Preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator

Abstract

The present invention discloses a preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator. This method uses the solvothermal method, by mixing metal ions or clusters and organic ligands in a high-boiling-point solvent and reacting under high temperature and high pressure conditions to generate MOF. The solid polymer synthesized by this method is mainly composed of metal ion ZrCl4 and organic ligand 2-aminoterephthalic acid. The sensor is obtained by modifying the synthesized solid polymer with alizarin complexone indicator to obtain a colorimetric and ratio fluorescence dual-response sensor. The present invention designs and prepares a colorimetric and ratio fluorescence dual-response sensor, which can accurately detect pH based on ultraviolet absorption and fluorescence intensity, and the detection range is 4.5-7.5, which can meet the detection requirements of the freshness and safety of aquatic products.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterial synthesis, and particularly relates to a preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator. Background Art

[0002] Alizarin is a natural coloring agent extracted from the roots of madder. Since ancient times, it has been used as a red fabric dye in industry and also as a staining reagent in biological research. Alizarin has also attracted wide attention as an acid-base indicator. With the change of pH value, two hydroxyl groups of alizarin combine with the carbonyl oxygen atom to form an intramolecular hydrogen bond, changing from yellow to purple. Since microorganisms decompose and release volatile compounds to change the pH value, alizarin has been used to develop pH-sensitive indicators in combination with various types of polymers such as cellulose / chitosan, cellulose / starch, cellulose acetate, and silica gel. However, alizarin is almost insoluble in water and it is difficult to detect the pH of aqueous solutions. Alizarin complexone indicator, namely 3-alizarin methylamine-N,N-diacetic acid, is easily soluble in alkaline aqueous solutions, its color changes with different pH values, and it is slightly soluble in water when pH>5, having the potential to detect the pH of aqueous solutions.

[0003] Establishing sensors can further improve the efficiency of pH detection. Many MOF-based fluorescence sensors are being used for pH detection. Compared with traditional detection methods, metal-organic frameworks have outstanding advantages such as high specific surface area, rich and diverse framework structures, and high crystallinity, which make them have better conditions and potential for application in biosafety detection.

[0004] In summary, a pH sensor combining luminescent MOF and alizarin complexone indicator can perform real-time / on-site visual quantitative detection of pH, making the detection process portable, fast, and low-cost. Summary of the Invention

[0005] Based on this, the present invention discloses a preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator. This method adopts the solvothermal method, and by mixing metal ions or clusters and organic ligands in a high-boiling solvent, MOF is generated under high temperature and high pressure conditions. The solid polymer synthesized by this method mainly consists of metal ions ZrCl 4 and the organic ligand 2-aminoterephthalic acid. The sensor is obtained by modifying the synthesized solid polymer with alizarin complexone indicator to obtain a colorimetric and ratio fluorescence dual-response sensor. The present invention designs and prepares a colorimetric and ratio fluorescence dual-response sensor, which can accurately detect pH based on ultraviolet absorption and fluorescence intensity, and the detection range is 4.5 - 7.5, which can meet the detection requirements of the freshness and safety of aquatic products.

[0006] An object of the present invention is to provide a preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator, and its preparation and screening process is as follows: by heating, mixing and stirring a solution of ZrCl 4 and 2-aminoterephthalic acid to obtain a reaction solution;

[0007] The reaction solution is washed, filtered and dried to obtain a solid polymer A. Among them, the detergent used during washing is absolute ethanol; the peak data of the fluorescence emission spectrum of the solid polymer A is detected and recorded.

[0008] The solid polymer A is physically mixed with an alizarin complexone indicator solution to obtain a mixed solution. Among them, the solvent used during mixing is distilled water.

[0009] The mixed solution is centrifuged, filtered and dried to obtain a solid polymer B.

[0010] The solid polymer B is added to distilled water at 1 mg / mL, and after ultrasonic oscillation, solution A is obtained. The peak data of the ultraviolet absorption and the peak data of the fluorescence emission spectrum of solution A are detected and recorded. The peak of the ultraviolet absorption appears in two absorption bands of 385±5 nm and 494±5 nm, and the fluorescence emission peak appears in two excitation bands of 424±5 nm and 449±5 nm.

