Fluorescent probe for monitoring formaldehyde, preparation method, application and portable sensor

Abstract

The invention discloses a fluorescent probe for monitoring formaldehyde, a preparation method, application and a portable sensor. The structural formula of the fluorescent probe for monitoring formaldehyde is shown as a formula (I): # imgabs0 #, in which R1 is selected from any one of C1-C2 alkyl, phenyl and substituted phenyl; the substituted phenyl is preferably selected from alkyl substituted phenyl, and more preferably selected from C1-C3 alkyl substituted phenyl; r2 is selected from any one of oxygen atoms and sulfur atoms; r3 is selected from any one of cyano and carboxyl; a is selected from any one of a group shown in a formula (II) and a group shown in a formula (III): # imgabs No.1. The fluorescent probe provided by the invention has relatively strong fluorescence emission performance in both solution and solid states, can be used for monitoring formaldehyde in real time and has relatively high sensitivity and selectivity, and the preparation method of the fluorescent probe provided by the invention is simple in process, convenient to operate and suitable for industrial production. Control is easy, and cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemicals, and in particular to a fluorescent probe for monitoring formaldehyde, a preparation method and application thereof, and a portable sensor. Background Art

[0002] Formaldehyde is a reactive carbonyl compound that plays an important role in construction, furniture, textiles and industrial chemicals. However, as a common indoor pollutant, gaseous formaldehyde is continuously released from formaldehyde-based products. Inhalation of formaldehyde (concentrations in the air above 0.1 mg / m 3 ) can cause headaches, a tingling throat, and difficulty breathing. Furthermore, long-term exposure to formaldehyde may cause cancer. Therefore, developing a simple and sensitive method for detecting gaseous formaldehyde is imperative.

[0003] Conventional methods for detecting gaseous formaldehyde, such as high-performance liquid chromatography, spectrophotometry, and gas chromatography, suffer from drawbacks such as high cost and complex operation, significantly hindering their application. While other gaseous formaldehyde detection methods (such as piezoelectric, potentiometry, and electrochemical methods) enable simple detection of gaseous FA, their long-term stability and selectivity still need to be improved. In contrast, fluorescent probes offer significant advantages such as low cost, ease of use, simple operation, and high selectivity.

[0004] Fluorescence analysis involves the interaction of fluorescent probes with target analytes, detecting changes in their fluorescence signals, and subsequently determining the target analyte content. This method exhibits excellent selectivity, enabling real-time online detection and non-invasive testing of biological samples. Although formaldehyde fluorescent probes have garnered significant attention and extensive research, their availability remains limited. These probes suffer from complex molecular structures, multiple preparation steps, and slow response times, hindering their application in the testing and evaluation of formaldehyde in materials, environments, and complex systems. Consequently, there is an urgent need for the development of formaldehyde fluorescent probes with simpler structures, ease of preparation, and rapid response times. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a fluorescent probe for monitoring formaldehyde, a preparation method and use thereof, and a portable sensor.

[0006] One of the purposes of the present invention is to provide a fluorescent probe for monitoring formaldehyde, the structural formula of which is shown in formula (I):

[0007]

[0008] Wherein, R1 is selected from any one of a C1-C2 hydrocarbon group, a phenyl group, and a substituted phenyl group; the substituted phenyl group is preferably selected from an alkyl-substituted phenyl group, more preferably selected from a C1-C3 alkyl-substituted phenyl group; R2 is selected from any one of an oxygen atom and a sulfur atom; R3 is selected from any one of a cyano group (-CN) and a carboxyl group (-COOH); and A is selected from any one of the groups represented by the following formula (II) and the groups represented by the following formula (III):

[0009] (amino); (allylamino group); the curve marks the substitution position (the same below).

[0010] In a preferred embodiment of the present invention,

[0011] The R1 is selected from any one of C1 to C2 hydrocarbon groups; and / or, R2 is selected from any one of oxygen atoms and sulfur atoms; and / or, R3 is selected from any one of cyano groups and carboxyl groups; and / or, A is selected from the group represented by formula (III).

