Preparation and application of reactive fluorescent probe DQC for detecting SO3 < 2->

Abstract

The invention provides, designs and synthesizes a reactive fluorescent probe DQC for detecting SO3 < 2->. The probe can determine the existence and concentration of SO3 < 2-> ions by measuring the intensity change of a fluorescence emission peak of the fluorescent probe in a water phase. Experiments show that the reactive fluorescent probe DQC shows specific fluorescent response to SO3 < 2->, and the change of fluorescence intensity in an aqueous solution has linear correlation with the concentration of SO3 < 2->. Meanwhile, the DQC / PVA blended hydrogel is prepared, and when SO2 gas exists in a gas phase environment, the blended hydrogel can display the existence of sulfur dioxide in the environment through visual color and fluorescence intensity changes. The research provides a solution which is low in cost and easy to operate for in-situ monitoring of atmospheric pollutants, and has definite practical potential in the fields of environmental supervision and industrial safety.

Description

Technical Field

[0001] The present invention belongs to the field of analytical chemistry, and particularly relates to the preparation and application of a reactive fluorescent probe DQC for detecting SO3 2- . Background Art

[0002] Sulfite ion (SO3 2- ) is a hydrate derivative of sulfur dioxide and is widely used as a food additive (such as a wine preservative). It can inhibit the growth and reproduction of microorganisms, prevent food from oxidizing, discoloring and deteriorating, thereby extending the shelf life of food. As an important active sulfur species, sulfite has excellent antioxidant and antibacterial abilities and is usually used in the food industry, pharmaceutical industry and chemical industry. However, excessive sulfite residues bring many hazards. Some components in food can be converted into sulfite ions under certain conditions. Long-term intake of food containing excessive sulfite preservative residues will affect the normal metabolism of the human body. Moreover, sulfite may also cause allergic reactions in asthma patients and sulfite-sensitive people, leading to symptoms such as dyspnea, rash, and gastrointestinal discomfort, seriously affecting physical health.

[0003] Traditional sulfite detection techniques such as ion chromatography, electrochemistry analysis, spectrophotometry, etc. can achieve quantitative detection to a certain extent, but these methods often have limitations such as expensive instrument equipment, complex operation, requiring professional technical personnel to operate, and cumbersome sample pretreatment, and it is difficult to meet the needs of on-site real-time detection and high-throughput analysis.

[0004] This patent develops a fluorescent probe DQC for detecting SO3 2- and its hydrogel sensing platform through molecular structure innovation and material composite strategy. The probe detects SO3 2 - ions through fluorescence spectral signals, and has characteristics such as rapid response and high selectivity. At the same time, the probe is blended with polyvinyl alcohol to form a transparent hydrogel film, which can quickly detect sulfur dioxide in the environment. Summary of the Invention

[0005] The purpose of the present invention is to provide the preparation and application of a reactive fluorescent probe DQC for detecting SO3 2- .

[0006] The technical solution to achieve the purpose of the present invention is as follows:

[0007] The preparation and application of a reactive fluorescent probe DQC for detecting SO3 2- , and the structure of this material is as follows:

[0008]

[0009] The preparation method of the reactive fluorescent probe DQC for detecting SO3 in the present invention 2- comprises the following steps:

