JP7804512B2 - sensor - Google Patents

Description

The present invention relates to a sensor.

Sensors generally have a detection element (receptor) that enables highly sensitive and selective detection of target analytes. A wide variety of materials are used as receptors, including self-assembled monolayers, monolayers, DNA/RNA, proteins, antigens/antibodies, and polymers. With the recent development of AI and IoT, new applications are expected in the field of olfactory/gas sensors. In recent years, the waste of fruit and vegetables due to over-ripening during food transportation has been recognized as a major global problem. As fruit and vegetables ripen, they emit unique gases such as ethylene, ethanol, and acetaldehyde. When using sensors to manage food quality, it is particularly important to track the ethanol and aldehydes that result from anaerobic respiration of food.

Patent Document 1 describes a sensor in which a porous or granular material is coated on a sensor body that detects a physical parameter, and the analyte molecules are detected by measuring a change in the physical parameter caused by the analyte molecules being adsorbed by the porous or granular material.

Patent document 2 describes a nanomechanical sensor that uses a receptor material made of a low-hygroscopic material to prevent the receptor layer from being adversely affected by water.

International Publication No. 2016/121155 International Publication No. 2018/221283

While the technology described in Patent Document 1 achieves high sensitivity, selectivity, and stability, the electrical signal is significantly attenuated except in dry atmospheres, significantly limiting the environments in which it can be used as an olfactory sensor.

The technology described in Patent Document 2 can reduce the effect of water contained in the sample on the sensor output, expanding the range of use of the sensor. However, the low solubility of the receptor material can easily reduce throughput when applying ink.

The present invention was made in consideration of the problems inherent in the above-mentioned conventional technology, and its purpose is to provide a sensor with a sensitive film that has excellent resistance to humidity effects, can measure highly hydrophilic gases such as ethanol and aldehydes without significant attenuation of the electrical signal even under relatively high humidity conditions, and has a high coating throughput.

In order to solve the above problems, the inventors of the present application conducted extensive research and experimentation, and as a result, unexpectedly discovered that the above problems could be solved, leading to the completion of the present invention.

That is, the present invention includes the following aspects.
[1]
A sensor having a sensitive membrane,
the sensitive film has absorption peaks in the range of 1600 to 1800 cm ⁻¹ and the range of 1350 to 1450 cm ⁻¹ in infrared total reflection absorption measurement,
the peak intensity ratio (A/B) of the absorption peak maximum (A) in the 1600 to 1800 ^cm region to the absorption peak maximum (B) in the 1350 to 1450 ^cm region is 0.1 to 4.0;
sensor.
[2]
The absorption peak in the 1350 to 1450 ^cm region includes an absorption peak derived from an interatomic bond between a silicon atom and an aromatic carbon atom.
The sensor described in [1].
[3]
The absorption peak in the 1600 to 1800 ^cm region includes an absorption peak derived from a carbonyl group.
The sensor according to [1] or [2].
[4]
The absorption peak in the region of 1600 to 1800 cm ⁻¹ includes an absorption peak of a carbonyl group that forms an amide bond.
The sensor according to any one of [1] to [3].
[5]
The sensitive film has a structure containing a unit represented by the formula RSiO _3/2 (wherein R represents an organic functional group).
The sensor according to any one of [1] to [4].
[6]
the organic functional group contains at least one amide bond;
The sensor according to [5].
[7]
The organic functional group contains at least one type of aromatic ring.
The sensor according to [5] or [6].
[8]
It is a surface stress sensor.
The sensor according to any one of [1] to [7].

The present invention provides a sensor with a sensitive film that has excellent resistance to humidity effects, is capable of measuring highly hydrophilic gases such as ethanol and aldehydes without significant attenuation of the electrical signal even under relatively high humidity conditions, and has a high application throughput (hereinafter simply referred to as throughput).

1 shows examples of optical microscope photographs of chips coated with the sensitive films of Example 1 and Comparative Example 3. 1 shows the results of microscopic ATR spectra of Example 1 and Comparative Example 1. 1 shows the response of Example 1 to ethanol at humidity levels of 0% and 50%. 1 shows the responsiveness of Comparative Example 1 to ethanol at humidity levels of 0% and 50%.

The following describes in detail an embodiment of the present invention (hereinafter referred to as the "present embodiment"); however, the present invention is not limited to this embodiment, and various modifications are possible without departing from the spirit of the present invention.

1. Sensor The sensor of this embodiment is a sensor having a sensitive film, wherein the sensitive film has absorption peaks in the 1600 to 1800 cm ⁻¹ region and the 1350 to 1450 cm ⁻¹ region in infrared total reflection absorption measurement, and the peak intensity ratio (A/B) of the absorption peak maximum (A) in the 1600 to 1800 cm ⁻¹ region to the absorption peak maximum (B) in the 1350 to 1450 cm ⁻¹ region is 0.1 to 4.0.

The sensor of this embodiment includes, but is not limited to, a sensor body of a type that detects physical parameters. Examples of physical parameters include, but are not limited to, surface stress, stress, force, surface tension, pressure, mass, elasticity, Young's modulus, Poisson's ratio, resonant frequency, frequency, volume, thickness, viscosity, density, magnetic force, magnetic quantity, magnetic field, magnetic flux, magnetic flux density, electrical resistance, electrical quantity, permittivity, power, electric field, charge, current, voltage, electric potential, mobility, electrostatic energy, capacitance, inductance, reactance, susceptance, admittance, impedance, conductance, plasmon, refractive index, luminous intensity, temperature, and various other physical parameters.

The sensor of this embodiment is not particularly limited, but may be, for example, a sensor in which a sensitive film (sometimes referred to as a "receptor layer" in this technical field) is provided directly on the sensor body. In other words, the sensor of this embodiment can be configured to detect, via the sensor body, a change in a physical parameter caused by the sensitive film adsorbing sample molecules. As described above, there are no particular limitations on the sensor body that can be used in this embodiment, as long as it detects a change caused in the sensitive film disposed on its surface by the adsorption of a substance to be detected.

The sensor of this embodiment can also be used as a surface stress sensor (MSS). The surface stress sensor is preferably a four-point fixed piezoelectric element type surface stress sensor. In this case, the surface stress sensor can be fabricated by coating at least a portion of the surface of the sensor body made of a piezoelectric element with a sensitive film. When the coated sensitive film adsorbs the substance to be detected, the stress change induced in the sensitive film is detected and the body outputs a signal.

Furthermore, a different type of sensor body may be used, but is not limited to, a QCM (quartz crystal microbalance) device. A QCM device is a mass sensor that measures minute changes in mass by utilizing the property that when a substance is adsorbed onto the electrode surface of a quartz crystal oscillator to which an AC electric field is applied, the resonant frequency decreases depending on the mass, viscoelasticity, etc. of the adsorbate, and is capable of in-situ measurement. When the sensor body of this embodiment is used as a QCM device, for example, by forming the sensitive film of this embodiment on the surface of the electrode, the sensor body detects the mass change that occurs when the sensitive film adsorbs the substance to be detected, and outputs a signal.

In addition, various conductive materials can be used as electrodes for the QCM, but if the sensitive film in this embodiment is made conductive, the sensitive film can also be used as an electrode for the QCM.

