The goal behind this work is to prepare, characterize, and study the antimicrobial behavior of zirconia (ZrO₂) nanoparticles (NPs). Various techniques, such as X-ray diffraction (XRD), were used for studying the mineralogical structure and crystal size. The microstructure and chemical composition of the prepared particles were analyzed using a scanning electron microscope attached with an energy-dispersive X-ray analysis (EDAX) unit. The antagonistic ability against several Gram-negative and Gram-positive bacteria, including Salmonella paratyphi, Pseudomonas aeruginosa, Alcaligenes aquatilis, Escherichia coli, Streptococcus pneumoniae, and Staphylococcus aureus, was assessed using the well diffusion method. The results of XRD and scanning electron microscopy (SEM) analyses revealed that the prepared material exhibited the phase of zirconium nanoparticles with particle sizes ranging between 40 and 75 nm. The antimicrobial test results demonstrated that the inhibitory effect increased with the increase of concentration. The inhibitory effect was more pronounced against Gram-positive bacteria, as indicated by the larger size of the inhibitory zone. At a 9% dimethyl sulfoxide (DMSO) concentration, the inhibitory zone had a diameter of 3.50 mm for S. aureus compared to a diameter of 3.40 mm for S. pneumoniae. The use of zirconium oxide nanoparticles reduced the diameter of the inhibitory zone when tested against S. aureus at a 3% DMSO concentration (0.50 mm diameter) and against S. pneumoniae (0.40 mm diameter). Zirconia nanoparticles were also evaluated for their antifungal activity against several species, including Aspergillus niger, Aspergillus flavus, and Penicillium sp. The size of the inhibitory zone indicated the susceptibility of microorganisms to nanozirconium oxide, resulting in a stronger inhibition of Penicillium sp. at a 100% DMSO concentration (4.50 mm diameter) compared to A. niger and A. flavus (3.00 mm diameter). The results for Penicillium sp. at a 3% DMSO concentration showed a diameter of the inhibitory zone of 0.90 mm, while for A. niger and A. flavus, the diameter was 0.80 mm. Thus, our findings demonstrate that the zirconium oxide nanoparticles possess the capability to reduce the inhibition zone effectively for both bacterial and fungal activities.

The study aimed to prepare Al2O3 nanoparticles (NPs) from aluminum wastes (originate from aluminum workshops as waste) and tested its antimicrobial activity against bacteria (Gram-negative): Escherichia coli ATCC25922, Salmonella Typhimurium ATCC14028, Pseudomonas aeruginosa ATCC27853, Alcaligenes aquatilis and bacteria (Gram-positive): Staphylococcus aureus ATCCBAA977 and Streptococcacea pneumonia ATCC49619, types of Fungal Aspergillus niger, Aspergillus flavus and Penicillium sp. The nanomaterial prepared were confirmed using X-ray diffraction (XRD), Scan electron microscope (SEM) with Energy dispersive X-ray analysis (EDAX) techniques. The structural refinement of this material has been achieved by the Rietveld method. The shape, the cell parameters and the atomic positions were deduced for each allotropy form appearing at different calcination temperature (700–1300 °C) with particle size less than 100 nm. Results obtained by XRD denoted that alumina that obtained is crystallite nano-particles, with size ranged from 15 nm at 90 °C to 50 nm at 1300 °C, that confirms that calcination temperature direct influences the crystallite growth. EDX analyses show only the presence of two peaks for aluminum and oxygen. The aluminum NPs had antimicrobial activities. The diameter of the inhibitory zone shows the sensitivity of the microorganism to Al2O3 NPs especially at 30 % dimethyl sulfoxide (DMSO). Furthermore, the inhibitory effect of Al2O3 NPs increases with decreasing of the DMSO concentration.

This study presents a novel multifunctional Lac@CMC-Cu@Fe₃O₄ nanocomposite for the efficient immobilization of laccase designed to overcome limitations in enzyme stability, reusability, and catalytic performance. The nanocomposite integrates magnetite (Fe₃O₄) for rapid magnetic separation, carboxymethyl cellulose (CMC) as a biocompatible matrix for covalent enzyme attachment, and copper nanoparticles to enhance catalytic activity. The immobilization achieved an impressive yield of 87%, with comprehensive characterization by XRD, FT-IR, FESEM, EDX, BET, and VSM confirming successful synthesis and enzyme attachment. Kinetic analysis revealed a remarkable 37% increase in maximum reaction velocity (Vmax = 111 µmol/min) compared to free laccase (81.3 µmol/min), despite a moderate increase in Km from 1.54 to 3.22 mM. The immobilized biocatalyst demonstrated superior thermal stability, retaining 53% activity at 60 °C versus 17% for the free enzyme, and exhibited a broader pH tolerance, maintaining 41% activity at pH 8.0. Notably, the biocatalyst showed enhanced performance in organic solvents, with 153% activation in acetone. Operational reusability was exceptional, retaining 84% activity after 15 cycles, and storage stability was significantly improved, maintaining 68% activity after 90 days compared to only 11% for free laccase. This magnetically separable nanobiocatalyst represents a promising, scalable platform for sustainable industrial and environmental applications.