[0010] Weigh 1.1212 g of 1,2 - cyclohexanedione and 1.658 g of 4 - methoxyo - phenylenediamine, dissolve them in 60 mL of acetonitrile, stir at 80 °C for 6 hours, then remove the solvent to obtain a viscous solid, and purify it by silica gel column chromatography to obtain a light yellow powder compound 1; dissolve 1.7141 g of compound 1 in 50 mL of anhydrous toluene, add 1.5132 g of sodium borohydride in an ice bath, stir for 15 minutes, then slowly add 10 mL of glacial acetic acid dropwise. After the addition is complete, heat the reaction solution to 110 °C and stir for 6 h. After the reaction is completed, slowly add 200 mL of water. Wash the organic phase with saturated sodium carbonate solution, dry it with anhydrous sodium sulfate, and then purify it by silica gel column chromatography to obtain a brownish - yellow viscous liquid compound 2; add 3 mL of N,N - dimethylformamide to a round - bottom flask, stir for 30 min in an ice - water bath, then slowly add 2.4 mL of POCl3 and 1.1 g of compound 2 to the round - bottom flask, heat to 75 °C and stir for 4 hours. After cooling to room temperature, pour the reaction mixture into 100 mL of ice water, neutralize it with 1 mol / L NaOH solution. Extract the product three times with ethyl acetate, dry it with anhydrous sodium sulfate, remove the solvent, dissolve it in 20 mL of DCM solution, slowly add 2.4 mL of BBr3 to the round - bottom flask under the condition of an ice - water bath, stir at 0 °C for 12 h, then pour the reaction mixture into 100 mL of ice water and neutralize it with NaHCO3; finally, extract the reaction solution with dichloromethane, dry the organic component with anhydrous sodium sulfate, remove the solvent, and purify it by silica gel column chromatography to obtain a brown viscous liquid compound 3; dissolve 0.5768 g of compound 3 in 20 mL of ethanol, add 0.2784 g of ethyl acetoacetate and 0.10 g of piperidine, stir at 78 °C for 4 h, then neutralize it with 1 mol / L HCl solution. After filtration, separation and recrystallization, a red solid compound 4 is obtained; mix 354.5 mg of compound 4 and 346.1 mg of compound 3 evenly with 10 mL of methanesulfonic acid, stir at 90 °C for 6 hours. After the reaction is completed, add 1 mol / L HClO4 solution dropwise to the reaction solution and stir. Slowly add the mixture dropwise to ice water. The obtained precipitate is washed three times with saturated brine and dried in an oven for 24 hours, and then purified by silica gel column chromatography to obtain a black - green solid, which is the reactive fluorescent probe DQC.

[0011] The reactive fluorescent probe DQC for detecting SO3 described in the present invention 2- can be used to detect SO3 in the aqueous phase 2- and can be made into a transparent hydrogel film by blending with polyvinyl alcohol, and can be used to detect sulfur dioxide in the environment.

[0012] Compared with the prior art, the significant advantages of the present invention are as follows: (1) A reactive fluorescent probe DQC for detecting SO3 in aqueous phase is synthesized in the present invention, which has the advantages of strong selectivity and relatively low detection limit. (2) The raw materials selected in the present invention have low cost, the synthesis method is simple, the reaction conditions are mild, the yield is relatively high, the post-treatment steps are few, and large-scale production is easy to achieve. (3) The reactive fluorescent probe DQC prepared in the present invention can be made into a transparent hydrogel film by blending with polyvinyl alcohol, and can be used for rapid detection of sulfur dioxide in the environment, having good application prospects. 2- (2) The raw materials selected in the present invention have low cost, the synthesis method is simple, the reaction conditions are mild, the yield is relatively high, the post-treatment steps are few, and large-scale production is easy to achieve. (3) The reactive fluorescent probe DQC prepared in the present invention can be made into a transparent hydrogel film by blending with polyvinyl alcohol, and can be used for rapid detection of sulfur dioxide in the environment, having good application prospects. Description of the Drawings

[0013] Figure 1 1H NMR spectrum of fluorescent probe DQC 1 (CDCl3, 400 MHz)

[0014] Figure 2 13C NMR spectrum of fluorescent probe DQC 13 (CDCl3, 101 MHz)

[0015] Figure 3 1H NMR spectra of fluorescent probe DQC before and after reaction with SO3 2- before and after reaction 1 (400M, DMSO)

[0016] Figure 4 (A) UV absorption spectrum of fluorescent probe DQC (B) Fluorescence emission spectrum of fluorescent probe DQC (In the inset are the photos of fluorescent probe DQC before and after reaction with SO3 under ambient light and ultraviolet light) 2- before and after reaction with SO3 under ambient light and ultraviolet light)

[0017] Figure 5 (A) Fluorescence emission spectra of probe DQC in the coexistence of different competitive anions and SO3 2- (B) Histogram of fluorescence intensity of probe DQC in the coexistence of different competitive anions and SO3 2- coexistence

[0018] Figure 6 (A) Fluorescence emission spectra of probe DQC with the addition of SO3 2- changing with time (B) Curve of fluorescence emission intensity at 650 nm changing with time

