Formation and Reaction of Metal-containing Nanoparticles in Organic/Inorganic Hybrid Aerogels
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EE5.10.1
Formation and Reaction of Metal-containing Nanoparticles in Organic/Inorganic Hybrid Aerogels Chunhua Yao and William M. Risen, Jr. Department of Chemistry, Brown University Providence, RI 02912, U.S.A ABSTRACT Synthesis of hybrid aerogel materials that contain both selectively reactive nanoparticles and nanoparticles with appreciable magnetic susceptibilities will be reported. This has been achieved by a two stages process. First silica-bioderived polymer hybrid aerogels with incorporated metal ions were synthesized and then reduced by photolytically induced chemical reductions or decompositions. For example, silica-chitosan hybrid gels were prepared, Au(III) ions were coordinated to the chitosan, and, after forming the Au(III)-silica-chitosan aerogel by SCL extraction, UV photolysis afforded gold nanoparticles of controlled size in the aerogel . Second, an iron-containing organometallic compound, such as iron carbonyl itself, was absorbed into the aerogel, and then heating or photolysis afforded reduced metal decomposition products. Ferromagnetic organic/inorganic hybrid products containing Au(0) nanoparticles were obtained. Their size (TEM), crystallographic, optical and magnetic properties are discussed. Reactions of thiol compound with the metal nanoparticles in the aerogels were studied. INTRODUCTION There are a number of potential applications, especially in medicine, for small particles that are ferromagnetic and that interact in a selective manner with biologically active molecules. A particular one involves binding a molecule of interest in the blood system to the particles and then separating these particles from the blood by magnetic separation. One approach is to form magnetic particles, coat them in a biocompatible coating and then derivatize the outer surface so that they will bind to the molecule of interest [1,2]. Another application involves enhancement of magnetic resonance images (MRI) in diagnosis, while another involves selectively locating treatment agents, whether chemical or radiological, in particular areas to be treated. As promising as the leading work has been, challenges remain. Some are associated with the size of nanoparticles and attendant issues, such as their removal and their potential deleterious transport in mammalian systems. Others have to do with the instability, indeed combustibility, of nanoscale metal particles in air, and their tendency to clump together. In the present research, another potentially useful approach has been explored. The idea is to combine (1) the generalized absorption capacity of silica-based aerogel with (2) the specific adsorption capability of gold nanoparticles and (3) the potential for growing well-dispersed ferromagnetic particles in the aerogel particles. The aerogel particles can be of any size from the 100nm range up to larger monolithic structures. In previous work [3-7], we have shown that silica-bioderived polymer aerogel, especially chitosan-silica, or X-SiO2, can be produced with high porosity and BET surface areas in the 5001100
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