Few-layer MoS2 nanosheets-deposited on Bi2MoO6 microspheres: A Z-scheme visible-light photocatalyst with enhanced activity

Effective Nanocomposite Based on Bi2MoO6/MoS2/AuNRs for NIR-II Light-Boosted Photodynamic/Chemodynamic Therapy

Bi₂MoO₆ (BMO) nanoparticles (NPs) have been widely used as a photocatalyst to decompose organic pollutants, but their potential for photodynamic therapy (PDT) is yet to be explored. Normally, the UV absorption property of BMO NPs is not suitable for clinical application because the penetration depth of the UV light is too small. To overcome this limitation, we rationally designed a novel nanocomposite based on Bi₂MoO₆/MoS₂/AuNRs (BMO-MSA), which simultaneously possesses both the high photodynamic ability and POD-like activity under NIR-II light irradiation. Additionally, it has excellent photothermal stability with good photothermal conversion efficiency. The as-prepared BMO-MSA nanocomposite could induce the germline apoptosis of Caenorhabditis elegans (C. elegans) via the cep-1/p53 pathway after being illuminated by light with a wavelength of 1064 nm. The in vivo investigations confirmed the ability of the BMO-MSA nanocomposite for the induction of DNA damage in the worms, and the mechanism was approved by determining the egl-1 fold induction in the mutants that have a loss of function in the genes involved in DNA damage response mutants. Thus, this work has not only provided a novel PDT agent, which may be used for PDT in the NIR-II region, but also introduced a new approach to therapy, taking advantage of both PDT and CDT effects.

Bismuth-based semiconductors applied in photocatalytic reduction processes: fundamentals, advances and future perspectives

Bismuth-based semiconductors (BBSs) with their typical layered structures and unique electronic properties are considered an attractive visible light-responsive photocatalysts. Recently, BBS exhibited promising properties and was rapidly developed in photoreduction reactions. In this review, we firstly focus on the photoreduction reactions of BBS with a description of the basic principles. Specifically, the restrictive factors of the photoreduction reactions and the design directions of the catalysts are addressed. BBS photocatalysts, such as bismuth oxide, bismuth halide oxide and bismuth-based oxygenates, are presented in terms of the catalyst material design, crystal structure and other features. Furthermore, the primary applications of BBS in photoreduction reactions are described, including CO₂ reduction, N₂ reduction, H₂ evolution, and nitrate reduction. Additionally, the advances and shortages of BBS applied in these processes are summarized and comprehensively discussed. Future works for BBS applied in photoreduction processes are also proposed.

Sunlight-induced enhanced photocatalytic reduction of chromium (VI) and photocatalytic degradation of methylene blue dye and ciprofloxacin antibiotic by Sn3O4/SnS2 nanocomposite

Detection of residual organic and inorganic species in water bodies, including drinking water, has led to developing strategies for their removal. Here, we report a very efficient method of removing Cr(VI), organic dye, and antibiotic from water using a type-II heterojunction based on Sn₃O₄/SnS₂ solar photocatalyst. The toxic Cr(VI) species are reduced by photocatalytic methodology, while methylene blue (MB) dye and ciprofloxacin (CIP) antibiotics are removed by photocatalytic degradation. The structural, compositional, morphological, and optical properties of the hydrothermally synthesized photocatalyst have been studied. Under sunlight exposure, more than 99.9% of Cr(VI) is reduced within 60 min at a reaction rate of 0.066 min^-1. While 99.6% of MB and 90% of CIP degradation are achieved in 90 min and 120 min, corresponding to photocatalytic degradation rates of 0.043 min^-1 and 0.019 min^-1, respectively. The total organic carbon after degradation corresponded to 85.1% for MB and 72.4% for CIP mineralization. The observed photocatalytic degradation is attributed to in situ generation of reactive oxygen species (ROS), e.g., superoxide radicals and hydroxyl radicals. The role of ROS towards photocatalytic degradation of MB and CIP, respectively, was confirmed from ROS scavenging studies. The MB and CIP degradation mechanism has been discussed by analyzing their degradation products.

