Solar Light Illumination Research Articles

Synthesis of a TBA‐Based Polymeric Photocatalyst for Boosting the Selective Bio‐Reduction of Furfural Under Solar Light Illumination

AbstractPhotocatalyst‐enzyme coupled system for harnessing solar light stands out as a highly promising avenue that facilitates bio‐transformation and produces solar fuels. This study explores the integration of a metal‐free photocatalyst in the bio‐reduction of furfural to produce furfuryl alcohol. However, the bio‐reduction of furfural to produce furfuryl alcohol faces challenges due to harsh reaction conditions and expensive catalysts. Likewise, photocatalysts confront various research obstacles, including the absence of long‐lasting photogenerated charge carriers (electrons and holes), stability, and reusability. This work introduces an eco‐friendly and benign catalytic system, featuring an easily prepared photocatalyst using TBA (2,4,6‐tribromo aniline) by standard Ullman coupling. The newly designed polymeric tribromo aniline (PTBA) is cost‐effective, with outstanding light harvesting characteristics, appropriate energy band gap, and remarkably enhanced ability for transfer and migration of photo‐generated carriers. The research aims to optimize parameters for efficient conversion of furfural to produce furfuryl alcohol and also the photocatalytic production of NADH (80.08 %) from consumed NAD+. The photocatalytic efficiency was estimated by the yield percentage of this organic transformation. The absence of metals in the photocatalyst enhances sustainability, showcasing its potential in the green synthesis of furfuryl alcohol which is a valuable chemical with diverse applications.

Constructing functionalized carbon quantum dots on amino-rich graphitic carbon nitride to enhance CO2 photocatalytic reduction: Critical role of functional group modulation

Carbon quantum dots (CQDs) decoration have been widely acknowledged as promising strategy in photocatalysis, yet in-depth understanding of the effect of different functionalized CQDs on CO2 photocatalytic reduction is still lacked. Herein, three kinds of functionalized CQDs, i.e. carboxylic CQDs (CCQDs), amino CQDs (NCQDs) and sulfonated CQDs (SCQDs), were homogeneously anchored on amino-rich g-C3N4 (U1W1-CN) to investigate their CO2 reduction behaviors under simulated solar-light illumination. Structural analysis demonstrated that potential amide covalent bonds formed between U1W1-CN and CCQDs, and noncovalent conjugations might exist between U1W1-CN and SCQDs, while strong electrostatic attraction between U1W1-CN and NCQDs. Performance tests showed CQDs decoration greatly enhanced the CO2 reduction activity, with 7%CCQDs/U1W1-CN exhibiting the optimal CO and CH4 productions of 40.94 μmol g−1 and 2.2 μmol g−1 under 4 h light irradiation, markedly higher than those of 7%SCQDs/U1W1-CN and 7%NCQDs/U1W1-CN. After comprehensive analysis, it was found that CCQDs decoration endowed U1W1-CN with better CO2 adsorption and activation. And due to the potential amide covalent bonds formed between CCQDs and U1W1-CN, 7%CCQDs/U1W1-CN delivered the largest electron density and most abundant COOH– intermediates, contributing much to its superior CO2 reduction activity over 7%NCQDs/U1W1-CN and 7%SCQDs/U1W1-CN. It is expected that the critical role of functional group modulation on CQDs in enhancing CO2 photocatalytic reduction revealed in this work can provide valuable insights into the rational design of more advanced photocatalysts for targeted reactions.

