• Journal of Biosystems Engineering
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• v.37 no.3
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• pp.209-213
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• 2012

Purpose: This study was performed to develop a simple, disposable thin-film optical nitrate sensor. Methods: The sensor was fabricated by applying a nitrate-selective polymer membrane on the surface of a thin polyester film. The membrane was composed of polyvinylchloride (PVC), plasticizer, fluorescent dye, and nitrate-selective ionophore. Fluorescence intensity of the sensor increased on contact with a nitrate solution. The fluorescence response of the optical nitrate sensor was measured with a commercial fluorospectrometer. Results: The optical sensor exhibited linear response over four concentration decades. Conclusions: Nitrate ion concentrations in plant nutrient solutions can be determined by direct optical measurements without any conditioning before measurements.

• Journal of Environmental Science International
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• v.29 no.8
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• pp.801-808
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• 2020

In this study, an effective fluorescence pH sensor based on conjugated polyelectrolyte micelles (CPMs) was devised for detecting extremely acidic conditions. An amphiphilic coumarin derivative (CC12-N), a building block, was prepared, into which an ionizable amino group, aryl amine, was incorporated as a potential hydrophilic moiety. This monomer displays self-assembled micelle formation in extremely acidic pH ranges, giving a hydrophobic π-extended conjugated system at the inner part and hydrophilic functionality at the periphery, resulting in efficient fluorescence intensity enhancement. This new micelle-based fluorescence provides an efficient sensing platform for detecting very low pH values in the presence of competing substances.

• Textile Coloration and Finishing
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• v.24 no.4
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• pp.233-238
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• 2012

The opto-functional materials have been developed as a promising research topic toward the end uses for optical materials and applications. The attractive area in this part was the design of sensor molecules for detecting harmful environmental factors. These harmful factors impart undesired effects on wide range of chemical and biological phenomenon. In this context, many researchers have studied luminescence chemosensor materials. These sensor molecules showed optical signals such as color or fluorescence change by detecting harmful environmental factors. In this study, the novel fluorescence chemosensor 1 has been designed and synthesized through reaction of rhodamine 6g hydrazide and 2-hydroxy-1-naphthaldehyde. The chemosensor 1 had been analyzed by UV-Vis and fluorescence spectrophotometer. We found that this chemosensor 1 has 'off-on' and dual type sensing properties toward $Cu^{2+}$ and $Mg^{2+}$.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.5
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• pp.432-441
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• 2006

2D fluorescence sensors produce a great deal of spectral data during fermentation processes, which can be analyzed using a variety of statistical techniques. Principal component analysis (PCA) and a self-organizing map (SOM) were used to analyze these 2D fluorescence spectra and to extract useful information from them. PCA resulted in scores and loadings that were visualized in the score-loading plots and used to monitor various fermentation processes with recombinant Escherichia coli and Saccharomyces cerevisiae. The SOM was found to be a useful and interpretative method of classifying the entire gamut of 2D fluorescence spectra and of selecting some significant combinations of excitation and emission wavelengths. The results, including the normalized weights and variances, indicated that the SOM network is capable of being used to interpret the fermentation processes monitored by a 2D fluorescence sensor.

• Journal of Microbiology and Biotechnology
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• v.25 no.4
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• pp.503-510
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• 2015

The iLOV protein belongs to a family of blue-light photoreceptor proteins containing a light-oxygen-voltage sensing domain with a noncovalently bound flavin mononucleotide (FMN) as its chromophore. Owing to advantages such as its small size, oxygen-independent nature, and pH stability, iLOV is an ideal candidate over other reporter fluorescent proteins such as GFP and DsRed. Here, for the first time, we describe the feasibility of applying LOV domain-based fluorescent iLOV as a metal sensor by measuring the fluorescence quenching of a protein with respect to the concentration of metal ions. In the present study, we demonstrated the inherent copper sensing property of the iLOV protein and identified the possible amino acids responsible for metal binding. The fluorescence quenching upon exposure to Cu²⁺ was highly sensitive and exhibited reversibility upon the addition of the metal chelator EDTA. The copper binding constant was found to be 4.72 ± 0.84 µM. In addition, Cu²⁺-bound iLOV showed high fluorescence quenching at near physiological pH. Further computational analysis yielded a better insight into understanding the possible amino acids responsible for Cu²⁺ binding with the iLOV protein.

