Quantum size effects in the redox potentials, resonance Raman spectra, and electronic spectra of CdS crystallites in aqueous solution

Rossetti, R.; Nakahara, S.; Brus, L. E.

doi:10.1063/1.445834

Cited by 868 publications

(436 citation statements)

References 21 publications

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“…The relationship between size and optical spectra was first established and confirmed for ZnS and CdS colloidal semiconductor nanoparticles (NPs) by Rosetti et al [1][2][3]. Since then, numerous investigations have been carried out to synthesize colloidal semi-conductors (NCs), and the interest continues to increase [4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 95%

Laser-assisted synthesis, and structural and thermal properties of ZnS nanoparticles stabilised in polyvinylpyrrolidone

Onwudiwe

Krüger

Jordaan

et al. 2014

Applied Surface Science

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Research Highlights-Zinc sulphide (ZnS) nanoparticles were synthesised by laser irradiation -The structural and morphological properties of the prepared samples were analysed -Larger particles were obtained by using Na 2 S instead of TAA as the sulphur source.-Phonon softening and line broadening of the peaks were observed -Size reduction occurred in the samples obtained from both sources Graphical Abstract AbstractZinc sulphide (ZnS) nanoparticles have been synthesised by a green approach involving laser irradiation of an aqueous solution of zinc acetate (Znac 2 ) and sodium sulphide (Na 2 S·9H 2 O) or thioacetamide (TAA) in polyvinylpyrrolidone (PVP). The structural and morphological properties of the prepared samples were analysed using a transmission electron microscope, TEM, a high resolution transmission electron microscope, HRTEM, X-ray diffraction, and Raman spectroscopy.The thermal properties were studied using a simultaneous thermal analyser (SDTA). Better dispersed and larger particles were obtained by using sodium sulphide (Na 2 S) instead of TAA as the sulphur source. X-ray diffraction (XRD) analyses and Raman measurement show that the particles have a cubic structure, which is usually a low temperature phase of ZnS. There were phonon softening and line broadening of the peaks which are attributed to the phonon confinement effect. The average crystallite size of the ZnS nanoparticles estimated from the XRD showed a reduction in size from 13.62 to 10.42 nm for samples obtained from Na 2 S, and 9.13 to The absorption spectra showed that the nanoparticles exhibit quantum confinement effects.

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Section: Introductionmentioning

confidence: 95%

Laser-assisted synthesis, and structural and thermal properties of ZnS nanoparticles stabilised in polyvinylpyrrolidone

Onwudiwe

Krüger

Jordaan

et al. 2014

Applied Surface Science

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“…In the last three decades since their fi rst reports appeared, [1][2][3][4][5] colloidal semiconductor quantum dots (QDs) attracted continuously increasing interest in different fi elds, including photonics [6][7][8][9][10] and optoelectronics. [11][12][13][14] Improving the characteristics and quality of QDs regarding synthetic Figure 1 a, a stable interface between the MeOH solution and the underlying NaCl-QD mixture instead of an instantaneous mixing is crucial for a successful crystallization.…”

Section: Introductionmentioning

confidence: 99%

Liquid–Liquid Diffusion‐Assisted Crystallization: A Fast and Versatile Approach Toward High Quality Mixed Quantum Dot‐Salt Crystals

Adam

Wang

Dubavik

et al. 2015

Adv Funct Materials

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2638www.MaterialsViews.com wileyonlinelibrary.com approaches, [ 15,16 ] effi ciency, [ 17,18 ] extending their spectral range [19][20][21] and environmental friendliness using less toxic materials [22][23][24] sparked industrial applications. Those started with the demonstration of a 40 in. display prototype presented by Samsung [ 25 ] and followed by the foundation of QD Vision, Inc., [ 26 ] whose QDs are now used in the latest series of Sony products. All of the mentioned applications require long-term stability of the QDs under various conditions including high temperatures as well as high intensity illumination. Packaging of the QDs within polymer or inorganic matrices is one way to address these issues, while improving the processability of the QDs at the same time. Commonly used polymers, such as polystyrene and poly(methylmethacrylate) [ 27 ] are relatively less stable and tight in comparison to their inorganic counterparts. Inorganic matrices on the other hand can incorporate the QDs directly from their melt, e.g., using the Czochralski approach, [ 28 ] coated as a thin fi lm directly on their surface [ 29,30 ] or, as recently developed by our group, grown as mixed crystals at ambient temperatures from a saturated salt solution. [ 31 ] Using this method, different types of QDs can be incorporated due to the low thermal stress and, by choosing the proper matrix-QD system, the photoluminescence quantum yields (PL-QYs) are enhanced upon incorporation. [ 32,33 ] Here, a new, fast, and versatile method for the incorporation of colloidal quantum dots (QDs) into ionic matrices enabled by liquid-liquid diffusion is demonstrated. QDs bear a huge potential for numerous applications thanks to their unique chemical and physical properties. However, stability and processability are essential for their successful use in these applications. Incorporating QDs into a tight and chemically robust ionic matrix is one possible approach to increase both their stability and processability. With the proposed liquid-liquid diffusion-assisted crystallization (LLDC), substantially accelerated ionic crystallization of the QDs is shown, reducing the crystallization time needed by one order of magnitude. This fast process allows to incorporate even the less stable colloids including initially oil-based ligandexchanged QDs into salt matrices. Furthermore, in a modifi ed two-step approach, the seed-mediated LLDC provides the ability to incorporate oilbased QDs directly into ionic matrices without a prior phase transfer. Finally, making use of their processability, a proof-of-concept white light emitting diode with LLDC-based mixed QD-salt fi lms as an excellent color-conversion layer is demonstrated. These fi ndings suggest that the LLDC offers a robust, adaptable, and rapid technique for obtaining high quality QD-salts.

