JP2010038840A - Chemical substance sensing element, chemical msubstance sensing apparatus, manufacturing method of surface decoration carbon nano structure, and manufacturing method of chemical substance sensing element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chemical substance sensing element for selectively and sensitively detecting a specific substance in an atmosphere, reducing a size and a measurement time, and maintaining a performance for a long time, a chemical substance sensing apparatus, a manufacturing method of a surface decoration carbon nano structure included in the chemical substance sensing element, and a manufacturing method of chemical substance sensing element. <P>SOLUTION: The chemical substance sensing element includes the carbon nano structure 74 having a complex ion 72 for selectively reacting on a nitric monoxide (NO) 76 as the specific substance in the atmosphere, and a cationic functional group 73 having an ion bond to the complex ion 72. The carbon nano structure 74 has a surface decoration by the complex ion 72 through the ion bond. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a chemical substance sensing element for detecting a specific substance in an atmosphere, and in particular, a technology that improves the sensitivity and selectivity of a chemical substance sensing element with respect to a measurement target gas and enables rapid and simple detection. About.

  Japan is aging and declining birthrate, and in the near future it is predicted that one in three people will be 65 years of age or older. Under such circumstances, the urgent need is to curb national medical expenses. For this reason, the enhancement of preventive medicine has attracted attention. This is because medical expenses can be reduced if the number of people who get sick is reduced by the improvement of preventive medicine.

  In order to enhance preventive medicine, a system that can manage health by using health information measured by familiar devices is necessary. There are biological samples such as blood, urine, sweat, saliva and exhaled breath as an index for easily grasping an individual's health condition. Such a biological sample contains a plurality of substances (hereinafter referred to as “markers”) whose numerical values change due to disease or signs thereof, such as blood glucose level in blood. Therefore, there is a high possibility that an individual's health status can be grasped by measuring the amount of change in the marker, and health management and early detection of a disease can be performed by constantly measuring the marker. Among the above-mentioned biological samples, exhaled breath has little physical damage because it includes a plurality of types of markers, can be sampled and measured quickly and easily, and the measurement target is gaseous and can be measured non-invasively. From the point, it can be said that it is the most suitable biological sample for measurement.

  Non-Patent Document 1 shows the relationship between a disease and a marker during expiration. A part of this is quoted in Table 1.

Gas chromatography and chemiluminescence methods are known as methods for measuring markers in exhaled breath, but these measuring methods are practical because they require large and expensive measuring instruments and require familiarity with operation methods. is not. Although measurement using an oxide semiconductor gas sensor is also known, the detection limit is as low as 10 ³ ppm level and the sensitivity is low, and it is not suitable for measuring a marker in exhaled breath having a concentration on the order of ppm from ppb. Furthermore, since it is necessary to heat to 300 ° C. in order to operate as a gas sensor, it is not practical.

  As a method for solving such a problem, Non-Patent Document 2 proposes a gas sensor using carbon nanotubes (hereinafter sometimes referred to as “CNT (Carbon Nano Tube)”). CNT is a tubular carbon material having a diameter of nano order, and has a structure in which a graphene sheet is rolled into a cylindrical shape. This graphene sheet is obtained by continuously forming a two-dimensional graphite structure in which six carbon atoms form a regular hexagonal plate structure and are bonded. Since CNT has high conductivity and is a nano-order material, the gas sensor disclosed in Non-Patent Document 2 can realize ultra-small size, low power consumption and portability, and is simple and practical. Ideal as a health check device. However, since the selectivity with respect to the gas to be measured is low, the resistance change occurs in the same way regardless of which gas molecules approach, and there is a problem that a qualitative analysis of a substance present in the atmosphere cannot be performed.

  As shown in Table 1, nitric oxide (NO), which is one of the markers during expiration, is detected at a high concentration in the expiration of asthma patients. In addition, it is one of in vivo neurotransmitters and is known to play an important role in immune responses and blood pressure regulation. Therefore, by detecting the concentration of nitric oxide (NO) in exhaled breath, it is possible to know the prediction and extent of the disease, and the high-performance nitric oxide sensor (hereinafter referred to as “NO sensor”). Realization is desired.

Non-Patent Document 3 proposes a NO sensor using CNTs. The NO sensor disclosed in Non-Patent Document 3 improves the selectivity for the gas to be measured by modifying the CNT surface with a substance that reacts with a specific substance. That is, by using a CNT whose surface is modified with polyethyleneimine that reacts with nitrogen dioxide (NO ₂ ), and further providing a catalyst for converting nitrogen monoxide to nitrogen dioxide, it is a specific marker in the exhaled breath. Nitric oxide (NO) is detected.

Wenting Tsao et al., “Breath Analysis: Potential for Clinical Diagnosis and Exposure Assessment”, Clinical Chemistry, 52: 5, p. 800-p. 811, 2006 (Wenqing Cao et al., “Breath Analysis: Potential for Clinical Diagnosis and Exposure Assessment”, Clinical Chemistry, vol. 52: 5, p. Riichiro Saito, “Outline and Issues of Carbon Nanotubes”, Functional Materials, vol. 21, no. 5, p. 6-p. 14, May 2001 issue Alexander Star et al., “Carbon Nanotube Sensor for Breathing Components”, Nanotechnology, Vol. 18, p. 375502 (7 pp), 2007 (Alexander Star et al., “Carbon nanotube sensors for exhaled breath components”, Nanotechnology, vol. 18, p. 375502 (7 pp), 2007).

  In general, the nitric oxide concentration in the breath of a healthy person is about 10 ppb, and the nitric oxide concentration in the breath of an asthmatic patient is about 50 ppb. Therefore, nitric oxide (NO) in the breath is detected. Therefore, a NO sensor for which the detection lower limit is as high as the ppb level is required. In the NO sensor disclosed in Non-Patent Document 3, such a high sensitivity level that can detect nitric oxide (NO) in exhaled air has not been achieved.

In addition, the NO sensor disclosed in Non-Patent Document 3 does not operate normally unless the catalyst used is in an environment with a humidity of about 15% to 30%, so the humidity of the measurement target gas must be adjusted. Further, in order to detect an accurate amount of nitric oxide, nitrogen dioxide (NO ₂ ) contained in the measurement target gas must be removed in advance. Therefore, when measuring nitric oxide (NO) in exhaled air by the NO sensor disclosed in Non-Patent Document 3, not only the catalyst but also nitrogen dioxide (NO ₂ ) contained in about 4% in the exhaled air. A configuration necessary for pretreatment such as removal and humidity adjustment has to be provided, and there is a problem that the apparatus becomes large. In addition, there is a problem that the measurement time becomes long because a multi-step process is required for the measurement.

  In addition to the NO sensor using CNT surface-modified with a polymer compound such as polyethyleneimine as disclosed in Non-Patent Document 3, CNT surface-modified with a metal complex that reacts with nitric oxide (NO) is used. An NO sensor is conceivable. When these metal complexes are physically modified on the CNT surface in the same manner as in the prior art, the adhesion of the metal complex to the CNT is insufficient, so that the metal complex is easily detached from the CNT and the performance of the NO sensor is prolonged. There is a problem that it is difficult to maintain over a period of time.

  The present invention has been made in view of the above-described problems, and its object is to detect a specific substance in the atmosphere with high selectivity and high sensitivity, and to achieve downsizing of the apparatus and shortening of measurement time. Furthermore, there are provided a chemical substance sensing element, a chemical substance sensing device, a method for producing a surface-modified carbon nanostructure included in the chemical substance sensing element, and a method for producing the chemical substance sensing element capable of maintaining performance over a long period of time. Is to provide.