[0012] In a preferred embodiment of the present invention,

[0013] The R1 is selected from a methyl group; and / or R2 is selected from an oxygen atom; and / or R3 is selected from any one of a cyano group and a carboxyl group, preferably a cyano group; and / or A is selected from a group represented by formula (III).

[0014] A second object of the present invention is to provide a method for preparing the fluorescent probe of the first object of the present invention, comprising the steps of reacting a compound represented by the following formula (IV) with a compound represented by the following formula (V) in a reaction medium in the presence of a catalyst and a basic additive;

[0015]

[0016] In the formula, R1 is selected from any one of a C1-C2 hydrocarbon group, a phenyl group, and a substituted phenyl group; the substituted phenyl group is preferably selected from an alkyl substituted phenyl group, more preferably selected from a C1-C3 alkyl substituted phenyl group; R2 is selected from any one of an oxygen atom and a sulfur atom; R3 is selected from any one of a cyano group and a carboxyl group; A is selected from any one of a group represented by formula (II) and a group represented by formula (III); preferably,

[0017] The R1 is selected from any one of C1 to C2 hydrocarbon groups; and / or, R2 is selected from any one of oxygen atoms and sulfur atoms; and / or, R3 is selected from any one of cyano groups and carboxyl groups; and / or, A is selected from the group represented by formula (III).

[0018] In the present invention, the compound represented by formula (IV) and the compound represented by formula (V) can be obtained from commercial sources or prepared by the disclosed preparation methods in the prior art; preferably,

[0019] When A is selected from the group represented by formula (III), the preparation method of the compound represented by formula (IV) comprises:

[0020] Will (wherein R1 is selected from any one of a C1-C2 hydrocarbon group, a phenyl group, and a substituted phenyl group; the substituted phenyl group is preferably selected from an alkyl-substituted phenyl group, more preferably selected from a C1-C3 alkyl-substituted phenyl group) and ammonia in methanol and stirred at 0-10°C for 5-60 minutes. After heating to 15-35°C, vicinal di-tertiary alcohol propenylboronic acid ester is added and stirring is continued for 5-24 hours. The solvent is removed under reduced pressure, and the crude product is purified by column chromatography to obtain the compound of formula (IV) when A is selected from the group of formula (III).

[0021] Among them, ammonia and The molar ratio of propenyl boric acid octa-di-tertiary alcohol ester is preferably (5-20):1; The molar ratio of is preferably (1 to 3): 1. In the present invention, It can be obtained from commercial sources or prepared by a method disclosed in the prior art.

[0022] In a preferred embodiment of the present invention,

[0023] The reaction medium is selected from at least one organic solvent, preferably selected from at least one of tetrahydrofuran and 1,4-dioxane; and / or,

[0024] The catalyst is selected from at least one of a divalent copper compound and a Pd(0) compound, preferably a combination of a divalent copper compound and a Pd(0) compound; the divalent copper compound is preferably copper acetate monohydrate; and / or the Pd(0) compound is preferably tetrakistriphenylphosphine palladium; and / or,

[0025] The alkaline additive is selected from at least one of organic amines, preferably at least one of triethylamine, pyridine, and N,N-diisopropylethylamine (DIPEA).

[0026] In a preferred embodiment of the present invention,

[0027] The molar ratio of the compound represented by formula (IV), the compound represented by formula (V), the catalyst and the alkaline additive is 1:(0.5-5):(0.1-3):(0.1-5), preferably 1:(2-3):(0.1-3):(1-3); and / or,

[0028] The mass ratio of the reaction medium to the compound represented by formula (IV) is (5-20):1, preferably (10-20):1.

[0029] In a preferred embodiment of the present invention,

[0030] The reaction time is 4 to 48 hours, preferably 10 to 30 hours; preferably, the reaction is carried out under heating reflux conditions; further preferably, the temperature of the heating reflux reaction is within 20°C above or below the boiling point of the reaction medium used in the reaction, preferably within 20°C above the boiling point of the reaction medium used in the reaction.

[0031] The present invention can adopt the following specific technical solutions:

[0032] The compound represented by formula (IV) and the compound represented by formula (V) are dissolved in 1,4-dioxane, a divalent copper compound and / or a Pd(0) compound is used as a catalyst, and a reflux reaction is carried out for 4 to 48 hours under the action of an alkaline additive; after the reaction is completed, column chromatography is used to separate and obtain a fluorescent probe with a structure represented by formula (I).

