JP2018530740A - Tin-doped photocatalytic formaldehyde sensing material, method for producing the same, and formaldehyde sensor - Google Patents

Abstract

The present invention relates to a tin-doped photocatalytic formaldehyde sensing material containing zinc oxide nanoparticles and a tin-based additive, a method for producing the same, and a formaldehyde sensor. When producing the material, first, a solution A in which zinc oxide nanoparticles synthesized in advance are uniformly dispersed in a tin salt solution is obtained, and then a precipitate in which all of the solvent is evaporated while stirring the solution A is obtained. The product B is obtained, and then the precipitate B is sintered at a high temperature to obtain the product C which is a photocatalytic formaldehyde sensing material. This method provides a low-cost, high-sensitivity, high-selectivity photocatalytic formaldehyde sensing material, which can lower the detection limit of formaldehyde to 0.1 ppm and increase the ethanol selectivity of the material.

Description

Detailed Description of the Invention

  〔Technical field〕

  The present invention belongs to the technical field of formaldehyde gas monitoring measurement and formaldehyde sensor, and specifically relates to a tin-doped photocatalytic formaldehyde sensing material, a method for producing the same, and a formaldehyde sensor.

[Background Technology]
Long-term contact with formaldehyde gas that exceeds safe concentration standards is harmful to human health and causes burning in the eyes and throat, breathing difficulties and life-threatening diseases such as nasal cancer and myeloid leukemia there is a possibility. At present, formaldehyde is the most concerned indoor pollutant gas in China because formaldehyde pollution in China is very serious and about 70% of the houses just after they are installed have the problem of formaldehyde contamination.

  Sensor technology is very important for products that control air quality. This is because when consumers have doubts about the true role of a product that controls air quality, they will begin to doubt that product. Conventionally, commercial sensors are mainly based on electrochemistry, and such sensors are very expensive because platinum electrodes are used. Also, the accuracy, stability and selectivity of this type of sensor are all insufficient.

  Compared to electrochemical sensors, semiconductor sensors have special advantages such as low cost and long service life, and have a lot of room for improvement. All the conventional commercial sensors need to operate at 200 ° C. or higher, but at this temperature, almost all organic contaminants react and are detected, so the selectivity by the sensor is very low. Thus, in order to improve the selectivity to gas, some researchers have produced photocatalytic semiconductor formaldehyde sensors that operate at room temperature. However, in practice, these sensors have a lower detection limit (greater than 1 ppm). ) Remained high. Table 1 lists conventional sensing materials and their challenges.

ところで、中国特許出願ＣＮ２００７１５３３４１（ホルムアルデヒド空気感知材料およびホルムアルデヒド空気センサ装置の製造方法）には、ホルムアルデヒドガス感知材料およびその製造方法、並びにホルムアルデヒドガスセンサデバイスの製造方法が開示されている。該感知材料はＳｎＯ_２−ＴｉＯ_２二元ナノ粉末からなり、Ｔｉ／Ｓｎのモル比が０．２〜０．５であり、且つ２％〜５％のカドミウムがドープされているものである。また、該材料を無水エタノールおよびポリエチレングリコールと共混練して得たペーストを電極管に均一に塗布し、該電極管を４００℃下で２〜４時間焼きなました後、溶接、エージング、シールすることにより、ホルムアルデヒドガスセンサが得られる。該センサは、動作温度が低く、ホルムアルデヒドに対する感度が高く、且つベンゼン、トルエン、キシレン、アンモニア等の室内汚染ガスからの干渉に対する耐性が非常に高く、更に応答時間と回復時間が非常に短いという特性を有し、主に室内装で生じたホルムアルデヒドガスの検知に用いられる。しかしながら、該センサの動作温度は２６０〜３００℃であり、このような温度下ではほとんどすべての室内有機汚染物が感知材料の表面で酸化されることになるため、材料による選択性が不十分であり、特にエタノールとホルムアルデヒドとを十分に区別することができない。また、該技術の検知下限値は２０ｐｐｍであり、安全濃度基準（０．０６ｐｐｍ）より２桁も高い。

