JP2021073433A - Chemical sensor element, manufacturing method of chemical sensor element, and chemical sensor - Google Patents

Abstract

To realize a chemical sensor element which comprises a detection material less influenced by adhesion of vapor, while maintaining good detection sensitivity for detection object gas.SOLUTION: A chemical sensor element comprises a detection material containing a siloxane compound which contains: 50 mol% or more of a Q unit and a T unit with respect to the whole; and 10 mol% - 80 mol% of the Q unit, and 90 mol% - 20 mol% of the T unit when a total of the Q unit and the T unit is defined as 100 mol%.SELECTED DRAWING: None

Description

The present disclosure relates to a chemical sensor element, a method for manufacturing a chemical sensor element, and a chemical sensor including the chemical sensor element.

Quantification of gas molecules in the atmosphere or gas molecules by measuring changes in the characteristics of the detection material (for example, mass, dielectric constant, volume, etc.) due to adsorption of molecules to the detection material (adsorption medium) made of a polymer or the like. There is a known method for identifying the gas.

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

International Publication WO 2016/121155 (Published August 4, 2016)

However, in Patent Document 1, all the porous materials have a larger response to water vapor than the gas to be detected. Therefore, in an actual use environment where water vapor is mixed, erroneous detection occurs due to water vapor in the atmosphere. Alternatively, the adsorption of the detection target gas is hindered by the adsorption of water vapor into the pores, and the detection ability for the detection target gas is reduced.

One aspect of the present disclosure is to realize a chemical sensor device including a detection material in which the influence of water vapor adsorption is reduced while maintaining good detection sensitivity to a gas to be detected.

In order to solve the above problems, the chemical sensor element according to one aspect of the present disclosure contains 50 mol% or more of Q units and T units, and the total of Q units and T units is 100 mol%. Occasionally, 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, the method for producing a chemical sensor element according to one aspect of the present disclosure contains tetraalkoxysilane and trialkoxysilane in an amount of 50 mol% or more of the total alkoxysilane, and tetraalkoxysilane and trialkoxysilane. Hydrolyzing alkoxysilanes to hydroxysilanes in an alkoxysilane solution containing 10 mol% to 80 mol% tetraalkoxysilanes and 90 mol% to 20 mol% trialkoxysilanes, where the total amount of silanes is 100 mol%. It includes a hydrolysis step of the above and a condensation step of condensing the hydroxysilane by intermolecular dehydration.

According to one aspect of the present disclosure, it is possible to reduce the influence of water vapor adsorption in the chemical sensor element while maintaining good detection sensitivity with respect to the detection target gas.

(A) is a perspective view showing an external configuration of the chemical sensor element according to one embodiment, (b) is a top view showing a detection unit in the chemical sensor element according to one embodiment, and (c) is a top view. , (B) is a cross section taken along the line AA. It is a figure which shows the main part structure of the chemical sensor in one Embodiment. It is a figure which shows the log-log graph which shows the gas concentration dependence of the capacitance change per 1ppm of each detection target gas about Examples 1 to 4 and Comparative Example 1. It is a figure which shows the log-log graph which shows the gas concentration dependence of the capacitance change per 1ppm of each detection target gas about Examples 5-8 and Comparative Example 3. It is a figure which shows the graph which shows the change of the capacitance with respect to water vapor (relative humidity 1%) and each detection target gas 500ppm for each Example and comparative example. It is a figure which shows the change of the capacitance with respect to acetone and water vapor of each concentration measured by using the sensor element manufactured in Example 1. FIG. It is a figure which shows the spectrum ^{of 29} Si-NMR about Example 6.

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

[1. Chemical sensor element]
The chemical sensor element according to the embodiment of the present disclosure contains 50 mol% or more of Q units and T units, and has 10 mol of Q units when the total of Q units and T units is 100 mol%. A detection material containing a siloxane compound containing% to 80 mol% and 90 mol% to 20 mol% of T units is provided. The chemical sensor element according to the present embodiment may be mounted on, for example, a chemical sensor described later.

