In the recent decade, zinc oxide nanoparticles (ZnO NPs) have been widely explored owing to their versatile properties and prodigious demands in the drug delivery, medical, energy storage, cosmetics, and the healthcare sectors. Therefore, the current work opts for an environmentally benign method to prepare ZnO NPs. The leaf extract of Calendula officinalis L. acts as a reducing agent for the metal ions; therefore, in the current research, ZnO NPs were prepared via green route by using Calendula officinalis leaf extract. Furthermore, the ZnO NPs were analysed with different spectroscopic techniques to confirm the structure and stability of nanomaterials. The prepared ZnO NPs were characterized by XRD, FE-SEM, FT-IR and UV–Vis studies. Also, the antioxidant and antimicrobial properties of the synthesized ZnO NPs were investigated. The XRD result of synthesized ZnO NPs showed the crystalline size 28.23 nm with wurtzite hexagonal structure along with the most intense peak (101). Following preliminary confirmations of the intended ZnO NPs, both big and small agglomerated forms were observed in the FE-SEM, which is often used to determine their exterior assembly. Further, the results of Fourier transform infrared spectroscopy (FT-IR) indicated the formation of pure ZnO NPs with an absorption peak of the Zn–O bond between 4000 cm⁻¹ and 500 cm⁻¹ and no discernible peak in the monitoring range. The UV–Vis spectrum of the green synthesized ZnO NPs were revealed two prominent absorption peaks at 355 nm and 370 nm with energy band gap of 2.986 eV. Using the 1, 1-di phenyl-2-picrylhydrazyl (DPPH) test, the antioxidant activity of the described ZnO NPs was assessed. It demonstrated how, ZnO NPs significantly increased their antioxidant activity by scavenging 1, 1-di phenyl-2-picrylhydrazyl (DPPH) free radicals. It could be seen that synthesis of the naturally occurring plant product ZnO NPs have been acting as an alternate of chemical antioxidant. The antimicrobial analysis was also performed with the help of disk diffusion method where three multi-drug resistant human pathogens namely Staphylococcus aureus, Klebsiella pneumoniae and E.coli were used. The Zone of Inhibition diameter values are 35.2 mm ± 0.9, 23.6 mm ± 0.1 and 13.5 mm ± 0.1, respectively, which showed that the ZnO NPs was highly effective against S. aureus. Thus, the green synthesis method of ZnO NPs using leaf extract of Calendula officinalis is evidence that it is superior and environmentally friendly method for the preparation of ZnO NPs and hence it can be utilized in various nano-medicine approaches.

The over-production of free radicals in the body causes oxidant damage in the body. Currently, zinc oxide nanoparticles (ZnO NPs) are gaining attention of most scientists because of their excellent physical, chemical, and biological properties. In this work, the ZnO NPs were synthesized using the petal extract of C. officinalis L. An absorbance spectrum of the synthesized ZnO NPs was recorded using an ultraviolet-visible (UV–Vis) spectrophotometer. The absorbance band around 368 nm confirms the formation of ZnO NPs. The transmission electron microscopy (TEM) analysis clearly shows that the most of the ZnO NPs are spherical in shape with average particle size ∼ 16 nm. The field emission scanning electron microscope (FE-SEM) result demonstrates the spherical morphology with large agglomeration of the particles. The energy-dispersive x-ray spectroscopy (EDS) result confirms the presence of Zn in the synthesized NPs’. The x-ray diffraction (XRD) peaks represent the crystalline structure of the ZnO NPs with average particle size ∼ 27.22 nm. Fourier transform infra-red (FT-IR) spectrum of synthesized ZnO NPs was recorded in the range of 4000-500 cm⁻¹. The ester and carboxylic groups were found at 1017 cm⁻¹, 952 cm⁻¹, 688 cm⁻¹, 609 cm⁻¹, and 514 cm⁻¹ due to the presence of Zn-O band stretch in the FT-IR spectrum. Further synthesized material was evaluated by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay to evaluate its antioxidant activity. It showed that ZnO NPs exhibited significant antioxidant activity through scavenging DPPH free radicals. Thus, it could be seen that the synthesis of naturally occurring plant product ZnO NPs acts as an alternative chemical antioxidant. Hence, the herbal synthesized ZnO NPs are proven to be a potent antioxidant agent and can be used in several medicinal applications.

The green synthesis of nanomaterials has drawn researchers from all over the world over the past few decades in a huge surge of interest. The aim of this research was to use Kinnow peel extract to synthesize titanium dioxide (TiO ₂ ) nanoparticles (NPs) in an environmentally friendly and efficient manner. This method seeks to improve antioxidant qualities while using fewer hazardous chemicals in the production of NPs. Using ultraviolet visible (UV–Vis) spectroscopy, the formation of crystalline TiO ₂ NPs was first verified by a distinctive absorbance peak at 235 nm. Further characterization was performed using X–ray diffraction (XRD), field emission–scanning electron microscopy (FE-SEM), energy–dispersive X–ray spectroscopy (EDX), transmission electron microscopy (TEM), and Fourier transform infrared (FT–IR) spectroscopy. The antioxidant potentials of the green-synthesized TiO ₂ NPs were evaluated using DPPH and FRAP assays. The results demonstrated potent free radical scavenging activity, comparable to ascorbic acid, a well-known standard antioxidant. These findings suggest that TiO ₂ NPs possess effective antioxidant properties and highlighting Kinnow peel extract as an eco-friendly sustainable and alternative to conventional synthesis routes. Moreover, the study indicate that the green-synthesized TiO ₂ NPs could serve a promising candidate to replace the conventional antioxidant drugs, such as ascorbic acid.