Search Results (3,858)

A series of single-walled carbon nanotube/titanium dioxide (SWCNTs/TiO₂) composites were prepared by the incorporation of various concentrations (0, 5, 10, 20 V.%) of SWCNTs in TiO₂. The prepared solutions were successfully formed on silicon and quartz substrates using the sol–gel spin-coating approach at 600 °C in ambient air. The X-ray diffraction method was used to investigate the structure of the samples. The absorbance and transmittance data of the samples were measured using a UV–vis spectrophotometer. Through the analysis of these data, both the linear and nonlinear optical properties of the samples were examined. Wemple–DiDomenico’s single-oscillator model was used to calculate the single-oscillator energy and dispersion energy. Finally, all samples’ photocatalytic performance was studied by the photodegradation of methylene blue (MB) in an aqueous solution under UV irradiation. It is found that the photocatalytic efficiency increases when increasing the SWCNT content. This research offers a new perspective for the creation of new photocatalysts for environmental applications. Full article

Vacancy defect graphitic carbon nitride (g-C₃N₄) and conjugated polyimide (PI) polymer photocatalysts have become increasingly recognized as metal-free photocatalysts featuring an appropriate bandgap. The narrow absorption spectrum of visible light and the rapid recombination rate of the photoexcited charge carriers in PI polymers and g-C₃N₄ impede its photocatalytic performance. The presence of oxygen vacancies (OVs) in PI polymer photocatalysts, as well as nitrogen vacancies (NVs) and carbon vacancies (CVs) in g-C₃N₄, can significantly enhance the migration of photogenerated electrons. Adding vacancies to improve the electronic structure and band gap width can greatly enhance the photocatalytic efficiency of PI polymers and g-C₃N₄. Defect engineering is important for increasing the photocatalytic ability of PI-polymer and g-C₃N₄. There remains a notable absence of thorough review papers covering the synthesis, characterization, and applications of vacancy-rich PI-polymer and g-C₃N₄ in photocatalysis. This review paper examines the roles of OVs in PI-polymer, NVs, and CVs in g-C₃N₄ and thoroughly summarizes the preparation approaches employed before and after, as well as during polymerization. This review scrutinizes spectroscopic characterization techniques, such as EPR, XPS, PAS, XRD, FTIR, and NMR, for vacancy defect analysis. We also reviewed the role of vacancies, which include light absorption, photogenerated charge carrier separation, and transfer dynamics. This review could serve as a comprehensive understanding, a vacancy-engineered design framework, and a practical guide for synthesizing and characterizing. Full article

Nb-Sn, V-Sn mixed-metal oxides and Nb-Si, V-Si metal oxide–silicas were successfully synthesized through a “soft” templating method, in which appropriate amounts of metal salts (either niobium(V) chloride, or vanadium(IV) oxide sulfate hydrate or tin(II) chloride dihydrate) or tetraethyl orthosilicate (TEOS) were mixed with hexadecyltrimethylammonium chloride (HDTA) or sodium dodecyl sulfate (SDS) solutions to obtain a new series of mesoporous oxides, followed by calcination at different temperatures. As-obtained samples were characterized by SEM, TEM, XRD, and UV-Vis spectra techniques. The photocatalytic activities of the samples were evaluated by degradation of methyl orange II (MO) under simulated sunlight irradiation. The effects of metal species and calcination temperature on the physicochemical characteristic and photocatalytic activity of the samples were investigated in detail. The results indicated that, compared to pure oxides, mixed-metal oxide showed superior photocatalytic performance for the degradation of MO. A maximum photocatalytic discoloration rate of 97.3% (with MO initial concentration of 0.6·10⁻⁴ mol/dm³) was achieved in 300 min with the NbSiOx material, which was much higher than that of Degussa P25 under the same conditions. Additionally, the samples were tested in the photochemical oxidation process, i.e., advanced oxidation processes (AOPs) to treat the commercial non-ionic surfactant: propylene oxide ethylene oxide polymer mono(nonylphenyl) ether (N8P7, PCC Rokita). A maximum of 99.9% photochemical degradation was achieved in 30 min with the NbSiOx material. Full article

