Search Results (804)

Green technologies are actively being used to produce nanosized zinc oxide, which is in demand for water purification processes to remove pollutants. Despite the success of the green synthesis of ZnO nanoparticles, no scientific approach exists for selecting plant extracts to produce nanoparticles with the desired properties. This study shows that the antioxidant activity of the plant extracts used is a key parameter influencing the properties of the resulting ZnO nanoparticles. This conclusion is based on the results of nanoparticle synthesis with the use of various plant extracts. The antioxidant activity of the extracts increases in the following order: plum–gooseberry–black currant–strawberry–sea buckthorn. The synthesized ZnO nanoparticles were characterized by UV–visible spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The catalytic properties of ZnO nanoparticles were tested under the degradation of a synthetic methylene blue dye after exposure to UV light. We found that with an increase in the AOA of plant extracts, the size of the nanoparticles decreases, while their photocatalytic activity increases. The smallest (d = 13 nm), most uniform in size (polydispersity index 0.1), and most catalytically active ZnO nanoparticles with a small band gap (2.85 eV) were obtained using the sea buckthorn extract with the highest AOA, pH 10 of the reaction mixture and 0.1 M Zn(CH₃COO)₂∙2H₂O as a precursor salt. ZnO nanoparticles synthesized in the sea buckthorn extract demonstrated the highest dye photodegradation efficiency (96.4%) compared with other nanoparticles. The established patterns demonstrate the “antioxidant activity–size–catalytic activity” triad can be considered as a practical guide for obtaining ZnO nanoparticles of a given size and with given properties for environmental remediation applications. Full article

Porous photocatalysts from agricultural waste, i.e., apricot and peach shell, with titanium dioxide were prepared by a carbonaceous method, the adsorption and photocatalytic degradation and its kinetics about methylene blue (MB) were studied systematically. The properties of the prepared composite sorbents were characterized using Brunauer–Emmett–Teller, surface area, scanning electron microscopy, and energy dispersive spectroscopy analyses. Several key factors, including radiation, pH, temperature, initial MB concentration, contact time, and sorbent dosage, as well as photocatalytic activity were investigated. All the waste-TiO₂ adsorbents showed improved adsorption and photodegradation performance compared to commercial charchoal-TiO₂. The produced materials presented high specific surface areas especially those derived from apricot shell-TiO₂ with a combination of type I and IV adsorption isotherms with a hysteresis loop indicating micro and mesopore structures. In addition, under UV radiation, the composite sorbents exhibited greater MB removal efficiency than non-radiated composite sorbents. The examined conditions have shown the best MB adsorption results at pH greater than 7.5, temperature 30 °C, contact time 120 min, initial concentration 0.5 mg/L MB, and sorbent dosage equal to 2.0 g/L C/MB. The total removal rate of MB is 98.5%, while the respective amount of commercial charcoal-TiO₂ is equal to 75.0%. The kinetic model that best describes the experimental data of MB degradation from the photocatalytic materials is the pseudo-second order model. In summary, this work highlights the effectiveness and feasibility of transforming agricultural waste into carbonaceous composite sorbent for the removal of cationic dyes from wastewater. Future work will involve scaling up the synthesis of the catalyst and evaluating its performance using bed reactors for industrial processes. Full article

Titanium oxide (TiO₂) is of great interest in solar cell manufacturing, hydrogen production, and organic compound photodegradation. The synthesis variables and methodology affect the morphology, texture, crystalline structure, and phase mixtures of TiO₂, which, in turn, affect the optical and catalytic properties of TiO₂. In this work, the effect of acetic acid as a catalyst and chelating agent on the morphology, texture, crystal structure, optical properties, and photocatalytic activity of TiO₂ samples obtained using the sol–gel method with sodium dodecyl sulfate (SDS) as a template was investigated. The results indicated that acetic acid not only catalyzes the hydrolysis of the TiO₂ precursor but also acts as a chelating agent, causing a decrease in crystallite size from 18.643 nm (T7 sample, pH = 6.8, without addition of acetic acid) to 16.536 nm (T2 sample, pH = 2). At pH 2 and 3, only the anatase phase was formed (T2 and T3 samples), whereas at pH 5 and 6.8, in addition to the anatase phase, the brookite phase (11.4% and 15.61% for samples T5 and T7, respectively) was formed. The band-gap value of TiO₂ decreased with decreasing pH during synthesis. Although the T2 sample had the highest specific surface area and pore volume (232.02 m²g⁻¹ and 0.46 gcm⁻³, respectively), the T3 sample had better efficiency in methylene blue dye photodegradation because its bird-nest-like morphology improved photon absorption, promoting better photocatalytic performance. Full article

