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  • American Association for the Advancement of Science (AAAS)
  • Copernicus
  • MDPI Publishing
  • 1
    Publication Date: 2019
    Description: 〈p〉Chemically made colloidal semiconductor quantum dots have long been proposed as scalable and color-tunable single emitters in quantum optics, but they have typically suffered from prohibitively incoherent emission. We now demonstrate that individual colloidal lead halide perovskite quantum dots (PQDs) display highly efficient single-photon emission with optical coherence times as long as 80 picoseconds, an appreciable fraction of their 210-picosecond radiative lifetimes. These measurements suggest that PQDs should be explored as building blocks in sources of indistinguishable single photons and entangled photon pairs. Our results present a starting point for the rational design of lead halide perovskite–based quantum emitters that have fast emission, wide spectral tunability, and scalable production and that benefit from the hybrid integration with nanophotonic components that has been demonstrated for colloidal materials.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2011-07-21
    Description: Magnetoelectric (ME) composites that simultaneously exhibit ferroelectricity and ferromagnetism have recently gained significant attention as evident by the increasing number of publications. These research activities are direct results of the fact that multiferroic magnetoelectrics offer significant technological promise for multiple devices. Appropriate choice of phases with co-firing capability, magnetostriction and piezoelectric coefficient, such as Ni-PZT and NZFO-PZT, has resulted in fabrication of prototype components that promise transition. In this manuscript, we report the properties of Ni-PZT and NZFO-PZT composites in terms of ME voltage coefficients as a function of frequency and magnetic DC bias. In order to overcome the problem of toxicity of lead, we have conducted experiments with Pb-free piezoelectric compositions. Results are presented on the magnetoelectric performance of Ni-NKN, Ni-NBTBT and NZFO-NKN, NZFO-NBTBT systems illustrating their importance as an environmentally friendly alternative.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by MDPI Publishing
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  • 3
    Publication Date: 2019
    Description: 〈p〉Chemically made colloidal semiconductor quantum dots have long been proposed as scalable and color-tunable single emitters in quantum optics, but they have typically suffered from prohibitively incoherent emission. We now demonstrate that individual colloidal lead halide perovskite quantum dots (PQDs) display highly efficient single photon emission with optical coherence times as long as 80 ps, an appreciable fraction of their 210 ps radiative lifetimes. These measurements suggest that PQDs should be explored as building blocks in sources of indistinguishable single photons and entangled photon pairs. Our results present a starting point for the rational design of lead halide perovskite-based quantum emitters with fast emission, wide spectral-tunability, scalable production, and which benefit from the hybrid-integration with nano-photonic components that has been demonstrated for colloidal materials.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Natural Sciences in General
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  • 4
    Publication Date: 2011-09-10
    Description: The identification of similarities in the material requirements for applications of interest and those of living organisms provides opportunities to use renewable natural resources to develop better materials and design better devices. In our work, we harness this strategy to build high-capacity silicon (Si) nanopowder-based lithium (Li)-ion batteries with improved performance characteristics. Si offers more than one order of magnitude higher capacity than graphite, but it exhibits dramatic volume changes during electrochemical alloying and de-alloying with Li, which typically leads to rapid anode degradation. We show that mixing Si nanopowder with alginate, a natural polysaccharide extracted from brown algae, yields a stable battery anode possessing reversible capacity eight times higher than that of the state-of-the-art graphitic anodes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kovalenko, Igor -- Zdyrko, Bogdan -- Magasinski, Alexandre -- Hertzberg, Benjamin -- Milicev, Zoran -- Burtovyy, Ruslan -- Luzinov, Igor -- Yushin, Gleb -- New York, N.Y. -- Science. 2011 Oct 7;334(6052):75-9. doi: 10.1126/science.1209150. Epub 2011 Sep 8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21903777" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2009-06-13
    Description: Similar to the way that atoms bond to form molecules and crystalline structures, colloidal nanocrystals can be combined together to form larger assemblies. The properties of these structures are determined by the properties of individual nanocrystals and by their interactions. The insulating nature of organic ligands typically used in nanocrystal synthesis results in very poor interparticle coupling. We found that various molecular metal chalcogenide complexes can serve as convenient ligands for colloidal nanocrystals and nanowires. These ligands can be converted into semiconducting phases upon gentle heat treatment, generating inorganic nanocrystal solids. The utility of the inorganic ligands is demonstrated for model systems, including highly conductive arrays of gold nanocrystals capped with Sn2S6(4-) ions and field-effect transistors on cadmium selenide nanocrystals.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kovalenko, Maksym V -- Scheele, Marcus -- Talapin, Dmitri V -- New York, N.Y. -- Science. 2009 Jun 12;324(5933):1417-20. doi: 10.1126/science.1170524.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of Chicago, Chicago, IL 60637, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19520953" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2017-10-01
