GC/MS screening of buckthorn phytochemicals and their use to synthesize ZnO nanoparticles for photocatalytic degradation of malachite green dye in water

Cashew gum-assisted synthesis of Zn0.98Nd0.02O photocatalyst: pH-dependent green approach and photocatalytic degradation of ciprofloxacin and ibuprofen pharmaceutical pollutants

The presence of pharmaceutical residues in aquatic environments represents a serious environmental problem, with negative impacts on ecosystems and public health. The removal of these contaminants from wastewater is a challenge that requires innovative and sustainable strategies. In this study, a green synthesis approach, assisted by cashew gum, was employed to synthesize the Zn0.98Nd0.02O photocatalysts at varying pH levels (5, 7, 9, 11, and 13) via the sol-gel method. The effects of synthesis pH on structural, optical, and photocatalytic properties were systematically investigated. The structural analysis revealed a hexagonal wurtzite structure, with crystallite sizes ranging from 69 nm (pH 5) to 235 nm (pH 9). Micrography images showed that pH significantly influenced morphology, with particles ranging from agglomerates to more dispersed spherical shapes. Porosity analysis indicated mesoporous structures with surface areas varying between 2.2 and 5.2 m2/g, depending on pH. Photoluminescence (PL) spectra highlighted the presence of oxygen-related defects, with emission peaks shifting due to structural disorder induced by doping and pH variation. Optical studies also indicated a tunable bandgap (3.284-3.218 eV) and Urbach energy (50.96-75.30 meV), signifying increased structural disorder at higher pH. Photocatalytic performance was evaluated against Ciprofloxacin (CIP) and Ibuprofen (IBU), achieving degradation efficiencies of 97.5 % (CIP at pH 7) and 74.1 % (IBU at pH 13) under UV light. Kinetic studies confirmed pseudo-first-order behavior with rate constants of 2.14 × 10-2 min-1 for CIP and 8.99 × 10-3 min-1 for IBU. Reactive species analysis identified hydroxyl radicals (•OH) as dominant contributors to pollutant degradation. Reusability tests demonstrated >96 % CIP removal over four cycles and consistent structural stability, validated via XRD. This study highlights the potential of the Zn0.98Nd0.02O photocatalysts synthesized under eco-friendly conditions for addressing pharmaceutical pollutants in wastewater treatment.

Sustainable and facile fabrication of chitosan-coated silver-doped zinc oxide nanocomposites exploiting Bergera koenigii foliage for enhanced photocatalysis and antibacterial activity

Industrial and academic chemical pollutants such as Eriochrome Black-T (EBT) and murexide dyes are widely used in academic institution as well as industries, when eluted into rivers, delineate the ill effect on human and aquatic life. Herein, green and ecofriendly synthesis of silver doped-Zinc oxide nanoparticles (Ag/ZnO NPs) and chitosan coated Ag/ZnO nanoparticles (CS/Ag/ZnO NPs) using Bergera koenigii extract to solve environmental issues have been reported for the first time. Spherical and agglomerated particles with crystalline flakes like morphology of Ag/ZnO NPs and CS/Ag/ZnO NPs respectively have been ascertained by Scanning electron morphology (SEM) analyses and XRD. XRD analysis revealed the average crystallite size of 42.16 nm and 48.45 nm for Ag/ZnO NPs with 5 % and 10 % Ag concentration respectively, lesser than crystallite size of 47.394 nm and 52.38 nm for CS-5 % Ag/ZnO NC and CS-10 % Ag/ZnO NC respectively. All the synthesized NPs and NC demonstrated remarkable antibacterial potential against both gram +ve and gram -ve bacteria. Additionally, all the materials showed very high time-dependent photocatalytic degradation activity (>98 %) of EBT and murexide in 12 min. Remarkably, all active nano-catalysts exhibit high durability, and displayed recyclability for >8 cycles. In nutshell, chitosan coated nano-catalyst showed drastic improvement in photocatalytic and antibacterial activities.

