Nanostructure deposition

Konstandopoulos, A. G. Convective-diffusive deposition of fractal-like aggregates and the microstructure and properties of the resulting nanostructured deposits (to be submitted) (2007). 

All the metallic nanostructures deposited by laser electrodispersion on both types of silicon substrates were found to be exceedingly active in the above processes. The activity was orders of magnitude higher than that of typical supported catalysts prepared by the standard techniques. Such a high activity is presumably due not only to the small size and amorphous state of nanoparticles, but also to the influence exerted by the charge effects discussed above. 

The dissimilarities between the charge states of nickel nanostructures deposited onto substrates of well-conducting p- and n-type silicon (unoxidized) were manifested in different catalytic activities in the reaction of carbon tetrachloride addition to olefins. It was shown that negatively charged nanoparticles on an n-type Si substrate have a two times higher activity, compared with positively charged particles on a p-type Si substrate (see Figure 15.10). 

In addition to the benefits of MEF from metal nanostructures deposited onto solid supports that are very useful in surface bioassays, MEF can also be observed from individual nanostructures in bioassays carried out in solution. In this regard, fluorophores and metal nanostructures can be assembled in core-shell architecture and can be used as fluorescent nanoparticles as indicators in biological plications such as imaging of cellular activity or single-molecule sensing. 

Next, the template-assisted nanostructured deposition of NiO was tried, following the experimental method of Sonavane et al. for the electrodeposition of nontemplated coatings [62]. For this purpose a 0.5M aqueous NiCl bath containing 0.1 M KCl was prepared, which was complexed using EDTA and pH-adjusted to 8 by addition of KOH. Electrodeposition was conducted in a three-electrode cell at a potential of -1.1 V versus Ag/AgCl for lOOmin. The obtained DG-structure NiO film of about 1 ttm thickness is presented in Fig. 5.5. This preparation technique has two major disadvantages firstly, the very slow deposition rate, and secondly, the transparency of the deposit complicates the anyway difficult preparation route. In Chap. 6, a more elegant approach for nanostructured NiO deposition is presented that overcomes these issues. 

The planar order of nanostructures deposited by chemical routes has become an important issue, because of the competition with solid-state nanotechnology cap>able of the fabrication of fine two-dimensional structures. The main concern is with the layers of nanopartides produced by chemical self-assembly, because methods of electrostatic self-assembly and LB is not capable of producing two-dimensional ordered arrays of nanopartides. The features of the lateral arrangement of particles, which are buried under layers of either closely packed amphiphilic compounds or polymers, are usually smeared and difficult to observe. In the case of relatively thick (quasi-3D) films, produced by electrodeposition and sol-gel techniques, the morphology study usually reveals polycrystallites. Therefore, the quality of these materials can be assessed by the size of the crystallites and by the presence of preferential orientation, which may cause anisotropy of the electrical and optical prop>erties of materials. 

The original substrate structure used for our early photosensitization experiments was a fractal derived by hydrolysis of an organo-titanium compound but it has since been replaced with a nanostructure deposited from colloidal suspension. This evidently provides a much more reproducible and controlled porous high surface area nanotexture. Further, since... 

Su, Z. J., C. Yang, B. H. Xie et al. 2014. Scalable fabrication of MnOj nanostructure deposited on free-standing Ni nanocone arrays for ultrathin, flexible, high-performance micro-supercapacitor. Energy and Environmental Science 7 2652-2659. 

Figure 43. Silver nanostructures deposited on glass during electroplating (A). Panels B and C ate consecutive magnification of the marked area on panel A. Bright-field image.

Figure 12.9 TEM images of the silica nanostructures deposited in 20 nm AAO membranes at (a) -125 V, (b) -1.10V, and (c) -0.95 V versus SCE. Scale bars 100 nm. (Reproduced with permission from Ref [37].)...

Torres, M. (2009) Study of ferroelectric PbTiOa nanostructures deposited onto substrates and prepared by a novel microemulsion mediated synthesis. PhD. thesis, Universidad Carlos in de Madrid. November. 

In designing layered nanostructures, deposited material forms continuous layers but to achieve the same, deposition must take place in a very controlled manner. Moreover, factors such as temperature, pH of the electrolyte, electrolyte concentration, current density, and deposition time must be kept in mind as they greatly affect the quality of the material deposited. 

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