JP2000081426A - Method and element for detecting nitrogen dioxide gas and nitrogen dioxide gas detecting device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect nitrogen dioxide gas more easily and accurately. SOLUTION: This detecting method includes dipping a porous material 103 in a detecting agent solution 101 which is a mixture of a diazotization reagent and a coupling reagent, impregnating the detecting agent solution into the porous material 103, together with an acid, to prepare a detecting element 103a, and detecting nitrogen oxide gas from a change in color that occurs after the detecting element 103a has been exposed to air 104, i.e., the subject of detection, for a predetermined time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitrogen dioxide gas detection method, a nitrogen dioxide gas detection element, and a nitrogen dioxide gas detection device using the same.

[0002]

2. Description of the Related Art At present, there is a problem of the influence on the environment by SO ₂ and NO _x . SO ₂ and NO _x are generated by the combustion of fossil fuels and cause acid rain and photochemical smog. In Japan, environmental standards have been set for these pollutants, for example, in the concentration of nitrogen dioxide (NO ₂ ) in the atmosphere, and the monitoring stations constantly perform gas concentration measurements in various places by automatic measurement methods. As an environmental standard, the average value per day per hour is approximately 60 ppb or less.

[0003] These gas concentration measuring instruments can measure a very small amount of gas of several ppb, but are expensive and require maintenance. In addition, in the case of automatic measurement, enormous costs such as power are required, and there are many restrictions such as the necessity of securing a power supply and an installation place. However, in order to accurately conduct gas concentration distribution surveys and global environmental impact assessments, it is necessary to monitor the environment nationwide by increasing the number of observation points. For this purpose, a cumulative use of a gas sensor or a simple measurement method (or a monitoring device) that is inexpensive, small, and easy to use can be considered.

At present, semiconductor gas sensors, solid electrolyte gas sensors, electrochemical gas sensors, quartz oscillation gas sensors, and the like have been widely developed. However, these have been developed to evaluate the response in a short time, and few have been developed for monitoring which requires data accumulation. Further, the detection sensitivity can not address the concentration (for example, NO _x in about 10 ppb) of the actual environment for is about 1 ppm. In many cases, the effects of other gases cannot be ignored. How to use a detector tube gas meter
It was developed for the purpose of short-time measurement on the spot, and its cumulative use is difficult. Furthermore, there is a problem that the measurer must go to the site and individual differences occur when reading colors. In many cases, interference or interference of another gas becomes a problem.

[0005] Air is taken in by the pump as a simple measurement, direct collection (direct collection method) of NO _x gas in the sampling bag, collecting a solid adsorbent (solid collected method)
Alternatively, a method of collecting the liquid in an absorbing solution (liquid collecting method) and analyzing the collected gas by gas chromatography is general. However, both methods require transport of not only samples but also peripheral devices such as pumps. For the direct collection method, the size of the sampling bag is limited,
Difficult to accumulate. The solid collecting method and the liquid collecting method have a problem that a process for detecting the collected gas is required.

As a simple monitoring method that does not require suction or the like, use of a passive (passive) sampler for environmental measurement has attracted attention. The passive samplers for NO _x, there is a nitration plate method and triethanolamine (TEA) badge method. We are examining the effects of wind speed, temperature, and humidity, and are examining the quantitativeness. On the other hand, for measurement after sampling, a method of washing a sample to form a solution and analyzing the solution by ion chromatography and absorption spectroscopy was generally used. However, there is a problem in that these samplers require time and labor such as washing before collection and analysis.

As a method of solving the above problems, nitrogen dioxide gas is reacted with a detecting agent adsorbed in the pores of a porous material, which is a transparent matrix adsorbent, and then transmitted by a spectrophotometer. There has been proposed a nitrogen dioxide gas detection method characterized by measuring an absorption spectrum and detecting the amount of nitrogen dioxide gas. However, in this detection method, since a highly reactive detection agent was used, a side reaction occurred, and the sensitivity of the reaction product with the target nitrogen dioxide gas in the visible UV absorption spectrum did not increase, and There is a problem that a side reaction product interferes with the visible UV absorption spectrum and sufficient accuracy cannot be obtained.

[0008]

SUMMARY OF THE INVENTION To summarize the above, conventionally, to detect nitrogen dioxide gas with high accuracy on the order of ppb in accordance with the environmental standard value, an expensive and large-scale apparatus configuration is required. There is a problem that it takes time and effort to easily detect nitrogen dioxide gas.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to make it possible to detect nitrogen dioxide gas more simply and accurately.