[0033] A third object of the present invention is to provide an indazole compound as a fluorescent probe for monitoring formaldehyde, wherein the structural formula of the indazole compound is:

[0034]

[0035] Wherein, R1 is selected from any one of a C1-C2 hydrocarbon group, a phenyl group, and a substituted phenyl group; the substituted phenyl group is preferably selected from an alkyl-substituted phenyl group, more preferably selected from a C1-C3 alkyl-substituted phenyl group; and / or, R2 is selected from any one of an oxygen atom and a sulfur atom; and / or, R3 is selected from any one of a cyano group and a carboxyl group; and A is selected from any one of the groups represented by the following formula (II) and the groups represented by the following formula (III):

[0036]

[0037] In a preferred embodiment of the present invention,

[0038] The R1 is selected from any one of C1 to C2 hydrocarbon groups; and / or, R2 is selected from any one of oxygen atoms and sulfur atoms; and / or, R3 is selected from any one of cyano groups and carboxyl groups; and / or, A is selected from the group represented by formula (III).

[0039] In a preferred embodiment of the present invention,

[0040] The R1 is selected from a methyl group; and / or R2 is selected from an oxygen atom; and / or R3 is selected from any one of a cyano group and a carboxyl group, preferably a cyano group; and / or A is selected from a group represented by formula (III).

[0041] In a preferred embodiment of the present invention,

[0042] When the indazole compound is used to monitor formaldehyde, the indazole compound is first prepared to a concentration of 1×10 -3 ~1×10 -5 mol / L solution and test its fluorescence spectrum, then add formaldehyde test solution and test its fluorescence spectrum again, compare the fluorescence spectrum changes before and after adding formaldehyde test solution; judge whether the formaldehyde test solution contains formaldehyde by the fluorescence spectrum changes before and after adding formaldehyde test solution; preferably,

[0043] The concentration is 1×10 -3 ~1×10 -5 The medium in the mol / L solution of the indazole compound is a mixture of dimethyl sulfoxide and water, wherein the volume ratio of dimethyl sulfoxide to water in the mixture is preferably (0.2 to 5):1; and / or,

[0044] After adding the formaldehyde test solution, react at 20-50°C for 5-60 minutes before testing.

[0045] A fourth object of the present invention is to provide a portable formaldehyde sensor, which is obtained by loading the fluorescent probe of the first object of the present invention or the fluorescent probe obtained by the preparation method of the second object of the present invention onto a solid substrate; preferably, the solid substrate is at least one of paper and board, preferably at least one of paper test paper, filter paper, and thin-layer chromatography; further preferably, the portable formaldehyde sensor is a formaldehyde detection test strip. The formaldehyde detection test strip can achieve simple and sensitive detection of gaseous formaldehyde.

[0046] The fluorescent probe for monitoring formaldehyde of the present invention contains a novel indazole fluorescent group in its structure and has aggregation-induced emission properties. Compared with fluorophores with aggregation-induced quenching properties, the novel indazole fluorescent group of the present invention still emits strong fluorescence in the aggregated state. The reaction mechanism of the indazole fluorescent group with formaldehyde is shown below (here only the fluorescent probe is used as an example). For example:

[0047]

[0048] The formaldehyde fluorescent probe of the present invention has strong fluorescence emission performance in both solution and solid state, can be used for real-time monitoring of formaldehyde, and has high sensitivity and selectivity. In addition, the preparation method of the fluorescent probe provided by the present invention is simple in process, easy to operate, easy to control, and low in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is the mass spectrum of the fluorescent probe shown in I-1 (see Example 1 for details). Figure 1The test data of the mass spectrum are as follows: Mass spectrometry (ESI-MS, m / z): calcd.for [C 16 H 12 N5O+H] + 290.1042; found 290.1042. Figure 1 The molecular weight detected by mass spectrometry was consistent with the theoretical molecular weight, proving the accuracy of the synthesized molecular structure.

