Optimization of Organic Capping Material on Silver Nanoparticles by Chemical Reduction and It Functionalization for Plasmonic Sensor Application Qoid Abrori Syakuro, Yoda Taruna, Setiya Rahayu, Herman, Priastuti Wulandari
Physics of Magnetism and Photonics Research Division,
Faculty of Mathematics and Natural Sciences,
Institut Teknologi Bandung, Jl. Ganesha No. 10 Bandung
40132, West Java, Indonesia.
*pwulandari[at]itb.ac.id
Abstract
The application of metal nanoparticles related to the nanotechnology in medicine and optoelectronic devices have shown remarkable results. It has been known that metal nanoparticles such as gold and silver show unique optical properties called localized surface placement resonance (LSPR). LSPR is an effect that corresponds to the interaction between electromagnetic wave and the conductive matter of the metal nanoparticles. This interaction generates coherent localized plasmon oscillations with frequency that depends on the size and shape of the nanoparticle. In general, metal nanoparticles need capping material in order to prevent metal core from aggregation and also to provide surface passivation. In the application of biosensor, organic material such as thiol-derivatives and citrate are often used because of its high affinity with gold and silver, LSPR enhancement effect, and the ability to link biomolecule for biosensor application.
Herein, we present the optimization study of organic capping molecules on silver nanoparticles (AgNP) by used of modified chemical reduction method to form stable AgNP with homogenous in size and shape. In our case, we modified the capping materials of AgNP by used of trisodium citrate and 3-mercaptopropionic acid (3-MPA) which both solved in water and they are easy to functionalize with biomaterial for application in plasmonic sensor. The optimization of AgNP was done by varying the ratio among the concentration of the precursor (AgNO3), reducing agent and capping materials. We investigated the optical characteristic of the AgNP by UV-Vis spectroscopy and its chemical characteristic through FTIR spectroscopy, while the morphology of AgNP was captured by TEM. Our AgNP products show bright yellow to dark brown color of solution with the plasmonic absorbance peak for citrate capped AgNP (Ag-Citrate) at 410-424 nm and 3-MPA capped AgNP (Ag-MPA) at 428-440 nm. FTIR spectra show the difference shift of COO- bond for Ag-Citrate and Ag-MPA. The TEM images for both samples of AgNP show the spherical shape with the range of diameter size 5-38 nm which depend on the given ratio of material concentration in the synthesis process.
