Direct Z-scheme heterostructure of p-CuAl2O4/n-Bi2WO6 composite nanofibers for efficient overall water splitting and photodegradation

Carboxylated nanodiamonds@CuAl2O4@TiO2 nanocomposite for the dispersive micro-solid phase extraction of nickel at trace levels from food samples

Heavy metal pollution poses a significant health risk, necessitating regular environmental monitoring for public safety. Elevated nickel concentrations can disrupt ecosystems and impact human health. This study presents a nano-sorbent can be used for dispersive micro-solid phase extraction of nickel. The nano-sorbent was characterized using FT-IR, XRD, FESEM, BET, and BJH. It demonstrated remarkable efficiency due to its nanoscale properties, optimizing results in exceptional extraction performance with minimal interference from common ions. A flame atomic absorption spectrometer was utilized for all measurements. It has a low LOD (0.29 μg L-1) and RSDs% (7.3 % and 6 % intra-day and inter-day, respectively), minimal variation, and a precisely accurate correlation (0.997). It can be used on black tea, green tea, carrots, coffee beans, tuna fish, herring fish, tobacco, soil, natural water, and wastewater samples. The accuracy of the method was assessed by analyzing TMDA-64.3 fortified water and NIST 1573a tomato leaves certified reference materials.

CAZ Composite Photocatalysts for H2 Production and Degradation under Visible Light

g-C3N4/Ag-ZnO (CAZ) composite photocatalysts were synthesized successfully by the hydrothermal method. The photocatalytic performance of photocatalysts was assessed through experiments measuring both hydrogen (H2) production and the degradation of methylene blue (MB). The H2 production rate of 60% CAZ reached 2.450 mmol·g-1·h-1, which was 8.5 times that of g-C3N4. 25% CAZ degraded 99.14% of MB dye within 40 min, and its degradation rate constant was 12.4 times that of g-C3N4. CAZ composite photocatalysts have good synergistic properties in degradation and hydrogen production and exhibit better photocatalytic performance. A Z-scheme photocatalytic system mechanism of CAZ has been proposed for the enhanced H2 production and photocatalytic degradation rate.

Co(II)-Based Metal-Organic Framework Derived CA-CoNiMn-CLDHs with Peroxidase-like Activity for Colorimetric Detection of Phenol

Given the serious harm of toxic phenol to human health and the ecological environment, it is urgent to develop an efficient, low-cost and sensitive nanoenzyme-based method to monitor phenol. MOF-derived nanozyme has attracted wide interest due to its hollow polyhedra structure and porous micro-nano frameworks. However, it is still a great challenge to synthesize MOF-derived multimetal synergistic catalytic nanoenzymes in large quantities with low cost. Herein, we reported the synthetic strategy of porous hollow CA-CoNiMn-CLDHs with ZIF-67 as templates through a facile solvothermal reaction. The prepared trimetallic catalyst exhibits excellent peroxidase-like activity to trigger the oxidative coupling reaction of 4-AAP and phenol in the presence of H2O2. The visual detection platform for phenol based on CA-CoNiMn-CLDHs is constructed, and satisfactory results are obtained. The Km value for CA-CoNiMn-CLDHs (0.21 mM) is lower than that of HRP (0.43 mM) with TMB as the chromogenic substrate. Because of the synergistic effect of peroxidase-like activity and citric acid functionalization, the built colorimetric sensor displayed a good linear response to phenol from 1 to 100 μM with a detection limit of 0.163 μM (3σ/slope). Additionally, the CA-CoNiMn-CLDHs-based visual detection platform possesses high-chemical stability and excellent reusability, which can greatly improve economic benefits in practical applications.

