Magnetic rare earth doped indium vanadate composite nanosheet and preparation method thereof

Abstract

The application relates to a magnetic rare earth doped indium vanadate composite nanosheet and a preparation method thereof, and relates to the technical field of nanometer material synthesis and mass spectrometry analysis. The magnetic rare earth doped indium vanadate composite nanosheet comprises InVO4:Sm nanosheets and Fe3O4 nanoparticles uniformly distributed on the surfaces of the InVO4:Sm nanosheets. A method for preparing the magnetic rare earth doped indium vanadate composite nanosheet comprises the following steps: 1, two kinds of reaction solutions are respectively prepared; 2, InVO4:Sm nanosheets are prepared; and 3, composite nanosheets are prepared. The magnetic rare earth doped indium vanadate nanosheet can be used as a MALDI-MS matrix, is suitable for analyzing small molecule analytes (mass-to-charge ratio less than 1000), has the characteristics of low background interference, high signal-to-noise ratio and good signal stability, and fills the blank of the existing MALDI-MS matrix which is not suitable for analyzing small molecule analytes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nanomaterial synthesis and mass spectrometry, in particular to a magnetic rare earth doped indium vanadate composite nanosheet and a preparation method thereof. BACKGROUND

[0002] Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-MS) can be traced back to 1987 when it was first proposed by German scientists Hillenkamp and Karas. As a kind of "soft ionization" technology, MALDI-MS technology has been dominant in the analysis of macromolecules, especially biological molecules such as proteins, peptides, lipids, and sugars since its inception, because it avoids high-temperature heating and directly uses laser to impact small-molecule matrix to make analyte molecules obtain energy and ionize into gas phase, which can effectively analyze macromolecular parent ion peaks.

[0003] The basic principle of MALDI-MS technology can be simply summarized as follows: the analyte is mixed with the matrix solution, and the analyte is distributed in the matrix solution in a highly dispersed state to form a mixed solution. The mixed solution is dropped on the surface of the target plate and evaporated to form a dry spot. A pulsed laser is used to irradiate the matrix and sample mixture. The matrix can absorb laser energy and be excited and desorbed. The excitation process is accompanied by matrix explosion, so that the analyte is brought into the gas phase and gradually ionized. The ionization process does not cause the chemical bonds of the analyte to break, and usually only (a large amount of) molecular ions and / or (a small amount of) molecular ion multimers are produced. The molecular ion obtains kinetic energy under the action of a strong electric field and enters the field-free region of the flight tube. The mass of the molecular ion is proportional to the square of its flight time, so the mass (mass-to-charge ratio) information of the molecular ion can be obtained by measuring its flight time.

[0004] The commonly used organic matrixes for MALDI-MS technology include 9-aminoacridine (9-AA), 2,5-dihydroxybenzoic acid (DHB), alpha-cyano-4-hydroxycinnamic acid (CHCA), sinapinic acid (SA), etc. However, these commonly used organic matrixes are not suitable for the analysis of small molecule analytes, and the reasons are as follows: 1. These organic matrixes often produce obvious matrix-related signals in the low mass range with a mass-to-charge ratio less than 1000, which seriously interferes with the mass spectrum analysis and quantitative analysis of small molecule analytes, i.e., there is a problem of low signal-to-noise ratio and high background interference; 2. These organic matrixes are prone to uneven crystallization (i.e., the sweet spot effect) when crystallized with small molecule analytes, resulting in poor repeatability of the mass spectrum signal (i.e., poor signal stability).

[0005] In summary, if a MALDI-MS matrix with low background interference, high signal-to-noise ratio, and good signal stability can be developed, it will be of great significance to promote the application and development of MALDI-MS technology in the detection of small molecule analytes. SUMMARY

[0006] The present application aims to overcome the deficiencies of the prior art and provide a magnetic rare earth doped indium vanadate composite nanosheet and a preparation method thereof, which is suitable for analyzing small molecule analytes (mass-to-charge ratio less than 1000) when it is used as a MALDI-MS matrix, has the characteristics of low background interference, high signal-to-noise ratio and good signal stability, and fills the gap of the existing MALDI-MS matrix which is not suitable for small molecule analyte analysis.

[0007] The technical solution of the present application is: a magnetic rare earth doped indium vanadate composite nanosheet, which comprises InVO4:Sm samarium element, a second m is in lowercase, Sm nanosheet and Fe3O4 nanoparticles uniformly distributed on the surface of the InVO4:Sm nanosheet.

[0008] The further technical solution of the present application is: it has typical two-dimensional material characteristics, which are: electrons can only move freely in two dimensions in the non-nanoscale plane; the width of the InVO4:Sm nanosheet is between 200-800nm, the thickness of the InVO4:Sm nanosheet is between 4-5nm, and the particle size of the Fe3O4 nanoparticles is between 15-25nm.

[0009] The technical solution of the present application is: a method for preparing the above-mentioned magnetic rare earth doped indium vanadate composite nanosheet, the steps are as follows:

[0010] S01, two kinds of reaction solutions are prepared respectively:

[0011] The following two solutions are prepared respectively: 1, take brominated cetylpyridine, n-butanol and n-octane and mix them in a ratio of 1.35:(15-30):(80-100), fully stir to form an oily solution, wherein the brominated cetylpyridine is in units of mg, the n-butanol is in units of ml, and the n-octane is in units of ml; 2, take indium salt and samarium salt and mix them to form an aqueous solution, wherein the concentration of the indium salt is 10mmol / ml and the concentration of the samarium salt is 0.5mmol / ml; mix the above oily solution and aqueous solution in a volume ratio of 115:5, fully stir, and form reaction liquid A after full emulsification;

[0012] The following two solutions are prepared respectively: 1, take brominated cetylpyridine, n-butanol and n-octane and mix them in a ratio of 1.35:(15-30):(80-100), fully stir to form an oily solution, wherein the brominated cetylpyridine is in units of mg, the n-butanol is in units of ml, and the n-octane is in units of ml; 2, take ammonium metavanadate and configure it into an aqueous solution with a concentration of 9.1mmol / ml; mix the above oily solution and aqueous solution in a volume ratio of 125:5.5, fully stir, and form reaction liquid B after full emulsification;

