1,720,969 research outputs found
Stimuli-Responsive Surface Ligands for Direct Lithography of Functional Inorganic Nanomaterials
No full textConspectus Colloidal nanocrystals (NCs)have emerged as a diverse class ofmaterials with tunable composition, size, shape, and surface chemistry.From their facile syntheses to unique optoelectronic properties, thesesolution-processed nanomaterials are a promising alternative to materialsgrown as bulk crystals or by vapor-phase methods. However, the integrationof colloidal nanomaterials in real-world devices is held back by challenges in making patterned NC films with the resolution, throughput, andcost demanded by device components and applications. Therefore, suitableapproaches to pattern NCs need to be established to aid the transitionfrom individual proof-of-concept NC devices to integrated and multiplexedtechnological systems. In this Account, we discuss the developmentof stimuli-sensitivesurface ligands that enable NCs to be patterned directly with goodpattern fidelity while retaining desirable properties. We focus onrationally selected ligands that enable changes in the NC dispersibilityby responding to light, electron beam, and/or heat. First, we summarizethe fundamental forces between colloidal NCs and discuss the principlesbehind NC stabilization/destabilization. These principles are appliedto understanding the mechanisms of the NC dispersibility change uponstimuli-induced ligand modifications. Six ligand-based patterningmechanisms are introduced: ligand cross-linking, ligand decomposition,ligand desorption, in situ ligand exchange, ion/ligandbinding, and ligand-aided increase of ionic strength. We discuss examplesof stimuli-sensitive ligands that fall under each mechanism, includingtheir chemical transformations, and address how these ligands areused to pattern either sterically or electrostatically stabilizedcolloidal NCs. Following that, we explain the rationale behind theexploration of different types of stimuli, as well as the advantagesand disadvantages of each stimulus. We then discuss relevantfigures-of-merit that should be consideredwhen choosing a particular ligand chemistry or stimulus for patterningNCs. These figures-of-merit pertain to either the pattern quality(e.g., resolution, edge and surface roughness, layer thickness), orto the NC material quality (e.g., photo/electro-luminescence, electricalconductivity, inorganic fraction). We outline the importance of theseproperties and provide insights on optimizing them. Both the patternquality and NC quality impact the performance of patterned NC devicessuch as field-effect transistors, light-emitting diodes, color-conversionpixels, photodetectors, and diffractive optical elements. We alsogive examples of proof-of-concept patterned NC devices and evaluatetheir performance. Finally, we provide an outlook on further expandingthe chemistry of stimuli-sensitive ligands, improving the NC patternquality, progress toward 3D printing, and other potential researchdirections. Ultimately, we hope that the development of a patterningtoolbox for NCs will expedite their implementation in a broad rangeof applications.
Slow-Injection Growth of Seeded CdSe/CdS Nanorods with Unity Fluorescence Quantum Yield and Complete Shell to Core Energy Transfer
Full text linkA two-step process has been developed
for growing the shell of
CdSe/CdS core/shell nanorods. The method combines an established fast-injection-based
step to create the initial elongated shell with a second slow-injection
growth that allows for a systematic variation of the shell thickness
while maintaining a high degree of monodispersity at the batch level
and enhancing the uniformity at the single-nanorod level. The second
growth step resulted in nanorods exhibiting a fluorescence quantum
yield up to 100% as well as effectively complete energy transfer from
the shell to the core. This improvement suggests that the second step
is associated with a strong suppression of the nonradiative channels
operating both before and after the thermalization of the exciton.
This hypothesis is supported by the suppression of a defect band,
ubiquitous to CdSe-based nanocrystals after the second growth
A Low Reabsorbing Luminescent Solar Concentrator Employing π-Conjugated Polymers
Full text linkA highly efficient thin-film luminescent solar concentrator (LSC) utilizing two π-conjugated polymers as antennae for small amounts of the valued perylene bisimide Lumogen F Red 305 is presented. The LSC exhibits high photoluminescence quantum yield, low reabsorption, and relatively low refractive indices for waveguide matching. A Monte Carlo simulation predicts the LSC to possess exceptionally high optical efficiencies on large scales.National Science Foundation (U.S.) (Graduate Research Fellowship Program (Grant No. 1122374))Eni S.p.A. (Firm) (Eni-MIT Solar Frontiers Alliance
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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