In this paper, ZnO nanoparticles (NPs) were greenly synthesized at different pH values of 4, 6, 9.5, and 11 via Portulaca oleracea leaf extract, and the effect of pH on the optical and structural properties was studied. UV-Vis spectrophotometers and FTIR spectroscopy characterized the optical properties. Meanwhile, the structural properties were characterized via Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Furthermore, their photocatalytic dye degradation was examined against methyl orange dye. The characterization results have confirmed the successful biosynthesis of ZnO nanoparticles with a size ranging between 22.17 to 27.38 nm. The synthesis pH value significantly influenced ZnO NPs’ optical and morphological properties. The results have also indicated the high performance of the greenly synthesized ZnO NPs for dye degradation.

Chitosan was used in the sol-gel synthesis of zinc oxide nanoparticles (ZnO NPs) as a capping agent in order to control the size, morphology, optical bandgap, photocatalytic efficiency, and antimicrobial activity. Different chitosan sources were used for the sol-gel synthesis of ZnO NPs, namely chitosan of shrimp shells, crab shells, and Streptomyces griseus bacteria. The photocatalytic efficiency was studied by using the methylene blue (MB) photodegradation test, and the antibacterial activity of the different types of ZnO NPs was investigated by the agar well diffusion technique. The particle size of ZnO NPs varied between 20 and 80 nm, and the band gap energy ranged between 2.7 and 3.2 eV. Due to the different chitosan sources, the ZnO NPs showed different antibacterial activity against Listeria innocua, Bacillus Subtiliis, Staphylococcus Aureus, Salmonella Typhimurium and Pseudomonas Aeruginosa. The ZnO NPs with lower band gap values showed better antibacterial results compared to ZnO NPs with higher band gap values. The MB dye removal of ZnO (shrimp shells), ZnO (crab shells), and ZnO (Streptomyces griseus) reached 60%, 56%, and 44%, respectively, at a contact time of 60 min, a low initial MB dye concentration of 6 × 10⁻⁵ M, a solution temperature of 25 °C, and a pH = 7.

Chitosan is one of the most abundant biopolymers in nature with high economic value due to its biocompatibility, biodegradability, lack of toxicity, and antifungal activity. In this study, chitosan was extracted from three different sources: Blaps lethifera (CSB), Pimelia fernandezlopezi (CSP), and Musca domestica (CSM). The ash content (AC), moisture content (MC), fat binding capacity (FBC), water binding capacity (WBC), and deacetylation degree (DD) were determined for the prepared chitosans. The effect of the DD of chitosan on the antibacterial activity of gram (positive/negative) bacteria and the azo dyes (methylene blue, MB) removal from wastewater was also investigated. Chitosan extracts showed good antibacterial activity against Listeria innocua, Bacillus subtiliis, Staphylococcus aureus, Salmonella typhimurium, and Pseudomonas aeruginosa. The MB dye removal of CSB-chitosan, CSP-chitosan, and CSM-chitosan reached 37%, 87%, and 26%, respectively, at a contact time of 2 h, a low initial dye concentration MB of 13 ppm, a solution temperature of 25 °C, and a pH = 7. Graphical Abstract

Metal and metal oxide nanoparticles are gaining traction in inorganic catalysis and photocatalysis, driving the development of eco-friendly methods. This study introduces an eco-friendly and cost-effective approach for synthesizing Al₂O₃ nanoparticles (NPs) using extracts derived from the leaves of Calligonum comosum L. The primary objective of this investigation is to assess the photocatalytic efficacy of the synthesized catalyst in addressing organic pollutants. The Al₂O₃ NPs exhibit a spherical morphology with crystalline arrangements, as evidenced by an average crystallite size of 25.1 nm in the XRD analysis. The band gap energy of the Al₂O₃ NPs is determined to be 2.86 eV. In terms of mechanical properties, the Al₂O₃ NPs show significant potential in enhancing both flexural and compressive properties, thereby making them a viable choice for improving the mechanical performance of composites. Notably, the Young’s modulus of the hybrid composite (comprising plant material and Al₂O₃ NPs) exhibits a remarkable increase of 34.4% in flexion and 78.3% in compression compared to the plant material alone. The catalytic performance of the Al₂O₃ NPs is evaluated using methylene blue (MB) as a cationic dye and Rose Bengal (RB) as an anionic dye. Impressively, the Al₂O₃ NPs demonstrate degradation efficiencies of 98.2% for MB and 90.5% for RB. The degradation processes occur under solar light irradiation, with a contact time of 120 m, a maintained pH of 7, and a temperature of 25 °C. This study found that Al₂O₃ nanoparticles are a promising, cost-effective, and environmentally friendly option for water treatment.