A Cr-based two-dimensional MOF oxide mimicking enzyme activity 6+ Rapid detection method and test paper

Abstract

This invention belongs to the field of heavy metal detection technology, specifically relating to a Cr detection method based on two-dimensional MOFs oxide mimicking enzyme activity. 6+ Rapid detection method and test strip. This invention first prepares two-dimensional MOF nanomaterials with a layered structure using a surfactant-mediated method, then mixes them with BR buffer, TMB, and halide ions to form a catalytic reaction system, and finally uses a quantitative analysis standard curve to rapidly test the Cr content of the sample. 6+ Concentration, while in Cr 6+ A rapid detection test strip was prepared based on the rapid detection method to achieve Cr 6+ Visual detection. This invention does not rely on large instruments or professional operators. The reagents are stable, safe, and highly sensitive. The test strips are easy to use, and Cr levels as low as 50 ppb can be qualitatively determined with the naked eye. 6+ The entire process is simple and quick, and can be used to detect Cr in samples such as water in basic environmental environments. 6+ On-site, rapid, and highly sensitive detection of content.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heavy metal detection, and particularly relates to a kind of Cr 6+ Fast detection method and test paper. BACKGROUND

[0002] Chromium is widely used in modern industry such as electroplating, metallurgy, tanning, dyeing and other industries. The discharge of three wastes in factories leads to the continuous release of heavy metal chromium into the environment, causing serious harm to human health, and is one of the must-measure items of environmental monitoring. Chromium in nature has various valence states, and the common ones are Cr 3+ and Cr 6+ , which have significant differences in biological activity. Among them, Cr 3+ is a trace element essential for the human body, while Cr 6+ has relatively stronger mobility and carcinogenic properties, which is more harmful to human health, and is a recognized human respiratory carcinogen. Therefore, the World Health Organization has clearly stipulated that the Cr 6+ in groundwater cannot exceed 50 ppb. Traditional heavy metal chromium detection often relies on large instruments and professional operators, with high detection cost, and can only detect the total chromium content in the sample, and cannot selectively detect Cr 6+ ; The fast detection method popular on the market has low sensitivity, relies on toxic and harmful reagents such as mercury and expensive reagents such as antibodies, and cannot meet the needs of the majority of the grassroots for trace, economical, safe and accurate screening of heavy metal Cr 6+ in environmental water and other samples.

[0003] Nanoprotease has similar activity to natural enzymes, and compared with natural enzymes, it has higher stability, more flexible structure and composition design, and adjustable catalytic activity, which has attracted the attention of researchers in recent years, and has been widely used in the analysis and detection of inorganic ions, toxins, bacteria and other fields. Metal-organic frameworks (MOFs) are ordered porous crystalline materials formed by metal centers and organic ligands through coordination, which are a typical nanometer enzyme material. According to the structure, it can be divided into two-dimensional MOFs and three-dimensional MOFs. Compared with three-dimensional MOFs, two-dimensional MOFs have ultra-thin thickness and large surface area, which can expose more surface active sites, enhance the interaction with substrate molecules such as TMB in the color reaction system of nanometer enzyme, and improve the adsorption amount, thereby providing powerful conditions for improving the catalytic reaction efficiency and the detection sensitivity of the target. At the same time, the ultra-thin lateral size can effectively shorten the diffusion distance of substrate molecules such as TMB in the color reaction system, and accelerate the catalytic response to the substrate molecules. Therefore, it is necessary to use MOF nanometer material to realize the on-site, rapid, simple and high-sensitivity detection of Cr 6+ . SUMMARY

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the present application realizes the on-site, rapid, simple and high-sensitivity detection of Cr 6+ based on the mediation of halogen ions and the activity of two-dimensional MOFs oxide mimetic enzyme.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0006] The first aspect of the present application provides a rapid detection method based on the activity of two-dimensional MOFs oxide mimetic enzyme, which comprises the following steps: 6+

[0007] S1, first, the metal ion with variable valence, organic ligand, surfactant and benzoic acid are dissolved in a mixed solvent of ethanol and N,N-dimethylformamide, then heated under stirring, and finally obtained two-dimensional MOFs nanomaterials after washing and resuspension;

[0008] S2, the two-dimensional MOFs nanomaterials of step S1, BR buffer solution, 3,3',5,5'-tetramethylbenzidine (TMB) solution and halogen ion solution are mixed to form a catalytic reaction system, then different concentrations of Cr 6+ standard solution is added for reaction, finally the change value of absorbance of TMB oxidation product at 652nm after the addition of Cr 6+ is tested by ultraviolet-visible spectrophotometer, and a quantitative analysis standard working curve is drawn with Cr 6+ concentration as abscissa and absorbance change value as ordinate;

[0009] S3, the sample to be tested containing Cr 6+ is added to the catalytic reaction system of step S2, and the absorbance value at 652nm after reaction is detected, and the concentration of Cr 6+ in the sample to be tested is calculated according to the quantitative analysis standard working curve drawn in step S2.

