. Compared with TiO2, the prepared TiO2/ZnO photocatalysts showed superior properties in the photodegradation of a Tartrazine water solution. The target photocatalysts’ enhanced photocatalytic activities can be explained by their reduced band gap energy, improved surface physicochemical characteristics, separation of photo-induced electron–hole pairs, and lowered recombination rate. Higher photocatalytic activity was observed for powders annealed at 500 °C, with the 10TiO2/90ZnO (mol%) sample exhibiting the highest photocatalytic degradation of the used organic dye.

Boosting Photocatalytic Hydrogen Evolution by a Light Coupling and Charge Carrier Confinement Strategy

AbstractHigh‐performance photocatalysis requires efficient light absorption and low charge carrier recombination rates. Herein, a light coupling and charge carrier confinement strategy is demonstrated to simultaneously enhance the light absorption efficiency and suppress the charge carrier recombination for high‐performance photocatalysis. The strategy is achieved by the delicate incorporation of catalysts into a dual‐core‐shell structure (e.g., CdS@SiO2@NaYF4:Yb/Tm), in which CdS (catalyst), SiO2, and NaYF4:Yb/Tm serve as shell, outer core, and inner core, respectively. Interestingly, the absorbed light can be confined within the CdS layer through multiple reflections between the CdS and SiO2 interfaces, achieving light confinement. This confinement endows a longer light residence time, enhanced light reabsorption and reutilization efficacy, and a higher concentration of photogenerated charge carriers per unit of time. Moreover, the insulating SiO2 can confine the photogenerated charge carriers within CdS layer, thus shortening their diffusion length for reduced recombination rates. Notably, when employed as the photocatalyst, this dual‐core‐shell structure showed a superb photocatalytic hydrogen evolution rate up to 74.67 mmol g−1 h−1, which is 11 times higher than that of pristine CdS. This work provides a new strategy for the design and synthesis of high‐performance photocatalysts.

Exploring the photocatalytic breakdown of organic pollutants using intercalated ZnO/SiO2 nanocomposites

The increasing prevalence of organic pollutants in water sources necessitates the development of efficient and cost-effective photocatalysts for their degradation. ZnO nanoparticles (NPs) have been widely studied for their photocatalytic properties; however, their application is hindered by low photocatalytic efficiency and high recombination rates of photogenerated carriers. This manuscript explores the enhanced photocatalytic performance of intercalated ZnO/SiO2 nanocomposites (NCs), synthesized through a combination of co-precipitation and Stöber methods, as a solution to these challenges. A comprehensive analysis of the structural, optical elemental and Morphological properties of both ZnO NPs and ZnO/SiO2 NCs was conducted using various characterization techniques, including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV–Vis spectrometry and Brunauer-Emmett-Teller (BET) analysis. Through, XRD analysis, the calculated crystallite sizes of ZnO NPs and ZnO/SiO₂ NCs were found to be 36 nm and 39 nm respectively. TEM images illustrated that the ZnO NPs and ZnO/SiO₂ NCs have crystallized in elongated spherical morphology. XPS and FTIR analyses provided the signature band details the presence of Cu and Si in their Zn2⁺ and Si⁴⁺ oxidation states. The optical bandgap energies were calculated to be 3.38 eV for ZnO NPs and 3.22 eV for ZnO/SiO₂ NCs. The enhanced photocatalytic efficiency of the ZnO/SiO2 NCs achieved an impressive degradation rate of 92 % for Rhodamine B (RhB), compared to a relatively lower rate of 81 % for pure ZnO NPs for the degradation of RhB under visible light due to its lower bandgap, high surface area, and lower electron-hole recombination rate. BET surface area measurements revealed that ZnO nanoparticles have a surface area of 11.234 m2/g, while ZnO/SiO₂ NCs show 57.118 m2/g, highlighting SiO₂'s enhancement. The NCs demonstrated exceptional reusability for degradation, sustaining high efficiency across multiple cycles. Its ability to scavenge superoxide radicals highlighted the effectiveness of the ZnO/SiO₂ NCs in environmental remediation, especially for wastewater treatment.