In this embodiment, the term "adsorption" refers to the phenomenon in which the concentration of another substance acting as an adsorbate at the interface of any object increases compared to the surrounding area of the interface, and includes not only physical adsorption but also chemical adsorption due to chemical bonding or biochemical reactions.

1.1. Sensitive Film The sensitive film of this embodiment has absorption peaks in the 1600 to 1800 cm ⁻¹ region and the 1350 to 1450 cm ⁻¹ region in infrared total reflection absorption measurement, and the peak intensity ratio (A/B) of the absorption peak maximum (A) in the 1600 to 1800 cm ⁻¹ region to the absorption peak maximum (B) in the 1350 to 1450 cm ⁻¹ region is 0.1 to 4.0.

With the peak intensity ratio (A/B) in the range of 0.1 to 4.0, sensors with this sensitive film have excellent humidity resistance and throughput.

When calculating the above absorption peaks and peak intensity ratios (A/B), baseline correction was performed by setting the baseline where no peaks existed to an absorbance of 0. A peak was defined as one with a maximum absorbance value of 0.02 or greater.

Here, the peak intensity ratio (A/B) of the absorption peak maximum (A) in the 1600 to 1800 ^cm region to the absorption peak maximum (B) in the 1350 to 1450 ^cm region is not particularly limited, but can be adjusted, for example, by changing the amount of carbonyl groups introduced into the organic functional groups.

Furthermore, it is preferable that the absorption peaks in the 1350 to 1450 cm ⁻¹ region include an absorption peak derived from an interatomic bond between a silicon atom and an aromatic carbon atom, which tends to result in excellent resistance to humidity effects.

Here, the absorption peak in the region of 1350 to 1450 cm ⁻¹ is not particularly limited, but for example, when the sensitive film has an organic functional group derived from a silane coupling agent, it can be adjusted by changing the type of organic functional group.

Furthermore, the absorption peaks in the 1600 to 1800 ^cm region preferably include an absorption peak derived from a carbonyl group, and more preferably include an absorption peak derived from a carbonyl group that forms an amide bond, which tends to improve throughput.

Here, the absorption peak in the region of 1600 to 1800 cm ⁻¹ is not particularly limited, but for example, when the sensitive film has an organic functional group derived from a silane coupling agent, it can be adjusted by changing the type of organic functional group.

1.1.1 Organic-inorganic hybrid The sensitive film in this embodiment preferably includes a structure represented by RSiO _3/2 from the viewpoints of having high sensitivity, excellent resistance to humidity influences, and not significantly attenuating sensitivity and electrical signals even in a relatively high humidity environment. Here, R represents an organic functional group. Furthermore, hereinafter, a molecular chain including a structure represented by RSiO _3/2 is also referred to as an organic-inorganic hybrid.

There are no particular limitations on the method for introducing the structure represented by RSiO _3/2 , but examples thereof include including a silane coupling agent in the monomer units that constitute the sensitive film.

The sensitive film in this embodiment may have a uniform thickness distribution of the organic-inorganic hybrid, or a coffee-ring shape in which the thickness is thicker at the edges. In the case of a coffee-ring shape, the thickness of the thinnest part of the sensitive film in the center and the thickest part at the edges are preferably typically 10 nm or more and 50 μm or less. From the viewpoint of shortening the drying time during manufacturing and increasing productivity, the film thickness is preferably 10 nm or more and 30 μm or less, and from the viewpoint of increasing sensitivity, it is more preferably 10 nm or more and 20 μm or less. Furthermore, the maximum thickness of the sensitive film in this embodiment is preferably 30 μm or less.

To use the surface stress sensor (MSS) coated with the sensitive film of this embodiment as an olfactory sensor, it is preferable that the organic functional groups and gas molecules interact in the gas phase and diffuse into the sensitive film, generating stress, thereby detecting the gas.

In this embodiment, the organic-inorganic hybrid preferably has an organic group having a carbonyl group (e.g., a carboxyl group, an ester group, a urethane group, a urea group, an amide group, etc.). Among these, an organic group having an amide group is preferred. An example of an organic group having an amide group is an organic group represented by -NH-CO- ^R1 . Examples of ^R1 include linear or branched hydrocarbon groups which may have a substituent such as a halogen atom (e.g., linear or branched _C1-8 alkyl groups such as a 3-chloropropyl group or an octyl group), alicyclic hydrocarbon groups which may have a substituent such as a halogen atom (e.g., a _C5-6 cycloalkyl group such as a cyclohexyl group), monovalent alicyclic hydrocarbon groups which may have a substituent such as a halogen atom (e.g., a _C5-6 cycloalkyl group such as a cyclohexyl group), and aromatic hydrocarbon groups which may have a substituent such as a halogen atom (e.g., a phenyl group or a pentafluorophenyl group).

In this embodiment, the organic-inorganic hybrid preferably contains an organic functional group that includes one or more aromatic rings. When the organic functional group includes an aromatic ring, humidity resistance tends to be improved. The aromatic ring is not particularly limited and can be selected appropriately taking into account the application of the sensor, etc., but examples include aromatic hydrocarbon groups such as phenyl, naphthyl, p-tolyl, and biphenyl; substituted aromatic hydrocarbon groups such as 4-chlorophenyl, 4-methoxyphenyl, 4-aminophenyl, and pentafluorophenyl; heterocyclic hydrocarbon groups such as 3-furyl, 3-thienyl, 2-pyridyl, 3-pyridyl, and 4-pyridyl; and metallocenes such as ferrocenyl. The organic functional group used in this embodiment can be selected appropriately and may include one or more of the above-mentioned aromatic rings.

In organic-inorganic hybrids, a spacer structure such as an alkanediyl group (having 1 to 18 carbon atoms), an ether group, a carbonyl group, a carboxyl group, an amide group, a urethane bond, a urea bond, an imide group, or an imine group may be sandwiched between the carbonyl group and the silicon atom, or between the aromatic ring and the silicon atom. Hereinafter, a structure having a spacer between the aromatic ring and the silicon atom will also be referred to as having a "structure not directly bonded to an aromatic ring." From the perspective of responsiveness and sensitivity, it is preferable not to sandwich such a spacer between the aromatic ring and the silicon atom, and for the aromatic carbon atom to be directly bonded to the silicon atom in the organic-inorganic hybrid (hereinafter, also referred to as having a "structure directly bonded to an aromatic ring").

In addition, from the viewpoint of humidity resistance, the organic-inorganic hybrid of this embodiment preferably includes a copolymer structure of a monomer unit having a directly bonded aromatic ring structure and a monomer unit having a non-directly bonded aromatic ring structure and a carbonyl group. In addition, from the viewpoint of achieving both humidity resistance and selectivity to various gas molecules, the organic-inorganic hybrid of this embodiment preferably includes a copolymer structure of a monomer unit having a directly bonded aromatic ring structure and a monomer unit having an aromatic ring structure and a carbonyl group. In addition, from the viewpoint of responsiveness to highly polar gases and odor molecules, the organic functional group of this embodiment preferably includes a functional group containing one or more atoms selected from the group consisting of nitrogen atoms, oxygen atoms, sulfur atoms, halogen atoms such as fluorine, chlorine, bromine, and iodine atoms, boron atoms, and phosphorus atoms. Among these, from the viewpoint of stability, the organic functional group preferably includes a functional group containing one or more atoms selected from the group consisting of nitrogen atoms, oxygen atoms, sulfur atoms, and fluorine atoms.

