KR100859768B1 - Measurement apparatus and method for impedance and changing mass - Google Patents

Abstract

A method and an apparatus for measuring impedance and a mass variation are provided to accurately measure the mass variation on a surface of an electrode in nanogram scales by using an electrochemical cell to minimize interferences. An apparatus for measuring impedance and a mass variation includes an electrochemical cell(30), a high speed impedance measuring unit(10), a crystal vibration scale unit(20), and a controller. The high speed impedance measuring unit measures the impedance of an electrochemical solution, which is electrically connected to the electrochemical cell. The crystal vibration scale unit is electrically connected to the electrochemical cell and reads a variation in a frequency according to a mass variation of a working electrode of the high speed impedance measuring unit. The controller processes the data read from the high speed impedance measuring unit and the crystal vibration scale unit and displays the processed result.

Description

{Measurement apparatus and method for impedance and changing mass}

1 is a plan view of an embodiment according to the present invention.

2 is a cross-sectional view of an electrochemical cell according to the present invention.

3 is an exemplary view of a high speed impedance process according to the present invention.

4 is a diagram according to the system application of the present invention.

The present invention relates to a high-speed impedance and mass change measuring device, and more particularly, the electrochemical cell having a structure that minimizes the occurrence of interference during the electrochemical reaction, the surface change of the working electrode on the impedance during the electrochemical reaction occurs The present invention relates to a compound measuring device capable of measuring the effect in real time and measuring the mass change on the surface of the electrode with a precision of nanogram (ng).

In some crystals, such as quartz and rochelle salt, mechanical stress on the crystal surface generates an electric field proportional to the magnitude of the stress. This phenomenon is called the piezoelectric effect. Conversely, applying an electric field to these crystals, including crystals, creates mechanical stress, which is called the reverse piezoelectric effect. The crystals that cause the piezoelectric effect have something in common: they belong to the group of centroasymmetry. These anisotropic crystals have a polar axis direction due to dipoles by atoms arranged in the crystal lattice. Therefore, mechanical stress on these crystals results in displacement of the atoms, resulting in charges due to the shift of the dipoles. The electric charge generated when stressing a crystal varies with dipole orientation and crystal plane. The Quartz Crystal Microbalance (QCM) is based on the fact that when an alternating electric field is applied to the crystal, the crystal is subjected to periodic physical forces, causing vibrations in the crystal. If the electrodes are coated with metal on both sides and AC voltage is applied to them, the oscillation is caused by the resonance frequency of the crystal. If the weight change of the electrode comes, the resonance frequency changes to detect the weight change occurring at the electrode. In addition, when one of the metal electrodes in contact with the crystal is used as a working electrode of an electrochemical cell, the change of the resonance frequency according to the potential change of the working electrode is measured. The weight change corresponding to the generated electrode reaction can be seen.

The reactor mechanism for these phenomena can be determined by determining the dissolution of a substance at the electrode, the change in surface morphology, and the change in weight of the membrane resulting from chemical reactions, including redox reactions. Until the 1970s, crystals were not known to vibrate in solution due to viscosity effects. However, Konash, Bastiaans, Nomura et al. Have expanded their applicability with the publication of research using quartz crystal microbalances (QCM) to measure the mass change of crystal surface in solution.

Electrochemical quartz crystal microbalance (QCM) using a quartz crystal microbalance (QCM) for electrochemistry began to be used as a working electrode by coating a quartz crystal surface with metal. The balance (EQCM) has been used for various studies such as deposition, desorption, dissolution, mass transfer of polymers on the electrode surface, or substrate concentration measurement using enzymatic reaction. On the quartz crystal, in addition to gold (Au), various metals such as aluminum (Al), chromium (Cr), copper (Cu), and silver (Ag) can be deposited. Because of the electric field applied along the direction of the polar axis, shearing deformation occurs due to the tendency to rearrange the polarity, which is proportional to the applied electric field. This deformation is elastic, and the staggering deformation occurs in the opposite direction as the electric field changes direction. If an alternating current voltage is applied to the crystal, a twisting strain that is equilibrium with the crystal plane occurs repeatedly, which depends on the crystal symmetry, the direction and magnitude of the electric field, and the angle at which the crystal is cut. Different. Thus, this staggering deformation occurs only for the crystal cut in any particular direction.