[0010] The present application uses surfactant as a mediation molecule, metal ion with variable valence as a metal center, organic ligand and benzoic acid as control molecules, obtains two-dimensional MOFs with lamellar structure, then mixes it with BR buffer solution, 3,3',5,5'-tetramethylbenzidine (TMB) and halogen ions to form a catalytic reaction system, based on the mediation of halogen ions, the activity of two-dimensional MOFs oxide mimetic enzyme is regulated by Cr 6+ , a method for selective detection of Cr 6+ is constructed, realizing the on-site, rapid, simple and high-sensitivity detection of Cr 6+ in environmental water and other samples.

[0011] ​Preferably, in step S1, the metal ions with variable valence are selected from Cu 2+ , Ce 3+ , Ce 4+ , the organic ligand is TCPP, the surfactant is PVP, and the volume ratio of ethanol and N,N-dimethylformamide is 1:3.

[0012] Preferably, in step S1, the concentration of the metal ions with variable valence is 0.05-0.5mg / mL, the concentration of the organic ligand is 0.1-0.5mg / mL, the concentration of the surfactant is 0.1-1mg / mL, and the concentration of the benzoic acid is 1-10mg / mL.

[0013] Preferably, in step S1, the heating treatment is 90-95℃ oil bath heating for 3-5h.

[0014] Preferably, in step S2, the pH of the BR buffer is 2-5, the concentration of the TMB solution is 0.5mM-30mM, the concentration of the halide ion solution is 0.1M-2M, and the halide ion in the halide ion solution is selected from I - , Cl - , Br - ; and the volume ratio of the two-dimensional MOFs nanomaterial, the BR buffer, the TMB solution and the halide ion solution is 0.5-20:150-170:5-15:5-15.

[0015] Preferably, in step S2, the concentration of the Cr 6+ standard solution is 0.5ppb, 5ppb, 10ppb, 25ppb, 50ppb, 100ppb, 0.25ppm, 0.5ppm, 1ppm, 1.5ppm, 2ppm, 2.5ppm, 3ppm, 4ppm and 5ppm, respectively, the test wavelength of the absorbance is 652nm, and the equation of the quantitative analysis standard working curve drawn is: y=0.69973x+0.00415, R 2 is 0.9989, x is the Cr 6+ concentration, y is the absorbance change value at 652nm, and the linear range for detecting Cr 6+ is 0.5ppb-2ppm.

[0016] Preferably, in step S2, the reaction time after adding the Cr 6+ standard solution into the catalytic reaction system is 2-5min, and the reaction temperature is 20-25℃.

[0017] Preferably, in step S1, the washing is sequentially performed with ethanol and water, and the solution for resuspension is water.

[0018] The second aspect of the present application provides a kind of Cr 6+ Rapid detection test paper, the Cr 6+ Preparation method of rapid detection test paper is: test paper is placed in the catalytic reaction system described in the first aspect and is soaked and treated, after drying, it is obtained.

[0019] The Cr 6+ In the first aspect of the present application 6+ On the basis of rapid detection test method, rapid detection test paper is prepared, the visualization detection of Cr 6+ Is realized, further promote the on-site, rapid, simple, high sensitive detection of Cr 6+ In the sample of basic environmental water etc.And, the present application does not need to rely on large instrument and professional operator, reagent is stable, safe and environment-friendly, high sensitivity, the Cr 6+ Of 50ppb can be detected by naked eye using test paper.

[0020] Preferably, the soaking treatment time is 2-5h, and the drying is room temperature drying.

[0021] The third aspect of the present application provides the application of the Cr 6+ Rapid detection test paper based on two-dimensional MOFs oxide mimetic enzyme activity of the second aspect, specifically: different concentrations of Cr 6+ Standard solution is added to the rapid detection test paper to make colorimetric card, and the Cr 6+ Concentration of the sample to be measured is directly read out by colorimetric card according to the color change of the sample to be measured on the rapid detection test paper.

[0022] Preferably, the concentration of the standard solution of Cr 6+ Is 0, 50, 100, 250, 500, 1000ppb respectively.

