Search Results (98)

Ubiquitous nitrate (NO₃⁻) in groundwater sources is considered a hazard compound for human health. Photo-catalytic reduction by Ag-TiO₂/formic acid/visible light represents an emerging method for NO₃⁻ removal without secondary pollution. In this contribution, the removal of NO₃⁻ by photo-catalytic reduction and the selectivity of N₂ were systematically investigated under varied conditions, including concentrations of Ag-TiO₂, NO₃⁻, and formic acid (HCOOH). The removal efficiency of NO₃⁻ reached 84.47%, 82.68% of which was converted to N₂ under the optimal conditions: NO₃⁻ at 50 mg-N/L, Ag-TiO₂ at 1.0 g/L, HCOOH at 20.05 mmol/L, and reaction time at 120 min. The removal of NO₃⁻ was enhanced mainly by CO₂⁻ rather than by photo-generated electrons or HCOO⁻. The results of this study indicated that the production of ·CO₂⁻ by Ag-TiO₂ and HCOOH under visible light catalysis can achieve efficient NO₃⁻ removal. Full article

The development of efficient and sustainable photocatalysts for wastewater treatment remains a critical challenge in environmental remediation. In this study, a ternary photocatalyst, Cu-Cu₂O/g-C₃N₄, was synthesized by embedding copper-copper oxide heterostructural nanocrystals onto g-C₃N₄ nanosheets via a simple deposition method. Structural and optical characterization confirmed the successful formation of the heterostructure, which combines the narrow bandgap of Cu₂O, the high stability of g-C₃N₄, and the surface plasmon resonance (SPR) effect of Cu nanoparticles. The photocatalytic performance was evaluated through the degradation of Rhodamine B (RhB) in a photo-Fenton-like reaction system under visible light irradiation. Among the catalysts tested, the 30 wt% Cu-Cu₂O/g-C₃N₄ composite exhibited the highest catalytic efficiency, achieving a reaction rate constant approximately 3 times and 1.5 times higher than those of Cu-Cu₂O and g-C₃N₄, respectively. Mechanistic studies suggest that the heterostructure facilitates efficient charge separation and promotes the reduction of Cu²⁺ to Cu⁺, thereby enhancing ∙OH radical generation. The catalyst also demonstrated excellent stability and reusability across a wide pH range. These findings provide a new strategy for designing highly efficient photocatalysts for organic pollutant degradation, contributing to the advancement of advanced oxidation processes for environmental applications. Full article

The utilization of the photo catalytic activation of permonosulfate (PMS) for the combined breakdown of pollutants has become a focal point in research. Layered double hydroxides (LDHs) have a unique layered structure which is conducive to the adsorption and diffusion of reactants, and can provide more active sites for photocatalytic reactions. The anions between the layers can be exchanged with a variety of substances so that specific catalytically active species can be introduced as needed. LDHs themselves have certain catalytic activity, which can produce synergistic catalysis between LDHs and the supported photocatalytic active substances, and further improve the degradation effect of antibiotics. In actual wastewater treatment, LDHs as a catalyst carrier have a good application prospect. However, the poor activation effect is attributed to the low separation efficiency of catalyst carriers and insufficient active sites. In this study, a dual active site system consisting of Co and Fe, known as CoFe-LDHs@MoS₂, was developed as a catalyst to facilitate the synergistic degradation of norfloxacin (NOF) by PMS under visible light. The findings demonstrate that the material possesses an effective capacity for the synergistic degradation of NOF. A comprehensive investigation was conducted to assess the impact of different catalysts, PMS dosage, degradation systems (Vis, PMS, or Vis PMS), catalyst dosage, NOF concentration, pH, and cycle times on the degradation performance. The active free radicals, degradation pathways, and intermediate toxicity were elucidated through capture experiments, Electron Paramagnetic Resonance Spectrometer (ESR) analysis, a liquid mass spectrometry (LC-MS) toxicity assessment, and theoretical calculations. This research offers a novel approach for designing catalysts with exposed high activity sites for the effective removal of NOF from environmental water. Full article

