A colorimetric / fluorescent dual-mode nanozyme sensor, a preparation method thereof and application thereof in formaldehyde detection

Abstract

The application provides a colorimetric / fluorescent dual-mode nanoscale enzyme sensor, a preparation method thereof and application thereof in formaldehyde detection, the sensor comprising a metal organic framework nanoscale enzyme AIE-MOF@PCN-222 loaded with AIE-MOF material, hydrogen peroxide and a color developing substrate o-phenylenediamine OPD; the metal organic framework nanoscale enzyme PCN-222 in the AIE-MOF@PCN-222 can oxidize the colorless OPD into yellow 2,3-diaminophenazine DAP, and generate an ultraviolet absorption peak at 450 nm and a strong fluorescence emission peak at 560 nm; the AIE-MOF@PCN-222 has a strong fluorescence emission peak at 446 nm, and can form a ratio fluorescent sensor with the fluorescence signal of the DAP. The application integrates the excellent catalytic capacity of the nanoscale enzyme and the luminescence characteristics of the AIE-MOF into one system, and realizes high-sensitivity formaldehyde detection.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biosensing, and particularly relates to a colorimetric / fluorescent dual-mode nanozyme sensor, a preparation method thereof and application thereof in detecting formaldehyde. BACKGROUND

[0002] Formaldehyde (HCHO) is a highly reactive and toxic carbonyl compound that poses a serious and ongoing threat to global food safety and public health. According to the International Agency for Research on Cancer (IARC), formaldehyde is classified as a Group 1 carcinogen because of its clear association with nasopharyngeal cancer, leukemia, and other malignancies. However, the illegal use of formaldehyde as a preservative in various foods (such as seafood, dairy products, fruits, and vegetables) remains a cause for concern. These practices aim to extend shelf life, enhance appearance appeal, or mask signs of spoilage. In addition to the risk of carcinogenesis, formaldehyde can also cause acute toxicity reactions, including gastrointestinal discomfort, respiratory complications, nerve damage, and organ failure. Therefore, sensitive, specific, rapid, and reliable detection of trace formaldehyde residues in complex environments is a major challenge in the field of food safety monitoring and medicine. There is an urgent need for innovative analytical methods, especially those suitable for on-site screening, to prevent contaminated products from entering the supply chain.

[0003] Natural enzymes, as environmentally friendly biocatalysts, have the advantages of high selectivity and high-efficiency catalysis. However, under harsh conditions such as strong acid / strong base, high temperature, and organic solvents, natural enzymes have insufficient stability, short service life, and are difficult to recover, which limits their industrial-scale application. In contrast, nanozymes (nanomaterials biomimetic enzymes) overcome the shortcomings of natural enzymes and have the following advantages: (1) high stability: they can maintain catalytic activity in extreme pH, high temperature, and organic solvent environments; (2) easy to obtain and low cost: compared to the complex preparation and purification process of natural enzymes, nanozymes can be conveniently prepared through chemical synthesis, with simple process and easy scale-up; (3) catalytic performance can be regulated: by adjusting synthesis parameters such as precursor ratio, reaction time, and temperature, the morphology and size can be precisely regulated, and the catalytic activity can be further improved through surface modification.

[0004] AIE effect (aggregation-induced emission) refers to a class of molecules that emit little light in dilute solution, but emit significantly enhanced light in aggregated or solid state. Unlike traditional fluorescent materials, which exhibit aggregation-caused quenching (ACQ) and reduced emission intensity in condensed or solid state, AIE-MOFs exhibit the opposite behavior: they emit weak light in solution but strong fluorescence in aggregated or solid state. This inherent AIE property makes them particularly suitable for integration into solid-state MOF structures for robust sensing applications.

[0005] With the development of detection technology, various methods based on different principles have been applied to formaldehyde detection, such as chromatography, electrochemical method, fluorescence method, colorimetric method, etc. Among these methods, colorimetric method and fluorescence method have attracted a lot of researchers' attention due to their accurate results and simple operation. SUMMARY

[0006] In view of the above technical problems, the present application provides a colorimetric / fluorescent dual-mode nanosensor and a preparation method thereof and application thereof in detecting formaldehyde. The colorimetric / fluorescent dual-mode nanosensor can realize real-time / in-situ visual quantitative detection of formaldehyde, has high sensitivity, and the detection limits of colorimetric method and fluorescence method are 14.5 nM and 1.78 nM respectively. The detection process is convenient, fast and low in cost.

[0007] To solve the above technical problems, the present application adopts the following technical solutions:

[0008] In a first aspect, a colorimetric / fluorescent dual-mode nanosensor is provided, comprising an AIE metal organic framework nanosensor (AIE-MOF@PCN-222) loaded with an aggregation-induced emission metal organic framework (AIE-MOF) material, hydrogen peroxide and a color developing substrate ortho-phenylenediamine (OPD). The AIE-MOF@PCN-222 is a zirconium metal organic framework nanosensor PCN-222 material loaded with an AIE-MOF. The AIE-MOF is self-assembled from zirconium metal ions and an organic ligand tetra[4-(3,5-dicarboxyphenyl)]tetraphenyl ethylene. The PCN-222 is self-assembled from zirconium metal ions and a tetracarboxyphenyl iron porphyrin. The PCN-222 nanosensor in the AIE-MOF@PCN-222 can oxidize the colorless color developing substrate ortho-phenylenediamine OPD into yellow 2,3-diaminophenazine (DAP), and generate an ultraviolet absorption peak at 450 ± 25 nm and a strong fluorescence emission peak at 560 ± 5 nm. The AIE-MOF has a strong fluorescence emission peak at 446 ± 10 nm, and can form a ratio fluorescence sensor with the fluorescence signal of 2,3-diaminophenazine DAP.