Specific examples of the organic functional group other than those described above in this embodiment are not limited to the following: a linear or branched hydrocarbon group which may have a substituent such as a halogen atom (for example, a linear or branched C _1-8 alkyl group such as a 3-chloropropyl group or an octyl group); an alicyclic hydrocarbon group which may have a substituent such as a halogen atom (for example, a C _5-6 cycloalkyl group such as a cyclohexyl group); an organic group having an unsaturated bond (for example, a vinyl group, an allyl group, a (meth)acrylic group, a (meth)acryloyloxyalkyl group (for example, a (meth)acryloyloxyC _1-3 alkyl group such as a (meth)acryloyloxypropyl group)); an organic group having an oxygen atom (for example, an epoxy group, a glycidyloxyalkyl group (for example, a glycidyloxyC 1-3 alkyl group such as a 3-glycidyloxypropyl group)); _1-3 alkyl group), (epoxycycloalkyl)alkyl group (for example, a 2-(3,4-epoxycyclohexyl)ethyl group, etc.), a hydroxy group, an alkyl ether group), an organic group having a sulfur atom (for example, a mercapto group, a mercaptoalkyl group (for example, a mercaptoC _1-3 alkyl group such as a mercaptopropyl group), a sulfide group), an organic group having a nitrogen atom (for example, an amino group (for example, a primary amino group, a secondary amino group, a tertiary amino group), an aminoalkyl group (for example, an aminoC _1-3 alkyl group such as an aminopropyl group), an (aminoalkylamino)alkyl group (for example, a 3-(2-aminoethylamino)propyl group), an imidazolyl group, an imidazolylalkyl group (for example, a 3-(2-imidazolin-1-yl)propyl group), an alkylaminoalkyl group (for example, a 3-(dimethylamino)propyl group), an oxime group, an imide group, an imine group, a nitrile group), a halogen group, an organic group having a phosphorus atom (for example, a phosphonic group, a phosphate group), and the like. Among these, from the viewpoint of excellent throughput, it is preferable to use an amide group as the organic functional group. From the viewpoint of availability, it is preferable to use one or more selected from the group consisting of an optionally substituted linear or branched hydrocarbon group, an optionally substituted alicyclic hydrocarbon group, an optionally substituted aromatic hydrocarbon group, a vinyl group, an allyl group, a (meth)acryloyloxyalkyl group, a glycidyloxyalkyl group, an (epoxycycloalkyl)alkyl group, a mercaptoalkyl group, an aminoalkyl group, an (aminoalkylamino)alkyl group, an imidazolylalkyl group, an alkylaminoalkyl group, and a hydroxy group. These functional groups can be appropriately selected and used, and one type can be used alone or two or more types can be used in combination.

Among these, the organic functional group is preferably an organic functional group derived from a silane coupling agent. Silane coupling agents are not particularly limited, but examples include hydrolyzable metal oxides such as alkoxysilane, acetoxysilane, and chlorosilane. Among these, alkoxysilane is preferred as the hydrolyzable metal oxide in terms of ease of handling and the versatility of the functional group, and trifunctional alkoxysilane is more preferred in terms of reactivity.

Trifunctional alkoxysilanes may be copolymerized with mono-, di-, or tetrafunctional alkoxysilanes, but copolymerization with tetrafunctional alkoxysilanes is preferred from the standpoint of increasing the Young's modulus of the organic-inorganic hybrid and improving its sensitivity.

The trifunctional alkoxysilane is not particularly limited, but for example, a silane coupling agent having a methoxy group, an ethoxy group, or an isopropoxy group in the alkoxy group can be used.

Aromatic silane coupling agents are not particularly limited, but examples include phenyltrialkoxysilane, nitrobenzeneamidotrialkoxysilane, benzyltrialkoxysilane, 4-chlorophenyltrialkoxysilane, phenylaminopropyltrialkoxysilane, 4-aminophenyltrialkoxysilane, naphthyltrialkoxysilane, 4-methoxytrialkoxysilane, pentafluorophenyltrialkoxysilane, ferrocenyltrialkoxysilane, biphenyltrialkoxysilane, 3-furyltrialkoxysilane, 3-thienyltrialkoxysilane, 2-pyridyltrialkoxysilane, 3-pyridyltrialkoxysilane, and 4-pyridyltrialkoxysilane, but are not limited to these.

Non-aromatic silane coupling agents are not particularly limited, but examples include 3-(2-aminoethylamino)propyltrialkoxysilane, 3-mercaptopropyltrialkoxysilane, vinyltrialkoxysilane, cyclohexyltrialkoxysilane, 3-glycidyloxypropyltrialkoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrialkoxysilane, 3-(dimethylamino)propyltrialkoxysilane, 3-(2-imidazolin-1-yl)propyltrialkoxysilane, 3-aminopropyltrialkoxysilane, 3-(methacryloyloxy)propyltrialkoxysilane, 3-(acryloyloxy)propyltrialkoxysilane, allyltrialkoxysilane, methyltrialkoxysilane, and ethyltrialkoxysilane. Examples of suitable alkoxysilanes include, but are not limited to, alkoxysilane, propyltrialkoxysilane, butylalkoxysilane, hexyltrialkoxysilane, octyltrialkoxysilane, decyltrialkoxysilane, dodecyltrialkoxysilane, octadecyltrialkoxysilane, 3-ureidopropyltrialkoxysilane, cyclohexylaminopropyltrialkoxysilane, hexafluorophenyltrialkoxysilane, 3-chloropropyltrialkoxysilane, 3-bromopropyltrialkoxysilane, 3-piperazinopropyltrialkoxysilane, 3-morpholinopropyltrialkoxysilane, 3-allylaminopropyltrialkoxysilane, norbornyltrialkoxysilane, and piperidinopropyltrialkoxysilane.

When two or more types of silane coupling agents are copolymerized, the molar ratio of aromatic silane coupling agent to non-aromatic silane coupling agent is preferably 1:10 to 1:5, with 1:5 to 1:1 being preferred from the standpoint of heat resistance, and 1:1 to 10:1 being preferred from the standpoint of suppressing a decrease in signal intensity under humid conditions.

The organic functional groups in the sensor of this embodiment can be identified by subjecting the sensitive film on the sensor body to surface elemental analysis using techniques such as scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy (XPS), and infrared attenuated total reflection spectroscopy (ATR).

In this embodiment, from the viewpoint of sensitivity and stability in a humid environment, the porosity as a volume fraction of the sensitive film is 10% or less. From the viewpoint of further improving sensitivity, 5% or more is more preferable, and from the viewpoint of suppressing a decrease in sensitivity in a humid environment, 3% or less is even more preferable. The porosity can be adjusted to the above range, for example, by adjusting the ratio of the filler to the structure expressed as RSiO _3/2 . The porosity is not particularly limited, and is a value measured, for example, by the following method or a method that will be understood by those skilled in the art to be equivalent thereto.