Apart from the quartz crystal balance, in general, the impedance measurement measures the impedance of the electrolyte solution at high speed at each frequency by applying all frequency components having the same amplitude and phase to the electrolyte solution at the same time. The method of measuring impedance through mass transfer and electron transfer has been common. However, the measurement of the impedance is difficult to measure the mass change of the electrode surface, and at the same time, it is difficult to measure the effect of the high-speed impedance and the surface change of the working electrode on the impedance in real time. Using a scale device, an apparatus for measuring the change in electrochemical impedance at high speed and at the same time measuring the change in mass of the electrode surface was intended.

The present invention has been made to solve the above problems, an object of the present invention is to provide an electrochemical cell of a structure that minimizes the occurrence of interference during the electrochemical reaction surface change of the working electrode in the process of the electrochemical reaction occurs The present invention provides a multimeter capable of measuring the effect on impedance in real time and measuring the change of mass on the surface of the electrode with nanogram (ng) precision.

The present invention for solving the above technical problem, the electrochemical cell unit (electrochemical cell) that the electrochemical reaction occurs; A high-speed impedance measurement unit capable of measuring impedance of an electrochemical solution electrically connected to the electrochemical cell unit; A quartz oscillation device electrically connected to the electrochemical cell unit for reading a change in frequency according to a mass change of a working electrode of the high speed impedance measuring unit; And a control device for processing and displaying data read from the high speed impedance measuring unit and the quartz crystal balance device. It provides a high-speed impedance and mass change composite measuring device, characterized in that it comprises a high-speed measurement of the electrochemical impedance change at the same time, and at the same time it is possible to measure the mass change of the electrode surface using an electrochemical quartz oscillation balance.

In addition, the electrochemical cell unit, the passive oscillator electrode provided on both sides of the crystal oscillator in the crystal oscillation balance device; An RF oscillator sensor coupled to a side of a quartz crystal of the quartz crystal balance; And fastening means for fixing both sides of the crystal oscillator, thereby providing a high-speed impedance and mass change composite measuring device to minimize the interference caused by the high-speed impedance measurement and the crystal vibration scale being connected together. It is possible to provide an electrochemical cell of the optimal structure.

In addition, the present invention is characterized in that the crystal oscillation device is a high-speed impedance and mass change characterized in that it comprises a frequency meter for measuring the change in frequency occurring on the crystal oscillator electrode and an RF oscillator for measuring the signal of the RF Oscillator sensor It provides a compound measuring device to increase the efficiency of mass measurement.

In addition, the present invention can stabilize the vibration of the crystal oscillator by providing a high-speed impedance and mass change composite measuring device, characterized in that the fixing means is an O-ring (O-Ring) that can fix both sides of the crystal oscillator Make sure

In addition, the present invention is electrically connected to the electrochemical cell unit and the high-speed impedance measuring unit and the electrochemical cell unit for measuring the impedance of the electrochemical solution (electrochemical cell) and the electrochemical solution that is electrically connected to the electrochemical cell unit in which the electrochemical reaction occurs And a crystal oscillation scale device for reading a change in frequency according to the mass change of the working electrode of the high speed impedance measurer, and a control device for processing and displaying data read from the high speed impedance measurer and the crystal oscillation scale device. Using a measuring device, by providing a high-speed impedance and mass change composite measurement method characterized in that the impedance measured by the high-speed impedance measurement unit and the mass value measured by the quartz crystal vibration scale device independently provided by the electrochemical reaction In the process, surface change of working electrode Beating effect measured in real time and at the same time to determine the amount of change in mass at an accuracy of nano-grams.

In addition, the present invention, the impedance measured by the high-speed impedance measurement unit,

Measuring current data; Fitting the current data;

Fourier transforming the fitted current data value; And forming a frequency spectrum through the Fourier-transformed measurement value, thereby providing a high-speed impedance and mass change complex measurement method, which reduces errors caused by filtering current and reduces noise generated at high frequencies. Make it work.

Hereinafter, with reference to the accompanying Figures 2 and 3 will be described the configuration and operation of the present invention.

