阅读说明：本技术 气体传感器元件及使用其的气体检测装置 (Gas sensor element and gas detection device using same ) 是由 吉田大哲 高桥美枝 福田一人 关良平 于 2021-05-28 设计创作，主要内容包括：气体传感器元件具有层叠结构,所述层叠结构中依次层叠有：支撑基材；第一发光层,其设置于支撑基材上,且包含在第1峰值波长处发光的第1发光粒子；传感器层,其设置于第一发光层上,且吸附气体分子；第二发光层,其设置于传感器层上,且包含在与上述第1峰值波长不同的第2峰值波长处发光的第2发光粒子；以及保护层,其设置于第二发光层上,所述气体传感器元件具有贯通层叠结构的一部分或全部的开孔部。(The gas sensor element has a laminated structure in which: supporting a substrate; a first light emitting layer disposed on the support substrate and including 1 st light emitting particles emitting light at a 1 st peak wavelength; a sensor layer disposed on the first light emitting layer and adsorbing gas molecules; a second light emitting layer provided on the sensor layer and including 2 nd light emitting particles emitting light at a 2 nd peak wavelength different from the 1 st peak wavelength; and a protective layer provided on the second light-emitting layer, wherein the gas sensor element has a hole portion penetrating a part or all of the laminated structure.)

1. A gas sensor element having a laminated structure in which:

supporting a substrate;

a first light emitting layer disposed on the support substrate and comprising 1 st light emitting particles emitting at a 1 st peak wavelength;

a sensor layer disposed on the first light emitting layer and adsorbing gas molecules;

a second light emitting layer disposed on the sensor layer and including 2 nd light emitting particles emitting light at a 2 nd peak wavelength different from the 1 st peak wavelength; and

a protective layer disposed on the second light emitting layer,

the gas sensor element has an opening portion that penetrates a part or all of the laminated structure.

2. The gas sensor element according to claim 1, wherein the opening portion penetrates from the protective layer at least until the sensor layer is exposed.

3. The gas sensor element according to claim 1 or 2, wherein a film thickness of the sensor layer is 1nm or more and 100nm or less.

4. The gas sensor element according to any one of claims 1 to 3, wherein the 2 nd peak wavelength of the light emission of the 2 nd light-emitting particle contained in the second light-emitting layer, which is measured by a method according to JIS K0120, the general rule of fluorometric analysis of Japanese Industrial products, is different from the 1 st peak wavelength of the light emission of the 1 st light-emitting particle contained in the first light-emitting layer by at least 10nm or more.

5. A gas detection device is provided with:

the gas sensor element according to any one of claims 1 to 4;

an excitation energy source that causes the gas sensor element to emit light; and

and a light receiving unit that receives light emitted from the gas sensor element excited by the excitation energy source.

Technical Field

The present invention relates to a gas sensor element for gas detection and a gas detection device using the gas sensor element.

Background

Conventionally, a semiconductor type sensor has been used as a gas sensor capable of detecting various types of gases such as a combustible gas and a toxic gas. The semiconductor sensor is mainly composed of a heater coil, a metal oxide semiconductor element, and an electrode for measuring the resistance of the semiconductor element. In the semiconductor sensor, the gas to be detected and the metal oxide semiconductor element are electrochemically reacted with each other in a state where the metal oxide semiconductor element is heated by the heater coil, whereby the resistance value of the metal oxide semiconductor element is changed, and the gas can be detected. Further, by adding an impurity to the metal oxide semiconductor, it is also possible to impart selectivity based on a gas to a change in resistance value due to the detection target gas.

As a method for detecting a plurality of gases using one semiconductor type sensor, there is a gas detection device as shown in patent document 1. Patent document 1 discloses the following method: the influence on the resistance value of the metal oxide semiconductor is examined for each gas type, and the concentration of each gas is detected from the resistance value of the metal oxide semiconductor by taking this influence into consideration.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 6309062

Disclosure of Invention

In order to solve the above problem, a gas sensor element according to the present invention has a laminated structure in which:

supporting a substrate;

a first light-emitting layer provided on the support substrate and including 1 st light-emitting particles emitting light at a 1 st peak wavelength;

a sensor layer which is provided on the first light-emitting layer and adsorbs gas molecules;

a second light-emitting layer that is provided on the sensor layer and contains 2 nd light-emitting particles that emit light at a 2 nd peak wavelength different from the 1 st peak wavelength; and

a protective layer disposed on the second light emitting layer,

the gas sensor element has an opening portion penetrating a part or all of the laminated structure.

