Mapping the spatial distribution of charge carriers in quantum-confined heterostructures

Quantum-confined nanostructures are considered ‘artificial atoms’ because the wavefunctions of their charge carriers resemble those of atomic orbitals. For multiple-domain heterostructures, however, carrier wavefunctions are more complex and still not well understood. We have prepared a unique series of cation-exchanged HgxCd1−xTe quantum dots (QDs) and seven epitaxial core–shell QDs and measured their first and second exciton peak oscillator strengths as a function of size and chemical composition. A major finding is that carrier locations can be quantitatively mapped and visualized during shell growth or cation exchange simply using absorption transition strengths. These results reveal that a broad range of quantum heterostructures with different internal structures and band alignments exhibit distinct carrier localization patterns that can be used to further improve the performance of optoelectronic devices and enhance the brightness of QD probes for bioimaging.

[1]  Todd A. Brun,et al.  Quantum Computing , 2011, Computer Science, The Hardware, Software and Heart of It.

[2]  Pedram Khalili Amiri,et al.  Quantum computers , 2003 .

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

[4]  Guglielmo Lanzani,et al.  Tetrapod-shaped colloidal nanocrystals of II-VI semiconductors prepared by seeded growth. , 2009, Journal of the American Chemical Society.

[5]  G. Scholes,et al.  Electronic States and Exciton Fine Structure in Colloidal CdTe Nanocrystals , 2009 .

[6]  T. Lian,et al.  Wave function engineering for efficient extraction of up to nineteen electrons from one CdSe/CdS quasi-type II quantum dot. , 2012, Journal of the American Chemical Society.

[7]  M. Rosen,et al.  Quantum size level structure of narrow-gap semiconductor nanocrystals: Effect of band coupling , 1998 .

[8]  Louis E. Brus,et al.  Electronic wave functions in semiconductor clusters: experiment and theory , 1986 .

[9]  Louis E. Brus,et al.  Electron-electron and electron-hole interactions in small semiconductor crystallites : The size dependence of the lowest excited electronic state , 1984 .

[10]  P. Kamat.  Manipulation of Charge Transfer Across Semiconductor Interface. A Criterion That Cannot Be Ignored in Photocatalyst Design. , 2012, The journal of physical chemistry letters.

[11]  M. Bawendi,et al.  Type-II quantum dots: CdTe/CdSe(core/shell) and CdSe/ZnTe(core/shell) heterostructures. , 2003, Journal of the American Chemical Society.

[12]  Jingbo Li,et al.  Shape Effects on Electronic States of Nanocrystals. , 2003, Nano letters.

[13]  Shuming Nie,et al.  Compact quantum dots for single-molecule imaging. , 2012, Journal of visualized experiments : JoVE.

[14]  Arthur J. Nozik,et al.  Synthesis and Characterization of Surface-Modified Colloidal CdTe Quantum Dots , 1993 .

[15]  Xiaogang Peng,et al.  Experimental Determination of the Extinction Coefficient of CdTe, CdSe, and CdS Nanocrystals , 2003 .

[16]  Y. Kayanuma,et al.  Quantum-size effects of interacting electrons and holes in semiconductor microcrystals with spherical shape. , 1988, Physical review. B, Condensed matter.

[17]  Shuming Nie,et al.  Bioconjugated quantum dots for in vivo molecular and cellular imaging. , 2008, Advanced drug delivery reviews.

[18]  Victor I. Klimov,et al.  Optical Nonlinearities and Ultrafast Carrier Dynamics in Semiconductor Nanocrystals , 2000 .

[19]  A. Mohs,et al.  Tuning the optical and electronic properties of colloidal nanocrystals by lattice strain. , 2009, Nature nanotechnology.

[20]  G. Bester.  SCIENTIFIC HIGHLIGHT OF THE MONTH : ” Electronic Excitations in Nanostructures : An Empirical Pseudopotential based Approach Electronic Excitations in Nanostructures : An Empirical Pseudopotential based Approach , 2008 .

[21]  François Hache,et al.  Absorption and intensity-dependent photoluminescence measurements on CdSe quantum dots: assignment of the first electronic transitions , 1993 .

[22]  F. García-Santamaría,et al.  Suppressed auger recombination in "giant" nanocrystals boosts optical gain performance. , 2009, Nano letters.

[23]  U. Banin,et al.  Tunneling and optical spectroscopy of semiconductor nanocrystals. , 2003, Annual review of physical chemistry.

[24]  P. Guyot-Sionnest,et al.  Intraband spectroscopy and band offsets of colloidal II-VI core/shell structures. , 2007, The Journal of chemical physics.

[25]  M. Kovalenko,et al.  Quasi-seeded growth of ligand-tailored PbSe nanocrystals through cation-exchange-mediated nucleation. , 2008, Angewandte Chemie.

[26]  Qiang Zhao,et al.  Size-Dependent Optical Properties of Zinc Blende Cadmium Telluride Quantum Dots , 2012 .

[27]  E. Aydil,et al.  Hot-Electron Transfer from Semiconductor Nanocrystals , 2010, Science.

