• Journal of Soil and Groundwater Environment
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• v.27 no.3
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• pp.41-49
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• 2022

This study utilized citric acid as a floating agent in biological denitrification process and assessed its role under different carbon supplying conditions. Several microcosm tests including citric acid active (CAA), precipitating tablet release active (PTRA) and floating tablet release active (FTRA) were conducted to evaluate nitrate denitrification efficacy. In CAA reactors, nitrate removal was accompanied by the formation of denitrification by-products such as nitrite and nitrous oxide, with the extent of nitrate removal being proportional to citric acid concentration. These results suggest that citric acid induced heterotrophic biological denitrification. PTRA reactor that incorporated CAA and the same electron donor showed a similar denitrification efficiency to CAA reactor. FTRA reactor, which contained the same amount of fumarate as PTRA, enhanced denitrification by 7% as compared to the PTRA reactor. The overall results of this work indicate that surplus citric acid can be efficiently utilized in heterotrophic denitrification.

• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2531-2536
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• 2010

Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been employed to investigate the molecular structures and absorption spectra of two dyes containing diphenylaniline and 4-diphenylamino-diphenylaniline as donor moiety (TPA1 and TPA3). The geometries indicate that the strong conjugation is formed in the dyes. The electronic structures suggest that the intramolecular charge transfer from the donor to the acceptor occurs, and the electron-donating capability of 4-diphenylamino-diphenylaniline is stronger than that of diphenylaniline. The computed highest occupied molecular orbital (HOMO) energy levels are -5.31 and -4.90 eV, while the lowest unoccupied molecular orbital (LUMO) energies are -2.29 and -2.26 eV for TPA1 and TPA3, respectively, revealing that the interfacial charge transfer between the dyes and the semiconductor electrode are electron injection processes from the photon-excited dyes to the semiconductor conduction band. Furthermore, all the experimental absorption bands of TPA1 and TPA3 have been assigned according to the TDDFT calculations.

• Korean Journal of Materials Research
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• v.10 no.7
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• pp.478-481
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• 2000

Single phase $Pb(Mg_{1/3}Nb_{2/3})O_3$ ceramics doped by 10 mol% of electron donors such as $La^3,\; Pr^{3+,4+},\; Nd^{3+},\; Sm^{3+}$, were synthesized and their B-site cationic ordering structures were investigated by XRD and TEM. In the XRD patterns, only fundamental reflections were observed for the undoped $Pb(Mg_{1/3}Nb_{2/3})O_3$, while the (h/2 $\textsc{k}$/2ι/2)(h,$\textsc{k}$,ι all odd) superlattice reflections resulting from the 1:1 ordering induced unit cell doubling were also observed for the donor-doped $Pb(Mg_{1/3}Nb_{2/3})O_3$. In the TEM selected area diffraction patterns, the (h/2 k/2 l/2)(h,k,l all odd) superlattice reflection spots as well as the fundamental reflection spots were observed for all the samples, but the relative intensities of the superlattice reflection spots to the fundamental reflection spots were significantly enhanced by the donor-doping. In the TEM dark-field images, antiphase boundaries were observed only for the donor-doped $Pb(Mg_{1/3}Nb_{2/3})O_3$. It was therefore experimentally verified that doping by electron donors such as $La^3,\; Pr^{3+,4+},\; Nd^{3+},\; Sm^{3+}$, enhances the B-site cationic 1:1 ordering in $Pb(Mg_{1/3}Nb_{2/3})O_3$. These experimental results were interpreted in terms of the charge compensation mechanism.

• Korean Chemical Engineering Research
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• v.52 no.1
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• pp.92-97
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• 2014

Perchlorate ($ClO_4^-$) is an emerging contaminant of soil/groundwater and surface water. $ClO_4^-$ has been shown to inhibit iodide uptake into the thyroid gland and cause a reduction in thyroid hormone production. $ClO_4^-$ is highly soluble and very stable in water. Biodegradation by $ClO_4^-$-reducing bacteria (PRB) is considered the most important factor in natural attenuation of $ClO_4^-$. Rivers in an industrial complex have potential to be contaminated with $ClO_4^-$ discharged from point or non-point sources. In this study, water samples were taken from the rivers running through the Gumi industrial complexes and used for batch test to analyze $ClO_4^-$-degradation potential of river microorganisms. The results of 83-h batch culture showed that $ClO_4^-$-removal efficiency of all samples was 0.77% or less without addition of an external electron ($e^-$) donor. However $ClO_4^-$-removal efficiency was higher when an $e^-$ donor (acetate, thiosulfate, $S^0$, or $F^0$) was added into the batch culture, showing up to 100% removal efficiency. The removal efficiency was various depending on type of $e^-$ donor and site of sampling. When acetate was used as an $e^-$ donor, the highest $ClO_4^-$-removal efficiency was observed among the $e^-$ donors used in this study, suggesting that activity of heterotrophic PRB was dominant. The results of this study provide basic information on natural attenuation of $ClO_4^-$ by river microorganisms. The information can be useful to prepare a strategy to enhance efficiency of $ClO_4^-$ biodegradation for in situ bioremediation.