Piezo-photocatalysis is a promising solution to address both water pollution and the energy crisis. However, the recombination of electron–hole pairs often leads to poor performance, rendering current piezoelectric photocatalysts unsuitable for industrial water treatment. To overcome this issue, oxygen vacancies (V) and Ag nanoparticles (NPs) are introduced into Bi₄Ti₃O₁₂ (BTO) nanosheets, forming Schottky junctions (BTO-V/Ag). These 2D/3D structures offer more exposed active sites, shorter carrier separation distances, and improved piezo-photocatalytic performance. Additionally, the photothermal effect of Ag NPs supplies additional energy to counteract adsorption changes caused by active species, promoting the generation of more active species. The rate constant of the optimized BTO-V/Ag-2 in the piezo-photocatalytic degradation of nizatidine (NZTD) was 4.62 × 10⁻² min⁻¹ (with a removal rate of 98.34%), which was 4.32 times that of the initial BTO. Moreover, the composite catalyst also showed good temperature and pH response. This study offers new insights into the regulatory mechanisms of piezo-photocatalysis at the Schottky junction. Full article

Carbon nitrides are polymeric materials with a broad range of applications, including photocatalysis. Among them, graphitic carbon nitride (g-C₃N₄), a low-cost material, is an excellent photocatalyst under visible light irradiation owing to its features such as correct band positions, high stability and non-toxicity. g-C₃N₄ is a metal-free material that is easily synthesized by polymerizing nitrogen-rich compounds and is an efficient heterogeneous catalyst for many reaction procedures due to its distinctive electronic structure and the benefits of the mesoporous texture. In addition, in situ or post-modification of g-C₃N₄ can further improve catalytic performance or expand its application for remediating environmental pollution. Water pollution from organic compounds such as pesticides and pharmaceuticals is increasing dramatically and is becoming a serious problem around the world. These pollutants enter water supplies in a variety of ways, including industrial and hospital wastewater, agricultural runoff, and chemical use. To solve this problem, photocatalysis is a promising technology. Without the use of other oxidative chemicals, g-C₃N₄ uses renewable solar energy to transform harmful pollutants into harmless products. As a result, much recent research has focused on the photocatalytic activity of g-C₃N₄ for wastewater treatment. For this reason, the main objective of this paper is to contribute a chronological overview of the bibliometrics on g-C₃N₄ for the removal of pesticides and pharmaceuticals from water using the tools BibExcel, Bibliometrix and R-Studio IDE. A bibliometric analysis was performed using the Science Citation Index Expanded (WoS^©) database to analyze the scientific literature published in the field over the last 10 years. The results were used to identify limitations and guide future research. Full article

This study investigates the photocatalytic degradation of tetracycline hydrochloride (TCH) using a TiO₂/CdS composite nanocatalyst synthesized on flexible nickel foam via a dipping–pull method. By comparing the photocatalytic degradation of TCH by TiO₂/CdS with different precursor ratios, it was found that TiO₂/CdS-1.43% exhibited better photocatalytic degradation performance. The X-ray diffraction (XRD) pattern of the TiO₂/CdS composite retains the characteristic peaks of both TiO₂ and CdS, indicating the successful formation of the composite. According to the analysis of ultraviolet–visible spectroscopy (UV–Vis), the absorption edge of TiO₂/CdS is approximately 530 nm. The transmission electron microscopy (TEM) images show Cd and S evenly, densely distributed in TiO₂/CdS, further validating its successful synthesis. X-ray photoelectron spectroscopy (XPS) analysis reveals that Cd and Ti elements exist in the forms of Cd²⁺ and Ti⁴⁺, respectively. TiO₂/CdS loading uniformity on the nickel foam was assessed using super-depth microscopy. The removal efficiency of 10 L of 20 mg/L TCH solution achieved 53.89%, respectively, under response surface methodology—Box–Behnken design (RSM–BBD) optimal conditions (28 g catalyst, 325 rpm, pH = 9.04 within 150 min). Furthermore, five successive cycling experiments demonstrated strong stability, with a catalyst loss of only 4.44%. Finally, free radical scavenging experiments revealed that ·O₂⁻ radicals are the primary active species. This study highlights the potential of TiO₂/CdS composites supported on nickel foam for efficient photocatalytic degradation of antibiotic pollutants in water. Full article

