Free metal nanoparticles obtained by laser ablation in water and organic solvents: Size manipulation, easy functionalization and bioconjugation

Key issue for metal nanoparticles (MNP) applications is their functionalization, that mainly depends on MNP surface accessibility and on solvents compatibility with functional molecules. Often reduction methods require long and expensive processes to overcome these two limits and to obtain a satisfactory MNP functionalization. An alternative is represented by laser ablation synthesis of metal nanoparticles in liquid solution (LASiS). LASiS provides stable colloidal solutions in water or in organic solvents, without any ligands or chemicals. Therefore MNP surface is usually free and functionalization occurs directly. However, LASiS does not allow a good control of MNP average size and size distribution. We show how this problem can be faced with good results by chemical free laser manipulation techniques for MNP size reduction and increase, inspired by top down and bottom up approaches. These techniques also allow a very easy bioconjugation of gold nanoparticles with bovine serum albumine with picomoles sensitivity.