JP3447210B2 - Quartz resonator for chemical substance measurement and chemical substance detection device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal oscillator with a carbon film for detecting the concentration of chemical substances in a gas and a liquid, and a chemical substance detecting device using the same.

[0002]

2. Description of the Related Art Conventionally, a gas sensor using a semiconductor sensor has been widely used as a gas sensor.
At present, it is not perfect in terms of selectivity, response speed, and recovery time after response. On the other hand, the detection method using a crystal oscillator has been developed because the sensitive film can be variously changed and can be used not only in the gas phase but also in the liquid. In particular, it has been reported that selectivity can be obtained for gas types by using multiple quartz oscillators coated with different types of lipid membranes. However, there was a problem that it was affected by the concentration of water vapor. On the other hand, by using a quartz oscillator formed with an organic thin film also as an electrochemical analyzer, the chemical substance in the solution can be changed by the relationship between the resonance frequency change and the surface potential change, and the relationship between the resonance frequency change and the current change accompanying potential scanning. A method for obtaining the concentration of is also proposed.

In chemical measurement using such a crystal unit, an organic thin film is often used as a sensitive film for covering the surface of the crystal unit. In addition to this, a carbon thin film having excellent adsorption characteristics is used. It is possible to form. But,
The carbon thin film formed by the sputtering method or the like has a poor stability as a film and is not sufficiently stable at the present time.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a carbon film-covered crystal oscillator which can be stably used for measurement in the field of chemical measurement, can obtain a highly sensitive response, and can be manufactured at low cost, and The object is to provide a chemical substance detection device using this crystal oscillator.

[0005]

In order to solve the above-mentioned problems, the present inventors have found that an amorphous carbonized thin film has good adhesion by sintering an organic material on the electrodes of a quartz oscillator. The inventors have found that they can be obtained and have devised a crystal oscillator for chemical substance measurement according to the present invention. This amorphous carbon thin film is obtained by coating a quartz crystal resonator with a thin film of an organic substance that leaves amorphous non-graphitizable carbon when fired in an inert atmosphere in advance.
It can be obtained by sintering.

Furthermore, by dispersing carbon powder in the amorphous carbon film of the carbon film-covered crystal resonator of the present invention, it has become possible to enhance the sensitivity and selectivity to chemical substances. As the crystal oscillator of the present invention, a Y-plate crystal oscillator having a shear vibration mode is suitable. In this case, metal electrodes are formed on both sides of the crystal plate, and a carbon thin film is further formed on the metal electrodes. The carbon thin film can be formed on both surfaces of the electrode or only on one surface. This Y
The plate crystal unit naturally includes a unit whose cut angle is slightly deviated from the Y plate in consideration of temperature characteristics such as AT cut and BT cut.

By forming the amorphous carbon film of the present invention to have a thickness of 0.1 to 10 μm, the resonance resistance can be suppressed to a sufficiently small value, and a quartz vibration with a carbon film having a stable resonance frequency is achieved. You can get a child. A crystal resonator having an amorphous carbon film formed by sintering on an electrode configured as described above, and a resonance frequency measuring device for measuring the change in the resonance frequency can provide a stable and highly sensitive response. Realized a chemical substance detection device. Furthermore, by constructing this chemical substance detection device with a plurality of crystal oscillators having amorphous carbon films containing different types of carbon powder and corresponding resonance frequency measuring devices, the carbon film-covered crystal vibration devices We constructed a chemical substance detection device that can identify the type of chemical substance based on the difference in response sensitivity of the child to various gas components.

Next, an electrochemical analyzer including a quartz oscillator having an amorphous carbon film formed by sintering on an electrode, a resonance frequency measuring device, and an electrochemical measuring device was realized.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings. FIG. 1 is a cross-sectional view of a crystal oscillator with a carbon film of the present invention, in which electrodes 2 are formed on both surfaces of an AT-cut crystal plate 1, and a lead wire 3 is connected to the electrode 2. Has been done. Then, the amorphous carbon film 4 is formed on the electrode 2. This amorphous carbon thin film can be obtained by coating a quartz oscillator with a thin film of an organic substance that leaves amorphous non-graphitizable carbon when fired in an inert atmosphere in advance, and then sintering it. it can. The properties of this amorphous carbon film differ depending on the type of the organic material used as the raw material. For example, when a chlorinated vinyl chloride resin or furan resin is used, a glassy carbon film can be formed. The thickness of this amorphous carbon film is 0.1 to 10 μm.
By forming it between m, the resonance resistance of the crystal resonator can be suppressed sufficiently small, and a carbon-coated crystal resonator having a stable resonance frequency can be obtained.

Further, as shown in FIG. 2, graphite powder 5 such as carbon black, fullerene, graphite whiskers, and graphite fine particles is dispersed in the amorphous carbon film 4 of the carbon film-covered crystal resonator of the present invention. It is possible to configure a carbon film-covered crystal unit having enhanced sensitivity and selectivity to chemical substances. The firing temperature can be selected in the range of 160 to 1600 ° C., and the adsorption property of the carbon film can be changed by changing the firing temperature. The firing temperature must be lower than the melting point of the electrode material or crystal. It is also possible to use the carbon film also as an electrode for driving the crystal oscillator without separately providing the electrode.