By the way, Chinese Patent Application CN2007153341 (Method for Manufacturing Formaldehyde Air Sensing Material and Formaldehyde Air Sensor Device) discloses a formaldehyde gas sensing material, a method for manufacturing the same, and a method for manufacturing a formaldehyde gas sensor device. The sensing material is made of SnO ₂ —TiO ₂ binary nanopowder, has a Ti / Sn molar ratio of 0.2 to 0.5, and is doped with 2% to 5% cadmium. Also, a paste obtained by co-kneading the material with absolute ethanol and polyethylene glycol is uniformly applied to an electrode tube, the electrode tube is annealed at 400 ° C. for 2 to 4 hours, and then welded, aged, and sealed. Thus, a formaldehyde gas sensor is obtained. The sensor is characterized by low operating temperature, high sensitivity to formaldehyde, very high resistance to interference from indoor pollutant gases such as benzene, toluene, xylene, ammonia, etc., and very short response time and recovery time. It is mainly used to detect formaldehyde gas generated in the room interior. However, the operating temperature of the sensor is 260-300 ° C., and under such temperatures almost all indoor organic contaminants will be oxidized on the surface of the sensing material, so the selectivity by the material is insufficient. In particular, ethanol and formaldehyde cannot be sufficiently distinguished. Moreover, the detection lower limit of this technique is 20 ppm, which is two orders of magnitude higher than the safe concentration standard (0.06 ppm).

[Content of the Invention]
The present invention provides a low-cost, high-sensitivity, high-selectivity tin-doped photocatalytic formaldehyde sensing material and a formaldehyde sensor using the material.

  The technical solution in the present invention is as follows.

  The photocatalytic formaldehyde sensing material according to the present invention includes zinc oxide nanoparticles and a tin-based additive.

  Furthermore, the particle diameter of the zinc oxide nanoparticles is 20 nm to 50 nm, more preferably 30 nm.

  Furthermore, the tin-based additive is tin oxide, and tin oxide accounts for 0.3% to 5%, more preferably 2% of the total weight of zinc oxide and tin oxide.

The method of synthesizing the photocatalytic formaldehyde sensing material is as follows:
(1) a step of uniformly dispersing zinc oxide nanoparticles synthesized in advance in a tin salt solution to obtain a solution A;
(2) evaporating all of the solvent while stirring the solution A to obtain a precipitate B;
Sintering the precipitate B at a high temperature to obtain a product C which is a photocatalytic formaldehyde sensing material (3).

  Further, the method includes a step (4) of preparing a slurry by pulverizing the product C and uniformly dispersing it in a solvent, and applying the slurry to an electrode and drying to obtain a thin-film sensing material.

Further, the tin salt in step (1) is preferably stannous sulfate (SnSO ₄ ), and tin chloride (SnCl ₄ ), stannous oxalate (SnC ₂ O ₄ ), or the like may be used. Among these, when stannous sulfate is used, the performance of the obtained photocatalytic formaldehyde sensing material is the best.

  Further, in step (2), the solvent is evaporated at 80 to 120 ° C., preferably 80 ° C. so that the sample is completely dried after evaporating with stirring at 80 ° C. until all of the solvent is evaporated. Dry under 12 h and dry under 120 ° C. for 2 h.

  Further, in step (3), the sintering is performed at 400 to 500 ° C. The optimum sintering temperature is 450 ° C.

  A formaldehyde sensor according to the present invention is a formaldehyde sensor using the photocatalytic formaldehyde sensing material, and includes an electrode coated with the photocatalytic formaldehyde sensing material and ultraviolet rays for irradiating the electrode region when performing detection. An ultraviolet light source to be provided; and a detection circuit connected to the electrode for detecting a change in a photoconductive effect generated on the formaldehyde sensing material when the electrode region is irradiated with ultraviolet light, and for measuring a content of formaldehyde Is a formaldehyde sensor.

  The present invention provides a photocatalytic formaldehyde sensing material with low cost, high sensitivity and high selectivity. By optimizing the amount of tin doped into zinc oxide, the lower limit of detection of formaldehyde is reduced to 0.1 ppm, and the ethanol selectivity by the material is improved. Compared with the prior art, the present invention can greatly reduce the cost, increase the selectivity, and further significantly improve the detection lower limit.

