CN108982631B - Graphene monoatomic gold composite material and preparation method and application thereof - Google Patents
Graphene monoatomic gold composite material and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a graphene monoatomic gold composite material and a preparation method and application thereof, wherein a three-dimensional graphene/carbon nitride composite is obtained by carrying out hydrothermal treatment on graphene and carbon nitride; then respectively generating a large amount of atomic gold in the carbon material by an anodic electrochemical method; finally, combining the atomic noble metal gold and the carbon material to form the graphene monoatomic gold composite material, namely the three-dimensional graphene/carbon nitride supported monodisperse gold atom composite catalyst. The synthesized three-dimensional gel/monoatomic gold compound has a large specific surface area, a hierarchical pore structure and a large number of active sites. The electrochemical sensor constructed by the composite material is applied to the detection of the activity of hydrogen peroxide and glucose, has good selectivity, and can further realize the detection in actual samples such as human serum samples, honey, cancer cells and the like.
Description
Technical Field
The invention relates to a graphene monoatomic gold composite material, a preparation method and application thereof, in particular to preparation of graphene-based monoatomic gold and application thereof in biological detection of hydrogen peroxide, glucose and the like, and belongs to the field of electrochemical sensing.
Background
Hydrogen peroxide (H) in vivo2O2) Generally, the content of enzymatic reaction products involved in catalase derived from cells in vivo is important in the fields of organisms, foods, medicines, environmental analysis, and the like. Abnormal content of H in human body2O2Can cause the diseases such as Parkinson's disease, cardiovascular diseases and even tumors, so the high-sensitivity detection of H2O2The content is attracting more and more attention.
In China, with the increasing improvement of living standard of people, more and more diabetics exist. Diabetes is a common chronic and non-infectious disease. In most cases, the timing of blood glucose, i.e., glucose in the blood, is critical to diabetic patients. Although some blood glucose monitors are on the market today, the continuous research of glucose sensors with high sensitivity, low detection limit and good selectivity has been a long-standing concern.
Compared with fluorescence spectroscopy, colorimetric spectroscopy and electrochemical luminescence, the electrochemical method is widely applied to the field of constructing biosensing due to the advantages of cheap instruments, simple operation, high sensitivity, good selectivity and the like. It is known to peroxidize by immobilizing horseradishUse of enzyme (HRP) for H on the surface of electrochemically active materials2O2Is the most classical electrochemical assay H2O2The method (1). However, HRP is expensive, complex to purify and unstable in solution, so it is necessary to replace HRP with other enzymes or to construct electrochemical sensing directly using an enzyme-free system for highly sensitive H2O2And (6) detecting.
In recent years, due to rapid development of nanomaterial science, a variety of novel inorganic nanomaterials have been widely used to construct electrochemical sensors for highly sensitive H2O2And (6) detecting. The noble metals reported therein as catalysts for the electrochemical catalysis of H2O2The reduction is mainly concentrated in the nano-form. The nano-form of the catalytic active center is limited to a part of atoms exposed on the surface, but most bulk atoms cannot participate in the reaction, so that the catalytic activity is not high or the active sites are wasted. In order to increase the catalytic active sites and to disperse the active sites as uniformly as possible, the catalyst is usually made to exist in the form of atomic states as small as possible to improve the catalytic efficiency.
Graphene (Gr) is a two-dimensional novel material in the form of six-membered monolayer sheets with sp2 hybridized carbon atoms, which has gained increasing attention due to its unique physicochemical properties, such as large specific surface area, good electrical conductivity, high mechanical strength, good biocompatibility. In recent years, two-dimensional carbon materials like graphene, such as carbon nitride (g-C)3N4) Boron Nitride (BN), etc. have also attracted the interest of researchers. Especially g-C3N4Due to high nitrogen content, good chemical and thermal stability, special optical properties and the like, the g-C3N4A great deal of research has been conducted. But the g-C is limited due to its inherently low conductivity and small surface area3N4The application in electrochemistry.
Disclosure of Invention
The invention aims to provide a graphene monoatomic gold composite material and a preparation method thereof. The invention provides the application of the composite material as an electrochemical catalyst in detecting hydrogen peroxide and glucose, and has the advantages of sensitive detection, simple operation, good stability and the like.
In the invention, graphene and carbon nitride are firstly subjected to solvent heat treatment to obtain the graphene/carbon nitride composite. Then, combining the noble metal in an atomic state with the carbon material to form a novel carbon material as a catalyst; the specific method comprises the following steps: the graphene/carbon nitride is used as a carbon matrix, and a large amount of atomic gold is further fixed through chemical bonding to be used as a catalyst, so that the graphene/carbon nitride composite material is used for detecting small molecules such as hydrogen peroxide and glucose, and can also be used for analyzing small molecules in actual samples such as human serum, honey and cancer cells.
