With well bioactive and nontoxic, hydroxyapatite (HAp) was employed to seal the nanopores of mesoporous silica (MCM-41) to realize the pH-responsive controlled release. First, MCM-41 was modified with cationic polymer, poly-(diallyldimethylammoniumchloride) (PA). And after the addition of Ca2+/PO43?, HAp precipitation can take place based on the cationic sites derived from PA. It is a simple and effective way to obtain HAp coating MCM-41 system (MHAs). The structure of the system was characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, N2 adsorption–desorption and so on. Metformin hydrochloride was used as the model drug, and the drug release performance and the release kinetics of the system were investigated in detail. Because of the degradation of HAp under acid condition, the drug loading MHAs showed a well pH-sensitive controlled release behavior. From above investigation, MHAs is a promising platform to construct a pH-responsive controlled drug delivery system, especially for some low pH tissues, such as inflammatory and tumor. 相似文献
A novel mesoporous silica tubes (MMT) which possessed pH-sensitive controlled release ability had been fabricated and synthesized by using carbon nanotubes (CNTs) as template. The sample replicated the morphologies of the CNTs successfully. The Brunauer–Emmett–Teller surface area of the materials can reach 1,017 m2 g?1 with the pore size of 3.8 nm. As a model drug, metformin HCl was applied to study the drug loading and control release ability of the materials. MMT possesses higher drug loading ratio (36 %) than that of MCM-41 (27.5 %). The release kinetics were studied in simulated gastric fluid (pH = 1.2) and in simulated proximal intestine fluid (pH = 7. 4), respectively. The result shows that the delivery systems exhibit well pH-sensitive control release ability and the as-synthesized materials have potential application in biomedical field. 相似文献
Molecular sieves MCM-41 were synthesized from rice husk ash (RHA) as alternative sources of silica, called RHA MCM-41. The material was synthesized by a hydrothermal method from a gel with the molar composition 1.00 CTMABr:4.00 SiO2:1.00 Na2O:200.00 H2O at 100 °C for 120 h with pH correction. The cetyltrimethylammonium bromide (CTMABr) was used as a structure template. The material was characterized by X-ray powder diffraction, FTIR, TG/DTG, and surface area determination by the BET method. The kinetics models proposed by Ozawa, Flynn–Wall, and Vyazovkin were used to determine the apparent activation energy for CTMA+ species decomposition from the pores of MCM-41 material. The results were compared with those obtained from the MCM-41 synthesized with silica gel. The synthesized material had specific surface area, size, and pore volume as specified by mesoporous materials developed from conventional sources of silica. 相似文献
An enzyme immobilized on a mesoporous silica nanoparticle can serve as a multiple catalyst for the synthesis of industrially useful chemicals. In this work, MCM-41 nanoparticles were coated with polyethylenimine (MCM-41@PEI) and further modified by chelation of divalent metal ions (M = Co2+, Cu2+, or Pd2+) to produce metal-chelated silica nanoparticles (MCM-41@PEI-M). Thermomyces lanuginosa lipase (TLL) was immobilized onto MCM-41, MCM-41@PEI, and MCM-41@PEI-M by physical adsorption. Maximum immobilization yield and efficiency of 75 ± 3.5 and 65 ± 2.7% were obtained for MCM@PEI-Co, respectively. The highest biocatalytic activity at extremely acidic and basic pH (pH = 3 and 10) values were achieved for MCM-PEI-Co and MCM-PEI-Cu, respectively. Optimum enzymatic activity was observed for MCM-41@PEI-Co at 75 °C, while immobilized lipase on the Co-chelated support retained 70% of its initial activity after 14 days of storage at room temperature. Due to its efficient catalytic performance, MCM-41@PEI-Co was selected for the synthesis of ethyl valerate in the presence of valeric acid and ethanol. The enzymatic esterification yield for immobilized lipase onto MCM-41@PEI-Co was 60 and 53%, respectively, after 24 h of incubation in n-hexane and dimethyl sulfoxide media.