[0010]

According to the method for detecting nitrogen dioxide gas of the present invention, first, a diazotizing reagent which reacts with nitrite ions to form a diazo compound and an azo dye is formed by coupling with a diazo compound. A sensing element in which a mixture of a coupling reagent and an acid is arranged in the pores of a transparent porous body is prepared. Next, the first transmittance is determined by measuring the light transmittance of the sensing element. Next, the sensing element is exposed to the gas to be measured for a predetermined time. Next, after that, the light transmittance of the sensing element is measured to determine the second transmittance. Then, the nitrogen dioxide gas in the gas to be measured is detected based on the difference between the first transmittance and the second transmittance. As a result of this configuration, when the sensing element is exposed to an atmosphere in which nitrogen dioxide gas is present, nitrous acid ions and a diazotizing reagent by the nitrogen dioxide gas adsorbed in the pores of the sensing element are diazotized to generate a diazo compound, The diazo compound and the coupling reagent couple to form an azo dye.
Accordingly, the sensing element is colored and a difference is generated between the first transmittance and the second transmittance, whereby nitrogen dioxide gas can be detected.

Further, the nitrogen dioxide gas sensing element of the present invention comprises a transparent porous body, a diazotizing reagent which is disposed in the pores of the porous body and reacts with nitrite ions to form a diazo compound, A coupling reagent that is arranged in the pores of the body together with the diazotizing reagent and couples with the diazo compound to generate an azo dye, and an acid arranged in the pores of the porous body together with the diazotizing reagent. . As a result of this configuration, when nitrogen dioxide gas enters the pores of the nitrogen dioxide gas sensing element and adsorbs nitrogen dioxide, the resulting nitrite ions react with the diazotizing reagent to form diazo compounds. However, this is coupled with the coupling reagent to form an azo dye, so that the nitrogen dioxide gas sensing element is colored.

Further, according to the nitrogen dioxide gas detecting device of the present invention, a light emitting portion for emitting light, a light receiving surface is disposed opposite to a light emitting surface of the light emitting portion, and the light receiving portion responds to the amount of light received by the light receiving surface. A light detection unit that outputs the electric signal, a detection element disposed between the light emitting unit and the light detection unit, and at least an electric meter that measures a state of the electric signal output by the light detection unit,
The sensing element is disposed together with a transparent porous body, a diazotizing reagent that is arranged in the pores of the porous body and reacts with nitrite ions to generate a diazo compound, and a diazotizing reagent in the pores of the porous body. The coupling agent was formed from a coupling reagent that forms an azo dye by coupling with a diazo compound, and an acid disposed together with the diazotization reagent in the pores of the porous body.
As a result of this configuration, when nitrogen dioxide gas infiltrates into the pores of the sensing element and adsorbs nitrogen dioxide, the resulting nitrite ions react with the diazotizing reagent to form a diazo compound. Since the coupling reagent couples to generate an azo dye, the detection element is colored. On the other hand, since the light emitted from the light emitting unit enters the light detecting unit via the detecting element, a change in the color of the detecting element is measured by an electric meter as a change in the electric signal output from the light detecting unit. .

[0013]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment First, a method for detecting nitrogen dioxide (NO ₂ ) gas according to a first embodiment of the present invention will be described. First,
The method of manufacturing the sensing element for nitrogen dioxide gas will be described. As shown in FIG. 1A, as a diazotizing reagent, sulfanilic acid (S), which is an aromatic amine, is used.
A) Detector solution 101 obtained by dissolving A) and N, N-dimethylnaphthylamine (DMNA) as a coupling reagent in a mixture of water and ethanol.
Is made in the container 102. Here, the concentration of sulfanilic acid was 0.02 mol / l.

Next, as shown in FIG. 1B, a porous body 103, which is a porous glass having an average pore diameter of 4 nm, was immersed in the detection agent solution 101. As the porous body 103, Vycor 7930 manufactured by Corning Incorporated was used. Vycor 7930 has an average pore size of 4 nm. In addition, the porous body 10
3 is a chip size of 8 (mm) × 8 (mm) and a thickness of 1 (mm). Vycor 7930 is a borosilicate glass, which separates an alkali component from other components centering on silicon by heating, and by performing an acid treatment in this state, elutes the alkali component to form a porous body. It was done. As described above, since the acid treatment is performed in the manufacturing process, the inside of the pores of Vycor 7930 is in an acidic environment. That is, the state is such that the acid is previously present.

If the inside of the pores of the porous body is not in an acidic state, the inside of the pores may be brought into an acidic environment by using an acid environment or the like by performing acid washing in advance. At this time, the porous body only needs to have a pH of 1, for example. Note that a porous body made of an organic polymer may be used as the transparent porous body. The porous body 103 shown above is immersed in the detection agent solution 101 for 2 hours,
After impregnating the pores of No. 03 with the detecting agent solution, they are air-dried, and then left in a nitrogen gas stream for half a day to be dried, as shown in FIG. . Here, the detection element is formed in a plate shape, but is not limited thereto, and may be formed in a fiber shape.

Next, a method for detecting nitrogen dioxide gas using the sensing element 103a will be described.
As shown in (d), the absorbance of the sensing element 103a in the thickness direction is measured. In FIG. 1D, I ₀
Is the incident signal light intensity, and I is the transmitted light intensity. Next, FIG.
As shown in (e), for example, the sensing element 103a is exposed to the detection target air 104 in which nitrogen dioxide having a concentration of 300 ppb is present for about 3 hours. Then, the sensing element 103a is taken out of the air 104 to be detected, and the absorbance in the thickness direction of the sensing element 103a is measured again as shown in FIG.