  The chemical substance sensing element according to the first aspect of the present invention includes a carbon nanostructure having a cationic functional group that ionically bonds with a complex ion that selectively reacts with a specific substance in an atmosphere. The surface is modified by complex ions through ionic bonds.

  Thereby, the specific substance in the atmosphere can be detected with high selectivity and high sensitivity. In addition, since the specific substance in the atmosphere can be directly detected without being converted to another substance, the configuration and process required for the conversion and the configuration and process required for the pretreatment accompanying the conversion can be omitted. Therefore, the chemical substance sensing element can be downsized and the measurement time can be shortened. In addition, the complex ion is firmly fixed to the surface of the carbon nanostructure due to surface modification via ionic bond between the complex ion and the cationic functional group, so the chemical substance sensing element has high selectivity over a long period of time. And high sensitivity can be maintained.

  Preferably, the complex ion is represented by the following general formula (1). Thereby, nitric oxide can be detected with high selectivity and high sensitivity. Moreover, since it can detect directly, without converting nitric oxide into nitrogen dioxide, the structure and process which are required for conversion, and the structure and process which are required for the pre-processing accompanying conversion can be omitted. Therefore, the chemical substance sensing element can be downsized and the measurement time can be shortened.

（式中、Ｍは鉄原子及びコバルト原子からなるグループから選択される金属原子であり、ｎは２〜３の整数であり、ｍは０〜１の整数である。）

(In the formula, M is a metal atom selected from the group consisting of iron atom and cobalt atom, n is an integer of 2 to 3, and m is an integer of 0 to 1.)

  More preferably, the carbon nanostructure is made of a carbon-based conductive material selected from the group consisting of carbon nanotubes, carbon nanofibers, carbon nanohorns, and fullerenes. Since the carbon nanostructure selected from such a group has a nano-order fine structure, the responsiveness and the detection lower limit are greatly improved. Therefore, it is possible to detect a very small amount of a specific substance on the order of ppb, which is difficult with a conventional sensing element.

  More preferably, the cationic functional group is an ammonium group. Since the ammonium group can be easily introduced into the carbon nanostructure, the convenience of the chemical substance sensing element can be further improved.

  A chemical substance sensing device according to a second aspect of the present invention includes the above-described chemical substance sensing element and a detection unit that is electrically connected to the chemical substance sensing element and detects a change in electrical resistance of the chemical substance sensing element. Including. As described above, since the chemical substance sensing device includes the above-described chemical substance sensing element, a specific substance in the atmosphere can be detected with high selectivity and high sensitivity, and further downsizing of the apparatus and reduction of measurement time can be achieved.

  The method for producing a surface-modified carbon nanostructure according to the third aspect of the present invention is a cationic functional group-introduced carbon nanostructure that is a carbon nanostructure having a cationic functional group introduced on the surface in the first step. In the second step, a surface modification solution containing a metal complex containing a complex ion that selectively reacts with a specific substance in the atmosphere and a first solvent is prepared in the second step. After the cationic functional group-introduced carbon nanostructure is introduced into the prepared surface modification solution, the surface modification is a carbon nanostructure that is surface-modified with the complex ions described above by irradiating with ultrasonic waves. Carbon nanostructures are manufactured. Thus, since the cationic functional group-introduced carbon nanostructure can be uniformly dispersed in the surface modification solution by using ultrasonic waves, the surface of the carbon nanostructure can be uniformly modified with complex ions. Therefore, a surface-modified carbon nanostructure capable of detecting a specific substance in the atmosphere with higher selectivity and sensitivity can be produced. Further, since the complex ions modify the surface of the carbon nanostructure through ionic bonds, the complex ions can be firmly fixed on the surface of the carbon nanostructure. Therefore, a surface-modified carbon nanostructure capable of maintaining high selectivity and high sensitivity over a long period can be produced.

  Preferably, the first step includes a step of preparing a cationic functional group introduction solution containing an aromatic molecule having a cationic functional group and a second solvent, and the cationic functional group introduction solution. Irradiating with ultrasonic waves after introducing the carbon nanostructure. As described above, since the carbon nanostructure can be uniformly dispersed in the cationic functional group introduction solution by using ultrasonic waves, the cationic functional group can be uniformly introduced on the surface of the carbon nanostructure. . In addition, since the cationic functional group is introduced to the surface of the carbon nanostructure by electrostatic chemisorption by π-π stacking interaction, the cationic functional group should be firmly fixed on the surface of the carbon nanostructure. Can do.

  Preferably, in the first step, a cationic functional group-introduced carbon nanostructure is produced by introducing a cationic functional group into the carbon nanostructure by a covalent bond. Thus, since the cationic functional group is introduced to the surface of the carbon nanostructure by a covalent bond, the cationic functional group can be firmly fixed to the surface of the carbon nanostructure.

  The method for producing a chemical substance sensing element according to the fourth aspect of the present invention includes a step of producing a sheet-like substrate including the surface-modified carbon nanostructure produced by the method for producing a surface-modified carbon nanostructure. Including. As a result, the surface-modified carbon nanostructure can react with a specific substance in the atmosphere in a uniform state, so that the chemical substance sensing can detect the specific substance with higher selectivity and sensitivity. An element can be manufactured.

  According to the present invention, the chemical substance sensing element includes a carbon nanostructure having a cationic functional group that ionically bonds with a complex ion that selectively reacts with a specific substance in an atmosphere, and the carbon nanostructure includes a complex ion. Is surface modified via ionic bonds. Therefore, the specific substance in the atmosphere can be detected with high selectivity and high sensitivity. In addition, since the specific substance in the atmosphere can be directly detected without being converted to another substance, the configuration and process required for the conversion and the configuration and process required for the pretreatment accompanying the conversion can be omitted. Therefore, the chemical substance sensing element can be downsized and the measurement time can be shortened. In addition, the complex ion is firmly fixed to the surface of the carbon nanostructure due to surface modification via ionic bond between the complex ion and the cationic functional group, so the chemical substance sensing element has high selectivity over a long period of time. And high sensitivity can be maintained.

  In the following description and drawings, the same reference numerals and names are assigned to the same components. Their functions are also the same. Therefore, detailed description thereof will not be repeated each time.

−Configuration−
FIG. 1 is a configuration diagram of a chemical substance sensing device 20 including a chemical substance sensing element 32 according to an embodiment of the present invention. Referring to FIG. 1, chemical substance sensing device 20 includes DC power supply 30, chemical substance sensing element 32 according to the present embodiment, one end of which is connected to the positive terminal of DC power supply 30, and chemical substance sensing element 32. An input is connected to a load resistor 34 connected between the other end of the DC power source 30 and the negative terminal of the DC power supply 30 and a contact point between the chemical substance sensing element 32 and the load resistor 34 to amplify a potential change at the contact point. And an amplifier 36. When detecting a chemical substance in the atmosphere, a DC voltmeter (not shown) is connected to the other terminal of the amplifier 36 in order to measure this potential change.

  FIG. 2 is a diagram showing a configuration of the chemical substance sensing element 32, FIG. 2A is a side view, and FIG. 2B is a top view. Referring to FIG. 2, a chemical substance sensing element 32 is a carbon that is formed on a surface of a substrate 48 and the surface of the substrate 48 and is modified by ionic bonds with complex ions that selectively react with a specific substance in the atmosphere. It includes a chemical substance sensing unit 42 composed of an assembly of nanostructures, and electrodes 44 and 46 arranged at both ends of the chemical substance sensing unit 42.