[0009] According to the scheme of the present application, the AIE-MOF@PCN-222 is composed of a MOF-on-MOF structure, the core of which is a metal organic framework nanosensor PCN-222 with peroxidase characteristics, and the surface of which is loaded with an AIE-MOF. The AIE-MOF@PCN-222 not only retains the peroxidase characteristics of PCN-222, but also has the fluorescence characteristics of AIE-MOF.

[0010] According to the scheme of the present application, the present application adopts an organic ligand tetra[4-(3,5-dicarboxyphenyl)]tetraphenyl ethylene with an AIE group and zirconium (Zr) metal ions (Zr 4+Compared with other MOFs materials, the cluster self-assembly forms a metal organic framework AIE-MOF material which can produce stronger fluorescence emission in the aggregation state. The application adopts a four [4-(3, 5-dicarboxyphenyl) tetraphenyl ethylene ligand and a zirconium ion cluster self-assembly to form a zirconium-based AIE-MOF material. The material triggers strong fluorescence emission in the aggregation state, the emission peak overlaps with the excitation spectrum of the catalytic product DAP to achieve efficient energy transfer, and the polycarboxy structure enhances the coordination stability and PCN-222 surface loading capacity, maintains the structural integrity in the liquid phase detection system, and has high sensitivity fluorescence response and excellent stability. According to the scheme of the application, the application adopts an organic ligand four carboxyphenyl porphyrin iron and a zirconium (Zr) metal ion (Zr 4+ ) cluster self-assembly to form a metal organic framework nanoscale enzyme PCN-222 material which can produce peroxidase-like activity. The application takes PCN-222 as the core and loads AIE-MOF, which fully gives play to the advantages of the high specific surface area and open channel of PCN-222 to provide a large number of catalytic sites, ensures that the catalytic reaction is efficiently carried out in the core, and effectively avoids the quenching effect of metal ions on the fluorescence of AIE molecules, which leads to signal weakening, realizes the double reservation of catalytic activity and fluorescence signal under the premise of maintaining the integrity of the PCN-222 channel.

[0011] According to the scheme of the application, the application adopts an organic ligand four carboxyphenyl porphyrin iron and a zirconium (Zr) metal ion (Zr 4+ ) cluster self-assembly to form a metal organic framework nanoscale enzyme PCN-222 material, and on this basis, in-situ synthesis of a metal organic framework AIE-MOF material formed by a four [4-(3, 5-dicarboxyphenyl) tetraphenyl ethylene organic ligand and a zirconium (Zr) metal ion (Zr 4+ ) cluster self-assembly to obtain a final product AIE metal organic framework nanoscale enzyme (AIE-MOF@PCN-222) material. After mixing the material with hydrogen peroxide and a color developing substrate o-phenylenediamine (OPD), a nanoscale enzyme biosensor is prepared. The PCN-222 can oxidize the colorless o-phenylenediamine (OPD) into yellow 2, 3-diaminophenazine (DAP), and produce an ultraviolet absorption peak at 450 ± 5 nm and a strong fluorescence emission peak at 560 ± 5 nm. The zirconium-based aggregation-induced emission metal organic framework (AIE-MOF) in the AIE metal organic framework nanoscale enzyme (AIE-MOF@PCN-222) has a strong fluorescence emission peak at 446 ± 10 nm, which can constitute a ratio fluorescence sensor with the fluorescence signal of 2, 3-diaminophenazine (DAP).

[0012] As a preferred embodiment, the particle size of the AIE metal organic framework nanoscale enzyme (AIE-MOF@PCN-222) material is 3860 nm. The colorimetric / fluorescent dual-mode nanoscale enzyme sensor of the present application has a detection limit of 14.5 nM and 1.78 nM for formaldehyde, respectively, and can realize real-time / in-situ visual quantitative detection of formaldehyde, making the detection process portable, rapid and low-cost, and meeting the needs of food safety and medical clinical detection.