The measurement of absorbance twice (absorption spectroscopy)
The results are shown in FIG. For the transmitted light measurement wavelength of 350 nm or less,
Porous glass (Vycor 793) constituting the sensing element
0) Not measured due to its own absorption. In FIG. 2, the measurement result of the absorbance before exposure to the air to be detected is indicated by a broken line, and the measurement result of the absorbance after exposure is indicated by a solid line. First, in both the solid line and the dashed line, absorptions considered to be water absorptions exist at wavelengths around 1350 nm and 1900 nm. This absorption changed depending on the humidity of the air to be detected and the standing time of the sensing element. Therefore, in the method for detecting nitrogen dioxide gas using the detection element according to the first embodiment, the effective measurement wavelength range is determined to be 350 to 1000 nm.

The wavelength of 400 to 600 nm, especially 5
At around 30 nm, a large change is observed between the solid line and the broken line. That is, in the measurement of the absorbance after exposure to the air to be detected, absorption at a wavelength of 530 nm appears. Therefore, by exposing to the air to be detected, a new substance having a light absorption of a wavelength of 530 nm is generated in the sensing element. This product can be assumed to be an azo dye formed by coupling N, N-dimethylnaphthylamine to a diazo compound formed by the reaction of sulfanilic acid and nitrite ions. Nitrogen dioxide turns into nitrite ions when dissolved in water. In addition, since only one absorption peak newly appeared, it can be confirmed that other side reactions did not occur.

As described above, the porous sensing element is a transparent matrix adsorbent having a plurality of pores 301 having an average pore diameter of, for example, 20 nm or less, as shown in FIG. Then, this sensing element (porous body) 302
In the hole 301, a diazotizing reagent and a coupling reagent are arranged together with an acid. Then, when such a porous body is exposed to the air, the moisture in the air is actually adsorbed in the pores to form a thin water film. As a result, a thin film 303 of an aqueous solution (detection agent solution) in which a diazotizing reagent, a coupling reagent and an acid are dissolved is formed on the inner wall of the hole 301 of the porous sensing element 302. I have.
Then, the nitrogen dioxide molecule 3
04 encounters them and causes the following two reactions.

First, as shown in FIG. 3B, nitrite ions 311 generated by dissolving nitrogen dioxide in water are used.
Reacts with a sulfanilic acid 312, which is a diazotizing reagent, to form a diazo compound 313. Then, the diazo compound 313 and N, N-dimethylnaphthylamine 314 as a coupling reagent are coupled to generate an azo compound (coupling compound) 315. Here, the azo compound (azo dye) generally contains 2
It has light absorption in any wavelength range from 00 to 2000 nm. For example, it is known that the azo compound 315 shown in FIG. 3C has an absorption wavelength around 500 to 550 nm. This is consistent with the results shown in FIG.

Therefore, for example, the azo compound can be detected (quantified) by measuring its absorption spectrum with a spectrophotometer (absorptiometer). Note that diazotization is a reaction in which an aromatic primary amine (ArNH ₂ ) reacts with a nitrite ion (NO ₂ ⁻ ) in the presence of two or more equivalents of an acid to form a diazo compound (ArN ₂ ⁺ ). is there. Therefore, the above-described reaction does not occur basically except for nitrogen dioxide gas. Here, this reaction is performed by ArNH ₂ + NO ₂
^- + 2H ⁺ → ArN ₂ ⁺ + 2H ₂₀
Theoretically requires 2 equivalents of acid. That is, as described above, it is necessary to dispose (support) the diazotizing reagent and the coupling reagent together with the required amount of acid in the pores of the porous body. Although the above-described reaction can occur even in the gas phase, as described above, since a state without moisture cannot exist in an actual environment, a thin film of water is substantially formed in the pores of the sensing element. And the above-mentioned reaction will take place in the aqueous solution.

As described above, the azo compound formed as a result of the adsorption of the nitrogen dioxide gas is measured by light absorption, whereby the nitrogen dioxide gas can be measured indirectly. Here, for example, if the porous body is made of a material that transmits light in the light absorption wavelength range of the azo compound, by measuring the light absorption characteristics of the porous body that has adsorbed nitrogen dioxide gas, the adsorbed nitrogen dioxide can be measured. The gas can be detected.

In the first embodiment, as described above,
This is a result of exposing the sensing element to air having a nitrogen dioxide concentration of 300 ppb for 3 hours. As a result of the measurement of the absorbance, as shown in FIG. 2, the change in the absorbance at a wavelength of 530 nm is as high as about 0.1, and a high sensitivity sub-pp
An m-level nitrogen dioxide gas can be detected. The measurement is performed in a holder for measuring a thin film of an absorptiometer according to the first embodiment.
It was easy to perform simply by putting in the sensing element. Then, if the relationship between the difference in the absorbance and the concentration is obtained, the ppb level can be quantified. The change in absorbance at the maximum absorption wavelength per exposure amount (concentration (ppb) × exposure time (hour)) was determined as a sensitivity index. In the case of the first embodiment (FIG. 2), the change in absorbance when exposed to 300 ppb of nitrogen dioxide gas for 3 hours is 0.1, and the sensitivity index is 1.1 × 10 ⁻⁴ ppb ⁻¹ · hr. ^{It was -1} and very high sensitivity was obtained.

