JP7313678B2 - Aldehyde detection sensor and system using the same - Google Patents

Description

The present invention relates to an aldehyde detection sensor that utilizes changes in electrical signals and a system using the same.

Formaldehyde is one of the volatile organic compounds (VOC) and is known to be harmful to the human body when it exceeds a certain amount. Formaldehyde is contained in, for example, plywood, lacquer, building materials, etc., and is released into the atmosphere indoors to cause diseases such as sick house syndrome and cancer. According to the World Health Organization (WHO), the indoor formaldehyde concentration standard is 0.08 ppm or less.

In recent years, a formaldehyde sensor using hydroxylamine salts has been developed (see, for example, Patent Document 1). Patent Document 1 reports a sensor and a system using the same that constantly monitor formaldehyde by detecting acid vapor generated by reacting formaldehyde and hydroxylamine salts as a change in the electrical resistance value of carbon materials such as carbon nanotubes. It has been reported that the sensor has high sensitivity, excellent selectivity, and can be used repeatedly in the atmosphere. Furthermore, it has been shown that the amount of change in electrical resistance value is correlated with the formaldehyde concentration, and quantification based on a calibration curve is also possible.

However, when the principle is to detect the amount of change in electrical resistance value as described above, the gas introduced into the sensor is guaranteed not to contain at least the detection target (formaldehyde or aldehyde in Patent Document 1 and this specification). It is common practice to switch from a gas (hereinafter referred to as a blank gas) to a gas containing a detection target (hereinafter referred to as a sampling gas) to obtain a difference in electrical resistance between the blank gas and the sampling gas. Therefore, in actual measurement, it is necessary to prepare a blank gas by some method.

As a method of preparing blank gas, a high-pressure cylinder filled with clean gas is conceivable, and Patent Document 1 also adopts this method, but it is difficult to mount a high-pressure cylinder on a small portable sensor. Also, if the sensor also responds to changes in relative humidity, it is desirable to match the relative humidity of the blank gas and the sampling gas, but a complicated device is required to adjust the relative humidity by humidification or dehumidification.

As another method, it is possible to use the sampling gas as a blank gas by contacting the sampling gas with an adsorbent or catalyst to remove formaldehyde or convert it to another chemical substance to inactivate it.

Also, if the sensor has been stored in an atmosphere containing formaldehyde for a long time, the response of the sensor is saturated, and it is necessary to flow the blank gas for a sufficiently long time to restore the electrical resistance of the sensor to the state under the blank gas. Otherwise, almost no change in electrical resistance is observed when the sampling gas is introduced. Therefore, it is considered desirable to store the electrical resistance variable sensor in a blank gas.

Therefore, it is desired to develop a technique that enables formaldehyde to be detected as a change in electrical resistance even in situations where blank gas cannot be prepared.

WO2019/049693

In view of the above, an object of the present invention is to provide an aldehyde detection sensor that detects aldehyde as a change in electric signal without preparing a blank gas, and a system using the same.

A variable electrical resistance sensor in which a reaction section and a response section are separated from each other but always integrated as disclosed in Patent Document 1 requires blank gas in order to obtain the amount of change in electrical resistance. While it is easy to prepare a blank gas for test measurements in a laboratory, the inventor of the present application conceived that preparing a blank gas for a small portable sensor would result in an increase in the size and cost of the sensor, which could pose a serious technical problem, and came up with the present invention as a solution.

An aldehyde detection sensor according to the present invention includes a reaction section that reacts with aldehyde in a sampling gas to generate acid vapor, a response section that changes an electrical signal by the acid generated in the reaction section and is positioned apart from the reaction section, and a switching mechanism that switches a separation state between the reaction section and the response section, wherein the switching mechanism switches between a standby state in which acid generated in the reaction section does not reach the response section and an operating state in which acid generated in the reaction section reaches the response section. To solve the above problems.
The response section may include an electrode supporting a semiconductor material whose electrical resistance changes as the electrical signal changes due to the acid.
The aldehyde may be formaldehyde.
The reaction section may contain at least hydroxylamine salts.
The hydroxylamine salts may be neutralized salts selected from the group consisting of halides, nitrates, and trifluoroacetates of hydroxylamine ( _NH2OH ) or _NH2OR (R is an aromatic, cyclic or acyclic carbon compound, or derivative thereof).
The hydroxylamine salts may be supported on porous materials.
The hydroxylamine salt is in a crystal or powder state, and the hydroxylamine salt may be enclosed in a porous filter having air permeability.
Said porous filter may be selected from the group consisting of hydrophobic polymers, hydrophilic polymers, porous glasses, porous carbon materials and porous oxides.
The hydrophobic polymer may be polytetrafluoroethylene (PTFE).
The semiconductor material may be a carbon material or a conductive polymer.
The carbon material may be a carbon material selected from the group consisting of carbon nanotubes, carbon nanohorns, graphene, fullerenes and derivatives thereof.
The conductive polymer may be a conductive polymer selected from the group consisting of polythiophene, polyaniline, polypyrrole, polyacetylene, polyparaphenylene vinylene, polyparaphenylene and derivatives thereof.
A spacer may be provided between the reaction section and the response section.
The switching mechanism may move the reaction section and/or the response section to switch between the standby state and the operating state.
The switching mechanism may be a shielding wall inserted between the reaction section and the response section, and may switch between the standby state and the operating state depending on whether or not the shielding wall is inserted.
The switching mechanism may switch the flow direction of the sampling gas to switch between the standby state and the operating state depending on whether the response section is upstream or the reaction section is upstream.
An aldehyde detection system according to the present invention comprises an aldehyde detection sensor and detection means, wherein the aldehyde detection sensor is the aldehyde detection sensor described above, and the detection means detects a change in an electrical signal generated by the aldehyde detection sensor, thereby solving the above problems.
The aldehyde detection sensor is connected to a power supply, and the detection means may be an ammeter or a voltmeter.
The aldehyde may be formaldehyde.

The aldehyde detection sensor of the present invention is provided with a switching mechanism for switching the separation state between the reaction section and the response section, and the switching mechanism switches between a state in which the acid generated in the reaction section does not reach the response section (hereinafter referred to as a standby state) and a state in which the acid generated in the reaction section reaches the response section (hereinafter referred to as an operating state), so aldehyde can be detected as a change in electrical signal without preparing a blank gas. As a result, the size and cost of the sensor can be reduced. By combining the sensor of the present invention with various detection devices, an aldehyde detection system can be provided.