The sensitive film, cross-sectioned by dicing, is then fixed to the processing stage and processed using FIB milling, followed by cross-sectional SEM observation. The microstructured layer is extracted from the image obtained through cross-sectional SEM observation, and the voids present in the organic-inorganic hybrid are further extracted. For extraction, the area around the voids in the obtained image has bright contrast due to the edge effect, while the voids themselves have dark contrast. This can be extracted by performing binarization processing using image analysis software, or by performing binarization processing that colors the microstructured layer white and the voids, substrate, and background black. Additionally, areas that cannot be fully captured by binarization processing can be manually identified and supplemented. The ratio of the area of the portion corresponding to the voids in the extracted void image to the area of the microstructured layer and the portion corresponding to the voids can be calculated as the void ratio in the microstructured layer. This process is performed on several fields of view, and the number average value can be used to determine the void ratio.

The porosity, as a volume fraction, of the above-mentioned sensitive film is preferably 10% or less. This allows for highly hydrophilic gases such as ethanol and aldehyde to be measured with high sensitivity without significant attenuation of the electrical signal, even under relatively high humidity conditions. Furthermore, there is a tendency for the sensitive film to continue to deteriorate even after reflow processing or long-term use, allowing for continuous measurement.

1.1.2. Manufacturing Method of Organic-Inorganic Hybrids There are no particular limitations on the manufacturing method of organic-inorganic hybrids, but they are mainly manufactured using a sol-gel method. Specifically, a hydrolyzable silane compound (including a silane coupling agent) is hydrolyzed and condensed under acidic or basic conditions in the presence of water to obtain a condensate of the silane coupling agent, i.e., an organic-inorganic hybrid containing a structure represented by RSiO3 _/2 .

Among these, it is more preferable to hydrolyze, condense, and surface-modify the silane coupling agent in the presence of a catalyst, as this allows for adjustment of the reaction rates of hydrolysis and condensation.

Types of catalysts include acid catalysts and base catalysts. Acid catalysts are not particularly limited, but include inorganic acids and organic acids. Inorganic acids include, but are not limited to, hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, phosphoric acid, and boric acid. Organic acids include, but are not limited to, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oxalic acid, maleic acid, methylmalonic acid, benzoic acid, p-aminobenzoic acid, p-toluenesulfonic acid, benzenesulfonic acid, trifluoroacetic acid, formic acid, malonic acid, sulfonic acid, phthalic acid, fumaric acid, citric acid, tartaric acid, citraconic acid, malic acid, and glutaric acid. Base catalysts include, for example, inorganic bases and organic bases. Examples of inorganic bases include, but are not limited to, alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide; alkali or alkaline earth metal carbonates such as lithium carbonate, potassium carbonate, and sodium carbonate; and metal bicarbonates such as potassium bicarbonate and sodium bicarbonate. Examples of organic bases include, but are not limited to, trialkylamines such as triethylamine and ethyldiisopropylamine; N,N-dialkylaniline derivatives having 1 to 4 carbon atoms such as N,N-dimethylaniline and N,N-diethylaniline; and pyridine derivatives that may have an alkyl substituent having 1 to 4 carbon atoms, such as pyridine and 2,6-lutidine. These catalysts can be used alone or in combination.

Furthermore, from the standpoint of reaction efficiency, it is preferable to add a catalyst in an amount that brings the pH of the hydrolysis and condensation reaction system to a range of 0.01 to 6.0, or to a pH of 8 to 14. To further increase efficiency, it is more preferable to carry out the sol-gel reaction under basic conditions of pH 8 to 14.

The hydrolysis and condensation reactions for producing organic-inorganic hybrids can also be carried out in an organic solvent. Examples of organic solvents that can be used in condensation reactions include alcohols, esters, ketones, ethers, aliphatic hydrocarbon compounds, aromatic hydrocarbon compounds, and amide compounds.

Examples of the alcohol include, but are not limited to, monohydric alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol; polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, glycerin, trimethylolpropane, and hexanetriol; and monoethers of polyhydric alcohols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether.

Examples of the esters include, but are not limited to, methyl acetate, ethyl acetate, butyl acetate, and gamma-butyrolactone. Examples of ketones include, but are not limited to, acetone, methyl ethyl ketone, and methyl isoamyl ketone.

In addition to the monoethers of polyhydric alcohols mentioned above, the ethers include, but are not limited to, polyhydric alcohol ethers in which all of the hydroxyl groups of polyhydric alcohols have been alkyl-etherified, such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, and diethylene glycol diethyl ether; tetrahydrofuran; 1,4-dioxane; anisole; and the like.

Examples of the aliphatic hydrocarbon compounds include, but are not limited to, hexane, heptane, octane, nonane, decane, etc.

Examples of the aromatic hydrocarbon compounds include, but are not limited to, benzene, toluene, xylene, etc.

Examples of the amide compound include, but are not limited to, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, etc.

Among the above solvents, alcohols such as methanol, ethanol, isopropanol, and butanol; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ethers such as ethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether; and amide compounds such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone are preferred because they are easily miscible with water. These solvents may be used alone or in combination.

When incorporating a filler into an organic-inorganic hybrid, the organic-inorganic hybrid may be produced in the presence of the filler, or the filler may be incorporated into the organic-inorganic hybrid. A silane coupling agent condensate may be dissolved in a commercially available dispersion filler, or the filler and silane coupling agent may be dispersed using a ball mill or jet mill. Alternatively, the hybrid may be produced by simultaneously condensing an alkoxysilane and a filler. However, simultaneous condensation of an alkoxysilane and a filler is preferred for improving the solvent dispersibility of the filler and improving inkjet coating properties. When a colloidal filler is treated using the sol-gel method in the presence of a silane coupling agent, the condensate of the silane coupling agent modifies the filler surface and fills the gaps. The pore volume can be adjusted by adjusting the amount of alkoxysilane. If hydroxyl groups are present on the filler surface, the surface hydroxyl groups and the hydroxyl groups generated by hydrolysis of the alkoxysilane interact and form ether bonds through a condensation reaction, enhancing the compatibility between the filler and the condensate and resulting in a more stable sensor film.

Fillers can also be surface-modified using organic functional groups. This modification can be carried out by surface-modifying the filler while it is dispersed in a dispersion medium. Specifically, for example, an organic-inorganic hybrid can be produced by adding the above-mentioned silane coupling agent to a uniform dispersion of metal oxide containing alcohol and water in the presence of a catalyst.

The organic-inorganic hybrid can be recovered by separating the precipitate or gel by centrifugation or filtration, or it can be isolated by removing the volatile solvent using an evaporator, etc.

The introduction of organic functional groups into organic-inorganic hybrids can be confirmed by ATR. Carbonyl groups (C═O bonds) can be identified based on absorption peaks in the wavenumber region of 1600 to 1800 cm ^−1. Substituents having C═O bonds are not particularly limited, but examples include carbonyl groups, amide groups, urea groups, urethane groups, ester groups, carboxylic acid groups, and acid anhydride groups.

Of these, amide groups, urea groups, and ester groups are preferred from the perspective of organic-inorganic hybrid synthesis, with amide groups being more preferred from the perspective of solubility in organic solvents and throughput. The reasons for this are thought to be, but are not limited to, as follows: the bond between the nitrogen atom and hydrogen atom (N-H bond) of the amide group forms a hydrogen bond with molecules in the solvent that becomes the ink, thereby improving solubility.

