CN111196602B - Preparation method and application of double-heteroatom-doped porous graphene-like nano carbon sheet - Google Patents
Preparation method and application of double-heteroatom-doped porous graphene-like nano carbon sheet Download PDFInfo
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Abstract
The invention discloses a preparation method and application of a double-heteroatom-doped porous graphene nano carbon sheet, which comprises the steps of firstly regulating and controlling a heteroelement carbon source by a sodium chloride template method, preparing a nitrogen and sulfur double-doped porous carbon nanosheet through heat treatment, then using the material as a novel carbon substrate of a matrix-assisted laser desorption ionization time-of-flight mass spectrum, and analyzing organic environmental pollutants small molecules (m/z < 700) by mass spectrometry, wherein the novel matrix can also be used for atmospheric haze (PM/z < 700), and 2.5 ) And analyzing the composition and content of the small molecules of the medium-environment pollutants. The method can also be used for the analysis and quantitative detection of different kinds of amino acid biomolecules. When the porous carbon material doped with the double hetero atoms is used as a new matrix for detecting environmental pollutant molecules, the porous carbon material has the advantages of low background interference peak, high ionic strength and the like.
Description
Technical Field
The invention relates to a preparation method of a porous graphene nano carbon sheet doped with double hetero atoms and application of the material as a new matrix in matrix-assisted laser desorption ionization time-of-flight mass spectrometry for detecting atmospheric haze and small-molecule environmental pollutants in the environment, and belongs to the cross field of materials and analytical chemistry.
Background
In recent years, most northern cities have severe haze weather in cold winter. And PM 2.5 (atmospheric particulates with an aerodynamic equivalent diameter of less than 2.5 μm) are the main factors causing haze, and may cause various human diseases such as lung injury and diastolic dysfunction. These disadvantages have been reported in the literature (allergy Toxicol.,2007,19, 811-832)Factor generation and PM 2.5 The content of heavy metals and organic compounds in the product is related. Wherein, the nitrophenol environmental pollutant micromolecules comprise 4-nitrocatechol, nitroguaiacol and the like, and mainly come from building dyes, pesticides, fuel combustion, biomass combustion and the like; the hydroxyl polycyclic aromatic hydrocarbon environmental pollutants such as 1-hydroxyl-pyrene and the like come from incomplete combustion of wood, coal and the like. They are not only in PM 2.5 Has high concentration content, and can be combined with DNA to cause gene mutation. Therefore, it is necessary to adopt an effective method for detecting the molecules of the organic environmental pollutants with high sensitivity.
However, the current detection method has many difficulties, inaccuracy, inconvenience and high cost.
Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) has been widely used for biomacromolecule analysis due to its advantages of high sensitivity, high throughput, very small sample usage, fast response speed, etc. However, when the conventional matrixes of alpha-cyano-4-hydroxycinnamic acid (CHCA), 2, 5-dihydroxybenzoic acid (DHB) and Sinapic Acid (SA) are irradiated by laser, structural fragments are generated, so that serious background interference peaks appear in the range of m/z < 700, and the application of MALDI-TOF MS in small molecule detection is influenced. Recently, researchers have synthesized a variety of new materials (porous silicon, metal particles, metal oxides, and carbon-based materials) instead of traditional matrices to avoid their background noise, enabling analytical detection applications for a variety of small molecule compounds. Among them, carbon-based species like fullerene, graphite, carbon nanotube, graphene, etc. exhibit good ionization (LDI) efficiency due to their remarkable charge mobility and optical absorption properties, and can be used as a novel MALDI matrix.
