Morphostructural studies of pure and mixed metal oxide nanoparticles of Cu with Ni and Zn

Optimization of trimetallic Cu-Cr-Ca nanoparticle-catalyzed transesterification of amla (Phyllanthus emblica L.) seed oil: analytical characterization and fuel properties of biodiesel

Renewable energy sources are experiencing a surge in demand, motivating substantial study into biodiesel synthesis from non-edible oil sources as a strategy to offset the conflict between food and fuel. The present work focuses on optimizing the trimetallic Cu-Cr-Ca oxide nanoparticle-catalyzed transesterification of a non-food amla (Phyllanthus emblica L.) seed oil, producing high yields of good quality amla oil methyl esters (AOMEs)/biodiesel. Response surface methodology was used to optimize the transesterification process by employing a central composite design with a total of 30 experimental trials, including (24) factorial, (2(2)) axial, and (6) central points. The transesterification process was catalyzed by a newly synthesized trimetallic Cu-Cr-Ca nano-catalyst. Statistical analysis demonstrated the model's significance (p < 0.0001) with a high predicted R 2 value (0.9958) closely aligned with an adjusted R 2 value (0.9982). The optimal AOME yield of 92% was achieved at a 9 : 1 methanol-to-oil molar ratio, using 3 g of Cu-Cr-Ca catalyst at 85 °C and 5 h. GC-MS analysis of the produced methyl esters revealed the presence of 85.98% unsaturated and 14.03% saturated fatty acids, indicating the successful accomplishment of the transesterification reaction. FTIR ester stretching peaks at 1734 and 1739 cm-1 further confirmed the completion of transesterification. The fuel properties of AOMEs show potential as an alternative green energy fuel compared with ASTM standards, supporting the optimized nano-catalyzed transesterification for producing Phyllanthus emblica L. seed oil biodiesel with acceptable physico-chemical properties.

Eco-friendly synthesis of ZnO, CuO, and ZnO/CuO nanoparticles using extract of spent Pleurotus ostreatus substrate, and their antioxidant and anticancer activities

Biosynthesis techniques for nanomaterials have advanced significantly, promoting eco-friendly synthesis chemistry as a sustainable alternative to conventional methods. This study presents a novel and environmentally friendly approach for synthesizing nanoparticulate ZnO, CuO, and ZnO/CuO nanocomposites using aqueous extracts of Pleurotus ostreatus spent substrate, is reported. The structural, optical, and morphological properties of the synthesized NPs were analysed. A hexagonal phase of ZnO NPs and a monoclinic phase of CuO NPs were obtained according to the X-ray diffraction analysis. A reduction in the peak intensity of these metal oxides was observed in the ZnO/CuO NPs due to reduced crystallinity. The absorption spectra, obtained from the UV-vis analysis, showed peaks at 354, 365, and 525 nm for the ZnO, CuO, and ZnO/CuO NPs, respectively. An anticancer assay of the NPs was conducted using human embryonic kidney (HEK 293) and cervical carcinoma (HeLa) cell lines, while a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay was used for the antioxidant evaluation. The ZnO, CuO, and ZnO/CuO NPs showed higher antioxidant potency with IC50 of 2.15, 2.16, and 3.18 µg/mL, respectively, than the ascorbic acid (4.25 µg/mL). This indicates that the nanoparticles were more effective in capturing DPPH free radicals. Anticancer assays showed strong cytotoxic effects for all nanoparticles, with ZnO NPs exhibiting the highest activity (IC50: 1.94 μM for HEK 293 cells, 3.23 μM for HeLa cells), surpassing CuO and ZnO/CuO NPs. Cell viability for both HEK 293 and HeLa cells decreased as nanoparticle concentration increased, confirming dose-dependent cytotoxicity. The green synthesized metal oxides and their composite have the potential for biomedical applications.