Stabilizing gold nanoparticles（AuNPs） within a desired size range is critical to realize their promising catalytic performance in many important reactions.Herein,we investigate the anti-sintering properties of cubic...Stabilizing gold nanoparticles（AuNPs） within a desired size range is critical to realize their promising catalytic performance in many important reactions.Herein,we investigate the anti-sintering properties of cubic mesoporous silica（FDU-12） as a function of pore entrance size.Simple adjustments to the type of organic template and reaction temperature enable the successful synthesis of FDU-12 with controllable entrance sizes（ 3,3-5 and 7 nm）.Excellent anti-sintering properties are observed for FDU-12 with a sub-5-nm entrance size（3-5 nm） over a wide loading concentration（1.0-8.3 wt%） and the AuNPs can be stabilized within a 4.5-5.0-nm range after calcination at 550 ℃in air for 5 h.Smaller entrance size（ 3 nm） prevents ingress of 3-nm AuNPs to the mesopores and results in low loading capacity and sintering.Conversely,FDU-12 possessing a larger entrance size（7 nm） shows promising anti-sintering properties at high loading concentrations,although catalytic performance is significantly lost at lower concentrations（e.g.2.1 wt%,14.2 ± 5.5 nm）.Different anti-sintering mechanisms are proposed for each of the different FDU-12 entrance sizes.Additionally,catalytic data indicates that the obtained 4.5-nm AuNPs supported on FDU-12 with a sub-5-nm entrance size exhibit excellent mass-specific activity（1544 mmol g_（Au）^（-1） h^（-1）） and selectivity（ 99%）at 230 ℃ for the gas-phase selective oxidation of cyclohexanol.展开更多
1 Introduction Since its first discovery in 1992, ordered mesoporous silica material with large pore size, high surface area, and high pore volume has attracted great attention for the potentially wide application in...1 Introduction Since its first discovery in 1992, ordered mesoporous silica material with large pore size, high surface area, and high pore volume has attracted great attention for the potentially wide application in catalysis, adsorption, separation, and ion exchange, etc. However, the poor hydrothermal stability of mesoporous silica has limited its wide application in industry. Therefore, in the last 10 years, many studies have been dedicated to improving the hydrothermal stability of mesoporous silica. Xiao et al.展开更多
Mesoporous silica nanoparticles （MSNs） are promising for drug delivery and other biomedical applications owing to their excellent chemical stability and biocompatibility. For these applications, a hollow morphology ...Mesoporous silica nanoparticles （MSNs） are promising for drug delivery and other biomedical applications owing to their excellent chemical stability and biocompatibility. For these applications, a hollow morphology with thin shell and open mesopores is preferred for MSNs in order to maximize the loading capacity of drugs. Herein we report a novel and direct synthesis of such an ideal drug delivery system in a dilute and alkaline solution of benzylcetyl- dimethylammonium chloride and diethylene glycol hexadecyl ether. The mixed surfactants can guide the formation of MSNs with cubic Ia3d mesostructure, and at a concentration of sodium hydroxide between 9.8 and 13.5 mM, hollow MSNs with uniform sizes of 90-120 nm and a single-unit-cell-thick shell are formed. A mechanism for the formation of the hollow Ia3d MSNs, designated as MMT-2, is proposed based on in situ small-angle X-ray scattering measurements and other analyses. MMT-2 exhibits much higher loading capacity of ibuprofen and degrades faster in simulated body fluid and phosphate buffered saline than non-hollow MSNs. The degradation of MMT-2 can be significantly retarded by modification with polyethylene glycol. More interestingly, the degradation of MMT-2 involves fragmentation instead of void formation, a phenomenon beneficial for their elimination. The results demonstrate the uniqueness of the hollow Ia3d MSNs and the great potential of the material for drug delivery and biomedical applications.展开更多
Highly ordered cubic Zr-doped mesoporous silica was directly prepared with Evaporation-Induced Self Assembly method(EISA) with triblock copolymers(Pluronic P123) as the structure-directing agents.The mesoporous materi...Highly ordered cubic Zr-doped mesoporous silica was directly prepared with Evaporation-Induced Self Assembly method(EISA) with triblock copolymers(Pluronic P123) as the structure-directing agents.The mesoporous material was characterized via small-angle powder X-ray diffraction(XRD),transmission electron microscopy(TEM),and nitrogen adsorption.The results show that the product has a face-centered cubic structure with space group of Fd3m.N2 sorption revealed that the Zr-doped mesoporous silica has not only ordered structures,but also high surface area(550 m2/g),large pore volume(0.66 cm3/g),as well as uniform pore size(4.0 nm).展开更多
Cubic mesoporous titaniumcontaining silica(TiMCM48) can be synthesized by using mixed surfactants CTABC nHN 2(n=8,10,12,14) as templates in basic medium.Characterization results obtained from the determination of XRD,...Cubic mesoporous titaniumcontaining silica(TiMCM48) can be synthesized by using mixed surfactants CTABC nHN 2(n=8,10,12,14) as templates in basic medium.Characterization results obtained from the determination of XRD,TEM and N 2adsorption show that the products possess highquality TiMCM48.The effect of the chain length of the alkylamine and the ratio of titanium to silicium on the structure of the cubic mesophases were investigated.It was revealed that the mesophase transition from cubic to lamellar structure occurred with increasing alkylamine chain length and Ti/Si ratio.展开更多
