The current work aims to enhance the structural, optical, photocatalytic, and cytotoxic properties of CuO NPs at varied rGO concentrations of 5% and 10%. In the present work, a one-step hydrothermal method was successfully applied to prepare rGO/CuO NCs at different concentrations of RGO. The novelty of this work was to enhance the structural, optical, photocatalytic, and cytotoxic properties of CuO using the addition of rGO sheets. XRD, TEM, SEM-EDX, XPS, FTIR, UV-vis, PL, and DLS techniques were used to characterize the prepared samples. XRD data confirmed the formation of the monoclinic phase of CuO with a decrease in crystallite size, from 21.14 nm for CuO to 16.94 nm for the 10% rGO/CuO NCs nanocomposite. SEM and TEM images verified the uniform anchoring and excellent dispersion of CuO nanoparticles on the rGO sheets, and the EDX spectra showed the presence of Cu, O, and C elements in the obtained rGO/CuO NCs. DLS measurements showed that the hydrodynamic radius dropped from 69.98 ± 17.81 nm for CuO to 51.72 ± 10.48 nm for 10% rGO/CuO NCs. The zeta potential values remained negative for all samples, ranging from −20.50 ± 8.69 mV for CuO to −25.60 ± 9.08 mV for 10% rGO/CuO NCs, suggesting enhanced colloidal stability with rGO incorporation. Furthermore, FTIR and XPS analyses confirmed that Cu–O–C bonding formed between CuO and rGO. UV-Vis analysis revealed a redshift in the absorption edges as rGO content increased, reducing the band gap from 3.65 eV to 3.60 eV. Additionally, PL spectra showed a marked reduction in emission intensity due to a decrease in the recombination rate between electron (e⁻)–holes (h⁺) pairs. The CuO/(10%)rGO NCs showed the best photocatalytic performance with a 93.56% degradation of methylene blue (MB) after 120 min under UV irradiation, and followed pseudo-first-order kinetics with k = 0.0203 min⁻¹. Cytotoxicity studies on HT1080 cells showed a dose-dependent decrease in viability. 10% rGO/CuO NCs exhibited the highest cytotoxicity effect, resulting in 58% and 50% viability at 1.4 mg/mL, respectively. The presented results showed that the presence of rGO in CuO NPs played a role in enhancing the structural stability, charge mobility, and biological reactivity of Cu NPs. This study highlighted that the rGO/CuO NCs are a promising multi-functional material for environmental and biomedical applications.

This study evaluated the effects of adding zinc oxide nanoparticles (ZnNP), L-arginine (L-Arg), or a combination of both to the diets of growing rabbits to mitigate the physiological and productive consequences of heat stress. Two hundred and eighty 35-day-old New Zealand White rabbits were randomly assigned to four experimental treatments, with 70 rabbits per treatment and seven replicates (10 rabbits/replicate). The control group (Ctr) received the base diet without additives, while the diets of the other groups were fortified with arginine (L-Arg; 3 g/kg), zinc oxide nanoparticles (ZnNP; 40 mg/kg), or a combination of both (Arg-Zn). The results showed that the combined Arg-Zn significantly improved weight gain rate, feed conversion rate, carcass weight, and nutrient digestibility compared to the control group (p < 0.05). At the physiological level, we observed increased serum levels of total antioxidant capacity (T-AOC), glutathione peroxidase (GPx), superoxide dismutase (SOD), immunoglobulin G (IgG), immunoglobulin A (IgA), and triiodothyronine (T3), along with decreased levels of malondialdehyde (MDA), alanine aminotransferase (ALT), and aspartate aminotransferase (AST, p < 0.05) in Arg-Zn-fed rabbits. However, adding the Arg-Zn mixture contributed to a reduction in pathogenic bacteria counts and increased the volatile fatty acid (VFA) levels. At the molecular level, the gene expression of the inflammatory cytokines IL-6 and tumor necrosis factor alpha (TNF-α) decreased; however, the gene expression of claudins-1 (CLDN-1), cationic amino acid transporter-1 (CAT-1), mucin-2 (MUC-2), sodium-glucose co-transporter-1 (SGLT-1), and interferon gamma (IFNγ) increased (p < 0.05) in Arg-Zn-fed rabbits. These results suggest that dietary supplementation with ZnNP and L-Arg may serve as an effective nutritional strategy for improving growth performance, antioxidant status, immune function, and intestinal integrity in rabbits exposed to high ambient temperatures.