Schematic diagram showing an exemplary aldehyde detection sensor of the present invention. Schematic diagram showing another exemplary aldehyde detection sensor of the present invention. FIG. 4 is a schematic diagram illustrating yet another exemplary aldehyde detection sensor of the present invention; Schematic diagram showing the aldehyde detection system of the present invention 1 shows a system with an aldehyde detection sensor according to Example 1. FIG. FIG. 2 shows the response characteristics of the sensor according to Example 1 to formaldehyde. FIG. 4 is a diagram showing the response characteristics of the sensor according to Example 2 to a blank gas. FIG. 4 is a diagram showing the response characteristics of the sensor according to Example 2 to formaldehyde. A diagram showing a procedure for manufacturing a reaction part according to Example 3. FIG. 3 shows a system with an aldehyde detection sensor according to Example 3; FIG. 4 is a diagram showing the response characteristics of the sensor according to Example 3 to formaldehyde. FIG. 4 shows the response characteristics of the sensor according to Example 4 to acetaldehyde.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same number is given to the same element, and the description is omitted.

(Embodiment 1)
Embodiment 1 describes an aldehyde detection sensor of the present invention.

FIG. 1 is a schematic diagram showing an exemplary aldehyde detection sensor of the present invention.

The aldehyde detection sensor 100 of the present invention (hereinafter sometimes simply referred to as the sensor of the present invention) includes a reaction section 120 that produces acid by reaction with the aldehyde to be detected, and a response section 150 that produces a change in electrical signal due to the acid generated in the reaction section 120. Further, in the sensor 100 of the present invention, the reaction section 120 and the response section 150 are separated from each other, and a switching mechanism 180 is further provided for switching between a standby state in which the acid vapor generated in the reaction section 120 does not reach the response section 150 and an operating state in which the acid vapor generated in the reaction section 120 reaches the response section 150 at an arbitrary timing. The switching mechanism 180 allows aldehydes to be detected by the change in electrical signal that occurs when switching from the standby state to the active state using only the sampling gas without preparing a blank gas.

As used herein, segregated is intended to be physically unmixed. The separation condition for distinguishing between the standby state and the operating state varies depending on the concentration of aldehyde contained in the sampling gas, the flow rate and direction of the sample gas, the internal space capacity of the sensor, the shield inserted between the reaction section and the response section, the amount of hydroxylamine salts contained in the reaction section, etc., in addition to the separation distance between the reaction section 120 and the response section 150. Therefore, it is difficult to define the separation condition. , it can be judged whether or not a response to aldehyde is detected when switching from a blank gas to a sampling gas containing aldehyde, and a sensor can be designed and constructed based on this judgment method. As such, it is desirable to design the sensor using a blank gas, but it should be noted that a blank gas is not required for actual measurements.

The operating principle of the sensor 100 of the present invention will now be described. In the sensor of the present invention, the switching mechanism 180 puts the sensor 100 in the above-described standby state before the power is turned on or before the start of measurement after the power is turned on, and the response unit 150 does not detect acid regardless of whether acid vapor is generated in the reaction unit 120. The electrical signal of the response unit 150 in the standby state, eg, the electrical resistance value, is recorded as R ₀ . Note that when a constant voltage is applied to the response section 150, the current value _I0 can be used instead of the electrical resistance value as the electrical signal according to Ohm's law.

At the start of measurement, the switching mechanism 180 switches the sensor 100 of the present invention to the operating state, and volatile acid (eg, hydrochloric acid) generated in the reaction section 120 by reaction with aldehyde diffuses into the response section 150.

Note that when switching from the standby state to the operating state, there is a possibility that an increase or decrease in the electric signal can be seen in the response unit 150 due to an environmental change such as the reaction unit 120 approaching the response unit 150, but this pseudo signal can be handled by estimating in advance using a blank gas and subtracting it from the measured value each time.

Here, it is assumed that the reaction section 120 contains hydroxylamine salts 110 that react with formaldehyde among aldehydes to generate acid vapor. For simplicity, the case of hydroxylamine hydrochloride will be described as the hydroxylamine salt 110, but other hydroxylamine salts 110 also generate an acid by a similar condensation reaction.
HCHO+ _NH2OH.HCl → _H2C =NOH+ _H2O +HCl

In addition to containing the hydroxylamine salts 110, the reaction section 120 that reacts with the aldehyde to generate acid vapor may also contain hydrazine salts, amine salts, and the like. Methylated and acetylated hydroxylamine salts may also be used. For simplicity, the case where the reaction section 120 contains the hydroxylamine salts 110 will be described below.

Note that the aldehyde is not limited to formaldehyde, and acetaldehyde and benzaldehyde can be similarly reacted in the reaction unit 120 to generate acid, but formaldehyde is preferable.

When the response unit 150 includes a semiconductor material 130 that causes a change in electrical signal by acid, which will be described later, the electrical resistance value of the semiconductor material 130, in the case of p-type, often drops due to hole injection due to adsorption of acid. The electrical resistance value R _t (or the current value I _t ) of the response unit 150 is measured after a certain period of time has passed since the operating state, and if the electrical resistance value changes, it can be determined that the sampling gas contains aldehyde. Furthermore, the concentration of aldehyde can be converted from the correlation (separately prepared calibration curve) between the relative change in electrical resistance value and the aldehyde concentration represented by the following formula.
Amount of relative change in electrical resistance value (%)=(R _t −R ₀ )/R ₀ ×100

After the measurement is completed, the switching mechanism 180 switches the sensor 100 of the present invention to the standby state again, and regardless of the presence or absence of aldehyde under the sampling gas, the acid molecules adsorbed to the semiconductor material 130 are equilibrium-desorbed. After a certain period of time, the electrical signal (electrical resistance value) recovers to the state before the start of measurement, and repeated measurements can be performed.

By adopting such a mechanism, it is possible to restore the electrical signal (electrical resistance value) of the sensor 100 even when purging with an aldehyde-containing gas without preparing a blank gas, detect whether or not aldehyde is contained in the sampling gas, and repeatedly quantify the concentration when aldehyde is detected. The aldehyde to be detected by the aldehyde detection sensor of the present invention is not limited to aldehyde contained in the atmosphere, and may be aldehyde generated by oxidation or reduction of organic matter such as combustion.

Each component of the sensor 100 of the present invention is described in detail below.
Hydroxylamine salts 110 are neutralized salts obtained by neutralizing hydroxylamine (NH ₂ OH) with a volatile strong acid, illustratively selected from the group consisting of halides, nitrates, and trifluoroacetates. A mixture of a neutralized salt of a non-volatile acid such as a sulfate, a phosphate, and a borate and a salt of a volatile strong acid such as NaCl is also included in the aforementioned halides, nitrates, and trifluoroacetates.

These hydroxylamine salts 110 are readily available or can be synthesized. Among them, those that generate highly volatile strong acids when reacting _with aldehydes strongly hole-dope the semiconductor _material 130 _and are preferable for high-sensitivity detection _of aldehydes.

