Man-kit Leung

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We report the direct measurement of the 7Be solar neutrino signal rate performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso. The interaction rate of the 0.862 MeV 7Be neutrinos is 49+/-3stat+/-4syst counts/(day.100 ton). The hypothesis of no oscillation for 7Be solar neutrinos is inconsistent with our measurement at the 4sigma(More)
Substituent effects on the photophysical and electrochemical properties of 1,7-diaryl-substituted perylene diimides (1,7-Ar(2)PDIs) have been carefully explored. Progressive red-shifts of the absorption and emission maxima were observed when the electron-donating ability of these substituents was increased. Linear Hammett correlations of 1/lambda(max)(More)
Five rigid oxadiazole (OXD) containing silanes, denoted 1-5, have been developed with high morphological stability. Disruption of the π-aromatic conjugation by introduction of Si atoms leads to a large band gap and high triplet energy. Among the OXDs we studied, 2,5-bis(triphenylsilylphenyl)-1,3,4-oxadiazole 5 is the best host for FIrpic, with a(More)
Geo–neutrinos, electron anti–neutrinos produced in β decays of naturally occurring radioactive isotopes in the Earth, are a unique direct probe of our planet’s interior. We report the first observation at more than 3σ C.L. of geo–neutrinos, performed with the Borexino detector at Laboratori Nazionali del Gran Sasso. Anti–neutrinos are detected through the(More)
Dye-doped organic light-emitting diode of ITO/alpha-NPB (70 nm)/Bebq(2)-1 (7 nm)/BCP (5 nm)/Bebq(2) (33 nm)/LiF (1 nm)/Al (150 nm) shows red electroluminescence with the efficiency of 2.9 cd/A at 100 cd/m(2) and maximum brightness of 62000 cd/m(2). The physical organic aspects of the current-induced fluorescent quenching effect are discussed. [structure:(More)
Equilibria between two conformational isomers of pyrid-2-yl ureas, the (E,Z) and (Z,Z) forms, have been studied in DMF-d(7) at -70 degrees C. Most of them show a small preference for the (E,Z) form with an equilibrium constant K(i) around 1-2. However, the K(i) value for 1-methyl-2-(3-(pyrid-2-yl)ureido)pyridinium iodide (12) was found to be 14.2 +/- 1.2.(More)
The fluorescence and phosphorescence of 2,2'-bis(5-phenyl-1,3,4-oxadiazol-2-yl)biphenyl shows good spectral matching with the absorption spectra of the MLCT1 and MLCT3 transitions of Ir(ppy)3. The red-shift of the 0-0 band in the phosphorescence at 77 K is due to the intramolecular pi-pi interactions between the oxadiazole side chains. Maximum brightness of(More)
A new class of hydrogen-bonded ladders based on hydrogen-bonded dimerization of oligo-alpha-aminopryidines has been demonstrated. Jorgensen's model can be successfully applied to this hydrogen-bonding system in nonpolar solvents. The results show the competitive enthalpy/entropy compensation relationship upon dimerization. Although increasing the number of(More)
Results of background measurements with a prototype of the Borexino detector were used to search for 478 keV solar axions emitted in the M1-transitions of Li ∗ . The Compton conversion of axion to a photon A+ e→ e+γ, axioelectric effect A+ e+Z → e+Z, decay of axion in two photons A→ 2γ and Primakoff conversion on nuclei A+Z → γ+Z are considered. The upper(More)