Preparation and characterization of a novel cobalt-substitution cadmium aluminate spinel for the photodegradation of azo dye pollutants

Modern-year organic contaminants have been highly observed in ecosystems since they are not removed entirely and remain dangerous. Semiconductor binary oxide photocatalysts have been well accredited as capable technology for ecological contaminants degradation in the existence of visible irradiation. In this research, novel Co ions doped CdAl₂O₄ materials were fabricated by a facile co-precipitation approach. The fabricated pure and Co-doped CdAl₂O₄ exhibited the typical peaks of CdAl₂O₄ with the E_g of 3.66, 3.24, 2.57, and 2.41 eV respectively. The HR-TEM microstructures revealed that the Co (0.075 M) doped CdAl₂O₄ has rod-like morphology, and some places are spherical with particle sizes reaching 21 nm. The PL peaks of the Co (0.075 M)-CdAl₂O₄ are much lesser than that of the other dopant and pure CdAl₂O₄, representing much more effectual separation of generated e^- and h⁺ at the interface which in fact outcomes in superior expected photodegradation behaviours. The Co (0.075 M)-CdAl₂O₄ catalyst demonstrated the highest performances of 92 and 94% toward the degradation of both dyes, respectively, owing to the lowest e^- and h⁺ recombination rate. The Co (0.075 M) doped CdAl₂O₄ photocatalyst revealed outstanding reusability and stability under visible irradiation, retaining the performance of about 83 and 86% after the fifth consecutive run of BB and BG elimination. A probable photodegradation mechanism of Co (0.075 M) doped CdAl₂O₄ was suggested since the photoexcited h⁺, OH^- and O₂^- species contributed to the removal process, and that was affirmed by the scavenging test and ESR analysis. This research offers new ways to improve the photodegradation performance of the Co-doped CdAl₂O₄ catalyst that will be employed in pharmaceutical applications and wastewater treatment.

Electrospun composite nanofibers as novel high-performance and visible-light photocatalysts for removal of environmental pollutants: A review

Environmental pollution caused by industries and human manipulations is coming a serious global challenge. On the other hand, the world is facing an energy crisis caused by population growth. Designing solar-driven photocatalysts which are inspired by the photosynthesis of plant leaves is a fantastic solution to use solar energy as green, available, and unlimited energy containing ∼50% visible light for the removal of environmental pollutants. The polymeric and non-polymeric-based electrospun composite nanofibers (NFs) are as innovative photocatalytic candidates which increase photocatalytic activity and transition from UV light to visible light and overcome the aggregation, photocorrosion, toxicity, and hard recycling and separation of the nanosized powder form of photocatalysts. The composite NFs are fabricated easily by either embedding the photocatalytic agents into the NFs during electrospinning or via their decorating on the surface of NFs post-electrospinning. Polyacrylonitrile-based, tungsten trioxide-based, zinc oxide-based, and titanium dioxide-based composite NFs were revealed as the most reported composite NFs. All the lately investigated electrospun composite NFs indicated long-term stability, high photocatalytic efficiency (∼> 80%) within a short time of light radiation (10-430 min), and high stability after several cycles of use. They were applied in various applications including degradation of dyes/antibiotics, water splitting, wastewater treatment, antibacterial usage, etc. The photogenerated species especially holes, O₂^∙-, and ^.OH were mostly responsible for the photocatalytic mechanism and pathway. The electrospun composite NFs have the potential to use in large-scale productions in condition that their thickness and recycling conditions are optimized, and their toxicity and detaching are resolved.

Recent Advances in Semiconductor Heterojunctions and Z-Schemes for Photocatalytic Hydrogen Generation

The formation of semiconductor heterojunctions and Z-schemes is still a very prominent and efficient strategy of materials chemists to extend the absorption range of semiconductor combinations. Moreover, the spatial separation of photoexcited charge carriers and thereby the reduction of their recombination ultimately lead to increased photocatalytic activities. The present article reviews recent trends in semiconductor heterojunctions and Z-schemes with a focus on hydrogen generation and water splitting, exhibiting specific needs for charge carrier separation. We also included recent material trends, i.e. 2D/2D combinations, direct Z-schemes, MOFs and COFs, and combinations with upconversion materials.

