In situ ion exchange synthesis of the Bi4Ti3O12/Bi2S3 heterostructure with enhanced photocatalytic activity

Molecularly Imprinted Polymer Functionalized Bi2S3/Ti3C2TX MXene Nanocomposites for Photoelectrochemical/Electrochemical Dual-Mode Sensing of Chlorogenic Acid

We report the proof-of-concept of molecularly imprinted polymer (MIP) functionalized Bi2S3/Ti3C2TX MXene nanocomposites for photoelectrochemical (PEC)/electrochemical (EC) dual-mode sensing of chlorogenic acid (CGA). Specifically, the in-situ growth of the Bi2S3/Ti3C2TX MXene served as a transducer substrate for molecularly imprinted polymers such as PEC and EC signal generators, due to its high surface area, suitable bandwidth and abundant active sites. In addition, the chitosan as a binder was encapsulated into MIP by means of phase inversion on a fluorine-doped tin dioxide (FTO) electrode. In the determination of CGA as an analytical model, the dual-mode sensor based on MIP functionalized Bi2S3/Ti3C2TX MXene nanocomposites had good selectivity, excellent stability and acceptable reproducibility, which displayed a linear concentration range from 0.0282 μM to 2824 μM for the PEC signal and 0.1412 μM to 22.59 μM for the EC signal with a low detection limit of 2.4 nM and 43.1 nM, respectively. Importantly, two dual-response mode with different transduction mechanisms could mutually conform to dramatically raise the reliability and accuracy of detection compared to single-mode detection. This work is a breakthrough for the design of dual-mode sensors and will provide a reasonable basis for the construction of dual-mode sensor platforms.

Transition metal sulfides meet electrospinning: versatile synthesis, distinct properties and prospective applications

One-dimensional (1D) electrospun nanomaterials have attracted significant attention due to their unique structures and outstanding chemical and physical properties such as large specific surface area, distinct electronic and mass transport, and mechanical flexibility. Over the past years, the integration of metal sulfides with electrospun nanomaterials has emerged as an exciting research topic owing to the synergistic effects between the two components, leading to novel and interesting properties in energy, optics and catalysis research fields for example. In this review, we focus on the recent development of the preparation of electrospun nanomaterials integrated with functional metal sulfides with distinct nanostructures. These functional materials have been prepared via two efficient strategies, namely direct electrospinning and post-synthesis modification of electrospun nanomaterials. In this review, we systematically present the chemical and physical properties of the electrospun nanomaterials integrated with metal sulfides and their application in electronic and optoelectronic devices, sensing, catalysis, energy conversion and storage, thermal shielding, adsorption and separation, and biomedical technology. Additionally, challenges and further research opportunities in the preparation and application of these novel functional materials are also discussed.

Interfacial engineering of Bi2S3/Ti3C2Tx MXene based on work function for rapid photo-excited bacteria-killing

In view of increasing drug resistance, ecofriendly photoelectrical materials are promising alternatives to antibiotics. Here we design an interfacial Schottky junction of Bi2S3/Ti3C2Tx resulting from the contact potential difference between Ti3C2Tx and Bi2S3. The different work functions induce the formation of a local electrophilic/nucleophilic region. The self-driven charge transfer across the interface increases the local electron density on Ti3C2Tx. The formed Schottky barrier inhibits the backflow of electrons and boosts the charge transfer and separation. The photocatalytic activity of Bi2S3/Ti3C2Tx intensively improved the amount of reactive oxygen species under 808 nm near-infrared radiation. They kill 99.86% of Staphylococcus aureus and 99.92% of Escherichia coli with the assistance of hyperthermia within 10 min. We propose the theory of interfacial engineering based on work function and accordingly design the ecofriendly photoresponsive Schottky junction using two kinds of components with different work functions to effectively eradicate bacterial infection.

Preparation and Photocatalytic Performance for Degradation of Rhodamine B of AgPt/Bi4Ti3O12 Composites

Loading a noble metal on Bi₄Ti₃O₁₂ could enable the formation of the Schottky barrier at the interface between the former and the latter, which causes electrons to be trapped and inhibits the recombination of photoelectrons and photoholes. In this paper, AgPt/Bi₄Ti₃O₁₂ composite photocatalysts were prepared using the photoreduction method, and the effects of the type and content of noble metal on the photocatalytic performance of the catalysts were investigated. The photocatalytic degradation of rhodamine B (RhB) showed that the loading of AgPt bimetallic nanoparticles significantly improved the catalytic performance of Bi₄Ti₃O₁₂. When 0.10 wt% noble metal was loaded, the degradation rate for RhB of Ag_0.7Pt_0.3/Bi₄Ti₃O₁₂ was 0.027 min⁻¹, which was respectively about 2, 1.7 and 3.7 times as that of Ag/Bi₄Ti₃O₁₂, Pt/Bi₃Ti₄O₁₂ and Bi₄Ti₃O_12. The reasons may be attributed as follows: (i) the utilization of visible light was enhanced due to the surface plasmon resonance effect of Ag and Pt in the visible region; (ii) Ag nanoparticles mainly acted as electron acceptors to restrain the recombination of photogenerated electron-hole pairs under visible light irradiation; and (iii) Pt nanoparticles acted as electron cocatalysts to further suppress the recombination of photogenerated electron-hole pairs. The photocatalytic performance of Ag_0.7Pt_0.3/Bi₄Ti₃O₁₂ was superior to that of Ag/Bi₄Ti₃O₁₂ and Pt/Bi₃Ti₄O₁₂ owing to the synergistic effect between Ag and Pt nanoparticles.