• Journal of Sensor Science and Technology
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• v.32 no.5
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• pp.307-312
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• 2023

To measure the flow velocity and direction in the near field of an unmanned underwater vehicle, an optical measurement unit containing an image sensor and a phosphor-integrated pillar that mimics the neuromasts of a fish was constructed. To analyze pillar movement, which changes with fluid flow, fluorescence image analysis was conducted. To analyze the flow velocity, mean force analysis, which could determine the relationship between the light intensity of a fluorescence image and an external force, and length-force analysis, which could determine the distance between the center points of two fluorescence images, were employed. Additionally, angle analysis that can determine the angles at which pixels of a digital image change was selected to analyze the direction of fluid flow. The flow velocity analysis results showed a high correlation of 0.977 between the external force and the light intensity of the fluorescence image, and in the case of direction analysis, omnidirectional movement could be analyzed. Through this study, we confirmed the effectiveness of optical flow sensors equipped with phosphor-integrated pillars.

• Journal of Sensor Science and Technology
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• v.6 no.5
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• pp.362-368
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• 1997

The remote real-time uranium concentration analysis using nitrogen laser, optode, photomultiplier and optical fiber is studied. The optode for the remote collection of uranium fluorescence is designed. The fluorescence intensity at time zero is calculated in order to exclude the quenching effect and the temperature fluctuation and used for more precise estimation. The fluorescence change is very sensitive to the uranium concentration change. The method shows the detection limit of 0.06ppm and the linearity between 0.1ppm and 2ppm of the aqueous uranium concentration.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.12
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• pp.668-673
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• 2013

In this study, specimens with nano-sized porous thin films were manufactured by injecting fluorescence solution into the pores. We intended to find out the difference of the fluorescence intensity in each region of the specimen through an experimental apparatus that makes a temperature field. Before conducting experiments, the optimized manufacturing conditions were determined by analysis of all parameters that influence the emission intensity, and the experiments were carried out with the specimens produced in the optimized conditions. Then, the calibration curves of the fluorescence intensity versus temperature were performed by taking the intensity distributions from the specimen in various temperature fields. The surfaces of specimens were coated with Rhodamine-B (Rh-B) fluorescent dye and measured based on the fluorescence intensity. Silica (SiO2) nanoporous structure with 1-um thickness was constructed on a cover glass, and fluorescence dye was absorbed into these porous thin films.

• Analytical Science and Technology
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• v.8 no.3
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• pp.221-227
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• 1995

The fiber optic fluorosensor that shows a specific selectivity for calcium ion is studied. This sensor employs protein Calmodulin(CaM) which forms a fluorescent chelate with $Ca^{2+}$. A dialysis membrane is used to entrap a fluorescein isothiocyanate-labeled CaM solution at the common end of a bifurcated fiber optic bundle. The sensing mechanism of this sensor is based on the shifts in the fluorescence spectrum of metal-calmodulin complexes which FCaM forms a chelate with $Ca^{2+}$. Upon binding with $Ca^{2+}$, CaM undergoes a conformational change which induces a change in the fluorescence of FCaM. This change in fluorescence signal which is measured by photomultiflier tube is related to the concentration of $Ca^{2+}$ for calibration curve. Detection limit for $Ca^{2+}$ and the interference effects by $Mg^{2+}$, $Eu^{3+}$ and $La^{3+}$ for this sensor are studied. Response time and life time for this fluorosensor are also investigated.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2415-2418
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• 2008

Polydiacetylenes (PDAs) are very attractive chemical substances which have distinctive features of color change and fluorescence emission by thermal or chemical stress. Especially, when PDAs contact with solutions of a particular pH, such as a strong alkaline sodium hydroxide (NaOH) solution or a strong acidic hydrogen chloride (HCl) solution, PDAs change their color from non-fluorescent blue to fluorescent red. In this study, we propose a novel method to detect alkaline pH using PDAs and NaOH solutions by hydrodynamic focusing on a microfluidic chip. Preliminary results indicate that the fluorescent intensity of PDAs increases in respond to the NaOH solution concentrations. Also, the fluorescence is quenched back when the PDAs are in contact with a HCl solution. These results are useful in a microfluidic PDA sensor chip design for pH detection.