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Fluorescence Efficiency (fluorescence + efficiency)
Selected AbstractsMacroporous monolithic chiral stationary phases for capillary electrochromatography: New chiral monomer derived from cinchona alkaloid with enhanced enantioselectivityELECTROPHORESIS, Issue 17 2003Michael Lämmerhofer Abstract A new chiral monomer derived from cinchona alkaloid, namely O -9-(tert -butylcarbamoyl)-11-[2-(methacryloyloxy)ethylthio]-10,11-dihydroquinine 1, was employed for the preparation of enantioselective monolithic capillary columns by an in situ copolymerization with 2-hydroxyethyl methacrylate 2 (HEMA), ethylene dimethacrylate 3 (EDMA) in the presence of cyclohexanol and 1-dodecanol as porogens (UV or thermal initiation of azobisisobutyronitrile (AIBN) as radical initiator). The porous properties and the electrochromatographic behavior of the new chiral monoliths were comparatively evaluated with previously described analogs obtained from O -9-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydroquinidine 4 as chiral monomer. Despite close structural and physicochemical similarities of the both chiral monomers, the pore distribution profiles of the resulting monoliths were shifted typically towards larger pore diameters with the new monomer 1. Once more, it was confirmed that a low cross-linking (10 wt% related to total monomers) and a pore diameter of about 1 ,m in the dry state provides the best electrochromatographic efficiency as a result of lower resistance to mass transfer (smaller C-term contribution to peak broadening) and more homogeneous flow profile (smaller A-term). Most importantly, as expected the new poly(1 - co -HEMA- co -EDMA) monoliths showed enhanced enantioselectivities and in addition faster separations as compared to poly(4 - co -HEMA- co -EDMA) analogs, which represents a significant improvement. Further, the elution order was reversed owing to the pseudoenantiomeric behavior of quinine- and quinidine-derived monomers. Fluorescence-labeled 9-fluorenylmethoxycarbonyl (FMOC), dansyl (DNS), 7-dimethylaminosulfonyl-1,3,2-benzoxadiazol-4-yl (DBD), carbazole-9-carbonyl (CC) amino acids could be separated with resolution values between 2 and 4 (with efficiencies typically between 100,000 and 200,000 plates/m) and fluorescence detection (variable wavelength fluorescence detector in-line with UV) yielding routinely a gain in detection sensitivities up to two orders of magnitude without specific optimization of the conditions with regards to fluorescence efficiency. [source] Synthesis and Physical Chemistry of s -Tetrazines: Which Ones are Fluorescent and Why?EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 35 2009Yong-Hua Gong Abstract New fluorescent tetrazines have been prepared and their electrochemistry and fluorescence efficiency evaluated. The occurrence of fluorescence as well as the wavelength were found to be strongly dependent on the substituents, which have to be electronegative heteroatoms. This has been rationalized through a computational study that showed that the crucial factor is the nature of the HOMO, which determines the existence or not of fluorescence. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Highly Efficient Non-Doped Blue Organic Light-Emitting Diodes Based on Fluorene Derivatives with High Thermal Stability,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2005L. Tao Abstract A new series of blue-light-emitting fluorene derivatives have been synthesized and characterized. The fluorene derivatives have high fluorescence yields, good thermal stability, and high glass-transition temperatures in the range 145,193,°C. Organic light-emitting diodes (OLEDs) fabricated using the fluorene derivatives as the host emitter show high efficiency (up to 5.3,cd,A,1 and 3.0,lm,W,1) and bright blue-light emission (Commission Internationale de L'Eclairage (CIE) coordinates of x,=,0.16, y,=,0.22). The performance of the non-doped fluorene-based devices is among the best fluorescent blue-light-emitting OLEDs. The good performance of the present blue OLEDs is considered to derive from: 1),appropriate energy levels of the fluorene derivatives for good carrier injection; 2),good carrier-transporting properties; and 3),high fluorescence efficiency of the fluorene derivatives. These merits are discussed in terms of the molecular structures. [source] Effect of conformation on the chemiluminescence efficiency of light-producing 2-methyl-6-(4-methoxyphenyl)imidazo[1,2-,]pyrazin-3(7H)-onesLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 6 2001Katsunori Teranishi Abstract Analogues of the light-producing substrate 2-methyl-6-(4-methoxyphenyl)imidazo[1,2-,]pyrazin-3(7H)-one, with restrictions on the dihedral angles between the pyrazine and the 4-methoxyphenyl rings, were synthesized. These compounds were used to investigate the effects of the conformation between the pyrazine and 4-methoxyphenyl rings on their chemiluminescence efficiencies in aqueous solutions. The effects of the conformation on the chemiluminescence efficiencies were clearly observed; the decrease of the dihedral angle caused a light-enhancing effect and, conversely, the increase of the angle dramatically decreased the chemiluminescence efficiency. These effects on the chemiluminescence efficiencies are attributed to the influence of the conformation on the fluorescence efficiency of the emitter. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||