Biogenic Zinc Oxide Nanoparticles as a Promising Antibacterial Agent: Synthesis and Characterization

Nanotechnology has gained popularity in recent years due to its wide-ranging applications within the scientific community. The three main methods for synthesizing nanoparticles are physical, chemical, and biological. However, the adverse effects associated with physical and chemical methods have led to a growing interest in biological methods. Interestingly, green synthesis using plants has gained prominence in developing new treatments for bacterial infections. Zinc oxide nanoparticles (ZnO NPs) produced using environmentally friendly methods are more biocompatible and have potential applications as antibacterial agents in the biomedical field. As a result, this review discusses the green synthesis of ZnO NPs, factors influencing optimal synthesis, characterization techniques, and the antibacterial activity of some plant-mediated ZnO NPs. It also provides a comprehensive and analytical exploration of ZnO NP biosynthesis, the role of phytochemical compounds as reducing and stabilizing agents, the mechanism of action of their antibacterial properties and further highlights the challenges and prospects in this innovative research area.

Exploitation of green synthesized chromium doped zinc oxide nanorods (NRs) mediated by flower extract of Rhododendron arboreum for highly efficient photocatalytic degradation of cationic dyes Malachite green (MG) and Fuchsin basic (FB)

In this work, green method to synthesize chromium-doped zinc oxide (ZnO) nanorods (NRs) using an aqueous flower extract from Rhododendron arboretum is explored. Herein, chromium-doped ZnO NRs were prepared with different amount of chromium doping, varied as 2-10%. The green synthesized products underwent substantial analysis through X-ray diffraction (XRD), spectroscopic such as ultraviolet spectroscopy(UV-Vis) and scanning electron microscopy (SEM) methods. All samples were found to have hexagonal wurtzite ZnO, with average particle sizes of 52.41, 56.6, 54.44, 53.05, and 56.99 nm, respectively, for 2, 4, 6, 8, and 10% chromium doping in ZnO NRs. The Cr-doped ZnO NRs exhibited remarkable photocatalytic degradation activity of cationic dyes under UV-light, i.e., Malachite Green and Fuchsin Basic with degradation of 99.604 and 99.881%, respectively in 90 min. The reusability tests for these green synthesized Cr-doped ZnO NRs have also been carried out, showed 9-11 cycles with 85% of degradation efficiency. In addition, the Cr-doped ZnO NRs exhibited high selectivity for cationic dyes when experiments against mixture of dyes were performed. Photodegradation kinetics followed the pseudo-first-order model. The flower-extract-stabilized chromium-doped ZnO NRs demonstrated high photocatalytic activity toward malachite green and fuchsin basic dyes, potential material for pollution remediation.

Ficus-mediated green synthesis of manganese oxide nanoparticles for adsorptive removal of malachite green from surface water

The extract of ficus leaves was used to prepare manganese (IV) oxide nanoparticles (MnO2 NPs) for the first time. Several different analytical techniques were used to characterize the prepared MnO2 NPs. MnO2 has spherical crystals that are ~ 7 nm on average in size and have 149.68 m2/g of surface area and 0.91 cm3/g of total pore volume. Malachite green (MG) dye was then taken out of the water by adsorption using MnO2 NPs. Optimization of various adsorption parameters resulted in 188.68-277.78 mg/g maximum adsorption capacities at 298-328 K tested temperatures and 99.6% removal of 50 mg/L MG within 90 min using MnO2 dose of 0.01 g at pH 10 and 298 K. The results were tested using pseudo-first order, pseudo-second order, intraparticle diffusion, Elovich, and Liquid film kinetic models as well as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The most likely models to describe the adsorption process at 298 K are pseudo-second-order kinetics (R2 = 0.997) with a rate constant of 4 × 10-4 g/(mg.min) and Langmuir isotherm (R2 = 0.973). Additionally, the positive values of enthalpy change (3.91-67.81 kJ/mol) and the negative values of Gibb's free energy (- 3.38 to - 19.7 kJ/mol) indicate that the process is endothermic, spontaneous, and thermodynamically feasible. MnO2 NPs sustained their adsorption efficiency at 90.4% after 5 sorption cycles. MnO2 appears to be more selective for MG in studies examining the adsorption of various cationic dyes. Lately, the biosynthesized MnO2 NPs can be utilized to remove MG from aqueous solutions effectively.