A MXene-based nanooxidase, preparation method and application in detecting mercury ions

Abstract

The present invention relates to the field of nanomaterials and analytical detection technology, and discloses a MXene-based nano-oxidase, a preparation method, and its application in detecting mercury ions. The method comprises mixing a MXene solution with a potassium chloroplatinite solution, uniformly dispersing the mixture through ultrasonic vibration, and reacting the mixture at 160-200°C for 5-7 hours to obtain the obtained product. The mass ratio of the added MXene to the potassium chloroplatinite is 45-55:8-8.5. The beneficial effect of the present invention is that the MXene is modified by potassium chloroplatinite to prepare a Pt / MXene composite MXene-based nano-oxidase, which can simulate the reaction between oxidase and Hg 2+ Specific binding occurs, producing a color change reaction, thereby providing a simple and efficient colorimetric biosensor for detecting Hg 2+ The method has good selectivity and high sensitivity; at the same time, the preparation method of the MXene-based nanooxidase is simple, further expanding the application potential of MXene.

Description

Technical Field

[0001] The present invention relates to the field of nanomaterials and analytical detection technology, and in particular to a MXene-based nanooxidase, a preparation method and application thereof in detecting mercury ions. Background Art

[0002] As we all know, mercury is one of the most toxic metals. The accumulation of mercury in the human body can cause severe damage to the central nervous system. Therefore, based on the selective interaction of mercury (II) with organic small molecules, synthetic polymers, DNAzymes, proteins and metal nanoclusters, people are committed to developing colorimetric, fluorescent and electrochemical Hg 2+ Sensors. It has been reported that mercury ions are deposited on the surface of Au nanoparticles via Hg-Au mercury disproportionation to change their peroxidase-like activity. However, Au 3+ , Pt 4 + and Pb 2+ ions can also be deposited on bimetallic Pt-Au nanoparticles and react with Hg 2+ The sensor system is causing interference.

[0003] It is reported that platinum nanomaterials exhibit four types of enzyme activities, including superoxide dismutase, catalase, oxidase and peroxidase. At present, many studies are devoted to controlling the particle size and nanostructure of platinum by modifying Pt nanoparticles with dendrimers, DNA and proteins. For example, Li et al. (BSA-stabilized Pt nanozymefor peroxidase mimetics and its application on colorimetric detection of mercury (II) ions [J]. Biosensors and Bioelectronics, 2015, 66: 251-258.) showed that 74% Pt 0 and 26% Pt 2+ The K of TMB by Pt nanoparticles coated with apoferritin m The K of H2O2 is 0.22mM. mis 187.25 mM; in addition, Fu et al. (DNA-based platinum nanozymes for peroxidase mimetics [J]. The Journal of Physical Chemistry C, 2014, 118 (31): 18116-18125.) showed that i-motif DNA has been used as a nucleation template to synthesize Pt nanozymes with an average size of 2.9 nm, which have an affinity for TMB 8 times higher and an affinity for H2O2 10 times lower than that of natural horseradish peroxidase.

[0004] Although Pt nanoclusters / nanoparticles possess high peroxidase-like activity, their peroxidase-mimicking properties require the use of H₂O₂. However, H₂O₂ is unstable and easily decomposes, severely impacting the accuracy and stability of the assay. Therefore, developing an oxidase-mimicking enzyme that avoids the effects of H₂O₂ has become a new development trend.

[0005] As an emerging graphene-like two-dimensional material, MXene has been considered a powerful alternative for sensing applications in recent years, with the advantages of rapid, simple and label-free detection. However, the application potential of MXene in colorimetric sensing has yet to be developed, and there is no research on the use of MXene nanomaterials to detect Hg 2+ reports. Summary of the Invention

[0006] The technical problem to be solved by the present invention is how to provide a MXene-based nanooxidase with a simple preparation method, which can simulate the reaction between oxidase and Hg 2+ Specific binding occurs to produce a color change reaction, used for Hg 2+ The detection of MXene has expanded the application potential of MXene.

[0007] The present invention solves the above technical problems through the following technical means:

[0008] In a first aspect, the present invention proposes a MXene-based nanooxidase, comprising mixing a MXene solution with a potassium chloroplatinite solution, uniformly dispersing the mixture through ultrasonic vibration, and reacting the mixture at 160-200°C for 5-7 hours; wherein the mass ratio of the added MXene to potassium chloroplatinite is 45-55:8-8.5.

[0009] Beneficial effect: The present invention uses potassium chloroplatinite to modify MXene to prepare Pt / MXene composite MXene-based nanooxidase, which can simulate the reaction between oxidase and Hg 2+ Specific binding occurs, Hg 2+The MXene-based nanooxidase forms a platinum amalgam with Pt to produce a color change reaction. At the same time, the Pt in the MXene-based nanooxidase is evenly dispersed on the MXene, making the formation of the platinum-amalgam easier and facilitating rapid detection. This provides a simple and efficient colorimetric biosensor for detecting Hg 2+ method; and the preparation method of the MXene-based nanooxidase is simple, further expanding the application potential of MXene.

