• Journal of Soil and Groundwater Environment
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• v.19 no.5
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• pp.18-25
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• 2014

Traditional investigation procedures of soil and groundwater contamination are followed by soil gas sampling, soil sampling, groundwater sampling, establishment of monitoring wells, and groundwater monitoring. It often takes several weeks to obtain the analysis reports, and sometimes, it needs supplemental sampling and analysis to delineate the polluted area. Laser induced fluorescence (LIF) system is designed for the detection of free-phase petroleum pollutants, and it is suitable for on-site real-time site investigation when coupling with a direct push testing tool. Petroleum products always contain polycyclic aromatic hydrocarbon (PAH) compounds possessing fluorescence characteristics that make them detectable through LIF detection. In this study, LIF spectroscopy of 5 major fuel products was conducted to establish the databank of LIF fluorescence characteristic spectra, including gasoline, diesel, jet fuel, marine fuel and low-sulfur fuel. Multivariate statistical tools were also applied to distinguish LIF fluorescence characteristic spectra among the mixtures of selected fuel products. This study successfully demonstrated the feasibility of identifying fuel species based on LIF characteristic fluorescence spectra, also LIF seemed to be uncovered its powerful ability of tracing underground petroleum leakages.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.35-36
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• 2006

Excited-state intramolecular proton transfer (ESIPT) is a phototautomerization occurring in the excited states of the molecules possessing a cyclic intramolecular or solvent-bridged hydrogen bond. Recently, we have developed novel ESIPT chromophores, molecules, dendrimers and polymers which show very high fluorescence quantum efficiency combined with the characteristic features of optical switching, fluorescence patterining, lasing, and electroluminescence. Broad overview of these topics will be given in this talk.

• Journal of Photoscience
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• v.2 no.1
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• pp.19-25
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• 1995

Picosecond time-resolved and static protein fluorescence spectra and absorption spectra of octopus rhodopsin, a photorecepting protein, are measured and compared with those of bacteriorhodopsin, a photon-induced proton pumping protein, to understand the protein conformations and functions of octopus rhodopsin and its deprotonated photocycle intermediate. The bluer and weaker absorption of retinal indicates that octopus rhodopsin is better in thermal noise suppression but less efficient in light harvesting than bacteriorhodopsin. The protein fluorescence of octopus rhodopsin shows the characteristic of Trp only and the uantum efficiency and lifetime variations may result primarily from variations in the coupling strength with the retinal. The stronger intensity by four times and larger red shift by 12 nm of fluorescence suggest that octopus rhodopsin has more open and looser structure compared with bacteriorhodopsin. Fluorescence decay profiles reveal two decay components of 300 ps (60%) and 2 ns (40%). The deprotonation of protonated Schiff's base increases the shorter decay time to 500 ps and enhances the fluorescence intensity by 20%. The fluorescence and its decay time from Trp residues near retinal are influenced more by the deprotonation. The increase of fluorescence intimates that protein structure becomes loosened and relaxed further by the deprotonation of protonated Schiff's base. The driving force of sequential changes initiated by absorption of a photon is too exhausted after the deprotonation to return the intermediate to the ground state of the begun rhodopsin form.

• Macromolecular Research
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• v.12 no.3
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• pp.282-289
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• 2004

We have extensively characterized the fluorescence behavior of unsaturated polyester (UP) resin in the absence and presence of a 1,3-bis-(l-pyrenyl)propane (BPP) fluorescent probe at various dynamic and isothermal cure histories by means of a steady-state fluorescence technique using a front-face illumination equipment. In addition, we explored the effect of the fluorescence intensity on the relaxation of the fluorescent probe in the UP resin by resting the dynamically and isothermally cured resin at ambient temperature and pressure for 24 h. The monomer fluorescence intensity, which has two characteristic peaks at 376 and 396nm, changed noticeably depending on the cure temperature and time and provided important information with respect to the molecular and photophysical responses upon curing. The result of the fluorescence study indicates that the increased local viscosity and restricted molecular mobility of the UP resin surrounding the BPP probe after curing are both responsible for the enhancement of the monomer fluorescence intensity. Our results also demonstrate that once the BPP probe has enough time to rearrange and become isolated prior to fluorescence, a sufficient amount of fluorescence is emitted. Therefore, we note that the fluorescence behavior of this UP resin system is influenced strongly by the relaxation process of the fluorescent probe in the resin as well as process used to cure the resin.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.211-220
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• 2013

