Ion probe based on 2-(2-hydroxybenzene) benzothiazole as well as synthesis method and application of ion probe

Abstract

The invention discloses an ion probe based on 2-(2-hydroxybenzene) benzothiazole as well as a synthesis method and application of the ion probe. The ion probe is abbreviated as [DBU-HBT], a DMF solution of [DBU-HBT] and an aqueous solution of agarose are mixed and left to stand to form hydrogel, the problem of loading of a water-insoluble probe in the hydrogel is solved, meanwhile, the aggregation-induced effect of the probe is reserved, the requirement of a portable device is met, and a new thought is provided for on-site detection of the pH of a beverage in the environment.

Description

Technical Field

[0001] This invention relates to the field of ion probe technology, specifically to an ion probe based on 2-(2-hydroxybenzene)benzothiazole (HBT), its synthesis method, and its application. This ion probe, loaded onto an agarose hydrogel, can be used for rapid and convenient detection of pH in beverages. Background Technology

[0002] The pH value of beverages is a core quality and safety indicator. For neutral to acidic beverages (pH range of approximately 1-8), precise pH control is crucial for maintaining flavor, ensuring safety, and optimizing production. However, in the context of the high-speed operation of the modern beverage industry and the diversification of consumption scenarios, traditional pH testing methods, such as precision laboratory pH meters, suffer from drawbacks such as large size, high equipment cost, and the need for calibration, making rapid pH detection of beverages impossible. Therefore, there is an urgent need to develop rapid, accurate, and field-applicable pH testing technologies.

[0003] Hydrogels are functional materials composed of a three-dimensional cross-linked hydrophilic network, capable of absorbing and retaining large amounts of water within their structure. With their excellent biocompatibility and mechanical flexibility, hydrogels have shown broad application prospects in many fields such as gas detection and biosensors. However, due to the typically high water content of hydrogels, most probes with poor water solubility tend to precipitate within the hydrogel due to insufficient solubility, leading to reduced probe loading efficiency and decreased stability. This problem significantly limits the range of functional probes that can be used in hydrogels. Therefore, developing a hydrogel capable of effectively loading probes with poor water solubility has significant practical needs and research value.

[0004] This invention discloses an ion probe based on 2-(2-hydroxybenzene)benzothiazole (HBT) and its synthesis method. This ion probe, loaded onto a hydrogel, can be used for rapid and convenient pH detection in beverages. The invention involves mixing an aqueous solution of agarose and a solution of the ion probe in N,N-dimethylformamide (DMF), followed by cooling to form a gel. The process is simple and involves few steps. The developed ion probe exhibits an aggregation-inducing effect, resulting in enhanced fluorescence intensity in aqueous solutions. Because the ion probe is sensitive to acidity, its fluorescence is rapidly quenched in acidic solutions. This invention uses DMF to load the ion probe onto an agarose hydrogel, solving the problem of loading poorly water-soluble probes into hydrogels, preserving the high-brightness fluorescence signal resulting from the aggregation-inducing effect of the probe, and meeting the requirements of portable devices. This provides a new approach for loading poorly water-soluble probes and for on-site pH detection in environmental solutions. Summary of the Invention

[0005] The present invention aims to provide an ion probe based on 2-(2-hydroxybenzene)benzothiazole (HBT), its synthesis method, and its applications. This probe exhibits aggregation-induced emission (AIE) and has poor water solubility; therefore, aggregation occurs in aqueous solutions, resulting in significantly enhanced fluorescence. Simultaneously, the probe is sensitive to acidity, and its fluorescence is quenched in acidic solutions.

[0006] The present invention further describes the assembly of a portable hydrogel detection device by loading the probe with a DMF solution onto the hydrogel, which is applied to the rapid, sensitive, and quantitative detection of pH in beverages.

[0007] The technical solution of the present invention is as follows: An ion probe based on 2-(2-hydroxybenzene)benzothiazole, abbreviated as [DBU-HBT], has the following structural formula: [DBU-HBT] The synthesis method of the ion probe [DBU-HBT] based on 2-(2-hydroxybenzene)benzothiazole described in this invention is as follows: 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 2-(2-hydroxybenzene)benzothiazole (HBT) were dissolved in acetonitrile and reacted under stirring and reflux at 80-90°C for 5-18 h. The solvent was then removed by vacuum evaporation and dried under an inert atmosphere to obtain the ion probe [DBU-HBT]. The preferred molar ratio of 1,8-diazabicyclo[5.4.0]undec-7-ene to 2-(2-hydroxybenzene)benzothiazole is 1:1; It is preferred to dry at 60~100℃ in a nitrogen atmosphere.

