Ligand Shell Structure in Lead Sulfide–Oleic Acid Colloidal Quantum Dots Revealed by Small-Angle Scattering

Nanocrystal quantum dots are generally coated with an organic ligand layer. These layers are a necessary consequence of their chemical synthesis, and in addition they play a key role in controlling the optical and electronic properties of the system. Here we describe a method for quantitative measurement of the ligand layer in 3 nm diameter lead sulfide–oleic acid quantum dots. Complementary small-angle X-ray and neutron scattering (SAXS and SANS) studies give a complete and quantitative picture of the nanoparticle structure. We find greater-than-monolayer coverage of oleic acid and a significant proportion of ligand remaining in solution, and we demonstrate reversible thermal cycling of the oleic acid coverage. We outline the effectiveness of simple purification procedures with applications in preparing dots for efficient ligand exchange. Our method is transferrable to a wide range of colloidal nanocrystals and ligand chemistries, providing the quantitative means to enable the rational design of ligand-exchange procedures.

[1]  Yun Liu,et al.  Quantification of a PbClx Shell on the Surface of PbS Nanocrystals , 2019, ACS Materials Letters.

[2]  Yun Liu,et al.  Characterization of colloidal nanocrystal surface structure using small angle neutron scattering and efficient Bayesian parameter estimation. , 2019, The Journal of chemical physics.

[3]  Z. Hens,et al.  Size and Concentration Determination of Colloidal Nanocrystals by Small-Angle X-ray Scattering , 2018, Chemistry of Materials.

[4]  N. J. Davis,et al.  Singlet Fission and Triplet Transfer to PbS Quantum Dots in TIPS-Tetracene Carboxylic Acid Ligands. , 2018, The journal of physical chemistry letters.

[5]  F. Castellano,et al.  Thermally activated delayed photoluminescence from pyrenyl-functionalized CdSe quantum dots. , 2018, Nature chemistry.

[6]  T. Hanrath,et al.  Entropic, Enthalpic, and Kinetic Aspects of Interfacial Nanocrystal Superlattice Assembly and Attachment , 2018 .

[7]  E. Weiss,et al.  Enhancing the Rate of Quantum-Dot-Photocatalyzed Carbon-Carbon Coupling by Tuning the Composition of the Dot's Ligand Shell. , 2017, Journal of the American Chemical Society.

[8]  E. Weiss,et al.  Electronic Processes within Quantum Dot-Molecule Complexes. , 2016, Chemical reviews.

[9]  Christopher B. Murray,et al.  Exploiting the colloidal nanocrystal library to construct electronic devices , 2016, Science.

[10]  F. Castellano,et al.  Direct observation of triplet energy transfer from semiconductor nanocrystals , 2016, Science.

[11]  Xin Li,et al.  Hybrid Molecule-Nanocrystal Photon Upconversion Across the Visible and Near-Infrared. , 2015, Nano letters.

[12]  T. Hanrath,et al.  Confined-but-connected quantum solids via controlled ligand displacement. , 2013, Nano letters.

[13]  S. King,et al.  Small Angle Neutron Scattering Using Sans2d , 2011 .

[14]  Zeger Hens,et al.  Size-tunable, bright, and stable PbS quantum dots: a surface chemistry study. , 2011, ACS nano.

[15]  J. Ilavsky,et al.  The Absolute Calibration of a Small-Angle Scattering Instrument with a Laboratory X-ray Source , 2010 .

[16]  Pete R. Jemian,et al.  Irena: tool suite for modeling and analysis of small‐angle scattering , 2009 .

[17]  Gregory D. Scholes,et al.  Colloidal PbS Nanocrystals with Size‐Tunable Near‐Infrared Emission: Observation of Post‐Synthesis Self‐Narrowing of the Particle Size Distribution , 2003 .

[18]  S. King,et al.  SANS at Pulsed Neutron Sources: Present and Future Prospects , 1997 .

[19]  F. Bates,et al.  Absolute calibration of small‐angle neutron scattering data , 1987 .