Triangle CeO2/g-C3N4 heterojunctions: Enhanced light-driven photocatalytic degradation of methylparaben

In this work, an efficient photocatalytic system for methylparaben (MP) removal, using solar (λ > 360 nm) and visible (λ > 420 nm) light-driven CeO2/g-C3N4 (CeO2/CN) heterojunctions is reported for the first time. The physicochemical properties of pure CeO2, CN, and CeO2/CN composites were investigated using characterization techniques, such as XRD, FESEM-EDS, TEM, UV–Vis, PL, XPS, and electrochemical spectroscopy. Among the catalysts with different mass ratios of CeO2, 10 %CeO2/CN showed the best photocatalytic performance. This is attributed to the enhanced charge carrier’s separation because of the proper band-edge alignment between CN and CeO2 components, and the strong visible light absorbance. The photocatalytic degradation of MP followed the first-order kinetics, and the 10 %CeO2/CN catalyst exhibited a 3.8- and 11.3-times higher reaction rate (k) constant than that of pure CN, investigated under solar and visible light illumination, respectively. Further, scavenger trapping experiments confirmed that hydroxyl radicals (OH.) and dissolved oxygen are the predominant active species in MP oxidation over 10 %CeO2/CN composite catalyst. 1H NMR and LCMS-HPLC results and observations showed complete degradation of MP (0.1 g/L) to CO2 and H2O after 7 h of solar irradiation, due to the absence of the representative peaks of MP and its organic degradation products (e.g. phenols, benzoates).

Rational Design of Mesoporous ZnFe2O4@g-C3N4Heterojunctions for Environmental Remediation and Hydrogen Evolution.

Mesoporous catalysts with a high specific surface area, accessible pore structures, and appropriate band edges are desirable for optimal charge transfer across the interfaces, suppress electron-hole recombination, and promote redox reactions at the active sites. The present study demonstrates the rational design of mesoporous ZnFe2O4@g-C3N4magnetic nanocomposites (MNCs) with different pore sizes and pore volumes following a combination of facile thermal itching and thermal impregnation methods. The MNCs preserve the structural, morphological, and physical attributes of their counterparts while ensuring their effectiveness and superior catalytic capabilities. The morphological analysis confirms the successful grafting and confinement of ZnFe2O4 nanoparticleswith the polymeric g-C3N4 nanosheets to form heterojunctions with numerous interfaces. The MNCs possess uniformly distributed small mesopores (pore size <4 nm), ample active sites, and a high specific surface area of 62.50 m2/g. The mesoporous ZnFe2O4@g-C3N4notably improve hydrogen evolution rate and methylene bluedye degradation. The optimal loading weight of ZnFe2O4 is 20%, in which the MNCs display the highest hydrogen evolution rate of 1752 µmolg-1h-1 and photo-Fenton dye degradation rate constants of 0.147 min-1, upon solar-light illumination. Furthermore, the photocatalysts demonstrate recyclability over five consecutive cycles, confirming their stability, while easy separation using a simple magnet underscores practical utility.

A self-powered photoelectrochemical and non-enzymatic glucose sensor based on ERGO/ZnONWs/CdS photoanode

We have developed an efficient, self-powered, non-enzymatic photoelectrochemical (PEC) glucose sensor operating in the visible spectrum. The sensor is based on electrochemically reduced graphene oxide (ERGO) and zinc oxide (ZnO) nanowalls (NWs) decorated with cadmium sulfide (CdS) quantum dots (QDs). We used a one-pot electrochemical process to grow vertically aligned ZnONWs on ERGO, followed by using the sequential ionic layer adsorption and reaction (SILAR) technique to decorate the ZnONWs with CdS QDs. The resulting ERGO/ZnONWs/CdS photoelectrode exhibits a three-dimensional hierarchical morphology, providing a large surface area for enhanced surface-substrate interactions and increased optical path length, leading to high absorptivity at visible light. Under one solar light illumination without a bias voltage, the electrode generated a significantly higher photocurrent density (1150 µAcm-2) in the presence of glucose (15.00 mM) than in the absence of glucose (150 µAcm-2). As a PEC glucose sensor, the ERGO/ZnONWs/CdS photoelectrode demonstrated two linear correlations in the glucose concentration range of 0.01–1.00 mM and 1.00–15.00 mM. The sensor has 430.06 and 25.75 µA cm-2mM-1 sensitivities and a low detection limit (1.1 µM). This novel visible light-mediated self-powered electrochemical sensing platform is cost-effective, reproducible, and stable for non-enzymatic glucose detection.