[0013] S02, preparing InVO4:Sm nanosheets:

[0014] A, under stirring, the reaction liquid A is added dropwise into the reaction liquid B, the volume ratio of the reaction liquid A and the reaction liquid B is 1:1, after the dropwise addition is completed, the stirring is continued to mix the reaction liquid A and the reaction liquid B thoroughly to form a mixed solution, and then nitric acid is added to adjust the pH of the mixed solution to 1-2;

[0015] B, the mixed solution after the pH adjustment is transferred into a stainless steel autoclave, and hydrothermal reaction is carried out at 170-190℃ for 20h, and then the reaction is naturally cooled to room temperature, and the precipitate generated in the reaction is InVO4:Sm nanosheets;

[0016] C, the centrifuge is used to separate the solution after the reaction into solid and liquid, the separated precipitate is washed thoroughly, and then the precipitate is vacuum dried, and the preparation of InVO4:Sm nanosheets is completed;

[0017] S03, preparing composite nanosheets:

[0018] A, the following two kinds of liquids are prepared respectively: 1, the prepared InVO4:Sm nanosheets are dispersed in deionized water by ultrasonic oscillation, a dispersion liquid with a concentration of 1mg / ml is configured, and the dispersion liquid is purged with high-purity nitrogen to remove dissolved oxygen in the dispersion liquid; 2, iron chloride and ferrous sulfate are taken and added into deionized water to dissolve thoroughly to obtain a dissolution liquid, wherein the concentration of the iron chloride is 0.08mmol / ml, and the concentration of the ferrous sulfate is 0.04mmol / ml;

[0019] B, the dissolution liquid and the dispersion liquid are mixed according to a volume ratio of 1:1 to obtain a mixed liquid, the mixed liquid is heated in a water bath at 83-87℃ and reacts under an oxygen-free condition for 60min to obtain intermediate solution A, ammonia water and hydrazine hydrate are added into the intermediate solution A to obtain intermediate solution B, wherein the volume ratio of the ammonia water to the intermediate solution A is 10:100, and the volume ratio of the hydrazine hydrate to the intermediate solution A is 0.1:100; the intermediate solution B is heated in a water bath at 93-97℃ and reacts under an oxygen-free environment for 60min to obtain a final solution containing magnetic rare earth doped indium vanadate composite nanosheets;

[0020] C, the centrifuge is used to separate the final solution obtained in the reaction into solid and liquid, and the separated precipitate is washed thoroughly, and the preparation of the magnetic rare earth doped indium vanadate composite nanosheets is completed.

[0021] The further technical solutions of the present application are: in the process of preparing the reaction liquid A in S01 step, the stirring equipment in the mixing process of cetylpyridinium bromide, n-butanol and n-octane is a magnetic stirrer, the stirring time is 30 min, and the stirring speed is 5000-7000 r / min; in the process of preparing the reaction liquid A in S01 step, the stirring equipment in the mixing process of the oily solution and the aqueous solution is a magnetic stirrer, the stirring time is 150 min, and the stirring speed is 7000-10000 r / min; in the process of preparing the reaction liquid B in S01 step, the stirring equipment in the mixing process of cetylpyridinium bromide, n-butanol and n-octane is a magnetic stirrer, the stirring time is 30 min, and the stirring speed is 5000-7000 r / min; in the process of preparing the reaction liquid B in S01 step, the stirring equipment in the mixing process of the oily solution and the aqueous solution is a magnetic stirrer, the stirring time is 150 min, and the stirring speed is 7000-10000 r / min; in S02 step, the stirring equipment involved after dropwise addition is completed is a magnetic stirrer, the stirring time is 2 h, and the stirring speed reaches more than 7000 r / min, so as to avoid the oil-water layering phenomenon; in S02 step, the washing operation is to wash 3 times with deionized water first, and then wash 3 times with ethanol; in S03 step, the high-purity nitrogen is nitrogen with a purity of not less than 99.99%; in S03 step, the washing operation is to wash 3 times with deionized water first, and then wash 3 times with ethanol.

[0022] The further technical solutions of the present application are: in the process of preparing the reaction liquid A in S01 step, the mixing ratio of cetylpyridinium bromide, n-butanol and n-octane is 1.35:15:100, wherein the cetylpyridinium bromide is in a weight unit of mg, the n-butanol is in a volume unit of ml, and the n-octane is in a volume unit of ml; in the process of preparing the reaction liquid B in S01 step, the mixing ratio of cetylpyridinium bromide, n-butanol and n-octane is 1.35:25:100, wherein the cetylpyridinium bromide is in a weight unit of mg, the n-butanol is in a volume unit of ml, and the n-octane is in a volume unit of ml; in the process of preparing the reaction liquid A in S01 step, the indium salt is indium nitrate or indium chloride, and the samarium salt is samarium nitrate or samarium acetate; in S03 step, the temperature of the first water bath heating is 85℃, and the temperature of the second water bath heating is 95℃; in S03 step, the concentration of ammonia water is 28%, and the concentration of hydrazine hydrate is 1 mol / L.

[0023] The technical solution of the present application is: a small molecule analyte mixed in an interference solution is detected by a MALDI-MS method, a magnetic rare earth doped indium vanadate composite nanosheet is used as a MALDI-MS matrix, the small molecule analyte is mixed in an interference solution, and the mass-to-charge ratio of the molecule of the small molecule analyte is less than 1000;

[0024] The method is as follows:

[0025] I, magnetic rare earth doped indium vanadate composite nanosheet is taken into ethanol solution, and is uniformly dispersed by ultrasonic, and a dispersion liquid with a concentration of 1.0 mg / mL is prepared; the volume ratio of ethanol to water in the ethanol solution is 3:1;

[0026] II, the dispersion liquid and the interference solution are mixed in a test tube according to a volume ratio of 1:1 to form a mixed liquid, a magnetic field is applied outside the test tube, the magnetic rare earth doped indium vanadate composite nanosheet is enriched on the inner wall of the test tube on the side of the magnetic field, then the mixed liquid in the test tube is poured out, and the magnetic rare earth doped indium vanadate composite nanosheet stained with the target small molecule analyte is left in the test tube;

[0027] III, the magnetic rare earth doped indium vanadate composite nanosheet in the test tube is taken out and dispersed in an ethanol solution with a volume ratio of ethanol to water of 3:1 to obtain a detection liquid, and the volume ratio of the ethanol solution in this step to the mixed liquid in the previous step is 0.01:1;

[0028] IV, the detection liquid is dotted on the surface of a stainless steel target plate, and MALDI-MS analysis is performed after natural drying, so that the detection of the small molecule analyte mixed in the interference solution is realized.

