Meso-porous silica

Thomas and his colleagues in Cambridge have pioneered the development of nanoparticles prepared from cluster compounds and supported in meso-porous silica.31 Highly active and effective catalysts have been developed for a number of hydrogenation reactions. The significant factors controlling... 

Curved structures are not only limited to carbon and the dichalcogenides of Mo and W. Perhaps the most well-known example of a tube-like structure with diameters in the nm range is formed by the asbestos mineral (chrysotil) whose fibrous characteristics are determined by the tubular structure of the fused tetrahedral and octahedral layers. The synthesis of meso-porous silica with well-defined pores in the 2-20 nm range was reported by Beck and Kresge.6 The synthetic strategy involved the self-assembly of liquid crystalline templates. The pore size in zeolitic and other inorganic porous solids is varied by a suitable choice of the template. However, in contrast to the synthesis of porous compounds, the synthesis of nanotubes is somewhat more difficult. 

Vinu and others219 exploited 31P CP/MAS NMR spectroscopy together with other instrumental techniques to describe physicochemical characterisation of a catalyst consisting of tungstophosphoric acid supported on zirconia and meso-porous silica MCM-41 and MCM-48. 

The rare earth exchanged zeolites (LaHY, LaHB) and meso porous silica-alumina (2-4 nm diameter pores) were prepared previously [5], The unit cell composition of LaHY is (H Na, La,4Al52 Si,3940384). MSA is in the acid form, Si/Al = 50. The adsorption isotherm for LaHY yields a maximum of ca. 4 isobutane molecules per supercage (or 0.6 molc./Al). Triflic acid (Aldrich) was manipulated under dry nitrogen atmosphere. 

Catalyst support. A review of the chemistry that employs silica-supported catalysts for the Heck reaction and a report on development of a diphosphine ligand linked to meso-porous silica MCM-41 for PdCl2 (with Cul to promote the Sonogashita coupling ) have appeared. 

Adsorption Cellulose, chitine (chitosan), nylon, polypropylene fibres, polymer nets and membranes, wood, lignine, ion-exchange resins, polyurethane foam, polyacrylamide (Porous) glass, clay,bentonite, zeolithes, ceramics, meso-porous silica, metal oxides (Fe, Ti, Mg), metal phosphates, mineral powder... 

Luo et al. mention the possibility to infiltrate a binary PS crystal (130 and 210 nm) with a P123 block copolymer silica sol-gel solution, yielding meso-porous silica walls alongside two types of macropores [127]. 

Finally, a very interesting approach has been suggested by the same group to apply an ionic liquid to the preparation of Ru nanopartides of defined size on a meso-porous silica support [279]. The authors made use of the ionic liquid [TGA] [lactate] to customize particles obtained by reduction of dissolved RuQs on the silica support. However, prior to catalysis, the ionic liquid film was removed thermally by heating to 220 °C for 3 h. In this way a quite active catalyst for the hydrogenation of benzene to cyclohexane (TOFs up to 83 h at 10 bar H2 pressure) was obtained. Such an approach obviously combines successfully features of SILP catalysis (see Section 5.6 for details) with the use of catalytic nanopartides. 

Several authors successfully demonstrated the potential of micro- and meso-porous silica materials as well as zeolites as carriers. Corma et al. anchored car-bapalladacycles on high surface area inorganic supports and converted aryl... 

Gross, A.F., Diehl, M.R., Beverly, K.C., Richman, E.K., Tolbert, S.H. Controlling magnetic coupling between cobalt nanoparticles through nanoscale confinement in hexagonal meso-porous silica J. Rhys. Chem. B 107, 5475-5482 (2003)... 

Limnell, T., Santos, H.A., Makila, E. et al. 2011. Drug delivery formulations of ordered and nonordered meso-porous silica Comparison of three drug loading methods. J. Pharmacol. Sci. 100 3294-3306. 

Recently, monochromophoric amines of this type have been grafted onto the surface of small-sized boehmite nanoparticles to generate recyclable devices for ATP sensing to be able to operate in an aqueous solution (Figure 23). In another strategy for ATP detection, organic fluorophores were attached to the surface of meso-porous silica materials. 

Y. Xu, Z. Wu, L. Zhang, H. Lu, P. Yang, P. A. Webley, et al, Highly specific enrichment of glycopeptides using boronic acid-functionalized meso-porous silica, A a/. Chem., 2009, 81(1), 503-508. 

Meso porous silica, hexagon ally ordered (MCM41) > BET 660 m / g Vp = 0.6 cm / g Adsorption isotherms (N, 77 K) show hysteresis (lUPAC Type IV, cp. Chap. 7) ... 

Telomerase expression, specific to cancer cells, is responsible for their uncontrolled division [ 175]. Ju ef al. described an elegant platform for fluorescence imaging of telomerase activity in cancer cells, an approach amenable to evaluate both tumor load and response to treatment [176]. Fluorescein and black hole quencher were loaded in meso-porous silica nanoparticles, the pores were then sealed by a telomerase DNA template probe. Telomerase detection was achieved by telomerase-induced detachment of the probe for its amplification, followed by liberation of the fluorophore. Interestingly, this probe allowed intracellular quantitation of telomerase activity. Signal was decreased after treatment with telomerase inhibitors, suggesting its usefulness as a disease monitoring tool in vivo. 

Yan, H., Teh, C., Sreejith, S., Zhu, L., Kwok, A., Fang, W., et al. (2012). Functional meso-porous silica nanoparticles for photothermal-controUed drug dehvery in vivo. Angewandte Chemie International Edition, 51, 8373-8377. http //dx.doi.org/10.1002/anie.201203993. 

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