Study On Preparation And Application Of Vesiclular Mesoporous Silica

Vesiclular mesoporous silica with well-defined multilamellar structure have been prepared at mild conditions, through a dual-templating way by using didodecyldimethylammonium bromide(DDAB)/cetyltrimethylammonium bromide (CTAB) as structure directing agent and tetraethylorthosilicate (TEOS) as silica source. By changing the molar ratio of CTAB and DDAB, a transformation from the mesoporous spheroid with wormlike porous obtained at1:0.312to multilamellar vesicles (1:0.6251:1.104) with controllable wall thickness. When the molar ratio changed from1:0.625to1:0.832, the number of layers of vesicular silica decreased from7to4, and the size of inner hollow space increased34times. When molar ratios raised to1:1.104, not only result in the number of layers reduced to2, the space between layers and the thick of layers meanwhile increased. Furthermore, the multilamellar vesicular structure is very stable even after being calcined, which demonstrated a good selective adsorption capacity for effectively load drug molecules for deliver. The MH loading capacity was measured to be as high as54.1wt%, and the loaded MH could continue to gently release in vitro study. The silicon vesicles with controlled number of layers, hierarchical porosity, and interconnected sponge-like walls are promising candidates for applications in nanoreactors, selective sorption, and controlled release.We take advantage of inorganic salts of sodium fluoride to induced non-ionic-anionic surfactant vesicle-like template formed in aqueous solution. Vesicle-like silica mesoporous materials (MVS0.1，MVS0.2)were synthesized by hydrolysis and condensation of the silicon source under two defferent concentration of sodium fluoride. SEM and TEM images show that the size of these vesicles are between100300nm, thickness of multilayer structure is about5.5nm, layer spacing is about46nm. SAXRD and N2adsorption–desorption isotherms indicates that the vesicular silica possesses long range framework order and a stable structure, MVS0.1，MVS0.2modified materials with357cm3g-1and483cm3g-1of huge specific surface area, respectively. Compared to the free enzyme, immobilized enzyme shows better adaptability to the environment, the higher catalytic activity, and good repeated utilization. The optimum reaction temperature increased from40°C to50°C, the highest activity from510U/g to640U/g, the activity of reused after5times keep increase from49.8%to55%of immobilized CRL of MVS-0.2compared with MVS0.1immobilized CRL. Resolution of racemic ibuprofen was achieved by esterification catalyzed from immobilized enzyme. HPLC analysis of the data obtained, enzyme immobilized in vesicle-like mesoporous silica can improve the enantiomeric excess(ee) and enantiomeric ratio(E) to48%and96%when the phosphate buffer (pH7.0) solution is0.5%. Vesicle-like mesoporous silica immobilized enzyme catalytic resolution reaction has significant effect, indicating it has more potential applications in the enzymatic resolution reaction.