[0029] A further technical solution of the present application is that the small molecule analyte is a quinolone antibiotic or an angiotensin converting enzyme inhibitor; and the interference solution is milk or artificially synthesized urine.

[0030] Compared with the prior art, the present application has the following advantages:

[0031] 1. The magnetic rare earth doped indium vanadate nanosheet can be used as a MALDI-MS matrix, is suitable for analyzing small molecule analytes (with a mass-to-charge ratio less than 1000), has low background interference, high signal-to-noise ratio, and good signal stability, and fills the gap of the existing MALDI-MS matrix which is not suitable for analyzing small molecule analytes.

[0032] 2. Electron microscope results prove that the magnetic rare earth doped indium vanadate nanosheet has the characteristics of two-dimensional material and large specific surface area, and the uniform distribution of Fe3O4 nanoparticles on the surface of the InVO4:Sm nanosheet further increases the specific surface area, which is beneficial to the adsorption of small molecule analytes and helps to improve the matrix-assisted laser desorption negative ionization efficiency.

[0033] 3. The MALDI-MS test results prove that the magnetic rare earth doped indium vanadate nanosheet has very low matrix interference signal, and the signal-to-noise ratio of the analyte signal in the negative ion mode is high, the spectrum is easy to analyze, and the nanosheet also shows good salt tolerance for MALDI-MS analysis of analytes containing high concentrations of salt.

[0034] 4. The MALDI-MS analysis results of quinolone antibiotics and angiotensin converting enzyme inhibitors as representatives of small molecule drugs prove that the magnetic rare earth doped indium vanadate nanosheets can realize the quantitative analysis of trace analytes in actual samples at the level of picomole by magnetic extraction, and the detection sensitivity is high. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A transmission electron microscope image of the composite nanosheets prepared in Example 1;

[0036] Figure 2 An atomic force microscope image of the composite nanosheets prepared in Example 1;

[0037] Figure 3 An energy spectrum element analysis image of the composite nanosheets prepared in Example 1;

[0038] Figure 4 An ultraviolet-visible absorption spectrum image of the composite nanosheets prepared in Example 1;

[0039] Figure 5 A photo of the dispersion liquid of the composite nanosheets prepared in Example 1 under the action of a magnetic field;

[0040] Figure 6 A MALDI-MS spectrum comparison result of sparfloxacin in negative ion mode using the composite nanosheets and 9-AA as the MALDI-MS matrix, respectively;

[0041] Figure 7 A MALDI-MS spectrum comparison result of enoxacin in negative ion mode using the composite nanosheets and 9-AA as the MALDI-MS matrix, respectively;

[0042] Figure 8 A MALDI-MS spectrum comparison result of captopril in negative ion mode using the composite nanosheets and 9-AA as the MALDI-MS matrix, respectively;

[0043] Figure 9 A MALDI-MS spectrum comparison result of enalapril in negative ion mode using the composite nanosheets and 9-AA as the MALDI-MS matrix, respectively;

[0044] Figure 10 A linear relationship between the mass spectrum signal intensity and the concentration of sparfloxacin in negative ion mode using the composite nanosheets as the MALDI matrix;

[0045] Figure 11 A linear relationship between the mass spectrum signal intensity and the concentration of captopril in negative ion mode using the composite nanosheets as the MALDI matrix. DETAILED DESCRIPTION

[0046] Example 1

[0047] The magnetic rare earth doped indium vanadate composite nanosheet comprises InVO4:Sm nanosheet and Fe3O4 nanoparticles uniformly distributed on the surface of the InVO4:Sm nanosheet. It has typical two-dimensional material characteristics, that is, electrons can only make planar free movement in two dimensions of non-nanoscale (1-100 nm); wherein the width of the InVO4:Sm nanosheet (the distance between the two most distant points on the edge of the InVO4:Sm nanosheet) is between 200-800 nm, the thickness of the InVO4:Sm nanosheet is between 4-5 nm, and the particle size of the Fe3O4 nanoparticles is between 15-25 nm.

[0048] The preparation method of the above-mentioned magnetic rare earth doped indium vanadate composite nanosheet is as follows:

[0049] S01, two kinds of reaction solutions are prepared respectively:

[0050] The following two solutions are prepared respectively: 1, take brominated cetyl pyridine, n-butanol and n-octane to mix according to the ratio of 1.35:15:100, fully stir to form an oily solution, wherein the brominated cetyl pyridine is in units of mg, the n-butanol is in units of ml, and the n-octane is in units of ml; 2, take indium salt (selecting indium nitrate) and samarium salt (selecting samarium nitrate) to mix and configure into an aqueous solution, wherein the concentration of the indium salt is 10 mmol / ml, and the concentration of the samarium salt is 0.5 mmol / ml; mix the above-mentioned oily solution and aqueous solution according to the volume ratio of 115:5, fully stir, and form reaction solution A after fully emulsifying.

[0051] The following two solutions are prepared respectively: 1, take brominated cetyl pyridine, n-butanol and n-octane to mix according to the ratio of 1.35:25:100, fully stir to form an oily solution, wherein the brominated cetyl pyridine is in units of mg, the n-butanol is in units of ml, and the n-octane is in units of ml; 2, take ammonium metavanadate to configure an aqueous solution with a concentration of 9.1 mmol / ml; mix the above-mentioned oily solution and aqueous solution according to the volume ratio of 125:5.5, fully stir, and form reaction solution B after fully emulsifying.

[0052] In the process of preparing reaction solution A in this step, the stirring equipment in the mixing process of brominated cetyl pyridine, n-butanol and n-octane is a magnetic stirrer, the stirring time is 30 min, and the stirring speed is 5000-7000 r / min.

