• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.2941-2948
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• 2011

A nanogap formed by a metal nanoparticle and a flat metal substrate is one kind of "hot site" for surface-enhanced Raman scattering (SERS). The characteristics of a typical nanogap formed by a planar Au and either an Au and Ag nanoparticle have been well studied using 4-aminobenzenethiol (4-ABT) as a probe. 4-ABT is, however, an unusual molecule in the sense that its SERS spectral feature is dependent not only on the kinds of SERS substrates but also on the measurement conditions; thus further characterization is required using other adsorbate molecules such as 1,4-phenylenediisocyanide (1,4-PDI). In fact, no Raman signal was observable when 1,4-PDI was selfassembled on a flat Au substrate, but a distinct spectrum was obtained when 60 nm-sized Au or Ag nanoparticles were adsorbed on the pendent -NC groups of 1,4-PDI. This is definitely due to the electromagnetic coupling between the localized surface plasmon of Au or Ag nanoparticle with the surface plasmon polariton of the planar Au substrate, allowing an intense electric field to be induced in the gap between them. A higher Raman signal was observed when Ag nanoparticles were attached to 1,4-PDI, irrespective of the excitation wavelength, and especially the highest Raman signal was measured at the 632.8 nm excitation (with the enhancement factor on the order of ${\sim}10^3$), followed by the excitation at 568 and 514.5 nm, in agreement with the finite-difference timedomain calculation. From a separate potential-dependent SERS study, the voltage applied to the planar Au appeared to be transmitted without loss to the Au or Ag nanoparticles, and from the study of the effect of volatile organics, the voltage transmission from Au or Ag nanoparticles to the planar Au also appeared as equally probable to that from the planar Au to the Au or Ag nanoparticles in a nanogap electrode. The response of the Au-Ag nanogap to the external stimuli was, however, not the same as that of the Au-Au nanogap.

• Composites Research
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• v.27 no.4
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• pp.146-151
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• 2014

In this study, the experimental study has been performed by varying the polarization of the electric field and impact force to check the piezoelectric characteristics of piezoelectric paint sensor. Piezoelectric paint sensor used in this study is composed of epoxy resin with a hardener and PNN-PZT powder in 1:1 weight ratio. The dimensions of the paint sensor specimen are $40{\times}40{\times}1mm^3$ and regular specimens were made using a mold. The voids are removed from the specimen in the vacuum desiccator. Both upper side and bottom side of the paint sensor were coated with silver paste for making an electrode and then dried at room temperature for a day. The poling treatment has been carried out under controlled conditions of the electric field in order to check the effect of piezoelectric sensitivities, while the poling temperature was fixed at room temperature and the poling time was set to 30 min. The piezoelectric sensitivities have been measured by comparing output voltage from paint sensor with output force from impact hammer when the impact hammer hits the paint sensor. In result, the effect of the electric field has been evaluated for the sensitivity and describe the result.

• Journal of Electrochemical Science and Technology
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• v.11 no.2
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• pp.172-179
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• 2020

The impact of effective parameters on the electrodeposition rate optimization of Au-Cu alloy at high thicknesses on the silver substrate was investigated in the present study. After ensuring the formation of gold alloy deposits with the desired and standard percentage of gold with the cartage of 18K and other standard karats that should be observed in the manufacturing of the gold and jewelry artifacts, comparing the rate of gold-copper deposition by direct and pulsed current was done. The rate of deposition with pulse current was significantly higher than direct current. In this process, the duty cycle parameter was effectively optimized by the "one factor at a time" method to achieve maximum deposition rate. Particular parameters in this work were direct and pulse current densities, bath temperature, concentration of gold and cyanide ions in electrolyte, pH, agitation and wetting agent additive. Scanning electron microscopy (SEM) and surface chemical analysis system (EDS) were used to study the effect of deposition on the cross-sections of the formed layers. The results revealed that the Au-Cu alloy layer formed with concentrations of 6gr·L^-1 Au, 55gr·L^-1 Cu, 24 gr·L^-1 KCN and 1 ml·L^-1 Lauryl dimethyl amine oxide (LDAO) in the 0.6 mA·cm^-2 average current density and 30% duty cycle, had 0.841 ㎛·min^-1 Which was the highest deposition rate. The use of electrodeposition of pure and alloy gold thick layers as a production method can reduce the use of gold metal in the production of hallow gold artifacts, create sophisticated and unique models, and diversify production by maintaining standard karats, hardness, thickness and mechanical strength. This will not only make the process economical, it will also provide significant added value to the gold artifacts. By pulsating of currents and increasing the duty cycle means reducing the pulse off-time, and if the pulse off-time becomes too short, the electric double layer would not have sufficient growth time, and its thickness decreases. These results show the effect of pulsed current on increasing the electrodeposition rate of Au-Cu alloy confirming the previous studies on the effect of pulsed current on increasing the deposition rate of Au-Cu alloy.