A review on hierarchical Bi2MoO6 nanostructures for photocatalysis applications

This overview provides comprehensive understanding and development trends of hierarchical Bi2MoO6 nanostructures as photocatalysts for efficient photocatalysis applications.

New Aptamer/MoS2/Ni-Fe LDH Photoelectric Sensor for Bisphenol A Determination

Here, a new type of PEC aptamer sensor for bisphenol A (BPA) detection was developed, in which visible-light active MoS₂/Ni-Fe LDH (layered double hydroxide) heterostructure and aptamer were used as photosensitive materials and biometric elements, respectively. The combination of an appropriate amount of MoS₂ and Ni-Fe LDH enhances the photocurrent response, thereby promoting the construction of the PEC sensor. Therefore, we used a simple in situ growth method to fabricate a MoS₂/Ni-Fe LDH sensor to detect the BPA content. The aptasensor based on aptamer/MoS₂/Ni-Fe LDH displayed a linear range toward a BPA of 0.05-10 to 50-40,000 ng L^-1, and it has excellent stability, selectivity and reproducibility. In addition, the proposed aptamer sensor is effective in evaluating real water samples, indicating that it has great potential for detecting BPA in real samples.

Direct Z-scheme CuInS2/Bi2MoO6 heterostructure for enhanced photocatalytic degradation of tetracycline under visible light

The construction of direct Z-scheme heterojunctions with high photocatalytic degradation ability is a theme of importance in both environmental and materials sciences, but still retains many unresolved challenges. In this article, we report the construction of Z-scheme CuInS₂/Bi₂MoO₆ heterostructure by in-situ hydrothermal reactions, demonstrating superior photocatalytic activity towards the degradation of tetracycline under visible light, compared to their individual components: that is to say 8 and 2.5 times those of CuInS₂ and Bi₂MoO₆, respectively. The photocatalytic performance of CuInS₂/Bi₂MoO₆ heterostructure is mainly ascribed to the effective charge transfer at the interface through the construction of a direct Z-scheme heterojunction, combined with a ternary sulfide semiconductor absorbing light in the useful region of the solar spectrum. This photocatalyst provides new insights on the fundamental aspects governing the mechanisms responsible for multicomponent photodegradation, while constituting already a promising candidate for practical environmental applications.

Construction of Bi2MoO6/CdS heterostructures with enhanced visible light photocatalytic activity for fuel denitrification

In this work, a novel step-scheme (S-scheme) Bi₂MoO₆/CdS heterojunction (HJ) photocatalyst (PC) was successfully prepared by a two-step solvothermal method for the first time. One-dimensional CdS nanorods were prepared by a simple solvothermal method as a synthesis template. Then, a Bi₂MoO₆ precursor was added to obtain a series of Bi₂MoO₆/CdS HJ composite catalytic materials with different morphologies. The photocatalytic performance of the catalyst was investigated by simulating fuel denitration as a probe reaction under visible light excitation (>420 nm). When compared with pure Bi₂MoO₆ and CdS, the 0.65-Bi₂MoO₆/CdS composite shows the highest photocatalytic activity for pyridine degradation. Degradation of pyridine reached 81% after 240 min of visible light excitation. The degradation rate of 0.65-Bi₂MoO₆/CdS reached 0.4471 h^-1, which was 1.8 and 3.2 times higher than that of CdS (0.2493 h^-1) and Bi₂MoO₆ (0.1427 h^-1), respectively. Combined with a series of characterisation results, the improvement in pyridine degradation activity was mainly attributed to (1) the S-scheme HJ structure between Bi₂MoO₆ and CdS, which greatly promoted the separation of photogenerated electrons and holes while retaining its strong redox ability, (2) the large specific surface area, which provided abundant active sites and efficient adsorption performance and catalytic performance, and (3) the special morphology, which induced multiple reflections of light, thereby improving absorption and utilisation of light. Moreover, after four cycles of pyridine denitrification, the samples still exhibited high activity, indicating good stability and recyclability of the composite catalyst. These findings provide a basis for the development of composite PCs for efficient fuel denitration under visible light irradiation.

