Fabrication of layered (CdS-Mn/MoS2/CdTe)-promoted TiO2 nanotube arrays with superior photocatalytic properties

Impact of alternate Mn doping in ternary nanocomposites on their structural, optical and antimicrobial properties: Comparative analysis of photocatalytic degradation and antibacterial activity

The present study was done to investigate and compare the photocatalytic and antibacterial activity of two in situ Manganese doped ternary nanocomposites. The dual ternary hybrid systems comprised Mn-doped Ag₂WO₄ coupled with MoS₂-GO and Mn-doped MoS₂ coupled with Ag₂WO₄-GO. Both hierarchical alternate Mn-doped ternary heterojunctions formed efficient plasmonic catalysts for wastewater treatment. The novel nanocomposites were well-characterized using XRD, FTIR, SEM-EDS, HR-TEM, XPS, UV-VIS DRS, and PL techniques confirming the successful insertion of Mn⁺² ions in respective host substrates. The bandgap of the ternary nanocomposites evaluated by the tauc plot showed them visible light-active nanocomposites. The photocatalytic ability of both Mn-doped coupled nanocomposites was investigated against the dye methylene blue. Both ternary nanocomposites showed excellent sunlight harvesting ability for dye degradation in 60 min. The maximum catalytic efficiency of both photocatalysts was obtained at a solution pH value of 8, photocatalyst dose and oxidant dose of 30 mg/100 mL and 1 mM for Mn-Ag₂WO₄/MoS₂-GO, 50 mg/100 mL, 3 mM for Mn-MoS₂/Ag₂WO₄-GO keeping IDC of 10 ppm for all photocatalysts. The nanocomposites showed excellent photocatalytic stability after five successive cycles. The response surface methodology was used as a statistical tool for the evaluation of the photocatalytic response of several interacting parameters for dye degradation by ternary composites. The antibacterial activity was determined by the inactivation of gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria by support-based doped ternary hybrids.

Application of visible light active photocatalysis for water contaminants: A review

Organic water pollutants are ubiquitous in the natural environment arising from domestic products as well as current and legacy industrial processes. Many of these organic water pollutants are recalcitrant and only partially degraded using conventional water and wastewater treatment processes. In recent decades, visible light active photocatalyst has gained attention as a non-conventional alternative for the removal of organic pollutants during water treatment, including industrial wastewater and drinking water treatment. This paper reviews the current state of research on the use of visible light active photocatalysts, their modified methods, efficacy, and pilot-scale applications for the degradation of organic pollutants in water supplies and waste streams. Initially, the general mechanism of the visible light active photocatalyst is evaluated, followed by an overview of the major synthesis techniques. Because few of these photocatalysts are commercialized, particular attention was given to summarizing the different types of visible light active photocatalysts developed to the pilot-scale stage for practical application and commercialization. The organic pollutant degradation ability of these visible light active photocatalysts was found to be considerable and in many cases comparable with existing and commercially available advanced oxidation processes. Finally, this review concludes with a summary of current achievements and challenges as well as possible directions for further research. PRACTITIONER POINTS: Visible light active photocatalysis is a promising advanced oxidation process (AOP) for the reduction of organic water pollutants. Various mechanisms of photocatalysis using visible light active materials are identified and discussed. Many recent photocatalysts are synthesized from renewable materials that are more sustainable for applications in the 21st century. Only a small number of pilot-scale applications exist and these are outlined in this review.

New anti-tumor strategy based on acid-triggered self-destructive and near-infrared laser light responses of nano-biocatalysts integrating starvation–chemo–photothermal therapies

Background

Inherent limitations of single cancer therapy are overcome by multi-therapy modality, which integrates characteristics of each therapeutic modality and material chemistry. The multi-modal method has the potential for becoming one of the next generation options for cancer treatments. Photothermal therapy (PTT) is an efficient, non-invasive treatment method that can be used on various cancer types. We propose an acid-triggered self-destructing nano-biocatalyst integrated starvation/chemical/photothermal triple therapy that is based on design principles and biomedical applications of GOx cancer treatment methods.

