Hoi-Lun Kwong

Low-Temperature Synthesis of CuInSe2 Nanotube Array on Conducting Glass Substrates for Solar Cell Application

Highly ordered arrays of Cu-rich and -deficient CuInSe(2) nanotubes as well as ZnO/CuInSe(2) core/sheath nanocables have been synthesized on glass substrates by using ZnO nanorod arrays as sacrificial templates via a low-cost solution method. Chemical conversions from hexagonal ZnO to cubic ZnSe, hexagonal CuSe and tetragonal CuInSe(2) are demonstrated as a novel means for synthesis of I-III-VI nanomaterials. Large differences in their solubility product constant (K(sp)) are crucial for direct exchange in the conversions. In solvothermal reaction of ZnO/CuSe core/shell nanocables with InCl(3), the triethylene glycol solvent serves as a reducing agent for the reduction of cupric (Cu(2+)) to cuprous (Cu(+)) ions and also as an agent for the dissolution of ZnO cores. The absorption coefficient of the CuInSe(2) nanotubes in the visible region is on the order of 10(4) cm(-1). Photoelectrochemical solar cells were fabricated with arrays of ZnO/Cu(1.57±0.10)In(0.68±0.10)Se(2) and ZnO/CuSe nanocables. It was found that power conversion efficiency of the ZnO/Cu(1.57±0.10)In(0.68±0.10)Se(2) cell is about two times higher than that based on ZnO/CuSe.

Carbon Nanoparticle-based Ratiometric Fluorescent Sensor for Detecting Mercury Ions in Aqueous Media and Living Cells

A novel nanohybrid ratiometric fluorescence sensor is developed for selective detection of mercuric ions (Hg(2+)), and the application has been successfully demonstrated in HEPES buffer solution, lake water, and living cells. The sensor comprises water-soluble fluorescent carbon nanoparticles (CNPs) and Rhodamine B (RhB) and exhibits their corresponding dual emissions peaked at 437 and 575 nm, respectively, under a single excitation wavelength (350 nm). The photoluminescence of the CNPs in the nanohybrid system can be completely quenched by Hg(2+) through effective electron or energy transfer process due to synergetic strong electrostatic interaction and metal-ligand coordination between the surface functional group of CNPs and Hg(2+), while that of the RhB remains constant. This results in an obviously distinguishable fluorescence color variation (from violet to orange) of the nanohybrid solution. This novel sensor can effectively identify Hg(2+) from other metal ions with relatively low background interference even in a complex system such as lake water. The detection limit of this method is as low as 42 nM. Furthermore, the sensing technique is applicable to detect Hg(2+) in living cells.

A novel chiral terpyridine macrocycle as a fluorescent sensor for enantioselective recognition of amino acid derivativesElectronic supplementary information (ESI) available: plots for estimation of binding constants for tpy macrocycle 1 with (R)-PhEtOMe. See http://www.rsc.org/suppdata/cc/b3/b313960c/

Terpyridine macrocycle 1 is shown to be a strong chelating agent for organic ammonium salts and also a useful chromophore in fluorescent sensing. It exhibits very good enantioselectivity (K(obs)(S)/K(obs)(R)= 3.8) in chiral discrimination of alpha-phenylglycine methyl ester hydrochloride (PhEtOMe).

Blue and white organic electroluminescent devices based on 9,10-bis(2'-naphthyl)anthracene

Abstract A blue emitting material, 9,10-bis(2 ′ -naphthyl)anthracene (BNA), was synthesized and used as a host emitting material in organic light-emitting devices (OLEDs). Devices with a configuration of indium–tin oxide/α-naphthylphenylbiphenyl diamine/BNA-based emitting layer/tris(8-hydroxyquinoline) aluminum/Mg:Ag have been constructed. When BNA was used without adding any dopant, the device emits blue light with a peak at 444 nm. A high-performance white light OLED was obtained by doping the BNA layer simultaneously with perylene and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) (a red emitting dopant).

High-efficiency nondoped white organic light-emitting devices

High-efficiency nondoped white organic light-emitting devices (WOLEDs) were demonstrated by using both the intrinsic and exciplex emissions from a single electroluminescent material, 4,4′,4″-trispyrenylphenylamine (TPyPA). The simple device structure of indium tin oxide/N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine/TPyPA/4,7-diphenyl-1,10-phenanthroline/LiF∕Al exhibited a luminance of 10000cd∕m2 at a low driving voltage of 4.5V, and high current and power efficiencies of 9.4cd∕A and 9.0lm∕W, respectively. Such WOLED showed excellent color stability and purity with the Commission Internationale de L’Eclairage coordinates of (0.31, 0.35), which remained unchanged over a wide range of luminance from 100to20000cd∕m2.

