• Textile Coloration and Finishing
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• v.25 no.1
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• pp.13-17
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• 2013

A new assembly derived from 2,3-dibromo-5,6,7,8-tetrafluoroquinizarin and sodium diethyl-carbamodithiolate, was prepared as an efficient $Fe^{3+}$ colorimetric chemosensor with high selectivity over other cations $Fe^{3+}$, $Na^+$, $Mg^{2+}$, $Pb^{2+}$, $Cd^{2+}$, $Ni^{2+}$, $Ca^{2+}$, $Cu^{2+}$, $Hg^{2+}$, $Zn^{2+}$ : from the dark blue to brown color change that is visible by eyes. This assembly produced large bathochromic shift of 228 nm in the presence of $Fe^{3+}$ compared with the corresponding absorption maximum of the parent dye.

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.118.3-118
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• 1998

• Journal of Sensor Science and Technology
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• v.17 no.3
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• pp.203-209
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• 2008

Thick film formaldehyde (HCHO) gas sensors were fabricated by using $La_1_{-x}Sr_xMO_3$ (M= Fe, Co, Mn) ceramics. The powders of $La_1_{-x}Sr_xMO_3$ (M=Fe, Co, Mn) were synthesized by conventional solid-state reaction method. By using the $La_1_{-x}Sr_xMO_3$ (M=Fe, Co, Mn) paste, the thick-film formaldehyde sensors were prepared on the alumina substrate by silkscreen printing method. The experimental results revealed that $La_1_{-x}Sr_xMO_3$ (M= Fe, Co, Mn) ceramic powder has a perovskite structure and the thick-film sensor shows excellent gas-sensing characteristics to formaldehyde gas (sensitivity of $La_{0.8}Sr_{0.2}FeO_3$, S= 14.7 at operating temperature of $150^{\circ}C$ in 50 ppm HCHO ambient).

• Carbon letters
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• v.23
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• pp.38-47
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• 2017

In this study, magnetite ($Fe_3O_4$) nanoparticles were electrochemically synthesized in an aqueous electrolyte at a given potential of -1.3 V for 180 s. Scanning electron microscopy revealed that dendrite-like $Fe_3O_4$ nanoparticles with a mean size of < 80 nm were electrodeposited on a glassy carbon electrode (GCE). The $Fe_3O_4/GCE$ was utilized for sensing chloramphenicol (CAP) by cyclic voltammetry and square wave voltammetry. A reduction peak of CAP at the $Fe_3O_4/GCE$ was observed at 0.62 V, whereas the uncoated GCE exhibited a very small response compared to that of the $Fe_3O_4/GCE$. The electrocatalytic ability of $Fe_3O_4$ was mainly attributed to the formation of Fe(VI) during the anodic scan, and its reduction to Fe(III) on the cathodic scan facilitated the sensing of CAP. The effects of pH and scan rate were measured to determine the optimum conditions at which the $Fe_3O_4/GCE$ exhibited the highest sensitivity with a lower detection limit. The reduction current for CAP was proportional to its concentration under optimized conditions in a range of $0.09-47{\mu}M$ with a correlation coefficient of 0.9919 and a limit of detection of $0.09{\mu}M$ (S/N=3). Moreover, the fabricated sensor exhibited anti-interference ability towards 4-nitrophenol, thiamphenicol, and 4-nitrobenzamide. The developed electrochemical sensor is a cost effective, reliable, and straightforward approach for the electrochemical determination of CAP in real time applications.

• Journal of Sensor Science and Technology
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• v.30 no.4
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• pp.210-217
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• 2021

Gas sensors based on semiconducting metal oxides have attracted considerable attention for various applications owing to their facile, cheap, and small-scale manufacturing processes. Hematite (α-Fe₂O₃) is widely considered as a promising candidate for a gas-sensing material owing to not only its abundance in the earth's crust and low price but also its chemical stability and suitable bandgap energy. However, only a few studies have been performed in this direction because of the low gas response and sluggish response of hematite-based gas sensors. Nanostructures present a representative solution to both overcome these disadvantages and exploit the desirable features to produce high-performance gas sensors. However, several challenges remain for adopting gas sensors based on metal oxide nanostructures, such as improving cost efficiency and facilitating mass production. This review summarizes the recent studies on gas sensors based on hematite nanostructures. It also provides useful insights into various strategies for enhancing the gas-sensing properties of gas sensors based on hematite nanostructures.