[0010] Preferably, the MXene solution is obtained by dispersing the MXene material with water, and the concentration is 0.9 to 1.1 g / L; the potassium chloroplatinite solution is obtained by dispersing the potassium chloroplatinite solid with water, and the concentration is 8 to 8.5 g / L.

[0011] Preferably, the preparation method of the MXene material comprises the following steps:

[0012] (1) Mix lithium fluoride with 8-10 mol / L hydrochloric acid and continue stirring for 30-60 minutes; add 18-22 ml of hydrochloric acid for every 1 g of lithium fluoride;

[0013] (2) slowly adding Ti3AlC2 to the mixed solution of step (1) according to the mass ratio of lithium fluoride to Ti3AlC2 of 1:0.5-1, and continuously stirring at a temperature of 35-40°C for 23-25h;

[0014] (3) centrifuging the reaction solution of step (2), and repeatedly ultrasonicating and centrifuging the precipitate with deionized water until the pH of the supernatant after centrifugation is 4 to 5;

[0015] (4) adding ethanol to the reaction solution, ultrasonicating and centrifuging, and collecting the lower precipitate;

[0016] (5) Add deionized water to the lower sediment, shake well, perform ultrasonic treatment, and centrifuge to collect the dark brown upper liquid as the lesser dispersion liquid;

[0017] (6) Repeat step (5) for 5 to 10 times, and vacuum dry the collected dispersion for 10 to 12 hours to obtain the MXene material.

[0018] Preferably, the frequency of the ultrasonic treatment in step (3) is 40-50 Hz, and the time is 10-12 min; the speed of the centrifugation is 3000-4000 rpm, and the time is 10-12 min.

[0019] Preferably, in step (4), the volume ratio of ethanol to hydrochloric acid is 1:0.9-1.1; the centrifugal speed is 10000-12000 rpm, and the time is 10-12 min.

[0020] Preferably, the centrifugal speed in step (5) is 3000-4000 rpm, and the time is 3-5 min.

[0021] The second aspect of the present invention provides a method for preparing the MXene-based nanooxidase, comprising the following steps:

[0022] (1) Mix lithium fluoride with 8-10 mol / L hydrochloric acid and continue stirring for 30-60 minutes; add 18-22 ml of hydrochloric acid for every 1 g of lithium fluoride;

[0023] (2) slowly adding Ti3AlC2 to the mixed solution of step (1) according to the mass ratio of lithium fluoride to Ti3AlC2 of 1:0.5-1, and continuously stirring at a temperature of 35-40°C for 23-25h;

[0024] (3) centrifuging the reaction solution of step (2), repeatedly ultrasonicating the precipitate with deionized water at a frequency of 40 Hz for 10 to 12 minutes and centrifuging at a speed of 3000 to 4000 rpm for 10 to 12 minutes until the pH of the supernatant after centrifugation is 4 to 5;

[0025] (4) adding ethanol to the reaction solution at a volume ratio of ethanol to hydrochloric acid of 1:0.9 to 1.1, ultrasonically treating the solution, and centrifuging the solution at 10,000 to 12,000 rpm for 10 to 12 minutes to collect the precipitate.

[0026] (5) Deionized water was added to the lower layer of sediment, and after shaking and ultrasonic treatment, the mixture was centrifuged at a speed of 3000-4000 rpm for 3-5 min, and the dark brown upper liquid was collected as a thin layer of dispersion;

[0027] (6) Repeat step (5) 5 to 10 times, and vacuum dry the collected dispersion for 10 to 15 hours to obtain the MXene material;

[0028] (7) dispersing the above MXene material in water to prepare a 0.9-1.1 g / L MXene solution, and dispersing potassium chloroplatinite solid in water to prepare an 8-8.5 g / L potassium chloroplatinite solution;

[0029] (8) The two solutions were mixed in a volume ratio of 50:1, and ultrasonically vibrated to disperse them evenly. The mixture was then reacted at 160-200 °C for 5-7 h, cooled naturally to room temperature, dialyzed, and vacuum-dried to obtain MXene-based nanooxidase.

[0030] Preferably, the molecular weight cut-off of the dialysis bag used in the dialysis in step (8) is 1000 kDa.

[0031] The third aspect of the present invention proposes an application of the MXene-based nanooxidase in detecting mercury ions.

