Ag2S QDs integration with MnO2 nanosheets for the sensitive detection of Cr (VI) via the redox reaction induced photoelectrochemical variation

The heavy metal Cr (VI) will remain, accumulate, and migrate after entering the environment or ecosystem, causing serious harm to the environment. Here, a photoelectrochemical sensor was developed for Cr (VI), utilizing the Ag₂S quantum dots (QDs) and MnO₂ nanosheets as photoactive components. By introducing Ag₂S QDs with a narrow gap, a staggered energy level match is created which effectively prevents the carrier recombination in MnO₂ nanosheets, resulting in an enhanced photocurrent response. In the presence of the electron donor, l-ascorbic acid (AA), the photocurrent of the Ag₂S QDs and MnO₂ nanosheets modified photoelectrode is further enhanced. As AA has the ability to convert Cr (VI) to Cr (Ⅲ), the photocurrent may decline due to the decrease in the electron donors when Cr (VI) is added. This phenomenon can be utilized for the sensitive detection of Cr (VI) over a wider linear range (100 pM-30 μM) with a lower detection limit of 6.46 pM (S/N = 3). This work using the strategy that the targets induced the variations of the electron donor shows the advantages of good sensitivity and nice selectivity. The sensor holds many advantages such as simple fabrication process, economical material expense, and consistent photocurrent signals. It also holds significant potential for environmental monitoring and serves as a practical photoelectric sensing approach for detecting Cr (VI).

Boosting room-temperature NO2 detection via in-situ interfacial engineering on Ag2S/SnS2 heterostructures

The effective detection of hazardous gases has become extremely necessary for the ecological environment and public health. Interfacial engineering plays an indispensable role in the development of innovative materials with exceptional properties, thus triggering a new revolution in the realization of high-performance gas sensing. Herein, the rational designed Ag₂S/SnS₂ heterostructures were synthesized via a facile in-situ cation-exchange method. The coshared S atoms derived from in-situ interfacial engineering enable intimate atomic-level contact and strong electron coupling between SnS₂ and Ag₂S, which efficiently assist interfacial charge redistribution and transport as confirmed theoretically and experimentally. Benefiting from the high-quality interface of the heterostructures, the resultant Ag₂S/SnS₂ sensor delivered an ultrahigh response (286%) together with short response/recovery time (17 s/38 s) to 1 ppm NO₂. The sensor also demonstrated superior sensing selectivity and reliable repeatability at room-temperature. Such excellent sensing performance could be synergistically ascribed to the junction effect and interfacial engineering of Ag₂S/SnS₂ heterostructures, which not only modulates the electronic properties of SnS₂ but also provides abundant adsorption sites for gas sensing. This study offers guidance for engineering heterostructures with high-quality interface, which might stimulate the exploitation of other novel materials and widen their potential applications.

Self-powered photoelectrochemical biosensor with inherent potential for charge carriers drive

Self-powered photoelectrochemical (PEC) sensing platform without external voltage has provided a breakthrough in the development of biosensors, however, it is necessary to find suitable Fermi energy level difference between photoanode materials and photocathode materials as the driving force. Herein, the self-powered PEC sensor was developed to combine the advantages of both the photoanode (SnS₂/In₂S₃) and the photocathode (CuInS₂). The sufficient Fermi level differentiation between the photoanode with the photocathode not only resulted in an evident photocurrent response vis tuning the electron transfer but avoided redox reactions of extra electron donors/acceptors to enhance the accuracy of the sensor. The biological target was immobilized on the photocathode, which allowed the sensor to possess a good anti-interference capability for the detection of real samples. The proposed PEC sensor exhibits good sensitivity for the cytokeratin 19 fragment (CYFRA21-1) detection and a low limit of detection (LOD) of 6.57 fg mL^-1. Moreover, the as-purposed PEC system with good anti-interference capability and accuracy has implications for the detection of other biomarkers.

Synergistic effects of Tin sulfide Nitrogen-doped titania Nanobelt-Modified graphitic carbon nitride nanosheets with outstanding photocatalytic activity

Designing efficient ternary nanostructures is a feasible approach for energy production under simulated solar irradiation. In this study, excellent photoexcited charge carrier separation and enhanced visible-light response were achieved with nitrogen-doped titania nanobelts (N-TNBs), whose 1D geometry facilitated the fabrication of a heterostructure with SnS₂ on the surface of graphitic carbon nitride (g-C₃N₄). We established the design of SnS₂@N-TNB and SnS₂@N-TNB/g-C₃N₄ heterostructures by in situ hydrothermal and ultrasonication processes, and achieved commendable simulated solar light driven photocatalytic H₂ generation. UV-vis diffuse reflectance spectroscopy analysis revealed a red shift in the absorption spectra of the SnS₂@N-TNB and SnS₂@N-TNB/g-C₃N₄ samples. The H₂ produced via SnS₂@N-TNB-10/g-C₃N₄ (6730.8 µmol/g/h) was 2.6 times higher than that produced by SnS₂@N-TNB (2515.1 µmol/g/h), and 299 times higher than that produced by N-TNB (22.5 µmol/g/h). The improved photocatalytic H₂ production was attributed to the maximum interface contact between SnS₂@N-TNB and g-C₃N₄, and to the improved visible-light absorption and effective charge-carrier separation. Therefore, the present study provides novel insights for combining the advantages of ternary materials to improve the conversion of solar energy to H₂ fuel.