(Siloxane compound)
The siloxane compound is a general term for compounds containing 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 called M unit, D unit, T unit, and Q unit in ascending order of the number of oxygen atoms bonded to silicon atoms (R1 represents a substituent independently of each other in the following structural formula). Generally, a siloxane compound is composed of any combination of M units, D units, T units and Q units.

In the present embodiment, the siloxane compound contains Q units and T units in an amount of 50 mol% or more of the total 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, further preferably 80 mol% or more, and 90 mol% of the total 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 total siloxane compound.

In addition to the Q unit and the T unit, the siloxane compound in the present embodiment may further contain at least one of the M unit and the D 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, preferably 10 mol% or less, of the total siloxane compound.

M units can be introduced, for example, for surface modification. In one example, the content of M units is preferably 10 mol% or less, more preferably 5 mol% or less, and 3 mol%, from the viewpoint of maintaining the porosity of the detection material. The following is more preferable. In one example, from the viewpoint of hydrophobization of the detection material, it is preferably 0.1 mol% or more, and more preferably 1 mol% or more of the whole.

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

Further, the siloxane compound in the present embodiment contains 10 mol% to 80 mol% of Q units and 90 mol% to 20 mol% of T units when the total of 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 gas to be detected, the ratio of Q units is preferably 10 mol% to 80 mol% when the total of Q units and T units is 100 mol%. When the detection target gas is a low-polarity gas such as toluene, the ratio of Q units is preferably 20 mol% to 60 mol% when the total of Q units and T units is 100 mol%. More preferably, it is 20 mol% to 50 mol%. When the detection target gas is a neutral gas such as acetone, the ratio of Q units is preferably 20 mol% to 80 mol% when the total of Q units and T units is 100 mol%. When the detection target gas is a highly polar gas such as ethanol, it is preferably 20 mol% or more, more preferably 40 mol% or more. On the other hand, from the viewpoint of suppressing the influence of water vapor, when the total of Q units and T units is 100 mol%, the ratio of Q units is preferably 80 mol% or less, and is 60 mol% or less. Is more preferable, 40 mol% or less is further preferable, and 20 mol% or less is particularly preferable. Considering both the viewpoint of high sensitivity to the gas to be detected and the viewpoint of suppressing the influence of water vapor, the siloxane compound in the present embodiment has Q units when the total of Q units and T units is 100 mol%. Is preferably 10 mol% to 80 mol%, more preferably 20 mol% to 80 mol%, further preferably 10 mol% to 60 mol%, and 20 to 50 mol%. Is particularly preferable.

The siloxane compound preferably contains 20 mol% to 60 mol% of Q units. In this range, the detection sensitivity of 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, the 29} Si-NMR method.

Examples of the substituent R1 in the T unit include a hydrogen atom, a fluorine atom, a hydrocarbon group, a fluorocarbon group and the like. 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 in the chain hydrocarbon is not particularly limited, but is preferably 1 to 10, more preferably 1 to 3, and even more preferably 1 from the viewpoint of retaining micropores. .. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, a phenyl group, a fluorophenyl group and the like. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, an aminopropyl group and the like. 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 carbon number of the chain hydrocarbon is not particularly limited. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, a phenyl group and the like. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group and the like. The two substituents R1 may be the same 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 carbon number of the chain hydrocarbon is not particularly limited. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, a phenyl group and the like. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group and the like. The three substituents R1 may be the same or different from each other.

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

In the present embodiment, due to the improvement of hydrophobicity (due to the substituent R1) by the T unit and the formation of micropores by the Q unit, the influence of the adsorption of water vapor is exerted while maintaining good detection sensitivity with respect to the gas to be detected. It is believed that a chemical sensor element with reduced detection material can be realized, but is not limited to this theory.

(Detection material)
In the chemical sensor device according to the present embodiment, the detection material contains the above-mentioned siloxane compound.

