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Fenoll D, Sodupe M, Solans-Monfort X. Influence of Capping Ligands, Solvent, and Thermal Effects on CdSe Quantum Dot Optical Properties by DFT Calculations. ACS OMEGA 2023; 8:11467-11478. [PMID: 37008094 PMCID: PMC10061629 DOI: 10.1021/acsomega.3c00324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 03/07/2023] [Indexed: 06/19/2023]
Abstract
Cadmium selenide nanomaterials are very important materials in photonics, catalysis, and biomedical applications due to their optical properties that can be tuned through size, shape, and surface passivation. In this report, static and ab initio molecular dynamics density functional theory (DFT) simulations are used to characterize the effect of ligand adsorption on the electronic properties of the (110) surface of zinc blende and wurtzite CdSe and a (CdSe)33 nanoparticle. Adsorption energies depend on ligand surface coverage and result from a balance between chemical affinity and ligand-surface and ligand-ligand dispersive interactions. In addition, while little structural reorganization occurs upon slab formation, Cd···Cd distances become shorter and the Se-Cd-Se angles become smaller in the bare nanoparticle model. This originates mid-gap states that strongly influence the absorption optical spectra of nonpassivated (CdSe)33. Ligand passivation on both zinc blende and wurtzite surfaces does not induce a surface reorganization, and thus, the band gap remains nonaffected with respect to bare surfaces. In contrast, structural reconstruction is more apparent for the nanoparticle, which significantly increases its highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap upon passivation. Solvent effects decrease the band gap difference between the passivated and nonpassivated nanoparticles, the maximum of the absorption spectra being blue-shifted around 20 nm by the effect of the ligands. Overall, calculations show that flexible surface cadmium sites are responsible for the appearance of mid-gap states that are partially localized on the most reconstructed regions of the nanoparticle that can be controlled through appropriate ligand adsorption.
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Lv L, Liu S, Li J, Lei H, Qin H, Peng X. Synthesis of Weakly Confined, Cube-Shaped, and Monodisperse Cadmium Chalcogenide Nanocrystals with Unexpected Photophysical Properties. J Am Chem Soc 2022; 144:16872-16882. [PMID: 36067446 DOI: 10.1021/jacs.2c05151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Zinc-blende CdSe, CdS, and CdSe/CdS core/shell nanocrystals with a structure-matched shape (cube-shaped, edge length ≤30 nm) are synthesized via a universal scheme. With the edge length up to five times larger than exciton diameter of the bulk semiconductors, the nanocrystals exhibit novel properties in the weakly confined size regime, such as near-unity single exciton and biexciton photoluminescence (PL) quantum yields, single-nanocrystal PL nonblinking, mixed PL decay dynamics of exciton and free carriers with sub-microsecond monoexponential decay lifetime, and stable yet extremely narrow PL full width at half maximum (FWHM < 0.1 meV) at 1.8 K. Their monodisperse edge length, shape, and facet structure enable demonstration of unexpected yet size-dependent PL properties at room temperature, including unusually broad and abnormally size-dependent PL FWHM (∼100 meV), nonmonotonic size dependence of PL peak energy, and dual-peak single-exciton PL. Calculations suggest that these unusual properties should be originated from the band-edge electron/hole states of the dynamic-exciton, whose exciton binding energy is too small to hold the photogenerated electron-hole pair as a bonded Wannier exciton in a weakly confined nanocrystal.