Drawings

Fig. 1 is a schematic structural sectional view showing a sectional structure of a gas sensor element according to embodiment 1.

Fig. 2 is a schematic diagram showing a configuration of a gas detection device using the gas sensor element of embodiment 1.

Fig. 3 is a diagram showing a spectrum of light emission before gas detection in the gas detection method of embodiment 1.

Fig. 4 is a diagram showing a spectrum of light emission after gas detection in the gas detection method of embodiment 1.

FIG. 5 is Table 1 showing conditions and gas concentration indexes in examples and comparative examples.

Description of the reference numerals

1: gas sensor element

1 a: supporting substrate

1 b: a first light-emitting layer

1 c: sensor layer

1 d: second luminescent layer

1 e: protective layer

1 f: opening part

2: gas detection device

2 a: excitation energy source

2 b: light receiving part

2 c: light energy

2 d: luminescence

Detailed Description

In the conventional configuration, the resistance of the metal oxide semiconductor does not change for a gas of 0.1ppm or less, and therefore there is a problem that it is difficult to detect a gas of 0.1ppm or less.

The present invention has been made to solve the above conventional problems, and an object thereof is to provide a gas sensor element and a gas detection device, which can detect a gas concentration of 0.1ppm or less by causing a reaction of the gas sensor element even with a low-concentration gas.

The gas sensor element of claim 1 has a laminated structure in which:

supporting a substrate;

a first light-emitting layer provided on the support substrate and including 1 st light-emitting particles emitting light at a 1 st peak wavelength;

a sensor layer which is provided on the first light-emitting layer and adsorbs gas molecules;

a second light-emitting layer that is provided on the sensor layer and contains 2 nd light-emitting particles that emit light at a 2 nd peak wavelength different from the 1 st peak wavelength; and

a protective layer disposed on the second light emitting layer,

the gas sensor element has an opening portion penetrating a part or all of the laminated structure.

In the gas sensor element according to claim 2, in the above-described aspect 1, the opening portion may penetrate at least from the protective layer until the sensor layer is exposed.

In the gas sensor element according to claim 3, in the above-described 1 st or 2 nd aspect, the sensor layer may have a film thickness of 1nm or more and 100nm or less.

In the gas sensor element according to claim 4, in any one of the above 1 to 3, the 2 nd peak wavelength of the light emission of the 2 nd light-emitting particle contained in the second light-emitting layer, which is measured by a method according to the general rules of fluorescence photometry analysis of japanese industrial standards (JIS K0120), may differ from the 1 st peak wavelength of the light emission of the 1 st light-emitting particle contained in the first light-emitting layer by at least 10 nm.

The gas detection device of claim 5 includes:

the gas sensor element according to any one of the above 1 to 4;

an excitation energy source that causes the gas sensor element to emit light; and

and a light receiving unit that receives light emitted from the gas sensor element excited by the excitation energy source.

As described above, according to the gas sensor element and the gas detection device using the gas sensor element of the present invention, even if the concentration of the gas to be detected is 0.1ppm or less, the emission spectra of the first light-emitting layer and the second light-emitting layer change due to the change in the film thickness of the sensor layer, and the gas concentration of 0.1ppm or less can be detected.

Hereinafter, a gas sensor element and a gas detection device according to an embodiment will be described with reference to the drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

(embodiment mode 1)

< gas sensor element >

Fig. 1 is a schematic cross-sectional view showing a cross-sectional structure of a gas sensor element 1 according to embodiment 1. The gas sensor element 1 of embodiment 1 has a laminated structure in which a first light-emitting layer 1b, a sensor layer 1c, a second light-emitting layer 1d, and a protective layer 1e are laminated on a plate-shaped support substrate 1a in this order from the surface of the support substrate 1 a. The first light-emitting layer 1b contains 1 st light-emitting particles that emit light at a 1 st peak wavelength. The sensor layer 1c adsorbs gas molecules. The second light emitting layer 1d contains 2 nd light emitting particles emitting light at a 2 nd peak wavelength different from the 1 st peak wavelength. Further, the opening portion 1f penetrates from the protective layer 1e at least until the sensor layer 1c is exposed in the in-plane vertical direction Z.