The invention provides a graphene monoatomic gold composite material, which is prepared by mixing graphene (Gr) and carbon nitride (g-C)3N4) The preparation method comprises the steps of obtaining a three-dimensional graphene/carbon nitride (3D G-CN) compound through solvent heat treatment, and then combining atomic noble metal gold with a carbon material to form a graphene monoatomic gold composite material, namely a three-dimensional graphene/carbon nitride supported monodisperse gold atom composite catalyst, wherein the composition of the graphene monoatomic gold composite material comprises 0.001 wt% of ~ 1.0.0 wt%, 64 wt% of ~ 98.399wt% of graphene/carbon nitride, 0.5 wt% of ~ 20.0.0 wt% of gold nanoclusters, 0.1 wt% of ~ 5.0.0 wt% of gold nanoparticles and 1 wt% of ~ 10 wt% of heteroatoms.
The carbon nitride interface assembled graphene forms a porous three-dimensional graphene/carbon nitride network structure with a specific surface area of about 100-400 m2The pore size distribution is 0.1-2nm, 2-50 nm, 50-100 nm and other hierarchical pores, and the gold is in the form of monodisperse gold atoms including but not limited to gold clusters and nano-scale gold particles.
The graphene monatomic gold has the electrocatalytic performance of redox electron transfer, and can be used for targeted sensing analysis and detection of biomolecules such as hydrogen peroxide and glucose.
The electrochemical sensor constructed by the graphene monoatomic gold can be used for detecting and analyzing human serum, honey and cancer cell actual samples.
The invention also provides a method for efficiently and simply preparing the three-dimensional graphene/carbon nitride loaded monodisperse gold atom composite catalyst with controllable quantity and variety of monodisperse gold atoms by an anodic electrochemical oxidation method. The noble metal is distributed in the graphene/carbon nitride composite in a single-atom form, and the existence form and the amount of the gold can be regulated and controlled according to specific conditions. The carbon material has wide practical value in the fields of electrocatalysis, energy storage and the like.
The invention provides a preparation method of the graphene monoatomic gold composite material, which comprises the following steps of:
the specific technical scheme of the method comprises the following steps:
(1) performing freeze drying treatment on a dicyandiamide solution (20 mg/mL ~ 100 mg/mL), then performing heat treatment on the obtained solid sample in an inert atmosphere, and performing ultrasonic centrifugation on the heat-treated sample to obtain thin-layer carbon nitride;
(2) mixing the thin-layer carbon nitride obtained in the step (1) with electrochemically stripped graphene, and performing solvothermal, washing and freeze drying treatment to obtain a three-dimensional graphene/carbon nitride gel compound;
(3) modifying the gel of the three-dimensional graphene/carbon nitride obtained in the step (2) on the surface of an electrode, and obtaining the three-dimensional graphene/carbon nitride/gold composite catalyst in the electrolyte of chloroauric acid by adopting a three-electrode system through an anodic electrochemical method.
The following process is specifically described:
in the step (1), the dicyandiamide solution is subjected to heat treatment by adopting solid powder obtained by freeze drying treatment under liquid nitrogen in advance; after the heat treatment, the carbon nitride is dissolved by ultrasonic waves by using an organic solvent isopropanol and is further centrifuged to obtain thin-layer carbon nitride with good solubility.
The specific process comprises the following steps:
keeping a dicyandiamide aqueous solution (20 mg/mL ~ 100 mg/mL) in a liquid nitrogen environment for freeze drying, carrying out heat treatment on the obtained sample at a heating temperature of 400 ℃ and ~ 600 ℃ for 1 ~ 3h under an argon atmosphere by adopting a heating rate of 2 ℃ and/or ~ 4 ℃ and/or 354 ℃ and/or min, then cooling to room temperature to obtain a large piece of carbon nitride, dissolving the large piece of carbon nitride (100 mg and ~ 400 mg) in 100 mL of isopropanol solution, carrying out ultrasonic treatment for 2 ~ 6 hours, standing, collecting supernatant, and obtaining a thin-layer carbon nitride nanosheet solution with a final concentration of 1mg/mL ~ 4 mg/mL by adopting a rotary evaporation device;
the specific process of the step (2) comprises the following steps:
firstly, synthesizing graphene by an electrochemical stripping method, and soaking the graphene into H2SO4And HNO3Carrying out ultrasonic treatment for 10 ~ 20 hours in a mixed solution with the volume ratio of 1:3, then pouring the solution into a filter flask, adding water into a 0.22 mu m microporous filter membrane, carrying out suction filtration, washing and removing excessive acid, finally, collecting a filter cake, and re-dispersing with distilled water to obtain graphene with the final concentration of 1mg/mL ~ 4 mg/mL;
uniformly mixing 10 mL of the treated graphene (1 mg/mL ~ 4 mg/mL) and 10 mL of thin-layer carbon nitride nanosheet (1 mg/mL ~ 4 mg/mL) under ultrasonic waves, transferring the mixed solution into a 50 mL high-pressure reaction kettle with a polytetrafluoroethylene inner container, reacting for 6 ~ 12 hours at the temperature of 150 ℃ and ~ 200 ℃ by using solvent heat to obtain three-dimensional cylindrical gel, repeatedly washing by using distilled water, and freeze-drying overnight to obtain the three-dimensional graphene/carbon nitride (3D G-CN) compound.