[0053] In the process of preparing the reaction liquid A, the stirring equipment for mixing the oily solution and the aqueous solution is a magnetic stirrer, the stirring time is 150 min, and the stirring speed is 7000-10000 r / min.

[0054] In the process of preparing the reaction liquid B, the stirring equipment for mixing the cetyl pyridinium bromide, the n-butanol and the n-octane is a magnetic stirrer, the stirring time is 30 min, and the stirring speed is 5000-7000 r / min.

[0055] In the process of preparing the reaction liquid B, the stirring equipment for mixing the oily solution and the aqueous solution is a magnetic stirrer, the stirring time is 150 min, and the stirring speed is 7000-10000 r / min.

[0056] S02, preparation of InVO4:Sm nanosheets:

[0057] A, under stirring, the reaction liquid A is added dropwise into the reaction liquid B, the volume ratio of the reaction liquid A to the reaction liquid B is 1:1, after the dropwise addition is completed, the stirring is continued, so that the reaction liquid A and the reaction liquid B are fully mixed to form a mixed solution, and then nitric acid is added to adjust the pH of the mixed solution to 1-2;

[0058] B, the mixed solution after the pH adjustment is transferred into a stainless steel autoclave, and then hydrothermal reaction is carried out at 170-190℃ for 20 h, and then natural cooling is carried out to room temperature, and the precipitate generated in the reaction is InVO4:Sm nanosheets;

[0059] C, the centrifuge is used to separate the solution after the reaction into solid and liquid, the precipitate separated out is fully washed, and then vacuum drying is carried out on the precipitate, so that the preparation of the InVO4:Sm nanosheets is completed.

[0060] In this step, the stirring equipment involved in the continuous stirring after the dropwise addition is completed is a magnetic stirrer, the stirring time is 2 h, and the stirring speed is above 7000 r / min, so that the oil-water separation phenomenon is avoided.

[0061] In this step, the washing operation is that the deionized water is used for washing 3 times, and then the ethanol is used for washing 3 times.

[0062] S03, preparation of composite nanosheets:

[0063] A, the following two kinds of liquids are prepared respectively for standby: 1, the prepared InVO4:Sm nanosheets are dispersed in deionized water by ultrasonic oscillation, a dispersion liquid with a concentration of 1 mg / ml is configured, the dispersion liquid is purged with high-purity nitrogen, so that the dissolved oxygen in the dispersion liquid is removed; 2, iron chloride and ferrous sulfate are taken and added into deionized water to be dissolved fully, so that a dissolution liquid is obtained, wherein the concentration of the iron chloride is 0.08 mmol / ml, and the concentration of the ferrous sulfate is 0.04 mmol / ml.

[0064] B, the above-mentioned dissolving solution and dispersion solution are mixed according to a volume ratio of 1:1 to obtain a mixed solution, the mixed solution is heated in a water bath at 85°C and reacts under an oxygen-free condition for 60 min to obtain intermediate solution A, then ammonia water and hydrazine hydrate are added to the intermediate solution A to obtain intermediate solution B, wherein the volume ratio of ammonia water to intermediate solution A is 10:100, and the volume ratio of hydrazine hydrate to intermediate solution A is 0.1:100; the intermediate solution B is heated in a water bath at 95°C and reacts under an oxygen-free environment for 60 min to obtain a final solution containing magnetic rare earth doped indium vanadate composite nanosheets;

[0065] C, the final solution obtained by the reaction is subjected to solid-liquid separation by using a centrifuge, and the separated precipitate is washed thoroughly to complete the preparation of the magnetic rare earth doped indium vanadate composite nanosheet.

[0066] In this step, the concentration of ammonia water is 28%, and the concentration of hydrazine hydrate is 1 mol / L.

[0067] In this step, the high-purity nitrogen gas has a purity of not less than 99.99%.

[0068] In this step, the washing operation is to wash 3 times with deionized water first, and then 3 times with ethanol.

[0069] The magnetic rare earth doped indium vanadate composite nanosheet (hereinafter referred to as composite nanosheet) prepared in this embodiment is characterized in terms of physical and chemical properties, and the results are shown in Figures 1-5 .

[0070] As shown in Figure 1 , the composite nanosheet prepared in this embodiment is observed by transmission electron microscopy, and it is found that it has a two-dimensional nanosheet structure, and particles (i.e. Fe3O4 nanoparticles) with a size of 15-25 nm are uniformly distributed on its surface.

[0071] As shown in Figure 2 , the atomic force microscopy results prove that the thickness of the InVO4:Sm nanosheet is 4-5 nm, and the height of the loaded Fe3O4 nanoparticles is 13-21 nm, which is comparable to the observation results of the transmission electron microscope.

[0072] As shown in Figure 3 , the energy spectrum analysis results show that the composite nanosheet prepared in this embodiment has In, V, Fe, O, Sm and other elements, which is consistent with the theoretical composition of the composite nanosheet (molecular formula: InVO4:Sm / Fe3O4).

[0073] As shown in Figure 4As shown, the UV-visible absorption spectrum shows that the composite nanosheets prepared in this example have strong UV absorption at 355 nm, indicating that they can absorb the laser energy of the MALDI-MS instrument and meet the basic conditions for being a MALDI-MS matrix.

[0074] like Figure 5 As shown, the composite nanosheets prepared in this example are dispersed in deionized water and can be attracted to the tube wall by the action of an external magnetic field, proving that they also have the ability of magnetic enrichment.

[0075] Example 2:

[0076] Compared with Example 1, the difference between this embodiment and Example 1 is that some parameters in the preparation process of magnetic rare earth-doped indium vanadate composite nanosheets have the following differences.

[0077] In step S01, during the preparation of reaction solution A, cetylpyridinium bromide, n-butanol, and n-octane are mixed in a ratio of 1.35:25:100 and stirred thoroughly to form an oily solution, wherein cetylpyridinium bromide is expressed in weight units of mg, n-butanol is expressed in volume units of ml, and n-octane is expressed in volume units of ml.

