A supramolecular fluorescent probe for visual detection of CrO4 2- ions and its preparation method and application

Abstract

The present invention discloses a supramolecular fluorescent probe for visual detection of CrO4 2‑ , its preparation method and application. The supramolecular fluorescent probe is assembled from symmetric tetramethyl cucurbit[6]uril and (E)-4-(4-hydroxystyryl)pyridinium-1-chloride in an aqueous solution. The application of the supramolecular fluorescent probe in detecting the content of CrO4 2‑ ions comprises the following application steps: 1) preparing a standard solution of the supramolecular fluorescent probe; 2) adding aqueous solutions of CrO4 2‑ with different concentrations to the standard solution of the supramolecular fluorescent probe, calculating the change value ΔI of the fluorescence emission spectrum intensity before and after addition, and making a standard curve; 3) adding a sample to be tested to the standard solution of the supramolecular fluorescent probe, and then qualitatively and quantitatively detecting CrO4 2‑ according to the fluorescence change graph and the standard curve; 4) the detection of the content of CrO4 2‑ in water can be carried out by using a smartphone for assistance. The present invention has the characteristics of low analysis cost, simple, sensitive, rapid, real-time and visual operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of analytical chemistry, and particularly relates to a supramolecular fluorescent probe for visual detection of CrO4 2- ions, a preparation method thereof, and an application thereof. Background Art

[0002] Hexavalent chromium generally exists in water in the forms of chromate, dichromate, etc. It has good industrial properties and is widely used in industrial production such as metal alloys, chromate pigments, textile dyes, and tanneries. During these industrial production processes, a large amount of chromium(VI)-rich waste will be generated. If not properly treated, chromium(VI) will enter systems such as soil and water (wastewater, surface water, groundwater), etc. The increasing concentration of chromium(VI) entering the environmental system will cause chromium pollution, which is a serious environmental threat and has an inestimable impact on our environment and health. It is worth noting that hexavalent chromium in the environment mainly exists in the form of CrO4 2- ions. Chromate is not easily converted into other valence states, can stably exist in soil and water, has high toxicity, is mobile, and is easily absorbed by organisms and accumulated in the body. Excessive exposure will endanger the health of animals, plants, and humans. CrO4 2- has strong oxidizing properties. Cr(VI) accumulated in the human body will damage cells, DNA, proteins, cell membranes, etc., resulting in varying degrees of damage to the skin, eyes, blood, respiratory system, immune system, etc. Severe cases may cause various health diseases (such as lung cancer).

[0003] Existing technologies, such as fluorescent probes for detecting multiple metal ions in water, their preparation methods, and applications, have certain deficiencies: First, this method is used to detect multiple metal ions existing in water, and the specificity is poor; Second, the Cr 3+ detected by this method is generally considered to have lower toxicity than hexavalent chromium. Summary of the Invention

[0004] The object of the present invention is to provide a fluorescent probe based on a supramolecular assembly of symmetric tetramethylhexacyclic cucurbituril, a preparation method thereof, and an application thereof. And a method for simply, portably, real-timely, and intelligently and visually detecting the content of CrO4 2- ions in water.

[0005] The technical solution of the present invention: A supramolecular fluorescent probe for visual detection of CrO4 2- ions, whose molecular formula is C 80 H 88 N 48 O 24 @C 26 H 24 Cl2N2O2, and its structural formula is as follows:

[0006]

[0007] A supramolecular fluorescence probe for visual detection of CrO4 2- ions, which is prepared by using the supramolecular interaction between (E)-4-(4-hydroxystyryl)pyridin-1-ium chloride and symmetric tetramethyl cucurbit[6]uril.

[0008] The molecular formula of the (E)-4-(4-hydroxystyryl)pyridin-1-ium chloride is C 13 H 12 ClNO, and its structural formula is as follows:

[0009]

[0010] The above-mentioned supramolecular fluorescence probe for visual detection of CrO4 2- ions, and its preparation method includes the following steps:

[0011] (1) Weigh symmetric tetramethyl cucurbit[6]uril, and then dissolve it in water to obtain solution A;

[0012] (2) Weigh (E)-4-(4-hydroxystyryl)pyridin-1-ium chloride, and then dissolve it in water to obtain solution B;

[0013] (3) Mix solution A and solution B, and then react at room temperature to obtain the supramolecular fluorescence probe.

