For many years, the biological process of producing nanoparticles was underutilized. The synthesis of nanoparticles using physical or chemical processes are the most commonly used methods for creating nanoparticles. However, these two techniques have a number of drawbacks, including high energy requirements, the use of hazardous chemicals, toxic compounds or by-products or waste, pollution, high production costs, and non-biodegradability approach. Also, the rapid global development has resulted in the depreciation of the eco-system due to the release of toxic compounds into the environment. This degradation in the earth's ecosystem has focused researchers' attention to the biological or green creation of nanoparticles. As a result, green nanoparticle synthesis will be the best option to the physicochemical approach of nanoparticle synthesis (1, 2, 3).
Green synthesis, also known as the biological method, is an environmentally friendly, natural, and long-term method of producing nanoparticles using biodegradable and renewable resources and biocompatible reagents. Plant extracts, microorganisms (moulds, yeasts, fungi, bacteria, algea), natural polymers, sugars, marine extracts, metabolites, and enzymes are among the biodegradable and renewable materials used in the synthesis of these nanoparticles. During the creation of nanoparticles, these natural compounds operate as capping, reducing, and/or stabilizing agents. The use of green chemistry in the synthesis of nanoparticles has numerous advantages, including simplicity, low energy consumption, the use of moderate temperature and pressure, cost effectiveness, eco-friendliness, mass productivity, one-pot technique, and therapeutic application (4, 5,6, 7).
Natural components found in plant extracts include alkaloids, flavonoids, saponins, steroids, tannins, and other nutritional compounds. These chemicals can be obtained from a variety of plant parts, including leaves, stems, roots, shoots, flowers, barks, and seeds. Because of the presence of active agents such as polyphenols and antioxidants, plant parts such as fruit exocarp and latex are used for nanoparticle synthesis, particularly metal nanoparticles. Plant extracts are the most commonly used biological reducing or capping agent in green synthesis, particularly for large-scale production of nanoparticles, due to their abundance in the environment and the biodegradability of their waste product. Microorganisms can also be used to make nanoparticles, but the rate of synthesis is slower than in routes involving plant-mediated synthesis, and some microbial biomass waste products are not environmentally friendly. Fungi are gaining traction in the biosynthesis of nanomaterials (2, 7).
Green synthesis can be used to create many sorts of nanoparticles. Green synthesis produces nanoparticles that are also known as inorganic nanoparticles. Metal nanoparticles, metal salts, and oxides are examples of inorganic nanoparticles. Metallic nanoparticles like silver, copper, gold, iron, zinc, and platinum have unique thermal, optical, magnetic, physiochemical, and antibacterial capabilities. Metal nanoparticle synthesis using plants has the added benefit of producing stabilized nanoparticles because plant biomolecules have the dual effect of reducing and capping the biosynthesized nanoparticles. Silver nanoparticles are the most prevalent green chemistry nanomaterials. Because of its simplicity, green synthesis of silver nanoparticles has received a lot of attention over the years. For example, the basic requirement for green synthesis of silver nanoparticles is silver nitrate and a natural reducing agent. Silver piqued people's curiosity because of its unique physical and chemical qualities. This is due to their significant anti-angiogenesis, anti-fungi, antibacterial, and anti-inflammatory properties. Gold nanoparticles are also produced biologically; however, they are considered less intriguing than silver nanoparticles (7, 8, 9, 10, 11).
In summary, green synthesis is a bottom-up approach to producing low-cost, non-toxic nanoparticles. This method makes use of natural entities found in our environment and can lead to the development of nanoparticles with predetermined properties for specific applications in medicine, electronics, the energy sector, food, water, and waste management.
References
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3. Li, X., Xu, H., Chen, Z.S. and Chen, G., 2011. Biosynthesis of nanoparticles by microorganisms and their applications. Journal of nanomaterials, 2011, pp.1-16.
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7. Kharissova, O.V., Dias, H.R., Kharisov, B.I., Pérez, B.O. and Pérez, V.M.J., 2013. The greener synthesis of nanoparticles. Trends in biotechnology, 31(4), pp.240-248.
8. Mubayi, A., Chatterji, S., K Rai, P. and Watal, G., 2012. Evidence based green synthesis of nanoparticles. Advanced materials letters, 3(6), pp.519-525.
9. Adebayo-Tayo, B.C., Akinsete, T.O. and Odeniyi, O.A., 2016. Phytochemical composition and comparative evaluation of antimicrobial activities of the juice extract of Citrus aurantifolia and its silver nanoparticles. Nigerian Journal of Pharmaceutical Research, 12(1), pp.59-64.
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11. El-Chaghaby, G.A. and Ahmad, A.F., 2011. Biosynthesis of silver nanoparticles using Pistacia lentiscus leaves extract and investigation of their antimicrobial effect. Oriental journal of chemistry, 27(3), p.929.