The integration of graphene-based materials with metal–organic frameworks (G@MOFs) has emerged as a promising strategy for advanced wastewater treatment owing to their synergistic physicochemical properties. This review systematically compiles and critically analyzes recent advances in the synthesis, structural characterization, and application of G@MOFs for the removal of organic and inorganic micropollutants. Special emphasis is placed on how the unique combination of high surface area, tunable pore structures, and abundant active sites in G@MOFs enhances adsorption, photodegradation, and catalytic degradation mechanisms. Compared to conventional adsorbents and standalone MOFs, G@MOFs exhibit superior removal capacities, stability, and reusability. This paper also identifies key challenges in large-scale applications, regeneration, and potential environmental risks, providing a future outlook on optimizing synthesis routes and tailoring functional composites for sustainable water treatment technologies. The novelty of this review lies in providing the first dedicated, systematic evaluation of G@MOFs for wastewater micropollutant removal, integrating synthesis strategies, performance benchmarking, techno-economic aspects, environmental safety, and future application prospects into a unified framework. Full article

The environmental persistence of antibiotic residues in aquatic systems represents a critical global challenge, with photolysis serving as a primary abiotic degradation pathway. Traditional approaches to studying antibiotic photodegradation and transformation product (TP) identification face significant limitations, including complex reaction mechanisms, multiple concurrent pathways, and analytical challenges in characterizing unknown metabolites. The integration of artificial intelligence (AI) and machine learning (ML) technologies has begun to transform this field, offering new capabilities for predicting photodegradation kinetics, elucidating transformation pathways, and identifying novel metabolites. This comprehensive review examines current applications of AI/ML in antibiotic photolysis research, analyzing developments from 2020 to 2025. Key advances include quantitative structure–activity relationship (QSAR) models for photodegradation prediction, deep learning approaches for automated mass spectrometry interpretation, and hybrid computational–experimental frameworks. Machine learning algorithms, particularly Random Forests, support vector machines, and Neural Networks, have demonstrated capabilities in handling multi-dimensional environmental datasets across diverse antibiotic classes, including fluoroquinolones, β-lactams, tetracyclines, and sulfonamides. Despite progress in this field, challenges remain in model interpretability, standardization of datasets, validation protocols, and integration with regulatory frameworks. Future directions include machine-learning-enhanced quantum dynamics for improving mechanistic understanding, real-time AI-guided experimental design, and predictive tools for environmental risk assessment. Full article

This study presents the synthesis and characterization of novel kaolinite niobium and kaolinite titanium niobium nanocomposites and their application as heterogeneous photocatalysts. Utilizing a hydrolytic sol–gel route, we combined kaolinite with isopropyl alcohol, acetic acid, titanium (IV) isopropoxide, and ammonium niobium oxalate, followed by heat treatment at 400, 700, and 1000 °C. X-ray diffraction confirmed the retention of kaolinite’s characteristic reflections, with basal spacings indicating the presence of semiconductors on the external surfaces and edges. Heating treatment not allowing the crystallization of anatase until 1000 °C reveals that Nb⁵⁺ could inhibit the transition to titanium crystalline phases (anatase and rutile). The bandgap energies decreased with clay mineral support, averaging 2.50 eV, and absorbing up to 650 nm. The model reaction of terephthalic acid hydroxylation accomplished by photoluminescence spectroscopy demonstrated that KaolTiNb400 presented a higher rate of *OH production, achieving 591 mmol L⁻¹ min⁻¹ compared to pure KaolNb400 173 mmol L⁻¹ min⁻¹. Photodegradation studies revealed significant photocatalytic activity, with the KaolTiNb400 nanocomposite achieving the highest efficiency, demonstrating 90% removal of methylene blue (combining adsorption and degradation) after 24 h of UV light irradiation. These materials also exhibited promising results for the degradation of the antibiotics Triaxon^® (40%) and Loratadine (8%), highlighting their potential for organic pollutants’ removal. In both cases the presence of byproducts is detected. Full article