Efficient ofloxacin degradation via photo-Fenton process over eco-friendly MIL-88A(Fe): Performance, degradation pathways, intermediate library establishment and toxicity evaluation

The high-throughput production of the eco-friendly MIL-88A(Fe) was achieved under mild reaction conditions with normal pressure and temperature. The as-prepared MIL-88A(Fe) exhibited efficient photo-Fenton catalytic ofloxacin (OFL) degradation upon visible light irradiation with good stability and reusability. The OFL (20.0 mg/L) was completely degraded within 50 min under visible light with the aid of MIL-88A(Fe) (0.25 g/L) and H₂O₂ (1.0 mL/L) in aqueous solution (pH = 7.0). The hydroxyl radicals (·OH) are the main active species during the photo-Fenton oxidation process. Meanwhile, the degradation intermediates and the corresponding degradation pathways were identified and proposed with the aid of both ultra-high performance liquid chromatography tandem quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) and density functional theory (DFT) calculations. Finally, the degradation product library was firstly established to identify intermediate transformation products (TPs) with their variation of concentration, and their corresponding toxicologic activities were assessed via Toxtree and T.E.S.T software as well. Finally, the MIL-88A is efficient and stable with four cycles' catalysis operations, demonstrating good potential for water treatment.

High-activity daisy-like zeolitic imidazolate framework-67/reduced grapheme oxide-based colorimetric biosensor for sensitive detection of hydrogen peroxide

Colorimetric biosensors, based on enzyme-like nanomaterials, have come into the spotlight in virtue of their visual detection. Herein, a daisy-like zeolitic imidazolate framework-67/reduced grapheme oxide (ZIF-67/rGO) nanozyme with unique 3D hierarchical structures has been designed to realize visual detection of hydrogen peroxide (H₂O₂) that is recognized as a strong oxidizing agent or reactive oxygen species associated with oxidative stress in biological systems. The daisy-like ZIF-67/rGO is prepared by a facile one-step liquid-phase method conducted under room temperature. The successful introduction of rGO endows the daisy-like ZIF-67/rGO nanozyme with abundant porous structure, high specific surface area, and good charge transfer capability, which significantly accelerates the adsorbability and recognition towards the substrates and the oxidation rate of TMB-H₂O₂ reaction, and thus improving the nanozyme activity observably. It is conductive to nanozyme-modulated H₂O₂ determination. The established colorimetric biosensor platform based on ZIF-67/rGO nanozyme exhibits remarkable sensitivity and high specificity for the application in visual detection of H₂O₂. The detection limit of ZIF-67/rGO-based biosensor platform is as low as 3.81 μM, which is nearly 8 times lower than that of ZIF-67-based biosensor platform. Moreover, its potential applicability as an ideal platform for colorimetric biosensors is demonstrated by testing the concentration of H₂O₂ in milk samples, which sheds light on the promising application of the proposed biosensing system in point-of-care detection.

Highly efficient and selective photocatalytic CO2 reduction of MIL-125(Ti) based on LiFePO4 and CuO QDs surface-interface regulation

In this study, the CuO quantum dots was encapsulated MIL-125 (Ti) MOF by a simple oxidation method, and then further formed LiFePO4/CuO@MIL-125(Ti) with LiFePO4 loading. Due to the protection of...

Piezoelectric polarization modulated novel Bi2WO6/g-C3N4/ZnO Z-scheme heterojunctions with g-C3N4 intermediate layer for efficient piezo-photocatalytic decomposition of harmful organic pollutants

It is of great significance to understand the role of carrier in piezocatalysis of composites by studying the separation mode of carriers under dynamic polarization field. Herein, the separation and migration pathways of carriers under piezoelectric field are investigated by synthesizing heterojunctions with Bi₂WO₆ (BWO) nanosheets grown vertically on g-C₃N₄ (CN) coated ZnO nanorods and directly on ZnO. Compared with the photocatalysis, the piezocatalytic efficiency of Rhodamine B (RhB) by BWO/ZnO is significantly increased to 0.121 min^-1, which indicated the polarization field promotes band tilt and Z-scheme formation. After introducing the CN interlayer, the piezocatalytic efficiency of BWO/CN/ZnO is further improved (0.217 min^-1), which can be attributed to the unique core-shell structure with Z-scheme heterojunctions. This unique structure provides more active sites and excited carrier concentration, the intermediate layer CN also reduces the direct contact and recombination of electrons and holes controlled by polarization potential at the interface between BWO and ZnO. This work deeply analyzes the influence of carrier concentration, separation efficiency and transport process on piezocatalysis, which provides a reference for the design of efficient catalysts.

