Oxide replica

Because the SCR width depends not only on doping density but also on bias, the average pore density is expected to decrease with the square root of bias. This, however, is not observed. An increase in bias often leads to the formation of breakdown-type mesopores at the macropore walls. Because these spiking pores show diameters on the order of a few tens of nanometers they are hard to identify even in an SEM. Spiking pores can be identified if they are enlarged by subsequent chemical etching, as shown in Fig. 8.10. Details of their branched morphology become visible by formation of an oxide replica and after etchback of the sub-... 

Fig. 3 LHS Euclidean macropore array in p-type silicon (Kim et al. 2009) RHS Fractal-like oxide replica of tire pore volume in n-type silicon (Tondare et al. 2008)...

Zhang, W., Zhang, D., Fan, T., Ding, J., Gu, J., Guo, Q. and Ogawa, H. (2006) Biomimetic zinc oxide replica with structural color using butterfly (Ideopsis similis) wings as templates. Bioinspired Biomimcry, 1, 89-95. 

Figure 5. Oxide replica of aluminum etch tunnels grown in IN HC1+6N H2SO4 at The replica is formed...

Most research on the structure of skeletal catalysts has focused on nickel and involved methods such as x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS), electron diffraction, Auger spectroscopy, and x-ray photoelectron spectroscopy (XPS), in addition to pore size and surface area measurements. Direct imaging of skeletal catalyst structures was not possible for a long while, and so was inferred from indirect methods such as carbon replicas of surfaces [54], The problem is that the materials are often pyrophoric and require storage under water. On drying, they oxidize rapidly and can generate sufficient heat to cause ignition. 

Scheme 10.3 Amplified detection of Viral DNA by the generation of a redox-active replica and the bioelectrocatalyzed oxidation of glucose. Reprinted with permission from Ref. 94. Copyright 2002 American Chemical Society.

Advance planning for the possibility of an accident will greatly minimize the consequences. A common hazard is found when a bench scale operation is scaled up when this scale-up occurs in an overutilized laboratory area. Solvents in small and large quantities may be found in the immediate vicinity and batches of oxidizers, expls and similar hazardous ingredients may be present where they may be exposed to ignition by one or more mechanisms. Often other personnel are present within the structure not knowing of the potentially hazardous operations which are conducted in their immediate vicinity. Exits and walk-ways may be blocked by materia-als, equipment or personnel in transit. While there is no safe expl, proplnt or pyrot material, familiarity does breed complacency. We are reminded of a recent expl of a BlkPdr replica plant (Ref 80) which resulted in the loss of life and the destruction of the plant. Nevertheless,... 

In addition to creating semiconductor or metal replicas of the channels of mesoporous materials, which are expected to display electron and hole quantum confinement effects, forming fibers of polymers could lead to materials with novel electrical, magnetic, optical or mechanical properties. To this end, oxidative polymerization of aniline within the channels of mesoporous silica has been reported [91]. Convincing spectroscopic evidence for intrachannel polymerization of aniline to poly(aniline) was provided. Extracted polymer had a molecular weight considerably smaller than that of the bulk material under similar conditions indicative of a diffusion constraint imposed upon the polymerization and growth of monomer inside the channel space of mesoporous silica. 

Fig. 5 Immobilized nucleic acid assays utilizing redox-active moieties, a Amplified detection of viral DNA by generation of a redox-active replica and the bioelectrocatalyzed oxidation of glucose (Reprinted with permission from [200]. Copyright(2002) American Chemical Society), b Alternative formats for the capture on a gold electrode SAM of solution-extended primers or direct surface extension of primer with electrotides (adapted from [185]). c Ferrocene-labelled hairpin for electrochemical DNA hybridization detection. A Fc-hairpin-SH macromolecule is immobilized on a gold electrode. When a complementary DNA target strand binds to the hairpin, it opens and the ferrocene redox probe is separated from the electrode, producing a decrease in the observed current (Reprinted with permission from [203], Copyright(2004) American Chemical Society)...

After anodization and subsequent selective dissolution of anodic oxide the aluminum surface is a replica of back side of anodic alumina. Such surfece structure has ultrasharp tips with 20-100 nm height distanced ixom 10 to 500 nm, respectively. It is obvious that external part of anodic alumina has tip-like morphology too. However partial tip dissolution and smoothing during anodization in acidic solutions results in increasing of tip radii [4]. Thus taking into account known experimental results and our observations it can be concluded that the proposed approach allows to form sharp tips. 

Compact, continuous, and uniform anatase nanotubules with diameters in the range 50-70 nm were produced inside PAO nano-templates by pressure impregnating the PAO pores with titanium isopropoxide and then oxidatively decomposing the reagent at 500 °C [230], Cleaning the surface of the template and repeating the process several times produced titania nanotubules with a wall thickness of 3 nm per impregnation. The tube exteriors appeared to be faithful replicas of the pores in which they were formed. 

Two kinds of template, viz. hard template and soft template, are usually available for nanocasting processes. The true liquid crystal templating synthesis can be considered a soft-template process. In general, the hard template means an inorganic solid. For example, mesoporous silica as a template to replicate other materials, such as carbon or metal oxides, by which the pore structure of the parent can be transferred to the generated porous materials. A 3-D pore network in the template is necessary to create a stable replica. Mesoporous silica and carbon are commonly used templates for nanocasting synthesis. 

Fig. 7 TEM image showing the CdS replica of the Hi phase of an oligo(ethylene oxide) oleyl ether amphiphile (inset). Reproduced with permission from [34]. 1996 by the Nature Publishing Group...

The channels in the PDMS replica are sealed by bonding a flat piece of PDMS following surface oxidization in air plasma. The oxidized PDMS surfaces bond when brought into conformal contact forming an irreversible... 

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