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Affiliation(s)
- Liulin Lv
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Shaojie Liu
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Jiongzhao Li
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Haixin Lei
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Haiyan Qin
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Xiaogang Peng
- Key Laboratory of Excited-State Materials of Zhejiang Province, and Department of Chemistry, Zhejiang University, Hangzhou 310027, China
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Camargo FA, Ben-Shahar Y, Nagahara T, Panfil YE, Russo M, Banin U, Cerullo G. Visualizing Ultrafast Electron Transfer Processes in Semiconductor-Metal Hybrid Nanoparticles: Toward Excitonic-Plasmonic Light Harvesting. NANO LETTERS 2021; 21:1461-1468. [PMID: 33481610 PMCID: PMC7883410 DOI: 10.1021/acs.nanolett.0c04614] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Recently, it was demonstrated that charge separation in hybrid metal-semiconductor nanoparticles (HNPs) can be obtained following photoexcitation of either the semiconductor or of the localized surface plasmon resonance (LSPR) of the metal. This suggests the intriguing possibility of photocatalytic systems benefiting from both plasmon and exciton excitation, the main challenge being to outcompete other ultrafast relaxation processes. Here we study CdSe-Au HNPs using ultrafast spectroscopy with high temporal resolution. We describe the complete pathways of electron transfer for both semiconductor and LSPR excitation. In the former, we distinguish hot and band gap electron transfer processes in the first few hundred fs. Excitation of the LSPR reveals an ultrafast (<30 fs) electron transfer to CdSe, followed by back-transfer from the semiconductor to the metal within 210 fs. This study establishes the requirements for utilization of the combined excitonic-plasmonic contribution in HNPs for diverse photocatalytic applications.
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Affiliation(s)
- Franco
V. A. Camargo
- Dipartimento
di Fisica, IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milan 20133, Italy
| | - Yuval Ben-Shahar
- Institute
of Chemistry and Center for Nanoscience & Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
- Department
of Physical Chemistry, Israel Institute
for Biological Research, P.O. Box 19, Ness-Ziona 74100, Israel
| | - Tetsuhiko Nagahara
- Dipartimento
di Fisica, IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milan 20133, Italy
- Department
of Chemistry and Materials Technology, Kyoto
Institute of Technology, Matsugasaki, Kyoto 6068585, Japan
| | - Yossef E. Panfil
- Institute
of Chemistry and Center for Nanoscience & Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Mattia Russo
- Dipartimento
di Fisica, IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milan 20133, Italy
| | - Uri Banin
- Institute
of Chemistry and Center for Nanoscience & Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Giulio Cerullo
- Dipartimento
di Fisica, IFN-CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milan 20133, Italy
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4
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Ayari S, Quick MT, Owschimikow N, Christodoulou S, Bertrand GHV, Artemyev M, Moreels I, Woggon U, Jaziri S, Achtstein AW. Tuning trion binding energy and oscillator strength in a laterally finite 2D system: CdSe nanoplatelets as a model system for trion properties. NANOSCALE 2020; 12:14448-14458. [PMID: 32618327 DOI: 10.1039/d0nr03170d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We present a theoretical study combined with experimental validations demonstrating that CdSe nanoplatelets are a model system to investigate the tunability of trions and excitons in laterally finite 2D semiconductors. Our results show that the trion binding energy can be tuned from 36 meV to 18 meV with the lateral size and decreasing aspect ratio, while the oscillator strength ratio of trions to excitons decreases. In contrast to conventional quantum dots, the trion oscillator strength in a nanoplatelet at low temperature is smaller than that of the exciton. The trion and exciton Bohr radii become lateral size tunable, e.g. from ∼3.5 to 4.8 nm for the trion. We show that dielectric screening has strong impact on these properties. By theoretical modeling of transition energies, binding energies and oscillator strength of trions and excitons and comparison with experimental findings, we demonstrate that these properties are lateral size and aspect ratio tunable and can be engineered by dielectric confinement, allowing to suppress e.g. detrimental trion emission in devices. Our results strongly impact further in-depth studies, as the demonstrated lateral size tunable trion and exciton manifold is expected to influence properties like gain mechanisms, lasing, quantum efficiency and transport even at room temperature due to the high and tunable trion binding energies.