[0032] Preferably, the application of the MXene-based nanooxidase in detecting mercury ions comprises the following steps:

[0033] The aqueous solution of the sample to be tested was mixed evenly with the MXene-based nanooxidase dispersion and incubated at room temperature for 25 to 30 minutes. Buffer solution and TMB solution were added and incubated at room temperature for 10 to 15 minutes at a pH of 3.5 to 4.0. The absorbance at 652 nm was measured by ultraviolet spectroscopy and the known concentration of Hg was substituted. 2+ The Hg content in the sample to be tested was calculated from the standard curve drawn using the same method as the standard solution. 2+ concentration.

[0034] Beneficial effect: The present invention combines MXene-based nanooxidase with Hg-containing 2+ Mix the sample, incubate for 30 minutes, add buffer solution and TMB, and a color reaction will occur. Then, through ultraviolet spectrum analysis and relevant standard curve calculation, Hg 2+ The relevant verification test also confirmed that the colorimetric sensing method based on MXene-based nanooxidase provided in this application can simply and effectively detect Hg 2+ , and has the advantages of good selectivity and high sensitivity.

[0035] Preferably, the concentration of the MXene-based nanooxidase dispersion is 0.5 mg / mL, the buffer solution uses a 0.1 mol / L HAc-NaAc buffer solution, and the concentration of the TMB solution is 1 mmol / L.

[0036] Preferably, the volume ratio of the MXene-based nanooxidase dispersion, the test sample aqueous solution, the buffer solution, and the TMB solution is 4:1:4 to 5:1.

[0037] The advantages of the present invention are:

[0038] 1. This application uses potassium chloroplatinite to modify MXene to prepare Pt / MXene composite MXene-based nanooxidase, which can simulate the reaction between oxidase and Hg 2+ Specific binding occurs, Hg 2+ The MXene-based nanooxidase forms a platinum amalgam with Pt to produce a color change reaction. At the same time, the Pt in the MXene-based nanooxidase is evenly dispersed on the MXene, making the formation of the platinum-amalgam easier and facilitating rapid detection. This provides a simple and efficient colorimetric biosensor for detecting Hg 2+The method of preparing the MXene-based nanooxidase is simple, further expanding the application potential of MXene.

[0039] 2. This invention combines MXene-based nanooxidase with Hg-containing 2+ Mix the sample, incubate for 30 minutes, add buffer solution and TMB, and a color reaction will occur. Then, through ultraviolet spectrum analysis and relevant standard curve calculation, Hg 2+ The relevant verification test also confirmed that the colorimetric sensing method based on MXene-based nanooxidase provided in this application can simply and effectively detect Hg 2+ , and has the advantages of good selectivity and high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of the preparation process of Example 1 of the present application.

[0041] Figure 2 This is a morphology diagram of the MXene-based nanooxidase prepared in Example 1 of the present application.

[0042] Figure 3 The different concentrations of Hg in Example 1 of this application 2+ Color change diagram of standard solution in reaction system.

[0043] Figure 4 The different concentrations of Hg in Example 1 of this application 2+ UV spectrum of the standard solution.

[0044] Figure 5 This is a standard curve diagram drawn in Example 1 of the present application.

[0045] Figure 6 This is a diagram showing the relationship between various metal ions and enzyme activity in Experimental Example 1 of this application. DETAILED DESCRIPTION

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0047] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0048] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0049] The present invention provides a MXene-based nano-oxidase, a preparation method and its application in detecting mercury ions. The preparation method of the MXene-based nano-oxidase comprises the following steps:

[0050] (1) Mix lithium fluoride with 8-10 mol / L hydrochloric acid and continue stirring for 30-60 minutes; add 18-22 ml of hydrochloric acid for every 1 g of lithium fluoride;

[0051] (2) slowly adding Ti3AlC2 to the mixed solution of step (1) according to the mass ratio of lithium fluoride to Ti3AlC2 of 1:0.5-1, and continuously stirring at a temperature of 35-40°C for 23-25h;

[0052] (3) centrifuging the reaction solution of step (2), repeatedly ultrasonicating the precipitate with deionized water at a frequency of 40 to 50 Hz for 10 to 12 minutes and centrifuging at a speed of 3000 to 4000 rpm for 10 to 12 minutes until the pH of the supernatant after centrifugation is 4 to 5;

[0053] (4) adding ethanol to the reaction solution at a volume ratio of ethanol to hydrochloric acid of 1:0.9 to 1.1, ultrasonically treating the solution, and centrifuging the solution at 10,000 to 12,000 rpm for 10 to 12 minutes to collect the precipitate.