  Hereinafter, the chemical substance sensing unit 42, the electrode 44 and the electrode 46, and the substrate 48 constituting the chemical substance sensing element 32 will be described in detail.

[Chemical substance sensing unit 42]
The chemical substance sensing unit 42 may be referred to as a carbon nanostructure whose surface is modified through ionic bonds with complex ions that selectively react with a specific substance in the atmosphere (hereinafter referred to as “surface-modified carbon nanostructure”). ). When a chemical substance adheres to the surface of the carbon nanostructure, electron transfer occurs and an electromotive force is generated. In other words, a potential difference or a change in electrical resistance occurs between two points of the carbon nanostructure. If this change in electrical resistance is detected, chemical substances can be detected (sensing). In addition, if the surface of the carbon nanostructure is modified with a complex ion that selectively reacts with a specific substance, the change in electrical resistance described above will be linked to the behavior of the complex ion modified on the surface. The chemical substance sensing element 32 capable of detecting only the substance can be obtained.

  The complex ion is not particularly limited as long as it selectively reacts with a specific substance in the atmosphere. For example, a complex ion represented by the above general formula (1) and an iron atom (Fe) as a central metal atom Or what is selected from the group which consists of complex ions etc. containing a cobalt atom (Co) can be used. Among these, it is preferable to use the complex ion represented by the above general formula (1) because it has a high selectivity for the nitric oxide molecule (NO) which is a specific substance in the atmosphere.

Hereinafter, the complex ion represented by the general formula (1) will be described in detail. Referring to the general formula (1), the complex ion is composed of a central metal atom (M) and a ligand coordinated to the central metal atom (M). The central metal atom (M) is a metal atom selected from the group consisting of an iron atom (Fe) and a cobalt atom (Co), particularly a trivalent metal atom, that is, Fe (III) or Co (III). Preferably there is. The ligand forms a planar four-coordinate coordination structure. In this ligand, two adjacent atoms among the four atoms coordinated to the central metal atom (M) (hereinafter sometimes referred to as “coordinating atoms”) are amido nitrogen atoms (N). The other two atoms are thiol sulfur atoms (S). Here, the amido nitrogen atom (N) is a nitrogen atom constituting a group obtained by removing a proton (H) from a secondary amide group (—CONH—) composed of carbonyl and amine, that is, —CON ^—. The nitrogen atom which comprises group represented by-is shown. In addition, the thiol sulfur atom, a sulfur atom constituting a group formed by removing a proton (H) from a thiol group (-SH), i.e., -S ^- indicates that the sulfur atom constituting a group represented by. Coordinating atoms are electron-pair donors that donate unshared electron pairs of each to the central metal atom (M), and these coordinating atoms take a planar four-coordinated coordination structure. The electron pair is more effectively donated to the central metal atom (M). Moreover, in General formula (1), n is an integer of 2-3, m is an integer of 0-1.

  Such complex ions have a property of selectively reacting with nitric oxide molecules (NO) in the atmosphere, ie, reactivity with other chemical species is significantly higher than reactivity with nitric oxide molecules (NO). It has low properties. Therefore, other chemical species are difficult to adsorb to complex ions. This is because the above complex ion has four coordination atoms having a large electron donating property and forms a planar four-coordinate coordination structure, and donates an electron pair to the central metal atom (M). This is considered to be due to the fact that this has been done effectively. In addition, the hydrogen bond formed by the exogenous molecule with respect to the carbonyl oxygen of the ligand is considered to be a factor for exhibiting selective reactivity with the nitric oxide molecule (NO).

The chemical substance sensing unit 42 composed of an aggregate of carbon nanostructures surface-modified with the complex ion represented by the general formula (1) is highly selective and sensitive to nitric oxide (NO). Can be detected. Furthermore, since the nitrogen monoxide (NO) can be detected directly without converting to nitrogen dioxide (NO _2), configuration and processes required for conversion, and can eliminate the configuration and processes required before processing involved in conversion. Therefore, the chemical substance sensing element 32 can be downsized and the measurement time can be shortened.

  Hereinafter, a specific structure of a representative complex ion represented by the general formula (1) will be described.

Exemplary compound (1)

Exemplary compound (2)

Exemplary compound (3)

Exemplary compound (4)

  The carbon nanostructure is preferably made of a carbon-based conductive material selected from the group consisting of carbon nanotubes (CNT), carbon nanofibers, carbon nanohorns, and fullerenes, and more preferably made of CNTs. Such carbon nanostructures can be produced using conventional methods. Moreover, what was processed with hydrochloric acid for impurity removal can also be used. Since the carbon nanostructure selected from the above group has a nano-order fine structure, the chemical substance sensing unit 42 composed of an aggregate of carbon nanostructures has greatly improved responsiveness and detection limit. To do. That is, the time from when the chemical substance adheres to the surface of the carbon nanostructure until the change in electric resistance of the carbon nanostructure occurs is very short due to the conductivity and nanostructure of the carbon nanostructure. In addition, due to the feature point that the surface area of carbon nanostructure is large and the feature point that all the constituent atoms constitute the surface, the influence of adhesion by chemical substances is reflected in the electrical resistance. Loss due to electron scattering is extremely small. Therefore, according to the carbon nanostructure selected from the above group, it is possible to confirm the presence of a small amount of a specific substance of about ppb order, for example, nitric oxide (NO), which is difficult with a conventional sensing element. Become. In the case where the carbon nanostructure is composed of carbon nanotubes, the above-described effects are more remarkably exhibited. In this way, by detecting a small amount of a specific substance in the order of ppb, it is possible to obtain the chemical substance sensing element 32 capable of measuring a marker in exhaled breath. Therefore, it becomes possible to easily grasp an individual's health condition.

  Further, as the chemical substance sensing unit 42, a carbon nanostructure having such conductivity and a complex ion surface-modified one is used. Therefore, by measuring the change in conductivity, that is, the change in resistance, the atmosphere is measured. It is possible to detect a specific substance in it. Therefore, it is not necessary to provide a configuration such as an electrolyte as compared with a chemical substance sensing element or the like that uses a change in electrochemical behavior of an electrolytic solution containing complex ions, so that the element can be further downsized. The amount of surface modification of the complex ion with respect to the carbon nanostructure may be appropriately adjusted so that a specific substance in the atmosphere can be detected with high selectivity and high sensitivity according to the type of the complex ion.

  The carbon nanostructure has a cationic functional group that ion-bonds with a complex ion on the surface. The cationic functional group is not particularly limited as long as it can form an ionic bond with a complex ion. For example, an ammonium group, a trimethylammonium group, a triethylammonium group, a pyridinium group, an imidazolium group, a guanidinium group, a phosphonium group. Etc. can be used. Among these, it is preferable to use an ammonium group that can further improve the convenience of the chemical substance sensing element 32 because it can be easily introduced into the carbon nanostructure. In this way, the complex ion is more firmly fixed to the surface of the carbon nanostructure due to the surface modification via the ionic bond between the complex ion and the cationic functional group, so that the chemical substance sensing is performed for a longer period of time. The high selectivity and high sensitivity of the element 32 can be maintained.

  The amount of the cationic functional group introduced into the carbon nanostructure may be appropriately adjusted so that the surface modification amount of the complex ion with respect to the carbon nanostructure becomes a desired amount. A method for introducing a cationic functional group into the carbon nanostructure and a method for calculating the introduction amount will be described later.

