Publications by authors named "Hee Un Kim"

We have synthesized and characterized a blue phosphorescent iridium(III) complex (dfpypy)2Ir(tftamp), which contains 2',6'-difluoro-2,3'-bipyridine (dfpypy) as the main ligand and 4-methyl-2-(3'-trifluoromethyl-1'H-1',2',4'-triazol-5'-yl)pyridine (tftamp) as the ancillary ligand. The photophysical, electrochemical, and electroluminescent (EL) properties of (dfpypy)2Ir(tftamp) were investigated. Vacuum-deposited blue and white organic light-emitting diodes (OLEDs) were fabricated using (dfpypy)2Ir(tftamp) in 1,3-bis(carbazol-9-yl)benzene (mCP) as the emitting layer.

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A new fullerene derivative, [6,6]-dibenzo[b,d]thiophene-C61-butyric acid methyl ester (DBTC61BM) was synthesized from C60 using tosylhydrazone, and used as an electron-acceptor material for poly(3-hexylthiophene) (P3HT)-based organic photovoltaic cells. The synthesized DBTC61BM was used to modify the basic structure of [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) by replacing the aromatic part with dibenzo[b,d]thiophene. The solubilities of DBTC61BM and PC61BM are similar; they have good solubilities in common organic solvents such as dichloromethane, chloroform, toluene, and 1,2-dichlorobenzene.

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We synthesized a novel red-emitting iridium(III) complex, bis[2-(5-(9H-carbazole-9-yl)thiophene-2-yl)benzo[d]thiazole]iridium(III)acetylacetonate ([(CTBT)21 r(acac)]), for use in phosphorescent organic light-emitting diodes. The photophysical and electrochemical properties of [(CTBT)2Ir(acac)] were characterized using photoluminescence (PL) and cyclic voltammetry. The photophysical properties of [(CTBT)2Ir(acac)] included PL emission at 630 nm.

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(E)-2,2'-Dibromo-7,7'-bis(diphenylamino)-9,9'-bifluorenylidene (BDPABF) was synthesized as a new non-fullerene-type electron acceptor for organic photovoltaic cells. The UV-visible absorption spectra of BDPABF showed two main bands at 319 and 474 nm in a chloroform solution and 320 and 481 nm as a solid thin film. The optical band gap of BDPABF was determined to be 2.

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Semiconducting copolymers composed of 10-(2'-hexylphenothiazine) (PTZ), 9,9-dioctyl-dithienylfluorene (DTF8), {(2E,2'E)-3,3'-[2,5-bis(octyloxy)-1,4-phenylene]-bis[2-(thiophen-2-yl)acrylonitrile]} (OPTAN), and benzo-[1,2,5]-thiadiazole (BT) units, i.e., poly(PTZ-co-OPTAN-co-BT) and poly(DTF8-co-OPTAN-co-BT), were synthesized through Pd(0)-catalyzed Suzuki coupling with appropriate control of the monomer ratio.

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A series of aryl-substituted fullerene derivatives were prepared in which the aromatic moiety of [6,6]-phenyl C61-butyric acid methyl ester (PC61BM) was modified by replacing the monocyclic phenyl ring with bicyclic naphthalene (NC61BM), tricyclic anthracene (AC61BM), and tetracyclic pyrene (PyC61BM). The PC61BM derivatives were synthesized from C60 using tosylhydrazone and were tested as electron acceptors in poly(3-hexylthiophene) (P3HT)-based organic photovoltaic cells (OPVs). The lowest unoccupied molecular orbital (LUMO) energy level of NC61BM (-3.

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Energy is currently one of the most important problems humankind faces. Depletion of traditional energy sources such as coal and oil results in the need to develop new ways to create, transport, and store electricity. In this regard, the sun, which can be considered as a giant nuclear fusion reactor, represents the most powerful source of energy available in our solar system.

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A cyclometalated iridium(II) complex, bis(2-thiophen-2-yl-quinolinato)(acetoacetonate)iridium(II) [(tq)2Ir(III)(acac)] was synthesized for use in phosphorescent organic light-emitting diodes. The photophysical and electrochemical properties of the iridium(Ill) complex were characterized by UV-visible absorption, photoluminescence, and cyclic voltammetry. The maximum UV-visible absorption of (tq)2Ir(acac) was observed at 289 nm.

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We have found that 9,9'BF can be used as an electron acceptor for P3HT-based OPVs while similar devices using 4,4'BP do not show any photovoltaic effect. This can be related to the respective aromaticity and antiaromaticity of the reduced forms of 9,9'BF or 4,4'BP. The OPV device fabricated using P3HT and 9,9'BF exhibited a PCE of 2.

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Background And Objectives: This study was aimed at evaluating the significance of blood pressure (BP) load in ambulatory blood pressure monitoring (ABPM) in obese children and adolescents.

Subjects And Methods: ABPM was conducted for 60 selected patients who had visited Sunlin Hospital between January 2008 and August 2008. Patients were classified into 3 groups; an obese group whose body mass index (BMI) was > the 95th percentile, an overweight group whose BMI was > the 85th percentile but less than the 95th percentile, and a normal group whose BMI was below the 85th percentile.

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