[0008] A hydrogel loaded with an ion probe [DBU-HBT] was prepared according to the following method: The DMF (N,N-dimethylformamide) solution of the ion probe [DBU-HBT] was mixed with an aqueous solution of agarose (AG), and the mixture was ultrasonically dispersed. The mixture was then placed at room temperature under an inert atmosphere and allowed to stand for 30 minutes to form a hydrogel. The preferred mass ratio of ion probe [DBU-HBT] to agarose is 1:10~20; The preferred concentration of the DMF solution for the ion probe [DBU-HBT] is 3-4 mg / mL; The preferred concentration of agarose in aqueous solution is 30-50 mg / mL.

[0009] The hydrogel containing the ion-loaded probe [DBU-HBT] described in this invention can be used for rapid, sensitive, and portable detection of pH in beverages. Specific application methods are as follows: (1) Draw the standard curve The hydrogel loaded with the ion probe [DBU-HBT] was added to a series of buffer solutions with different pH values. After 10 seconds, the hydrogel was removed and the fluorescence spectrum at 400~700 nm was detected. A standard curve was plotted with the pH value of the buffer solution on the x-axis and the fluorescence intensity of the hydrogel on the y-axis. The buffer solution is selected from: phosphate-sodium dihydrogen phosphate buffer solution and disodium hydrogen phosphate-citric acid buffer solution; the pH range of the buffer solution is 1~8; Preferably, the fluorescence spectrum at 460 nm is detected within the pH range of 8 to 4; and the fluorescence spectrum at 510 nm is detected within the pH range of 4 to 1. (2) Actual sample testing The sample to be tested was sonicated (100~350W) to remove air bubbles, and a hydrogel loaded with ion probe [DBU-HBT] was added. After 10s, the hydrogel was removed and the fluorescence spectrum of 400~700nm was detected. The measured fluorescence intensity was substituted into the standard curve of step (1) to calculate the pH value of the sample to be tested.

[0010] Furthermore, the hydrogel loaded with the ion probe [DBU-HBT] was added to a series of buffer solutions with different pH values, and removed after 10 seconds. The fluorescence change of the hydrogel was recorded under a 365nm UV lamp to create a fluorescence standard colorimetric card. Within the pH range of 8 to 1, the color of the fluorescence standard colorimetric card gradually changes from strong blue fluorescence to darker and finally to green fluorescence; In actual sample testing, the sample to be tested is sonicated to remove air bubbles, and then a hydrogel loaded with ion probe [DBU-HBT] is added. After 10 seconds, the sample is removed and the fluorescence change of the hydrogel is observed under a 365nm ultraviolet lamp. The pH value of the actual sample is determined by comparing it with the fluorescence standard colorimetric card.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention designs and prepares an ion probe [DBU-HBT] based on 2-(2-hydroxybenzene)benzothiazole, which can be used for rapid, sensitive, and portable detection of pH in beverages. In aqueous solutions, the probe exhibits a bright fluorescence signal due to aggregation-induced emission, providing clear, visually visible fluorescence sensing. In acidic environments, the fluorescence of [DBU-HBT] is quenched; while in strongly acidic environments, the protonated probe exhibits green fluorescence due to precipitation.

[0012] This invention provides a significant fluorescence color change signal by loading a single fluorescent molecule. An ion probe-loaded hydrogel is prepared by simply mixing a DMF solution of [DBU-HBT] with an AG solution. The hydrogel loading retains the aggregation-induced effect of the probe, providing a bright fluorescence signal; loading the probe onto the hydrogel meets the requirements of portable devices. This invention provides a new approach to the loading problem of water-insoluble probes and to the on-site detection of solution pH in the environment. Attached Figure Description

[0013] Figure 1 : The 1H NMR spectrum of the ion probe [DBU-HBT] synthesized in this invention in deuterated dimethyl sulfoxide.

[0014] Figure 2 The carbon NMR spectrum of the ion probe [DBU-HBT] synthesized in this invention in deuterated dimethyl sulfoxide.

[0015] Figure 3 Three-dimensional fluorescence spectra of HBT and the ion probe [DBU-HBT] synthesized in this invention.

[0016] Figure 4 Two-dimensional fluorescence spectra of HBT and the ion probe [DBU-HBT] synthesized in this invention.