[0011] Solution A is mixed with BR buffer solutions of different pH values to obtain solution B. The peak data of the fluorescence emission spectrum of solution B is detected and recorded. Using the functional relationship between different pH values in solution B and the fluorescence emission peak ratio values, the relationship between different pH values in solution B and the fluorescence response of solution A for detecting pH is obtained.

[0012] Among them, the sensor is characterized in that the sensor is composed of alizarin complexone indicator, ZrCl 4 and 2-aminoterephthalic acid, and the structures of the alizarin complexone indicator and 2-aminoterephthalic acid are as follows:

[0013]

[0014] Further, 320 mg of ZrCl 4 and 300 mg of 2-aminoterephthalic acid are respectively dissolved in 20 mL of DMF, and ultrasonic treatment is carried out until completely dissolved.

[0015] Further, the solid polymer A is synthesized by a solvothermal method.

[0016] Further, pour the 2-aminoterephthalic acid solution into a 50 mL eggplant-shaped flask, place it in silicone oil at 80 °C, turn on the magnetic stirrer, add 1 mL of acetic acid, and then slowly dropwise add the ZrCl4 solution into the eggplant-shaped flask.

[0017] Further, after the dropping is completed, stir for 30 min, turn off the magnetic stirrer, and keep heating at 80 °C for 24 h.

[0018] Further, take out the eggplant-shaped flask from the silicone oil bath after 4 h. After the solution cools to room temperature, equally transfer the solution to 4 50 mL centrifuge tubes, with 10 mL of solution in each tube. Then add 10 mL of absolute ethanol to each tube and centrifuge at 10000 rpm, 4 °C for 20 min. Discard the supernatant, add another 10 mL of absolute ethanol, and centrifuge. Repeat this step 3 times.

[0019] Further, discard the supernatant, and place the finally obtained precipitate in an oven at 75 °C until it is completely dry.

[0020] Another object of the present invention is to provide a metal-organic framework for pH detection.

[0021] Further, weigh 51 mg of alizarin complexone and dissolve it in 10 mL of distilled water. Pour the obtained alizarin complexone solution into a test tube containing UiO-66-NH 2 powder. After stirring at 200 rpm for 16 h, centrifuge at 10000 rpm, 4 °C for 20 min. Discard the supernatant, add 10 mL of distilled water to the obtained precipitate for washing and centrifuging. Repeat 3 times, and then place it in an oven at 75 °C for drying.

[0022] Further, quantitatively mix acetic acid, phosphoric acid, boric acid, and sodium hydroxide solution to obtain BR buffer solutions with different pH values.

[0023] Further, measure 0.575 mL of acetic acid and 0.685 mL of phosphoric acid, and make up the volume to the mark in 250 mL volumetric flasks respectively.

[0024] Further, weigh 0.618 g of boric acid, fully dissolve it and transfer it to a 250 mL volumetric flask to make up the volume to the mark, obtaining 250 mL of 0.04 mol / L acetic acid solution, phosphoric acid solution, and boric acid solution respectively. Mix the three acid solutions evenly to obtain the BR buffer solution.

[0025] Further, weigh 4 g of sodium hydroxide, fully dissolve it and transfer it to a 500 mL volumetric flask to make up the volume to the mark, obtaining 0.2 mol / L sodium hydroxide solution, which is stored in a refrigerator at 4 °C.

[0026] Further, 750 mL of BR buffer was evenly divided into 9 equal parts, each part being 83.33 mL. Sodium hydroxide solution was added dropwise to each part to adjust the pH to 2.5; 3.5; 4.5; 5; 5.5; 6.5; 7.5; 8.5; 9.5.

[0027] Further, the peak ratio values of the ultraviolet absorption of a series of solution B with different pH values will show a continuous upward trend as the pH value increases; the fluorescence emission peak ratio values of the fluorescence emission spectrum will also show a continuous upward trend as the pH value increases.

