WO2019172251A1

WO2019172251A1 - Chemical sensor element, method for producing chemical sensor element, and chemical sensor

Info

Publication number: WO2019172251A1
Application number: PCT/JP2019/008624
Authority: WO
Inventors: 裕喜雄竹中; 岩田　昇
Original assignee: シャープ株式会社
Priority date: 2018-03-06
Filing date: 2019-03-05
Publication date: 2019-09-12
Also published as: JP2021073433A

Abstract

A chemical sensor element including a detection material which retains satisfactory detection sensitivity to gases to be detected and is less influenced by the adsorption of water vapor. The detection material comprises a siloxane compound which comprises Q units and T units in an amount of 50 mol% or more with respect to the whole material, the proportion of the Q units and the proportion of the T units with respect to the sum of the Q units and T units, which is taken as 100 mol%, being 10-80 mol% and 90-20 mol%, respectively.

Description

Chemical sensor element, chemical sensor element manufacturing method, and chemical sensor

The present disclosure relates to a chemical sensor element, a method for manufacturing a chemical sensor element, and a chemical sensor. This application claims the priority based on Japanese Patent Application No. 2018-039930 for which it applied on March 6, 2018, and uses all the indications of this application for this application.

Quantification of gas molecules in the atmosphere or gas molecules by measuring changes in the properties of the detection material (for example, mass, dielectric constant, volume, etc.) accompanying the adsorption of molecules to a detection material (adsorbent medium) composed of a polymer, etc. A method of performing identification is known.

For example, Patent Document 1 exemplifies various porous materials (porous silica or the like) as a detection film in a sensor using a crystal resonator that detects a change in mass.

International Publication No. WO2016 / 121155 (released on August 4, 2016)

However, in Patent Document 1, any porous material has a greater response to water vapor than the detection target gas. Therefore, in an actual use environment where water vapor is mixed, erroneous detection occurs due to water vapor in the atmosphere. Or adsorption | suction of detection object gas is inhibited by water vapor | steam adsorb | sucking to a pore, and the detection capability with respect to detection object gas falls.

An object of one aspect of the present disclosure is to realize a chemical sensor element including a detection material in which the influence of water vapor adsorption is reduced while maintaining good detection sensitivity for a detection target gas.

In order to solve the above-described problem, the chemical sensor element according to one embodiment of the present disclosure includes at least 50 mol% of the Q unit and T unit, and the total of the Q unit and T unit is 100 mol%. Sometimes, a detection material containing a siloxane compound containing 10 mol% to 80 mol% of Q units and 90 mol% to 20 mol% of T units is provided.

In order to solve the above problems, a method for manufacturing a chemical sensor element according to one embodiment of the present disclosure includes tetraalkoxysilane and trialkoxysilane in an amount of 50 mol% or more of the total alkoxysilane, and includes tetraalkoxysilane and trialkoxy Hydroxysilane is hydrolyzed to hydroxysilane in an alkoxysilane solution containing 10 mol% to 80 mol% tetraalkoxysilane and 90 mol% to 20 mol% trialkoxysilane, when the total amount of silane is 100 mol%. And a condensation step of condensing the hydroxysilane by intermolecular dehydration.

According to one aspect of the present disclosure, the chemical sensor element can reduce the influence of water vapor adsorption while maintaining good detection sensitivity for the detection target gas.

(A) is a perspective view which shows the external appearance structure of the chemical sensor element which concerns on one Embodiment, (b) is a top view which shows the detection part in the chemical sensor element which concerns on one Embodiment, (c) 4B is a cross-sectional view taken along line AA in FIG. It is a figure which shows the principal part structure of the chemical sensor in one Embodiment. FIG. 5 is a logarithmic graph showing gas concentration dependence of capacitance change per 1 ppm of each detection target gas for Examples 1 to 4 and Comparative Example 1. FIG. 6 is a logarithmic graph showing gas concentration dependence of capacitance change per 1 ppm of each detection target gas for Examples 5 to 8 and Comparative Example 3. It is a figure which shows the graph which shows the electrostatic capacitance change with respect to water vapor | steam (1% of relative humidity) and each detection object gas 500ppm about each Example and a comparative example. It is a figure which shows the change of the electrostatic capacitance with respect to acetone and water vapor | steam of each density | concentration measured using the sensor element produced in Example 1. FIG. 6 is a diagram showing a ²⁹ Si-NMR spectrum relating to Example 6. FIG.

Hereinafter, an embodiment of the present disclosure will be described below.

[1. Chemical sensor element)
The chemical sensor element according to an embodiment of the present disclosure includes 50 mol% or more of the Q unit and T unit, and 10 mol of the Q unit when the total of the Q unit and T unit is 100 mol%. And a detection material containing a siloxane compound containing 80% by mole to 80% by mole and 90% by mole to 20% by mole of T units. The chemical sensor element according to the present embodiment can be mounted on a chemical sensor described below, for example.