According to this gas sensor element, even if the concentration of the gas to be detected is 0.1ppm or less, the emission spectra of the first light-emitting layer 1b and the second light-emitting layer 1d change due to a change in the film thickness of the sensor layer 1c, and the gas concentration of 0.1ppm or less can be detected.

Hereinafter, the members constituting the gas sensor element 1 will be described.

< supporting base Material >

The support substrate 1a may be any member as long as it can form the first light-emitting layer 1b on the support substrate 1a, and for example, a polymer film such as PET, a glass substrate, or the like may be used.

< first light-emitting layer >

The first light-emitting layer 1b is formed by stacking 1 st light-emitting particles, for example, semiconductor particles, having a property of emitting light at the 1 st peak wavelength by absorbing excitation energy. As the 1 st light-emitting particles, semiconductor nanoparticles having a core of cadmium sulfide, cadmium selenide, cadmium telluride, zinc sulfide, zinc selenide, zinc telluride, copper indium sulfide, silver indium sulfide, indium phosphide or the like, perovskite-type semiconductor nanoparticles such as cesium lead halide, semiconductor nanoparticles having a core of silicon, carbon or the like, or the like are used. Instead of the semiconductor particles, organic pigments such as merocyanine and perylene, which are reported to have forster resonance energy transfer, may be used. The lamination method is not particularly limited, and examples thereof include a Layer by Layer method (hereinafter, also referred to as "LBL method"). Here, the LBL method is a method in which a base material to be formed is alternately immersed in a dilute solution of a cationic compound and an anionic compound to spontaneously adsorb an electrolyte polymer on the base material to form a film, and is easy to control the material at a molecular level and excellent in productivity. Instead of stacking the light-emitting particles, the light-emitting particles may be dispersed in a glass phase and sealed in the first light-emitting layer 1 b.

< sensor layer >

The material of the sensor layer 1c needs to have both film-forming properties for the first light-emitting layer 1b and the second light-emitting layer 1d, and adsorbability for the detection target gas. The method for forming the first light-emitting layer 1b is not particularly limited, and for example, a method capable of controlling a thin film such as an LBL method or a spin coating method can be used. The material of the sensor layer 1c is not particularly limited, but is partially limited by the method used. For example, in the LBL method, polyallylamine and polydiallyldimethylammonium chloride can be used as the cationic polymer, polyacrylic acid, polystyrenesulfonic acid, and polyisoprenesulfonic acid can be used as the anionic polymer, and the ionic polymer, silicone resin, polyvinyl chloride, polyurethane, polyvinyl alcohol, polypropylene, polyacrylamide, polycarbonate, polyethylene terephthalate, and the like can be used without particular limitation as long as they are soluble in the spin coating method.

The high-order structure of the polymer may be controlled by selecting the material of the sensor layer 1c and changing the film formation process conditions of the sensor layer 1c, so that the selectivity of the adsorbed gas may be given to the sensor layer 1 c. The thickness of the sensor layer 1c is, for example, 1nm or more and less than 1 μm, and preferably 100nm or less. When the thickness is less than 1nm, the sensor layer 1c cannot stably adsorb the detection target gas. When the thickness is 1 μm or more, the distance between the first light-emitting layer 1b and the second light-emitting layer 1d is too long, and the light emission spectrum of the gas sensor element does not change due to forster resonance energy transfer (hereinafter, also referred to as "FRET phenomenon") described later before and after adsorption of the gas to be detected. The light described in this specification is not limited to electromagnetic waves in the visible light region.