  In addition, there are traditional semiconductor sensors that use zinc oxide and tin oxide as sensitive materials. However, the principle of the conventional heated semiconductor sensor is significantly different from that of the photocatalytic sensor of the present invention. The effect of the contained tin is also different. In the conventional heated semiconductor sensor, tin oxide itself is a sensitive material, and when VOC (volatile organic compound) reacts with oxygen on the surface of tin oxide, the electric resistance value of tin oxide changes and detection is possible. Realized. On the other hand, the photocatalytic sensor of the present invention uses tin oxide as an additive for zinc oxide, which is a sensitive material, and tin oxide itself has no ability as a photocatalyst. In addition, the effect | action by a tin oxide is extending the lifetime of the photo-induced carrier production | generation capability of zinc oxide, and improving the capability as a photocatalyst of a zinc oxide.

[Mode for Carrying Out the Invention]
Hereinafter, the present invention will be described in detail with reference to specific examples and drawings in order to make the above objects, features, and advantages of the present invention easier to understand.

  FIG. 1 is a flowchart of a method for synthesizing a photocatalytic formaldehyde sensing material of the present invention, which includes the following steps.

1) Disperse pre-synthesized zinc oxide nanoparticles in a tin salt solution (eg SnSO ₄ + deionized water).

  2) Evaporate the solution, preferably at 80-120 ° C., more preferably at 80 ° C. with stirring until all of the solvent is evaporated, then completely dry the sample Dry at 80 ° C. for 12 h and at 120 ° C. for 2 h.

  3) The obtained precipitate is sintered for a certain period of time at 400 to 500 ° C. (the optimum sintering temperature is 450 ° C.), and tin oxide derived from tin salt is obtained after sintering.

  4) The obtained solid product is pulverized to a powder and dispersed in an ethanol solution to prepare a slurry.

  Then, the intended formaldehyde sensor is obtained by spin-coating the obtained slurry on a comb-shaped electrode and drying the solvent.

  Zinc oxide nanoparticles (20 to 50 nm, optimum particle diameter 30 nm) have a large specific surface area, so that they easily adsorb formaldehyde and have good photoconductive properties. In order to detect formaldehyde, a tin-based additive is very important, and the amount of tin added is a point of the present invention. The weight ratio of tin (the ratio of tin oxide to the total weight of tin oxide and zinc oxide) is 0.3% to 5%, and the optimal ratio is 2%. Further, the anion of the tin-based additive is important, and sulfate ion is most preferable. Also, the sintering temperature is very important. The sintering temperature is 400 to 500 ° C, and the optimum temperature is 450 ° C. Further, the solvent for preparing the slurry before spin coating on the electrode is very important, and it is preferable to use absolute ethanol.

Example 1 Material Synthesis and Measurement Step 1: Synthesis of Zinc Oxide Nanoparticles 10.77 g ZnSO ₄ .7H ₂ O (375 mmol) was dissolved in 25 mL deionized water and the resulting solution was 50 mL 100 g. / L (1.36 mmol / L) was added dropwise to NH ₄ HCO ₃ solution and stirred for 1 h in a 40 ° C. water bath. The supernatant was removed and the precipitate was washed three times with 15 mL of deionized water each time, after which the precipitate was dried at 80 ° C. for 12 h and then dried at 120 ° C. for 2 h. After completion of drying, the sample was placed in a muffle furnace and sintered at 500 ° C. for 2 hours.

Step 2: Addition of tin 0.4 g of preformed zinc oxide nanoparticles are weighed and dispersed in 60 mL of a tin salt solution (SnSO ₄ : 0.007 g), and this solution is stirred at 80 ° C. with a solvent. All was evaporated. Thereafter, the precipitate was dried at 80 ° C. for 12 hours and then dried at 120 ° C. for 2 hours. Next, the precipitate was sintered at 450 ° C.

Step 3: Preparation of sensor The solid product was pulverized to a fine powder and uniformly dispersed in absolute ethanol to prepare a slurry. Thereafter, the prepared slurry was applied to the electrode, and ethanol was evaporated with a dryer (1 min) to obtain a thin-film sensing material.

(Method for producing sensor electrode)
In this example, a sensor electrode substrate having a comb-shaped electrode pattern was manufactured by using a normal method for manufacturing a PCB substrate. The groove width of the comb-shaped electrode was 100 μm, and the electrode portion was subjected to gold plating. In addition, a sensitive material was dropped onto the upper comb-tooth region, and the two lower large electrodes were connected to a detection circuit. When measuring formaldehyde, the comb-shaped electrode is directly irradiated with ultraviolet rays of 365 nm, and the detection circuit detects a change in the photoconductive effect generated on the sensitive material by the ultraviolet rays.