(Siloxane compound)
The siloxane compound is a general term for compounds including a siloxane bond in which a silicon atom and an oxygen atom are bonded. In general, a silicon atom in a siloxane compound can have up to three substituents. They are referred to as M unit, D unit, T unit, and Q unit in the order of decreasing number of oxygen atoms bonded to silicon atoms (in the following structural formula, R1 represents a substituent independently of each other). In general, the siloxane compound is composed of any combination of M units, D units, T units, and Q units.

In this embodiment, the siloxane compound contains 50 mol% or more of the Q unit and the T unit in the whole siloxane compound. The total content of the Q unit and the T unit is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and more preferably 90 mol% of the entire siloxane compound. % Or more is particularly preferable. In one example, the total content of Q units and T units may be 100 mol% of the entire siloxane compound.

The siloxane compound in this embodiment may further include at least one of an M unit and a D unit in addition to the Q unit and the T unit. That is, in addition to the Q unit and the T unit, only the M unit, only the D unit, or both the M unit and the D unit may be further included. The total of M units and D units is 50 mol% or less of the entire siloxane compound, and preferably 10 mol% or less.

M units can be introduced, for example, for surface modification. In one example, the content of the M unit is preferably 10 mol% or less, more preferably 5 mol% or less, more preferably 3 mol%, from the viewpoint of maintaining the porosity of the detection material. More preferably, it is as follows. In one example, from the viewpoint of hydrophobizing the detection material, the total content is preferably 0.1 mol% or more, and more preferably 1 mol% or more.

In one example, the content of the D unit is preferably 10 mol% or less, more preferably 5 mol% or less, and is not included at all, from the viewpoint of maintaining the porosity of the detection material. More preferably.

Further, the siloxane compound in the present embodiment contains 10 mol% to 80 mol% and Q units of 90 mol% to 20 mol% when the total of the Q units and T units is 100 mol%. By setting the ratio of the Q unit and the T unit within this range, it is possible to achieve both good sensitivity to the detection target gas and reduction of the influence of water vapor.

From the viewpoint of high sensitivity to the detection target gas, when the total of the Q unit and the T unit is 100 mol%, the ratio of the Q unit is preferably 10 mol% to 80 mol%. When the detection target gas is a low-polarity gas such as toluene, the ratio of the Q unit is preferably 20 to 60 mol% when the total of the Q unit and the T unit is 100 mol%. More preferably, it is 20 mol% to 50 mol%. When the detection target gas is a medium polar gas such as acetone, the ratio of the Q unit is preferably 20 to 80 mol% when the total of the Q unit and the T unit is 100 mol%. When the detection target gas is a highly polar gas such as ethanol, it is preferably 20 mol% or more, and more preferably 40 mol% or more. On the other hand, from the viewpoint of suppressing the influence of water vapor, when the total of the Q unit and the T unit is 100 mol%, the ratio of the Q unit is preferably 80 mol% or less, and 60 mol% or less. Is more preferably 40 mol% or less, and particularly preferably 20 mol% or less. Considering both the viewpoint of high sensitivity to the detection target gas and the viewpoint of suppressing the influence of water vapor, the siloxane compound in the present embodiment has the Q unit when the total of the Q unit and the T unit is 100 mol%. Is preferably 10 mol% to 80 mol%, more preferably 20 mol% to 80 mol%, still more preferably 20 mol% to 60 mol%, and more preferably 30 to 70 mol%. It is particularly preferred that

The siloxane compound preferably contains 20 mol% to 60 mol% of Q units. In this range, the detection sensitivity of a low polarity gas (toluene or the like) can be improved.

The proportion of each unit in the siloxane compound can be quantified using, for example, ²⁹ Si-NMR method.

Examples of the substituent R1 in the T unit include a hydrogen atom, a fluorine atom, a hydrocarbon group, and a fluorocarbon group. The substituent R1 in the T unit is preferably a hydrocarbon group or a fluorocarbon group. The hydrocarbon group may be a chain hydrocarbon or a cyclic hydrocarbon. Further, the hydrocarbon group may be unsubstituted or substituted. The number of carbon atoms of the chain hydrocarbon is not particularly limited, but is preferably 1 to 10, more preferably 1 to 3, and still more preferably 1 from the viewpoint of micropore retention. . Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, a phenyl group, and a fluorophenyl group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, and an aminopropyl group. The substituent R1 in the T unit is preferably a methyl group or a phenyl group from the viewpoint of thermal stability.

Examples of the substituent R1 in the D unit include a hydrogen atom and a hydrocarbon group. The hydrocarbon group may be a chain hydrocarbon or a cyclic hydrocarbon. The number of carbon atoms of the chain hydrocarbon is not particularly limited. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, and a phenyl group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and an isobutyl group. The two substituents R1 may be the same as or different from each other.

Examples of the substituent R1 in the M unit include a hydrogen atom and a hydrocarbon group. The hydrocarbon group may be a chain hydrocarbon or a cyclic hydrocarbon. The number of carbon atoms of the chain hydrocarbon is not particularly limited. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, and a phenyl group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and an isobutyl group. The three substituents R1 may be the same as or different from each other.

