JPS6353460A - Organic semiconductor gas sensor element - Google Patents

Abstract

PURPOSE:To obtain a sensor element excellent in resistance to oxidation and chemical resistance, by providing an electrode on a molding comprising a non- soluble non-melting substrate with a specified skelton structure as obtained by thermally treating a condensate of an aromatic hydrocarbon compound having a phenolic hydroxide group and aldehyde. CONSTITUTION:A molding 1 is formed which comprises a non-soluble non- melting substrate having a polyacene-based skelton structure with atomic ratio of 0.6-0.15 in hydrogen atom/carbon atom as obtained thermally treating an aromatic condensation polymer as condensate of an aromatic hydrocarbon compound having a phenolic hydroxide group and aldehyde. A gold evaporated film 2 is deposited on the molding 1 with a vacuum evaporating machine and a copper wire 3 adheres to the evaporation surface thereof by a silver conductive paste 4 to mount at least two electrodes. Thus, a gas sensor element can be obtained superior in resistance to oxidation and chemical resistance.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an organic semiconductor gas sensor element, and more particularly to an aromatic gas sensor element that is a condensation product of an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde. The present invention relates to an organic semiconductor gas sensor element that exhibits a sensor function through changes in electrical conductivity caused by adsorption and desorption of polar gas using a heat-treated polymer.

[Conventional technology] Polymer materials have excellent moldability, light weight, and safety.

Therefore, by taking advantage of these properties of polymer materials, organic polymer materials that have electrical semiconductivity are desired in many industrial fields including the electronics industry. Early organic semiconductors were difficult to form into films or plates, and their uses were limited. In recent years, organic semiconductors with relatively excellent moldability, typified by polyacetylene, have become available. However, polyacetylene has the drawback of being easily oxidized by oxygen. For this reason, it is difficult to handle in the air and lacks practicality as an industrial material.

In addition, Japanese Patent Application Laid-Open No. 58-13 filed by the same applicant as the present application
Publication No. 6649 describes a heat-treated aromatic condensation polymer consisting of carbon, hydrogen and oxygen, which contains an insoluble and infusible polyacene skeleton structure with an atomic ratio of hydrogen atoms/carbon atoms of 0.6 to 0.15. A sexual substrate is disclosed. The above-mentioned insoluble and infusible substrate has excellent heat resistance and oxidation resistance. However, there is no description of an organic semiconductor gas sensor element using the above-mentioned insoluble and infusible substrate.

Also, JP-A-60-15 filed by the same applicant as the present application.
No. 2554 discloses a heat-treated aromatic condensation polymer consisting of carbon, hydrogen and oxygen, which has an atomic ratio of hydrogen atoms/carbon atoms of 0.60 to 0.15, and has a specific surface area value determined by the BET method. An insoluble and infusible substrate containing a boriacene skeleton having an area of 600 m2/1 or more is disclosed.

However, the specification of this prior application does not mention anything about an organic semiconductor gas sensor element using the above-mentioned insoluble and infusible substrate.

In addition, an earlier patent application filed in 1986 by the same applicant as the present application
No. 58803 is still unpublished, but in the same earlier application, it is a heat-treated product of an aromatic condensation polymer consisting of carbon, hydrogen and oxygen, and the atomic ratio of hydrogen atoms / carbon atoms is 0.
．． It has a boriacene skeleton structure of 6 to 0.05, and B
Specific surface area value by ET method is at least 600 m2/I
As described above, a porous organic semiconductor having communicating pores with an average pore diameter of 10 μm or less has been proposed. The specification of this prior application also mentions a sensor material as one of the uses of the porous organic semiconductor, but does not describe any specific example regarding an organic semiconductor gas sensor element.

On the other hand, as society becomes more advanced in advanced technology, various sensors are becoming increasingly important both socially and industrially. Since the proposal of gas sensors using oxide semiconductor elements such as tin oxide and zinc oxide, gas sensor elements using various inorganic materials such as porous ceramics have been developed and are used in many industrial fields and homes. There is. Gas sensors using organic substances are also being developed, and humidity sensors using hygroscopic polymers are already in use, but they have many drawbacks. For example, it has been pointed out that the humidity sensor described above tends to deteriorate due to moisture absorption due to moisture absorption and shrinkage due to dehumidification.

However, an organic semiconductor gas sensor element with excellent oxidation resistance and chemical resistance has not yet been developed, despite the great social need in today's biotechnology era.

[Problem that the invention attempts to solve]

An object of the present invention is to provide an organic semiconductor gas sensor element.

Another object of the present invention is to provide an organic semiconductor gas sensor element with excellent oxidation resistance and chemical resistance (ζ).

Still another object of the present invention is to adsorb and desorb gas molecules.
An object of the present invention is to provide an organic semiconductor gas sensor element that utilizes the fact that electrical conductivity changes with ζ.