Methods

Scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potentials were used to analyze the physical as well as chemical properties of MoS2@DOX/GOx@MnO2 (M@D/G@M). Further, Fourier transform infra-red (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were used to assess the compositions of the nanocatalysts. The biological effects of M@D/G@M on cells were studied in vitro by inverted fluorescence microscopy, confocal laser scanning microscopy (CLSM), flow cytometry, CCK-8 test, and hemolysis test. Treatment effects of the nanocatalysts were evaluated in MHCC-97H tumor BALB/c mice, whose body weights, tumor local temperature, tumor volumes, and tumor histological changes were evaluated.

Results

There was a high DOX encapsulation efficiency of M@D/G@M (90.233%). The photothermal conversion efficiency (η) of M@D/G@M is 25.2%, and its oxygen production within 5 min reached 27.5 mg L−1. Cell internalization analysis showed that within 4 h, M@D/G@M was almost completely absorbed by HepG2 cells. Further, the highest red fluorescence and apoptosis effects of dead cells (59.07% apoptosis) as well as the lowest tumor volume index of mice (0.2862%) were observed in the M@D/G@M + pH6.0 + NIR treatment group.

Conclusions

Our findings inform the development and applications of multi-modal methods in tumor therapy.

Simultaneous Enhancement of Charge Separation and Hole Transportation in a W:α-Fe2O3/MoS2 Photoanode: A Collaborative Approach of MoS2 as a Heterojunction and W as a Metal Dopant

In this study, a facile approach has been successfully applied to synthesize a W-doped Fe₂O₃/MoS₂ core-shell electrode with unique nanostructure modifications for photoelectrochemical performance. A two-dimensional (2D) structure of molybdenum disulfide (MoS₂) and tungsten (W)-doped hematite (W:α-Fe₂O₃) overcomes the drawbacks of the α-Fe₂O₃ and MoS₂ semiconductor through simple and facile processes to improve the photoelectrochemical (PEC) performance. The highest photocurrent density of the 0.5W:α-Fe₂O₃/MoS₂ photoanode is 1.83 mA·cm^-2 at 1.23 V vs reversible hydrogen electrode (RHE) under 100 mW·cm² illumination, which is higher than those of 0.5W:α-Fe₂O₃ and pure α-Fe₂O₃ electrodes. The overall water splitting was evaluated by measuring the H₂ and O₂ evolution, which after 2 h of irradiation for 0.5W:α-Fe₂O₃/MoS₂ was determined to be 49 and 23.8 μmol.cm^-2, respectively. The optimized combination of the heterojunction and metal doping on pure α-Fe₂O₃ (0.5W:α-Fe₂O₃/MoS₂ photoanode) showed an incident photon-to-electron conversion efficiency (IPCE) of 37% and an applied bias photon-to-current efficiency (ABPE) of 26%, which are around 5.2 and 13 times higher than those of 0.5W:α-Fe₂O₃, respectively. Moreover, the facile fabrication strategy can be easily extended to design other oxide/carbon-sulfide/oxide core-shell materials for extensive applications.

Fabrication of TiO2/Fe2O3/CdS systems: effects of Fe2O3and CdS content on superior photocatalytic activity

A heterostructured material of CdS and Fe₂O₃ nanoparticle-modified TiO₂ nanotube array (NTA) photoelectrode (TiO₂/Fe₂O₃/CdS) is reported in this work. TiO₂/Fe₂O₃ was prepared by annealing TiO₂ NTAs pre-loaded with Fe(OH)₃, which was uniformly clung to TiO₂ NTAs using sequential chemical bath deposition (S-CBD). Subsequently, CdS nanoparticles were deposited on TiO₂/Fe₂O₃ using the successive ion layer adsorption and reaction (SILAR) technique. Three-dimensional (3D) TiO₂/Fe₂O₃/CdS samples generated a photocurrent of approximately 4.92 mA cm⁻², with a photoconversion efficiency of 4.36%, which is more than 20 times higher than that of bare TiO₂ NTAs (0.22%) and 6 times that of TiO₂/Fe₂O₃ (0.71%). The photocatalytic activity was evaluated by the degradation of p-nitrophenol (PNP) under visible light (λ > 420 nm). The TiO₂/Fe₂O₃/CdS exhibited the best photocatalytic activity among all samples. Almost all PNP was degraded by TiO₂/Fe₂O₃/CdS within 120 min. The enhancement of photocatalytic activity could be attributed to the promoted photo-induced electron and hole separation and migration on the basis of photoluminescence spectra, photocurrent measurements, and open-circuit photovoltage responses. In addition, the newly synthesized TiO₂/Fe₂O₃/CdS can maintain high photocatalytic efficiency for five reuse cycles. Our findings provide a new idea for the low cost synthesis of high performance photocatalysts for the photodegradation of organic pollutants in aqueous solution.

