Silver-nanoparticle dispersion from the consolidation of Ag-attached silica colloid
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Jong Soon Kim Nanux Inc., Kimhae, Kyungnam, 621-881, Korea
Byungwoo Parka) School of Materials Science and Engineering, Seoul National University, Seoul 151-744, Korea (Received 4 October 2003; accepted 16 January 2004)
Silver nanoparticles dispersed in a silica matrix were made by the consolidation of a Ag-attached silica colloid, which was synthesized via the electrolysis of a pure Ag electrode, the reduction of Ag+ ions by H2, and the nucleation and growth of Ag particles on the silica nanoparticles in water. This simple process produced Ag/silica nanocomposites with a high concentration and narrow size distribution of nanoparticles, which was confirmed by transmission electron microscopy and x-ray diffraction. As estimated by Raman and photoluminescence measurements, the quantity of broken oxygen bonds was increased with increasing Ag concentration due to the intervention of Ag ions as structural modifiers in the silica network structure. Ag ions in the matrix are probably a residue of the Ag+ ions that could not be reduced by H2 during the electrolysis/reduction reaction. The optical-absorption spectra and the HCl-soaking test suggested that a chemical-interface damping effect, which was caused by electron transfer from the metal particles to the oxide matrix, dominates the optical-absorption properties in this system.
I. INTRODUCTION
Metallic nanoparticles dispersed in a dielectric matrix have attracted a great deal of attention as materials for nonlinear photonic devices because of their unique property of the enhanced third-order optical susceptibility at the visible band.1–6 This property depends on the chemistry and the microstructures of the metallic particles as well as their size, shape, and size distribution.5–8 Several methods, such as ion-exchange, multitarget sputtering, ion implantation, sol-gel, and so forth, have been used to control the chemical and structural factors effectively.1–10 Despite some notable properties, these processes have a few limitations. These include low nanocluster concentrations, difficulties in mass production, a large amount of carbon contamination, and so forth. A new simple method was developed to improve these shortcomings by the consolidation of Ag-attached silica (a-SiO2) colloid. High metallic-nanoparticle concentrations up to approximately 6 vol% (10.5 wt%), compared to the range of 10−6 to 10−3 vol% obtained using other a)
Address all correspondence to these authors. e-mail: [email protected]; [email protected] DOI: 10.1557/JMR.2004.0187 1400
http://journals.cambridge.org
J. Mater. Res., Vol. 19, No. 5, May 2004 Downloaded: 17 Oct 2014
conventional methods,4 were attained through this process. In addition, this method is suitable for massive/ inexpensive and carbon/toxic-free production due to the simple electrochemical process and the least additives. Moreover, complexly shaped systems can be produced through the ceramic colloidal processing technology, such as tape casting, robocasting, slip casting, and so forth.11 By varying the Ag concentration, th
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