The shape of the detection material is not particularly limited, but may be, for example, a film-like shape or a fibrous shape. The size of the detection material is not particularly limited, and may be appropriately designed depending on the type of the chemical sensor on which the chemical sensor element is mounted, the type of the gas to be detected, 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 further preferably 10 μm or less from the viewpoint of adsorption / desorption rate. .. Further, the detection material preferably has a film thickness of 0.1 μm or more, and is preferably porous, from the viewpoint of detection sensitivity to the detection target gas. That is, in applications where both the adsorption / desorption rate and the detection sensitivity are important, the gas detection material is preferably porous of 0.1 μm or more and 10 μm or less.

Further, the detection material may further contain other compounds (polymers and the like) that do not affect the detection. Examples of other compounds include surface-modified silica nanoparticles contained for increasing the amount of adsorption. The other compound is preferably 10% by weight or less of the total detection material.

(Other members)
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, for example, the same as that of a conventionally known configuration except that the detection material is replaced with that of 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. 1 (c) is a cross section taken along the line AA of FIG. 1 (b).

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-shaped electrode 4 and a detection material 5.

The comb-shaped electrode 4 is formed in a plane on the substrate 2 via the insulating layer 6. The comb-shaped electrode 4 is formed by combining a first electrode 4a and a second electrode 4b made of a conductive material. Both the first electrode 4a and the second electrode 4b are formed in a comb shape, and the other comb tooth portion is arranged between two adjacent comb tooth portions so that they do not come into contact with each other. Have been placed. As a result, the comb tooth portions of the first electrode 4a and the comb tooth portions of the second electrode 4b are arranged so as to be alternately arranged.

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

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

The detection material 5 is formed so as to exist at least between the comb tooth portion of the first electrode 4a and the comb tooth portion of the second electrode 4b of the comb electrode 4, and the comb tooth portion and the first electrode 4a of the first electrode 4a. It may be formed so as to cover the portion of the two electrodes 4b where the comb teeth are aligned.

In the chemical sensor element according to the present embodiment, as shown in Examples described later, the influence of adsorption of water vapor in the gas to be measured is reduced. Therefore, the occurrence of erroneous detection and the decrease in the detection ability for the gas to be detected are suppressed. In addition, it maintains good detection sensitivity for the gas to be detected.

[2. Chemical sensor]
The chemical sensor according to the embodiment of the present disclosure includes the above-mentioned chemical sensor element. The above-mentioned chemical sensor element included in the chemical sensor according to the present embodiment may be one or a plurality.

The specific configuration of the chemical sensor is not particularly limited, and may be, for example, a conventionally known type of chemical sensor. Chemical sensors include, for example, capacitance, dielectric capacitance, amount of electricity, electrical resistance, power, electrolysis, charge, current, voltage, potential, dielectric constant, mobility, electrostatic energy, capacitance, inductance, reactorance, susceptibility, etc. Admitance, impedance, conductance, plasmon, refractive potential, luminosity, temperature, surface stress, stress, force, surface tension, pressure, mass, elasticity, Young ratio, Poisson ratio, resonance frequency, frequency, volume, thickness, viscosity, density, Examples thereof include chemical sensors of the type 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 the present embodiment detects the presence or absence of the "detection target gas" in the "measurement target gas", measures the amount or concentration of the "detection target gas" in the "measurement target gas", and / or ". The type of "detection target gas" in "measurement target gas" is discriminated. The “measurement target gas” refers to the entire gas that can contain the detection target gas. "Detection target gas" refers to a specific gas that is the target of detection of presence / absence, measurement of amount or concentration, and / or type determination. For example, when measuring the concentration of acetone in air, the "measurement target gas" is air and the "detection target gas" is acetone.

Examples of the gas to be measured include air, factory exhaust, food gas, biological exhaled gas, biological skin gas, and biological excrement gas.

Examples of the gas to be detected include volatile organic compound (VOC) gas, redox gas, flammable gas, fragrance and the like. More specifically, toluene, acetone, methanol, ethanol, IPA, formaldehyde, acetaldehyde, chloroform, isobutane, hydrocarbons, methane, ethane, ethylene, propane, butane, hydrogen, nitrogen oxides, sulfur oxides, carbon monoxide. , Carbon dioxide, acetic acid, formic acid, ammonia and the like. The detection target gas may be a polar gas or a non-polar gas (low polar gas) such as hexane and toluene.