Step 4: Formaldehyde detection The UV light source produces a photocatalytic effect on sensitive materials and is used to detect formaldehyde. As the ultraviolet light source, an ultraviolet lamp having a wavelength of 365 nm or an ultraviolet light emitting diode having a wavelength of 385 nm may be used. When the ultraviolet light source is turned on, the electrical resistance of the sensor starts to decrease due to the photoconductive effect of the zinc oxide material, and after a predetermined time (usually 5 minutes), the electrical resistance value becomes a stable value. The electric resistance value in the case of clean air is R ₀ . If the sensor is moved from clean air into air containing formaldehyde, the electrical resistance of the sensor will similarly decrease. After a predetermined time (typically 3 minutes), the electrical resistance value becomes a stable value, the electric resistance value in this case the R _s. The formaldehyde concentration can be calculated from R _s / R ₀ based on a predetermined correlation. After the detection, formaldehyde adsorbed on the sensing material is decomposed and removed by the effect of the photocatalyst, so that the electric resistance value of the sensor can be automatically restored to _R0 .

<Example 2> Introduction of tin from different sources (Fig. 2)
_a) SnCl 4 · _5H 2 O
0.400 g of synthesized ZnO particles were weighed and dissolved in 110 ml of deionized water, and 0.009 g of SnCl ₄ .5H ₂ O was added. The solution was then sonicated for 5 min and heated with stirring with a magnetic stirrer until all of the solvent was evaporated. The obtained solid was placed in an oven at 80 ° C. and dried for 8 hours, and the oven temperature was adjusted to 120 ° C. and dried for 2 hours. Thereafter, it was put in a 450 ° C. muffle furnace and sintered for 4 hours.

b) SnC ₂ O ₄
0.400 g of synthesized ZnO particles were weighed and dissolved in 110 ml of deionized water, and 0.00056 g of SnC ₂ O ₄ was added. The solution was then sonicated for 5 min and heated with stirring with a magnetic stirrer until all of the solvent was evaporated. The obtained solid was placed in an oven at 80 ° C. and dried for 8 hours, and the oven temperature was adjusted to 120 ° C. and dried for 2 hours. Thereafter, it was put in a 450 ° C. muffle furnace and sintered for 4 hours.

c) SnSO ₄
0.400 g of synthesized ZnO particles were weighed and dissolved in 80 ml of deionized water, and 0.007 g of SnSO ₄ was added. The solution was then sonicated for 5 min and heated with stirring with a magnetic stirrer until all of the solvent was evaporated. The obtained solid was placed in an oven at 80 ° C. and dried for 8 hours, and the oven temperature was adjusted to 120 ° C. and dried for 2 hours. Thereafter, it was put in a 450 ° C. muffle furnace and sintered for 4 hours.

FIG. 2 shows the response intensity of the sample to 1 ppm formaldehyde for each tin-based additive. When SnSO ₄ is used, it can be seen that the effect of detecting formaldehyde is the best, that is, the performance of the obtained photocatalytic formaldehyde sensing material is the best.

<Example 3> Different Sn contents, that is, weight ratio of tin oxide to "zinc oxide + tin oxide" (FIG. 3)
a) 0.3% 0.400 g of pre-synthesized ZnO nanoparticles were weighed and dissolved in 110 ml of deionized water, 0.002 g of SnSO ₄ was added, and the solution was sonicated for 5 min. . The solution was heated with stirring with a magnetic stirrer until all of the solvent had evaporated. The obtained solid was put in an oven at 80 ° C. and dried for 8 hours, further adjusted to an oven temperature of 120 ° C. and dried for 2 hours, and then placed in a muffle furnace at 450 ° C. for 4 hours.

b) In the case of 1% 0.400 g of pre-synthesized ZnO nanoparticles were weighed and dissolved in 110 ml of deionized water, 0.007 g of SnSO ₄ was added, and the solution was sonicated for 5 min. The solution was heated with stirring with a magnetic stirrer until all of the solvent had evaporated. The obtained solid was put in an oven at 80 ° C. and dried for 8 hours, further adjusted to an oven temperature of 120 ° C. and dried for 2 hours, and then placed in a muffle furnace at 450 ° C. for 4 hours.