As the diazotizing reagent, for example,
A compound having an aromatic amino such as benzene, naphthalene or biphenyl or a heteroaromatic such as thiophene or thiazole and having a primary amino group or an acetamido group may be used. The coupling reagent may be an aromatic group such as benzene, naphthalene or biphenyl or a heteroaromatic group such as thiophene or thiazole.
A compound having a tertiary), an alkoxyoxy group, or a hydroxyl group may be used.

As a method for introducing the diazotizing reagent and the coupling reagent into the pores of the porous body, as described above, other than the method of impregnating the two as a solution into the porous body, introducing the solution into the pores and drying the porous body. In addition, there is a method in which both are vapor-deposited and introduced into a hole, and a method in which both are melted and introduced into a hole. In these cases, an acidic environment may be established by introducing an acid into the pores of the porous body in advance. In addition, there is a method in which both are used alone or mixed with another compound, and these are introduced into pores when a porous body is produced by a sol-gel method. As described above, according to the first embodiment, since the sensing element having the diazotizing reagent and the coupling reagent in the pores of the porous body is used, the adsorption area of the nitrogen dioxide gas to be detected is increased. However, the sensitivity and the storage capacity can be increased as compared with the conventional method.

Further, the porous body constituting the sensing element is
Since it has a high transmittance in a wavelength region of about 400 to 1000 nm, by measuring the transmittance of the sensing element, the change in absorbance due to the azo dye generated by adsorption of nitrogen dioxide to the sensing element is measured. Can be measured. That is, according to the first embodiment, if the absorbance of the sensing element is measured before and after the sensing element is exposed to the air to be detected, the nitrogen dioxide gas adsorbed on the sensing element can be detected. Nitrogen dioxide gas can be easily detected. Then, in the measurement of the absorbance, a change in a single peak may be observed, so that the measurement is easy. According to the sensing element in the first embodiment, as shown in FIG. 4, when the concentration of nitrogen dioxide gas in the air to be measured increases,
The light transmittance of the detection element at a predetermined wavelength decreases. The predetermined wavelength is approximately 530n here.
m.

As described above, according to the first embodiment, a small sensing element is used, and the nitrogen dioxide gas can be detected by this optical change, so that the nitrogen dioxide gas can be detected very simply and accurately. It has the effect of being able to detect. Here, when the porous body constituting the sensing element is made of glass (borosilicate glass), the average pore diameter is 20 n.
m or less, the visible UV wavelength region (wavelength 200 to
In the measurement of the transmission spectrum at 2000 nm), light was transmitted in the visible light region (350 to 800 nm). However, when the average pore size became larger, a sharp decrease in transmittance was observed in the visible region.

FIG. 5 shows the above results. In FIG. 5, the dotted line shows the transmittance of quartz glass, the one-dot chain line shows the transmittance of a porous body made of borosilicate glass having a pore diameter of 2.5 nm, and the solid line shows the transmittance of Vycor 7930 used in the first embodiment described above. The dashed line indicates a pore diameter of 20 n made of borosilicate glass.
m shows the transmittance of the porous body. The samples indicated by the one-dot chain line and the broken line are manufactured by Geltech (GELTECH).
It is made of. In all cases, the thickness in the transmittance measurement direction was 1 mm. Therefore, it is preferable that the above-mentioned porous body has an average pore diameter of 20 nm or less. Also, 350-80
A porous body transparent in the visible light region of 0 nm is used. By the way, in Embodiment 1 described above, the specific surface area of the porous body is 100 m ² or more per gram.

Embodiment 2 Next, a second embodiment of the present invention will be described.
First, a method for manufacturing the nitrogen dioxide gas sensing element according to the second embodiment will be described. Sulfanilamide (SFA) as a diazotizing reagent, N, N-dimethylnaphthylamine (DMNA) as a coupling reagent, and ethanol A detection agent solution dissolved in the mixture is prepared. Here, the concentration of sulfanilamide is 0.02 mol
1 / l, and the concentration of N, N-dimethylnaphthylamine was 0.005 mol / l.

Next, an average pore diameter of 4 nm was added to the detection agent solution.
Was immersed. As the porous body, Vycor 7930 manufactured by Corning Incorporated was used as in the first embodiment. Vycor 7930 has an average pore size of 4 nm. The porous body is 8 (mm) × 8 (mm) and has a thickness of 1 mm.
(Mm). Then, the porous body is immersed in the detecting agent solution for 2 hours, impregnated with the detecting agent solution in the pores of the porous body, air-dried, and left to dry in a nitrogen gas stream for half a day. Thus, the second embodiment
Was prepared.

