• Bulletin of the Korean Chemical Society
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• 제13권3호
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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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• 제11권2호
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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.

• 한국물환경학회지
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• 제23권6호
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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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• 제12권3호
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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.

• 대한환경공학회지
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• 제28권2호
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• pp.223-228
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• 2006

본 연구에서는 fluorescence derivatization 기법과 HPLC를 이용하여 수중에 nanograms per liter로 존재하는 극미량 N-nitrosodimethylamine(NDMA)를 분석하고자 하였다. 이를 위해 먼저 다양한 조건 하에서의 fluorescence intensity를 측정함으로써 derivatization 기법을 최적화하였는데, fluorescence detector의 excitation/emission wavelength는 340 nm(excitation)과 530 nm(emission)에서, denitrosation 후 용액의 pH는 9-12의 범위에서, 그리고 dansyl chloride의 농도는 330-500 mg/L 범위에서, 최대 fluorescence intensity를 보여주였다. 용매추출을 통한 수질 시료의 분석에서, 표준농도와 검출농도의 차이는, 저농도(10-200 ng/L) 범위에서 12-162%, 고농도(100-1000 ng/L) 범위에서 6-23%를 보여, 저농도 범위에서 더 많은 차이가 나는 것으로 나타났으나, 두 농도 범위 모두 표준농도와 검출농도의 평균 대비율이 1에 매우 근접해 있어, 수십에서 수백 nanograms NDMA per liter의 분석이 가능함을 보여주었다. 하수처리장 처리수에 주입한 NDMA의 분석에서도 다른 물질에 의한 간섭없이 정확한 농도 검출이 가능했는데, 이는 목적물질을 선별적으로 분석해내는 derivatization 과정에 의한 것으로 나타났다. HPLC와 fluorescence derivatization 기법을 이용한 NDMA의 분석은 상수 및 하수를 사용하는 다양한 실험 연구에서 NDMA를 분석하는 방법으로 효과적으로 사용될 수 있을 것이다.

• Restorative Dentistry and Endodontics
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• 제25권2호
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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.

• 마이크로전자및패키징학회지
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• 제23권3호
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• pp.37-41
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• 2016

본 논문에서는 긴 작동거리(working distance, WD)를 가지는 근적외선 형광 이미징 시스템을 소개하고, gain, 노출시간, 작동거리, 확대배율 등 측정 변수에 의한 형광 영상의 차이에 대해 분석하였다. 노출시간이 길수록, 확대배율이 클수록 형광신호는 더욱 강해지고, gain이 클수록 형광신호도 강해지지만, 배경신호도 함께 증가하여 SBR은 나빠질 수 있다. 제안한 시스템은 레이저 조사 방식으로 인해 작동거리가 짧은 경우 레이저 조사 영역의 강도 분포가 균일하지 못해서 형광신호가 약해지며, 그에 따른 해결방안을 제안하였다.

• 한국광학회지
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• 제12권3호
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• pp.177-183
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• 2001

KrF 레이저를 여기광원으로 사용하여 희박연소화염과 매연화염에서 각각 청색편이된 NO형광 신호를 측정하였다. 두 화염에 대해서 여기광의 세기와 NO 첨가량에 따른 NO 신호와 배경잡음의 세기를 계측하고 그 결과를 정성적으로 분석하였다. 또한 희박연소화염에서 위치에 따른 NO 신호의 세기도 관측하였다.

• Macromolecular Research
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• 제17권6호
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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.

• 한국전기전자재료학회논문지
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• 제17권4호
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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.