[0013] In a second aspect, the present application also provides a preparation method of the colorimetric / fluorescent dual-mode nanoscale enzyme sensor, which specifically comprises the following steps:

[0014] Step 1: synthesis of metal organic framework nanoscale enzyme PCN-222: dissolve zirconium metal salt and iron tetracarboxyphenyl porphyrin in N,N-dimethylformamide (DMF) solvent, then add benzoic acid as a regulator, and perform a solvothermal reaction, then wash, filter and dry the obtained solution to obtain zirconium-based metal organic framework nanoscale enzyme PCN-222 powder material;

[0015] Step 2: synthesis of AIE metal organic framework nanoscale enzyme (AIE-MOF@PCN-222): dissolve the zirconium-based metal organic framework nanoscale enzyme PCN-222 obtained in step 1, zirconium metal salt and tetrakis[4-(3,5-dicarboxyphenyl)]tetraphenyl ethylene in N,N-dimethylformamide (DMF) solvent, then add benzoic acid as a regulator, and perform a solvothermal reaction, then wash, filter and dry the obtained solution to obtain zirconium-based AIE metal organic framework nanoscale enzyme (AIE-MOF@PCN-222) powder material;

[0016] Step 3: preparation of colorimetric / fluorescent dual-mode nanoscale enzyme sensor: disperse the AIE metal organic framework nanoscale enzyme (AIE-MOF@PCN-222) obtained in step 2 in an aqueous medium, and mix with color developing substrate OPD and hydrogen peroxide in a phosphate buffer solution to obtain the colorimetric / fluorescent dual-mode nanoscale enzyme sensor.

[0017] As a preferred embodiment, in step 1, the zirconium metal salt is selected from zirconium tetrachloride, and the mass ratio of zirconium metal salt to iron tetracarboxyphenyl porphyrin is 1:(0.5-1); the temperature of the solvothermal reaction is 120°C, the reaction time is 24-48 h, the washing agent used in the washing is anhydrous ethanol, and the drying method is oven drying at a drying temperature of 60-75°C.

[0018] As a preferred embodiment, in step 2, the zirconium metal salt is selected from zirconium tetrachloride, and the mass ratio of the zirconium metal salt to tetrakis[4-(3,5-dicarboxyphenyl)]tetraphenyl ethylene is 1:(0.3-0.7); the solvent thermal reaction temperature is 120°C, the reaction time is 24-48h, the washing agent used in washing is anhydrous ethanol, and the drying method is oven drying, and the drying temperature is 60-75°C.

[0019] As a preferred embodiment, in step 3, in the colorimetric / fluorescent dual-mode nanosensor, the OPD concentration is 1.4±0.1mM, the hydrogen peroxide concentration is 0.4±0.1mM, and the mass concentration of AIE-MOF@PCN-222 is 0.04-0.08mg / mL.

[0020] In a third aspect, the present application also provides the application of the colorimetric / fluorescent dual-mode nanosensor or the colorimetric / fluorescent dual-mode nanosensor prepared by the preparation method thereof in formaldehyde detection.

[0021] In a fourth aspect, the present application also provides a method for detecting formaldehyde by using the colorimetric / fluorescent dual-mode nanosensor, which specifically comprises the following steps:

[0022] Step S1: mixing the colorimetric / fluorescent dual-mode nanosensor with a series of formaldehyde solutions with different concentrations in proportion to prepare a reaction system, and after reaction at 25-30°C for 20-30min, performing spectral detection by using an ultraviolet-visible spectrophotometer and a fluorescence spectrometer, drawing a correction curve by taking the value of the formaldehyde concentration as the abscissa and taking the ratio of the ultraviolet peak value of the colorimetric / fluorescent dual-mode nanosensor at 450nm and the fluorescence intensity peak values at 446nm and 560nm as the ordinate;

[0023] Step S2: mixing the colorimetric / fluorescent dual-mode nanosensor with the formaldehyde solution to be detected in proportion to prepare a reaction system, and after reaction at 25-30°C for 20-30min, performing spectral detection by using an ultraviolet-visible spectrophotometer and a fluorescence spectrometer, calculating the formaldehyde concentration in the sample according to the correction curve obtained in step S1 by using the ultraviolet absorption change of the colorimetric / fluorescent dual-mode nanosensor at 450nm and the fluorescence intensity change at 446nm and 560nm, and realizing the detection of formaldehyde.

[0024] As a preferred embodiment, the preparation method of the reaction system of the step S1 and the step S2 comprises: adding 100 μL of AIE-MOF@PCN-222 solution, 100 μL of OPD solution, 100 μL of hydrogen peroxide solution and 100 μL of formaldehyde solution, using NaAc-HAc buffer to make up to 2.5 mL, and preparing 2.5 mL of reaction system; the formaldehyde solution uses ultrapure water as a solvent, the OPD solution has a concentration of 35 mM, and the solvent is anhydrous ethanol; the hydrogen peroxide solution has a concentration of 10 mM.

[0025] As a preferred embodiment, the spectral detection is performed by using an ultraviolet-visible spectrophotometer and a fluorescence spectrometer, the absorption value A 450 at the ultraviolet absorption peak of 450 nm is recorded, the fluorescence intensity F 446 at 446 nm and the fluorescence intensity F 560 at 560 nm are recorded, the ratio of F 446 / F 560 is calculated to obtain the fluorescence intensity ratio value, the functional relationship between the ultraviolet absorption peak value A 450 and the fluorescence intensity ratio value F 446 / F 560 and the formaldehyde concentration is obtained to obtain a correction curve, and the concentration of the formaldehyde to be detected is calculated by using the correction curve.