Exploring the impact of calcination parameters on the crystal structure, morphology, and optical properties of electrospun Fe2TiO5 nanofibers

Nanostructured Fe₂TiO₅ (pseudobrookite), a mixed metal oxide material holds significant promise for utilization in energy and environmental applications. However, its full application is still hindered due to the difficulty to synthesize monophasic Fe₂TiO₅ with high crystallinity and a large specific surface area. Herein, Fe₂TiO₅ nanofibers were synthesized via a versatile and low-cost electrospinning method, followed by a calcination process at different temperatures. We found a significant effect of the calcination process and its duration on the crystalline phase in the form of either pseudobrookite or pseudobrookite–hematite–rutile and the morphology of calcined nanofibers. The crystallite size increased whereas the specific surface area decreased with an increase in calcination temperature. At higher temperatures, the growth of Fe₂TiO₅ nanoparticles and simultaneous coalescence of small particles was noted. The highest specific surface area was obtained for the sample calcined at 500 °C for 6 h (S_BET = 64.4 m² g⁻¹). This work opens new opportunities in the synthesis of Fe₂TiO₅ nanostructures using the electrospinning method and a subsequent optimized calcination process for energy-related applications.

Nanostructured Fe₂TiO₅ (pseudobrookite), a mixed metal oxide material holds significant promise for utilization in energy and environmental applications.

Rational design of n-Bi12TiO20@p-BiOI core-shell heterojunction for boosting photocatalytic NO removal

Bismuth titanate (Bi₁₂TiO₂₀) with unique sillenite structure has been shown to be an excellent photocatalyst for environmental remediation. However, the narrow light-responsive range and rapid recombination of photoinduced electrons-holes limit the photocatalytic performance of Bi₁₂TiO₂₀. To overcome the limitations, a practical and feasibleway is to fabricate heterojunctions by combining Bi₁₂TiO₂₀ with suitable photocatalysts. Here, using a facile chemical precipitation method, a novel and hierarchical core-shell structure of n-Bi₁₂TiO₂₀@p-BiOI (BTO@BiOI) heterojunction was rationally designed and synthesized by loading BiOI nanosheets on BTO nanofibers. The constructed BTO@BiOI composites exhibited significant charge transfer ability due to the synergistic effects of the built-in electric field between BTO and BiOI as well as close interfacial contacts. In addition, the narrow bandgapcharacteristics of the BiOI led to wide light absorption ranges. Therefore, the BTO@BiOI heterojunction exhibited an improved photocatalytic performance under visible light irradiation. The NO removal efficiency of optimal BTO@BiOI was 45.7%, which was significantly higher compared tothat of pure BTO (3.6%) or BiOI (23.1%). Moreover, the cycling experiment revealed that BTO@BiOI composite has a good stability and reusability. The possible mechanism of photocatalytic NO oxidation over BTO@BiOI was investigated in detail.

Simple fabrication of Z-scheme MgIn2S4/Bi2WO6 hierarchical heterostructures for enhancing photocatalytic reduction of Cr(vi)

Direct Z-scheme MgIn2S4/Bi2WO6 hierarchical heterostructures were simply fabricated, exhibiting distinctly enhanced photocatalytic activity for Cr(vi) reduction under simulated sunlight irradiation.