• Analytical Science and Technology
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• v.8 no.4
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• pp.481-486
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• 1995

Quenching experiments by photoinduced electron transfer between a charged donor and a neutral acceptor were carried out in acetonitrile, dichloromethane and mixed solvents of acetonitrile and dichloromethane. Tris(2, 2'-bipyridine) ruthenium(II) ($[Ru(bpy)_3]^{2+}$) which has 2+ charge and dicyanobis (2, 2'-bipyridine) ruthenium(II) ($Ru(bpy)_2(CN)_2$) which has no charge were used as electron donors, and a series of tris(${\beta}$-diketonato) ruthenium (III) was used as acceptor. In dichloromethane, $[Ru(bpy)_3]^{2+}$ and its counter ions ($ClO{_4}^-$) form ion pair. In the estimate of ${\Delta}G$ of electron transfer, the electrostatic potential between counter ions and product ion pair produced by electron transfer must be taken into account. A similar effect of counter ions was found in mixed solvents of 10, 30, 50, 70 and 90% acetonitrile ratio in volume. The effect of counter ion on ${\Delta}G$ became smaller with the increase in acetonitrile ratio. The result in mixed solvents suggests that $[Ru(bpy)_3]^{2+}$ and its counter ions form ion pair even in 90% acetonitrile solution.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.3
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• pp.196-200
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• 2019

In this study, photoluminescence (PL) analysis was performed to evaluate the optical properties of commercial ZnO substrates. Particular attention was paid to the bound exciton (BX) luminescence, which is usually the strongest emission intensity of commercial substrates. At 15 K, PL analysis revealed that the BX peak due to donor-type impurities (donor-bound-exciton; DX) dominated, while two-electron satellite (TES) emission, donor-accepter pair (DAP) emission, and LO-phonon replica emission were also observed. The impurity concentration of the ZnO substrate was determined to be $10^{15}$ to $10^{16}/cm^3$ by examination of the temperature variation of DAP, while the half width and intensity change of the luminescence revealed that the temperature change of BX can be interpreted almost the same as the analysis of free-exciton emission.

• Rapid Communication in Photoscience
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• v.3 no.1
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• pp.1-15
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• 2014

We summarize recent studies on photoinduced electron- and energy-transfer processes of various supramolecules including imide group(s) as a component. Recently, imides have been employed in various functional molecular systems, because of their excellent photophysical and electron accepting properties. Our research group also employed imides in various supramolecular systems such as donor-acceptor dyads, quantum dots, DNA, and so on. First, we summarize fundamental properties of imides such as photophysical and electrochemical properties. Then, photoinduced processes of imides in the supramolecular systems are described to show their applicability in the various fields.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.831-834
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• 2000

Characteristics of organic light-emitting diodes(OLEDs) were studied with devices made by PECCP[poly(3,6-N-2-ethylhexyl carbazolyl cyanoterephthalidene)] Langmuir-Blodget(LB) films. The emissive organic material was synthesized and named PECCP, which has a strong electron donor group and an electron accepter group in main chain repeated unit. The LB technique was employed to investigate the identification of the recombination zone in the ITO/PECCP LB films/Alq$_3$/Al structure by varying the LB film thickness. PECCP was considered as an emissive layer and Alq$_3$was used as an electron-transport layer. We measured current-voltage(I-V) characteristics, UV/visible absorption, PL spectrum, and EL spectrum of those devises.

• Bulletin of the Korean Chemical Society
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• v.18 no.6
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• pp.567-573
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• 1997

Photoinduced electron transfer from the charge-transfer excited states of Ru(tpy)(bpy(COOH)₂)$CN^+$, Ru(tpy)(bpy(COOH)₂)$Cl^+$, Ru(tpy)(bpy(COOH)₂)H₂+O², and Ru(tpy)(bqu(COOH)₂)$Cl^+$ to the conduction band of TiO₂ has been studied through photoelectrochemical methods. Ru(tpy)(bpy(COOH)₂)$CN^+$ produced the highest current density and open-circuit photovoltage, whereas Ru(tpy)(bqy(COOH)₂)$Cl^+$ produced the lowest values. A potential barrier was employed to explain the experimental result that the rate of the electron transfer increases with increasing the energy difference between the donor and acceptor. A sensitizer with a high current density yielded a high photovoltage and a high conversion efficiency. The reduction rate of the oxidized sensitizer decreased with the increases in the reduction potential of the sensitizer, resulting in a poor stability of a photoelectrochemical cell.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1485-1490
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• 2014

We have designed and developed a new ladder type tetrafused ${\pi}$-conjugated building block such as dihydroindolo[3,2-b]indole (DINI) and investigated its role as an electron rich unit. The photovoltaic properties of a new semiconducting ${\pi}$-conjugated polymer, poly[[5,10-bisoctyl-5,10-dihydroindolo[3,2-b]indole-[5,6- bis(octyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole]], represented by PDINI-OBTC8 are described. The new polymer PDINI-OBTC8 was synthesized in donor-acceptor (D-A) fashion, where fused ${\pi}$-conjugated tetracyclic DINI, and 5,6-bis(octyloxy)-4,7-di(thiophen-2-yl) benzo[c][1,2,5]thiadiazole (OBTC8) were employed as electron rich (donor) and electron deficient (acceptor) moieties, respectively. The conventional bulk heterojunction (BHJ) device structure ITO/PEDOT:PSS/PDINI-OBTC8:PCB71M/LiF/Al was utilized to fabricate polymer solar cells (PSCs), which comprises the blend of PDINI-OBTC8 and [6,6]-phenyl-$C_{71}$-butyric acid methyl ester ($PC_{71}BM$) in BHJ network. A BHJ PSC that contain PDINI-OBTC8 delivered power conversion efficiency (PCE) value of 1.68% with 1 vol% of 1,8-diidooctane (DIO) under the illumination of A.M 1.5G 100 $mW/cm^2$.