| Within the field of biomolecule analysis, research in separation techniques is immeasurable. The increasingly complex samples, particularly in proteomics, demands higher speed than is offered by currently available techniques. I have investigated silica colloidal crystals as a new medium for bioanalytical separations. Monodisperse silica colloids can be synthesized by the Stober process [1] and assembled into crystalline structures [2]. High packing density, increased surface/volume ratio, optical diffraction and narrow photonic band gaps are potentially useful characteristics of the long-range ordering of silica colloids in the structure of colloidal crystals [3, 4]. Silica colloidal crystals developed in this study were used in a wide variety of bioanalytical techniques including no-flow electrochromatography, sieving elecrophoresis, isoelectric focusing, and microarray analysis. The steps taken to develop the material, and its potential applications will be discussed further. The resulting material is robust for practical analytical applications, uniform in pore size to produce high efficiency, and chemically active for surface modification.; Silica colloidal crystals made from the previous methods owe their limitations for practical analytical use to the formation of cracks after crystallization, are extremely fragile, and can come apart easily in aqueous solutions. The full potential for practical applications of silica colloidal crystals can be realized upon sufficient hardening to withstand sonication for at least 3 h. The steps needed to prepare the material include calcination at 350°C, 450°C, 550°C in succession before self-assembly to avoid cracks, while sintering at 1000°C after crystallization increases stability. Rehydroxylation of the silica surface is performed because the surface becomes dehydroxylated almost to completion during sintering. A base additive is used for rehydroxylation because it catalyzes the hydrolysis of the Si-O-Si siloxane bridge sites to form silanol groups. This approach for making silica colloidal crystals results in long-range ordering, homogeneous pore size, free of cracks, sufficiently robust for handling, and chemically reactive surface, therefore, it is expected to advance such fields as photonic crystals, micro-fluidics, microarray, electrochromatography and electrophoresis. |
