Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Crystal symmetry breaking and vacancies in colloidal lead chalcogenide quantum dots


Size and shape tunability and low-cost solution processability make colloidal lead chalcogenide quantum dots (QDs) an emerging class of building blocks for innovative photovoltaic, thermoelectric and optoelectronic devices. Lead chalcogenide QDs are known to crystallize in the rock-salt structure, although with very different atomic order and stoichiometry in the core and surface regions; however, there exists no convincing prior identification of how extreme downsizing and surface-induced ligand effects influence structural distortion. Using forefront X-ray scattering techniques and density functional theory calculations, here we have identified that, at sizes below 8 nm, PbS and PbSe QDs undergo a lattice distortion with displacement of the Pb sublattice, driven by ligand-induced tensile strain. The resulting permanent electric dipoles may have implications on the oriented attachment of these QDs. Evidence is found for a Pb-deficient core and, in the as-synthesized QDs, for a rhombic dodecahedral shape with nonpolar {110} facets. On varying the nature of the surface ligands, differences in lattice strains are found.

Your institute does not have access to this article

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Lattice distortion of the rock-salt structure in PbS QDs.
Figure 2: Size-dependent lattice expansion, ligands-induced tensile stress and dipole moment.
Figure 3: Morphology evolution of PbS QDs.
Figure 4: STEM analysis of the PbS QD structure and morphology.
Figure 5: Organic-to-inorganic ligand exchange and induced lattice strain.
Figure 6: Stoichiometry of homo-core-shell PbS QDs.


  1. Kovalenko, M. V. et al. Prospects of nanoscience with nanocrystals. ACS Nano 9, 1012–1057 (2015).

    CAS  Article  Google Scholar 

  2. Kovalenko, M. V., Scheele, M. & Talapin, D. V. Colloidal nanocrystals with molecular metal chalcogenide surface ligands. Science 324, 1417–1420 (2009).

    CAS  Article  Google Scholar 

  3. Ibañez, M. et al. Electron doping in bottom-up engineered thermoelectric nanomaterials through HCl-mediated ligand displacement. J. Am. Chem. Soc. 137, 4046–4049 (2015).

    Article  Google Scholar 

  4. Zhang, J., Gao, J., Miller, E. M., Luther, J. M. & Beard, M. C. High photocurrent PbSe solar cells with thin active layers. ACS Nano 8, 614–622 (2014).

    CAS  Article  Google Scholar 

  5. Lan, X., Masala, S. & Sargent, E. H. Charge-extraction strategies for colloidal quantum dot photovoltaics. Nature Mater. 13, 233–240 (2014).

    CAS  Article  Google Scholar 

  6. Zagorac, D., Doll, K., Schön, J. C. & Jansen, M. Sterically active electron pairs in lead sulfide? An investigation of the electronic and vibrational properties of PbS in the transition region between the rock salt and the α-GeTe-type modifications. Chem. Eur. J. 108, 10929–10936 (2012).

    Article  Google Scholar 

  7. Bozin, E. S. et al. Entropically stabilized local dipole formation in lead chalcogenides. Science 330, 1660–1663 (2010).

    CAS  Article  Google Scholar 

  8. Kastbjerg, S. et al. Direct evidence of cation disorder in thermoelectric lead chalcogenides PbTe and PbS. Adv. Funct. Mater. 23, 5477–5483 (2013).

    CAS  Article  Google Scholar 

  9. Moreels, I. et al. Size-tunable, bright, and stable PbS quantum dots: a surface chemistry study. ACS Nano 5, 2004–2012 (2011).

    CAS  Article  Google Scholar 

  10. Moreels, I., Fritzinger, B., Martins, J. C. & Hens, Z. Surface chemistry of colloidal PbSe nanocrystals. J. Am. Chem. Soc. 130, 1581–1586 (2008).

    Article  Google Scholar 

  11. Zherebetsky, D. et al. Hydroxylation of the surface of PbS nanocrystals passivated with oleic acid. Science 344, 1380–1383 (2014).

    Article  Google Scholar 

  12. Anderson, N. C., Hendricks, M. P., Choi, J. J. & Owen, J. S. Ligand exchange and the stoichiometry of metal chalcogenide nanocrystals: spectroscopic observation of facile metal-carboxylate displacement and binding. J. Am. Chem. Soc. 135, 18536–18548 (2013).

    CAS  Article  Google Scholar 

  13. Kim, D., Kim, D.-H., Lee, J.-H. & Grossman, J. C. Impact of stoichiometry on the electronic structure of PbS quantum dots. Phys. Rev. Lett. 110, 196802 (2013).

    Article  Google Scholar 

  14. Cervellino, A., Frison, R., Bertolotti, F. & Guagliardi, A. DEBUSSY 2.0—the new release of a Debye user system for nanocrystalline and/or disordered materials. J. Appl. Crystallogr. 48, 2026–2032 (2015).

    CAS  Article  Google Scholar 

  15. Chattopadhyay, T., Boucherlet, J. X. & von Schnering, H. G. Neutron diffraction study on the structural phase transition in GeTe. J. Phys. C 20, 1431–1440 (1987).

    CAS  Article  Google Scholar 

  16. Berger, R. et al. Surface stress in the self-assembly of alkanethiols on gold. Science 276, 2021–2024 (1997).

    CAS  Article  Google Scholar 

  17. 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).

    CAS  Article  Google Scholar 

  18. Klokkenburg, M. et al. Dipolar structures in colloidal dispersions of PbSe and CdSe quantum dots. Nano Lett. 7, 2931–2936 (2007).

