Plant materials for the synthesis of nanomaterials: Greener sources

Abstract

Nanomaterials (NMs) from a wide variety of sources have been used to degrade pollutants and have been widely reported for several different environmental applications. The conventional chemical processes used to generate NMs may have significant drawbacks, such as defective surface formation, poor production rate, high cost, and high energy requirements. Chemical synthesis procedures usually include the use of toxic chemicals, the generation of hazardous byproducts, and the potential release of precursor chemicals into the environment. The search for greener procedures to generate environmentally friendly, nontoxic processes for synthesizing NMs is needed to avoid the environmental impacts of treatment processes as much as possible. Using biologically mediated synthetic protocols to generate NMs has significantly increased over the last few years. These protocols have important advantages, such as: (i) being an eco-friendly method that does not use toxic chemicals, (ii) being lower in cost because they avoid highpressure and high-energy expenses, and (iii) being able to produce small-sizedNMs. Several different biological resources have previously been used to synthesize nanoparticles, including microorganisms (e.g., bacteria, fungi, yeasts, algae, and viruses) and plant extracts. In particular, plant extracts have very interesting characteristics that suggest they are highly cost-effective source for generating NMs. Recent reports suggest that several herb and/or plant constituents possess high levels of antioxidant compounds (i.e., polyphenols, sugars, and amino acids) that can be used as reducing and capping agents for NMs, and their use in synthesizing nanoparticles is suitable for upscaling and generating stable products. Various plant extracts have been used to synthesize different NMs. This work provides an overview of the different methods and plant materials used to synthesize NMs and their possible environmental applications, as well as an analysis of the perspectives and challenges of carrying out this novel methodology.