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

In general, heating is often required to desorb the gas molecules from the detection material on which the gas molecules are adsorbed. On the other hand, when the detection material in the present embodiment is used, heating is not essential, so that 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, for example, the same as that of a conventionally known configuration, except that the detection material is replaced with that of 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 showing 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 making the chemical sensor element 1 ready to react with gas, various controls for detecting the reaction as a signal, and the like.

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

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

(Another example of a chemical sensor)
The chemical sensor according to the present embodiment may further include a sensor element for quantifying water vapor in the gas. Further, the chemical sensor according to the present embodiment may be one that quantifies water vapor and volatile organic compounds in the gas to be measured based on the difference in the signal amount of each sensor element. For a specific configuration and quantification method of such a chemical sensor, see, for example, Japanese Patent No. 5893982.

A chemical sensor including a plurality of chemical sensor elements (chemical sensor element and / or other sensor element according to the present embodiment) can be paraphrased as a “chemical sensor array”.

In the chemical sensor according to this embodiment, as shown in Examples described later, the influence of adsorption of water vapor in the gas to be measured is reduced. Therefore, the occurrence of erroneous detection and the decrease in the detection ability for the gas to be detected are suppressed. In addition, it maintains good detection sensitivity for the gas to be detected.

In particular, the chemical sensor according to the present embodiment can detect the gas to be detected even in an actual use environment where water vapor is present, and by using it in combination with a humidity sensor element and taking the difference in the amount of signal change of each sensor element. For example, it can detect up to 1 ppm. Further, 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. Manufacturing method of chemical sensor element]
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 contains 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%. In an alkoxysilane solution containing 10 mol% to 80 mol% of tetraalkoxysilane and 90 mol% to 20 mol% of trialkoxysilane, a hydrolysis step of hydrolyzing alkoxysilane to hydroxysilane and the above-mentioned hydroxy. It includes a condensation step of condensing silane by intermolecular dehydration.

According to the method for manufacturing a chemical sensor element according to the present embodiment, [1. The chemical sensor element according to the present embodiment described in [Chemical sensor element] can be manufactured.

In the present disclosure, "alkoxysilane" is intended to be a general term for tetraalkoxysilane, trialkoxysilane, dialkoxysilane, and monoalkoxysilane.

(Hydrolyzed 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 carbon number 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, a fluorophenyl group and the like. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group and the like. The substituent R2 in 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 or different from each other.

In the above formula, the substituent R1 of the trialkoxysilane is described in the above [1. Since it is the same as the description of the T-unit substituent R1 in the chemical sensor element], it is omitted here. The substituent R2 of the 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 or different from each other. In one example, the trialkoxysilane is preferably methyltrialkoxysilane or phenyltrialkoxysilane, more preferably methyltrimethoxysilane or phenyltrimethoxysilane.

Tetraalkoxysilanes can be Q-unit precursors in siloxane compounds. Trialkoxysilanes can be T-unit precursors in siloxane compounds.

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

Dialkoxysilanes and monoalkoxysilanes are represented by the following structural formulas.

In the above formula, the substituent R1 of the dialkoxysilane is described in the above [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 the 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 the hydrolysis rate. The two substituents R2 may be the same or different from each other.

In the above formula, the substituent R1 of the monoalkoxysilane is described in the above [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.

Dialkoxysilanes can be precursors of D units in siloxane compounds. The monoalkoxysilane can be a precursor of M units in a siloxane compound.

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

In one example, the content of the monoalkoxysilane is preferably 10 or less, more preferably 5 mol% or less, and 3 mol% or less of the entire alkoxysilane from the viewpoint of maintaining the porosity of the detection material. Is more preferable. In one example, from the viewpoint of hydrophobization of the detection material, it is preferably 0.1 mol% or more, and more preferably 1 mol% or more of the whole.

