Controlled size manipulation of free gold nanoparticles by laser irradiation and their facile bioconjugation

The average size of gold nanoparticles (AuNP), obtained by laser ablation in solution, is reduced to a few nanometers or increased to tens of nanometers using laser treatments with different strategies. The techniques do not require any stabilizing molecules and the AuNP surface is free from strongly linked ligands. This allowed one-step, immediate and very efficient functionalization of AuNP with commonly used proteins like bovine serum albumin (BSA), which can be detected, using small nanoparticles, down to 3 picomoles and with a 1 : 10 concentration ratio of BSA : AuNP.