Whether or not the carbonyl group is derived from a carbonyl group that forms an amide bond can be determined by observing the stretching vibration of the N—H bond in the region of 3000 to 3400 cm ⁻¹ or by using X-ray photoelectric spectroscopy such as XPS.

The bond between a silicon atom and a carbon atom (Si—C bond) can be identified based on the absorption peak in the wave number region of 1350 to 1450 cm ⁻¹ .

This can also be confirmed by thermal weight loss measurements. In order to eliminate the effects of adsorbed water, the thermal weight loss rate of the organic component (combined inorganic filler (i) and organic functional group (ii)) from 150°C to 1000°C is preferably 3% to 75% from the viewpoint of sensitivity, more preferably 5% to 65% from the viewpoint of humidity resistance, and even more preferably 5% to 60% from the viewpoint of thermal stability. In other words, the amount of organic functional groups in the organic-inorganic hybrid in this embodiment is not particularly limited, but is preferably 75% by weight or less, more preferably 65% by weight or less, from the viewpoint of balancing responsiveness to analytes and stability of the sensitive membrane.

1.2. Filler The sensitive film in this embodiment preferably further contains a filler. The use of a filler can improve the Young's modulus of the organic-inorganic hybrid and increase sensitivity. The filler in this embodiment is not particularly limited and can be selected from various known fillers. Specific examples include, but are not limited to, one or more selected from the group consisting of polymer beads such as polystyrene, polymethyl methacrylate, and polyphenylene oxide, spherical particles such as acrylic latex, metal nitrides such as silicon nitride, metal oxides such as silica, zirconia, titania, zinc oxide, aluminum oxide, and tin oxide, composite metal compounds such as barium titanate, strontium titanate, and ITO, and inorganic metal fillers such as gold, silver, copper, palladium, platinum, iron, and aluminum.

In this embodiment, the filler is preferably an inorganic filler from the viewpoints of dispersibility and coatability. From the same viewpoints, in this embodiment, metal compounds such as silica, zirconia, titania, and alumina, and inorganic metal fillers such as gold, silver, copper, palladium, platinum, iron, and aluminum are preferred. Metal oxides such as silica and zirconia are more preferred because they are less affected by moisture in humid conditions, and silica is even more preferred from an economical perspective. The inventors have discovered that when silica is used, the response attenuation of common hydrophilic gases such as ethanol and acetaldehyde is significantly improved even in humid conditions. The reasons for this are thought to be as follows, but are not limited to the following. Specifically, the hydroxyl groups bonded to the silica skeleton and silicon atoms are relatively hydrophobic compared to the titania skeleton or hydroxyl groups bonded to titanium atoms in Patent Document 1, and therefore hydrophobic interactions are thought to suppress adsorption inhibition due to moisture.

The shape of the filler is not particularly limited, but is preferably spherical, rod-like, plate-like, fibrous, or a combination of two or more of these, and more preferably spherical or chain-like. Note that "spherical" here refers to a nearly spherical shape, including not only a perfect sphere but also a spheroid, oval, etc.

The size of the spherical filler is not particularly limited, but from the viewpoint of maintaining the dispersibility of the ink, i.e., improving the coatability in inkjet printing, the average primary particle diameter is preferably 100 μm or less, from the viewpoint of improving sensitivity, 500 nm or less is more preferable, and from the viewpoint of further reducing voids, 200 nm or less is even more preferable. Here, the average primary particle diameter refers to the number average value. The above average primary particle diameter is the number average value of 50 particles measured using a scanning electron microscope as described in the Examples section of this specification, or a method that is understood by those skilled in the art to be equivalent thereto.

The chain-like filler preferably has a continuous chain structure, and preferred examples include a structure in which spherical particles are continuously connected in a straight line, a branched structure, a bent structure, or a ring-like structure (also called a "pearl necklace" structure), or a structure in which numerous thread-like structures are entangled and not observed as individual continuous spheres (also called a "network" structure).

It is not easy to define the primary particle diameter of fillers that form a continuous chain structure by assuming that they are all spherical, but the chain width can be observed by observation with a transmission or scanning electron microscope. The chain width is 1 nm to 200 nm, preferably 1 nm to 100 nm from the perspective of increasing the surface area, and more preferably 1 nm to 85 nm from the perspective of gas response sensitivity. The above average primary particle diameter is the number average value of 50 particles measured using a scanning electron microscope as described in the Examples section of this specification, or a method that will be understood by those skilled in the art to be equivalent, and is defined as the chain width.

Such metal oxides as fillers can be produced by a sol-gel method using a metal oxide precursor having tetrafunctional hydrolyzable groups such as alkoxy and chloro, or commercially available products can be used. Examples of metal oxide precursors having tetrafunctional hydrolyzable groups include tetraalkoxysilane, tetrachlorosilane, tetraalkoxytitanium, and tetraacetoxyzirconium. These tetrafunctional hydrolyzable inorganic metal oxides may be copolymerized with trifunctional hydrolyzable metal oxides, and the shape can be controlled by adjusting the concentration, temperature, pH, water content, etc. of the reaction system. It should be noted that, for example, when a filler is produced by emulsion polymerization, a structure represented by RSiO _3/2 may be obtained on the filler side. However, a filler having such a structure in the sensitive film is considered an organic-inorganic hybrid in this embodiment.

Commercially available fillers that can be used include the LEVASIL series (manufactured by H.C. Starck Co., Ltd.), the Quatron PL series (manufactured by Fuso Chemical Co., Ltd.), and the OSCAL series (manufactured by Catalysts and Chemicals Industries Co., Ltd.); powdery silica particles include, for example, Aerosil 130, Aerosil 300, Aerosil 380, Aerosil TT600, and Aerosil OX50 (manufactured by Nippon Aerosil Co., Ltd.), Sildex H31, Sildex H32, Sildex H51, Sildex H52, Sildex H121, and Sildex H122 (manufactured by Asahi Glass Co., Ltd.), E220A and E220 (manufactured by Nippon Silica Industry Co., Ltd.), SYLYSIA 470 (manufactured by Fuji Silysia Co., Ltd.), and SG Flake (manufactured by Nippon Sheet Glass Co., Ltd.), IPA-ST, IPA-ST-L, IPA-ST-ZL, ST-XS, ST-S, ST-30, ST-50T, ST-30L, ST-YL, ST-ZL, MP-1040, MP-2040, MP-4540M, ST-OXS, ST-OS, ST-O, ST-O-40, ST-OL, ST-OYL, ST-NXS, ST-NS, ST-N, ST-N-40, ST-CXS, ST-C, ST-CM, ST-AK, ST-AK-L, ST-AK-YL, OZ-S30K, SZ-S30K-AC, OZ-S30M, Cernax CX-S505M, IPA-ST-UP, MEK-ST-UP, ST-UP, ST-PS-S, ST-PS-M, ST-OUP, ST-PS-SO, ST-PS-MO, ST-AK-PS-S, etc. (manufactured by Nissan Chemical Industries, Ltd.), and SRD-K, SRD-M, SXR-CM, SZR-K, SZR-M (manufactured by Sakai Chemical Industries, Ltd.). Examples of powder fillers include Aerosil 130, 300, 380, TT600, and OX50 (all manufactured by Nippon Aerosil Co., Ltd.), Sildex H31, H32, H51, H52, H121, and H122 (all manufactured by Asahi Glass Co., Ltd.), E220A and E220 (all manufactured by Nippon Silica Industry Co., Ltd.), SYLYSIA 470 (manufactured by Fuji Silysia Co., Ltd.), and SG Flake (manufactured by Nippon Sheet Glass Co., Ltd.).

