NATUREIVol 439 5 January 2006 LETTERS 2. Guarini, K W, Black, C T. Yeung S H L Optimization of diblock copolymer 22. Yin, Y. Alivisatos, A P Colloidal nanocrystal synthesis and the film self assembly. Adv Mater. 14, 1290-1294 (2002). rganic-inorganic interface Nature 437, 664-670 (200- 3. Red, F.X., Cho, K-S, Murray, C B. O'Brien, S. Three-dimensional binary 23. Korgel, B. A, Fullam, S, Connolly, S& Fitzmaurice, D Assembly and superlattices of magnetic nanocrystals and semiconductor quantum dots. Ntue423.968-971(200 hys. Chem. B1028379-8388(1998 4. Kiely, C.J., Fink, J, Brust, M., Bethel, D. Schiffrin, D J. Spontaneous ordering 24. Cho, K-S, Talapin, D. V Gaschler, W. Murray, C B. Designing PbSe f bimodal ensembles of nanoscopic gold clusters. Nature 396, 444-446 nanowires and nanorings through oriented attachment of nanoparticles. 1. Am Chem. soc.127,7140-7147(2005) 5. Shevchenko, E. V. et al. Colloidal 25. Ohara, P C Leff, D. V. Heath, J.R. Gelbart, W. M. 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Nature 320, 340-342 (1986) Acknowledgements We thank V. Perebeinos, A van blaaderen, v Crespi L. Herman and L E Brus for discussions and r. l sandstrom for technic niversality and perfection. J. Am. Chem. Soc. 125, 15589-15598(2003). upport. This work was partially supported by the MRSEC Program of the 15. Cottin, X& Monson, P. A Substitutionally ordered solid solutions of hard heres. J. Chem. Phys.102,3354-3360(1995) National Science Foundation, and by the New York State Office of Science Technology and Academic Research (NYSTAR). S.o. is grateful for support from 16. Sanders, J. V s Murray, M. J Ordered ar nts of spheres of two different sizes in opal. Nature 275, 201-203(1978) 17. Hachisu, S& Yoshimura, S Optical demonstration of crystalline Author Contributions E V.S. and D V.T. contributed equally to this work. E.V.S. uperstructures in binary mixtures of latex globules. Nature 283, 188-189 and D V.T. carried out syntheses of nanoparticles, and E V.S. investigated 18. Shim, M. Guyot-Sionnest, P Permanent dipole moment and charges modelling and structural assignment of self-assembled binary superlattices. in colloidal semiconductor quantum dots. J. Chem. Phys. 111, 6955-6964 E.V.S., D.V.T. and N A.K. studied electrophoretic mobility of nanoparticles and 19. Krauss, T. D& Brus, L.E. Charge, polarizability, and photoionizat S.O. and C B M. initiated and supervised the work. D V.T. and C.B.M. wrote the paper. All authors discussed the results and commented on the manuscript. 20. Islam, M. A& Herman, I P Electrodeposition of patterned Cdse films using thermally charged nanocrystals. Appl. Phys. Lett. 80, Author Information sandpermissions. The author no competing 21. OBrien, R W.& White, L R Electrophoretic mobility of a spherical colloida financial interests. Correspondence and requests fo should be article. J. Chem. Soc. Farad. Trans. 1 74, 1607-1626(1978). addressedtoDV.T.(dvtalapinalblgov)orC.B.M.(cbmurray@us.ibm.com) 2006 Nature Publishing Group© 2006 Nature Publishing Group 2. Guarini, K. W., Black, C. T. & Yeung, S. H. I. Optimization of diblock copolymer thin film self assembly. Adv. Mater. 14, 1290–-1294 (2002). 3. 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). 4. Kiely, C. J., Fink, J., Brust, M., Bethel, D. & Schiffrin, D. J. Spontaneous ordering of bimodal ensembles of nanoscopic gold clusters. Nature 396, 444–-446 (1998). 5. Shevchenko, E. V. et al. Colloidal synthesis and self-assembly of CoPt3 nanocrystals. J. Am. Chem. Soc. 124, 11480–-11485 (2002). 6. Saunders, A. E. & Korgel, B. A. Observation of an AB phase in bidisperse nanocrystal superlattices. ChemPhysChem 6, 61–-65 (2005). 7. Shevchenko, E. V., Talapin, D. V., O’Brien, S. & Murray, C. B. Polymorphism in AB13 nanoparticle superlattices: An example of semiconductor-metal metamaterials. J. Am. Chem. Soc. 127, 8741–-8747 (2005). 8. Murray, M. J. & Sanders, J. V. Close-packed structures of spheres of two different sizes II. The packing densities of likely arrangements. Phil. Mag. A 42, 721–-740 (1980). 9. Eldridge, M. D., Madden, P. A. & Frenkel, D. Entropy-driven formation of a superlattice in a hard-sphere binary mixture. Nature 365, 35–-37 (1993). 10. Leunissen, M. E. et al. Ionic colloidal crystals of oppositely charged particles. Nature 437, 235–-240 (2005). 11. Bartlett, P. & Campbell, A. I. Three-dimensional binary superlattices of oppositely charged colloids. Phys. Rev. Lett. 95, 128302 (2005). 