-Manufacturing method of surface modified carbon nanostructure-
Hereinafter, the 1st manufacturing method which is an example of the manufacturing method of a surface modification carbon nanostructure, and the 2nd manufacturing method which is another example are demonstrated.

(First manufacturing method)
FIG. 3 is a process diagram showing the procedure of the first manufacturing method. Referring to FIG. 3, the first manufacturing method includes steps S100 to S103 that proceed in this order. A surface-modified carbon nanostructure can be manufactured through steps S100 to S103.

  In step S100, a cationic functional group introduction solution containing an aromatic molecule having a cationic functional group and a solvent is prepared. In step S101, a carbon nanostructure is introduced into the cationic functional group introduction solution. After that, an ultrasonic wave is irradiated. By this Step S100 and Step S101, a carbon nanostructure having a cationic functional group introduced on its surface (hereinafter referred to as “cationic functional group-introduced carbon nanostructure”) can be produced.

  In step S100 and step S101, the cationic functional group is introduced on the surface of the carbon nanostructure for the following reason. That is, this is because the aromatic ring of the aromatic molecule having a cationic functional group and the carbon 6-membered ring of the carbon nanostructure are electrostatically adsorbed by the π-π stacking interaction. The π-π stacking interaction is an action caused by a dispersion force acting between an aromatic ring having a planar structure and abundantly delocalized electrons by a π electron system and a carbon 6-membered ring. It shows the action of arranging and stabilizing an aromatic ring and a carbon 6-membered ring so as to stack coins.

  The aromatic molecule having a cationic functional group may be a molecule having a structure such as the above-mentioned cationic functional group and an aromatic ring capable of π-π stacking with the carbon 6-membered ring of the carbon nanostructure. If it does not specifically limit. For example, when it has an ammonium group as a cationic functional group, it is produced from 1-pyrenemethylamine, 1-aminopyrene, dimethyl-pyren-1-yl-methylamine, or diethyl-pyren-1-yl-amine, etc. An organic ammonium salt composed of an organic ammonium ion and a halide ion such as a chloride ion or a counter anion such as a hydroxide ion can be used. Among these, it is preferable to use 1-pyrenemethylamine hydrochloride because it is relatively easily available in a salt state.

  The solvent used in the cationic functional group introduction solution is not particularly limited as long as the aromatic molecule having a cationic functional group is soluble. For example, water, alcohol such as methanol, Or these mixed solvents etc. can be used. Among these, from the viewpoint of excellent safety and solubility, it is preferable to use water, and it is particularly preferable to use pure water having an electric conductivity of 0.067 μS / cm or less. The concentration and amount of the cationic functional group introduction solution, and the input amount of the carbon nanostructure may be appropriately adjusted so that the introduction amount of the cationic functional group to the carbon nanostructure becomes a desired value. . Since the surface modification amount of the complex ion for the carbon nanostructure depends on the introduction amount of the cationic functional group to the carbon nanostructure, the introduction amount of the cationic functional group depends on the desired surface modification amount of the complex ion. It is preferable to be determined based on this.

  In step S101, ultrasonic irradiation is performed by generating ultrasonic waves such as a generally used ultrasonic cleaner (for example, a commercial product (trade name: Sure ultrasonic cleaner CS-20, manufactured by Ishizaki Electric Co., Ltd.)). This can be done using an apparatus. The frequency of the ultrasonic wave to be irradiated may be appropriately set so that the carbon nanostructure is uniformly dispersed in the cationic functional group introduction solution, but it is preferably 40 kHz to 60 kHz. The time for irradiating the ultrasonic wave may be set as appropriate so as to ensure the introduction of the cationic functional group. For example, the time is 0.1 hour to 1 hour, which does not evaporate all the solvent. Is preferred.

  The cationic functional group-introduced carbon nanostructure produced as described above is preferably dried by air drying or the like after being taken out of the cationic functional group-introducing solution. In the obtained cationic functional group-introduced carbon nanostructure, whether or not a cationic functional group has been introduced is confirmed by X-ray photoelectron spectroscopy (XPS (X-ray photoelectron spectroscopy)) XPS spectrum, And in IR spectrum etc. obtained by IR spectroscopy (IR (Infrared spectroscopy)), it can carry out based on whether the peak derived from the introduced cationic functional group, for example, an ammonium group can be confirmed.

  Thus, in the first manufacturing method, the cationic functional group-introduced carbon nanostructure is manufactured through Step S100 and Step S101. That is, in step S100, a cationic functional group introduction solution containing an aromatic molecule having a cationic functional group and a solvent is prepared, and in step S101, carbon nano-particles are added to the prepared cationic functional group introduction solution. After putting the structure, ultrasonic waves are irradiated. As described above, since the carbon nanostructure can be uniformly dispersed in the cationic functional group introduction solution by using ultrasonic waves, the cationic functional group can be uniformly introduced on the surface of the carbon nanostructure. . In addition, since the cationic functional group is introduced to the surface of the carbon nanostructure by electrostatic chemisorption by π-π stacking interaction, the cationic functional group should be firmly fixed on the surface of the carbon nanostructure. Can do.

  In the first manufacturing method, in step S102, a solution for surface modification containing a metal complex containing the above complex ion that selectively reacts with a specific substance in the atmosphere and a solvent is prepared, and in step S103, the solution is prepared. After introducing the cationic functional group-introduced carbon nanostructure into the surface modification solution, ultrasonic waves are irradiated.

  A metal complex contains the complex ion mentioned above and its counter cation. The counter cation is not particularly limited as long as it can promote the surface modification of the carbon nanostructure with complex ions. For example, the counter cation is selected from the group consisting of sodium ion, lithium ion, potassium ion, and the like. Can be used. Among these, it is particularly preferable to use sodium ions. When the counter cation is selected from such a group, the ion exchange reaction between the cationic functional group and the counter cation is more likely to proceed. That is, since complex ions are generally bulky and large ions, they form stable ionic bonds with relatively large counter cations such as the cationic functional groups described above. In contrast, ionic bonds formed from complex ions and relatively small counter cations such as those selected from the above group are unstable. Since the ion exchange reaction proceeds so as to form a more stable ionic bond, by using one selected from the above group as a counter cation in the metal complex, the ion exchange reaction can be further facilitated. And the surface-modified carbon nanostructure can be more easily produced.

  The solvent used for the surface modification solution is not particularly limited as long as the metal complex is soluble. For example, water, alcohol such as methanol or ethanol, or a mixed solvent thereof is used. it can. Among these, it is preferable to use water from the viewpoint that the ion exchange reaction easily proceeds, and it is particularly preferable to use pure water.

  The concentration and amount of the surface modification solution, and the input amount of the cationic functional group-introduced carbon nanostructure may be adjusted as appropriate so that the surface modification amount of the complex ion with respect to the carbon nanostructure has a desired value. Good. Here, the surface modification amount is the amount (mg / mg) of complex ions that are surface-modified with respect to 1 mg of the carbon nanostructure.

  In step S103, irradiation with ultrasonic waves generates ultrasonic waves such as a generally used ultrasonic cleaner (for example, a commercially available product (trade name: Sure ultrasonic cleaner CS-20, manufactured by Ishizaki Electric Co., Ltd.)). This can be done using an apparatus. The frequency of the ultrasonic wave to be irradiated may be appropriately set so that the ion exchange reaction proceeds smoothly, but is preferably 40 kHz to 60 kHz. The time for irradiating the ultrasonic wave is not particularly limited as long as the ion exchange reaction is completed with certainty, but for example, it is preferably 1 hour to 3 hours so that the solvent does not completely evaporate.