[0017] Figure 5 This invention uses the fluorescence intensity of [DBU-HBT] as the ordinate and wavelength as the abscissa to show the fluorescence spectrum of the probe in solutions with different water contents; the upper part of the figure shows the fluorescence visualization effect of the probe in solutions with different water contents under a 365nm wavelength ultraviolet lamp.

[0018] Figure 6 Visualization of [DBU-HBT] under a 365nm UV lamp in buffer solutions at pH 8 and 1.

[0019] Figure 7 This invention uses the fluorescence intensity of [DBU-HBT] as the ordinate and wavelength as the abscissa to show the fluorescence spectrum in buffer solutions at different pH values.

[0020] Figure 8 This invention uses the fluorescence intensity of [DBU-HBT] at 460 nm and 510 nm as the ordinate and the solution pH as the abscissa to obtain the linear range calibration curve.

[0021] Figure 9 The image shows the visualization of a hydrogel prepared using DMF and ethanol as probe solvents under an inert gas atmosphere for 1 hour, under a 365nm UV lamp.

[0022] Figure 10This invention uses the fluorescence intensity of the [DBU-HBT]-loaded hydrogel as the ordinate and the water content of the hydrogel as the abscissa to create a bar chart showing the fluorescence intensity changes of the hydrogel at different water contents.

[0023] Figure 11 This invention uses the fluorescence intensity of the [DBU-HBT]-loaded hydrogel as the ordinate and the pH of the solution as the abscissa to obtain the fluorescence spectrum of the response to solutions at different pH values.

[0024] Figure 12 The present invention is based on the [DBU-HBT] hydrogel, and the fluorescence images were taken under a 365 nm lamp after detecting solutions with different pH values. Detailed Implementation

[0025] The present invention will be further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0026] In the following embodiments, All chemical reagents and solvents used were commercially available analytical grade. The fluorescence spectroscopy measurement conditions were set with an excitation wavelength of 380 nm, an emission wavelength of 400–600 nm, and excitation and emission slit widths of 2.5 nm and 2.5 nm, respectively.

[0027] Example 1: Synthesis of ion probe [DBU-HBT]

[0028] 1,8-diazabicyclo[5.4.0]undec-7-ene (1.52 g, 0.01 mol) and 2-(2-hydroxybenzene)benzothiazole (2.27 g, 0.01 mol) were placed in a single-necked flask, dissolved in 40 mL of acetonitrile, and reacted thoroughly at 85 °C for 6 h with stirring. After the reaction was completed, the solvent was removed by evaporation under reduced pressure, and the product was dried at 80 °C under a nitrogen atmosphere for 12 h to obtain the ionized product [DBU-HBT].

[0029] Example 2: Fluorescence properties of the ion probe [DBU-HBT] and its sensitive detection of solution pH.

[0030] (1) Fluorescence properties of the HBT ionization product [DBU-HBT]: Accurately weigh [DBU-HBT] and dissolve it in tetrahydrofuran to prepare a solution of 1.0 × 10⁻⁶. -2 The standard stock solution of M was prepared in the same manner to a concentration of 1.0 × 10⁻⁶. -2 M's HBT solution. The above solutions were poured into separate quartz dishes, and their three-dimensional and two-dimensional fluorescence spectra were measured. The results are as follows... Figure 3 , Figure 4As shown, the fluorescence of the ionized product exhibits a significant red shift, and the fluorescence intensity is significantly enhanced.

[0031] (2) AIE effect of [DBU-HBT] in aqueous solution fluorescence: Accurately weigh [DBU-HBT] and dissolve it in DMF to prepare a solution of 1.0 × 10⁻⁶. -2 The standard stock solution of M was added to a centrifuge tube, and then diluted to 1.0 mL with water and DMF. After mixing well, the solution was poured into a quartz dish, and the fluorescence spectra were measured at different water contents (0–90%), with a probe concentration of 0.1 mM. The results are as follows: Figure 5 As shown.

[0032] (3) [DBU-HBT] detection of solution pH: In a solution with a water content of 90% and a probe concentration of 0.1 mM, the fluorescence of the probe was gradually quenched as the solution pH changed from 8 to 1, and the fluorescence intensity at 460 nm gradually decreased. Under strongly acidic conditions, the fluorescence intensity at 510 nm gradually increased, as shown in the results. Figure 7 As shown, fluorescence intensity exhibits a good linear relationship with solution pH. Figure 8 As shown, the equation of the linear standard correction curve is fitted as follows: F （pH=8-4） = 1021.58x- 3853.30 (R 2 = 0.996); F (pH=4-1) =-22.84x+ 111.05 (R) 2 =0.996).

