Selective formation of monodisperse CdSe nanoparticles on functionalized self-assembled monolayers using chemical bath deposition

Using CdSe chemical bath deposition (CBD) we demonstrate the selective growth and deposition of monodisperse nanoparticles on functionalized self-assembled monolayers (SAMs) using time-of-flight secondary ion mass spectrometry and scanning electron microscopy. We show that the deposition mechanism involves both ion-by-ion growth and cluster-by-cluster deposition. On –COOH terminated SAMs strongly adherent CdSe nanoparticles form via a mixed ion-by-ion and cluster-by-cluster mechanism. Initially, Cd2+ ions form complexes with the terminal carboxylate groups. The Cd2+-carboxylate complexes then act as the nucleation sites for the ion-by-ion growth of CdSe. After a sufficient concentration of Se2− has formed in solution via the hydrolysis of selenosulfate ions, the deposition mechanism switches to cluster-by-cluster deposition. On –OH and –CH3 terminated SAMs monodisperse CdSe nanoparticles are deposited via cluster-by-cluster deposition and they do not bind strongly to the surface. Finally, under the appropriate experimental conditions we demonstrate the selective deposition of CdSe nanoparticles on patterned –CH3/–COOH SAMs.