Nanoparticle size reduction during laser ablation in aqueous solutions of cyclodextrins

The femtosecond laser ablation of gold in aqueous solution has been useded to produce colloidal gold nanoparticles. We consider the effect of size reduction through the use of aqueous cyclodextrin (α-CD, β-CD or γ-CD) solutions. Both the size reduction and the colloid stability depend on the type of CD, with the smallest, almost monodispersed and extremely stable particles prepared with β-CD, followed by slightly larger ones fabricated in γ-CD and β-CD. Several studies were carried out to elucidate the nature of the interaction between the gold and CDs. in particular, we studied the influence of pH on the size distribution and the electric charge of the gold particles surface. We examined the gold surface composition and determined the nature of the chemical groups on the gold. This enabled us to develop a model of chemical interactions between the gold and the CDs, which includes both a hydrophobic interaction of the Au⁰ with the interior cavity of the CD and a hydrogen bonding of -O groups, on the partially oxidized gold surface, with -OH groups of the CDs. These nanoparticles are of importance in biosensing applications.