[0054] (5) Deionized water was added to the lower sediment, and after shaking and ultrasonic treatment, the mixture was centrifuged at 3000-4000 rpm for 3-5 min, and the dark brown upper liquid was collected as the dispersion;

[0055] (6) Repeat step (5) 5 to 10 times, and vacuum dry the collected dispersion for 10 to 15 hours to obtain the MXene material;

[0056] (7) dispersing the above MXene material in water to prepare a 0.9-1.1 g / L MXene solution, and dispersing potassium chloroplatinite solid in water to prepare an 8-8.5 g / L potassium chloroplatinite solution;

[0057] (8) The two solutions were mixed at a volume ratio of 50:1, ultrasonically vibrated to disperse them evenly, and then reacted at 160-200 °C for 5-7 h. After naturally cooling to room temperature, the mixture was dialyzed using a 1000 kDa dialysis bag and then vacuum dried to obtain MXene-based nanooxidase.

[0058] The application of MXene-based nanooxidase in the detection of mercury ions includes the following steps:

[0059] 100 μL of Hg with a concentration of 0 to 10 μmol / L 2+ The standard solution was mixed evenly with 400 μL of 0.5 mg / mL MXene-based nanooxidase dispersion and incubated at room temperature for 25 to 30 minutes. Then, 400 μL of 0.1 mol / L HAc-Na buffer solution and 100 μL of 1 mmol / L TMB solution were added to the mixture. The mixture was incubated at room temperature for 10 to 15 minutes at a pH of 3.5 to 4.0. The UV spectrum and its absorbance at 652 nm were measured. The concentrations of Hg in the mixture were determined by UV spectroscopy. 2+ UV spectrum of the standard solution and Hg 2+ The concentration of the standard solution is the horizontal axis, and the absorbance value at 652nm is the vertical axis to draw a standard curve.

[0060] In the same manner as above, 100 μL of the sample solution to be tested was mixed evenly with 0.5 mg / mL of MXene-based nanooxidase dispersion and incubated at room temperature for 25 to 30 min. Then, 400 μL of 0.1 mol / L HAc-Na buffer solution and 100 μL of 1 mmol / L TMB solution were added to the mixture, and the mixture was incubated at room temperature for 10 to 15 min at a pH of 3.5 to 4.0. The absorbance at 652 nm was measured and substituted into the standard curve to calculate the Hg in the sample to be tested. 2+ concentration.

[0061] Example 1

[0062] This embodiment provides a MXene-based nanooxidase, a preparation method and its application in detecting mercury ions, such as Figure 1 As shown, the preparation method of MXene-based nanooxidase includes the following steps:

[0063] (1) Mix 2 g of lithium fluoride with 40 ml of 9 mol / L hydrochloric acid in a polytetrafluoroethylene beaker and stir continuously for 45 min.

[0064] (2) 1.5 g of Ti3AlC2 was slowly added to the mixed solution of step (1) and stirred at a temperature of 35-40°C for 24 h.

[0065] (3) The reaction solution of step (2) was centrifuged, and the supernatant was discarded after centrifugation. 50 mL of deionized water was added to the centrifuge tube, and the precipitate was shaken to mix the deionized water evenly. The centrifuge tube was placed in an ultrasonic cleaning machine and ultrasonicated at a frequency of 40 Hz for 10 minutes. The tube was taken out and centrifuged at a speed of 3500 rpm for 10 minutes. This was repeated several times until the pH of the supernatant after centrifugation was 4 to 5.

[0066] (4) 40 ml of ethanol was added to the above centrifuge tube as an intercalating agent, and Ti3AlC2 was separated by ultrasonic treatment. The mixture was then centrifuged at 10,000 rpm for 10 min to collect the lower precipitate.

[0067] (5) Add 20 ml of deionized water to the above lower layer of sediment, shake well, and ultrasonicate, then centrifuge at 3500 rpm for 3 min, and collect the dark brown upper liquid as the lesser layer dispersion.

[0068] (6) Repeat step (5) 5 to 10 times, and vacuum dry the collected dispersion for 12 h to obtain the MXene material.

[0069] (7) The above MXene material was dispersed in water to prepare a 1.0 mg / mL MXene solution, and potassium chloroplatinite solid was dispersed in water to prepare an 8.3 mg / mL potassium chloroplatinite solution for later use.

[0070] (8) The two solutions were mixed in a volume ratio of 50:1, ultrasonically vibrated to disperse them evenly, and then reacted at 180 °C for 6 h. After naturally cooling to room temperature, they were dialyzed using a 1000 kDa dialysis bag and then vacuum dried to obtain a Pt / MXene composite material, namely, a MXene-based nanooxidase.

[0071] The morphology of MXene-based nanooxidase was analyzed by electron microscopy. Figure 2 As shown in the figure, MXene-based nanooxidase has a two-dimensional planar structure, and Pt nanoparticles are evenly dispersed on the MXene base, which has a large specific surface area. 2+ When Hg 2+ It has stronger binding ability with the substrate.

