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Emission Efficiency (emission + efficiency)
Selected AbstractsFluorescent 5-Alkynyl-2,-Deoxyuridines: High Emission Efficiency of a Conjugated Perylene Nucleoside in a DNA DuplexCHEMBIOCHEM, Issue 5 2006Mikhail V. Skorobogatyi Abstract Four fluorescent 5-alkynyl-2,-deoxyuridines were studied in DNA oligonucleotides and their duplexes. The fluorescence response to hybridization differs dramatically for nucleosides containing a perylene fluorochrome either conjugated or not conjugated to the nucleobase. The conjugated nucleoside, 5-(perylen-3-ylethynyl)-2,-deoxyuridine, shows enhanced long-wavelength emission in the DNA duplex, in contrast to the blue fluorescence of perylene on a flexible linker (in 5-[(perylen-3-yl)methoxyprop-1-ynyl]-2,-deoxyuridine), which is quenched upon duplex formation. [source] Bionanotechnology: Enhancement of Aggregation-Induced Emission in Dye-Encapsulating Polymeric Micelles for Bioimaging (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Mater. Amphiphilic block copolymers can form polymer micelles for delivering hydrophobic fluorescent probes with aggregation-induced emission properties, as presented by A. K.-Y. Jen et al. on page 1413. By itself, 1,1,2,3,4,5-hexaphenylsilole (HPS) exhibits dramatically enhanced blue-green fluorescent emission efficiencies when encapsulated within the hydrophobic core of a polymeric micelle. When HPS is co-encapsulated with bis(4-(N -(1-naphthyl) phenylamino)-phenyl)fumaronitrile, effective orange-red fluorescence resonance energy transfer can be demonstrated within live RAW 264.7 cells. Illustration provided by Brent Polishak. [source] Analysis of Improved Efficiency of InGaN Light-Emitting Diode With Bottom Photonic Crystal Fabricated by Anodized Aluminum OxidxeADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Sang-Wan Ryu Abstract The improved performance of a bottom photonic crystal (PC) light-emitting diode (LED) is analyzed based on internal quantum efficiency (,int) and light-extraction efficiency (,ex). The bottom PC is fabricated by anodized aluminum oxide nanopatterns and InGaN quantum wells (QWs) are grown over it. Transmission electron microscopy images reveal that threading dislocations are blocked at the nanometer-sized air holes, resulting in improved optical emission efficiency of the QWs. From temperature-dependent photoluminescence measurements, the enhancement of ,int is estimated to be 12%. Moreover, the enhancement of ,ex is simulated to be 7% by the finite-difference time-domain method. The fabricated bottom PC LED shows a 23% higher optical power than a reference, which is close to the summation of enhancements in ,int and ,ex. Therefore, the bottom PC improves LED performance through higher optical quality of QWs as well as increased light extraction. [source] High-efficiency stimulated Raman scattering from alcohols: theory and experimentsJOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2005Lorenzo Echevarrķa Abstract The coherent Raman emission from primary alcohols [CH3(CH2)nOH, n = 0,10], 2-propyl alcohol and tert -butyl alcohol was studied using a frequency-doubled Nd:YAG pump laser (532 nm). We show that increases in the chain length (CH2 groups) and the number of CH3 groups in the alcohols (CH3 > CH2) enhance the Raman emission efficiency. Theoretical density functional theory (DFT) calculations and frequency scaling allow one to associate the vibrational wavenumbers with the molecular fragment responsible for the vibration. We obtained good agreement between the observed phenomena and the predictions of the theory. Copyright © 2005 John Wiley & Sons, Ltd. [source] Electron localization and emission mechanism in wurtzite (Al, In, Ga)N alloysPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2010Qihang Liu Abstract The electronic structures of wurtzite InGaN and AlGaN alloys are investigated using the first-principle density functional theory calculation. The results indicate that some short In,N,In atomic chains and small In,N atomic condensates composed of a few In and N atoms can be randomly formed in InGaN alloys. The electrons at the top of valence bands can be effectively localized in the vicinity of the In,N,In zigzag chains (weak localization) and the In,N atomic condensates (strong localization). These localized electrons extremely enhance the emission efficiency of InGaN alloys. [source] Reflectance and photoluminescence studies of InGaN/GaN multiple-quantum-well structures embedded in an asymmetric microcavityPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006D. Y. Lin Abstract Using reflectance (R) and photoluminescence (PL) measurements InGaN/GaN multiple-quantum-well (MQW) structures embedded in an asymmetric microcavity with different thickness of stacking pairs have been studied. The asymmetric microcavity structures are composed of a cavity sandwitched between the air/semiconductor interface and a mirror using distributed Bragg reflector (DBR). For the DBR with thinner AlN layers the high-reflectivity stop band locates at higher photon energy. The luminescence efficiency and the spectrum of InGaN/GaN multiple-quantum-well structures will be modified by the microcavity. A comparison of PL with R spectra shows that the emission efficiency can be enhanced by matching up the luminescence spectrum coming from the MQW and the high-reflectivity stop band. From the blue shift of the cavity modes as a function of incident angles the refractive index and cavity length can be determined. By measuring the PL spectra as a function of emission angle, it is found that the PL spectra were predominatly determined by microcavity resonances. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of growth interruption on In-rich InGaN/GaN single quantum well structuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Soon-Yong Kwon Abstract We successfully grew In-rich InGaN/GaN single quantum well structures by metal-organic chemical vapor deposition and confirmed their formation by optical and structural measurements. Relatively high growth temperature (730 °C) for InGaN layer facilitated the formation of 2-dimensional quantum well structures, presumably due to high adatom mobility. As the growth interruption time increased, the PL emission efficiency from InGaN layer improved with peak position blue-shifted and the dislocation density decreased by one order of magnitude. The high resolution cross-sectional TEM images clearly showed that the In-rich InGaN layer thickness reduced from 2.5 nm (without GI) to about 1 nm (with 10 s GI) and the InGaN/GaN interface became very flat with 10 s GI. We suggest that decomposition and mass transport processes on InGaN during GI is responsible for these phenomena. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||