DNA-mediated assembly of gold nanoparticles influenced by cations

Short double-stranded DNA with a thiol-group is used for the gold nanoparticle assembly. Only in the presence of high concentrations of NaCl particle webs are growing. A possible mechanism, why the salt is necessary is given. In case of single-stranded DNA we show, that first the DNA is completely attached to the gold surface and can be detached within one hour until the strand is completely upstanding. High concentrations of MgCl/sub 2/ allow no growing of particle webs. In this case no distinction between singleand double-stranded DNA is possible. Investigations were carried out with absorption spectroscopy.