[0072] The application of MXene-based nanooxidase in the detection of mercury ions includes the following steps:

[0073] (1) The MXene-based nanooxidase prepared above was dispersed in water to form a 0.5 mg / mL MXene-based nanooxidase dispersion for later use.

[0074] (2) 100 μL of Hg with concentrations of 0, 0.05, 0.2, 0.3, 0.5, 0.6, and 0.7 μmol / L were added. 2+The standard solution was mixed evenly with 400 μL of 0.5 mg / mL MXene-based nanooxidase dispersion and incubated at room temperature for 30 min. Then, 400 μL of 0.1 mol / L HAc-NaAc buffer solution and 100 μL of 1 mmol / L TMB solution were added to the mixture and incubated at room temperature for 10 min at pH 4.0. The reaction system turned blue. 2+ The color change of the standard solution in the reaction system is as follows Figure 3 As shown in the figure, Hg in each centrifuge tube from right to left 2+ As the concentration increases, the color gradually deepens.

[0075] Determination of Hg at different concentrations by UV spectroscopy 2+ UV spectrum of the standard solution, the results are as follows Figure 4 As shown, Hg 2+ As the concentration increases, it can be seen that the absorbance of each group of standard solutions reaches its highest at a wavelength of 652nm.

[0076] Then Hg 2+ The concentration of the standard solution is the horizontal axis, and the absorbance value at 652nm is the vertical axis. Draw a standard curve. The result is as follows Figure 5 The standard curve regression equation is: Y = 0.56-0.1C Hg 2+ , R 2 =0.99, indicating that Hg 2+ There is a feasible and linear relationship between concentration and absorbance. The colorimetric sensing method based on MXene-based nanooxidase provided in this application can simply and effectively detect Hg 2+ In addition, the detection limit of the standard curve LOD = 9nmol / L, LOD = 3S / σ, S is the relative standard deviation, σ is the slope of the standard curve, the method of this application detects Hg 2+ Concentration also has the advantage of high sensitivity.

[0077] (3) Take tap water as the water sample to be tested, take 100 μL of tap water and 400 μL of 0.5 mg / mL MXene-based nanooxidase dispersion, mix them evenly, and incubate them at room temperature for 30 min; then add 400 μL of 0.1 mol / L HAc-NaAc buffer solution and 100 μL of 1 mmol / L TMB solution to the above mixture, incubate them at room temperature for 10 min under the condition of pH = 4.0; then use ultraviolet spectroscopy to measure the absorbance value of the water sample to be tested at 652 nm, substitute it into the above standard curve, and calculate the Hg in tap water. 2+ The concentration is 37.0nmol / L.

[0078] Example 2

[0079] This embodiment provides a MXene-based nano-oxidase, a preparation method, and its application in detecting mercury ions. The preparation method of the MXene-based nano-oxidase comprises the following steps:

[0080] (1) Mix 2 g of lithium fluoride with 44 ml of 8 mol / L hydrochloric acid in a polytetrafluoroethylene beaker and stir continuously for 30 min.

[0081] (2) 1.0 g of Ti3AlC2 was slowly added to the mixed solution of step (1) and stirred at a temperature of 35-40°C for 23 h.

[0082] (3) The reaction solution of step (2) was centrifuged, and the supernatant was discarded after centrifugation. 50 mL of deionized water was added to the centrifuge tube, and the precipitate was shaken to mix the deionized water evenly. The centrifuge tube was placed in an ultrasonic cleaning machine and ultrasonicated at a frequency of 40 Hz for 11 minutes. The tube was taken out and centrifuged at a speed of 3000 rpm for 12 minutes. This was repeated several times until the pH of the supernatant after centrifugation was 4 to 5.

[0083] (4) 40 ml of ethanol was added to the above centrifuge tube as an intercalating agent, and Ti3AlC2 was separated by ultrasonic treatment. The mixture was then centrifuged at 12000 rpm for 11 min to collect the lower precipitate.

[0084] (5) Add 20 ml of deionized water to the lower layer of sediment, shake well, and ultrasonicate, then centrifuge at 3000 rpm for 5 min to collect the dark brown upper liquid as the dispersion.

[0085] (6) Repeat step (5) 5 to 10 times, and vacuum dry the collected dispersion for 10 hours to obtain the MXene material.

[0086] (7) The above MXene material was dispersed in water to prepare a 0.9 mg / mL MXene solution, and the potassium chloroplatinite solid was dispersed in water to prepare an 8.0 mg / mL potassium chloroplatinite solution for later use.

[0087] (8) The above two solutions were mixed in a volume ratio of 50:1, ultrasonically vibrated to make them uniformly dispersed, and then reacted at 160 °C for 7 h. After naturally cooling to room temperature, they were dialyzed using a 1000 kDa dialysis bag and then vacuum dried to obtain a Pt / MXene composite material.