Straightforward Synthesis of SnO2/Bi2S3/BiOCl-Bi24O31Cl10 Composites for Drastically Enhancing Rhodamine B Photocatalytic Degradation under Visible Light

The pursuit of robust photocatalysts that can completely degrade organic contaminants with high performance as well as high energy efficiency, simplicity in preparation, and low cost is an appealing topic that potentially promotes photocatalysts for being used widely. Herein, we introduce a new and efficient SnO2/Bi2S3/BiOCl-Bi24O31Cl10 (SnO2/Bi2S3-Bi25) composite photocatalyst by taking advantage of the robust, simple, and potentially scalable one-pot synthesis, including the hydrothermal process followed by thermal decomposition. Interestingly, we observed the formation of BiOCl-Bi24O31Cl10 (abbreviated as Bi25) heterojunctions derived from reactions between Bi2S3 and SnCl4·5H2O precursor solutions under the hydrothermal condition and thermal decomposition of BiOCl. This Bi25 heterojunction acts as an interface to reduce the recombination of photogenerated electron-hole (e--h+) pairs as well as to massively enhance the visible light harvesting, thereby significantly enhancing the photocatalytic degradation performance of the as-prepared composite photocatalyst. In detail, the photocatalytic degradation of Rhodamine B (RhB) activated by visible light using 15% SnO2/Bi2S3-Bi25 shows the efficiency of 80.8%, which is superior compared to that of pure Bi2S3 (29.4%) and SnO2 (0.1%). The SnO2/Bi2S3-Bi25 composite photocatalyst also presents an excellent photostability and easy recovery from dye for recycling. The trapping test revealed that the photogenerated holes play a crucial factor during the photocatalytic process, whereas superoxide radicals are also formed but not involved in the photocatalytic process. Successful fabrication of SnO2/Bi2S3-Bi25 composite photocatalysts via a straightforward method with drastically enhanced photocatalytic performance under visible light activation would be useful for practical applications.

Synthesis of heterojunction photocatalysts composed of Ag 2 S quantum dots combined with Bi 4 Ti 3 O 12 nanosheets for the degradation of dyes

Facilitating the separation of photogenerated electron/hole pairs and widening the light-responsive region are crucial to enhance the overall photocatalytic performance of photocatalysts. To achieve this aim, here we have prepared Ag₂S/Bi₄Ti₃O₁₂ heterojunction composite photocatalysts by assembling Ag₂S quantum dots onto the surface of Bi₄Ti₃O₁₂ nanosheets. Transmission electron microscopy observation demonstrates that two types of Ag₂S quantum dots separately with size of 40-70 and 7-17 nm are uniformly assembled onto the surface of large-sized Bi₄Ti₃O₁₂ thin nanosheets. The as-prepared Ag₂S/Bi₄Ti₃O₁₂ heterojunction composites exhibit much enhanced light absorption (particularly in the visible and near-infrared region) and highly efficient separation of electrons and holes photogenerated in Bi₄Ti₃O₁₂. Rhodamine B (RhB) aqueous solution was chosen as the target organic pollutant to evaluate the photocatalytic performance of the samples under simulated sunlight irradiation. It is found that the Ag₂S/Bi₄Ti₃O₁₂ heterojunction composites manifest significantly enhanced photocatalytic activity toward the RhB degradaton. In particular, the 15wt% Ag₂S/Bi₄Ti₃O₁₂ composite exhibits the highest photocatalytic activity, which is ca. 2.8 and 4.0 times higher than bare Bi₄Ti₃O₁₂ and Ag₂S, respectively. The enhanced photocatalytic activity of the composites can be explained as a result of the Z-scheme electron transfer from the conduction band of Bi₄Ti₃O₁₂ to the valence band of Ag₂S, and thus more photogenerated holes in the valence band of Bi₄Ti₃O₁₂ and electrons in the conduction band of Ag₂S are able to participate in the photocatalytic reactions. Active species trapping experiments were carried out, from which it is concluded that photogenerated holes and •O₂^- radicals play the dominant and secondary role in the photocatalysis, respectively.