< second light-emitting layer >

The second light-emitting layer 1d is formed by stacking 2 nd light-emitting particles, for example, semiconductor particles, having a property of emitting light at a 2 nd peak wavelength different from the 1 st peak wavelength by absorbing excitation energy. As the 2 nd light-emitting particles, semiconductor nanoparticles having a core of cadmium sulfide, cadmium selenide, cadmium telluride, zinc sulfide, zinc selenide, zinc telluride, copper indium sulfide, silver indium sulfide, indium phosphide or the like, perovskite-type semiconductor nanoparticles such as cesium lead halide, semiconductor nanoparticles having a core of silicon, carbon or the like, or the like are used. Instead of the semiconductor particles, organic pigments such as merocyanine and perylene, which are reported to have forster resonance energy transfer, may be used. The method of stacking and depositing is not particularly limited, and for example, the LBL method is exemplified. Instead of stacking the light-emitting particles, the light-emitting particles may be dispersed in a glass phase and sealed in the second light-emitting layer 1 d.

The 2 nd peak wavelength of the light emission of the 2 nd light-emitting particle (for example, semiconductor particle, organic pigment, or the like) constituting the second light-emitting layer 1d needs to be different from the 1 st peak wavelength of the 1 st light-emitting particle constituting the first light-emitting layer 1b by 10nm or more. When the difference between the emission peaks of the light emission of the first light-emitting layer 1b and the second light-emitting layer 1d is less than 10nm, it becomes difficult to detect a change in the emission spectrum of the gas sensor element due to the FRET phenomenon, which will be described later.

< protective layer >

The material constituting the protective layer 1e needs to have a function of chemically and physically protecting the second light-emitting layer 1 d. In order to facilitate measurement of the emission spectrum of the gas sensor element 1, it is preferable that the emission of the first light-emitting layer 1b and the second light-emitting layer 1d and the light from the excitation energy source be transmitted by 30% or more, respectively. As the material, for example, a polymer material such as silica or an alicyclic epoxy resin, or a thin film of a metal or a compound thereof such as Pt, Au, Ti, or Al can be used.

< opening part >

The opening portion 1f needs to penetrate through the protective layer 1e at least in the in-plane vertical direction Z of the gas sensor element 1 until the sensor layer 1c is exposed. The light-emitting layer may penetrate through the first light-emitting layer 1b and the support base 1 a. The shape of the opening portion 1f in the in-plane direction of the gas sensor element 1 may be a hole shape or a groove shape, and the shape is not limited. The shape of the opening portion 1f in the vertical direction Z of the gas sensor element 1 may be rectangular or tapered, and this shape is also arbitrary. The area of the opening portion 1f in the film in-plane direction in the protective layer 1e and the second light-emitting layer 1d is preferably 1% or more and less than 50%, respectively. When the area of the opening portion 1f is less than 1%, the sensor layer 1c hardly adsorbs the detection target gas, and when 50% or more, the amount of light emission in the second light-emitting layer 1d decreases. In order to facilitate adsorption of the gas to be detected on the sensor layer 1c, it is preferable that the plurality of opening portions 1f be formed as uniformly as possible in the entire gas sensor element 1. The hole forming means may be any means as long as the laminated structure of the gas sensor element 1 is maintained, and methods such as dry etching, wet etching, laser hole forming, and the like are not limited.

In addition, in order to increase the emission intensity from the gas sensor element 1, the above-described film structure may be provided on both surfaces of the supporting base 1 a. In this case, it is desirable to detect light emission from the first light-emitting layer 1b and the second light-emitting layer 1d formed on both surfaces of the support substrate Ja. Therefore, it is preferable to select a material that transmits light emitted from the first light-emitting layer 1b and the second light-emitting layer 1d and light from the excitation energy source 2a by 30% or more as the support substrate 1 a.

Next, the principle of gas detection in the gas sensor element of embodiment 1 will be explained. As the plurality of light-emitting particles, a case where the fluorescence spectrum of one light-emitting particle (donor) overlaps with the excitation spectrum of the other light-emitting particle (acceptor) is considered. In this case, it is known that if the two luminescent particles are close, the excitation energy excites the behavior of the acceptor before the donor excited by the excitation energy emits light. This behavior is called forster resonance energy transfer (FRET phenomenon) and depends on the distance between the light-emitting donor and acceptor emitting particles.

