Reversible Gelation of II–VI Nanocrystals: The Nature of Interparticle Bonding and the Origin of Nanocrystal Photochemical Instability


  • We thank G. Auner for the use of the Raman microscope. This work was supported by NSF (DMR-0094273 and DMR-0701161) and the Donors of the Petroleum Research Fund, administered by the American Chemical Society. The electron microscopy work was performed on a JEOL 2010 purchased under NSF grant DMR-0216084.


original image

Programmable assembly and disassembly: Chemical and spectroscopic studies show that Se[BOND]Se bond formation is responsible for the oxidation-induced aggregation of thiolate-capped CdSe nanocrystals to gels. Treatment with reducing agents leads to Se[BOND]Se bond cleavage and dispersion of the gel. This process can be cycled, resulting in successively smaller particles (see picture; MUA = 11-mercaptoundecanoic acid, TMAH = tetramethylammonium hydroxide).