Study of colloids of Ag nanoparticles from Mentha Piperita leaf extract and their antibacterial effect

Ag nanoparticles have been synthesized by `green nano route' from Mentha Piperita leaf extract with a view to study the formation of particles at different time intervals of chemical reduction. The nanoparticles in colloidal solutions were characterized by using AFM, DLS and UV vis spectrophotometer. It was found from DLS measurements that the average particle size varies with time of reaction, i.e., 20 nm after 2 days, 28 nm after 5 days, and 39 nm after 11 days. After 11 days the average nanoparticle size remains the same till 15 days or so. In addition, the extract particles were found to merge with Ag nanoparticles. AFM images show extract components on or around the Ag nanoparticles. The particles in a particular solution vary in size, i.e., variation of size as measured was 10 nm to 90 nm in a solution after 11 days of reaction. The observations and measurements revealed the non-uniformity of size and their dispersity in the colloidal solution all through from 5 min to 11 days. The nanoparticles were sustained in respect of their average size and dispersity after 11 to 15 days. Antibacterial effect of Ag nanoparticles, thus produced, was observed on E.Coli, and could be utilized till 15 days or later for inhibition of bacterial growth.