Gold layer

For the purpose of calibration and particle size calculations, it was decided to confirm the reported particle sizes of the various latices supplied by Dow and Polysciences, using scanning electron microscopy. Unfortunately, after subtracting the thickness of the gold layer with which the particles were coated from the size shown on the micrographs, some inconsistencies were noted with respect to the measured sizes of the particles and their elution behaviour. It was therefore decided to assume the reported sizes as true values with the exception of the 5T nm particle. 

Figure 10. Reflectivity for the geometry consisting of an SF14 glass prism, 50 nm thick gold layer, and a dielectric, as a function of the angle of incidence for two different refractive indices of the dielectric wavelength = 682 nm.

We also found that a gold layer was not required nor advantageous for general use of the technique. 

Fig. 10. A SPR Detection realized in a BIAcore system. A fan of polarized light passes a prism and is focused at the interface to an aqueous phase under conditions of total reflection. An evanescent wave enters the solvent phase. If the prism is coated with a thin gold layer at the interface the free electrons in the metal absorb energy from the evanescent wave for a distinct angle, depending on the refractive index of the solvent near the interface. B The gold layer can be modified with, e.g., a carboxydextrane matrix, where catcher molecules can be immobilized by standard chemistry. If a ligand is applied with the aqueous phase it may interact with the catcher and accumulate in the matrix, causing a shift in the resonance angle. If no specific binding occurs the refractive index in proximity of the sensor is less affected...

Figure 3.18 UPS spectra of silver and gold layers on a ruthenium (001) substrate show the evolution of the d-band as a function of the silver dimensions. Note also the changes in work function reflected in the width of the spectra of Ag (courtesy of K. Wandelt, Bonn [47]).

Practical metal catalysts frequently consist of small metal particles on an oxide support. Suitable model systems can be prepared by growing small metal aggregates onto single crystal oxide films, a technique whereby the role of the particle size or of the support material may be studied. [37] A quite remarkable example of the variation of the catalytic activity with particle size has recently been found for finely dispersed Au on a Ti02 support, which was revealed to be highly reactive for combustion reactions. [38] On the basis of STM experiments it was concluded that this phenomenon has to be attributed to a quantum size effect determined by the thickness of the gold layers. 

The pores in a commercially available polycarbonate filtration membrane (Poretics) were used as templates to form the nanotubules (pore diameter = 50 nm pore density = 6 X 10 pores cm thickness = 6 pm). As before, the electrolessly plated Au deposits both on the pore walls and the membrane faces [71]. The gold surface layers on the membrane faces allow us to make electrical contact to the Au nanotubules within the pores. The thickness of the gold layers deposited on the pore walls can be controlled... 

Fig. 7 presents another example of a very high-contrast waveguide - a rectangular buried waveguide covered by a gold layer. Strong hybridization of the waveguide mode with the antisymmetric surface plasmon is clearly manifested. 

Figure 7. Left cross-section of a buried waveguide covered by a gold layer. Right Field distribution of a quasi-TM-polarized mode. (Courtesy of J. Petracek, TU Bmo.)...

Figure 4. Reflectivity in the Kretschmarm geometry of ATR consisting of an SF14 glass prism (refractive index - 1.65), a gold layer (thickness - 50 nm), and a low refractive index dielectric medium (refractive index - 1.32), and wavelength - 800 nm.

Figure 6. Left MO effects of a Co/Au multilayer with a 12 nm thick Co layer and a gold layer of 31 nm, in the transversal configuration of the magnetization. Right reflectivity of the multilayer compared with the case of a gold layer of 50 nm.

Recent work has expanded this knowledge by first electrodeptositing a gold layer on the device surface and then applying an organic layer to the electrodeptosited surface (3). In this case, the device was a pacemaker lead. The organic layer was utilized to prevent... 

Successive Reduction of Metal Ions. Successive reduction of two metal salts can be considered as one of the most suitable methods to prepare core/shell structured bimetallic particles (Fig. 9.1.3). In 1970, Turkevich and Kim tried to grow gold on Pd nanoparticles to obtain gold-layered Pd nanoparticles (39). The deposition of one... 

In an earlier study, Turkevich and Kim proposed gold-layered palladium nanoparticles (39). Three types of Au/Pd bimetallic nanoparticles, such as Au-core/Pd-shell, Pd-core/Au-shell, and random alloyed particles, are prepared by the application of successive reduction. Two kinds of layered Pd/Pt bimetallic nanoparticles were also reported by successive reduction (43). However, detailed analyses of the structure of these bimetallic nanoparticles were not carried out at that time. Only the difference of UV-Vis spectra between the bimetallic nanoparticles and the physical mixtures of the corresponding monometallic nanoparticles was discussed. 

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