Synthesis of Germanium Nanoclusters with Irreversibly Attached Functional Groups:  Acetals, Alcohols, Esters, and Polymers

Germanium nanoclusters of average diameter 4 nm were prepared with covalently bound termination groups. Chloride-terminated nanoclusters were reacted with a Grignard reagent to form acetal-containing surface-terminated nanoclusters. Treatment with acid yielded hydroxyl-containing surface-terminated nanoclusters, and treatment with an acid bromide and base yielded an ester-containing surface-terminated nanocluster. Atom transfer radical polymerization (ATRP) was used to graft polymer chains from the surfaces of the nanoparticles to yield hybrid nanostructures. Changes of the termination group in the nanoclusters did not alter the photophysics of the original nanoclusters, a result that is consistent with a stable nanocluster surface. The nanoclusters were characterized by HRTEM (high-resolution transmission electron microscopy), NMR, FTIR, UV−vis, and fluorescence spectroscopy.