doi:10.1038/nindia.2015.26 Published online 24 February 2015
By using the cell-free extract of a pathogenic bacterium, researchers have synthesized gold nanoparticles that can catalyse the degradation of methylene blue, a dye harmful to humans1. The nanoparticles could be synthesized from the bacterial extract in a few minutes, and thus the method is a rapid and ecofriendly way to produce gold nanoparticles with catalytic properties.
The researchers synthesized the gold nanoparticles by mixing solutions of hydrogen tetrachloroaurate with extracts of Staphylococcus epidermidis, a bacterium that naturally colonizes the human skin and is often spread through medical devices.
The scientists prepared the nanoparticles at various temperatures. They found that increasing the temperature from 35 to 115 degrees Celsius decreased synthesis time from 15 hours to 10 minutes. Sophisticated imaging techniques revealed that the nanoparticles were spherical with sizes between 20 and 25 nanometres.
To probe the catalytic activities of the nanoparticles, the researchers added a colloidal solution of the nanoparticles to a blue solution of methylene blue and sodium borohydride. Addition of the nanoparticles changed the solution from blue to colourless, indicating that the nanoparticles aided degradation of methylene blue.
A drop containing the nanoparticles degraded methylene blue in a few seconds, which is much faster than other processes that use silver and gold nanoparticles to degrade the same dye.
1. Srinath, B. S. et al. Rapid biosynthesis of gold nanoparticles by Staphylococcus epidermidis: its characterisation and catalytic activity. Mater. Lett. 146, 23−25 (2015)