Colloidal suspensions are widely used to study processes such as melting, freezing1,2,3 and glass transitions4,5. This is because they display the same phase behaviour as atoms or molecules, with the nano- to micrometre size of the colloidal particles making it possible to observe them directly in real space3,4. Another attractive feature is that different types of colloidal interactions, such as long-range repulsive1,3, short-range attractive5, hard-sphere-like2,3,4 and dipolar3, can be realized and give rise to equilibrium phases. However, spherically symmetric, long-range attractions (that is, ionic interactions) have so far always resulted in irreversible colloidal aggregation6. Here we show that the electrostatic interaction between oppositely charged particles can be tuned such that large ionic colloidal crystals form readily, with our theory and simulations confirming the stability of these structures. We find that in contrast to atomic systems, the stoichiometry of our colloidal crystals is not dictated by charge neutrality; this allows us to obtain a remarkable diversity of new binary structures. An external electric field melts the crystals, confirming that the constituent particles are indeed oppositely charged. Colloidal model systems can thus be used to study the phase behaviour of ionic species. We also expect that our approach to controlling opposite-charge interactions will facilitate the production of binary crystals of micrometre-sized particles, which could find use as advanced materials for photonic applications7.
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Hachisu, S., Kobayashi, Y. & Kose, A. Phase separation in monodisperse latexes. J. Colloid Interf. Sci. 42, 342–348 (1973)
Pusey, P. N. & van Megen, W. Phase behaviour of concentrated suspensions of nearly hard colloidal spheres. Nature 320, 340–342 (1986)
Yethiraj, A. & van Blaaderen, A. A colloidal model system with an interaction tunable from hard sphere to soft and dipolar. Nature 421, 513–517 (2003)
Kegel, W. K. & van Blaaderen, A. Direct observation of dynamical heterogeneities in colloidal hard-sphere suspensions. Science 287, 290–293 (2000)
Pham, K. N. et al. Multiple glassy states in a simple model system. Science 296, 104–106 (2002)
Islam, A. M., Chowdhry, B. Z. & Snowden, M. J. Heteroaggregation in colloidal dispersions. Adv. Colloid Interf. 62, 109–136 (1995)
Vlasov, Y. A., Bo, X. Z., Sturm, J. C. & Norris, D. J. On-chip natural assembly of silicon photonic bandgap crystals. Nature 414, 289–293 (2001)
Royall, C. P., Leunissen, M. E. & van Blaaderen, A. A new colloidal model system to study long-range interactions quantitatively in real space. J. Phys. Condens. Matter 15, S3581–S3596 (2003)
Hachisu, S. & Yoshimura, S. in Physics of Complex and Supermolecular Fluids (eds Safran, S. A. & Clark, N. A.) 221–240 (Wiley, New York, 1987)
Schofield, A. B. Binary hard-sphere crystals with the cesium chloride structure. Phys. Rev. E 64, 051403 (2001)
Hunt, N., Jardine, R. & Bartlett, P. Superlattice formation in mixtures of hard-sphere colloids. Phys. Rev. E 62, 900–913 (2000)
Saunders, A. E. & Korgel, B. A. Observation of an AB phase in bidisperse nanocrystal superlattices. Chemphyschem 6, 61–65 (2005)
Redl, F. X., Cho, K. S., Murray, C. B. & O'Brien, S. Three-dimensional binary superlattices of magnetic nanocrystals and semiconductor quantum dots. Nature 423, 968–971 (2003)
Bosma, G. et al. Preparation of monodisperse, fluorescent PMMA-latex colloids by dispersion polymerization. J. Colloid Interf. Sci. 245, 292–300 (2002)
Bresme, F., Vega, C. & Abascal, J. L. F. Order-disorder transition in the solid phase of a charged hard sphere model. Phys. Rev. Lett. 85, 3217–3220 (2000)
Velikov, K. P., Christova, C. G., Dullens, R. P. A. & van Blaaderen, A. Layer-by-layer growth of binary colloidal crystals. Science 296, 106–109 (2002)
Gelinck, G. H. et al. Flexible active-matrix displays and shift registers based on solution-processed organic transistors. Nature Mater. 3, 106–110 (2004)
