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Electrospun polyacrylonitrile (PAN) nanofibers integrated with different loadings of the photosensitizer rose bengal (RB) were synthesized for photodynamic inactivation of bacteria. Our results suggest that the ionic strength in the medium does not significantly affect the RB release from the RB-integrated electrospun PAN nanofibers (RBiEPNs), which could release RB effectively in phosphate-buffered saline (PBS), physiological saline (0.85% NaCl), and deionized H 2 O. However, the pH of the medium significantly influenced the release of RB. A larger amount of RB was released in PBS at a higher pH (RB release: pH 9.0 > pH 7.4 > pH 5.0). The RBiEPNs depicted high antimicrobial efficacy against both Gram-negative Escherichia coli ( E. coli ) and Gram-positive Bacillus subtilis ( B. subtilis ) bacteria under white light irradiation. The antimicrobial efficacy was potent and immediate against the bacterial cells, especially B. subtilis . The RBiEPNs containing 0.33 wt% RB demonstrated complete bacterial kills for B. subtilis and E. coli cells with log reductions of 5.76 and 5.94 in 30 s and 40 min, respectively. The generation of intracellular reactive oxygen species (iROS) was examined after white light treatment of the bacterial cells in the presence of the RBiEPNs. A significant correlation was found between the amount of iROS and the antimicrobial efficacy of the RBiEPNs. The high antimicrobial efficacy could be attributed to several factors, such as the encapsulation efficiency, loading capacity, and RB release behavior of the RBiEPNs, the presence of white light, and the generation of iROS. Taken together, the facile incorporation of a photosensitizer into polymeric nanofibers via blend electrospinning offers a feasible strategy for water disinfection. 

Herein, we report an effective strategy to maximize the antimicrobial activity of CuWO 4 /CuS hybrid composites, prepared by simply mixing CuWO 4 and CuS nanopowders with varying weight ratios in phosphate buffered saline solution by ultrasound. The tested bacteria included Gram negative (G − ) pathogenic bacteria Salmonella typhi , Gram positive (G + ) pathogenic bacteria Staphylococcus aureus , and G + bacteria Bacillus subtilis . The as-prepared composites exhibited much enhanced antibacterial efficiency compared with individual CuWO 4 and CuS nanopowders under white light irradiation. The checkerboard array analysis revealed that the combination of 8 μg mL −1 CuWO 4 and 2 μg mL −1 CuS was the most efficient and generated the optimal synergistic effect, showing a complete killing effect on all the tested bacteria from 3 strains with ∼5.8 log cell reduction. The significantly enhanced catalytic efficiency can be ascribed to the formation of a type-II heterojunction between CuWO 4 and CuS, which can effectively improve the charge separation efficiency and increase the light absorption. Moreover, the hybrid composites prepared by ultrasound-assisted physical mixing can effectively increase the interface area, which greatly facilitates the charge mobility and transfer in the interfaces between CuWO 4 and CuS. This study offers new insights into the integration of different semiconductors to optimize their synergistic effect on antimicrobial activities for water disinfection. 

Two-dimensional (2D) molybdenum ditelluride (MoTe 2 ) is an interesting material for fundamental study and applications, due to its ability to exist in different polymorphs of 2H, 1T, and 1T′, their phase change behavior, and unique electronic properties. Although much progress has been made in the growth of high-quality flakes and films of 2H and 1T′-MoTe 2 phases, phase-selective growth of all three phases remains a huge challenge, due to the lack of enough information on their growth mechanism. Herein, we present a novel approach to growing films and geometrical-shaped few-layer flakes of 2D 2H-, 1T-, and 1T′-MoTe 2 by atmospheric-pressure chemical vapor deposition (APCVD) and present a thorough understanding of the phase-selective growth mechanism by employing the concept of thermodynamics and chemical kinetics involved in the growth processes. Our approach involves optimization of growth parameters and understanding using thermodynamical software, HSC Chemistry. A lattice strain-mediated mechanism has been proposed to explain the phase selective growth of 2D MoTe 2 , and different chemical kinetics-guided strategies have been developed to grow MoTe 2 flakes and films. 

The field of photovoltaics is revolutionized in recent years by the development of two–dimensional (2D) type‐II heterostructures. These heterostructures are made up of two different materials with different electronic properties, which allows for the capture of a broader spectrum of solar energy than traditional photovoltaic devices. In this study, the potential of vanadium (V)‐doped WS₂is investigated, hereafter labeled V‐WS₂, in combination with air‐stable Bi₂O₂Se for use in high‐performance photovoltaic devices. Various techniques are used to confirm the charge transfer of these heterostructures, including photoluminescence (PL) and Raman spectroscopy, along with Kelvin probe force microscopy (KPFM). The results show that the PL is quenched by 40%, 95%, and 97% for WS₂/Bi₂O₂Se, 0.4 at.% V‐WS₂/Bi₂O₂Se, and 2 at.% V‐WS₂/Bi₂O₂Se, respectively, indicating a superior charge transfer in V‐WS₂/Bi₂O₂Se compared to pristine WS₂/Bi₂O₂Se. The exciton binding energies for WS₂/Bi₂O₂Se, 0.4 at.% V‐WS₂/Bi₂O₂Se and 2 at.% V‐WS₂/Bi₂O₂Se heterostructures are estimated to be ≈130, 100, and 80 meV, respectively, which is much lower than that for monolayer WS₂. These findings confirm that by incorporating V‐doped WS₂, charge transfer in WS₂/Bi₂O₂Se heterostructures can be tuned, providing a novel light‐harvesting technique for the development of the next generation of photovoltaic devices based on V‐doped transition metal dichalcogenides (TMDCs)/Bi₂O₂Se.

 

Recently, a zipper two-dimensional (2D) material Bi 2 O 2 Se belonging to the layered bismuth oxychalcogenide (Bi 2 O 2 X: X = S, Se, Te) family, has emerged as an alternate candidate to van der Waals 2D materials for high-performance electronic and optoelectronic applications. This hints towards exploring the other members of the Bi 2 O 2 X family for their true potential and bismuth oxysulfide (Bi 2 O 2 S) could be the next member for such applications. Here, we demonstrate for the first time, the scalable room-temperature chemical synthesis and near-infrared (NIR) photodetection of ultrathin Bi 2 O 2 S nanosheets. The thickness of the freestanding nanosheets was around 2–3 nm with a lateral dimension of ∼80–100 nm. A solution-processed NIR photodetector was fabricated from ultrathin Bi 2 O 2 S nanosheets. The photodetector showed high performance, under 785 nm laser illumination, with a photoresponsivity of 4 A W −1 , an external quantum efficiency of 630%, and a normalized photocurrent-to-dark-current ratio of 1.3 × 10 10 per watt with a fast response time of 100 ms. Taken together, the findings suggest that Bi 2 O 2 S nanosheets could be a promising alternative 2D material for next-generation large-area flexible electronic and optoelectronic devices.