Gold coating

A detailed study by Grieser and co-workers [169] of the forces between a gold-coated colloidal silica sphere and a gold surface reveals the preferential adsorption of citrate ions over chloride to alter the electrostatic interaction. 

Figure Bl.19.36. Image of the frictional force distribution of a pattern consisting of areas of CH -tenuinated and areas of COOH-tenninated molecules attached to gold-coated silicon. The tip was also fiinctionalized in (a) with CH3 species and in (b) with COOH species. The bright regions correspond to the higher friction force, which in (a) is observed on the CH areas and in (b) on the COOH areas. (Taken from [187], figure 3.)...

Instrumental Interface. Gc/fdr instmmentation has developed around two different types of interfacing. The most common is the on-the-fly or flow cell interface in which gc effluent is dkected into a gold-coated cell or light pipe where the sample is subjected to infrared radiation (see Infrared and raman spectroscopy). Infrared transparent windows, usually made of potassium bromide, are fastened to the ends of the flow cell and the radiation is then dkected to a detector having a very fast response-time. In this light pipe type of interface, infrared spectra are generated by ratioing reference scans obtained when only carrier gas is in the cell to sample scans when a gc peak appears. 

Decorative. Titanium nitride has a golden color and is used extensively to coat steel and cemented carbide substrates for watch cases, watch bands, eyeglass frames, etc. It provides exceUent scratch resistance as weU as the desired aesthetic appearance, and it replaces gold coatings used previously. 

A.STM B735, Std. Test Methodfor Porosity in Gold Coatings on Metal Substrates by NitricMcid Vapor, American Society for Testing and Materials, Philadelphia, Pa., 1992. 

In the thermal production of gold coatings on ceramics and glass, paints are used which comprise Au chloro-complexes and sulfur-containing resins dissolved in an organic solvent. It seems likely that polymeric species are responsible for rendering the gold soluble. 

Gold coatings on separable electric contacts and slip rings make use of the high hardness possible with electrodeposition to resist wear. Rhodium is another metal which can be exceptionally hard. Thick coatings have a cracked-sealed structure similar to that of chromium. 

The hardness of such coatings may reach a maximum of about 400 Hy as compared with approximately 50 Hy for a soft gold deposit. A series of corrosion studies in industrial and marine atmospheres by Baker" has indicated that the protective value of hard gold coatings is comparable with that of the pure metal, and that a thickness of only 0-002 5 mm gives good protection to copper base alloys during exposure for six months. 

In addition to the use of cyclohexane, dimethylformamide (DMF) was used as a good solvent. So as to pick up the thiol-modified terminal, gold-coated cantilevers were used. The nominal values of their spring constant ki were 30 or 110 pN nm . A typical force-extension curve measured in cyclohexane is shown in Figure 21.4. The solvent temperature was kept at about 35°C, which corresponded to its temperature for PS chains. Thus, a chain should behave as an ideal chain. The slope at the lowest extension limit (dashed line in Figure 21.4) was 1.20 X lO" N m . ... 

Changes in thermal stability and mass due to the formation of CdS nanoparticles in LB films were examined [180]. The LB films were formed onto gold-coated quartz oscillators from monolayers of arachidic acid or nonacosa-10,12-diynoic acid on CdCH containing subphases. The films were exposed to H2S gas until the mass change indicated complete conversion of Cd to CdS. The thermal stability of the H2S-treated films was reduced, with significant mass loss initiating at 55°C, compared to minimal mass loss in the untreated films up to at least 80°C under mild vacuum. The average CdS-particle size... 

FIG. 23 Schematic drawing of using microcontact printing for obtaining hydrophobic areas on a gold-coated substrate. After pattern transfer (a and b), incubation with an S-layer protein solution (c) leads to the formation of a protein monolayer on the hydrophobic areas only. 

Alkali fuel cells containing KOH and platinum- and gold-coated electrodes were developed for the space program, but these are too expensive for down-to-earth vehicles. In addition, these cells require pure oxygen rather than CO2 -containing air. 

Some of the [Au(N,0)Cl2] derivatives, namely 58a, 59a and 59b, which have been tested for cytotoxic activity against various human tumor cell lines, have shown significant effects [144]. Compound 57 is a potential alternative to dimethylgold (III) P diketonates and can be used as a starting material for gold coatings by the CVD method [140]. Recent studies have shown that the long-term stability of these... 

Kruger, S., Stener, M. and Rosch, N. (2001) Relativistic density functional study of gold coated magnetic nickel clusters. Journal of Chemical Physics, 114, 5207-5215. 

Zhou, H.S., Honma, 1., Komiyama, H. and Haus, J.W. (1994) Controlled synthesis and quantum-size effect in gold-coated nanoparticles. Physical Review B - Condensed Matter, 50, 12052-12057. 

Xu, X., Cortie, M.B. and Stevens, M. (2005) Effect of glass pre-treatment on the nucleation of semi-transparent gold coatings. Materials Chemistry and Physics, 94, 266-274. 

Munthe J, Xiao Z, Schroeder WH, Lindqvist O. 1991. Removal of gaseous mercury from air using a gold coated denuder. Atmos Environ 24A 2271-2274. 

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