The graphene/carbon nitride gel compound is of a three-dimensional porous structure, takes mesopores as a main existence mode, and has lower mass density (5 mg/cm)3~15 mg/cm3）。
In the step (3), the monodisperse gold atoms synthesized by the anodic electrochemical method are loaded on the three-dimensional graphene/carbon nitride compound, and the electrochemical method adopts a three-electrode system, namely: the three-dimensional graphene/carbon nitride modified glassy carbon electrode is used as a working electrode, the silver/silver chloride/saturated potassium chloride electrode is used as a reference electrode, and the platinum wire is used as a counter electrode to assemble a three-electrode system.
The specific process comprises the following steps:
glassy carbon electrodes of alpha-Al with particle sizes of 1.0, 0.3 and 0.05 μm, respectively2O3Polishing the paste, cleaning with ethanol and water for 1 min, and blowing with nitrogen for use. Dissolving the prepared three-dimensional graphene/carbon nitride sample in distilled water in advance: isopropyl alcohol: perfluorosulfonic acid is added in a volume ratio of 1: 1: 0.01 of the mixed solutionTo obtain a final concentration of 1mg/mL ~ 3 mg/mL, 5 ~ 10. mu.L of the solution was applied dropwise to the surface of the cleaned glassy carbon electrode and dried for further use.
And (2) assembling a three-electrode system by taking the modified glassy carbon electrode as a working electrode, taking a silver/silver chloride/saturated potassium chloride electrode as a reference electrode and taking a platinum wire as a counter electrode, wherein an electrolyte is a sulfuric acid solution containing 0.1 mM ~ 3.0.0 mM chloroauric acid, scanning for 2 ~ 10 circles at a scanning speed of 0.01V/s ~ 0.10.10V/s by adopting a cyclic voltammetry method, washing off the gold which is not specifically adsorbed, drying the obtained three-dimensional graphene/carbon nitride/monodisperse gold atom compound, and using the compound as a catalyst for electrochemical catalysis of reduction of hydrogen peroxide.
The cyclic voltammetry is adopted, the potential range is-0.2 ~ 1.5.5V, the time of each electrolysis is 0.5 ~ 2 min, the electrolyte adopts the traditional water system electrolyte, and the price is low.
The water system electrolyte is a mixture of medium strong acid and chloroauric acid; the medium-strong acid is one of sulfuric acid, hydrochloric acid and phosphoric acid.
In the method, the existence form of gold can be regulated by regulating the scanning rate and the number of scanning cycles, so that a three-dimensional graphene/carbon nitride/monodisperse gold atom compound, a three-dimensional graphene/carbon nitride/gold cluster compound, a three-dimensional graphene/carbon nitride/gold nanoparticle compound and the like can be obtained respectively.
The three-dimensional graphene/carbon nitride/monodisperse gold atom composite prepared by the invention has a hierarchical porous structure, and noble metal gold is uniformly distributed in the three-dimensional graphene/carbon nitride composite;
the preparation method provided by the invention is simple, can realize large-scale production and meets the actual industrial application.
The invention also provides application of the three-dimensional composite material of graphene gold as a catalyst for electrochemically catalyzing hydrogen peroxide reduction, and the three-dimensional composite material of graphene gold can be indirectly used for high-sensitivity detection of glucose and glucose oxidase.
When the compound is applied, 5 muL of ~ 10 muL of the compound is dripped on the surface of a glassy carbon electrode and dried, the compound is placed in 0.2M ~ 1.0.0M phosphoric acid buffer solution (pH 7.0), ~ 20 mM hydrogen peroxide with the concentration of 20nM is continuously added by adopting a chronoamperometry, the current intensity is continuously enhanced along with the increase of the concentration of the hydrogen peroxide, and finally, the compound can be used for quantitative detection of the concentration of the hydrogen peroxide.
When detecting glucose, soaking the glassy carbon electrode modified by the composite into 10 mg/mL glucose oxidase solution for half an hour, then washing and airing to be used as a working electrode, continuously adding glucose with the concentration of 10 mu M ~ 10 mM into phosphate buffer solution with the electrolyte of 0.2M ~ 1.0.0M, and observing the change of current intensity along with the continuous addition of the glucose by adopting a chronoamperometry.
When detecting glucose oxidase, soaking the glassy carbon electrode modified by the composite into a glucose oxidase solution with the concentration of 0.1 mg/mL ~ 20mg/mL for half an hour, then washing and airing to be used as a working electrode, adding 2 mM glucose into a phosphoric acid buffer solution with the electrolyte of 0.2M ~ 1.0.0M, and recording the change of current intensity along with the continuous change of the glucose oxidase by adopting a chronoamperometry.
