Nano-crystallites

Synthesis and characterization of nearly monodispersed CdX semiconductor nano crystallites were studied [163]. 

The investigation of anodic oxide on various metals shows that at first usually amorphous structures are formed with a dense coverage of the terraces with grains, which change to nano-crystallites with time. The extent and the rate of this change depend on the system under study. This crystallization occurs for Cr within hours [127], whereas Cu keeps the amorphous grain structure for a very few minutes only and develops a well-ordered, faceted, crystalline layer covering the whole electrode surface [128, 129], In the next section, the details of the structure of layers formed on Cu are discussed, followed by a summary of some other more reactive metals like Ni and Cr. 

Flg. 25 (a) and (b) low-resolution TEM images of CdSe nanotubes. Inset shows a typical ED pattern (c) HREM image of the CdSe nanotube showing walls containing several nano-crystallites. (Reproduced with permission from ref. 28). 

However, while the above was a rather crude approach to fabricate more porous electrode layers with oxidic support materials, a more elegant way was chosen for home-made ATO by 3D morphology engineering. ATO powder with unique hollow-sphere morphology was synthesized by ultrasonic spray p)irolysis (USP). Depending on precursor concentration and temperature, this process yields a powder composed of individual nano-crystallites forming the shells of hollow spheres with a controlled nano- and microporosity [98]. This offers efficient mass transport and is assumed to prevent the collapse of the electrode structure with time during operation. 

This method yields relatively large size silver nano-crystallites of 60-80 nm With a plasmon resonance wavelength of -420 nm. Sodium Borohydride as a reductant will give smaller sized silver nanoparticles with plasmon absorption around 380 nm. 

R. Vallepu, A. Mikuni, R. Komatsu, and K. Ikeda, "Synthesis of Liebenbeigite Nano-Crystallites from Silicate Precursor Gels Prepared by Geopolymerization," J. Mineral. Petrol. Sci., 100 [4], 159-67 (2005). 

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