Sustainable scalable solid-state synthesis of highly efficient synergetic 2D/0D micro/nanostructured g-C3N4/CdS photocatalysts for hydrogen production and water purification

Highly efficient synergetic photocatalysts based on graphitic carbon nitride (g-C3N4) and cadmium sulfide (CdS) semiconductors with 2D/0D micro/nanostructure were successfully prepared by easy scalable mechanochemical method and investigated. An in-depth study of electrons' binding energy of semiconductors and their influence on the photocatalytic activity of nanocomposites has been performed. The synthesized materials were applied for the photodegradation of Orange II dye and photocatalytic hydrogen evolution. The obtained experimental results revealed that nanocomposite with 20 wt% of g-C3N4 and 80 wt% of CdS is able to completely decompose Orange II molecules after two hours of visible light irradiation. The mechanism and pathways of photocatalytic reactions have been proposed. The nanocomposite composed of 60 wt% g-C3N4 and 40 wt% CdS, decorated by a platinum (Pt) co-catalyst, demonstrated the peak hydrogen evolution rate (HER) of 2254.54 μmolh−1 g−1 after 4th hour of solar light illumination. This remarkable achievement, with an apparent quantum efficiency (AQE) of 2.0%, occurred on the fourth hour of solar light irradiation. Furthermore, under continuous visible light irradiation, the sample with the same composition is capable of producing hydrogen. The peak HER rate recorded was 246.14 μmolh−1 g−1 (AQE = 0.44%) after 2.5 h, and this remained consistently the same throughout the entire duration of the process.

Transparent Luminescent down-conversion coating for improved performance and enhanced stability of carbon-based perovskite solar cells

Methylammonium lead halide-based perovskite solar cells (PSCs) perform superior photovoltaic performance, nevertheless, demonstrate limited light utilization and instability within the ultraviolet (UV) range. Lanthanide-based down-conversion (DC) materials can mitigate the photoinduced deterioration by resolving spectrum mismatched losses. Particularly, lanthanide complexes possess a broad UV absorbing region thus can convert absorbed UV light to visible or near-infrared light, exhibiting large pseudo-Stoke's shift while they could allow spectrum responsiveness of the PSCs in the UV.Therefore, the DC material may enhance the photovoltaic performance by converting high-energy photons to low-energy photons whilst may also perform as UV shielding material, and finally may both develop PSCs' efficiency and stability. Herein, a novel transparent luminescent down-converting layer (LDC) based on a highly emitting Europium complex in a siloxane matrix was used as an external coating to PSCs with the purpose of improving the solar cells' performance extending their response in the UV region while improving cells’ photostability. The conducted studies indicated that the LDC coating may additionally serve as an anti-reflective and UV-shielding layer simultaneously, resulting in better light-harvesting ability of the perovskite. As a result, short circuit current (Jsc) amplification by the presence of LDC re-emitting the absorbed UV light to the visible and the best carbon-based perovskite solar cell (C-PSC) revealed a 16.13 % overall performance in comparison to the 15.38 % obtained for the control device. Furthermore, photostability tests demonstrated that the unencapsulated LDC-modified devices prepared under ambient conditions retained 75 % of their initial PCE after 8 h under artificial solar light illumination whereas the control devices remained at 40 % at the same conditions. These findings suggest that the LDC layer decreases the UV degradation for PCEs, resulting in PCE and stability enhancement.