The invention has the beneficial effects that:
(1) the electrolyte adopted by the process is low in price and can be recycled.
(2) The preparation method of the three-dimensional graphene/carbon nitride loaded monodisperse gold atom composite catalyst has the advantages of low cost, high efficiency and strong safety, and can realize large-scale industrial production.
(3) The three-dimensional composite material of graphene and gold used and prepared by the invention is composed of monodisperse gold atoms, graphene, carbon nitride, gold clusters, nano gold particles and the like. The graphene, the carbon nitride and the single-atom gold play a certain role in electrochemical reduction of hydrogen peroxide, the graphene has high electron conductivity, and the synergistic effect of the graphene, the carbon nitride and the single-atom gold in the composite material can be more beneficial to electrochemical reduction of the hydrogen peroxide and is used for detection with high sensitivity, wide linear range and high selectivity.
(4) The monatomic gold is uniformly dispersed in the three-dimensional graphene/carbon nitride through Au-Cl and Au-N bonding, wherein the three-dimensional structure has a large specific surface area, and more monatomic gold is more conveniently loaded.
(5) The graphene gold three-dimensional composite catalyst prepared by the invention is applied to electrocatalysis H2O2During detection, the method has good selectivity, and can be further used for H in human serum samples, cancer cells and other actual samples2O2And (6) detecting.
(6) The graphene gold three-dimensional composite catalyst prepared by the invention has good selectivity when being applied to electrocatalytic glucose detection, and can be further applied to glucose detection in human serum samples, honey and other actual samples.
Drawings
FIG. 1 shows (a) SEM and (b) TEM morphology of three-dimensional graphene/carbon nitride composite (3D G-CN) in example 1, and the inset in FIG. 1a is an electron photograph of 3D G-CN.
Figure 2 XRD patterns of (a) graphene, (b) carbon nitride and (c) 3D G-CN in example 1.
FIG. 3 BET plot of 3D G-CN complex in example 1.
FIG. 4 is a STEM graph showing (a) bright field and (b) dark field corresponding to 3D G-CN (3D G-CN/Au atoms) complex in which monodisperse gold atoms are supported in example 4.
FIG. 5 is a STEM map of (a) bright field and (b) dark field corresponding to 3D G-CN (3D G-CN/Au) complex with single atom gold and gold nanoclusters in example 5.
FIG. 6. 3D G-CN/Au complex as catalyst in example 6 after continuous addition of hydrogen peroxide to 0.2M phosphoric acid buffer solution (pH 7.0) (a) response curve of current over time and (b) enlarged view over time from 0 to 200 s.
FIG. 7 is a study on the selectivity of different small biological molecules in the process of using 3D G-CN/Au complex as a catalyst for detecting hydrogen peroxide in example 7.
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) And (3) carrying out freeze drying treatment on a 20mg/mL dicyandiamide (DCDA) solution, and then heating the obtained solid sample to 600 ℃ for two hours under an argon atmosphere at a temperature rise rate of 2.3 ℃/min to obtain a large piece of carbon nitride. (2) Dissolving 100 mg of large-piece carbon nitride in 100 mL of isopropanol solution and carrying out ultrasonic treatment for 5 hours, standing to collect supernatant, and obtaining thin-layer carbon nitride nanosheets with final concentration of 4 mg/mL by using a rotary evaporation device. (3) Ultrasonically and uniformly mixing the acid-treated electrochemical stripping graphene (2 mg/mL) and the thin-layer carbon nitride nanosheet (4 mg/mL), transferring the mixed solution into a high-pressure reaction kettle with a 50 mL polytetrafluoroethylene liner, and carrying out a solvothermal reaction at 180 ℃ for 12 hours to obtain the three-dimensional cylindrical gel. And repeatedly washing with distilled water, and freeze-drying overnight to obtain the three-dimensional graphene/carbon nitride (3D G-CN) composite. The nitrogen content was 7.79%, the carbon content was 82.95%, and the oxygen content was 9.27% as determined by analysis.
The SEM and TEM characteristics of the prepared 3D G-CN are shown in figure 1, and it can be seen from figure 1a that the surface of the compound has a porous, irregular and folded stacked three-dimensional structure, meanwhile, the electronic photograph in the inset of figure 1a can clearly show the three-dimensional shape similar to a cylinder, and the gel compound has good elasticity and low mass density. It is further evident from fig. 1b that the carbon nitride is tightly stacked in the graphene layer, forming a layer-by-layer composite structure. The characterization of the prepared composite material corresponding to XRD is shown in figure 2, the corresponding angles of the acid-treated graphene are 12.5 degrees and 25.66 degrees, the corresponding angles of the single carbon nitride are 13.1 degrees and 27.3 degrees, however, the corresponding angle of 3D G-CN obtained by solvothermal treatment is shifted to 25.4 degrees leftwards, which shows that the composite is successfully compounded into a three-dimensional composite structure by layer-by-layer assembly. The BET characterization of this material is shown in FIG. 3. As can be seen from FIG. 3, the specific surface of the 3D G-CN complex is about 278.92 m2The average pore diameter is 8.9 nm, and mesopores are mainly present.
