Nanowires nanowire alloys

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... 

Seeger, H. Terrones, M. Riihle, D. R. M. Walton, H.W. Kroto, J.L. Hutchison, Alloy nanowires Invar inside carbon nanotubes, Chem. Commun., vol. 5, pp. 471-472, 2001. 

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.

Surface-Mediated Synthesis of Metal/Alloy Nanowires Using Mesoporous Templates... 

Isolation and Characterization of Metal/Alloy Nanowires Free from the Silica Supports 615... 

Extraction of nanowires from mesoporous supports is important and desirable for their application as a building block for electronic devices and catalyst preparation. In addition, more detailed characterization of metal/alloy nanowires is available by their extraction from the sihca templates. Isolation of the Pt nanowires from mesoporous templates has also been tried by dissolving FSM-16 and HMM-1 with aqueous HF or NaOH solution, but the nanowires were readily decomposed into Pt aggregates. However, the Pt nanowires were successfully extracted as their original forms from the sihca templates using HF and [NBu4]Cl as a surfactant in a benzene/ethanol solution. It is reasonably implied that the extracted wires are... 

Shape/Size Dependency in Catalysis of Metal/Alloy Nanowires and Particles in Mesoporous Silica Templates... 

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... 

We have overviewed some strategies for the surface-mediated fabrication of metal and alloy nanoscale wires and particles in mesoporous space, and their structural characterization and catalytic performances. Extension of the present approaches for metal/alloy nanowires may lead to the realization of the prospechve tailored design of super active, selective and stable catalysts applicable in industrial processes. The organometallic clusters and nanowires offer exciting and prospechve opportunities for the creahon of new catalysts for industry. Various metal/ alloy nanowires and nanoparhcles in the anisotropic arrangement in porous supports would help in understanding the unexpected electronic and optic properties due to the quantum effect, which are relevant to the rational design of advanced electronic and optic devices. 

Recently, the VLS growth method has been extended beyond the gas-phase reaction to synthesis of Si nanowires in Si-containing solvent (Holmes et al, 2000). In this case 2.5-nm Au nanocrystals were dispersed in supercritical hexane with a silicon precursor (e.g., diphenylsilane) under a pressure of 200-270 bar at 500°C, at which temperature the diphenylsilane decomposes to Si atoms. The Au nanocrystals serve as seeds for the Si nanowire growth, because they form an alloy with Si, which is in equilibrium with pure Si. It is suggested that the Si atoms would dissolve in the Au crystals until the saturation point is reached then they are expelled from the particle to form a nanowire with a diameter similar to the catalyst particle. This method has an advantage over the laser-ablated Si nanowire in that the nanowire diameter can be well controlled by the Au particle size, whereas liquid metal droplets produced by the laser ablation process tend to exhibit a much broader size distribution. With this approach, highly crystalline Si nanowires with diameters ranging from 4 nm to 5 nm have been produced by Holmes et al. (2000). The crystal orientation of these Si nanowires can be controlled by the reaction pressure. 

Fig. 20. (a) Measured R(T)/R(270 K) for 40-nm bismuth nanowires prepared with alloys of different Te doping levels, (b) The calculated temperature dependence of for 40-nm undoped and Te-doped bismuth nanowires of different Nd. The dashed and solid lines are fitting curves corresponding to undoped and Te-doped Bi nanowires, respectively. 

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