Alternatively, hydroxylamine salts 110 are neutralized salts of organic compounds selected from the group consisting of halides, nitrates, and trifluoroacetates of hydroxylamine derivatives NH _OR (R is an aromatic, cyclic or acyclic hydrocarbon compound, or a derivative thereof). Among them, R is an aromatic benzene ring, a benzyl group, or a 4-nitrobenzyl group, such as halides ( _NH2OR.HCl , _NH2OR.HBr ), _{trifluoroacetates} ( _{NH2OR.CF3COOH} ), and O-benzylhydroxylamine hydrochloride. As used herein, the term "derivative" means a compound or the like that has been modified to such an extent that the original structure and properties do not change significantly even when a functional group is introduced, oxidized, reduced, or atom-substituted.

Alternatively, the hydroxylamine salts 110 may be a solid material NH ₂ OQ (where Q is a polymer, polymer beads, silica gel, etc.) in which hydroxylamine is supported on the surface of a polymer or inorganic compound, and neutralized by treatment with halogen acid, nitric acid, or trifluoroacetic acid.

The structure of the response unit 150 is not particularly limited as long as acid causes a change in electrical signal, but preferably includes a semiconductor material 130 that causes a change in electrical resistance value (or current value) due to adsorption of acid. The semiconducting material 130 may be carried by electrodes, for example. This facilitates detection of changes in electrical signals. Such semiconductor materials 130 include carbon materials, conductive polymers, inorganic semiconductors, and the like. Whether the electrical resistance value increases or decreases due to acid adsorption depends on the properties of the semiconductor material, but either property can be used. Many p-type semiconductors whose electric resistance value is reduced by hole doping have their electric resistance value reduced by acid adsorption, and the carbon nanotube used in this specification is a p-type semiconductor, and it is known that the electric resistance value is reduced by contact with acid.

Carbon materials are, for example, materials selected from the group consisting of carbon nanotubes, carbon nanohorns, graphene, fullerenes, and derivatives thereof. It is known that these materials change their electric resistance values due to acid adsorption. Among them, carbon nanotubes are preferred because they are readily available and have excellent electrical properties and stability. As derivatives, those having functional groups such as amine and carboxylic acid on the surface, and those coated with a dispersant or the like are intended.

Carbon nanotubes are classified into single-walled, double-walled, and multi-walled carbon nanotubes according to the number of graphene layers, and any of them can be used in the present invention. Among them, a part of single-walled carbon nanotube (SWCNT) is preferable because it has semiconducting properties and easily causes a change in electric resistance value against acid. In addition, the surface of SWCNT is a hydrophobic and stable graphene sheet, which is less responsive to changes in humidity and less susceptible to denaturation by acid.

Whether the SWCNT becomes a semiconductor or a metal is determined by the chirality of the winding of the graphene sheet, and the synthesized SWCNT is a mixture containing a semiconductor and a metal at a ratio of 2:1. For the purpose of increasing the response sensitivity of SWCNTs to acid vapor, that is, the amount of change in electrical resistance value, semiconducting SWCNTs can be separated and purified to provide the semiconducting SWCNTs as the semiconductor 130 . As a method for separating and refining semiconductors, the column separation method described in Patent Document 1 and the like can be employed.

In addition, usually by dispersing SWCNTs forming a bundle structure due to strong π-π interaction one by one and then coating them on an electrode, the surface area of SWCNTs that can come into contact with acid vapor increases, so the response sensitivity to acid vapor increases, thereby increasing the detection sensitivity of aldehyde. As a method for dispersing SWCNTs, in addition to ultrasonic treatment in a solvent, a combination of dispersion treatment with a dispersant can be employed. As the dispersant, in addition to the supramolecular polymer described in Patent Document 1, a π-conjugated polymer such as polyfluorene and an amphipathic surfactant such as sodium dodecylsulfate can be employed. An organic solvent and water can be used as the solvent. Among organic solvents, ortho-dichlorobenzene is known to have high dispersibility of SWCNTs and is preferable.

The conductive polymer used as the semiconductor material 130 is, for example, a conductive polymer selected from the group consisting of polythiophene, polyaniline, polypyrrole, polyacetylene, polyparaphenylene vinylene, polyparaphenylene and derivatives thereof. These conductive polymers can be used as the semiconductor material 130 in the response section 150 because their electrical resistance changes when they come into contact with acid vapor.

For example, in the case of polythiophene, which is a p-type semiconductor, conductivity is increased by hole-doping with an acid, such as PEDOT (poly(3,4-ethylenedioxythiophene)-PSS (poly(4-styrenesulfonic acid))), which is widely put into practical use. In addition, conductive polymers containing basic functional groups such as polyaniline and polypyrrole have a high affinity with acid molecules, and the electrical resistance value changes as the bandgap changes due to the adsorption of acid molecules, which is more preferable. .

As the inorganic semiconductor, an inorganic oxide semiconductor proven as a gas sensor such as SnO ₂ (tin oxide), In ₂ O ₃ (indium oxide), ZnO (zinc oxide), Fe ₂ O ₃ (iron oxide) can be used.

It is preferable that the semiconductor material 130 has an internal space and a high specific surface area so that acid can be easily adsorbed thereon, and a porous body or a mesh structure (network) may be formed.

The semiconducting material 130 is preferably carried on an electrode 140 made of commonly used electrode materials, where the electrode 140 illustratively consists of a material selected from the group consisting of Au, Pt, Ag and alloys thereof, or conductive carbon materials such as glassy carbon. The shape of the electrode 140 varies depending on the method for detecting the change in electrical resistance value, but is exemplified by a comb-shaped electrode (eg, FIG. 1). Thus, electrode 140 is located on substrate 160 in FIG.

When the hydroxylamine salt 110 is in a crystal or powder state, it may be supported on a porous material as shown in FIG. 1, or may be packaged in a porous filter with air permeability as shown in FIG. This facilitates handling of the reaction section 120 and facilitates switching between the standby state and the operating state by changing the state of separation between the reaction section 120 and the semiconductor material 130 .

Such a porous material may be made of a material that is not reactive with hydroxylamine salts 110 and has pores that can support hydroxylamine salts 110 . Exemplary materials are materials selected from the group consisting of paper represented by filter paper and the like, hydrophobic polymers, hydrophilic polymers, polymer filters, porous glass, porous carbon materials and porous oxides. These are porous materials that are readily available commercially.

The aforementioned porous filter may be made of a material that is air permeable and allows the encapsulated hydroxylamine salt 110 powder to react with the aldehyde and also allows the generated volatile acid to reach the semiconductor material 130. Exemplary are filter materials selected from the group consisting of paper represented by filter paper, hydrophobic polymers, hydrophilic polymers, porous glass, porous carbon materials and porous oxides. For the purpose of preventing wetting with water, a porous filter made of a hydrophobic polymer such as polytetrafluoroethylene (PTFE) is preferred.

