水热法合成介孔氧化硅材料的结构及表面特性

以十六烷基三甲基溴化氨 (CTMABr)为模板剂 ,利用碱性水热法制备了介孔氧化硅材料 ,并采用小角度XRD、HRTEM、BET和FT IR等测试手段研究了其孔的结构、表面N2 吸附特性和孔径分布情况。结果表明 :碱性水热法制得的介孔氧化硅材料具有规则的六方结构 ,介孔的最可几半径为 1 9mm ,比表面积为 5 42 8m2 / g ,孔容为 0 4 5 6cm3/ g。     

Pharmacological activity of ibuprofen released from mesoporous silica

Novel drug delivery systems (DDS) to improve the pharmacokinetic profile of hydrophobic drugs following oral administration are an area of keen interest in drug research. An ideal DDS should not adversely affect drug activity, be capable of delivering a therapeutic dose of drug, and allow homogenous drug loading and drug release. Mesoporous silica has been proposed for this application, with ibuprofen employed as the model drug. It was hypothesised that mesoporous silica MCM-41 is capable of delivering a pharmacologically therapeutic dose of ibuprofen. Ibuprofen-loaded MCM-41 can be prepared reproducibly at a drug to carrier ratio of 30% (wt/wt). The release profile was seen to be 90% within 2 h. Initial assessment of COX-1 inhibitory activity suggests the absence of adverse effects attributable to drug-carrier interaction. The results of this study provide further evidence in support of the proposed use of mesoporous silica in drug delivery.     

Catalytic properties of composite materials based on mesoporous silica and zirconium hydrogen phosphate

We have synthesized composite materials based on SBA-15 mesoporous silica and zirconium phosphate. The materials have been characterized by scanning electron microscopy, transmission electron microscopy, inductively coupled plasma mass spectrometry, X-ray diffraction, BET measurements, ³¹P NMR spectroscopy, and thermogravimetry, and have been employed as catalysts for ethanol dehydration. Even though their catalytic activity is somewhat lower than that of fine-particle zirconium phosphates with layered and framework structures, they offer an increased ethylene yield at low temperatures.     

Improving bioavailability of silybin by inclusion into SBA-15 mesoporous silica materials

Mesoporous silica SBA-15 (SC) and template occluded SBA-15 (SP) were used to increase the bioavailability of silybin, an extremely poorly water soluble drug. Silybin was introduced into SC and SP by assembling or self-assembling methods. The results of X-ray powder diffraction, differential scanning calorimetry (DSC) and N2 adsorption-desorption experiment indicated that amorphous silybin was successfully introduced into the mesopores in both SC and SP samples. The transmission electron micrograph (TEM) images revealed that the structure of the mesoporous materials was not destroyed after the drug loading. Results of dissolution rate tests and animal experiments showed that both SC and SP can significantly improve the bioavailability of silybin, SP was thus preferred because the template needs not to be removed by calcination or extraction.     

Electroactive response of mesoporous silica and its nanocomposites with conducting polymers

Electroactive response of suspensions of mesoporous silica and its nanocomposites with conducting polyaniline and copolyaniline inside its channels were examined under an electric field, mainly focusing on their rheological characteristics. Initially these conducting polymer/mesoporous silica nanocomposites were synthesized and their physical properties were studied by scanning electron microscopy, transmission electron microscopy and N₂-adsorption isotherm. Then, mesoporous silica and its nanocomposites were dispersed in silicone oil as an electrorheological (ER) material. Typical ER behaviors of shear stress and shear viscosity curves as a function of electric field and shear rate were observed. Without an electric field, the suspensions behaved almost like a Newtonian fluid. However, under an electric field, their shear stresses increased with shear rate, demonstrating a yield stress. Compared with mesoporous silica and polyaniline, polyaniline/mesoporous silica-based ER fluid showed enhanced ER performance due to the anisotropic characteristics. In addition, it was found that a suggested shear stress model (Cho–Choi–Jhon model) well described the flow curves.     

Immobilization of amphiphilic dendron on silica particles toward the application to ultrahigh pressure liquid chromatography

Amphiphilic poly(amido amine) (PAMAM) dendrons were immobilized on the surface of silica particles, following the solid phase strategy. PAMAM dendrons were constructed by the repetitive feeding of methyl acrylate and ethylenediamine as the monomers. The peripheral functionalization of amine to long alkyl ends generated the amphiphilic PAMAM dendron on the silica surface. These amphiphilic dendron-modified silica particles were applicable as new packing materials for ultrahigh pressure liquid chromatography.     

Self-assembly of nanohydroxyapatite in mesoporous silica

A novel material hexagonal mesoporous silica-hydroxyapatite (HMS-HA) has been developed based on self-assembly of nanohydroxyapatite in mesoporous silica in situ. The structural and textural properties of the materials are, respectively, characterized via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N(2) adsorption, thermogravimetic analysis, and high-resolution transmission electron spectroscopy (HRTEM). Variable crystallinity of HA involved in the mesopores yields from different sintering temperature, and correspondingly determines different degradation manners. This biocompatible new material hybridized nanoporosity to well acknowledge biofunctional scaffold (HA). It promises a high potential for application in drug and gene delivery.     