FIG. 6 shows absorption spectra before and after the sensing element according to the second embodiment is exposed to the air to be measured. The broken line indicates the state before the exposure. The solid line indicates the result after exposing the sensing element of the second embodiment to air in which nitrogen dioxide gas having a concentration of 300 ppb exists for 3 hours. As is clear from FIG. 6, the solid line shows only one new absorption peak near the wavelength of 530 nm. The absorption around 530 nm is due to the diazo compound in which sulfanilamide is diazotized and N,
It is thought to be due to the azo dye formed as a result of coupling of N-dimethylnaphthylamine. The change in the absorbance was as high as about 0.1, and it was found that high-sensitivity detection of ppb-level nitrogen dioxide gas was possible even with the detection of nitrogen dioxide gas using the sensing element of the second embodiment. . Similarly to the first embodiment, the sensitivity index of this second embodiment (FIG. 6) is 1.3 × 10 ⁻⁴ pp.
b ⁻¹ · hr ⁻¹ , indicating that a very high sensitivity was obtained.

Third Embodiment Next, a third embodiment of the present invention will be described.
First, a method for manufacturing a nitrogen dioxide gas sensing element according to the third embodiment will be described. Acetanilide (AA) is used as a diazotizing reagent, and N, N-dimethylnaphthylamine (DMNA) is used as a coupling reagent. A detection agent solution dissolved in the liquid is prepared. Here, the concentration of acetanilide (AA) is 0.02 mol.
/ L, and the concentration of N, N-dimethylnaphthylamine was 0.005 mol / l. Next, a porous body having an average pore diameter of 4 nm was immersed in the detection agent solution. For this porous body, Corning Vycor 7930 was used as in the first and second embodiments. This Vycor 79
30 is an average pore diameter of 4 nm. The porous body has a thickness of 8 (m
m) × 8 (mm) and a chip size of 1 (mm) in thickness.

Then, the porous body is immersed in the detecting agent solution for 2 hours, impregnated with the detecting agent solution in the pores of the porous body, air-dried, and left in a nitrogen gas stream for half a day. By drying, the sensing element of the third embodiment was manufactured. FIG. 7 shows absorption spectra before and after exposing the sensing element of the third embodiment to the air to be measured. The broken line indicates the state before the exposure. The solid line shows the result after exposing the sensing element of the third embodiment to air in which nitrogen dioxide gas having a concentration of 300 ppb is present for 3 hours. In the third embodiment, as shown in FIG. 7, a new absorption appears near the wavelength of 460 nm in the solid line. Although this absorbance is about 0.03, it is possible to detect ppb level nitrogen dioxide gas with sufficiently high sensitivity. Similarly to the first and second embodiments, the sensitivity index of the third embodiment (FIG. 7) is 3.3 × 10 ⁻⁵ ppb ^−1.
hr ^-1 .

Embodiment 4 Next, a fourth embodiment of the present invention will be described.
First, a method for manufacturing the nitrogen dioxide gas sensing element according to the fourth embodiment will be described. First, 0.0428 g of N, N as a coupling reagent was placed in an Erlenmeyer flask.
Taking dimethyl-1-naphthylamine (DMNA);
100 ml of ethanol was added to this to dissolve, and about 0.
A 0025 mol / l solution was prepared. In another Erlenmeyer flask, 0.6888 g of a diazotizing reagent was added.
Was dissolved in 100 ml of ethanol to prepare a solution of about 0.04 mol / l.

Next, each of these solutions was added in an amount of 10 ml.
Then, they were mixed to prepare a detection agent solution. The detection agent solution was transferred to a Petri dish, and a porous body having an average pore diameter of 4 nm was immersed therein for about 2 hours, and the porous body was impregnated with the detection agent solution. As this porous body, similarly to Embodiments 1 to 3 described above, Vycor 7930 manufactured by Corning Incorporated was used. Vycor 7930 has an average pore size of 4 nm.
The porous body is 8 (mm) × 8 (mm) and has a thickness of 1 (m).
m). Next, the porous body impregnated with the detection agent solution was taken out of the petri dish and air-dried for 24 hours to evaporate the solvent, thereby obtaining a detection element. The detection element thus produced was colorless and transparent visually.

This sensing element is provided with a nitrogen dioxide concentration of 200 p.
When exposed to a pb dry nitrogen atmosphere, the color changed from colorless and transparent to pink under visual observation. As a result of measuring this change with an absorptiometer, a change was observed as shown in FIG. In FIG. 8, the measurement results of the sensing element that appeared colorless and transparent at the beginning are shown by broken lines, and the measurement results of the sensing element that changed to pink are shown by solid lines. This change was irreversible. Further, the concentration of nitrogen dioxide is set to 100 ppb to 100 pb.
When changed in the range of pm, almost the same spectral change was observed except for the intensity of light absorption.