• Polymer(Korea)
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• v.35 no.5
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• pp.375-377
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• 2011

$PbTiO_3$/P(VDF/TrFE) 0~3 composites thin films with 0.10 and 0.13 of ceramic volume fraction factor have been fabricated by two-step spin coating technique and analyzed. 0~3 connectivity of $PbTiO_3$/P(VDF/TrFE) composites film was observed successfully by SEM micrography. The SEM picture confirmed 0~3 connectivity. And, in all the properties, 0~3 $PbTiO_3$/P(VDF/TrFE) composites film was superior to P(VDF/TrFE) copolymer. Therefore, with a good low-dielectric constant and a high pyroelectric coefficient, the composite thin films can be used for a new pyroelectric infrared sensor of higher performance.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.19-24
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• 1999

$In_2O_3$-based thick films for the ozone detection of ppb range have been investigated. The $In_2O_3$ sensing layer is quite sensitive to ozone, but the saturated stable sensitivity cannot be obtained at the ozone exposure of 100 ppb for 5 min. The addition of $Fe_2O_3$ into $In_2O_3$ indicates some improvement in response time and sensitivity, but it seems the improvement is not good enough for real applications. Firing of $In_2O_3$:$Fe_2O_3$ powder induces remarkable improvement in response and recovery, although the sensitivity decrease. The sensing layer fired at $1300^{\circ}C$ and operated $550^{\circ}C$ shows excellent properties of fast response time, saturated stable sensitivity and rapid recovery characteristics to 100 ppb ozone exposure for 5 min. Especially, it shows the reproducibility of the sensor signal for repeated measurements and the linearity between the ozone concentration and the sensor resistance. The preliminary results clearly demonstrated that the sensor can be successfully applied for the ozone detection of ppb range.

• Journal of Magnetics
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• v.5 no.2
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• pp.44-49
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• 2000

Computer simulation of sensing current effects on the magnetic and magnetoresistance properties of a crossed spin-valve head is carried out. The spin-valve head has the following layer structure: Ta (8.0 nm)/NiMn (25 nm)/NiFe (2.5 nm)/Cu (3.0 nm)/NiFe (5.5 nm)/Ta (3.0 nm), and it is 1500 nm long and 600 nm wide. Even with a high pinning field of 300 Oe and a high hard-biased field of 50 Oe, the ideal crossed spin-valve structure, which is essential to the symmetry of the output signal and hence high density recording, is not realized mainly due to large interlayer magnetostatic interactions. This problem is solved by applying a suitable magnitude of sensing currents along the length direction generating magnetic fields in the width direction. The ideal spin-valve head is expected to show good symmetry of the output signal. This has not been shown explicitly in the present simulation, however, The reason for this is possibly related to the simple assumption used in this calculation that each magnetic layer consists of a single domain.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.474-479
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• 1993

An interferometric fiber-optic magnetic field sensor is constructed by bonding a Co-Fe-B metallic glass transducer developed here by the melt-spun method to a single mode fiber arm in the fiber Mach-Zehnder interferometer and is tested. The bias field for the peak ac-sensitivity was observed near 0.97 Oe and the minimum detectable magnetic field was 3.9${\times}10^{-5}$ Oe(rms)/${\sqrt{Hz}}$ a 3 kHz. The output of the ac field sensor becomes saturated near the input signal level of 1 Oe(rms). The Co- Fe-B transducer exhibits peak response near 500 Hz.

• Electrical & Electronic Materials
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• v.4 no.1
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• pp.31-37
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• 1991

습도센서용 기판으로 사용하기 위한 MgFe$_{2}$O$_{4}$ 세라믹스의 성능개선을 위하여 Li$_{2}$CO$_{3}$와 V$_{2}$O$_{5}$를 첨가한 MgFe$_{2}$O$_{4}$-LiMgVO$_{4}$ 세라믹스를 만들고, 기공율, 기공분포, 센서특성, 응답속도 등을 조사하여 다음의 결과를 얻었다. 기공율은 MgFe$_{2}$O$_{4}$ 세라믹스가 29[%]에서 34[%]인데 비하여 본 연구결과는 34.5[%]에서 39[%]로 증가하였으며 센서특성은 $10^{7}$ [.OMEGA.] 단위의 변화에서 $10^{7}$ [.OMEGA.]에서 $10^{6}$[.OMEGA.] 단위로 변화함을 알수 있었고 응답속도는 10초정도 빨라졌음을 알수 있었다. 또한 기공분포를 이용하여 모형 센서를 제안하여 시뮬레이션을 하고 실제 특성과 이론적인 특성을 비교하였다.