[0026] As a preferred embodiment, in the presence of hydrogen peroxide and under acidic conditions, AIE-MOF@PCN-222 can oxidize colorless OPD to yellow DAP; due to the activation of ions in the buffer solution, AIE-MOF@PCN-222 can emit bright green fluorescence at 446 nm, after the addition of formaldehyde, the catalytic ability of AIE-MOF@PCN-222 is inhibited, resulting in a decrease in the content of DAP and a lighter solution color, as a colorimetric detection signal, AIE-MOF@PCN-222 can emit green fluorescence at 446 ± 10 nm, DAP can emit yellow fluorescence at 560 ± 5 nm, a decrease in the content of DAP will result in a decrease in the fluorescence intensity at 560 ± 5 nm, and an increase in the fluorescence intensity of AIE-MOF@PCN-222 at 446 ± 10 nm; through the colorimetric / fluorescent dual-mode nanosensor, the ratio of the ultraviolet absorption value at 450 nm and the fluorescence intensity at 446 nm and 560 nm to the concentration of the detected substance presents a linear relationship, so as to realize the detection of the concentration of formaldehyde in the measured substance, and the condition of the ultraviolet-visible light spectrum includes that the observation range of the ultraviolet-visible light spectrum is 350-550 nm; the fluorescence excitation wavelength is 380-400 nm, and the fluorescence emission spectrum observation range is 410-650 nm.

[0027] The technical principle of the present application is that in the presence of hydrogen peroxide, AIE-MOF@PCN-222 can catalyze colorless OPD to become yellow DAP as a colorimetric detection signal, after the addition of formaldehyde, the catalytic ability of AIE-MOF@PCN-222 is inhibited, resulting in a decrease in the content of DAP and a lighter solution color, as a colorimetric detection signal, AIE-MOF@PCN-222 can emit green fluorescence at 446 ± 10 nm, DAP can emit yellow fluorescence at 560 ± 5 nm, and a decrease in the content of DAP will result in a decrease in the fluorescence intensity at 560 ± 5 nm, and an increase in the fluorescence intensity of AIE-MOF@PCN-222 at 446 ± 10 nm. According to the concentration change of the detected formaldehyde, the content of yellow DAP in the sensor solution decreases, the solution color becomes lighter, the fluorescence intensity of DAP decreases, and the fluorescence intensity of AIE-MOF@PCN-222 increases, and then the ultraviolet absorption intensity of DAP and the ratio of the fluorescence intensity of DAP and AIE-MOF@PCN-222 to the concentration of the detected substance present a linear relationship, so as to realize the quantitative detection of the concentration of formaldehyde in the measured substance.

[0028] Advantages of the present application:

[0029] 1. The application uses zirconium-based metal organic framework PCN-222 with high stability as a carrier to synthesize an aggregation-induced emission metal organic framework AIE-MOF with high brightness on the surface, solving the problems of difficult recovery and low stability of free enzymes;

[0030] 2. The colorimetric / fluorescent dual-mode nanoenzyme sensor constructed based on AIE-MOF@PCN-222 integrates the excellent catalytic ability of nanoenzyme and the luminescent characteristics of AIE-MOF in one system, is simple in design, convenient to operate, has high selectivity and detection stability for formaldehyde, and reduces the detection time and cost;

[0031] 3. The formaldehyde detection method established by the application has high detection sensitivity, and the detection limits are 14.5 nM and 1.78 nM, respectively, which meets the relevant requirements of the national standard, and has good anti-interference and stability. DETAILED DESCRIPTION

[0032] In order to more clearly illustrate the technical solutions in the application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0033] Figure 1 is the SEM diagram of PCN-222 in Example 1 of the application and AIE-MOF@PCN-222 in Example 2 and the TEM diagram of AIE-MOF@PCN-222.

[0034] Figure 2 is the particle size distribution diagram of AIE-MOF@PCN-222 in Example 2 of the application.

[0035] Figure 3 is the catalytic ability verification diagram of AIE-MOF@PCN-222 in Example 2 of the application.

[0036] Figure 4 is the sunlight image of the colorimetric / fluorescent dual-mode nanoenzyme sensor solution under different concentrations of formaldehyde in Example 4 of the application.

[0037] Figure 5 is the fluorescence image of the colorimetric / fluorescent dual-mode nanoenzyme sensor solution under different concentrations of formaldehyde in Example 4 of the application.

[0038] Figure 6 is the ultraviolet-visible spectrum and fluorescence emission spectrum of the colorimetric / fluorescent dual-mode nanoenzyme sensor solution under different concentrations of formaldehyde in Example 4 of the application.

[0039] Figure 7 is the colorimetric detection curve of the colorimetric / fluorescent dual-mode nanosensor solution under different concentrations of formaldehyde in the embodiment 4 of the present application.

[0040] Figure 8 is the fluorescence detection curve of the colorimetric / fluorescent dual-mode nanosensor solution under different concentrations of formaldehyde in the embodiment 4 of the present application.

[0041] Figure 9 is the analysis graph of exploring the selectivity and anti-interference of the colorimetric / fluorescent dual-mode nanosensor in the verification example 2 of the present application. DETAILED DESCRIPTION

[0042] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0043] Unless otherwise specified, the various raw materials used in the embodiments are commercially available conventional raw materials, and the technical means used is the conventional means well known to those skilled in the art.