Preferably, the porous material has a specific surface area ranging from 10 m ² /g to 5000 m ² /g, a pore diameter ranging from 10 nm to 100 μm, and a pore volume ranging from 0.05 cm ³ /g to 0.90 cm ³ /g. This allows carrying as much of the hydroxylamine salts 110 as are needed for the reaction and without future replacement.

As shown in FIG. 1, in the sensor 100 of the present invention, a spacer 170 may be positioned between the reaction section 120 and the response section 150, and the material of the spacer 170 is not particularly limited.

The switching mechanism 180 is not limited as long as it can switch between the standby state and the operating state, but as shown in FIG. 1, the reaction unit 120 may be moved to switch between the standby state and the operating state. In FIG. 1, the reaction section 120 and the response section 150 are maintained in a separated state via a spacer, and the reaction section 120 is movable by a switching mechanism 180 composed of a hinge section. In the operating state, the reaction unit 120 and the response unit 150 face each other and are separated from each other, and in the standby state, the reaction unit 120 is separated from the response unit 150. Even if acid vapor is generated in the reaction section 120 in the standby state, it is sufficiently diluted before it reaches the response section 150 by diffusion, and is not detected by the response section 150 . In order to prevent the acid generated in the response section 150 from reaching the reaction section 120, a solid base (for example, polyvinylpyridine) that adsorbs acid may be placed in the sensor chamber.

Although FIG. 1 shows a configuration in which the reaction section 120 is movable, the response section 150 may be moved, or both the reaction section 120 and the response section 150 may be moved. As the switching mechanism 180 for changing the separation state, an electrically operated device such as a motor, a gear, an electrostatic actuator, or an electromagnetic valve may be employed, or a manual device such as a switch may be employed. There is no particular limitation on how to move the reaction section 120 and/or the response section 150, and it may be a linear movement or a rotational movement.

In addition, the sensor 100 may include a heating device (not shown) to heat the reaction section 120 and/or the response section 150 to room temperature or higher so as to be in a constant temperature state. Room temperature or higher is illustratively 40° C. or higher and 100° C. or lower. By keeping the reaction section 120 and/or the response section 150 in a constant temperature state of room temperature or higher, it is possible to eliminate the influence of temperature changes in the environment, increase the reaction rate in the reaction section 120, increase the desorption rate of the acid adsorbed on the response section 150, and the like.

FIG. 2 is a schematic diagram illustrating another exemplary aldehyde detection sensor of the present invention.

The aldehyde detection sensor 200 of FIG. 2 is the same as that of FIG. 1 except that the switching mechanism is a shielding wall 210 . The shielding wall 210 is inserted between the reaction section 120 and the response section 150 to shield acid vapor. By sliding or opening/closing the shielding wall 210, it is possible to switch between a standby state in which the shielding wall 210 shields the acid vapor between the reaction section 120 and the response section 150, and an operating state in which the acid vapor is not shielded.

The shielding wall 210 may employ an electrically actuated device such as a motor, gear, electrostatic actuator, electromagnetic valve, shutter, or the like, or may employ a manual device such as a switch.

FIG. 3 is a schematic diagram illustrating yet another exemplary aldehyde detection sensor of the present invention.

The aldehyde detection sensor 300 of FIG. 3 is the same as that of FIG. By switching from the standby state in which the reaction section 120 is downstream of the response section 150 below the flow path to the operating state in which the reaction section 120 is upstream of the response section 150, the diffusion direction of acid vapor is controlled. When the reaction section 120 is located downwind (downstream) of the response section 150 below the flow path, the acid vapor generated in the reaction section 120 cannot diffuse to the response section 150 and enters a standby state. Further, when the reaction section 120 is located on the windward side (upstream) of the response section 150 below the flow path, the acid vapor generated in the reaction section can diffuse to the response section 150, so that the reaction section 150 is in an operating state.

Although the reaction section 120 and the response section 150 are housed in the sensor chamber 320 in FIG. 3, the sensor chamber 320 is not essential, but housing the reaction section 120 and the response section 150 in the sensor chamber 320 is preferable from the viewpoint of efficiently controlling the diffusion direction of the acid vapor.

An exemplary manufacturing process for the aldehyde detection sensor 100 of the present invention will now be described.

First, a substrate 160 having electrodes 140 is prepared. A semiconductor material 130 is dispersed in a solvent. The solvent is not particularly limited as long as it is volatile, and o-dichlorobenzene is an example. This dispersion or suspension is then drop-cast onto the electrode 140 . After drying the solvent, the responsive portion 150 is obtained.

Hydroxylamine salts 110 are then added to a solvent such as methanol and the solution is drop cast or dipped into a porous material or the like. The reaction part 120 is obtained by drying and removing the solvent. If the spacer 170 is installed in the response section 150 and the reaction section 120 is placed on the spacer 170, the reaction section 120 is placed in an operating state. By making the reaction part 120 movable using the switching mechanism 180, the sensor 100 of the present invention can be obtained that can switch between the operating state and the standby state at any timing.

With reference to FIGS. 1 to 3, the response section 150 has been described as using an electrode having a semiconductor material 130 that produces a change in electrical signal with acid, but is not limited to this. The response unit 150 can employ any element that produces a change in electrical signal in response to acid, for example, an element that produces a change in capacitance, an element that produces a change in resonance frequency (e.g., crystal oscillator microbalance), an element that produces mechanical displacement (e.g., a cantilever), and the like. By combining these with the reaction section 120 and the switching mechanism 180, aldehyde can be detected without using a blank gas.

(Embodiment 2)
Embodiment 2 describes a system using the formaldehyde detection sensor of the present invention described in Embodiment 1. FIG.

FIG. 4 is a schematic diagram showing the formaldehyde detection system of the present invention.

The formaldehyde detection system 400 of the present invention (hereinafter sometimes simply referred to as the system of the present invention) comprises the formaldehyde detection sensor 100 (FIG. 1) of the present invention and detection means 410 for detecting changes in electrical signals from the sensor 100. In FIG. 4, system 400 of the present invention is connected to power supply 420 . The power source 420 may be a fixed power source, or may be a battery or the like. If a battery is used as the power supply 420, a portable and small system 400 can be provided.

Detecting means 410 is not particularly limited as long as it can detect changes in electrical signals, but for example, an ammeter or a voltmeter is employed when the electrical signal is an electrical resistance value or a current value. With an ammeter, if the voltage of the power supply 420 is known, the change in electrical resistance of the semiconductor material 130 can be detected by measuring the magnitude of the current. The voltage may be direct current or alternating current. The detecting means 410 detects a change in the electrical resistance value when the sensor 100 is in the operating state and the electrical resistance value when it is in the standby state. The detection means 410 may be driven by a power source different from the power source 420 .

Alternatively, the system 400 may include a control unit (not shown) in which erroneous response data based on temperature and humidity are stored in advance in a database, and the control unit may compare changes in the electrical signal of the response unit 150 of the sensor 100 of the present invention detected by the detection means 410 with the data stored in the database of the control unit, distinguish between correct responses and erroneous responses, and perform concentration correction.

