Gold particles

STM and AFM profiles distort the shape of a particle because the side of the tip rides up on the particle. This effect can be corrected for. Consider, say, a spherical gold particle on a smooth surface. The sphere may be truncated, that is, the center may be a distance q above the surface, where q < r, the radius of the sphere. Assume the tip to be a cone of cone angle a. The observed profile in the vertical plane containing the center of the sphere will be a rounded hump of base width 2d and height h. Calculate q and r for the case where a - 32° and d and h are 275 nm and 300 nm, respectively. Note Chapter XVI, Ref. 133a. Can you show how to obtain the relevent equation ... 

Figure C2.6.7. Fractal aggregate of gold particles with a = 12 0.7 nm, obtained under DLCA conditions, with = 1.74 (reproduced with pennission from [65]. Copyright 1984 Elsevier Science Publishers B.V).

Wei G T, Liu F K and Wang C R C 1999 Shape separation of nanometre gold particles by size-exclusion chromatography Anal. Chem. in press... 

Flueli M, Buffat P A and Borel J P 1988 Real time observation by high resolution electron microscopy (HREM) of the coalescence of small gold particles in the electron beam Surf. Sc/. 202 343... 

Buffat P and Borel J P 1976 Size effect on the melting temperature of gold particles Phys. Rev. A 13 2287... 

A gene gun is a device to introduce DNA into cells in vivo. The DNA is attached to gold particles, which are introduced under high velocity into the target tissue. 

The coprecipitation (CP) method was the first method that was found to be effective in depositing nanosized gold particles on base metal oxide surfaces [1, 16]. In this method, an aqueous solution of HAuCLj and the nitrate of a base metal is poured, under vigorous stirring, into an aqueous solution of Na2C03 at 70°C in a short period (within 3 min). The adequate concentration of both the solutions is 0.1-0.4M. The pH of the mixed solution can be maintained at about 9 by using... 

The turnover frequency (TOP) based on surface-exposed atoms significantly increases with a decrease in the diameter of the gold particle from 5 nm [66]. This feature is unique to gold, because other noble metals usually show TOFs that decrease or remain the same with a decrease in the diameter [7]. The decrease in particle size gives rise to an increase in corner or edge and perimeter of NPs and change in electronic structure however, the origin of size effects on catalytic activity for CO oxidation is not clear. 

Streptavidin with attached gold particles was added to mixtures of pl6 and B2x-pl6, starting with no biotin and increasing the molar ratio up to 1% of B2x-pl6. This increased the amount of streptavidin attached to fibrils, demonstrating that the amount of biotin present in the fibrils was dependent on this ratio. 

It was also observed at 1% B2x-pl6 that gold particles had a tendency to be found with an approximate 50 nm spacing (Fig. 17), implying that binding occurs regularly. This is not fully understood this distance is equivalent to approximately 100-120 peptides along a single sheet filament, but as fibrils consist of several... 

Inspired by the elastin-based side-chain polymers, Lemieux et al. prepared elastin-based stimulus-responsive gold nanoparticles. To this end, they capped gold particles with a layer of a single repeat of thiol-functionalized VPGVG peptides (Fig. 17a). These nanoparticles showed LCST behavior, which was modulated by varying the pH of the solution [131]. 

The cospreading of hexanethiol-capped gold particles with the cross-linking agent 4,4 -thiobisbenzenethiol (TBBT) has been reported as a means of producing cross-linked monolayers of hexanethiol-capped Au nanoparticles [125]. In the presence of TBBT, the... 

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