The present invention relates to an apparatus for measuring electrochemical impedance changes at high speed and at the same time measuring electrode surface mass changes using an electrochemical crystal oscillator (EQCM).

The configuration of the present invention comprises a high-speed impedance measurement device 10 and a crystal oscillation balance device 20 which is bonded to the electrochemical cell unit and the electrochemical cell unit 30 in which the electrochemical reaction takes place.

In particular, the high-speed impedance measuring apparatus generates a DC voltage which is a reaction voltage between the step voltage and the electrolytic solution according to a predetermined control signal, and applies the signal voltage generated at the portion outputting the DC voltage to the electrolytic solution at a high speed and stable signal voltage. Potentiostat 13 (Potentiostat), the reference electrode 16 for checking whether the signal electrode applied to the signal voltage applied from the electrostatic crisis and the reference electrode 16 that is correctly applied to the electrolytic solution of the signal voltage, applied from the counter electrode And a working electrode for measuring a current flowing through the electrolytic solution according to the signal voltage, and a current / voltage converter 12 for converting the current flowing from the working electrode into a voltage.

In particular, the crystal oscillation balance device is configured to stably oscillate the crystal oscillator and to read the frequency according to the mass change of the working electrode and includes a frequency counter 14 and an oscillator 15. .

Referring to FIG. 3, the electrochemical cell unit 30 has a high-speed impedance measurement device 10 and a crystal vibration balance device bonded thereto, and a crystal crystal 33 that is a crystal oscillator inside the crystal vibration balance device (Quartz Crystal). ).

Looking at the operation of the present invention through the above configuration, both sides of the crystal oscillator, which is a component forming the electrochemical cell portion of the present invention is coated with metal to make electrodes, according to the signal of the input voltage to oscillate the vibration of the crystal resonance frequency As the frequency of the crystal oscillator changes according to the weight change of the electrode, the change in mass occurring in the electrode can be detected.

In particular, the electrochemical impedance is measured by processing a signal obtained by applying a small and small potential signal (less than 20 mV) of less than several tens of milliseconds (ms) to the electrochemical cell, and measuring the electrochemical impedance from the frequency change measured using the electrochemical crystal oscillator. The change in mass at the surface of one electrode is measured simultaneously.

Since the above two signals are obtained from the same electrode, one (high-impedance) signal is very fast and the other is a low-speed signal (frequency measurement for mass change). Therefore, interference between signals should be minimized. In order to minimize the occurrence of interference during the electrochemical reaction, the system is designed to operate the signal applying system and the data collecting device independently.

There are two kinds of voltages applied to the crystal oscillator electrode formed in the electrochemical cell 30. An alternating voltage is applied to the first crystal oscillator 33 and the crystal oscillator vibrates with a natural frequency (9-10 MHz). Second, the electrochemically active potential is injected into the crystal oscillator electrode and a small step potential (5-20mV) is injected after a certain time. These two types of voltages act as noises to each other. In order to minimize this, the electrochemically occurring electrode faces 34 are tied to a common ground of two potentials. This has the effect that the alternating voltage applied to the other side is separated from the electrochemical side. In particular, in the present invention, in order to stabilize the vibration of the crystal oscillator, it is preferable to minimize contact of other materials by fixing both sides of the crystal oscillator with an O-ring 32.

The high-speed impedance and mass change composite measuring device is formed so that the mass measurement and the impedance measurement can be independently collected in operation and data in separate devices. Specifically, the mass measurement data is obtained one data per second, the impedance measurement is formed to obtain 8000 data in 80 milliseconds. In order to obtain both data at the same time, it is essential to configure the device independently, and in particular, in order to minimize the occurrence of interference during the electrochemical reaction in measuring both data, the electrochemical cell having the above-described structure is formed. .

Referring to Figure 3 will be described the process of the high-speed impedance according to the present invention.

In the impedance data processing, the conventional data processing processes the data in the manner of current data-> derivative-> Fourier transform-> frequency spectrum. However, in order to solve the problem that the noise is severely changed at high frequency when the data is Fourier changed, the signal filtering is performed in the conventional method. However, the signal distortion generated during the filtering process of the signal acted as a factor to increase the error.