[0078] The composite nanosheets prepared in this example were analyzed according to the five characterization test methods described in Example 1. The results showed that the composite nanosheets prepared in this example had a sheet-like two-dimensional nanostructure similar to the composite nanosheets prepared in Example 1, and Fe3O4 nanoparticles with a size of 14 to 23 nm were evenly distributed on the surface of the nanosheets.

[0079] Example 3:

[0080] Compared with Example 1, the difference between this embodiment and Example 1 is that some parameters in the preparation process of magnetic rare earth-doped indium vanadate composite nanosheets have the following differences.

[0081] In step S01, during the preparation of reaction solution B, cetylpyridinium bromide, n-butanol, and n-octane are mixed in a ratio of 1.35:25:100 and stirred thoroughly to form an oily solution, wherein cetylpyridinium bromide is expressed in weight units of mg, n-butanol is expressed in volume units of ml, and n-octane is expressed in volume units of ml.

[0082] The composite nanosheets prepared in this example were analyzed according to the five characterization test methods described in Example 1. The results showed that the composite nanosheets prepared in this example had a sheet-like two-dimensional nanostructure similar to the composite nanosheets prepared in Example 1, and Fe3O4 nanoparticles with a size of 14 to 23 nm were evenly distributed on the surface of the nanosheets.

[0083] Example 4:

[0084] The embodiment is compared with the embodiment 1, and the difference is only that some parameters in the preparation process of the magnetic rare earth doped indium vanadate composite nanosheet exist the following differences.

[0085] In the process of preparing the reaction liquid A in the S01 step, cetylpyridinium bromide, n-butanol and n-octane are mixed in a ratio of 1.35:25:100, fully stirred to form an oily solution, wherein the cetylpyridinium bromide is in a unit of mg, the n-butanol is in a unit of ml, and the n-octane is in a unit of ml.

[0086] In the process of preparing the reaction liquid B in the S01 step, cetylpyridinium bromide, n-butanol and n-octane are mixed in a ratio of 1.35:25:100, fully stirred to form an oily solution, wherein the cetylpyridinium bromide is in a unit of mg, the n-butanol is in a unit of ml, and the n-octane is in a unit of ml.

[0087] According to the five characterization test methods described in the embodiment 1, the composite nanosheet prepared in the embodiment is analyzed, and the results show that the composite nanosheet prepared in the embodiment has a similar sheet-shaped two-dimensional nanostructure as the composite nanosheet prepared in the embodiment 1, and the Fe3O4 nanoparticles with a size of 14-23 nm are uniformly distributed on the surface of the nanosheet.

[0088] Embodiment 5:

[0089] The embodiment is compared with the embodiment 1, and the difference is only that some parameters in the preparation process of the magnetic rare earth doped indium vanadate composite nanosheet exist the following differences.

[0090] In the process of preparing the reaction liquid A in the S01 step, the indium salt is indium chloride.

[0091] According to the five characterization test methods described in the embodiment 1, the composite nanosheet prepared in the embodiment is analyzed, and the results show that the composite nanosheet prepared in the embodiment has a similar sheet-shaped two-dimensional nanostructure as the composite nanosheet prepared in the embodiment 1, and the Fe3O4 nanoparticles with a size of 14-23 nm are uniformly distributed on the surface of the nanosheet.

[0092] Embodiment 6:

[0093] The embodiment is compared with the embodiment 1, and the difference is only that some parameters in the preparation process of the magnetic rare earth doped indium vanadate composite nanosheet exist the following differences.

[0094] In the process of preparing the reaction liquid A in the S01 step, the samarium salt is samarium acetate.

[0095] The composite nanosheets prepared in this example were analyzed according to the five characterization test methods described in Example 1, and the results showed that the composite nanosheets prepared in this example had similar sheet-shaped two-dimensional nanostructures to the composite nanosheets prepared in Example 1, and Fe3O4 nanoparticles with a size of 14-23 nm were uniformly distributed on the surface of the nanosheets.

[0096] Example 7

[0097] This example is compared with Example 1, and the only difference is that some parameters in the preparation process of the magnetic rare earth doped indium vanadate composite nanosheets are as follows.

[0098] In the process of preparing reaction solution A in S01, the indium salt is indium chloride.

[0099] In the process of preparing reaction solution A in S01, the samarium salt is samarium acetate.

[0100] The composite nanosheets prepared in this example were analyzed according to the five characterization test methods described in Example 1, and the results showed that the composite nanosheets prepared in this example had similar sheet-shaped two-dimensional nanostructures to the composite nanosheets prepared in Example 1, and Fe3O4 nanoparticles with a size of 14-23 nm were uniformly distributed on the surface of the nanosheets.

[0101] Example 8

[0102] This example is compared with Example 1, and the only difference is that some parameters in the preparation process of the magnetic rare earth doped indium vanadate composite nanosheets are as follows.

[0103] In the process of preparing reaction solution A in S01, cetylpyridinium bromide, n-butanol and n-octane were mixed in a ratio of 1.35:25:100, fully stirred to form an oily solution, wherein the cetylpyridinium bromide was in units of mg, the n-butanol was in units of ml, and the n-octane was in units of ml.

[0104] In the process of preparing reaction solution B in S01, cetylpyridinium bromide, n-butanol and n-octane were mixed in a ratio of 1.35:25:100, fully stirred to form an oily solution, wherein the cetylpyridinium bromide was in units of mg, the n-butanol was in units of ml, and the n-octane was in units of ml.

[0105] In the process of preparing reaction solution A in S01, the indium salt is indium chloride.

[0106] In the process of preparing reaction solution A in S01, the samarium salt is samarium acetate.

[0107] The composite nanosheets prepared in the present example were analyzed according to the five characterization test methods described in Example 1, and the results showed that the composite nanosheets prepared in the present example had similar sheet-shaped two-dimensional nanostructure as the composite nanosheets prepared in Example 1, and the Fe3O4 nanoparticles with a size of 14-23 nm were uniformly distributed on the surface of the nanosheets.

[0108] A quinolone antibiotic determination method based on MALDI-MS technology, using the above composite nanosheet as the MALDI-MS matrix, the quinolone antibiotics include sparfloxacin and enoxacin.

