JP3646165B2 - Manufacturing method of chemical sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a chemical sensor, and more particularly to a method for manufacturing a chemical sensor that can be suitably used as a humidity sensor and a gas sensor.
[0002]
[Prior art]
Environmental pollution caused by various environmental hormones including dioxins and sick house syndrome due to radiation of chemical substances such as formaldehyde from building materials are serious social problems. In order to fundamentally solve these problems, it is necessary to identify the pollution source and take measures against it. To that end, it is indispensable to investigate the actual conditions of environmental pollutants.
[0003]
However, even a very small amount of the target chemical substance adversely affects the living body. In order to investigate the exposure situation, a highly sensitive chemical measurement technique of ppm to ppt level is required. Currently, the use of a large and expensive apparatus and the long measurement time including the sample pretreatment are the bottleneck. For this reason, if a small, lightweight, and highly sensitive chemical sensor is developed, real-time measurement of chemical substances at the site where the environment is actually polluted becomes possible, which can greatly contribute to the actual investigation of pollution.
[0004]
In view of the situation as described above, an object of the present invention is to provide a method for manufacturing a novel chemical sensor that is small, lightweight, and highly sensitive.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is a method of manufacturing a chemical sensor comprising a crystal resonator and a nanoporous thin film on the crystal resonator,
The nanoporous films, a block copolymer of a hydrophilic polymer and a hydrophobic polymer, a mixed solution of an oxide precursor, organic was deposited on the quartz crystal - were prepared inorganic composite film Then, it is related with the manufacturing method of a chemical sensor characterized by decomposing and removing only organic substance from the organic-inorganic composite film by irradiating the organic-inorganic composite film with vacuum ultraviolet light.
[0006]
In developing the chemical sensor, the present inventors paid attention to a crystal resonator used in an electronic circuit such as a timepiece, a computer, or a communication device. When a substance adheres to the surface of the crystal resonator, the oscillation frequency decreases in accordance with the adhering mass. Therefore, the quartz resonator can be suitably used as a means for measuring an extremely small amount of mass change at the nanogram level.
[0007]
Moreover, since the nanoporous thin film has a large number of pores of the order of nm penetrating on its surface, it has a very large specific surface area. Therefore, by constituting the nanoporous thin film from a material that is sensitive only to a predetermined substance to be detected, the amount of adsorption to the substance increases, and even when the substance is present in a very small amount, the substance Can be detected with sufficient sensitivity. Therefore, according to the present invention, a small, light and highly sensitive chemical sensor can be provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments of the invention.
In the chemical sensor of the present invention, it is necessary to have a nanoporous thin film on a quartz resonator. This nanoporous thin film can be produced, for example, as follows.
[0009]
FIG. 1 is a conceptual diagram for explaining a manufacturing process of the nanoporous thin film. First, as shown in FIG. 1A, a block copolymer and an oxide precursor of a hydrophilic polymer and a hydrophobic polymer are dissolved in, for example, an acidic solution, and the block copolymer is dissolved. And a mixed solution composed of the oxide precursor. Next, the mixed solution is formed on the quartz resonator by a spin casting method or the like.
[0010]
Then, as shown in FIG. 1 (b), rod-like micelles with a diameter of several nanometers are formed in which the hydrophilic polymer is arranged outside the hydrophobic polymer constituting the block copolymer, and An organic-inorganic composite film is formed in which the oxide precursor is surrounded in a matrix form outside the liquid crystal micelles formed by regularly arranging them.
[0011]
Next, vacuum ultraviolet light is irradiated to the organic-inorganic composite film. Then, only the organic matter constituting the organic-inorganic composite film is decomposed and removed, and a nanoporous thin film having pores of the order of nm penetrating the surface can be obtained. For example, an excimer lamp can be used as the vacuum ultraviolet light source. And the intensity | strength is arbitrarily set according to the thickness, material composition, etc. of the said organic-inorganic composite film.
[0012]
The thickness of the organic-inorganic composite film is not particularly limited, but is preferably 10 nm to 1000 nm. As a result, pores in the order of nm can be formed easily and with high density.
[0013]
Further, instead of irradiating the organic-inorganic composite film with vacuum ultraviolet light, the organic matter in the organic-inorganic composite film may be burned and removed by performing a heat treatment at 300 ° C. or higher in the atmosphere. it can. However, in such a high temperature treatment, the crystal resonator that supports the organic-inorganic composite film may be damaged. Furthermore, the volumetric shrinkage of the organic-inorganic composite film increases, and the finally obtained nanoporous thin film may be broken or peeled off due to thermal stress caused by the volume shrinkage.