Example 2
(1) And (3) carrying out freeze drying treatment on a 20mg/mL dicyandiamide (DCDA) solution, and then heating the obtained solid sample to 600 ℃ for two hours under an argon atmosphere at a temperature rise rate of 2.3 ℃/min to obtain a large piece of carbon nitride. (2) Dissolving 100 mg of large-piece carbon nitride in 100 mL of isopropanol solution and carrying out ultrasonic treatment for 5 hours, standing to collect supernatant, and obtaining thin-layer carbon nitride nanosheets with the final concentration of 2 mg/mL by adopting a rotary evaporation device. (3) Ultrasonically and uniformly mixing the electrochemically stripped graphene (2 mg/mL) treated by acid and the thin-layer carbon nitride nanosheet (2 mg/mL), transferring the mixed solution into a high-pressure reaction kettle with a 50 mL polytetrafluoroethylene liner, and carrying out a solvothermal 180-degree-temperature reaction for 12 hours to obtain the three-dimensional cylindrical gel. Repeatedly washing with distilled water, and freeze-drying overnight to obtain three-dimensional graphene/carbon nitride (3D G)1-(CN)1) The complex of (1). The nitrogen content was 5.26%, the carbon content was 85.47%, and the oxygen content was 9.27% as determined by analysis.
Example 3
(1) And (3) carrying out freeze drying treatment on a 20mg/mL dicyandiamide (DCDA) solution, and then heating the obtained solid sample to 600 ℃ for two hours under an argon atmosphere at a temperature rise rate of 2.3 ℃/min to obtain a large piece of carbon nitride. (2) Dissolving 100 mg of large-piece carbon nitride in 100 mL of isopropanol solution and carrying out ultrasonic treatment for 5 hours, standing to collect supernatant, and obtaining thin-layer carbon nitride nanosheets with final concentration of 1mg/mL by using a rotary evaporation device. (3) Ultrasonically and uniformly mixing the electrochemically stripped graphene (2 mg/mL) treated by acid and the thin-layer carbon nitride nanosheet (1 mg/mL), transferring the mixed solution into a high-pressure reaction kettle with a 50 mL polytetrafluoroethylene liner, and carrying out a solvothermal 180-degree-temperature reaction for 12 hours to obtain the three-dimensional cylindrical gel. Repeatedly washing with distilled water, and freeze-drying overnight to obtain three-dimensional graphene/carbon nitride (3D G)2-(CN)1) The complex of (1). The nitrogen content was 4.13%, the carbon content was 86.6%, and the oxygen content was 9.27% as determined by analysis.
Example 4
mu.L of the solution (2 mg/mL) from example 1 above was modified with a glassy carbon electrode as the working electrode, a silver/silver chloride/saturated potassium chloride electrode as the reference electrode and a platinum wire as the counter electrode to assemble a three-electrode system, the electrolyte being a sulfuric acid solution containing 0.5mM chloroauric acid. Scanning for 2 circles at a scanning rate of 0.02V/s by adopting a cyclic voltammetry method, washing away the gold which is not specifically adsorbed, obtaining a 3D G-CN/Au atoms compound, and airing the compound to be used as a catalyst for later use. The content of the single-atom gold is 0.23 wt% by analysis and detection.
The STEM characterization of the prepared 3D G-CN/Au atoms is shown in fig. 4, only the carbon complex can be seen in the bright field of fig. 4a, but not only the formation of the three-dimensional network structure of the complex by the graphene and the carbon nitride can be clearly seen in the dark field of fig. 4b, but also the distribution of the poly-monodispersed gold atoms in the complex can be seen.
Example 5
mu.L of the solution (2 mg/mL) from example 1 above was modified with a glassy carbon electrode as the working electrode, a silver/silver chloride/saturated potassium chloride electrode as the reference electrode and a platinum wire as the counter electrode to assemble a three-electrode system, the electrolyte being a sulfuric acid solution containing 0.5mM chloroauric acid. Scanning for 5 circles at a scanning speed of 0.02V/s by adopting a cyclic voltammetry method, washing off gold which is not specifically adsorbed, and then obtaining a compound of single gold atoms and gold nanoclusters loaded on 3D G-CN (3D G-CN/Au), and airing the compound to be used as a catalyst for later use. Through analysis and detection, the content of single-atom gold is 0.23 wt%, and the content of gold nanoclusters is 6.5 wt%.