Enhanced Structural, Optical, and photovoltaic properties of Sm-Doped MAPbI2Br perovskite solar cells

Samarium-enhanced methylammonium lead iodide bromide (Sm-MAPbI2Br) thin films were applied onto FTO-glass substrates. X-ray diffraction (XRD) analysis revealed an enlargement in grain size to 29.09 nm, a decrease in dislocation line density to 4.32 x 1015 m−2, an expansion in d-spacing to 5.18 Å, a reduction in lattice constant to 1.59 Å, and a diminished volume in the cubic crystal lattice of MAPbI2Br. The incorporation of Sm2+ ions resulted in a narrowed band gap energy (1.95 eV), an augmented refractive index (2.65), and a decreased extinction coefficient (2.24). The solar cell constructed with a 5 % Sm2+ doping level demonstrated an enhanced open-circuit voltage of 1.05 V, a notable increase in short-circuit current density to 9.87 mA/cm2, a fill factor of 0.80, and an elevated efficiency reaching 9.32 %. Comparative analyses suggest that the cell with 5 % Sm2+ doping experiences a lower rate of recombination compared to undoped MAPbI2Br-based cells. EIS is used to investigate enhanced charge transport in hybrid MAPbI2Br devices, emphasizing the impact of a Sm-doped thin layer on carrier dynamics. The robustness of the open-circuit voltage highlights the potential of layering MAPbI2Br in the development of highly efficient solar cells.

Cu-doped NaNbO3 nanorods: Enhanced photocatalytic activity for RhB dye removal and antibacterial activity against E. coli

Sodium niobate (NaNbO3) nanorods with Cu (0.00, 0.01, 0.02 and 0.04 mmol) insertion were prepared by the microwave-assisted hydrothermal method and the photocatalytic and antibacterial activity was explored for the first time. X-ray diffraction confirms the coexistence of two orthorhombic phases (P21ma and Pbma) for all samples, with the percentage of each phase being strongly influenced by doping. The micrographs reveal that doping did not alter the shape or size of the grains (nanorods, with a diameter of ∼200 nm and a length of tens micrometers). The samples of pure NaNbO3 and those with 0.01 and 0.02 mmol of Cu showed an average band gap value of 3.08 eV. However, the sample containing 0.04 mmol of Cu exhibited a slight redshift. The photocatalytic activity of the samples was assessed by the removal of Rhodamine B dye (RhB), under ultraviolet light. All doped samples exhibited superior performance, with the sample containing 0.02 mmol of Cu showing the best photocatalytic activity, achieving 100 % RhB removal in 50 min. This was attributed to a lower rate of recombination of photogenerated charges, as evaluated through photoluminescence analysis. Additionally, the photocatalyst demonstrated excellent recyclability over three cycles. Pure NaNbO3 nanorods showed no antibacterial activity, but doping with 0.04 mmol of Cu reduced the growth of Escherichia coli.

Chlorine-Modified Soluble Melem-Based Graphitic Carbon Nitrite: Facile Synthesis, Catalytic Property and Ultrafast 2D IR Spectroscopic Characterization.

On the basis of thermal etching bulk graphitic carbon nitride (g-C3N4), a mild hydrochloric acid treatment method was used in this work to produce g-C3N4 nano-sheets (CNNS) and further carbon nitride with chloride-modification (CNCl). The latter has thinner layer and smaller particle size and exhibit greatly improved dispersibility and solubility in water, DMSO and other polar solvents. A typical photocatalytic reaction in solution driven by CNCl shows a significantly improved photocatalytic performance over bulk g-C3N4 and CNNS. Steady-state analytical tools including SEM, mass, UV-Vis, and IR spectroscopies, and time-resolved two-dimensional infrared (2D IR) vibrational spectroscopy, were used together in this work. Better solubility, more flexible structure, smaller size, easier generation of free radicals and lower recombination rate of electron-hole pair, are believed to be reasons for the superior photocatalytic performance of CNCl.