[0023] Compared with the prior art, the beneficial effects of the present application are:

[0024] The present application discloses a kind of Cr 6+ Rapid detection method and test paper based on two-dimensional MOFs oxide mimetic enzyme activity, first using surfactant mediated method to prepare two-dimensional MOFs nanomaterial with sheet structure, then it is mixed with BR buffer solution, 3,3',5,5'-tetramethyl benzidine (TMB), halogen ion constitutes catalytic reaction system, then the method for drawing quantitative analysis standard working curve is used to test the Cr 6+ Concentration of sample to be measured, while on the basis of Cr 6+ Rapid detection method, rapid detection test paper is prepared, the visualization detection of Cr 6+visualization detection. In the present application, the two-dimensional MOFs nanomaterials are simple in synthesis process and good in stability; the addition of halogen ions in the present application can promote the Cr 6+ oxidase mimetic enzyme activity of the two-dimensional MOFs oxides, thereby accelerating the reaction speed and improving the reaction sensitivity; the Cr 6+ in the present application has a regulating effect on the activity of the two-dimensional MOFs oxides 3+ , thereby fundamentally guaranteeing the selective detection of the Cr 6+ ; the method in the present application does not need to rely on large instruments and professional operators in the use process, and the reagent is stable, safe, high in sensitivity, simple in operation of test paper, and qualitative judgment of Cr 6+ as low as 50ppb can be made by naked eyes, and the whole process is simple and fast. Therefore, the Cr 6+ rapid detection method and test paper in the present application can realize the on-site, rapid and high-sensitivity detection of the Cr 6+ content in the environmental water and other samples at the grassroots level. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a TEM characterization diagram of the two-dimensional MOFs nanomaterials;

[0026] Figure 2 is a UV-visible absorption spectrum diagram of the Cr 6+ detection;

[0027] Figure 3 is a kinetic experiment diagram of the reaction system before (left) and after (right) the addition of sodium chloride;

[0028] Figure 4 is a standard working curve for detecting Cr 6+ ;

[0029] Figure 5 is a selective experiment result for detecting Cr 6+ ; (from left to right, the ions added are Pb 2+ , Cd 2+ , Hg 2+ , As 3+ , As 5+ , Ag + , Fe 3+ , Zn 2+ , Mn 2+ , Cr 3+ , Br - , Cr 6+ , wherein the Cr 6+ concentration is 250ppb, and the concentration of other ions is all 1ppm;

[0030] Figure 6The response graph of the rapid detection test paper to different concentrations of Cr 6+ (from left to right, the Cr 6+ concentrations are 0, 50, 100, 250, 500, and 1000 ppb, respectively). DETAILED DESCRIPTION

[0031] The specific embodiments of the present application are further described below. It should be noted that the description of these embodiments is intended for purposes of illustration, and is not intended to limit the present application. Furthermore, the various features of the present application described in the various embodiments below can be combined with each other unless specifically stated otherwise.

[0032] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials used in the following examples are all commercially available unless otherwise specified.

[0033] Example 1 A Cr 6+ rapid detection method and test paper based on the oxide mimetic enzyme activity of two-dimensional MOFs

[0034] 1. Preparation of two-dimensional MOFs nanomaterials

[0035] First, 9 mg of Cu(NO3)2, 0.1124 g of benzoic acid, 10 mg of polyvinylpyrrolidone (PVP), and 4 mg of tetrakis(4-carboxyphenyl)porphyrin (TCPP) were sequentially added to 5 mL of anhydrous ethanol and 15 mL of N,N-dimethylformamide (DMF) and ultrasonically dissolved; then, under stirring (1200 rpm), it was placed in an oil bath at 95°C for 3-5 h of heating treatment; finally, it was cooled to room temperature, sequentially washed with anhydrous ethanol and deionized water (8000 rpm, 5 min) for 3 times, and then all the products were resuspended in 10 mL of deionized water, with a concentration of 0.1 mg / mL after resuspension.

[0036] The two-dimensional MOFs nanomaterials synthesized above were subjected to TEM testing, as shown in FIG. 1, the obtained MOFs material has a sheet structure, and some parts have wrinkles. Figure 1

[0037] 2. Cr 6+ rapid detection method

[0038] First, 160 μL of BR buffer (pH = 4), 10 μL of two-dimensional MOFs nanomaterials, 10 μL of TMB solution (10 mM), and 10 μL of NaCl solution (2 M) were mixed at room temperature to form a catalytic reaction system, and then 10 μL of Cr 6+ ​standard solution, continue mixing reaction for 5 min. Finally, test Cr 6+ The change of absorbance value of TMB oxidation product at 652 nm before and after adding.