Next, when the sensing element was exposed to the atmosphere (air) having a nitrogen dioxide concentration of 10 ppb, a change in the absorbance as shown in FIG. 9 was observed. In FIG. 9, the measurement results of the initially colorless and transparent sensing element are indicated by broken lines.
The measurement results after exposure to the sample air are shown by solid lines. And this change was also irreversible. As shown above,
Even if the sensing element according to the fourth embodiment is used, nitrogen dioxide gas can be detected, and nitrogen dioxide gas in the atmosphere can be detected.

Embodiment 5 Hereinafter, a fifth embodiment of the present invention will be described.
Here, a detection device for nitrogen dioxide gas using the above-described detection element will be described. As shown in FIG. 10, this nitrogen dioxide gas detection device irradiates, for example, light emitted from a light emitting unit 1001 composed of an LED emitting light of a predetermined wavelength to a detection element 1002, and transmits the transmitted light to a light receiving unit. 1
At 003, light is received. The light receiving unit 1003 photoelectrically converts the received light and outputs a signal current. In addition, the conversion amplification unit 1
In 004, the output signal current is amplified and the current-
Perform voltage conversion. The A / D converter 1005 converts the voltage signal into a digital signal. Then, the digital signal is output from the output detection unit 1006 as a detection result.

Here, the sensing element 1002 is, for example, the sensing element of the above-described first to fourth embodiments. For the light emitting unit 1001, a green LED having an emission wavelength of 530 nm may be used, for example. Also, the light receiving unit 1003
Is, for example, a photodiode. As the photodiode, for example, one having sensitivity to a wavelength of 190 to 1000 nm may be used. Also, the light emitting unit 100
1 and the light receiving unit 1003 are arranged such that the light emitting portion and the light receiving portion face each other. Then, for example, with this detection device using the detection element of the fourth embodiment, the nitrogen dioxide concentration is 100 p.
When nitrogen dioxide gas was detected in a dry nitrogen atmosphere and air (air) of pb to 100 ppm, an output different from that in the initial state where the sensing element was not exposed to nitrogen dioxide was obtained. Thus, according to the fifth embodiment, the nitrogen dioxide gas detection device can be simply configured.

Embodiment 6 Hereinafter, a sixth embodiment of the present invention will be described.
Hereinafter, the above-described nitrogen dioxide gas detection device will be described in more detail. In particular, the configuration of the light emitting unit and the light receiving unit will be described. In the sixth embodiment, as shown in FIG. 11, a substrate 1101 of about 12 cm × 6 cm
An LED 1102 that emits green light having a wavelength of 550 nm;
The phototransistor 1103 is arranged so that the light receiving surface is arranged to face the light emitting surface of the LED 1102.
This phototransistor has photosensitivity in a wavelength range of 450 to 1100 nm. And these LEDs 11
02 and the phototransistor 1103, the terminal plate 110
Two AA batteries 110 connected in series via 4
5 is supplied with power.

The power is supplied to the switch 11.
06 so that it can be turned on and off. That is, the circuit is assembled using the terminals of the terminal plate 1104. The terminal number 1 is the wiring of the phototransistor 1103, the terminal number 2 is the wiring of the switch 1106, the terminal number 3 is the wiring of the LED 1102, and the terminal number 4 is the switch 1
The wiring between the battery 106 and the battery 1105 is connected to the terminal number 5 by the battery 11.
05, the LED 1102, and the wiring of the phototransistor 1103 are connected. The resistors 1107 and 1108 are provided so that the output voltage from the phototransistor 1103 is on the order of one digit (V).

Then, the detecting element 1110 as described in the first to third embodiments is arranged between the LED 1102 and the phototransistor 1103, and the voltmeter is provided between the terminal numbers 1 and 2 of the terminal plate 1104. By connecting to and measuring the voltage, this nitrogen dioxide gas detection device
The nitrogen dioxide gas adsorbed on the sensing element 1110 is measured. Thus, according to the sixth embodiment, 12 cm
A highly accurate nitrogen dioxide gas detection device can be constructed in an area of about 6 cm. Further, since a commercially available battery can be configured as a power source, nitrogen dioxide gas can be detected more easily.

[0043]

As described above, in the method for detecting nitrogen dioxide gas of the present invention, first, a diazotizing reagent which reacts with nitrite ions to form a diazo compound and a azo dye by coupling with a diazo compound are used. A sensing element is prepared in which a mixture of a coupling reagent and an acid to be generated is arranged in the pores of a transparent porous body. Next, the first transmittance is determined by measuring the light transmittance of the sensing element. Next, the sensing element is exposed to the gas to be measured for a predetermined time. Next, after that, the light transmittance of the sensing element is measured to determine the second transmittance. Then, the nitrogen dioxide gas in the gas to be measured is detected based on the difference between the first transmittance and the second transmittance. As a result of this configuration, when the sensing element is exposed to an atmosphere in which a nitrogen dioxide gas is present, nitrous acid ions and a diazotizing reagent by the nitrogen dioxide gas adsorbed in the pores of the sensing element are diazotized to generate a diazo compound, The diazo compound and the coupling reagent couple to form an azo dye. Accordingly, the sensing element is colored and a difference is generated between the first transmittance and the second transmittance, whereby nitrogen dioxide gas can be detected. Therefore, after exposing the sensing element to the atmosphere to be measured, the change in the color of the sensing element can be observed, so that the nitrogen dioxide gas can be detected more easily and accurately than in the conventional method.