The porous carbon material has the characteristics of high electrical conductivity, large specific surface area, good chemical stability, good thermal conductivity and the like, and furthermore, the electron donating/receiving performance of a graphite layer of the carbon material can be changed by doping of the heteroatom, so that the combination of the two attracts a great deal of attention, and the porous carbon material has been applied to numerous fields such as electrochemical sensing, MALDI-TOF MS, a supercapacitor, a sodium ion battery, oxygen reduction and the like. Among them, shih et al (chem. Commun., 2017)53,5725) N-doped porous carbon materials are obtained by direct carbonization of metal organogels, which are useful as MALDI matrices for the detection of small molecular weight biomolecules. Compared with a single porous carbon material, the N-doped porous carbon material matrix has higher signal-to-noise ratio (S/N) and stronger salt tolerance when detecting small molecules. Although N-doped porous carbon materials have been successfully applied to MALDI-TOF MS analysis of small molecule compounds, so far, the use of porous carbon materials based on double heteroatom doping for the detection of PM by MALDI-TOF MS has not been reported 2.5 And (3) small molecular compounds of medium environmental pollutants.
Disclosure of Invention
The invention aims to provide a preparation method of a porous graphene nano carbon sheet doped with double hetero atoms, and in addition, the invention also provides application of the material as a new matrix in matrix-assisted laser desorption ionization time-of-flight mass spectrometry for detecting atmospheric haze and small-molecule environmental pollutants in the environment.
The double-heteroatom-doped porous graphene-like nano carbon material consists of flaky nano carbon sheets with three-dimensional graphene-like, wherein the thickness of the nano carbon sheets is 2-50 nanometers, and the specific surface area of the nano carbon sheets is 500m 2 /g～750m 2 The pore size distribution is 0.1-2nm, 2-50nm, 50-100nm and other hierarchical pores. The heteroatoms in the material include, but are not limited to, sulfur and nitrogen atoms.
The double-heteroatom-doped porous graphene-like carbon sheet comprises the following components in percentage by mass:
70-88.0 wt% of porous carbon, 6-15.0 wt% of nitrogen atom, 1-5.0 wt% of sulfur atom and 5-10.0 wt% of oxygen atom.
The preparation method of the double-heteroatom-doped porous graphene-like carbon sheet comprises the following steps:
step 1: under the conditions of room temperature and stirring, respectively adding thiourea, citric acid or sodium citrate and sodium chloride into secondary water until the thiourea, the citric acid or sodium citrate and the sodium chloride are completely dissolved, freezing the obtained mixed solution under liquid nitrogen, and then placing the mixed solution into a freeze dryer for drying for later use;
step 2: and (2) putting the solid powder obtained in the step (1) in an argon atmosphere for high-temperature carbonization, then adopting secondary water washing treatment, and drying to obtain the nitrogen and sulfur-double-doped porous carbon (N, S-C) nanosheet.
Further:
in the step 1, 0.2g to 1.5g of thiourea, 1.0g to 3.0g of citric acid or sodium citrate and 15g to 20g of sodium chloride are taken respectively and added into secondary water to be completely dissolved; the resulting mixed solution was then frozen under liquid nitrogen and then thoroughly dried in a lyophilizer for use.
And 2, placing the solid powder obtained in the step 1 in an argon atmosphere for high-temperature carbonization, specifically heating to 700-900 ℃ at a heating rate of 2-5 ℃/min for heat treatment for 1-3 h, after the temperature is reduced to room temperature, washing the obtained product with secondary water to remove redundant sodium chloride, and drying to obtain the nitrogen and sulfur double-doped porous carbon (N, S-C) nanosheet.
The nitrogen and sulfur double-doped porous graphene nano carbon material obtained by the invention is of a three-dimensional nano flaky structure, has a mode of existence with mesopores as main macropores and a specific surface area of 500m 2 /g～750m 2 /g。
In the preparation process, the existence form of three-dimensional pore canals of the porous carbon can be regulated and controlled by changing the contents of thiourea, citric acid or sodium citrate and sodium chloride, so that the three-dimensional mesoporous porous carbon, the three-dimensional macroporous porous carbon nanosheet and the like can be respectively obtained.
According to the preparation method, the sodium chloride is used as a template, the nitrogen and sulfur co-doped porous graphene nano carbon sheet is obtained through low-temperature freezing self-assembly and high-temperature carbonization treatment by utilizing the hydrogen bond effect between thiourea and citric acid, the preparation method is simple, the cost is low, and the preparation method can realize large-scale production and meet the practical industrial application.