Mycotoxins are highly toxic secondary metabolites that can pose a serious threat to food safety, human health, and the environment. As a promising detoxification method, photocatalysis has shown great potential for mycotoxin degradation due to its high efficiency, low cost, and green advantages. Heterogeneous photocatalysis using a semiconductor as a mediator is now regarded as an effective approach for mycotoxin degradation. The aim of this study was to review the recent developments, mainly in the photocatalytic degradation of mycotoxin (e.g., AFB1, FB1, DON, and ZEN). The principle, feasibility, and main semiconducting catalysts of mycotoxin photodegradation are introduced and discussed, including metal oxides (transition, noble, and rare earth metals), carbons (graphene, carbon nitride, and biochar) and other composites (MOFs and LDHs). This review will contribute to the development of semiconductor photocatalysts and photocatalytic degradation for mycotoxins decontamination. Full article

This review focuses on the research progress related to carbon dots (CDs) derived from Chinese herbal medicines and tea, covering preparation methods, physicochemical properties, and application fields. It elaborates on preparation approaches like hydrothermal, solvothermal, microwave-assisted, and ultrasonic-assisted methods, and their influence on CDs’ structure and properties. It also explores CDs’ structural and optical properties. The application fields include antibacterial, sensing, bioimaging, photocatalysis, hemostasis, and energy. Carbon dots show antibacterial activity by destroying bacterial cell membranes, they can detect various substances in sensing, are important for bioimaging, degrade organic pollutants in photocatalysis, have hemostatic and anti-inflammatory effects, and can be used as battery anode materials. Despite progress, challenges remain in improving yield, quantum yield, property control, and understanding their mechanism of action. This review provides a reference for related research and looks ahead to future directions. Full article

This research employs 2-methylene-tetrahydronaphtalene-1-ones and N-cyclopropylanilines as starting materials, integrating photocatalysis and organic phosphoric acid catalysis to synthesize 2-amino-spiro[4.5]decane-6-ones via a [3 + 2] cycloaddition approach. This method boasts the advantage of mild reaction conditions that are photocatalyst-free and metal catalyst-free. It achieves 100% atom conversion of the substrates, aligning with the principles of green chemistry. Additionally, it attains a high diastereoselectivity result of up to 99:1, demonstrating good stereoselectivity. In the derivatives of 2-methylene-tetrahydronaphtalene-1-ones, substrates with alkane rings of different sizes or thiophene replacing the phenyl ring are also amenable to this method, enabling the synthesis of different [4.4], [4.5], and [4.6] spirocyclic compounds. In the derivatives of N-cyclopropylanilines, substrates with para-fluoro and meta-fluoro substitutions are also amenable to this method. Finally, a preliminary mechanistic investigation was conducted, proposing a plausible reaction mechanism pathway initiating from the intermediate N-cyclopropylanilines with chiral phosphoric acid. Full article