[0044] Embodiment 1

[0045] The present embodiment first provides a MOF material, and the synthesis method thereof comprises the following steps:

[0046] 70 mg of ZrCl4, 50 mg of iron tetracarboxyphenyl porphyrin and 2.7 g of benzoic acid were respectively dissolved in 5 mL of DMF, and ultrasonic treatment was performed until complete dissolution.

[0047] The mixed solution was placed in silicon oil at 120℃, and a magnetic stirrer was opened to stir at a speed of 200 rpm for 30 min. The magnetic stirrer was closed, and heating at 120℃ was maintained for 24 h.

[0048] After the heating was completed, the solution was cooled to room temperature, and the solution was equally transferred to 50 mL centrifuge tubes. Then, 10 mL of anhydrous ethanol was added, and centrifugation was performed at 12000 rpm, 4℃ for 20 min.

[0049] The supernatant was removed, 10 mL of anhydrous ethanol was added, and centrifugation was performed. This step was repeated 3 times.

[0050] The finally obtained precipitate was placed in a 75℃ oven until complete drying. The PCN-222 material was obtained.

[0051] The PCN-222 was characterized, Figure 1Fig. 1a is a SEM image of PCN-222, from which it can be seen that the synthesized PCN-222 has a rod-like structure and uniform size.

[0052] Example 2

[0053] This example first provides an AIE-MOF@PCN-222 material, and the synthesis method thereof comprises the following steps:

[0054] Take 70 mg of PCN-222 in a 20 mL brown glass sample bottle, add 15 mL of ultrapure water, and ultrasonic for 1 h to make it completely dispersed, to obtain solution C.

[0055] Dissolve 70 mg of ZrCl4, 33 mg of tetra[4-(3,5-dicarboxyphenyl)]tetraphenyl ethylene and 2.7 g of benzoic acid in 5 mL of DMF respectively, and ultrasonic until completely dissolved, then mix the solutions and ultrasonic for 30 min to obtain solution D.

[0056] Add solution D to solution C at one time, place in a silicon oil bath at 120°C, open the magnetic stirrer to stir at a speed of 200 rpm, stir for 30 min, turn off the magnetic stirrer, and keep heating at 120°C for 48 h.

[0057] After heating, take the flask out of the silicon oil bath, and when the solution cools to room temperature, transfer the solution equally into two 50 mL centrifuge tubes, 12.5 mL of solution in each tube, and then add 10 mL of anhydrous ethanol to each tube, centrifuge at 12000 rpm, 4°C, for 20 min.

[0058] Discard the supernatant, add 10 mL of anhydrous ethanol, and centrifuge, repeat this step for 3 times.

[0059] Put the finally obtained precipitate in a 75°C oven until completely dried. Obtain the AIE-MOF@PCN-222 material.

[0060] Characterize the AIE-MOF@PCN-222, Figure 1 Fig. 1b and Figure 1 Fig. 1c are respectively SEM and TEM images of AIE-MOF@PCN-222, from which it can be seen that the synthesized AIE-MOF@PCN-222 has slight agglomeration compared with PCN-222, and the rod-like PCN-222 is loaded with spherical AIE-MOF on the surface. From Figure 2 (dynamic light scattering DLS), it can be seen that the particle size of AIE-MOF@PCN-222 is 3860 nm.

[0061] Verification Example 1

[0062] To verify the catalytic activity of AIE-MOF@PCN-222, 20 mg of AIE-MOF@PCN-222 obtained in Example 2 was dissolved in 10 mL of ultrapure water.

[0063] Subsequently, 100 μL of AIE-MOF@PCN-222 solution, 100 μL of OPD solution, and 100 μL of hydrogen peroxide solution were taken, and the volume was made up to 2.5 mL using NaAc-HAc buffer with a pH value of 3.8. After 20-30 min of reaction, the ultraviolet absorption intensity at 450 nm was recorded using a UV-visible spectrophotometer, and the absorbance values of AIE-MOF@PCN-222 and hydrogen peroxide and the mixed solution of OPD and hydrogen peroxide at 450 nm were determined.

[0064] As Control 1: PCN-222 was used instead of AIE-MOF@PCN-222, and the other conditions were the same. The reaction system was configured, and the absorbance value at 652 nm was recorded.

[0065] As Control 2: No OPD solution was added to the reaction system, and the other conditions were the same. The absorbance value at 652 nm was recorded.

[0066] As Control 3: This control was a blank control. No AIE-MOF@PCN-222 was added to the reaction system, and the other conditions were the same. The absorbance value at 652 nm was recorded.

[0067] As shown in Table 1, AIE-MOF@PCN-222 still retained high catalytic activity, and the catalytic activity came from the synthesized PCN-222 nanoscale enzyme. Figure 3

[0068] Example 3

[0069] The present embodiment further provides a preparation method of a colorimetric / fluorescent dual-mode nanoscale enzyme sensor, specifically comprising the following steps:

[0070] 20 mg of AIE-MOF@PCN-222 obtained in Example 2 was dissolved in 10 mL of ultrapure water. Subsequently, 100 μL of AIE-MOF@PCN-222 solution, 100 μL of OPD solution, and 100 μL of hydrogen peroxide solution were taken, and the volume was made up to 2.5 mL using NaAc-HAc buffer with a pH value of 3.8. After 20-30 min of reaction, a colorimetric / fluorescent dual-mode nanoscale enzyme sensor was obtained.