Highly efficient activation of peroxymonosulfate by Co3O4/Bi2WO6 p-n heterojunction composites for the degradation of ciprofloxacin under visible light irradiation

Photocatalytic technology assisted via peroxymonosulfate (PMS) has good potential in water treatment. In this study, the Co₃O₄/Bi₂WO₆ composite was constructed via an in-situ calcination process and used to activate PMS for the degradation of ciprofloxacin (CIP) under visible light irradiation. The obtained 5 wt% Co₃O₄/Bi₂WO₆(CBWO-2) can highly effectively remove 86.2% CIP within 5 min visible light irradiation in presence of PMS. The excellent degradation performance of Co₃O₄/Bi₂WO₆/PMS system can be attributed to the synergistic effect between p-n heterojunction and PMS activation. The conduction band and valence band deviation between Co₃O₄ and Bi₂WO₆ were calculated by XPS techniques. Besides, DFT calculations were performed to further confirm the internal structure between Co₃O₄ and Bi₂WO₆. This work not only provides an approach to fabricate heterostructures but also indicated that Co₃O₄/Bi₂WO₆/PMS/Vis system is a potential environment remediation alternative for the efficient removal of recalcitrant organic compounds from wastewaters.

Visible Light-Driven Photoelectrocatalytic Water Splitting Using Z-Scheme Ag-Decorated MoS2/RGO/NiWO4 Heterostructure

Herein, we have successfully constructed a solid-state Z-scheme photosystem with enhanced light absorption capacity by combining the optoelectrical properties of AgNPs with those of the MoS2/RGO/NiWO4 (Ag-MRGON) heterostructure. The Ag-MRGON Z-scheme system demonstrates improved photo-electrochemical (PEC) water-splitting performance in terms of applied bias photon-to-current conversion efficiency (ABPE), which is 0.52%, and 17.3- and 4.3-times better than those of pristine MoS2 and MoS2/NiWO4 photoanodes, respectively. The application of AgNPs as an optical property enhancer and RGO as an electron mediator improved the photocurrent density of Ag-MRGON to 3.5 mA/cm2 and suppressed the charge recombination to attain the photostability of ∼2 h. Moreover, the photocurrent onset potential of the Ag-MRGON heterojunction (i.e., 0.61 VRHE) is cathodically shifted compared to those of NiWO4 (0.83 VRHE), MoS2 (0.80 VRHE), and MoS2/NiWO4 heterojunction (0.73 VRHE). The improved PEC water-splitting performance in terms of ABPE, photocurrent density, and onset potential is attributed to the facilitated charge transfer through the RGO mediator, the plasmonic effect of AgNPs, and the proper energy band alignments with the thermodynamic potentials of hydrogen and oxygen evolution.

Efficient reduction of Cr(VI) by a BMO/Bi2S3 heterojunction via synergistic adsorption and photocatalysis under visible light

The development of efficient visible light driven photocatalyst is the premise of the progress of photocatalytic technology. In this paper, a well-designed orthorhombic Bi₂MoO₆/Bi₂S₃ (BMO/Bi₂S₃) composite was obtained by a two-step fabrication route. Using MoO₃ nanobelt as a sacrificial template, BMO nanosheet-based framework was prepared by refluxing process. Through anion exchange reaction of the synthesized BMO to introduce Bi₂S₃ nanosheets, and BMO/Bi₂S₃ heterojunction was successfully constructed. Simultaneously, the Bi₂S₃ loading percentage of BMO/Bi₂S₃ was controlled by tuning the anion exchange time. The intimate interfacial contact between the BMO framework and Bi₂S₃ nanosheets endows the nanocomposites with high adsorption and photocatalytic removal of Cr(VI). Photocatalytic tests show that BMO/Bi₂S₃-1 composite possess the highest activity with 100 % removal rate of Cr(VI) in 15 min. The dramatically enhanced adsorption and photocatalytic capacity of BMO/Bi₂S₃ photocatalysts can be ascribed to the frame structure, large surface area and numerous nanochannels. In addition, the BMO/Bi₂S₃ photocatalyst is highly stable during the reaction and can be used repeatedly. These features indicate that the BMO/Bi₂S₃ composite could be used for environmental remediation and wastewater treatment.