Computational Study of Magic-Size CdSe Clusters with Complementary Passivation by Carboxylic and Amine Ligands

Voznyy, Oleksandr; Mokkath, Junais Habeeb; Jain, Ankit; Sargent, Edward H.; Schwingenschlögl, Udo

doi:10.1021/acs.jpcc.5b10908

Cited by 35 publications

(51 citation statements)

References 32 publications

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“…The thermal dissociation of Cd(II)‐PEI complexes eliminates this additional factor of electron confinement resulting in a decrease of the excitation energy without any actual change in the NC size. Similar effects were reported to arise from the substitution of electron‐donating to electron‐accepting ligands on the surface of “magic‐size” CdX clusters . We believe that such effects can be (at least partially) responsible for the reversible shifts of the PL band maximum for the present case of AIS‐GSH NCs.…”

Section: Resultssupporting

confidence: 82%

“…Similar effects were reported to arise from the substitution of electron-donating to electron-accepting ligands on the surface of "magic-size" CdX clusters. [33,34] We believe that such effects can be (at least partially) responsible for the reversible shifts of the PL band maximum for the present case of AIS-GSH NCs. Definitely, we cannot exclude other possible factors that may contribute to the observed spectral shifts, including a variation of the spatial exciton confinement arising from the thermal lattice expansion as well as a temperature dependence of the population of lattice defects and various recombination events.…”

Section: Variations Of the Pl Band Maximum Positionmentioning

confidence: 75%

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Temperature‐Dependent Photoluminescence of Silver‐Indium‐Sulfide Nanocrystals in Aqueous Colloidal Solutions

et al. 2019

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The temperature dependence of the photoluminescence (PL) intensity of colloidal semiconductor nanocrystals (NCs) makes them an appealing option in bio‐sensing applications. Here, we probed the temperature‐dependent PL behavior of aqueous glutathione (GSH)‐capped Ag−In−S (AIS) NCs and their core/shell AIS/ZnS heterostructures. We show that both core and core‐shell materials reveal strong PL quenching upon heating from 10 to 80 °C, which is completely reversible upon cooling. The PL quenching is assigned to the thermally activated dissociation of complexes formed by ligands with the metal cations on the NC surface and the introduction of water into the NC coordination sphere. This unique mechanism of the thermal PL quenching results in a much higher temperature sensitivity of the aqueous colloidal AIS (AIS/ZnS) NCs as compared with previously reported analogs capped by covalently bound ligands. Our results are expected to stimulate further studies on aqueous ternary NCs as colloidal luminescent nano‐thermometers applicable for ratiometric temperature sensing.

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Section: Resultssupporting

confidence: 82%

Section: Variations Of the Pl Band Maximum Positionmentioning

confidence: 75%

Temperature‐Dependent Photoluminescence of Silver‐Indium‐Sulfide Nanocrystals in Aqueous Colloidal Solutions

et al. 2019

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“…The solved atomic structures [9] of the CdSe nanoparticles under study allow DFT total energy minimization calculations to be carried out to find relaxed structures. It is computationally demanding to simulate vi- brational properties of nanoparticles with the full ligand coverage, given the large number of surface ligands and the multitude of different possible ligand arrangements [27] that are not exactly known from the experiments [6,9]. For simplicity, the nanoparticle surfaces were passivated with pseudo-hydrogen atoms (H * ) with fractional charges that fully saturate the dangling bonds of the surface Cd atoms and keep the nanoparticles charge neutral (see Methods section).…”

Section: Combined Experiments With Dft Provide Insights Into Structurementioning

confidence: 99%

Size-Dependent Lattice Dynamics of Atomically Precise Cadmium Selenide Quantum Dots