The removal of low-concentration NOx contamination in the urban atmosphere has been regarded as an urgent issue to be solved in the context of urbanization. In the past few decades, TiO₂ photocatalysis has been intensively investigated as an economical, efficient, and environmentally friendly means for the abatement of low-concentration NOx. Up to now, however, there have been few reviews focusing on TiO₂-based photocatalysts for photocatalytic NO removal. In this review article, we will summarize the latest advances in the photocatalytic removal of NOx contamination with TiO₂-based photocatalysts, which have been endowed with the reputation of being star catalysts for atmospheric environment remediation. We will begin with a survey of the mechanistic investigations of photocatalytic NOx removal, focusing on the in situ Fourier Transform Infrared Spectroscopy (in situ FTIR) and Electron Paramagnetic Resonance (EPR) studies and the theoretical calculation of reaction pathways with Density Functional Theory. We will then introduce the test methods and the ISO standards for photocatalytic NOx removal and discuss the effect of reaction parameters (catalyst mass, irradiation conditions, temperature, and humidity). Meanwhile, we also elaborate the latest modification methods to enhance photocatalytic efficiency and summarize the progress in recent years in modified TiO₂-based photocatalysts applied in NOx abatement. Lastly, we will put forward some feasible suggestions. In the end, this review may provide some inspiration in designing more effective TiO₂-based photocatalysts for removing NOx contamination from the ambient atmosphere. Full article

Zinc oxide (ZnO) semiconductors are renowned for their cost-effective synthesis and superior catalytic attributes, making them prominent in environmental remediation applications. This study presents the synthesis of ZnO nanoparticles (NPs) with distinct morphologies, achieved by modulating citric acid concentrations in an ultrasonic-assisted hydrothermal process. The photocatalytic efficacy of these ZnO NPs in degrading malachite green (MG), a persistent environmental pollutant, was thoroughly investigated. Our findings reveal a strong correlation between the morphological features of ZnO catalysts and their photodegradation performance. Among the synthesized NPs, the chrysanthemum-shaped ZnO (denoted as USZ-0.1) demonstrated exceptional photocatalytic activity, attributed to its enhanced surface area and optimized nano-crystal aggregation. This structure facilitated the generation of a higher concentration of reactive oxygen species, leading to over 96.5% degradation of MG within 40 min under simulated sunlight in an acidic medium. This study underscores the potential of morphological manipulation in enhancing the photocatalytic properties of ZnO NPs for environmental applications. Full article

Zinc oxide (ZnO) photocatalysts have emerged as a promising material for environmental and energy applications due to their exceptional photocatalytic properties. Initially recognized for their efficiency under ultraviolet (UV) light, recent advancements have focused on enhancing ZnO’s visible light activity (VLA) to address its inherent limitations. This review provides an overview of ZnO’s structure, electronic properties, and photocatalytic mechanisms. Various strategies for modifying ZnO to harness visible light, including metal and non-metal doping, dye sensitization, and semiconductor coupling, are discussed. Special emphasis is placed on the mechanisms behind visible light absorption and reactive oxygen species (ROS) generation, as deduced through physicochemical and photoelectrochemical analyses. The applications of ZnO in environmental remediation are comprehensively explored, particularly for water treatment, disinfection, and air purification. The photocatalytic degradation of pollutants, including persistent organic compounds, pharmaceuticals, dyes, and pesticides, using ZnO is reviewed and compared with conventional UV-activated ZnO materials. This review underscores the potential of ZnO as an efficient and sustainable solution for environmental purification. Full article

Tramadol is a widely used pain medication detected in wastewater treatment plants, prompting concerns about its impact on the environment and the effectiveness of wastewater treatment. Nitrogen-doped carbon quantum dots (NCQDs) can be used to remove pollutants from the contaminated water sources. However, NCQDs can hardly be recovered after applications, leading to high regeneration costs. Thus, this study aims to explore the use of magnetite nitrogen-doped carbon quantum dots (magnetite NCQDs) fabricated from empty fruit bunches (EFBs) to remove tramadol from wastewater treatment. Various analytical methods were conducted to characterize the magnetite NCQDs. Magnetite NCQDs showed excellent separation and aggregate-free properties. This study investigated the effect of the initial concentration of tramadol, the dosage of magnetite NCQD adsorbent, and the contact time while keeping other parameters constant. Tramadol was efficiently adsorbed within 40 min with an adsorption efficiency of over 85.9% and further photodegraded by 4.5% after being exposed to UV light after undergoing photocatalysis for 50 min. Magnetite NCQDs exhibited outstanding properties in removing tramadol after undergoing five cycles. This research provides a promising approach for developing a highly efficient adsorbent for treating tramadol-contaminated wastewater. Full article

