Methylene blue (MB) dye and Staphylococcus aureus (S. aureus) bacteria in wastewater are the two significant problems currently. Researchers have been looking for materials that can combat these two problems at the same time. In the present study, we describe the synthesis of spherical copper oxide (CuO) nanoparticles (NPs) by the chemical precipitation method and evaluate their photocatalytic performance against MB dye and antibacterial efficacy against S. aureus. CuO NPs were produced using copper acetate monohydrate (Cu(CH3COO)2·H2O) as the precursor and sodium hydroxide (NaOH) as the reducing agent. Synthesized CuO NPs were characterized using a combination of techniques, including ultraviolet–visible spectroscopy, X-ray diffraction, transmission electron microscopy, selected area electron diffraction, Fourier transform infrared, and energy-dispersive X-ray diffraction analysis. All the analyses indicated that monoclinic CuO NPs were formed with a spherical shape and an average particle size of 6.2 nm. Photocatalytic experiments indicated that 55.5% of a 10 ppm MB dye solution was degraded by the prepared nano-CuO photocatalyst only after 60 min. Additionally, synthesized CuO NPs demonstrated, to some extent, the zone of inhibition on the S. aureus bacterium’s cell wall. It is inspiring that CuO NPs can be used to solve two problems of MB dye contamination and S. aureus bacterial infection simultaneously.

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This paper presents the experimental forced convective heat transfer coefficient (HTC) of nanorods (NRs) zinc oxide–ethylene glycol nanofluids (ZnO–EG NFs) in laminar flow. First, ZnO NRs were synthesized using a hydrothermal method that uses zinc acetate dihydrate [Zn(CH3COO)2·2H2O] as a precursor, sodium hydroxide as a reducing agent, and polyvinylpyrrolidone (PVP) as a surfactant. The hydrothermal reaction was performed at 170 °C for 6 h in a Teflon-lined stainless-steel tube autoclave. The sample’s X-ray diffraction (XRD) pattern confirmed the formation of the hexagonal wurtzite phase of ZnO, and transmission electron microscopy (TEM) analysis revealed the NRs of the products with an average aspect ratio (length/diameter) of 2.25. Then, 0.1, 0.2, and 0.3 vol% of ZnO–EG NFs were prepared by adding the required ZnO NRs to 100 mL of EG. After that, time-lapse sedimentation observation, zeta potential (ζ), and ultraviolet-visible (UV–vis) spectroscopy was used to assess the stability of the NFs. Furthermore, the viscosity (μ) and density (ρ) of NFs were measured experimentally as a function of vol% from ambient temperature to 60 °C. Finally, the HTC of NFs was evaluated utilizing a vertical shell and tube heat transfer apparatus and a computer-based data recorder to quantify the forced convective HTC of NFs in laminar flow at Reynolds numbers (Re) of 400, 500, and 600. The obtained results indicate that adding only small amounts of ZnO NRs to EG can significantly increase the HTC, encouraging industrial and other heat management applications.