[0014]
On the other hand, irradiation with vacuum ultraviolet light as described above can be performed at room temperature without heating the organic-inorganic composite film. Therefore, since no thermal stress is applied to the obtained nanoporous thin film, the nanoporous thin film can be easily obtained without causing the breakage and peeling as described above or without damaging the crystal resonator. However, the irradiation of the vacuum ultraviolet light may be performed in an appropriate heating atmosphere as long as the nanoporous thin film does not break or peel due to the thermal stress as described above and does not cause thermal damage to the crystal unit. it can. For example, it can be carried out at a temperature of 100 ° C. or lower, preferably 50 ° C. or lower.
[0015]
That is, even when the environmental temperature changes due to external factors, the organic matter constituting the organic-inorganic composite film is decomposed and removed by irradiation with vacuum ultraviolet light without causing destruction or peeling due to thermal stress. By doing so, a nanoporous thin film can be obtained easily.
[0016]
As described above, the nanoporous thin film needs to be composed of a material that is sensitive only to the substance depending on the type of the substance to be detected. For example, when the amount of water vapor is detected, that is, when the chemical sensor of the present invention is used as a humidity sensor, the nanoporous thin film is made of, for example, silica. Such a nanoporous thin film made of silica includes, for example, the block copolymer is composed of an olefin oxide copolymer such as a polyethylene oxide-polypropylene oxide copolymer, and the oxide precursor is tetraethoxysilane or the like. It can be easily formed by following the manufacturing method using vacuum ultraviolet light as described above.
[0017]
Further, instead of constituting the nanoporous thin film itself from a material sensitive to a predetermined substance, chemical modification is performed in the pores of the nanoporous thin film, and functional groups sensitive to the predetermined substance are attached in the pores. It can also be coated.
[0018]
A nanoporous thin film is formed by a simple process of spin casting and irradiation with vacuum ultraviolet light from a mixed solution of a block copolymer of a hydrophilic polymer and a hydrophobic polymer and an oxide precursor. Because of this simplicity, the block copolymer is required to be composed of a hydrophilic polymer and a hydrophobic polymer, and the types thereof are limited. As a result, the types of materials constituting the nanoporous thin film are also limited, and the types of substances that can be detected are also limited.
[0019]
On the other hand, in the chemical sensor of the present invention, the actual substance is detected by chemically reacting and adsorbing the substance with the inner surfaces of the pores constituting the nanoporous thin film. Therefore, the type of material constituting the inner surface of the pore is essentially a problem. For this reason, if chemical modification is performed in the pores of the nanoporous thin film as described above, the selection range of the material constituting the inner surface of the pores can be increased. Detection can be possible.
[0020]
In particular, when the nanoporous thin film is made of silica, the inner surface of the nanoporous thin film is chemically modified by applying a silane coupling treatment. In this case, the silane coupling agent used reacts easily with the hydroxyl group on the inner surface of the pore of the nanoporous thin film, and as a result, a functional group sensitive to the substance to be detected can be attached to the inner surface of the pore. .
[0021]
When a nanoporous thin film made of silica is produced from an organic-inorganic composite film through a high temperature treatment at 300 ° C. or higher, the hydroxyl groups are not separated from the nanoporous thin film and hardly remain on the inner surfaces of the pores. Therefore, in this case, as described above, it is preferable to produce a nanoporous thin film by irradiating with vacuum ultraviolet light at a temperature of 100 ° C. or lower, preferably 50 ° C. or lower at which a hydroxyl group does not leave.
[0022]
In particular, amino groups easily react with NOx gas, SOx gas, and the like. Therefore, by coating amino surfaces on the pore inner surface of the nanoporous thin film made of silica by silane coupling treatment, amino groups can react with NOx gas and SOx gas on the inner surface of the pores, and can be adsorbed. Gas sensors for these polluted gases can be constructed.
[0023]
【Example】
Hereinafter, the present invention will be described based on specific examples.
[0024]
(Production of chemical sensor)
First, a block copolymer consisting of three blocks of polyethylene oxide-polypropylene oxide-polyethylene oxide (molecular weight 5800), tetraethoxysilane, hydrochloric acid, and water are mixed at a molar ratio of 0.017: 1: 6: 167. The mixed solution was prepared. Next, a polymer-silica composite film having a thickness of 0.1 μm was formed from this mixed solution on a quartz resonator by spin casting.
[0025]
In this polymer-silica composite membrane, rod-like micelles composed of polyethylene oxide, which is a hydrophilic polymer, are regularly arranged outside the polypropylene oxide, which is a hydrophobic polymer of the block copolymer. The liquid crystal micelles formed in this manner are configured such that silica is surrounded on the outside in a matrix.