1.3. Other Components In addition to the organic-inorganic hybrid, the sensitive film in this embodiment may contain, but is not limited to, any particles, ionic compounds, resins, low-molecular-weight compounds, and other components. The above components are not particularly limited, but for example, they may be blended into a coating liquid and applied to the surface of the sensor body, thereby obtaining a sensor having a sensitive film containing the above additives.

2. Sensor Manufacturing Method The sensor of this embodiment can be manufactured by any method, including, but not limited to, various methods for forming a sensitive film on the sensor body. The sensitive film of this embodiment can be manufactured by, for example, dispersing an organic-inorganic hybrid in an organic solvent to prepare a coating liquid and then coating the coating liquid on the sensor body. An inkjet device can be suitably used to apply the coating liquid to the sensor chip. The inkjet device ejects droplets of the coating liquid (hereinafter also referred to as ink), which are applied to the sensor to form the sensitive film. An example of a sensitive film formed on a chip is shown in FIG. 1. The sensor 1 is configured to include a chip 3 corresponding to the sensor body and a sensitive film 2 formed on its surface. In the example shown in FIG. 1, such a configuration is provided in four locations.

The method for coating the organic-inorganic hybrid on the surface of the sensor body (e.g., the MSS sensor body) is not particularly limited, but examples include coating methods using dip coating, spray coating, spin coating, inkjet spotting, casting, doctor blades, etc.

For coating a 300 μm diameter MSS membrane, inkjet and microjet methods are preferred, with microjet coating being more preferred from the standpoint of productivity.

The sensitive membrane can be manufactured, for example, by dispersing an organic-inorganic hybrid in an organic solvent and applying the resulting dispersion to the MSS chip. The organic-inorganic hybrid is dispersed in the organic solvent at a concentration of 0.1 g/L to 50 g/L to form the coating solution. From the perspective of productivity, the concentration is preferably 0.5 to 50 g/L, and from the perspective of preventing nozzle clogging, a concentration of 0.5 to 15 g/L is more preferable.

The organic solvent used to disperse the organic-inorganic hybrid may be any solvent capable of dispersing the organic-inorganic hybrid. Its boiling point is preferably between 80°C and 250°C, and more preferably between 100°C and 250°C to prevent a decrease in productivity due to nozzle clogging. It is even more preferable to have a boiling point between 100°C and 200°C to reduce the drying time and increase productivity.

Examples of organic solvents include, but are not limited to, alcohol solvents, ester solvents, ketone solvents, ether solvents, aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, and amide solvents.

Examples of alcohol solvents include, but are not limited to, monohydric alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol; polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, glycerin, trimethylolpropane, and hexanetriol; and monoethers of polyhydric alcohols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether.

Examples of ester solvents include methyl acetate, ethyl acetate, butyl acetate, and gamma-butyrolactone.

Ketone solvents include, but are not limited to, acetone, methyl ethyl ketone, methyl isoamyl ketone, etc.

Examples of ether solvents include, but are not limited to, polyhydric alcohol ethers in which all of the hydroxyl groups of polyhydric alcohols have been alkyl-etherified, such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, and diethylene glycol diethyl ether; tetrahydrofuran; 1,4-dioxane; anisole; and the like.

Aliphatic hydrocarbon solvents include, but are not limited to, hexane, heptane, octane, nonane, decane, etc.

Aromatic hydrocarbon solvents include, but are not limited to, benzene, toluene, xylene, etc.

Amide solvents include, but are not limited to, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, etc.

These organic solvents may be used alone or in combination of two or more.

Among these organic solvents, N,N-dimethylformamide and propylene glycol monomethyl ether are preferred due to their excellent safety and solubility. In particular, when the organic-inorganic hybrid of this embodiment has an amide group in the organic functional group, it is preferable to use N,N-dimethylformamide as the organic solvent from the perspective of improving throughput. The reason for this is thought to be, but is not limited to, as follows: the nitrogen-hydrogen atom bond (N-H bond) of the amide group in the organic-inorganic hybrid forms a hydrogen bond with molecules in the solvent that will become the ink, thereby improving solubility.

The present embodiment will be explained in detail below using examples and comparative examples, but the present embodiment is not limited to these.

The above-mentioned surface stress sensor was produced by coating the surface of the sensor body made of a piezoelectric element with the sensitive film produced in each example of this embodiment, and the various physical properties of the sensors in each example and comparative example were evaluated according to the following (1) to (3).

(1) Identification of organic functional group species in organic-inorganic hybrids and calculation of peak intensity ratios The organic functional groups in organic-inorganic hybrids were identified by measuring the sensitive film on the sensor body using the ATR method under the following conditions. The peak intensity ratio was calculated from the "absorbance at the maximum of the absorption peak in the wavenumber region of 1600 to 1800 cm ^-1 " / "absorbance at the maximum of the absorption peak in the wavenumber region of 1350 to 1450 cm ^-1 " (A/B) of the identified organic functional groups.

(Measurement conditions)
Apparatus used: IRAffinity-1 (Shimadzu Corporation)
Measurement method: ATR method (prism: ZnSe)
Detector: DLATGS
Aperture size: auto
IR incident angle to ATR crystal: 30°
Resolution; 4cm ^-1
Number of scans: 32

(2) Humidity Resistance The sample was subjected to a 60-minute 250 ppm ethanol purge at 25°C followed by a 60-minute nitrogen purge, which was repeated three times. The signal from the third measurement was used. The attenuation rate (%) was calculated as follows: 100 x ("the intensity of the signal measured at the third measurement under dry conditions" - "the intensity of the signal measured at the third measurement under 50% RH") / ("the intensity of the signal measured at the third measurement under dry conditions"). The attenuation rate was used to evaluate humidity resistance according to the following criteria.
[Evaluation criteria]
S: The attenuation rate is 20% or less.
A: The attenuation rate is more than 20% and 40% or less.
B: The attenuation rate is more than 40% and not more than 60%.
C: The attenuation rate is more than 60%.

(3) Throughput The organic-inorganic hybrid was dispersed in an organic solvent and applied at an ink concentration of 15 mg/mL. The throughput was evaluated according to the following evaluation criteria.
[Evaluation criteria]
A: Application was successful.
B: The nozzle was clogged midway, causing splits and other problems.
C: Precipitation of the sample occurred.