Simple synthesis of hierarchically ordered mesocellular mesoporous silica materials hosting crosslinked enzyme aggregates

Hierarchically ordered mesocellular mesoporous silica materials (HMMS) were synthesized using a single structure-directing agent. The mesocellular pores are synthesized without adding any pore expander; the pore walls are composed of SBA-15 type mesopores. Small-angle X-ray scattering revealed the presence of uniform pore structures with two different sizes. Using HMMS as a nanoscopic template, hierarchically ordered mesocellular mesoporous carbon (HMMC) and polymer (HMMP) materials were synthesized. HMMS was used as a host for enzyme immobilization. To improve the retention of enzymes in HMMS, we adsorbed enzymes, and then employed crosslinking using glutaraldehyde (GA). The resulting crosslinked enzyme aggregates (CLEAs) show an impressive stability with extremely high enzyme loadings. For example, 0.5 g alpha-chymotrypsin (CT) could be loaded in 1 g of silica with no activity decrease observed with rigorous shaking over one month. In contrast, adsorbed CT without GA treatment resulted in a lower loading, which further decreased due to continuous leaching of adsorbed CT under shaking. The activity of crosslinked CT aggregates in HMMS was approximately 10 times higher than that of the adsorbed CT, which represents a 74-fold increase in activity per unit weight of HMMS due to higher CT loading.     

Synthesis of mesoporous silica materials (MCM-41) from iron ore tailings

Highly ordered mesoporous materials were successfully synthesized by using the iron ore tailings as the silica source and n-hexadecyltrimethyl ammonium bromide as the template. The samples were detail characterized by powder X-ray diffraction, scanning electron microscope, high-resolution transmission electron microscopy and N₂ physisorption. The as-synthesized materials had high surface area of 527 m² g⁻¹ and the mean pore diameter of 2.65 nm with a well-ordered two-dimensional hexagonal structure. It is feasible to prepare mesoporous MCM-41 materials using the iron ore tailings as precursor.     

介孔SiO_2纳米微球的生物相容性研究进展

介孔SiO2纳米微球(MSNs)具有良好的理化性能,在疾病诊治方面具有广阔的应用前景,但若要成功应用于人体,需要完善其生物相容性研究。MSNs对于细胞的毒性与MSNs能否被摄取进入细胞,以及进入细胞的量有关,并取决于细胞的类型和MSNs本身的性状。通过一系列物理和化学方法的改进,可以明显改善MSNs的血液相容性,降低溶血作用。介孔SiO2纳米微球经静脉注射后分布于动物的肝脏、脾脏、肾脏、心脏、肠胃、肌肉和肺脏,其毒性作用与浓度有关;MSNs作为一种异物进入体内后可能会诱发机体产生一定程度的超敏反应。介孔SiO2纳米微球具有较好的生物相容性,但其采用何种方式应用仍需进一步研究。     

Recent advances in functionalization of mesoporous silica

Mesoporous silica with regular geometries have been recently paid much attention owing to their scientific importance and great potentials in practical applications such as catalysis, adsorption, separation, sensing, medical usage, ecology, and nanotechnology. Especially, applications often require immobilization of the related functional groups in the mesopores. In order to achieve desire applications, modification of these mesoporous silica are indispensable. In this review, recent progresses of functionalization of mesoporous silica are comprehensively summarized. In the first parts, advances in three major methods, grafting (post-synthetic modification), co-condensation (direct synthesis), and techniques related with periodic mesoporous organosilicates, are explained. In the latter parts, new concepts for functionalization of mesoporous silica including functional template method and lizard template method are introduced. Most of the examples described here have been published in a new millennium.     

Hybrid surfactant-templated mesoporous silica formed in ethanol and its application for heavy metal removal

With cetyltrimethylammonium (CTAB) and tetramethylammonium hydroxide (TMAOH) as hybrid surfactant templates, a mesoporous adsorbent (adsorbent C) was synthesized in ethanol via the integration of "One-step" procedure and "Evaporation-Induced Self-Assembly" procedure. During the synthesis, TMAOH served as the subsidiary structure-directing agent. Adsorbent C exhibited higher pore diameter (centered at 6.1 nm), BET surface area (421.9 m(2)/g) and pore volume (0.556 cm(3)/g) than the other two adsorbents only using P123 (adsorbent A) or CTAB (adsorbent B) as the surfactant. The adsorbents were also characterized by XRD and FTIR spectroscopy. The adsorption of copper, zinc, lead, iron, silver and manganese ions on adsorbent C was investigated by contrast tests with adsorbent A and B. The experimental data showed that adsorbent C possessed better adsorption properties than the counterparts. The order of adsorption capacity for six metal ions was Mn(2+)相似文献   

