A fluorescent probe for identifying formaldehyde and a preparation method and application thereof

Abstract

The application belongs to the technical field of analysis and detection, and discloses a fluorescent probe for identifying and detecting formaldehyde as well as a preparation method and application thereof. A structural formula of the fluorescent probe is shown as formula (I). The fluorescent probe itself has almost no fluorescence in a PBS buffer system, but can specifically react with formaldehyde to generate a product with strong green fluorescence. The fluorescent probe can reach a maximum response value after reacting with formaldehyde for only 15 minutes, and the fluorescence intensity is significantly enhanced by 300 times at 518 nm. The fluorescent probe has high and specific selectivity for formaldehyde. The minimum detection limit of the probe for formaldehyde is 0.088 micromoles, and the probe can be used for detecting and analyzing formaldehyde in liquid environments, air environments, chemical samples and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of analytical detection technology, and particularly relates to a fluorescent probe for identifying and detecting formaldehyde as well as a preparation method and application thereof. BACKGROUND

[0002] Formaldehyde is colorless and is generally considered as one of the main environmental pollutants. It is reported that formaldehyde is toxic to human body at a high content and causes irritation of respiratory tract, eyes and skin. The irritation of respiratory tract caused by formaldehyde usually includes local redness or pain. The irritation usually involves local redness, swelling, itching or pain, which also appears in eye and skin irritation. In addition, formaldehyde is also considered as a suspected carcinogen. However, due to the large use of medium density fiberboard and particle board based on formaldehyde-containing adhesives (amino resin, phenolic resin, etc.) in many building materials, the concentration of formaldehyde in the environment air is increasing. However, due to the large use of medium density fiberboard and particle board based on formaldehyde-containing adhesives (amino resin, phenolic resin, etc.) in many building materials, the concentration of formaldehyde in the environment air is increasing, although the formaldehyde release amount in building products has been decreasing. But indoor formaldehyde has attracted great attention due to its cumulative harm to human beings. Therefore, it is very important to develop a rapid and simple method for detecting formaldehyde.

[0003] There are many methods for detecting formaldehyde. The common laboratory detection methods at present include spectrophotometry and chromatography. The spectrophotometry refers to the standards of JF 11283-2007, SC / T 3025-2006, GB / T 5009.49-2008 and SN / T 2183-2008, and acetylacetone is used to determine formaldehyde, but the results of the method are easily affected by temperature and reaction time. The chromatography mainly includes high performance liquid chromatography and gas chromatography. These methods have high sensitivity and good selectivity, but need complex pretreatment operation and pre-concentration treatment, especially the required instrument is relatively expensive, and the technical requirements for the operator are relatively high, so the routine instrument detection method cannot meet the demand of on-site rapid screening analysis.

[0004] The fluorescence detection method has the advantages of simple operation, high sensitivity, lower detection limit than the conventional method, and can be well applied to actual sample detection, thereby providing a new idea for the detection of low content aldehyde compounds. In addition, an organic small molecule fluorescent probe capable of performing fluorescence detection on formaldehyde is synthesized and applied to specific recognition and detection of formaldehyde in air environment. SUMMARY

[0005] In order to solve the above-mentioned deficiencies and shortcomings of the prior art, the primary purpose of the present application is to provide a fluorescent probe. The fluorescent probe is a two-photon fluorescent probe with naphthalene as a parent body.

[0006] Another object of the present application is to provide a preparation method of the fluorescent probe, which has simple synthesis steps and high yield.

[0007] Still another object of the present application is to provide an application of the fluorescent probe in detecting formaldehyde.

[0008] The object of the present application is achieved by the following technical solutions.

[0009] A fluorescent probe for recognizing and detecting formaldehyde, wherein the structure of the fluorescent probe is shown in formula (I):

[0010]

[0011] (I).

[0012] The preparation method of the fluorescent probe for recognizing and detecting formaldehyde comprises the following steps:

[0013] S1. Dissolving 4-bromo-1,8-naphthalene anhydride and o-phenylenediamine in an organic solvent, refluxing for 1-12 hours under nitrogen protection, precipitating and drying to obtain an intermediate product;

[0014] S2. Dissolving the intermediate product and hydrazine hydrate in an ethylene glycol monomethyl ether solution, refluxing for 3-6 hours under nitrogen protection, precipitating and drying to obtain the fluorescent probe for recognizing and detecting formaldehyde.

