Phyto-Nanofabrication: Plant-Mediated Synthesis of Metal and Metal Oxide Nanoparticles

Phyto-Nanofabrication: Plant-Mediated Synthesis of Metal and Metal Oxide Nanoparticles

Israt Jahan
DOI: 10.4018/978-1-7998-8936-6.ch003
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Green synthesis of metallic nanoparticles through natural entities (i.e., bacteria, actinomycetes, yeast, fungus, microalgae, seaweed, plants, and plant-derived materials) has become an advantageous and ecofriendly approach. However, phytocompounds of plant extract have achieved huge attention since by utilizing them high yield NPs with desirable size and shape, which can be produced through single-step synthesis scheme. Plants retain diverse biochemicals that exhibit strong hyper-accumulating potential, crucial for metallic ion reduction to metallic NPs, like platinum, gold, silver, titanium oxide, iron oxide, copper oxide, zinc oxide, palladium, etc. Here, previously published studies were reviewed for providing the latest scientific evidence on biosynthesis of metal and metal oxide NPs using different plant materials, especially medicinal plants and food and agro-wastes.
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Introduction And Background

Utilization of metal and metal oxide nanoparticles (NPs) in various areas such as cosmetic, pharmaceutical, health care, drug delivery, food processing and packaging, photonics, surface coatings, biosensors, agricultural sectors, fuel cells, piezoelectric components, microelectronic fabrication, and toxic elements elimination and many other environmental applications has become a foreseeable tendency over the last decade (Hussain et al., 2016; Iravani, 2011; M. Rai & Ingle, 2012; Vijayaraghavan & Ashokkumar, 2017). This is due to the fact that they possess nano-scale structure with a high proportion of surface area as well as exhibit enhanced catalytic, morphological, physiochemical, electrical, magnetic, optical, mechanical, and biological characteristics, which differ from those of bulk materials (Ishak et al., 2019; Kamat, 2002). Because of possessing these unique and fascinating properties, metal and metal oxide nanoparticles have become the focus of intensive studies over the last few years, and many studies have been accompanied synthesizing these nanoparticles applying different approaches.

Two routes are mainly followed for the production of nanoparticles, i.e., the ‘top-down’ approach where NPs are formed by size reduction and decomposing of larger macro particles into fine particles (Ahmed et al., 2016), and ‘bottom-up’ approach that involves the assembly of small substances to synthesize nanoparticles through the oxidation of metallic ions into zero-valent metal particles (Zheng et al., 2016). Top-down process consists of physical and chemical methods whereas bottom-up approach can be achieved through wet chemical methods (Figure 1).

Nevertheless, these approaches require a significant amount of harmful and toxic ingredients, prolonged reaction times, enormous consumption of energy, expensive instrumentations, and also produce non-eco-friendly toxic by-products, which increase the cost of the experiment as well as intensify environmental toxicity (Shah et al., 2015; Soundarrajan et al., 2012; B. Zheng et al., 2013). Therefore, green chemistry by using environment-friendly materials for nanoparticle production has become more acceptable and has been established as a superior, advantageous, and alternative synthesis approach over other conventional techniques (Chandra et al., 2020). Green synthesis of metallic nanoparticles is in the category of bottom-up approach, and the nanoparticle formation mechanisms are similar to the chemical reduction process (reduction of metal ions to nanoparticles). Major emphases of this approach are i) utilizing harmless solvents/reagents for synthesis, ii) modeling, adapting, and development of an inexpensive, facile, and energy-saving synthesis protocol, iii) involving diverse biological entities available in natural surroundings, and iv) fabrications of nontoxic and biocompatible nanoparticles for further applications (Jahan et al., 2019; Malik et al., 2014). To evaluate and differentiate the biocompatibility of synthesized silver nanoparticles, comparisons were conducted using both chemical reduction (conventional wet-chemistry) and plant-mediated green synthesis of AgNPs, and comparatively lower phytotoxicity and cytotoxicity were observed in AgNPs from green synthesis (Kummara et al., 2016).

Key Terms in this Chapter

Nanostructured Materials: Materials whose structural elements - clusters, crystallites, or molecules - have dimensions in the 1 to 100 nm range.

Green Chemistry: An area of chemistry and chemical engineering focused on the design of products and processes that minimize or eliminate the use and generation of hazardous substances.

Thermodynamics: Is the study of the relations between heat, work, temperature, and energy.

Capping Agent/Stabilizing Agent: A substance that provides colloidal stability along with preventing agglomeration and stopping the uncontrolled growth of synthesized nanoparticles.

Metal Nanoparticles: Are the particles of metal atoms with diameters between 1 nm and about a few hundreds of nanometers.

Reducing Agent: A substance that reduces a chemical compound usually by donating electrons.

Nanotechnology: The branch of technology that deals with dimensions and tolerances of less than 100 nanometres, especially the manipulation of individual atoms and molecules.

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