JP6877394B2 - Liquid film materials for chemical sensors and chemical sensors - Google Patents

Description

Embodiments of the present invention relate to liquid film materials for chemical sensors and chemical sensors.

A chemical sensor using a biological substance as a receptor is used by protecting the biological substance with a liquid film because the activity of the biological substance decreases when it dries. However, since the liquid film may evaporate and disappear under atmospheric pressure, there is a demand for a liquid film that does not easily disappear even under atmospheric pressure.

An object to be solved by the present invention is to provide a liquid film material for a chemical sensor and a chemical sensor that are hard to disappear even under atmospheric pressure.

The liquid film material for a chemical sensor of the embodiment includes an ionic liquid and water. In the liquid film material, the amount of moisture absorbed and the amount of moisture released are in equilibrium.

The chemical sensor of the embodiment includes a sensitive film, a biological substance fixed on the surface of the sensitive film, and a liquid film containing the sensitive film and the liquid film material for the chemical sensor of the embodiment, which covers the sensitive film and the biological substance.

FIG. 1 is a cross-sectional view showing an example of the chemical sensor of the embodiment. FIG. 2 is a plan view showing an example of the chemical sensor of the embodiment. FIG. 3 is a flowchart showing an example of a method for detecting a target substance using the chemical sensor of the embodiment. FIG. 4 is a schematic view showing a state when the chemical sensor of the embodiment is used. FIG. 5 is a diagram showing a chemical sensor including a plurality of types of sensor elements. FIG. 6 is a diagram showing changes over time in the concentration of water in a liquid film material containing water and choline dihydrogen phosphate. FIG. 7 is a diagram showing the relationship between the drain current of the chemical sensor and the gate voltage.

Hereinafter, various embodiments will be described with reference to the drawings. Each figure is a schematic view for facilitating the understanding of the embodiment, and the shape, dimensions, ratio, etc. may differ from the actual ones, but these are appropriately redesigned in consideration of the following explanations and known techniques. can do.
The liquid film material for chemical sensors and the chemical sensor will be described. First, the liquid film material for chemical sensors will be described.

[Liquid film material for chemical sensors]
The liquid film material for a chemical sensor of the embodiment contains an ionic liquid and water, and the amount of moisture absorbed and the amount of moisture released are in equilibrium. The "moisture absorption amount" according to the present embodiment indicates the amount of water absorbed (absorbed) from the atmosphere by the liquid film material of the embodiment. Further, the "moisture release amount" according to the present embodiment indicates the amount of water released (humidified) from the liquid film material of the embodiment into the atmosphere.

The amount of moisture absorbed and released is, for example, the weight of the liquid film material immediately after preparing a liquid film material containing an ionic liquid and water and allowing the prepared liquid film material to stand at room temperature for a predetermined time. , It can be measured by comparing with the weight of the liquid film material after the lapse of a predetermined time. Here, when the weight of the liquid film material after the elapse of a predetermined time is larger than the weight of the liquid film material immediately after standing, the weight difference can be expressed as the amount of moisture absorbed. Further, when the weight of the liquid film material immediately after standing is larger than the weight of the liquid film material after a lapse of a predetermined time, the weight difference can be expressed as the amount of moisture released.

As a result of various studies on the liquid film material used for the liquid film of the chemical sensor that detects the target substance in the gas sample, the present inventors have found that the liquid film material containing an ionic liquid and water can be placed under atmospheric pressure. , I found that it is hard to disappear without being dried.

However, the present inventors have found that when a liquid film material containing an ionic liquid and water is simply applied to a liquid film of a chemical sensor, the following problems occur.

That is, a liquid film material containing an ionic liquid and water, in which the amount of moisture absorbed and the amount of moisture released are not in equilibrium, releases (releases moisture) the water of the liquid film material into the atmosphere when placed under atmospheric pressure. Alternatively, since the liquid film material absorbs (absorbs moisture) water from the atmosphere, the concentration of the ionic liquid changes with time. Specifically, the liquid film material releases the free water into the atmosphere when water (free water) that is not bound as water molecules exists in the ionic liquid. Alternatively, if there is an ionic liquid that can bind to water molecules, the ionic liquid absorbs moisture from the atmosphere. As a result, the concentration of the ionic liquid in the liquid film material changes with time. When such a liquid film material is applied to a chemical sensor, a change over time in the concentration of the ionic liquid appears as a variable factor when the measured value of the target substance in the gas sample is detected by the chemical sensor. Therefore, it is difficult for a chemical sensor that applies a liquid film material containing an ionic liquid and water as a liquid film, in which the amount of moisture absorbed and the amount of moisture released are not in equilibrium, to detect the target substance in the gas sample with high accuracy. I found out that there is.