[0015] The synthesis route of the fluorescent probe molecule for recognizing and detecting formaldehyde is as follows:

[0016] ,

[0017] The yield of the intermediate product (II) is 70-90%, and the yield of the fluorescent probe molecule (I) is 60-70%.

[0018] Preferably, the molar ratio of the 4-bromo-1,8-naphthalene anhydride to the o-phenylenediamine in step S1 is 1:(1-5); and the mass ratio of the 4-bromo-1,8-naphthalene anhydride to the organic solvent is 1:(5-20).

[0019] Preferably, the organic solvent in step S1 is one or more of dichloromethane, methanol, ethanol, ethyl acetate or acetic acid.

[0020] Preferably, 5. The preparation method of the fluorescent probe for recognizing and detecting formaldehyde according to claim 2, wherein the molar ratio of the intermediate product to the hydrazine hydrate in step S2 is 1:(0.5-1.2); the mass ratio of the intermediate product to the ethylene glycol monomethyl ether solution is 1:(10-25), and the concentration of the hydrazine hydrate is 80-99%.

[0021] Preferably, the purification in steps S1 and S2 is silica gel chromatography purification.

[0022] More preferably, the eluent used in the silica gel column chromatography purification in step S1 is dichloromethane, and the eluent used in the silica gel column chromatography purification in step S2 is dichloromethane and methanol in a volume ratio of (20-30):1.

[0023] The application of the fluorescent probe for identifying and detecting formaldehyde is mixing the fluorescent probe with a PBS phosphate buffer solution, and adding a to-be-detected solution to detect the content of formaldehyde.

[0024] The molecular formula of the fluorescent probe of the application is C 18 H 12 N4O, and the relative molecular mass is 301. The fluorescent probe is a brownish-brown odorless solid powder, and is easily soluble in solvents such as methanol and acetonitrile. The fluorescent probe undergoes stable photo-induced electron transfer. The hydrazine group is the most common formaldehyde (FA) recognition group, and has strong electron-donating ability. Connecting the hydrazine group with a fluorescent group will produce photo-induced electron transfer (PET) effect from the hydrazine group to the fluorescent group, so that such a probe hardly emits fluorescence in the initial state. After the hydrazine group reacts with formaldehyde to generate a hydrazone, the PET effect is destroyed, the fluorescence of the fluorescent group is restored, and thus the FA is identified through the “off-on” phenomenon of fluorescence. Therefore, by using this reaction mechanism, a highly specific formaldehyde fluorescent probe can be designed. In the presence of formaldehyde, the color of the probe solution changes from yellow to green under visible light, and the fluorescence intensity significantly increases under ultraviolet light irradiation, so that the formaldehyde can be detected through the change of fluorescence intensity.

[0025] Before the fluorescent probe of the application reacts with formaldehyde in a PBS phosphate buffer (0.01 mol / L, pH=7.4), the fluorescent probe has almost no fluorescence under the irradiation of excitation light at 443 nm due to the PET effect from the hydrazine group to the fluorescent group. When the formaldehyde molecules react with the hydrazine group to generate an intermolecular nucleophilic substitution reaction, the PET effect in the fluorescent probe is destroyed, and the fluorescent probe emits significant green fluorescence at about 518 nm. Based on the fluorescence properties of the fluorescent probe of the application, the fluorescent probe can specifically identify formaldehyde, and is used for the detection and analysis of formaldehyde in biological samples, environmental samples, chemical samples and the like. In addition, the fluorescent probe prepared in the application has good light stability, high selectivity, fast detection and high sensitivity.

[0026] The above fluorescent probe is used for preparing a kit or test paper for detecting formaldehyde.

[0027] The application provides a preparation method of a test paper for detecting formaldehyde, which comprises the following steps:

[0028] (1) dissolving the above fluorescent probe in acetonitrile to obtain a solution containing the fluorescent probe;

[0029] (2) coating the solution obtained in step (1) on filter paper or immersing the filter paper in the solution obtained in step (1), and then drying the filter paper to obtain a test paper for detecting formaldehyde.