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Affiliation(s)
- Sabrine Ayari
- Laboratoire de Physique des Materiaux, Faculte des Sciences de Bizerte, Universite de Carthage, Jarzouna 7021, Tunisia
| | - Michael T Quick
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
| | - Nina Owschimikow
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
| | | | | | - Mikhail Artemyev
- Research Institute for Physical Chemical Problems of Belarusian State University, 220006 Minsk, Belarus
| | - Iwan Moreels
- Department of Chemistry, Ghent University, Krijgslaan 281 - S3, 9000 Gent, Belgium
| | - Ulrike Woggon
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
| | - Sihem Jaziri
- Laboratoire de Physique des Materiaux, Faculte des Sciences de Bizerte, Universite de Carthage, Jarzouna 7021, Tunisia and Laboratoire de Physique de la Matiere Condensee, Departement de Physique, Faculte des Sciences de Tunis, Campus Universitaire, 1060 Tunis, Tunisia
| | - Alexander W Achtstein
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
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Bose S, Shendre S, Song Z, Sharma VK, Zhang DH, Dang C, Fan W, Demir HV. Temperature-dependent optoelectronic properties of quasi-2D colloidal cadmium selenide nanoplatelets. NANOSCALE 2017; 9:6595-6605. [PMID: 28475189 DOI: 10.1039/c7nr00163k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Colloidal cadmium selenide (CdSe) nanoplatelets (NPLs) are a recently developed class of efficient luminescent nanomaterials suitable for optoelectronic device applications. A change in temperature greatly affects their electronic bandstructure and luminescence properties. It is important to understand how and why the characteristics of NPLs are influenced, particularly at elevated temperatures, where both reversible and irreversible quenching processes come into the picture. Here we present a study of the effect of elevated temperatures on the characteristics of colloidal CdSe NPLs. We used an effective-mass envelope function theory based 8-band k·p model and density-matrix theory considering exciton-phonon interaction. We observed the photoluminescence (PL) spectra at various temperatures for their photon emission energy, PL linewidth and intensity by considering the exciton-phonon interaction with both acoustic and optical phonons using Bose-Einstein statistical factors. With a rise in temperature we observed a fall in the transition energy (emission redshift), matrix element, Fermi factor and quasi Fermi separation, with a reduction in intraband state gaps and increased interband coupling. Also, there was a fall in the PL intensity, along with spectral broadening due to an intraband scattering effect. The predicted transition energy values and simulated PL spectra at varying temperatures exhibit appreciable consistency with the experimental results. Our findings have important implications for the application of NPLs in optoelectronic devices, such as NPL lasers and LEDs, operating much above room temperature.
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Affiliation(s)
- Sumanta Bose
- School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
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Achtstein AW, Scott R, Kickhöfel S, Jagsch ST, Christodoulou S, Bertrand GHV, Prudnikau AV, Antanovich A, Artemyev M, Moreels I, Schliwa A, Woggon U. p-State Luminescence in CdSe Nanoplatelets: Role of Lateral Confinement and a Longitudinal Optical Phonon Bottleneck. PHYSICAL REVIEW LETTERS 2016; 116:116802. [PMID: 27035317 DOI: 10.1103/physrevlett.116.116802] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Indexed: 05/26/2023]
Abstract
We evidence excited state emission from p states well below ground state saturation in CdSe nanoplatelets. Size-dependent exciton ground and excited state energies and population dynamics are determined by four independent methods: time-resolved PL, time-integrated PL, rate equation modeling, and Hartree renormalized k·p calculations-all in very good agreement. The ground state-excited state energy spacing strongly increases with the lateral platelet quantization. Depending on its detuning to the LO phonon energy, the PL decay of CdSe platelets is governed by a size tunable LO phonon bottleneck, related to the low exciton-phonon coupling, very large oscillator strength, and energy spacing of both states. This is, for instance, ideal to tune lasing properties. CdSe platelets are perfectly suited to control the exciton-phonon interaction by changing their lateral size while the optical transition energy is determined by their thickness.
