Search results for "LUMO"

Warm white LED light by frequency down-conversion of mixed yellow and red Lumogen®

2013

This work reports on the benefits and promising opportunities offered by white LED hybrid technology, based on a mixing perylene-based dyes in order to obtain a warm white light for frequency-down conversion. In a standard Ce:YAG-based white LED, the white light appears cold due to the weakness of red wavelength components in the emission spectrum. In order to obtain a warmer white, one possible solution is to add a red phosphor to the yellow one to move the chromatic coordinates properly, though the luminous efficiency drastically decreases due to the increased light absorption of the coating layer. It is generally believed that the low efficiency of warm white LEDs is the main issue today…

Hybrid LEDs pave way to new lighting applications

2013

Many analysts agree that the global lighting market is close to a real revolution: the LED revolution. One of the most widespread solutions for the production of white LEDs is the conversion of a part of the light, coming from a known source, by exciting one or more materials that emit at a longer wavelength. The result is an emission spectrum given by the superposition of the single source and the photoexcited material; the big advantage is that the phenomenon of photoluminescence replaces the further integration of other solid-state devices of different colors. The photoluminescence of a perylene-based polymer dye turned out to be a good substitute for conventional inorganic color convers…

On the development of a new approach to the design of lanthanide-based materials for solution-processed OLEDs

2019

The targeted design of lanthanide-based emitters for solution-processed organic light-emitting diodes (OLEDs) resulted in obtaining an NIR OLED with one of the highest efficiencies among ytterbium-based solution-processed OLEDs (30 μW W-1). The design was aimed at the combination of high luminescence efficiency with solubility and charge carrier mobility. The latter was achieved thanks to the introduction of the purposefully selected neutral ligands, which combine electron mobility and the ability to sensitize lanthanide luminescence. Besides, the HOMO and LUMO energies and charge carrier mobility of solution-processed thin films of coordination compounds were measured experimentally for th…

The development and role of task motivation and task values during different phases of the school career

2010

Dropout intentions in secondary education : Student temperament and achievement motivation as antecedents

2023

Introduction As early school leaving and dropping out from education pose a challenge for later life adjustment, it is important to identify antecedent factors for the risk of school dropout to tailor individual support for adolescents. Consequently, this study examines the role of adolescents' motivational beliefs and behaviors (i.e., success expectations, planning, and task-avoidance) as well as their temperament (i.e., extraversion/surgency, negative affectivity, effortful control, and affiliativeness) in their dropout intentions in the first year of upper secondary education. Methods Participants were Finnish adolescents' (n = 536; 57% girls, mean age 12.39 at outset, standard deviation…

Motivaciâ k izučeniû russkogo âzyka v finskih professional'nyh institutah

2009

Design, Construction, and Characterization of a New Regioisomer and Diastereomer Material Based on the Spirooxindole Scaffold Incorporating a Sulphon…

2020

The 1,3-dipolar cycloaddition reaction is one of the most rapid, and efficient protocols to access, and construct highly divergent heterocycle chiral auxiliaries. Free catalyst synthesis of spirooxindole scaffold incorporating sulphone moiety via one pot&ndash

Cruciform Electron Acceptors Based on Tetraindeno-Fused Spirofluorene

2017

Two cruciform tetraindenospirofluorene-based acceptors embedding carbonyl (Spiro-4O) and dicyanovinylene (Spiro-8CN) functionalities are synthesized in high yields. Single-crystal X-ray analysis reveals a one-dimensional π–π stacking arrangement for Spiro-4O, while Spiro-8CN adopts a unique two-dimensional isotropic π-interaction. Cyclic voltammetry suggests a high electron affinity of −3.76 eV for Spiro-8CN. Such a packing motif and low LUMO energy for Spiro-8CN are important for bulk electron transport.

Widespread contribution of methane-cycle bacteria to the diets of lake profundal chironomid larvae.

2008

Reports of unexpectedly 13C-depleted chironomid larvae in lakes have led to an hypothesis that significant transfer of detrital organic matter to chironomid larvae may occur via methane-cycle bacteria. However, to date little is known of how such transfer might vary across species and lakes. We gathered data from 87 lakes to determine how widespread this phenomenon might be and to define boundaries for its likely magnitude. Carbon stable isotope values of chironomid larvae varied greatly between taxa. Very marked 13C-depletion was evident only in certain taxa, especially Chironomus plumosus, C. anthracinus, and C. tenuistylus, all characteristic of eutrophic or dystrophic lakes and known to…

Synthesis, Spectroscopic, and Structural Investigation of the Cyclic [N(PR2E)2]+ Cations (E = Se, Te; R = iPr, Ph):  the Effect of Anion and R-Group …

2006

Two-electron oxidation of the [N(PiPr2E)2]- anion with iodine produces the cyclic [N(PiPr2E)2]+ (E =Se, Te) cations, which exhibit long E-E bonds in the iodide salts [N(PiPr2Se)2]I (4) and [N(PiPr2Te)2]I (5). The iodide salts 4 and 5 are converted to the ion-separated salts [N(PiPr2Se)2]SbF6 (6) and [N(PiPr2Te)2]SbF6 (7) upon treatment with AgSbF6. Compounds 4-7 were characterized in solution by multinuclear NMR, vibrational, and UV-visible spectroscopy supported by DFT calculations. A structural comparison of salts 4-7 and [N(PiPr2Te)2]Cl (8) confirms that the long E-E bonds in 4, 5, and 8 can be attributed primarily to the donation of electron density from a lone pair of the halide counte…