[0109] The steps are as follows:

[0110] I. Take the composite nanosheet and add it to an ethanol solution (the volume ratio of ethanol to water is 4:1), ultrasonically disperse it uniformly, and prepare a dispersion liquid with a concentration of 1.0 mg / mL;

[0111] II. Take 1 μL of the dispersion liquid twice and spot it on different positions on the surface of a stainless steel target plate, and after natural drying, form two liquid spots, drop 1 μL of sparfloxacin solution (concentration of 8 nmol / μL) on one liquid spot, and drop 1 μL of enoxacin solution (concentration of 8 nmol / μL) on the other liquid spot, and after natural drying, form two sample layers;

[0112] III. Perform MALDI-MS analysis on the two sample layers respectively, that is, realize qualitative and quantitative detection of the target substances.

[0113] The variable control in the above method is as follows:

[0114] Under the premise of keeping other steps and parameters unchanged, the concentration of the dispersion liquid in step I is made to be 0.6 mg / mL. Qualitative and quantitative detection of the target substances can still be realized, and the detection results remain unchanged.

[0115] Under the premise of keeping other steps and parameters unchanged, the concentrations of the sparfloxacin solution and the enoxacin solution in step II are both adjusted to 0.8 nmol / μL, and the deprotonation peaks [M-H] - of the two small molecule drugs can still be detected.

[0116] Quinolone antibiotics as typical small molecule analytes can be used to evaluate the ability of the composite nanosheet as a MALDI-MS matrix for MALDI-MS analysis of small molecule drugs.

[0117] For example, Figure 6The figure shows the MALDI-MS spectra of sparfloxacin in negative ion mode using composite nanosheets and 9-AA as MALDI-MS matrices. The results show that using 9-AA as the MALDI matrix will produce matrix background interference signals, and the mass spectrometry signal intensity and signal-to-noise ratio of sparfloxacin are not high. However, using composite nanosheets as the MALDI matrix has good matrix-assisted laser desorption ionization efficiency, and the deprotonated peak of sparfloxacin [MH] - The signal is strong and the matrix background interference signal is negligible.

[0118] like Figure 7 Figure 2 shows a comparison of MALDI-MS spectra of enoxacin in negative ion mode using the composite nanosheet and 9-AA as MALDI-MS matrices. The results show that using 9-AA as the MALDI matrix produces matrix background interference signals, resulting in low mass spectrometry signal intensity and signal-to-noise ratio for enoxacin. However, using the composite nanosheet as the MALDI matrix achieves excellent matrix-assisted laser desorption ionization efficiency, with a strong deprotonated peak [MH]-signal for enoxacin and negligible matrix background interference signals.

[0119] A method for determining angiotensin-converting enzyme inhibitors based on MALDI-MS technology uses the composite nanosheet as a MALDI-MS matrix. The angiotensin-converting enzyme inhibitors include captopril and enalapril.

[0120] Here are the steps:

[0121] Ⅰ. Add the composite nanosheets to an ethanol solution (the volume ratio of ethanol to water is 4:1) and disperse them evenly by ultrasonication to prepare a dispersion with a concentration of 1.0 mg / mL.

[0122] II. Take 1 μL of the dispersion twice and spot it on different positions on the surface of the stainless steel target plate. After natural drying, two liquid spots are formed. Add 1 μL of captopril solution (concentration of 8 nmol / μL) on one liquid spot and 1 μL of enalapril solution (concentration of 8 nmol / μL) on the other liquid spot. After natural drying, two sample layers are formed.

[0123] III. Perform MALDI-MS analysis on the two sample layers separately, thus achieving qualitative and quantitative detection of the target object.

[0124] The variables in the above method are controlled as follows:

[0125] While keeping other steps and parameters unchanged, the concentration of the dispersion in step I was adjusted to 0.6 mg / mL. Qualitative and quantitative detection of the target compound was still possible, and the test results remained unchanged.

[0126] Under the premise of keeping other steps and parameters unchanged, the concentrations of captopril solution and enalapril solution in step II were adjusted to 0.8 nmol / μL, and the deprotonated peak [MH]-signals of these two small molecule drugs could still be detected.

[0127] Angiotensin-converting enzyme inhibitors, as typical small molecule analytes, can be used to evaluate the ability of the composite nanosheets as a MALDI-MS matrix for MALDI-MS analysis of small molecule drugs.

[0128] like Figure 8 The figure shows the MALDI-MS spectra comparison results of captopril in negative ion mode using composite nanosheets and 9-AA as MALDI-MS matrices. The results show that using 9-AA as the MALDI matrix will produce matrix background interference signals, and the mass spectrometry signal intensity and signal-to-noise ratio of captopril are not high. However, using composite nanosheets as the MALDI matrix has good matrix-assisted laser desorption ionization efficiency, and the deprotonated peak of captopril [MH] - The signal is strong and the matrix background interference signal is negligible.

[0129] like Figure 9 The figure shows the MALDI-MS spectra comparison results of enalapril in negative ion mode using composite nanosheets and 9-AA as MALDI-MS matrices. The results show that using 9-AA as the MALDI matrix will produce matrix background interference signals, and the mass spectrometry signal intensity and signal-to-noise ratio of enalapril are not high. However, using composite nanosheets as the MALDI matrix has good matrix-assisted laser desorption ionization efficiency, and the deprotonated peak of enalapril [MH] - The signal is strong and the matrix background interference signal is negligible.

[0130] A MALDI-MS detection method for quinolone antibiotics mixed in an interfering solution uses the magnetic rare earth-doped indium vanadate composite nanosheets as a MALDI-MS matrix, the small molecule analyte is mixed in the interfering solution, and the quinolone antibiotic is specifically sparfloxacin.

[0131] Here are the steps:

[0132] Ⅰ. Add the composite nanosheets to an ethanol solution (the volume ratio of ethanol to water is 3:1) and disperse them evenly by ultrasonication to prepare a dispersion with a concentration of 1.0 mg / mL.