[0088] The application of the MXene-based nanooxidase provided in this embodiment in the detection of mercury ions is to use the MXene-based nanooxidase prepared in this embodiment to draw a standard curve according to the same operation as in Example 1, and to measure the Hg 2+ The concentration is 36.5nmol / L.

[0089] Example 3

[0090] This embodiment provides a MXene-based nano-oxidase, a preparation method, and its application in detecting mercury ions. The preparation method of the MXene-based nano-oxidase comprises the following steps:

[0091] (1) Mix 2 g of lithium fluoride and 36 ml of 60 mol / L hydrochloric acid in a polytetrafluoroethylene beaker and stir continuously for 30 min.

[0092] (2) Slowly add 2.0 g of Ti3AlC2 to the mixed solution of step (1) and continue stirring at a temperature of 35-40°C for 25 h.

[0093] (3) The reaction solution of step (2) was centrifuged, and the supernatant was discarded after centrifugation. 50 mL of deionized water was added to the centrifuge tube, and the precipitate and the deionized water were evenly mixed by shaking. The centrifuge tube was placed in an ultrasonic cleaning machine and ultrasonicated at a frequency of 40 Hz for 12 minutes. The tube was taken out and centrifuged at a speed of 4000 rpm for 11 minutes. This was repeated several times until the pH of the supernatant after centrifugation was 4 to 5.

[0094] (4) 40 ml of ethanol was added to the above centrifuge tube as an intercalating agent, and Ti3AlC2 was separated by ultrasonic treatment. The mixture was then centrifuged at 11000 rpm for 12 min to collect the lower precipitate.

[0095] (5) Add 20 ml of deionized water to the lower layer of sediment, shake well, and ultrasonicate, then centrifuge at 4000 rpm for 4 min to collect the dark brown upper liquid as the dispersion.

[0096] (6) Repeat step (5) 5 to 10 times, and vacuum dry the collected dispersion for 15 h to obtain the MXene material.

[0097] (7) The above MXene material was dispersed in water to prepare a 1.1 mg / mL MXene solution, and the potassium chloroplatinite solid was dispersed in water to prepare an 8.5 mg / mL potassium chloroplatinite solution for later use.

[0098] (8) The two solutions were mixed at a volume ratio of 50:1, and ultrasonically vibrated to disperse them evenly. The mixture was then reacted at 200 °C for 5 h. After cooling naturally to room temperature, the mixture was dialyzed using a 1000 kDa dialysis bag and then vacuum dried to obtain a Pt / MXene composite material.

[0099] The application of the MXene-based nanooxidase provided in this embodiment in the detection of mercury ions is to use the MXene-based nanooxidase prepared in this embodiment to draw a standard curve according to the same operation as in Example 1, and to measure the Hg 2+ The concentration is 36.8nmol / L.

[0100] Test Example 1

[0101] The MXene-based nanooxidase prepared in Example 1 was used as a control group, and Hg 2+ 、Cu 2+ , Pb 2+ , K + Mg 2+ 、Fe 2+ 、Ba 2+ 、Zn 2+ , Ca 2+ 、Fe 3+ Cr 2+ The metal ion solution was evenly mixed with 0.5 mg / mL MXene-based nanooxidase dispersion and incubated at room temperature for 30 minutes; then, 400 μL of 0.1 mol / L HAc-NaAc buffer solution and 100 μL of 1 mmol / L TMB solution were added to each of the above mixed solutions, and incubated at room temperature for 10 minutes at pH = 4.0; the absorbance of each reaction system at 652 nm was then determined by ultraviolet spectroscopy.

[0102] After adding metal ions to MXene-based nanooxidase, the two combine to produce a color reaction. The higher the measured absorbance value, the higher the binding strength of MXene-based nanooxidase and metal ions, indicating that the MXene-based nanooxidase has a stronger selectivity for the metal ion. However, the enzyme activity of MXene-based nanooxidase in the system after the reaction is lower, that is, the measured absorbance value is negatively correlated with the residual enzyme activity of the system. After measuring the absorbance value of each group of water samples to be tested, the enzyme activity of the system after adding distilled water to the reaction is recorded as 100%, and a relationship diagram between metal ions and enzyme activity of each group is obtained. The results are shown as follows: Figure 6 shown.

[0103] from Figure 6 It can be seen that Hg 2+The enzyme activity of MXene-based nanooxidase in the reaction system is significantly lower than that of other metal ions, indicating that other metal ions have little interference with MXene-based nanooxidase, which further illustrates that the colorimetric sensing detection method based on MXene-based nanooxidase provided in this application is effective for Hg 2+ Has good selectivity; In addition, the above-mentioned addition of Hg 2+ The concentration of Hg is 50 μmol / L, and the concentrations of other metal ions are all 0.5 mmol / L, indicating that even if the concentrations of other metal ions are very high, the interference with MXene-based nanooxidase is still small, further illustrating the detection method of this application for Hg 2+ Has good selectivity.