[0071] The concentration of the OPD solution was 35 mM, and the solvent was anhydrous ethanol. The concentration of the hydrogen peroxide solution was 10 mM.

[0072] Example 4

[0073] ​The embodiment provides a colorimetric / fluorescent dual-mode nanoscale enzyme detection method for detecting formaldehyde, and specifically comprises the following steps.

[0074] 100 μL of formaldehyde solution with different concentrations to be detected is added to the colorimetric / fluorescent dual-mode nanoscale enzyme sensor prepared in Example 3, and a 2.5 mL reaction system is prepared, and the color change of the solution is observed under sunlight and ultraviolet light source.

[0075] Figure 4 is a sunlight image of the colorimetric / fluorescent dual-mode nanoscale enzyme sensor solution under different concentrations of formaldehyde. As can be seen from the figure, with the increase of the formaldehyde concentration, the color of the solution gradually changes from yellow to colorless.

[0076] Figure 5 is a fluorescence image of the colorimetric / fluorescent dual-mode nanoscale enzyme sensor solution under different concentrations of formaldehyde. As can be seen from the figure, with the increase of the formaldehyde concentration, the fluorescence of the solution changes from bright yellow to light green.

[0077] The ultraviolet-visible spectrophotometer and the fluorescence spectrophotometer are used to determine the ultraviolet-visible absorption spectrum and the fluorescence emission spectrum, the observation range of the ultraviolet-visible spectrum is 350-550 nm, the fluorescence excitation wavelength is 380-400 nm, and the observation range of the fluorescence emission spectrum is 410-650 nm.

[0078] Figure 6 is the ultraviolet-visible spectrum and the fluorescence emission spectrum of the colorimetric / fluorescent dual-mode nanoscale enzyme sensor solution under different concentrations of formaldehyde, wherein Figure 6 6a in is the ultraviolet-visible spectrum, Figure 6 6b in is the fluorescence emission spectrum.

[0079] The function relationship between the different formaldehyde concentration values of the solution and the ultraviolet-visible absorption peak values and the fluorescence emission peak values is used to obtain the formaldehyde concentration values corresponding to the ultraviolet-visible absorption peak values and the fluorescence emission peak values in the solution.

[0080] Figure 7 is a colorimetric detection curve of the colorimetric / fluorescent dual-mode nanoscale enzyme sensor solution under different concentrations of formaldehyde, wherein the x-axis is the value of the formaldehyde concentration, and the y-axis is the ultraviolet-visible absorption peak value.

[0081] The ultraviolet-visible absorption peak value is A 450 The ultraviolet-visible absorption peak value near 450±5 nm is monitored by multiple parallel experiments, and the average value is obtained.

[0082] The function relationship between the ultraviolet-visible absorption peak value and the formaldehyde concentration is Y=-0.0076X+0.5291 (R 2= 0.9922), wherein Y represents the UV-visible absorption peak value of 450 nm, and X represents the value of formaldehyde concentration. Therefore, the formaldehyde concentration of the colorimetric / fluorescence dual-mode nanosensor containing an unknown concentration of formaldehyde can be measured as A 450 The formaldehyde concentration can be calculated by the above formula, and the quantitative analysis of formaldehyde is realized.

[0083] According to the detection limit calculation formula 3σ / S, in which σ is the standard deviation of the blank response value, and S is the slope of the detection curve. Through the above linear relationship calculation, it can be obtained that the detection limit of the colorimetric / fluorescence dual-mode nanosensor for detecting formaldehyde by colorimetry is 14.5 nM.

[0084] Figure 8 is the fluorescence detection curve of the colorimetric / fluorescence dual-mode nanosensor solution under different concentrations of formaldehyde, in which the x-axis is the value of the formaldehyde concentration, and the y-axis is the fluorescence intensity ratio value.

[0085] The fluorescence intensity ratio value calculation method is: R = F 446 / F 560 .

[0086] F 446 : the fluorescence intensity value of the sensor-containing solution at 446 nm in the corresponding fluorescence spectrum;

[0087] F 560 : the fluorescence intensity value of the sensor-containing solution at 560 nm in the corresponding fluorescence spectrum;

[0088] F 446 , F 560 The fluorescence intensity values near 446 nm and 560 nm are monitored by multiple parallel experiments, and the average values are obtained.

[0089] The functional relationship between the fluorescence intensity ratio and the formaldehyde concentration is: Y = 0.0272X + 0.5292 (R 2 = 0.9921), wherein Y represents the ratio of the fluorescence intensity peak at 446 nm to the fluorescence intensity peak at 560 nm, and X represents the value of the formaldehyde concentration. Therefore, the formaldehyde concentration of the colorimetric / fluorescence dual-mode nanosensor containing an unknown concentration of formaldehyde can be measured as F 446 / F 560 , and the formaldehyde concentration can be calculated by the above formula, and the quantitative analysis of formaldehyde is realized.

[0090] According to the detection limit calculation formula 3σ / S, in which σ is the standard deviation of the blank response value, and S is the slope of the detection curve. Through the above linear relationship calculation, it can be obtained that the detection limit of the colorimetric / fluorescence dual-mode nanosensor for detecting formaldehyde by colorimetry is 14.5 nM.