[0050] Figure 2 This is the H-NMR spectrum of the fluorescent probe shown in I-1 (see Example 1 for details). Figure 2 The test data of the nuclear magnetic hydrogen spectrum are as follows: 1 H NMR (400MHz, DMSO-d6, ppm) δ = 4.35 (s, 3H, NCH3-H), δ = 5.24 (s, 2H, NH2-H), δ = 6.88 (d, J = 8.0Hz, 1H, Ph-H), δ = 7.00 (s, 1H, Ph-H), δ=7.24 (d, J=4.0Hz, 1H, furan-H), δ=7.49 (d, J=8.0Hz, 1H, Ph-H), δ=7.68 (d, J=4.0Hz, 1H, furan-H), δ=8.20 (s, 1H, alkene-H). Figure 2 The above data most directly indicate that the fluorescent probe shown in I-1 was successfully synthesized.

[0051] Figure 3 Graph showing the changes in fluorescence properties of probe I-2 before and after the reaction with formaldehyde in Application Example 2, wherein Curve 1 is the fluorescence curve before the reaction with formaldehyde, and Curve 2 is the fluorescence curve after the reaction with formaldehyde. DETAILED DESCRIPTION

[0052] The present invention will be described in detail below with reference to specific embodiments and the accompanying drawings. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0053] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0054] The detection instruments used in the embodiments of the present invention are shown in Table 1:

[0055] Table 1

[0056]

[0057] Example 1

[0058] Synthesis of fluorescent probe I-1:

[0059]

[0060] To a dry Shrek tube, IV-1 (147 mg, 1 mmol, CAS No. 50593-24-3), copper acetate monohydrate (300 mg, 1.5 mmol), V-1 (432 mg, 3 mmol, CAS No. 3237-22-7), and 0.2 mL of pyridine were added and dissolved in 3 mL of 1,4-dioxane. Tetrakistriphenylphosphine palladium (58.8 mg, 0.05 mmol) was quickly added. Under argon, the mixture was stirred at 25°C for 5 minutes and then heated to 120°C and refluxed for 24 hours. After the reaction, the reaction solution was cooled to room temperature, diluted with 20 mL of dichloromethane, and filtered. The organic phases were combined and evaporated under reduced pressure. The mixture was separated by column chromatography (developing solvent: dichloromethane:petroleum ether = 1:1, 300-400 mesh silica gel). 112 mg of the fluorescent probe represented by Formula I-1 was obtained in a 39% yield.

[0061] Example 2

[0062] Synthesis of fluorescent probe I-2:

[0063]

[0064] 1-Methyl-1H-indazole-5-carbaldehyde (806 mg, 5 mmol, CAS No. 872607-89-1) was mixed with 25% aqueous ammonia (3.78 mL, 50 mmol) in 50 mL of methanol and stirred at 0°C for 30 minutes. After heating to 25°C, 1-di-propenylboronic acid ester (924 mg, 6 mmol) was added and stirring continued for 12 hours. The solvent was removed under reduced pressure, and the crude product was purified by column chromatography using ethanol / dichloromethane (v / v 1:10) to obtain Compound IV-2 (660 mg, 38% yield) as a solid.

[0065] To a dry Shrek tube, IV-2 (200 mg, 1 mmol), copper acetate monohydrate (300 mg, 1.5 mmol), V-1 (432 mg, 3 mmol, CAS No. 3237-22-7), and 0.2 mL of pyridine were added and dissolved in 3 mL of 1,4-dioxane. Tetrakistriphenylphosphine palladium (58.8 mg, 0.05 mmol) was quickly added. Under argon, the mixture was stirred at 25°C for 5 minutes and then heated to 120°C and refluxed for 24 hours. After the reaction, the reaction solution was cooled to room temperature, diluted with 20 mL of dichloromethane, and filtered. The organic phases were combined and evaporated under reduced pressure. Column chromatography was performed (developing solvent: dichloromethane:petroleum ether = 1:1, 300-400 mesh silica gel). 132 mg of the fluorescent probe represented by Formula I-2 was obtained in a yield of 38.7%.