[0104] Example 4

[0105] Using the MXene-based nanooxidase prepared in Example 1, the Hg content in lake water and tap water samples was detected by spike recovery test. 2+ The lake water was collected from Dongpu Reservoir in Hefei City and the Hg concentration was 5 μmol / L. 2+ Standard solution, tap water and lake water samples were divided into three groups 1, 2, and 3, with five parallel tests in each group, and different volumes of Hg were added to the three groups of samples. 2+ Standard solution, so that the 1st, 2nd and 3rd group samples are spiked with Hg 2+ The concentrations were 0, 0.5, and 1 μmol / L, respectively.

[0106] The above samples were mixed evenly with 0.5 mg / mL MXene-based nanooxidase dispersion and incubated at room temperature for 30 minutes. 400 μL of 0.1 mol / L HAc-NaAc buffer solution and 100 μL of 1 mmol / L TMB solution were added to each mixed solution. The mixture was incubated at room temperature for 10 minutes at pH = 4.0. Distilled water was used as a blank control. The absorbance of each reaction system at 652 nm was measured by ultraviolet spectroscopy. The absorbance values ​​of each group of samples were substituted into the standard curve in Example 1 to calculate the corresponding Hg 2+ Concentration. Hg in each group of samples 2+ The concentration determination values, spike recovery rates and relative standard deviations (RSDs) are shown in Table 1.

[0107] Table 1 Results of mercury ions in actual water samples

[0108]

[0109]

[0110] The spiked recovery of groups 2 and 3 samples = (measured value of spiked sample - measured value of sample 1) ÷ spiked amount × 100%.

[0111] From Table 1, we can see that Hg in water samples 2+ The recovery rate varied from 110% to 140%, and the relative standard deviation (RSD) was less than 3.8%, indicating that the MXene-based nanooxidase-based colorimetric sensing provided in this application has potential application value in actual samples.

[0112] Comparative Example 1

[0113] Using ICP-Mass, Hg in lake water and tap water samples was detected using the same spike recovery test. 2+ Hg in each group of samples 2+ The concentration determination values, spike recovery rates and relative standard deviations (RSDs) are shown in Table 2.

[0114] Table 2 Results of mercury ions in actual water samples

[0115]

[0116] The spiked recovery of groups 2 and 3 samples = (measured value of spiked sample - measured value of sample 1) ÷ spiked amount × 100%.

[0117] By comparing Table 1 and Table 2, it can be seen that the recovery rate and relative standard deviation (RSD) of mercury ion detection using the MXene-based nanooxidase of the present application are comparable to those of the existing ICP-Mass method, indicating that the colorimetric sensor based on the MXene-based nanooxidase provided in the present application has good accuracy and stability in actual samples, and the method is simpler, the required instruments are cheaper, the reaction is faster, and the results are more intuitive and accurate.

[0118] The implementation principle of this application is: MXene is modified with potassium chloroplatinite to prepare a Pt / MXene composite MXene-based nanooxidase, which can simulate the reaction between oxidase and Hg 2+ Specific binding occurs, Hg 2+ The MXene-based nanooxidase forms a platinum amalgam with Pt to produce a color change reaction. At the same time, the Pt in the MXene-based nanooxidase is evenly dispersed on the MXene, making the formation of the platinum-amalgam easier and facilitating rapid detection. This provides a simple and efficient colorimetric biosensor for detecting Hg 2+ The method has good selectivity and high sensitivity; and the preparation method of the MXene-based nanooxidase is simple, further expanding the application potential of MXene.

[0119] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. Application of a MXene-based nanooxidase in detecting mercury ions, characterized by: The MXene-based nanooxidase is prepared by mixing a MXene solution with a potassium chloroplatinite solution, uniformly dispersing the mixture through ultrasonic vibration, and reacting the mixture at 160-200°C for 5-7 hours. The mass ratio of the added MXene to the potassium chloroplatinite is 45-55:8-8.

5. The preparation method of the MXene comprises the following steps: (1) Mix lithium fluoride with 8-10 mol / L hydrochloric acid and continue stirring for 30-60 min; add 18-22 ml of hydrochloric acid for every 1 g of lithium fluoride; (2) Slowly add Ti3AlC2 into the mixed solution of step (1) at a mass ratio of lithium fluoride to Ti3AlC2 of 1:0.5~1, and continue stirring at a temperature of 35~40 ℃ for 23~25 h; (3) Centrifuging the reaction solution of step (2), and repeatedly ultrasonicating and centrifuging the precipitate with deionized water until the pH of the supernatant after centrifugation is 4-5; (4) Add ethanol to the above reaction solution, treat with ultrasound and centrifugation, and collect the lower precipitate; (5) Add deionized water to the lower sediment, shake well, and then perform ultrasonic and centrifugal treatment to collect the dark brown upper liquid as the lesser dispersion liquid; (6) Repeat step (5) 5 to 10 times, and vacuum dry the collected dispersion for 10 to 12 h to obtain MXene.

