Synergetic photocatalytic effect between 1 T@2H-MoS2 and plasmon resonance induced by Ag quantum dots

Plasmon AgNPs/MoS2/ZnO nanorods array ternary heterojunctions enabling high-efficiency solar-light energy utilization for photocatalysis and recyclable SERS detection

BACKGROUND

Surface-enhanced Raman scattering (SERS) has gained widespread use in molecule-level detection benefiting from its high sensitivity, nondestructive data acquisition, and capacity for providing molecular fingerprint information. However, the strong adhesion of target molecules to the substrate (known as the "memory effect") inherently hinders the reusability of SERS substrates. Research has shown that self-cleaning SERS substrates based on versatile semiconductor materials with SERS enhancement capabilities and solar photocatalytic properties offer an effective platform for the sensitive detection and degradation of harmful molecules.

RESULTS

In this research, a resuable SERS-active substrate was facilely fabricated by anchoring silver nanoparticles (AgNPs) to the edges of MoS2 nanosheet decorated on ZnO nanorod arrays (NRAs). This innovative design exhibited a remarkable SERS enhancement factor (EF) of 4.6 × 107 and demonstrated significant solar photocatalytic efficiency. Such superior characteristics of ternary plasma heterojunction were ascribable to the synergistic effect of the "Schottky barrier" and "hot spots" between MoS2 and AgNPs, the inherent chemical enhancement proficiency of the MoS2/ZnO NRAs heterojunction, as well as the ultrafast electron transfer within the ternary heterojunction.

SIGNIFICANCE

The developed ternary heterojunction substrate enabled highly sensitive SERS detection of trace amounts of organic molecules. Moreover, this SERS substrate exhibited self-cleaning and recyclability via solar-light-driven photocatalysis. This bifunctional recyclable SERS substrate proved capable of meeting various requirements for routine monitoring of environmental organic pollutants and provided a robust avenue for advancing energy utilization materials that serve as high-performance SERS sensors and catalysts.

Coexisting Phases in Transition Metal Dichalcogenides: Overview, Synthesis, Applications, and Prospects

Over the past decade, significant advancements have been made in phase engineering of two-dimensional transition metal dichalcogenides (TMDCs), thereby allowing controlled synthesis of various phases of TMDCs and facile conversion between them. Recently, there has been emerging interest in TMDC coexisting phases, which contain multiple phases within one nanostructured TMDC. By taking advantage of the merits from the component phases, the coexisting phases offer enhanced performance in many aspects compared with single-phase TMDCs. Herein, this review article thoroughly expounds the latest progress and ongoing efforts on the syntheses, properties, and applications of TMDC coexisting phases. The introduction section overviews the main phases of TMDCs (2H, 3R, 1T, 1T', 1Td), along with the advantages of phase coexistence. The subsequent section focuses on the synthesis methods for coexisting phases of TMDCs, with particular attention to local patterning and random formations. Furthermore, on the basis of the versatile properties of TMDC coexisting phases, their applications in magnetism, valleytronics, field-effect transistors, memristors, and catalysis are discussed. Lastly, a perspective is presented on the future development, challenges, and potential opportunities of TMDC coexisting phases. This review aims to provide insights into the phase engineering of 2D materials for both scientific and engineering communities and contribute to further advancements in this emerging field.

Advances in Hole Transport Materials for Layered Casting Solar Cells

Huge energy consumption and running out of fossil fuels has led to the advancement of renewable sources of power, including solar, wind, and tide. Among them, solar cells have been well developed with the significant achievement of silicon solar panels, which are popularly used as windows, rooftops, public lights, etc. In order to advance the application of solar cells, a flexible type is highly required, such as layered casting solar cells (LCSCs). Organic solar cells (OSCs), perovskite solar cells (PSCs), or dye-sensitive solar cells (DSSCs) are promising LCSCs for broadening the application of solar energy to many types of surfaces. LCSCs would be cost-effective, enable large-scale production, are highly efficient, and stable. Each layer of an LCSC is important for building the complete structure of a solar cell. Within the cell structure (active material, charge carrier transport layer, electrodes), hole transport layers (HTLs) play an important role in transporting holes to the anode. Recently, diverse HTLs from inorganic, organic, and organometallic materials have emerged to have a great impact on the stability, lifetime, and performance of OSC, PSC, or DSSC devices. This review summarizes the recent advances in the development of inorganic, organic, and organometallic HTLs for solar cells. Perspectives and challenges for HTL development and improvement are also highlighted.