The application of the double-heteroatom-doped porous graphene-like carbon sheet is to serve as a MALDI matrix material when a matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) is used for detecting a small molecular weight compound.
The small molecular weight compounds include organic environmental pollutant small molecules (4-nitrocatechol, nitroguaiacol, and 1-hydroxy-pyrene) and amino acid molecules (tryptophan, aspartic acid, glutamic acid, threonine, phenylalanine, methionine, and serine).
The small molecular weight compound is a compound with m/z < 1000, and preferably a compound with the molecular weight of below 700.
The samples analyzed by the method of the invention cover a complex mixing system including atmospheric haze (PM) besides pure products and simple mixtures 2.5 ) And so on.
When the nitrogen and sulfur co-doped porous graphene-like carbon sheet is used as a MALDI matrix, the concentration of the matrix solution is 0.1 mg/mL-10 mg/mL.
In the mass spectrometric detection of matrix-assisted laser desorption ionization flight time, the concentration of the analyte to be detected is 0.5 mug/mL-0.5 mg/mL.
When in application, 0.5-1 mul of matrix solution can be dripped on a matrix auxiliary laser desorption ionization target plate and naturally dried at room temperature to obtain the thin-layer matrix. And dripping 0.5-1 mu L of analyte solution on the surface of the matrix layer to perform secondary crystallization on mixed crystals formed by the sample and the matrix, naturally drying the mixed crystals at room temperature, and performing laser desorption ionization mass spectrometry after drying.
When in application, the matrix solution and the analyte solution to be detected can also be mixed in equal volume, 1 mu L-2 mu L of the mixed solution is directly dripped on a matrix-assisted laser desorption ionization target plate, and the mixture is naturally air-dried at room temperature and subjected to mass spectrometry after being dried.
The invention uses a nitrogen and sulfur double-doped porous graphene-like nano carbon sheet as a MALDI matrix for mass spectrometry, and usually a time-of-flight mass analyzer is selected, but other mass analyzers can be used for substitution.
The double-heteroatom-doped porous graphene nanocarbon sheet has large specific surface area, high conductivity and good ultraviolet absorption performance, and can be used as a novel MALDI-TOF MS matrix for analytical detection of small molecular weight compounds (m/z < 1000) and the like. The double-heteroatom-doped porous graphene-like nano carbon sheet is used as a MALDI-TOF MS new matrix and can also be used for quantitative analysis of organic environmental pollutant micromolecules in an atmospheric haze actual sample.
The invention has the beneficial effects that:
1. the invention adopts citric acid or sodium citrate, thiourea and sodium chloride as raw materials, has low cost and wide sources, can be produced in large scale and meets the application of actual industrialization.
2. The nitrogen and sulfur double-doped porous graphene-like nanocarbon sheet prepared by the invention has a graphene-like structure and consists of heteroatom nitrogen, sulfur, oxygen, porous carbon and the like. The porous carbon has large specific surface area, high electron transfer capacity and good ultraviolet absorption capacity, the heteroatom nitrogen and sulfur have strong electron donating capacity, and the double-heteroatom-doped porous carbon material can be used as a new matrix to replace the traditional matrix for MALDI mass spectrometry.
3. The nitrogen and sulfur double-doped porous graphene nanocarbon sheet prepared by the invention is used as a new MALDI matrix, has a lower matrix background interference peak in a low molecular weight range (m/z less than 700), and ensures MALDI-TOF MS analysis with high sensitivity.
4. When the nitrogen and sulfur double-doped porous graphene nano carbon sheet prepared by the invention is used as a MALDI new matrix for analyzing and detecting small-component compounds, the nitrogen and sulfur double-doped porous graphene nano carbon sheet has low background signals and high ionic strength.
