Facile phyto-mediated synthesis of gold nanoparticles using Eupatorium odoratum leaf extract and its size-dependent catalytic activity

In this work, gold nanoparticles have been prepared using the leaf extract of Eupatorium odoratum assisted with microwave irradiation. The role of pH on the synthesis of gold nanoparticles has also been studied. At higher value of pH, size of nanoparticles got highly diminished, going below 10 nm. A probable mechanism of formation of such small nanoparticles has been proposed in this Letter. The effects of different parameters such as reaction time, temperature and pH variation on the final morphology of gold nanoparticles have been investigated. The characterisation of the samples has been carried out by transmission electron microscope, UV–Vis absorption spectroscope, Fourier transform infrared spectroscope and zeta potential analysis. Further, a comparative study of catalytic activity of gold nanoparticles of two different sizes was performed by monitoring the reduction of 2,4,6-trinitrophenol. Experimental study showed that smaller nanoparticles are more efficient in their catalytic activity than their larger counter parts. The consistency in sizes and shapes, higher stability and rapid synthesis are the major advantages of this synthesis method. Thus, this procedure of synthesis of gold nanoparticles may offer an attractive alternative to the existing ones and opens a full range of possibilities for various analytical applications.