Catalytic decontamination of organic/inorganic pollutants in water and green H2 generation using nanoporous SnS2 micro-flower structured film

Recycling water and generation of H₂ simultaneously as a green technology can be a key attraction in establishing environmental sustainability. Towards this endeavor, nanoporous SnS₂ film electrodes deposited by a solution process on nickel foam demonstrate a promising electrocatalytic activity towards generation of H₂ gas at cathode while the anodic reaction leads to the decomposition of urea-waste at the rate of 10 mA cm^-2 in 1 M KOH with a lower cell-potential of 1.38 V vs RHE. The SnS₂ electrode also demonstrates an excellent catalytic activity towards hydrogen evolution reaction in a wide pH range (0-14). In addition, the SnS₂ film deposited on an FTO-substrate shows 97.56% photocatalytic-degradation of methylene-blue dye within 180 min under irradiation of visible light with a good recyclability of the photocatalyst, suggesting its high potentiality for the practical application. The demonstrated good electro- and photo-catalytic activities can be ascribed to the nanoporous structure of SnS₂ film in a flower like 3D-fashion, offering availability of abundant active catalytic sites. Our results demonstrate the application of SnS₂ nanoporous film as catalyst can be a significant greenery path for the removal of harmful inorganic/organic hazardous wastes from waste-water with simultaneous generation of green H₂ fuel.

Fabrication of the novel Ag-doped SnS2@InVO4 composite with high adsorption-photocatalysis for the removal of uranium (VI)

A novel Ag-doped SnS₂@InVO₄ composite was successfully synthesized for efficient uranium removal from wastewater through a facile hydrothermal method. The structure, morphology and optical property of materials were characterized using various instruments. The results proved that Ag-doped SnS₂@InVO₄ composite presented as hexangular nanosheets with about 4.87 nm pore size and 101.58 m²/g specific surface area. Further characterization demonstrated that photo-adsorption ability of visible light was enhanced and band gap was narrowed. The adsorption kinetics and isotherm of U(VI) on Ag-doped SnS₂@InVO₄ composite could be depicted via the Langmuir model and pseudo-second-order mode, and the maximum adsorption capacity of U(VI) reached 167.79 mg/g. The elimination of U(VI) of as-synthesized composites was studied by a synergy of adsorption and visible-light photocatalysis, and the optimal content of InVO₄ was found to be 2 wt% with the highest removal efficiency of 97.6%. In addition, compared with pure SnS₂ and Ag-doped SnS₂, the Ag-doped SnS₂@InVO₄ composites exhibited superior photocatalytic performance for the conversion of soluble U(VI) to insoluble U(IV) under visible light. The excellent photocatalytic performance was mainly attributed to numerous surface-active sites, strong optical adsorption ability and narrow band gap. Simultaneously, the heterojunction between Ag-doped SnS₂ and InVO₄ promoted the separation and transfer of photoexcited charges. The cyclic experiments indicated the Ag-doped SnS₂@InVO₄ composite remained good structural stability and reusability. Finally, the possible mechanism was discussed based on the experimental analysis.

In situ construction efficient visible-light-driven three-dimensional Polypyrrole/Zn3In2S6 nanoflower to systematically explore the photoreduction of Cr(VI): Performance, factors and mechanism

Photoreduction of highly toxic Cr(VI) has been regarded as an efficient and green method to achieve water purification. In this process, better charge carrier separation is vital to achieving excellent performance. Besides, it is vital to systematically explore the influencing factors and reaction mechanism. Herein, a novel 3D PPy/Zn₃In₂S₆ nanoflower composite was successfully fabricated via in-situ polymerization. The remarkable conductivity of PPy provides a good electron transport path to facilitate the separation and migration of charge carriers, which benefits to the activity improvement. The results show that 5% PPy/Zn₃In₂S₆ exhibits superior photocatalytic activity with almost 100% Cr(VI) reduction just within 24 min and 99.4% of Methyl orange (MO) is degraded in 25 min. On this basis, factors of different catalyst dosage, concentration, ions and pH under the reduction system were systematically investigated. Especially, different organic acids were in-depth analyzed and the activity could be significantly enhanced just adding 0.1 mmol organic acids. 5% 3D PPy/Zn₃In₂S₆ nanoflower composites (with tartaric acid) exhibits superior photocatalytic activity, which can achieve 100% photoreduction of Cr(VI) just within 6 min. Finally, a possible reaction mechanism was proposed. Moreover, 3D PPy/Zn₃In₂S₆ nanoflower also presented an efficient photodegradation activity for organic pollution.

