Free silver nanoparticles synthesized by laser ablation in organic solvents and their easy functionalization

Stable colloidal solutions of free silver nanoparticles (AgNPs) have been synthesized without reducing and stabilizing agents in pure acetonitrile and N,N-dimethylformamide by laser ablation of the bulk metal. Synthesis in tetrahydrofuran and dimethyl sulfoxide gave nanoparticles surrounded by a carbon shell or included in a carbon matrix. Mie theory for free and core@shell spheres accounts for the UV-vis spectra of the nanoparticles and allows their structural characterization. Transmission electron microscopy confirms the structure of the synthesized AgNPs. It is shown that free nanoparticles can be immediately functionalized, without further treatments, in the organic solvent used for the synthesis with molecules which are soluble in the same solvent.