Effects of a Lead Chloride Shell on Lead Sulfide Quantum Dots.

The size of a quantum-confined nanocrystal determines the energies of its excitonic transitions. Previous work has correlated the diameters of PbS nanocrystals to their excitonic absorption; however, we observe that PbS quantum dots synthesized in saturated dispersions of PbCl2 can deviate from the previous 1Sh-1Se energy vs diameter curve by 0.8 nm. In addition, their surface differs chemically from that of PbS quantum dots produced via other syntheses. We find that these nanocrystals are coated in a shell that is measurable in transmission electron micrographs and contains lead and chlorine, beyond the monatomic chlorine termination previously proposed. This finding has implications for understanding the growth mechanism of this reaction, the line width of these quantum dots' photoluminescence, and electronic transport within films of these nanocrystals. Such fundamental knowledge is critical to applications of PbS quantum dots such as single-photon sources, photodetectors, solar cells, light-emitting diodes, lasers, and biological labels.

[1]  R. Stroud,et al.  Synthesis and Characterization of PbS/ZnS Core/Shell Nanocrystals , 2018, Chemistry of Materials.

[2]  G. Gigli,et al.  Quantum-Confined and Enhanced Optical Absorption of Colloidal PbS Quantum Dots at Wavelengths with Expected Bulk Behavior. , 2017, Nano letters.

[3]  M. Luisier,et al.  Influence of the Surface of a Nanocrystal on its Electronic and Phononic Properties , 2016, 1611.09930.

[4]  M. Kovalenko,et al.  Crystal symmetry breaking and vacancies in colloidal lead chalcogenide quantum dots. , 2016, Nature materials.

[5]  Cherie R. Kagan,et al.  Building devices from colloidal quantum dots , 2016, Science.

[6]  F. So,et al.  Inorganic UV-Visible-SWIR Broadband Photodetector Based on Monodisperse PbS Nanocrystals. , 2016, Small.

[7]  Taeghwan Hyeon,et al.  The surface science of nanocrystals. , 2016, Nature materials.

[8]  M. Bawendi,et al.  Evolution of the Single-Nanocrystal Photoluminescence Linewidth with Size and Shell: Implications for Exciton-Phonon Coupling and the Optimization of Spectral Linewidths. , 2016, Nano letters.

[9]  Noah D Bronstein,et al.  Hydroxylation of the surface of PbS nanocrystals passivated with oleic acid , 2014, Science.

[10]  Moungi G Bawendi,et al.  Energy level modification in lead sulfide quantum dot thin films through ligand exchange. , 2014, ACS nano.

[11]  W. Tisdale,et al.  Monodisperse, air-stable PbS nanocrystals via precursor stoichiometry control. , 2014, ACS nano.

[12]  Jianbo Gao,et al.  Diffusion-controlled synthesis of PbS and PbSe quantum dots with in situ halide passivation for quantum dot solar cells. , 2014, ACS nano.

[13]  N. Anderson,et al.  Soluble, Chloride-Terminated CdSe Nanocrystals: Ligand Exchange Monitored by 1H and 31P NMR Spectroscopy , 2013 .

[14]  W. Peukert,et al.  Determination of the quantum dot band gap dependence on particle size from optical absorbance and transmission electron microscopy measurements. , 2012, ACS nano.

[15]  Cherie R. Kagan,et al.  Thiocyanate-capped PbS nanocubes: ambipolar transport enables quantum dot based circuits on a flexible substrate. , 2011, Nano letters.

[16]  Jianhui Yang,et al.  Surface-functionalization-dependent optical properties of II-VI semiconductor nanocrystals. , 2011, Journal of the American Chemical Society.

[17]  L. Cademartiri,et al.  Emerging strategies for the synthesis of highly monodisperse colloidal nanostructures , 2010, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[18]  E. Weiss,et al.  Relaxation of exciton confinement in CdSe quantum dots by modification with a conjugated dithiocarbamate ligand. , 2010, ACS nano.

[19]  I. Moreels,et al.  Size-dependent optical properties of colloidal PbS quantum dots. , 2009, ACS nano.

[20]  Ludovico Cademartiri,et al.  Size-dependent extinction coefficients of PbS quantum dots. , 2006, Journal of the American Chemical Society.

[21]  Ludovico Cademartiri,et al.  Multigram scale, solventless, and diffusion-controlled route to highly monodisperse PbS nanocrystals. , 2006, The journal of physical chemistry. B.

[22]  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 .

[23]  Young Woon Kim,et al.  Generalized and facile synthesis of semiconducting metal sulfide nanocrystals. , 2003, Journal of the American Chemical Society.

[24]  G. Hodes,et al.  Reversible adsorption-enhanced quantum confinement in semiconductor quantum dots , 2002 .

[25]  P. Guyot-Sionnest,et al.  Synthesis and Characterization of Strongly Luminescing ZnS-Capped CdSe Nanocrystals , 1996 .

[26]  Alexander L Efros,et al.  Suppression of auger processes in confined structures. , 2010, Nano letters.