Here, a case where semiconductor nanoparticles are used for both the donor and the acceptor will be described. The semiconductor nanoparticles are nano-sized particles having a semiconductor crystal, and have a characteristic that an emission spectrum changes depending on a particle diameter due to a quantum size effect. Further, even if the particle diameter is the same, the particle has a characteristic that the emission spectrum changes depending on the material, and various emission spectra can be realized.

When the materials have the same particle size and different material systems, the material itself has a larger energy gap and emits light on the short wavelength side. In addition, when the particle diameters are different from each other with the same material, the smaller particle diameter exhibits light emission on the short wavelength side and the larger particle diameter exhibits light emission on the long wavelength side due to the quantum size effect. When a semiconductor nanoparticle exhibiting light emission on the short wavelength side is referred to as a semiconductor nanoparticle a and a semiconductor nanoparticle exhibiting light emission on the long wavelength side is referred to as a semiconductor nanoparticle B, the emission spectra of the semiconductor nanoparticle a and the semiconductor nanoparticle B are represented by the emission peak intensities in a state where the distances between the semiconductor nanoparticle a and the semiconductor nanoparticle B are sufficiently separated. When the distance between the semiconductor nanoparticle a and the semiconductor nanoparticle B is closer than a predetermined distance according to the thickness of the sensor layer, the semiconductor nanoparticle A, B is excited according to the distance, energy transfer from the semiconductor nanoparticle a to the semiconductor nanoparticle B occurs before the semiconductor nanoparticle a emits light, and the energy to be emitted from the semiconductor nanoparticle a is used for emission of the semiconductor nanoparticle B. As a result, it appears that the emission peak intensity of the semiconductor nanoparticle a decreases and the emission peak intensity of the semiconductor nanoparticle B increases (for example, fig. 3). Conversely, when the sensor layer swells and the distance between the semiconductor nanoparticles a and the semiconductor nanoparticles B becomes longer, the distance decreases as compared to when the semiconductor nanoparticles A, B are excited and the energy transfer from the semiconductor nanoparticles a to the semiconductor nanoparticles B approaches. As a result, the emission peak intensity of the semiconductor nanoparticle a increases and the emission peak intensity of the semiconductor nanoparticle B decreases as compared to when they are close to each other (for example, fig. 4).

The same principle applies to the case of using an organic dye. When the FRET phenomenon occurs, the emission peak intensity of the light-emitting particle or dye molecule emitting light on the short wavelength side decreases, and the emission peak intensity of the light-emitting particle or dye molecule emitting light on the long wavelength side increases. In order to easily confirm the FRET phenomenon, it is preferable that the emission peak wavelength on the short wavelength side and the emission peak wavelength on the long wavelength side are separated by 10nm or more. More preferably 30nm or more. If the difference between the emission peak wavelengths is less than 10nm, the emission peak wavelengths of the two overlap, and it is difficult to detect the change in the respective emission peak intensities.

In this gas sensor element, one of the first light-emitting layer 1b and the second light-emitting layer 1d is composed of 1 st light-emitting particles that function as a donor or acceptor, the other is composed of 2 nd light-emitting particles that function as an acceptor or donor, and the sensor layer 1c is formed between the layers thereof, utilizing the above principle. With this configuration, the distance between the donor luminescent particles and the acceptor luminescent particles can be changed by changing the film thickness of the sensor layer 1 c. If the gas to be detected physically and chemically adsorbs to the sensor layer 1c, the sensor layer 1c swells, and the film thickness of the sensor layer 1c changes, and the light emission spectrum of the gas sensor element 1 changes due to the FRET phenomenon in response to the change in the film thickness of the sensor layer 1 c. Therefore, by measuring the light emission spectrum of the gas sensor element 1, it is possible to convert into an increase in the film thickness of the sensor layer 1c, that is, an amount of adsorption of the detection target gas, and the amount of adsorption of the detection target gas to the sensor layer 1c depends on the detection target gas concentration in the atmosphere, so that the gas concentration in the atmosphere can be detected.

