Epitaxial Growth of Highly Luminescent CdSe/CdS Core/Shell Nanocrystals with Photostability and Electronic Accessibility

Peng, Xiaogang; Schlamp, M. C.; Kadavanich, and Andreas V.; Alivisatos, A. Paul

doi:10.1021/ja970754m

Cited by 2,380 publications

(2,344 citation statements)

References 42 publications

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“…The varying results for QY changes after peptide coating for samples [1][2][3][4][5] show that the shell composition/structure is a major factor in the QY of peptide-coated NCs. In all cases besides CdSe/ZnS, QY and emission changes similar to those in Table 1 were acquired with cores of different sizes.…”

Section: Discussionmentioning

confidence: 99%

Enhancing the Photoluminescence of Peptide-Coated Nanocrystals with Shell Composition and UV Irradiation

et al. 2005

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The composition and structure of inorganic shells grown over CdSe semiconductor nanocrystal dots and rods were optimized to yield enhanced photoluminescence properties after ligand exchange followed by coating with phytochelatin-related peptides. We show that, in addition to the peptides imparting superior colloidal properties and providing biofunctionality in a single-step reaction, the improved shells and pretreatment with UV irradiation resulted in high quantum yields for the nanocrystals in water. Moreover, peptide coating caused a noticeable red-shift in the absorption and emission spectra for one of the tested shells, suggesting that exciton-molecular orbital (X-MO) coupling might take place in these hybrid inorganic-organic composite materials.

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Section: Discussionmentioning

confidence: 99%

Enhancing the Photoluminescence of Peptide-Coated Nanocrystals with Shell Composition and UV Irradiation

et al. 2005

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“…In addition, although NR 6 has the longest CdS rod length, we achieved almost the same amount ($8 nm) of blue-shied ASE from NR 6 when compared to NR 5 . It is also shown that both NR 5 and NR 6 have the same radiative lifetime, which conrms that photoluminescence lifetimes are a good indicator of connement. Finally, optical gain thresholds down to 3 mJ cm À2 are achieved 5 Normalized decomposed ASE and spontaneous emission spectra of (a) NR 4 , (b) NR 5 and (c) NR 6 samples under intense twophoton optical pumping.…”

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confidence: 81%

Type-tunable amplified spontaneous emission from core-seeded CdSe/CdS nanorods controlled by exciton–exciton interaction

et al. 2014

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Type-tunable optical gain performance of core-seeded CdSe/CdS nanorods is studied via two-photon optical pumping. Controlling the Colloidal semiconductor nanocrystals have recently arisen as promising candidates to be utilized as active gain media for lasing applications. 1,2 With their band gap tunability (via size and shape modications), efficient band edge emission (even at room temperature), discrete band structure, and synthesis through facile wet-chemistry, it is possible to achieve colortunable, low-threshold, temperature insensitive and solution processed lasers from colloidal quantum dots (CQDs). [2][3][4][5][6] However, there are various problems and challenges associated with CQD-based lasers. One way of achieving stimulated emission from the CQDs is through multi-exciton generation. When multiple excitons are formed, the Auger recombination (AR) process becomes more pronounced and inhibits optical gain in CQDs. [7][8][9] In addition, high intensity optical pumping, which is required for stimulated emission, can photo-damage the sample and decrease the stability. 10 To address these issues, CQDs having suppressed AR and exhibiting a higher absorption cross-section, which can increase the stability of CQDs by lowering the optical gain threshold, are strongly required.As a subclass of nanocrystals, core/shell nanorods (NRs) have been extensively considered for lasing applications and optical gain studies to overcome these problems with possibility of engineering their electronic structure for longer gain lifetime and increased absorption cross-section. 11-14 From different varieties of core/shell NRs, core-seeded CdSe/CdS NRs have become quite attractive. With advances in the colloidal synthesis of CdSe/CdS core/shell NRs, it is possible to synthesize highly efficient and crystalline CdSe/CdS core/shell NRs having a narrow size distribution by nely controlling their shape and size. 15,16 Furthermore, due to shallow band offset for electrons in the CdSe/CdS core/shell material system, a partial separation of electron and hole wavefunctions is observed which is known as the quasi type-II electronic structure that contributes to the suppression of Auger recombination, which is highly critical for achieving lasing. 11,[16][17][18] The other advantage of having a lower energy barrier for electrons in CdSe/CdS NRs is that, by simply changing their core and shell sizes, it is possible to tailor the electron and hole wavefunction overlap and tune CdSe/CdS NRs from type-I-like to quasi-type-II-like band alignment, which can be an important design consideration when engineering the gain/loss mechanisms in practical lasing systems. [19][20][21][22][23] Moreover, due to the narrower band gap of CdS with respect to ZnS, the absorption cross-section of CdSe/CdS core/shell NRs is greatly enhanced. 13 With all of these aforementioned promises, in the nanocrystal lasing context, CdSe/CdS NRs have become one of the most heavily studied materials systems. 18,24 Recently, singlemode, single-exciton and tunable laser emis...

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“…The solution of CdSe seeds in TOP can be added to the reaction mixture either together with TOPS or 30-60s later, i.e., during the induction period. CdS easily nucleates at the surface of CdSe seeds [11,17]. We found that the structure of the CdSe seeds determined the morphology of CdSe/CdS nano-heterostructures.…”

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confidence: 83%

“…In this work we compared w-CdSe and zb-CdSe nanocrystals for seeded growth of CdSe/CdS nano-hererostructures with different morphologies. Combining CdSe and CdS in a single nanostructure creates a material with heterogeneous carrier confinement or "mixed dimentionality" where holes are confined to CdSe while electrons can move freely between CdSe and CdS phases, spreading over the entire nanostructure [11,17]. Previously we synthesized structures consisting of a spherical CdSe nanocrystal connected to a CdS nanorod [17].…”

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confidence: 99%

Seeded Growth of Highly Luminescent CdSe/CdS Nanoheterostructures with Rod and Tetrapod Morphologies

et al. 2007

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We have demonstrated that seeded growth of nanocrystals offers a convenient way to design nanoheterostructures with complex shapes and morphologies by changing the crystalline structure of the seed. By using CdSe nanocrystals with wurtzite and zinc blende structure as seeds for growth of CdS nanorods, we synthesized CdSe/CdS heterostructures nanorods and nano-tetrapods, respectively. Both of these structures showed excellent luminescent properties, combining high photoluminescence efficiency (~80% and ~50% for nanorods and nano-tetrapods, correspondingly), giant extinction coefficients (~2·10 7 M -1 cm -1 and ~1.5·10 8 M -1 cm -1 at 350 nm for nanorods and nano-tetrapods, correspondingly) and efficient energy transfer from the CdS arms into the emitting CdSe core. † Current address:

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Epitaxial Growth of Highly Luminescent CdSe/CdS Core/Shell Nanocrystals with Photostability and Electronic Accessibility

Cited by 2,380 publications

References 42 publications

Enhancing the Photoluminescence of Peptide-Coated Nanocrystals with Shell Composition and UV Irradiation

Enhancing the Photoluminescence of Peptide-Coated Nanocrystals with Shell Composition and UV Irradiation

Type-tunable amplified spontaneous emission from core-seeded CdSe/CdS nanorods controlled by exciton–exciton interaction

Seeded Growth of Highly Luminescent CdSe/CdS Nanoheterostructures with Rod and Tetrapod Morphologies

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