Photoredox-catalyzed phosphonylation of bromo-substituted 1,10-phenanthrolines under visible light irradiation was studied. The reaction was shown to proceed under mild conditions with Eosin Y as a photocatalyst in DMSO under blue light irradiation. It is transition-metal-free and affords the target phosphonate-substituted 1,10-phenanthrolines in moderate yields (26–51%) in 22 to 40 h. The rate and selectivity of the reaction depend largely on the position of the bromine atom, as well as on the nature and position of other substituents in the 1,10-phenanthroline core. Full article

Photocatalytic degradation is a leading technology for complete mineralization of organic dyes in the ocean. In this work, a new viologen-bearing silver-thiocyanate-based photocatalyst, i.e., {(i-PrV)[Ag₂(SCN)₄]}_n (i-PrV²⁺ = isopropyl viologen) has been synthesized and structurally determined, with results showing that it can exhibit excellent degradation performance on rhodamine B (RhB) in artificial seawater. The planar i-PrV²⁺ dications are confined in the free voids of the [Ag₂(SCN)₄]_n²ⁿ⁻ layer with a two-dimensional (6,3) mesh, and strong C-H···S hydrogen bonds contribute to its structural stabilization. This photocatalyst was further characterized by powder X-ray diffraction (PXRD), UV-Vis, fluorescence, and photo/electrical responsive measurements, pointing to its application in visible-light-driven catalysis. Interestingly, using this photocatalyst, good photocatalytic degradation performance on rhodamine B in artificial seawater could be observed. The dye pollutant could be degraded with a high degradation ratio of 87.82% in 220 min. This work provides a promising catalyst for organic dye-type ocean pollutant treatments. Full article

Due to a rise in industrial pollutants in modern life, the climate and energy crisis have grown more widespread. One of the best ways to deal with dye degradation, hydrogen production, and carbon dioxide reduction issues is the photocatalytic technique. Among various methods, catalytic technology has demonstrated tremendous promise in recent years as a cheap, sustainable, and environmentally benign technology. The expeditious establishment of carbon-based metal nanoparticles as catalysts in the disciplines of materials and chemical engineering for catalytic applications triggered by visible light is largely attributed to their advancement. There have been many wonderful catalysts created, but there are still many obstacles to overcome, which include the cost of catalysts being reduced and their effectiveness being increased. Carbon-based materials exhibit a unique combination of characteristics that make them ideal catalysts for various reaction types. These characteristics include an exceptional electrical conductivity, well-defined structures at the nanoscale, inherent water repellency, and the ability to tailor surface properties for specific applications. This versatility allows them to be effective in diverse catalytic processes, encompassing organic transformations and photocatalysis. The emergence of carbon-based nanostructured materials, including fullerenes, carbon dots, carbon nanotubes, graphitic carbon nitride, and graphene, presents a promising alternative to conventional catalysts. This review focuses on the diverse functionalities of these materials within the realm of catalysis materials for degradation, hydrogen production, and carbon dioxide reduction. Additionally, it explores the potential for their commercialization, delving into the underlying mechanisms and key factors that influence their performance. It is anticipated that this review will spur more research to develop high-performance carbon-based materials for environmental applications. Full article

Triazole derivatives of fluorescein-containing N,N-dimethylaminopropyl fragments and their ammonium salts were synthesized with yields of 74–85%. The resulting compounds exhibit fluorescent properties in the green region of the visible spectrum. The critical aggregation concentration (CAC) was estimated using a pyrene fluorescent probe corresponding to a range of 0.28–1.43 mM, and at concentrations above the CAC, the compounds form stable aggregates ranging from 165 to 202 nm. A relative quantum yield of 5–24% has been calculated based on fluorescence and UV spectra. The best value is shown by a derivative containing a tetradecyl substituent. When studying the photocatalytic properties of synthesized compounds through the reaction between N-substituted 1,2,3,4-tetrahydroisoquinoline and malonic ester, the mono-tetradecyl derivative demonstrated the best results. According to gas chromatography–mass spectrometry (GC-MS) data, the conversion of the initial heterocycle reached 95%. Therefore, these resulting compounds have the potential to act as an effective photocatalysts. Full article