[0030] The test paper of the present application can be used for rapid detection of formaldehyde in air. When detecting, the test paper is only needed to be placed in the air environment for a few minutes, and then the color change of the test paper under 365 nm excitation light is observed using a hand-held ultraviolet lamp to know whether formaldehyde exists in the air. As a preferred embodiment of the preparation method of the test paper for detecting formaldehyde.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] The naphthalimide of the fluorescent probe of the present application has an emission wavelength in the visible light region, and the fluorescent probe has good light stability, and high specificity, sensitivity and selectivity in detecting formaldehyde.

[0033] The fluorescent probe of the present application is very fast and convenient in detecting formaldehyde: when detecting the formaldehyde content in a liquid environment, only a certain amount of test sample is dissolved in a fluorescent probe solution of a specific concentration, the fluorescence intensity of the test mixed liquid at 518 nm is tested, the concentration of formaldehyde is converted through a standard curve, and the reaction can be completed in 15 min; when detecting the formaldehyde content in an air environment, only the test paper is needed to be placed in the air environment, and then the color change of the test paper under 365 nm excitation light is observed using a hand-held ultraviolet lamp to know whether formaldehyde exists in the air.

[0034] The raw materials of the fluorescent probe of the present application are simple and easy to obtain, and the preparation process is simple, convenient and low in synthesis cost.

[0035] The fluorescent probe of the present application has a minimum detection limit of 0.088 μmol / L, and can be applied to fluorescent imaging of formaldehyde in air. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 NMR spectrum of intermediate II of Example 1;

[0037] Figure 2 Mass spectrum of intermediate II of Example 1;

[0038] Figure 3 NMR spectrum of the fluorescent probe of Example 1;

[0039] Figure 4 NMR spectrum of the fluorescent probe of Example 1;

[0040] Figure 5 Mass spectrum of the fluorescent probe of Example 1;

[0041] Figure 6 The fluorescence selectivity diagram of the fluorescent probe in Example 1 is shown, with an excitation wavelength of 443 nm.

[0042] Figure 7 The fluorescence spectra of the fluorescent probe of Example 1 with different concentrations of formaldehyde added are shown.

[0043] Figure 8 The response time diagram of the fluorescent probe in Example 1 to 200 μmol / L formaldehyde is shown.

[0044] Figure 9 The test strips were prepared and their color changed under a 365nm ultraviolet lamp containing only acetone, toluene, chloroform, ethylenediamine, ethyl acetate, isocyanate, hydrazine hydrate, and formaldehyde, respectively.

[0045] Figure 10 The regression curve of the fluorescent probe in the low concentration range of formaldehyde is shown as an application example. Detailed Implementation

[0046] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. Example

[0047] A method for preparing a fluorescent probe molecule for identifying and detecting formaldehyde:

[0048] 4-Bromo-1,8-naphthalene anhydride (1.0 g, 3.6 mmol) and o-phenylenediamine (0.486 g, 4.5 mmol) were added to a two-necked flask containing 20 mL of acetic acid solution. Under nitrogen protection, the reaction was heated to 100 °C and refluxed for 4 h before being stopped. The mixture was poured into ice water, and a precipitate formed. The precipitate was filtered to obtain a crude yellow solid powder. The obtained solid was dried and purified by silica gel chromatography (dichloromethane). The product was then dried in a vacuum oven at 40 °C for 24 h to obtain a yellow solid powder, which was the intermediate product (1.1 g, yield 89%).

[0049] Figure 1 The 1H NMR spectrum of the intermediate product of Example 1; as shown Figure 1 As shown, the hydrogen spectrum is specifically... 1 H NMR (600 MHz, Chloroform- d ) δ 8.75 (ddd, J= 23.6, 7.3, 1.2 Hz, 1H), 8.59-8.50 (m, 1H), 8.50-8.39 (m, 2H), 8.00 (dd, J = 17.5, 7.8 Hz, 1H), 7.81 (tt, J = 8.4, 7.3 Hz, 2H), 7.48-7.42 (m, 2H). In addition, the product was confirmed by mass spectrometry, Figure 2 The mass spectrum of the intermediate product (II) of Example 1 is shown in Figure 2 The mass spectrum of the intermediate product (II) of Example 1 is shown in

[0050] The intermediate product (1.1 g, 3.6 mmol) and 80 wt% hydrazine hydrate (218 uL, 3.6 mmol) were added to a two-necked flask containing 20 mL of ethylene glycol monomethyl ether, and the reaction was heated under nitrogen protection at 125°C reflux for 6 h. The mixture was poured into ice water, and the precipitate was collected by suction filtration to obtain a crude product of red-brown solid powder. The obtained solid was dried and purified by silica gel column chromatography (dichloromethane:methanol, 25:1, by volume); the obtained product was placed in a vacuum drying oven at 40°C for 24 h to obtain a brown-brown solid powder (0.756 g, yield 70%), which was the fluorescent probe.