This study investigated the dielectric and photocatalytic properties of green-synthesized titanium dioxide nanoparticles (TiO₂ NPs), which are widely utilized semiconductor materials known for their excellent optical, structural, and electronic characteristics. The TiO₂ NPs were synthesized via a green precipitation method from the aqueous extract of Cymbopogon proximus. A comprehensive set of analytical techniques—UV–Vis spectroscopy, XRD, FTIR, TEM, EDX, and DLS—was employed to determine their optical response, crystalline structure, functional groups, morphology, elemental composition, and particle size distribution. UV–Vis analysis revealed a characteristic absorption peak at 327 nm, and the band gap energy, calculated via the Tauc plot method, was 3.16 eV. The XRD results confirmed the formation of a tetragonal TiO₂ phase with an average crystallite size of approximately 4 nm. TEM images further supported the spherical to quasitetragonal morphology and revealed that the aggregated clusters formed conjoint nanostructures. The photocatalytic activity of the TiO₂ NPs was evaluated using a 0.5 mM RhB dye solution under UV–visible irradiation. The synthesized nanoparticles achieved a photodegradation efficiency of 97% after 50 h, with a corresponding rate constant of 0.073402 h⁻¹, indicating their potential for effective photocatalytic pollutant removal. Furthermore, the dielectric behavior of the TiO₂ NPs was examined at room temperature. The material exhibited a high dielectric constant at low frequencies due to interfacial (Maxwell–Wagner) polarization, along with frequency-dependent AC conductivity attributed to charge-carrier hopping mechanisms. These dielectric properties, combined with strong photocatalytic performance, underscore the suitability of green-synthesized TiO₂ NPs for applications in environmental remediation, energy-storage devices, and advanced technologies. Full article

A nanocomposite combining the photocatalytic activity of ZnO and TiO₂ with the adsorption capacity of halloysite was developed for the degradation of ciprofloxacin hydrochloride (CIP). Characterization was performed by UV-Vis diffuse reflectance spectrophotometry, X-ray fluorescence, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. The results revealed uniform dispersion of ZnO and TiO₂ particles on the halloysite surface and the formation of heterojunctions, contributing to efficient adsorption and photocatalytic degradation. XRD and XPS analyses confirmed the presence of Ti⁴⁺ in the anatase phase, supporting the high photocatalytic potential of the synthesized samples. Photodegradation tests of CIP (30 mg L⁻¹) showed that the 5Zn-Ti-Hal sample achieved the highest removal efficiency (71.45%), with a predominance of photocatalysis (42.57%) over adsorption (28.58%). Bioassays demonstrated a significant antibacterial effect against Staphylococcus aureus (50.35% inhibitory effect) and no toxicity to Artemia salina (100% survival). These results indicate that ZnO–TiO₂–halloysite nanocomposites are a promising green technology for aquatic remediation, offering efficient CIP degradation, antibiotic inactivation, and environmental safety. Full article

The pervasive discharge of synthetic dyes into aquatic ecosystems poses a significant threat due to their chemical stability, low biodegradability, and carcinogenicity. Conventional dye remediation methods—such as biological treatments, coagulation, and adsorption—have demonstrated limited efficiency and poor reusability, particularly against resilient azo dyes. Cerium oxide (CeO₂) nanoparticles have gained traction as photocatalysts owing to their redox-active surfaces and oxygen storage capabilities; however, issues like particle agglomeration and rapid charge recombination restrict their catalytic performance. To address these challenges, this study presents the novel synthesis of a graphene oxide–cerium oxide (GO-CeO₂) nanocomposite via a facile in situ hydrothermal approach, using graphite from lead pencils as a sustainable precursor. The composite was structurally characterized using UV–visible spectroscopy, XRD, FTIR, and TEM. The GO matrix not only facilitates uniform dispersion of CeO₂ nanoparticles but also enhances interfacial electron mobility and active site availability. The nanocomposite demonstrated exceptional photocatalytic degradation efficiencies for methyl orange (94%), methyl red (98%), congo red (96%), and 4-nitrophenol (85.6%) under sunlight irradiation, with first-order rate constants significantly exceeding those of pure CeO₂. Notably, GO–CeO₂ retained strong catalytic activity over four degradation cycles, confirming its recyclability and structural stability. Total organic carbon (TOC) analysis revealed 79% mineralization of methyl orange, outperforming CeO₂ (45%), indicating near-complete conversion into benign byproducts. This work contributes a scalable, low-cost, and highly active heterogeneous photocatalyst for wastewater treatment, combining green synthesis principles with improved photodegradation kinetics. Its modular architecture and reusability make it a promising candidate for future environmental remediation technologies and integrated photocatalytic systems. Full article