Based on the above-mentioned investigation results, the present inventors have developed a liquid film material for a chemical sensor containing an ionic liquid and water and having an equilibrium between the amount of moisture absorbed and the amount of moisture released. Even when such a liquid film material is placed under atmospheric pressure, the amount of water released into the atmosphere and the amount of water absorbed from the atmosphere are balanced, so that the concentration of the ionic liquid does not change over time. .. As a result, when the liquid film material is applied to the chemical sensor, the concentration of the ionic liquid does not change with time, so that it does not appear as a variable factor when the measured value of the target substance in the gas sample is detected by the chemical sensor. Therefore, the chemical sensor to which the liquid film material is applied as a liquid film can detect the target substance in the gas sample with high accuracy.

As described above, according to the embodiment, it is possible to provide a liquid film of a chemical sensor that is hard to disappear without being dried even when placed under atmospheric pressure and can detect a target substance in a gas sample with high accuracy.

The ionic liquid in the liquid film material for a chemical sensor of the embodiment is, for example, a salt composed of a cation and an anion.

The cation is, for example, a cation having an imidazolium-based skeleton, a pyridinium-based skeleton, a pyrrolidinium-based skeleton, a piperidinium-based skeleton, an ammonium-based skeleton, a choline-based skeleton, a sulfonium-based skeleton, or a phosphonium-based skeleton. Anion, for example, monoatomic anion ^{(Cl -, Br -, I} - , etc.), fluorine-based inorganic anion ^_(BF 4 ^-, PF ₆ -, etc.), non-fluorine-based inorganic anion ^_(NO 3 ^{-, NO} ₂ -, etc.), fluorine organic anion _{^{(CF 3 SO 3 -, (}} CF 3 SO 2) 2 N -, (CF 3 SO 2) 3 C -, (C 2 F 5 SO 2) 2 N - , etc.), or a non-fluorine organic Anions ((CN) ₂ N ⁻ , CH ₃ COO ^−, etc.).

When a cation and / or anion has a hydrophilic group such as a hydroxyl group, a carboxyl group, or an amino group, the ionic liquid composed of such a cation and / or anion can form a hydrogen bond with a water molecule. .. If the cation and / or anion has a hydrophobic group, such as an alkyl group, the ionic liquid consisting of such a cation and / or anion may have a high affinity for the target material in the gaseous sample.

In some embodiments, the water is bound as a water molecule to the ionic liquid described above. In some embodiments, water is hydrogen bonded to the ionic liquid described above as water molecules.

In some embodiments, the ionic liquid is, for example, choline dihydrogen phosphate. Choline dihydrogen phosphate exists as a solid ionic liquid substance under normal temperature and pressure. When choline dihydrogen phosphate is used as an ionic liquid, it can be used after adding a desired amount of water to choline dihydrogen phosphate, for example.

In some embodiments, when the liquid film material for a chemical sensor of the embodiment contains choline dihydrogen phosphate and water, the total weight percentage of choline dihydrogen phosphate and water is 100% by weight. In addition, the concentration of choline dihydrogen phosphate is 59% by weight or more and 61% by weight or less (the concentration of water is 39% by weight or more and 41% by weight or less). The concentration of choline dihydrogen phosphate is preferably 60% by weight (the concentration of water is 40% by weight).

In some embodiments, the liquid film material for a chemical sensor of the embodiment is used to cover and protect biological material.

The liquid film material for a chemical sensor of the embodiment can be prepared, for example, by allowing the above-mentioned ionic liquid to stand for a long period of time in a state where moisture and water vapor in the atmosphere can enter and exit. The place where the ionic liquid is placed may be a closed space, an atmosphere, or a place where the temperature, humidity, etc. can be controlled, such as a constant temperature and humidity chamber. Further, in order to increase the amount of moisture absorbed by the ionic liquid, a container containing the ionic liquid may be installed in the vicinity of a container containing a large amount of water, or a container containing the ionic liquid may be installed in a high humidity environment. You may. When the concentration of the ionic liquid in which the amount of moisture absorbed and the amount of moisture released are in equilibrium, a predetermined amount of water may be added to the ionic liquid and the mixture may be stirred to prepare the mixture. The liquid film material for the chemical sensor of the embodiment is preferably composed of an ionic liquid and water.