[0039] 1 ppm Cr 6+ For example, the test conditions are: the scanning wavelength range is 800-450 nm, and the UV-Vis absorption spectrum of the process and the UV-Vis absorption spectrum in the presence or absence of sodium chloride are as shown in Figure 2 The results show that the presence of NaCl can significantly improve the Cr 6+ The catalytic activity of two-dimensional MOFs nanomaterials is regulated. Further, by monitoring the change of absorbance value of TMB oxidation product at 652 nm after adding 1 ppm Cr 6+ for different time (0-35 min), the corresponding reaction kinetics curve is drawn with reaction time as abscissa and absorbance change value as ordinate, and the results are as shown in Figure 3 From which it can be seen that the addition of NaCl greatly improves the speed of color reaction, and the reaction saturation time is shortened from 30 min to 5 min, and the reaction is more complete.

[0040] Finally, with Cr 6+ concentration as abscissa (x) and 652 nm absorbance change value as ordinate (y), the standard working curve as shown in Figure 4 is obtained. The curve equation is y=0.69973x+0.00415, R 2 =0.9989. The linear range for detecting Cr 6+ is 0.5 ppb-2 ppm.

[0041] In addition, the selectivity experiment of common ions for detecting Cr 6+ was carried out. The concentration of Cr 6+ is 250 ppb, and the concentration of other ions (Pb 2 + , Cd 2+ , Hg 2+ , As 3+ , As 5+ , Ag + , Fe 3+ , Zn 2+ , Mn 2+ , Cr 3+ , Br - ) is 1 ppm, and the results are as shown in Figure 5 From the test results, it can be seen that common ions have little effect on the detection of Cr 6+ , and Cr 3+The signal after adding is also weak and can be ignored, indicating that the method of the application can selectively detect Cr 6+ .

[0042] 3、Cr 6+ Test paper and visual detection method

[0043] Cut the conventional filter paper into 0.5 cm x 0.5 cm in size, and place it in a mixed solution of BR buffer solution (pH 4.0), two-dimensional MOFs nanomaterials, 3,3',5,5'-tetramethylbenzidine (TMB) solution (10 mM) and NaCl solution (2 M) at a volume ratio of 16:1:1:1, soak for 2 h, and then take it out and dry at room temperature to obtain Cr 6+ rapid test paper.

[0044] Drop the standard solution (0, 50, 100, 250, 500, 1000 ppb) containing Cr 6+ onto the rapid test paper, and observe the color change after 1-2 min of reaction. As shown in Figure 6 , with the increase of the concentration of Cr 6+ , the blue color of the test paper becomes darker and darker, and the Cr 6+ as low as 50 ppb can be detected by the naked eye. It can be seen that by making a standard colorimetric card, the concentration of Cr 6+ in the test solution can be directly read according to the color change of the test solution on the rapid test paper. 6+

[0045] Example 2 Application of Cr 6+ rapid detection method based on two-dimensional MOFs oxide mimetic enzyme activity

[0046] Centrifuge the East Lake water, mountain spring water and tap water (12000 rpm, 5 min) to remove impurities. Then, add 100, 500 and 1000 ppb Cr 6+ standard solution as Cr 6+ simulation sample, mix well, and then detect Cr 6+ according to the method of Example 1. By measuring the absorbance change value of TMB oxidation product at 652 nm before and after the addition, and according to the working curve obtained in Example 1, the concentration and recovery rate of Cr 6+ in the simulation sample are calculated, and the specific test results are shown in Table 1. 6+

[0047] As can be seen from Table 1, the recovery rates of the three groups of East Lake water, three groups of mountain spring water and three groups of tap water simulation samples are all between 96% and 103%, which indicates that the method of the application has good effect in actual sample detection.

[0048] Table 1 Cr​​6+ Test results of the simulation samples

[0049]

[0050] As can be seen from the above, the application uses Cr 6+ The catalytic activity of the two-dimensional MOFs nanomaterial is effectively regulated, the efficiency of the color reaction is further improved, and the sensitivity of the detection is improved. 6+ Meanwhile, the above-mentioned catalytic system is prepared into a visual detection test paper, which provides strong scientific and technological support for the on-site and rapid detection of Cr 6+ in the environment and other samples at the grassroots level.

[0051] The embodiments of the application are described in detail above, but the application is not limited to the described embodiments. For those skilled in the art, various changes, modifications, replacements and variations of the embodiments can be made without departing from the principles and spirits of the application, and still fall within the protection scope of the application.