Photodynamic inactivation (PDI) represents a promising strategy to overcome bacterial resistance by combining light, oxygen, and a photosensitizer (PS) to generate reactive oxygen species (ROS) that damage essential cellular components. Combining PDI with conventional antibiotics (ATBs) may further enhance bacterial eradication through complementary mechanisms. In this study, the tetracationic 5,10,15,20-tetra(4-N,N,N-trimethylammoniophenyl)porphyrin (TMAP⁴⁺) was evaluated in combination with ATBs: ampicillin (AMP) and rifampicin (RIF) against Staphylococcus aureus and cephalexin (CFX) against Escherichia coli. The photostability of all agents was assessed under the experimental irradiation conditions, and no evidence of physical interaction between TMAP⁴⁺ and the ATBs was detected. AMP and CFX remained photostable, while RIF exhibited only minimal photodegradation under white light, confirming its stability during PDI treatments. The antimicrobial assays revealed that irradiation significantly enhanced the bactericidal activity of TMAP⁴⁺. When combined with ATBs, photoactivated TMAP⁴⁺ led to a pronounced reduction in the minimum inhibitory concentration (MIC) values of AMP and RIF for S. aureus and of CFX for E. coli, indicating additive effects. Growth curve analyses corroborated these results, showing delayed bacterial growth and decreased maximal optical densities in the combined treatments compared to single agents. Overall, these findings demonstrate that the photodynamic process can potentiate the antimicrobial effect of conventional ATBs without compromising their stability, supporting the potential of PS–ATB combination therapies as a valuable approach to improve antibacterial efficacy and mitigate ATB resistance. Full article

In this paper, by employing an eco-friendly and green approach, semiconductor CuO/ZnO nanocomposite are synthesized using an aqueous extract of Urtica urens. FT-IR, XRD, TEM, SAED, EDX, TGA, and UV-Vis spectroscopy were used for semiconductor characterization. The data revealed the successful formation of crystalline spherical nanocomposites with sizes ranging from 5 to 45 nm. The main components of the synthesized nanocomposites were Cu, Zn, and O, which had different weights and atomic percentages. The maximum absorbance of nanocomposites was 358 nm, with a direct bandgap of 2.25 eV, which is suitable for photocatalysis under visible light. The maximum photocatalytic activity of the synthesized semiconductor nanocomposites for photodegradation of methylene blue dye was 95.8%, where it was 44.5% and 65.5% for monometallic CuO and ZnO, respectively. The optimum conditions for maximum photocatalytic activity were a pH of 9, a dye concentration of 5 mg L⁻¹, and nanocomposite concentration of 1.0 mg mL⁻¹ after 70 min. The reusability of the synthesized semiconductor was promising for the fourth cycle, with a reduced capacity of 5%. Complementary investigations, antimicrobial activity and cytotoxic activity, were performed to increase the application of semiconductor nanocomposites. The data revealed the promising activity of the nanocomposite against E. coli, P. aeruginosa, B. subtilis, S. aureus, C. parapsilosis, C. albicans, and C. tropicalis with low MICs ranging between 50 and 25 µg mL⁻¹. Additionally, compared with normal cell line, the synthesized nanocomposite targeted the cancer cell line HepG2 with a low IC50 value of 69.9 µg mL⁻¹ (vs. IC50 220 µg mL⁻¹ of normal cell line HFB4). Overall, the green-synthesized semiconductor CuO/ZnO nanocomposite showed promising activity as environmental contaminant cleaner and was integrated with antimicrobial and in vitro cytotoxic activities. Full article

