Extinction coefficient per CdE (E = Se or S) unit for zinc-blende CdE nanocrystals
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The extinction coefficient of semiconductor nanocrystals is a key parameter for understanding both the quantum confinement and applications of the nanocrystals. The existing extinction coefficients of CdE (E = Se, S) nanocrystals were found to have an unacceptable deviation for the zinc-blende CdE quantum dots (QDs). The analysis reveals that, in addition to the interference of impurities, the commonly applied extinction coefficient per CdE nanocrystal is sensitive to the size, shape, and density of the surface ligands of nanocrystals. The extinction coefficient per CdE unit does not depend on accurate information of the size, shape, and number of surface ligands of the nanocrystals. A new three-step purification scheme was developed to investigate three classes of possible impurities for accurate determination of the extinction coefficient per CdE unit, including CdE clusters not considered previously. Given that the sole ligands of zinc-blende CdE nanocrystals are cadmium fatty acid salts (CdFa2), a universal formula for the nanocrystals can be written as (CdE)n(CdFa2)m. The n: m ratio was accurately determined for purified nanocrystals. The resulting extinction coefficients per unit for both CdSe and CdS QDs were found to decrease exponentially as the size of the QDs increases, with the corresponding bulk value as the large-size limit.
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Extinction coefficient per CdE (E = Se or S) unit for zinc-blende CdE nanocrystals
Abstract
The extinction coefficient of semiconductor nanocrystals is a key parameter for understanding both the quantum confinement and applications of the nanocrystals. The existing extinction coefficients of CdE (E = Se, S) nanocrystals were found to have an unacceptable deviation for the zinc-blende CdE quantum dots (QDs). The analysis reveals that, in addition to the interference of impurities, the commonly applied extinction coefficient per CdE nanocrystal is sensitive to the size, shape, and density of the surface ligands of nanocrystals. The extinction coefficient per CdE unit does not depend on accurate information of the size, shape, and number of surface ligands of the nanocrystals. A new three-step purification scheme was developed to investigate three classes of possible impurities for accurate determination of the extinction coefficient per CdE unit, including CdE clusters not considered previously. Given that the sole ligands of zinc-blende CdE nanocrystals are cadmium fatty acid salts (CdFa2), a universal formula for the nanocrystals can be written as (CdE)n(CdFa2)m. The n: m ratio was accurately determined for purified nanocrystals. The resulting extinction coefficients per unit for both CdSe and CdS QDs were found to decrease exponentially as the size of the QDs increases, with the corresponding bulk value as the large-size limit.
References(48)
Brus, L. E. Electron-electron and electron-hole interactions in small semiconductor crystallites: The size dependence of the lowest excited electronic state. J. Phys. Chem. 1984, 80, 4403-4409.
Colvin, V. L.; Schlamp, M. C.; Alivisatos, A. P. Light-emitting diodes made from cadmium selenide nanocrystals and a semiconducting polymer. Nature 1994, 370, 354-357.
Coe, S.; Woo, W. K.; Bawendi, M.; Bulović, V. Electroluminescence from single monolayers of nanocrystals in molecular organic devices. Nature 2002, 420, 800-803.
Dai, X. L.; Zhang, Z. X.; Jin, Y. Z.; Niu, Y.; Cao, H. J.; Liang, X. Y.; Chen, L. W.; Wang, J. P.; Peng, X. G. Solution-processed, high-performance light-emitting diodes based on quantum dots. Nature 2014, 515, 96-99.
Bruchez, M. Jr.; Moronne, M.; Gin, P.; Weiss, S.; Alivisatos, A. P. Semiconductor nanocrystals as fluorescent biological labels. Science 1998, 281, 2013-2016.
Chan, W. C. W.; Nie, S. M. Quantum dot bioconjugates for ultrasensitive nonisotopic detection. Science 1998, 281, 2016-2018.
Klimov, V. I.; Mikhailovsky, A. A.; Xu, S.; Malko, A.; Hollingsworth, J. A.; Leatherdale, C. A.; Eisler, H. J.; Bawendi, M. G. Optical gain and stimulated emission in nanocrystal quantum dots. Science 2000, 290, 314-317.
Fan, F. J.; Voznyy, O.; Sabatini, R. P.; Bicanic, K. T.; Adachi, M. M.; McBride, J. R.; Reid, K. R.; Park, Y. S.; Li, X.; Jain, A. et al. Continuous-wave lasing in colloidal quantum dot solids enabled by facet-selective epitaxy. Nature 2017, 544, 75-79.
Michler, P.; Kiraz, A.; Becher, C.; Schoenfeld, W. V.; Petroff, P. M.; Zhang, L. D.; Hu, E.; Imamoglu, A. A quantum dot single-photon turnstile device. Science 2000, 290, 2282-2285.
Lin, X.; Dai, X. L.; Pu, C. D.; Deng, Y. Z.; Niu, Y.; Tong, L. M.; Fang, W.; Jin, Y. Z.; Peng, X. G. Electrically-driven single-photon sources based on colloidal quantum dots with near-optimal antibunching at room temperature. Nat. Commun. 2017, 8, 1132.