Design and fabrication of magnetically recoverable SnO2/CoFe2O4 nanocomposite for enhanced visible light-driven wastewater treatment

This study emphasizes the critical importance of ensuring the availability of clean and secure water resources amid global concerns about water contamination, highlighting the necessity for effective and enduring methods to eliminate hazardous pollutants. The research introduces a sustainable approach to environmental protection through the creation of a high-performance photocatalyst, employing a co-precipitation route to incorporate CoFe2O4 onto SnO2 for efficient wastewater treatment under solar light irradiation. Comprehensive composition and morphological studies of the SnO2/CoFe2O4 composites are conducted using techniques such as XRD, SEM, TEM, Raman, UV–Vis, PL spectra, and FT-IR spectra. The synergistic behavior of the SnO2/CoFe2O4 composite results in efficient separation of electron/hole pairs, reducing the recombination rate and leading to improved photocatalytic performance under solar-light illumination. Notably, the rate constant for Chromium (VI) removal reaches 87 % and the degradation of Rhodamine 6G attains 92 % within 105 mins intervals. The catalyst demonstrates stability and ease of regeneration through a five-cycle recycle study, further supporting its potential for practical application in wastewater treatment.

Unbiased overall photoelectrocatalytic water-splitting over micropyramid Si/In2O3/CuO/ZnO photocathode and Ni/BiVO4 photoanode under simulated solar-light illumination

Micropyramid Si/In2O3/CuO/ZnO photocathode and Ni/BiVO4 photoanode have been synthesized using a magnetron sputtering method with different conditions and characterized for a photoelectrochemical water-splitting process. The as-designed heterojunction of Si/In2O3/CuO/ZnO photocathode successfully induces a facile electron transfer to generate hydrogen in 0.5 M H2SO4. Similarly, Ni/BiVO4 photoanode evolves oxygen in 0.1 M Na2B4O7. Both photoreactions are done under concentrated solar-light irradiation (AM 1.5G, 500 mA/cm2). The analysis shows that IPCE values of photocathode and photoanode reached 40 and 60 % at 300 and 400 nm wavelengths, respectively. Furthermore, the ABPE of photocathode and photoanode achieved 14.9% and 0.8% at 0.21 and 1.15 VRHE, respectively. Photoelectrochemical analysis indicates that half cells of the photocathode and photoanode can reach photocurrents of ∼120 and ∼20 mA/cm2 at 0 and 1.23 VRHE, respectively. The outstanding performances indicate a facile charge transfer during redox reactions at the photocathode and photoanode. In addition, combining the photoelectrodes to form a cell configuration of Si/In2O3/CuO/ZnO//Ni/BiVO4 with a proton exchange membrane generates an unbiased photocurrent of 0.26 mA/cm2 at 0.55 VRHE. The combined cell has been tested for its stability in splitting water molecules into hydrogen and oxygen, indicating a promising result to overcome energy and environmental issues.

Development of 2D/2D h-MoO3/Ag/g-C3N4 heterojunction photocatalyst with enhanced photocatalytic performance for the detoxification of methylene blue and tetracycline under solar light illumination

In this study, direct thermal polycondensation, hydrothermal, and ultrasonic techniques were used to fabricate photocatalysts consisting of bare g-C3N4 (GCN), h-MoO3 (MoO3), MoO3/g-C3N4 (MGCN), and MoO3/Ag/g-C3N4 (MAGCN) composites. These methods were used to improve the photocatalytic effect, especially for environmental applications. The surface and chemical properties of the fabricated samples were investigated by XRD, FT-IR, FE-SEM, HR-TEM, UV-DRS, XPS, and PL analysis. Bare and composite photocatalysts were tested for photodegradation of the methylene blue (MB) dye and tetracycline (TC) antibiotic under solar irradiation. The MAGCN composite material exhibits remarkable efficiency in degrading 99% of MB dye and 90% of TC antibiotic within a time frame of 60 min when exposed to sunlight irradiation. The degradation rate constants (k) of MB and TC in the most active MAGCN photocatalyst were 11.02 and 7.03 times higher than those of pristine GCN, respectively. The scavenger reaction shows that the most important reactive species in the photocatalytic process are superoxide and photogenerated holes. The outstanding photocatalytic efficiency of the MAGCN catalyst was demonstrated by the fact that Ag nanoparticles act as mediators of fast charge transfer, resulting in higher absorption of sunlight, enhanced charge separation/transfer, and regeneration by MoO3 and GCN. The MAGCN photocatalyst exhibits remarkable activity, maintains its performance over six consecutive reaction cycles, and exhibits excellent stability and reusability. Intermediates were analyzed by GC-MS, and suitable degradation pathways were proposed. These results enable the development of an effective Z-scheme heterojunction photocatalyst and facilitate its wide application in the degradation of organic pollutants in wastewater.