Further, the nitrogen dioxide gas sensing element of the present invention comprises a transparent porous body, a diazotizing reagent which is disposed in the pores of the porous body and reacts with nitrite ions to produce a diazo compound, A coupling reagent is provided in the pores of the body together with the diazotizing reagent and couples with the diazo compound to form an azo dye, and an acid is disposed in the pores of the porous body together with the diazotizing reagent. As a result of this configuration, when nitrogen dioxide gas enters the pores of the nitrogen dioxide gas sensing element and adsorbs nitrogen dioxide, the resulting nitrite ions react with the diazotizing reagent to form diazo compounds. However, this is coupled with the coupling reagent to form an azo dye, so that the nitrogen dioxide gas sensing element is colored. Therefore, since the nitrogen dioxide gas detection element can detect the nitrogen dioxide gas by observing the change in color, the use of the nitrogen dioxide gas detection element makes it easier and more accurate than the conventional method. Nitrogen gas can be detected.

Further, the nitrogen dioxide gas detecting device of the present invention has a light emitting portion for emitting light, and a light receiving surface which is disposed opposite to a light emitting surface of the light emitting portion and which responds to the amount of light received by the light receiving surface. A light detection unit that outputs the electric signal, a detection element disposed between the light emitting unit and the light detection unit, and at least an electric meter that measures a state of the electric signal output by the light detection unit,
The sensing element is disposed together with a transparent porous body, a diazotizing reagent that is arranged in the pores of the porous body and reacts with nitrite ions to generate a diazo compound, and a diazotizing reagent in the pores of the porous body. The coupling reagent was formed from a coupling reagent that couples with a diazo compound to form an azo dye, and an acid disposed in the pores of the porous body together with the diazotization reagent. As a result of this configuration, when nitrogen dioxide gas infiltrates into the pores of the sensing element and adsorbs nitrogen dioxide, the resulting nitrite ions react with the diazotizing reagent to form a diazo compound. Since the coupling reagent couples to generate an azo dye, the detection element is colored. On the other hand, since the light emitted from the light emitting unit enters the light detecting unit via the detecting element, a change in the color of the detecting element is measured by an electric meter as a change in the electric signal output from the light detecting unit. . Therefore, the nitrogen dioxide gas can be detected with high accuracy by arranging the nitrogen dioxide gas detection device in the atmosphere to be measured, so that the nitrogen dioxide gas can be detected more simply and accurately than the conventional method. Become like

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a method for detecting nitrogen dioxide (NO ₂ ) gas according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing two measurement results of absorbance in the detection method of Example 1.

FIGS. 3A and 3B are an explanatory diagram showing a configuration of a sensing element of Example 1 and an explanatory diagram showing a reaction occurring therein.

FIG. 4 is a correlation diagram showing the relationship between the concentration of nitrogen dioxide and the transmittance in the sensing element of Example 1.

FIG. 5 is a correlation diagram showing a relationship between a porous body made of glass and optical transmittance.

FIG. 6 is a characteristic diagram showing a detection result according to the second embodiment of the present invention.

FIG. 7 is a characteristic diagram showing a detection result according to the third embodiment of the present invention.

FIG. 8 is a characteristic diagram showing a detection result in the fourth embodiment of the present invention.

FIG. 9 is a characteristic diagram showing another detection result according to the fourth embodiment of the present invention.

FIG. 10 is a configuration diagram showing a schematic configuration of a nitrogen dioxide gas detection device according to a fifth embodiment of the present invention.

FIG. 11 is a configuration diagram showing a schematic configuration of a nitrogen dioxide gas detection device according to a sixth embodiment of the present invention.

[Explanation of symbols]

101: detecting agent solution, 102: container, 103: porous body,
103a: sensing element, 104: air to be detected, 301
... holes, 302 ... sensing element (porous body), 303 ... thin film of aqueous solution (detection agent solution), 304 ... nitrogen dioxide molecules.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shiro Matsumoto 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Yoko Maruo 3-9-1, Nishishinjuku, Shinjuku-ku, Tokyo No. Within Nippon Telegraph and Telephone Corporation (72) Takashi Oyama Inventor Takashi Oyama 3-19-2, Nishishinjuku, Shinjuku-ku, Tokyo F-term within Nippon Telegraph and Telephone Corporation (reference) 2G042 AA01 BA05 BB07 CA01 CB01 DA08 EA01 FA01 FA11 FB02 GA05 2G054 AA01 AB07 CA06 CB10 CD04 CE02 EA04 EA06 EB01 EB04 EB05 FA06 FA12 FA13 FA32 FA33 FB02 FB03 GA02 GA03 GB01 JA07 JA09