[0019] Figure 7 (A) Fluorescence emission spectra of DQC at different equivalent concentrations of SO3 2- (B) Curve of fluorescence emission intensity of DQC at 650 nm changing with the added concentration of SO3 2- (C) Linear correlation between fluorescence emission intensity of DQC and concentration of SO3 2- (D) DQC solution and DQC + SO32- Fluorescence emission intensity of the solution at different pH values

[0020] Figure 8 Preparation of DQC / PVA blend hydrogel and its method for detecting SO2 in gas phase

[0021] Figure 9 Photos of DQC / PVA blend hydrogel before and after reaction with sulfur dioxide gas Detailed implementation manners

[0022] (I) Synthesis and structural characterization of reactive fluorescent probe DQC

[0023] (II) Selective response ability of reactive fluorescent probe DQC to SO3 2-

[0024] (III) Quantitative detection of reactive fluorescent probe DQC to SO3 2-

[0025] (IV) Preparation of DQC / PVA blend hydrogel and its detection of SO2 in gas phase

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Example 1

[0028] Synthesis and structural characterization of reactive fluorescent probe DQC

[0029] ​​1.1212 g of 1,2 - cyclohexanedione and 1.658 g of 4 - methoxyo - phenylenediamine were weighed and dissolved in 60 mL of acetonitrile. After stirring at 80 °C for 6 hours, the solvent was removed to obtain a viscous solid. The compound 1 was obtained as a light - yellow powder through silica gel column chromatography; 1.7141 g of compound 1 was dissolved in 50 mL of anhydrous toluene. 1.5132 g of sodium borohydride was added in an ice - bath, and the mixture was stirred for 15 minutes. Then, 10 mL of glacial acetic acid was slowly added dropwise. After the addition, the reaction solution was heated to 110 °C and stirred for 6 h. After the reaction was completed, 200 mL of water was slowly added. The organic phase was washed with saturated sodium carbonate solution, dried with anhydrous sodium sulfate, and then purified by silica gel column chromatography to obtain a brown - yellow viscous liquid compound 2; 3 mL of N,N - dimethylformamide was added to a round - bottom flask. After stirring for 30 min in an ice - water bath, 2.4 mL of POCl3 and 1.1 g of compound 2 were slowly added to the round - bottom flask. The mixture was heated to 75 °C and stirred for 4 hours. After cooling to room temperature, the reaction mixture was poured into 100 mL of ice water, neutralized with 1 mol / L NaOH solution. The product was extracted three times with ethyl acetate, dried with anhydrous sodium sulfate. After removing the solvent, it was dissolved in 20 mL of DCM solution. 2.4 mL of BBr3 was slowly added to the round - bottom flask under ice - bath conditions. After stirring at 0 °C for 12 h, the reaction mixture was poured into 100 mL of ice water and neutralized with NaHCO3; finally, the reaction solution was extracted with dichloromethane. The organic component was dried with anhydrous sodium sulfate. After removing the solvent, it was purified by silica gel column chromatography to obtain a brown - viscous liquid compound 3; 0.5768 g of compound 3 was dissolved in 20 mL of ethanol. 0.2784 g of ethyl acetoacetate and 0.10 g of piperidine were added. After stirring at 78 °C for 4 h, it was neutralized with 1 mol / L HCl solution. After filtration, separation, and recrystallization, a red solid compound 4 was obtained; 354.5 mg of compound 4 and 346.1 mg of compound 3 were mixed evenly with 10 mL of methanesulfonic acid. After stirring at 90 °C for 6 hours, after the reaction was completed, 1 mol / L HClO4 solution was added dropwise to the reaction solution and stirred. The mixture was slowly added dropwise to ice water. The obtained precipitate was washed three times with saturated brine and dried in an oven for 24 hours. It was purified by silica gel column chromatography to obtain a black - green solid probe DQC (yield 21.3%).

[0030] The specific preparation route is as follows:

[0031] For the reactive fluorescent probe DQC 1 1H NMR spectrum, 13 13C NMR spectrum are shown in the attached Figure 1 , 2 of the specification respectively.