Photocatalytic H₂ evolution has been regarded as a promising technology to alleviate the energy crisis. Designing graphitic carbon nitride materials with a large surface area, short diffusion paths for electrons, and more exposed reactive sites are beneficial for hydrogen evolution. In this study, a facile method was proposed to dope P into a graphitic carbon nitride framework by calcining melamine with 2-aminoethylphosphonic acid. Meanwhile, PCN nanosheets (PCNSs) were obtained through a thermal exfoliation strategy. Under visible light, the PCNS sample displayed a hydrogen evolution rate of 700 μmol·g⁻¹·h⁻¹, which was 43.8-fold higher than that of pure g-C₃N₄. In addition, the PCNS photocatalyst also displayed good photostability for four consecutive cycles, with a total reaction time of 12 h. Its outstanding photocatalytic performance was attributed to the higher surface area exposing more reactive sites and the enlarged band edge for photoreduction potentials. This work provides a facile strategy to regulate catalytic structures, which may attract great research interest in the field of catalysis. Full article

Semiconductor hollow spheres have garnered significant attention in recent years due to their unique structural properties and enhanced surface area, which are advantageous for various applications in catalysis, energy storage, and sensing. The present study explores the surfactant-assisted synthesis of bismuth ferrite (BiFeO₃) hollow spheres, emphasizing their enhanced visible-light photocatalytic activity. Utilizing a novel, facile, two-step evaporation-induced self-assembly (EISA) approach, monodisperse BiFeO₃ hollow spheres were synthesized with a narrow particle size distribution. The synthesis involved Bi/Fe citrate complexes as precursors and the triblock copolymer Pluronic P123 as a soft template. The BiFeO₃ hollow spheres demonstrated outstanding photocatalytic performance in degrading the emerging pollutants Rhodamine B and metronidazole under visible-light irradiation (100% degradation of Rhodamine B in <140 min and of metronidazole in 240 min). The active species in the photocatalytic process were identified through trapping experiments, providing crucial insights into the mechanisms and efficiency of semiconductor hollow spheres. The findings suggest that the unique structural features of BiFeO₃ hollow spheres, combined with their excellent optical properties, make them promising candidates for photocatalytic applications. Full article

In this study, titanium oxide TiO₂ nanoparticles were produced using the sol–gel approach of green synthesis with pectin as the reducing agent. The synthetized TiO₂ nanoparticles with pectin were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), visible light absorption (UV–Vis) and the BET method. The structure and morphology of the TiO₂ powder were described with SEM, revealing uniform monodisperse grains with a distribution of 80% regarding sizes < 250 nm; the resulting crystal phase of synthetized TiO₂ was identified as an anatase and rutile phase with a crystallinity size estimated between 27 and 40 nm. Also, the surface area was determined by nitrogen adsorption–desorption using the Brown–Emmet–Teller method, with a surface area calculated as 19.56 m²/g, typical of an IV type isotherm, indicating mesoporous NPs. UV–Vis spectra showed that sol–gel synthesis reduced the band gap from the 3.2 eV common value to 2.22 eV after estimating the optical band gap energy using the adsorption coefficient; this translates to a possible extended photo response to the visible region, improving photoactivity. In addition, the power conversion of the photoelectrode was compared based on similar assembly techniques of TiO₂ electrode deposition. Quantum dot crystals were deposited ionically on the electrode surface, as two different paste formulations based on a pectin emulsifier were studied for layer deposition. The results confirm that the TiO₂ paste with TiO₂-synthesized powder maintained good connections between the nanocrystalline mesoporous grains and the deposited layers, with an efficiency of 1.23% with the transparent paste and 2.27% with the opaque paste. These results suggest that pectin could be used as a low-cost, functional sol–gel catalysis agent for the synthesis of controlled NPs of metal oxide. It demonstrates interesting optical properties, such as an increase in photo response, suggesting further applications to photocatalysts and biomedical features. Full article