One siloxane compound may contain a plurality of types of T units having different structures, or a single type of T unit. One siloxane compound may include a plurality of types of D units having different structures, or may include a single type of D unit. One siloxane compound may contain a plurality of types of M units having different structures, or a single type of M unit.

In this embodiment, due to the improvement in hydrophobicity (by the substituent R1) by the T unit and the formation of micropores by the Q unit, the influence of water vapor adsorption is maintained while maintaining good detection sensitivity for the detection target gas. It is believed that chemical sensor elements with reduced sensing material can be realized, but are not limited to this theory.

(Detection material)
In the chemical sensor element according to the present embodiment, the detection material includes the above-described siloxane compound.

The shape of the detection material is not particularly limited, but may be, for example, a film shape or a fiber shape. The size of the detection material is not particularly limited, and may be appropriately designed depending on the type of chemical sensor on which the chemical sensor element is mounted, the type of detection target gas, and the like. In one example, when the detection material is in the form of a film, the thickness of the film is preferably 1 mm or less, more preferably 100 μm or less, and even more preferably 10 μm or less from the viewpoint of the adsorption / desorption rate. . In addition, from the viewpoint of detection sensitivity for the detection target gas, the detection material preferably has a film thickness of 0.1 μm or more, and is preferably porous. That is, in applications where both adsorption / desorption rate and detection sensitivity are important, the gas detection material is preferably a porous material having a size of 0.1 μm or more and 10 μm or less.

Further, the detection material may further contain other compounds (polymer or the like) that do not affect the detection. Examples of other compounds include surface-modified silica nanoparticles that are contained to increase the amount of adsorption. It is preferable that other compounds are 10 weight% or less of the whole detection material.

(Other parts)
The chemical sensor element may further include other members. Examples of other members include electrodes and substrates.

(Example of chemical sensor element)
The specific configuration of the chemical sensor element according to the present embodiment is the same as, for example, a conventionally known configuration except that the detection material is replaced with that in the present embodiment. An example of the chemical sensor element according to the present embodiment will be described with reference to FIG. FIG. 1A is a perspective view showing an external configuration of the chemical sensor element 1. FIG. 1B is a top view showing the detection unit 3 in the chemical sensor element 1. FIG. 1C is a cross-sectional view taken along line AA in FIG.

As shown in FIG. 1A, the chemical sensor element 1 includes a substrate (semiconductor circuit) 2 and a detection unit 3. As shown in FIG. 1B, the detection unit 3 includes a comb electrode 4 and a detection material 5.

The comb electrode 4 is formed in a plane on the substrate 2 with the insulating layer 6 interposed therebetween. The comb electrode 4 is formed by combining a first electrode 4a and a second electrode 4b made of a conductive material. The first electrode 4a and the second electrode 4b are both formed in a comb shape, and the other one comb tooth portion is disposed between two adjacent comb tooth portions so as not to contact each other. Has been placed. As a result, the comb teeth of the first electrode 4a and the comb teeth of the second electrode 4b are arranged alternately.

The terminal 4 c of the first electrode 4 a and the terminal 4 d of the second electrode 4 b are electrically connected to the substrate 2 through the via hole 7. Further, a protective film made of a metal or semiconductor oxide or nitride may be formed on the comb electrode 4. Further, the via hole 7 may be filled with a conductive material.

The material forming the comb-shaped electrode 4 is mainly composed of a highly conductive metal such as aluminum, copper, gold, silver, titanium, indium, and tin, and these metals alone, alloys of these metals or alloys with other metals, Alternatively, it can be a conductive oxide such as indium tin oxide.

The detection material 5 is formed so as to be present at least between the comb teeth of the first electrode 4a and the comb teeth of the second electrode 4b in the comb-shaped electrode 4, and the comb teeth of the first electrode 4a You may form so that the part with which the comb-tooth part of 2 electrode 4b is located in a line may be covered.

In the chemical sensor element according to the present embodiment, the influence due to the adsorption of water vapor in the measurement target gas is reduced as shown in the examples described later. Therefore, the occurrence of erroneous detection and a decrease in detection capability for the detection target gas are suppressed. Moreover, the favorable detection sensitivity with respect to detection object gas is hold | maintained.

[2. Chemical sensor)
A chemical sensor according to an embodiment of the present disclosure includes the above-described chemical sensor element. The chemical sensor according to the present embodiment may include one or more chemical sensor elements.

The specific configuration of the chemical sensor is not particularly limited, and may be a conventionally known type of chemical sensor, for example. Examples of chemical sensors include capacitance, dielectric capacitance, electric quantity, electrical resistance, power, electrolysis, charge, current, voltage, potential, dielectric constant, mobility, electrostatic energy, capacitance, inductance, reactance, susceptance, Admittance, impedance, conductance, plasmon, refractive index, light intensity, temperature, surface stress, stress, force, surface tension, pressure, mass, elasticity, Young's modulus, Poisson's ratio, resonance frequency, frequency, volume, thickness, viscosity, density, Examples include chemical sensors that detect based on physical parameters such as magnetic force, magnetic quantity, magnetic field, magnetic flux, or magnetic flux density.