12. Bolhuis, P. G., Frenkel, D., Mau, S.-C. & Huse, D. A. Entropy difference between the face-centred cubic and hexagonal close-packed crystal structures. Nature 388, 235–-236 (1997). 13. Pusey, P. N. & van Megen, W. Phase behaviour of concentrated suspensions of nearly hard colloidal spheres. Nature 320, 340–-342 (1986). 14. Wong, S., Kitaev, V. & Ozin, G. A. Colloidal crystal films: Advances in universality and perfection. J. Am. Chem. Soc. 125, 15589–-15598 (2003). 15. Cottin, X. & Monson, P. A. Substitutionally ordered solid solutions of hard spheres. J. Chem. Phys. 102, 3354–-3360 (1995). 16. Sanders, J. V. & Murray, M. J. Ordered arrangements of spheres of two different sizes in opal. Nature 275, 201–-203 (1978). 17. Hachisu, S. & Yoshimura, S. Optical demonstration of crystalline superstructures in binary mixtures of latex globules. Nature 283, 188–-189 (1980). 18. Shim, M. & Guyot-Sionnest, P. Permanent dipole moment and charges in colloidal semiconductor quantum dots. J. Chem. Phys. 111, 6955–-6964 (1999). 19. Krauss, T. D. & Brus, L. E. Charge, polarizability, and photoionization of single semiconductor nanocrystals. Phys. Rev. Lett. 83, 4840–-4843 (1999). 20. Islam, M. A. & Herman, I. P. Electrodeposition of patterned CdSe nanocrystal films using thermally charged nanocrystals. Appl. Phys. Lett. 80, 3823–-3825 (2002). 21. O’Brien, R. W. & White, L. R. Electrophoretic mobility of a spherical colloidal particle. J. Chem. Soc. Farad. Trans. II 74, 1607–-1626 (1978). 22. Yin, Y. & Alivisatos, A. P. Colloidal nanocrystal synthesis and the organic–-inorganic interface. Nature 437, 664–-670 (2005). 23. Korgel, B. A., Fullam, S., Connolly, S. & Fitzmaurice, D. Assembly and self-organization of silver nanocrystal superlattices: Ordered “soft spheres”. J. Phys. Chem. B 102, 8379–-8388 (1998). 24. Cho, K.-S., Talapin, D. V., Gaschler, W. & Murray, C. B. Designing PbSe nanowires and nanorings through oriented attachment of nanoparticles. J. Am. Chem. Soc. 127, 7140–-7147 (2005). 25. Ohara, P. C., Leff, D. V., Heath, J. R. & Gelbart, W. M. Crystallization of opals from polydisperse nanoparticles. Phys. Rev. Lett. 75, 3466–-3469 (1995). 26. Rabani, E., Reichman, D. R., Geissler, P. L. & Brus, L. E. Drying-mediated self-assembly of nanoparticles. Nature 426, 271–-274 (2003). 27. Prasad, B. L. V., Stoeva, S. I., Sorensen, C. M. & Klabunde, K. J. Digestive ripening of thiolated gold nanoparticles: The effect of alkyl chain length. Langmuir 18, 7515–-7520 (2002). 28. Hyeon, T., Lee, S. S., Park, J., Chung, Y. & Na, H. B. Synthesis of highly crystalline and monodisperse maghemite nanocrystallites without a size-selection process. J. Am. Chem. Soc. 123, 12798–-12801 (2001). 29. Hines, M. A. & Scholes, G. D. Colloidal PbS nanocrystals with size-tunable near-infrared emission: Observation of post-synthesis self-narrowing of the particle size distribution. Adv. Mater. 15, 1844–-1849 (2003). 30. Zhang, Y.-W., Sun, X., Si, R., You, L.-P. & Yan, C.-H. Single-crystalline and monodisperse LaF3 triangular nanoplates from a single-source precursor. J. Am. Chem. Soc. 127, 3260–-3261 (2005). Supplementary Information is linked to the online version of the paper at www.nature.com/nature. Acknowledgements We thank V. Perebeinos, A. van Blaaderen, V. Crespi, I. Herman and L. E. Brus for discussions and R. L. Sandstrom for technical support. This work was partially supported by the MRSEC Program of the National Science Foundation, and by the New York State Office of Science, Technology and Academic Research (NYSTAR). S.O. is grateful for support from the DOE and an NSF CAREER award. Author Contributions E.V.S. and D.V.T. contributed equally to this work. E.V.S. and D.V.T. carried out syntheses of nanoparticles, and E.V.S. investigated formation of binary nanoparticle superlattices. E.V.S. and D.V.T. performed modelling and structural assignment of self-assembled binary superlattices. E.V.S., D.V.T. and N.A.K. studied electrophoretic mobility of nanoparticles and worked on modelling self-assembly phenomena in binary nanoparticle colloids. S.O. and C.B.M. initiated and supervised the work. D.V.T. and C.B.M. wrote the paper. All authors discussed the results and commented on the manuscript. Author Information Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests. Correspondence and requests for materials should be addressed to D.V.T. (dvtalapin@lbl.gov) or C.B.M. (cbmurray@us.ibm.com). NATURE|Vol 439|5 January 2006 LETTERS 59