[Chemical sensor]
FIG. 1 is a cross-sectional view showing an example of the chemical sensor of the embodiment, and FIG. 2 is a plan view showing an example of the chemical sensor of the first embodiment.

The chemical sensor 10 includes a substrate 1. On the surface 1a of the substrate 1, a sensitive film 2, a source electrode 3 connected to one end of the sensitive film 2, and a drain electrode 4 connected to the other end of the sensitive film 2 are provided. A wall portion 5 is erected on the surface 1a of the substrate 1, and the wall portion 5 surrounds the sensitive film 2 in a plan view and covers the outer peripheral surfaces of the source electrode 3 and the drain electrode 4. A receptor 6, which is a biological substance, is immobilized on the surface 2a of the sensitive film 2. A liquid film 7 is arranged on the surface 2a of the sensitive film 2 so as to cover the receptor 6. The liquid film 7 includes the liquid film material for the chemical sensor of the above-described embodiment. Further, the gas sample 9 containing the target substance 8 is taken into the liquid film 7.

Since the liquid film 7 contains the above-mentioned liquid film material for a chemical sensor, it contains an ionic liquid and water, and the amount of moisture absorbed and the amount of moisture released are in equilibrium. That is, in the liquid film 7, since the amount of water released into the atmosphere and the amount of water absorbed from the atmosphere are balanced, the concentration of the ionic liquid does not change with time. Since there is no such change in the concentration of the ionic liquid with time, the measured value does not fluctuate in the chemical sensor 10. Therefore, the chemical sensor 10 provided with the liquid film 7 can hardly disappear without being dried even when placed under atmospheric pressure, and can detect the target substance in the gas sample with high accuracy. The liquid film 7 is preferably made of the above-mentioned liquid film material for chemical sensors.

The liquid film 7 acts as a medium for carrying the target substance 8 from the gas sample 9 to the receptor 6. Since the liquid film 7 contains water and is arranged so as to cover the receptor 6, denaturation or damage due to drying of the receptor 6 can be prevented.

The liquid film 7 contains an ionic liquid, and the ionic liquid has a high boiling point and is difficult to evaporate. Therefore, even if the liquid film 7 is formed thinly, there is no possibility that the liquid film 7 is dried and the receptor 6 is dried and the receptor is inactivated. Here, the thickness of the liquid film 7 refers to, for example, the shortest distance from the surface 2a of the sensitive film 2 to the interface between the liquid film 7 and the gas in FIG. When the liquid film 7 is formed thinly, the target substance 8 in the gas sample 9 taken into the liquid film 7 easily reaches the receptor 6. Therefore, a highly sensitive chemical sensor can be configured.

The liquid film 7 contains an ionic liquid, and when the cation and / or anion of the ionic liquid has the above-mentioned hydrophobic group, it may have a high affinity for the target substance in the gas sample. As a result, the uptake of the target substance into the liquid film 7 is improved, and a highly sensitive chemical sensor can be constructed.

In some embodiments, an additional liquid film (also referred to as a second liquid film, not shown) may be arranged on the surface of the liquid film 7 so as to cover the surface of the liquid film 7. The second liquid film is, for example, a non-polar solvent (toluene, hexane, etc.) having a low affinity for the target substance. Such a second liquid film prevents non-target substances (contaminants) from entering the liquid film 7 from the atmosphere, and the chemical sensor does not show fluctuations in the measured values derived from the non-target substances, so that the sensitivity is high. A chemical sensor can be configured.

Hereinafter, each configuration will be described in detail.
The substrate 1 has, for example, a rectangular plate shape. The substrate 1 is made of, for example, silicon, glass, ceramics, a polymer material, a metal, or the like. The size of the substrate 1 is not limited, but is, for example, 10 mm × 10 mm × 0.5 mm (width × length × thickness).

The substrate 1 may be provided with an insulating film (not shown) on the surface 1a side, for example. The insulating film is formed of an electrically insulating material such as silicon oxide, silicon nitride, aluminum oxide, a polymer material, or a self-assembling film of organic molecules. The substrate 1 may include an insulating film provided on the surface 1a side and a conductor layer that functions as a gate electrode. In this case, the thickness of the insulating layer should be as thin as possible within a range that does not impair the insulating property, and is preferably about several nm, for example. Such a thin film can be formed by, for example, an ALD (Atomic Layer Deposition) method.

