Letter | Published:

Binary nanocrystal superlattice membranes self-assembled at the liquid–air interface

Nature volume 466, pages 474477 (22 July 2010) | Download Citation

Abstract

The spontaneous organization of multicomponent micrometre-sized colloids1 or nanocrystals2 into superlattices is of scientific importance for understanding the assembly process on the nanometre scale and is of great interest for bottom-up fabrication of functional devices. In particular, co-assembly of two types of nanocrystal into binary nanocrystal superlattices (BNSLs) has recently attracted significant attention2,3,4,5,6,7,8, as this provides a low-cost, programmable way to design metamaterials4 with precisely controlled properties that arise from the organization and interactions of the constituent nanocrystal components9. Although challenging, the ability to grow and manipulate large-scale BNSLs is critical for extensive exploration of this new class of material. Here we report a general method of growing centimetre-scale, uniform membranes of BNSLs that can readily be transferred to arbitrary substrates. Our method is based on the liquid–air interfacial assembly of multicomponent nanocrystals and circumvents the limitations associated with the current assembly strategies, allowing integration of BNSLs on any substrate for the fabrication of nanocrystal-based devices10. We demonstrate the construction of magnetoresistive devices by incorporating large-area (1.5 mm × 2.5 mm) BNSL membranes; their magnetotransport measurements clearly show that device magnetoresistance is dependent on the structure (stoichiometry) of the BNSLs. The ability to transfer BNSLs also allows the construction of free-standing membranes and other complex architectures that have not been accessible previously.

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Acknowledgements

A.D. and C.B.M. acknowledge the financial support from the US Army Research Office (ARO) under award number MURI W911NF-08-1-0364. J.C., P.M.V. and J.M.K. are grateful for support from the NSF MRSEC programme under award number DMR-0520020. We thank C. Kagan for access to the thermal evaporator.

Author information

Affiliations

  1. Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

    • Angang Dong
    •  & Christopher B. Murray
  2. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

    • Jun Chen
    •  & Christopher B. Murray
  3. Department of Physics & Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

    • Patrick M. Vora
    •  & James M. Kikkawa

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Contributions

A.D. and C.B.M. conceived and designed the experiments. A.D. studied the Fe3O4–FePt and Fe3O4–CoPt3 nanocrystal systems, and J.C. studied the Fe3O4–Fe3O4 system and the CaB6-type Fe3O4–FePt system. A.D. and J.C. carried out BNSL structural characterization and magnetoresistive device fabrication. A.D., J.C., P.M.V. and J.M.K. studied the magnetotransport of BNSL membranes. A.D. and C.B.M. wrote the paper. All authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Angang Dong or Christopher B. Murray.

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https://doi.org/10.1038/nature09188

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