Alternatively, the control unit (not shown) may include a measurement program including switching between the standby state and the operating state, timing for measuring the electrical resistance value or the current value, etc. Based on the measurement program, the switching mechanism 180 of the sensor 100 may automatically switch between the standby state and the operating state.

The operation of system 400 will now be described. A constant voltage, for example, is applied from a power supply 420 to the sensor 100 of the present invention. A sampling gas is supplied to the sensor 100 placed in a standby state manually or by a control unit (not shown), and the detection means 410 detects the value of the electric signal (for example, the electric resistance value) of the sensor 100 at that time. Next, while the sampling gas is being supplied, the sensor 100 is brought into operation, and the detection means 410 detects the value of the electric signal of the sensor 100 at that time. The detection means 410 may measure after the value of the electric signal in each state is stabilized. When the sensor 100 is placed in a standby state and the sampling gas is supplied, the value of the electrical signal of the sensor 100 returns to its original value.

The value of the electrical signal in the standby state is compared with the value of the electrical signal in the operating state, and when a change in the electrical signal is observed, it can be determined that the sampling gas contains aldehyde. Moreover, since the magnitude of the change in the electric signal at that time correlates with the concentration of aldehyde, the concentration can also be calculated. The value of the electric signal detected by the detection means 410 may be recorded in a memory or the like of the control unit, and the value of the electric signal in the standby state may be compared with the value of the electric signal in the operating state.

Although the system 400 including the aldehyde detection sensor 100 is described in FIG. 4, the aldehyde detection sensor 200 (FIG. 2) and the aldehyde detection sensor 300 (FIG. 3) may be similarly used in place of the sensor 100.

EXAMPLES The embodiments of the present invention will be described in more detail below with reference to Examples, but the present invention is not limited to the scope of these Examples.

[Reagents and materials]
Reagents and materials used in the following examples are described. All reagents were used as received without purification. Two types of hydroxylamine salts represented by the following formulas were used and purchased from Tokyo Kasei Kogyo Co., Ltd.

Purified SWCNTs (PT200) from NanoC, USA were purchased and used as single-walled carbon nanotubes (SWCNTs). As electrodes, comb-shaped electrodes made of Au formed on a silicon substrate (manufactured by BVT Technologies, No. CC1.W1) were used. A distance between electrodes of 200 μm was used.

Poly(3-hexylthiophene-2,5-diyl) is available from E.I. E. Nesterov et al., Macromolecules, 2014, Vol. 47, p. cis-(2,2'-bithiophen)-5-ylbromo[1,3-bis(diphenylphosphino)propane]nickel(II) synthesized according to A. 506-516; Staubitz et al., Organic Letters, 2013, Vol. 15, p. 2-bromo-3-hexyl-5-iodothiophene synthesized according to 4666-4669.

I will explain in detail. A Schlenk tube containing a magnetic stirrer was dried by heating under vacuum, and was placed under an argon atmosphere using a vacuum line. 99 mg of 2-bromo-3-hexyl-5-iodothiophene and 2.5 mL of dehydrated tetrahydrofuran treated with a solvent refiner (manufactured by Nikko Hansen) were added and cooled to -20°C. To this solution, 214 μL of a 1.3 mol/L isopropylmagnesium chloride-lithium chloride complex in tetrahydrofuran solution (manufactured by Aldrich) was added dropwise at −20° C., stirred for 20 minutes, and then stirred at room temperature for 70 minutes.

To the reaction mixture, 0.2 mL of dehydrated tetrahydrofuran solution containing 5.4 mg of cis-(2,2'-bithiophen)-5-ylbromo[1,3-bis(diphenylphosphino)propane]nickel(II) was added and reacted at room temperature for 22 hours. After completion of the reaction, 1 mL of 3 mol/L hydrochloric acid was added to the reaction mixture, stirred for 30 minutes, and extracted with chloroform. The resulting organic layer was dried over sodium sulfate, filtered to remove the drying agent, and the solvent was distilled off under reduced pressure.

The resulting crude product was dissolved in 2.5 mL of tetrahydrofuran, added dropwise to 20 mL of methanol, and the resulting dispersoid was precipitated using a centrifuge. After repeating the decantation of the supernatant and the washing of the precipitate with methanol three times, the precipitate was dried under reduced pressure to obtain 35 mg of a deep red solid.

The molecular weight of this solid was determined by gel permeation chromatography (GPC) measurement. The molecular weights were Mw=25100 g/mol, Mn=21200 g/mol and Mw/Mn=1.17, and it was confirmed that the polymer poly(3-hexylthiophene-2,5-diyl) was synthesized. The obtained solid tetrahydrofuran solution had an orange to red color and had an absorption wavelength characteristic of polythiophene.

[Example 1]
In Example 1, O-4-nitrobenzylhydroxylamine hydrochloride was used as the hydroxylamine salt 110 (FIG. 1), SWCNT manufactured by NanoC was used as the semiconductor material 130 (FIG. 1), and an aldehyde detection sensor equipped with the switching mechanism 180 (FIG. 1), which is a DC motor, was manufactured.

FIG. 5 is a diagram showing a system with an aldehyde detection sensor according to Example 1. FIG.

SWCNTs (21.9 mg) were suspended in 29.1 mL of o-dichlorobenzene (o-DCB). The suspension was sonicated for 30 minutes at room temperature. The resulting suspension (approximately 0.5 mL) was diluted 10-fold with o-DCB and sonicated for an additional 30 minutes at room temperature to obtain o-DCB containing 0.1 mg/mL SWCNTs. The SWCNTs were dispersed and no visible SWCNT aggregates were observed. Approximately 1 microliter was drop-cast onto the comb electrode and dried to remove o-DCB. Six sensors were produced, and the electrical resistance value was measured with an electrical resistance meter, and was within the range of 30 to 80 kΩ. The electrode portion was rubbed with a cotton swab to partially remove the SWCNTs, thereby adjusting the electrical resistance to about 300 kΩ, thereby unifying the resistance of the sensor. Thus, the sensor responsive portion 150 (FIGS. 1 and 5) was manufactured. A spacer 170 (FIGS. 1 and 5), 0.2 mm thick and made of vinyl tape material, was then placed over the responsive section.

O-4-Nitrobenzyl hydroxylamine hydrochloride was added to methanol until saturation. One drop of the supernatant solution was drop-cast onto a PTFE membrane filter (Merck Millipore Omnipore, pore size 0.2 μm, JGWP04700). The methanol was dried in the atmosphere, and a rectangular piece of 6 mm in width and 3 mm in height was cut out with scissors to manufacture the reaction section 120 (FIGS. 1 and 5). About 0.2 mg of O-4-nitrobenzylhydroxylamine hydrochloride supported on the reaction part was estimated. Although O-4-nitrobenzylhydroxylamine hydrochloride is consumed by the reaction with formaldehyde, the amount of 0.2 mg is sufficiently excessive compared to formaldehyde (HCHO) present in the air at ppm order.