Adsorption removal and photocatalytic degradation of azithromycin from aqueous solution using PAC/Fe/Ag/Zn nanocomposite

The improper use of antibiotics and their discharge into the environment can have serious and hazardous consequences. The purpose of this research is to synthesize an activated carbon impregnated magnetite composite (PAC/Fe), prepare PAC/Fe/Ag/Zn nanocomposites, and innovate by simultaneously synthesizing two metals, zinc and silver, on magnetically activated carbon and check its ability to remove azithromycin antibiotic (AZT) from an aqueous solution via UV system. PAC/Fe/Ag/Zn nanocomposites were characterized by various techniques including XRD, FESEM, and EDX. A series of batch experiments were carried out under various experimental conditions such as pH of the solution (3-11), contact time (0-120 min), initial concentration of AZT (10-40 ppm), amount of PAC/Fe/Ag/Zn nano-absorbent (0.01-0.04 g/l), and recoverability and reuse. Some common isotherm models were used for the study of AZT adsorption removal and finding the best model. Also, kinetic studies of AZT removal were performed by fitting the experimental data on first-order and second-order models. In this system, under optimal conditions of pH = 9, 120 min with 0.04 g/l of PAC/Fe/Ag/Zn, 99.5% of 10 ppm AZT were degraded under UV-C irradiation. Furthermore, the obtained results of isotherm and kinetic studies revealed that Langmuir (R² = 0.9336) isotherm model, and the pseudo-first-order kinetic model (R² = 0.9826) had the highest correlation with the experimental data of AZT antibiotic adsorption. Finally, the reusability experiments showed that PAC/Fe/Ag/Zn nanocomposites have a high ability of antibiotic adsorption and high stability after four cycles of application (99.5 to 40%).

A simple sensing platform based on a 1T@2H-MoS2/cMWCNTs composite modified electrode for ultrasensitive detection of illegal Sudan I dye in food samples

The work presented here describes a highly sensitive and simple electrochemical sensor for the detection of Sudan I dye based on a nanocomposite made of MoS₂ heterogeneous nanosheets (1T@2H-MoS₂) and carboxylated carbon nanotubes (cMWCNTs) (1T@2H-MoS₂/cMWCNTs). XPS results indicate that the content of 1T phase MoS₂ was estimated to be 72% in 1T@2H-MoS₂. Electron microscopy results show that the tubular cMWCNTs are uniformly interwoven in MoS₂ nanosheets to form a three-dimensional network structure. Due to the synergistic electrocatalytic ability and high electroactive surface area, the 1T@2H-MoS₂/cMWCNTs modified electrode demonstrated excellent analytical performance for Sudan I, including simple operation, good stability and a wide linear range from 5.00 × 10^-9 to 2.00 × 10^-6 mol L^-1 and 2.00 × 10^-6 to 1.00 × 10^-4 mol L^-1 with an ultra-low detection limit of 1.56 × 10^-9 mol L^-1. The recoveries of Sudan I from spiked real samples (chilli powder and ketchup) were in the range of 95.60% to 106.10% with low RSD (<5%), indicating that the 1T@2H-MoS₂/cMWCNTs modified electrode is a promising tool for the analysis of illegal Sudan I in food samples.

Tailoring the fusion effect of phase-engineered 1T/2H-MoS2 towards photocatalytic hydrogen evolution

Enhanced photocatalytic hydrogen evolution on 30-1T/2H-MoS2 with a higher concentration of the 1T phase was achieved due to the higher availability of electrons and dense active sites after the incorporation of the 1T phase in 2H-MoS2.

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.