[0066] Example 3

[0067] Synthesis of fluorescent probe I-3:

[0068]

[0069] To a dry Shrek tube, IV-2 (200 mg, 1 mmol), copper acetate monohydrate (300 mg, 1.5 mmol), V-2 (480 mg, 3 mmol, CAS No. 28162-32-5), and 0.2 mL of pyridine were added and dissolved in 3 mL of 1,4-dioxane. Tetrakistriphenylphosphine palladium (58.8 mg, 0.05 mmol) was quickly added. Under argon, the mixture was stirred at 25°C for 5 minutes and then heated to 120°C and refluxed for 24 hours. After the reaction, the reaction solution was cooled to room temperature, diluted with 20 mL of dichloromethane, and filtered. The organic phases were combined and vacuum evaporated. Column chromatography was performed (developing solvent: dichloromethane:petroleum ether = 1:1, 300-400 mesh silica gel). 154 mg of the fluorescent probe represented by Formula I-3 was obtained in a 43% yield.

[0070] Application Test Example 1

[0071] I-2 of Example 2 was dissolved in dimethyl sulfoxide (analytical grade) to prepare 1.0×10 -3 M (M represents mol / L) stock solution; then prepare 1.0×10 -2 Prepare a 3 mL test system solution with a 1:1 dimethyl sulfoxide:water ratio. Add 30 μL of this stock solution to the 3 mL test system solution, followed by 60 μL of the formaldehyde solution. Incubate the resulting mixture at 37°C for 20 minutes. Mix thoroughly and transfer the mixture to an optical quartz cuvette (10 × 10 mm) for fluorescence spectrum analysis. Figure 3 The probe I-2 in this example (concentration is 1.0×10-5 mol·L -1 ) Changes in fluorescence spectrum before and after adding formaldehyde solution (20 times the equivalent of I-2). Figure 3 As shown, when no formaldehyde aqueous solution was added, I-2 had basically no fluorescence signal; when formaldehyde aqueous solution was added, with 500 nm as the excitation wavelength, the maximum emission peak appeared at about 630 nm, showing excellent responsiveness.

[0072] It can be seen from the application test example 1 that the fluorescent probe of the present invention has strong fluorescence emission performance and can be used for real-time monitoring of formaldehyde. A fluorescent probe, when A in the fluorescent probe shown in formula (I) is The fluorescence response effect is better than that of A. The fluorescence response effect is When the fluorescent probe reacts with formaldehyde, it generates Schiff base, which is unstable and easily hydrolyzed, which may lead to unstable or weak fluorescence signals and may cause errors in formaldehyde monitoring.

[0073] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

[0074] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of conflict, the definitions in this specification shall prevail.

[0075] When this specification uses the prefix "well known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, the objects introduced by the prefix include those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become generally recognized in the art to be suitable for similar purposes.

[0076] The endpoints and any values ​​of the ranges disclosed in this application document are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and a separate point value, and the separate point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0077] In the context of this specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0078] Moreover, any embodiment described herein may be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas thus formed shall be deemed as part of the original disclosure or original record of the present invention, and shall not be regarded as new content that has not been disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A fluorescent probe for monitoring formaldehyde, the structural formula of which is shown in formula (I): in, R1 is selected from any one of a C1-C2 hydrocarbon group, a phenyl group, and a substituted phenyl group; the substituted phenyl group is preferably selected from an alkyl substituted phenyl group, and more preferably selected from a C1-C3 alkyl substituted phenyl group; R2 is selected from any one of an oxygen atom and a sulfur atom; R3 is selected from any one of a cyano group and a carboxyl group; A is selected from any one of the following groups represented by formula (II) and formula (III):

2. The fluorescent probe according to claim 1, characterized in that: The R1 is selected from any one of C1-C2 hydrocarbon groups; and / or, R2 is selected from any one of oxygen atoms and sulfur atoms; and / or, R3 is selected from any one of cyano groups and carboxyl groups; and / or, A is selected from the group represented by formula (III).

3. The fluorescent probe according to claim 2, characterized in that: The R1 is selected from a methyl group; and / or, R2 is selected from an oxygen atom; and / or, R3 is selected from any one of a cyano group and a carboxyl group, preferably a cyano group; and / or, A is selected from a group represented by formula (III).