The prepared STEM characterization of 3D G-CN/Au is shown in fig. 5, and the carbon complexes and gold nanoclusters can be seen in the bright field of fig. 5a, while the carbon complexes and gold nanoclusters can be seen clearly in the dark field of fig. 5b, and the polydisperse gold atoms can be seen in the complexes.
Example 6
The electrochemical catalytic hydrogen peroxide reduction test comprises the following steps:
(1) the 3D G-CN/Au electrode prepared in the above way is dried and then used as a working electrode, a silver/silver chloride/saturated potassium chloride electrode is used as a reference electrode, and a platinum wire is used as a counter electrode to assemble a three-electrode system. The electrolyte was 0.2M phosphoric acid buffer (pH 7.0).
(2) The electrolyte was purged with nitrogen for half an hour to remove excess oxygen interference prior to testing, after which the electrode was activated by 200 cycles at a scan rate of 500 mV/s over a potential range (-0.9V ~ 0.2.0.2V) using cyclic voltammetry under a continuous nitrogen environment.
(3) To an electrolyte solution of 0.2M phosphoric acid buffer solution (pH 7.0), H was continuously added at a concentration of 20nM ~ 20 mM2O2By chronoamperometry, recording the following H2O2Constant addition of (2), change of current intensity.
(4) The test results are shown in FIG. 6. As can be seen from the current versus time curve of FIG. 6a, the current intensity increases with increasing addition of hydrogen peroxide. 3D G-CN/Au complex can be used as an effective catalyst for catalyzing H2O2And (4) reducing. Also, FIG. 6b is an enlarged view of the corresponding I-t curve over a period of 0-200 s, which is clearly shown when H is present at a lower concentration2O2The current response was still possible, thus indicating that the complexes could be used for highly sensitive H2O2And (6) detecting.
Example 7
And (3) observing the selectivity of different biological micromolecules in the process of electrochemically detecting hydrogen peroxide.
The selectivity results are shown in FIG. 7. As can be seen from the current vs. time curve of FIG. 7, 5 μ MH was added first2O2As time goes on, the current increases. After that, we added continuously 300. mu.M Ascorbic Acid (AA), 300. mu.M Dopamine (DA), 300. mu.M sodium chloride (NaCl) and 300. mu.M glucose, no change in current was observed. However, when we added 5. mu. M H to the solution again2O2The current continues to increase. Thus indicating that we constructed biosensor pair H2O2The selectivity is good when the detection is carried out.
Example 8
The prepared 3D G-CN/Au modified glassy carbon electrode is soaked in a glucose oxidase (10 mg/mL) solution for half an hour, then the glassy carbon electrode is taken out, the enzyme which is not adsorbed on the surface is washed away by distilled water, the electrode is dried and then is used as a working electrode, a silver/silver chloride/saturated potassium chloride electrode is used as a reference electrode and a platinum wire is used as a counter electrode to assemble a three-electrode system, glucose (10 mu M ~ 10 mM) with different concentrations is continuously added into a phosphate buffer solution (pH 7.0) with an electrolyte of 0.2M, a chronoamperometry is adopted, the change of the current intensity along with the continuous addition of the glucose is recorded, and the current intensity is continuously increased along with the increase of the glucose concentration through analysis and detection, so the prepared 3D G-CN/Au composite serving as a catalyst can be used for detecting the high-sensitivity glucose concentration.
Example 9
Soaking the prepared glassy carbon electrode modified by 3D G-CN/Au into glucose oxidase solutions with different concentrations (0.1 mg/mL ~ 20 mg/mL) for half an hour, then taking out the glassy carbon electrode, washing the glassy carbon electrode out of the glassy carbon electrode by using distilled water, taking the electrode as a working electrode after being dried in the air, assembling a three-electrode system by taking a silver/silver chloride/saturated potassium chloride electrode as a reference electrode and a platinum wire as a counter electrode, adding glucose (2.0 mM) into a phosphate buffer solution (pH 7.0) with an electrolyte of 0.2M, recording the change of current intensity along with the continuous change of the glucose oxidase by adopting a time counting current method, and analytically detecting that the glucose solution generates more H under the catalytic action of the glucose oxidase along with the continuous increase of the concentration of the glucose oxidase2O23D G-CN/Au as catalyst promotes more H2O2Further causing an increasing current intensity. Therefore, the prepared 3D G-CN/Au compound as a catalyst can be used for detecting the concentration of high-sensitivity glucose oxidase.
Example 10
Diluting serum of different human bodies with 0.2M phosphoric acid buffer solution (pH 7.0), and adding H2O2Mixing with diluted serum solution to obtain H with different concentrations2O2. And (3) airing the prepared 3D G-CN/Au modified glassy carbon electrode to be used as a working electrode, using a silver/silver chloride/saturated potassium chloride electrode as a reference electrode and using a platinum wire as a counter electrode to assemble a three-electrode system. In the electrolyte, the solution is buffered by 0.2M phosphoric acidAdding H with different concentrations into the solution (pH 7.0)2O2By chronoamperometry, recording the following H2O2Constant addition of (2), change of current intensity. Analytically detected as H2O2The current intensity is continuously increased. Therefore, the prepared 3D G-CN/Au compound as a catalyst can be used for high-sensitivity H in human serum2O2And (4) detecting the concentration.
