%0 Journal Article
%T Electroless Deposited Gold Nanoparticles on Glass Plates as Sensors for Measuring the Dielectric Constant of Solutions
%A Y. Kobayashi
%A Y. Ishii
%J Journal of Nanoparticles
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/841582
%X This work describes a method for the deposition of Au nanoparticles on glass plates (Au-glass). An electroless metal plating technique was extended to the Au nanoparticle deposition. The technique consisted of three steps that took place on the glass plate: (1) adsorption of Sn2+ ions, (2) deposition of metallic Ag nuclei generated by reducing Ag+ ions with Sn2+ ions on the Sn-adsorbed sites, and (3) deposition of Au nanoparticles by reducing Au+ ions on the Ag surface. TEM observation revealed that metallic Au nanoparticles with a size of £¿nm were formed on the glass surface. A surface plasmon resonance absorption peak was observed, and its peak wavelength redshifted by immersing the Au-glass into a solution with a large dielectric constant. The redshift corresponded qualitatively to the calculation by the Mie theory accompanying the Drude expression, which was based on the change of the dielectric constant of the solution. The obtained results indicated that the Au-glass functioned as a sensor for measuring the dielectric constant of the solution. 1. Introduction Nanometer-sized particles have special interest because they are expected to exhibit unique properties different from those of bulk material [1, 2], which is called ¡°size effect.¡± Among various nanoparticles, nanoparticles of metals such as Au and Ag show a special optical property like surface plasmon resonance (SPR) absorption, which depends on particle size and particle shape [1, 3, 4]. Since the SPR absorption is also dependent on environment around the particles such as dielectric constant [1, 3, 4], this dependence can be used to measure dielectric constants of materials [3, 4]. Nanoparticles tend to aggregate, which deteriorates their unique properties derived from the size effect. Immobilizing the nanoparticles on supports such as powders and plates is a candidate to prevent the aggregation. Recently, there have been some reports on deposition of metal nanoparticles on submicron-sized particles [5¨C8]. Frequently, the deposition techniques involve simple mixing of a metal nanoparticle colloid solution and a suspension of submicron-sized spheres [6, 9, 10]. In this technique, however, aggregation of the nanoparticles during the deposition cannot be negligible, and it is necessary to remove excess undeposited nanoparticles out of the suspension. An electroless metal plating technique can make metallic films plated on insulating support materials [11¨C13]. In our previous work, Au nanoparticles were successfully deposited on silica spheres by the technique [14]. The technique consists of
%U http://www.hindawi.com/journals/jnp/2013/841582/