Dzubiella, J., Hoffmann, G. P. & Löwen, H. Lane formation in colloidal mixtures driven by an external field. Phys. Rev. E 65, 021402 (2002)
Löwen, H. & Dzubiella, J. Nonequilibrium pattern formation in strongly interacting driven colloids. Faraday Discuss. 123, 99–105 (2003)
Pusey, P. N. General discussion. Faraday Discuss. 123, 177 (2003)
Dresselhaus, M. S., Dresselhaus, G. & Eklund, P. C. Science of Fullerenes and Carbon Nanotubes Ch. 8 (Academic, London, 1996)
Caballero, J. B., Puertas, A. M., Fernandez-Barbero, A. & de las Nieves, F. J. Oppositely charged colloidal binary mixtures: A colloidal analog of the restricted primitive model. J. Chem. Phys. 121, 2428–2435 (2004)
Maskaly, G. R. Attractive Electrostatic Self-Assembly of Ordered and Disordered Heterogeneous Colloids. PhD thesis, Massachusetts Institute of Technology (2005)
Bartlett, P. & Campbell, A. I. Three-dimensional binary superlattices of oppositely charged colloids. Phys. Rev. Lett. (in the press)
Underwood, S. M., van Megen, W. & Pusey, P. N. Observation of colloidal crystals with the cesium-chloride structure. Physica A 221, 438–444 (1995)
Biancaniello, P. L., Kim, A. J. & Crocker, J. C. Colloidal interactions and self-assembly using DNA hybridization. Phys. Rev. Lett. 94, 058302 (2005)
van Blaaderen, A. & Vrij, A. Synthesis and characterization of colloidal dispersions of fluorescent, monodisperse silica spheres. Langmuir 8, 2921–2931 (1992)
Hunter, R. J. Zeta Potential in Colloid Science Ch. 4 (Academic, London, 1981)
O'Brien, R. W. & White, L. R. Electrophoretic mobility of a spherical colloidal particle. J. Chem. Soc. Faraday Trans. II 74, 1607–1626 (1978)
Frenkel, D. & Smit, B. Understanding Molecular Simulations Ch. 5, 10 (Academic, London, 2002)
Weiss, J. A., Oxtoby, D. W., Grier, D. G. & Murray, C. A. Martensitic transition in a confined colloidal suspension. J. Chem. Phys. 103, 1180–1190 (1995)
We thank R. P. A. Dullens, D. Derks, N. A. M. Verhaegh, P. Vergeer and C. M. van Kats for particle synthesis, A. D. Hollingsworth for solvent characterization, J. H. J. Thijssen for help with the pictures of the Bragg reflections and both P.N. Pusey and A.B. Schofield for pointing out the resemblance between our LS6-structure and certain fullerene compounds. This work is part of the research program of the ‘Stichting voor Fundamenteel Onderzoek der Materie’ (FOM), which is financially supported by the ‘Nederlandse organisatie voor Wetenschappelijk Onderzoek’ (NWO). Author contributions M.E.L. and C.G.C. investigated the phase behaviour of the experimental binary systems, A.-P.H. and M.D. performed the computer simulations, A.-P.H. and R.v.R. calculated the Madelung energies, C.P.R. worked on the lane formation, A.I. on the Bragg scattering, A.I.C. made different plus/minus systems and A.v.B. initiated the work and co-wrote the paper together with M.E.L.
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
Experimental details of the laser light powder diffraction measurements that we performed to determine the lattice parameter of the CsCl-type PMMA crystals. (DOC 19 kb)
Listing of the laser light powder diffraction data of the CsCl-type PMMA crystals, including the diffraction angles, the peak assignments and the calculated lattice parameter. (DOC 26 kb)
A photograph of the Bragg reflections from CsCl-type binary crystals under white light illumination, revealing complete freezing of the sample into large, differently oriented crystallites. (DOC 666 kb)
Plot of the laser light powder diffraction data of Supplementary Table 1, confirming the peak assignments and giving 2.364±0.010 m for the lattice parameter. (DOC 39 kb)
Confocal images of the CsCl-type crystal growth showing the strongly ordered initial liquid phase and the rapid, homogeneous nucleation of differently oriented crystallites. (DOC 918 kb)
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Leunissen, M., Christova, C., Hynninen, A. et al. Ionic colloidal crystals of oppositely charged particles. Nature 437, 235–240 (2005). https://doi.org/10.1038/nature03946
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