et al. 2019

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Material properties depend sensitively on the atomic arrangements and atomic bonding, but these are notoriously difficult to measure in nanosized atomic clusters due to the small size of the objects and the challenge of obtaining bulk samples of identical clusters. Here we have combined the recent ability to make gram quantities of identical semiconductor quantum-dot nanoparticles with the ability to measure lattice dynamics on small sample quantities of hydrogenated materials using high energy resolution inelastic x-ray scattering (HERIX), to measure the size-dependence of the phonon density of states (PDOS) in CdSe quantum dots. The fact that we have atomically precise structural models for these nanoparticles allows the calculation of the PDOS using Density Functional Theory (DFT), providing both experimental and theoretical confirmations of the important role that the inertia of the surface capping species plays on determining the lattice dynamics.Colloidal semiconducting nanocrystals, commonly called quantum dot nanoparticles, have been studied exhaustively over the last thirty years due to their unique optoelectronic properties: size-tunable band-gaps, narrow, highly efficient photoluminescence, and long-term stability. For these reasons, they have started appearing in various products on the market ranging from television displays [1,2] to solid-state lightbulbs [3] and biological labels [4,5]. However, despite their commercial success, further development has been hindered by the lack of a detailed understanding of fundamental nanoparticle structure-property relationships, an important example of which is the nature of their lattice dynamics and how it is modified from bulk behavior by nanoparticle size [6]. Although lattice dynamics has a significant effect on the structural, mechanical and electronic properties of materials, it remains poorly understood for small crystallites because current techniques are best suited for bulk single-crystals. In the case of nanoparticles, this requirement is particularly problematic because their structures are often poorly defined, making it challenging even to determine the atomic structure [7], a prerequisite to un-FIG. 1. Structure representation of the cadmium selenide quantum dots in the current study. Their chemical compositions and surface capping ligands are shown.derstanding dynamics and properties.With the development of techniques such as the pair distribution function (PDF) which allows to obtain structure solution from powder x-ray scattering experiments [8], our ability to measure the structure of nanomaterials has improved. Using the PDF methods, we recently reported the first complete structural solution of a set of atomically-precise cadmium selenide quantum dots [9], shown in Fig. 1. Unlike even the most monosdisperse nanoparticle samples which generally possess some degree of heterogeneity in size, shape, and/or composition [10], the class of atomically precise nanoparticles that we prepared have well-defined structures and chemical formulas. We hav...

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“…In this work, we seek to elucidate the impact of the external electric field on the optical dynamics of a realistic SQD using the linear combination of atomic orbitals (LCAO) real-time-propagation-time-dependent density functional theory (rt-TDDFT) technique and transition contribution maps (TCMs). As a proof of concept, we choose cadmium-selenide (CdSe) due to its prevalence in the literature as a convenient model system for application in light-emitting diodes and solar cells [29][30][31][32]. From a theoretical point of view, classical techniques (with the use of local dielectric functions) allow complete characterization of the interaction of light with systems of basically any shape and composition [33][34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

Optical features of ligated semiconducting quantum dots subjected to an electric field

Mokkath

2021

Int J of Quantum Chemistry

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Semiconducting quantum dots (SQDs) are attractive materials for optoelectronic applications due to the size-tunable band gaps, colloidal stability, and low-cost solution processability. In this article, we investigate the modulations in the optical features of COOH + NH3 capped tetrahedral-shape CdSe SQD in response to the external electric field. We base our calculations on an approach which combines the linear combination of atomic orbitals (LCAO) real-time-propagation-time-dependent density functional theory (rt-TDDFT) technique (LCAO-rt-TDDFT) and transition contribution maps (two-dimensional visualization of Kohn-Sham single electron-single hole transitions). Among other insights, our study indicates that electric field causes a redistribution of the oscillator strengths, early onset of absorption, and ligand-derived trap states near the top of the valence band. These theoretical findings explain the origins of the electric field induced optical features of ligated SQDs.

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Computational Study of Magic-Size CdSe Clusters with Complementary Passivation by Carboxylic and Amine Ligands

Cited by 35 publications

References 32 publications

Temperature‐Dependent Photoluminescence of Silver‐Indium‐Sulfide Nanocrystals in Aqueous Colloidal Solutions

Temperature‐Dependent Photoluminescence of Silver‐Indium‐Sulfide Nanocrystals in Aqueous Colloidal Solutions

Size-Dependent Lattice Dynamics of Atomically Precise Cadmium Selenide Quantum Dots

Optical features of ligated semiconducting quantum dots subjected to an electric field

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