The sensitive film 2 is a film whose physical properties change when the structure of the substance bound thereto, the state of electric charge, or the like changes. The sensitive film 2 is formed of, for example, a substance whose electrical resistance changes. The sensitive film 2 is a single-layer graphene film having a thickness of one carbon atom. The graphene film may be provided in a plurality of layers. The size of the sensitive film 2 is not limited, but can be, for example, 0.1 to 500 μm × 0.1 to 500 μm (width × length). Practically, if it is 10 to 100 μm × 10 to 100 μm, it is easy to manufacture. Graphene has very good electrical properties (eg 1000 times that of silicon), which makes it a highly sensitive chemical sensor.

The sensitive film 2 is, for example, a film of a conductor such as polymer, gold (Au), silver (Ag), copper (Cu), nickel (Ni), silicon (Si), silicide, or its nanowires, or graphene or carbon nanotubes. , Molybdenum disulfide (MoS ₂ ) or tungsten dicelenide (WSe ₂ ) or the like.

The source electrode 3 and the drain electrode 4 are, for example, gold (Au), silver (Ag), copper (Cu), palladium (Pd), platinum (Pt), nickel (Ni), titanium (Ti), chromium (Cr). Alternatively, it is formed of a metal such as aluminum (Al) or a conductive substance such as zinc oxide (ZnO), indium tin oxide (ITO), IGZO, and a conductive polymer.

The source electrode 3 and the drain electrode 4 are electrically connected to a power source (not shown). _{When a voltage (source / drain voltage (V sd} )) is applied to the source electrode 3 and the drain electrode 4 from, for example, a current (source / drain current (source / drain current (V sd)) is applied from the source electrode 3 to the drain electrode 4 via the sensitive film 2. _Isd )) is configured to flow. At this time, the sensitive film 2 which is a graphene film functions as a channel with respect to the source electrode 3 and the drain electrode 4.

The wall portion 5 is formed of, for example, an electrically insulating material. The insulating material of the wall portion 5 is, for example, a polymer substance such as acrylic resin, polyimide, polybenzoxazole, epoxy resin, phenol resin, polydimethylsiloxane, or fluororesin, or an inorganic substance such as silicon oxide, silicon nitride, or aluminum oxide. It is an insulating film, a self-assembled film of organic molecules, or the like.

Receptor 6 is a biological substance as described above. As the receptor 6, for example, a fragment of an olfactory receptor can be used. Receptor 6 is a fragment of an olfactory receptor that contains a sequence of sites that bind to target substance 8. For example, such a sequence comprises a ligand binding site located extracellularly of the olfactory receptor. Receptor 6 can be produced, for example, by obtaining the amino acid sequence of the ligand binding site from the database of olfactory receptors and synthesizing an oligopeptide having the amino acid sequence. The receptor 6 may be one that binds to the target substance, for example, the sequence of the ligand binding site may be partially modified, or a new sequence may be added. As the receptor 6, for example, an animal olfactory receptor can be used as the olfactory receptor. Animals are, for example, vertebrates or insects. For example, olfactory receptors such as humans and flies can be used.

The receptor 6 can be immobilized on the sensitive membrane 2 by, for example, adding a modifying group to the receptor 6 and / or the sensitive membrane 2 and binding the two by chemical synthesis. The state in which the receptor 6 is fixed to the sensitive membrane 2 indicates a state in which the receptor 6 is chemically bonded to the sensitive membrane 2.

In some embodiments, on the surface 2a of the sensitive membrane 2, in addition to the receptor 6, a blocking agent (not shown) may be arranged to cover the surface 2a. As the blocking agent, for example, metal oxides (Al ₂ O ₃ , HfO _2, etc.), proteins, organic molecules, lipid membranes, peptides, nucleic acids and the like can be used. By providing such a blocking agent, it is possible to prevent the non-target substance 11 (for example, contaminants) contained in the gas sample 9 from binding to the surface of the sensitive film 2.

The target substance 8 is a substance contained in a gas and can be a ligand for an animal olfactory receptor. The target substance 8 is, for example, a volatile organic compound (VOC) such as an odorant substance or a pheromone substance. The target substance 8 is, for example, alcohols, esters, aldehydes, ketones, and the like, but is not limited thereto. Most of such target substances 8 are substances having low solubility in water.

