Single-crystal metallic nanostructures

Iron carbonyls have been also used to fabricate nanostructures of potential use in catalysis. In this context, the preparation at room temperature of nano-sized a-Fe single crystals over carbon micro-grid films has been reported. The particles were prepared by electron beam induced deposition using Fe(CO)s as precursor [77]. The use of a focused electron beam to induce metal deposition from carbonyl compounds opens a new route for the preparation of nano-sized metal particles. 

The fuel cell is an electrochemical reactor, the required output of which is the energy released rather than the reaction product. The main fields of its application include transport systems, stationary power generation, and combined heat and power sources. What emerges from the specialist literature is that, despite the innovations and improvements made in recent years, there is still much room for further developments. " Central to the success of fuel-cell technology are the catalyst systems. This is where bi- and multi-metallic nanostructured colloids, especially those of small particle size (1-2.5 nm), scattering as nearly perfect single crystals , are important. They offer improved efficiency and tolerance against CO-... 

Nanoparticles fabricated in such a way possess a good adhesion to the surface. Previously it was shown that surface relief strongly affects the topology of gold deposition. A pretextured semiconductor surfaces can be used as templates for ID, 2D ordered nanostructure fabrication [4]. The polished (100) surfaces of n-GaAs single crystal were used for the metal deposition. Typical gold nanoparticle ensembles are shown in Fig. la. Silver nanoparticles (Fig. lb) are of 30 - 60 nm in diameter and uniformly cover the surface. 

A laser ablation technique for the preparation of boron nanowires was published almost contemporary to the previous work. Crystalline boron nanowires with tetragonal structure have been reported to form via laser treatment on boron rods, doped with 10% of a half-and-half mixture of Ni and Co metal powders. A Nd/YAG laser of 532 nm wavelength, 10 Hz frequency, and 3.5 W power was applied on the B/NiCo target. It was then kept in a furnace at 1250°C, under flowing argon gas for 30 min. The x-ray diffraction data predicted that nanowires with crystalline structure and crystals are mostly single crystal in nature. The role of the catalyst in formation of the nanostructure has also been examined and proven to be vital. 

Figure 11.5 Schematic of conventional shapes of face-centered cubic (fee) metal nanostructures. The shapes in the top row are single crystals, in the second row are particles with twin defects or stacking faults, and in the...

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