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

Enhanced oxygen anions generation on Bi2S3/Sb2S3 heterostructure by visible light for trace H2S detection at room temperature

Bismuth sulfide (Bi2S3) possesses unique properties that make it a promising material for effective hydrogen sulfide (H2S) detection at room temperature. However, when exposed to light, the oxygen anions (O2-(ads)) adsorbed on the surface of Bi2S3 can react with photoinduced holes, ultimately reducing the ability to respond to H2S. In this study, Bi2S3/Sb2S3 heterostructures were synthesized, producing photoinduced oxygen anions (O2-(hv)) under visible light conditions, resulting in enhanced H2S sensing capability. The Bi2S3/Sb2S3 heterostructure sensor exhibits a two-fold increase in sensing response to 500 ppb H2S under in door light conditions relative to its performance in darkness. Additionally, the sensing response of the Bi2S3/Sb2S3 sensor (Ra/Rg= 23.3) was approximately five times higher than pure Bi2S3. The improved sensing performance of the Bi2S3/Sb2S3 heterostructures is attributable to the synergistic influence of the heterostructure configuration and light modulation, which enhances the H2S sensing performance by facilitating rapid charge transfer and increasing active sites (O2-(hv)) when exposed to visible light.

Enhanced photocatalytic performance of SnS2 under visible light irradiation: strategies and future perspectives

Tin(II) sulfide (SnS2) has emerged as a promising candidate for visible light photocatalytic materials. As a member of the transition metal dichalcogenides (TMDs) family, SnS2 features a band gap of approximately 2.20 eV and a layered structure, rendering it suitable for visible light activation with a high specific surface area. However, the application of SnS2 as a visible light photocatalyst still requires improvement, particularly in addressing the high recombination of electrons and holes, as well as the poor selectivity inherent in its perfect crystal structure. Therefore, ongoing research focuses on strategies to enhance the photocatalytic performance of SnS2. In this comprehensive review, we analyze recent advances and promising strategies for improving the photocatalytic performance of SnS2. Various successful approaches have been reported, including controlling the reactive facets of SnS2, inducing defects in the crystal structure, manipulating morphologies, depositing noble metals, and forming heterostructures. We provide a detailed understanding of these phenomena and the preparation techniques involved, as well as future considerations for exploring new science in SnS2 photocatalysis and optimizing performance.

Efficient visible-light-driven S-scheme AgVO3/Ag2S heterojunction photocatalyst for boosting degradation of organic pollutants

The traditional semiconductor photocatalysts for solving the related environmental aggravation are often challenged by the recombination of photogenerated carriers. Designing an S-scheme heterojunction photocatalyst is one of the keys to tackling its practical application problems. This paper reports an S-scheme AgVO₃/Ag₂S heterojunction photocatalyst constructed via a straightforward hydrothermal approach that exhibits outstanding photocatalytic degradation performances to the organic dye Rhodamine B (RhB) and antibiotic Tetracycline hydrochloride (TC-HCl) driven by visible light. The results show that AgVO₃/Ag₂S heterojunction with a molar ratio of 6:1 (V6S) possesses the highest photocatalytic performances, 99% of RhB can be almost degraded by 0.1 g/L V6S within 25 min light illumination, and about 72% of TC-HCl can be photodegraded with the act of 0.3 g/L V6S under 120 min light irradiation. Meanwhile, the AgVO₃/Ag₂S system exhibits superior stability and maintains high photocatalytic activity after 5 repeated tests. Moreover, the EPR measurement and radical capture test identify that superoxide radicals and hydroxyl radicals mainly contribute to the photodegradation process. The present work demonstrates that constructing an S-scheme heterojunction can effectively inhibit the recombination of carriers, providing insights into the fabrication of applied photocatalysts for practical wastewater purification treatment.

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.

Special Issue: Smart Nanomaterials for Environmental Remediation

Nanomaterials that can be reversibly or irreversibly changed in structures and properties by the influence of external chemical and physical stimuli are defined as smart nanomaterials [...].

Enhancement in Photoelectrochemical Performance of Optimized Amorphous SnS2 Thin Film Fabricated through Atomic Layer Deposition

Two-dimensional (2D) nanomaterials have distinct optical and electrical properties owing to their unique structures. In this study, smooth 2D amorphous tin disulfide (SnS₂) films were fabricated by atomic layer deposition (ALD), and applied for the first time to photoelectrochemical water splitting. The optimal stable photocurrent density of the 50-nm-thick amorphous SnS₂ film fabricated at 140 °C was 51.5 µA/cm² at an oxygen evolution reaction (0.8 V vs. saturated calomel electrode (SCE)). This value is better than those of most polycrystalline SnS₂ films reported in recent years. These results are attributed mainly to adjustable optical band gap in the range of 2.80 to 2.52 eV, precise control of the film thickness at the nanoscale, and the close contact between the prepared SnS₂ film and substrate. Subsequently, the photoelectron separation mechanisms of the amorphous, monocrystalline, and polycrystalline SnS₂ films are discussed. Considering above advantages, the ALD amorphous SnS₂ film can be designed and fabricated according to the application requirements.

The Roles of Nanomaterials in Conventional and Emerging Technologies for Heavy Metal Removal: A State-of-the-Art Review

Heavy metal (HM) pollution in waterways is a serious threat towards global water security, as high dosages of HM poisoning can significantly harm all living organisms. Researchers have developed promising methods to isolate, separate, or reduce these HMs from water bodies to overcome this. This includes techniques, such as adsorption, photocatalysis, and membrane removal. Nanomaterials play an integral role in all of these remediation techniques. Nanomaterials of different shapes have been atomically designed via various synthesis techniques, such as hydrothermal, wet chemical synthesis, and so on to develop unique nanomaterials with exceptional properties, including high surface area and porosity, modified surface charge, increment in active sites, enhanced photocatalytic efficiency, and improved HM removal selectivity. In this work, a comprehensive review on the role that nanomaterials play in removing HM from waterways. The unique characteristics of the nanomaterials, synthesis technique, and removal principles are presented. A detailed visualisation of HM removal performances and the mechanisms behind this improvement is also detailed. Finally, the future directions for the development of nanomaterials are highlighted.