The gas sample 9 is, for example, a gas to be analyzed that may contain the target substance 8. The gas sample 9 is, for example, the atmosphere, exhaled breath, other gas generated from an analysis target such as a living body or an object, or air around the analysis target. The gaseous sample 9 may contain the non-target substance 11.

The chemical sensor of the above-described embodiment has a configuration of a graphene field effect transistor (also referred to as a graphene FET), but is not limited to the graphene FET, and is a case where a biological material such as a receptor 6 is used. If there is, for example, another charge detection element, surface plasmon resonance element (SPR), surface elastic wave (SAW) element, piezoelectric thin film resonance (FBAR) element, crystal transducer microbalance (QCM) element, or MEMS cantilever element. Etc. can be configured.

Hereinafter, a method for detecting a target substance using the chemical sensor of the embodiment will be described with reference to the flowchart shown in FIG.
The method for detecting the target substance includes, for example, the following steps. From the results of (S1) preparing the chemical sensor of the embodiment, (S2) bringing the gas sample into contact with the liquid film, (S3) detecting the change in the physical properties of the sensitive film, and (S4) the detection result, the gas To determine the presence or absence or amount of target substance in the sample.
Hereinafter, the principle of detecting the target substance by performing each of the above steps will be described.

In the step (S2), the gas sample 9 is brought into contact with the liquid film 7 of the chemical sensor 10. The state of the chemical sensor at this time is shown in FIG. When the gas sample 9 comes into contact with the liquid film 7, the target substance 8 enters the liquid film 7 ((a) and (b) in FIG. 4) and binds to the receptor 6 ((c) in FIG. 4). On the other hand, the non-target substance 11 (contaminant) does not bind to the receptor 6 ((d) in FIG. 4). The physical characteristics of the sensitive membrane 2 are changed by the binding between the target substance 8 and the receptor 6 ((c) in FIG. 4). The physical characteristics are, for example, the electrical resistance of the sensitive film.

In the step (S3), a change in physical properties is detected as a change in an electrical signal. The electrical signal is, for example, a current value, a potential value, a capacitance value, an impedance value, or the like. The change in the electric signal is, for example, an increase, decrease, disappearance of the electric signal, a change in the integrated value within a specific time, or the like. When the graphene FET described above is used, the change in physical properties can be detected as, for example, a change in the current value between the source and drain when a constant voltage is applied as the gate voltage and the drain voltage. Alternatively, it may be detected as a change in the gate voltage value while the source-drain current value is kept constant. Information on changes in electrical signals is sent, stored, and processed, for example, to an electrically connected data processing unit.

In the step (S4), the presence or absence or amount of the target substance 8 in the gas sample 9 is determined from the detection result. For example, it may be determined that the target substance 8 is present in the gas sample 9 when a change in the electrical signal occurs, and it may be determined that the target substance 8 does not exist when the change does not occur. Further, it may be determined that the target substance 8 is present when the electrical signal changes more than a preset threshold value, and it may be determined that the target substance 8 does not exist when the change is smaller than the threshold value. Such a threshold can be obtained, for example, by subjecting a gas sample known to contain a target substance to an analysis of a chemical sensor to obtain a change value of an electrical signal. Alternatively, the amount of the target substance may be determined by the amount of change. In that case, the amount of the target substance may be determined by creating a calibration curve of the amount of change with respect to the concentration of the target substance using a target substance having a known concentration and comparing it with the calibration curve.

By the steps described above, the chemical sensor of the embodiment can detect the target substance in the gas sample.

The method for detecting the target substance may be carried out by an apparatus that automatically performs each step. Such an apparatus includes, for example, a chemical sensor 10, a liquid feeding unit that feeds the liquid film material of the embodiment for forming the liquid film 7 onto the sensitive film 2 of the chemical sensor 10, and a liquid film of the chemical sensor 10. Stores a sample introduction unit for bringing the gas sample 9 into contact with 7, a detection unit that converts changes in the physical characteristics of the sensitive film 2 into changes in the electrical signal, and information on the electrical signal obtained from the detection unit. It includes a data processing unit for processing and a control unit for controlling the operation of each of these units. The operations of the above steps (S2) to (S4) may be executed by the input of the operator of the apparatus, or may be executed by the program included in the control unit.