[0028] Further, the functional relationship between the different pH values of the solution B and the peak ratio values of the ultraviolet absorption gives the pH value corresponding to the peak ratio values of the ultraviolet absorption in the solution B; the functional relationship between the different pH values of the solution B and the fluorescence emission peak ratio values gives the pH value corresponding to the fluorescence emission peak ratio values in the solution B.

[0029] Further, the calculation method of the ultraviolet peak ratio value is: R = A 494 / A 385 ; the calculation method of the fluorescence emission peak ratio value is: R = F 424 / F 449 .

[0030] A 494 : The absorption intensity at 494 nm in the ultraviolet absorption corresponding to the sensor-containing solution;

[0031] A 385 : The absorption intensity at 385 nm in the ultraviolet absorption corresponding to the sensor-containing solution;

[0032] F 424 : The fluorescence intensity at 424 nm in the fluorescence emission spectrum corresponding to the sensor-containing solution;

[0033] F 449 : The fluorescence intensity at 449 nm in the fluorescence emission spectrum corresponding to the sensor-containing solution;

[0034] Further, A 385 and A 494 are obtained by monitoring the ultraviolet absorption peaks near 385 ± 5 nm and 494 ± 5 nm through multiple parallel experiments and calculating the average value; F 424 and F 449 are obtained by monitoring the emission peaks near 424 ± 5 nm and 449 ± 5 nm through multiple parallel experiments and calculating the average value.

[0035] For the application of the sensor in pH detection, the steps are as follows:

[0036] Further, 1400 μL of BR buffer solutions with different pH values were each taken and mixed with 600 μL of solution A to obtain solution B.

[0037] Further, incubate at 25 °C for 5 - 10 min, and observe the color change of the solution under daylight and ultraviolet light sources respectively.

[0038] Further, the color change of solution B from acidic to basic under daylight is from light yellow to pink; the color change of solution B from acidic to basic under ultraviolet light is from bright blue to blue-violet.

[0039] Further, ultraviolet absorption measurement was carried out using an ultraviolet spectrophotometer, with the absorption spectrum wavelength range of 300 - 600 nm; fluorescence emission spectrum measurement was carried out using a fluorescence spectrophotometer, with the fluorescence excitation wavelength range of 340 - 355 nm and the fluorescence emission spectrum observation range of 370 - 600 nm.

[0040] Further, the pH value corresponding to the detected substance was obtained using the functional relationship between the obtained ultraviolet peak ratio value and the pH value; the pH value corresponding to the detected substance was obtained using the functional relationship between the obtained fluorescence emission peak ratio value and the pH value.

[0041] Further, the sensor can perform colorimetric and fluorescence responses with different sensitivities to pH.

[0042] Advantages and positive effects of the present invention:

[0043] 1. The present invention uses the fluorescence of 2-aminoterephthalic acid as the fluorescence detection signal for pH, and based on the fluorescence quenching strategy, shows obvious fluorescence intensity changes, realizing visual detection.

[0044] 2. The present invention uses alizarin complexone as the colorimetric detection signal for pH, shows obvious color changes, and realizes visual detection.

[0045] 3. The sensor can perform real-time / on-site visual quantitative detection of pH, making the detection process portable, fast and low-cost.

[0046] 4. The present invention provides a preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone, and this sensor has the ability to detect the pH of aqueous solutions. Description of the Drawings

[0047] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0048] Figure 1 is the crystal structure of the UiO-66-NH 2 material provided in Example 1.

[0049] Figure 2 is the infrared spectrogram of UiO-66-NH 2 before and after mixing with alizarin complexone.

[0050] Figure 3 is the X-ray diffraction pattern of UiO-66-NH 2 before and after mixing with alizarin complexone.

[0051] Figure 4 is the scanning electron micrograph of UiO-66-NH 2 before and after mixing with alizarin complexone.

[0052] Figure 5 is the N 2 adsorption-desorption isotherm of UiO-66-NH 2 before and after mixing with alizarin complexone.

[0053] Figure 6 is the pore size distribution diagram of UiO-66-NH 2 before and after mixing with alizarin complexone.

[0054] Figure 7 is the EDS spectrum of UiO-66-NH 2 before and after mixing with alizarin complexone, including (7a) and (7b).