Therefore, in the system according to the present invention, the data was processed in the process of current data-> current data fitting-> derivative-> Fourier transform-> frequency spectrum. Impedance data processing was performed by fitting current data to reduce noise. Referring to (a) to (c) of FIG. 3 as an example, (a) represents fitting the current data, and (b) is a graph of the derivative of the fitting current value. , (c) is a graph in which a spectrum of frequencies is formed using the processed data. As described above, the high-speed impedance data processing according to the present invention has an advantage of lowering noise generation and error rate by fitting current data.

Figure 4 is a real-time observation of the formation process of the self-assembled monomolecular film using the high-speed impedance and mass change composite measuring device of the present invention (a) is a graph showing the change in the frequency of the crystal oscillator according to the adsorption process in accordance with the mass change (B) It is a graph showing the frequency spectrum according to the adsorption process. The present invention has the advantage of measuring the effect of the surface change of the working electrode on the impedance in the process of the electrochemical reaction in real time and at the same time observe the amount of mass change with nanogram (ng) precision. In particular, such a composite measuring device and method is a real-time observation of the formation process of the self-assembled monomolecular film, real-time simultaneous measurement of the impedance and mass change in the Nafion thin film used in fuel cells, charge-mass change between the electrochemical reaction in the thin film and Impedance changes can be measured and are particularly useful for observing reactions in chemical systems with low reproducibility.

In the detailed description of the invention as described above, specific embodiments have been described. However, various modifications are possible within the scope of the present invention without departing from the scope of the present invention. The technical idea of the present invention should not be limited to the described embodiments of the present invention. It must be decided by one thing.

According to the present invention, an electrochemical cell having a structure that minimizes the occurrence of interference during an electrochemical reaction is capable of measuring in real time the effect of the surface change of the working electrode on the impedance during the electrochemical reaction and at the electrode surface. There is an effect that can measure the mass change with the precision of nanogram (ng).

Claims (6)

An electrochemical cell unit in which an electrochemical reaction occurs; A high-speed impedance measurement unit capable of measuring impedance of an electrochemical solution electrically connected to the electrochemical cell unit; A crystal oscillation balance device electrically connected to the electrochemical cell unit for reading a change in frequency according to a mass change of a working electrode of the high speed impedance measuring unit; And A control device for processing and displaying data read from the high-speed impedance measurement unit and the quartz crystal balance device; High-speed impedance and mass change composite measuring device comprising a. The method according to claim 1, The electrochemical cell unit,  Passive oscillator electrodes provided on both sides of the crystal oscillator in the crystal oscillation balance device; An RF oscillator sensor coupled to a side of a quartz crystal of the quartz crystal balance; And Fixing means for fixing both sides of the crystal oscillator; High-speed impedance and mass change composite measuring device comprising a. The method according to claim 2, The quartz crystal balance device includes a high frequency impedance measuring device for measuring a change in frequency occurring on the crystal oscillator electrode and an oscillator for measuring a signal of the RF oscillator sensor. Change composite measuring device. The method according to claim 3, The fastening means is a high-impedance and mass change composite measuring device, characterized in that the O-ring (O-Ring) that can fix both sides of the crystal oscillator. A high-speed impedance measurement unit capable of measuring the impedance of an electrochemical cell unit in which an electrochemical reaction occurs and an electrochemical solution electrically connected to the electrochemical cell unit, and the high-speed impedance measurement by being electrically connected to the electrochemical cell unit Using a complex measuring device including a crystal vibration scale device for reading a change in frequency according to the mass change of the negative working electrode, and a high speed impedance measurement unit and a control device for processing and displaying data read from the quartz vibration scale device So, A high-impedance impedance and mass change complex measurement method, characterized in that for measuring the impedance measured by the high-speed impedance measuring unit and the mass value measured by the crystal oscillation scale device independently. The method according to claim 5, The impedance measured by the fast impedance measuring unit is Measuring current data; Fitting the current data; Fourier transforming the fitted current data value; And Forming a frequency spectrum using the Fourier transformed measurement value; High-speed impedance and mass change composite measurement method comprising a.

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