Competent CuS QDs@Fe MIL101 heterojunction for Sunlight-driven degradation of pharmaceutical contaminants from wastewater

In this study, we introduce an advanced photocatalyst developed by integrating copper sulfide quantum dots (CuS QDs) with an iron-based metal–organic framework (MOF), specifically Fe MIL101. The resulting CuS QDs@Fe MIL101 photocatalyst is engineered to efficiently degrade meloxicam (MLX) under simulated sunlight. The heterojunctions were generated by incorporating different concentrations of CuS QDs (5 %, 10 %, 15 %, 20 %, and 50 %) into the Fe MIL101 MOF matrix using the microwave-assisted hydrothermal method. The results of the XRD and the TEM studies confirmed the formation of the heterojunctions, which maintain the structural integrity of both CuS QDs and Fe MIL101. The BET measurements indicated a decrease in surface area upon CuS QDs incorporation, attributed to porés blockage and structural modifications. UV–Vis diffuse reflectance spectroscopy (DRS) revealed a redshift in absorption edges as CuS QDs content increased, enhancing visible light absorption. Photoluminescence (PL) investigations revealed that the 15 % CuS QDs@Fe MIL101 heterojunction had an effective charge separation and low recombination rates. The zeta potential analysis revealed a negative surface charge, indicating an overall electronegative characteristic. The photocatalytic performance, assessed through the degradation of MLX, demonstrated that the 15 % CuS QDs@Fe MIL101 heterojunction achieved the maximum degradation efficiency, reaching 96 % after 45 min of irradiation at a dosage of 0.1 g/L. This exceptional performance is attributed to potent charge separation, improving visible light absorption, high surface area and adsorption capacity. Various scavengers were used to investigate the roles of different reactive species, revealing holes as the predominant active species in the photocatalytic degradation process. These results highlight the potential of 15 % CuS QDs@Fe MIL101 heterojunctions as efficient photocatalyst for environmental remediation from pharmaceutical pollutants under simulated sunlight. These findings highlight the potential for application of CuS QDs@Fe MIL101 in real-world wastewater treatment systems, particularly in addressing pharmaceutical contaminants like meloxicam in industrial effluents.

Recent innovations in engineering Zinc Oxide (ZnO) nanostructures for water and wastewater treatment: Pushing the boundaries of multifunctional photocatalytic and advanced biotechnological applications

Owing to its rapid advancement in nanotechnology, latest publications (recent 5 years) related to zinc oxide (ZnO) in various aspects and applications have been reviewed. Trend has shifted to the innovation of pristine ZnO nanostructures functionalized with elemental dopants and heterojunction to improve the photoactivities on micropollutant degradation and heavy metals removal as well as the antibacterial effect towards microorganisms. The fundamentals of improved photoactivities (i.e., low recombination rate of charge carrier and effective charge transfer) and enhanced antibacterial properties (i.e., dissolution of ions and generation of reactive oxygen species) are accentuated. Subsequently, a detailed examination is undertaken to elucidate the key impacts of ZnO on actual wastewater treatment systems. This review concludes with a consolidated overview on the recent advances of ZnO for environmental wastewater decontamination and the future prospects on tailoring ZnO based on their photocatalytic and antibacterial properties to match various expectations from practical applications while minimising the adverse impacts on surrounding environment.

Bismuth-based photocatalysts enhanced by sulfur/oxygen vacancies for the selective reduction of carbon dioxide into methane