Type I semiconductor heterojunction BiOI/HKUST-1 composites were prepared through a solvothermal method, with optimisation of the molar ratio and solvothermal reaction temperature. Comprehensive characterisation was conducted to assess the physical and chemical properties of the prepared materials. These composites were then evaluated for their ability to activate persulfate (PMS) and degrade high concentrations of azo dye orange II (AO7) under visible light conditions. The influence of various parameters, including catalyst dosage, PMS dosage, and initial AO7 concentration, were investigated. The AO7 degradation followed a pseudo-second order kinetic, and under visible light irradiation for 60 min, a degradation efficiency of 94.9% was achieved using a BiOI/HKUST-1 dosage of 0.2 g/L, a PMS concentration of 0.5 mmol/L, and an AO7 concentration of 200 mg/L. The degradation process involved a synergistic action of various active species, with O₂⁻, ¹O₂, and h⁺ playing a pivotal role. Both BiOI and HKUST-1 could be excited by visible light, leading to the generation of photogenerated electron-hole pairs (e⁻-h⁺); BiOI can efficiently scavenge the generated e⁻, enhancing the separation rate of e⁻-h⁺ and subsequently improving the degradation efficiency of AO7. These findings highlight the excellent photocatalytic properties of BiOI/HKUST-1, making it a promising candidate for catalysing PMS to enhance the degradation of azo dyes in environmental waters. Full article

The degradation of organic dyes poses a significant challenge in achieving sustainable environmental solutions, given their extensive usage across various industries. Iron oxide (Fe₂O₃) nanoparticles are studied as a reliable technique for remediating dye degradation. The objective of this research is to improve methods of nanomaterial-based environmental remediation. The solvothermal technique is used to synthesize carbon-modified Fe₂O₃ nanoparticles that exhibit the capability to modify their size morphology and increase reactivity, and stability for MO photodegradation. Their inherent qualities render them highly advantageous for biomedical applications, energy storage, environmental remediation, and catalysis. The mean crystallite size of the modified Fe₂O₃ nanoparticles is approximately 20 nm. These photocatalysts are tested for their ability to degrade methyl orange (MO) under Visible light radiation and in presence of hydrogen peroxide reagent. The optimal degradation efficiency (97%) is achieved with Fe₂O₃@C in the presence of H₂O₂ by meticulously controlling the pH, irradiation time, and photocatalyst dosage. The enhanced photocatalytic activity of the Fe₂O₃@C nanoparticles, compared to pure Fe₂O₃, is attributed to the conductive carbon layer, which significantly reduces electron-hole recombination rates. To summarize, Fe₂O₃@C nanoparticles not only offer a promising technique for the degradation of MO dye pollutants but also have an advantage for environmental remediation due to their increased stability and reactivity. Full article

This study aims to advance the field of green chemistry and catalysis by exploring alternatives to conventional non-renewable energy sources. Emphasis is placed on hydrogen as a potential fuel, with a focus on the catalytic properties of Ni(II) complexes when coordinated with o-phenylenediamine and diimine ligands. We report the synthesis and comprehensive characterization, with various physical and spectroscopic techniques, of three heteroleptic Ni(II) complexes: [Ni(1,10-phenanthroline)(o-phenylene diamine)] (1), [Ni(2,2-dimethyl-2,2-bipyridine)(o-phenylene diamine)] (2), and [Ni(5,5-dimethyl-2,2-bipyridine)(o-phenylene diamine)] (3). The catalytic activity of these complexes for hydrogen evolution was assessed through photochemical studies utilizing visible light irradiation. Two distinct photosensitizers, fluorescein and quantum dots, were examined under diverse conditions. Additionally, their electrocatalytic behavior was investigated to elucidate the hydrogen evolution reaction (HER) mechanism, revealing a combined proton-coupled electron transfer (PCET)/electron-coupled proton transfer (ECPT) mechanism attributed to the chemical nature of the diamine ligand. The influence of ligand substituent position, ligand chemical nature, and photosensitizer type on catalytic performance was systematically studied. Among the complexes investigated, complex 2 demonstrated superior catalytic performance, achieving a turnover number (TON) of 3357 in photochemical experiments using fluorescein as a photosensitizer. Conversely, complex 1 exhibited the highest TON of 30,066 for HER when quantum dots were employed as the photosensitizer. Full article

