Small particles with a diameter of between one and one hundred nanometers, known as nanoparticles, are used in many ways [1]. Since nanoparticles have extremely different physical, chemical, and biological properties from bulk materials, including a high surface area, material science has seen a wide range of applications of nanomaterial-based technologies in recent decades [2]. It is possible to produce metal and metal oxide nanoparticles, which have uses in biotechnology, medicine, and numerous other industrial fields [3]. Because of the many uses for these materials, methodologies and procedures for synthesizing and characterizing nanoparticles are essential [4].
Zinc oxide nanoparticles (ZnO NPs) are the most interesting of these metal oxides because they are safe, easy to make, and affordable to produce [5]. Zinc oxide is now classified as GRAS (generally recognized as safe) metal oxide by the U.S. Food and Drug Administration (U.S. FDA) [6]. ZnO is a large exciton binding energy (60 meV) semiconductor with a wide band gap around 3.37 eV [7]. ZnO NP is a specialty material having products in the semiconductor, piezoelectric, and pyroelectric domains [8]. It has a wide range of uses in UV light emitters, chemical sensors, spin electronics, transparent electronics, personal care items, and specially blended paints and coatings [9–14].
Generally, three methods are used for producing nanomaterials: chemical, biological, and physical. For many years in the recent past, the physical and chemical routes of nanomaterial manufacturing have confirmed detrimental hazardous consequences on humans. These chemically induced processes take less time to complete, however the chemicals involved are hazardous and not environmentally friendly [15]. To produce nanoparticles, biological synthesis pathways have an advantage over chemical and physical synthesis techniques for the reasons mentioned above [16]. The biosynthetic pathway is a green, safe, and biocompatible method for producing nanoparticles for use in biomedical applications using plants and microorganisms. Fungi, algae, bacteria, and plants can also be used to perform out this synthesis. A variety of nanoparticles have been synthesized using plant components, including leaves, fruits, roots, stems, and seeds, since their extract contains phytochemicals that function as reducing and stabilizing agents [17,18].
Melon (Cucumis melo L.) belongs to the Cucurbitaceae family, like watermelon and pumpkin, and has worldwide economic importance [19]. It has high antioxidant activity due to its phenolic content and has been identified as an important source of phytochemicals with potential health benefits. Melon is rich in important vitamins and is also a good source of pro-vitamin A. Industrial processing of melon and separation of the desired part of the fruit involves the production of by-products consisting of large quantities of peel and seeds [20,21].
The aim of this study is to synthesize ZnO NPs for the first time with an environmentally friendly method using the seeds and peel of melon fruit. In the first stage of this study, the Soxhlet extraction method was used to obtain polyphenol-rich extract from the peel and seeds of the melon fruit, which has a great industrial value, and water-ethanol were used as extraction solvents for cleaner technologies. This has been considered an environmentally friendly approach. In the second stage, it was aimed to use the extract obtained from melon by-products as a reducing, capping and stabilizing agent in the synthesis of ZnO NPs with the green synthesis. ZnO NPs were characterized by using of FTIR, XRD, SEM-EDX, TEM, UV-Vis, UV-DRS, DLS and Zetasizer. The antioxidant capacity content of the extract and ZnO NPs, 2,2-diphenyl-1-picrylhydrazyl (DPPH), and the amount of total phenolic content (TPM) were determined spectrophotometrically using the Folin-Ciocalteu method. This nanomaterial, synthesized with an environmentally friendly method, is intended to be used in biomedical applications and to contribute to the world of science.