Experimental results on the process of self-assembly of Au nanoparticles under their exposure to picosecond laser radiation in water are presented. Self-assembly of Au NPs into nanowires occurs under laser ablation of a bulk Au target, which is cathodically biased with respect to a Pt anode. Similar process is observed in excess of free electrons in solution due to presence of beta-active ions, e.g., Tritium. Self-assembly of Au NPs into nanowires also occurs under laser exposure of their dense colloidal solution to picosecond laser radiation and proceeds in an avalanche-like way. Possible mechanisms of self-assembly are discussed. (C) 2015 Elsevier B.V. All rights reserved.