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“…As the size of a nanostructure approaches the exciton Bohr radius, optical properties critical to device applications, such as bandgap and photoluminescence ͑PL͒ lifetime, are affected greatly by the quantum confinement effect. [1][2][3] PL lifetime is related to light-matter interaction; that is, the radiative decay of the exciton polariton and various nonradiative processes, such as leak by deep-level traps, lowlying surface states, and multiphonon scattering. There are several studies on the light-matter interaction in lowdimensional nanostructures of semiconductors.…”

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confidence: 99%

Time-resolved photoluminescence of the size-controlled ZnO nanorods

Hong

Joo

Park

et al. 2003

Applied Physics Letters

135

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Size dependence of the time-resolved photoluminescence ͑TRPL͒ has been investigated for the ZnO nanorods fabricated by catalyst-free metalorganic chemical vapor deposition. The nanorods have a diameter of 35 nm and lengths in the range of 150 nm to 1.1 m. The TRPL decay rate decreases monotonically as the length of the nanorods increases in the range of 150 to 600 nm. Decrease of the radiative decay rate of the exciton-polariton has been invoked to account for the results. There has been a great interest in low-dimensional lightemitting nanostructures for highly integrated photoelectronic device applications. As the size of a nanostructure approaches the exciton Bohr radius, optical properties critical to device applications, such as bandgap and photoluminescence ͑PL͒ lifetime, are affected greatly by the quantum confinement effect. [1][2][3] PL lifetime is related to light-matter interaction; that is, the radiative decay of the exciton polariton and various nonradiative processes, such as leak by deep-level traps, lowlying surface states, and multiphonon scattering. There are several studies on the light-matter interaction in lowdimensional nanostructures of semiconductors. 4 -8 The exciton polariton luminescence is, however, quite sensitive to the concentration of defects and structural factors of the nanostructures, and it is not easy to separate the radiative recombination and nonradiative processes.In this letter, we report time-resolved PL ͑TRPL͒ of the size-controlled ZnO nanorods. ZnO is a wide-bandgap semiconductor enabling ultraviolet light-emitting diodes and photonic devices. It shows efficient PL at room temperature due to the large exciton binding energy of ϳ60 meV. 9 ZnO can be fabricated in many different nanostructures, such as quantum dots, 10-12 nanowires, 13-18 and quantum wells, 19 and we have shown in a previous report that high quality singlecrystal nanorods can be grown without using any metal catalyst. 14 The samples were grown on Al 2 O 3 (00•1) substrates by catalyst-free metalorganic vapor phase epitaxy. Details of the ZnO nanorod fabrication has been described elsewhere. 20 A series of different size ZnO nanorods was prepared by controlling the growth time. Care has been taken to ensure the same condition other than the growth time to keep the impurity concentration constant. Samples with the growth time from 30 to 120 min were selected for the PL study. The sizes of the nanorods thus selected were determined to be 29-40 nm in diameter and 150-1100 nm in length by field-emission scanning electron microscopy, as summarized in Table I. The length of the rods increases almost linearly by the growth time with a small standard deviation. The diameter, however, stays nearly constant, with somewhat larger uncertainty.For the optical characterization of the ZnO nanorods, time-integrated PL ͑TIPL͒ and TRPL were measured. Output of a Kerr lens mode-locked Ti:sapphire laser at 700 nm was doubled to 350 nm to serve as an excitation source in both TIPL and TRPL experiments. TRPL was measured by ...

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Quantum size effects in the redox potentials, resonance Raman spectra, and electronic spectra of CdS crystallites in aqueous solution

Cited by 868 publications

References 21 publications

Laser-assisted synthesis, and structural and thermal properties of ZnS nanoparticles stabilised in polyvinylpyrrolidone

Laser-assisted synthesis, and structural and thermal properties of ZnS nanoparticles stabilised in polyvinylpyrrolidone

Liquid–Liquid Diffusion‐Assisted Crystallization: A Fast and Versatile Approach Toward High Quality Mixed Quantum Dot‐Salt Crystals

Time-resolved photoluminescence of the size-controlled ZnO nanorods

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