Fabrication and characterization of gold nanoparticles by femtosecond laser ablation in an aqueous solution of cyclodextrins

Gold nanoparticles were produced by femtosecond laser ablation of a gold metal plate in an aqueous solution of alpha-cyclodextrin (CD), beta-CD, or gamma-CD. The gold nanoparticles exhibited the UV-vis absorption spectrum with a maximum absorption band at 520 nm, similar to that of gold nanoparticles chemically prepared in a solution, The size distribution of the nanoparticles measured by transmission electron microscopy (TEM) shifted to a drastically smaller size of similar to2-2.4 nm and narrower size distribution of less than 1-1.5 nm fwhm with an increase in the concentration of cyclodextrins. Both the particle size and size distribution were also dependent on the type of cyclodextrins used in aqueous solution. In particular, the gold colloids resulting from ablation in 10 mM beta-CD were conspicuously stable under aerobic conditions without any protective agent present. CDs formed an inclusion complex with ablated atoms to reduce the total concentration of embryonic nanoparticles formed in the plume CDs, as evident by Raman spectroscopy. The consecutive particle growth due to the mutual coalescence between nanoclusters and their neighboring free gold atoms was severely limited in the presence of CDs.