Titanium dioxide (TiO₂) thin films sensitized with curcumin were fabricated to investigate the influence of sensitization on their spectroscopic, optical, and photocatalytic properties. TiO₂ films were prepared using different curcumin concentrations and characterized by FTIR, UV–Vis, and diffuse reflectance spectroscopy (DRS). The adsorption kinetics of curcumin on TiO₂ were analyzed, and the photocatalytic performance was evaluated through methylene blue (MB) photodegradation under visible-light irradiation. FTIR spectra confirmed the successful anchoring of curcumin onto the TiO₂ surface, while optical characterization revealed a significant enhancement in visible-light absorption. The band gap decreased from 3.2 eV (pure TiO₂) to 1.8 eV (curcumin-sensitized TiO₂). Furthermore, the curcumin adsorption onto semiconductor data fitted the pseudo-second-order kinetic model, yielding a maximum adsorption capacity of 12.0 mg·g⁻¹. Density Functional Theory (DFT) calculations indicated that ligand-to-metal charge transfer (LMCT) transitions are responsible for the improved visible-light response. Photocatalytic tests demonstrated that all curcumin-sensitized TiO₂ films were active under visible irradiation, confirming curcumin as an effective natural sensitizer for enhancing TiO₂-based photocatalytic coatings. Full article

To enhance the photocatalytic performance of TiO₂ nanotubes (NTs) for the degradation of Amido Black as an organic pollutant, electrodeposition of bismuth vanadate (BiVO₄) nanostructures was successfully applied. The effect of electrodeposited BiVO₄ (25 s, 50 s, 150 s, 250 s), followed by a thermal treatment on TiO₂-NTs, was studied. The structures of the as-prepared samples were characterized by X-ray diffraction (XRD). Morphological behavior was investigated using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), both coupled with EDX. Optical characterizations were performed using photoluminescence and diffuse reflectance spectroscopy. The BiVO₄/TiO₂ NTs sample with 50 s deposition time gave the highest photocatalytic performance for Amido Black degradation, 99.4% after 150 min under UV light. This result has been achieved due to the structure and the optical properties of the sample. The heterojunction of both catalysts showed the synergetic effect on the photocatalytic performance where they remained stable after five cycling runs. Furthermore, quenching tests were conducted and proved that superoxide radicals (O₂^•) are the main active species during photodegradation process. Full article

The development of photocatalyst material is vital for the practical application of environmental purification, solar energy conversion, and chemical production. In this work, a spherical Bi(C₆N₇O₃) photocatalyst is successfully prepared by replacing K⁺ of rod-shaped K₃[C₆N₇O₃] with Bi³⁺ ions through the ion exchange method, which demonstrates an improved homogeneous photodegradation efficiency over antibiotics in water compared to pristine K₃[C₆N₇O₃]. Under visible light irradiation, Bi(C₆N₇O₃) degraded 81% of tetracycline hydrochloride within 60 min, and the rate constant was 1.8 and 79.1 times greater than K₃[C₆N₇O₃] and bulk g-C₃N₄, respectively. Scavenger experiments revealed that superoxide radicals and holes are the primary active species in the photocatalytic process. This study presents a promising route for designing high-performance visible-light photocatalysts by a simple ion-exchange approach for environmental applications. Full article

In the aspect of water purification, a photoactive hybrid material based on reduced graphite oxide (RGO) with covalently, coordinatively, and through van der Waals interactions bonded zirconium(IV) phthalocyanine (PcZr) is proposed. In the material, the phthalocyanine complex plays the role of photosensitizer, while RGO is considered a carrier, ensuring high surface area and supporting PcZr activation. The central metal atom of PcZr directly interacts with lateral active oxygen-containing surface groups of graphite oxide, mainly –OH and –COOH. Thus, the proposed method of synthesis under solvothermal conditions allowed obtaining a relatively high concentration of the dye (0.2 wt.%) in the system based on a partially reduced and exfoliated graphite oxide. Optical studies confirmed the presence of PcZr through absorption and luminescence spectra. Additionally, effective generation of reactive oxygen species was demonstrated by testing the transformation of a dye indicator (diphenylisobenzofuran). Photocatalytic activity of the system was confirmed by photooxidizing selected organic dyes (methylene blue, Rhodamine B, Brilliant Green, and Eriochrome Black T) in a water medium, tested in slightly acidic conditions under red light. The greatest overall decrease in absorption during the photodegradation test was observed for Brilliant Green, reaching 88% after 3 h of irradiation. Full article