[0133] II. A group of sparfloxacin solutions with concentration between 0.005-1.2 nmol / ml and gradient distribution are prepared, and the group of sparfloxacin solutions are added into a group of interference solutions (interference solution is milk) in a one-to-one corresponding manner, so as to form a group of mixed solutions (containing target small molecule analyte); the volume ratio of sparfloxacin solution to interference solution in the mixed solution is 1:1;

[0134] III. The dispersion liquid and each mixed solution are mixed in different test tubes in an equal volume of 1:1, and shaken for 90 min at room temperature; a magnetic field is applied outside the test tube (the magnetic field is provided by a permanent magnet), so that the composite nanosheet is enriched on the inner wall of the test tube on the side of the magnetic field, and then the liquid components in the test tube are poured out, and the test tube is left with the composite nanosheet contaminated with the target small molecule analyte;

[0135] IV. The composite nanosheet contaminated with the target small molecule analyte in each test tube is taken out and dispersed in an ethanol solution (the volume ratio of ethanol to water is 4:1), and the volume ratio of the ethanol solution to the mixed solution is 0.01:1, so as to obtain a group of detection solutions.

[0136] V. Each detection solution is punctuated on the surface of a stainless steel target plate, and after natural drying, MALDI-MS analysis is performed.

[0137] The analysis results are shown in Figure 10 When the composite nanosheet is used as a magnetic enrichment material and a MALDI matrix at the same time, sparfloxacin shows a good linear relationship (R 2 = 0.989) in the range of 0.015-0.5 nmol / mL, and the detection limit is 0.0075 nmol / mL, so that the detection of trace quinolone antibiotics mixed in an interference solution is realized.

[0138] A method for detecting an angiotensin converting enzyme inhibitor mixed in an interference solution by MALDI-MS, which uses the above-mentioned magnetic rare earth doped indium vanadate composite nanosheet as a MALDI-MS matrix, the small molecule analyte is mixed in an interference solution, and the angiotensin converting enzyme inhibitor is specifically captopril.

[0139] The steps are as follows:

[0140] I. The composite nanosheet is added into an ethanol solution (the volume ratio of ethanol to water is 3:1), and ultrasonic dispersion is performed to prepare a dispersion liquid with a concentration of 1.0 mg / mL;

[0141] II. A group of captopril solutions with concentrations ranging from 0.002 to 2.7 nmol / ml are prepared, and the group of captopril solutions are added to a group of interference solutions (artificial synthetic urine) in a one-to-one correspondence, thereby forming a group of mixed solutions (containing target small molecule analytes);

[0142] III. The dispersion liquid and each mixed solution are mixed in different test tubes in a 1:1 ratio, and shaken for 90 min at room temperature. A magnetic field is applied outside the test tube (provided by a permanent magnet), so that the composite nanosheets are enriched on the inner wall of the test tube on the side of the magnetic field. Then, the liquid components in the test tube are poured out, and the test tube is left with the composite nanosheets contaminated with the target small molecule analytes;

[0143] IV. The composite nanosheets contaminated with the target small molecule analytes in each test tube are taken out and dispersed in an ethanol solution (ethanol and water in a volume ratio of 4:1). The volume ratio of the ethanol solution to the mixed solution is 0.01:1, thereby obtaining a group of detection solutions.

[0144] V. Each detection solution is spotted on the surface of a stainless steel target plate, and after natural drying, MALDI-MS analysis is performed.

[0145] The analysis results are shown in Table 1. Figure 11 As shown in Table 1, when the composite nanosheets are used as both a magnetic enrichment material and a MALDI matrix, captopril shows a good linear relationship (R 2 = 0.991) in the range of 0.05 to 2.5 nmol / mL, and the detection limit is 0.0021 nmol / mL, thereby achieving the detection of trace amounts of angiotensin-converting enzyme inhibitors mixed in an interference solution.

Claims

1. Magnetic rare earth doped indium vanadate composite nanosheets, characterized by: The invention comprises InVO4:Sm nanosheets and Fe3O4 nanoparticles uniformly distributed on the surface of the InVO4:Sm nanosheets.

2. The magnetic rare earth-doped indium vanadate composite nanosheet according to claim 1, wherein: It has typical two-dimensional material characteristics, namely: electrons can only move freely in a two-dimensional non-nanoscale plane; the width of the InVO4:Sm nanosheet is between 200-800nm, the thickness of the InVO4:Sm nanosheet is between 4-5nm, and the particle size of the Fe3O4 nanoparticles is between 15-25nm.

3. A method for preparing the magnetic rare earth doped indium vanadate composite nanosheets according to any one of claims 1 or 2, characterized in that the steps as follows: S01, prepare two reaction solutions respectively: The following two solutions were prepared separately:

1. Cetylpyridinium bromide, n-butanol, and n-octane were mixed in a ratio of 1.35:(15-30):(80-100), and stirred thoroughly to form an oily solution, wherein cetylpyridinium bromide is expressed in mg by weight, n-butanol is expressed in ml by volume, and n-octane is expressed in ml by volume; 2. Indium salt and samarium salt were mixed and prepared into an aqueous solution, wherein the concentration of the indium salt was 10 mmol / ml and the concentration of the samarium salt was 0.5 mmol / ml; the above-mentioned oily solution and aqueous solution were mixed in a volume ratio of 115:5, stirred thoroughly, and formed reaction solution A after being fully emulsified; Prepare the following two solutions separately:

1. Mix cetylpyridinium bromide, n-butanol, and n-octane in a ratio of 1.35:(15-30):(80-100) and stir thoroughly to form an oily solution, wherein cetylpyridinium bromide is expressed in mg by weight, n-butanol is expressed in ml by volume, and n-octane is expressed in ml by volume; 2. Prepare an aqueous solution of ammonium metavanadate with a concentration of 9.1 mmol / ml; mix the above oily solution and aqueous solution in a volume ratio of 125:5.5, stir thoroughly, and form reaction solution B after sufficient emulsification; S02, preparation of InVO4:Sm nanosheets: A, under stirring, adding reaction solution A dropwise to reaction solution B, with the volume ratio of reaction solution A to reaction solution B being 1:1, continuing to stir after the dropwise addition is completed to allow reaction solution A and reaction solution B to be fully mixed to form a mixed solution, and then adding nitric acid to adjust the pH of the mixed solution to 1-2; B. The pH-adjusted mixed solution was transferred into a stainless steel autoclave and subjected to a hydrothermal reaction at 170-190°C for 20 h. The mixture was then naturally cooled to room temperature. The resulting precipitate was InVO4:Sm nanosheets. C. The reaction solution is separated into solid and liquid using a centrifuge, the separated precipitate is fully washed, and then the precipitate is vacuum dried to complete the preparation of InVO4:Sm nanosheets; S03, preparation of composite nanosheets: A. Prepare the following two liquids separately:

1. Disperse the prepared InVO4:Sm nanosheets in deionized water by ultrasonic vibration to prepare a dispersion with a concentration of 1 mg / ml, and purge the dispersion with high-purity nitrogen to remove dissolved oxygen in the dispersion; 2. Take ferric chloride and ferrous sulfate and dissolve them fully in deionized water to obtain a solution, wherein the concentration of ferric chloride is 0.08 mmol / ml and the concentration of ferrous sulfate is 0.04 mmol / ml; B. The above-mentioned dissolving solution and dispersion solution are mixed in a volume ratio of 1:1 to obtain a mixed solution, and the mixed solution is placed in a water bath at 83-87° C. and reacted in an oxygen-free environment for 60 minutes to obtain an intermediate solution A, and then ammonia water and hydrazine hydrate are added to the intermediate solution A to obtain an intermediate solution B, wherein the volume ratio of ammonia water to intermediate solution A is 10:100, and the volume ratio of hydrazine hydrate to intermediate solution A is 0.1:100; the intermediate solution B is placed in a water bath at 93-97° C. and reacted in an oxygen-free environment for 60 minutes to obtain a final solution containing magnetic rare earth-doped indium vanadate composite nanosheets; C. Use a centrifuge to separate the solid and liquid of the final solution obtained by the reaction, and fully wash the separated precipitate to complete the preparation of the magnetic rare earth doped indium vanadate composite nanosheets.

4. The method for preparing magnetic rare earth-doped indium vanadate composite nanosheets according to claim 3, wherein: During the preparation of reaction solution A in step S01, the stirring device during the mixing of cetylpyridinium bromide, n-butanol and n-octane is a magnetic stirrer, the stirring time is 30 minutes, and the stirring speed is 5000-7000 r / min; During the preparation of reaction solution A in step S01, the stirring equipment during the mixing of the oily solution and the aqueous solution was a magnetic stirrer, the stirring time was 150 min, and the stirring speed was 7000-10000 r / min; During the preparation of reaction solution B in step S01, the stirring device during the mixing of cetylpyridinium bromide, n-butanol and n-octane is a magnetic stirrer, the stirring time is 30 minutes, and the stirring speed is 5000-7000 r / min; During the preparation of reaction solution B in step S01, the stirring device during the mixing of the oily solution and the aqueous solution is a magnetic stirrer, the stirring time is 150 minutes, and the stirring speed is 7000-10000 r / min; in step S02, the stirring device involved in continuing the stirring after the dropwise addition is completed is a magnetic stirrer, the stirring time is 2 hours, and the stirring speed reaches 7000 r / min or more to avoid oil-water stratification; In step S02, the washing operation is to first wash with deionized water three times and then wash with ethanol three times; in step S03, the high-purity nitrogen is nitrogen with a purity of not less than 99.99%; in step S03, the washing operation is to first wash with deionized water three times and then wash with ethanol three times.

5. The method for preparing magnetic rare earth-doped indium vanadate composite nanosheets according to claim 4, wherein: In the process of preparing reaction solution A in step S01, the mixing ratio of cetylpyridinium bromide, n-butanol and n-octane is 1.35:15:100, wherein cetylpyridinium bromide is expressed in weight unit mg, n-butanol is expressed in volume unit ml, and n-octane is expressed in volume unit ml; in the process of preparing reaction solution B in step S01, the mixing ratio of cetylpyridinium bromide, n-butanol and n-octane is 1.35:25:100, wherein cetylpyridinium bromide is expressed in weight unit mg, n-butanol is expressed in volume unit ml, and n-octane is expressed in volume unit ml; in the process of preparing reaction solution A in step S01, the indium salt is indium nitrate or indium chloride, and the samarium salt is samarium nitrate or samarium acetate; in step S03, the temperature of the first water bath heating is 85°C, and the temperature of the second water bath heating is 95°C; in step S03, the concentration of ammonia water is 28%, and the concentration of hydrazine hydrate is 1 mol / L.

6. A MALDI-MS detection method for small molecule analytes mixed in an interfering solution, using the magnetic rare earth-doped indium vanadate composite nanosheets according to any one of claims 1 to 5 as a MALDI-MS matrix, characterized in that: The small molecule analyte is mixed in the interfering solution, and the mass-to-charge ratio of the small molecule analyte is less than 1000; Here’s how: Ⅰ. Add magnetic rare earth-doped indium vanadate composite nanosheets to an ethanol solution and disperse them evenly by ultrasonication to prepare a dispersion with a concentration of 1.0 mg / mL; the volume ratio of ethanol to water in the ethanol solution is 3:1; II. The dispersion and the interference solution are mixed in a test tube at a volume ratio of 1:1 to form a mixed solution. A magnetic field is applied to the outside of the test tube to enrich the magnetic rare earth-doped indium vanadate composite nanosheets on the inner wall of the test tube on the side of the magnetic field. The mixed solution in the test tube is then poured out, leaving the magnetic rare earth-doped indium vanadate composite nanosheets contaminated with the target small molecule analyte in the test tube. III. All the magnetic rare earth-doped indium vanadate composite nanosheets in the test tube were removed and dispersed in an ethanol solution with a volume ratio of ethanol to water of 3:1 to obtain a detection solution. The volume ratio of the ethanol solution in this step to the mixed solution in the previous step was 0.01:1; IV. Spot the detection liquid on the surface of the stainless steel target plate and perform MALDI-MS analysis after natural drying, thereby realizing the detection of small molecule analytes mixed in the interfering solution.

7. The MALDI-MS detection method for small molecule analytes mixed in an interfering solution according to claim 6, wherein: The small molecule analyte is a quinolone antibiotic or an angiotensin converting enzyme inhibitor; and the interfering solution is milk or artificial synthetic urine.

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