New idea for the low cost synthesis of high performance photocatalysts for the photodegradation of organic pollutants in aqueous solution.

2D MoS2 nanosheets on 1D anodic TiO2 nanotube layers: an efficient co-catalyst for liquid and gas phase photocatalysis

One-dimensional TiO₂ nanotube layers with different dimensions were homogeneously decorated with 2D MoS₂ nanosheets via atomic layer deposition and employed for liquid and gas phase photocatalysis. The 2D MoS₂ nanosheets revealed a high amount of exposed active edge sites and strongly enhanced the photocatalytic performance of TiO₂ nanotube layers.

Recent Advances and Applications of Semiconductor Photocatalytic Technology

Along with the development of industry and the improvement of people’s living standards, peoples’ demand on resources has greatly increased, causing energy crises and environmental pollution. In recent years, photocatalytic technology has shown great potential as a low-cost, environmentally-friendly, and sustainable technology, and it has become a hot research topic. However, current photocatalytic technology cannot meet industrial requirements. The biggest challenge in the industrialization of photocatalyst technology is the development of an ideal photocatalyst, which should possess four features, including a high photocatalytic efficiency, a large specific surface area, a full utilization of sunlight, and recyclability. In this review, starting from the photocatalytic reaction mechanism and the preparation of the photocatalyst, we review the classification of current photocatalysts and the methods for improving photocatalytic performance; we also further discuss the potential industrial usage of photocatalytic technology. This review also aims to provide basic and comprehensive information on the industrialization of photocatalysis technology.

Fabrication of CdTe QDs/BiOI-Promoted TiO2 Hollow Microspheres with Superior Photocatalytic Performance Under Simulated Sunlight

Hollow and heterostructured architectures are recognized as an effective approach to improve photocatalytic performance. In this work, ternary TiO₂/CdTe/BiOI with hollow structure was constructed via a step-by-step method. In addition, the effect of TiO₂ structural regulation and the energy band alignment of BiOI and CdTe quantum dots (CdTe QDs) with TiO₂ in TiO₂/CdTe/BiOI on photocatalytic dye removal were also studied. The results reveal that the TiO₂/CdTe/BiOI heterostructures with hollow substrates exhibit much higher photocatalytic activities than pure TiO₂, P25, TiO₂/CdTe, and TiO₂/BiOI and ternary TiO₂/CdTe/BiOI with solid substrates. For TiO₂(H)/CdTe/BiOI, several synergistic factors may be responsible for the remarkable visible-light photodegradation performance, such as strong visible-light absorption by BiOI and larger specific surface area.

Self-assembled nano-leaf/vein bionic structure of TiO2/MoS2 composites for photoelectric sensors

Inspired by the leaf/vein structure of leaves which effectively supports the photosynthesis of green plants, a nano-leaf/vein bionic structure of self-assembled TiO₂/MoS₂ composites is applied to induce the reversible photochromic reactions of methylene blue (MB) for the first time. This reversible photochromic phenomenon gives a novel performance for the TiO₂/MoS₂ composites and expands their applications. Similar to the case where the natural vein network in leaves ensures the efficient material transfer and energy exchange for photosynthesis, the bionic internal MoS₂ vein network in the composites ensures the efficient separation and directional transfer of photo-generated carriers to restrain the photocatalytic degradation reactions and to enhance the reversible photochromic reactions. Furthermore, the photosensitive applications of the TiO₂/MoS₂/MB systems with such a self-assembled nano-leaf/vein bionic structure are discussed with two typical photoelectric sensory models for both controllers and detectors.