Synthesis of new silicas with high stable and large mesopores and macropores for biocatalysis applications (original) (raw)
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Synthesis of mesoporous silica particles with controlled pore structure
Ceramics International, 2009
Silica particles, with controllable porosity, were synthesized using two different precursors, tetraethylortosilicate (TEOS) and sodium silicate, but without the addition of template. Characteristics of silica particles (aggregates) prepared by these two methods were compared. The pore structure was tuned only by changing the processing parameters, such as precursor concentration, base concentration, temperature and reaction time. The pore structure of prepared silica particles (aggregates) is strongly influenced by processing conditions and easy controllable in broad range of the specific surface area, pore size, size distribution and pore volume. However, the silica particles synthesized from TEOS have very low total pore volume (ranging from 0.06 to 0.2 cm 3 /g) and a large portion of pores smaller than 4 nm. On the other side, the silica particles prepared from sodium silicate can be defined as a mesoporous silica with the average pore size up to $20 nm and much higher total pore volume (ranging from 0.8 to 1.5 cm 3 /g), which are important advantages for their application in encapsulation of enzymes.
One-pot synthesis of bimodal (macro-meso, micro-mesoporous) silica by polyHIPE: parameter studies
Journal of Porous Materials, 2019
Porous silica with hierarchical organization of pore structure is desired for a variety of applications such as, chromatography, sensing, control release, scaffold for biomedical applications and catalysis. Highly porous polymers obtained from high internal phase emulsion (HIPE) templating route have attracted increasing attention of researchers due to their hierarchical porous and interconnected structure with high porosity and low density. The novel method adopted in our approach combines redox initiated polymerization using HIPE polymerization and an in-situ sol-gel processing technique followed by calcination to obtain highly porous materials. The obtained materials have reminiscent of polyHIPE morphology containing pores and interconnected pore throats in micrometer size range with mesopores on the wall of macropores. The effect of concentration of TEOS, volume of dispersed phase, crosslinker concentration, shear rate and surfactant concentration as well as variation in calcination temperatures on the properties of silica materials were examined.
Engineering of efficient biocatalysts using nanostructured mesoporous silicate carriers
2008
Comparative studies of the biocatalysts with invertase immobilized on three nanostructured silicate carriers: mesoporous cellular foams and two types of SBA-15 materials using three highly recommended protein bonding methods are reported. Invertase was attached to the surface by: physical adsorption followed by its crosslinking, adsorption on aminated MS followed by its crosslinking, and covalent bonding with aminated MS via GLA spacer. Experiments clearly indicate that activity of the aminated MCF-based biocatalysts is significantly higher than of both SBA-15-based counterparts. The microenvironment of proteins and porous texture of supports appear the most important factors for enzyme activity expression, and in this respect the unique properties of aminated MCFs can hardly be matched.
2011
During last years the interest for nanotechnology and mesoporous silica materials has increased due to benefits that these materials can provide. Typical characteristics of mesoporous materials are a large surface area and pore volume, well-ordered and uniform pores with adjustable pores between 2 and 50 nm. Pore dimensions are comparable to many biological molecules, like enzymes, and may therefore be suitable as a support in enzyme encapsulation The aim of this project was to synthesize mesoporous particles with a fixed pore size in order to optimize enzyme encapsulation. The specific pore size was determined based on previous studies on encapsulated lipase from mucor miehei where the optimal pore size was found to be 9 nm. Through this project different synthesis has been studied, different types of surfactants have been used (Pluronic 123, CTAB) as well as different types of silica sources such as TEOS or sodium silicate solutions. The synthesis conditions have been varied in or...
Australian Journal of Chemistry, 2014
Phenylalanine ammonia lyase (PAL, E.C.4.3.1.24), was entrapped in ultra-large-pore mesoporous silica (ULPS, 23 nm pore diameter) generating a recyclable, separable biocatalyst. The entrapped ULPS-PAL materials showed excellent stabilization, even after significant exposure to prolonged heating. Additionally, the entrapped ULPS-PAL materials showed extremely high catalytic activity in the deamination of l-phenylalanine to trans-cinnamic acid in aqueous solution and were recovered and recycled up to five times without any observable loss in activity. This approach is simple and capitalizes on the facile synthesis and easy recoverability of mesoporous silicas to generate a stable, reusable PAL-based biocatalyst.