[28]  Shuming Nie,et al.  Bright and compact alloyed quantum dots with broadly tunable near-infrared absorption and fluorescence spectra through mercury cation exchange. , 2011, Journal of the American Chemical Society.

[29]  Tobias Vossmeyer,et al.  CdS Nanoclusters: Synthesis, Characterization, Size Dependent Oscillator Strength, Temperature Shift of the Excitonic Transition Energy, and Reversible Absorbance Shift , 1994 .

[30]  Archil Avaliani,et al.  Quantum Computers , 2004, ArXiv.

[31]  A. Alivisatos,et al.  Synthesis of PbS nanorods and other ionic nanocrystals of complex morphology by sequential cation exchange reactions. , 2009, Journal of the American Chemical Society.

[32]  Yuh‐Lang Lee,et al.  Highly Efficient Quantum‐Dot‐Sensitized Solar Cell Based on Co‐Sensitization of CdS/CdSe , 2009 .

[33]  Weller,et al.  Quantum-dot quantum well CdS/HgS/CdS: Theory and experiment. , 1994, Physical review. B, Condensed matter.

[34]  Xiaogang Peng,et al.  Epitaxial Growth of Highly Luminescent CdSe/CdS Core/Shell Nanocrystals with Photostability and Electronic Accessibility , 1997 .

[35]  Moungi G. Bawendi,et al.  On the Absorption Cross Section of CdSe Nanocrystal Quantum Dots , 2002 .

[36]  G. Konstantatos,et al.  Nanostructured materials for photon detection. , 2010, Nature nanotechnology.

[37]  Dmitri V Talapin,et al.  Seeded growth of highly luminescent CdSe/CdS nanoheterostructures with rod and tetrapod morphologies. , 2007, Nano letters.

[38]  Norris,et al.  Measurement and assignment of the size-dependent optical spectrum in CdSe quantum dots. , 1996, Physical review. B, Condensed matter.

[39]  M. Kovalenko,et al.  Prospects of colloidal nanocrystals for electronic and optoelectronic applications. , 2010, Chemical reviews.

[40]  Shuming Nie,et al.  Semiconductor nanocrystals: structure, properties, and band gap engineering. , 2010, Accounts of chemical research.

[41]  M. Bawendi,et al.  (CdSe)ZnS Core-Shell Quantum Dots - Synthesis and Characterization of a Size Series of Highly Luminescent Nanocrystallites , 1997 .

[42]  S. Ivanov,et al.  Inverted Core/Shell Nanocrystals Continuously Tunable between Type-I and Type-II Localization Regimes , 2004 .

[43]  Yongan Yang,et al.  Synthesis of metal-selenide nanocrystals using selenium dioxide as the selenium precursor. , 2008, Angewandte Chemie.

[44]  M. Kovalenko,et al.  Exciton–Exciton Interaction and Optical Gain in Colloidal CdSe/CdS Dot/Rod Nanocrystals , 2009, Advanced materials.

[45]  T. Lian,et al.  Controlling charge separation and recombination rates in CdSe/ZnS type I core-shell quantum dots by shell thicknesses. , 2010, Journal of the American Chemical Society.

[46]  Calvin Curtis,et al.  Absorption cross-section and related optical properties of colloidal InAs quantum dots. , 2005, The journal of physical chemistry. B.

[47]  James McBride,et al.  Structural basis for near unity quantum yield core/shell nanostructures. , 2006, Nano letters.

[48]  T. Lian,et al.  Multiple exciton dissociation in CdSe quantum dots by ultrafast electron transfer to adsorbed methylene blue. , 2010, Journal of the American Chemical Society.

[49]  D. Ritchie,et al.  An entangled-light-emitting diode , 2010, Nature.

[50]  Norris,et al.  Band-edge exciton in quantum dots of semiconductors with a degenerate valence band: Dark and bright exciton states. , 1996, Physical review. B, Condensed matter.

[51]  Monica Nadasan,et al.  Synthesis and micrometer-scale assembly of colloidal CdSe/CdS nanorods prepared by a seeded growth approach. , 2007, Nano letters.

[52]  A. Pattantyus-Abraham,et al.  Photostability of Colloidal PbSe and PbSe/PbS Core/Shell Nanocrystals in Solution and in the Solid State , 2007 .

[53]  E. Weiss,et al.  Simultaneous determination of the adsorption constant and the photoinduced electron transfer rate for a CdS quantum dot-viologen complex. , 2011, Journal of the American Chemical Society.

[54]  V. Bulović,et al.  Quantum dot light-emitting devices with electroluminescence tunable over the entire visible spectrum. , 2009, Nano letters.

[55]  Y. C. Cao,et al.  One-pot synthesis of high-quality zinc-blende CdS nanocrystals. , 2004, Journal of the American Chemical Society.

[56]  Yadong Yin,et al.  Cation Exchange Reactions in Ionic Nanocrystals , 2004, Science.

[57]  J. Luther,et al.  Semiconductor quantum dots and quantum dot arrays and applications of multiple exciton generation to third-generation photovoltaic solar cells. , 2010, Chemical reviews.

[58]  Zhou,et al.  Quantum confinement in semiconductor heterostructure nanometer-size particles. , 1993, Physical review. B, Condensed matter.