基金supported by the National Natural Science Foundation of China(21222307,21373181,21403197,91545113,21503189)the Fundamental Research Funds for the Central Universities(2014XZZX003-02)+1 种基金Zhejiang Provincial Natural Science Foundation(LY15B030009)China Postdoctoral Science Foundation(2014M550333,2015T80636)~~
文摘Stabilizing gold nanoparticles（AuNPs） within a desired size range is critical to realize their promising catalytic performance in many important reactions.Herein,we investigate the anti-sintering properties of cubic mesoporous silica（FDU-12） as a function of pore entrance size.Simple adjustments to the type of organic template and reaction temperature enable the successful synthesis of FDU-12 with controllable entrance sizes（ 3,3-5 and 7 nm）.Excellent anti-sintering properties are observed for FDU-12 with a sub-5-nm entrance size（3-5 nm） over a wide loading concentration（1.0-8.3 wt%） and the AuNPs can be stabilized within a 4.5-5.0-nm range after calcination at 550 ℃in air for 5 h.Smaller entrance size（ 3 nm） prevents ingress of 3-nm AuNPs to the mesopores and results in low loading capacity and sintering.Conversely,FDU-12 possessing a larger entrance size（7 nm） shows promising anti-sintering properties at high loading concentrations,although catalytic performance is significantly lost at lower concentrations（e.g.2.1 wt%,14.2 ± 5.5 nm）.Different anti-sintering mechanisms are proposed for each of the different FDU-12 entrance sizes.Additionally,catalytic data indicates that the obtained 4.5-nm AuNPs supported on FDU-12 with a sub-5-nm entrance size exhibit excellent mass-specific activity（1544 mmol g_（Au）^（-1） h^（-1）） and selectivity（ 99%）at 230 ℃ for the gas-phase selective oxidation of cyclohexanol.
基金Supported by the National Natural Science Foundation of China(Nos.20401015 and 50574082)Beijing(China) Municipal Natural Science Foundation(No.2082022)the Innovation Project of the Chinese Academy of Sciences(Nos.CXJJ-171 and CXJJ-210)
文摘1 Introduction Since its first discovery in 1992, ordered mesoporous silica material with large pore size, high surface area, and high pore volume has attracted great attention for the potentially wide application in catalysis, adsorption, separation, and ion exchange, etc. However, the poor hydrothermal stability of mesoporous silica has limited its wide application in industry. Therefore, in the last 10 years, many studies have been dedicated to improving the hydrothermal stability of mesoporous silica. Xiao et al.
文摘Mesoporous silica nanoparticles （MSNs） are promising for drug delivery and other biomedical applications owing to their excellent chemical stability and biocompatibility. For these applications, a hollow morphology with thin shell and open mesopores is preferred for MSNs in order to maximize the loading capacity of drugs. Herein we report a novel and direct synthesis of such an ideal drug delivery system in a dilute and alkaline solution of benzylcetyl- dimethylammonium chloride and diethylene glycol hexadecyl ether. The mixed surfactants can guide the formation of MSNs with cubic Ia3d mesostructure, and at a concentration of sodium hydroxide between 9.8 and 13.5 mM, hollow MSNs with uniform sizes of 90-120 nm and a single-unit-cell-thick shell are formed. A mechanism for the formation of the hollow Ia3d MSNs, designated as MMT-2, is proposed based on in situ small-angle X-ray scattering measurements and other analyses. MMT-2 exhibits much higher loading capacity of ibuprofen and degrades faster in simulated body fluid and phosphate buffered saline than non-hollow MSNs. The degradation of MMT-2 can be significantly retarded by modification with polyethylene glycol. More interestingly, the degradation of MMT-2 involves fragmentation instead of void formation, a phenomenon beneficial for their elimination. The results demonstrate the uniqueness of the hollow Ia3d MSNs and the great potential of the material for drug delivery and biomedical applications.
文摘Highly ordered cubic Zr-doped mesoporous silica was directly prepared with Evaporation-Induced Self Assembly method(EISA) with triblock copolymers(Pluronic P123) as the structure-directing agents.The mesoporous material was characterized via small-angle powder X-ray diffraction(XRD),transmission electron microscopy(TEM),and nitrogen adsorption.The results show that the product has a face-centered cubic structure with space group of Fd3m.N2 sorption revealed that the Zr-doped mesoporous silica has not only ordered structures,but also high surface area(550 m2/g),large pore volume(0.66 cm3/g),as well as uniform pore size(4.0 nm).
文摘Cubic mesoporous titaniumcontaining silica(TiMCM48) can be synthesized by using mixed surfactants CTABC nHN 2(n=8,10,12,14) as templates in basic medium.Characterization results obtained from the determination of XRD,TEM and N 2adsorption show that the products possess highquality TiMCM48.The effect of the chain length of the alkylamine and the ratio of titanium to silicium on the structure of the cubic mesophases were investigated.It was revealed that the mesophase transition from cubic to lamellar structure occurred with increasing alkylamine chain length and Ti/Si ratio.