[0055] Figure 8 is the XPS spectrum of UiO-66-NH 2 before and after mixing with alizarin complexone.

[0056] Figure 9 is the Zeta potential diagram of the sensor solution at different pH values provided in Example 7.

[0057] Figure 10 is the colorimetric image of the sensor solution at different pH values provided in Example 7.

[0058] Figure 11 is the fluorescence image of the sensor solution at different pH values provided in Example 7.

[0059] Figure 12 is the ultraviolet absorption spectrum of the sensor solution at different pH values provided in Example 7.

[0060] Figure 13 It is the fluorescence emission spectrum of the sensor solution at different pH values provided in Example 7.

[0061] Figure 14 It is the ratio of the ultraviolet absorption peaks of the sensor solution at different pH values provided in Example 7.

[0062] Figure 15 It is the ratio of the fluorescence emission peaks of the sensor solution at different pH values provided in Example 7.

[0063] Figure 16 It is the pH ultraviolet detection curve of the sensor solution at different pH values provided in Example 7.

[0064] Figure 17 It is the pH fluorescence detection curve of the sensor solution at different pH values provided in Example 7. Detailed implementation manners

[0065] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts fall within the scope of protection of the present invention.

[0066] Unless otherwise specified, all kinds of raw materials used in the embodiments are commercially available conventional raw materials, and the technical means used are conventional means well-known to those skilled in the art.

[0067] Example 1

[0068] This example first provides a MOF material, and its synthesis method includes the following steps: Dissolve 320 mg of ZrCl 4 and 300 mg of 2-aminoterephthalic acid in 20 mL of DMF respectively, and perform ultrasonic treatment until completely dissolved.

[0069] Pour the 2-aminoterephthalic acid solution into a 50 mL eggplant flask, place it in silicone oil at 80 °C, and turn on the magnetic stirrer to stir at a speed of 200 rpm.

[0070] Add 1 mL of acetic acid, and then slowly drop the ZrCl4 solution into the eggplant flask.

[0071] After the dropping is completed, stir for 30 min, turn off the magnetic stirrer, and keep heating at 80 °C for 24 h.

[0072] After 24 h, the eggplant-shaped flask was taken out from the silicone oil bath. After the solution was cooled to room temperature, the solution was equally transferred into 4 50-mL centrifuge tubes, with 10 mL of solution in each tube. Then, 10 mL of absolute ethanol was added to each tube, and centrifugation was carried out at 10000 rpm, 4 °C for 20 min.

[0073] The supernatant was removed, and then 10 mL of absolute ethanol was added and centrifuged. This step was repeated 3 times. The finally obtained precipitate was placed in an oven at 75 °C until it was completely dry. UiO-66-NH 2 material was obtained, and its crystal structure was as Figure 1 shown.

[0074] Example 2

[0075] This example further provides a method for preparing BR buffer solutions with different pH values, which specifically includes the following steps:

[0076] 0.575 mL of acetic acid and 0.685 mL of phosphoric acid were measured and made up to the mark in 250-mL volumetric flasks respectively.

[0077] 0.618 g of boric acid was weighed, and after being fully dissolved, it was transferred to a 250-mL volumetric flask and made up to the mark to obtain 250 mL of 0.04 mol / L acetic acid solution, phosphoric acid solution and boric acid solution respectively. The three acid solutions were mixed evenly to obtain the BR buffer solution.

[0078] 4 g of sodium hydroxide was weighed, and after being fully dissolved, it was transferred to a 500-mL volumetric flask and made up to the mark to obtain 0.2 mol / L sodium hydroxide solution, which was stored in a refrigerator at 4 °C.

[0079] 750 mL of BR buffer was equally divided into 9 portions, with 83.33 mL in each portion. Sodium hydroxide solution was added dropwise to each portion to adjust the pH to 2.5; 3.5; 4.5; 5; 5.5; 6.5; 7.5; 8.5; 9.5.

[0080] Example 3

[0081] This example provides a preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator, which specifically includes the following steps:

[0082] 51 mg of alizarin complexone was weighed and dissolved in 10 mL of distilled water.