[0051] The product was characterized by nuclear magnetic resonance hydrogen spectrum, and the results are shown in Figure 3 The product was characterized by nuclear magnetic resonance hydrogen spectrum, and the results are shown in 1 H NMR (600 MHz, DMSO- d 6) δ 8.74-8.66 (m, 1H), 8.54 (dt, J = 8.4, 1.2 Hz, 1H), 8.48-8.43 (m, 2H), 7.86-7.79 (m, 1H), 7.73-7.65 (m, 1H), 7.43 (pd, J = 7.2, 1.5 Hz, 2H), 7.29 (dt, J = 8.7, 1.3 Hz, 1H). The product was characterized by nuclear magnetic resonance carbon spectrum, and the results are shown in Figure 4 The product was characterized by nuclear magnetic resonance carbon spectrum, and the results are shown in 13C NMR (151 MHz, DMSO) δ 160.12, 154.48, 149.63, 143.73, 135.34, 131.85, 128.56, 127.13, 126.27, 125.16, 124.76, 124.39, 119.67, 119.61, 119.12, 115.65, 107.01, 104.81. In addition, the assistant proof was carried out by mass spectrometry, and the results were as follows Figure 5 The synthesized product was determined to be the fluorescent probe (I) by analysis, and the molecular formula of the probe was C 18 H 12 N4O.

[0052] Application Example

[0053] Probe fluorescence selectivity experiment: PBS phosphate buffer solution (0.01 mol / L, pH = 7.4) was prepared, and a methanol solution of the fluorescent probe with a concentration of 1 mmol / L was prepared with methanol. Figure 6 The fluorescence selectivity of the fluorescent probe of Example 1 is shown in the figure, the excitation wavelength is 443 nm; the selectivity of the fluorescent probe for formaldehyde is detected by a fluorescence spectrophotometer. Under the excitation condition of 443 nm, the fluorescent probe I (5 μmol / L) alone has a weak fluorescence emission intensity at 518 nm in the PBS buffer solution, and when formaldehyde (200 μmol / L) is added, the fluorescence emission intensity at 472 nm is obviously enhanced, but the fluorescence emission intensity of the solution system of the other substances (isopropyl alcohol, hydrazine hydrate, aniline, glutaraldehyde, epichlorohydrin, dimethyl phthalate, amine chloride, amine sulfate, manganese sulfate, aluminum nitrate, potassium persulfate, calcium chloride, potassium dihydrogen phosphate, disodium hydrogen phosphate, formaldehyde, copper sulfate) in the PBS phosphate buffer solution has no obvious change compared with the fluorescence emission intensity of the fluorescent probe in the PBS phosphate buffer solution. The experimental results show that the fluorescent probe has good specific selectivity for formaldehyde.

[0054] Minimum detection limit experiment: a good detection limit is one of the standards for testing whether a probe molecule has application value. PBS phosphate buffer solution (0.01 mol / L, pH = 7.4) was prepared, and a fluorescent probe solution with a concentration of 1 mμmol / L was prepared with methanol. The concentration of the fluorescent probe was fixed at 5 μmol / L, and the response intensity of the fluorescent probe to different concentrations of formaldehyde was measured, Figure 7 The fluorescence intensity change of the fluorescent probe of Example 1 with different concentrations of formaldehyde was measured; from Figure 7It can be seen that with the increase of formaldehyde concentration, the fluorescence emission intensity of the probe at 518 nm in PBS phosphate buffer solution (0.01 mol / L, pH = 7.4) is continuously enhanced. It is found that the fluorescence emission intensity of the solution is linear with the formaldehyde concentration in the range of 0-200 μmol / L (R 2 = 0.9902), and the regression curve of formaldehyde in the low concentration range is shown in Figure 10 , and the regression curve is y = 808.39 + 34.35x (R 2 = 0.990). The calculated detection limit (LOD = 3σ / k) is 0.088 μmol / L, where k is the slope of the fitting straight line, and σ is the standard deviation of the fluorescence probe detection without formaldehyde. Figure 8 The response time diagram of the fluorescence probe for 200 μM (μmol / L) formaldehyde is shown in Figure 8 It can be seen that when the fluorescence intensity detection is performed at about 13-15 min, it is found that the change amplitude of the fluorescence intensity value is very small, which indicates that the reaction is basically complete, and the reaction of the fluorescence probe with formaldehyde has reached the end point within 15 min. The analysis of the reaction time curve shows that the fluorescence probe can rapidly detect formaldehyde.