According to the method for detecting a target substance using the chemical sensor of the embodiment, it is possible to prevent the detection of a non-target substance (contaminant) because a receptor that binds to the target substance is used. Therefore, it is possible to detect a target substance without being affected by impurities even under conditions where the composition of the substance contained in the gas is different.

Hereinafter, one unit including the substrate 1, the sensitive film 2, the source electrode 3, the drain electrode 4, the wall portion 5, one type of receptor 6, and the liquid film 7 will be referred to as a “sensor element”. In some embodiments, one chemical sensor may be equipped with a plurality of types of sensor elements. Each of the plurality of types of sensor elements has different types of receptors 6 and can detect different types of target substances.
A chemical sensor including a plurality of types of sensor elements will be described with reference to FIG.

The chemical sensor 20 in this example includes a sensor element A having a sensitive film 2A on which the receptor 6A is fixed, a sensor element B having a sensitive film 2B on which the receptor 6B is fixed, and a sensitive sensor element B having the receptor 6C fixed. The sensor element C including the membrane 2C and the sensor element D including the sensitive membrane 2D to which the receptor 6D is fixed are provided.

The sensitive films 2A to 2D of each sensor element are configured so that changes in their physical properties can be individually detected.

The number, type, arrangement, etc. of sensor elements mounted on one chemical sensor are not limited to those shown in FIG. Further, a plurality of chemical sensor elements of each type may be provided.

A method for detecting a target substance when the chemical sensor includes a plurality of types of chemical sensor elements will be described with reference to the example of FIG.

In such a method for detecting a target substance, the above steps (S1) to (S3) are similarly performed using the chemical sensor 20 of FIG. In the step (S3), electrical signals are individually obtained from the sensor elements A to D. The type of the target substance mixture containing a plurality of target substances may be specified from the type (type of receptor fixed therein) and the number of sensor elements in which the change of the electrical signal occurs in the step (S4). For example, when the change of the electric signal occurs in the sensor elements A and B, the target substance mixture I is present in the gas sample, and when the change of the electric signal occurs in the sensor elements A, C and D, the gas sample. It can be determined that the target substance mixture II is present therein. Alternatively, in a chemical sensor including a plurality of each sensor element, the presence or absence of a specific target substance mixture may be determined by the intensity ratio of the electrical signals detected from the sensor elements A, B, C, and D. In addition, the type of the target substance mixture contained in the gas sample can be specified by the intensity ratio.

A target substance mixture is a mixture of a plurality of target substances in a specific combination. For example, the target substance mixture is associated with one specific "odor", and the presence or absence or amount of the "odor" is determined by the above method. You may. It is also possible to link the "smell" and the cause of emitting the "smell" in advance, and to identify the cause of emitting the odor by such detection.

<Test Example 1>
First, water and choline dihydrogen phosphate as an ionic liquid were prepared to prepare the following liquid film materials 1 to 3.
(Liquid film material 1)
1001.75 g of choline dihydrogen phosphate was added to 186.22 g of water and stirred to prepare liquid film material 1 (concentration of choline dihydrogen phosphate: 85% by weight, concentration of water: 15% by weight). ..
(Liquid film material 2)
1014.91 g of choline dihydrogen phosphate was added to 435.41 g of water and stirred to prepare liquid film material 2 (concentration of choline dihydrogen phosphate: 70% by weight, concentration of water: 30% by weight). ..
(Liquid film material 3)
1010.58 g of choline dihydrogen phosphate was added to 1499.22 g of water and stirred to prepare liquid film material 3 (concentration of choline dihydrogen phosphate: 40% by weight, concentration of water: 60% by weight). ..

Each of these liquid film materials 1 to 3 is transferred to an open beaker and allowed to stand at room temperature (room temperature and humidity are not controlled), and the concentration of water contained in the liquid film materials 1 to 3 [% by weight]. The measurement of was started. Then, the water concentration of the liquid film materials 1 to 3 was measured after a lapse of a predetermined time from the start of standing. The measurement results are shown in FIG.

As shown in FIG. 6, the liquid film material 1 having a water concentration of 15% by weight and the liquid film material 2 having a water concentration of 30% by weight each increase in water concentration with the lapse of time from the start of measurement. did. On the 16th day, both the liquid film materials 1 and 2 became liquid film materials having a water concentration of 40% by weight (a concentration of choline dihydrogen phosphate of 60% by weight). After the 16th day, the water concentration did not increase or decrease from 40% by weight over time.