[0083] The obtained alizarin complexone solution was poured into a test tube containing UiO-66-NH 2 powder. After stirring at 200 rpm for 16 h, centrifugation was carried out at 10000 rpm, 4 °C for 20 min. The supernatant was removed, and the obtained precipitate was added with 10 mL of distilled water for washing and centrifugation. After repeating 3 times, it was placed in an oven at 75 °C for drying treatment.

[0084] For UiO-66-NH 2 and alizarin complexone@UiO-66-NH 2 were characterized, Figure 2 - 8 which were the infrared spectra, X-ray diffraction patterns, scanning electron micrographs, N 2 adsorption-desorption isotherms, pore size distribution maps, EDS spectra, and XPS spectra of UiO-66-NH 2 before and after mixing with alizarin complexone, respectively.

[0085] Alizarin complexone@UiO-66-NH 2 powder was added to distilled water at 1 mg / mL and sonicated to obtain suspension A.

[0086] Example 4

[0087] This example provides a detection method for a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator, which specifically includes the following steps:

[0088] Suspension A needs to be shaken well before use.

[0089] 1000 μL of suspension A was measured and mixed with 1000 μL of BR buffer solutions with different pH values, and incubated at 25 °C for 5 - 10 min. The color changes of the solution were observed under daylight and ultraviolet light sources, respectively.

[0090] Ultraviolet absorption measurement was performed using a UV spectrophotometer, with the absorption spectrum wavelength range of 300 - 600 nm; fluorescence emission spectrum measurement was performed using a fluorescence spectrophotometer, with the fluorescence excitation wavelength range of 340 - 355 nm and the fluorescence emission spectrum observation range of 370 - 600 nm.

[0091] The calculation method for the ultraviolet peak ratio value is: R = A 494 / A 385 ; the calculation method for the fluorescence emission peak ratio value is: R = F 424 / F 449 .

[0092] A 320 : the absorption intensity at 494 nm in the ultraviolet absorption of the sensor-containing solution;

[0093] A 390 : the absorption intensity at 385 nm in the ultraviolet absorption of the sensor-containing solution;

[0094] F 424 : the fluorescence intensity at 424 nm in the fluorescence emission spectrum of the sensor-containing solution;

[0095] F 450 : the fluorescence intensity at 449 nm in the fluorescence emission spectrum of the sensor-containing solution;

[0096] A 385 ,A 494 Obtained by monitoring the absorption peaks near 385±5 nm and 494±5 nm through multiple parallel experiments and calculating the average value. F 424 ,F 449 Obtained by monitoring the emission peaks near 424±5 nm and 449±5 nm through multiple parallel experiments and calculating the average value.

[0097] The pH value corresponding to the peak ratio value of ultraviolet absorption in the solution is obtained from the functional relationship between different pH values of the solution and the peak ratio value of ultraviolet absorption; the pH value corresponding to the peak ratio value of fluorescence emission in the solution is obtained from the functional relationship between different pH values of the solution and the peak ratio value of fluorescence emission.

[0098] Example 5

[0099] This example provides a detection method for a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator, which specifically includes the following steps:

[0100] Suspension A needs to be shaken well before use.

[0101] Measure 400 μL of suspension A and mix it with 1600 μL of BR buffer solution with different pH values, and incubate at 25 °C for 5-10 min. Observe the color change of the solution under sunlight and ultraviolet light sources respectively.

[0102] Use an ultraviolet spectrophotometer to perform ultraviolet absorption measurement, with the absorption spectrum wavelength range of 300-600 nm; use a fluorescence spectrophotometer to perform fluorescence emission spectrum measurement, with the fluorescence excitation wavelength range of 340-355 nm and the fluorescence emission spectrum observation range of 370-600 nm.

[0103] The calculation method for the ultraviolet peak ratio value is: R = A 494 / A 385 ; The calculation method for the fluorescence emission peak ratio value is: R = F 424 / F 449 .

