Abstract
Nanoparticles (NPs), particles having one or more dimensions below 100 nm, are currently being synthesized through chemical and physical methods on an industrial scale. However, these methods for the synthesis of NPs do not fit with sustainable development goals. NP synthesis, through chemical and physical methods, requires high temperatures and/or pressures resulting in high energy consumption and the generation of large amounts of waste. In recent years, research into the synthesis of NPs has shifted to more green and biological methods, often using microorganisms. A biological approach has many advantages over chemical and physical methods. Reactions are catalysed in aqueous solutions at standard temperature and pressure (cost effective and low energy syntheses). This method does not require solvents or harmful chemicals, making NP biosynthesis a greener and more eco-friendly method. Furthermore, NP synthesis by microbes does not require the use of pure starting materials; thus it can simultaneously be used for the bioremediation of contaminated water, land and waste, and the biosynthesis of NPs. Therefore the biosynthesis of NPs contributes to the sustainable development goals, while the alternative physical and chemical methods exclusively utilize scarce and expensive resources for NP synthesis.