Patent ID: 7364920

Claim:
A method for assaying presence of a specific substance at sites on a substrate, comprising: (a) providing conditions allowing formation of nucleation centers on sites containing said substance; (b) contacting said substrate with a treatment composition comprising a reagent and a soluble gold-providing agent that is a gold-containing molecule or complex, the composition being kinetically stable such that upon such exposure gold metal is essentially not deposited on the substrate unless a nucleation center is present thereon, and in the presence of a nucleation center at said sites, gold atoms are released from said gold-providing agent and deposited onto said nucleation center to form gold metal deposits at said sites; and (c) detecting metallic gold deposits on said substrate, a gold deposit at a site on the substrate indicating presence of said substance at said site; wherein said gold-providing agent is Au I (SNC) 2 − or KAu I (SNC) 2 .