The chemical sensor according to this embodiment detects the presence or absence of “detection target gas” in “measurement target gas”, measures the amount or concentration of “detection target gas” in “measurement target gas”, and / or “ The type of “detection target gas” in “measurement target gas” is determined. The “measurement target gas” refers to the entire gas that can contain the detection target gas. The “detection target gas” refers to a specific gas that is a target of presence / absence detection, amount or concentration measurement, and / or type discrimination. For example, when measuring the concentration of acetone in the air, the “measurement target gas” is air, and the “detection target gas” is acetone.

Measured gas includes air, factory exhaust, food gas, living exhalation gas, living body skin gas, living body excretion gas, and the like.

Examples of detection target gases include volatile organic compound (VOC) gases, redox gases, flammable gases, and fragrances. More specifically, toluene, acetone, methanol, ethanol, IPA, formaldehyde, acetaldehyde, chloroform, isobutane, hydrocarbon, methane, ethane, ethylene, propane, butane, hydrogen, nitrogen oxide, sulfur oxide, carbon monoxide , Carbon dioxide, acetic acid, formic acid, and ammonia. The detection target gas may be a polar gas or a nonpolar gas (low polarity gas) such as hexane or toluene.

In one example, in the chemical sensor according to this embodiment, the detection target is a volatile organic compound (toluene, acetone, methanol, ethanol, IPA, formaldehyde, acetaldehyde, chloroform, etc.) in the gas. In one example, the chemical sensor according to the present embodiment measures a change in capacitance accompanying adsorption of a volatile organic compound to a detection material.

Generally, in order to desorb the gas molecule from the detection material on which the gas molecule is adsorbed, heating is often required. On the other hand, when the detection material in the present embodiment is used, since heating is not essential, the power consumption required for driving the chemical sensor may be small.

(Example of chemical sensor)
The specific configuration of the chemical sensor according to the present embodiment is the same as, for example, a conventionally known configuration except that the detection material is replaced with that in the present embodiment. An example of a specific configuration of the chemical sensor according to the present embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating a main configuration of the chemical sensor 10.

The chemical sensor 10 includes at least one chemical sensor element 1, a control unit 20, a signal processing unit 30, and an output unit 40. The chemical sensor 10 is connected to the external device 50 via the output unit 40.

The control unit 20 performs various controls for bringing the chemical sensor element 1 into a state capable of reacting with gas, various controls for detecting the reaction as a signal, and the like.

The signal processing unit 30 performs preprocessing of the output from the output unit 40 for the electrical signal obtained from the chemical sensor element 1. The signal processing unit 30 performs, for example, filtering for reducing noise, baseline correction, analog-digital conversion, and the like. The signal processing unit 30 transmits the preprocessed electrical signal to the output unit 40.

The output unit 40 is for outputting the electrical signal preprocessed by the signal processing unit 30 to the external device 50. Note that the output unit 40 may output the electrical signal to the external device 50 either by wire or wirelessly. The external device 50 is a device that uses an electrical signal input from the output unit 40, that is, a gas detection or measurement result of the chemical sensor 10.

(Another example of chemical sensor)
The chemical sensor according to the present embodiment may further include a sensor element that quantifies water vapor in the gas. Furthermore, the chemical sensor according to the present embodiment may quantitate water vapor and volatile organic compounds in the measurement target gas based on the difference in signal amount of each sensor element. The specific structure and quantitative method of such a chemical sensor may be referred to, for example, Japanese Patent No. 5893798.

Note that a chemical sensor including a plurality of chemical sensor elements (chemical sensor elements and / or other sensor elements according to the present embodiment) can also be referred to as a “chemical sensor array”.

In the chemical sensor according to the present embodiment, the influence due to the adsorption of water vapor in the measurement target gas is reduced as shown in the examples described later. Therefore, the occurrence of erroneous detection and a decrease in detection capability for the detection target gas are suppressed. Moreover, the favorable detection sensitivity with respect to detection object gas is hold | maintained.

In particular, the chemical sensor according to the present embodiment can detect a detection target gas even in an actual use environment where water vapor exists, and in combination with a humidity sensor element, the difference in signal change amount of each sensor element is obtained. For example, it is possible to detect up to 1 ppm. In addition, the chemical sensor according to the present embodiment can be quantified over a wide concentration range of, for example, 1 ppm to 1000 ppm even in an environment where water vapor is present.

[3. Chemical Sensor Element Manufacturing Method]
The siloxane compound contained in the detection material is obtained, for example, by a sol-gel reaction using a mixture of alkoxysilanes such as tetraalkoxysilane and trialkoxysilane as a precursor.

The method for manufacturing a chemical sensor element according to an embodiment of the present disclosure includes tetraalkoxysilane and trialkoxysilane in an amount of 50 mol% or more of the total alkoxysilane, and the total of tetraalkoxysilane and trialkoxysilane is 100 mol%. A hydrolysis step of hydrolyzing the alkoxysilane to hydroxysilane in an alkoxysilane solution containing 10 mol% to 80 mol% tetraalkoxysilane and 90 mol% to 20 mol% trialkoxysilane; A condensation step of condensing silane by intermolecular dehydration.