[0014] The concentration of symmetric tetramethyl cucurbit[6]uril in solution A is 1.0×10 -3 mol / L; the concentration of (E)-4-(4-hydroxystyryl)pyridin-1-ium chloride in solution B is 1.0×10 -3 mol / L.

[0015] In step (3), solution A and solution B are mixed according to the molar ratio of symmetric tetramethyl cucurbit[6]uril to (E)-4-(4-hydroxystyryl)pyridin-1-ium chloride of 1:1.

[0016] An application of the above-mentioned supramolecular fluorescence probe in detecting the content of CrO4 2- ions in water.

[0017] Furthermore, a method for qualitatively and quantitatively detecting CrO4 2- ions in water by using the above-mentioned supramolecular fluorescence probe.

[0018] Furthermore, the application method includes the following steps:

[0019] (1) Take the supramolecular fluorescent probe and dilute it with secondary water at pH = 7 to obtain a probe standard solution with a concentration of 5.0×10 -5 mol / L;

[0020] (2) Add aqueous solutions containing different concentrations of CrO4 2- to the probe standard solution and mix evenly to form a series of gradient standard solutions. Then, with a fixed excitation wavelength of 280 nm, perform fluorescence emission spectroscopy measurements and plot the fluorescence intensity change curve at an emission wavelength of 496 nm; or take a quartz fluorescence cuvette and add a probe standard solution with a concentration of 5.0×10 -5 mol / L, and then accurately add the CrO4 2- standard solution, mix evenly, perform fluorescence emission spectroscopy measurements with a fixed excitation wavelength of 280 nm, and then, according to the above operation, successively add a quantitative CrO4 2- standard solution, and at an emission wavelength of 496, measure a series of fluorescence curves containing different concentrations of CrO4 2- , and stop the titration operation until the change in the ordinate value of the fluorescence curve is slow;

[0021] (3) According to the curve in step (2), calculate the change value ΔI of the fluorescence emission spectrum intensity at 496 nm before and after adding each gradient standard solution, and plot a linear relationship graph, then the CrO4 2- ions in the aqueous solution to be detected can be qualitatively and quantitatively tested using the linear relationship graph;

[0022] (4) By installing software on a smartphone, the actual sample can be quantitatively detected in real time for the content of CrO4 2- in the sample; specifically: add a fluorescent probe to the standard solutions at each concentration gradient, successively load them into cuvettes, take a photo in the detection platform to read the RGB value, and make a standard curve with the G / B value and the concentration; add a fluorescent probe to the sample to be tested, then load the solution into a cuvette, load the cuvette into the detection platform, turn on the ultraviolet lamp, take a photo with a smartphone and read the RGB value of the fluorescence color of the solution, and compare it with the standard curve to quantitatively detect the content of CrO4 2- in it.

[0023] In the method for detecting CrO4 2- in water using the aforementioned fluorescent probe, if the fluorescence intensity at an emission wavelength of 496 nm decreases significantly after adding the aqueous solution of the sample to be tested, it indicates that the detection solution contains CrO4 2- , and if there is no obvious change, it indicates that the water does not contain CrO4 2- or the content is lower than the detection limit of the probe; or if the color of the solution in the fluorescence cuvette quenches when photographed with the mobile phone, it indicates that the detection solution contains CrO42- , if there is no obvious change, it indicates that the water does not contain CrO4 2- or the content is lower than the detection limit of this probe.

[0024] Advantages of the present invention

[0025] The fluorescent probe prepared by the present invention is a novel supramolecular probe based on symmetric tetramethyl cucurbit[6]uril, which can specifically detect CrO4 in water 2- specifically.

[0026] The detection method of the present invention has the advantages of high sensitivity, good specificity, convenient operation and rapid determination. According to the different changes in fluorescence intensity, CrO4 in water can be 2- quantitatively detected, with the advantages of quantitative detection. Different concentrations of CrO4 were added to the standard solution of the fluorescent probe with a concentration of 5.0×10 -5 mol / L prepared by the present invention and detected in sequence. The detection results are as 2- shown. Using this figure to draw a standard curve as shown in Figure 4 , and the detection limit was calculated to be 5.74×10 Figure 4 mol / L. -7 mol / L.

[0027] In addition, the present invention also has the advantage of on-site visualization: assisted by a smart phone, under the irradiation of a 395 nm ultraviolet lamp, simply take a photo with the mobile phone and identify the RGB value of the fluorescence color of the sample to be tested. By comparing the standard curve, CrO4 in the sample to be tested can be 2- quantitatively detected. The standard curve obtained by fitting the curve of the ratio of the green and blue channels (G / B) to the corresponding CrO4 2- concentration is shown in Figure 6 .