Reducing carbon dioxide (CO2) into methane (CH4) through photocatalysis technology can effectively decrease carbon emissions and ease the energy crisis. However, the low photocatalytic efficiency and high electron-hole recombination rates still hinder the large-scale utilization of photocatalysis. Vacancy engineering can reduce electron-hole pair complexation, however, the effects of oxygen (O) and sulfur (S) vacancies on the CO2 reduction properties of bismuth (Bi)-based photocatalysts are unclear. This study prepared different Bi-based photocatalysts, including α-Bi2O3, α-Bi2O3-X, Bi2S3, and Bi2S3-X. The introduction of vacancies was found to greatly increase the specific surface areas, effectively reduce electron-hole recombination, decrease charge transfer resistance, and enhance electron transfer, leading to enhanced CH4 production. Comparatively, Bi2S3-X has substantially demonstrated a superior efficiency in the photocatalytic conversion of CO2 to CH4 compared to Bi2S3, while α-Bi2O3-X exhibited slightly higher than α-Bi2O3. There are more S vacancies in Bi2S3-X (x=0.581) than O vacancies in α-Bi2O3-X (x=0.329), leading to its superior photocatalytic activity, with CO and CH4 production rates of 3.706 μmol·g−1·h−1 and 7.697 μmol·g−1·h−1, respectively. Moreover, the CH4 selectivity of Bi2S3-X reaches 67.50 %, which is 1.67 times that of α-Bi2O3-X. Therefore, Bi2S3-X holds great promise as a photocatalyst for CO2 reduction. This work proves that in Bi-based photocatalyst, S vacancy is more effective than O vacancy in enhancing the selective reduction of CO2 to CH4, offering a pathway for achieving selective CO2 reduction to CH4.

Ag3PO4 anchored SnWO4 Z-scheme heterojunction for reactive blue 21 degradation: Performance analysis and mechanism insights

The Ag3PO4–SnWO4 heterostructured nanocomposites have been prepared by the chemical precipitation process. The prepared nanocomposites were examined through XRD, TEM, UV–visible NIR, PL, BET, Mott Schottky, EIS, and ESR measurements. The diffraction peaks of Ag3PO4–SnWO4 nanocomposite showed the peaks of SnWO4 nanoparticles that are orthorhombic in the Ag3PO4 tetragonal structure, which suggested that they are present in the mixed phase of the composite. Photoluminescence spectra displayed efficiency in charge separation of e−-h+ pairs in Ag3PO4–SnWO4-1 nanocomposite. The Ag3PO4–SnWO4 nanocomposites have been examined for degrading the aqueous solution of reactive blue (RB 21) under natural sunlight irradiation. The superior photoactivity of Ag3PO4–SnWO4-1 could be ascribed to the existence of a heterostructure between Ag3PO4 and SnWO4 nanoparticles that improved the light absorption ability of the heterostructure. Also, a low rate of recombination of electron and hole pairs between Ag3PO4 and SnWO4 nanoparticles was observed. The Mott–Schottky plot revealed both Ag3PO4 and SnWO4 as n type semiconductor with flat-band potential values as 0.34 and −0.54 eV respectively. The photocatalytic rate reached the fastest on the incorporation of 100 mg SnWO4 compared to pristine Ag3PO4 and SnWO4 particles with 91.4% degradation efficiency and a rate constant of 0.257 min−1. The photogenerated O2∙−, h+ and ∙OH radicals indicated by the radical trapping experiment were mainly liable for the RB 21 degradation.

Fabrication of In-doped CdSe/Zn3In2S6 type II heterojunction composite for efficient photocatalytic hydrogen evolution

Conversion of water into renewable hydrogen energy using solar energy is one of the ideal methods to address the current environmental pollution and increasing energy demand. Thus developing the photocatalyst with high efficiency, stability, and a low electron-hole recombination rate becomes very important. In this paper, Zn3In2S6 microspheres were synthesized by hydrothermal method, and then In-doped CdSe nanoparticles were loaded on the surface of Zn3In2S6 microspheres to form Cd0.9In0.1Se/Zn3In2S6 type II heterojunction. Under simulated sunlight irradiation, the photocatalytic hydrogen production of Cd0.9In0.1Se/Zn3In2S6 reached 11.41 mmol h−1 g−1, which was 4.61 times and 1.97 times that of Cd0.9In0.1Se and Zn3In2S6, respectively. The experimental results showed that the formation of type II heterojunction could improve the photocatalytic hydrogen production efficiency by shortening the charge transport distance and inhibiting the recombination of electron-hole pairs. This work will provide new ideas and insights for the development of photocatalytic hydrogen production technology.