Metal-doped carbonaceous materials have garnered significant attention in recent years due to their versatile applications in various fields, including catalysis, energy storage, environmental remediation, electronics, and sensors, as well as reinforcement. This study investigates the synthesis and characterization of a composite material featuring a carbonaceous matrix doped with copper, focusing on the thermolysis of glycine as a precursor. The synthesis methodology involved utilizing glycine and copper acetate monohydrate in varying ratios, with the mixture subjected to heating in ceramic crucibles at temperatures ranging from 450 to 550 °C, with pyrolysis yields over the 5 to 39% interval. The pristine and Cu-doped samples obtained at 500 °C underwent characterization using a diverse array of techniques, including scanning and transmission electron microscopies, multi-elemental analysis by energy dispersive X-ray spectroscopy, CHNS elemental analysis, X-ray photoelectron spectroscopy, X-ray powder diffraction, infrared and Raman spectroscopies, ultraviolet-visible spectroscopy, and terahertz time-domain spectroscopy, along with conductivity measurements. Under optimized conditions, copper (at 6.5%) was present primarily in the free metallic form, accompanied by traces of tenorite (CuO) and cuprite (Cu₂O). The carbonaceous matrix exhibited a 6:1 ratio of graphitic carbon to a carbon-nitrogen compound with the formula C₂H₂N₂O₂, such as isomers of diazetidinedione, according to multi-elemental analysis results. Conductivity measurements disclosed a significant increase in conductivity compared to the product of glycine thermolysis, showcasing the enhanced electrical properties of the new composite. Additionally, terahertz measurements showed the potential of the material as a broadband absorber for the fabrication of terahertz devices and provided compelling evidence of a significant improvement in radiation absorption upon copper doping. In conclusion, this research sheds light on the promising properties of copper-doped carbonaceous composites obtained by glycine pyrolysis, offering insights into their potential applications in emerging technological domains. Full article

Polyaniline (PANI) constitutes a very propitious conductive polymer utilized in several biomedical, as well as environmental applications, including tissue engineering, catalysis, and photocatalysis, due to its unique properties. In this study, nano-PANI/N-TiO₂ and nano-PANI/Ag-TiO₂ photocatalytic composites were fabricated via aniline’s oxidative polymerization, while the Ag-and N-chemically modified TiO₂ nanopowders were synthesized through the sol–gel approach. All produced materials were fully characterized. Through micro-Raman and FT-IR analysis, the co-existence of PANI and chemically modified TiO₂ particles was confirmed, while via XRD analysis the composites’ average crystallite size was determined as ≈20 nm. The semi-crystal structure of polyaniline exhibits higher photocatalytic efficiency compared to that of other less crystalline forms. The spherical-shaped developed materials are innovative, stable (zeta potential in the range from −26 to −37 mV), and cost-effective, characterized by enhanced photocatalytic efficiency under visible light (energy band gaps ≈ 2 eV), and synthesized with relatively simple methods, with the possibility of recycling and reusing them in potential future applications in industry, in wastewater treatment as well as in biomedicine. Thus, the PANI-encapsulated Ag and N chemically modified TiO₂ nanocomposites exhibit high degradation efficiency towards Rhodamine B dye upon visible-light irradiation, presenting simultaneously high biocompatibility in different normal cell lines. Full article