284091 Surfactant Imprinting of Stӧber Silica Particles for Application in Saccharide and Chiral Separations
Synthesis of monodisperse silica particles by precipitation from an ethanol/water ammonia solution was reported by Stӧber nearly four decades ago. The particles are easy to synthesize and readily tunable in the submicron particle size range, which has led to many application based on modifications of the synthesis. Here we report the synthesis and characterization of Stӧber particles imprinted at their surface with n-octyl-β-D-glucopyranoside (C8G1), with the aim of creating selective adsorption sites for separation of D-glucose. The strategy is to add the surfactant shortly after the precipitation of the silica nanoparticles so that the silicates are still in a liquid-like state but the surfactants are not incorporated inside of the particles to generate mesopores. Particles have been synthesized with various ratios of C8G1 and cetyltrimethylammonium bromide (CTAB) to find the most suitable surfactant combination for enhanced selective adsorption. Selectivity of the material has been demonstrated for separation of glucose and xylose. Chiral separation of D-glucose from L-glucose will also be discussed.
The synthesized particles are characterized using nitrogen adsorption, scanning electron microscopy and dynamic light scattering analysis to determine their size and the absence of mesopores. Attenuated total reflection Fourier transform infrared spectroscopy and high-performance liquid chromatography will be used to analyze adsorption of sugars through a series of depletion measurements. Adsorption isotherms will be presented for saccharides and the data will be modeled based on one- and two-site Langmuir adsorption models. Large increases in affinity and selectivity are demonstrated to be possible by this approach. For instance, imprinting Stӧber particles with a 1:1 mixture of C8G1 and CTAB leads to an enhancement in binding affinity towards D-glucose of 49 and a selectivity for D-glucose over D-xylose of over 70 based on the single-component adsorption parameters.