2. The use of the MXene-based nanooxidase in detecting mercury ions according to claim 1, characterized in that: The MXene solution is obtained by dispersing the MXene material with water, and the concentration is 0.9-1.1 g / L; the potassium chloroplatinite solution is obtained by dispersing potassium chloroplatinite with water, and the concentration is 8-8.5 g / L.

3. The use of the MXene-based nanooxidase in detecting mercury ions according to claim 1, characterized in that: In the step (4), the volume ratio of ethanol to hydrochloric acid is 1:0.9-1.

1.

4. The use of the MXene-based nanooxidase in detecting mercury ions according to claim 1, characterized in that: The frequency of the ultrasonic treatment in step (3) is 40-50 Hz, the time is 10-12 min, the centrifugal speed is 3000-4000 rpm, and the time is 10-12 min; the centrifugal speed in step (4) is 10000-12000 rpm, and the time is 10-12 min; the centrifugal speed in step (5) is 3000-4000 rpm, and the time is 3-5 min.

5. The use of the MXene-based nanooxidase in detecting mercury ions according to any one of claims 1 to 4, characterized in that: The preparation method of MXene-based nanooxidase comprises the following steps: (1) Mix lithium fluoride with 8-10 mol / L hydrochloric acid and continue stirring for 30-60 min; add 18-22 ml of hydrochloric acid for every 1 g of lithium fluoride; (2) Slowly add Ti3AlC2 into the mixed solution of step (1) at a mass ratio of lithium fluoride to Ti3AlC2 of 1:0.5~1, and continue stirring at a temperature of 35~40 ℃ for 23~25 h; (3) The reaction solution of step (2) was centrifuged, and the precipitate was repeatedly ultrasonicated with deionized water at a frequency of 40 Hz for 10 to 12 minutes and centrifuged at a speed of 3000 to 4000 rpm for 10 to 12 minutes until the pH of the supernatant after centrifugation was 4 to 5; (4) Add ethanol to the reaction solution at a volume ratio of ethanol to hydrochloric acid of 1:0.9-1.

1. After ultrasonic treatment, centrifuge at 10,000-12,000 rpm for 10-12 min and collect the lower precipitate. (5) Add deionized water to the lower layer of sediment, shake well, and ultrasonicate, then centrifuge at 3000-4000 rpm for 3-5 min, and collect the dark brown upper liquid as the dispersion layer; (6) Repeat step (5) 5 to 10 times, and vacuum dry the collected dispersion for 10 to 15 hours to obtain the MXene material; (7) The above-mentioned MXene material is dispersed in water to prepare a 0.9-1.1 g / L MXene solution, and potassium chloroplatinite solid is dispersed in water to prepare an 8-8.5 g / L potassium chloroplatinite solution; (8) The two solutions were mixed at a volume ratio of 50:1, and ultrasonic vibration was used to disperse them evenly. The mixture was then reacted at 160-200 °C for 5-7 h, cooled naturally to room temperature, and dialyzed and vacuum-dried to obtain MXene-based nanooxidase.

6. The use of the MXene-based nanooxidase in detecting mercury ions according to claim 1, characterized in that: The method comprises the following steps: uniformly mixing the aqueous solution of the sample to be tested with the MXene-based nanooxidase dispersion and incubating at room temperature for 25-30 min; adding a buffer solution and a TMB solution and incubating at room temperature for 10-15 min at a pH of 3.5-4.0, and measuring the absorbance at 652 nm by ultraviolet spectroscopy, and substituting the known concentration of Hg into the absorbance. 2+ The Hg content in the sample to be tested was calculated from the standard curve drawn using the same method as the standard solution. 2+ concentration.

7. The use of the MXene-based nanooxidase in detecting mercury ions according to claim 6, characterized in that: The concentration of the MXene-based nanooxidase dispersion is 0.5 mg / mL, the buffer solution uses a 0.1 mol / L HAc-NaAc buffer solution, and the concentration of the TMB solution is 1 mmol / L.

8. The use of the MXene-based nanooxidase in detecting mercury ions according to claim 7, characterized in that: The volume ratio of the MXene-based nanooxidase dispersion, the test sample aqueous solution, the buffer solution, and the TMB solution is 4:1:4 to 5:1.

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