The chemical sensor element manufacturing method according to the present embodiment [1. The chemical sensor element according to this embodiment described in “Chemical sensor element” can be manufactured.

In the present disclosure, “alkoxysilane” is intended to be a generic name for tetraalkoxysilane, trialkoxysilane, dialkoxysilane, and monoalkoxysilane.

(Hydrolysis step)
Tetraalkoxysilane and trialkoxysilane are represented by the following structural formulas.

In the above formula, the substituent R2 of the tetraalkoxysilane is a hydrocarbon group. The hydrocarbon group may be a chain hydrocarbon or a cyclic hydrocarbon. The number of carbon atoms of the chain hydrocarbon is not particularly limited. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, a fluoroalkyl group, a phenyl group, and a fluorophenyl group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and an isobutyl group. The substituent R2 in the tetraalkoxysilane is preferably a methyl group or an ethyl group from the viewpoint of hydrolysis rate, and more preferably a methyl group from the viewpoint of thermal durability. The four substituents R2 may be the same as or different from each other.

In the above formula, the substituent R1 of trialkoxysilane is the same as described in [1. Since it is the same as the description of the substituent R1 of the T unit in the chemical sensor element], it is omitted here. The substituent R2 of trialkoxysilane is a hydrocarbon group. The hydrocarbon group may be a chain hydrocarbon or a cyclic hydrocarbon. The substituent R2 in the trialkoxysilane is preferably a methyl group or an ethyl group from the viewpoint of hydrolysis rate. The three substituents R2 may be the same as or different from each other. In one example, the trialkoxysilane is preferably methyltrialkoxysilane or phenyltrialkoxysilane, more preferably methyltrimethoxysilane or phenyltrimethoxysilane.

Tetraalkoxysilane can be a precursor of the Q unit in the siloxane compound. The trialkoxysilane can be a precursor of T units in the siloxane compound.

The alkoxysilane solution may further contain at least one of dialkoxysilane and monoalkoxysilane in addition to tetraalkoxysilane and trialkoxysilane. That is, in addition to tetraalkoxysilane and trialkoxysilane, dialkoxysilane alone, monoalkoxysilane alone, or both dialkoxysilane and monoalkoxysilane may be further included. The sum total of dialkoxysilane and monoalkoxysilane is 50 mol% or less and preferably 10 mol% or less of the entire alkoxysilane.

Dialkoxysilane and monoalkoxysilane are represented by the following structural formulas.

In the above formula, the substituent R1 of dialkoxysilane is the same as described in [1. Since it is the same as the description of the substituent R1 of the D unit in the chemical sensor element], it is omitted here. The substituent R2 of dialkoxysilane is a hydrocarbon group. The hydrocarbon group may be a chain hydrocarbon or a cyclic hydrocarbon. The substituent R2 in the dialkoxysilane is preferably a methyl group or an ethyl group from the viewpoint of hydrolysis rate. The two substituents R2 may be the same as or different from each other.

In the above formula, the substituent R1 of the monoalkoxysilane is the same as described in [1. Since it is the same as the description of the substituent R1 of the M unit in the chemical sensor element], it is omitted here. The substituent R2 of the monoalkoxysilane is a hydrocarbon group. The hydrocarbon group may be a chain hydrocarbon or a cyclic hydrocarbon. The substituent R2 in the monoalkoxysilane is preferably a methyl group or an ethyl group from the viewpoint of hydrolysis rate.

Dialkoxysilane can be a precursor of the D unit in the siloxane compound. The monoalkoxysilane can be a precursor of M units in the siloxane compound.

The total content of tetraalkoxysilane and trialkoxysilane is 50 mol% or more of the entire alkoxysilane, preferably 60 mol% or more, more preferably 70 mol% or more, and more than 80 mol%. It is more preferable that it is 90 mol% or more. In one example, the total content of tetraalkoxysilane and trialkoxysilane may be 100 mol% of the total alkoxysilane.

In one example, the content of monoalkoxysilane is preferably 10 or less, more preferably 5 mol% or less, and more preferably 3 mol% or less of the entire alkoxysilane from the viewpoint of maintaining the porosity of the detection material. More preferably. In one example, from the viewpoint of hydrophobizing the detection material, the total content is preferably 0.1 mol% or more, and more preferably 1 mol% or more.

In one example, the content of dialkoxysilane is preferably 10 mol% or less, more preferably 5 mol% or less, and entirely included from the viewpoint of maintaining the porosity of the detection material. More preferably not.

Further, the alkoxysilane solution in the present embodiment has a tetraalkoxysilane content of 10 mol% to 80 mol% and a trialkoxysilane content of 90 mol% to 20 mol, when the total of tetraalkoxysilane and trialkoxysilane is 100 mol%. Contains mol%. By setting the ratio of both in this range, it is possible to manufacture a chemical sensor element that can achieve both good sensitivity to the detection target gas and reduction of the influence of water vapor.

