Photocatalytic Performance of Undoped and Al-Doped ZnO Nanoparticles in the Degradation of Rhodamine B under UV-Visible Light:The Role of Defects and Morphology

Controlled solvothermal synthesis of self-assembled SrTiO3 microstructures for expeditious solar-driven photocatalysis dye effluents degradation

In this work, the self-assembled SrTiO3 (STO) microstructures were synthesized via a facile one-step solvothermal method. As the solvothermal temperature increased from 140 °C to 200 °C, the STO changed from a flower-like architecture to finally an irregularly aggregated flake-like morphology. The photocatalytic performance of as-synthesized samples was assessed through the degradation of rhodamine B (RhB) and malachite green (MG) under simulated solar irradiation. The results indicated that the photocatalytic performance of STO samples depended on their morphology, in which the hierarchical flower-like STO synthesized at 160 °C demonstrated the highest photoactivities. The photocatalytic enhancement of STO-160 was benefited from its large surface area and mesoporous configuration, hence facilitating the presence of more reactive species and accelerating the charge separation. Moreover, the real-world practicality of STO-160 photocatalysis was examined via the real printed ink wastewater-containing RhB and MG treatment. The phytotoxicity analyses demonstrated that the photocatalytically treated wastewater increased the germination of mung bean seeds, and the good reusability of synthesized STO-160 in photodegradation reaction also promoted its application in practical scenarios. This work highlights the promising potential of tailored STO microstructures for effective environmental remediation applications.

Enhanced photocatalytic efficiency of porous ZnO coral-like nanoplates for organic dye degradation

ZnO nanomaterials have been extensively used as photocatalysts for the removal of pollutants in aqueous environments. This study explores the enhanced photocatalytic performance of porous ZnO coral-like nanoplates synthesized via a one-pot wet-chemical method and subsequent annealing treatment. Characterization through scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, photoluminescence (PL) spectroscopy, and Brunauer-Emmett-Teller (BET) measurements confirmed the nanoplates' porous structure, single-crystal structure, 100 nm thickness, and 80 nm pore size. These unique structural characteristics of the ZnO coral-like nanoplates enabled effective photodegradation of the organic dye rhodamine B (RhB) under visible light irradiation. Under simulated sunlight, the ZnO photocatalyst exhibited exceptional performance, achieving a 97.3% removal rate of RhB after 210 minutes of irradiation. The prepared ZnO photocatalyst also showed remarkable photostability and regeneration capability for RhB photodegradation with a decreased efficiency of less than 15% after eight testing cycles. The potential mechanism of the ZnO photocatalyst toward RhB degradation was also studied and is discussed in detail.

Green Synthesis of Er-Doped ZnO Nanoparticles: An Investigation on the Methylene Blue, Eosin, and Ibuprofen Removal by Photodegradation

We present a study on the green synthesis of undoped and Er-doped ZnO compounds using Mangifera indica gum (MI). A set of tests were conducted to assess the structure of the material. The tests included X-ray diffraction, Raman, and Fourier-transform infrared spectroscopy. Optical properties were studied using diffuse reflectance and photoluminescence. Morphological and textural investigations were done using SEM images and N2 adsorption/desorption. Furthermore, photocatalytic tests were performed with methylene blue (MB), yellow eosin (EY), and the pharmaceutical drug ibuprofen (IBU) under UV irradiation. The study demonstrated that replacing the stabilizing agent with Mangifera indica gum is an effective method for obtaining ZnO nanoparticles. Additionally, the energy gap of the nanoparticles exhibits a slight reduction in value. Photoluminescence studies showed the presence of zinc vacancies and other defects in both samples. In the photocatalytic test, the sample containing Er3+ exhibited a degradation of 99.7% for methylene blue, 81.2% for yellow eosin, and 52.3% for ibuprofen over 120 min. In the presence of methyl alcohol, the degradation of MB and EY dyes is 16.7% and 55.7%, respectively. This suggests that hydroxyl radicals are responsible for the direct degradation of both dyes. In addition, after the second reuse, the degradation rate for MB was 94.08%, and for EY, it was 82.35%. For the third reuse, the degradation rate for MB was 97.15%, and for EY, it was 17%. These results indicate the significant potential of the new semiconductor in environmental remediation applications from an ecological synthesis.

Quasi-Diamond Platelet-Shaped Zinc Oxide Nanostructures Display Enhanced Antibacterial Activity

The current study compares the antibacterial activity of zinc oxide nanostructures (neZnO). For this purpose, two bacterial strains, Escherichia coli (ATCC 4157) and Staphylococcus aureus (ATCC 29213) were challenged in room light conditions with the aforementioned materials. Colloidal and hydrothermal methods were used to obtain the quasi-round and quasi-diamond platelet-shape nanostructures. Thus, the oxygen vacancy (VO ) effects on the surface of neZnO are also considered to assess its effects on antibacterial activity. The neZnO characterization was achieved by X-ray diffraction (XRD), a selected area electron diffraction (SAED) and Raman spectroscopy. The microstructural effects were monitored by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Furthermore, optical absorption ultraviolet visible spectrophotometry (UV-Vis) and X-ray photoelectron spectroscopy (XPS) analyses complement the physical characterization of these nanostructures; neZnO caused 50 % inhibition (IC50 ) at concentrations from 0.064 to 0.072 mg/mL for S. aureus and from 0.083 to 0.104 mg/mL for E. coli, indicating an increase in activity against S. aureus compared to E. coli. Consequently, quasi-diamond platelet-shaped nanostructures (average particle size of 377.6±10 nm) showed enhanced antibacterial activity compared to quasi-round agglomerated particles (average size of 442.8±12 nm), regardless of Vo presence or absence.

