• Microbiology and Biotechnology Letters
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• v.27 no.3
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• pp.252-259
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• 1999

Anoxic sediments collected from Shiwha-ho area were used to find the relationship between the heavy-metal, organic content and anaerobic respiration bacteria by most probable number (MPN) method. Analysis of the sediments showed that COD content was higher in the sediments collected from Ansan-cheon and Shiwha-ho than those collected from sea area nearby. Particularly noticeable was the fact that heavy metal concentration was much higher in the sediments of Shiwha-ho area contaminated by heavy-metal, although they were rich in electron donor and electron acceptor for Fe(III)-reducing bacteria using lactate as an electron donor was in the range of 1.1$\times$106-4.6$\times$107MPNs/ml in the sediments collected from the sea-side of the lake, which were lower in heavy-methal concentration and higher in Fe-Mn content than those from other region. The number of Fe(III)-reducing bacteria using acetate as an electron donor was in the rang eof 4.3$\times$102-8.1$\times$105MPNs/ml in the same sediments. Chromate-reducing bacteria were more populated(4.6$\times$104-8.1$\times$105MPNs/ml) in the sediments contaminated by heavy metals. The number of sulfate-reducing bacteria wee counted in the sediments collected from the more contaminate inner-side than those from the sea-side of the lake.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.41-44
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• 2014

In this paper, we will investigate the activation energies of Nb for $TiO_2$ using Hall effect measurement and photoluminescence (PL) system. Nb-doped $TiO_2$ thin film was grown on $SrTiO_3$ substrate by pulsed laser deposition (PLD) technique. After measurements, activation energies of niobium donor were 14.52 meV in Hall effect measurement, and 6.72 meV in PL measurement, respectively. These results showed different tendencies which are measured from the samples with acceptor materials. Therefore, it is thought that more research on activation energies for dopants of shallow donor level is expected.

• 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.

• Journal of Soil and Groundwater Environment
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• v.19 no.1
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• pp.54-62
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• 2014

To better understand dissimilatory iron and sulfate reduction (DIR and DSR) by subsurface microorganisms, we investigated the effects of sulfate and electron donors on the microbial goethite (${\alpha}$-FeOOH) reduction. Batch systems were created 1) with acetate or glucose (donor), 2) with goethite and sulfate (acceptor), and 3) with aquifer sediment (microbial source). With 0.2 mM sulfate, goethite reduction coupled with acetate oxidation was limited. However, with 10 mM sulfate, 8 mM goethite reduction occurred with complete sulfate reduction and x-ray absorption fine-structure analysis indicated the formation of iron sulfide. This suggests that goethite reduction was due to the sulfide species produced by DSR bacteria rather than direct microbial reaction by DIR bacteria. Both acetate and glucose promoted goethite reduction. The rate of goethite reduction was faster with glucose, while the extent of goethite reduction was higher with acetate. Sulfate reduction (10 mM) occurred only with acetate. The results suggest that glucose-fermenting bacteria rapidly stimulated goethite reduction, but acetate-oxidizing DSR bacteria reduced goethite indirectly by producing sulfides. This study suggests that the availability of specific electron donor and sulfate significantly influence microbial community activities as well as goethite transformation, which should be considered for the bioremediation of contaminated environments.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.1075-1080
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• 2004

Dextransucrase (DSRB742) from Leuconostoc mesenteroides NRRL B-742CB is a glucosyltransferase that catalyzes the synthesis of dextran using sucrose, or the synthesis of oligosaccharides when acceptor molecules, like maltose, are present. The DSRB742 gene (dsrB742) was cloned and the properties were characterized. In order to identify critical amino acid residues, the DSRB742 amino acid sequence was aligned with glucosyltransferase sequences, and three amino acid residues reported as sucrose binding amino acids in Streptococcus glucosyltransferases were selected for site-directed mutagenesis experiments. Asp-533, Asp-536, and His-643 were independently replaced with Ala or Asn. D533A and D536A dextransucrases showed reduced dextran synthesis activities, 2.3% and 40.8% of DSRB742 dextransucrase, respectively, and D533N, D536N, H643A, end H643N dextransucrases showed complete suppression of dextran synthesis activities altogether. Additionally, D536N dextransucrase showed complete suppression of oligosaccharide synthesis activities. However, modifications at Asp-533 or at His-643 retained acceptor reaction activities in the range of 8.4% to 21.3% of DSRB742 acceptor reaction activity. Thus at least two carboxyl groups of Asp-533 and Asp-536, and His-643 as a proton donor, are essential for the catalysis process.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.2
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• pp.9-14
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• 2009