Baron, R.; Huang, C. H.; Bassani, D. M.; Onopriyenko, A.; Zayats, M.; Willner, I. Hydrogen-bonded CdS nanoparticle assemblies on electrodes for photoelectrochemical applications. Angew. Chem., Int. Ed. 2005, 44, 4010-4015.
Zhu, H. M.; Song, N. H.; Lian, T. Q. Controlling charge separation and recombination rates in CdSe/ZnS type I core−shell quantum dots by shell thicknesses. J. Am. Chem. Soc. 2010, 132, 15038-15045.
Di Corato, R.; Bigall, N. C.; Ragusa, A.; Dorfs, D.; Genovese, A.; Marotta, R.; Manna, L.; Pellegrino, T. Multifunctional nanobeads based on quantum dots and magnetic nanoparticles: Synthesis and cancer cell targeting and sorting. ACS Nano 2011, 5, 1109-1121.
Nan, W. N.; Niu, Y.; Qin, H. Y.; Cui, F.; Yang, Y.; Lai, R. C.; Lin, W. Z.; Peng, X. G. Crystal structure control of zinc-blende CdSe/CdS core/shell nanocrystals: Synthesis and structure-dependent optical properties. J. Am. Chem. Soc. 2012, 134, 19685-19693.
Leatherdale, C. A.; Woo, W. K.; Mikulec, F. V.; Bawendi, M. G. On the absorption cross section of CdSe nanocrystal quantum dots. J. Phys. Chem. B 2002, 106, 7619-7622.
Sun, J. J.; Goldys, E. M. Linear absorption and molar extinction coefficients in direct semiconductor quantum dots. J. Phys. Chem. C 2008, 112, 9261-9266.
Vossmeyer, T.; Katsikas, L.; Giersig, M.; Popovic, I. G.; Diesner, K.; Chemseddine, A.; Eychmueller, A.; Weller, H. CdS nanoclusters: Synthesis, characterization, size dependent oscillator strength, temperature shift of the excitonic transition energy, and reversible absorbance shift. J. Phys. Chem. 1994, 98, 7665-7673.
Schmelz, O.; Mews, A.; Basché, T.; Herrmann, A.; Müllen, K. Supramolecular complexes from CdSe nanocrystals and organic fluorophors. Langmuir 2001, 17, 2861-2865.
Yu, W. W.; Qu, L. H.; Guo, W. Z.; Peng, X. G. Experimental determination of the extinction coefficient of CdTe, CdSe, and CdS nanocrystals. Chem. Mater. 2003, 15, 2854-2860.
Jasieniak, J.; Smith, L.; van Embden, J.; Mulvaney, P.; Califano, M. Re-examination of the size-dependent absorption properties of CdSe quantum dots. J. Phys. Chem. C 2009, 113, 19468-19474.
Karel Čapek, R.; Moreels, I.; Lambert, K.; De Muynck, D.; Zhao, Q.; Van Tomme, A.; Vanhaecke, F.; Hens, Z. Optical properties of zincblende cadmium selenide quantum dots. J. Phys. Chem. C 2010, 114, 6371-6376.
Nirmal, M.; Norris, D. J.; Kuno, M.; Bawendi, M. G.; Efros, A. L.; Rosen, M. Observation of the "dark exciton" in CdSe quantum dots. Phys. Rev. Lett. 1995, 75, 3728-3731.
Gao, Y.; Peng, X. G. Photogenerated excitons in plain core CdSe nanocrystals with unity radiative decay in single channel: The effects of surface and ligands. J. Am. Chem. Soc. 2015, 137, 4230-4235.
Pu, C. D.; Qin, H. Y.; Gao, Y.; Zhou, J. H.; Wang, P.; Peng, X. G. Synthetic control of exciton behavior in colloidal quantum dots. J. Am. Chem. Soc. 2017, 139, 3302-3311.
Qin, H. Y.; Meng, R. Y.; Wang, N.; Peng, X. G. Photoluminescence intermittency and photo-bleaching of single colloidal quantum dot. Adv. Mater. 2017, 29, 1606923.
Zhou, J. H.; Zhu, M. Y.; Meng, R. Y.; Qin, H. Y.; Peng, X. G. Ideal CdSe/CdS core/shell nanocrystals enabled by entropic ligands and their core size-, shell thickness-, and ligand-dependent photoluminescence properties. J. Am. Chem. Soc. 2017, 139, 16556-16567.
Niu, Y.; Pu, C. D.; Lai, R. C.; Meng, R. Y.; Lin, W. Z.; Qin, H. Y.; Peng, X. G. One-pot/three-step synthesis of zinc-blende CdSe/CdS core/shell nanocrystals with thick shells. Nano Res. 2017, 10, 1149-1162.
Li, Z.; Ji, Y. J.; Xie, R. G.; Grisham, S. Y.; Peng, X. G. Correlation of CdS nanocrystal formation with elemental sulfur activation and its implication in synthetic development. J. Am. Chem. Soc. 2011, 133, 17248-17256.