[0028] In summary, the method of the present invention has good specificity for detecting CrO4 2- anions. CrO4 2- is one of the hexavalent chromium, which is highly toxic, easily accumulates in the body, and is a strong mutagen. Qualitative and quantitative detection of CrO4 2- is of great significance for environmental control and human health protection; the method of the present invention uses a smart phone to assist in detection, does not require large instruments, samples on-site and adds a fluorescent probe, and takes a photo with a smart phone to read the RGB value, so as to quantitatively detect CrO4 in water in real time, quickly and visually 2- ions. Description of the drawings

[0029] Figure 1It is the molecular structure diagrams of symmetric tetramethyl cucurbit[6]uril (abbreviated as TMeQ[6]) and (E)-4-(4-hydroxystyryl)pyridin-1-ammonium chloride (abbreviated as G); where: (a) The front view of the molecular structure of compound TMeQ[6]; (b) The top view of the molecular structure of compound TMeQ[6]; (c) The molecular structure diagram of compound G; (d) The schematic explanatory representation of compounds G and TMeQ[6].

[0030] Figure 2 It is the fluorescence spectra of TMeQ[6] and G; where: (a) Each time 3 μL of 1.0×10 -5 mol / L of TMeQ[6] (the molar equivalent increases from 0, 0.1, 0.2, 0.3, 0.4, 0.5... to 2.0) was added to the G solution with C(G) = 1.0×10 -3 mol / L, and the fluorescence spectra (λ em = 496 nm.); (b) At 496 nm, the curve of fluorescence intensity versus N TMeQ[6] / N G ; (c) The fluorescence job plot; (d) The plot of the ultraviolet job method of G and TMeQ[6] processed by origin software.

[0031] Figure 3 It is the NMR titration and interaction mode diagrams of TMeQ[6] and G; where (a) Symmetric tetramethyl cucurbit[6]uril; (b) The molar ratio of G to symmetric tetramethyl cucurbit[6]uril is 1:1; (c) G.

[0032] Figure 4 It is the fluorescence diagrams and standard curves; where (a) The fluorescence spectra of the probe for specific selection of different anions; (b) Under the excitation of a 395 nm ultraviolet lamp, the fluorescence photos of the probe for specific selection of different anions; (c) The fluorescence titration diagram of the probe for CrO4 2- ; (d) The standard curve diagram for calculating the detection limit using the diagram in (c).

[0033] Figure 5 It is the comparison of fluorescence quenching rates after adding interfering substances to the probe; where (a) The fluorescence quenching rate diagram of the probe after first adding CrO4 2- ions and then adding different interfering substances; (b) The fluorescence quenching rate diagrams of the probe when adding CrO4 2- and different interfering substances respectively.

[0034] Figure 6 It is the schematic diagram of the smartphone-assisted visual quantitative detection of the CrO4 2- content in the sample.

[0035] Figure 7 It is the flow chart of the smartphone-assisted visual detection. Detailed implementation mode

[0036] The present invention will be further described below in conjunction with embodiments, but it shall not be used as a basis for limiting the present invention.

[0037] Embodiment 1

[0038] A preparation method of a supramolecular fluorescent probe for visual detection of CrO4 2- ions is as follows:

[0039] (1) Take symmetric tetramethyl cucurbituril, add secondary water to dissolve it, and prepare a symmetric tetramethyl cucurbituril solution with a concentration of 1.0×10 -3 mol / L (referred to as solution A);

[0040] (2) Take (E)-4-(4-hydroxystyryl)pyridin-1-ammonium chloride, add secondary water to dissolve it, and prepare a (E)-4-(4-hydroxystyryl)pyridin-1-ammonium chloride solution with a concentration of 1.0×10 -3 mol / L (referred to as solution B);

[0041] (3) According to the molar ratio of symmetric tetramethyl cucurbituril to (E)-4-(4-hydroxystyryl)pyridin-1-ammonium chloride of 1:1, mix the symmetric tetramethyl cucurbituril solution with a concentration of 1.0×10 -3 mol / L and the (E)-4-(4-hydroxystyryl)pyridin-1-ammonium chloride solution with a concentration of 1.0×10 - 3 mol / L, and place it at room temperature for reaction for 10-20 min to obtain the supramolecular fluorescent probe.

