• Bulletin of the Korean Chemical Society
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• v.13 no.3
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• pp.325-331
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• 1992

By using the general theoretical framework proposed recently for treating the fluorescence quenching kinetics, we investigate the effect of light pulse intensity on the decay of fluorescence which follows excitation of fluorophors by the light pulse of very short but finite duration. It is seen that conventional theory breaks down when the exciting light pulse has a pulse width comparable to the fluorescent lifetime and its intensity is very high. We also find that even when the light intensity is not too high, conventional theory may fail in either of the following cases: (i) when the quencher concentration is high, (ii) when there is an attractive potential of mean force between the fluorophor and quencher, or (iii) when the energy transfer from the fluorophor to the quencher may also occur at a distance, e.g., via dipole-dipole interaction. The validity of the predictions of the present theory may thus be tested by fluorescence quenching experiments performed under such situations.

• Journal of Photoscience
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• v.11 no.32
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• pp.83-87
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• 2004

A porphyrin compound containing a crown ether moiety (Por-Crown) and its zinc complex (ZnPor-Crown) have been prepared and the effect of the addition of alkali metal on their fluorescence has been investigated. As alkali metal cations were added, the absorption and fluorescence maxima did not change. However, the absorbance and intensity of fluorescence increased dramatically. Among the alkali metal cations tested, addition of K$^{+}$ and Cs$^{+}$ showed strongest enhancement of absorbance and fluorescence intensity of Por-Crown and ZnPor-Crown.own.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.863-871
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• 2007

Spectroscopic characteristics of river water from four major watersheds in the Ulsan area were measured to examine their potential for estimating water quality parameters. The total 176 river samples were collected from 44 sites of small streams within the watersheds during the year 2006. Spectroscopic characteristics investigated included protein-like fluorescence (FLF) intensity, fulvic-like fluorescence (FLF) intensity, terrestrial humic-like fluorescence (TLF) intensity, UV absorbance at 254 nm, and UV absorbance difference at 220 nm and 254 nm. Protein-like fluorescence intensity showed linear relationships with biochemical oxygen demand (BOD), chemical oxygen demand (COD), total phosphorous (TP) concentrations of the samples with the correlation of 0.784, 0.779, and 0.733, respectively. Due to the UV absorption characteristics of nitrate at 220 nm, UV absorbance difference at 220 nm and 254 nm was selected to represent total nitrogen (TN) concentration. Exclusion of some samples with PLF intensity higher than 5.0 improved the correlation between the UV absorbance difference and TN as demonstrated by the increase of the correlation coefficient from 0.392 to 0.784. Instead, for the samples with PLF intensity lower than 5.0, the highest correlation of TN was achieved with UV absorbance at 254 nm. The results suggest that PLF intensity could be used as the estimation index for BOD, COD, and TP concentration of river water, and as the primary screening index for the prediction of TN using UV absorbance difference. Some BOD-based water quality levels among the river water were statistically discriminated by the PLF intensity. Low p-values were obtained from the t-tests on the samples with the first level and the second level (p=0.0003) and the samples with the second and the third levels (p=0.0413). Our combined results demonstrated that the selected spectroscopic characteristics of river water could be utilized as a tool for on-site real-time monitoring and/or the primary estimation of water quality.

• 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.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.2
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• pp.223-228
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• 2006

High-performance liquid chromatography(HPLC) and fluorescence derivatization were applied for a trace-level N-nitrosodimethylamine(NDMA) analysis of water samples. Fluorescence intensity was optimized with the excitation wavelength of 340 nm and the emission wavelength of 530 nm. pH adjustment after denitrosation was necessary to get a maximum intensity at pH between 9 and 12. Maximum intensity was found with a dansyl chloride concentration of 330 to 500 mg/L. Percentile error in the water sample analyses through solid phase extraction was 12-162% and 6-23% for the lower concentration level(10-200 ng/L NDMA) and the higher level(100-1000 ng/L NDMA), respectively, showing more discrepancy in lower level. However, the average ratios of estimated NDMA to the standard NDMA were close to 1 for both concentration ranges, presenting this HPLC method could detect from tens to hundreds nanograms NDMA per liter. Accurate determination of NDMA, which was injected to a wastewater effluent, revealed the selectivity of fluorescence derivatization for the target compound(NDMA) in the presence of complex interfering compounds. The HPLC with fluorescence derivatization may be applicable for determining NDMA of water and wastewater samples fur various research purposes.

