Infrared-Emitting Colloidal Nanocrystals: Synthesis, Assembly, Spectroscopy, and Applications

Photonics and Optoelectronics Group, Physics Department and Centre for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Munich, Germany.
Small (Impact Factor: 8.37). 05/2007; 3(4):536-57. DOI: 10.1002/smll.200600625
Source: PubMed

ABSTRACT Semiconductor nanocrystals produced by means of colloidal chemistry in a solvent medium are an attractive class of nanometer-sized building blocks from which to create complex materials with unique properties for a variety of applications. Their optical and electronic properties can be tailored easily, both by their chemical composition and particle size. While colloidal nanocrystals emitting in the infrared region have seen a burst of attention during the last decade there is clearly a paucity of review articles covering their synthesis, assembly, spectroscopic characterization, and applications. This Review comprehensively addresses these topics for II-VI, III-V, and IV-VI nanocrystals, examples being HgTe and Cd(x)Hg(1-) (x)Te, InP and InAs, and PbS, PbSe, and PbTe, respectively. Among the applications discussed here are optical amplifier media for telecommunications systems, electroluminescence devices, and noninvasive optical imaging in biology.

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    • "Colloidal lead sulfide nanocrystals, or quantum dots (PbS QDs), with a band gap of 0.41 eV at RT have attracted much attention due to their ability to absorb and emit light with tunable wavelength in the near infrared region [1] [2]. It was found that PbS QDs have a number of unusual properties – a large Stokes shift of the photoluminescence (PL), depending on the size of quantum dots [3] [4] [5], and an unusually long PL decay time [5] [6]. "
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    ABSTRACT: Nonradiative fluorescence resonance energy transfer (FRET) between lead sulfide quantum dots (QDs) of two different sizes embedded in porous matrix is observed by a fluorescence spectroscopy. Analysis of decays of photoluminescence from QD mixture shows that energy transfer in studied systems is determined by static quenching, specific for direct contact between QD-donor and QD-acceptor in the QDs close-packed ensembles. From steady-state spectral analysis it was found that efficiency of energy transfer depends on the molar ratio QD-donor/QD-acceptor and energy transfer from the donor to the acceptor passes by several channels.
    Proceedings of SPIE - The International Society for Optical Engineering 09/2013; 8807:88070W-(1-6). DOI:10.1117/12.2023035 · 0.20 Impact Factor
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    • "In recent years an enormous interest has aroused in PbS-based nanomaterials because of their unique optical and emission properties , which have tremendous applications in lasers [1], light emitting devices [2] [3], detectors [4], solar cells [5] [6], single electron devices [1], optical switches [7], telecommunication [8] [9], and biological imaging [10]. In order to modify the surface and electronic properties, these particles have been synthesized in a variety of organized media such as surfactants [11] [12], polymers [13] [14], micelles [15] [16], vesicles [17], zeolites [18] [19], Langmuir–Blodgett films [20] and glasses [21] [22]. "
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    ABSTRACT: The deposition of Q-ZnS layer as shell at the interface of Q-ZnS/PbS produces ZnS/PbS/ZnS nanocomposite. The electronic properties of the nanocomposite have been examined as a function of thickness of ZnS shell and in the presence of excess [Zn2+]. The monolayer of ZnS shell red shifts the onset of absorption of precursor ZnS/PbS accompanied with an increase in absorption coefficient in the wavelength range of 200–600nm having an excitonic absorption at 280nm. These particles display relatively intense blue-shifted 505nm (2.45eV) emission associated with a tremendous enhancement of fluorescence lifetime to 150ns from 5.5ns, observed for precursor ZnS/PbS. The addition of Zn2+ further improves the charge separation in this system. These electronic changes are understood by the distribution of traps of varied energy (160–365meV) at the interface and confinement of e−–h+ on the entire heterostructure.
    Journal of Photochemistry and Photobiology A Chemistry 12/2009; 208(2):195-202. DOI:10.1016/j.jphotochem.2009.09.015 · 2.50 Impact Factor
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    Conference Paper: Asynchronous unison
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    ABSTRACT: Unbounded and bounded designs of asynchronous unison systems are discussed. It is shown that both systems are stabilizing in the sense that their steady state behaviors do not depend on their initial states. The systems can therefore tolerate memory and reconfiguration faults that may yield them in arbitrary states. It is also shown that unison systems are useful in designing multiphase systems
    Distributed Computing Systems, 1992., Proceedings of the 12th International Conference on; 07/1992
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