Still another object of the present invention is to provide an organic semiconductor gas sensor element in the form of a film, plate, cylinder, or the like.

Still another object of the present invention is to provide an organic semiconductor gas sensor element that is capable of repeatedly adsorbing and desorbing gas molecules and is stable against repeated adsorption and desorption.

Further objects and advantages of the present invention will become apparent from the description below.

According to the present invention, the above-mentioned objects and advantages of the present invention are a heat-treated product of an aromatic condensation polymer which is a combination of an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde, and which has a hydrogen atom/carbon atom ratio. Atomic ratio is 0.6-0.1
This is achieved by an organic semiconductor gas sensor element characterized in that a molded body 1ζ consisting of an insoluble and infusible substrate having a polyacene skeleton structure as shown in No. 5 is attached with at least two electrodes.

The aromatic condensation polymer in the present invention is a condensate of a hydrocarbon compound having a phenolic hydroxyl group and an aldehyde. Preferred are, but are not limited to, phenols, where X and y are each independently 0.1 or 2.

It can be methylene-bisphenols represented by the following, or it can also be hydroxy-biphenyls or hydroxynaphthalenes. Among these, phenols, particularly phenol, are practically preferred.

The aromatic condensation polymer in the present invention further includes one of aromatic hydrocarbon compounds having a phenolic hydroxyl group.
It is also possible to use a modified aromatic polymer in which part of the polymer is substituted with an aromatic hydrocarbon compound having no phenolic hydroxyl group, such as xylene, toluene, etc., such as a modified aromatic polymer that is a condensation product of phenol, xylene, and formaldehyde. can.

Also, as an aldehyde, if only formaldehyde is used,
Although other aldehydes such as acetaldehyde and furfural can also be used, formaldehyde is preferred. The phenol-formaldehyde condensate may be a novolac type, a resol type, or a composite thereof.

The organic semiconductor gas sensor element of the present invention utilizes a heat-treated aromatic condensation polymer as described above, and can be manufactured, for example, as follows.

An initial condensate of an aromatic hydrocarbon metal compound having a phenolic hydroxyl group or an aromatic hydrocarbon compound having a phenolic hydroxyl group, an aromatic hydrocarbon compound having no phenolic hydroxyl group, and aldehydes is prepared, and this initial condensate is prepared. is poured into a suitable mold, heated to a temperature of, for example, 50 to 200°C, and cured and converted into a film-like or cylindrical form within the mold, and then this cured product is placed in a non-oxidizing atmosphere. Heat to a temperature of 350 to 800°C (including vacuum), preferably 400 to 700°C.

The preferred rate of temperature increase during heat treatment varies somewhat depending on the aromatic polymer used, the degree of curing treatment, its shape, etc., but in general, a relatively high rate of temperature increase should be used from room temperature to a temperature of about 300°C. is possible,
For example, a rate of 100° C./hour is also possible.

When the temperature reaches 300°C or higher, the aromatic condensation polymer starts to thermally decompose, producing water vapor (H2O), hydrogen, methane,
- It is advantageous to raise the temperature at a sufficiently slow rate, since gases such as carbon oxides begin to evolve.

Heating and heat treatment of the aromatic polymer are performed in a non-oxidizing atmosphere. Examples of the non-oxidizing atmosphere include nitrogen, argon, helium, neon, carbon dioxide, etc., and nitrogen is preferably used.

Such a non-oxidizing atmosphere does not have a round shape whether it is stationary or flowing.

Thus, by the above-mentioned heating and heat treatment, a molded body made of an insoluble and infusible substrate used in the organic semiconductor gas sensor element of the present invention can be obtained, but it can also be produced in the following manner.

An aqueous solution containing the above-mentioned initial condensate and an inorganic salt is prepared, and this aqueous solution is poured into a suitable mold. Next, while suppressing the evaporation of water, the aqueous solution is poured into a film-like or cylindrical shape in the mold. The cured body is then heated to a temperature of 350' to 800°C in a non-oxidizing atmosphere, and the resulting heat-treated body is washed to remove inorganic salts contained in the heat-treated body. do.

The above-mentioned inorganic salt used together with the initial condensate is removed in a later step and is a pore-forming agent used to provide communicating pores to the cured product, such as zinc chloride, sodium phosphate, potassium hydroxide, or potassium sulfide. be. Among these, zinc chloride is preferably used. The inorganic salt can be used in an amount of, for example, 2.5 to 10 times the weight of the initial condensate. The aqueous solution of the initial condensate and the inorganic salt can be cleaved using, for example, water in an amount of 0.1 to 1 times the weight of the inorganic salt, although it varies depending on the type of inorganic salt used. The aqueous solution is then poured into a suitable mold and heated to a temperature of, for example, 50 to 200°C. During this heating, it is important to suppress evaporation of water in the aqueous solution.