[0091] Example 5

[0092] The embodiment provides a colorimetric / fluorescent dual-mode detection method for detecting formaldehyde, and specifically comprises the following steps:

[0093] Step (1): referring to the reference example 4, the fluorescence detection curve and the colorimetric detection curve of the colorimetric / fluorescent dual-mode nanosensor solution are obtained, and the function relationship between the ultraviolet-visible absorption peak and the formaldehyde concentration and the function relationship between the fluorescence emission peak and the formaldehyde concentration are obtained;

[0094] Step (2): 100 μL of formaldehyde solution to be detected (the concentration is unknown, and 10 mM formaldehyde solution is diluted several times to prepare) is added to the colorimetric / fluorescent dual-mode nanosensor prepared in the example 3 to prepare a 2.5 mL reaction system, and spectrum detection is performed by using an ultraviolet-visible spectrophotometer and a fluorescence spectrometer, through the ultraviolet absorption change of the colorimetric / fluorescent dual-mode nanosensor at 450 nm and the fluorescence intensity change at 446 nm and 560 nm, the formaldehyde concentration in the sample is calculated according to the detection curve and the function relationship obtained in the step (1), and the average value is 550 μM.

[0095] Example 6

[0096] The embodiment provides a colorimetric / fluorescent dual-mode detection method for detecting formaldehyde, and specifically comprises the following steps:

[0097] Step (1): referring to the reference example 4, the fluorescence detection curve and the colorimetric detection curve of the colorimetric / fluorescent dual-mode nanosensor solution are obtained, and the function relationship between the ultraviolet-visible absorption peak and the formaldehyde concentration and the function relationship between the fluorescence emission peak and the formaldehyde concentration are obtained;

[0098] Step (2): 100 μL of formaldehyde solution to be detected (the concentration is unknown, and 10 mM formaldehyde solution is diluted several times to prepare) is added to the colorimetric / fluorescent dual-mode nanosensor prepared in the example 3 to prepare a 2.5 mL reaction system, and spectrum detection is performed by using an ultraviolet-visible spectrophotometer and a fluorescence spectrometer, through the ultraviolet absorption change of the colorimetric / fluorescent dual-mode nanosensor at 450 nm and the fluorescence intensity change at 446 nm and 560 nm, the formaldehyde concentration in the sample is calculated according to the detection curve and the function relationship obtained in the step (1), and the average value is 550 μM.

[0099] Verification example 2

[0100] The colorimetric / fluorescent dual-mode nanosensor is prepared according to the example 3, and Na 2+ , Mg 2+ , K + , Ca 2+, His, Suc, Glu, Arg, etc. as interference substances, the selectivity and anti-interference of the colorimetric / fluorescence dual-mode nanosensor for detecting formaldehyde were explored, wherein the concentration of the interference substances was 100 times that of the formaldehyde solution, after reacting at 25-30 DEG C for 20-30 min, the spectrum was detected by ultraviolet-visible spectrophotometer and fluorescence spectrometer, and the ultraviolet absorption change of the colorimetric / fluorescence dual-mode nanosensor at 450 nm and the fluorescence intensity change at 446 nm and 560 nm were detected.

[0101] Figure 9 Fig. 9 is a diagram showing the selectivity and anti-interference analysis of the colorimetric mode (9a) and the fluorescence mode (9b), it can be seen from the diagram that only in the presence of formaldehyde, the ultraviolet absorption value and the fluorescence intensity of the colorimetric / fluorescence dual-mode nanosensor have obvious changes, which indicates that the sensor has good selectivity and anti-interference for formaldehyde detection.

[0102] It is apparent for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, but can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all aspects as illustrative and not restrictive, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended to embrace all changes falling within the meaning and range of equivalents of the claims.

Claims

1. A colorimetric / fluorescent dual-mode nanozyme sensor, characterized in that, The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm.

2. The colorimetric / fluorescent dual-mode nanosensor according to claim 1, wherein, The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm.

3. A method for preparing a colorimetric / fluorometric dual-mode nanosensor according to claim 1 or 2, characterized in that, The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm. The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm. The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm. The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm.

4. The preparation method of a colorimetric / fluorescent dual-mode nanosensor according to claim 3, characterized in that, The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm. The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm. The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm. The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm. The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm. The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm. The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm. The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm. The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm. The AIE-MOF@PCN-222 is composed of MOF-on-MOF structure, the core is metal organic framework nanometer enzyme PCN-222 with peroxidase characteristics, and the surface is loaded with AIE-MOF, which not only retains the peroxidase characteristics of PCN-222 but also has the fluorescence characteristics of AIE-MOF, and the particle size of the AIE-MOF@PCN-222 material is 3860 nm.

5. The preparation method of a colorimetric / fluorescent dual-mode nanosensor according to claim 3, characterized in that, In step 2, the zirconium metal salt is selected from zirconium tetrachloride, and the mass ratio of the zirconium metal salt to tetrakis[4-(3,5-dicarboxyphenyl)]tetraphenyl ethylene is 1:(0.3-0.7); the temperature of the solvothermal reaction is 120°C, the reaction time is 24-48 h, the washing agent used in the washing is anhydrous ethanol, and the drying method is oven drying at a drying temperature of 60-75°C.

