A "macrocyclic effect" on the formation of capped silver nanoparticles in DMF

The formation of silver nanoparticles in the presence of various macrocyclic thiol compounds in N,N'-dimethylformamide (DMF) solution was investigated in situ through visible spectrophotometric and photon correlation spectroscopic measurements. While temperature, solvent nature, and the concentration of thiol compounds are important parameters in the process of metal cluster and particle generation, the chemical structure of the thiol capping molecules also plays a crucial role at determining the average particle size. In this work, we report, for the first time, the existence of a "macrocyclic effect" on silver particle formation by using two types of thiol macrocyclic compounds, thiolated beta-cyclodextrins (beta-CD) and thiolated cavitands. Perthiolated beta-CD was found to be more efficient as a capping ligand than monothiolated beta-CD. Similarly, a tetrathiolcavitand derivative was also more efficient than a simple monothiol model compound. The macrocyclic thiol ligands led to more stable and smaller particles, a finding that may prove useful in future wet schemes for the preparation of metal nanoparticles functionalized with organic monolayers.