• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.256-257
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• 2005

We fabricated self-assembled monolayers(SAMs) onto quartz crystal microbalance(QCM) using viologen, which has been widely used as electron acceptor and electron transfer mediator. The viologen derivative exist in three redox states, namely. These redox reactions are highly reversible and can be cycled many times without significant side reactions, respectively. We studied the characteristics of charge transfer using different electrolyte solutions by electrochemical quartz crystal microbalance (EQCM). From the data, the redox peak currents were nearly equal charges during redox reaction and existed to an excellent linear interrelation between the scan rates and first redox peak currents. The redox reactions of viologen were highly reversible and the EQCM has been employed to monitor the electrochemically induced adsorption of SAMs during the redox reactions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.10
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• pp.820-825
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• 1998

We deposited stearic acid LB films by using Langmuir-Blodgett (LB)method and investigated anisotropy electrical conduction characteristics by I-V measurement for horizontal direction and vertical direction. Also, we measured gad response between deposited LB films and organic gas for various temperature(0~8$0^{\circ}C$) by 9MHz At-cut quartz crystal microbalance. The LB films have electrical conduction characteristics such as semiconducting and insulating properties. The is, the conductivity of LB films for the horizontal and vertical direction is about 10\ulcornerS/cm and 10\ulcorners/cm, respectively. the frequency shift of stearic acid LB films for the organic gases depended on the mass change by the surface adsorption and the inner penetration to the sensing films. The resonant frequency shift of the quartz crystal microbalance for temperature properties of LB films is thought to the effect of the rearrangement or the damage pf LB films above the melting point and the mobility increasement of the organic gas by the temperature rising.

• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.267-272
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• 1999

We attached a fiber tip on the branch of a quartz crystal oscillator in order to make a feedback control system for near field optical microscope. The electrical impedance of the quartz crystal oscillator depends on the distance between the surface of the sample and the tip caused by the surface damping. Using this method, we can directly monitor the distance between the sample and the tip without inserting extra beam which might give extra optical noise. We characterize the XY scanning resolution and the amplitude of the vibrating tip and the Z-dependent decay of the evanescent wave.

• KSBB Journal
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• v.15 no.5
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• pp.497-500
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• 2000

Liposomes and proteoliposomes, artificial membranes, can interact with many solutes, such as drugs, peptides and proteins. The immobilization of (prot대)liposomes as supramolecular aggregates on gold surfaces have potential applications in nano and biosensor technology. We demonstrated a quartz crystal analyzer (QCA) based method to monitor the construction of multi-layers of unilamellar liposomes based on avidin-biotin binding on gold surfaces using a quartz crystal microbalance (QCM). Thus, the QCA provides an on line and efficient method of detecting the construction of protein membranes, which has applications in biosensing systems.

• Journal of Sensor Science and Technology
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• v.17 no.5
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• pp.380-386
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• 2008

Quartz crystal microbalance immunosensor has a capacity to perform a label-free and real time detection of a trace amount of analyte through the specific interaction between antibody and antigen. However, immobilization of antibody molecules on the sensor surface is a troublesome procedure for researchers who are not experienced in chemistry. Protein G has a specific affinity to antibody and would serve as a capturing agent for antibody when immobilized on the sensor surface. In this work, we prepared a protein G sensor chip by immobilizing protein G on the surface of quartz crystal microbalance and examined its capability to detect human haptoglobin or human transferrin with unpurified corresponding antiserum. Specific and dose dependent response was observed when the protein G chip was used for detection of antigens after saturated with antiserum. We also verified several advantageous aspects of the protein G chip such as improved flexibility and sensitivity.

• Journal of Sensor Science and Technology
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• v.32 no.3
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• pp.147-153
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• 2023

Metal-organic frameworks (MOFs) of cobalt gallate were synthesized and deposited on gold electrodes using self-assembly monolayers (SAMs) and hydrothermal processing. These MOF films exhibit strong adsorption capabilities for gaseous particulates, and the use of SAMs allows the synthesis and deposition processes to be completed in a single step. When cobalt gallate is mixed with SAMs, a coordination bond is formed between the cobalt ion and the carboxylate or hydroxyl groups of the SAMs, particularly under hydrothermal conditions. Additionally, the quartz crystal microbalance (QCM) gas sensor accurately measures the number of particulates adsorbed on the MOF films in real-time. Thus, the QCM gas sensor is a valuable tool for quantitatively measuring gases, such as SO₂, NO₂, and CO₂. Furthermore, the QCM MOF film gas sensor was more effective for gas adsorption than the MOF particles alone and allowed the accurate modeling of gas adsorption. Moreover, the QCM MOF films accurately detect the adsorption-desorption mechanisms of SO₂ and NO₂, which exist as gaseous particulate matter, at specific gas concentrations.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.3
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• pp.238-244
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• 1994