< gas detecting apparatus >

Next, fig. 2 is a schematic diagram showing the configuration of a gas detection device 2 using the gas sensor element 1 of embodiment 1. The gas detection device 2 using the gas sensor element 1 of embodiment 1 is composed of the gas sensor element 1, an excitation energy source 2a for emitting light from the gas sensor element 1, and a light receiving unit 2b for receiving light emitted from the gas sensor element 1 excited by the excitation energy source 2 a.

The following describes the components constituting the gas detection device 2.

< excitation energy Source >

The gas sensor element 1 is caused to emit light by the excitation energy source 2 a. As the excitation energy source 2a, a laser light source may be used. In this case, in order to improve the detection sensitivity of the light emission from the gas sensor element 1, it is preferable to use a wavelength cut filter or the like to selectively provide the wavelength of the light energy 2c from the excitation energy source 2a, thereby suppressing the influence of the excitation wavelength. When the semiconductor nanoparticles are used in either or both of the first light-emitting layer 1b and the second light-emitting layer 1d of the gas sensor element 1, the intensity of the excitation spectrum of the semiconductor nanoparticles is large in the short wavelength region, and therefore the wavelength of the excitation energy source 2a is preferably 200nm or more and 600nm or less.

In fig. 2, the excitation energy source 2a is disposed at an angle and a distance from the film surface of the gas sensor element 1, but the angle and the distance are not limited.

< light receiving part >

The light receiving unit 2b receives the light emitted from the gas sensor element 1 excited by the excitation energy source 2 a. As the light receiving unit 2b, a beam splitter in which a condensing lens, an optical fiber, and the like are combined may be used. Instead of the spectroscope, a CCD, a CMOS, an image sensor, or the like, which can analyze the light emission 2d from the gas sensor element 1 by chromaticity and luminance and calculate the chromaticity and luminance, may be used.

< method for detecting gas >

Next, a gas detection method in the embodiment will be described.

(1) First, as a state before contact with the detection target gas, the gas sensor element 1 is irradiated with light by the excitation energy source 2a to cause the gas sensor element 1 to emit light, and the light emission state of the gas sensor element 1 is recorded by the light receiving unit 2 b.

(2) After the gas sensor element 1 is brought into contact with the gas to be detected, the gas sensor element 1 is irradiated with light again from the excitation energy source 2a to emit light from the gas sensor element 1, and the light emission state of the gas sensor element 1 is recorded in the light receiving unit 2 b.

(3) By comparing the light emission states of the gas sensor element 1 before and after the detection target gas is brought into contact with each other, it is possible to determine whether or not the gas sensor element 1 detects the detection target gas.

In fig. 2, the light receiving unit is disposed to face the gas sensor element and to be spaced apart from the gas sensor element, but the light receiving unit is not limited to this as long as it can detect light emission from the gas sensor element.

Therefore, according to the present embodiment, even at a concentration of 0.1ppm or less, the film thickness of the sensor layer 1c changes before and after the gas to be detected is brought into contact with the gas sensor element 1, and the emission spectra of the first light-emitting layer 1b and the second light-emitting layer 1d measured by the light-receiving section 2b change, so that the gas concentration of 0.1ppm or less can be detected.

[ examples ] A method for producing a compound

The following examples are described in detail.

(example 1)

The gas sensor element was manufactured by the following manufacturing method.

(method for manufacturing gas sensor element)

A quartz glass substrate having a PDDA/PAA film formed on the surface thereof was used as the supporting base material 1 a. The method for producing the supporting base 1a is described below.

(1) In order to impart the film-forming property of the first light-emitting layer 1b to a quartz glass substrate of 6.5mm × 17.5mm × 0.8mm, the above quartz glass substrate was ultrasonically cleaned in the order of acetone and methanol, then dried by spraying nitrogen gas, and immersed in piranha solution (3: 1 mixed solution of 96% sulfuric acid and 30% aqueous hydrogen peroxide) heated to 150 ℃ for 90 minutes, thereby imparting hydroxyl groups to the substrate surface.