[0032] Example 2

[0033] The reactive fluorescent probe DQC for SO3 2-Selective response ability

[0034] Several common anions (SO3 2- , CH2COO - , Br - , Cl - , ClO - , ClO4 - , CO3 2- , F - , H2PO4 - , HCO3 - , HS - , HSO3 - , I - , NO2 - , PO4 3- , S 2- , S2O3 2- , SO4 2- ) are selected to explore the selective response ability of the probe DQC to SO3 2- .

[0035] The selectivity of a fluorescent probe is one of the important indicators of the response efficiency of a fluorescent sensor to a target. Excellent selectivity can respond only to a single target ion and exclude the interference of other ions, so the target can be accurately identified. To explore the selectivity of the probe DQC to SO3 2- , the ultraviolet-visible spectrum and fluorescence spectrum of the fluorescent probe DQC solution are tested in this patent. 5 mM of different anions such as SO3 2- , CH2COO - , Br - , Cl - , ClO - , ClO4 - , CO3 2- , F - , H2PO4 - , HCO3 - , HS - , HSO3 - , I - , NO2 - , PO4 3- , S 2- , S2O3 2- , SO4 2- etc. are added to the 1 mM DQC solution, and after stirring and standing for 15 min, spectral tests are carried out. It can be found that different anions can cause different changes in the spectral signals ( Figure 4 ). When there is only the probe DQC and anions other than SO3 2-When anions other than DQC are added, it can be found that the absorption peak at 410nm of its UV absorption spectrum does not change significantly compared with that of the solution containing only DQC. The solution always appears blue with naked eye without obvious color change ( Figure 4 A) When SO3 2- When added to the probe solution, it can be found that the ultraviolet absorption peak at 410nm is red-shifted, and the solution changes from blue to yellow-green when observed with the naked eye. Similar rules can also be found in the fluorescence emission spectrum. The ratio of the fluorescence emission intensity of the probe DQC solution at 550nm and 650nm (I 550 / I 650 ) and SO3 2- I of DQC solution 550 / I 650 There have been very obvious changes ( Figure 4 B), added SO3 2- Probe Solution I 550 / I 650 Is the probe DQC solution I 550 / I 650 4.7 times of SO3 2- When the anions other than 2-hydroxy-2-nitropropene were added to the probe DQC solution, it was found that most of the anions had I 550 / I 650 There is no obvious change, among which ClO - 、H2PO4 - , HS - PO4 3- , S 2- Although the addition of 550 / I 650 There was also a slight change, but it was far less than adding SO3 2- Time I 550 / I 650 The results of UV-visible spectroscopy and fluorescence emission spectroscopy show that the probe DQC has a significant effect on SO3 2- It has a highly specific recognition ability and is used to make SO3 2- Specific recognition sensors have great potential.

[0036] Whether the fluorescent probe can work stably in a complex environment is one of the important indicators to measure the performance of the probe. Therefore, this patent conducted a coexistent anion competition experiment to explore the effect of DQC on SO3 under the interference of other ions. 2- Continue to add SO3 to the solution of the above selective experiment 2- After being shaken thoroughly, the solution was left to stand for 15 minutes for testing. By comparing the fluorescence emission spectrum of the solution containing only the DQC probe, it was found that all the solutions containing SO3 2-The fluorescence emission spectrum of the mixed solution changes significantly ( Figure 5 A). In the bar chart, the blue part represents the addition of SO3 2- of the mixed solution I 550 / I 650 , and the yellow part represents I 2- of the DQC probe and anions other than SO3 550 / I 650 ( Figure 5 B). It can be seen that the anti-interference ability of the probe DQC is very strong. Even in a very complex environment, when combined with SO3 2- , the fluorescence can change from red to yellow and the color of the solution can change from blue to yellow-green, indicating that the probe DQC can work very stably even in a complex ionic environment.