In one example, the content of the dialkoxysilane is preferably 10 mol% or less, more preferably 5 mol% or less, and completely contained, from the viewpoint of maintaining the porosity of the detection material. It is more preferable that it is not.

Further, the alkoxysilane solution in the present embodiment contains 10 mol% to 80 mol% of tetraalkoxysilane and 90 mol% to 20 mol% of trialkoxysilane 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 capable of achieving both good sensitivity to the detection target gas and reduction of the influence of water vapor.

From the viewpoint of high sensitivity to the gas to be detected, the ratio of tetraalkoxysilane is preferably 10 mol% to 80 mol% when the total of tetraalkoxysilane and trialkoxysilane is 100 mol%. When the detection target gas is a low-polarity gas such as toluene, the proportion of tetraalkoxysilane is 20 mol% to 60 mol% when the total of tetraalkoxysilane and trialkoxysilane is 100 mol%. Is preferable, and 20 mol% to 50 mol% is more preferable. When the detection target gas is a neutral gas such as acetone, the proportion of tetraalkoxysilane is 20 mol% to 80 mol% when the total of tetraalkoxysilane and trialkoxysilane is 100 mol%. Is preferable. When the detection target gas is a highly polar gas such as ethanol, the proportion 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, the ratio of tetraalkoxysilane is preferably 80 mol% or less, preferably 60 mol% or less, when the total of tetraalkoxysilane and trialkoxysilane is 100 mol%. It is more preferably 40 mol% or less, and particularly preferably 20 mol% or less. Considering both the viewpoint of high sensitivity to the gas to be detected and the viewpoint of suppressing the influence of water vapor, the siloxane compound in the present embodiment has a total of tetraalkoxysilane and trialkoxysilane of 100 mol%. The proportion of tetraalkoxysilane is preferably 10 to 80 mol%, more preferably 10 mol% to 60 mol%, still more preferably 20 mol% 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 trialkoxysilanes. The alkoxysilane solution may contain a plurality of types of dialkoxysilanes having different structures, or may contain one type of dialkoxysilanes. 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, tetrahydrofuran and the like. As the solvent, ethanol is preferable from the viewpoint of high solubility of the intermediate of the precursor. The amount of the solvent is not particularly limited, but is, for example, 0.1 L to 10 L per mole of alkoxysilane, preferably 1 L to 3 L.

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

The alkoxysilane solution may contain components other than alkoxysilane. Examples of such a component include monohalosilane in which X is Cl, Br or I in the following formula. 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 T-unit silane. Therefore, when it has an unreacted silanol group, the hydrophobicity of the detection film can be enhanced.

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

By the hydrolysis step, the substituent R2 (at least a part, preferably all) in the alkoxy group of the alkoxysilane is substituted with a hydrogen atom to produce a hydroxysilane. In the present disclosure, the term "hydroxysilane" refers to a compound in which at least one of the substituents R2 in the (one or more) alkoxy groups of an alkoxysilane is substituted with a hydrogen atom and has at least one hydroxy group.

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

The hydroxysilane (tetrahydroxysilane, etc.) obtained by hydrolyzing tetraalkoxysilane can be a precursor of the Q unit in the siloxane compound. The hydroxysilane (trihydroxysilane, etc.) obtained by hydrolyzing trialkoxysilane can be a precursor of the T unit in the siloxane compound.

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

In the above formula, the substituent R1 of dihydroxysilane is described in the above [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 the monohydroxysilane is the above [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 hydroxysilane (dihydroxysilane, etc.) obtained by hydrolyzing the dialkoxysilane can be a precursor of the D unit in the siloxane compound. The hydroxysilane (monohydroxysilane, etc.) obtained by hydrolyzing monoalkoxysilane can be a precursor of M units in a siloxane compound.

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

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

The reaction conditions of the condensation reaction are not particularly limited and may be appropriately set 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 pressure of the condensation reaction may be, for example, atmospheric pressure or 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 carried out in an open system from the viewpoint of removing the acid catalyst.