5. The nitrogen and sulfur double-doped porous graphene nanocarbon sheet prepared by the invention can be used as a MALDI (matrix-assisted laser desorption ionization) new matrix for atmospheric haze (PM) 2.5 ) And analyzing the composition and content of the small molecules of the medium-environment pollutants.
6. Compared with other electrochemistry, fluorescence and colorimetric methods, the MALDI-MS method has high flux, high sensitivity and reliable m/z signal peak when detecting the atmospheric haze micromolecules.
7. The nitrogen and sulfur double-doped porous carbon material prepared by the invention can be used as a MALDI new matrix and can also be used for the analysis and quantitative detection of different kinds of amino acid biomolecules.
8. The nitrogen and sulfur double-doped porous carbon material prepared by the invention is used as a new MALDI matrix, and has higher sensitivity than graphene oxide or reduced graphene oxide matrix.
9. The invention provides a novel method for testing environmental pollution molecules and biomolecules efficiently and accurately.
Drawings
Fig. 1 is (a) SEM and (b) TEM topography of nitrogen and sulfur double-doped porous graphene-like nanocarbon sheets (N, S-C) in example 1.
FIG. 2 is a BET plot of N, S-C nanoplatelets from example 1.
FIG. 3 is a FT-IR plot of N, S-C nanoplatelets from example 1.
FIG. 4 is an XPS plot of N, S-C nanoplatelets from example 1. Wherein a is the full spectrum peak of the N, S-C nano sheet, and b, C and d respectively correspond to the C1S, N1S and S2 p sub-peaks of the N, S-C nano sheet.
FIG. 5 is the mass spectra of the conventional organic small molecule CHCA and N, S-C nanosheets as MALDI matrix in example 4 under negative ion mode.
FIG. 6 is mass spectra of conventional organic small molecule CHCA and N, S-C nanosheets as MALDI matrix for detection of (a) 4-nitrocatechol, (b) nitroguaiacol, and (C) 1-hydroxy-pyrene alone, respectively, in example 5 in negative ion mode.
FIG. 7 is a mass spectrum of a mixture solution of 4-nitrocatechol, nitroguaiacol and 1-hydroxy-pyrene as a MALDI matrix for analysis of a mixture solution of 4-nitrocatechol, nitroguaiacol and 1-hydroxy-pyrene environmental pollutants in example 6 using conventional organic small molecule CHCA and N, S-C nanosheets, respectively.
FIG. 8 shows that in example 7, conventional organic small-molecule CHCA and N, S-C nanosheets are respectively used as MALDI matrixes for atmospheric haze (PM) in a negative ion mode 2.5 ) Mass spectrogram for analyzing small and medium molecular environmental pollutants.
Detailed Description
The present invention is further illustrated by, but is not limited to, the following examples.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.
Example 1:
1. 0.65g of thiourea, 1.401g of citric acid and 17.55g of sodium chloride were dissolved in secondary water at room temperature with stirring until completely dissolved, and then the mixed solution was frozen in liquid nitrogen and dried in a lyophilizer until a powder was reserved.
2. And heating the sample to 750 ℃ at a heating rate of 5 ℃/min under an argon atmosphere, keeping for 2 hours, cooling to room temperature, washing the obtained product with secondary water to remove redundant sodium chloride, and drying to obtain the nitrogen and sulfur double-doped porous graphene nano carbon sheet (N, S-C). Analysis and detection prove that the carbon content is 80.68 percent, the oxygen content is 6.62 percent, the nitrogen content is 10.86 percent, and the sulfur content is 1.84 percent.