From the viewpoint of high sensitivity to the detection target gas, when the total of tetraalkoxysilane and trialkoxysilane is 100 mol%, the ratio of tetraalkoxysilane is preferably 10 mol% to 80 mol%. When the detection target gas is a low-polarity gas such as toluene, the ratio of tetraalkoxysilane is 20 to 60 mol% when the total of tetraalkoxysilane and trialkoxysilane is 100 mol%. And more preferably 20 to 50 mol%. When the detection target gas is a medium polarity gas such as acetone, the ratio of tetraalkoxysilane is 20 mol% to 80 mol% when the total of tetraalkoxysilane and trialkoxysilane is 100 mol%. Is preferred. When the detection target gas is a highly polar gas such as ethanol, the ratio of tetraalkoxysilane is preferably 20 mol% or more when the total of tetraalkoxysilane and trialkoxysilane is 100 mol%, More preferably, it is 40 mol% or more. On the other hand, from the viewpoint of suppressing the influence of water vapor, when the total of tetraalkoxysilane and trialkoxysilane is 100 mol%, the proportion of tetraalkoxysilane is preferably 80 mol% or less, and 60 mol% or less. Is more preferably 40 mol% or less, and particularly preferably 20 mol% or less. Considering both the viewpoint of high sensitivity to the detection target gas and the viewpoint of suppressing the influence of water vapor, the siloxane compound in the present embodiment is, when the total of tetraalkoxysilane and trialkoxysilane is 100 mol%, The proportion of tetraalkoxysilane is preferably 10 to 80 mol%, more preferably 10 to 60 mol%, and still more preferably 20 to 50 mol%.

The alkoxysilane solution may contain a plurality of types of tetraalkoxysilanes having different structures, or may contain one type of tetraalkoxysilane. The alkoxysilane solution may contain a plurality of types of trialkoxysilanes having different structures, or may contain one type of trialkoxysilane. The alkoxysilane solution may contain a plurality of types of dialkoxysilanes having different structures, or may contain one type of dialkoxysilane. The alkoxysilane solution may contain a plurality of types of monoalkoxysilanes having different structures, or may contain one type of monoalkoxysilane.

Examples of the solvent include methanol, ethanol, propanol, toluene, and tetrahydrofuran. The solvent is preferably ethanol from the viewpoint of high solubility of the precursor intermediate. The amount of the solvent is not particularly limited, but is, for example, 0.1 L to 10 L, preferably 1 L to 3 L, per 1 mol of alkoxysilane.

Hydrolysis requires the same number of moles of water as the alkoxy group of the alkoxysilane, but an equal amount of water may be added to the solvent or may be performed using water in the gas phase of the reaction system. . A catalyst may be used for the hydrolysis. Examples of the catalyst include acids such as formic acid, acetic acid and hydrochloric acid. Formic acid is preferred from the viewpoint of easy removal of the catalyst. The amount of the catalyst is not particularly limited, but is, for example, 0.001 L to 1 L, preferably 0.01 L to 0.1 L per mole of alkoxysilane.

The alkoxysilane solution may contain components other than alkoxysilane. Such components include monohalosilanes where X is Cl, Br or I in the formula below. Here, the substituent R1 is the same as described above. Further, 1,1,1,3,3,3-hexamethyldisilazane (HMDS) may be used. When monoalkoxysilane, monohalosilane, or HMDS is reacted with a silanol group, it becomes a silane of T unit. Therefore, when it has an unreacted silanol group, the hydrophobicity of the detection film can be increased.

The reaction conditions for hydrolysis are not particularly limited, and may be set as appropriate according to the composition of the alkoxysilane in the solution, the solvent, and the like. In one example, the hydrolysis temperature may be, for example, 0 to 100 ° C., preferably 30 to 70 ° C. The reaction time for the hydrolysis can be, for example, 1 minute to 48 hours, preferably 6 hours to 24 hours. Hydrolysis is preferably performed in a closed system from the viewpoint of preventing gelation of the siloxane compound accompanying the volatilization of the solvent.

In the hydrolysis step, substituents R2 (at least part, preferably all) in the alkoxy group of alkoxysilane are replaced with hydrogen atoms, and hydroxysilane is produced. In the present disclosure, “hydroxysilane” refers to a compound having at least one hydroxy group in which at least one substituent R2 in the alkoxy group (s) of alkoxysilane is substituted with a hydrogen atom.

Examples of the hydroxysilane obtained by hydrolyzing tetraalkoxysilane include tetrahydroxysilane represented by the following structural formula. Examples of the hydroxysilane obtained by hydrolyzing trialkoxysilane include trihydroxysilane represented by the following structural formula.

In the above formula, the substituent R1 of trihydroxysilane is the same as described in [1. Since it is the same as the description of the substituent R1 of the T unit in the chemical sensor element], it is omitted here.

Hydroxysilane (tetrahydroxysilane or the like) obtained by hydrolyzing tetraalkoxysilane can be a precursor of Q unit in the siloxane compound. Hydroxysilane (such as trihydroxysilane) obtained by hydrolyzing trialkoxysilane can be a precursor of T unit in the siloxane compound.