ZnO doped C: Facile synthesis, characterization and photocatalytic degradation of dyes

Carbon doped ZnO nanoparticles have been synthesized from the thermal decomposition of Zinc citrate precursor. The precursor was synthesized from semi-solid paste and then subjected to calcination at 700 °C to produce ZnO nanoparticles. The precursor and ZnO were characterized by Fourier Transform Infrared Spectroscopy, UV-visible (UV-Vis) spectra, Transmission Electron Microscope, Field Emission Scanning Electron Microscope, Energy Dispersive Analysis by X-ray (EDAX), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results ensured the formation of hexagonal 2D-ZnO nanoparticles with a layer thickness of 25 nm. The optical band gap of ZnO was determined and found to be 2.9 eV, which is lower than the bulk. Photocatalytic degradation of Fluorescein dye as an anionic dye and Rhodamine B as a cationic dye was evaluated via C-ZnO NPs under UV irradiation. ZnO displayed 99% degradation of Fluorescein dye after 240 min and a complete photocatalytic degradation of Rhodamine B dye after 120 min under UV irradiation.

Novel Sol-Gel Synthesis of TiO2 Spherical Porous Nanoparticles Assemblies with Photocatalytic Activity

For this study, the synthesis of TiO₂ nanomaterials was performed via a novel sol-gel method employing titanium butoxide as a metal precursor, Pluronic F127 as a templating agent, toluene as a swelling agent, and acidic water or ethanol as the reaction solvents. The method was designed by tailoring certain reaction parameters, such as the sequence of toluene addition, magnetic stirring, the type of reaction solvent, and the calcination conditions. Analysis of the specific surface area and porosity was carried out via N₂ physisorption, whereas the morphological features of the solids were investigated via transmission electron microscopy. The crystalline structure of both the dried powders and the calcined materials was evaluated using X-ray diffraction analysis. It transpired that the different phase compositions of the solids are related to the specific synthesis medium employed. Under the adopted reaction conditions, ethanol, which was used as a reaction solvent, promoted the local arrangement of dispersed anatase particles, the specific arrangement of which does not lead to rutile transformation. Conversely, the use of water alone supported high-particle packing, evolving into a rutile phase. The photodegradation of Rhodamine B was used as a target reaction for testing the photocatalytic activity of the selected samples.

Effective Adsorptive Removal of Coomassie Violet Dye from Aqueous Solutions Using Green Synthesized Zinc Hydroxide Nanoparticles Prepared from Calotropis gigantea Leaf Extract

The removal of color from dye wastewater is crucial, since dyes are extremely toxic and can cause cancer in a variety of life forms. Studies must be done to use cost-effective adsorbents for the removal of color from dye effluents to protect the environment. To our knowledge, virtually no research has been done to describe the possibility of using Calotropis gigantea leaf extract zinc hydroxide nanoparticles (CG-Zn(OH)2NPs) as an adsorbent for the decolorization of Coomassie violet (CV) from the aqueous emulsion, either in batch mode or continuously. In the present batch investigation, CV dye is removed from the synthetic aqueous phase using CG-Zn(OH)2NPs as an adsorbent. The synthesized nanoparticles were characterized using various instrumental techniques such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and Brunauer–Emmett–Teller (BET) surface area and pore volume, a particle size analyser, and zero-point charge. The decolorization efficacy of CV dye from an aqueous phase by the adsorbent was examined in batch mode by varying process parameters. The consequences of various experimental variables were optimized using response surface methodology (RSM) to achieve the maximum decolorization efficiency (90.74%) and equilibrium dye uptake, qe (35.12 mg g−1). The optimum pH, dye concentration, CG-Zn(OH)2NPs adsorbent dosage, and particle size were found to be 1.8, 225 mg L−1, 5 g L−1, and 78 μm, respectively for CV dye adsorption capacity at equilibrium. The adsorbent zero-point charge was found to be at pH 8.5. The Langmuir isotherm model provided a good representation of the equilibrium data in aqueous solutions, with a maximum monolayer adsorption capability (qmax) of 40.25 mg g−1 at 299 K. The dye adsorption rate follows a pseudo-second-order kinetic model at various dye concentrations, which indicated that the reaction is more chemisorption than physisorption. The negative values of ΔG and positive values of ΔH at different temperatures indicate that the adsorption process is spontaneous and endothermic, respectively. Reusability tests revealed that the prepared nanoparticles may be used for up to three runs, indicating that the novel CG-Zn(OH)2NPs seems to be a very promising adsorbent for the removal of Coomassie violet dye from wastewater.

Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants

Water is a scarce resource with a close and intricate nexus with energy [...].