SERS Activities of Green Synthesized Silver Nanoparticles

Spherical silver nanoparticles with average particle size of 11 nm having surface plasmon resonance peak at 440 nm are synthesized using fruit extract of Ananas comosus as reducing agent. The bright circular spots in the selected area electron diffraction pattern and the peaks corresponding to (111), (200), (220) and (311) planes in the X-ray diffraction pattern were evident for the crystallinity of face centered cubic structured nanoparticles. The surface-enhanced Raman scattering (SERS) activities of prepared silver nanoparticles were found to be size-dependent, the smaller nanoparticles showing higher SERS enhancement. The orientation of the pyridine molecule on the silver surface can be deduced from ring stretching vibrations, the ring breathing mode, in-plane and out-of-plane vibrations and the SERS surface selection rule. The SERS spectrum indicates that the pyridine adsorbed on the silver surface in a stand-on orientation via its nitrogen lone pair electrons. It is used to indicate the advantage of this green method of preparing silver based SERS colloids.