[0037] One of the significant advantages of a fluorescence probe is its ability to rapidly respond to the target substance. A rapid response can improve the efficiency of detecting the target substance. Therefore, in this paper, experiments were designed to detect the response speed of DQC to SO3 2- . The prepared SO3 2- ionic solution was added to the pre-prepared DQC probe solution, gently shaken, and quickly placed in a fluorescence spectrometer for detection. Since the response between DQC and SO3 2- occurs in real time, and the changes in the fluorescence emission intensities at 550 nm and 650 nm are sufficient to indicate its response to SO3 2- , in order to avoid errors caused by too long a single scan time, the wavelength scan range was reduced to 500 nm to 700 nm, with a scan interval of 10 s each time until I 550 / I 650 reached the maximum value. As Figure 6 shown, the fluorescence emission intensity of the probe DQC solution changed rapidly after the addition of SO3 2- ions. At the 10th second, I 550 / I 650 had already approached the maximum fluorescence emission intensity ratio. After 10 s, the increase trend of I 550 / I 650 slowed down, indicating that the probe DQC had completely reacted with SO3 2- ions very quickly. Due to the time required for the machine itself to scan, it was impossible to accurately measure the changes every second. Therefore, it is likely that the probe had completely reacted within 10 s, and the reaction speed was very rapid. It could also be observed with the naked eye that the DQC solution quickly changed from blue to yellow-green after the addition of the SO3 2- solution, indicating that DQC could also directly detect SO3 2- ions with the naked eye.

[0038] Example 3

[0039] Quantitative detection of SO3 by probe DQC 2-

[0040] This patent studied the quantitative relationship and detection limit between probe DQC and SO3 through quantitative analysis. Add 60 μL of standard probe solution (1 mM) to 3 mL of ethanol, and then gradually add 1 equivalent (2.4 μL, 5 mM) of SO3 2- ion solution. After mixing evenly, perform spectral testing. It can be found from the fluorescence emission spectrum ( 2- A), the ratio of fluorescence emission intensities at 550 nm and 650 nm gradually increases with the increase of SO3 Figure 7 concentration. When it reaches 27 equivalents, the fluorescence intensity reaches the maximum and no longer increases. At this time, the concentration of SO3 2- titrated to the end point is 108 μM. In the range of 5 - 11 eq., the fluorescence emission intensity of probe DQC is linearly correlated with the concentration ( 2- B). Therefore, a linear fit is performed in the range of 20 - 44 μM, and the linear fit equation is obtained as y = 0.03523x - 0.10892 ( Figure 7 C). From formula 1 and formula 2, the detection limit of the probe can be obtained as Figure 7 where S is the slope of the linear fit equation, and SD is the standard deviation of the fluorescence intensity ratio at 550 nm and 650 nm of the fluorescence spectra measured ten times for the DQC solution. The lowest detection limit of the fluorescence probe DQC can be calculated as 0.2808 μM.

[0041] To enable the fluorescence probe to achieve the best working state, a suitable pH range is essential. To find the best working environment, this patent tested the fluorescence intensity of the DQC probe in different pH environments (1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0) ( Figure 7 D). From the change of fluorescence emission intensity, it can be seen that DQC is sensitive to pH, and the fluorescence emission intensity will also change with the change of pH. However, in any pH condition, when SO3 2- ions are added to the DQC solution, a very significant increase in fluorescence emission intensity can be observed, indicating that the probe DQC has a high specific recognition ability for SO3 2- in the pH range of 1 - 12.

[0042] Example 4

[0043] ​​Application of DQC / PVA Blend Hydrogel in the Detection of Sulfur Dioxide (SO2)

[0044] The DQC / PVA blend hydrogel developed based on this fluorescent probe exhibits excellent visualization performance in the detection of gaseous sulfur dioxide (SO2).

[0045] The preparation of the DQC / PVA blend hydrogel and the method for SO2 detection are as Figure 8 shown.

[0046] Add 2 g of polyvinyl alcohol (PVA) to 8 mL of water, heat to 80 °C and continuously stir mechanically for 1 hour until the PVA is completely dissolved in the water. Then add 0.2 mL of the DQC standard probe solution and stir mechanically for 30 min to uniformly mix the probe in the solution. Slowly drop the mixed solution into a mold (60*20*2 mm), clamp it with a glass slide, and demold it after natural drying at ambient temperature for 24 h to obtain the DQC / PVA blend hydrogel.

