UV VISIBLE SPECTROSCOPIC ANALYSIS OF GREEN SYNTHESIZED SILVER NANO PARTICLES

S. Krishnaraj*, V. Balamurugan and S. Chandra Mohan

ABSTRACT

Green synthesis of AgNPs was carried out using Cardiospermum halicacabum leaves extract. Here plant extract plays dual role in biosynthesis as reducing as well as stabilizing agent. The mechanism of the reaction involves the reduction of aqueous metal ion in the presence of plant extract. The formation of AgNPs was confirmed by the visible colour change from colourless to brownish yellow colour with the addition of plant extract to silver nitrate solution. Further, it was quantitatively monitored by UV-Visible spectroscopic studies. It can be clearly seen that after 5 min, there was a change in the surface plasmon resonance (SPR) absorption of wavelength in the range of 400-500 nm. It can also be observed that, the intensity of the peak was gradually increases with increasing AgNO3 concentration, indicating the reduction of Ag+ to Ag0. This is due to the formation of AgNPs with the progress of the reaction because the intensity of the SPR is directly proportional to the density of the nanoparticles presented in that solution. It showed a distinct SPR band around 430 nm, indicating the formation of the AgNPs. The formation of AgNPs was confirmed by the UV Visible spectra. The dispersions of silver nanoparticles display intense colours due to the plasmon resonance absorption. The surface of a metal is like plasma, having free electrons in the conduction band and positively charged nuclei. Surface plasmon resonance (SPR) is a collective excitation of the electrons in the conduction band; near the surface of the nanoparticles. Electrons are limited to specific vibrations modes by the particle’s size and shape. Therefore, metallic nanoparticles have characteristic optical absorption spectrums in the UV-Visible region.

Keywords: Silver nanoparticles, UV-Vis, SPR, SEM.