The characteristic fluorescence properties of quercetin (QCT) and apigenin (API) were studied in various $CH_3OH-H_2O$ and $CH_3CN-H_2O$ mixed solvents. The structure of QCT is completely planar. API is not planar at the ground state but becomes nearly planar at the excited state. If the molecules are excited to the $S_1$ state in organic solvents, QCT exhibits no fluorescence due to excited state intramolecular proton transfer (ESIPT) between the -OH and the carbonyl oxygen, but API shows significant fluorescence because ESIPT occurs slowly. If the molecules are excited to the $S_2$ state, both QCT and API exhibit strong $S_2{\rightarrow}S_o$ emission without any dual fluorescence. As the $H_2O$ composition of both solvents increases, the fluorescence intensity decreases rapidly due to the intermolecular hydrogen bonding interaction. The theoretical calculation further supports these results. The change in fluorescence properties as a function of the solvatochromic parameters was also studied.

• Composites Research
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• v.23 no.3
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• pp.50-57
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• 2010

It is important to detect fibers in the sectional image of fiber reinforced cementitious composites (FRCC), since the fiber distribution is a crucial factor to predict or evaluate the mechanical performance of FRCC. In this paper, we investigated the fluorescence characteristics of Polyvinyl Alcohol (PVA) fibers, Polyethylene Terephthalate (PET) fibers, Polyethylene (PE) fibers, and Polypropylene (PP) fibers used in Engineered Cementitious Composites (ECC), which is a special kind of FRCC that incorporates synthetic fibers and exhibits extremely ductile behavior in uniaxial tension, to detect each fiber according to its type. Furthermore, optimum excitation and emission wavelengths were proposed on the basis of maximum difference of Relative Fluorescence Intensity (RFI) between two types of fibers used in the hybrid ECC. Optimum threshold values to discriminate two types of fibers using statistical tools were also proposed. Finally, images of four types of fibers obtained using a fluorescence microscope are compared.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.2
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• pp.149-154
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• 2022

In this paper, laser-induced fluorescence properties of four plastics were characterized through spectrometer analysis for real-time microplastic counting. Recently, environmental problems related to microplastics have emerged. In order to detect microplastics, analysis methods such as FT-IR and Raman are used. However, they have the disadvantages of being time-consuming and requiring a pretreatment process. In most plastic products on the market, 10% to 30% of plasticizers and reinforcing agents are added. Therefore, most microplastics present in seawater and freshwater emit fluorescence signals by 270 nm UV light source regardless of their type due to their molecular structure due to additives. Real-time microplastics counting is possible more easily by using the proposed laser-induced fluorescence detection method because of the fluorescence expression characteristic of 340 nm that appears due to the plasticizer of plastics.

• Journal of Korea Multimedia Society
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• v.22 no.12
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• pp.1339-1346
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• 2019

In the characteristic of the brain malignant, the blood vessels and tumors have the same color and shape, and the boundary distinction is not clear, Therefore, it is difficult to observe the naked eye. Because of the high invasiveness, the risk of recurrence is high. Therefore, complete resection of the tumor is essential. The method for distinguishing the boundary between blood vessels and tumors is a fluorescence contrast method using indocyanine green (ICG), a fluorescence contrast agent. In ICG, the concentration range analysis is very important because the fluorescence expression state varies depending on the concentration. However, since the analysis result of the fluorescence expression condition is insufficient according to the current concentration, this paper proposes by analyzing the initial protocol of the concentration range. 780 nm infrared light was irradiated to the ICG sample to observe the fluorescence expression through a near infrared (NIR) camera. The wavelength is measured by using a spectrum instrument (ocean view) to observe the fluorescence expression wavelength of 811nm. As a result of analyzing the mol concentration according to each sample, the fluorescence expression range was found to be 16.15-0.16M and the optimum fluorescence concentration on the brightest part was found to be 3.23-0.81M.

• Proceedings of the Korean Environmental Health Society Conference
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• 2005.06a
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• pp.386-393
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• 2005

The calcination characteristic of waste eggshell were examined by thermal gravimetric analysis (TGA), qualitative and quantitative analysis by X-ray fluorescence, and microstructural analysis by scanning electronic microscopy(SEM). The calcined sample was lager grain and pore size.

• Journal of the Korean Chemical Society
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• v.26 no.4
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• pp.218-223
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• 1982

The absorbance and fluorescence yields of chl-a vs. concentration of n-prOH in diethyl ether, benzene and iso-octane were shown the characteristic point which chl-a structures are changed to monomer by the solvation of oligomer, and the spectral differences of fluorescence excitation between oligomer and monomer were identified by fluorimetry. All the maximum wavelength of absorbance, fluorescence excitation and fluorescence emission were shifted to longer wavelength. The ratios of soret/red band were depended on the band intensions and the polarities of solution in organic solvents mixed with n-prOH.