White organic light-emitting diodes with a structure of indium-tin-oxide [ITO]/ N,N-diphenyl-N,N-bis-[4-(phenylm- tolvlamino)-phenyl]-biphenyl-4,4-diamine [DNTPD]/ [2,3-f:2, 2-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile [HATCN]/ 1,1- bis(di-4-poly-aminophenyl) cyclo -hexane [TAPC]/ emission layers doped with three color dopants/ 4,7-diphenyl-1,10- phenanthroline [Bphen]/ Cs2CO3/ Al were fabricated and evaluated. In the emission layer [EML], N,N-dicarbazolyl-3,5-benzene [mCP] was used as a single host and bis(2-phenyl quinolinato)-acetylacetonate iridium(III) [Ir(pq)2acac]/ fac-tris(2- phenylpyridinato) iridium(III) [Ir(ppy)3]/ iridium(III) bis[(4,6-di-fluoropheny)-pyridinato-N,C2] picolinate [FIrpic] were used as red/green/blue dopants, respectively. The fabricated devices were divided into five types (D1, D2, D3, D4, D5) according to the structure of the emission layer. The electroluminescence spectra showed three peak emissions at the wavelengths of blue (472~473 nm), green (495~500 nm), and red (589~595 nm). Among the fabricated devices, the device of D1 doped in a mixed fashion with a single emission layer showed the highest values of luminance and quantum efficiency at the given voltage. However, the emission color of D1 was not pure white but orange, with Commission Internationale de L'Eclairage [CIE] coordinates of (x = 0.41~0.45, y = 0.41) depending on the applied voltages. On the other hand, device D5, with a double emission layer of mCP:[Ir(pq)2acac(3%) +Ir(ppy)3(0.5%)]/ mCP:[FIrpic(10%)], showed a nearly pure white color with CIE coordinates of (x = 0.34~0.35, y = 0.35~0.37) under applied voltage in the range of 6~10 V. The luminance and quantum efficiency of D5 were 17,160 cd/m2 and 3.8% at 10 V, respectively.

New organic light-emitting diodes with structure of indium-tin-oxide[ITO]/N,N'-diphenyl-N, N'-bis-[4-(phenyl-m-tolvlamino)-phenyl]-biphenyl-4,4'-diamine[DNTPD]/1,1-bis-(di-4-poly-aminophenyl) cyclohexane[TAPC]/bis(10-hydroxy-benzo(h)quinolinato)beryllium[Bebq2]/Bebq2:iridium(III)bis(2-phenylquinoline-N,C2')acetylacetonate[(pq)2Ir(acac)]/ET-137[electron transport material from SFC Co]/LiF/Al using the selective doping of 5%-(pq)2Ir(acac) in a single Bebq2 host in the two wavelength (green, orange) emitter formation were proposed and characterized. In the experiments, with a 300Å-thick undoped emitter of Bebq2, two kinds of devices with the doped emitter thicknesses of 20Å and 40Å in the Bebq2:(pq)2Ir(acac) were fabricated. The device with a 20Å-thick doped emitter is referred to as "D-1" and the device with a 4Å-thick doped emitter is referred to as "D-2". Under an applied voltage of 9V, the luminance of D-1 and D-2 were 7780 cd/m2 and 6620 cd/m2, respectively. The electroluminescent spectrum of each fabricated device showed peak emissions at the same two wavelengths: 508 nm and 596 nm. However, the relative intensity of 596 nm to 508 nm at those wavelengths was higher in the D-2 than in the D-1. The D-1 and D-2 devices showed maximum current efficiencies of 5.2 cd/A and 6.0 cd/A, and color coordinates of (0.31, 0.50) and (0.37, 0.48) on the Commission Internationale de I'Eclairage[CIE] chart, respectively.

The desmutagenic activity of the water extract of Cassia tora L on the mutagenicity induced by 4- nitroquinoline 1-oxide (4-NQO) and N-methyl-N-nitro-N'-nitrosoguani-dine (MNNG) was studied using the SOS Chromotest with Escherichia coli PQ37. The inhibition rates of water extract of Cassia tora L. at concentration of 100 μg/assay were 27.5% and 40% against 4-NQO and MNNG. The water extract of Cassia tora L. was separated into methanol soluble and methanol insoluble parts. The methanol soluble part exhibited higher inhibition effects than the methanol insoluble part against the mutagenic activities of 4-NQO and MNNG. Step-wise fractionation of methanol soluble part was done to obtain methanol, ethyl acetate and water fractions. Among these fractions, water fraction had the strongest inhibitory effects of 23.0 and 19.0% against mutagenicities of MNNG and 4NQO, repectively. The results clearly indicated that the water fraction showed much stronger antimutagenicity against MNNG than 4NQO. The inhibition rates of aqueous fraction of methanol-soluble from water extracted Cassia tora L. at concentrations of 1.0 10, 100 and 250 μg/assay were 8.0%, 12.0%, 25.5% and 43.0%, respectively. The water fraction showed the inhibitory effects with dose response against the mutagenic activities induced by MNNG.

The desmutagenic activity of the water extract of Areca catechu L. on the mutagenicity induced by aflatoxin B1 (AFB1), N-methyl-N-nitro-N'-nitrosoguani-dine (MNNG), mitomycin C (MMC) and 4-nitroquinoline 1-oxide (4-NQO) was studied by using the SOS Chromotest with Escherichia coli PQ37. The inhibition rates of water extract of Areca catechu L. at concentration of 100μg/assay were 41.0%, 47%, 46%, and 32% against AFB1, MNNG, MMC and 4-NQO, respectively. The water extract of Areca catechu L. was separated into methanol soluble and methanol insoluble parts. The methanol insoluble part exhibited higher inhibition effect than the methanol soluble part against the mutagenic activities of MNNG. Step-wise fractionation of methanol insoluble part was done to obtain methanol, ethyl acetate and water fractions. Among these fractions, water fraction had the strongest inhibitory effect of 45.0% against mutagenicities of MNNG. The inhibition rates of aqueous fraction of methanol-insoluble from water extracted Areca catechu L. at concentrations of 1.61, 16.13, 161.29 and 322.58μg/mL were 12.0%, 24.0%, 47.5% and 62.0%, respectively. The water fraction showed the inhibitory effects with dose response against the mutagenic activity induced by MNNG.