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.3
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• pp.42-51
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• 1981

Boron was predeposited into p (100) Si wafer at 94$0^{\circ}C$ for 60minutes to make the back surface field. High tempreature diffusion process at 1145$^{\circ}C$ for 3 hours was immediately followed without removing boron glass to obtain high surface concentration Back boron was annealed at 110$0^{\circ}C$ for 40minutes after boron glass was removed. N+ layer was formed by predepositing with POCI3 source at 90$0^{\circ}C$ for 7~15 minutes and annealed at 80$0^{\circ}C$ for 60min1es under dry Of ambient. The triple metal layers were made by evaporating Ti, Pd, Ag in that order onto front and back of diffused wafer to form the front grid and back electrode respectively. Silver was electroplated on front and back to increase the metal thickness form 1~2$\mu$m to 3~4$\mu$m and the metal electrodes are alloyed in N2 /H2 ambient at 55$0^{\circ}C$ and followed by silicon nitride antireflection film deposition process. Under artificial illumination of 100mW/$\textrm{cm}^2$ fabricated N+PP+ cells showed typically the open circuit voltage of 0.59V and short circuit current of 103 mA with fill factor of 0.80 from the whole cell area of 3.36$\textrm{cm}^2$. These numbers can be used to get the actual total area(active area) conversion efficiency of 14.4%(16.2%) which has been improved from the provious N+P cell with 11% total area efficiency by adding P+ back.

• Analytical Science and Technology
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• v.12 no.4
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• pp.290-298
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• 1999

A study on the application of impedance phase angle for redox titration, acid-base titration, chelate titration and precipitation titration has been carried out. A constant alternating current was passed between two platinum electrodes. One of them was a polarizable micro-electrode of $0.1cm^2$ or $0.026cm^2$ surface area and the other a non-polarizable large electrode of $1cm^2$ surface area dipped in the solution to be titrated. The impedance and the phase angle of the titration cell were measured with lock-in amplifier to obtain well behaved titration curve respectively. In titration of oxalic acid vs. potassium permanganate, the end-point was obtained successfully from the phase angle titration curve. In this experiment, the concentration of 0.0005 M to 0.05 M, the current of $50{\mu}A$ and the frequency of near 50 Hz were used. In titration of phosphoric acid vs. sodium hydroxide, the first end-point was obtained successfully on the optimum experimental condition of 0.001 M concentration, $50{\mu}A$ current and 25~97 Hz frequency. However, the end-point in titration of cupric sulfate vs. disodium-EDTA couldn't be obtained clearly. The end-point was obtained with the out-of-phase impedance curve on the experimental condition of 0.01 M concentration, $100{\mu}A$ current, 5~35 Hz frequency range. In titration of sodium chloride vs. silver nitrate, the end-point was obtained successfully on the experimental condition of 0.1 M concentration, $100{\mu}A$ current and 5~47 Hz frequency range. This study showed that the impedance phase angle was applicable for the detection of the end-points in redox titration curve, acid-base titration curve, chelate titration curve and precipitation titration curve.

• Science of Emotion and Sensibility
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• v.23 no.2
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• pp.51-60
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• 2020

This study aimed to develop a modular smart clothing system for heart rate monitoring that reduces the inconvenience caused by battery charging and the large size of measurement devices. The heart rate monitoring system was modularized into a temporary device and a continuous device to enable heart rate monitoring depending on the requirement. The temporary device with near-field communication (NFC) and heart rate sensors was developed as a clothing attachment type that enables heart rate monitoring via smart phone tagging when required. The continuous device is based on Bluetooth Low Energy (BLE) communication and batteries and was developed to enable continuous heart rate measurement via a direct connection to the temporary device. Furthermore, the temporary device was configured to connect with a textile electrode made of a silver-based knitted fabric designed to be located below the pectoralis major muscle for heart rate measurement. Considering the user-experience factors, key functions, and the ease of use, we developed an application to automatically log through smart phone tagging to improve usability. To evaluate the accuracy of the heart rate measurement, we recorded the heart rate of 10 healthy male subjects with a modular smart clothing system and compared the results with the heart rate values measured by the Polar RS800. Consequently, the average heart rate value measured by the temporary system was 85.37, while that measured by the reference device was 87.03, corresponding to an accuracy of 96.73%. No significant difference was found in comparison with the reference device (T value = -1.892, p = .091). Similarly, the average heart rate measured by the continuous system was 86.00, while that measured by the reference device was 86.97, corresponding to an accuracy of 97.16%. No significant difference was found in terms of the heart rate value between the two signals (T value = 1.089, p = .304). The significance of this study is to develop and validate a modular clothing system that can measure heart rates according to the purpose of the user. The developed modular smart clothing system for heart rate monitoring enables dual product planning by reducing the price increase due to unnecessary functions.

• Science of Emotion and Sensibility
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• v.26 no.3
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• pp.149-160
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• 2023

This study develops a time-varying system-based noncontact fabric sensor that can measure cerebral blood-flow signals to explore the possibility of brain blood-signal detection and emotional evaluation. The textile sensor was implemented as a coil-type sensor by combining 30 silver threads of 40 deniers and then embroidering it with the computer machine. For the cerebral blood-flow measurement experiment, subjects were asked to attach a coil-type sensor to the carotid artery area, wear an electrocardiogram (ECG) electrode and a respiration (RSP) measurement belt. In addition, Doppler ultrasonography was performed using an ultrasonic diagnostic device to measure the speed of blood flow. The subject was asked to wear Meta Quest 2, measure the blood-flow change signal when viewing the manipulated image visual stimulus, and fill out an emotional-evaluation questionnaire. The measurement results show that the textile-sensor-measured signal also changes with a change in the blood-flow rate signal measured using the Doppler ultrasonography. These findings verify that the cerebral blood-flow signal can be measured using a coil-type textile sensor. In addition, the HRV extracted from ECG and PLL signals (textile sensor signals) are calculated and compared for emotional evaluation. The comparison results show that for the change in the ratio because of the activation of the sympathetic and parasympathetic nervous systems due to visual stimulation, the values calculated using the textile sensor and ECG signals tend to be similar. In conclusion, a the proposed time-varying system-based coil-type textile sensor can be used to study changes in the cerebral blood flow and monitor emotions.