This study focused on the preparation and investigation of g-C₃N₄/TiO₂ photocatalysts using different TiO₂ morphologies (anatase nanoparticles (TPs), poorly crystalline nanotubes (aTTs), and well-crystalline anatase nanorods (TRs)) and self-synthesized g-C₃N₄ (CN). The synthesis of the g-C₃N₄/TiO₂ composites was carried out using a mortar mixing technique and a g-C₃N₄ to TiO₂ weight ratio of 1:1. In addition, the g-C₃N₄/TiO₂ composites were annealed in a muffle furnace at 350 °C for 2 h in air. The successful formation of a g-C₃N₄/TiO₂ composite with a mesoporous structure was confirmed using the results of XRD, N2 physisorption, and FTIR analyses, while the results of microscopic analysis techniques confirmed the preservation of TiO₂ morphology in all g-C₃N₄/TiO₂ composites investigated. UV-Vis DR measurements showed that the investigated g-C₃N₄/TiO₂ composites exhibited visible-light absorption due to the presence of CN. The results of solid-state photoluminescence and electrochemical impedance spectroscopy showed that the composites exhibited a lower charge recombination compared to pure TiO₂ and CN. For example, the charge transfer resistance (RCT) of the CNTR/2 composite of TR and CN calcined in air for 2 h was significantly reduced to 0.4 MΩ, compared to 0.9 MΩ for pure TR and 1.0 MΩ for pure CN. The CNTR/2 composite showed the highest photocatalytic performance of the materials tested, achieving 30.3% degradation and 25.4% mineralization of bisphenol A (BPA) dissolved in water under visible-light illumination. In comparison, the pure TiO₂ and CN components achieved significantly lower BPA degradation rates (between 2.4 and 11.4%) and mineralization levels (between 0.6 and 7.8%). This was due to (i) the presence of Ti³⁺ and O-vacancies in the TR, (ii) enhanced heterojunction formation, and (iii) charge transfer dynamics enabled by a dual mixed type-II/Z scheme mechanism. Full article

This study presents an efficient and environmentally sustainable synthesis of ZnO nanoparticles using a starch-mediated sol-gel approach. This method yields crystalline mesoporous ZnO NPs with a hexagonal wurtzite structure. The synthesized nanoparticles demonstrated remarkable multifunctionality across three critical applications. In photocatalysis, the ZnO NPs exhibited exceptional efficiency, achieving complete degradation of methylene blue within 15 min at pH 11, significantly surpassing the performance of commercial ZnO. Under neutral pH conditions, the nanoparticles effectively degraded various organic dyes, including methylene blue, rhodamine B, and methyl orange, following pseudo-first-order kinetics. The methylene blue degradation process was aligned with the Langmuir–Hinshelwood model, emphasizing their advanced catalytic properties. For supercapacitor applications, the ZnO NPs attained a high specific capacitance of 550 F/g at 1 A/g, underscoring their potential as energy storage solutions. Additionally, the nanoparticles demonstrated strong UV-induced antiradical activity, with an EC₅₀ of 32.2 μg/mL in DPPH assays. Notably, the cytotoxicity evaluation revealed an LC₅₀ of 1648 μg/mL, indicating excellent biocompatibility. This study highlights a sustainable approach for the synthesis of multifunctional ZnO NPs that offers effective solutions for environmental remediation, energy storage, and biomedical applications. Full article