When dialkoxysilane and / or monoalkoxysilane is contained in the alkoxysilane solution, examples of the hydroxysilane obtained by hydrolysis include tetrahydroxysilane and trihydroxysilane represented by the following structural formulas, respectively. It is done.

In the above formula, the substituent R1 of dihydroxysilane is the same as described in [1. Since it is the same as the description of the substituent R1 of the D unit in the chemical sensor element], it is omitted here.

In the above formula, the substituent R1 of monohydroxysilane is the same as described in [1. Since it is the same as the description of the substituent R1 of the M unit in the chemical sensor element], it is omitted here.

Hydroxysilane (dihydroxysilane or the like) obtained by hydrolyzing dialkoxysilane can be a precursor of D unit in the siloxane compound. Hydroxysilane (monohydroxysilane etc.) obtained by hydrolyzing monoalkoxysilane can be a precursor of M unit in the siloxane compound.

(Condensation process)
In the condensation step, the hydroxysilane is condensed by intermolecular dehydration.

Examples of the solvent in the condensation step include methanol, ethanol, toluene, and tetrahydrofuran. As the solvent, ethanol is preferable from the viewpoint of solubility of hydroxysilane and siloxane compound. The amount of the solvent is not particularly limited, but is, for example, 0.1 L to 10 L, preferably 1 L to 3 L, per 1 mol of alkoxysilane. In addition, you may perform a hydrolysis process and a condensation process continuously in the same container.

The reaction conditions for the condensation reaction are not particularly limited, and may be set as appropriate according to the composition of hydroxysilane, the solvent, and the like. In one example, the temperature of the condensation reaction can be, for example, 20 to 100 ° C., preferably 40 to 80 ° C. The condensation reaction may be performed at atmospheric pressure, for example, or may be performed at a reduced pressure below atmospheric pressure. The reaction time of the condensation reaction can be, for example, 1 minute to 48 hours, preferably 1 hour to 24 hours. The condensation reaction is preferably performed in an open system from the viewpoint of removing the acid catalyst.

In the condensation step, intermolecular dehydration of hydroxysilane occurs, and a number of hydroxysilane molecules are polymerized (condensed). Thereby, a polymer (siloxane compound) is generated.

In addition, hydrolysis and condensation may occur simultaneously.

(Film formation process)
The manufacturing method according to the present embodiment may include a film forming step of forming a film by attaching a solution containing the polymer obtained in the condensation step to the electrode.

The explanation of the electrode is [1. Chemical sensor element].

Although the method of making it adhere is not specifically limited, For example, well-known methods, such as application | coating, spraying, and immersion, are mentioned. You may pass through the process of making a film thickness uniform by spin coat after these processes. After deposition, heating may be performed to evaporate the solvent. The heating conditions are not particularly limited, and may be set as appropriate according to the type of solvent. In one example, the heating temperature can be, for example, 100 ° C. to 400 ° C., preferably 200 ° C. to 300 ° C. The reaction time for heating can be, for example, 1 minute to 1 hour, preferably 10 minutes to 30 minutes.

Further, heating may be performed to cause further condensation reaction of the siloxane compound. The heating conditions are not particularly limited, and may be set as appropriate according to the composition of the alkoxysilane. In one example, the heating temperature can be, for example, 200 to 500 ° C., preferably 300 to 400 ° C. The reaction time for heating can be, for example, 1 hour to 48 hours, preferably 6 hours to 24 hours.

(Other processes)
As another step, a modification step for modifying the siloxane compound may be included. It is preferably performed after the condensation step or after the film formation step.

When performed after the condensation step, for example, HMDS or trialkylhalosilyl may be mixed with the solution containing the polymer. Thereby, a part of the terminal silanol group can be modified to M units.

When performing after the film forming step, for example, a solution containing HMDS or trialkylhalosilyl is dropped or exposed to steam such as heated HMDS. Thereby, a part of silanol group on the surface can be modified to M unit silica.

The specific method may be performed according to a known method. An example of modification of the silanol group by HMDS is shown below.

The manufacturing method according to this embodiment is described in [1. It is an example of the manufacturing method of the chemical sensor element demonstrated by [chemical sensor element], [1. The chemical sensor element described in [Chemical sensor element] may be manufactured by another manufacturing method.

The present disclosure also provides a chemical sensor element manufactured by the manufacturing method according to the present embodiment, and a chemical sensor including the chemical sensor element. These specific descriptions are given in [1. Chemical sensor element] and [2. Chemical sensor].

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

An example of the present disclosure will be described below.

[Production of chemical sensor elements]
A total of 4.0 mmoles of phenyltrimethoxysilane (PTMS) or methyltrimethoxysilane (MTMS), which is a precursor of T unit, and tetraethoxysilane (TEOS), which is a precursor of Q unit, are shown in Table 1. And dissolved in ethanol as a solvent. Further, appropriate amounts of formic acid and distilled water were added dropwise as catalysts. This was reacted with stirring in a closed system at 60 ° C. for 12 hours for hydrolysis.

Further, formic acid was volatilized by reacting at 60 ° C. for 12 hours while adding ethanol appropriately in an open system. In this way, a 10 wt% ethanol solution of each polymer not containing an insoluble gel was obtained.

