Site-selective deposition

Figure 9.4 Schematic illustration of site-selective deposition of CoTMPyP on gold NP surfaces and tuning the quantities of the as-anchored electiocatalysts by number density of gold NPs.65 (Reprinted with permission from W. Cheng et al., J. Phys. Chem. B 2004,108, 19146-19154. Copyright 2004 American Chemical Society.)...

Y. Masuda, S. Ieda, and K. Koumoto, Site-selective deposition of anatase of Ti02 in an aqueous solution using a seed layer, Langmuir 19(10), 4415-4419 (2003). 

Figure 2.88 shows a scanning electron micrograph that shows a side view of a sample after deposition of Pt particles. The site-selective deposition of Pt is clearly visible. It should be noted that not all nanopores are necessarily filled because, in the progressing oscillation, pores at different phases of their development exist on the surfaces and, depending on the process, some do not make contact with the... 

Figure 7.3 Prediction of site-selective deposition of nanomaterials in the respiratory tract during nose breathing. Reprinted with from Ref [51] with permission from Environmental Health Perspectives.

Laser ablation of polymer films has been extensively investigated, both for application to their surface modification and thin-film deposition and for elucidation of the mechanism [15]. Dopant-induced laser ablation of polymer films has also been investigated [16]. In this technique ablation is induced by excitation not of the target polymer film itself but of a small amount of the photosensitizer doped in the polymer film. When dye molecules are doped site-selectively into the nanoscale microdomain structures of diblock copolymer films, dopant-induced laser ablation is expected to create a change in the morphology of nanoscale structures on the polymer surface. 

Over single crystal surfaces with defect sites, vacuum deposition of gold vapor or size-selected gold anion clusters at low temperatures can lead to relatively homogeneous... 

Interestingly, it has been shown that some adatoms can be selectively deposited on step sites, taking advantage of the enhanced reactivity of these sites. Figure 7.5 shows the voltammogram of a Pt(775) surface in 0.5 M H2SO4. The hard sphere model for... 

On the other hand, if the hole flow in DNA could be artificially controlled to deposit at the desired site in DNA, it may enable site-selective oxidation and strand scission of DNA, which is desirable from a therapeutical standpoint. Furthermore, understanding DNA-mediated hole transfer is expected to lead to an additional application in the development of biosensors and bioelectronic devices [9]. Therefore, the regulation of the transfer rate and direction of the hole generated in DNA is of interest from the perspective of using DNA as a building block for electronic devices. 

Site-selection spectroscopy Maximum selectivity in frozen solutions or vapor-deposited matrices is achieved by using exciting light whose bandwidth (0.01-0.1 cm-1) is less than that of the inhomogeneously broadened absorption band. Lasers are optimal in this respect. The spectral bandwidths can then be minimized by selective excitation only of those fluorophores that are located in very similar matrix sites. The temperature should be very low (5 K or less). The techniques based on this principle are called in the literature site-selection spectroscopy, fluorescence line narrowing or energy-selection spectroscopy. The solvent (3-methylpentane, ethanol-methanol mixtures, EPA (mixture of ethanol, isopentane and diethyl ether)) should form a clear glass in order to avoid distortion of the spectrum by scatter from cracks. 

We have proved that when tin is selectively deposited on the base transition metal via SOMC/M, the resulting material exhibits active sites with high homogeneity. In both hi- and organobimetallic catalysts, the metal-metal interactions are favored, avoiding in this way the waste of metal promoter by direct interaction with the support material. 

While some of the Mississippian textiles are of similar structure to the Middle Woodland textiles, others are very complex materials and are lace-like in appearance. Many of the materials from Etowah are preserved by mineralization, and display green-colored deposits on their surfaces. Bast fiber, rabbit hair, and feathers have been identified (2, 11). The textiles from these two sites selected for analysis are representative of the complexity of structure and fineness of yarns seen in the materials they provide evidence of the sophisticated technology of prehistoric people in all phases of fiber collection, processing, yarn spinning, fabric manufacture and, when present, coloration. 

Site of synthesis, mechanism of transport and selective deposition of hydrocarbons... 

As a consequence when the difference between equilibrium potentials of the two half redox reactions is low, the modifying metal, during the preparation of a bimetallic catalyst by direct redox reaction, will be deposited selectively on specific sites of the parent metal (i.e. sites that are highly oxidizable such as comers, edges, etc.). However, the equilibrium potentials are defined by Nemst s law which provides facilities to fit the potential values by changing the concentrations of the oxidized and reduced forms (eqs 2 and 2 ) and so induces selective deposition of the modifier on the parent catalyst. 

In summary, the technique of catalytic reduction for the preparation of bimetallic catalysts can be extensively used with a variety of parent metals and re-ductants. However, some structure sensitivities of the reduction reactions become apparent and the modifying metal can be selectively deposited on specific sites of the parent-supported metal. Furthermore, such structure sensitivity depends on the nature of the re-ductant, and a given modifier can be deposited, according to the reductant used, selectively onto different parts of the metallic surface. In fact, a bimetallic catalyst can be tailored to provide the optimum activity, selectivity and lifetime for a given reaction. 

Coluccio ML, Das G, Mecarini E, Gentile E, Pujia A, Bava L, Tallerico R, Candeloro P, Liberale C, Angelis ED, Eabrizio ED (2009) Silver-based surface enhanced Raman scattering (SERS) substrate fabrication using nanolithography and site selective electroless deposition. Microelectron Eng 86 1085-1088... 

Arneth J.-D., Milde G., Kerndorff H., and Schleyer R. (1989) Waste deposit influences on groundwater quality as a tool for waste type and site selection for final storage quality. In The Landfill, Lecture Notes in Earth Sciences (ed. P. Baccini). Springer, Berlin, vol. 20, pp. 399-424. 

The routes toward improved design should start at the microscopic level, for example, via site-selective electrochemical deposition of Pt at the active three-phase boundary [146]. At this point, it is hard to estimate extra efforts to be invested in such procedures, but their prospects for optimized catalyst utilization are obvious. 

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