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Affiliation(s)
- Alexander W Achtstein
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Riccardo Scott
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Sebastian Kickhöfel
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Stefan T Jagsch
- Institute of Solid State Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Sotirios Christodoulou
- Department of Physics, University of Genoa, via Dodecaneso 33, IT-16146 Genova, Italy
- Istituto Italiano di Tecnologia, Via Morego 30, IT-16163 Genova, Italy
| | | | - Anatol V Prudnikau
- Institute for Physico-Chemical Problems, Belarusian State University, 220030 Minsk, Belarus
| | - Artsiom Antanovich
- Institute for Physico-Chemical Problems, Belarusian State University, 220030 Minsk, Belarus
| | - Mikhail Artemyev
- Institute for Physico-Chemical Problems, Belarusian State University, 220030 Minsk, Belarus
| | - Iwan Moreels
- Istituto Italiano di Tecnologia, Via Morego 30, IT-16163 Genova, Italy
| | - Andrei Schliwa
- Institute of Solid State Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Ulrike Woggon
- Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
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7
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Lin Z, Franceschetti A, Lusk MT. Size dependence of the multiple exciton generation rate in CdSe quantum dots. ACS NANO 2011; 5:2503-2511. [PMID: 21355556 DOI: 10.1021/nn200141f] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The multiplication rates of hot carriers in CdSe quantum dots are quantified using an atomistic pseudopotential approach and first-order perturbation theory. We consider both the case of an individual carrier (electron or hole) decaying into a trion and the case of an electron-hole pair decaying into a biexciton. The dependence on quantum dot volume of multiplication rate, density of final states, and effective Coulomb interaction are determined. We show that the multiplication rate of a photogenerated electron-hole pair decreases with dot size for a given absolute photon energy. However, if the photon energy is rescaled by the volume-dependent optical gap, then smaller dots exhibit an enhancement in carrier multiplication rate for a given relative photon energy. We find that holes have much higher multiplication rates than electrons of the same excess energy due to the larger density of final states (positive trions). When electron-hole pairs are generated by photon absorption, however, the net carrier multiplication rate is dominated by electrons because they have much higher excess energy on average. We also find, contrary to earlier studies, that the effective Coulomb coupling governing carrier multiplication is energy-dependent.
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Affiliation(s)
- Zhibin Lin
- Department of Physics, Colorado School of Mines, Golden, Colorado 80401, USA.
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9
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Mahler B, Lequeux N, Dubertret B. Ligand-controlled polytypism of thick-shell CdSe/CdS nanocrystals. J Am Chem Soc 2010; 132:953-9. [PMID: 20043669 DOI: 10.1021/ja9034973] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the synthesis of CdSe/CdS semiconductor core/shell nanocrystals with very thick (5 nm) CdS shells. As in the case of core CdSe nanocrystals, we show that a thick-shell CdSe/CdS core/shell structure can be synthesized in either a pure wurtzite (W) or a zinc-blende (ZB) crystal structure. While the growth of thick-shell wurtzite CdSe/CdS is quite straightforward, we observe that the growth of a CdS shell on zinc-blende CdSe cores is more difficult and leads to wurtzite/zinc-blende polytypism when primary amines are present during the shell formation. Using absorption spectra analysis to differentiate zinc blende from wurtzite CdSe, we show that primary amines can induce a nearly complete structural transformation of CdSe ZB cores into W cores. This better understanding of the CdSe ligand-dependent crystal structural evolution during shell growth is further used to grow large (10 nm)-diameter perfect zinc-blende CdSe core crystals emitting above 700 nm, and perfect ZB thick-shell CdSe/CdS nanocrystals. We observed that all thick-shell CdSe/CdS QDs have extremely reduced blinking events compared to thin-shell QDs, without any significant influence of crystalline structure and polytypism.
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Affiliation(s)
- Benoît Mahler
- Laboratoire de Physique et d'Etude des Matériaux, CNRS UPR5, ESPCI 10 rue Vauquelin, 75231 Paris, France
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