[0104] A 320 : The absorption intensity at 494 nm in the ultraviolet absorption of the solution containing the sensor;

[0105] A 390 : The absorption intensity at 385 nm in the ultraviolet absorption of the solution containing the sensor;

[0106] F 424 : The fluorescence intensity at 424 nm in the fluorescence emission spectrum of the solution containing the sensor;

[0107] F450 : The fluorescence intensity at 449 nm in the corresponding fluorescence emission spectrum of the sensor-containing solution;

[0108] A 385 , A 494 is obtained by monitoring the absorption peaks near 385 ± 5 nm and 494 ± 5 nm through multiple parallel experiments and calculating the average value. F 424 , F 449 is obtained by monitoring the emission peaks near 424 ± 5 nm and 449 ± 5 nm through multiple parallel experiments and calculating the average value.

[0109] The pH value corresponding to the peak ratio value of ultraviolet absorption in the solution is obtained from the functional relationship between different pH values of the solution and the peak ratio value of ultraviolet absorption; the pH value corresponding to the peak ratio value of fluorescence emission in the solution is obtained from the functional relationship between different pH values of the solution and the peak ratio value of fluorescence emission.

[0110] Example 6

[0111] This example provides a detection method for a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator, which specifically includes the following steps:

[0112] Suspension A needs to be shaken well before use.

[0113] Measure 800 μL of suspension A and mix it with 1200 μL of BR buffer solution with different pH values, and incubate at 25 °C for 5 - 10 min. Observe the color change of the solution under daylight and ultraviolet light sources respectively.

[0114] Use an ultraviolet spectrophotometer for ultraviolet absorption measurement, with the absorption spectral wavelength being 300 - 600 nm; use a fluorescence spectrophotometer for fluorescence emission spectral measurement, with the fluorescence excitation wavelength being 340 - 355 nm and the fluorescence emission spectral observation range being 370 - 600 nm.

[0115] The calculation method for the ultraviolet peak ratio value is: R = A 494 / A 385 ; The calculation method for the fluorescence emission peak ratio value is: R = F 424 / F 449 .

[0116] A 320 : The absorption intensity at 494 nm in the corresponding ultraviolet absorption of the sensor-containing solution;

[0117] A 390 : The absorption intensity at 385 nm in the corresponding ultraviolet absorption of the sensor-containing solution;

[0118] F 424: Fluorescence intensity at 424 nm in the fluorescence emission spectrum corresponding to the sensor-containing solution;

[0119] F 450 : Fluorescence intensity at 449 nm in the fluorescence emission spectrum corresponding to the sensor-containing solution; A 385 ,A 494 Obtained by monitoring the absorption peaks near 385 ± 5 nm and 494 ± 5 nm through multiple parallel experiments and calculating the average value. F 424 ,F 449 Obtained by monitoring the emission peaks near 424 ± 5 nm and 449 ± 5 nm through multiple parallel experiments and calculating the average value.

[0120] The pH value corresponding to the peak ratio value of ultraviolet absorption in the solution is obtained from the functional relationship between different pH values of the solution and the peak ratio value of ultraviolet absorption; the pH value corresponding to the peak ratio value of fluorescence emission in the solution is obtained from the functional relationship between different pH values of the solution and the peak ratio value of fluorescence emission.

[0121] Example 7

[0122] This example provides a detection method for a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator, which specifically includes the following steps:

[0123] Suspension A needs to be shaken well before use.

[0124] Measure 600 μL of suspension A and mix it with 1400 μL of BR buffer solution with different pH values, and incubate at 25 °C for 5 - 10 min. Observe the color change of the solution under daylight and ultraviolet light sources respectively.

[0125] Use an ultraviolet spectrophotometer to perform ultraviolet absorption measurement, with the absorption spectral wavelength being 300 - 600 nm; use a fluorescence spectrophotometer to perform fluorescence emission spectral measurement, with the fluorescence excitation wavelength being 340 - 355 nm and the fluorescence emission spectral observation range being 370 - 600 nm.

[0126] The calculation method for the ultraviolet peak ratio value is: R = A 494 / A 385 ; The calculation method for the fluorescence emission peak ratio value is: R = F 424 / F 449 .