Claims (10)

[Claims] 1. A mixture of a diazotizing reagent which reacts with nitrite ions to form a diazo compound, a coupling reagent which couples with the diazo compound to form an azo dye, and an acid, is filled in a pore of a transparent porous body. A first step of preparing a sensing element disposed at a position; a second step of measuring a light transmittance of the sensing element to obtain a first transmittance; and placing the sensing element in a gas to be measured for a predetermined time. A third step of exposing; a fourth step of measuring the light transmittance of the sensing element to obtain a second transmittance after the third step; and the first transmittance and the second transmittance. A method for detecting nitrogen dioxide gas, comprising detecting nitrogen dioxide gas in the gas to be measured based on a difference in rate. 2. The method for detecting nitrogen dioxide gas according to claim 1, wherein the average pore diameter of the porous body is larger than the diazotizing reagent and the coupling reagent can be contained, and 2
A method for detecting nitrogen dioxide gas, wherein the thickness is 0 nm or less. 3. The method for detecting nitrogen dioxide gas according to claim 1, wherein the diazotizing reagent is an aromatic compound such as benzene, naphthalene or biphenyl, or a heteroaromatic compound such as thiophene or thiazole. Wherein the coupling reagent is an aromatic compound such as benzene, naphthalene or biphenyl, or a heteroaromatic compound such as thiophene or thiazole. A method for detecting nitrogen dioxide gas, which is a compound having a tertiary amino group, an alkoxy group, or a hydroxyl group. 4. A transparent porous body, a diazotizing reagent which is arranged in the pores of the porous body and reacts with nitrite ions to generate a diazo compound, and a diazotizing reagent in the pores of the porous body together with the diazotizing reagent. A coupling reagent which is disposed and couples with the diazo compound to generate an azo dye, and an acid disposed together with the diazotizing reagent in the pores of the porous body. Sensing element. 5. The sensing element for nitrogen dioxide gas according to claim 4, wherein the average pore size of the porous body is larger than the diazotizing reagent and the coupling reagent can enter, and in addition, 2
A nitrogen dioxide gas detection element having a thickness of 0 nm or less. 6. The element for detecting nitrogen dioxide gas according to claim 4, wherein the diazotizing reagent is an aromatic compound such as benzene, naphthalene or biphenyl, or a heteroaromatic compound such as thiophene or thiazole. Wherein the coupling reagent is an aromatic compound such as benzene, naphthalene or biphenyl, or a heteroaromatic compound such as thiophene or thiazole. An element for detecting nitrogen dioxide gas, which is a compound having a tertiary amino group, an alkoxyoxy group, or a hydroxyl group. 7. A light emitting unit that emits light, a light detecting unit that is arranged with a light receiving surface facing a light emitting surface of the light emitting unit, and outputs an electric signal corresponding to the amount of light received by the light receiving surface; A sensing element disposed between the light emitting unit and the light detecting unit, and at least an electric meter that measures a state of an electric signal output by the light detecting unit, wherein the sensing element is a transparent porous body, A diazotizing reagent that is disposed in the pores of the porous body and reacts with nitrite ions to generate a diazo compound, and that is disposed together with the diazotizing reagent in the pores of the porous body and couples with the diazo compound. An apparatus for detecting nitrogen dioxide gas, comprising: a coupling reagent for generating an azo dye; and an acid disposed in the pores of the porous body together with the diazotizing reagent. 8. The apparatus for detecting nitrogen dioxide gas according to claim 7, wherein the average pore diameter of the porous body is larger than the diazotizing reagent and the coupling reagent can enter, and in addition, 2
An apparatus for detecting nitrogen dioxide gas, which has a diameter of 0 nm or less. 9. The apparatus for detecting nitrogen dioxide gas according to claim 7, wherein the diazotizing reagent is an aromatic compound such as benzene, naphthalene or biphenyl, or a heteroaromatic compound such as thiophene or thiazole. Wherein the coupling reagent is an aromatic compound such as benzene, naphthalene or biphenyl, or a heteroaromatic compound such as thiophene or thiazole. An apparatus for detecting nitrogen dioxide gas, which is a compound having a tertiary amino group, an alkoxy group, or a hydroxyl group. 10. The apparatus for detecting nitrogen dioxide gas according to claim 7, wherein the light emitting unit is configured by a light emitting diode, the light detection unit is configured by a phototransistor, and the light emission is further performed. A battery for supplying power to the diode and the phototransistor; a switch for turning on and off the supply of power from the battery to the light-emitting diode and the phototransistor; a voltage as an electric meter connected between the phototransistor and the battery A terminal plate having terminals for connecting the light emitting diode, the phototransistor, the battery, the switch, and the voltmeter respectively; and the light emitting diode, the phototransistor, the battery, the switch, A voltmeter, and a substrate on which the terminal plate is disposed. Detector of nitrogen dioxide gas, characterized in that.