That is, in an aqueous solution, the initial condensate is heated and gradually hardens, turning into salt! It is thought that communicating pores develop while separating lead and water, and a three-dimensional network structure grows.

- The thus obtained cured product is heat-treated by heating to a temperature of 350 to 700°C, preferably 400 to 600°C, in a non-oxidizing atmosphere (including a vacuum state) in the same manner as in the above-mentioned method. By sufficiently washing the obtained heat-treated body with water or dilute hydrochloric acid, the inorganic salts contained in the heat-treated body can be removed, and when it is then dried, it becomes a porous insoluble material with developed communicating pores and a large specific surface area. An infusible substrate can be obtained.

(Thus, by the method described above or below, it has a polyacene skeleton structure with an atomic ratio of hydrogen atoms / carbon atoms of 0.6 to 0.15, or in addition to this, an average pore diameter of 10 μm.
It has the following communicating holes, for example, communicating holes of 0.03 to 10 Itm, and has a specific surface area ratio of 600782 by BET method.
/1 or more, a molded body made of an insoluble and infusible substrate used in the organic semiconductor gas sensor element of the present invention is obtained.

The atomic ratio of hydrogen atoms/carbon atoms of the insoluble and infusible substrate is 0.
If it exceeds 6, the electrical conductivity is low and lacks practicality, and if it exceeds 0,
If it is less than 15, the increase in electrical conductivity due to gas adsorption is undesirable.

The molded article has excellent heat resistance, oxidation resistance, and chemical resistance.

In addition, the atomic ratio of oxygen atoms/carbon atoms is usually 0.06 or less,
Preferably it is 0.03 or less. Also, X-ray diffraction (CuK
2), the position of the main beak is expressed in 2θ as 2
It exists between 0.5 and 28.5 degrees, and in addition to the main peak, there is a broad peak between 41 and 46 degrees.

That is, it is understood that the above-mentioned molded article is one in which the polycyclic structure of poly7cene-based benzene is evenly and appropriately developed between polyacene-based molecules.

The molded article made of the insoluble and infusible substrate of the present invention is in the form of a film,
Although it is molded into a plate shape or a cylindrical shape, it is preferable to mold it into a film shape, and the thickness of this film is 0.01 to 500 μm, preferably 0.0 μm.
It is 1 to 10 μm.

The organic semiconductor gas sensor element of the present invention has at least two or more electrodes attached to a molded body made of the insoluble and infusible substrate. This electrode can be made of, for example, gold, platinum, copper, silver,
It may be attached using a method such as vapor deposition with a conductive metal such as aluminum, or it may be attached by applying a conductive paste such as silver or carbon. It is preferable to attach it. By attaching such an electrode, the electrical conductivity of the molded body can be directly measured.

The thus obtained organic semiconductor gas sensor element of the present invention is sensitive to polar gases by utilizing the fact that the electrical conductivity increases due to the adsorption of polar gases. A polar gas is a gas having a hyperbolic moment due to its molecular structure, and includes, for example, water vapor, alcohol gas such as methanol gas, acetone gas, and carbon oxide gas. When the organic semiconductor gas sensor element of the present invention is placed in the polar gas atmosphere and the polar gas is adsorbed, the electrical conductivity is, for example, 2 to 10.
,000 times, and then when the polar gas is desorbed, the electrical conductivity decreases to the value before adsorption of the polar gas. It is also possible to repeat adsorption and desorption of the polar gas,
The organic semiconductor gas sensor element of the present invention is extremely stable without deterioration even after repeated repetitions of this process. Furthermore, since the organic semiconductor gas sensor element of the present invention has electrical conductivity that changes depending on the concentration of the polar gas, it is also possible to sense the concentration of the polar gas.

In particular, by including an inorganic salt in the initial condensate, it has a large number of communicating pores and a specific surface area value of 600 m by the BET method.
The organic semiconductor gas sensor element of the present invention using a molded body made of an insoluble and infusible substrate of 2/g or more is capable of adsorbing a large amount of the polar gas and is sensitive to even a trace amount of gas. be able to.

As described above, the organic semiconductor gas sensor element of the present invention has excellent heat resistance, oxidation resistance, and chemical resistance, and its electrical conductivity changes in accordance with the adsorption and desorption of polar gases, and furthermore, the organic semiconductor gas sensor element of the present invention has excellent heat resistance, oxidation resistance, and chemical resistance. This is a good gas sensor element that does not deteriorate due to repeated use.

Example 1 (1) Methanol-soluble resol (approximately 60% concentration)
was deposited on a glass plate using a film applicator for approximately 15 minutes.
It was cured by heating at a temperature of 0° C. for 1 hour.