Simulated sunlight/periodate-triggered formation of toxic halogenated bisphenols in highly saline water.

Periodate (PI)-based oxidation using the activators, such as metal ions and light irradiation, has emerged as a feasible treatment strategy for the effective remediation of contaminated water and wastewater. Given the pervasive nature of PI residues and solar exposure during application, the role of solar light in remediating the challenging highly saline water matrices needs to be elucidated. In this study, bisphenol A (BPA) was selected as the targeted micropollutant, which can be efficiently eliminated by the simulated sunlight (SSL)/PI system in the presence of high-level Cl- (up to 846.0 mM) at pH 7.0. The presence of different background constituents of water, such as halides, nitrate, and dissolved organic matter, had no effect, or even accelerated BPA abatement. Particularly, the ubiquitous Br- or I- appreciably enhanced the BPA transformation efficiency, which may be ascribed to the generation of high-selective reactive HOBr or HOI. The in silico predictions suggested that the transformation products generated by halide-mediated SSL/PI systems via halogen substitutions showed greater persistence, bioaccumulation, and aquatic toxicity than BPA itself. These findings highlighted a widespread phenomenon during PI-based oxidative treatment of highly saline water, which needs special attention under solar light illumination.

Significance of homogeneous operation in light-assisted fixed-bed bioprocess under ammonia stress: Optimization, long-term operation and metagenomic analysis

Activating microbes with light is a promising strategy for addressing ammonia-stressed anaerobic digestion (AD). However, as a critical in-process parameter, homogenous operation, in light-assisted AD amended by bio-fixed bed has received limited attention. This research endeavors to establish a uniform-illuminated biosystem and assess its practical feasibility through a 90-day semi-continuous operation at pilot scale under solar light illumination. With optimal stirring mode (intermittent stirring for 3 min every 15 min), robust methane yields were achieved across various organic loads, reaching 88.7–94.3% of theoretical yield under high ammonium stress (3500 mg/L). The metagenomic analysis unveiled that uniform illumination triggered synergistic effects in AD, fostering a diversified microbial consortium, enhancing carbohydrate and methane metabolism, and facilitating the formation of an electroactive bio-cluster. This study underscores the significance of homogenous illumination in AD systems for efficient waste-to-energy conversion, highlighting the implementation of solar light as a greener approach for scale-up application.

Utilization of Electrocoagulated Sewage as a Photoelectrocatalyst for Water Splitting.

