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Microemulsion Approach to Non-Agglomerated and Crystalline Nanomaterials


  • The authors are grateful to the Center for Functional Nanostructures (CFN) of the Deutsche Forschungsgemeinschaft (DFG) at the University of Karlsruhe (TH) for financial support.

  • Dedicated to Professor Hartmut Bärnighausen on the occasion of his 75th birthday


A wide variety of different nanomaterials, including ZnO, (NH4)Y(C2O4)2·H2O, Y(OH)3, Y2O3, In2O3:Sn, CePO4:Tb, CaCO3, CuS, Co3[Co(CN)6]2, and K3[Co(NO2)6] are realized by a microemulsion approach. While heating the micellar system to reflux (200 to 215 °C), highly crystalline materials can be realized, which are still nanosized and do not agglomerate afterwards. Furthermore, a phase separation is initiated by the addition of diethylene glycol, which allows a facile removal of the nanomaterials by the application of low solvent quantitities, and again excludes agglomeration. Both aspects—the realization of highly crystalline materials and the facile separation of non-agglomerated particles—represent a useful extension of microemulsion techniques. Besides the number and quality of the nanomaterials, the success of the experimental approach is further proven by the realization of physical properties that are restricted to crystalline materials. Namely, these are the bright colors of Co3[Co(CN)6]2 and K3[Co(NO2)6] as pigments, the electrical conductivity of In2O3:Sn (ITO), and the luminescence of CePO4:Tb.

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