The phenolic resin was cut into pieces of 2 cm x 1 cm, then placed in a silicone electric furnace, heated at a rate of 40°C/hour under a nitrogen stream, and heat-treated to 600°C to form an insoluble film. A fusible substrate was obtained. The thickness of the film is 10 μm, and the electrical conductivity is 4 at room temperature.
When measured by the terminal method, it was 10-8 (0 cm)'. Further, elemental analysis revealed that the atomic ratio of hydrogen atoms/carbon atoms was 0.35. The shape of the peak from X-ray diffraction is a pattern based on the polyacene skeleton structure2.
A broad main peak was observed around 20 to 22 degrees, and a small peak was observed around 41 to 46 degrees.

By depositing gold on the film using a vacuum evaporation machine and bonding copper wire to the deposited surface with silver conductive paste! The poles were removed to obtain organic semiconductor gas sensor elements shown in FIGS. 1 and 2.

(2) Next, the organic semiconductor gas sensor element was placed in a gas atmosphere shown in Table 1, and its electrical conductivity was measured at room temperature. The results are summarized in Table 1 Iζ.

After that, when the gas atmosphere surrounding the organic semiconductor gas sensor element was removed, the electrical conductivity returned to the value before adsorption. The above operation was repeated 10 times, but the results were the same from the first to the 10th time.

Table 1 Example 2 (1) Water bath property An aqueous solution containing a mixture of resol (approximately 60% concentration)/subsalt chloride/water at a ratio of 10725/4 was formed into a film on a glass plate using a film applicator. Next, a glass plate was placed over the formed aqueous solution to prevent moisture from evaporating; the film was then heated at a temperature of about 100° C. for 1 hour to harden it.

The phenol tiA'A6 film is 2cm x 1cm.
After cutting, the plates were placed in a siliconite electric furnace and heated at a rate of 40° C./hour under a nitrogen stream to the predetermined temperature shown in Table 2 for heat treatment. Next, the heat-treated product was washed with dilute hydrochloric acid, then water, and then dried to obtain a film-like porous body. The thickness of the film is 5
The specific surface area value determined by the BET method was approximately 2000 m2/g/ at any heat treatment temperature. The measurement results of elemental analysis are summarized in Table 2.

Electrodes were attached in the same manner as in Example 1 to obtain a film-like organic semiconductor gas sensor element.

(2) Next, the organic semiconductor gas sensor element was placed in a water vapor atmosphere and its electrical conductivity was measured at room temperature.

The results are summarized in Table 2. After that, when the water vapor atmosphere in the organic semiconductor gas sensor element was removed, the electrical conductivity returned to the value before adsorption.

The above operation was repeated 10 times, all with the same result.

@Table 2 Example 3 A film-like organic semiconductor gas sensor element obtained in the same manner as in Example 2, No. 1, was placed in the gas atmosphere shown in Table @3, and its electrical conductivity was measured at room temperature.

The results are summarized in Table 3. When the gas atmosphere around the hindlimb organic semiconductor gas sensor element was removed, the electrical conductivity returned to the value before adsorption.

The above operation was repeated 10 times, all with the same result.

Table 3

[Brief explanation of the drawing]

FIG. 1 is a side view of an organic semiconductor gas sensor element according to an embodiment of the present invention, and FIG. 2 is a plan view thereof.
(2) is a molded body made of an insoluble and infusible substrate, (2) is a gold vapor-deposited film,
(3) represents a copper wire, and (4) represents a silver conductive paste. \1-also】′+

Claims (6)

[Claims] (1) A heat-treated product of an aromatic condensation polymer that is a condensation product of an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde, the atomic ratio of hydrogen atoms/carbon atoms being 0.
．． An organic semiconductor gas sensor element comprising at least two electrodes attached to a molded body made of an insoluble and infusible substrate having a polyacene skeleton structure having a molecular weight of 6 to 0.15. (2) The organic semiconductor gas sensor element according to claim 1, wherein the aromatic polymer is a condensate of phenol and formaldehyde. (3) The organic semiconductor gas sensor element according to claim 1, wherein the insoluble and infusible substrate has communicating pores with an average pore diameter of 10 μm or less. (4) The specific surface area value of the insoluble and infusible substrate by the BET method is 6.
Claim 1 which is 00 to 3000cm^2/g
The organic semiconductor gas sensor element described in . (5) Oxygen atom (O)/carbon atom (C
The organic semiconductor gas sensor element according to claim 1, having a polyacene-based skeleton structure in which the atomic ratio of ) is 0.06 or less. (6) The organic semiconductor gas sensor element according to claim 1, wherein the insoluble and infusible substrate exhibits a three-dimensional network structure through a large number of communicating holes.