title: Sunlight-induced rapid and efficient biogenic synthesis of silver nanoparticles using aqueous leaf extract ofOcimum sanctumLinn. with enhanced antibacterial activity.
abstract: BACKGROUND
  Nanotechnology is now regarded as a distinct field of research in modern science and technology with multifaceted areas including biomedical applications. Among the various approaches currently available for the generation of metallic nanoparticles, biogenic synthesis is of increasing demand for the purpose ofgreen nanotechnology. Among various natural sources, plant materials are the most readily available template-directing matrix offering cost-effectiveness, eco-friendliness, and easy handling. Moreover, the inherent pharmacological potentials of these medicinal plant extracts offer added biomedical implementations of the synthesized metal nanoparticles.
  
  
  RESULTS
  A robust practical method for eco-friendly synthesis of silver nanoparticles using aqueous leaf extract ofOcimum sanctum(Tulsi) as both reducing and capping agent, under the influence of direct sunlight has been developed without applying any other chemical additives. The nanoparticles were characterized with the help of UV-visible spectrophotometer and transmission electron microscopy (TEM). The prepared silver nanoparticles exhibited considerable antibacterial activity. The effects were more pronounced on non-endospore-forming Gram-positive bacteria viz.,Staphylococcus aureus,Staphylococcus epidermidis,and Listeria monocytogenesthan endospore-forming speciesBacillus subtilis.The nanoparticles also showed prominent activity on Gram-negative human pathogenicSalmonella typhimurium,Escherichia coli,Pseudomonas aeruginosa, and plant pathogenicPantoea ananatis.A bactericidal mode of action was observed for both Gram-positive and Gram-negative bacteria by the nanoparticles.
  
  
  CONCLUSIONS
  We have developed a very simple, efficient, and practical method for the synthesis of silver nanoparticles using aqueous leaf extract ofO. sanctumunder the influence of direct sunlight. The biosynthesis of silver nanoparticles making use of such a traditionally important medicinal plant without applying any other chemical additives, thus offers a cost-effective and environmentally benign route for their large-scale commercial production. The nanoparticles dispersed in the mother solution showed promising antibacterial efficacy. Graphical AbstractSunlight-induced rapid and efficient biogenic synthesis of silver nanoparticles using aqueous leaf extract ofOcimum sanctumLinn. with enhanced antibacterial activity.
authors.affiliation: Department of Chemistry, Laboratory of Natural Products and Organic Synthesis, Visva-Bharati (a Central University), Santiniketan, 731 235 West Bengal India.
authors.forename: Goutam
authors.initials: G
authors.lastname: Brahmachari
authors.affiliation: Department of Chemistry, Laboratory of Natural Products and Organic Synthesis, Visva-Bharati (a Central University), Santiniketan, 731 235 West Bengal India.
authors.forename: Sajal
authors.initials: S
authors.lastname: Sarkar
authors.affiliation: Department of Botany, Microbiology and Plant Pathology Laboratory, Visva-Bharati (a Central University), Santiniketan, 731 235 West Bengal India.
authors.forename: Ranjan
authors.initials: R
authors.lastname: Ghosh
authors.affiliation: Department of Botany, Microbiology and Plant Pathology Laboratory, Visva-Bharati (a Central University), Santiniketan, 731 235 West Bengal India.
authors.forename: Soma
authors.initials: S
authors.lastname: Barman
authors.affiliation: Department of Botany, Microbiology and Plant Pathology Laboratory, Visva-Bharati (a Central University), Santiniketan, 731 235 West Bengal India.
authors.forename: Narayan C
authors.initials: NC
authors.lastname: Mandal
authors.affiliation: Department of Chemistry, Laboratory of Natural Products and Organic Synthesis, Visva-Bharati (a Central University), Santiniketan, 731 235 West Bengal India.
authors.forename: Shyamal K
authors.initials: SK
authors.lastname: Jash
authors.affiliation: Department of Chemistry, Laboratory of Natural Products and Organic Synthesis, Visva-Bharati (a Central University), Santiniketan, 731 235 West Bengal India.
authors.forename: Bubun
authors.initials: B
authors.lastname: Banerjee
authors.affiliation: Department of Chemistry, Laboratory of Natural Products and Organic Synthesis, Visva-Bharati (a Central University), Santiniketan, 731 235 West Bengal India.
authors.forename: Rajiv
authors.initials: R
authors.lastname: Roy
keywords: Antibacterial activity; Mode of action; Nanomedicine; Ocimum sanctum; Silver nanoparticles; Sunlight