4. A method for preparing a fluorescent probe as claimed in any one of claims 1 to 3, comprising the step of reacting a compound represented by the following formula (IV) with a compound represented by the following formula (V) in a reaction medium in the presence of a catalyst and an alkaline additive; In the formula, R1 is selected from any one of a C1-C2 hydrocarbon group, a phenyl group, and a substituted phenyl group; the substituted phenyl group is preferably selected from an alkyl substituted phenyl group, and more preferably selected from an alkyl substituted phenyl group of C1-C3; R2 is selected from any one of an oxygen atom and a sulfur atom; R3 is selected from any one of a cyano group and a carboxyl group; A is selected from any one of the groups represented by formula (II) and the groups represented by formula (III).

5. The method according to claim 4, characterized in that: The reaction medium is selected from at least one of organic solvents, preferably selected from at least one of tetrahydrofuran and 1,4-dioxane; and / or, The catalyst is selected from at least one of a divalent copper compound and a Pd(0) compound; the divalent copper compound is preferably copper acetate monohydrate; and / or the Pd(0) compound is preferably tetrakistriphenylphosphine palladium; and / or, The alkaline additive is selected from at least one of organic amines, preferably selected from at least one of triethylamine, pyridine, and N,N-diisopropylethylamine.

6. The method according to claim 4, characterized in that: The molar ratio of the compound represented by formula (IV), the compound represented by formula (V), the catalyst and the alkaline additive is 1:(0.5-5):(0.1-3):(0.1-5), preferably 1:(2-3):(0.1-3):(1-3); and / or, The mass ratio of the reaction medium to the compound represented by formula (IV) is (5-20):1, preferably (10-20):

1.

7. The method according to claim 4, characterized in that: The reaction time is 4 to 48 hours, preferably 10 to 30 hours; preferably, the reaction is carried out under heating reflux.

8. Use of an indazole compound as a fluorescent probe for monitoring formaldehyde, wherein the structural formula of the indazole compound is: in, R1 is selected from any one of a C1-C2 hydrocarbon group, a phenyl group, and a substituted phenyl group; the substituted phenyl group is preferably selected from an alkyl substituted phenyl group, and more preferably selected from a C1-C3 alkyl substituted phenyl group; and / or, R2 is selected from any one of an oxygen atom and a sulfur atom; and / or, R3 is selected from any one of a cyano group and a carboxyl group; A is selected from any one of the following groups represented by formula (II) and formula (III):

9. The use according to claim 8, characterized in that: The R1 is selected from any one of C1-C2 hydrocarbon groups; and / or, R2 is selected from any one of oxygen atoms and sulfur atoms; and / or, R3 is selected from any one of cyano groups and carboxyl groups; and / or, A is selected from the group represented by formula (III).

10. The use according to claim 9, characterized in that: The R1 is selected from a methyl group; and / or, R2 is selected from an oxygen atom; and / or, R3 is selected from any one of a cyano group and a carboxyl group, preferably a cyano group; and / or, A is selected from a group represented by formula (III).

11. The use according to any one of claims 8 to 10, characterized in that: When the indazole compound is used to monitor formaldehyde, the indazole compound is first prepared to a concentration of 1×10 -3 ~1×10 -5 mol / L solution, and test its fluorescence spectrum, then add formaldehyde to the test solution and test its fluorescence spectrum again, and compare the changes in fluorescence spectrum before and after adding formaldehyde to the test solution; preferably, The concentration is 1×10 -3 ~1×10 -5 The medium in the solution of the indazole compound of 10 mol / L is a mixture of dimethyl sulfoxide and water, wherein the volume ratio of dimethyl sulfoxide to water in the mixture is preferably (0.2-5):1; and / or, After adding formaldehyde to the test solution, react at 20-50°C for 5-60 minutes before testing.

12. A portable formaldehyde sensor, obtained by loading the fluorescent probe according to any one of claims 1 to 3 or the fluorescent probe obtained by the preparation method according to any one of claims 4 to 7 onto a solid substrate. Preferably, the portable formaldehyde sensor is a formaldehyde detection test paper.

Images