As shown in FIG. 5, the reaction section 120 was fixed to the tip of a metal piece installed on the rotary shaft of the DC motor. A switching mechanism 180 was constructed to switch between an operating state in which the reaction unit 120 is close to the response unit 150 by about 0.2 mm and a standby state in which the reaction unit 120 is separated from the response unit 150 by about 4 cm, depending on the direction of rotation of the DC motor. The direction of rotation of the DC motor can be arbitrarily switched by the direction of application of the DC voltage, and the voltage should be applied only at the time of switching. A 1.5 V D-cell battery was used as the DC power supply, and the direction of application was manually switched.

The aldehyde detection sensor 500 including the reaction section 120, the response section 150, the spacer 170, and the switching mechanism 180 was housed in a commercially available plastic container with a capacity of 150 mL and fixed with double-sided tape. The two electric wires connected to the electrodes of the response unit 150 are exposed outside the plastic container through a horizontal hole made in the plastic container, and connected to an ammeter and a power supply 420 as a detection means 410 to form an aldehyde detection system.

In addition, the two electric wires of the DC motor, which is the switching mechanism 180, are also exposed outside the plastic container through a horizontal hole opened in the plastic container, and by applying a DC voltage to these wires, the direction of rotation of the DC motor can be controlled to switch between the standby state and the operating state.

During the measurement of the aldehyde concentration, the aforementioned plastic container is provided with a lid to eliminate the influence of outside air. A sampling gas was supplied into the container at a constant flow rate of 300 mL/mL through two holes opened in the lid, and the switch mechanism 180 was used to switch between the standby state and the operating state.

Air with a relative humidity of 50% and a formaldehyde concentration of 2.3 ppm was supplied as a sampling gas. In the examples of the specification of the present application, a change in current value normalized by {(I _(t) -I ₀ )/I ₀ }×100(%) was used as the sensor response. Here, I ₀ is the current value in the standby state, and I _(t) is the current value t seconds after entering the operating state. The voltage applied to the response section 150 is 0.1V. The results are shown in FIG. 1000 seconds was used as t.

FIG. 6 is a diagram showing the response characteristics of the sensor according to Example 1 to formaldehyde.

First, the sensor 500 was placed in a standby state, and air containing 50% humidity (blank gas) was introduced into the plastic container containing the sensor 500 at a flow rate of 300 mL/min. The detected current value showed a constant value of about 0.28 μA and was stable. As shown in FIG. 6, after 6600 seconds from initiation, it was switched to active state and remained active until 7600 seconds with no significant response greater than 1%. At 7600 seconds it was returned to standby and maintained until 8600 seconds, again with no significant response. From the above results, it has been clarified that the response unit 150 hardly responds even when switching between the standby state and the operating state in an atmosphere in which formaldehyde does not exist.

Next, at the time point of 8600 seconds in FIG. 6, the gas introduced into the sensor 500 was switched from the blank gas to the atmosphere (sampling gas) with a humidity of 50% containing 2.3 ppm of formaldehyde and maintained until 9600 seconds. However, since the sensor 500 was in a standby state, no increase in the current value was observed. At 9600 seconds, the standby state was switched to the active state, and when the state was maintained until 10600 seconds, an increase in the current value was observed, and a significant response was observed in the response section. While the sampling gas was still introduced, the state was switched to the standby state at 10600 seconds and maintained until 16000 seconds. It was found that the current value decreased and the response unit 150 that responded to formaldehyde recovered to the original state.

At 16000 seconds, the standby state was switched to the active state and maintained until 17000 seconds, whereupon the increase in current value accompanying the response to formaldehyde was reproduced. While the sampling gas was being introduced, the state was switched to the standby state at 17000 seconds and maintained until 24000 seconds. It was found that the current value decreased and the sensor 500 responding to formaldehyde recovered to the original state.

At 24000 seconds, the standby state was switched to the active state, and when it was maintained until 25000 seconds, the increase in current value accompanying the response to formaldehyde was reproduced. While the sampling gas was being introduced, the state was switched to the standby state at 25000 seconds and maintained until 30000 seconds. It was found that the current value decreased and the sensor 500 responding to formaldehyde recovered to its original state.

From the above results, the sensor of the present invention equipped with a switching mechanism for switching between the standby state and the operating state can detect formaldehyde as the amount of change in electrical resistance using only the sampling gas without using a blank gas. In the standby state, even in the presence of formaldehyde, the sensor response recovered and returned to the state before the response.

[Example 2]
In Example 2, hydroxylamine hydrochloride (NH ₂ OH.HCl) was used as the hydroxylamine salt 110 (FIG. 1), poly(3-hexylthiophene-2,5-diyl), which is a conductive polymer, was used as the semiconductor material 130 (FIG. 1), and an aldehyde detection sensor equipped with the switching mechanism 180 (FIG. 1), which is a DC motor, was manufactured.

A diagram showing a system equipped with an aldehyde detection sensor according to _Example 2 is similar to FIG.

0.6 mL of tetrahydrofuran was added to 0.45 mg of poly(3-hexylthiophene-2,5-diyl) and completely dissolved by sonication and heating to about 50°C. About 0.5 microliters of the resulting solution was drop-cast onto a comb electrode and dried to remove tetrahydrofuran. Six sensors were produced, and the electrical resistance value was measured with an electrical resistance meter, and found to be within the range of 15-30 MΩ. Thus, the responsive portion 150 (FIG. 1) of the sensor was manufactured. A spacer 170 (FIG. 1), 0.2 mm high and made of vinyl tape material, was then placed over the responsive section.

Hydroxylamine hydrochloride was added to methanol until saturation. One drop of the supernatant solution was drop-cast onto a hydrophilic PTFE membrane filter (Merck Millipore Omnipore, pore size 0.2 μm, JGWP04700). The methanol was dried in the atmosphere, and a rectangular piece with a width of 6 mm and a length of 3 mm was cut out with scissors to manufacture the reaction section 120 (FIG. 1). The amount of hydroxylamine hydrochloride supported on the reaction site was estimated at about 0.5 mg.

Example 2 is the same as Example 1 except that the hydroxylamine salt 120 and the semiconductor material 130 are changed.

As the sampling gas, air containing 50% humidity (blank gas) or air containing 50% relative humidity and 2.3 ppm formaldehyde concentration was supplied at a flow rate of 300 mL. The voltage applied to the response section 150 is 1.0V. The results are shown in FIGS. 7 and 8. FIG. 300 seconds was used as t.

FIG. 7 is a diagram showing the response characteristics of the sensor according to Example 2 to a blank gas.
FIG. 8 is a diagram showing the response characteristics of the sensor according to Example 2 to formaldehyde.