SEM and TEM characterization of the prepared N, S-C nanosheets are shown in FIG. 1, and as can be seen from FIG. 1a, the material exhibits correlated graphene-like nanosheets. It can further be observed from the TEM image of fig. 1b that the material is in the form of large sheets and that there are many types of pores. Also, the BET characterization of this material is shown in fig. 2. As can be seen from FIG. 2, the specific surface area of the N, S-C nanosheets is about 710.41m 2 The average pore diameter is about 9.1nm, and the structure takes mesopores as a main macropore as an auxiliary. To show the presence of heteroatoms in the porous carbon material, the FT-IR characterization of the material prepared is shown in FIG. 3, which is seen in FIG. 3 at 1383cm -1 Having C-N bonds at wavenumbers of 1631cm -1 At wave number, C = C bond, at 3450cm -1 Having O-H bonds at wavenumber of 881cm -1 Having C-S bonds at wavenumber and at 1164cm -1 S-O bonds at wavenumbers, etc. From the XPS characterization of FIG. 4a, it can be seen that the material has four elements C, N, S and O, and from FIG. 4b it can be observed that the C1S partial peak consists mainly of the C-C (284.7 eV), C-N (285.6 eV), C-S (287.4 eV) and O-C = O (290.5 eV) peaks. Further from FIG. 4c, it can be seen that the N1s peak is composed of pyridine N at 398.3eV, pyrrole N at 400.6eV, and oxidized N at 403.7eV, where pyridine N contributes to the ionization efficiency of the carbon material as a MALDI matrix and accelerates the capture of protons in the analyte for MALDI-TOF MS analysis in negative ion mode. At the same time, as can be seen from figure 4d, the S2 p peak mainly consists of-C-S-C-covalent bonds and C-SOx-groups. Furthermore, the introduction of S heteroatoms, may cause N,and the content of pyridine N in the S-C nanosheets is increased.
Example 2:
1. 1.3g of thiourea, 1.401g of citric acid and 17.55g of sodium chloride were dissolved in secondary water at room temperature with stirring until completely dissolved, and then the mixed solution was frozen in liquid nitrogen and dried in a freeze dryer until powder was reserved.
2. And heating the sample to 750 ℃ at a heating rate of 5 ℃/min under an argon atmosphere, keeping for 2h, cooling to room temperature, washing the obtained product with secondary water to remove redundant sodium chloride, and drying to obtain the nitrogen and sulfur double-doped porous graphene nano carbon sheet (N, S-C). The carbon content was 77.79%, the oxygen content was 6.62%, the nitrogen content was 12.66%, and the sulfur content was 2.93% by analytical detection.
Example 3:
1. 0.65g of thiourea, 2.802g of citric acid and 17.55g of sodium chloride were dissolved in secondary water at room temperature under stirring until completely dissolved, and then the mixed solution was frozen in liquid nitrogen and dried in a lyophilizer until a powder was reserved.
2. And heating the sample to 750 ℃ at a heating rate of 5 ℃/min under an argon atmosphere, keeping for 2h, cooling to room temperature, washing the obtained product with secondary water to remove redundant sodium chloride, and drying to obtain the nitrogen and sulfur double-doped porous graphene nano carbon sheet (N, S-C). Analysis and detection prove that the carbon content is 83.49 percent, the oxygen content is 3.81 percent, the nitrogen content is 10.86 percent, and the sulfur content is 1.84 percent.
Example 4:
1mg of the nitrogen and sulfur co-doped porous graphene-like nanocarbon sheets (N, S-C) in the example 1 is dispersed in a mixed solution of ethanol and water in a volume ratio of 1. Dissolving traditional organic micromolecule CHCA in a mixed solution of acetonitrile containing 0.1% trifluoroacetic acid and water in a volume ratio of 3. Respectively taking 1 mu L of each of the two matrix solutions, dripping the two matrix solutions on a MALDI stainless steel target plate, naturally drying at room temperature to form a thin matrix layer, and observing a matrix background peak within the range of 100-700 m/z.
As can be seen from FIG. 5, in the negative ion mode, m/z ranges from 100 to 700, and the traditional organic small molecule CHCA matrix has obvious background miscellaneous peaks, which seriously affect the signal of the object to be measured. In contrast, when N, S-C nanoplates were used as the MALDI matrix, negligible background noise could be obtained. Therefore, the N, S-C nanosheets can be used as a novel MALDI matrix for the detection of small molecular weight compounds.
