NMR Characterisation of the Organic/SiO2 Interfaces in Templated Porous Silica.

2006 ◽  
Vol 984 ◽  
Author(s):  
Niki Baccile ◽  
Guillaume Laurent ◽  
Thierry Azaïs ◽  
Florence Babonneau
Keyword(s):  
Mesoporous Silica ◽  
Benzoic Acid ◽  
Porous Silica ◽  
Polarization Transfer ◽  
Transfer Efficiency ◽  
One Dimensional ◽  
Surface Sites ◽  
Close Proximity ◽  
Lower Temperature

AbstractThis paper illustrates the use of a 1H-29Si-1H double CP sequence to investigate different organic/SiO2 interfaces in templated porous silica. The advantage of this sequence is to selectively edit, in a one-dimensional experiment, the protons that are in close proximity with the Si surface sites. In order to maximize the polarization transfer efficiency, some experiments have been recorded at lower temperature (238 K). Examples will concern surfactant/silica interactions in mesostructured silicas and the behavior of benzoic acid and 4-methoxychlorophenol, a common pesticide, encapsulated in mesoporous silica.

The Use of Mesoporous Systems for Preparation of One-Dimensional Ordered Magnetic Nanowires

2003 ◽  
Vol 788 ◽  
Author(s):  
Andrei A. Eliseev ◽  
Kirill S. Napolskii ◽  
Dmitry F. Gorozhankin ◽  
Alexei V. Lukashin ◽  
Yuri D. Tretyakov ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Data Storage ◽  
Magnetic Measurements ◽  
Decomposition Temperature ◽  
Silica Matrix ◽  
Information Storage ◽  
Molar Ratio ◽  
Magnetic Nanowires ◽  
One Dimensional ◽  
Novel Variant

ABSTRACTHere we report the synthesis and investigation of iron and iron oxide nanowire arrays using mesoporous silica as a host material. In the present work a novel variant of synthesis of ordered magnetic nanowires in the mesoporous silica matrix was suggested. The method is based on the incorporation of a hydrophobic metal compound into the hydrophobic part of silica-surfactant composite. The amount of iron intercalated into the mesoporous matrix was measured by chemical analysis. In all samples it corresponds well to with the molar ratio SiO2: Fe = 9:1. To provide crystallinity of nanowires additional thermal treatment was performed. Thus prepared nanocomposites were characterized by TEM, ED, SAXS, SANS, BET and magnetic measurements. The anisotropy parameters of nanowires were determined using two non-correlated methods: temperature dependence of magnetic susceptibility and small angle polarized neutron scattering. It was found that the particle length increases with the increasing of the decomposition temperature of the metal complex. Obviously it deals with crystallization and growth of metal particles inside the pores at a constant diameter of a single particle. For iron containing sample annealed at 375 °C (form factor of nanowire is about 40), the coercive force at room temperature was found to be 145 Oe at saturation magnetization of 1.2 emu/g, which is not far from modern information storage. It was shown that particles shape and size are in good agreement with that of the pores. Particles are uniform and well ordered in the silica matrix. Thus, the suggested method leads to one-dimensional anisotropic nanostructures which could find an application as high-density data storage magnetic media.

Rapid adsorption and entrapment of benzoic acid molecules onto mesoporous silica (FSM-16)

2005 ◽  
Vol 291 (2) ◽  
pp. 471-476 ◽  
Author(s):  
Yuichi Tozuka ◽  
Sara Sasaoka ◽  
Ayako Nagae ◽  
Kunikazu Moribe ◽  
Toshio Oguchi ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Benzoic Acid ◽  
Rapid Adsorption

Exploring the limits of polarization transfer efficiency in homonuclear three spin systems

2006 ◽  
Vol 181 (1) ◽  
pp. 126-134 ◽  
Author(s):  
Jorge L. Neves ◽  
Björn Heitmann ◽  
Timo O. Reiss ◽  
Heloiza H.R. Schor ◽  
Navin Khaneja ◽  
...  
Keyword(s):  
Polarization Transfer ◽  
Spin Systems ◽  
Transfer Efficiency

Rheological and Thermomechanical Properties of Meso and Non-Porous Silica Filled Epoxy Composites

2015 ◽  
Vol 815 ◽  
pp. 67-71
Author(s):  
Gang Li ◽  
Peng Li Zhu ◽  
Tao Zhao ◽  
Rong Sun ◽  
Daniel Lu
Keyword(s):  
Mechanical Properties ◽  
Thermal Expansion ◽  
Glass Transition ◽  
Mesoporous Silica ◽  
Coefficient Of Thermal Expansion ◽  
Porous Silica ◽  
Thermomechanical Properties ◽  
Epoxy Composites ◽  
Silica Microspheres ◽  
Silica Filler

