Fabrication and Plasmonic Properties of Silica Coated Au Nanorods

L.A. PÉREZ; G. I. LACCONI; E. A. CORONADO

Valparaiso, Chile

Simposio; SOLIDOS 2009; 2009

Paper # 92 Fabrcation and Plasmonic Properties of Silica Coated Au Nanorods L. A. Pérez, G. I . Lacconi and E. A. Coronado INFIQC, CLCM, Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba (5000), Argentina. email address: coronado@fcq.unc.edu.ar The design of simple and general synthetic strategies to coat as synthesized nanoparticles such that their surfaces can be easily modified would assist in translating promising new nanoparticles into new applications. Such interfacial coating are usually synthesized as a continuation of the nanoparticle fabrication process, using a synthetic route that is often nanoparticle or laboratory specific, and not easily transferable between materials, structures, and applications. For maximum adaptability, the ideal common platform coating should be potentially multifunctional, allowing both a surface for simple conjugation to target molecules and the ability to adjust its morphology to control the degree to which the encapsulated nanoparticle interacts with its surrounding environment. Silica is an excellent candidate for such a generalized platform coating as it is an extensively studied biomaterial with a surface that can be chemically modified with other ligands for conjugation to molecular targets. In this work, we report a simple strategy for the production of core-shell structures Au nanorods (NRs) coated with a silica shell using a single step synthetic strategy. Gold nanorods of different aspect ratios were prepared using the seed mediated growth method [1]. Then they were centrifuged twice in order to obtain Au NRs stabilized with cetyltrimethyl ammonium bromide (CTAB) without these surfactant molecules in the solution. Then different amounts of tethaethyl ortosilicate (TEOS) were added to the solution producing gold NRs coated with an spheroid silica shell, as shown on the TEM images (Figure 1). The surface plasmon resonances associated with the transverse and longitudinal surface plasmons experience a red and a blue shift respectively compared with the CTAB stabilized Au NRs, indicating a change in the dielectric properties of the surface coating. If we added TEOS to the Au NRs solution without centrifugation, a mesoporous silica shell is produced, indicating the importance role of the surfactant concentration on the quality of the silica coating, as it has been performed in recent work [2]. R e f e r e n c e s [1] I. Gorelikov and N. Matsuura, Nano Lett. 8, 369 (2008). [2] C. Wu and Q,, Xu Langmuir 25, 9441 (2009)