The surface-modified carbon nanostructure produced as described above is preferably taken out from the solution for surface modification and then dried under reduced pressure for a certain period of time together with drying by air drying or the like. The decompression condition is not particularly limited as long as the solvent can be completely removed, but it is preferable to dry at 1.0 × 10 ⁻⁶ MPa to 1.0 × 10 ⁻⁵ MPa for 1 to 3 hours.

  In the obtained surface-modified carbon nanostructure, confirmation of whether or not surface modification with complex ions has been made is based on the XRF spectrum obtained by XRF (X-ray Fluorescence Analysis), etc. This can be done based on whether or not a peak derived from a complex ion can be confirmed. Further, the surface modification amount of the complex ions with respect to the carbon nanostructure can be calculated based on the difference in absorbance derived from the complex ions in the UV-vis spectrum of the surface modification solution before and after Step S103. The UV-vis spectrum can be obtained by ultraviolet / visible spectroscopy.

(Second manufacturing method)
FIG. 4 is a process diagram showing the procedure of the second manufacturing method. Referring to FIG. 4, the second manufacturing method includes steps S200 to S202 that proceed in this order. A surface-modified carbon nanostructure can be manufactured through steps S200 to S202. In the second manufacturing method, step S201 and step S202 are the same as step S102 and step S103 in the first manufacturing method. Hereinafter, step S200 different from the first manufacturing method will be described.

  In step S200, a cationic functional group-introduced carbon nanostructure is produced by introducing a cationic functional group into the carbon nanostructure by a covalent bond. The method for introducing a cationic functional group into a carbon nanostructure by covalent bonding is not particularly limited as long as it is a method generally used in the art. For example, a cationic functional group may be introduced directly on the surface of the carbon nanostructure, or may be introduced via a spacer such as an alkylene group such as an ethylene group.

  For example, when an ammonium group is introduced directly to the surface of the carbon nanostructure as a cationic functional group, there is a method of introducing a carboxylic acid to the surface of the carbon nanostructure and then converting it to an ammonium group. More specifically, for example, after introducing the carbon nanostructure into a mixed acid of sulfuric acid: nitric acid = 3: 1, the carboxylic acid is introduced to the surface of the carbon nanostructure by a method of irradiating ultrasonic waves, etc. The carboxylic acid is converted to alcohol by reduction with a reducing agent such as lithium aluminum hydride (LAH), and further obtained under Mitsunobu reaction conditions using diethyl azodicarboxylate (DEAD) and triphenylphosphine. There is a method in which after the alcohol is converted into phthalimide, it is hydrolyzed with trifluoroacetic acid or the like. The solvent used under the above-described reduction reaction and Mitsunobu reaction conditions is not particularly limited as long as it is generally used in the field, and for example, tetrahydrofuran (THF) or the like can be used. The amount of the solvent may be appropriately adjusted according to the amount of raw material used.

  When introducing an ammonium group as a cationic functional group to the surface of the carbon nanostructure through a spacer such as an alkylene group, a condensing agent is used for the carboxylic acid and alkylenediamine introduced on the surface of the carbon nanostructure. And an amide bond to form an amide bond. The condensing agent is not particularly limited as long as it is generally used as a coupling agent in an amide bond forming reaction such as peptide synthesis. For example, N-hydroxybenzotriazole such as 1-hydroxybenzotriazole (HOBt) is used. , Carbodiimides such as dicyclohexylcarbodiimide (DCC), and O- (7-azabenzotriazol-1-yl) -N, N, N ′, N′-tetramethyluronium hexafluorophosphate (HATU), etc. Can be selected from the group consisting of Among these, it is preferable to use HATU from the viewpoint of easy handling and safety. The content of the condensing agent is not particularly limited as long as it is an amount generally used in the art, but for example, 1 mol to 1.5 mol with respect to 1 mol of a desired carboxylic acid for forming an amide bond. Preferably there is.

  In the amide bond forming reaction, a solvent may be used as necessary. The solvent is not particularly limited as long as it is generally used in the field, and for example, dimethylformamide (DMF) or tetrahydrofuran (THF) can be used. The amount of the solvent may be adjusted as appropriate according to the amount of the carbon nanostructure into which the carboxylic acid has been introduced. In the above amide bond formation reaction, an appropriate amount of a base such as N, N-diisopropylethylamine (DIEA) is added as necessary in order to further promote the reaction under basic conditions in the reaction system. You may do it.

  Since the surface modification amount of the complex ion for the carbon nanostructure depends on the introduction amount of the cationic functional group to the carbon nanostructure, the introduction amount of the cationic functional group depends on the desired surface modification amount of the complex ion. It is preferable to be determined based on this.

  Thus, in the second manufacturing method, in step S200, the cationic functional group-introduced carbon nanostructure is produced by introducing the cationic functional group into the carbon nanostructure by a covalent bond. Thus, since the cationic functional group is introduced to the surface of the carbon nanostructure by a covalent bond, the cationic functional group can be firmly fixed to the surface of the carbon nanostructure.

  As described above, the method for producing a surface-modified carbon nanostructure according to the present embodiment produces a cationic functional group-introduced carbon nanostructure in Step S100 and Step S101 or Step S200, and Step S102 or In step S201, a surface modification solution containing a metal complex containing a complex ion that selectively reacts with a specific substance in the atmosphere and a solvent is prepared. In step S103 or step S202, the surface modification solution is prepared. Then, after introducing the cationic functional group-introduced carbon nanostructure, the surface-modified carbon nanostructure is manufactured by irradiating ultrasonic waves. Thus, since the cationic functional group-introduced carbon nanostructure can be uniformly dispersed in the surface modification solution by using ultrasonic waves, the surface of the carbon nanostructure can be uniformly modified with complex ions. Therefore, a surface-modified carbon nanostructure capable of detecting a specific substance in the atmosphere with higher selectivity and sensitivity can be produced. Further, since the complex ions modify the surface of the carbon nanostructure through ionic bonds, the complex ions can be firmly fixed on the surface of the carbon nanostructure. Therefore, a surface-modified carbon nanostructure capable of maintaining high selectivity and high sensitivity over a long period can be produced.

-Manufacturing Method of Chemical Substance Sensing Element 32-
Hereinafter, the manufacturing method of the chemical substance sensing element 32 is demonstrated. 5A and 5B are diagrams for explaining an example of a method for manufacturing the chemical substance sensing unit 42. FIG. With reference to FIG. 5A and FIG. 5B, in an example of the manufacturing method of the chemical substance sensing unit 42, the surface-modified carbon nanostructure manufactured in the first manufacturing method or the second manufacturing method described above. The sheet-like substrate 56 including the surface-modified carbon nanostructure is produced by preparing the dispersion liquid 58 in which the body is dispersed and filtering the dispersion liquid 58.

  The dispersion solvent for dispersing the surface-modified carbon nanostructure in the dispersion liquid 58 is not particularly limited as long as the surface-modified carbon nanostructure can be dispersed. For example, water, methanol, ethanol or Dimethylformamide (DMF) or the like can be used. Among these, water is particularly preferable from the viewpoint of safety and cost. By dispersing the surface-modified carbon nanostructure using such a dispersion solvent, the substrate 56 including the carbon nanostructure that has been uniformly surface-modified can be formed with a uniform thickness. When a solvent in which the surface-modified carbon nanostructure is difficult to disperse is used as a solvent for dispersion, the surface-modified carbon nanostructure is locally aggregated, so that there is a possibility that the substrate 56 having a uniform thickness may not be formed. The amount of the dispersion solvent used in the dispersion 58 may be adjusted as appropriate according to the amount of the surface-modified carbon nanostructure to be dispersed.

