Template mesoporous silica

A mesoporous carbon-CNT hybrid has been prepared using a mesoporous silica template [262]. The template was mechanically mixed with (a) phthalocyanine (Pc) or (b) Ni-phthalocyanine (Ni-Pc) followed by heating to 900 °C in Ar. Upon cooling, the silica template was removed via washing with hydrofluoric acid. SEM images showed... 

Surface-Mediated Nanoscale Fabrication of Metal Particles and Wires Using Mesoporous Silica Templates and Their Shape/ Size Dependency in Catalysis... 

This chapter deals with the selective preparation, TEM/EXAFS/XPS characterization and catalysis of mono- and bimetallic nanowires and nanoparticles highly ordered in silica FSM-16, organosilica HMM-1 and mesoporous silica thin films. The mechanism of nanowire formation is discussed with the specific surface-mediated reactions of metal precursors in the restraint of nanoscale void space of mesoporous silica templates. The unique catalytic performances of nanowires and particles occluded in mesoporous cavities are also reviewed in terms of their shape and size dependency in catalysis as well as their unique electronic and magnetic properties for the device application. 

Figure 15.4a shows a typical TEM image of the Pt wires, which clearly extend as dark stripes along the length of the mesoporous channels. The Pt wires (3nm in diameter) are consistent with the pore diameter of FSM-16 (2.7nm), and their length ranges extend to several hundred nanometres, reflecting the 1D channel structure of mesoporous silica templates (Figure 15.1). Moreover, the high-...

Mechanism for Formation of p( Nanowires in Mesoporous Silica Templates... 

Figure 15.13 Pictorial representation of proposed mechanism for Pt nanowire formation in mesoporous silica templates such as FSM-16 and HMM-1 under UV-irradiation of H2PtCl6/ FSM-16 and H2PtCl6/HMM-l in the presence of methanol and water vapor.

We have reviewed the state of the art of the synthesis and applications of metal/ alloy nanowires and nanoparticles by surface-mediated fabrication using different mesoporous silica templates. New nanoscale materials are appearing one after another by the use of many kinds of mesoporous materials as templates, and we are facing a rapid advance of this research field. So far, many studies have focused... 

Among the inorganic templates, zeolite produces more regulated pores as compared to the silica template. If nano-channels in zeolite are completely filled with carbonaceous precursor and then the carbon materials are extracted from the zeolite framework, one can obtain the porous carbon of which structure reflects the porosity of the original zeolite template. The ordered mesoporous silica templates, e.g., MCM-4 838,39,47 and SBA-1547 have been employed to prepare the ordered porous carbons by the procedures involving the pore filling of the silica template with carbonaceous precursor followed by carbonization and silica dissolution. The resulting pore sizes of the ordered mesoporous carbons are smaller than about 10 nm. 

The principle of the carbon synthesis is shown in Fig. 1. Suitable carbon sources such as sucrose, furfuryl alcohol, phenol-resin monomers and acetylene gas are converted to carbon frameworks inside mesoporous silica template by pyrolysis. An effective method for the restriction of carbonization to inside the template is to incorporate a suitable catalyst such as Al, Sn and Fe onto the silica pore walls prior to the use as template. The template after the carbonization is removed using ethanol-water solution of HF or NaOH. 

S.D. Shen, Y.Q. Li, Z.D. Zhang, J. Fan, B. Tu, W.Z. Zhou, and D.Y. Zhao, A Novel Ordered Cubic Mesoporous Silica Templated with Tri-head Group Quaternary Ammonium Surfactant. Chem. Commun., 2002, 2212-2213. 

C.Z. Yu, B.Z. Tian, B. Fan, G.D. Stucky, and D.Y. Zhao, Salt Effect in the Synthesis of Mesoporous Silica Templated by Non-ionic Block Copolymers, Chem. Commun., 2001, 2726-2727. 

Wang D, Zhou WL, McCaughy BF, Hampsey JE, Ji Z, Jiang Y-B, HuifangXu TJ, Schmehl RH, O Connor C, Brinker CJ, Lu Y (2003) Electrodeposition of metaUic nanowire thin films using mesoporous silica templates. Adv Mater 15 130-133... 

S. C. Laha and R. Ryoo, Synthesis of thermally stable mesoporous cerium oxide with nanocrystalline Ifameworks using mesoporous silica templates, Chem. Commun., 17,2138-9 (2003). 

CMK-2 [114] is an ordered mesoporous carbon obtained from sucrose as a source of carbon and SBA-1 silica as template [Fig. 34b)]. Electron diffraction showed that this carbon is composed of c s iirtercoimected with two different types of pores (meso- and micropores). CMK-3 [115] is an ordered mesoporous carbon that was synthesized using SBA-15 mesoporous silica as template and sucrose as carbon source. The structure of CMK-3 was the faithful replica of the mesoporous silica template, as revealed by XRD and TEM. This carbon had a hi BET surface area (1500 n g % and a pore size around 4.5 nm. The systematic control of pore wall thickness of hexagonal mesoporous silica templates (by varying the ratio of surfactants CwTAB and CmEOg, Fig. 35) afforded a close control of the... 

CVD method using SBA-15 rods as templates (see Figure 4.12). When rod-like mesoporous silica templates synthesised at temperatures lower than 70 °C were used, hollow mesoporous nanotubules were obtained rather than solid core rods (Figure 4.12). ... 

Lee. K.B. Lee. S.M. Cheon, J. Size-controlled synthesis of Pd nanowires using a mesoporous silica template via chemical vapor infiltration. Adv. Mater. 2001, 13, 517. 

Huang, L., Wind, S.J., O brien, S.P., 2003. Controlled growth of single-walled carbon nanotubes from an ordered mesoporous silica template. Nano Lett. 3, 299—303. 

Other rod-type carbons with various structures have been synthesized with the SBA-1, SB A-IS and SBA-16 (IfU gc cage-type, cubic /m3m) mesoporous silica templates. These carbons (designated as CMK-2 [4], CMK-3 [S] and CMK-6 [IS, 16], respectively) exhibit very similar XRD patterns to those for their silica templates, as shown in Fig. 4. This result indicates that the structures are maintained in the same space groups during the synthesis of the carbons from silicas, unlike the case of the CMK-1 synthesis. It is therefore reasonable that these silica templates are composed of 3-dimensional (3-D) mesoporous networks of the same continuity. The carbon synthesis within the mesoporous networks of the same continuity gives the CMK-2, CMK-3 and CMK-6 mesoporous carbons corresponding to faithful replication of the template pore systems. 

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