[0127] A 320 : Absorption intensity at 494 nm in the ultraviolet absorption corresponding to the sensor-containing solution;

[0128] A 390 : Absorption intensity at 385 nm in the ultraviolet absorption corresponding to the sensor-containing solution;

[0129] F424 : The fluorescence intensity at 424 nm in the fluorescence emission spectrum corresponding to the sensor-containing solution;

[0130] F 450 : The fluorescence intensity at 449 nm in the fluorescence emission spectrum corresponding to the sensor-containing solution;

[0131] A 385 ,A 494 is obtained by monitoring the absorption peaks near 385 ± 5 nm and 494 ± 5 nm through multiple parallel experiments and calculating the average value. F 424 ,F 449 is obtained by monitoring the emission peaks near 424 ± 5 nm and 449 ± 5 nm through multiple parallel experiments and calculating the average value.

[0132] The pH value corresponding to the peak ratio value of ultraviolet absorption in the solution is obtained from the functional relationship between different pH values of the solution and the peak ratio value of ultraviolet absorption; the pH value corresponding to the peak ratio value of fluorescence emission in the solution is obtained from the functional relationship between different pH values of the solution and the peak ratio value of fluorescence emission.

[0133] Comparative Example 4, Example 5, Example 6. The detection method in this example is the same as that in the previous examples, with the only difference being: the amounts of suspension A and BR buffer solution are different.

[0134] Experiments have proved that the effect of this example is the best. The functional relationship between the peak ratio value of ultraviolet absorption and pH is: Y = 0.5497X - 1.88713 (R 2 = 0.99142). The functional relationship between the peak ratio value of fluorescence emission and pH is: Y = 0.36159X - 0.84353 (R 2 = 0.95624).

[0135] Therefore, the Zeta potential of the mixed solution in this example is tested, Figure 9 is the Zeta potential diagram of the sensor solution at different pH values.

[0136] Figure 10 - 11 are the daylight and fluorescence images of the sensor solution at different pH values provided in Example 1.

[0137] Figure 12 is the ultraviolet absorption spectrum of the sensor solution at different pH values.

[0138] Figure 13 is the fluorescence emission spectrum of the sensor solution at different pH values.

[0139] Figure 14 is the ultraviolet absorption peak ratio of the sensor solution at different pH values.

[0140] Figure 15is the fluorescence emission peak ratio of the sensor solution at different pH values.

[0141] Figure 16 Shows the pH ultraviolet detection curves of the sensor solution at different pH values.

[0142] Figure 17 Shows the pH fluorescence detection curves of the sensor solution at different pH values.

[0143] In summary, the sensor of the present invention has a sensitive response to pH. The ratio of its ultraviolet absorption peak to fluorescence emission peak increases with the increase of pH value and shows a linear relationship within a certain range.

[0144] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

Claims

1. Preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator, characterized in that, it includes: By dissolving ZrCl 4 and 2-aminoterephthalic acid in DMF respectively and carrying out a heating reaction; The reaction solution is passed through to obtain solid polymer A after washing, filtering, and drying. Among them, the detergent used during washing is anhydrous ethanol; the solid polymer A and alizarin complexone indicator are physically mixed to obtain a mixed solution. Among them, the solvent used during mixing is distilled water; the mixed solution is passed through to obtain solid polymer B after centrifugation, filtering, and drying; The solid polymer B is added to distilled water at a concentration of 1 mg / mL, and after ultrasonic oscillation, a suspension A is obtained. The peak data of the ultraviolet absorption and the peak data of the fluorescence emission spectrum of the suspension A are detected and recorded. The peak of the ultraviolet absorption appears in two absorption bands of 385±5 nm and 494±5 nm, and the fluorescence emission peak appears in two excitation bands of 424±5 nm and 449±5 nm; The suspension A is mixed with BR buffer solutions of different pH values to obtain solution B. The peak data of the fluorescence emission spectrum of solution B are detected and recorded. Using the functional relationship between different pH values in solution B and the fluorescence emission peak ratio values, the relationship between different pH values in solution B and the fluorescence response of the corresponding solution A for detecting pH is obtained; The synthesis method of the solid polymer A includes the following steps: (1) Dissolve 320 mg of ZrCl 4 and 300 mg of 2-aminoterephthalic acid in 20 mL of DMF respectively, and perform ultrasonic treatment until completely dissolved; (2) Pour the 2-aminoterephthalic acid solution into a 50 mL eggplant-shaped flask, place it in silicone oil at 80 °C, and turn on the magnetic stirrer to stir at a speed of 200 rpm; (3) Add 1 mL of acetic acid, and then slowly drop the ZrCl 4 solution into the eggplant flask; (4) After the dropping is completed, stir for 30 min, turn off the magnetic stirrer, and keep heating at 80 °C for 24 h; (5) After 24 h, take out the eggplant-shaped flask from the silicone oil bath. After the solution cools to room temperature, transfer the solution equally to 4 50 mL centrifuge tubes, with 10 mL of solution in each tube. Then add 10 mL of anhydrous ethanol respectively and centrifuge at 10000 rpm, 4 °C for 20 min; (6) Place the finally obtained precipitate in an oven at 75 °C until it is completely dry.

