"Green" nanotechnologies: synthesis of metal nanoparticles using plants

Abstract

While metal nanoparticles are being increasingly used in many sectors of the economy, there is growing interest in the biological and environmental safety of their production. The main methods for nanoparticle production are chemical and physical approaches that are often costly and potentially harmful to the environment. The present review is devoted to the possibility of metal nanoparticle synthesis using plant extracts. This approach has been actively pursued in recent years as an alternative, efficient, inexpensive, and environmentally safe method for producing nanoparticles with specified properties. This review provides a detailed analysis of the various factors affecting the morphology, size, and yield of metal nanoparticles. The main focus is on the role of the natural plant biomolecules involved in the bioreduction of metal salts during the nanoparticle synthesis. Examples of effective use of exogenous biomatrices (peptides, proteins, and viral particles) to obtain nanoparticles in plant extracts are discussed.

Keywords: biomatrices; bioreduction; metal nanoparticles; plant extracts; plant metabolites.

Fig. 1

Electron micrographs of the iron (A), silver (B), and gold (C) nanoparticles synthesized in extracts of N. benthamiana at room temperature

Fig. 2

The main types of plant metabolites involved in the synthesis of metal nanoparticles: A – terpenoids (eugenol); B,C – flavonoids (luteolin, quertcetin); D – a reducing hexose with the open chain form; E,F – amino acids (tryptophan (E) and tyrosine (F))

Fig. 3

A schematic representation of metal nanoparticle synthesis in a plant extract. The metal ions bind to the reducing metabolites and stabilizing agents and are reduced to metal atoms. The resulting complex of the metal ion and metabolite interacts with similar complexes forming a small metal nanoparticle. Next, growth and coalescence of separate small particles into larger ones occur through the coarsening process. This process continues until the particles assume a stable shape and size

Fig. 4

Formation of nanoparticles in plant extracts using biomatrices. A – A scheme of nanoparticle formation in the presence of the tobacco mosaic virus (TMV) as a biomatrix. Metal ions interacting with negatively charged groups on the TMV surface are reduced upon addition of a plant extract. The regular positioning of TMV active groups significantly increases the number of effective events of initiation, which increases the output of metal nanoparticles 3–5-fold. B,C – electron micrographs of gold nanoparticles produced in N. benthamiana extracts in the presence (B) and in the absence (C) of TMV particles

Fig. 5

Micrograph of the metallized tobacco mosaic virus obtained by transmission electron microscopy