Claims

1. A Cr enzyme activity mimicking enzyme activity based on two-dimensional MOFs oxides 6+ A rapid detection method, characterized in that, Includes the following steps: S1. First, metal ions with variable valence, organic ligands, surfactants and benzoic acid are dissolved in a mixed solvent of ethanol and N,N-dimethylformamide. Then, the mixture is heated under stirring conditions. Finally, after washing and resuspending, two-dimensional MOF nanomaterials are obtained. S2. The two-dimensional MOF nanomaterials from step S1, BR buffer, TMB solution, and halide ion solution are mixed to prepare a catalytic reaction system. Then, different concentrations of Cr are added. 6+ The standard solution was used for the reaction, and finally the Cr content was measured using a UV-Vis spectrophotometer. 6 + The change in absorbance of the TMB oxidation product at 652 nm after addition, expressed as Cr 6+ A quantitative analysis standard curve was plotted with concentration on the x-axis and absorbance change on the y-axis. S3, containing Cr 6+ The sample to be tested was added to the catalytic reaction system in step S2. After the reaction, its absorbance value at 652 nm was measured, and the Cr content in the sample was calculated based on the quantitative analysis standard curve plotted in step S2. 6+ The concentration.

2. The Cr enzyme activity mimicking enzyme activity based on two-dimensional MOFs oxides as described in claim 1 6+ A rapid detection method, characterized in that, In step S1, the metal ion with variable valence is selected from Cu. 2+ Ce 3+ Ce 4+ The organic ligand is TCPP, the surfactant is PVP, and the volume ratio of ethanol to N,N-dimethylformamide is 1:

3.

3. The Cr based on two-dimensional MOFs oxide mimicking enzyme activity as described in claim 1 6+ A rapid detection method, characterized in that, In step S1, the concentration of the variable valence metal ion is 0.05-0.5 mg / mL, the concentration of the organic ligand is 0.1-0.5 mg / mL, the concentration of the surfactant is 0.1-1 mg / mL, and the concentration of benzoic acid is 1-10 mg / mL.

4. The Cr based on two-dimensional MOFs oxide mimicking enzyme activity as described in claim 1 6+ A rapid detection method, characterized in that, In step S1, the heating treatment is oil bath heating at 90-95℃ for 3-5 hours.

5. A Cr enzyme activity mimicking two-dimensional MOFs based on oxides, as described in claim 1. 6+ A rapid detection method, characterized in that, In step S2, the pH of the BR buffer is 2-5, the concentration of the TMB solution is 0.5mM-30mM, and the concentration of the halide ion solution is 0.1M-2M. The halide ions in the halide ion solution are selected from I... - Cl - ,Br - The volume ratio of two-dimensional MOF nanomaterials, BR buffer, TMB solution and halide ion solution is 0.5-20:150-170:5-15:5-15.

6. A Cr enzyme activity mimicking enzyme activity based on two-dimensional MOFs oxides, as described in claim 1. 6+ A rapid detection method, characterized in that, In step S2, Cr 6+ The concentrations of the standard solutions were 0.5 ppb, 5 ppb, 10 ppb, 25 ppb, 50 ppb, 100 ppb, 0.25 ppm, 0.5 ppm, 1 ppm, 1.5 ppm, 2 ppm, 2.5 ppm, 3 ppm, 4 ppm, and 5 ppm, respectively. The absorbance was measured at a wavelength of 652 nm. The equation for the quantitative analysis standard working curve was: y = 0.69973x + 0.00415, R0 2 The value is 0.9989, and x represents Cr. 6+ Concentration, y is the absorbance change at 652 nm, Cr is detected 6+ The linear range is 0.5 ppb-2 ppm.

7. A Cr enzyme activity mimicking enzyme activity based on two-dimensional MOFs oxides, as described in claim 1. 6+ A rapid detection method, characterized in that, In step S2, Cr is added to the catalytic reaction system. 6+ The reaction time after standard solution is 2-5 min, and the reaction temperature is 20-25℃.

8. A Cr enzyme activity mimicking enzyme activity based on two-dimensional MOFs oxides 6+ Rapid test strips, characterized in that, The Cr 6+ The rapid test strip is prepared by immersing the test strip in the catalytic reaction system described in step S2 of claim 1, and then drying it.

9. A Cr enzyme activity mimicking two-dimensional MOFs based on oxides, as described in claim 8. 6+ Rapid test strips, characterized in that, The soaking time is 2-5 hours, and the drying is done by air drying at room temperature.

10. The Cr based on two-dimensional MOFs oxide mimicking enzyme activity as described in claim 8 or 9 6+ The application of rapid test strips is characterized by, First, different concentrations of Cr 6+ A standard solution is added to rapid test strips to create a colorimetric card, which is then used to determine the presence of Cr. 6+ The color change of the sample on the rapid test strip is directly read from the colorimetric card to determine the Cr content of the sample. 6+ concentration.

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