Electrocoagulation (EC) as a wastewater treatment process for the removal of pollutants has been demonstrated in numerous studies. However, proper management of solid waste generated after EC treatment is essential to minimize its environmental impact. Hence, more emphasis needs to be paid towards unused solid waste after EC treatment. The present study investigates the possibilities of utilizing waste released after the EC process as an electrocatalyst in the presence of sunlight. In this study, the sludge produced after domestic wastewater treatment by the EC process is collected and tested for water oxidation reaction under AM 1.5 illumination of simulated solar light. The sludge produced after EC treatment was characterized meticulously and confirmed to be the magnetite phase of iron oxide, which is used as a photoanode for photoelectrochemical (PEC) water splitting. The chemical composition of sludge is majorly dependent on the treatment time, which plays a crucial role in deciding the metal ions present in the sludge. After 30 min, which is the optimized time for EC treatment, sludge was studied as an efficient photoanode material. The band gap illumination of sludge (iron oxide) as working electrodes results in anodic current; the photocurrent appears at a bias of ca. 390 mV with respect to the flat-band potential. The PEC activity of waste is treatment-time dependent and decreases after reaching an optimal time of 30 min. A photocurrent density of 4.6 × 10-6 A cm-2 was found at the potential of 1.23 V (vs RHE) for sludge collected after 30 min of treatment time. It indicates that the sludge-derived photoanode has the potential to be an efficient component in PEC systems, contributing to the overall efficiency of water-splitting processes. Our experimental results show a new pathway of a "waste to energy" approach that aligns with the principles of circular economy and sustainable resource management.

Copper-decorated strategy based on defect-rich NH2-MIL-125(Ti) boosts efficient photocatalytic degradation of methyl mercaptan under sunlight

Photocatalysis has received significant attention as a technology that can solve environmental problems. Metal-organic frameworks are currently being used as novel photocatalysts but are still limited by the rapid recombination of photogenerated carriers, low photogenerated electron migration efficiency and poor solar light utilization rate. In this work, a novel photocatalyst was successfully constructed by introducing Cu species into thermal activated mixed-ligand NH2-MIL-125 (Ti) via defect engineering strategy. The constructed defect structure not only provided 3D-interconnected gas transfer channels, but also offered suitable space to accommodate introduced Cu species. For the most effective photocatalyst 0.2Cu/80%NH2-MIL-125 (300 °C) with optimized Cu content, the photocatalytic degradation rate of CH3SH achieved 4.65 times higher than that of pristine NH2-MIL-125 under visible light (λ > 420 nm). At the same time, it showed great degradation efficiency under natural sunlight, 100 ppm CH3SH was completely removed within 25 min in full solar light illumination. The improved catalytic efficiency is mainly due to the synergistic effect of the integrated Schottky junction and rich-defective NH2-MIL-125, which improved the bandgap and band position, and thus facilitated the separation and transfer of the photo-generated carriers. This work provided a facile way to integrate Schottky junctions and rich-defective MOFs with high stability. Due to its excellent degradation performance under sunlight, it also offered a prospective strategy for rational design of high-efficiency catalysts applied in environmental technologies.

Enhanced photocatalytic activity of Er doped ZnO nanospindles and nanorods for degradation of organic pollutants

Rare earth doping in ZnO is an efficient way to improve the photocatalytic performance. In the present work, Er doped ZnO nanospindles and nanorods were prepared through a simple cost effective wet chemical approach and were thoroughly characterized by FESEM, XRD, Raman spectroscopy, UV–vis-DRS, UV–vis absorption and PL spectroscopy. Nanospindle and nanorod-like morphologies of the fabricated samples were revealed by FESEM. XRD analyses revealed hexagonal wurtzite structure of Er doped ZnO nanostructures and confirmed Er doping into ZnO. PL studies showed increased defect concentration in ZnO nanostructures doped with Er ions. The photodegradation ability of nanostructures was investigated using cationic and anionic dyes and photodecomposition rate of 0.042 min−1 was achieved for MB decolorization using 0.5 % Er doped ZnO sample upon 32 min of solar light illumination. The probable photodecomposition mechanism supported by in-situ radical trapping experiments and repeatability test have also been discussed and results suggest that Er doped ZnO photocatalyst exhibit potential for use as commercial solar-active photocatalysts.

Microwave-assisted synthesis of ZnO structures for effective degradation of methylene blue dye under solar light illumination.

