Atomistic description of thiostannate-capped CdSe nanocrystals: Retention of four-coordinate SnS4 motif and preservation of Cd-rich stoichiometry

Loredana Protesescu, Maarten Nachtegaal, Oleksandr Voznyy, Olga Borovinskaya, Aaron J. Rossini, Lyndon Emsley, Christophe Copéret, Detlef Günther, Edward H. Sargent, Maksym V. Kovalenko*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

47 Scopus citations

Abstract

Colloidal semiconductor nanocrystals (NCs) are widely studied as building blocks for novel solid-state materials. Inorganic surface functionalization, used to displace native organic capping ligands from NC surfaces, has been a major enabler of electronic solid-state devices based on colloidal NCs. At the same time, very little is known about the atomistic details of the organic-to-inorganic ligand exchange and binding motifs at the NC surface, severely limiting further progress in designing all-inorganic NCs and NC solids. Taking thiostannates (K4SnS4, K4Sn2S6, K6Sn2S7) as typical examples of chalcogenidometallate ligands and oleate-capped CdSe NCs as a model NC system, in this study we address these questions through the combined application of solution 1H NMR spectroscopy, solution and solid-state 119Sn NMR spectroscopy, far-infrared and X-ray absorption spectroscopies, elemental analysis, and by DFT modeling. We show that through the X-type oleate-to-thiostannate ligand exchange, CdSe NCs retain their Cd-rich stoichiometry, with a stoichiometric CdSe core and surface Cd adatoms serving as binding sites for terminal S atoms of the thiostannates ligands, leading to all-inorganic (CdSe)core[Cdm(Sn2S7)yK(6y-2m)]shell (taking Sn2S76- ligand as an example). Thiostannates SnS44- and Sn2S76- retain (distorted) tetrahedral SnS4 geometry upon binding to NC surface. At the same time, experiments and simulations point to lower stability of Sn2S64- (and SnS32-) in most solvents and its lower adaptability to the NC surface caused by rigid Sn2S2 rings.

Original languageEnglish (US)
Pages (from-to)1862-1874
Number of pages13
JournalJournal of the American Chemical Society
Volume137
Issue number5
DOIs
StatePublished - Feb 11 2015

ASJC Scopus subject areas

  • General Chemistry
  • Biochemistry
  • Catalysis
  • Colloid and Surface Chemistry

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