PbSe/PbS and PbSe/PbSexS1-x Core/Shell Nanocrystals

Brumer, Maya; Kigel, Ariel; Amirav, Lilac; Sashchiuk, Aldona; Solomesch, Olga; Tessler, Nir; Lifshitz, Efrat

doi:10.1002/adfm.200400620

Cited by 153 publications

(170 citation statements)

References 27 publications

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“…The exciton absorption of the PbSe seed is red-shifted (by 0.1 and 0.25 eV for larger and smaller seed, respectively) from the expected value for the corresponding bare PbSe, 25 consistent with embedment in a PbS matrix. 21,26,27 The rods also show seed sizedependent NIR emission.…”

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confidence: 99%

Nanoheterostructure Cation Exchange: Anionic Framework Conservation

et al. 2010

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In ionic nanocrystals, especially transition metal chalcogenides, the cationic sub-lattice can be replaced with a different metal ion via a fast, simple, and reversible place-exchange, altering the composition of the nanocrystal, while preserving its size and shape. [1][2][3][4][5][6][7] It is generally assumed that during such an exchange, the anionic framework of the crystal is conserved, while the cations, due to their relatively smaller size and higher mobility, undergo replacement. This has not, however, been experimentally proven or utilized, as only single-phase nanocrystals have so far been transformed using cation exchange. Preservation of the anionic framework during cation exchange would enable transformation of multi-component nanoheterostructures, while conserving not only the nanostructure size and shape, but also the compositional interface between the constituents. This would greatly extend the domain of cation exchange to the design of ever more complex nanostructures. In this Communication, we demonstrate that, indeed, the anionic framework is preserved during cation exchange, and that this can be utilized for accessing customized nanoheterostructures.The model heterostructure selected is a seeded rod consisting of a spherical CdSe nanocrystal embedded in a CdS nanorod. [8][9][10] A unique functional feature of such a structural arrangement is the ability to design the relative band alignment of the two semiconductors across the interface, allowing independent tuning of the spatial distribution of electrons and holes along the elongated dimension. [11][12][13][14][15][16] The seeded rod is a canonical example of a nanoheterostructure that allows customization of electronic properties for applications such as force sensing, 17 photocatalysis, 18 optoelectronics, 19-21 and quantum information technology. 22 A 40-nm long CdSe/CdS seeded nanorod synthesized with a 3.9-nm seed (Supporting Information) exhibits absorption features (Fig. 1A) attributable to excitons in the CdSe seed (600 nm and 562 nm) and the CdS rod (460 nm) and strong photoluminescence (PL) due to exciton recombination in the seed (Fig. 1B). Complete cation exchange of the nanorods with Cu + results in the loss of CdS and CdSe excitonic features and the emergence of an absorption band-edge around 850 nm, typical of Cu chalcogenides (indirect bulk band gap ~1.2eV). Back-conversion of the Cu 2 Se/Cu 2 S seeded rod to Cd 2+ recovers all excitonic features of the original structure (Fig 1A, B, and D).The PL peak maximum, due to the confined nature of the emitting exciton in the seed, is known to be highly sensitive to the seed diameter (Fig. 1C). It is noteworthy that following two cycles of exchange, the PL peak recovered with a similar position as that of the initial nanorods. This indicates complete conservation of the selenide seed embedded in the sulfide rod Figure 1. A) Absorbance and B) photoluminescence (PL) spectrum of a 40-nm long CdS nanorod with an embedded 3.9-nm CdSe nanocrystal (top), following complete exchange with Cu ...

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confidence: 99%

Nanoheterostructure Cation Exchange: Anionic Framework Conservation

et al. 2010

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“…While this review focuses on the recent advances made for II-VI semiconductor nanocrystals, III-V (InP/ZnSe x S 1 − x ) and IV-VI semiconductors (PbSe/PbSe x S 1 − x ) have been synthesised as well with graded alloy composition [35][36][37][38]. In all cases superior robustness was reported compared to similar particles with hard interfaces.…”

Section: Synthetic Approaches and Structural Analysismentioning

confidence: 99%

Graded Shells in Semiconductor Nanocrystals

Boldt

2016

Zeitschrift Für Physikalische Chemie

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Abstract:The current state-of-the-art of the fabrication and photophysics of graded shells in quantum dots is reviewed. Graded shells, i.e. partially alloyed interfaces between core and shell or between two shells of semi conductor nanoheterostructures, have been demonstrated to improve fluorescence properties and suppress non-radiative pathways of exciton dynamics. By simply looking at linear optics on the level of single excitons this is reflected in increased photoluminescence quantum yields. However, it is shown that graded shells have further beneficial implications for band structure engineering and multiexciton dynamics such as optical gain and charge carrier multiplication.

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“…The preparation of PbSe/PbSe x S 1-x c/a-sh and PbSe x S 1-x /PbSe y S 1-y a-c/a-sh structures 19 is nearly identical to that of the core PbSe CQDs, described previosly using a single injection of the precursors into a single round flask. However, step (5) was altered by the use of an alternative chalcogen precursor stock solution.…”

Section: Theoretical Prediction Of the Electronic Properties Of Hetermentioning

confidence: 99%

“…The synthesis of core PbSe CQDs followed a modified procedure to that given by Murray et al 50 , following the procedure given in 19 7 COOH, 99.8%, Aldrich) and 8 mL TOP ((C 8 H 17 ) 3 P, Tech, Aldrich), under standard inert conditions in the glove box, and were inserted into a threeneck flask (flask I); (2) 10 mL of PhEt were inserted into a three-neck flask (flask II) under the inert conditions of a glove box; (3) both flasks were taken out of the glove box, placed on a Schlenk line and heated under a vacuum to 100 -120°C for an hour; (4) flask I was cooled to 45°C, while flask II was heated to 180 -210°C, both under a fledging of an argon gas; (5) 0.155 gr of selenium powder (Se, 99.995%, Aldrich) was dissolved in 2.0 mL TOP, forming a TOP:Se solution, under standard inert conditions of a glove box. Then, 1.7 mL of this solution was injected into flask I on the Schlenk line; (6) the content of flask I, containing the reaction precursors, was injected rapidly into the PhEt solution in flask II, reducing its temperature to 100 -130°C, leading to the formation of PbSe CQDs within the first 15 min of the reaction.…”

Section: Theoretical Prediction Of the Electronic Properties Of Hetermentioning

confidence: 99%

“…The preparation of PbSe/PbS c/sh CQDs by a two-injection process 19 begins with formation of core PbSe CQDs and their isolation from the initial reaction solution, according to the procedure described previolsy. Those core CQDs were re-dissolved in chloroform solution, forming a solution of 50 mg/mL weight concentration.…”

Section: Theoretical Prediction Of the Electronic Properties Of Hetermentioning

confidence: 99%

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