[0033] Example 3: Preparation of hydrogels loaded with ion probes [DBU-HBT]

[0034] 0.6 g of agarose (AG) was added to 20 mL of deionized water, heated to 90 °C, and stirred until dissolved to form an AG solution. 0.038 g of the ion probe DBU-HBT was dissolved in 10 mL of DMF to obtain a probe solution. The probe solution and AG solution were added dropwise to a centrifuge tube and then sonicated for 1 min to mix evenly. The mixture was then transferred dropwise into the cap of a 10 mL centrifuge tube and cooled at room temperature under nitrogen for 30 min. Finally, the hydrogel in the cap was removed to obtain a [DBU-HBT]-loaded hydrogel.

[0035] In the hydrogel preparation process, the choice of probe solvent needs to meet the following requirements: good solubility of the probe, good compatibility with agarose (not interfering with the subsequent preparation of agarose hydrogel), and low volatility to maintain the solvent ratio in the hydrogel, preserve the probe's AIE performance in the hydrogel, and ensure good hydrogel stability. DMF possesses the characteristics of high boiling point, low volatility, and good compatibility; therefore, DMF was chosen as the solvent.

[0036] To compare the performance differences of hydrogels prepared with different solvents, hydrogels with a water content of 70% were prepared using ethanol and DMF as probe solvents, respectively. Both hydrogels were placed in an inert gas atmosphere for 1 hour. The results are as follows: Figure 9 As shown, the probe precipitates out due to solvent evaporation in the hydrogel prepared with ethanol.

[0037] Example 4: Fluorescence properties of hydrogels supported by ion probe [DBU-HBT], sensitive to solution pH, and portable detection.

[0038] (1) AIE effect in [DBU-HBT] hydrogel: The aqueous solution of agarose and the DMF solution of the probe were mixed evenly in a centrifuge tube. The probe concentration was 0.5 mM. The water content varied depending on the ratio of the added solutions, resulting in hydrogels with water contents ranging from 40% to 90%. The fluorescence intensity of hydrogels with different water contents at 460 nm was measured, and the results are as follows: Figure 10 As shown.

[0039] (2) Detection of solution pH by [DBU-HBT] hydrogel

[0040] Prepare buffer solutions with pH values ​​of 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, and 8. Buffer solutions with pH values ​​of 1–2.5 consist of phosphate-sodium dihydrogen phosphate; buffer solutions with pH values ​​of 3.0–8.0 consist of disodium hydrogen phosphate-citric acid. The preparation methods for buffer solutions with pH values ​​of 2.5 and 3.0 are given as examples; the preparation methods for the other buffer solutions are similar.

[0041] Preparation of a phosphate-sodium dihydrogen phosphate buffer solution with pH 2.5: Weigh 12.0 g of anhydrous sodium dihydrogen phosphate, dissolve it, and dilute to 1 L to obtain a 0.1 M solution. Take 6.7 mL of 85% concentrated phosphoric acid, dilute with water to 100 mL, and obtain a 1 M phosphoric acid solution. Transfer 100 mL of the 0.1 M sodium dihydrogen phosphate solution to a clean beaker, insert a pH meter, and slowly add the phosphoric acid solution dropwise until the pH meter reads 2.5.

[0042] Preparation of a disodium hydrogen phosphate-citric acid buffer solution with a pH of 3.0: Weigh 28.40 g of anhydrous disodium hydrogen phosphate, dissolve and dilute to 1 L to obtain a 0.2 M solution. Weigh 21.01 g of citric acid monohydrate, dissolve and dilute to 1 L to obtain a 0.1 M solution. Transfer 100 mL of the citric acid solution to a clean beaker, insert a pH meter, and slowly add the disodium hydrogen phosphate solution dropwise until the pH meter reads 3.0.

[0043] A 70% water-content hydrogel was placed in buffer solutions of different pH values. After 10 seconds, it was removed, and its fluorescence intensity in the 400–700 nm range was measured. A good linear relationship was observed between the fluorescence intensity and the solution pH. Figure 11 As shown, the equation for the linear standard calibration curve of the hydrogel is fitted as follows: F （pH=8-4） = 1306.45x- 4978.44 (R 2 = 0.997); F (pH=4-1) =-42.18x+ 210.57 (R) 2 =0.997).