The condensation step causes intermolecular dehydration of hydroxysilane, and a large number of hydroxysilane molecules are polymerized (condensed). As a result, a polymer (siloxane compound) is produced.

In addition, hydrolysis and condensation may occur at the same time.

(Film formation process)
The production method according to the present embodiment may include a film forming step of adhering a solution containing a polymer obtained in the condensation step to an electrode to form a film.

The description of the electrodes is as follows: [1. Chemical sensor element].

The method of adhering is not particularly limited, and examples thereof include known methods such as coating, spraying, and dipping. After these steps, a step of making the film thickness uniform by spin coating may be performed. After adhesion, it may be heated to evaporate the solvent. The heating conditions are not particularly limited and may be appropriately set according to the type of solvent and the like. In one example, the heating temperature can be, for example, 100 ° C. to 400 ° C., preferably 200 ° C. to 300 ° C. The reaction time of heating can be, for example, 1 minute to 1 hour, preferably 10 minutes to 30 minutes.

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

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

When it is carried out after the condensation step, for example, HMDS, trialkylhalosilyl, or the like may be mixed with the solution containing the polymer. As a result, a part of the terminal silanol group can be modified to the M unit.

When performed after the film forming step, for example, a solution containing HMDS or trialkylhalosilyl or the like is dropped or exposed to heated vapor such as HMDS. This allows some of the silanol groups on the surface to be modified to M unit silica.

The specific method may be carried out 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. This is an example of the manufacturing method of the chemical sensor element described in [Chemical sensor element]. 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 same. Specific explanations of these are described in [1. Chemical sensor element] and [2. Chemical sensor].

[4. Summary]
As described above, the present disclosure includes the following.
(1) When Q units and T units are included in an amount of 50 mol% or more and the total of Q units and T units is 100 mol%, Q units are 10 mol% to 80 mol% and T units are 90. A chemical sensor element comprising a detection material containing a siloxane compound containing mol% to 20 mol%.
(2) The chemical sensor element according to (1), wherein the substituent in the T unit is a methyl group or a phenyl group.
(3) The chemical sensor element according to (1) or (2), wherein the siloxane compound contains 20 mol% to 60 mol% of the Q unit.
(4) A chemical sensor including the chemical sensor element according to any one of (1) to (3).
(5) The chemical sensor according to (4), wherein the detection target is a volatile organic compound in a gas.
(6) The chemical sensor according to (4) or (5), which measures a change in capacitance associated with adsorption of a volatile organic compound to the detection material.
(7) Further equipped with a sensor element for quantifying water vapor in the gas.
The chemical sensor according to any one of (4) to (6), which quantifies water vapor and volatile organic compounds in the gas to be measured based on the difference in the signal amount of each sensor element.
(8) When tetraalkoxysilane and trialkoxysilane are contained in an amount of 50 mol% or more of the total alkoxysilane and the total of tetraalkoxysilane and trialkoxysilane is 100 mol%, the amount of tetraalkoxysilane is 10 mol% to 80. In an alkoxysilane solution containing 90 mol% to 20 mol% of mol% and trialkoxysilane, a hydrolysis step of hydrolyzing alkoxysilane to hydroxysilane, and
A method for manufacturing a chemical sensor element, which comprises a condensation step of condensing the hydroxysilane by intermolecular dehydration.
(9) The method for producing a chemical sensor element according to (8), wherein the trialkoxysilane is methyltrialkoxysilane or phenyltrialkoxysilane.
(10) The method for manufacturing a chemical sensor element according to (8) or (9), which comprises a film forming step of adhering a solution containing a polymer obtained in the condensation step to an electrode to form a film.

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

An embodiment of the present disclosure will be described below.

[Manufacturing of chemical sensor elements]
The total amount of phenyltrimethoxysilane (PTMS) or methyltrimethoxysilane (MTMS), which is a precursor of T units, and tetraethoxysilane (TEOS), which is a precursor of Q units, is 4.0 mmol in the ratio shown in Table 1. Was mixed with and dissolved in ethanol as a solvent. Further, formic acid and distilled water were added dropwise as catalysts. This was reacted in a closed system at 60 ° C. for 12 hours with stirring for hydrolysis.