In the present study, epoxy based composite filled with meso and non-porous silica microspheres with similar size were prepared respectively and their rheological and thermo-mechanical properties were studied systematically. The results showed that the mesoporous silica/epoxy composites showed much higher viscosity, storage modulus and glass transition temperature (Tg) while lower coefficient of thermal expansion (CTE) than did epoxy composites with nonporous silica particles, which could be attributed to the stronger interface interaction between the mesoporous silica filler with larger specific surface area (BET) and the epoxy matrix.

SnxTi1−xO2 solid-solution-nanoparticle embedded mesoporous silica (SBA-15) hybrid as an engineered photocatalyst with enhanced activity

2016 ◽  
Vol 186 ◽  
pp. 353-370 ◽  
Author(s):  
N. R. Srinivasan ◽  
Rajdip Bandyopadhyaya
Keyword(s):  
Solid Solution ◽  
Mesoporous Silica ◽  
Porous Silica ◽  
Order Rate Constant ◽  
Reaction Rates ◽  
Charge Transfer Resistance ◽  
Transfer Resistance ◽  
New Strategy ◽  
Pore Blockage ◽  
Embedded Nanoparticles

Synthesis of hybrids of a porous host-material (with well-dispersed embedded nanoparticles inside the pore), wherein each nanoparticle has precisely controlled properties (size and composition) poses a generic challenge. To this end, a new strategy is proposed to form SnxTi1−xO2 solid-solution-nanoparticles inside the pores of sphere-like mesoporous silica (SBA-15), with different percentages of Sn in the nanoparticle (varying from 5 to 50 at%), for enhanced photocatalysis. X-ray diffraction confirms the formation of solid-solution nanoparticles in the porous silica hybrid, while the location of nanoparticles and elemental composition are identified using electron microscopy. The hybrid with 5 at% of Sn (Sn0.05Ti0.95O2-sphere-like SBA-15) shows the maximum photocatalytic activity for degradation of rhodamine-B dye (first order rate constant for degradation, k = 1.86 h−1), compared to both pure TiO2-sphere-like SBA-15 (k = 1.38 h−1) or pure SnO2-sphere-like SBA-15 (k = 0.14 h−1) or other hybrids in this series. XPS and PL spectra suggest the formation of more oxygen vacancies during the replacement of Ti4+ with Sn4+. Electrochemical studies reveal that there is a reduction of charge transfer resistance from 910 kΩ cm−2 for TiO2-sphere-like SBA-15, to 332 kΩ cm−2 for Sn0.05Ti0.95O2-sphere-like SBA-15. These results imply that the enhancement in photocatalytic performance is as a result of delay in recombination of charge carriers. Therefore, the approach followed in the present work to form solid-solution nanoparticles inside a porous host without causing pore blockage, would be a promising route towards increasing reaction rates in catalytic applications of hybrid materials.

Annealing of mesoporous silica loaded with silver nanoparticles within its pores from isothermal sorption

1998 ◽  
Vol 13 (10) ◽  
pp. 2888-2895 ◽  
Author(s):  
Weiping Cai ◽  
Lide Zhang ◽  
Huicai Zhong ◽  
Guoliang He
Keyword(s):  
Mesoporous Silica ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ag Nanoparticles ◽  
Porous Silica ◽  
Pore Wall ◽  
Ag Particles ◽  
Real Value ◽  
And Diffusion

Influences of annealing on the structure of mesoporous silica loaded with silver (Ag) nanoparticles, and on the coarsening of Ag particles within pores of the host were investigated from isothermal sorption. Doping a small amount of Ag nanoparticles into pores of silica and subsequent annealing decreases the measured values of specific surface area and pore volume of porous silica significantly. This is attributed to the presence and coarsening of Ag particles within pores or channels between pores, which result in more and more isolated and unmeasured free spaces. The measured value of a specific surface area for the doped samples cannot represent the real value, which is, in fact, unable to be measured directly. During additional annealing, Ag particles within silica coarsen mainly according to the mechanism of formation of Ag adatoms on pore wall and diffusion of the adatoms along with pore walls. Only the larger particles located in the larger pores can continuously grow. The smaller particles and those located in the channels or pores with smaller dimension will disappear. The activation energy of the ripening process was estimated to be about 0.60 eV, and the migration barrier of Ag adatom on the pore wall of silica is about 0.10 eV.

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