Example 5:
1mg of the nitrogen and sulfur double-doped porous graphene-like nanocarbon sheets (N, S-C) in example 1 are dispersed in a mixed solution of ethanol and water in a volume ratio of 1. 1 μ L of the matrix solution was applied dropwise onto a MALDI stainless steel target plate and allowed to air dry at room temperature to form a thin matrix layer. And additionally, independently dripping 1 mu L of 4-nitrocatechol, nitroguaiacol and 1-hydroxy-pyrene solution with the concentration of 0.01mg/mL on the matrix layer, naturally airing at room temperature, and performing mass spectrometry analysis on small molecules of organic environmental pollutants in an anion mode after drying.
As can be seen from FIG. 6a, when 4-nitrocatechol was detected in the negative ion mode using a conventional CHCA substrate, no characteristic deprotonation [ M-H ] of 4-nitrocatechol was observed] - In contrast, when the N, S-C nanosheet is used as the substrate, the m/z is at the position of 154.067, and a distinct high-intensity characteristic peak can be observed. Similarly, it can be seen from FIG. 6b that the characteristic deprotonation peak of nitroguaiacol is not observed in the negative ion mode for the conventional CHCA matrix, however, the typical deprotonation peak of nitroguaiacol can be detected at m/z168.065 with N, S-C as the matrix. As can be seen from FIG. 6C, the characteristic deprotonation peak of 1-hydroxy-pyrene was observed at the m/z 217.027 position regardless of whether CHCA substrate or N, S-C nanosheet substrate was used, but stronger signal intensity and higher signal-to-noise ratio of 1-hydroxy-pyrene were obtained when N, S-C nanosheet substrate was used. Therefore, the N, S-C nanosheets can be used for high-sensitivity detection of small molecules of single environmental pollutants in the negative ion mode when being used as a MALDI matrix.
Example 6:
1mg of the nitrogen and sulfur double-doped porous graphene-like nanocarbon sheets (N, S-C) in example 1 was dispersed in a mixed solution of ethanol and water in a volume ratio of 1. 1 mul of matrix solution was applied dropwise to a MALDI stainless steel target plate and allowed to air dry at room temperature to form a thin matrix layer. And dripping 1 mu L of mixed solution of 4-nitrocatechol, nitroguaiacol and 1-hydroxy-pyrene with the final concentration of 0.1mg/mL on the matrix layer, naturally airing at room temperature, and performing mass spectrometry analysis on the organic environmental pollutant micromolecule mixture in a negative ion mode after drying.
As can be seen from FIG. 7, when the mixture of small molecules of environmental pollutants is detected by using the conventional CHCA as a substrate in a negative ion mode, only low ionic strength peaks (m/z 154.047 and 217.044) of 4-nitrocatechol and 1-hydroxy-pyrene can be observed, and a plurality of high-strength ionic background peaks are accompanied. However, when using an N, S-C matrix, the typical deprotonation peaks of the three environmental pollutants can be clearly observed near the m/z 154.032, 168.051 and 217.022 positions, with high ionic strength and zero background interference peaks. Therefore, the N, S-C nanosheets can be used for high-sensitivity detection of small molecule mixtures of environmental pollutants in a negative ion mode when being used as a MALDI matrix.
Example 7:
1mg of the nitrogen and sulfur co-doped porous graphene-like nanocarbon sheets (N, S-C) in the example 1 is dispersed in a mixed solution of ethanol and water in a volume ratio of 1. 1 μ L of the matrix solution was applied dropwise onto a MALDI stainless steel target plate and allowed to air dry at room temperature to form a thin matrix layer. Collecting the air at the top of a nine-storey building in the fertilizer market by using a high-capacity aerosol sampler, adsorbing the collected aerosol particles on a quartz fiber membrane, and cutting the quartz fiber membrane into pieces of 1 × 1cm 2 The small square blocks are placed in 25mL of acetonitrile/dichloromethane mixed solution for ultrasonic extraction, and after refluxing, the small square blocks are redispersed in the acetonitrile/dichloromethane mixed solution. Dripping 1 μ L of the above atmospheric haze dispersion solution on the matrix layer, naturally drying at room temperature, and dryingAfter drying, it was used in MALDI-TOF MS for PM analysis in negative ion mode 2.5 Small molecules of medium environmental pollutants.
