Hydrothermally assisted magnetic ZnO/Carbon nanocomposites were prepared using the selective biowaste of pomelo orange. Initially, the carbon aerogel (CA) was prepared hydrothermally followed by a freeze-drying method. Furthermore, the iron oxide nanoparticles were deposited onto the surface of carbon using the co-precipitation method and we obtained magnetic carbon nanocomposite, i.e., Fe₃O₄/C (MNC). Moreover, the ZnO photocatalysts were incorporated onto the surface of MNC composites using a hydrothermal process, and we obtained ZnO/MNC composites. The ZnO/MNC (55%), ZnO/MNC (65%) and ZnO/MNC (75%) composites were prepared by a similar experimental method in order to change the weight ratio of ZnO NPs. Using a similar synthetic procedure, the standard ZnO and Fe₃O₄ nanoparticles were prepared without the addition of CA. The experimental results were derived from several analytical techniques, such as: X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman and diffuse reflectance spectroscopy (DRS-UV). The synthesized carbon, ZnO, Fe₃O₄, ZnO/MNC (55%), ZnO/MNC (65%) and ZnO/MNC (75%) composites were examined through the photocatalytic degradation of methylene blue (MB) under visible-light irradiation (VLI). The obtained results revealed that the composites were more active than carbon, ZnO and Fe₃O₄. In particular, the ZnO/MNC (75%) composites showed more activity than the rest of the composites. Furthermore, the recycling abilities of the prepared ZnO/MNC (75%) composites were examined through the degradation of MB under identical conditions and the activity remained constant up to the fifth cycle. The synthetic procedure and practical applications proposed here can be used in chemical industries, biomedical fields and energy applications.

In the past few years, substantial progress has been made in the field of microwave-assisted biosynthesis of gold nanoparticles (AuNPs) using quercetin (QT) as a natural reducing and stabilizing agent. This study explores the rapid and eco-friendly synthesis of AuNPs facilitated by microwave irradiation, offering a time-efficient alternative to conventional methods. The AuNPs were thoroughly characterized to confirm their morphology, size, crystalline structure, and surface plasmon resonance (SPR). The synthesized AuNPs were confirmed by visual color change from yellow to violet and characteristic SPR peak at 519 nm. Furthermore, XRD studies clearly confirmed the crystalline nature of the face-centered cubic structure of AuNPs. Moreover, TEM images reveal that the AuNPs were found to be more or less spherical and have a slightly variable morphology with an average diameter of 14 nm. The antibacterial properties of QT and AuNPs were evaluated against two different bacterial strains via Staphylococcus aureus and Escherichia coli, demonstrating significant activity, particularly due to the stabilizing effect of QT. Additionally, the catalytic efficiency of the AuNPs was evaluated by their ability to reduce 4-nitrophenol to 4-aminophenol, a model reaction for the catalytic activity. The results were promising, with the rate constant of QT-AuNPs determined to be 0.1016 s^-1. This work highlights the dual functionality of QT-mediated AuNPs in enhancing both antimicrobial and catalytic properties, contributing to their potential applications in the biomedical and environmental fields. This study highlights the dual role of QT-mediated AuNPs in enhancing antimicrobial and catalytic properties, paving the way for innovative applications in both the biomedical and environmental fields. The uniqueness lies in leveraging the natural properties of QT to simultaneously improve biological activity and catalytic efficiency, offering a sustainable and multifunctional QT-AuNP solution.