Example 11
Taking out the cultured human breast cancer cells (MCF-7), diluting with 0.2M phosphoric acid buffer solution (pH 7.0), and adding H2O2Mixing with diluted MCF-7 cell lysate solution to obtain H with different concentrations2O2. And (3) airing the prepared 3D G-CN/Au modified glassy carbon electrode to be used as a working electrode, using a silver/silver chloride/saturated potassium chloride electrode as a reference electrode and using a platinum wire as a counter electrode to assemble a three-electrode system. Adding H with different concentrations into 0.2M phosphoric acid buffer solution (pH 7.0) as electrolyte2O2By chronoamperometry, recording the following H2O2Constant addition of (2), change of current intensity. Analytically detected as H2O2The current intensity is continuously increased. Therefore, the prepared 3D G-CN/Au compound as a catalyst can be used for high-sensitivity H in human breast cancer cell environment2O2And (4) detecting the concentration.
Claims (10)
1. A graphene monatomic gold composite material is characterized in that: carrying out hydrothermal treatment on graphene and carbon nitride to obtain a three-dimensional graphene/carbon nitride compound; then combining the atomic noble metal gold with a carbon material to form a graphene monoatomic gold composite material, namely a three-dimensional graphene/carbon nitride supported monodisperse gold atom composite catalyst; the carbon nitride interface is assembled with graphene to form a porous three-dimensional graphene/carbon nitride network structure, and the specific surface area is 100 m2/g-400 m2(ii)/g, hierarchical pores with pore size distribution of 0.1-2nm, 2-50 nm and 50-100 nm, and gold form including monodisperse gold atoms, gold clusters and gold nanoparticles; comprises the following components: single divisionThe gold atom content is 0.001 wt% ~ 1.0.0 wt%, the graphene/carbon nitride content is 64 wt% ~ 98.399wt%, the gold nanocluster content is 0.5 wt% ~ 20.0.0 wt%, the gold nanoparticles content is 0.1 wt% ~ 5.0.0 wt%, and the heteroatom content is 1 wt% ~ 10 wt%;
the preparation method of the graphene monoatomic gold composite material comprises the following steps:
(1) carrying out freeze drying, high-temperature heat treatment and ultrasonic centrifugation on the dicyandiamide solution to obtain thin-layer carbon nitride;
the preparation method of the thin-layer carbon nitride comprises the steps of keeping a dicyandiamide aqueous solution with the concentration of 20mg/mL ~ 100 mg/mL in a liquid nitrogen environment for freeze drying, heating an obtained sample to 400 ℃ ~ 600 ℃ at the heating rate of 2 ℃/min ~ 4 ℃/min for heat treatment for 1 ~ 3h in an argon or nitrogen atmosphere, then cooling to room temperature to obtain a large-piece carbon nitride, dissolving the large-piece carbon nitride in an isopropanol solution, wherein the dosage ratio of the carbon nitride to the isopropanol solution is that every 100 mg ~ 400 mg of the carbon nitride is dissolved in 100 mL of the solution, carrying out ultrasonic treatment for 2 ~ 6 hours, then standing to collect supernatant, and obtaining a thin-layer carbon nitride nanosheet solution with the final concentration of 1mg/mL ~ 4 mg/mL by adopting a rotary evaporation device;
(2) mixing the thin-layer carbon nitride obtained in the step (1) with graphene, and performing solvothermal treatment, washing and freeze drying treatment to obtain a three-dimensional graphene/carbon nitride gel compound;
the preparation method of the graphene comprises the following steps: synthesizing graphene by an electrochemical stripping method, and soaking the graphene in H2SO4And HNO3Carrying out ultrasonic treatment for 10 ~ 20 hours in a mixed solution with the volume ratio of 1:3, then pouring the solution into a filter flask, adding water into a 0.22 mu m microporous filter membrane, carrying out suction filtration, washing and removing excessive acid, finally, collecting a filter cake, and re-dispersing with distilled water to obtain graphene with the final concentration of 1mg/mL ~ 4 mg/mL;
(3) modifying the three-dimensional graphene/carbon nitride gel obtained in the step (2) on the surface of an electrode, and obtaining the three-dimensional graphene monoatomic gold composite material in an electrolyte of chloroauric acid by adopting a three-electrode system through an anodic electrochemical deposition method.