Example 1
A solution of 43.4 g of phenyltrimethoxysilane and 46.6 g of 4-(trimethoxysilyl)benzeneamine in 340 g of 2-propanol was added to 288 g of water, 32 g of 28% aqueous ammonia, and 188 g of 2-propanol in a 2000 mL separable flask, and the mixture was allowed to react at 80°C for 3 hours. After cooling the reaction mixture in air, the precipitate was isolated by filtration. After thoroughly washing the sample with ethanol and drying under vacuum at 80°C, 5 g of the precipitate was dissolved in 500 mL of N,N-dimethylacetamide in a 2000 mL separable flask, and 1.5 g of triethylamine was added. Then, 4.1 g of o-toluoyl chloride was added at 0°C and the mixture was allowed to react at room temperature for 30 minutes. After the reaction, the reaction mixture was cooled to 0°C and saturated aqueous sodium bicarbonate was added to terminate the reaction. The mixture was then subjected to three liquid-liquid extractions with ethyl acetate, washed with saturated brine, dehydrated over anhydrous magnesium sulfate, and concentrated under reduced pressure using an evaporator. 10 mL of ethyl acetate was added to the solution, and the resulting solution was dropped into a stirred hexane/ethyl acetate = 10/1 solution. The precipitated solid was isolated by filtration. The sample was thoroughly washed and dried under vacuum at 80 °C, then dissolved in DMF to a concentration of 15 g/mL. A 2-propanol dispersion of silica microparticles, IPA-ST-ZL (a Nissan Chemical product), was adjusted to 15 mg/mL with DMF, and the above solution was mixed in a 6:4 ratio to obtain a coating solution. Thirteen drops of the coating solution, each 300 pL, were applied using an inkjet device to the surface of an MSS placed on a 40 °C hot plate, yielding a surface stress sensor with a sensitive film. The appearance is shown in Figure 1.

The organic functional group species were identified and the peak intensity ratio was calculated as described in (1) above. The results are shown in Figure 2 and Table 1. The effect of humidity resistance was investigated based on the method described in (2) above, and the results are shown in Figure 3. At 0% humidity (dry conditions), the maximum amplitude was 4.52 mV, and at 50% humidity, the maximum amplitude was 2.86 mV. The effect of humidity resistance calculated using the method described above was 37%.
Furthermore, the throughput was evaluated using the method (3) above. Since the ink could be dissolved to a concentration of 15 mg/ml and could be applied, it was rated A.
The following examples and comparative examples were also evaluated in the same manner as described above.

Example 2
A solution of 71.5 g of phenyltrimethoxysilane and 21.6 g of 3-aminopropyltrimethoxysilane in 207 g of 2-propanol was added to 288 g of water, 32 g of 28% aqueous ammonia, and 340 g of 2-propanol in a 2000 mL separable flask, and the mixture was allowed to react at 80 °C for 3 hours. After air-cooling the reaction solution, the precipitate was isolated by filtration. The sample was thoroughly washed with ethanol and dried under vacuum at 80 °C. 5 g of the precipitate was dissolved in 500 mL of N,N-dimethylacetamide in a 2000 mL separable flask, and 1.5 g of triethylamine was added. 1.5 g of p-toluoyl chloride was then added at 0 °C and the mixture was allowed to react at room temperature for 30 minutes. After the reaction, the reaction solution was cooled to 0 °C and saturated aqueous sodium bicarbonate was added to terminate the reaction. The mixture was then subjected to separation and extraction three times with ethyl acetate, washed with brine, dehydrated over anhydrous magnesium sulfate, and concentrated under reduced pressure using an evaporator. 10 mL of ethyl acetate was added thereto and the resulting solution was dropped into the stirred hexane solution, and the precipitated solid was isolated by filtration.

Example 3
The procedure of Example 2 was repeated except that 1.5 g of p-toluoyl chloride was changed to 2.4 g of 2,4,6-trichlorobenzoyl chloride.

Example 4
The procedure of Example 2 was repeated except that 1.5 g of p-toluoyl chloride and 0.8 g of acetyl chloride were added dropwise to a solution of hexane/ethyl acetate=10/1 instead of a hexane solution.

Example 5
The procedure of Example 2 was repeated except that 1.5 g of p-toluoyl chloride was added dropwise to 1.1 g of methoxyacetyl chloride in a hexane solution instead of a hexane/ethyl acetate=10/1 solution.

Example 6
The procedure of Example 2 was repeated except that 1.5 g of p-toluoyl chloride was added dropwise to 2.3 g of pentafluorobenzoyl chloride in a hexane solution, instead of a hexane/ethyl acetate=10/1 solution.

Example 7
The procedure of Example 2 was repeated except that 1.5 g of p-toluoyl chloride was changed to 2.1 g of 2,3,4,5-tetrafluorobenzoyl chloride.

Example 8
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was added dropwise to a hexane solution containing 3.1 g of 3,4-difluorobenzoyl chloride instead of a hexane/ethyl acetate=10/1 solution.

Example 9
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was changed to 4.1 g of pentafluorobenzoyl chloride.

Example 10
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was added dropwise to 3.9 g of 4-phenylbenzoyl chloride in a hexane/ethyl acetate=1/1 solution instead of a hexane/ethyl acetate=10/1 solution.

Example 11
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was added dropwise to 2.6 g of 2-thenoyl chloride in a hexane/ethyl acetate=1/1 solution instead of a 10/1 solution of hexane/ethyl acetate.

Example 12
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was added dropwise to a hexane solution containing 1.3 g of heptafluorobutyryl chloride instead of a hexane/ethyl acetate=10/1 solution.

Example 13
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was changed to 3.7 g of 4-(trifluoromethyl)benzoyl chloride.

Example 14
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was changed to 1.9 g of methoxyacetyl chloride.

Example 15
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was added dropwise to 2.3 g of 2-furoyl chloride in a hexane/ethyl acetate=1/1 solution instead of a hexane/ethyl acetate=10/1 solution.

Example 16
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was added dropwise to 2.5 g of benzoyl chloride in a hexane/ethanol=7/3 solution instead of a hexane/ethyl acetate=10/1 solution.

Example 17
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was added dropwise to 4.4 g of 2,4,6-trichlorobenzoyl chloride in a hexane/ethyl acetate=1/1 solution instead of a hexane/ethyl acetate=10/1 solution.

Example 18
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was added dropwise to 3.6 g of acetyl chloride in a hexane/ethyl acetate=1/1 solution instead of a hexane/ethyl acetate=10/1 solution.

Example 19
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was replaced with 3.8 g of 2,3,4,5-tetrafluorobenzoyl chloride.

Example 20
The procedure of Example 2 was repeated except that 1.5 g of p-toluoyl chloride was added dropwise to 1.4 g of benzoyl chloride in a hexane solution, instead of a hexane/ethyl acetate=10/1 solution.

Example 21
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was changed to 3.1 g of 3,4-difluorobenzoyl chloride.

Example 22
A solution of 50 g of 4-(trimethoxysilyl)benzeneamine in 230 g of 2-propanol was added to 250 g of water, 17.2 g of 28% aqueous ammonia, and 110 g of 2-propanol in a 2000 mL separable flask, and the mixture was allowed to react at 80°C for 3 hours. After cooling the reaction mixture in air, the precipitate was isolated by filtration. After thoroughly washing the sample with ethanol and drying under vacuum at 80°C, 5 g of the precipitate was dissolved in 500 mL of N,N-dimethylacetamide in a 2000 mL separable flask, and 1.5 g of triethylamine was added. Then, 2.1 g of benzoyl chloride was added at 0°C and the mixture was allowed to react at room temperature for 30 minutes. After the reaction, the reaction mixture was cooled to 0°C and saturated aqueous sodium bicarbonate was added to terminate the reaction. The mixture was then subjected to separation and extraction three times with ethyl acetate, washed with brine, dehydrated over anhydrous magnesium sulfate, and concentrated under reduced pressure using an evaporator. 10 mL of ethyl acetate was added thereto and the resulting solution was added dropwise to a stirred hexane/ethyl acetate=10/1 solution, and the precipitated solid was isolated by filtration.

