Preparation of Colloidal Gold Sol

A ddH2 0, filtered with 0.45 nm membrane filter and stored dust free and salt free in plastic bottles B 1% gold(III)chloride (tetrachloroauricadd) (w/v) inReagent A C 1% trisodium citrate (w/v) in Reagent A D aquaregia (chloronitrous acid) 1 vol. concentrated HCl+3 vol. concentrated HNO3 

E 1 % tannic acid (w/v) in Reagent A clear by centrifugation and store in a refrigerator for 1-2 days F 1% K2CO3 (w/v) in Reagent A 

To get gold colloids with reproducible size, the given volumes have to be observed exactly. Store the very hygroscopic gold(lll)chloride in a desiccator on anhydrous calcium carbonate powder. 

Clean an Erlenmeyer flask and a Teflon-coated stirrer bar with Soln. D and wash thoroughly with Reagent A. 

The cooled colloid is filled into and stored in a plastic flask cleaned with Soln. D. 

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