Synthesis silica nanowires

Figure 10.16 Synthesis of soluble organo-silica and inorganic silica nanowires, (a) ATRP polyinitiator PBIEM with DP = 3200 (b) CPB with side chains of 20 APTS units (c) Core-shell CPB with additional 57 OEGMA units (d) Soluble...

Figure 53 Synthesis of soluble organo-sllica and Inorganic silica nanowIres (a) ATRP polyinitlator PBIEM with DP=3200 (b) moiecuiar brush with side chains of 20 APTS units (c) core-shell molecular brush with additional 57 OEGMA units (d) soluble organo-silica hybrid nanowires with cross-iinked silsesquioxane network in the core and (e) inorganic silica nanowires after pyrolysis. Reprinted from Yuan, J. Xu, Y. Walther, A. etal. Nat. Mater. 2008, 7(9), 718-722, with permission from Nature Publishing Group. ...

The synthesis of silica nanowire arrays. Solid State Communications, 125(11-12), 629-31. 

Y.F. and Zhang, LD. (2005) Synthesis and photoluminescence of aligned straight silica nanowires on Si substrate. Solid State Communications, 138(7), 325-30. 

Qu, Y., Porter, R., Shan, F., Carter, J. and Guo, T. (2005) Synthesis of tubular gold and silver nanoshells using silica nanowire core templates. Langmuir, 22(14), 5357-74. 

Zeolites have ordered micropores smaller than 2nm in diameter and are widely used as catalysts and supports in many practical reactions. Some zeolites have solid acidity and show shape-selectivity, which gives crucial effects in the processes of oil refining and petrochemistry. Metal nanoclusters and complexes can be synthesized in zeolites by the ship-in-a-bottle technique (Figure 1) [1,2], and the composite materials have also been applied to catalytic reactions. However, the decline of catalytic activity was often observed due to the diffusion-limitation of substrates or products in the micropores of zeolites. To overcome this drawback, newly developed mesoporous silicas such as FSM-16 [3,4], MCM-41 [5], and SBA-15 [6] have been used as catalyst supports, because they have large pores (2-10 nm) and high surface area (500-1000 m g ) [7,8]. The internal surface of the channels accounts for more than 90% of the surface area of mesoporous silicas. With the help of the new incredible materials, template synthesis of metal nanoclusters inside mesoporous channels is achieved and the nanoclusters give stupendous performances in various applications [9]. In this chapter, nanoclusters include nanoparticles and nanowires, and we focus on the synthesis and catalytic application of noble-metal nanoclusters in mesoporous silicas. 

Figure 3. Schematic representation of the selective synthesis of metal nanowires and nanoparticles by the Sintering Controlled Synthesis approach, (a) Mesoporous silica, (b) impregnation of mesoporous silica with metal ions, (c) addition of water/alcohol vapors and UV-irradiation, or wet H2-reduction, (d) formation of metal nanowires, (e) dry H2-reduction, (f) formation of metal nanoparticles.

Similarly, monometallic Rh, Pd, and Au and bimetallic Pt-Rh and Pt-Pd nanowires were prepared in FSM-16 or HMM-1 by the photoreduction method [30,33,34]. The bimetallic wires gave lattice fringes in the HRTEM images, and the EDX analysis indicated the homogeneous composition of the two metals. These results show that the wires are alloys of Pt-Rh and Pt-Pd. Mesoporous silica films were also used as a template for the synthesis of uniform metal particles and wires in the channels [35,36]. Recently, highly ordered Pt nanodot arrays were synthesized in a mesoporous silica thin film with cubic symmetry by the photoreduction method [37]. The... 

Figure 15.1 Ordered nanoscale structures of mesoporous materials such as FSM-16 and HMM-1 (Et-HMM-1) as the silica and organosilica templates for surface-mediated synthesis of metal/alloy nanowires and nanoparticles.

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... 

There are several reports on the preparation of SiC nanowires in the literature but fewer on the preparation of SisKi nanowires.38-39 The methods employed for the synthesis of SiC nanowires have been varied. Since both SiC and Si3N, are products of the carbothermal reduction of SI02, it should be possible to establish conditions wherein one set of specific conditions favor one over the other. We have been able to prepare SijN nanowires,40 by reacting multiwalled carbon nanotubes produced by ferrocene pyrolysis with ammonia and silica gel at 1360... 

Zhao[266] demonstrated the successful synthesis of highly ordered mesoporous silicon carbides with unusually high surface areas (430-720 m2/g), uniform pore sizes (<3.5 nm), and extremely high thermal stabilities (up to 1400 °C) replicated by mesoporous silica hard templates via a one-step nanocasting process. Highly ordered 2-D hexagonal (p6m) and bicontinuous cubic (Ia3d) SiC nanowire arrays have been cast from the hard templates, mesoporous silica SBA-15 and KIT-6, respectively. 

F. Kleitz, S.H. Choi, and R. Ryoo, Cubic Ia3d Large Mesoporous Silica Synthesis and Replication to Platinum Nanowires, Carbon Nanorods and Carbon Nanotubes. Chem. Commun., 2003, 2136-2137. 

Interest in the synthesis and processing of mesoporous silica materials has grown extensively since their discovery in 1992, and the exciting potential that these films hold in low-k dielectrics, sensors, nanowire fabrication, catalysis, membrane separations, and many other applications will continue to fuel academic and industrial interest in these films. While there are many new synthesis routes for processing mesoporous silica thin films, spin coating and dip coating remain the most facile methods available. These methods deliver high quality reproducible films that can be used for any of the variety of applications. 

F. Klertz, S. H. Choi, R. Ryoo, Cubic la3d large mesoporous silica synthesis and replication to platinum nanowires, carbon nanorods and carbon nanotubes, Chem. Commun., 17,2136-7 (2003). 

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. 

Carbothermal route provides a general method for preparing crystaUine nanowires of oxides such as ZnO, Al Oj and Ga Oj, nitrides such as AIN and SijN, and carbides such as SiC [3], The set-up employed for the synthesis of oxide nanomaterials is shown in Figure 3.1. The method has enabled the synthesis of crystalhne nanowires of both silica and sihcon. In the case of GaN, it has been possible to dope it with Mn, Mg and Si to bestow useful optical and magnetic properties. Carbothermal reaction involving Ga Oj powder mixed with activated carbon or carbon nanotubes carried out at 1100 °C in flowing Ar yields nanowires, nanorods as well as novel nanostructures... 

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