Growth Process and CQDs-modified Bi₄Ti₃O12 Square Plates with Enhanced Photocatalytic Performance

Bi₄Ti₃O12 square plates were synthesized via a hydrothermal route, and their growth process was systematically investigated. Carbon quantum dots (CQDs) were prepared using glucose as the carbon source, which were then assembled on the surface of Bi₄Ti₃O12 square plates via a hydrothermal route with the aim of enhancing the photocatalytic performance. XRD (X-ray powder diffraction), SEM (scanning electron microscopy), TEM (transmission electron microscopy), UV-vis DRS (diffuse reflectance spectroscopy), XPS (X-ray photoelectron spectroscopy), FTIR (Fourier transform infrared spectroscopy), PL (photoluminescence) spectroscopy, EIS (electrochemical impedance spectroscopy) and photocurrent spectroscopy were used to systematically characterize the as-prepared samples. It is demonstrated that the decoration of CQDs on Bi₄Ti₃O12 plates leads to an increased visible light absorption, slightly increased bandgap, increased photocurrent density, decreased charge-transfer resistance, and decreased PL intensity. Simulated sunlight and visible light were separately used as a light source to evaluate the photocatalytic activity of the samples toward the degradation of RhB in aqueous solution. Under both simulated sunlight and visible light irradiation, CQDs@Bi₄Ti₃O12 composites with an appropriate amount of CQDs exhibit obviously enhanced photocatalytic performance. However, the decoration of excessive CQDs gives rise to a decrease in the photocatalytic activity. The enhanced photocatalytic activity of CQDs-modified Bi₄Ti₃O12 can be attributed to the following reasons: (1) The electron transfer between Bi₄Ti₃O12 and CQDs promotes an efficient separation of photogenerated electron/hole pairs in Bi₄Ti₃O12; (2) the up-conversion photoluminescence emitted from CQDs could induce the generation of additional electron/hole pairs in Bi₄Ti₃O12; and (3) the photoexcited electrons in CQDs could participate in the photocatalytic reactions.

Review on nanoscale Bi-based photocatalysts

Nanoscale Bi-based photocatalysts are promising candidates for visible-light-driven photocatalytic environmental remediation and energy conversion. However, the performance of bulk bismuthal semiconductors is unsatisfactory. Increasing efforts have been focused on enhancing the performance of this photocatalyst family. Many studies have reported on component adjustment, morphology control, heterojunction construction, and surface modification. Herein, recent topics in these fields, including doping, changing stoichiometry, solid solutions, ultrathin nanosheets, hierarchical and hollow architectures, conventional heterojunctions, direct Z-scheme junctions, and surface modification of conductive materials and semiconductors, are reviewed. The progress in the enhancement mechanism involving light absorption, band structure tailoring, and separation and utilization of excited carriers, is also introduced. The challenges and tendencies in the studies of nanoscale Bi-based photocatalysts are discussed and summarized.

Intimate contacted two-dimensional/zero-dimensional composite of bismuth titanate nanosheets supported ultrafine bismuth oxychloride nanoparticles for enhanced antibiotic residue degradation

Constructing a two-dimensional/zero-dimensional (2D/0D) composite with matched crystal structure, suitable energy band structure as well as intimate contact interface is an effective way to improve carriers separation for achieving highly photocatalytic performance. In this work, a novel bismuth titanate/bismuth oxychloride (Bi₄Ti₃O₁₂/BiOCl) composite consisting of 2D Bi₄Ti₃O₁₂ nanosheets and 0D BiOCl nanoparticles was constructed for the first time. Germinating ultrafine BiOCl nanoparticles on Bi₄Ti₃O₁₂ nanosheets can provide abundant contact interface and shorten migration distance of photoinduced carriers via two-step synthesis contained molten salt process and facile chemical transformation process. The obtained Bi₄Ti₃O₁₂/BiOCl 2D/0D composites exhibited enhanced photocatalytic performance for antibiotic tetracycline hydrochloride degradation. The rate constant of optimal Bi₄Ti₃O₁₂/BiOCl composite was about 4.4 times higher than that of bare Bi₄Ti₃O₁₂ although Bi₄Ti₃O₁₂/BiOCl composite appeared lesser photoabsorption. The enhanced photocatalytic performance can be mainly ascribed to matched crystal structure, suitable energy band structure and intimate contact interface between Bi₄Ti₃O₁₂ nanosheets and ultrafine BiOCl nanoparticles as well as unique 2D/0D composite structure. Besides, a probable degradation mechanism on the basis of active species trapping experiments, electrochemical impedance spectroscopy, photocurrent responses and energy band structures was proposed. This work may be stretched to other 2D/0D composite photocatalysts construction, which is inspiring for antibiotic residue treatment.

One-step synthesis of a hierarchical Bi2S3 nanoflower\In2S3 nanosheet composite with efficient visible-light photocatalytic activity

Hierarchical Bi₂S₃ nanoflower\In₂S₃ nanosheet composites were prepared and showed excellent visible-light photocatalytic activity.