Two-dimensional bimetallic CoFe selenite via metal-ion assisted self-assembly for enhanced oxygen evolution reaction

A 2D CoFe selenite crystals was used as an efficient OER catalyst, which was obtained in a high yield via a simple metal-ion self-assembly strategy under hydrothermal condition.

An advanced composite with ultrafast photocatalytic performance for the degradation of antibiotics by natural sunlight without oxidizing the source over TMU-5@Ni–Ti LDH: mechanistic insight and toxicity assessment

Pharmaceuticals are considered as emerging organic contaminants that have become a serious environmental problem, which endanger human health and environmental bio-diversity.

Ag2S-Sensitized NiO-ZnO Heterostructures with Enhanced Visible Light Photocatalytic Activity and Acetone Sensing Property

Visible light-driven Ag2S-grafted NiO-ZnO ternary nanocomposites are synthesized using a facile and cost-effective homogeneous precipitation method. The structural, morphological, and optical properties were extensively studied, confirming the formation of ternary nanocomposites. The surface area of the synthesized nanocomposites was calculated by electrochemical double-layer capacitance (C dl). Ternary Ag2S/NiO-ZnO nanocomposites showed excellent visible light photocatalytic property which increases further with the concentration of Ag2S. The maximum photocatalytic activity was shown by 8% Ag2S/NiO-ZnO with a RhB degradation efficiency of 95%. Hydroxyl and superoxide radicals were found to be dominant species for photodegradation of RhB, confirmed by scavenging experiments. It is noteworthy that the recycling experiments demonstrated high stability and recyclable nature of the photocatalyst. Moreover, the electrochemical results indicated that the prepared nanocomposite exhibits remarkable activity toward detection of acetone. The fabricated nanocomposite sensor showed high sensitivity (4.0764 μA mmol L-1 cm-2) and a lower detection limit (0.06 mmol L-1) for the detection of acetone. The enhanced photocatalytic and the sensing property of Ag2S/NiO-ZnO can be attributed to the synergistic effects of strong visible light absorption, excellent charge separation, and remarkable surface properties.

Strong Hollow Spherical La2NiO4 Photocatalytic Microreactor for Round-the-Clock Environmental Remediation

This work reports a moderate round-the-clock route to treating organic pollutants by utilizing a La₂NiO₄ hollow-sphere microreactor. A glycerol-assisted solvothermal route followed by an annealing process was applied for fabricating the catalyst. Both the physicochemical properties and the catalytic performance of the as-obtained microreactor for treating pollutants were discussed. The microreactor exhibited a strong ability to degrade phenol and anionic dyes in the absence of light irradiation, owing to its high surface area and positively charged surface. With the aid of visible-light irradiation, the degradation rate of the organic pollutants could be further accelerated due to the light multireflection in a hollow structure, which enhances the utilization of light. The present work indicates that the hollow-sphere La₂NiO₄ microreactor is effectively energy saving for environmental remediation.

Ag₂S Quantum Dots Based on Flower-like SnS₂ as Matrix and Enhanced Photocatalytic Degradation

Ag₂S quantum dots were dispersed on the surface of SnS₂ nanoflowers forming a heterojunction via in-situ ion exchange to improve photocatalytic degradation of RhB. All samples exhibit the hexagonal wurtzite structure. The size of Ag₂S@SnS₂ composites are ~ 1.5 μm flower-like with good crystallinity. Meanwhile, the E_g of 3% Ag₂S@SnS₂ is close to that of pure SnS₂. Consequently, the 3% Ag₂S@SnS₂ composite displays the excellent photocatalytic performance under simulated sunlight irradiation with good cycling stability, compared to the pure SnS₂ and other composites. Due to the blue and yellow luminescence quenching, the photogenerated electrons and holes is effectively separated in the 3% Ag₂S@SnS₂ sample. Especially, the hydroxyl radicals and photogenerated holes are main active species.

Novel magnetic Fe3O4@rGO@ZnO onion-like microspheres decorated with Ag nanoparticles for the efficient photocatalytic oxidation of metformin: toxicity evaluation and insights into the mechanisms

Emerging water contaminants, including pharmaceutical and personal care products, have become a major concern in water pollution, and several efforts have been made for the efficient removal of these contaminants.

Controllable fabrication of α-Ag2WO4 nanorod-clusters with superior simulated sunlight photocatalytic performance

This work presents the greatly boosted photoactivity of α-Ag₂WO₄ nanorod-clusters fabricated by adjusting the molar ratio of raw materials.

Graphene oxide-modified LaVO4 nanocomposites with enhanced photocatalytic degradation efficiency of antibiotics

Antibiotic TC was degraded into lower toxic products using novel GO/LaVO₄ composite photocatalysts under visible light.