Plant Extracts Promoted Preparation of Silver and Gold Nanoparticles: A Systematic Review Manobjyoti Bordoloi * Chemical Science and Technology Division CSIR North East Institute of Science & Technology Jorhat 785006, Assam, India * m.j.bordoloi.pub@gmail.com; mjb _ rrljt@yahoo.co.in Ranjan K. Sahoo † , Kashyap J. Tamuli ‡ , Surovi Saikia § and Partha P. Dutta ¶ Chemical Science and Technology Division CSIR North East Institute of Science & Technology Jorhat 785006, Assam, India † ranjank _ sahu@yahoo.com ‡ kashyap1309@gmail.com § surovisaikia@gmail.com ¶ partha184@gmail.com Received 1 August 2019 Accepted 23 December 2019 Published 17 February 2020 Eco-friendly synthesis of metal nanoparticles has accrued utmost interest by researchers in the last decade for their distinct properties making them applicable in di®erent ¯elds of science and technology. With regard to its low cost, low environmental e®ect, zero contamination and higher reducing potential, their synthesis by green chemistry procedure is an emerging area in nano- biotechnology. Plant-based nanoparticles produced are more stable, with high rate of synthesis and are suitable for large scale biosynthesis as compared to the use of microorganisms which require stringent control on cell cultures. Plant-based nanoparticles have advantages over other methods due to presence of biomolecules acting both as capping and reducing agents by in- creasing the rate of reduction and stabilization of nanoparticles. Furthermore, secondary meta- bolites present in plants are used for reducing metal ions in single step reaction. In this review paper, we have cited 265 research articles and have outlined 106 plant extract assisted gold and silver nanoparticles. The present review highlights the achievements of metal nanoparticle syn- thesis, especially silver and gold nanoparticles from plant extracts, along with factors liable for the synthesis of metal nanoparticles. It also focuses on the dye degrading properties and various biological activities of metal nanoparticles, their antimicrobial mechanism of action and the physicochemical properties that in°uence the biological e®ects of metallic nanoparticles. Biological activities of metal nanoparticles were also described, including the e®ect of physico- chemical properties of metal nanoparticles on biological activities. Keywords : Gold nanoparticles; silver nanoparticles; plant extracts; biological activities; physicochemical properties. * Corresponding author. 2030001-1 NANO: Brief Reports and Reviews Vol. 15, No. 2 (2020) 2030001 (24 pages) © World Scienti¯c Publishing Company DOI: 10.1142/S1793292020300017 NANO 2020.15. Downloaded from www.worldscientific.com by 54.162.69.248 on 07/22/20. Re-use and distribution is strictly not permitted, except for Open Access articles.