In this invention, polyimidazole ligands (PILs) incorporating pendant imidazole moieties for nanocrystal binding and either sulfonatebetaine, carboxybetaine, or phosphocholinebetaine moieties for water-solubilization have been developed. Greatly enhanced stability of nanocrystals (both over time and in wide pH range) was achieved by incorporating multi-dentate imidazole moieties which provide strong coordination of the ligand to the nanocrystal surface and prevent aggregation of nanocrystals. Synthesis of betaine PILs was developed by modifying the synthesis of recently developed PEG containing poly imidazole ligands (PEG PILs). These nanocrystals are compact, water soluble, and biocompatible.