This solution was applied on a comb-shaped electrode having a width and depth of 1 μm and spin-coated at 2000 rpm. Subsequently, the solvent remaining in the film was volatilized by heating at 200 ° C. for 1 hour. Furthermore, it heated at 400 degreeC for 6 hours, the dehydration condensation reaction was performed, and the transparent thin film about 1 micrometer thick which covers a comb-shaped electrode was obtained. Thus, the chemical sensor element provided with the detection material containing a siloxane compound was produced.

[Gas measurement method]
A gas-tech permeator (PD-1B-2) was used to generate each concentration of gas. Pure air was used as the carrier gas, and the gas to be detected having a predetermined concentration was exposed to the chemical sensor element by controlling the flow rate, and the capacitance change at that time was measured. Acetone, toluene, and ethanol were used as detection target gases.

〔result〕
The results are shown in FIGS. FIG. 3 is a log-log graph showing the gas concentration dependence of the capacitance change per 1 ppm of each detection target gas for Examples 1 to 4 and Comparative Example 1 in which the substituent of the T unit precursor is a phenyl group. FIG. FIG. 4 is a log-log graph showing the gas concentration dependency of the capacitance change per 1 ppm of each detection target gas for Examples 5 to 8 and Comparative Example 3 in which the substituent of the T unit precursor is a methyl group. FIG.

It was found that the larger the ratio of the Q unit of the siloxane compound of the detection material, the larger the amount of change in capacitance with respect to the detection target gas having the same concentration. In addition, the lower the concentration of the detection target gas, the greater the response amount per 1 ppm of the detection target gas, suggesting that the detection material has pores of 1 nm or less suitable for gas adsorption. It was.

Also, the tendency of the capacitance change to increase with respect to acetone, which is a polar gas, and toluene, which is a low-polarity gas, is not the result of a change in affinity for the gas on the pore surface, but a volatile organic compound. This shows that the pores capable of adsorbing the compound are increased.

FIG. 5 is a graph showing a change in capacitance with respect to water vapor (relative humidity 1%) and each detection target gas 500 ppm for each of the examples and comparative examples. There was a tendency for the amount of change in capacitance to increase as the proportion of TEOS increased. However, when the ratio of TEOS is 100%, the amount of change in capacitance with respect to water vapor increases rapidly, while the amount of change in capacitance with respect to the detection target gas decreases rapidly.

FIG. 6 is a diagram showing changes in electrostatic capacitance with respect to acetone and water vapor of each concentration measured using the chemical sensor element produced in Example 1. As shown in FIG. 6, the change in the amount of response due to water vapor was sufficiently small compared to acetone.

[Reference example]
The sample of Example 6 synthesized using MTMS 60% and TEOS 40% as a precursor was subjected to ²⁹ Si-NMR measurement by a single pulse method for 3 days on a solid fired at 300 ° C. for 1 hour. The obtained spectrum is shown in FIG. The ratio of (T2 + T3) :( Q3 + Q4) in the spectrum was 1: 0.652, indicating that the T units and the Q units were polymerized with the abundance ratio in the raw material monomers.

Claims

When the Q unit and the T unit are contained in an amount of 50 mol% or more and the total of the Q unit and the T unit is 100 mol%, the Q unit is 10 mol% to 80 mol%, the T unit is 90 mol% A chemical sensor element comprising a detection material containing a siloxane compound containing 20 mol%.
The chemical sensor element according to claim 1, wherein the substituent in the T unit is a methyl group or a phenyl group.
3. The chemical sensor element according to claim 1, wherein the siloxane compound contains 20 mol% to 60 mol% of the Q unit.
A chemical sensor comprising the chemical sensor element according to any one of claims 1 to 3.
The chemical sensor according to claim 4, wherein the detection target is a volatile organic compound in the gas.
The chemical sensor according to claim 4 or 5, which measures a change in capacitance accompanying adsorption of a volatile organic compound to the detection material.
It further comprises a sensor element that quantifies water vapor in the gas,
The chemical sensor according to any one of claims 4 to 6, wherein water vapor and volatile organic compounds in the measurement target gas are quantified based on a difference in signal amount of each sensor element.
Tetraalkoxysilane and trialkoxysilane are contained in an amount of 50 mol% or more of the total alkoxysilane, and when the total of tetraalkoxysilane and trialkoxysilane is 100 mol%, tetraalkoxysilane is contained in an amount of 10 mol% to 80 mol%, A hydrolysis step of hydrolyzing the alkoxysilane to hydroxysilane in an alkoxysilane solution containing 90 mol% to 20 mol% of trialkoxysilane;
A method for producing a chemical sensor element, comprising a condensation step of condensing the hydroxysilane by intermolecular dehydration.
The method for producing a chemical sensor element according to claim 8, wherein the trialkoxysilane is methyltrialkoxysilane or phenyltrialkoxysilane.
The method for producing a chemical sensor element according to claim 8 or 9, further comprising a film forming step in which a solution containing the polymer obtained in the condensation step is attached to an electrode to form a film.