On the other hand, in the liquid film material 3 having a water concentration of 60% by weight, the water concentration decreased with the lapse of time from the start of measurement. Then, on the 65th day, the liquid film material 3 became a liquid film material having a water concentration of 40% by weight (a concentration of choline dihydrogen phosphate of 60% by weight).

That is, the liquid film materials 1 and 2 have increased the concentration of water by absorbing (absorbing moisture) water from the atmosphere with the passage of time from the start of measurement. After the 16th day, the liquid film materials 1 and 2 had an equilibrium between the amount of moisture absorbed and the amount of moisture released at a concentration of 40% by weight of water (concentration of 60% by weight of choline dihydrogen phosphate). confirmed.

The concentration of water in the liquid film material 3 decreased by releasing (releasing moisture) water into the atmosphere with the passage of time from the start of measurement. Then, on the 65th day, the liquid film material 3 had a concentration of 40% by weight of water (concentration of 60% by weight of choline dihydrogen phosphate) in which the amount of moisture absorbed and the amount of moisture released were in equilibrium. confirmed.

<Test Example 2>
(Example 1)
Choline dihydrogen phosphate was added to water and stirred to prepare a liquid film material for a chemical sensor (concentration of choline dihydrogen phosphate: 60% by weight, concentration of water: 40% by weight). In the chemical sensor having the structure shown in FIG. 1 described above, the prepared liquid film material for the chemical sensor was used as the liquid film.
(Comparative Example 1)
Choline dihydrogen phosphate was added to water and stirred to prepare a liquid film material for a chemical sensor (concentration of choline dihydrogen phosphate: 70% by weight, concentration of water: 30% by weight). In the chemical sensor having the structure shown in FIG. 1 described above, the prepared liquid film material for the chemical sensor was used as the liquid film.
(Comparative Example 2)
Choline dihydrogen phosphate was added to water and stirred to prepare a liquid film material for a chemical sensor (concentration of choline dihydrogen phosphate: 40% by weight, concentration of water: 60% by weight). In the chemical sensor having the structure shown in FIG. 1 described above, the prepared liquid film material for the chemical sensor was used as the liquid film.

In the chemical sensor of Example 1, the change in drain current (Idrain [A]) when the gate voltage (V gate [V]) was changed immediately after assembly, and the same drain current 57 minutes after assembly. The change and the change in the drain current after 1038 minutes after assembly were measured.

Further, in the chemical sensor of Comparative Example 1, the change in the drain current when the gate voltage was changed immediately after the assembly, the change in the drain current 35 minutes after the assembly, and the same 47 minutes after the assembly. The change in drain current was measured respectively.

Further, in the chemical sensor of Comparative Example 2, the change in the drain current when the gate voltage was changed immediately after the assembly, the change in the drain current 2 minutes after the assembly, and the same 9 minutes after the assembly. The change in drain current was measured respectively.
The measurement results are shown in FIG.

As shown in FIG. 7, it was confirmed that the chemical sensor of Comparative Example 1 had a large change in electrical characteristics 35 minutes after assembly and a further large change in electrical characteristics 47 minutes after assembly. Was done. Further, it was confirmed that the chemical sensor of Comparative Example 2 had a large change in electrical characteristics 2 minutes after assembly, and further changed in electrical characteristics 9 minutes after assembly. In other words, in the chemical sensors of Comparative Examples 1 and 2, the charge neutral point, which is the minimum value of the drain current, changed significantly when several minutes to several tens of minutes had passed after assembly. This result indicates that the concentration of the ionic liquid changes over time. Therefore, it appears as a variable factor when the measured value of the target substance in the gas sample is detected by the chemical sensor. Therefore, it is difficult for the chemical sensors of Comparative Examples 1 and 2 to detect the target substance in the gas sample with high accuracy.