FIG. 3 shows a quartz resonator 6 having an amorphous carbon film formed by sintering on the electrode constructed as described above, and a resonance frequency measuring device 7 for measuring changes in the resonance frequency thereof. Thus, the chemical substance detection device can be configured. The result of having measured the alcohol gas concentration using this apparatus is shown in FIG. This result is obtained by fixing the crystal resonator 6 with amorphous carbon in the chamber 8 and alternately introducing alcohol gas and nitrogen gas to measure the resonance frequency of the crystal resonator. The response curves in FIG. 4 show the response to 8 ppm methanol, ethanol, propanol and recovery with nitrogen gas, respectively.
It can be seen that both the response after gas introduction and the recovery by nitrogen gas introduction have a fast response speed. For this measurement, a crystal oscillator with an amorphous carbon film heat-treated at 400 ° C. was used, but the sensitivity to various gases can be changed by changing the heat treatment temperature and the type of carbon powder. Further, in this measurement example, the result in the gas phase was shown,
Observation in liquid is also possible.

Further, as shown in FIG. 5, a plurality of crystal oscillators 6 each having an amorphous carbon film containing a carbon powder of a different kind, and a resonance frequency measuring device 7 corresponding to each of them.
Furthermore, the data processing device 9 can constitute a chemical substance detection device that can identify the type of chemical substance based on the difference in response sensitivity of each carbon film-coated crystal unit to various gas components.

Next, FIG. 6 shows the structure of an electrochemical analysis device composed of a crystal resonator 6 with an amorphous carbon film formed on an electrode by sintering, a resonance frequency measuring device 7, and an electrochemical measuring device 10. . The configuration of the electrochemical analyzer of FIG. 6 is such that the carbon film of the crystal resonator 6 with the amorphous carbon film is in contact with the solution 11 and the electrode on the opposite side is insulated from the solution 11. And held by cell 13,
It is held in the solution 11 stored in the container 16 together with the reference electrode 14 and the counter electrode 15. The crystal resonator 6 with the amorphous carbon film is connected to the resonance frequency measuring device 7, and the electrode on the side in contact with the solution with the carbon film is the working electrode, together with the reference electrode 14 and the counter electrode 15, and electrochemically. It is connected to the measuring device 10. Further, the resonance frequency measuring device 7 and the electrochemical measuring device 10 are connected to the data processing device 9.

With this electrochemical analyzer, the concentration of the chemical substance in the solution can be determined by measuring the relationship between the resonance frequency change and the surface potential change and the relationship between the resonance frequency change and the current change accompanying the potential scanning. .

[0015]

According to the present invention, it is possible to realize a carbon film-covered crystal oscillator capable of stably measuring a chemical substance with high sensitivity. By mixing the carbon powder into the amorphous carbon film, it was possible to achieve high sensitivity and selectivity.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a crystal resonator with a carbon film of the present invention.

FIG. 2 is a schematic sectional view of a crystal resonator with a carbon film of the present invention.

FIG. 3 is a block diagram of a chemical substance detection device of the present invention.

FIG. 4 is a diagram showing a measurement example of the chemical substance detection device of the present invention.

FIG. 5 is a block diagram of a chemical substance detection device of the present invention.

FIG. 6 is a block diagram of a chemical substance detection device using the electrochemical measurement device of the present invention.

[Explanation of symbols]

1 AT cut crystal plate 2 electrodes 3 lead wire 4 Amorphous carbon film 5 Graphite powder 6 Crystal oscillator 7 Resonance frequency measuring device 8 chambers 9 Data processing device 10 Electrochemical measuring device 11 solutions 12 O-ring 13 cells 14 Reference electrode 15 opposite poles 16 containers

─────────────────────────────────────────────────── ─── Continuation of front page (72) Kind of inventor ▲ People ▼ 1-8 Nakase, Mihama-ku, Chiba, Chiba Seiko Instruments Inc. (72) Inventor Yoshihisa Suda 5-23, Higashioi, Shinagawa-ku, Tokyo No. 37 Sanritsu Pencil Co., Ltd. (56) Reference JP-A-9-89740 (JP, A) JP-A-6-343018 (JP, A) JP-A-6-265459 (JP, A) JP-A-5 -312707 (JP, A) JP-A-4-347586 (JP, A) E.I. B. D. Bourdon, RH Prince, W.M. D. Moris on, R.M. C. Tennyson, Real-Time monitor for thin etching in atomic oxyenvironments, SURFACE & COATINGS TECHNOLOGY Y, March 15, 1992, Vol. 52 No. 1, p. 51-56 (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 5/02 JISST file (JOIS)

Claims (7)

(57) [Claims] [Claim 1] possess an amorphous carbon film is sintered formed on the electrode of the crystal oscillator, including graphite powder in the amorphous carbon film
A crystal oscillator for measuring chemical substances characterized by the following. 2. The crystal oscillator for chemical substance measurement according to claim 1, wherein the crystal oscillator is a Y-plate crystal oscillator. 3. A metal electrode is provided on both sides of the crystal unit.
The crystal oscillator for chemical substance measurement according to claim 2 , wherein a carbon film is provided only on one surface of the crystal resonator. 4. The thickness of the amorphous carbon film is 0.1 μm
The crystal oscillator for chemical substance measurement according to claim 1 , wherein the crystal oscillator is 10 μm or less. 5. A sinter formed on at least the electrode.
Crystal oscillator with an amorphous carbon film containing graphite powder, resonance
A chemical substance detection device composed of a frequency measurement device . 6. At least at least different types of black
A plurality of the quartz oscillator and its having an amorphous carbon film containing lead powder
The chemical substance detection device according to claim 5, which is configured by a resonance frequency measurement device corresponding to each of them . 7. A black layer formed by sintering on an electrode, at least.
A chemical substance detection device including a crystal oscillator having an amorphous carbon film containing lead powder , a resonance frequency measurement device , and an electrochemical measurement device.