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.

Highly efficient visible-light photoactivity of Z-scheme MoS2/Ag2CO3 photocatalysts for organic pollutants degradation and bacterial inactivation

Here, a novel Z-scheme MoS₂/Ag₂CO₃ heterojunction photocatalyst was assembled from two-dimensional MoS₂ nanosheets and Ag₂CO₃ nanoparticles through facile hydrothermal and in-situ precipitation method. The MoS₂/Ag₂CO₃ heterojunction exhibited much enhanced visible-light photocatalytic performance in probe experiment for organic pollutants degradation and Escherichia coli (E. coli) inactivation compared to pristine Ag₂CO₃ and MoS₂. The degradation rates of Lanasol Red 5B, rhodamine B, ciprofloxacin, and metronidazole reached 95%, 90%, 80%, and 72%, respectively. On the other hand, E. coli was completely inactivated in 80 min in the presence of 5%-MoS₂/Ag₂CO₃. The improved photocatalytic performance was ascribed to the enhanced photogenerated charge separation efficiency and increased lifetime of the charge carriers, proved by photoluminescence spectra, time-resolved fluorescence emission decay spectra, and electrochemical measures. In addition, the active species trapping and ESR experiments all indicated that holes (h⁺) exhibited a significant contribution and superoxide radicals (O₂^-) acted as assistants. Based on experiment results, the photocatalytic enhancement mechanism for organic pollutants degradation and E. coli inactivation was discussed. The effect of representative environmental factors on the degradation of Lanasol Red 5B was investigated. The experiment results indicated that the degradation efficiency was partially influenced in the presence of inorganic salt. Furthermore, the appearance of a small amount of Ag nanoparticles not only enhanced the charge transfer, but also improved the stability of photocatalyst. Overall, MoS₂/Ag₂CO₃ heterojunction has a great application potential for future water purification.

Photocatalytic oxidation of methanol to formaldehyde on bismuth-based semiconductors

Methanol is widely applied in photocatalysis as a scavenger of holes, and is also studied as a model system for heterogeneous photocatalysis for the production of formaldehyde. Compared to commercial processes for formaldehyde production via thermal catalytic methanol oxidation, photocatalytic oxidation of methanol to formaldehyde may be more promising when considering the following aspects: 1) lower reaction temperature and pressure (generally operated at room temperature and ambient pressure); 2) lower cost of the energy source (such as solar light) and 3) easy-to-design reactive system. Photocatalytic methanol oxidation was carried out using four different bismuth-based semiconductors (BBS), Bi₂WO₆, Bi₂MoO₆, BiOBr and BiVO₄, under varying system temperature (5-50 °C), bubbling speed (0.1-1.0 LPM), catalyst dosage (0.2-2.0 g/L), and initial methanol concentration (12.5-250 mM). It was found that the formaldehyde formation rate for all photocatalysts increased as a function of each of these system parameters. Of these four BBS, it was found that Bi₂WO₆ had the highest formaldehyde formation rate (0.081 mM/h). This work provides a new approach to produce formaldehyde using photocatalysis, and future work has also been proposed.

Ultrafine Au nanoparticles anchored on Bi2MoO6 with abundant surface oxygen vacancies for efficient oxygen molecule activation

Au NPs were anchored on Bi₂MoO₆ with rich SOVs to improve O₂ activation for photocatalytic degradation of phenol and dye.

Design and fabrication of polyaniline/Bi2MoO6 nanocomposites for enhanced visible-light-driven photocatalysis

PANI/Bi₂MoO₆ composites with improved photoelectrochemical performance and accessible interfacial active sites were fabricated for enhanced visible-light-driven photocatalytic degradation of RhB.