[0042] Embodiment 2

[0043] A method for determining the content of CrO4 in an unknown aqueous solution by using the supramolecular fluorescent probe of Embodiment 1 2- comprises the following steps:

[0044] (1) Preparation of CrO4 2- standard solution:

[0045] Accurately weigh an appropriate amount of the analytical pure standard of K2CrO4, dissolve it with secondary aqueous solution with pH = 7 to obtain a CrO4 -3 standard solution with a concentration of 2.0×10 2- mol / L (referred to as solution C);

[0046] (2) Determination of the standard curve:

[0047] Take 8 10-mL volumetric flasks, add 150 μL of solution A in Example 1 and 150 μL of solution B in Example 1 to each flask, mix well, and let stand at room temperature for 15 min to form a probe. Then, add 0 μM, 10.0 μM, 20.0 μM, 30.0 μM, 40.0 μM, 50.0 μM, 60.0 μM, and 70.0 μM of 2.0×10 -3 mol / L CrO4 2- standard solution respectively. Dilute to the mark with secondary aqueous solution with pH = 7 and shake well for standby; perform fluorescence emission spectroscopy measurement with a fixed excitation wavelength of 280 nm. Take the concentration of CrO4 2- as the abscissa, and the difference (I0 - I) between the fluorescence emission intensity (I0) of the probe at 496 nm and the fluorescence emission intensity (I) after adding different concentrations of CrO4 2- as the ordinate to plot the standard curve as shown in Figure 4 ; Load the standard solutions of each concentration gradient with the probe into a cuvette in turn, take a photo in the self-made detection platform to read the RGB value, and make a standard curve with the G / B value and the concentration as shown in Figure 6 . Calculate the detection limit of the fluorescence probe for detecting CrO4 2- from the slope s of the standard curve and the standard deviation σ of measuring 11 blank values. The formula is 3σ / s.

[0048] (3) Sample detection:

[0049] Take an aqueous solution containing CrO4 2- but with an unknown concentration, add the fluorescence probe standard solution, and then at an excitation wavelength of 280 nm, if there is an obvious decrease in fluorescence intensity at 496 nm, it indicates that the water sample contains CrO4 2- . After taking a photo and comparing with the standard curve, read the G / B value and compare it with the standard curve to obtain its concentration.

[0050] Take an aqueous solution without CrO4 2- , add the fluorescence probe standard solution, and then at an excitation wavelength of 280 nm, observe that there is no obvious change in fluorescence intensity at 496 nm, which indicates that the water sample does not contain CrO4 2- ; The fluorescence probe standard solution is prepared by diluting the probe with secondary water with pH = 7 to obtain a probe standard solution with a concentration of 5.0×10 -5 mol / L;

[0051] Example 3

[0052] A method for determining the content of CrO4 2- in an unknown aqueous solution using the supramolecular fluorescence probe of Example 1, comprising the following steps:

[0053] (1) Preparation of the probe standard solution:

[0054] Take the supramolecular fluorescent probe in Example 1, add secondary water with pH = 7 to dilute it, and prepare a probe standard solution with a concentration of 5.0×10 -5 mol / L;

[0055] (2) Determination of the standard curve:

[0056] Take a quartz fluorescence cuvette, add 3000 μL of the probe standard solution with a concentration of 5.0×10 -5 mol / L, and then accurately add 7.5 μL of the CrO4 -3 standard solution with a concentration of 2.0×10 2- mol / L, mix well, fix the excitation wavelength at 280 nm and perform fluorescence emission spectrum measurement; according to the above operation, continuously add a fixed amount of 7.5 μL of the CrO4 2- standard solution to the above 3000 μL of the probe solution, and at the emission wavelength of 496 nm, measure a series of fluorescence curves until the change in the ordinate value of the fluorescence curve is slow, then stop the titration operation; then use the CrO4 2- concentration as the abscissa, and the difference between the fluorescence emission intensity of the probe at 496 nm and the fluorescence emission intensity after adding different concentrations of CrO4 2- as the ordinate to obtain the standard curve. From the slope s of the standard curve and the standard deviation σ of measuring the blank value 11 times, calculate the detection limit of the fluorescence probe for detecting CrO4 2- , and the formula is 3σ / s;

[0057] (3) Sample detection:

[0058] Take an aqueous solution containing CrO4 2- but with an unknown concentration, add the prepared fluorescence probe standard solution into it, then put the solution into a cuvette, place the cuvette on the detection platform, turn on the ultraviolet lamp, take a photo with a smartphone and read the RGB value of the fluorescence color of the solution, and compare it with the standard curve to quantitatively detect the content of CrO4 2- in it.