First, the sensor was placed in a standby state, and air containing 50% humidity (blank gas) was introduced into the plastic container containing the sensor at a flow rate of 300 mL/min. As shown in FIG. 7, after 900 seconds from the start, the switch was switched to the operating state, and when the operating state was maintained until 1200 seconds, a decrease in the current value (increase in the resistance value) was observed. This is an effect due to the proximity of the reaction section 120 to the response section 150, and is different from the response to formaldehyde, and the direction of response (increase or decrease in current value) is also opposite to that of formaldehyde, making it easy to distinguish.

At 1200 seconds it was returned to standby and maintained until 1500 seconds with no significant response. From the above results, it has been clarified that the current value in the response unit 150 does not increase even if the standby state and the operating state are switched in an atmosphere in which formaldehyde does not exist.

Next, in the standby state, changes in the current value of the sensor according to Example 2 placed in an atmosphere of 50% humidity air (sampling gas) containing 2.3 ppm formaldehyde are shown from 0 to 600 seconds in FIG. 8. The current value was stable. On the other hand, at the time of 600 seconds in FIG. 8, the standby state was switched to the operating state and maintained until 900 seconds. While the sampling gas was being introduced, the state was switched to the standby state at 900 seconds and maintained until 2900 seconds. Immediately after the switching, the current value stopped increasing and a slight current value decrease (recovery) was observed. It can be expected that the response unit 150 will recover to the original state by being in the standby state for a sufficiently long time.

At 2900 seconds, the standby state was switched to the active state and maintained until 3200 seconds, whereupon the increase in current value accompanying the response to formaldehyde was reproduced. While the sampling gas was being introduced, the state was switched to the standby state at 3200 seconds and maintained until 4000 seconds. Immediately after the switching, the current value stopped increasing.

From the above results, it was shown that a wide range of hydroxylamine salts and semiconductor materials can be used for the reaction section 120 and the response section 150 that constitute the aldehyde detection sensor 100 of the present invention.

[Example 3]
In Example 3, O-4-nitrobenzylhydroxylamine hydrochloride was used as the hydroxylamine salt 110 (FIG. 2), SWCNT manufactured by NanoC was used as the semiconductor material 130 (FIG. 2), and an aldehyde detection sensor provided with the switching mechanism 210 (FIG. 2), which is a shielding wall, was manufactured. The same response unit 150 as in the first embodiment was used.

FIG. 9 is a diagram showing a procedure for manufacturing a reaction section according to Example 3;

As shown in FIG. 9, the reaction section 120 uses O-4-nitrobenzylhydroxylamine hydrochloride (manufactured by Tokyo Chemical Industry Co., Ltd.) as the hydroxylamine salt 110, and adopts a type in which the solid powder of the hydroxylamine salt 110 is sandwiched between porous filters.

As shown in FIG. 9, a vinyl tape made of vinyl chloride with a thickness of 2 mm (manufactured by Scotch) was punched with a leather punch to make a circular hole with a diameter of 4 mm. Two sets of constructs consisting of this vinyl tape and a hydrophobic membrane filter were prepared, and about 2 mg of O-4-nitrobenzyl hydroxylamine hydrochloride powder was placed on one of the hydrophobic membrane filter sites (the side of the vinyl tape not having the adhesive surface), and the other construct was covered so that the O-4-nitrobenzyl hydroxylamine hydrochloride was sandwiched between the two membrane filters, and the two constructs were adhered. As a result, the solid O-4-nitrobenzylhydroxylamine hydrochloride is sandwiched and held by the porous filter, and the acid vapor generated by the reaction with formaldehyde passes through the porous filter and reaches the response unit 150 in the operating state.

FIG. 10 is a diagram showing a system with an aldehyde detection sensor according to Example 3;

The reaction section 120 was placed on the response section 150 via a spacer 170 of vinyl tape material having a thickness of 0.2 mm (FIGS. 2 and 10). In Example 3, the reaction section 120 and the response section 150 are not movable.

Furthermore, between the reaction section 120 and the response section 150, a rectangular piece (width 1.6 cm, length 8.5 cm) of a gas barrier film (Lamizip, AL-D manufactured by Seinichi Co., Ltd.) that functions as a shielding wall for the acid vapor generated in the reaction section 120 was sandwiched, and the switching mechanism 210 (FIG. 2) for switching between the standby state and the operating state was formed by inserting and removing the small piece of the gas barrier film as shown in FIG.

The aldehyde detection sensor was housed in a commercially available plastic container with a capacity of 150 mL and fixed with double-sided tape. The two electric wires connected to the electrodes of the response unit 150 are exposed outside the plastic container through a horizontal hole made in the plastic container, and connected to an ammeter and a power supply 420 as a detection means 410 to form an aldehyde detection system 1000.

In addition, the gas barrier film, which is the switching mechanism 210, is partly exposed outside the plastic container through a hole (about 2.5 cm in width and about 2 mm in height) made in the plastic container.

During the measurement of the aldehyde concentration, as in Example 1, the aforementioned plastic container was covered with a lid to eliminate the influence of outside air. A sampling gas was supplied into the container at a constant flow rate of 300 mL/mL through two holes opened in the lid, and the switch mechanism 210 was used to switch between the standby state and the operating state.

Atmospheric air with a relative humidity of 50% and a formaldehyde concentration of 0.17 ppm or 2.3 ppm was supplied as the sampling gas. As the response of the sensor, a value obtained by normalizing the change in current value by {(I _(t) -I ₀ )/I ₀ }×100(%) was used. Here, I ₀ is the current value in the standby state, and I _(t) is the current value t seconds after entering the operating state. The voltage applied to the response section 150 is 1.0V. The results are shown in FIG. 100 seconds was used as t.

FIG. 11 is a diagram showing the response characteristics of the sensor according to Example 3 to formaldehyde.

First, in the sensor, the switching mechanism 210, which is a shielding plate (shielding wall), is placed between the reaction unit 120 and the response unit 150 in a standby state, and the air containing 50% humidity and 0.17 ppm formaldehyde (sampling gas) is introduced into the plastic container containing the sensor at a flow rate of 300 mL/min. The detected current value was almost constant and stable.

As shown in FIG. 11, after 1300 seconds from the start, it was switched to the operating state, and when the operating state was maintained until 1400 seconds, the current value increased, and a sufficient response was obtained within 100 seconds to formaldehyde at a low concentration of about twice the environmental standard (0.08 ppm). After returning to the standby state at 1400 seconds and maintaining it until 2300 seconds, it was observed that the sensor response gradually recovered. Furthermore, at 2300 seconds the sensor was armed and maintained until 2400 seconds, reproducing the response to formaldehyde.