c) In the case of 3% 0.400 g of pre-synthesized ZnO nanoparticles were weighed and dissolved in 110 ml of deionized water, 0.021 g of SnSO ₄ was added, and the solution was sonicated for 5 min. The solution was heated with stirring with a magnetic stirrer until all of the solvent had evaporated. The obtained solid was put in an oven at 80 ° C. and dried for 8 hours, further adjusted to an oven temperature of 120 ° C. and dried for 2 hours, and then placed in a muffle furnace at 450 ° C. for 4 hours.

d) In the case of 5% 0.400 g of pre-synthesized ZnO nanoparticles were weighed and dissolved in 110 ml of deionized water, 0.030 g of SnSO ₄ was added, and the solution was sonicated for 5 min. The solution was heated with stirring with a magnetic stirrer until all of the solvent had evaporated. The obtained solid was put in an oven at 80 ° C. and dried for 8 hours, further adjusted to an oven temperature of 120 ° C. and dried for 2 hours, and then placed in a muffle furnace at 450 ° C. for 4 hours.

  FIG. 3 shows the response intensity of the sample with respect to 1 ppm formaldehyde according to the tin doping ratio. When the weight ratio of tin oxide to “zinc oxide + tin oxide” is 1%, it can be seen that the response to formaldehyde is most remarkable and the effect is the best.

<Example 4> Different sample sintering temperatures (FIG. 4)
a) In the case of 350 ° C. 0.400 g of pre-synthesized ZnO nanoparticles were weighed and dissolved in 110 ml of deionized water, 0.007 g of SnSO ₄ was added, and the solution was sonicated for 5 min. The solution was heated with stirring with a magnetic stirrer until all of the solvent had evaporated. The obtained solid was put in an oven at 80 ° C. and dried for 8 hours, and further, the temperature of the oven was adjusted to 120 ° C. and dried for 2 hours. Thereafter, the samples were each sintered at 350 ° C. for 4 hours.

b) In the case of 400 ° C. 0.400 g of pre-synthesized ZnO nanoparticles were weighed and dissolved in 110 ml of deionized water, 0.007 g of SnSO ₄ was added, and the solution was sonicated for 5 min. The solution was heated with stirring with a magnetic stirrer until all of the solvent had evaporated. The obtained solid was put in an oven at 80 ° C. and dried for 8 hours, and further, the temperature of the oven was adjusted to 120 ° C. and dried for 2 hours. Thereafter, the samples were each sintered at 400 ° C. for 4 hours.

c) At 450 ° C. 0.400 g of pre-synthesized ZnO nanoparticles were weighed and dissolved in 110 ml of deionized water, 0.007 g of SnSO ₄ was added, and the solution was sonicated for 5 min. The solution was heated with stirring with a magnetic stirrer until all of the solvent had evaporated. The obtained solid was put in an oven at 80 ° C. and dried for 8 hours, and further, the temperature of the oven was adjusted to 120 ° C. and dried for 2 hours. Thereafter, the samples were each sintered at 450 ° C. for 4 hours.

d) At 500 ° C. 0.400 g of pre-synthesized ZnO nanoparticles were weighed and dissolved in 110 ml of deionized water, 0.007 g of SnSO ₄ was added, and the solution was sonicated for 5 min. The solution was heated with stirring with a magnetic stirrer until all of the solvent had evaporated. The obtained solid was put in an oven at 80 ° C. and dried for 8 hours, and further, the temperature of the oven was adjusted to 120 ° C. and dried for 2 hours. Thereafter, the samples were each sintered at 500 ° C. for 4 hours.

  FIG. 4 shows the response intensity of the tin-doped sample with respect to 1 ppm formaldehyde for each sintering temperature. It can be seen that the optimum sintering temperature is 450 ° C.

<Example 5> Comparison of tin-based additive and cadmium-based additive (FIG. 5)
0.400 g of pre-synthesized ZnO nanoparticles were weighed and dissolved in 110 ml of deionized water, 0.007 g of SnSO ₄ was added, and the solution was sonicated for 5 min. The solution was heated with stirring with a magnetic stirrer until all of the solvent had evaporated. The obtained solid was put in an oven at 80 ° C. and dried for 8 hours, and further, the temperature of the oven was adjusted to 120 ° C. and dried for 2 hours. Thereafter, the samples were each sintered at 450 ° C. for 4 hours.

