Study of spectral extinction cross section for silver nanospheres with and without coating

DANIEL C. SCHINCA; LUCÍA B. SCAFFARDI; JORGE O. TOCHO

Campinas-SP, BRAZIL

Congreso; Iberoamerican Conference on Optics (VI RIAO) and Latinamerican meeting on Optics, Lasers and Applications (IX OPTILAS); 2007

UNICAMP, BRAZIL

The study of optical properties of metallic nanoparticles has become an active research area due to the increasing development of applications of nanostructured materials to different areas such as biology, sensors industries, pharmaceutical and others. Silver nanoparticles are especially attractive due to its narrow plasmon resonance peak for potential use in low-loss optical nanodevices. Silver nanoparticles used in this work were obtained from chemical reduction of  AgNO3  in ethanol, using an aminosilane with different amino groups in alcohol solution as catalyst and a colloidal suspension as stabilizer for size control. The aminosilanes are used as surface modifiers to help avoid agglutination.  An optimal behavior was found for a ratio AgNO3: aminosilane of 1:3-5.  This work shows a comparison between theoretically calculated extinction cross sections for silver nanospheres with and without aminosilane coating. Besides, the influence of different environments on the localization and FWHM of the plasmon resonance is analyzed.            The Mie calculations used in this work include a size-dependent modification of the dielectric function to account for the reduced mean free path of the electrons produced by collisions with particle boundary for radii below 10 nm.  This modification is applied to the damping constant that includes now a term that depend inversely with the particle radius.