(2) Then, the quartz glass substrate was immersed in a 0.87 wt% PDDA (poly diallyldimethylammonium chloride) aqueous solution for 10 minutes by the LBL method, then washed with ultrapure water, immersed in a PAA (polyacrylic acid) aqueous solution diluted with ultrapure water so that the optical absorption intensity became 0.05 for 10 minutes, and then washed again with ultrapure water, thereby forming a PDDA/PAA film on the surface of the quartz glass substrate, and a quartz glass substrate having a PDDA/PAA film formed on the surface thereof was produced.

A light-emitting layer in which ZnSe semiconductor nanoparticles are stacked is used as the first light-emitting layer 1 b. A method for producing the first light-emitting layer 1b is described below.

(3) ZnSe semiconductor nanoparticles were prepared by solvothermal synthesis using NAC (N-acetyl L-cysteine) as a ligand. The semiconductor nanoparticles have a peak wavelength of light emission of 364nm and exhibit cationic properties depending on the nature of the ligand.

(4) The first light-emitting layer 1b was formed on the supporting substrate 1a by immersing the supporting substrate 1a in an aqueous solution in which the semiconductor nanoparticles were dispersed for 20 minutes by the LBL method and then washing with ultrapure water.

A sensor layer 1c is a layer in which PDDA and PAA are alternately stacked. A method for manufacturing the sensor layer 1c is described below.

(5) The film formation is performed on the first light-emitting layer 1b by repeating the film formation of 5 layers each in the order of PDDA and PAA in the same procedure as in the case of imparting the film-forming property of the first light-emitting layer 1b to the support base 1 a.

The light-emitting layer on which ZnSe semiconductor nanoparticles are laminated is used as the second light-emitting layer 1 d. A method for producing the second light-emitting layer 1d is described below.

(6) ZnSe semiconductor nanoparticles were made by solvothermal synthesis using NAC (N-acetyl L-cysteine) as ligand. In addition, the ZnSe semiconductor nanoparticles had a larger particle size due to a longer heating time than that in the case of producing the ZnSe semiconductor nanoparticles of the first light-emitting layer 1b, and the peak wavelength of light emission was shifted to the longer wavelength side by the quantum size effect to 385 nm.

(7) The sensor layer 1c is formed by an LBL method in the same manner as the first light-emitting layer 1 b.

The protective layer 1e was formed of a film formed of silicon dioxide. A method for producing the protective layer 1e is described below.

(8) A film was formed by milling a silica target disposed at an angle to the front surface of the ion gun with argon ions by a normal ion milling method, and providing the second light-emitting layer 1d surface at the sputtering destination of the silica target so that the film thickness became 500 nm.

(9) The opening portion 1f was formed with a photoresist on the surface of the protective layer 1e by spin coating, and cylindrical opening portions having a diameter of 100 μm were formed in a lattice shape at a pitch of 500 μm by using an exposure apparatus or an ion milling apparatus, and were allowed to penetrate in the in-plane vertical direction Z until the sensor layer 1c was exposed.

Next, a gas detection device was manufactured by the following configuration.

(constitution of gas detecting device)

A laser light source having a light emission wavelength of 300nm was used as the excitation energy source 2 a. The laser light source is disposed at a distance of 50cm from the gas sensor element 1 so that the incident angle of the laser light on the film surface of the gas sensor element 1 becomes 45 °.

The light receiving unit 2b uses a combination of a beam splitter, a condenser lens, and an optical fiber. The condenser lens is provided at a position 5cm away from the gas sensor element 1 so as to face the film surface of the gas sensor element 1.

(evaluation method)

Next, the evaluation method will be specifically described.

In order to examine whether or not the gas sensor element 1 can detect ammonia gas when a mixed gas of dry nitrogen gas and 0.005ppm ammonia gas is brought into contact with the gas sensor element 1, the gas detection device 2 was provided, and the emission spectra of the gas sensor element before and after 30 seconds of contact with the mixed gas were measured to calculate a gas concentration index Y described later. When the gas concentration index Y is 0.005 or more, it is determined that the gas can be detected, and when the gas concentration index Y is less than 0.005, it is determined that the gas cannot be detected.