Highly basic CaO nanoparticles in mesoporous carbon materials and their excellent catalytic activity

Highly basic CaO nanoparticles immobilized mesoporous carbon materials (CaO-CMK-3) with different pore diameters have been successfully prepared by using wet-impregnation method. The prepared materials were subjected to extensive characterization studies using sophisticated techniques such as XRD, nitrogen adsorption, HRSEM-EDX, HRTEM and temperature programmed desorption of CO2 (TPD of CO2). The physico-chemical characterization results revealed that these materials possess highly dispersed CaO nanoparticles, excellent nanopores with well-ordered structure, high specific surface area, large specific pore volume, pore diameter and very high basicity. We have also demonstrated that the basicity of the CaO-CMK-3 samples can be controlled by simply varying the amount of CaO loading and pore diameter of the carbon support. The basic catalytic performance of the samples was investigated in the base-catalyzed transesterification of ethylacetoacetate by aryl, aliphatic and cyclic primary alcohols. CMK-3 catalyst with higher CaO loading and larger pore diameter was found to be highly active with higher conversion within a very short reaction time. The activity of 30% CaO-CMK3-150 catalyst for transesterification of ethylacetoacetate using different alcohols increases in the following order: octanol > butanol > cyclohexanol > benzyl alcohol > furfuryl alcohol.     

Synthesis of spheroidal ordered mesoporous carbon materials from silica/P123/butanol composites

Spheroidal ordered mesoporous carbon materials with diameter of 2–10 μm were synthesized by direct carbonization of silica/triblock copolymer P123/butanol composites using P123 and butanol as the structure-directing agents and carbon precursors. The morphologies, structures and pore characteristics of the carbon materials were investigated by scanning and transmission electron microscopes, X-ray diffraction, and nitrogen sorption. It was found that the material possesses a cubic ordered mesoporous structure with Ia3d symmetry. The butanol addition directly affects the carbon morphology and pore structure. When the mass ratio of butanol to P123 is 0.5:1, the product exhibits a perfectly spheroidal morphology with a specific surface area of 1236 m² g⁻¹ and a total pore volume of 1.26 cm³ g⁻¹. The formation mechanism of the spheroidal ordered mesoporous carbon materials is discussed briefly.     

In situ synthesis of ordered mesoporous silica materials embedded in cotton fiber and their CO2 capture properties

Mesoporous silica/cotton fiber composite materials have been prepared in situ by using pluronics P123 (EO20PO70EO20) as template, tetraethyl orthosilicate as silica source and degreasing cotton as supporter. In order to avoid the hydrolysis of cotton fiber in a strong acidic media during the hydrothermal treatment, two kinds of methods were used to control the acidity of the reaction media. One was to adjust the pH to 5 after self-assembly in a strong acidic media; the other was a two-step route containing the pre-hydrolysis of TEOS and self-assembly in a weak acidic media. The resulting shaped composite materials presented the morphology of cotton fiber, and the silica particles mainly covered the surfaces of cotton fibers. These silica particles possessed a slightly ordered pore structure or a well ordered SBA-15 structure according to the difference in the synthetic methods. After modification with tetraethylenepentamine, these shaped composite materials exhibited considerable CO2 adsorption capacity. The use of cotton fiber has the advantages of shaping the powdery materials, dispersing the silica particles and avoiding the formation of moisture and sticky solid surfaces by overloaded tetraethylenepentamine.     

Chemiluminescence immunoassay based on dual signal amplification strategy of Au/mesoporous silica and multienzyme functionalized mesoporous silica

A chemiluminescent dual signal amplification strategy for the determination of α-fetoprotein (AFP) was proposed based on a sandwich immunoassay format. Monoclonal antibody of AFP immobilized on the gold nanoparticles doped mesoporous SiO₂ (Au/SiO₂) were prepared and used as a primary antibody. Horseradish peroxidase (HRP) and HRP-labeled secondary antibody (Ab₂) co-immobilized into the mesoporous SiO₂ nanoparticles (HRP-Ab₂/SiO₂) were used as the labeled immunological probe. Due to the high ratio surface areas and pore volumes of the mesoporous SiO₂, not only the amount of AFP monoclonal antibody but also the amount of the modified HRP and Ab₂ in HRP-Ab₂/SiO₂ were largely increased. Thus the chemiluminescent signal was amplified by using the system of luminol and H₂O₂ under the catalysis of HRP. Under the optimal conditions, two linear ranges for AFP were obtained from 0.01 to 0.5 ng mL⁻¹ and 0.5 to 100 ng mL⁻¹ with a detection limit of 0.005 ng mL⁻¹ (3σ). The fabricated signal amplification strategy showed an excellent promise for sensitive detection of AFP and other tumor markers.