Graphical Abstract Divalent metal chelated polyethylenimine coated MCM-41 (MCM-41@PEI-M) was used for immobilization of Thermomyces lanuginosa lipase catalyzing green apple flavor preparation
MCM-41 and SBA-15 silica materials with spherical morphology and different particle sizes were synthesized and modified by post-synthesis method with 3-aminopropyltriethoxysilane (APTES). A comparative study of the adsorption and release of a model drug, ibuprofen, were carried out. The modified and drug loaded mesoporous materials were characterized by XRD, TEM, N2 physisorption, thermal analysis, elemental analysis and FT-IR spectroscopy. Surface modification with amino groups resulted in high degree of ibuprofen loading and slow rate of release for MCM-41, whereas it was the opposite for SBA-15. The adsorbed drug content and the delivery rate can be predetermined by the choice of mesoporous material with the appropriate structural characteristics and surface functionality. 相似文献
Hexagonally ordered mesoporous silica material MCM-41 (SBET?=?1090?m2/g, pore size?=?31.2 ?) was synthesized and modified by 3-aminopropyl ligands. The differences in an uptake and subsequent release of anti-inflammatory drug naproxen from unmodified and amino modified MCM-41 samples were studied. The prepared materials were characterized by high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM), nitrogen adsorption/desorption, Fourier-Transform Infrared Spectroscopy (FT-IR), Small-angle X-ray scattering (SAXS), thermoanalytical methods (TG/DTA) and elemental analysis. The amount of the drug released was monitored with thin layer chromatography (TLC) with densitometric detection in defined time intervals. The amounts of the released naproxen from mesoporous silica MCM-41/napro and amine-modified silica sample A-MCM-41/napro were 95 and 90% of naproxen after 72?h. In this study we compare the differences of release profiles from mesoporous silica MCM-41 and mesoporous silica SBA-15. 相似文献
RuO2 nanoparticles were readily prepared from RuCl3·3H2O via the formation of Ru-hydroxide precursor, followed by calcination at 550 °C. Under similar conditions, uniform dispersion of spherical RuO2 nanoparticles over the surface of MCM-41 was also obtained. The synthesized materials were characterized by transmission electron microscopy (TEM), infrared spectroscopy (FT-IR), X-ray diffraction (XRD), BET surface area measurements, and magnetic measurements (VSM). The obtained RuO2 nanoparticles found application as catalyst in preparation of indolo[3,2-a]carbazoles from the reaction of indoles and benzils. Under mild reaction conditions, satisfactory yields of the desired products were obtained. Stabilization of RuO2 nanoparticles over the surface of MCM-41 (RuO2–MCM41), however, had the advantage of easy recycling, although a slight decrease in efficiency after five successive runs was observed. 相似文献
Adsorption and recovery of uranium by nanoporous MCM-41 from aqueous solutions (synthetic solution and uranium conversion facility liquid waste) were investigated by use of a fixed-bed column (1.2 cm diameter and 3.0 cm height). Adsorption was carried out at flow rates 0.2 and 0.5 mL min?1, which correspond to retention times of 10 and 6 min. The maximum breakthrough capacity for uranium ions was achieved by use of nanoporous MCM-41 at the optimum pH of 3.6 and flow rate 0.2 mL min?1 (61.95 μg g?1). The Thomas and Yan models were applied to the experimental data, by use of linear regression, to determine the characteristics of the column for process design. The breakthrough curves calculated from the models were in good agreement with the experimental data. The elution behavior of uranium on nanoporous MCM-41 was studied with different eluents; the results showed that 0.1 M HCl is good eluent for uranium recovery. The regenerated column could be used in a multitude of adsorption–desorption cycles. 相似文献