    Description: Colloidal quantum dots, and nanostructured semiconductors in general, carry the promise of overcoming the limitations of classical materials in chemical and physical properties and in processability. However, sufficient control of electronic properties, such as carrier concentration and carrier mobility, has not been achieved until now, limiting their application. In bulk semiconductors, modifications of electronic properties are obtained by alloying or doping, an approach that is not viable for structures in which the surface is dominant. The electronic properties of PbS colloidal quantum dot films are fine-tuned by adjusting their stoichiometry, using the large surface area of the nanoscale building blocks. We achieve an improvement of more than two orders of magnitude in the hole mobility, from below 10 –3 to above 0.1 cm 2 /V⋅s, by substituting the iodide ligands with sulfide while keeping the electron mobility stable (~1 cm 2 /V⋅s). This approach is not possible in bulk semiconductors, and the developed method will likely contribute to the improvement of solar cell efficiencies through better carrier extraction and to the realization of complex (opto)electronic devices.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 7
    Publication Date: 2017-12-23
    Description: The outstanding excitonic properties, including photoluminescence quantum yield ( PL ), of individual, quantum-confined semiconductor nanoparticles are often significantly quenched upon aggregation, representing the main obstacle toward scalable photonic devices. We report aggregation-induced emission phenomena in lamellar solids containing layer-controlled colloidal quantum wells (QWs) of hybrid organic-inorganic lead bromide perovskites, resulting in anomalously high solid-state PL of up to 94%. Upon forming the QW solids, we observe an inverse correlation between exciton lifetime and PL , distinct from that in typical quantum dot solid systems. Our multiscale theoretical analysis reveals that, in a lamellar solid, the collective motion of the surface organic cations is more restricted to orient along the [100] direction, thereby inducing a more direct bandgap that facilitates radiative recombination. Using the QW solids, we demonstrate ultrapure green emission by completely downconverting a blue gallium nitride light-emitting diode at room temperature, with a luminous efficacy higher than 90 lumen W –1 at 5000 cd m –2 , which has never been reached in any nanomaterial assemblies by far.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 8
    Publication Date: 2018-06-25
    Description: IJERPH, Vol. 15, Pages 1320: Risk Factors for Ventricular Septal Defects in Murmansk County, Russia: A Registry-Based Study International Journal of Environmental Research and Public Health doi: 10.3390/ijerph15071320 Authors: Anton A. Kovalenko Erik Eik Anda Jon Øyvind Odland Evert Nieboer Tormod Brenn Alexandra Krettek Cardiovascular malformations are one of the most common birth defects among newborns and constitute a leading cause of perinatal and infant mortality. Although some risk factors are recognized, the causes of cardiovascular malformations (CVMs) remain largely unknown. In this study, we aim to identify risk factors for ventricular septal defects (VSDs) in Northwest Russia. The study population included singleton births registered in the Murmansk County Birth Registry (MCBR) between 1 January 2006 and 31 December 2011. Infants with a diagnosis of VSD in the MCBR and/or in the Murmansk Regional Congenital Defects Registry (up to two years post-delivery) constituted the study sample. Among the 52,253 infants born during the study period there were 744 cases of septal heart defects (SHDs), which corresponds to a prevalence of 14.2 [95% confidence interval (CI) of 13.2–15.3] per 1000 infants. Logistic regression analyses were carried out to identify VSD risk factors. Increased risk of VSDs was observed among infants born to mothers who abused alcohol [OR = 4.83; 95% CI 1.88–12.41], or smoked during pregnancy [OR = 1.35; 95% CI 1.02–1.80]. Maternal diabetes mellitus was also a significant risk factor [OR = 8.72; 95% CI 3.16–24.07], while maternal age, body mass index, folic acid and multivitamin intake were not associated with increased risk. Overall risks of VSDs for male babies were lower [OR = 0.67; 95% CI 0.52–0.88].
    Print ISSN: 1661-7827
    Electronic ISSN: 1660-4601
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Published by MDPI Publishing
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  • 9
    Publication Date: 2017-11-10
    Description: Semiconducting lead halide perovskites (LHPs) have not only become prominent thin-film absorber materials in photovoltaics but have also proven to be disruptive in the field of colloidal semiconductor nanocrystals (NCs). The most important feature of LHP NCs is their so-called defect-tolerance—the apparently benign nature of structural defects, highly abundant in these compounds, with respect to optical and electronic properties. Here, we review the important differences that exist in the chemistry and physics of LHP NCs as compared with more conventional, tetrahedrally bonded, elemental, and binary semiconductor NCs (such as silicon, germanium, cadmium selenide, gallium arsenide, and indium phosphide). We survey the prospects of LHP NCs for optoelectronic applications such as in television displays, light-emitting devices, and solar cells, emphasizing the practical hurdles that remain to be overcome.
    Keywords: Materials Science
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
    Publication Date: 2012-12-11
    Description: In last few years in hydrology an interest to excess factor has appeared as a reaction to unsuccessful attempts to simulate and predict evolving hydrological processes, which attributive property is statistical instability. The article shows, that the latter has a place at strong relative multiplicative noises of probabilistic stochastic model of a river flow formation, phenomenological display of which are "the thick tails" and polymodality, for which the excess factor "answers", by being ignored by a modern hydrology in connection to the large error of its calculation because of insufficient duration of lines of observation over a flow. However, it is found out, that the duration of observation of several decades practically stabilizes variability of the excess factor, the error of which definition appears commensurable with an error of other calculated characteristics used in engineering hydrology.
    Print ISSN: 1812-2108
    Electronic ISSN: 1812-2116
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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