We investigated solution growth of silicon on borosilicate and quartz glass substrates in the temperature range of $800^{\circ}C~520^{\circ}C$. A thin Al-Si layer evaporated onto the substrate serves to improve the wetting between the substrate and the Al/Ga solvent. Nucleation takes place by a reaction of Al with $SiO_2$ from the substrate. We obtained silicon deposits with a grain size up to a few 100 $\mu\textrm{m}$. There was a perferential (111) orientation for the case of quartz glass substrates while there is a strong contribution of other orientations for the deposition of Si on borosilicate glass substrates.

• Journal of the Korean Ceramic Society
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• v.29 no.12
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• pp.981-989
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• 1992

This is a study on the effects of cristobalite transition of quartz in semi-vitrious whiteware body, as addition of alkali and alkali earth oxides, prepared by pottery stone, feldspar, kaolin and clay minerals. The amounts of ${\alpha}$-quartz to ${\alpha}$-cristobalite transition, F.O.C. (fraction of cristobalite), were increased with firing temperature. In MgO added body, ${\alpha}$-quartz was decreased and the formation of cristobalite was increased. Effects of K2O addition was remarkably decreased the formation of cristobalite. Additive effects of MgO and K2O were confirmed that it was very different to variation of transition temperature of metakaolinite to Si-Al spinel structure in thermal reaction of kaolinite minerals. Result CaO addition was ineffective to transition temperature, and the transition temperature in Na2O added body was decreased, but relative intensity of quartz and cristobalite crystal in XRD results was decreased. This was characterized by the effects on the formation of liquid phase much more.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.11a
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• pp.73.2-77
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• 2000

A possibility of the implementation of a quartz crystal sensor to the detennination of chemical oxygen demand is examined by checking the electrochemical behavior of the sensor in a glucose solution. Since the surface of a quartz crystal has to be oxidized, a relatively active metal is coated on the surface of a usual 9 MHz AT-cut crystal. The electrochemical behavior is investigated by measuring the changes of current, resonant frequency and resonant resistance while a constant potential is applied. The crystal is installed in a specially designed container, and a QUartz crystal analyzer is utilized to measure the frequency and resistance simultaneously. The variations of the measurements are examined at different concentrations of glucose solution and the effect of the concentration is analyzed to find a proper relation between the concentration and the measurements. It is fOlmd that a linear relation between the concentration of less than 900 Dpm and the peak current when a constant potential of -180 m V vs. Ag/ AgCI reference is applied.

• Resources Recycling
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• v.29 no.1
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• pp.25-34
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• 2020

Electrochemical Quartz Crystal microbalance is a tool that is capable of measuring nanogram-scale mass change on electrode surface. When applying alternating voltage to the quartz crystal with metal electrode formed on both sides, a resonant frequency by inverse piezoelectric effect depends on its thickness. The resonant frequency changes sensitively by mass change on its electrode surface; frequency increase with metal dissolution and decrease with metal deposition on the electrode surface. The relationship between resonant frequency and mass change is shown by Sauerbrey equation so that the mass change during metal dissolution can be measured in real time. Especially, it is effective in the case of reaction mechanism and rate studies accompanied by precipitation, volatilization, compound formation, etc. resulting in difficulties on ex-situ AA or ICP analysis. However, it should be carefully considered during EQCM experiments that temperature, viscosity, and hydraulic pressure of solution, and stress and surface roughness can affect on the resonant frequency. Application of EQCM was shown as a case study on leaching of platinum using aqueous chlorine for obtaining activation energy. A platinum electrode of quartz crystal oscillator with 1000 Å thickness exposed to solution was used as leaching sample. Electrogenerated chlorine as oxidant was purged and its concentration was controlled in hydrochloric acid solution. From the experimental results, platinum dissolution by chlorine is chemical reaction control with activation energy of 83.5 kJ/mol.