    CAS  Article  Google Scholar 

  19. Lee, S. M., Jun, Y. W., Cho, S. N. & Cheon, J. Single-crystalline star-shaped nanocrystals and their evolution: programming the geometry of nano-building blocks. J. Am. Chem. Soc. 124, 11244–11245 (2002).

    CAS  Article  Google Scholar 

  20. Dong, L., Chu, Y., Zuo, Y. & Zhang, W. Two-minute synthesis of PbS nanocubes with high yield and good dispersibility at room temperature. Nanotechnology 20, 125301 (2009).

    Article  Google Scholar 

  21. Huang, W.-C., Lyu, L.-M., Yang, Y.-C. & Huang, M. H. Synthesis of Cu2O nanocrystals from cubic to rhombic dodecahedral structures and their comparative photocatalytic activity. J. Am. Chem. Soc. 134, 1261–1267 (2012).

    CAS  Article  Google Scholar 

  22. Simon, P. et al. Interconnection of nanoparticles within 2D superlattices of PbS/oleic acid thin films. Adv. Mater. 26, 3042–3049 (2014).

    CAS  Article  Google Scholar 

  23. Boneschanscher, M. P. et al. Long-range orientation and atomic attachment of nanocrystals in 2D honeycomb superlattices. Science 344, 1377–1380 (2014).

    CAS  Article  Google Scholar 

  24. Matthew, K., Sundararaman, R., Letchworth-Weaver, K., Arias, T. A. & Hennig, R. G. Implicit solvation model for density-functional study of nanocrystal surfaces and reaction pathways. J. Chem. Phys. 140, 084106 (2014).

    Article  Google Scholar 

  25. Schapotschnikow, P., van Huis, M. A., Zandbergen, H. W., Vanmaekelberh, D. & Vlugt, T. J. H. Morphological transformations and fusion of PbSe nanocrystals studied using atomistic simulations. Nano Lett. 10, 3966–3971 (2010).

    CAS  Article  Google Scholar 

  26. Schliehe, C. et al. Ultrathin PbS sheets by two-dimensional oriented attachment. Science 329, 550–2936 (2010).

    CAS  Article  Google Scholar 

  27. Dirin, N. D. et al. Lead halide perovskites and other metal halide complexes as inorganic capping ligands for colloidal nanocrystals. J. Am. Chem. Soc. 136, 6550–6553 (2014).

    CAS  Article  Google Scholar 

  28. Ning, Z. et al. Quantum-dot-in-perovskite solids. Nature 523, 324–328 (2015).

    CAS  Article  Google Scholar 

  29. Li, D. et al. Direction-specific interaction control crystal growth by oriented attachment. Science 336, 1014–1018 (2012).

    CAS  Article  Google Scholar 

  30. van Huis, M. A., Kunneman, L. T., Overgaag, K., Zandbergen, H. W. & Vanmaekelberh, D. Low-temperature nanocrystal unification through rotations and relaxations probed by in situ transmission electron microscopy. Nano Lett. 10, 3966–3971 (2010).

    Article  Google Scholar 

  31. Casavola, M. et al. Anisotropic cation exchange in PbSe/CdSe core/shell nanocrystals of different geometry. Chem. Mater. 8, 3959–3963 (2008).

    Google Scholar 

  32. Wuttig, M. et al. The role of vacancies and local distortions in the design of new phase-change materials. Nature Mater. 6, 122–128 (2007).

    CAS  Article  Google Scholar 

  33. Cervellino, A. et al. Diffuse scattering from the lead-based relaxor ferroelectric PbMg1/3Ta2/3O3 . J. Appl. Crystallogr. 44, 603–609 (2011).

    CAS  Article  Google Scholar 

  34. VandeVondele, J. et al. Quickstep: fast and accurate density functional calculations using a mixed Gaussian and plane waves approach. Comput. Phys. Commun. 167, 103–128 (2005).

    CAS  Article  Google Scholar 

Download references


F.B. acknowledges University of Insubria for Junior Fellowship Grant 2013, M.V.K. acknowledges the European Union for financial support via FP7 ERC Starting Grant 2012 (Project NANOSOLID, GA No. 306733), D.N.D. thanks the European Union for Marie Curie Fellowship (PIIF-GA-2012-330524) and M.I. thanks AGAUR for her Beatriu i Pinós post-doctoral grant (2013 BP-A 00344). Synchrotron XRPD data were collected at the X04SA-MS Beamline of the Swiss Light Source. M. Döbeli is gratefully acknowledged for taking RBS spectra. Electron microscopy was performed at the Scientific Center for Optical and Electron Microscopy (ScopeM) at ETH Zürich. Computations were performed using the BlueGene/Q supercomputer at the SciNet HPC Consortium provided through the Southern Ontario Smart Computing Innovation Platform (SOSCIP). We thank N. Stadie and J. Mason for reading the manuscript.

Author information

Authors and Affiliations



A.G., N.M. and M.V.K. formulated the project. D.N.D. and M.I. synthesized the compounds and performed the optical properties characterization. A.C., F.B., R.F., A.G. and N.M. collected and analysed the X-ray total scattering data. F.K. collected and analysed the electron microscopy images. O.V. and E.H.S. performed DFT calculations. A.G. and N.M. wrote the manuscript, with the contribution of all authors.

Corresponding authors

Correspondence to Antonietta Guagliardi or Norberto Masciocchi.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 21618 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Bertolotti, F., Dirin, D., Ibáñez, M. et al. Crystal symmetry breaking and vacancies in colloidal lead chalcogenide quantum dots. Nature Mater 15, 987–994 (2016).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing