Gold Particle Size

Although the gold particle size has importance in systems, which do not contain reducible oxide, such as MgO [201], still the majority of data indicate that high activity is related to the gold/oxide interface. The importance of this experiment is further underlined by the fact that within a 4-10 nm range of Au particle size the system is active [183], but around the gold particle within a short distance the support must be defected in order to activate the reaction components. 

Figure 1. TEM image of a titania supported gold catalyst (1.7wt.% Au) prepared by deposition-precipitation (gold particle size = 5.3+ 0.3 nm, dispersion = 36%). (Reprinted from Reference [84], 2000, with permission from American Chemical Society).

Histograms of gold particle size distributions are shown in Figure 4. 

Ellis, I.O., Bell, J., and Bancroft, J.D. (1988) An investigation of optimal gold particle size for immuno-histological immunogold and immunogold-silver staining to be viewed by polarized incident light (EPI polarization) microscopy./. Histochem. Cytochem. 36, 121-124. 

Selection of a flotation technique for gold preconcentration depends very much on the ore mineralogy, gangue composition and gold particle size. There is no universal method for flotation of the gold-bearing minerals, and the process is tailored to the ore characteristics. A specific reagent scheme and flowsheet are required for each ore. 

Ascorbate reduction This method (7) entails the fairly rapid addition of sodium ascorbate to chloroauric acid while stirring. If the reaction is carried out on ice, the gold particle size range is between 6 and 8 nm. Higher temperatures tend to increase the particle size The method is also really of academic interest nowadays, since it is not easy to control the final sphere diameter. 

Examination of the low-frequency Raman modes is also claimed to provide a means of gold particle size determination.87,88... 

Figure 4.4 Average gold particle size versus solution pH in Au/TiC>2 catalysts prepared by DP and after calcination at 673 K in air circles 62 squares 65 triangles.67...

K. Alternatively, one may start with an aqueous ultrasonically dispersed suspension of titania containing HAuCLj, and proceed in the same way,125 but at a spray temperature of 673 K the gold particle size was larger (20 nm). All samples contained Au° and AU2O3 the presence of AU2O3 is surprising after such a temperature of treatment (Section 4.1.1). 

Influence of the Thermal Treatment on Gold Particle Size... 

Gold particle size depends not only on the method of preparation, but also on the conditions used for the subsequent treatment performed to obtain the metal. Indeed, as mentioned in the introduction to this chapter, for most methods gold is in the +3 oxidation state after drying (the so-called as... 

---