[0059] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent replacements or changes, and should be covered by the protection scope of the present invention.

Claims

1. A supramolecular fluorescent probe for visual detection of CrO4 2- ions, characterized in that: Its molecular formula is C 80 H 88 N 48 O 24 @C 26 H 24 Cl2N2O2, and its structural formula is: It is prepared from symmetric tetramethyl cucurbit[6]uril and (E)-4-(4-hydroxystyryl)pyridin-1-ium chloride.

2. The preparation method of a supramolecular fluorescent probe for visual detection of CrO4 2- ions, characterized in that It includes the following steps: 1) Take symmetric tetramethyl cucurbit[6]uril, and then dissolve it in water to obtain solution A; 2) Take (E)-4-(4-hydroxystyryl)pyridin-1-ium chloride, and then dissolve it in water to obtain solution B; 3) Mix solution A and solution B, and then react at room temperature to obtain the supramolecular fluorescent probe; The concentration of symmetric tetramethyl cucurbit[6]uril in the solution A is 1.0×10 -3 mol / L; the concentration of (E)-4-(4-hydroxystyryl)pyridin-1-ium chloride in the solution B is 1.0×10 -3 mol / L; In step 3), solution A and solution B are mixed according to the molar ratio of symmetric tetramethyl cucurbit[6]uril to (E)-4-(4-hydroxystyryl)pyridin-1-ium chloride being 1:

1.

3. The application of a supramolecular fluorescent probe for visual detection of CrO4 2- ions in the detection of CrO4 2- ion content in water.

4. The supramolecular fluorescence probe for visual detection of CrO4 2- ions and its application in detecting the content of CrO4 2- ions in water, characterized in that The application method is as follows: 1) Take the supramolecular fluorescent probe and dilute it with secondary water at pH = 7 to obtain a probe standard solution with a concentration of 5.0×10 -5 mol / L; 2) Add different concentrations of CrO4 to the probe standard solution 2- The aqueous solution was mixed evenly to form a series of gradient standard solutions, and then the fluorescence emission spectrum was measured with a fixed excitation wavelength of 280nm, and the fluorescence intensity change curve at the emission wavelength of 496nm was plotted; or a quartz fluorescence cuvette was taken and a concentration of 5.0×10 -5 mol / L probe standard solution, then accurately add CrO4 2- The standard solution was mixed evenly and the fluorescence emission spectrum was measured at a fixed excitation wavelength of 280 nm. Then, a certain amount of CrO4 was added gradually according to the above operation. 2- Standard solution, and measured a series of samples containing different concentrations of CrO4 at an emission wavelength of 496nm 2- The fluorescence curve can be stopped when the value of the vertical coordinate of the fluorescence curve changes slowly; 3) Calculate the change value ΔI of the fluorescence emission spectrum intensity at 496 nm before and after adding standard solutions of each gradient to the probe standard solution according to the curve in step 2), and plot a linear relationship graph, then the CrO4 in the aqueous solution to be measured can be detected by using the linear relationship graph. 2- Detection can be carried out; 4) It can be used for real-time quantitative detection of CrO4 in actual samples through smartphone-assisted means 2- Content: Add the fluorescent probe to the standard solutions at each concentration gradient, load them into the cuvettes in sequence, take pictures in the detection platform to read the RGB values, and then make a standard curve with the G / B value and the concentration; add the fluorescent probe to the sample to be tested, then load the solution into the cuvette, place the cuvette in the detection platform, turn on the ultraviolet lamp, take pictures with the smartphone and read the RGB values of the fluorescence color of the solution, and compare with the standard curve to quantitatively detect the content of CrO4 2- content.

5. The supramolecular fluorescence probe for visual detection of CrO4 2- ions and its application in detecting the content of CrO4 2- ions in water, characterized in that: In step 3), if the intensity of the fluorescence emission spectrum at 496 nm decreases significantly before and after adding the water to be tested, it indicates that the water to be tested contains CrO4 2- .

6. The application of the supramolecular fluorescent probe for visual detection of CrO4 2- ions in the detection of CrO4 2- ion content in water, characterized in that: In step 4), if the color of the solution in the fluorescence cuvette captured by the mobile phone shows quenching, it indicates that the detected solution contains CrO4 2- , and the content of CrO4 in the solution can be obtained by comparing the G / B value with the standard curve 2- . If there is no obvious change, it indicates that the water does not contain CrO4 2- or the content is lower than the detection limit of this probe.

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