2. The preparation method of the graphene monatomic gold composite material according to claim 1, wherein in the step (2), 10 mL of the thin-layer carbon nitride nanosheet solution with the concentration of 1mg/mL ~ 4 mg/mL and 10 mL of the thin-layer carbon nitride nanosheet solution with the concentration of 1mg/mL ~ 4 mg/mL are uniformly mixed under ultrasonic waves, then the mixed solution is transferred to a high-pressure reaction kettle with a 50 mL polytetrafluoroethylene inner container, a solvothermal reaction is adopted for 6 ~ 12 hours to obtain a three-dimensional cylindrical gel, the reaction temperature is controlled at 150 ℃ to ~ 200 ℃ and 200 ℃, and the three-dimensional graphene/carbon nitride gel composite material can be obtained by performing repeated washing with distilled water and freeze-drying overnight.
3. The method for preparing a graphene monatomic gold composite material according to claim 2, characterized in that: the graphene/carbon nitride gel composite is of a three-dimensional porous structure, takes mesopores as a main existence mode, and has the mass density of 5 mg/cm3~15 mg/cm3。
4. The method for preparing a graphene monatomic gold composite material according to claim 1, characterized in that: in the step (3), monodisperse gold atoms are synthesized by an anodic electrochemical method and loaded on the three-dimensional graphene/carbon nitride compound, and the electrochemical method adopts a three-electrode system, namely: the three-dimensional graphene/carbon nitride modified glassy carbon electrode is used as a working electrode, the silver/silver chloride/saturated potassium chloride electrode is used as a reference electrode, and the platinum wire is used as a counter electrode to assemble a three-electrode system.
5. The method for preparing the graphene monatomic gold composite material according to claim 4, characterized in that: in the step (3), the glassy carbon electrodes are respectively alpha-Al with the grain diameters of 1.0, 0.3 and 0.05 mu m2O3Polishing the paste, cleaning the paste for 1 minute by ethanol and water, drying the paste by using nitrogen for standby, dissolving the prepared three-dimensional graphene/carbon nitride sample in a mixed solution of distilled water, isopropanol and perfluorosulfonic acid in a volume ratio of 1: 1: 0.01 to enable the final concentration to be 1mg/mL ~ 3 mg/mL, and dripping 5 ~ 10 mu L of the solution to the cleaned glassDrying the surface of the carbon electrode for later use;
the modified glassy carbon electrode is used as a working electrode, a silver/silver chloride/saturated potassium chloride electrode is used as a reference electrode, a platinum wire is used as a counter electrode to assemble a three-electrode system, electrolyte is sulfuric acid solution containing 0.1 mM ~ 3.0.0 mM chloroauric acid, a cyclic voltammetry method is adopted to scan for 2 ~ 10 circles at a scanning speed of 0.01V/s ~ 0.10.10V/s, and after gold which is not specifically adsorbed is washed away, the three-dimensional graphene/carbon nitride/monodisperse gold atom composite is obtained and dried.
6. The preparation method of the graphene monatomic gold composite material according to claim 5, characterized in that a cyclic voltammetry method is adopted, the potential range is-0.2 ~ 1.5.5V, each time of electrolysis is 0.5 ~ 2 min, the electrolyte is a traditional water-based electrolyte, and the price is low;
the water system electrolyte is a mixture of medium strong acid and chloroauric acid; the medium-strong acid is one of sulfuric acid, hydrochloric acid and phosphoric acid.
7. An application of the graphene monatomic gold composite material of any one of claims 1 ~ 3 as a catalyst in electrochemical catalysis of hydrogen peroxide, glucose and glucose oxidase.
8. The application of claim 7, wherein 5 μ L ~ 10 μ L of graphene monoatomic gold composite material is dripped on the surface of a glassy carbon electrode and dried, and ~ 20 mM H20 nM is continuously added into a phosphoric acid buffer solution with 0.2M ~ 1.0M electrolyte2O2By chronoamperometry with H2O2And observing the change of the current intensity.
9. The application of the graphene monoatomic gold composite material modified glassy carbon electrode is characterized in that the glassy carbon electrode modified by the graphene monoatomic gold composite material is soaked into a 10 mg/mL glucose oxidase solution for half an hour, then washed and dried to serve as a working electrode, glucose with the concentration of 10 mu M ~ 10 mM is continuously added into a phosphoric acid buffer solution with the electrolyte of 0.2M ~ 1.0.0M, and the change of the current intensity is observed along with the continuous addition of the glucose by adopting a chronoamperometry.
10. The application of the graphene monoatomic gold composite material modified glassy carbon electrode is characterized in that the glassy carbon electrode modified by the graphene monoatomic gold composite material is soaked into a glucose oxidase solution with the concentration of 0.1 mg/mL ~ 20mg/mL for half an hour, then washed and aired to serve as a working electrode, 2 mM glucose is added into a phosphate buffer solution with the electrolyte of 0.2M ~ 1.0.0M, and the change of the current intensity along with the continuous change of the glucose oxidase is recorded by adopting a chronoamperometry.
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