  The filter medium 60 used for the filtration is not particularly limited as long as it has insulating properties and appropriate mechanical strength. However, a membrane filter or a silver membrane filter made of a polymer material such as a fluororesin is used. Glass fiber filter paper or filter paper can be used. Among these, it is particularly preferable to use a membrane filter made of Teflon (registered trademark) because of cost and ease of handling. As a filtration method, a general method such as reduced-pressure filtration or natural filtration can be used, but it is preferable to use reduced-pressure filtration from the viewpoint of a high filtration rate and easy formation of a substrate 56 having a uniform thickness. When natural filtration is used, since the filtration speed is slow, it may take a long time to form the substrate 56, and the substrate 56 with a uniform thickness may not be formed. The vacuum filtration is preferably performed using a vacuum filtration apparatus including a Buchner funnel 62 and a suction bottle (not shown), and more preferably after the dispersion liquid 58 is injected into the Buchner funnel 62. . When the dispersion 58 is injected after the pressure is reduced, there is a possibility that the base 56 having a thickness at the central portion larger than that of other portions may be formed. The substrate 56 manufactured as described above is preferably dried. The substrate 56 includes a substrate 48 and a chemical substance sensing unit 42. In this case, the substrate 48 is a filter medium 60, and the chemical substance sensing unit 42 is a filter material 64 remaining on the filter medium.

  Thus, in an example of the manufacturing method of the chemical substance sensing part 42, the sheet-like base | substrate 56 containing the surface modification carbon nanostructure manufactured by the above-mentioned 1st manufacturing method or the 2nd manufacturing method is produced. As a result, the surface-modified carbon nanostructure can react with a specific substance in the atmosphere in a uniform state, so that the chemical substance sensing can detect the specific substance with higher selectivity and sensitivity. The element 32 can be manufactured. Furthermore, the substrate 56 including the surface-modified carbon nanostructure is prepared by preparing a dispersion 58 in which the surface-modified carbon nanostructure is dispersed and drying the dispersion 58 by vacuum filtration or the like. As a result, the substrate 56 including the carbon nanostructure with the surface modified uniformly can be formed in a uniform thickness and in a short time.

  The substrate 56 including the surface-modified carbon nanostructure is cut so as to have a desired shape such as a strip shape and a desired size as necessary. Thereafter, the electrode 44 and the electrode 46 are formed to have a desired inter-electrode distance by a known method such as a vapor deposition method or a method of applying a conductive paste on both ends of the surface of the chemical substance sensing unit 42. The chemical substance sensing element 32 according to the present embodiment can be manufactured.

-Operation-
With reference to FIG.1 and FIG.2, the chemical substance sensing apparatus 20 which concerns on this Embodiment operate | moves as follows. A measurement target gas containing a specific substance is introduced onto the surface of the chemical substance sensing element 32 while applying a constant voltage to both ends of the chemical substance sensing element 32 and the load resistor 34 connected in series by the DC power source 30. When any substance in the measurement target gas adheres to the surface of the surface-modified carbon nanostructure constituting the chemical substance sensing unit 42 included in the chemical substance sensing element 32, the electrical resistance between the electrodes 44 and 46 changes. The change is detected as a change in the output voltage of the amplifier 36 by a DC voltmeter (not shown). By knowing the change in output voltage in this way, the presence of some substance in the measurement target gas can be confirmed.

  This is for the following reason. In the chemical substance sensing unit 42, since the individual carbon nanostructures are adjacent to each other and are in contact with each other, the whole is a collection of conductive materials. When any substance adheres to the surface of each carbon nanostructure constituting such a chemical substance sensing unit 42, the respective electrical resistances change and the sum of them changes as an output voltage change. Therefore, by knowing the change in the electrical resistance at both ends of the chemical substance sensing unit 42, it can be seen that some substance has adhered to the chemical substance sensing unit 42. Therefore, confirm that there is some substance in the measurement target gas. Can do.

  FIG. 6 is a diagram illustrating a state in which nitric oxide (NO) 76 is adsorbed on the surface of the carbon nanostructure 74 that has been surface-modified with complex ions 72 through ionic bonds. Referring to FIG. 6, carbon nano-particles in which complex ion 72 shown in exemplary compound (4) that selectively reacts with nitric oxide (NO) 76 in the atmosphere is surface-modified by ionic bond with cationic functional group 73. When the nitric oxide (NO) 76 approaches the structure 74, the nitric oxide (NO) 76 is selectively adsorbed on the complex ions 72 due to the selectivity by the complex ions 72. As described above, the complex ions 72 surface-modified on the carbon nanostructure 74 selectively capture the nitric oxide (NO) 76, and therefore, when the nitric oxide (NO) 76 is adsorbed and when it is not. The difference between the two is remarkably shown as a change in the overall electrical resistance of the chemical substance sensing unit 42. Therefore, by measuring the change in the electrical resistance of the chemical substance sensing unit 42, the presence or absence of the specific substance, nitric oxide (NO) 76, and the amount thereof are more sensitive than other substances. Can be detected.

<Action and effect>
According to the present embodiment, the chemical substance sensing element 32 includes a carbon nanostructure having a cationic functional group that ion-bonds with a complex ion that selectively reacts with a specific substance in the atmosphere. The surface is modified by complex ions through ionic bonds. Thereby, the specific substance in the atmosphere can be detected with high selectivity and high sensitivity. In addition, since the specific substance in the atmosphere can be directly detected without being converted to another substance, the configuration and process required for the conversion and the configuration and process required for the pretreatment accompanying the conversion can be omitted. Therefore, the chemical substance sensing element 32 can be downsized and the measurement time can be shortened. Further, the complex ion is firmly fixed to the surface of the carbon nanostructure by the surface modification through the ionic bond between the complex ion and the cationic functional group, so that the chemical substance sensing element 32 is highly selected over a long period of time. And high sensitivity can be maintained.

  Further, according to the present embodiment, the chemical substance sensing device 20 is electrically connected to the chemical substance sensing element 32 and the chemical substance sensing element 32, and detects a change in the electrical resistance of the chemical substance sensing element 32. An amplifier 36 and a DC voltmeter are included. As described above, since the chemical substance sensing device 20 includes the chemical substance sensing element 32, a specific substance in the atmosphere can be detected with high selectivity and high sensitivity, and further downsizing of the apparatus and reduction of measurement time can be achieved.

  Moreover, according to this Embodiment, the manufacturing method of the surface modification carbon nanostructure produces a cationic functional group introduction | transduction carbon nanostructure in step S100 and step S101, or step S200, and step S102 or step S201. In step S103 or step S202, a surface modification solution containing a metal complex containing a complex ion that selectively reacts with a specific substance in the atmosphere and a solvent is prepared. After introducing the cationic functional group-introduced carbon nanostructure, the surface-modified carbon nanostructure is produced by irradiating ultrasonic waves. Thus, since the cationic functional group-introduced carbon nanostructure can be uniformly dispersed in the surface modification solution by using ultrasonic waves, the surface of the carbon nanostructure can be uniformly modified with complex ions. Therefore, a surface-modified carbon nanostructure capable of detecting a specific substance in the atmosphere with higher selectivity and sensitivity can be produced. Further, since the complex ions modify the surface of the carbon nanostructure through ionic bonds, the complex ions can be firmly fixed on the surface of the carbon nanostructure. Therefore, a surface-modified carbon nanostructure capable of maintaining high selectivity and high sensitivity over a long period can be produced.

