Optical Properties of Silver Nanoparticles for Surface Plasmon Resonance (SPR)-Based Biosensor Applications

Abstract

It has been successfully carried out the synthesis of silver nanoparticles by chemical reduction method. Silver nitrate (AgNO 3 ) is used as the metal precursor and trisodium citrate as the reducing agent as well as the use of polyvinyl alcohol (PVA) as a stabilizer. The formation of silver nanoparticles was observed visually with discoloration (yellow). To excite surface plasmons, attenuated total reflection (ATR) method is used with Krestchmann configuration of the prism coupling. The maximum absorption band in the UV-Vis spectrometer shows a red shift of 429.43 nm wavelength for a colloidal solution of silver nanoparticles without PVA and 429.01 nm with PVA. The addition of PVA sharpened absorption spectrum curve and produce a broad absorption band which is indicative of a smaller particle size. TEM images showed that the morphology (crystallites) silver nanoparticles have nearly spherical geometry with dispersive particle distribution. Dispersibility of nanoparticles such as this could potentially be used as an active ingredient of SPR biosensor. The observation of the SPR phenomenon shows the SPR angle shift of 0.1° when a thin layer of silver as an active ingredient a biosensor coated with silver nanoparticles and 0.2° when silver nanoparticles with PVA. SPR angle shift and increase the reflectance values caused by changes in surface Plasmon, which can be a reference that the SPR phenomenon with the sensing surface modification using an additional layer of silver nanoparticles can increase sensitivity.