• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3625-3628
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• 2012

Fluorescent organic molecules that respond to changes in the $Fe^{2+}$ concentration with selectivity to other abundant di-valent metal ions will offer the ability to understand the dynamic fluctuations of the $Fe^{2+}$ ion in interesting media. The use of 6-Br-ppmbi, derived from 2-pyridin-2-yl-benzimidazole, for metal ion-selective fluorescence recognition was investigated. Screening of the main group and transition metal ions showed exclusive selectivity for $Fe^{2+}$ ions even in the presence of competing metal ions. In addition, the requirement for low concentrations of probe molecules to detect certain amounts of $Fe^{2+}$ ions make this sensor unique compared to previously reported $Fe^{2+}$ ion sensors.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3703-3706
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• 2010

Biomolecules specific to explosives can be exploited as chemical sensors. Peptides specific to immobilized dinitrotoluene (DNT) were identified using a phage display library. A derivative of DNT that contained an extended amine group, 4-(2,4-dinitrophenyl)butan-1-amine, was synthesized and immobilized using a self-assembled monolayer surface on gold. Filamentous M13 phages displaying random sequences of 12-mer peptides specific to the immobilized DNT-derivate were isolated from the M13 phage library by biopanning. A common peptide sequence was identified from the isolated phages and the synthesized peptides showed selective binding to DNT. When the peptide was immobilized on a quartz crystal microbalance (QCM) chip, it showed a binding signal to DNT, while toluene barely showed significant binding to the QCM chip. These results demonstrate that peptides screened by biopanning against immobilized DNT can be useful for quick and accurate detection of DNT.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.32-37
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• 2008

For a development of U-safety system, liquid/gas-sensors that are easy to carry and install in any place are needed. Therefore, in this work, we prepared porous gold using a templating method with nanoporous alumina, and it was used as sensing materials and electrode. The resulting materials showed high purity macroporous structure with $200{\sim}300\;nm$ of window-pore and $4.8\;m^2/g$ of surface area. Because porous gold had good electric conductivity, convenience to measure the change of electric resistivity and good reproducibility, it could be used as potential sensing materials. As a proof-of-concept test, the detection test for mercury ion was carried out.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.115-122
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• 2016

Melanin is a common name used for a certain type of natural dark pigments existing in living organisms, particularly in human hair, eyes, and skin. The unique free radical scavenging effect of melanine could help protecting cells and tissues from harmful UV light. While their exact molecular structures in nature are not still well defined, their multifunctional properties including electrical and ionic conductivities, antioxidation, wet adhesion, and metal ion chelation, are highlighted for the potential applications in bioorganic electronics including biomedical sensors and devices. In this mini-review, we will discuss sources, synthesis methods, structures and multifunctional properties of melanin materials in addition to current research directions on a wide range of applications.

• Current Optics and Photonics
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• v.1 no.1
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• pp.12-16
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• 2017

Color sensor systems based on M13 bacteriophage are being considerably researched. Although many studies on M13 bacteriophage-based chemical sensing of TNT, endocrine disrupting chemicals, and antibiotics have been undertaken, the fundamental physical and chemical properties of M13 bacteriophage-based nanostructures require further research. A simple M13 bacteriophage-based colorimetric sensor was fabricated by a simple pulling technique, and M13 bacteriophage was genetically engineered using a phage display technique to exhibit a negatively charged surface. Arrays of structurally and genetically modified M13 bacteriophage that can determine the polarity indexes of various alcohols were found. In this research, an M13 bacteriophage-based color sensor was used to detect various types of alcohols, including methanol, ethanol, and methanol/butanol mixtures, in order to investigate the polarity-related property of the sensor. Studies of the fundamental chemical sensing properties of M13 bacteriophage-based nanostructures should result in wider applications of M13 bacteriophage-based colorimetric sensors.

• Journal of Sensor Science and Technology
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• v.31 no.2
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• pp.115-119
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• 2022

A readout circuit for a mercury-cadmium-telluride (MCT)-amplified mid-wave infrared (IR) photodetector was realized and applied to noncontact chemical agent detectors based on a quantum cascade laser (QCL). The QCL emitted 250 times for each wavelength in 0.2-㎛ steps from 8 to 12 ㎛ with a frequency of 100 kHz and duty ratio of 10%. Because of the nonconstant QCL emission power during on-duty, averaging the photodetector signals is essential. Averaging can be performed in digital back-end processing through a high-speed analog-to-digital converter (ADC) or in analog front-end processing through an integrator circuit. In addition, it should be considered that the 250 IR data points should be completely transferred to a PC during each wavelength tuning period of the QCL. To average and minimize the IR data, we designed a readout circuit using the analog front-end processing method. The proposed readout circuit consisted of a switched-capacitor integrator, voltage level shifter, relatively low-speed analog-to-digital converter, and micro-control unit. We confirmed that the MCT photodetector signal according to the QCL source can be accurately read and transferred to the PC without omissions.