[0047] Add 1 g of Na2SO3 to a test tube, place a dropping funnel containing concentrated sulfuric acid above the test tube, hang the DQC / PVA blend hydrogel above the test tube, and when only a few drops of concentrated sulfuric acid are added to the test tube, a large amount of SO2 gas is generated inside the test tube. Experiments show that when the SO2 gas contacts the surface of the hydrogel, it can quickly dissolve in the aqueous phase environment inside the gel and be converted into sulfite ions (SO3 2- ), thereby triggering the specific recognition reaction of the probe molecule. This process causes the color of the hydrogel to change from blue to yellow-green within 5 seconds, and there is a significant change in the fluorescence signal from yellow to green under ultraviolet light excitation ( Figure 9 ). This immediate and intuitive dual-mode response characteristic enables the qualitative discrimination of SO2 in the air without relying on sophisticated instruments.

[0048] Compared with traditional detection methods, the DQC / PVA blend hydrogel has the following outstanding advantages: First, the flexible and transparent material properties allow it to be directly attached to the surface of industrial pipelines or ventilation equipment, and on-site real-time monitoring can be completed through naked-eye observation or a portable ultraviolet lamp; Second, the three-dimensional network structure of the gel matrix can effectively enrich trace amounts of SO2, significantly improving the gas detection sensitivity; Third, the material can still maintain a stable signal output in complex environments (such as high humidity and coexistence of multiple interfering gases). This research provides a low-cost and easy-to-operate solution for in-situ monitoring of atmospheric pollutants, and has clear practical potential in the fields of environmental supervision and industrial safety.

Claims

1. A method for detecting SO3 2- The reactive fluorescent probe DQC has the following structure:

2. A method for detecting SO3 as claimed in claim 1 2- The method for preparing the reactive fluorescent probe DQC comprises the following steps: 1.1212 g of 1,2-cyclohexanedione and 1.658 g of 4-methoxy-o-phenylenediamine were weighed and dissolved in 60 mL of acetonitrile. After stirring at 80° C. for 6 hours, the solvent was removed to obtain a viscous solid, which was purified by silica gel column chromatography to obtain a light yellow powder compound 1; 1.7141 g of compound 1 was dissolved in 50 mL of anhydrous toluene, 1.5132 g of sodium borohydride was added in an ice bath, stirred for 15 minutes, and then 10 mL of glacial acetic acid was slowly added dropwise. After the addition was complete, the reaction solution was heated to 110° C. and stirred for 6 hours. After the reaction was completed, 200 mL of water was slowly added, and the organic phase was washed with a saturated sodium carbonate solution, dried over anhydrous sodium sulfate, and then purified by silica gel column chromatography to obtain a brown-yellow viscous liquid compound 2; 3 mL of N,N-dimethylformamide was added to a round-bottom flask, stirred in an ice-water bath for 30 minutes, and then 2.4 mL of POCl3 and 1.1g of compound 2 were heated to 75°C and stirred for 4 hours. After cooling to room temperature, the reaction mixture was poured into 100mL of ice water and neutralized with 1mol / L NaOH solution. The product was extracted three times with ethyl acetate, dried over anhydrous sodium sulfate, and dissolved with 20mL of DCM solution after removing the solvent. 2.4mL of BBr3 was slowly added to a round-bottom flask under ice-water bath conditions. After stirring at 0°C for 12h, the reaction mixture was poured into 100mL of ice water and neutralized with NaHCO3; finally, the reaction solution was extracted with dichloromethane, the organic component was dried over anhydrous sodium sulfate, and after removing the solvent, it was purified by silica gel column chromatography to obtain a brown viscous liquid compound 3; 0.5768g of compound 3 was dissolved in 20mL of ethanol, 0.2784g of ethyl acetoacetate and 0.10g of piperidine were added, and after stirring at 78°C for 4h, 1mol / L HCl solution was neutralized, and red solid compound 4 was obtained after filtration separation and recrystallization; 354.5 mg of compound 4 and 346.1 mg of compound 3 were mixed evenly with 10 mL of methanesulfonic acid, and stirred at 90 ° C for 6 hours. After the reaction was completed, 1 mol / L HClO4 solution was added dropwise to the reaction solution and stirred, and the mixed solution was slowly added dropwise to ice water. The obtained precipitate was washed three times with saturated brine, dried in an oven for 24 hours, and purified by silica gel column chromatography to obtain a black-green solid, which is the reactive fluorescent probe DQC; The structures and the entire synthesis routes of compounds 1 to 4 and the fluorescent probe DQC are shown below:

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