Reduction of molecular aggregation and its application to the high-performance blue perylene-doped organic electroluminescent device

A nonplanar derivative of perylene, 2,5,8,11-tetra-tertbutylperylene (TBPe), was synthesized via the Friedel–Crafts alkylation reaction. Electroluminescent (EL) devices were made using TBPe or perylene as a dopant in bis(2-methyl-8-quinolinolato)(para-phenylphenolato)aluminum(III) and their EL performance was compared. Similar to the device doped with the parent perylene molecule, the device doped with TBPe also emitted strongly in the blue. As the concentration of TBPe increased from 1% to 5%, the color coordinates in CIE 1931 chromaticity of the TBPe-doped device changed only slightly from (0.168,0.273) to (0.175,0.273), whereas the perylene-doped device exhibited a much larger shift from (0.165,0.196) to (0.178,0.252). The constancy of EL color and efficiency with respect to TBPe dopant concentration is attributable to diminishing molecular aggregation in the nonplanar perylene derivative, TBPe, due to the steric hindrance of the tert-butyl groups.

Photoinduced C–C bond formation from alkyl halides catalysed by luminescent dinuclear gold(I) and copper(I) complexes

The photoluminescent properties of [Au2(µ-dppm)2]2+[dppm = bis(diphenylphosphino)methane], [Au2(µ-dmpm)3]2+[dmpm = bis(dimethylphosphino)methane] and [Cu2(µ-dppm)2(MeCN)4]2+ have been investigated. Irradiation of a degassed acetonitrile solution of benzyl chloride or 1-bromopentane in the presence of a sacrificial electron donor such as triethylamine and a catalytic amount of [Au2(µ-dppm)2]2+ led to the formation of bibenzyl or n-decane. Similar photoreactions with much lower yields of the C–C bond coupling products have also been observed with [Au2(µ-dmpm)3]2+ and [Cu2(µ-dppm)2(MeCN)4]2+ as catalysts. The mechanism of the photoreaction between alkyl halides and [Au2(µ-dppm)2]2+ has been investigated by steady-state photolysis, Stern–Volmer quenching and flash-photolysis studies.

NEW CHIRAL 2,2'-BIPYRIDINE DIOLS AS CATALYSTS FOR ENANTIOSELECTIVE ADDITION OF DIETHYLZINC TO BENZALDEHYDE

Abstract New C 2 -symmetric chiral 2,2′-bipyridine diols were prepared from readily available homochiral materials such as menthone and camphor. Their catalytic activities in the reaction of diethylzinc with benzaldehyde to give 1-phenyl-1-propanol were studied. In all cases, the yields were good and enantioselectivities up to 95% were observed.

Photoluminescence and electroluminescence of pyrazoline monomers and dimers

Abstract The photoluminescence (PL) and the electroluminescence (EL) behaviors of six derivatives of the pyrazoline dimer and monomer have been studied. It was found that the pyrazoline compounds with an aryl group attached to the 5-position of the pyrazoline ring have better film-forming property. Dimerization of the pyrazoline derivatives can improve the film-forming property while decrease the fluorescence yield. When these compounds were used in EL devices as fluorescence dopants in an N -arylbenzimidazoles trimer (TPBI), high efficiency EL was observed.

First enantioselective catalyst based on a chiral terpyridine: synthesis of new C2-symmetric 2,2′:6′,2′′-terpyridine ligands and copper-catalyzed enantioselective cyclopropanation of alkenes

Abstract New C2-symmetric chiral 2,2′:6′,2′′-terpyridines were prepared from readily available homochiral materials. Copper complexes of these ligands were prepared in situ and their catalytic activities in cyclopropanations of alkenes with alkyl diazoacetate to give cyclopropyl esters were studied. In all cases, the cyclopropyl ester yields were excellent and enantioselectivities up to 94% ee were observed. Competition experiments revealed that electron-donating substituents on styrene accelerate the reaction. Hammett plot exhibited a good linearity with negative ρ+ value (−0.79).