• Journal of Sensor Science and Technology
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• v.33 no.2
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• pp.70-77
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• 2024

In this study, a fluorescent ethanol sensor is developed to determine the ethanol concentration in the liquid phase. The sensor is developed using a complex of resazurin (RA)/resorufin (RO) and a hydrotalcite (HT) catalyst in a sol-gel matrix of methyltrimethoxysilane (MTMS) to produce a fluorescent ethanol-sensing membrane (RA/RO^*HT membrane). The operation mechanism of the RA/RO^*HT membrane is based on (i) the oxidation of ethanol to acetaldehyde and (ii) the reduction of RA to RO, through electron flows followed by EtOH ↔ HT ↔ RA/RO ↔ EtOH interactions. These possible redox reactions can lead to an increased fluorescence intensity of the RA/RO^*HT membrane as the ethanol concentration increases. The RA/RO^*HT membrane shows a linear detection range of 1-20 vol.% EtOH with limit of detection (LOD) of 0.178%. Additionally, the RA/RO^*HT membrane has high sensitivity and accuracy for determining the alcohol content in several Korean alcoholic beverages.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.348-351
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• 2011

In this research, we developed a sensor system which can easily detect several chelating agents using polydiacetylene(PDA) vesicles. In comparison to other sensors, PDA based sensor has several advantages. First, detection method is much simpler and faster because it does not require any labeling step in the experiment procedure. Second, significant color-transition from blue to red based upon external stimulus allows us the detection by naked eyes. Finally, it is also possible to perform quantitative analysis of the concentration of the chelating agent by measuring the colorimetric response. In this paper, five types of chelating agents were used, including EDTA, EGTA, NTA, DCTA and DTPA. Among them, EDTA and DCTA triggered especially strong color-transition. In conclusion, this study has led to a successful development of a color transition-based PDA sensor system for easy and rapid detection of chelating agents.

• Journal of Sensor Science and Technology
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• v.3 no.2
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• pp.33-39
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• 1994

A quartz crystal microbalance (QCM) sensor system for the detection of odorants, especially environmental pollutant, has been constructed by depositing various phospholipids, activated carbon and lead compound pigment onto the surface of the QCM. The characteristics of a QCM operating at 9 MHz deposited with phosphatidyl- choline were analysed. An explanation is given for different odorant affinities based on the monolayer properties of phospholipids. The identification of odorants is discussed in terms of a comparison of their normalized resonant frequency shift patterns and relative response intensities calculated from the response areas. Applying the lead compound pigment coated QCM, it was possible to detect sulfur compound specifically. Using a number of different lipid-coated QCMs, odorants could be identified by comparing the response patterns.

• Journal of the Korean Applied Science and Technology
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• v.21 no.4
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• pp.345-351
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• 2004

Highly ordered pure-silica MCM-41 materials possessing well-defined morphology have been successfully prepared with surfactant used as a template. The fabrication of mesoporous silica has received considerable attention due to the need to develop more efficient materials' for catalysis, separations, and chemical sensing. The surface modified MCM-41 was used as anadsorbent for biomolecules. Silica-supported organic groups and DNA adsorption on surface modified MCM-41 were investigated by FT-IR and UV-Vis spectrometer, respectively. The use of MCM-41 as the modification of electrode surfaces were investigated electrochemical properties of metal mediators with biomolecules. The modified ITO electrodes increased peak currents for a redox process of $[Ru(bpy)_3]^{2+}$ relative to the bare electrode. The electrochemical detection of DNA by cyclic voltammetry when the current is saturated in the presence of the mediator appeared more sensitive due to a higher catalytic current on the MCM-41 supported electrodes modified by carboxylic acid functional groups. The carboxyl or amine groups on the surface of MCM-41 interact and react with the $-NH_2$ groups of guanine and backbone, respectively. Highly ordered mesoporous materials with organic groups could find applications as DNA sensors.