At 2400 seconds in FIG. 11, it returned to the standby state. Furthermore, at 3300 seconds, while maintaining the standby state, the gas was switched to a blank gas with a humidity of 50%. No response was seen with this switch. Subsequently, at 4300 seconds, when switching to the operating state, a slight increase in the current value was observed. This is probably because the gas inside the plastic container was not sufficiently replaced. At 4400 seconds, the state was switched to the standby state, and purging with blank gas was continued. Switched to working state at 5700 seconds and maintained until 5800 seconds with negligible response. At 5800 seconds, it switched to the standby state and continued purging with blank gas.

At 7800 seconds, the sampling gas was switched to 50% relative humidity and 0.17 ppm formaldehyde. At 8200 seconds, it was switched to the working state and maintained until 8300 seconds, resulting in a response to formaldehyde. At 8300 seconds, it switched to the standby state. At 8700 seconds, the sampling gas was switched to a high concentration sampling gas containing 50% relative humidity and 2.3 ppm formaldehyde. A decrease in current value is observed, but this is due to a phenomenon associated with adsorption to SWCNTs, which is also observed in general organic solvent vapor.

At 9200 seconds, the device was switched to the operating state and maintained until 9300 seconds. A larger increase in current value was obtained than in the case of 0.17 ppm formaldehyde, indicating that the response intensity depends on the formaldehyde concentration. When the standby state was set at 9300 seconds, a rapid decrease in the current value was also observed. Characteristic response patterns associated with switching operations may be used for analysis of concentrations and chemical species.

From the above results, it was shown that various principles can be adopted for the switching mechanism for switching between the standby state and the operating state, that powdered hydroxylamine salts can be adopted for the reaction unit 120, and that there is a correlation between the response intensity and the formaldehyde concentration.

[Example 4]
In Example 4, the aldehyde detection sensor used in Example 3 was used to examine the response to acetaldehyde.

Air containing 70% relative humidity and 10 ppm acetaldehyde concentration was supplied as a sampling gas at a flow rate of 100 mL/min. The voltage applied to the response section 150 is 1.0V. The results are shown in FIG. Acetaldehyde was adjusted by collecting saturated vapor of acetaldehyde (manufactured by Sigma-Aldrich) with a syringe and mixing it with the air in a 5 L gas collection bag. The concentration was confirmed with a detector tube (92M, manufactured by Gastech).

FIG. 12 is a diagram showing the response characteristics of the sensor according to Example 4 to acetaldehyde.

As in Example 3, first, in the sensor, the switching mechanism 210, which is a shielding plate, was inserted between the reaction unit 120 and the response unit 150, and was placed in a standby state. Then, an atmosphere (sampling gas) containing 70% humidity and 10 ppm acetaldehyde was introduced into the plastic container containing the sensor at a flow rate of 100 mL/min. Since it was in the standby state, the current value was almost constant and stable.

As shown in FIG. 12, after 1000 seconds from the start, the device was switched to the operating state, and when the operating state was maintained until 1200 seconds, the current value increased, indicating a response to acetaldehyde. After returning to the standby state at 1200 seconds and maintaining it until 3000 seconds, it was observed that the sensor response gradually recovered.

From the above results, it became clear that the aldehyde detection sensor and the system using the same according to the present invention can be applied not only to formaldehyde but also to other aldehydes.

The aldehyde detection sensor of the present invention can detect aldehyde by a change in electric signal without preparing a blank gas. Since the aldehyde detection sensor of the present invention can constantly monitor aldehyde, it functions as an alarm type detection sensor. Since it is not necessary to prepare a blank gas, it is expected that the size and cost of the device can be reduced.

100, 200, 300, 500 Aldehyde detection sensor 110 Hydroxylamine salts 120 Reactor 130 Semiconductor material 140 Electrode 150 Responder 160 Substrate 170 Spacer 180, 210, 310 Switching mechanism 320 Sensor chamber 400, 1000 Aldehyde detection system 410 Detecting means 420 Power supply

Claims (16)

a reaction unit that reacts with the aldehyde in the sampling gas to generate acid vapor;
a response unit that changes an electrical signal by the acid generated in the reaction unit and is located apart from the reaction unit;
a switching mechanism for switching a separation state between the reaction unit and the response unit,
The switching mechanism is a shielding wall inserted between the reaction section and the response section that moves the reaction section and/or the response section. An aldehyde detection sensor that switches between a standby state in which acid generated in the reaction section does not reach the response section and an operating state in which acid generated in the reaction section reaches the response section, depending on whether the shield wall is inserted or not, or whether the flow direction of the sampling gas is switched so that the response section is upstream or the reaction section is upstream. 2. The sensor of claim 1, wherein the responsive portion comprises an electrode carrying a semiconductor material whose electrical resistance changes as the electrical signal changes with the acid. 3. A sensor according to claim 1 or 2, wherein the aldehyde is formaldehyde. The sensor according to any one of claims 1 to 3, wherein the reaction section contains at least hydroxylamine salts. 5. The sensor of claim 4, wherein the hydroxylamine salts are neutralized salts selected from the group consisting of halides, nitrates, and trifluoroacetates of hydroxylamine ( _NH2OH ) or _NH2OR , where R is an aromatic, cyclic or acyclic carbon compound or derivative thereof. 6. A sensor according to claim 4 or 5, wherein said hydroxylamine salts are supported on a porous material. The hydroxylamine salts are in a crystalline or powdered state,
6. The sensor according to claim 4 or 5, wherein said hydroxylamine salts are enclosed by a porous filter having air permeability. 8. The sensor of claim 7, wherein said porous filter is selected from the group consisting of hydrophobic polymers, hydrophilic polymers, porous glasses, porous carbon materials and porous oxides. 9. The sensor of Claim 8, wherein the hydrophobic polymer is polytetrafluoroethylene (PTFE). 3. The sensor of claim 2 , wherein the semiconductor material is a carbon material or a conductive polymer. 11. The sensor of claim 10, wherein the carbon material is a carbon material selected from the group consisting of carbon nanotubes, carbon nanohorns, graphene, fullerenes and derivatives thereof. 11. The sensor of claim 10, wherein the conductive polymer is a conductive polymer selected from the group consisting of polythiophene, polyaniline, polypyrrole, polyacetylene, polyparaphenylene vinylene, polyparaphenylene and derivatives thereof. The sensor according to any one of claims 1 to 12, comprising a spacer between said reaction portion and said response portion. An aldehyde detection system comprising an aldehyde detection sensor and detection means,
The aldehyde detection sensor is the aldehyde detection sensor according to any one of claims 1 to 13 ,
The system, wherein the detection means detects a change in electrical signal generated by the aldehyde detection sensor. 15. The system of claim 14 , wherein the aldehyde detection sensor is connected to a power supply and the detection means is an ammeter or a voltmeter. 16. A system according to claim 14 or 15 , wherein said aldehyde is formaldehyde.