6. The preparation method according to claim 3, characterized in that, In step 3, in the colorimetric / fluorescent dual-mode nanosensor, the OPD concentration is 1.4±0.1 mM, the hydrogen peroxide concentration is 0.4±0.1 mM, and the mass concentration of AIE-MOF@PCN-222 is 0.04-0.08 mg / mL.

7. The colorimetric / fluorescent dual-mode nanosensor according to claim 1 or 2 and / or the colorimetric / fluorescent dual-mode nanosensor obtained by the preparation method according to any one of claims 3-6, for use in formaldehyde detection.

8. Use according to claim 7, characterized in that, The colorimetric detection limit and the fluorescent detection limit are 14.5 nM and 1.78 nM, respectively.

9. A method for detecting formaldehyde using the colorimetric / fluorescent dual-mode nanosensor according to claim 1 or 2, characterized in that, The method comprises the following steps: Step S1: mixing the colorimetric / fluorescent dual-mode nanosensor with a series of formaldehyde solutions with different concentrations in a proportion to prepare a reaction system, performing spectral detection by using an ultraviolet-visible spectrophotometer and a fluorescence spectrometer after reaction at 25-30°C for 20-30 min, and drawing a correction curve by taking the value of the formaldehyde concentration as the abscissa and taking the ratio of the ultraviolet peak value of the colorimetric / fluorescent dual-mode nanosensor at 450 nm and the fluorescence intensity peak values at 446 nm and 560 nm as the ordinate; Step S2: mixing the colorimetric / fluorescent dual-mode nanosensor with a formaldehyde solution to be detected in a proportion to prepare a reaction system, performing spectral detection by using an ultraviolet-visible spectrophotometer and a fluorescence spectrometer after reaction at 25-30°C for 20-30 min, and calculating the formaldehyde concentration in the sample according to the correction curve obtained in step S1 to realize detection of formaldehyde.

10. The method of claim 9, wherein the colorimetric / fluorescent dual-mode nanosensor for detecting formaldehyde is characterized by, The preparation method of the reaction system in steps S1 and S2 comprises: adding 100 μL of AIE-MOF@PCN-222 solution, 100 μL of formaldehyde solution, 100 μL of OPD solution, and 100 μL of hydrogen peroxide solution, and using acetic acid-sodium acetate buffer to make up to 2.5 mL to prepare a 2.5 mL reaction system; the formaldehyde solution uses ultrapure water as the solvent, the OPD solution has a concentration of 35 mM and uses anhydrous ethanol as the solvent, and the hydrogen peroxide solution has a concentration of 10 mM.

11. The method of claim 9, wherein the colorimetric / fluorescent dual-mode nanosensor for detecting formaldehyde is characterized by, Spectra are detected by ultraviolet-visible spectrophotometer and fluorescence spectrometer, and the absorption value A of the ultraviolet absorption peak at 450 nm is recorded 450 , the fluorescence intensity F at 446 nm 446 , and the fluorescence intensity F at 560 nm 560 are recorded The fluorescence intensity ratio value is calculated by F 446 / F 560 , the function relationship between the ultraviolet absorption peak value A 450 and the fluorescence intensity ratio value F 446 / F 560 and the formaldehyde concentration is obtained to obtain a correction curve, and the concentration of the formaldehyde to be detected is calculated by using the correction curve The colorimetric / fluorescence dual-mode nanosensor presents yellow color and emits yellow fluorescence in the absence of formaldehyde, the ultraviolet absorption intensity at 450 nm decreases with the increase of the formaldehyde concentration, the color changes from yellow to colorless; the fluorescence intensity at 446 nm increases, the fluorescence intensity at 560 nm decreases, the fluorescence color changes from yellow to light green, and the content of formaldehyde is detected in colorimetric / fluorescence dual-mode.

12. The method of claim 9, wherein the colorimetric / fluorescent dual-mode nanosensor for detecting formaldehyde is characterized by, The AIE-MOF@PCN-222 can catalyze the colorless OPD to become yellow DAP, after adding formaldehyde, the formaldehyde inhibits the catalytic ability of AIE-MOF@PCN-222, resulting in the decrease of DAP content, and the solution color becomes lighter, as a colorimetric detection signal, AIE-MOF@PCN-222 can emit green fluorescence at 446 ± 10 nm, DAP can emit yellow fluorescence at 560 ± 5 nm, the decrease of DAP content will cause the decrease of fluorescence intensity at 560 ± 5 nm, the fluorescence intensity of AIE-MOF@PCN-222 at 446 ± 10 nm increases; through the colorimetric / fluorescence dual-mode nanosensor, the ratio of the fluorescence intensity at 446 nm and 560 nm and the concentration of the detected substance present a linear relationship, so as to realize the detection of the concentration of formaldehyde in the measured substance, the conditions of ultraviolet-visible light spectrum include: the observation range of ultraviolet-visible light spectrum is 350-550 nm; the fluorescence excitation wavelength is 380-400 nm, and the fluorescence emission spectrum observation range is 410-650 nm.

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