As can be seen in FIG. 8, no PM was observed when using conventional CHCA matrix 2.5 The deprotonation peak of any one of the environmental contaminant molecules. However, when N, S-C nanoplates were used as the substrate, the characteristic deprotonated MS peaks corresponding to 4-nitrocatechol, nitroguaiacol and 1-hydroxy-pyrene at positions 154.067, 168.056 and 217.028 in m/z were clearly observed, with strong ionic strength and high signal-to-noise ratio. While deprotonation peaks of some other environmental contaminants may be observed. Due to the lack of standards for other environmental contaminants, the compositional makeup of the deprotonated peaks of other small molecule environmental contaminants that may be present cannot be determined.
Example 8:
1mg of the nitrogen and sulfur double-doped porous graphene-like nanocarbon sheets (N, S-C) in example 1 was dispersed in a mixed solution of ethanol and water in a volume ratio of 1. 1 μ L of the matrix solution was applied dropwise onto a MALDI stainless steel target plate and allowed to air dry at room temperature to form a thin matrix layer. And dripping 1 mu L of 4-nitrocatechol solutions (0.001-0.1 mg/mL) with different concentrations on the matrix layer, naturally airing at room temperature, and performing quantitative MS analysis on the 4-nitrocatechol solutions in a negative ion mode after drying.
Example 9:
1mg of the nitrogen and sulfur double-doped porous graphene-like nanocarbon sheets (N, S-C) in example 1 was dispersed in a mixed solution of ethanol and water in a volume ratio of 1. 1 μ L of the matrix solution was applied dropwise onto a MALDI stainless steel target plate and allowed to air dry at room temperature to form a thin matrix layer. And dripping 1 mu L of nitroguaiacol solution (0.001-0.01 mg/mL) with different concentrations on the matrix layer, naturally drying at room temperature, and performing MS analysis on nitroguaiacol in a negative ion mode after drying.
Example 10:
1mg of the nitrogen and sulfur double-doped porous graphene-like nanocarbon sheets (N, S-C) in example 1 was dispersed in a mixed solution of ethanol and water in a volume ratio of 1. 1 μ L of the matrix solution was applied dropwise onto a MALDI stainless steel target plate and allowed to air dry at room temperature to form a thin matrix layer. And respectively dripping 1 mu L of 1-hydroxy-pyrene solution (0.0005-0.075 mg/mL) with different concentrations on the matrix layer, naturally airing at room temperature, and carrying out MS analysis on the 1-hydroxy-pyrene in a negative ion mode after drying.
Example 11:
1mg of the nitrogen and sulfur double-doped porous graphene-like nanocarbon sheets (N, S-C) in example 1 was dispersed in a mixed solution of ethanol and water in a volume ratio of 1. 1 mul of matrix solution was applied dropwise to a MALDI stainless steel target plate and allowed to air dry at room temperature to form a thin matrix layer. And dripping 1 mu L of aspartic acid, glutamic acid, threonine, phenylalanine, methionine and serine solution with the concentration of 1.0mM on the matrix layer, naturally airing at room temperature, and carrying out MS analysis on amino acid in an anion mode after drying.
Example 12:
1mg of the nitrogen-and-sulfur double-doped porous graphene-like carbon sheet (N, S-C) in example 1 was dispersed in a mixed solution of ethanol and water in a volume ratio of 1. 1 μ L of the matrix solution was applied dropwise onto a MALDI stainless steel target plate and allowed to air dry at room temperature to form a thin matrix layer. And dripping 1 mu L of tryptophan (0.01 mM-5.0 mM) solution with different concentrations on the matrix layer, naturally drying at room temperature, and drying for quantitative detection of tryptophan in a negative ion mode.