Example 23
The procedure of Example 22 was repeated except that 2.6 g of o-toluoyl chloride was changed to 2.6 g of o-toluoyl chloride.

Example 24
The procedure of Example 2 was repeated except that 1.5 g of p-toluoyl chloride was added dropwise to 2.3 g of diphenylcarbamoyl chloride in a hexane solution, instead of a hexane/ethyl acetate=10/1 solution.

Example 25
The procedure of Example 1 was repeated except that 4.1 g of o-toluoyl chloride was added dropwise to 4.1 g of diphenylcarbamoyl chloride in a hexane/ethyl acetate=1/1 solution instead of a hexane/ethyl acetate=10/1 solution.

Example 26
A solution of 4.8 g of ethyl 4-(triethoxysilyl)benzoate in 14.1 g of 2-propanol was added to 9.4 g of water, 1.0 g of 28% aqueous ammonia, and 14.9 g of 2-propanol in a 500 mL separable flask, and the mixture was allowed to react at 80°C for 3 hours. After air-cooling the reaction solution, the precipitate was collected and isolated by filtration. The sample was thoroughly washed and dried under vacuum at 80°C, and then dissolved in DMF to a concentration of 15 g/mL. Thereafter, the procedure was carried out in accordance with Example 1.

<Comparative Example 1>
Polystyrene (manufactured by Aldrich, weight-average molecular weight 35,000) was dissolved in DMF to a concentration of 10 g/mL. A 2-propanol dispersion IPA-ST-ZL (a Nissan Chemical product) was adjusted to 10 mg/mL in DMF, and the above-mentioned solution was mixed in a 6:4 ratio to obtain a coating solution. Twenty drops of the coating solution, each drop at 300 pL, were applied using an inkjet device onto the surface of an MSS placed on a hot plate at 40°C, to obtain a surface stress sensor with a sensitive film.
As in Example 1, the response signal to 100 ppm of ethanol at 0% and 30% humidity was confirmed, and the results are shown in Figure 4. Throughput was evaluated. When the ink concentration was 15 mg/mL, precipitation of the sample occurred, so it was given a grade of C.

<Comparative Example 2>
Silica-titania particles (granular) were synthesized according to the method described in WO 2016/121155. They were synthesized by co-hydrolysis and condensation polymerization of aminopropyltrimethoxysilane and titanium tetraisopropoxide (TTIP) in an aqueous solution of ammonia-based isopropanol (IPA) containing octadecylamine (ODA). The synthesis reaction was carried out using a Teflon microreactor with a Y-shaped micrometer-sized channel. Four precursor solutions were prepared: Solution 1: aminopropyltrimethoxysilane/IPA, Solution 2: H ₂ O/IPA/ammonia, Solution 3: TTIP/IPA, and Solution 4: H ₂ O/IPA. Solutions 1 through 4 were prepared with the same volume. The precursor solutions were simultaneously pumped at a constant rate using a syringe pump. Solutions 1 and 2, and solutions 3 and 4 were mixed in parallel microreactors, and the solutions discharged from both reactors were further mixed in another microreactor to form a single reaction solution. The reaction solution was discharged into a separately prepared precursor solution 5 (ODA/H2O/IPA) and stirred at a constant speed until the end of the discharge. The mixture was then left to stand at room temperature to obtain a nanoparticle ( _NH2 -STNP) dispersion. Since the nanoparticles were confirmed to have a structure represented by RSiO3 _/2 , they were treated as an organic-inorganic hybrid. After air-cooling the reaction solution, the precipitate was isolated by centrifugation at 6000 rpm for 10 minutes. The precipitate was then dissolved in DMAc and reacted with benzoyl chloride in the presence of triethylamine to modify the amino groups to amides. This was then dissolved in N,N-dimethylformamide to a concentration of 1 g/mL to obtain a coating solution. A surface stress sensor with a sensitive film was obtained by applying 300 droplets of the coating solution at a volume of 300 pL per droplet using a microjet onto the surface of an MSS placed on a hot plate at 80°C. Throughput was evaluated. When the ink concentration was 15 mg/mL, precipitation of the sample occurred, so the result was rated C.

<Comparative Example 3>
A solution of 54.2 g of phenyltrimethoxysilane in 120 g of 2-propanol was added to 180 g of water, 20 g of 28% aqueous ammonia, and 215 g of 2-propanol in a 2000 mL separable flask and reacted at 80°C for 3 hours. After air-cooling the reaction solution, the precipitate was isolated by filtration. The sample was thoroughly washed with ethanol, dried under vacuum at 80°C, and then dissolved in DMF to a concentration of 10 g/mL. A 2-propanol dispersion IPA-ST-ZL (a Nissan Chemical product) was adjusted to 10 mg/mL in DMF and mixed with the above solution in a 6:4 ratio to obtain a coating solution. Twenty drops of the coating solution, each 300 pL, were applied to the surface of an MSS placed on a hot plate at 40°C using an inkjet device to obtain a surface stress sensor with a sensitive film. Throughput was evaluated. At an ink concentration of 15 mg/mL, the nozzle clogged midway, resulting in splitting and other issues, resulting in a grade of B. Its appearance is shown in Figure 1.

The results of measurements (1) to (3) above for each of the above examples and comparative examples are shown in Table 1 below.

The sensor of the present invention can be used as an olfactory sensor for breath testing and odor management in hotels, automobiles, factories, and the like.

Claims (6)

A sensor having a sensitive membrane,
the sensitive film has absorption peaks in the range of 1600 to 1800 cm ⁻¹ and the range of 1350 to 1450 cm ⁻¹ in infrared total reflection absorption measurement,
the absorption peak in the 1350 to 1450 ^cm region includes an absorption peak derived from an interatomic bond between a silicon atom and an aromatic carbon atom;
the absorption peak in the region of 1600 to 1800 cm ^includes an absorption peak derived from a carbonyl group,
the peak intensity ratio (A/B) of the absorption peak maximum (A) in the 1600 to 1800 ^cm region to the absorption peak maximum (B) in the 1350 to 1450 ^cm region is 0.1 to 4.0;
sensor. The absorption peak in the region of 1600 to 1800 ^cm includes an absorption peak of a carbonyl group that forms an amide bond.
The sensor of claim 1 . The sensitive film has a structure containing a unit represented by the formula RSiO _3/2 (wherein R represents an organic functional group).
The sensor according to claim 1 or 2 . the organic functional group contains at least one amide bond;
The sensor of claim 3 . The organic functional group contains at least one type of aromatic ring.
5. The sensor according to claim 3 or 4 . It is a surface stress sensor.
A sensor according to any one of claims 1 to 5 .