MCM-41 was synthesized by a soft template technique. The specific surface area and pore volume of the MCM-41 were 805.9 m2/g and 0.795 cm3/g, respectively. MCM-41-supported manganese and cobalt oxide catalysts were prepared by an impregnation method. The energy dispersive X-ray spectroscopy clearly confirmed the existence of Mn, Co, and O, which indicated the successful loading of the active components on the surface of MCM-41. The structure and function of the catalysts were changed by modulating the molar ratio of manganese to cobalt. The 10%MnCo(6:1)/MCM-41 (Mn/Co molar ratio is 6:1) catalyst displayed the best catalytic activity according to the activity evaluation experiments, and chlorobenzene (1000 ppm) was totally decomposed at 270 °C. The high activity correlated with a high dispersion of the oxides and was attributed to the exposure of more active sites, which was demonstrated by X-ray diffraction and high-resolution transmission electron microscopy. The strong interactions between MnO2, Co3O4, MnCoOx, and MCM-41 indicated that cobalt promoted the redox cycles of the manganese system. The bimetal-oxide-based catalyst showed better catalytic activity than that of the single metal oxide catalysts, which was further confirmed by H2 temperature-programmed reduction. Chlorobenzene temperature-programmed desorption results showed that 10%MnCo(6:1)/MCM-41 had higher adsorption strength for chlorobenzene than that of single metal catalysts. And stronger adsorption was beneficial for combustion of chlorobenzene. Furthermore, 10%MnCo(6:1)/MCM-41 was not deactivated during a continuous reaction for 1000 h at 260 °C and displayed good resistance to water and benzene, which indicated that the catalyst could be used in a wide range of applications. 相似文献
In this paper, the synthesis of three types of porous materials (PMs) (porous Fe3O4, MIL-101 metal-organic framework (MOF), and MCM-41 mesoporous silica) by hydrothermal method was performed. The incorporation of Ag nanoparticles (Ag NPs) was carried out after the synthesis reaction of supports in MCM-41 and MIL-101 MOF. Ag core@ porous Fe3O4 core–shell system was prepared via a one-pot hydrothermal method. Ag-MIL-101 was obtained using Urtica dioica leaf extract as the green solvent and reducing agent. The antibacterial activity of Ag-PM nanocomposites (NCs) was investigated on both Gram-negative and Gram-positive bacteria. The size of the silver NPs was determined to be 12 and 30 nm in MCM-41 and MIL-101 MOF, respectively. The diameter of Ag core in Ag@Fe3O4 shell was ~135 nm. The antibacterial activity of Ag-PMs was in the order Ag-MCM-41 > Ag-MIL-101 > Ag core@Fe3O4 shell. The loading percent of Ag NPs in MCM-41 (84%) was more than that in MIL-101 (53%) and Fe3O4 (31%). The release of Ag+ ions from Ag-MCM-41, Ag-MIL-101, and Ag@Fe3O4 NCs was 46, 2, and 1 ppm, respectively. The release of the Ag+ ions and, consequently, the antibacterial activity of NCs depend on the uniform distribution, particles size, and the absence of aggregation of Ag NPs in PMs. 相似文献
Aromatic aldehydes were reacted in a one-pot reaction with enolizable ketones, acetonitrile, and acetyl chloride in the presence of Mn(bpdo)2Cl2/MCM-41 under reflux condition or at 80 °C to afford the corresponding β-acetamido ketones in good yields. 相似文献
(2-RInd)2ZrCl2 (R:Ph,H) catalyst was supported on MCM-41 and ethylene copolymerization behavior as well as microstructure of copolymers were studied. A steady rate–time profile behavior was observed for homo and copolymerization of ethylene using supported catalysts. It was noticed that increasing the comonomer content can result in lower physical properties. The obtained results indicated that (2-PhInd)2ZrCl2/MCM-41 had higher ability of comonomer incorporation than the non-substituted supported catalysts. The CCC, CCE, and ECC (C: comonomer, E: ethylene) triad sequence distribution in backbone of copolymers were negligible, that means no evidence could be detected for comonomer blocks. The polymer characterization revealed that utilizing 1-octene instead of 1-hexene as the comonomer leads to more heterogeneous distribution of chemical composition. The heterogeneity of the chemical composition distribution and the physical properties were influenced by the type of comonomer and catalyst. (2-PhInd)2ZrCl2/MCM-41 produced copolymers containing narrower distribution of lamellae (0.3–1 nm) than the copolymer produce using Ind2ZrCl2/MCM-41 (0.3–1.6 nm). 相似文献
A technique for solid-phase extraction utilizing pyridine-functionalized nanoporous silica (MCM-41, MCM-48 and SBA-15) was developed for the determination of gold in different samples using flame atomic absorption spectrometry. The effects of concentration and volume of eluent, pH of the solution, flow rate of extraction, sample volume and of potentially interfering ions on the efficiency of preconcentration and recovery was investigated. The limit of detection is lower than 45 pg mL?1. Under optimal conditions, the accuracy and precision (RSD%) of the method were calculated to be >99.5% and <0.7% for the two MCMs (41 and 48) and >89.5%, and <1.5% for SBA-15, respectively. The SPE technique was used to determine the concentration of gold in natural and industrial wastewater with satisfactory results.