Whether or not the gas to be detected can be detected by the gas sensor element 1 is examined by measuring the emission spectrum of the gas sensor element 1 before and after the gas to be detected is brought into contact with the gas sensor element 1 by a method according to the general rule of fluorometric analysis of japanese industrial standards (JIS K0120) and calculating a gas concentration index Y represented by the following formula (1). In addition, I₁、I₂As shown in fig. 3, the emission intensity at the peak wavelength on the short wavelength side and the emission intensity at the peak wavelength on the long wavelength side of the gas sensor element 1 before the target gas contacts are detected. In addition, I₁’、I₂' As shown in FIG. 4, the emission intensity at the peak wavelength on the short wavelength side and the emission intensity at the peak wavelength on the long wavelength side of the gas sensor element after the contact of the detection target gas are shown. The results of calculation of the conditions and the gas concentration index Y in the examples and comparative examples are shown in table 1 of fig. 5.

[ mathematical formula 1 ]

Gas concentration index:

comparative example 1

The emission spectrum of the gas sensor element 1 was measured and the gas concentration index Y was calculated in the same manner as in the example, except that the opening hole portion 1f was not provided. The results are shown in table 1 of fig. 5.

As is clear from example 1 and comparative example 1, in the case where the opening hole portion 1f is not provided, the sensor layer 1c cannot adsorb the gas to be detected, and therefore the gas sensor element 1 cannot detect the gas at 0.005 ppm.

Comparative example 2

The light emission spectrum of the gas sensor element 1 was measured in the same manner as in example except that the sensor layer 1c was formed on the first light-emitting layer 1b by an LBL method using PDDA and PAA in the order of 1 layer each, and the gas concentration index Y was calculated. The results are shown in table 1 of fig. 5.

As is clear from example 1 and comparative example 2, when the film thickness of the sensor layer 1c is less than 1nm, the sensor layer 1c cannot sufficiently adsorb the gas to be detected, and the film thickness of the sensor layer 1c does not sufficiently change, so that the gas sensor element 1 cannot detect the gas at 0.005 ppm.

Comparative example 3

The emission spectrum of the gas sensor element 1 was measured in the same manner as in example except that the sensor layer 1c was formed on the first light-emitting layer by an LBL method using PDDA and PAA in the order of PDDA and PAA to calculate the gas concentration index Y. The results are shown in table 1 of fig. 5.

As is clear from example 1 and comparative example 3, when the film thickness of the sensor layer 1c is 100nm or more, there is no change in the emission spectrum due to FRET phenomenon before and after the sensor layer 1c adsorbs the gas to be detected, and therefore the gas sensor element 1 cannot detect the gas at 0.005 ppm.

Comparative example 4

The light emission spectrum of the gas sensor element 1 was measured in the same manner as in the example, except that ZnSe semiconductor nanoparticles having a peak wavelength of light emission of 380nm prepared by a solvent thermal synthesis method were used as the particles constituting the first light-emitting layer 1 b. As a result, since the short-wavelength side light emission and the long-wavelength side light emission overlap each other, the peaks of the respective light emissions cannot be distinguished, and the gas concentration index Y cannot be calculated. As is clear from example 1 and comparative example 4, if the peak wavelength of the light emission of the second light-emitting layer 1d and the peak wavelength of the light emission of the first light-emitting layer 1b do not differ by at least 10nm, the gas sensor element 1 cannot detect a gas at 0.005 ppm.

Therefore, it is found that the gas sensor element 1 has a hole portion penetrating from the protective layer 1e at least until the sensor layer 1c is exposed, and when the film thickness of the sensor layer 1c is 1nm or more and 100nm or less and the peak wavelengths of light emission of the first light-emitting layer 1b and the second light-emitting layer 1d are separated by 10nm or more, 0.005ppm or more of gas can be detected.

In the present disclosure, any of the various embodiments and/or examples described above may be appropriately combined to realize the effects of the respective embodiments and/or examples.

Industrial applicability

According to the gas sensor element and the gas detection device using the gas sensor element of the present invention, a gas of 0.1ppm or less can be detected. Further, by giving selectivity of gas adsorption to the sensor layer depending on the kind of gas, it is possible to detect a combustible gas and a toxic gas at a low concentration of 0.1ppm or less and to distinguish between molecules that cause odor.