The effects of post-annealing temperature on the optical and electrical properties of P-doped ZnO thin films grown on sapphire substrate have been investigated under oxygen ambient. The XRD shows that regardless of the post-annealing temperature, all P-doped ZnO thin films indicate the c-axis orientation. The results of hall effect measurements indicate the P-doped ZnO thin film annealed at $850^{\circ}C$ exhibits p-type behavior with hole concentration of $1.18{\times}1016cm^{-3}$ and hole mobility of $0.96cm^2/Vs$. The low-temperature (10K) Photoluminescence results reveal that the peak related to the neutral-acceptor exciton (A0X), free electrons to neutral acceptor (FA) and donor acceptor pair (DAP) at 3.351ev, 3.283eV and 3.201eV are observed in the films showing p-type behavior with acceptor. The optimization of deposition and post-annealing conditions will certainly make the P-doped ZnO thin films promising materials for the application to the next generation of optical devices.

• Journal of Photoscience
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• v.11 no.1
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• pp.1-6
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• 2004

Molecular assembling is one of the current interests in the field of bottom-up nanotechnology. Self-assembled monolayers of sulfur-containing molecules or supramolecular assemblies via surface sol-gel processes formed on conductive supports are chemically robust and can be easily fabricated without sophisticated instruments. We have fabricated various types of molecular assemblies consisting of donor-acceptor pairs on the surfaces of gold and indium-tin-oxide electrodes. Build-up of three-dimensional multi structures consisting of thiol dyes and gold nanoparticles also has been successful. These assemblies showed clear photocurrent responses in photoelectro-chemical cells. In this article, we will describe recent progress on photoelectric conversion using molecular assemblies especially focused on our research results.

• Journal of Photoscience
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• v.9 no.2
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• pp.59-62
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• 2002

In chilling-sensitive plants, the donor side of Photosystem II is inhibited by the chilling treatment in the dark, while the acceptor side of Photosystem I is inhibited by the chilling under the moderate light. Since the addition of inhibitors of electron transfer from Photosystem II protects Photosystem I from chilling induced photoinhibition of Photosystem I, inhibition or down-regulation of Photosystem II activity in vivo may also protect Photosystem I from photoinhibition. It was revealed that dark-chilling pretreatment actually protected Photosystem I from photoinhibition. The results imply that down-regulation of Photosystem II under stress conditions may have a role to protect Photosystem I from photoinhibition.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.98-101
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• 2012

I studied the stability of organic photovoltaic cells in terms of P3HT:PCBM-71 blend ratio as a function of storage time. I obtained the best cell performance by optimizing the blend ratio of electron donor and electron acceptor within the active layer. In this study, I found that the more the P3HT:PCBM ratio increases within the active layer, the more the cell efficiency decreases as the storage time increases. As a result, the best optimized blend ratio was the 1:0.6 ratio of P3HT:PCBM-71, and cell efficiency of the device with the 1:0.6 blend ratio was 4.49%. The device with the best cell efficiency showed good stability.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.163-163
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• 2012

We observed strain evolution of P3HT crystals in P3HT:PCBM films and the effect of Al electrode on the evolution during real time annealing process. Based on simple assumptions, both relaxed lattice parameters and thermal expansion coefficient could be quantitatively determined. P3HT:PCBM films displayed tensile strain in as-prepared samples regardless of the presence of an Al layer. In the absence of Al layer, P3HT crystals showed only strain relaxation at an annealing temperature of $180^{\circ}C$. Meanwhile In the presence of an Al layer, the strain was relaxed and changed to compressive strain at around 120C annealing temperature, which indicated a tightening of the thiophene ring packing. These behaviors support the improved performance of devices fabricated by post annealing process.