10.22376/ijpbs.2019.10.1.p1-12 Volume 3 Issue 1 2012 (January - March) Nanobiotechnology has dynamically developed as an important field of modern research with potential effects in electronic and medicine due to growing needs of environmentally benign technologies. Gold nanoparticles have become a significant tool in the development of novel biological and chemical processes. The present study deals with cost effective and environment friendly synthesis of gold nanoparticles using lessThan i greaterThan Helianthus annuus lessThan /i greaterThan flower extract as reducing agent as well as capping agent. UV- visible spectra indicates a strong Plasmon resonance that is located at ~550 nm. Presence of this strong broad plasmon peak has been well documented for various Me- NPs with sizes ranging all the way from 2 to 100 nm. Transmission electron microscopy (TEM) analysis showed that the gold nanoparticles are polydispersed and ranged in size from 30-50 nm with an average size of 35 nm. Our results suggest that lessThan i greaterThan Helianthus annuus lessThan /i greaterThan mediated gold nanoparticles could act as an effective antimicrobial agent and prove as an alternative for the development of new antimicrobial agents to combat resistance problem. Liny P , Divya Tk, Barasa Malakar, Nagaraj B, Krishnamurthy Nb And Dinesh R Gold nanoparticles, Green synthesis, Helianthus annuus, antimicrobial activity and flower extract. 439-446