On the other hand, it was confirmed that the chemical sensor of Example 1 had almost no change in electrical characteristics even after 1038 minutes had passed after assembly. In other words, in the chemical sensor of Example 1, the charge neutral point, which is the minimum value of the drain current, did not change even after 1038 minutes had passed after assembly. This result indicates that the concentration of the ionic liquid does not change over time. Therefore, it does not appear as a variable factor when the measured value of the target substance in the gas sample is detected by the chemical sensor. Therefore, the chemical sensor of Example 1 can detect the target substance in the gas sample with high accuracy.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.
The inventions described in the claims of the original application of the present application are described below.
[1]
Contains ionic liquids and water,
A liquid film material for chemical sensors in which the amount of moisture absorbed and the amount of moisture released are in equilibrium.
[2]
The liquid film material for a chemical sensor according to [1], wherein the water is bound to the ionic liquid.
[3]
The liquid film material for a chemical sensor according to [2], wherein the bond is a hydrogen bond.
[4]
The liquid film material for a chemical sensor according to any one of [1] to [3], wherein the ionic liquid is choline dihydrogen phosphate.
[5]
The chemical according to [4], wherein the concentration of choline dihydrogen phosphate is 59% by weight or more and 61% by weight or less when the total weight percentage of the choline dihydrogen phosphate and the water is 100% by weight. Liquid film material for sensors.
[6]
The liquid film material for a chemical sensor according to any one of [1] to [5] used for covering and protecting a biological substance.
[7]
A chemical sensor for detecting a target substance in a gas sample.
Sensitive membrane and
Biological substances fixed on the surface of the sensitive film and
A chemical sensor comprising the sensitive film and a liquid film containing the liquid film material for a chemical sensor according to any one of [1] to [6], which covers the biological substance.
[8]
A chemical sensor for detecting a target substance in a gas sample.
Biological substances that bind to the target substance and
Sensitive membranes whose physical properties change due to the binding of the target substance and the biological substance,
A chemical sensor comprising the sensitive film and a liquid film containing the liquid film material for a chemical sensor according to any one of [1] to [6], which covers the biological substance.
[9]
The chemical sensor according to [7] or [8], wherein the biological substance is a receptor.
[10]
The chemical sensor according to any one of [7] to [9], further comprising a blocking agent on the surface of the sensitive film.
[11]
The chemical sensor according to any one of [7] to [10], wherein the target substance is an odorant.
[12]
The sensitive membrane contains graphene and
The chemical sensor according to any one of [7] to [11], further comprising a source electrode connected to one end of the sensitive film and a drain electrode connected to the other end of the sensitive film.

10, 20 ... Chemical sensor 1 ... Substrate 2, 2A, 2B, 2C, 2D ... Sensitive film 3 ... Source electrode 4 ... Drain electrode 5 ... Wall part 6, 6A, 6B, 6C, 6D ... Receptor 7 ... Liquid film 8 … Target substance 9… Gas sample 11… Non-target substance

Claims (10)

A chemical sensor for detecting a target substance in a gas sample.
Sensitive membrane and
Biological substances fixed on the surface of the sensitive film and
With the sensitive film and the liquid film covering the biological substance
With
The liquid film contains an ionic liquid and water, and is a chemical sensor containing a liquid film material for a chemical sensor in which the amount of moisture absorbed and the amount of moisture released are in equilibrium. A chemical sensor for detecting a target substance in a gas sample.
Biological substances that bind to the target substance and
Sensitive membranes whose physical properties change due to the binding of the target substance and the biological substance,
With the sensitive film and the liquid film covering the biological substance
With
The liquid film contains an ionic liquid and water, and is a chemical sensor containing a liquid film material for a chemical sensor in which the amount of moisture absorbed and the amount of moisture released are in equilibrium. The chemical sensor according to claim 1 or 2 , wherein the water is bound to the ionic liquid. The chemical sensor according to claim 3 , wherein the bond between the water and the ionic liquid is a hydrogen bond. The chemical sensor according to any one of claims 1 to 4 , wherein the ionic liquid is choline dihydrogen phosphate. The chemical according to claim 5 , wherein the concentration of choline dihydrogen phosphate is 59% by weight or more and 61% by weight or less when the total weight percentage of the choline dihydrogen phosphate and the water is 100% by weight. Sensor . The chemical sensor according to any one of claims 1 to 6, wherein the biological substance is a receptor. The chemical sensor according to any one of claims 1 to 7 , further comprising a blocking agent on the surface of the sensitive film. The chemical sensor according to any one of claims 1 to 8 , wherein the target substance is an odorant. The sensitive membrane contains graphene and
The chemical sensor according to any one of claims 1 to 9 , further comprising a source electrode connected to one end of the sensitive film and a drain electrode connected to the other end of the sensitive film.

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