Synthesis of colloidal silver particles with different sizes by seeding approach for surface enhanced raman scattering (SERS) studies

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Arts and Sciences, Department of Chemistry, Turkey

Approval Date: 2009




In this study, silver nanorods and nanospheroids were prepared both in aqueous solution and on the surface of glass slides through seed-mediated growth approach at room temperature and used as a surface enhanced Raman scattering (SERS) substrate. The synthesis of metallic nanorods was started with the production of silver nanospheres as seed utilizing sodium borohydride and trisodium citrate as reducing and capping agents, respectively. These seeds were then added to a growth solution containing additional silver salt, ascorbic acid and cetyltrimethylammonium bromide (CTAB.) Nanorod preparation conditions were first optimized in solution phase. The plasmon absorption of the formed nanocrystals was monitored by UV-Visible spectrometry. The largest red shift in the longitudinal plasmon resonance absorption of silver nanostructures was tried to be achieved in order to realize the highest electromagnetic enhancement in Raman measurements. The images of the formed nanorods were recorded using field emission scanning electron microscopy (FE-SEM). The optimized colloidal growth conditions were adopted for the growth of nanorods on the surface of the glass substrate. Sol-gel coated glass slides were used in order to increase the porosity on the surface for an effective seeding process. We reported the development of a novel SERS substrate prepared by growing silver nanorods directly on the surface of glass surface without using any linker molecule. The SERS performances of the nanorod growth surfaces were evaluated with crystal violet (CV), brilliant cresyl blue (BCB) and benzoic acid (BA). Some modifications such as the increase in the AgNO3 concentration in the growth solution and the addition of hydrocarbons to the growth solution were investigated for the enhancement of the SERS signal. The intense spectra obtained for the model compounds demonstrated the efficiency of the prepared substrate for the SERS enhancement and its potential as a SERS detection probe for chemical and biological analysis.