  Further, according to the present embodiment, the chemical substance sensing unit 42 is manufactured by producing the sheet-like substrate 56 including the surface-modified carbon nanostructure manufactured by the above-described surface-modified carbon nanostructure manufacturing method. . As a result, the surface-modified carbon nanostructure can react with a specific substance in the atmosphere in a uniform state, so that the chemical substance sensing can detect the specific substance with higher selectivity and sensitivity. The element 32 can be manufactured.

  In the above embodiment, ultrasonic irradiation is performed in step S103 and step S202 in the method of manufacturing a surface-modified carbon nanostructure. However, the present invention is not limited to such an embodiment. It may be configured to stir without irradiating.

  Although the said embodiment is concretely demonstrated using an Example and a comparative example below, the said embodiment is not specifically limited to a present Example, unless the summary is exceeded. Unless otherwise specified, in the examples and comparative examples, an XPS spectrum is measured using an X-ray photoelectron spectrometer (trade name: MICRO LAB 300A, manufactured by VG SCIENTIFIC), and an IR spectrum is measured. Uses an infrared spectrophotometer (trade name: 20D FTIR SPECTROMETER, manufactured by Nicolet), and an XRF spectrum is measured using a fluorescent X-ray analyzer (trade name: ZSX100s, manufactured by Rigaku Corporation), and UV. For the measurement of the -vis spectrum, an ultraviolet-visible spectrophotometer (trade name: U-3310 spectrometer, manufactured by Hitachi High-Technologies Corporation) was used.

-Test Example 1
Example 1
[Preparation of ammonium group-introduced CNT]
In the following manner, an ammonium group that is a cationic functional group was introduced on the surface of CNT that is a carbon nanostructure. 1-Pyrenemethylamine hydrochloride (manufactured by Aldrich) was dissolved in pure water to a concentration of 3 mmol / L to prepare a cationic functional group introduction solution. After adding 2 mg of SWCNT (trade name: Single-wall nanotube, manufactured by Honjo Chemical Co., Ltd.) to 25 mL of this cationic functional group introduction solution, an ultrasonic cleaner (trade name: Sure Ultrasonic Cleaner CS-20) (Ishizaki Electric Mfg. Co., Ltd.) was irradiated with ultrasonic waves at 46 kHz, and after dispersion of CNTs in pure water was confirmed, ultrasonic waves were further irradiated for 30 minutes. After ultrasonic irradiation, the membrane was filtered using a Teflon (registered trademark) membrane filter (trade name: OMNIPORE ^™ MEMBRANE FILTERS 0.2 μm (pore size) JG, manufactured by MILLIPORE) using a vacuum filtration device, and the filtrate was collected. And dried to obtain ammonium group-introduced CNT, which is a CNT having an ammonium group introduced on its surface. In the obtained ammonium group-introduced CNT, an XPS spectrum confirmed a peak (404 eV) derived from an ammonium group in the N1s region, and an IR spectrum confirmed a peak derived from 1-pyrenemethylamine (850 cm ⁻¹ ). .

[Production of surface-modified CNT]
As described below, surface modification of cobalt complex ions with respect to ammonium group-introduced CNTs was performed. For surface modification, a cobalt complex (Na [Co ^III (MMPPA)]) composed of a cobalt complex ion and a sodium ion shown in the exemplified compound (4) is dissolved in pure water to a concentration of 0.05 mmol / L. A solution was prepared. To 10 mL of the surface modification solution, 2 mg of the CNT introduced CNT obtained as described above was added, and then an ultrasonic wave of 46 kHz was applied for 30 minutes with an ultrasonic cleaner. After irradiation with ultrasonic waves, vacuum filtration is performed with a vacuum filter using a Teflon (registered trademark) membrane filter, and the filtrate is collected and dried, followed by drying at 9.3 × 10 ⁻⁶ MPa for 2 hours under reduced pressure. Thus, CNTs whose surface was modified with a cobalt complex ion (hereinafter referred to as “surface-modified CNT”) were obtained.

FIG. 7 is a graph showing the UV-vis spectrum of the solution for surface modification at the time of preparation and the UV-vis spectrum of the filtrate after filtration under reduced pressure. Referring to FIG. 7, the absorbance at 654 nm derived from cobalt complex ions in the UV-vis spectrum (shown as A in the graph) of the surface modification solution at the time of preparation is 0.1387, and the filtrate after filtration under reduced pressure In the UV-vis spectrum (shown as B in the graph), the absorbance at 654 nm was 0.0792, and the difference was 0.0595. The surface modification amount of the cobalt complex ion in the surface-modified CNT of Example 1 calculated based on the obtained difference value and the Lambert-Beer formula shown in the following formula (1) was 3.79 × 10 ^{− 2} mg / mg. As the molar extinction coefficient (ε), ε = 2800, which is the molar extinction coefficient of water, was used, and 1 cm was used as the cell length (l).

A = εcl (1)
(In the above formula (1), A represents absorbance, ε represents molar extinction coefficient, c represents concentration, and l represents cell length.)
(Example 2)
The surface of Example 2 was prepared in the same manner as in Example 1 except that a surface modification solution having a concentration of 0.0125 mmol / L was prepared and 0.5 mg of ammonium group-introduced CNT was added to 10 mL of the surface modification solution. Modified CNTs were obtained. The surface modification amount of cobalt complex ions in the surface-modified CNT of Example 2 was 3.26 × 10 ⁻² mg / mg.

(Example 3)
The surface of Example 3 was prepared in the same manner as in Example 1 except that a surface modifying solution having a concentration of 0.025 mmol / L was prepared and 0.5 mg of ammonium group-introduced CNT was added to 10 mL of the surface modifying solution. Modified CNTs were obtained. The surface modification amount of the cobalt complex ion in the surface-modified CNT of Example 3 was 4.68 × 10 ⁻² mg / mg.

Example 4
The surface of Example 4 was prepared in the same manner as in Example 1 except that a surface modification solution having a concentration of 0.05 mmol / L was prepared and 0.5 mg of ammonium group-introduced CNT was added to 10 mL of this surface modification solution. Modified CNTs were obtained. The surface modification amount of the cobalt complex ion in the surface-modified CNT of Example 4 was 4.63 × 10 ⁻² mg / mg.

  Table 2 shows the concentration of the surface modification solution used, the amount of ammonium group-introduced CNT used, and the amount of surface modification of cobalt complex ions in the surface-modified CNTs of Examples 1 to 4. FIG. 8 is a bar graph showing the surface modification amount of cobalt complex ions in the surface-modified CNTs in Examples 1 to 4.

Referring to Table 2 and FIG. 8, the surface modification of cobalt complex ion in the surface-modified CNT of Examples 1 to 4 was 4 × 10 -2 ^{mg / mg} approximately in any conditions. From this result, it can be seen that the surface modification amount of the cobalt complex ion depends on the introduction amount of the ammonium group in the ammonium group-introduced CNT.

-Test Example 2-
(Example 5)
A surface-modified CNT of Example 5 was obtained in the same manner as in Example 1 except that the following method for producing ammonium group-introduced CNT was used.

