Abstract

Doping is a process in which atomic impurities are intentionally added to a host material to modify its properties. It has had a revolutionary impact in altering or introducing electronic1,2, magnetic3,4, luminescent5,6, and catalytic7 properties for several applications, for example in semiconductors. Here we explore and demonstrate the extension of the concept of substitutional atomic doping to nanometre-scale crystal doping, in which one nanocrystal is used to replace another to form doped self-assembled superlattices. Towards this goal, we show that gold nanocrystals act as substitutional dopants in superlattices of cadmium selenide or lead selenide nanocrystals when the size of the gold nanocrystal is very close to that of the host. The gold nanocrystals occupy random positions in the superlattice and their density is readily and widely controllable, analogous to the case of atomic doping, but here through nanocrystal self-assembly. We also show that the electronic properties of the superlattices are highly tunable and strongly affected by the presence and density of the gold nanocrystal dopants. The conductivity of lead selenide films, for example, can be manipulated over at least six orders of magnitude by the addition of gold nanocrystals and is explained by a percolation model. As this process relies on the self-assembly of uniform nanocrystals, it can be generally applied to assemble a wide variety of nanocrystal-doped structures for electronic, optical, magnetic, and catalytic materials.

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Acknowledgements

We thank Y. Lai and D. Straus (University of Pennsylvania) for discussions about electrical characterization. This work received primary support from the Office of Naval Research MURI program (award number ONR-N00014-10-1-0942) for the development of the multicomponent assembly techniques, and secondary support from the US Department of Energy Office of Basic Energy Sciences, Division of Materials Science and Engineering (award number DE-SC0002158) for the development of the semiconductor nanocrystal chemistry and the characterization of electrical conductivity. Electron microscopy research was performed while A.C.J.-P. held a National Research Council Research Associateship Award at the National Institute of Standards and Technology. We thank K. Yager (Brookhaven National Laboratory) for help with SAXS experiments. Work performed at the National Synchrotron Light Source I (Brookhaven National Laboratory) was supported by the US Department of Energy, Office of Basic Energy Sciences, under contract number DE-SC0012704. C.R.K. thanks the Stephen J. Angello Professorship for support. C.B.M. is grateful for the support of the Richard Perry University Professorship.

Author information

Author notes

    • Matteo Cargnello
    • , Aaron C. Johnston-Peck
    •  & Benjamin T. Diroll

    These authors contributed equally to this work.

    • Matteo Cargnello

    Present address: Department of Chemical Engineering and SUNCAT Center for Interface Science and Catalysis, Stanford University, Stanford, California 94305, USA.

Affiliations

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

    • Matteo Cargnello
    • , Benjamin T. Diroll
    • , Cherie R. Kagan
    •  & Christopher B. Murray
  2. Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA

    • Aaron C. Johnston-Peck
    •  & Andrew A. Herzing
  3. Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

    • Eric Wong
  4. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

    • Bianca Datta
    • , Divij Damodhar
    • , Vicky V. T. Doan-Nguyen
    • , Cherie R. Kagan
    •  & Christopher B. Murray
  5. Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

    • Cherie R. Kagan

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Contributions

M.C., B.T.D. and C.B.M. conceived the idea for the study. M.C. prepared the samples and conducted initial characterization. A.C.J.-P. performed microscopy characterization and tomography reconstruction. B.D. and D.D. contributed to sample preparation and Voronoi analysis. V.V.T.D.-N. contributed to Voronoi analysis and Matlab programming. E.W. prepared electrical substrates and contributed to electrical characterization. M.C. and B.T.D. performed electrical characterization. A.A.H. supervised microscopy characterization. C.R.K. supervised electrical characterization. C.B.M. supervised the entire project. M.C. wrote the manuscript with contributions from all the authors.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Christopher B. Murray.

Extended data

Supplementary information

Videos

  1. 1.

    Tomography reconstruction of multilayer doped superlattices

    Video showing a YZ slice progression of the reconstruction volume of Au NC-PbSe NC doped superlattices reported in Figure 2 of the main text. Au NCs appear as bright spots in the ordered layers and are then isolated as single yellow spheres in the final reconstruction.

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DOI

https://doi.org/10.1038/nature14872

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