Optimization of Organic Capping Material on Silver Nanoparticles by Chemical Reduction and Its Functionalization for Plasmonic Sensor Application

Abstract

The application of metal nanoparticles in medicine and optoelectronic devices recently has shown remarkable results. In the application of biosensor, metal nanoparticles are functionalized by the used of organic materials such as thiol-derivatives and citrate because of their high affinity to metal such as gold and silver also those organic material is dispersed in water that can be applied directly to bio-materials. Herein, we present the optimization study of capping molecules Trisodium citrate and 3-mercaptopropionic acid (3-MPA) on silver nanoparticles (AgNP) by used of modified chemical reduction and exchange ligand methods to form stable AgNP. The optimization of AgNP was done by varying the ratio among the concentration of the precursor (AgNO3), reducing agent and capping materials. Our colloidal AgNP products show bright yellow to yellow-brownish colour with the plasmonic peak for citrate capped AgNP (Ag-Citrate) at 410-424 nm, 3-MPA capped AgNP (Ag-MPA) by direct method at 428-440 nm, and 3-MPA capped AgNP (Ag-MPA) by ligand exchange method at 436-462 nm. The chemical characteristics of our Ag-citrate and Ag-MPA show the differences coordination of COO- between free citrate or 3-MPA and after citrate or 3-MPA capped on Ag. In our experiment, the TEM images for both samples of AgNPs show the spherical shape with the range of diameter size 5-38 nm which depends on the given ratio of material concentration in the synthesis process. Our AgNP solution results with the open capping of citrate or 3-MPA then can be applied as probe sensor for plasmonic sensor application.