[Preparation of ammonium group-introduced CNT]
First, after introducing a carboxylic acid onto the surface of the carbon nanostructure CNT as described below, an ammonium group as a cationic functional group was introduced. After adding 5 mg of SWCNT (trade name: Single-wall nanotube, manufactured by Honjo Chemical Co., Ltd.) to a mixed acid composed of 1.5 mL of sulfuric acid and 0.5 mL of nitric acid, an ultrasonic cleaner (trade name: Sure ultrasonic cleaning) 46 kHz ultrasonic wave was irradiated for 1 hour with a device CS-20, manufactured by Ishizaki Electric Manufacturing Co., Ltd. After ultrasonic irradiation, the membrane was filtered using a Teflon (registered trademark) membrane filter (trade name: OMNIPORE ^™ MEMBRANE FILTERS 0.2 μm (pore size) JG, manufactured by MILLIPORE) using a vacuum filtration device, and the filtrate was collected. And dried to obtain a CNT having a carboxylic acid introduced on the surface (hereinafter referred to as “carboxylic acid-introduced CNT”). Next, 2 mg of the carboxylic acid-introduced CNT obtained as described above was added to 2 mL of ethylenediamine (trade name, manufactured by Wako Pure Chemical Industries, Ltd.), and then an ultrasonic wave of 46 kHz was applied using the ultrasonic cleaner described above. Irradiation was performed for 10 minutes, and dispersion of the carboxylic acid-introduced CNT in ethylenediamine was confirmed. After confirming the dispersion, 0.1 mg of HATU (condensing agent, manufactured by Sigma-Aldrich) was added, and ultrasonic waves were further irradiated for 4 hours. After ultrasonic irradiation, the solution was diluted with methanol, and filtered under reduced pressure with a vacuum filter using the above-mentioned Teflon (registered trademark) membrane filter. The residue was washed with methanol to remove the remaining HATU. The washed filtrate was collected and air-dried, and then dried at 9.3 × 10 ⁻⁶ MPa under reduced pressure for 2 hours to obtain ammonium group-introduced CNT. In the obtained ammonium group-introduced CNT, in the XPS spectrum, an ammonium group-derived peak (404 eV) was confirmed in the N1s region, and a carboxylic acid-derived peak (533 eV) was confirmed in the O1s region. In the IR spectrum, a peak (1720 cm ⁻¹ ) derived from a carbonyl group was confirmed.

FIG. 9 is a graph showing the UV-vis spectrum of the solution for surface modification at the time of preparation and the UV-vis spectrum of the filtrate after filtration under reduced pressure. Referring to FIG. 9, in the UV-vis spectrum (shown in C in the graph) of the surface modification solution at the time of preparation, the absorbance at 654 nm derived from cobalt complex ions is 0.055, and the filtrate after filtration under reduced pressure In the UV-vis spectrum (shown as D in the graph), the absorbance at 654 nm was 0.0001, and the difference was 0.0549. The amount of surface modification of cobalt complex ions in the surface-modified CNT of Example 5 calculated based on the obtained difference value and the Lambert-Beer equation shown in the above formula (1) was 3.25 × 10 ^{−. 2} mg / mg. As the molar extinction coefficient (ε), ε = 2800, which is the molar extinction coefficient of water, was used, and 1 cm was used as the cell length (l).
It was.

  In the XRF spectra of the surface-modified CNTs of Examples 1 to 5, a peak derived from cobalt complex ions was confirmed at 47.5 deg which is a 2θ angle.

  The embodiment disclosed herein is merely an example, and the present invention is not limited to the above-described embodiment. The scope of the present invention is indicated by each claim in the claims after taking into account the description of the detailed description of the invention, and all modifications within the meaning and scope equivalent to the wording described therein are included. Including.

It is a block diagram of the chemical substance sensing apparatus containing the chemical substance sensing element which concerns on one embodiment of this invention. It is the side view and top view which show the structure of a chemical substance sensing element. It is process drawing which shows the procedure of the 1st manufacturing method which is an example of the manufacturing method of a surface modification carbon nanostructure. It is process drawing which shows the procedure of the 2nd manufacturing method which is another example of the manufacturing method of a surface modification carbon nanostructure. It is a figure for demonstrating an example of the manufacturing method of a chemical substance sensing part. It is a figure which shows a mode that nitric oxide adsorb | sucks to the carbon nanostructure surface surface-modified by the complex ion through the ionic bond. It is a graph which shows the UV-vis spectrum of the solution for surface modification at the time of preparation, and the UV-vis spectrum of the filtrate after reduced pressure filtration. It is a bar graph which shows the surface modification amount of the cobalt complex ion in the surface modification CNT in Example 1- Example 4. It is a graph which shows the UV-vis spectrum of the solution for surface modification at the time of preparation, and the UV-vis spectrum of the filtrate after reduced pressure filtration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 Chemical substance sensing apparatus 30 DC power supply 32 Chemical substance sensing element 34 Load resistance 36 Amplifier 42 Chemical substance sensing part 44,46 Electrode 48 Substrate 56 Base body 58 Dispersion liquid 60 Filter medium 62 Buchner funnel 64 Filtrate 72 Complex ion 73 Cationic functional group 74 Carbon nanostructure 76 Nitric oxide

Claims (9)

A carbon nanostructure having a cationic functional group that ionically bonds with a complex ion that selectively reacts with a specific substance in an atmosphere;
A chemical substance sensing element, wherein the carbon nanostructure is surface-modified with the complex ions via the ionic bonds. The chemical substance sensing element according to claim 1, wherein the complex ion is represented by a general formula (1).

(In the formula, M is a metal atom selected from the group consisting of iron atom and cobalt atom, n is an integer of 2 to 3, and m is an integer of 0 to 1.)   The chemical substance sensing according to claim 1 or 2, wherein the carbon nanostructure is made of a carbon-based conductive material selected from the group consisting of carbon nanotubes, carbon nanofibers, carbon nanohorns, and fullerenes. element.   The chemical substance sensing element according to any one of claims 1 to 3, wherein the cationic functional group is an ammonium group. The chemical substance sensing element according to any one of claims 1 to 4,
A chemical substance sensing device, comprising: a detecting means which is electrically connected to the chemical substance sensing element and detects a change in electrical resistance of the chemical substance sensing element. A first step of producing a cationic functional group-introduced carbon nanostructure, which is a carbon nanostructure having a cationic functional group introduced on the surface;
A second step of preparing a surface modification solution comprising a metal complex containing a complex ion that selectively reacts with a specific substance in the atmosphere, and a first solvent;
A third step of irradiating the surface modification solution with ultrasonic waves after introducing the cationic functional group-introduced carbon nanostructure;
A method for producing a surface-modified carbon nanostructure, characterized by producing a surface-modified carbon nanostructure that is a carbon nanostructure that has been surface-modified with the complex ions by the first step to the third step. . The first step includes
Preparing a cationic functional group introduction solution comprising an aromatic molecule having a cationic functional group and a second solvent;
The method for producing a surface-modified carbon nanostructure according to claim 6, further comprising: irradiating an ultrasonic wave after introducing the carbon nanostructure into the cationic functional group introduction solution.   The said 1st step produces the said cationic functional group introduction | transduction carbon nanostructure by introduce | transducing the said cationic functional group into the said carbon nanostructure by a covalent bond. A method for producing a surface-modified carbon nanostructure. A method for producing a chemical substance sensing element, comprising the step of producing a sheet-like substrate comprising a surface-modified carbon nanostructure produced by the method according to any one of claims 6 to 8. .

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