2. The preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator according to claim 1, characterized in that, The sensor consists of alizarin complexone indicator, ZrCl 4 and 2-aminoterephthalic acid.

3. The preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator according to claim 1, characterized in that, The ZrCl 4 and 2-aminoterephthalic acid are respectively dissolved in 20 mL of DMF and subjected to ultrasonic treatment until completely dissolved.

4. The preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator according to claim 1, characterized in that, The solid polymer A is mixed with 51 mg of alizarin complexone indicator and 10 mL of distilled water is added for stirring.

5. The preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator according to claim 1, characterized in that, The preparation method of the BR buffer solution includes the following steps: S1. Measure 0.575 mL of acetic acid and 0.685 mL of phosphoric acid, and make up the volume in a 250 mL volumetric flask respectively; S2. Weigh 0.618 g of boric acid. After complete dissolution, transfer it to a 250 mL volumetric flask and make up the volume to the mark to obtain 250 mL each of 0.04 mol / L acetic acid solution, phosphoric acid solution and boric acid solution. Mix the three acid solutions evenly to obtain the BR buffer solution; S3. Weigh 4 g of sodium hydroxide. After complete dissolution, transfer it to a 500 mL volumetric flask and make up the volume to the mark to obtain 0.2 mol / L sodium hydroxide solution, and store it in a refrigerator at 4 °C; S4. Divide 50 mL of BR buffer into 9 equal parts, each part being 83.33 mL. Add sodium hydroxide solution dropwise to each part to adjust the pH to 2.5; 3.5; 4.5; 5; 5.5; 6.5; 7.5; 8.5; 9.

5.

6. According to the preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator as described in claim 1, characterized in that, the pH value corresponding to the peak ratio value of ultraviolet absorption in the solution B is obtained by using the functional relationship between the different pH values of the solution B and the peak ratio value of ultraviolet absorption.

7. According to the preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator as described in claim 1, characterized in that, the pH value corresponding to the peak ratio value of fluorescence emission in the solution B is obtained by using the functional relationship between the different pH values of the solution B and the peak ratio value of fluorescence emission.

8. According to the preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator as described in claim 1, characterized in that, The numerical calculation method of the ultraviolet peak ratio is: R = A 494 / A 385 , A 494 : the absorption intensity at 494 nm in the ultraviolet absorption of the sensor-containing solution; A 385 : Absorbance at 385 nm in the UV absorption of the sensor-containing solution.

9. According to the preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator as described in claim 1 or 7, characterized in that, The numerical calculation method of the fluorescence emission peak ratio value is: R = F 424 / F 449 , F 424 : the fluorescence intensity at 424 nm in the corresponding fluorescence emission spectrum of the sensor solution; F 449 : Fluorescence intensity at 449 nm in the corresponding fluorescence emission spectrum of the sensor solution.

10. According to the preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator as described in claim 1, characterized in that, Incubate at 25 °C for 5 - 10 min, and observe the color change of the solution under sunlight and ultraviolet light source.

11. According to the preparation method of a dual-mode MOF sensor for detecting pH based on alizarin complexone indicator as described in claim 1, characterized in that, it can perform colorimetric and fluorescence responses with different sensitivities to pH.

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