The presence of dyes in wastewater poses a high risk to both human health and the environment due to their potential toxicity and ecological impacts. Zinc(ii) oxide is a low-cost, non-toxic material that can serve as a sustainable and effective solution to the global water pollution crisis. In this study, we propose a facile one-step synthesis of various ZnO structures by microwave irradiation. The primary goal of this study was to explore the morphology-dependent photocatalytic activity of various ZnO structures, as well as the impact of interfering anions on the Methylene Blue (MB) photodegradation under solar light illumination. Photocatalytic activity studies show that the sample denoted as 0.56 M-ZnO with a sheet-like structure has remarkable catalytic activity under solar light illumination, reaching ∼96.6% degradation of 30 mL MB solution (3 × 10-5 M) within 40 minutes. The BET specific surface area and band gap of the optimal 0.56 M-ZnO sample were observed to be 12.42 m2 g-1 and 2.89 eV, respectively. It was shown that the presence of anions like Cl-, NO3-, and HCO3- can reduce the catalytic activity of 0.56 M-ZnO structure to some extent, although more than 70% MB degradation can still be obtained under neutral pH conditions. The superior catalytic efficacy observed in the 0.56 M-ZnO photocatalyst can be attributed to its improved crystallinity, large surface area, and enhanced production of hydroxyl radicals. The low-cost synthesis, combined with high photocatalytic activity collectively underscores the efficiency and practical usability of produced ZnO photocatalysts for dye degradation.

Assessment of solar light sensitive Chitosan integrated CeO2-CuO ternary composites for the efficient degradation of Malachite Green, Acid Blue 113 dyes and microbial studies

Ternary chitosan integrated CeO2-CuO composites were prepared via a facile co-precipitation technique and thoroughly characterized using FTIR spectroscopy, X-ray diffraction, UV-diffuse reflectance spectroscopy, Thermo gravimetric analysis, Scanning emission microscopy, Transmission electron microscopy and X-ray Photoelectron spectroscopy. The composite with 10 wt% CeO2-CuO on chitosan exhibited the highest efficiency of 92 % and 91 % in degrading malachite green (MG) and acid blue 113 (AB 113) respectively. This composite demonstrated efficient generation of electron-hole pairs, minimized recombination rates and facilitated rapid dye degradation under solar light illumination. Additionally, the composites displayed effective antibacterial activity against Serratia marcescens and Bacillus subtilis at a concentration of 100 µl, and exhibited promising anti-fungal activities against Candida albicans and Aspergillus niger. These findings suggest the potential of these composites for efficient dye degradation and demonstrate their promising antimicrobial properties, offering possibilities for diverse environmental and biomedical applications.

Unleashing the power of sunlight: Bi2O3/Sb2S3 photocatalysis for sustainable wastewater remediation of Tetracycline and Rhodamine-B