Further, in an open system, formic acid was volatilized by reacting at 60 ° C. for 12 hours while adding ethanol as appropriate. In this way, an ethanol solution of 10% by weight of each polymer containing no insoluble gel was obtained.

This solution was applied onto a comb electrode having a width and depth of 1 μm and spin coated at 2000 rpm. Then, it was heated at 200 ° C. for 1 hour to volatilize the solvent remaining in the membrane. Further, it was heated at 400 ° C. for 6 hours to carry out a dehydration condensation reaction to obtain a transparent thin film having a thickness of about 1 μm covering the comb-shaped electrode. In this way, a chemical sensor device including a detection material containing a siloxane compound was produced.

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

〔result〕
The results are shown in FIGS. 3-4. 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. It is a figure which shows. FIG. 4 is a log-log graph showing the gas concentration dependence 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. It is a figure which shows.

It was found that the larger the proportion of the Q unit of the siloxane compound in the detection material, the larger the amount of change in capacitance with respect to the detection target gas having the same concentration. Further, the lower the concentration of the detection target gas, the higher 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 adsorbing the gas. It was.

In addition, the fact that the amount of change in capacitance tends to increase with respect to acetone, which is a polar gas, and toluene, which is a low-polarity gas, is not the result of changes in the affinity of the pore surface for gas, but is volatile organic. It is shown that this is a result of the increase in the pores to which the compound can be adsorbed.

FIG. 5 is a graph showing a change in capacitance with respect to water vapor (relative humidity 1%) and 500 ppm of each detection target gas for each Example and Comparative Example. As the proportion of TEOS increased, the amount of change in capacitance tended to increase. However, when the ratio of TEOS is 100%, the amount of change in capacitance with respect to water vapor sharply increases, while the amount of change in capacitance with respect to the gas to be detected sharply decreases.

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

[Reference example]
²⁹ Si-NMR was measured for 3 days by the Single Pulse method on a solid obtained by calcining the sample of Example 6 synthesized with 60% MTMS and 40% TEOS as precursors 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 unit and the Q unit were polymerized with the abundance ratio in the raw material monomer.

The present disclosure can be used for chemical sensors for gas detection.

1 Chemical sensor element 2 Substrate 3 Detection unit 4 Comb electrode 4a 1st electrode 4b 2nd electrode 4c, 4d terminal 5 Detection material 6 Insulation layer 7 Via hole 10 Chemical sensor 20 Control unit 30 Signal processing unit 40 Output unit 50 External device

Claims (10)

When the Q unit and the T unit are included 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% and the T unit is 90 mol% to 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. The chemical sensor element according to claim 1 or 2, 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 a gas. The chemical sensor according to claim 4 or 5, which measures a change in capacitance associated with adsorption of a volatile organic compound to the detection material. Further equipped with a sensor element that quantifies water vapor in the gas,
The chemical sensor according to any one of claims 4 to 6, which quantifies water vapor and volatile organic compounds in the gas to be measured based on the difference in the signal amount of each sensor element. When tetraalkoxysilane and trialkoxysilane are contained in an amount of 50 mol% or more of the total alkoxysilane and the total of tetraalkoxysilane and trialkoxysilane is 100 mol%, the amount of tetraalkoxysilane is 10 mol% to 80 mol%. In an alkoxysilane solution containing 90 mol% to 20 mol% of trialkoxysilane, a hydrolysis step of hydrolyzing alkoxysilane into hydroxysilane, and
A method for manufacturing a chemical sensor element, which comprises a condensation step of condensing the hydroxysilane by intermolecular dehydration. The method for manufacturing a chemical sensor element according to claim 8, wherein the trialkoxysilane is methyltrialkoxysilane or phenyltrialkoxysilane. The method for manufacturing a chemical sensor element according to claim 8 or 9, further comprising a film forming step of adhering a solution containing a polymer obtained in the condensation step to an electrode to form a film.

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