Synthesis Of Hierarchically Mesoporous Silica And Their Application In Enzyme Immobilization

Hierarchically porous silicas have showed good application in the immobilization of enzyme,due to its excellent physicochemical properties,high specific surface areas and pore volumes.The muti-sacle pore structure of hierarchically porous silicas endow them good immobilization efficiency and high catalyrtic property for enzyme immobilization.The large pore can provide enough space for the enzyme immobilization,whereas the small pore can act as the transmission channel of the reactant molecules.However,the synthesis of well-defined hierarchically porous silicas is still a challenge since the control of well-ordered mesostructure and well-defined morphology was difficult,because of the mixing of different types of templates in the syntheses.This dissertation is aimed at the synthesis of hierarchically porous silicas,the exploration of the synthetic machenism and the investigation of their application in enzyme immobilization.The main contents are as follows:(1)Synthesis of SBA-1 nanoparticles and their application in lysozyme immobilizationThe synthesis of mesoporous silica nanoparticles is achieved by employing organic mesomorphous complexes of polyelectrolyte(poly(acrylic acid))and cationic surfactant(hexadecyl pyridinium chloride)as template,and tetrapropoxysilane as silica source.It is found that the pore size of the synthesized mesoporous silica nanoparticles can be tuned by the incorporation of 1,3,5-trimethylbenzene.By adjusting the amount of 1,3,5-trimethylbenzene in the synthesis,a series of silica nanoparticles with controlled pore size ranging from 2.5 nm to 5.3 nm is obtained.The adsorption properties of the mesoporous silica nanoparticles with different pore size against lysozyme are compared.The results show that mesoporous silica nanoparticles with proper pore size and well ordered pore structure benefit the adsorption and exhibit a low leaching rate.(2)Synthesis of hierarchically nanoporous SBA-1 particles and their application in papain immobilizationHierarchically nanoporous silica SBA-1(HSBA-1)particles were successfully fabricated by employing organic mesomorphous complexes of poly(methyl vinyl ether-alt-maleic acid)(P(MVE-alt-MA))polyelectrolyte and cationic surfactant(hexadecyl pyridinium chloride(CPC))as templates.The synthesized HSBA-1 possessed ordered mesopore of 2.9 nm and nanopores of 27 nm with well-defined morphologies and well-ordered cubic Pm(?)n mesostructure.The application of HSBA-1 as a scaffold for papain immobilization was studied.It was found that ascribed to the hierarchical pore structure the adsorption equilibrium time was low(2 h)and the optimum adsorption pH value was 8.5.The activity of the immobilized papain was examined.Compared with free enzyme,the immobilized papain showed improved thermastability and pH stability.(3)Synthesis of hollow mesoporous silica microspheresA facile and effective route has been developed for synthesis of hollow mesoporous silica microspheres(HMSM)by employing the functional core-shell polymeric microspheres of polystyrene-co-poly(N-(4-vinylbenzyl)-N,N-diethylamine hydrochloride)(PS-co-PVEAH)as template and tetraethoxysilane as silica source in the presence of cetyltrimethylammonium bromide(CTAB).Due to the inherently pendent catalyst of the Lewis alkaline of PVEAH segment on the template surface of the PS-co-PVEAH core-shell microspheres,the sol-gel process of TEOS is directed exclusively onto the template avoiding the formation of unwanted and irregular aggregates and therefore well-defined HMSM are fabricated.The products are characterized by various techniques including Transmission Electron Microscopy(TEM),Fourier Transform Infrared(FTIR)and Nitrogen Adsorption-Desorption Analysis.The results demonstrate that HMSM with size ranging from 256 nm to 148 nm and shell thickness of 9 nm to 16 nm can be controlled synthesized.The obtained HMSMs are anticipated to be good candidates for biomedical application such as enzyme immobilization,nano-drug delivery system and protein separation,etc.