• Journal of Powder Materials
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• v.24 no.6
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• pp.489-493
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• 2017

In this study, the surface passivation process for InP-based quantum dots (QDs) is investigated. Surface coating is performed with poly(methylmethacrylate) (PMMA) and thioglycolic acid. The quantum yield (QY) of a PMMA-coated sample slightly increases by approximately 1.3% relative to that of the as-synthesized InP/ZnS QDs. The QYs of the uncoated and PMMA-coated samples drastically decrease after 16 days because of the high defect state density of the InP-based QDs. PMMA does not have a significant effect on the defect passivation. Thioglycolic acid is investigated in this study for the effective surface passivation of InP-based QDs. Surface passivation with thioglycolic acid is more effective than that with the PMMA coating, and the QY increases from 1.7% to 11.3%. ZnS formed on the surface of the InP QDs and S in thioglycolic acid show strong bonding property. Additionally, the QY is further increased up to 21.0% by the photochemical reaction. Electron-hole pairs are formed by light irradiation and lead to strong bonding between the inorganic and thioglycolic acid sulfur. The surface of the InP core QDs, which does not emit light, is passivated by the irradiated light and emits green light after the photochemical reaction.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.458-460
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• 2008

Four kinds of copolymers with fluorene and biphenylamine units were synthesized by palladium-catalyzed polycondensation reaction. These polymers were characterized in terms of their UV/Visible and photoluminescence (PL) properties in solution and film state. These polymers were also studied as a hole transporting material in the polymer light emitting diode (PLED) devices.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1136-1137
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• 2006

The ultrahigh pressure process for synthesizing diamond grits is due to make a quantum leap: the raw materials will incorporate diamond seeds with a predetermined pattern. The result is doubling the diamond yield with a narrower size distribution. Moreover, the shape of diamond crystals can be precisely tuned. For example, diamond octahedra or diamond cubes, that are not available today, can be mass-produced. The new technology is now being implemented worldwide so the future diamond grits will have improved quality at reduced prices.

• Ceramist
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• v.23 no.2
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• pp.178-183
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• 2020

Solar energy conversion is now actively researching because of pollution. Especially silicon photocatalyst has big potential, because of wide absorption range. But low quantum yield of silicon photocatalyst can't be used for commercialization. This paper summarize mechanism of silicon photocatalyst. In addition, properties and current states of photo catalyst using nanomaterials of silicon are also introduced.

• Journal of Photoscience
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• v.9 no.3
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• pp.71-74
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• 2002

The fluorescent conjugated aromatic imine derivatives are systematically designed and synthesized as the high yield through the simple one-pot condensation reaction. The emission of the synthesized conjugated aromatic imine derivatives can be tuned efficiently in the range of about 100 nm by the change of electron donating groups constituting parent molecule, which shows the considerable quantum yields from 0.38 to 0.56.

• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.798-802
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• 1996

The photochemical decomposition of aqueous ammonia in the absence (saturated with argon) and the presence of O2 (saturated with air or oxygen) has been investigated using 184.9 nm UV light. The decomposition of ammonia depended on the concentration of oxygen in the solution. With increasing the concentration of oxygen, the decomposition of ammonia diminishes. Hydrazine is found the major product from the irradiation. In the presence of oxygen, hydrogenperoxide was also produced. The product yields depended also on the concentration of oxygen in the solution. The initial quantum yield of the products and of the ammonia decomposed were determined. Probable reaction mechanisms for the reaction were presented from the products analysis.

• Bulletin of the Korean Chemical Society
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• v.1 no.2
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• pp.68-70
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• 1980

1,4,5,8-Tetraazaphenanthrene, a new tetraazaheteroaromatic compound, has been synthesized photochemically in 90 % yield and quantum yield of $5.1{\times}10^{-2}$ from dilute benzene solutions of 1,2-bispyrazyl ethylene(BPE) in the presence of oxygen as an oxidant. Iodine was not appropriate oxidant because of strong complexing with BPE and also enhanced intersystem crossing of BPE and thereby decreasing the photocyclization of BPE. Salt effect, solvent effect, and quenching and sensitization studies on the photocyclization of BPE have shown that ($^l(n, {\pi}^*$) is the reactive state for the cyclization in comparison to ($^1{\pi}, {\pi}^*$) state for the ordinary stilbene derivatives.