Figure
A schematic model of modified mesoporous (MCM-41, MCM-48, SBA-15) with pyridine, and adsorption of Au(III) 相似文献
TiO2/MCM-41 composites with various titania content were prepared by loading titania into the mesopores of MCM-41 molecular sieves by sol-gel method, and were used as photocatalysts to degrade Rhodamine B (RhB) and phenol. The efficiency of organic contaminants removal was increased significantly compared with pure TiO2. Ti/Si ratio, namely, the content of TiO2 was determined by ICP-AES method. TiO2/MCM-41 composites were characterized by X-ray diffraction, UV-Vis absorption spectroscopy and N2 adsorption techniques. Experimental results demonstrated that most of the RhB was adsorbed instead of being degradated by TiO2/MCM-41 due to the large specific surface area of MCM-41, while most of phenol was degradated. It turned out that the TiO2/MCM-41 with the highest Ti/Si ratio of 0.8220 (wt) had the highest catalytic activity. 相似文献
Aminopropyl-functionalized mesoporous silicas, NH2-MCM-41 and NH2-SBA-15, as absorbents were utilized for rapid extraction, preconcentration and determination of trace amounts of silver. Flow rates of sample and eluent, pH, eluent solution, type, concentration and the least amount of eluent for desorption of silver ions were optimized; moreover, break through volume and the effect of various cationic interferences on the sorption of silver were evaluated. The extraction efficiency of silver ions was greater than 95% for MCM-41-NH2 and 85% for SBA-15-NH2 and the limit of detection (LOD) was less than 4 ng mL?1 for both functionalized mesoporous silicas. The preconcentration factor was greater than 210 and the relative standard deviation (RSD) was <2%. The adsorption capacity of the mesoporous silicas is higher than 143 mg g?1 for NH2-MCM-41 and 137 mg g?1 for NH2-SBA-15. Under similar experimental conditions the results for these solid phases were compared with each other. NH2-SBA-15, in spite of larger pore size diameter and adsorption of silver ions in higher flow rates has lower recovery and a higher RSD compared to MCM-41. This method has been applied to determine silver in photographic emulsions and real samples. 相似文献
Impregnation of as-synthesized MCM-41 silica by ethanolic solutions of rhodium(III) chloride was tested as an alternative to its introduction into the synthesis gel to get, after calcination and reduction by H2, highly dispersed metal(0) nanoparticles throughout the mesopores network. Rh(III) and Rh(0)–based solids thus obtained were analyzed by infrared spectroscopy, elemental analysis, transmission electron microscopy, N2 sorption, and X-ray diffraction. Materials with 1.6 wt % of rhodium could be obtained as a result of CTA+/Rh3+ exchange. The determining role of CTA+ was emphasized through blank experiments. In a second series of materials, ethanol was also exploited for its ability to reduce Rh(III). All Rh(0)-based solids were tested as catalysts in the hydrogenation of styrene under mild temperature and pressure conditions. Catalysis performances of the most efficient sample (reduced by H2) were further compared with those of a very similar material prepared by the introduction of Rh(III) directly into the synthesis gel of MCM-41 silica. Better cis selectivities in the hydrogenation of disubstituted arene derivatives were achieved with materials issued from the new preparation method. 相似文献
Due to the uncontrollable drug release, traditional chemotherapies could cause great side-effects and are detrimental to normal tissue or organs. Therefore, to avoid those side-effects, drug delivery system (DDS) which is capable of releasing drug molecules at target area with controllable rate according to the development of the disease or to certain functions of the organism/biological rhythm, has attracted especially focus in recent years. In this research, we devoted our efforts in constructing a core–shell nanocomposite to meet the above requirements. The superparamagnetic Fe3O4 nanoparticles were chosen as the core to introduce the magnetic guiding as well as site-specific properties in this novel drug carrier. The core was further encapsulated by silica-based molecular sieve MCM-41 (briefly denoted as MS in this research), which was consisted by immense highly ordered hexagonal tunnels to offer plenty cavity for molecules of drug. A light stimuli-responsive ligand, which is a derivative from light-responsive precursor 4,5-diazafluoren-9-one (indicated in the paper as DAFO), was further connected to the MCM-41 tunnels. The ligand can be excited by light and will flip over, making the tunnels of MCM-41 switch from close to open with light on and light off. The nanocomposite thus became capable of releasing drug molecules at certain wavelength of light. In the final, the nanoparticles were tested via SEM/TEM, XRD, FT-IR spectra, thermogravimetry and N2 adsorption/desorption to verify the structure. The MTT testing of our nanocomposite reveals no obvious cytotoxicity with non-morbid L929 murine fibroblast cells line, indicating that it could be used as a DDS candidate. The cargo releasing behaviors were studied on cytarabine loaded composite: DAFO@MS@Fe3O4 in simulated body fluids. 相似文献
In this work, we found that MCM-41 prepared using cetyltrimethyl ammonium bromide (CTAB) as the template could be used as a heterogeneous catalyst for the reaction of methanol with propylene oxide to produce propylene glycol methyl ether. 1-Methoxy-2-propanol was the predominant product. The influence of ratio of the reactants, reaction temperature, and time on the yield and selectivity was studied. The as-prepared MCM-41 proved to be an efficient and reusable catalyst, and the separation of the catalyst form the product was very easy.
The authors are grateful to the Ministry of Science and Technology of China (2006CB202504, 2009CB930802) and the National Natural Science Foundation of China (20932002). 相似文献