[0026]
Next, the polymer-silica composite film was placed in a vacuum vessel, and the inside of the vessel was evacuated to 10 Pa. Next, vacuum ultraviolet light having an intensity of 10 mW / cm ² and a wavelength of 172 nm was introduced from the excimer lamp into the vacuum container through an ultraviolet light introduction window provided in the vacuum container, and the polymer-silica composite film was irradiated for 3 hours. . As a result, the organic substance in the polymer-silica composite film was photochemically decomposed to obtain a nanoporous thin film having pores on the order of nm, thereby producing a chemical sensor.
[0027]
(Evaluation of chemical sensors)
FIG. 2 is a graph showing a mass change response when the chemical sensor obtained as described above is used as a humidity sensor. FIG. 2 shows a case where the environmental humidity is changed from 12% → 90% → 12%. In the figure, (a) shows the mass change responsiveness of the chemical sensor obtained in the above example. In addition, (b), (c), and (d) in the figure are chemical sensors in which a polymer-silica composite film before irradiation with vacuum ultraviolet light is formed on a crystal resonator, and a sputtering silica film is a crystal. The mass change responsiveness of the chemical sensor obtained by forming on the vibrator and the chemical sensor composed only of the quartz vibrator is shown as a reference.
[0028]
As is apparent from FIG. 2, it can be seen that the chemical sensor obtained in this example responds to changes in environmental humidity at high speed and with high sensitivity. On the other hand, in the chemical sensor having the polymer-silica composite film and the chemical sensor having the sputtering silica film, it can be seen that both the response speed and the sensitivity are deteriorated. Further, it can be seen that the quartz resonator alone does not function as a sensor.
[0029]
FIG. 3 is a graph comparing the responsiveness of the chemical sensor obtained in this example and a commercially available hygrometer to changes in environmental humidity. In FIG. 3, the responsiveness of the chemical sensor obtained in this example was measured by the change in the frequency of the crystal resonator, and the responsiveness of a commercially available hygrometer was measured by directly measuring the humidity. As is clear from FIG. 3, the chemical sensor obtained in this example shows sufficiently high responsiveness as compared with a commercially available humidity sensor, and particularly in the change from high humidity to low humidity indicated by A in the figure, It can be seen that the response is higher than that of a commercially available hygrometer.
[0030]
As described above, the present invention has been described in detail based on the embodiments of the present invention with specific examples. However, the present invention is not limited to the above contents, and all modifications and changes can be made without departing from the scope of the present invention. It can be changed.
[0031]
【The invention's effect】
As described above, according to the present invention, a novel chemical sensor that is small, lightweight, and highly sensitive can be provided.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram for explaining a production process of a nanoporous thin film constituting a chemical sensor according to the production method of the present invention.
FIG. 2 is a graph showing a mass change response when a chemical sensor obtained through the manufacturing method of the present invention is used as a humidity sensor.
FIG. 3 is a graph comparing the responsiveness to environmental humidity changes between the chemical sensor and a commercially available hygrometer when the chemical sensor obtained through the manufacturing method of the present invention is used as a humidity sensor.

Claims (9)

A method of manufacturing a chemical sensor comprising a crystal resonator and a nanoporous thin film on the crystal resonator,
The nanoporous films, a block copolymer of a hydrophilic polymer and a hydrophobic polymer, a mixed solution of an oxide precursor, organic was deposited on the quartz crystal - were prepared inorganic composite film Thereafter, the organic-inorganic composite film is manufactured by decomposing and removing only the organic matter from the organic-inorganic composite film by irradiating with vacuum ultraviolet light.   The organic-inorganic composite film includes a liquid crystal micelle formed by regularly arranging rod-like micelles formed by arranging the hydrophilic polymers on the outside of the hydrophobic polymer, and the oxide on the outside thereof. 2. The chemical sensor manufacturing method according to claim 1, wherein the precursor is surrounded by a matrix.   The method of manufacturing a chemical sensor according to claim 1 or 2, wherein the irradiation with the vacuum ultraviolet light is performed at a temperature of 100 ° C or lower.   The method of manufacturing a chemical sensor according to claim 1, wherein the nanoporous thin film is made of silica, and the chemical sensor is a humidity sensor.   The method for producing a chemical sensor according to claim 4, wherein the block copolymer is made of an olefin oxide copolymer, and the oxide precursor is made of alkoxysilane.   The method for producing a chemical sensor according to claim 1, wherein the inner surface of the pores of the nanoporous thin film is chemically modified.   The method of manufacturing a chemical sensor according to claim 6, wherein the nanoporous thin film is made of silica, and the chemical modification is performed by applying a silane coupling treatment to an inner surface of the nanoporous thin film.   The method for producing a chemical sensor according to claim 7, wherein an amino group is coated on the inner surface of the pore of the nanoporous thin film made of silica by the chemical modification to function as a sensor for NOx gas or SOx gas.   The method of manufacturing a chemical sensor according to claim 1, wherein the nanoporous thin film has pores on the order of nm.

Images