• ALGAE
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• v.29 no.4
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• pp.321-331
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• 2014

Vertebrata lanosa is an abundant and obligate red algal epiphyte of Ascophyllum nodosum that forms part of a complex and highly integrated symbiotic system that includes the ascomycete, Mycophycias ascophylli. As part of ongoing studies to resolve interactions among species in the symbiosis, we used pulse amplitude modulation fluorimetry of chlorophyll a fluorescence, from photosystem II (PSII), to measure the maximum quantum yield ($F_v/F_m$) of PSII [$QY(II)_{max}$] and relative photosynthetic electron transport rates (rETR), as a function of light intensity, in order to evaluate the photosynthetic capacity of the two algal symbionts in the field and in the laboratory under different treatments. Our primary question was 'Is the ecological integration of these species reflected in a corresponding physiological integration involving photosynthetic process?' In the laboratory we measured changes in $QY(II)_{max}$ in thalli of V. lanosa and A. nodosum over one week periods when maintained together in either attached or detached treatments or when maintained separated from each other. While the $QY(II)_{max}$ of PSII of A. nodosum remained high and showed no significant variation among treatments, V. lanosa showed decreasing performance in the following conditions: V. lanosa attached to A. nodosum, V. lanosa in the same culture, but not attached to A. nodosum, and V. lanosa alone. These results are consistent with observations in which rETR was reduced in V. lanosa maintained alone versus attached to A. nodosum. Values for $QY(II)_{max}$ in V. lanosa measured in the field in fully submerged thalli were similar to those measured in the laboratory when V. lanosa was attached to it obligate host A. nodosum. Our results provide evidence of a physiological association of the epiphyte and its host that reflects the known ecology.

• Journal of Photoscience
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• v.5 no.4
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• pp.169-174
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• 1998

Photosynthetic responses to dehydration were examined by the simulataneous measurement of O2 evolution and chlorophyll (Chl) fluorescence in green pepper leaves. Dehydration was induced by immersing the plant roots directly in the Hoagland solution containing varying concentration (2-30%) of polyethylene glycol(PEG-6000) . Water potential of the leaf was decreased time-and concentation -dependently by PEG-treatment. The decrease in water potential of leaf was correlated with the decrease in both the maximal photosynthesis (Pmax) and quantum yield of O2 evolution, but Pmax dropped more rapidly than quantum yield at all water deficit conditions tested. However, Chl fluorescence parameters were not affected much. Dehydration did not change the initial fluorescence (Fo) and maximum photochemical efficiency(Fv/Fm) of photosystem(PS) II. Both the photochemical quenching (qP) and non-photochemical quenching(NPQ) were not changed by dehydration under low PFR(50 $\mu$mols m-2s-1 ). In contrast, under high PFR(270$\mu$mols m-2s-1)qP was slightly decreased while NPQ was greatly increased. The fast induction kinetics of Chl fluroecence showed no change in Chl fluorescence pattern by dehydration at high PFR (640 $\mu$mols m-2s-1 ), but exhibited a significant drop in peak level(Fp)at low PRFR (70$\mu$mols m-2s-1 ). PS I oxidation and reduction kinetics revealed normal reduction but delayed oxidation to P-700+, suggesting no lesionin electron flow from PSII to PSI , but impaired electron transport to NADP+,These results suggest that water stress caused by PEG-treatment results in the reduction of photosynthesis, promarily due to the reducted electron trasport from PSI to NADP+ or hampered subsequent steps involving Calvin Cycle.

• Journal of the Korean Chemical Society
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• v.26 no.3
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• pp.172-178
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• 1982

A psoralen-DNA monoadduct analogue, 4',5'-dihydropsoralen (DHP) is synthesized and its photophysical properties such as fluorescence quantum yield (0.08), phosphorescence quantum yield (0.013), fluorescence lifetime (0.95ns), and phosphorescence lifetime(0.039s) were measured in ether solution and in frozen matrix state at 77K. The photocycloaddition reaction of DHP with tetramethylethylene(TME) was carried out in solution and in the frozen state. The major photoadduct was isolated and characterized by elemental analysis and physical methods such as UV, IR, NMR, and mass spectrometry. The major DHP-TME photoadduct was proved to be an 1 : 1 $C_4$-cycloadduct formed through 2 + 2 cycloaddition of the pyrone double bond of DHP to TME.