[0044] (3) Visual detection of solution pH by [DBU-HBT] hydrogel

[0045] Prepare buffer solutions with pH values ​​of 1, 2, 3, 4, 5, 6, 7, and 8 using the same method as described above.

[0046] A 70% water-content hydrogel was placed in buffer solutions of different pH values. After 10 seconds, it was removed and the fluorescence changes were recorded under a 365nm UV lamp. A fluorescence standard colorimetric card was then created to enable portable and rapid detection of solution pH. Figure 12 As shown.

Claims

1. An ion probe based on 2-(2-hydroxybenzene)benzothiazole, abbreviated as [DBU-HBT], has the following structural formula: [DBU-LBT].

2. The synthesis method of [DBU-HBT] as described in claim 1, characterized in that, The synthesis method is as follows: 1,8-diazabicyclo[5.4.0]undec-7-ene and 2-(2-hydroxybenzene)benzothiazole were dissolved in acetonitrile and reacted under reflux at 80-90°C for 5-18 h with stirring. The solvent was then removed by vacuum evaporation and dried under an inert atmosphere to obtain the ion probe [DBU-HBT].

3. The synthesis method of [DBU-HBT] as described in claim 2, characterized in that, The molar ratio of 1,8-diazabicyclo[5.4.0]undec-7-ene to 2-(2-hydroxybenzene)benzothiazole is 1:

1.

4. A hydrogel loaded with an ion probe [DBU-HBT], characterized in that, Prepared as follows: The DMF solution of [DBU-HBT] as described in claim 1 is mixed with an aqueous solution of agarose, and the mixture is ultrasonically dispersed until uniform. The mixture is then placed at room temperature under an inert atmosphere to form a hydrogel.

5. The hydrogel of the loaded ion probe [DBU-HBT] as described in claim 4, characterized in that, The mass ratio of [DBU-HBT] to agarose is 1:10~20.

6. The hydrogel of the loaded ion probe [DBU-HBT] as described in claim 4, characterized in that, The concentration of DMF solution for [DBU-HBT] is 3~4 mg / mL; the concentration of aqueous solution of agarose is 30~50 mg / mL.

7. The application of the hydrogel with the loaded ion probe [DBU-HBT] as described in claim 4 in the detection of pH in beverages.

8. The application as described in claim 7, characterized in that, The application method is as follows: (1) Draw the standard curve The hydrogel loaded with the ion probe [DBU-HBT] was added to a series of buffer solutions with different pH values. After 10 seconds, the hydrogel was removed and the fluorescence spectrum at 400~700 nm was detected. A standard curve was plotted with the pH value of the buffer solution on the x-axis and the fluorescence intensity of the hydrogel on the y-axis. The buffer solution is selected from: phosphate-sodium dihydrogen phosphate buffer solution and disodium hydrogen phosphate-citric acid buffer solution; the pH range of the buffer solution is 1~8; (2) Actual sample testing The sample to be tested was sonicated to remove air bubbles, and a hydrogel loaded with ion probe [DBU-HBT] was added. After 10 seconds, the hydrogel was removed and the fluorescence spectrum of 400~700nm was detected. The measured fluorescence intensity was substituted into the standard curve of step (1) to calculate the pH value of the sample to be tested.

9. The application as described in claim 8, characterized in that, In step (1), the fluorescence spectrum at 460 nm was detected in the buffer solution within the pH range of 8 to 4; and the fluorescence spectrum at 510 nm was detected in the buffer solution within the pH range of 4 to 1.

10. The application as described in claim 7, characterized in that, The application method is as follows: The hydrogel loaded with the ion probe [DBU-HBT] was added to a series of buffer solutions with different pH values. After 10 seconds, it was removed and the fluorescence change of the hydrogel was recorded under a 365nm UV lamp to prepare a fluorescence standard colorimetric card. In actual sample testing, the sample to be tested is sonicated to remove air bubbles, and then hydrogel loaded with ion probe [DBU-HBT] is added. After 10 seconds, it is taken out and the fluorescence change of the hydrogel is observed under a 365nm ultraviolet lamp. The pH value of the actual sample is determined by comparing it with the fluorescence standard colorimetric card. The buffer solution is selected from: phosphate-sodium dihydrogen phosphate buffer solution and disodium hydrogen phosphate-citric acid buffer solution; the pH range of the buffer solution is 1~8.

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