[0055] 3. Formaldehyde selective experiment of the fluorescence detection test paper in the air: the fluorescence probe is dissolved in methanol, and then the solution containing the fluorescence probe is uniformly loaded on the cut clean filter paper to prepare the fluorescence detection test paper for detecting formaldehyde. A rapid, efficient and simple detection method for formaldehyde in the air is established. The test paper is only needed to be placed in the air for 30 min at room temperature, and then the color change of the test paper is observed by using a handheld ultraviolet lamp with 365 nm irradiation, Figure 9 The color change diagram of the prepared test paper under 365 nm ultraviolet lamp irradiation in acetone, toluene, chloroform, ethylenediamine, ethyl acetate, isocyanate, hydrazine hydrate and formaldehyde respectively is shown in Figure 9 It can be seen from that the test paper is detected in acetone, toluene, chloroform, ethylenediamine, ethyl acetate, isocyanate, formaldehyde and hydrazine hydrate air environment respectively. Except that the test paper placed in the formaldehyde air environment shows obvious green fluorescence under the irradiation of the ultraviolet lamp, the fluorescence of the test paper in the remaining conditions is not obvious and is still light yellow, which proves that the prepared test paper has good selectivity and specificity and high stability. It can be seen that the test paper is not affected by other substances in the complex air environment, and has pertinence for the detection of formaldehyde.

[0056] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principles of the present application should be equivalent replacement manners and should be included in the protection scope of the present application.

Claims

1. A fluorescent probe for the identification of formaldehyde, characterized in that, The structural formula of the fluorescent probe is shown as formula (I):

2. The method of claim 1, wherein the method is characterized by: The method comprises the following steps: S1. Dissolving 4-bromo-1,8-naphthalene anhydride and o-phenylenediamine in an organic solvent, refluxing under nitrogen protection for 1-12 hours, precipitating and drying to obtain an intermediate product; S2. Dissolving the intermediate product and hydrazine hydrate in ethylene glycol monomethyl ether solution, refluxing under nitrogen protection for 3-6 hours, precipitating and drying, and then purifying through a silica gel column to obtain the fluorescent probe.

3. The method of claim 2, wherein the method is characterized by: The molar ratio of 4-bromo-1,8-naphthalene anhydride to o-phenylenediamine in step S1 is 1:(1-5), and the mass ratio of 4-bromo-1,8-naphthalene anhydride to the organic solvent is 1:(5-20).

4. The method of claim 2, wherein the method is characterized by: The organic solvent in step S1 is one or more of dichloromethane, methanol, ethanol, ethyl acetate or acetic acid.

5. The method of claim 2, wherein the method is characterized by: The molar ratio of the intermediate product to hydrazine hydrate in step S2 is 1:(0.5-1.2), the mass ratio of the intermediate product to ethylene glycol monomethyl ether solution is 1:(10-25), and the concentration of hydrazine hydrate is 80-99%.

6. The method of claim 2, wherein the method is characterized by: The purification in steps S1 and S2 is silica gel column chromatography purification.

7. The method of claim 6, wherein the method is characterized by: The eluent used for silica gel column chromatography purification in step S1 is dichloromethane, and the eluent used for silica gel column chromatography purification in step S2 is dichloromethane and methanol with a volume ratio of (20-30):

1.

8. The fluorescent probe for identifying and detecting formaldehyde according to claim 1 is applied to the detection of formaldehyde.

9. Use of the recognition fluorescent probe for detecting formaldehyde according to claim 8 in detecting formaldehyde, characterized in that, The fluorescent probe is mixed with a PBS phosphate buffer solution, and then a to-be-tested solution is added to detect the content of formaldehyde.

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