0.400 g of pre-synthesized ZnO nanoparticles were weighed and dissolved in 110 ml of deionized water, 0.016 g of 3CdSO ₄ · 8H ₂ O was added, and the solution was sonicated for 5 min. The solution was heated with stirring with a magnetic stirrer until all of the solvent had evaporated. The obtained solid was put in an oven at 80 ° C. and dried for 8 hours, and further, the temperature of the oven was adjusted to 120 ° C. and dried for 2 hours. Thereafter, the samples were each sintered at 450 ° C. for 4 hours.

The zinc oxide sensing material doped with SnSO ₄ and the zinc oxide sensing material doped with 3CdSO ₄ · 8H ₂ O were ground for the same time, and then dispersed in the same amount of absolute ethanol to form the comb electrode. It was applied and dried to evaporate the solvent. Thereafter, a light source was provided to produce a formaldehyde sensor. Thereafter, both the formaldehyde sensors were tested and compared for response to the same concentration of formaldehyde. FIG. 5 is a graph comparing the response intensity and response time of a tin-doped sample and a cadmium-doped sample with respect to 1 ppm formaldehyde. It can be seen that the response effect of the tin-doped sample to formaldehyde is superior to the response effect of the cadmium-doped sample.

  The above embodiment is only for explaining the technical solution of the present invention, and does not limit the present invention. For those skilled in the art, the technical solution of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be based on the description of the claims.

It is a flowchart of the synthesis | combining method of the photocatalyzed formaldehyde sensing material of this invention. It is the graph which compared the response intensity | strength of the sample with respect to 1 ppm formaldehyde according to the tin type additive. It is the graph which compared the response intensity | strength of the sample with respect to 1 ppm formaldehyde according to a tin dope ratio. It is the graph which compared the response intensity | strength of the tin dope sample with respect to 1 ppm formaldehyde according to sintering temperature. It is the graph compared about the response intensity | strength and response time of a tin dope sample and a cadmium dope sample with respect to 1 ppm formaldehyde.

Claims (10)

  A photocatalytic formaldehyde sensing material comprising zinc oxide nanoparticles and a tin-based additive. The zinc oxide nanoparticles have a particle size of 20 nm to 50 nm,
The photocatalytic formaldehyde sensing material according to claim 1, wherein the tin-based additive is tin oxide, and tin oxide accounts for 0.3% to 5% of the total weight of zinc oxide and tin oxide. The zinc oxide nanoparticles have a particle size of 30 nm,
3. The photocatalytic formaldehyde sensing material according to claim 2, wherein the tin oxide accounts for 2% of the total weight of zinc oxide and tin oxide. A method of synthesizing the photocatalytic formaldehyde sensing material of claim 1 comprising:
(1) a step of uniformly dispersing zinc oxide nanoparticles synthesized in advance in a tin salt solution to obtain a solution A;
(2) evaporating all of the solvent while stirring the solution A to obtain a precipitate B;
Sintering the precipitate B at a high temperature to obtain a product C which is a photocatalytic formaldehyde sensing material (3). The method according to claim ₄ , wherein the tin salt in step (1) is SnSO ₄ , SnCl ₄ or SnC ₂ O ₄ .   The method according to claim 4, wherein in step (2), all of the solvent is evaporated at 80 to 120 ° C.   The method according to claim 4, wherein the sintering is performed at 400 to 500 ° C. in step (3). The tin salt in step (1) is SnSO ₄ ;
In step (2), after stirring at 80 ° C. until all the solvent has evaporated, drying is performed at 80 ° C. for 12 h and drying at 120 ° C. for 2 h so that the sample is completely dried.
The method according to claim 4, wherein the sintering is performed at 450 ° C. in step (3).   The product C is pulverized to a fine powder and uniformly dispersed in a solvent to prepare a slurry. Subsequently, the slurry is applied to an electrode, and after drying, a thin film sensing material is obtained. The method of any one of -8. A formaldehyde sensor using the photocatalytic formaldehyde sensing material according to claim 1,
An electrode coated with the photocatalytic formaldehyde sensing material;
An ultraviolet light source that provides ultraviolet light to irradiate the electrode area when performing detection;
A detection circuit connected to the electrode and detecting a change in a photoconductive effect generated on the formaldehyde sensing material when the electrode region is irradiated with ultraviolet rays, and measuring a content of formaldehyde. Formaldehyde sensor.

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