A Review of Green Synthesis of Metal Nanoparticles Using Algae

Abstract

Green synthesis has become a reliable, sustainable, and ecological protocol for the synthesis of numerous nanomaterials such as metal oxides, hybrids, and bio-inspired materials in the field of materials science (Singh et al., 2018). Metallic nanoparticles are already intriguing scientists for more than a century and are now utilized widely in biomedical sciences and engineeri (Lespes et al., 2020). Due to their anomalous size (length spanning within 1–200 nm) and shape-dependent properties and attractive applications in medicine, biofuel production, catalysis, electronics, and biotechnology, the synthesis of metal nanoparticles is a major area of research in nanotechnology (Ganesan et al., 2020). Green synthesis is thus considered to be an important tool to reduce the ill side effects of nanoparticles commonly used in laboratories and industry by conventional synthesis methods. The present review discussed all the established green synthesis methods used worldwide but focused on algae-based green synthesis only. Among various microorganisms, microalgae are primitive microscopic plants, and they have significant advantages as cell factories for the production of nanoparticles compared to larger plants. Algae are aquatic filamentous photosynthetic organisms that fall under the kingdom of plantae. All these algae are broadly classified into two types: microalgae and macroalgae (Leaf et al., 2020). Macroalgaes can be counted under the naked eye whereas microscopes are required to observe microalgae. Unlike most biomass, both the algaes can be harvested several times in a single year. Algae also have the ability to grow without the help of any addition of outside chemicals or fertilizers. Microalgae grow extremely quickly and, on average, double their mass 10- fold faster than higher plants. It is known that various species of microalgae reduce metal ions. Algae are recognized as primitive microscopic plants and have few advantages, such as growth rate and nutrient requirements, for producing nanoparticles compared to higher plants (Jacob et al., 2021). The present review makes an attempt to improve researchers’ knowledge of green synthesis methodology of nanoparticle synthesis using different algal species and their various pros and cons.