Yang, Y. A.; Wu, H. M.; Williams, K. R.; Cao, Y. C. Synthesis of CdSe and CdTe nanocrystals without precursor injection. Angew. Chem., Int. Ed. 2005, 117, 6870-6873.
Ninomiya, S.; Adachi, S. Optical properties of cubic and hexagonal CdSe. J. Appl. Phys. 1995, 78, 4681-4689.
Efros, A. L.; Rosen, M.; Kuno, M.; Nirmal, M.; Norris, D. J.; Bawendi, M. Band-edge exciton in quantum dots of semiconductors with a degenerate valence band: Dark and bright exciton states. Phys. Rev. B 1996, 54, 4843-4856.
Murray, C. B.; Norris, D. J.; Bawendi, M. G. Synthesis and characterization of nearly monodisperse CdE (E = sulfur, selenium, tellurium) semiconductor nanocrystallites. J. Am. Chem. Soc. 1993, 115, 8706-8715.
Gao, Y.; Peng, X. G. Crystal structure control of CdSe nanocrystals in growth and nucleation: Dominating effects of surface versus interior structure. J. Am. Chem. Soc. 2014, 136, 6724-6732.
Chen, D. D.; Gao, Y.; Chen, Y. Y.; Ren, Y.; Peng, X. G. Structure identification of two-dimensional colloidal semiconductor nanocrystals with atomic flat basal planes. Nano Lett. 2015, 15, 4477-4482.
Peng, X. G.; Wickham, J.; Alivisatos, A. P. Kinetics of Ⅱ-Ⅵ and Ⅲ-Ⅴ colloidal semiconductor nanocrystal growth: "Focusing" of size distributions. J. Am. Chem. Soc. 1998, 120, 5343-5344.
Yu, W. W.; Peng, X. G. Formation of high-quality CdS and other Ⅱ-Ⅵ semiconductor nanocrystals in noncoordinating solvents: Tunable reactivity of monomers. Angew. Chem., Int. Ed. 2007, 46, 2559-2559.
Pu, C. D.; Zhou, J. H.; Lai, R. C.; Niu, Y.; Nan, W. N.; Peng, X. G. Highly reactive, flexible yet green se precursor for metal selenide nanocrystals: Se-octadecene suspension (Se-SUS). Nano Res. 2013, 6, 652-670.
Zhou, J. H.; Pu, C. D.; Jiao, T. Y.; Hou, X. Q.; Peng, X. G. A two-step synthetic strategy toward monodisperse colloidal CdSe and CdSe/CdS core/shell nanocrystals. J. Am. Chem. Soc. 2016, 138, 6475-6483.
Soloviev, V. N.; Eichhöfer, A.; Fenske, D.; Banin, U. Molecular limit of a bulk semiconductor: Size dependence of the "Band Gap" in CdSe cluster molecules. J. Am. Chem. Soc. 2000, 122, 2673-2674.
Yang, Y.; Li, J. Z.; Lin, L.; Peng, X. G. An efficient and surface-benign purification scheme for colloidal nanocrystals based on quantitative assessment. Nano Res. 2015, 8, 3353-3364.
Yang, Y.; Qin, H. Y.; Peng, X. G. Intramolecular entropy and size-dependent solution properties of nanocrystal-ligands complexes. Nano Lett. 2016, 16, 2127-2132.
Hassinen, A.; Moreels, I.; De Nolf, K.; Smet, P. F.; Martins, J. C.; Hens, Z. Short-chain alcohols strip X-type ligands and quench the luminescence of PbSe and CdSe quantum dots, acetonitrile does not. J. Am. Chem. Soc. 2012, 134, 20705-20712.
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. 2013, 135, 18536-18548.
Cao, Y. C.; Wang, J. H. One-pot synthesis of high-quality zinc-blende CdS nanocrystals. J. Am. Chem. Soc. 2004, 126, 14336-14337.
Zhai, X. M.; Zhang, R. B.; Lin, J. L.; Gong, Y. Q.; Tian, Y. F.; Yang, W.; Zhang, X. L. Shape-controlled CdS/ZnS core/shell heterostructured nanocrystals: Synthesis, characterization, and periodic dft calculations. Cryst. Growth Des. 2015, 15, 1344-1350.
Voigt, J.; Ost, E. On the dynamical behaviour of excitons in CdS single crystals. Ⅱ. Correlation between intrinsic excitonic absorption and photoconductivity. Phys. Status Solidi B 1969, 33, 381-389.
Voigt, J.; Spiegelberg, F.; Senoner, M. Band parameters of CdS and CdSe single crystals determined from optical exciton spectra. Phys. Status Solidi B 1979, 91, 189-199.
Klimov, V. I. Optical nonlinearities and ultrafast carrier dynamics in semiconductor nanocrystals. J. Phys. Chem. B 2000, 104, 6112-6123.
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Acknowledgements
This work was supported by the National Key Research and Development Program of China (No. 2016YFB0401600), Zhejiang postdoctoral natural science foundation (No. 2015M581919), and the Science and Technology Planning Project of Guangdong Province, China (No. 2015B090913001).
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