The use of heterojunction photocatalysts for pollutant decomposition has garnered significant interest in mitigating water contamination and environmental pollution. Our present study focuses on synthesizing Bi2O3/Sb2S3 heterojunction photocatalyst having variable mole ratios by employing a hydrothermal technique. Loading Sb2S3 onto Bi2O3 enables broad-spectrum solar light absorption, efficient segregation of charges, and enhanced surface area, which are excellent traits for photocatalysis. Both Bi2O3 and Sb2S3 showed nano-rod type morphology, while Sb2S3 was present as smaller nano-rods and Bi2O3 as larger ones. The photocatalytic performance of this heterojunction photocatalyst was examined using Rhodamine-B (RhB) and Tetracycline (TC) under solar light illumination for 120 min. Remarkable decomposition efficiency was achieved, with a 98.2% degradation rate observed for RhB having a rate constant of 0.03149 min−1. Similar experiments were conducted using other light sources as well, such as visible light and UV light. However, only 83% and 69% RhB degradation rates were attained with visible and UV light, respectively, indicating that natural sunlight is the superior light source for our catalyst. A 91.5% degradation rate was achieved for TC with the rate constant of 0.01749 min−1, in the presence of sunlight for 120 min. A small amount (0.3 g/L) of 1:3 Bi2O3/Sb2S3 (13BOSBS) photocatalyst was enough to bring such a good result. The photocatalytic activity of our catalyst, that is, 98.2% RhB degradation, is much higher than that of commercially available TiO2–P25 powder, as the latter only achieved 52% RhB degradation. The pH at which the surface of Bi2O3/Sb2S3 has a zero charge (pHpzc) was determined to be 5.37 and the maximum decomposition of RhB was achieved at pH 7. Reusability tests verified the remarkable stability of this catalyst, with about 74.4% of RhB degradation still present after seven consecutive cycles. Scavenger experiments highlighted the crucial role of •OH radicals in the photodecomposition mechanism, as the incorporation of DMSO significantly influenced the photocatalytic efficiency of the 13BOSBS composite, leading to a notable decrease to 37.5% in RhB degradation. For the RhB dye, the 13BOSBS catalyst demonstrated remarkable 90.2% and 85% reductions in COD and TOC, respectively. The commercially available TC powder substantially reduced 84% in COD and 80% in TOC, whereas there was a 78% reduction in COD and 73% in TOC for TC tablets. The degradation of the contaminants was followed by the formation of simpler intermediates, which were discovered using the GC-MS approach. Owing to its excellent attributes and simple synthesis method, the fabricated heterojunction offers a promising solution to prevent the persistent buildup of harmful toxic pollutants in industrial wastewater systems.

Rational construction of hollow ZnO@SnS2 core-shell nanorods: A way to boost catalytic removal of Cr (VI) ions, antibiotic and industrial dyes

Herein, the novel hollow ZnO@SnS2 core-shell nanorods with variable shell thickness have been synthesized by a chemical synthesis approach. The transmission electron microscopy (TEM) images signified the creation of a hollow core-shell nanostructure. The SnS2 layer coating on ZnO nanorods broadens visible light absorption and suppresses near-band edge emission of ZnO nanorods. Interestingly, the band gap (optical) of the developed ZnO nanorods decreased from 3.3 eV to 2.1 eV after the coating of SnS2 shell. Consequently, the coated hollow ZnO@SnS2 core-shell nanorods displayed a significant enhancement in catalytic activity for the decomposition of toxic industrial dyes, pharmaceutical pollutant tetracycline, and Cr(VI) ion in comparison to hollow ZnO NRs. The photon-induced charge carrier generation and separation were confirmed by the three-electrode electrochemical amperometric analysis and impedance analysis under illumination of simulated solar light (AM 1.5, One Sun). Moreover, an exceptionally higher photocurrent generation (∼10 times higher than ZnO nanorod). The improved ZnO@SnS2 core shell NRs catalytic activity was attributed to its core-shell structure, proper band structure, and effective charge carrier transfer across the core shell interface. This work offers new insights for the design and growth of visible light-active core shell nanorods for resolving environmental pollution and photocurrent generation.

Ag-lignin hybrid nanoparticles for high-performance solar absorption in photothermal antibacterial chitosan films

There is an urgent need for antimicrobial films based on sustainable resources and production methods. In this study, we present a bio-based nanocomposite film composed of chitosan (∼60 wt%), lignin nanoparticles (LNPs, ∼40 wt%), a small amount of glutaraldehyde (1.5 wt%), and a trace level of silver nanoparticles (AgNPs, 0.072 wt%). The uniform dispersion with LNPs prevented aggregation of metallic silver, resulting in small (diameter 3.3nm) AgNPs. The nanocomposite film absorbs 89% of radiation across the entire solar spectrum and exhibits a remarkable photothermally triggered antibacterial effect, which is further enhanced by the dark color of lignin. Under simulated solar light illumination, the nanocomposite films demonstrated a significant reduction in viable Escherichia coli count compared to control scenarios. The potential applications of these nanocomposites extend to sunlight-activated antimicrobial films and coatings, addressing the growing demand for sustainable and effective antimicrobial materials.