Claims (4)
1. The application of the porous graphene-like nano carbon sheet doped with the double hetero atoms is characterized in that: the matrix is used as MALDI matrix material when matrix-assisted laser desorption ionization time-of-flight mass spectrometry is used for detecting small molecular weight compounds; the small molecular weight compound is a compound with m/z less than 700;
the small molecular weight compound comprises organic environmental pollutant small molecules or amino acid small molecules;
when the double-heteroatom-doped porous graphene-like nano carbon sheet is used as a MALDI matrix, the concentration of a matrix solution is 0.1 mg/mL-10 mg/mL;
in matrix-assisted laser desorption ionization time-of-flight mass spectrometry, the concentration of an analyte to be detected is 0.5 mu g/mL-0.5 mg/mL;
the porous graphene-like nano carbon sheet material doped with the double hetero atoms is composed of a sheet-like nano carbon sheet with three-dimensional graphene, the thickness of the nano carbon sheet is 2-50 nanometers, and the specific surface area of the nano carbon sheet is 500m 2 /g~750 m 2 (iv) g, pore size distribution of 0.1-2nm, 2-50nm and 50-100nm hierarchical pores; the heteroatoms include, but are not limited to, sulfur, nitrogen atoms;
the composition of the double-heteroatom-doped porous graphene nano carbon sheet comprises the following components in percentage by mass:
the content of porous carbon is 70wt% -88.0 wt%, the content of nitrogen atoms is 6wt% -15.0 wt%, the content of sulfur atoms is 1wt% -5.0 wt%, and the content of oxygen atoms is 5wt% -10.0 wt%;
the porous graphene-like nano carbon sheet doped with the double hetero atoms is prepared by the following steps:
step 1: under the conditions of room temperature and stirring, respectively adding thiourea, citric acid or sodium citrate and sodium chloride into secondary water until the thiourea, the citric acid or sodium citrate and the sodium chloride are completely dissolved, freezing the obtained mixed solution under liquid nitrogen, and then placing the mixed solution into a freeze dryer for drying for later use;
step 2: and (2) putting the solid powder obtained in the step (1) in an argon atmosphere for high-temperature carbonization, then adopting secondary water washing treatment, and drying to obtain the nitrogen and sulfur double-doped porous graphene nano carbon sheet.
2. Use according to claim 1, characterized in that:
when the method is applied, 0.5-1 mu L of matrix solution is firstly dropwise coated on a matrix auxiliary laser desorption ionization target plate, and the thin-layer matrix is obtained by naturally drying at room temperature; dripping 0.5-1 mu L of analyte solution on the surface of the matrix layer, carrying out secondary crystallization on mixed crystals formed by the sample and the matrix, naturally drying at room temperature, and carrying out laser desorption ionization mass spectrometry after drying;
or mixing the matrix solution and the analyte solution to be detected in equal volume, directly dripping 1-2 mu L of the mixed solution on a matrix-assisted laser desorption ionization target plate, naturally drying at room temperature, and performing mass spectrometry after drying.
3. Use according to claim 1, characterized in that:
in the step 1, 0.2g to 1.5g of thiourea, 1.0g to 3.0g of citric acid or sodium citrate and 15g to 20g of sodium chloride are taken respectively and added into secondary water to be completely dissolved; the resulting mixed solution was then frozen under liquid nitrogen and then thoroughly dried in a lyophilizer for use.
4. Use according to claim 1, characterized in that:
in the step 2, the solid powder obtained in the step 1 is placed in an argon atmosphere for high-temperature carbonization, specifically, the solid powder is heated to 700-900 ℃ at the heating rate of 2-5 ℃/min for heat treatment for 1-3 h, after the solid powder is cooled to the room temperature, the obtained product is washed by secondary water to remove redundant sodium chloride, and the product is dried to obtain the nitrogen and sulfur double-doped porous graphene nanocarbon tablets.
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