• Restorative Dentistry and Endodontics
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• v.25 no.2
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• pp.225-234
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• 2000

The purpose of this study was to investigate the distribution and fluorescene intensity of vasoactive intestinal polypeptide(VIP) immunoreactive cells in rat trigeminal ganglion after inferior alveolar nerve axotomy. The animals were divided into normal and two experimental groups. The experimental animals were sacrificed at 14th and 28th day after inferior alveolar nerve axotomy. The trigeminal ganglion was removed and immersed in the 4% paraformaldehyde-0.2% picric acid in 0.1M phosphate buffer. Serial frozon sections about $16{\mu}m$ in thickness were cut with a cryostat. The immunofluorescence staining was performed. The rabbit anti-VIP(1 : 8,000) was used as primary antibody and fluorescene isothiocynate(FITC)-conjugated anti-rabbit IgG(1 : 80) as secondary antibody. The slides were observed under confocal laser scanning microscope. Three-dimensional images were constructed from 9 serial images(each $1{\mu}m$ in thickness) made by automatic optical sectioning. Unprocessed optical sections were obtained and stored on a optical disk. Color picture were printed by a video copy processor. The results were as follows; 1. The appearance of VIP immunoreactive cells in the mandibular part of trigeminal ganglion was 8.79${\pm}$1.99% in normal group and 39.16${\pm}$5.62% in 14 days, 16.25${\pm}$2.39% in 28 days after inferior alveolar nerve axotomy groups. 2. The relative fluorescence intensity of VIP immunoreactive cell bodies in the mandibular part of trigeminal ganglion was 134.40${\pm}$10.39 in normal group and 192.88${\pm}$14.06 in 14 days, 143.10${\pm}$5.02 in 28 days after nerve axotomy groups. Therefore, the relative fluorescence intensity of 14 days after nerve axotomy group was 43.3% higher than intensity of normal group. 3. In optical single section analysis of VIP immunoreactive cell bodies, white cell bodies(moderate fluorescence intensity) were the most abundant in normal and 28 days after nerve axotomy groups. Whereas, in 14 days after nerve axotomy group, red cell bodies(high fluorescence intensity) were the most abundant. 4. In optical serial section analysis of VIP immunoreactive cell bodies, red cell bodies(high fluorescence intensity) were observed in a part of the 9 sections of normal and 24 days after nerve axotomy groups. Whereas, red cell bodies were observed in all of the 9 sections of 14 days after nerve axotomy group. 5. The results indicates that number and fluorescence intensity of VIP immunoreactive cells were increased in the mandibular part of trigeminal ganglion following inferior alveolar nerve axotomy.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.37-41
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• 2016

In this paper, we introduced a near infrared fluorescence imaging system that has long working distance and analyzed on the effects of measurement variables such as gain, exposure time, working distance, magnification. Fluorescence signal intensity is growing up according to exposure time and magnification increasing, and it is getting stronger according to increase of gain, but the background signal intensity is getting stronger together. It causes low SBR. Due to a laser irradiation method, laser intensity distribution of the introduced system is not uniform and it makes fluorescence signal weak. So, we proposed a solution.

• Korean Journal of Optics and Photonics
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• v.12 no.3
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• pp.177-183
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• 2001

The KrF laser was employed to study NO fluorescence in lean-bum as well as in soot-bum flames. Blue-shifted NO fluorescence was observed in both of the flames. For both of the flames, the fluorescence intensity of NO and its relative background noise signal were measured with respect to the concentration of seeded NO molecule in the flame and the laser intensity. The results were analyzed qualitatively. Also, NO concentration distribution in the lean-bum flame was qualitatively determined from the intensity of the NO fluorescence. cence.

• Macromolecular Research
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• v.17 no.6
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• pp.403-410
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• 2009

Cytotoxicity is a severe problem of cadmium sulfide nanoparticles(CSNPs) for use in biological systems. In the present study, mercaptoacetic acid-coated CSNPs were conjugated with bovine serum albumin (BSA) to improve biocompatibility. The surface properties of the CSNPs and albumin-conjugated CSNPs (ACSNPs) were characterized by XRD, UV, FTIR, EA, TEM and DLS. Human breast cancer cells (KB cells) were then cultured in the presence of the nanoparticles to evaluate the cytotoxicity of CSNPs and ACSNPs. Finally, the fluorescence intensity of the nanoparticles' aqueous solution was examined using a fluorescence spectrometer. The results showed that the cell compatibility and fluorescence intensity of ACSNPs were higher than those of CSNPs. The strongly luminescent features of the biocompatible ACSNPs are promising for use in biological fields such as cellular labeling, intracellular tracking and molecular imaging.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.4
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• pp.404-409
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• 2004

We fabricated photo-sensor for fluorescence detection in LOC. LOC is high throughput screening system. Our LOC screens biochemical reaction of protein using the immunoassay, and converts biochemical reaction into electrical signal using LIF(Laser Induced Fluorescence) detection method. Protein is labeled with rhodamine intercalating dye and finger PIN photodiode is used as photo-sensor We measured fluorescence emission of rhodamine dye and analyzed tendency of fluorescence detection, according to photo-sensor size, light intensity, and rhodamine concentration. Detection current was almost linearly proportional to two parameters, intensity and concentration, and was inversely proportional to photo-sensor size. Integrated LOC consists of optical-filter deposited photo-sensor and PDMS microchannel detected 50 (pg/${mu}ell$) rhodamine. For integrated LOC including light source, we used green LED as the light source and measured emitted fluorescence.