Enzyme-functionalized mesoporous silica for bioanalytical applications
Analytical and Bioanalytical Chemistry, 2009
The unique properties of mesoporous silica materials (MPs) have attracted substantial interest for use as enzyme-immobilization matrices. These features include high surface area, chemical, thermal, and mechanical stability, highly uniform pore distribution and tunable pore size, high adsorption capacity, and an ordered porous network for free diffusion of substrates and reaction products. Research demonstrated that enzymes encapsulated or entrapped in MPs retain their biocatalytic activity and are more stable than enzymes in solution. This review discusses recent advances in the study and use of mesoporous silica for enzyme immobilization and application in biosensor technology. Different types of MPs, their morphological and structural characteristics, and strategies used for their functionalization with enzymes are discussed. Finally, prospective and potential benefits of these materials for bioanalytical applications and biosensor technology are also presented. Figure Enzyme-functionalized mesoporous silica fibers and their integration in a biosensor design. The immobilization process takes place essentially in the silica micropores.
Incorporation of chemical functionalities in the framework of mesoporous silica
Chem. Commun …, 2011
Mesoporous silica, which shows well-defined pore systems, tunable pore diameters (2-30 nm), narrow pore size distributions and high surface areas (4600 m 2 g À1 ), is frequently modified using different methodologies (including in situ and post-synthetic strategies) to introduce various chemical functionalities useful in applications like catalysis, separation, drug delivery, and sensing. This contribution aims to provide a critical overview of the various strategies to incorporate chemical functionalities in mesoporous silica highlighting the advantages of the in situ methods based on the bottom-up construction of mesoporous silica containing various chemical functionalities in its structure.
Hierarchical meso-macroporous silica
Hierarchical meso-macroporous silica (average mesopore diameter 20 nm) was synthesized and chemically modified to be used as a support for the immobilization of lipases from Candida antarctica B and Alcaligenes sp. and b-galactosidases from Bacillus circulans and Aspergillus oryzae. Catalytic activities and thermal stabilities of enzymes immobilized by multipoint covalent attachment in silica derivatized with glyoxyl groups were compared with those immobilized in glyoxyl-agarose, assessing biocatalyst performance under non-reactive conditions in aqueous medium. In the case of A. oryzae bgalactosidase and Alcaligenes sp. lipase, an additional step of amination was needed to improve immobilization yield. Specific activities of lipases immobilized in glyoxyl-silica were high (232 and 62 IU per gram, for C. antarctica B and Alcaligenes sp. respectively); thermal stabilities were higher than those immobilized in glyoxyl-agarose. Although in the case of b-galactosidases from B. circulans and A. oryzae, the specific activities (250 and 310 IU per gram, respectively) were lower than the ones obtained with glyoxyl-agarose, expressed activities were similar to values previously reported. Thermal stabilities of both b-galactosidases immobilized in glyoxyl-silica were higher than when glyoxyl-agarose was used as support. Results indicate that hierarchical meso-macroporous silica is a versatile support for the production of robust biocatalysts.
Synthesis of pore-enlarged mesoporous organosilicas under basic conditions
Microporous and Mesoporous Materials, 2004
A series of mesoporous organosilicas (MOs) in the ½3:2; 11:1 nm pore diameter range has been obtained in basic media by using 1,2-bis(triethoxysilyl)ethane (BTEE) or 1,2-bis(trimethoxysilyl)ethane (BTME) as a silica source, binary surfactant mixtures [CH 3 (CH 2 ) 17 NMe 2 (CH 2 ) 3 NMe 3 ] 2þ 2Br À (C 18-3-1 ) and [CH 3 (CH 2 ) 15 NMe 3 ] þ Br À (C 16 TABr) as structure-directing agents (SDAs), and TMB (mesitylene) or TPB (1,3,5-triisopropylbenzene) as swelling agents. Pore size control has been achieved via variation of (i) the binary surfactant ratio, (ii) base (sodium hydroxide) concentration, (iii) reaction time and temperature, and (iv) type of expander molecule. The surface morphology and silanol population of the dehydrated MOs was examined by TMDS (tetramethyldisilazane) silylation. The parent and functionalized MOs were characterized by powder X-ray diffraction, N 2 physisorption, elemental analysis, FTIR, and solid-state ( 1 H, 13 C, 29 Si) NMR spectroscopy. According to their PXRD patterns, the pore-enlarged MO materials do not display any long-range order, however, pore volumes >2 cm 3 /g. The type of hysteresis loop exhibited by the N 2 adsorption and desorption isotherm changed remarkably for MOs synthesized at low concentrations of divalent surfactant as well as base, which can be attributed to a change of pore topology. 29 Si MAS NMR spectroscopy revealed the prominent T 2 and T 3 peaks at )58and)58 and )58and)64 ppm, respectively, indicative of an intact wall and surface structure. The silyl group coverage was determined as 0.8-1.3 SiHMe 2 groups per nm 2 corresponding to approximately half of that found on purely siliceous periodic mesoporous silicas such as MCM-41 or MCM-48.