Preparation of hemin nanospheres-graphene composite and application thereof in detection of nitric oxide gas

Abstract

The present application relates to the technical field of gas sensitive material synthesis, in particular to a preparation of a hemin nanosphere-graphene composite material and its application in detecting nitric oxide gas, and provides a preparation method of the hemin nanosphere-graphene composite material, wherein the hemin is first treated at high temperature in a ketone solvent, and then the hemin nanosphere is obtained after purification and drying; and the hemin nanosphere and graphene oxide are subjected to alcohol thermal reaction to obtain the hemin nanosphere-graphene composite material. The hemin nanosphere-graphene composite material is prepared into a gas sensitive electrode and applied to the detection of nitric oxide gas, and the electrode has good effects, can work at room temperature, and has the characteristics of strong selectivity, high sensitivity, low power consumption, high stability and fast recovery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas sensitive material synthesis, in particular to a preparation of a hemin nanosphere-graphene composite material and application thereof in detection of nitric oxide gas. BACKGROUND

[0002] Fractional concentration of exhaled nitric oxide (FeNO) is a biological marker for detecting airway inflammation that is currently studied more. As the first non-invasive examination technology for directly detecting airway inflammation biological indicators in clinical routine in the world, FeNO detection plays a great role in diagnosing airway eosinophilic inflammation, predicting the effectiveness of steroid hormone treatment and assisting in diagnosing asthma. Therefore, it is of great significance to realize low-concentration NO detection.

[0003] Traditional resistance type NO detection materials are mostly metal oxide semiconductor sensing materials, such as zinc oxide and tungsten oxide. Since oxygen anions are involved in the sensing process, the working temperature of such substances is mostly higher than 180 DEG C, which undoubtedly increases the power consumption and also brings safety hazards. In addition, metal oxide-based gas sensors also have great shortcomings in selectivity and humidity resistance. Current studies have shown that graphene materials can realize room temperature detection of NO gas. Graphene has a large specific surface area, stable physical and chemical properties, and good room temperature conductivity, which can make up for the shortcomings of traditional metal oxide semiconductor sensing materials. However, the low sensitivity, slow response and recovery, and poor selectivity of graphene materials seriously hinder their practicality. Therefore, it is necessary to develop graphene sensing materials with high sensitivity and fast response and recovery rate for NO detection. SUMMARY

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the present application provides a preparation method of a hemin nanosphere-graphene composite material. The hemin nanosphere is coated into graphene through alcohol thermal reaction to obtain the composite material. The synthesis steps of the composite material are simple. The composite material prepared into a gas sensitive electrode has good effect in detecting nitric oxide gas, can be used at room temperature, and has the characteristics of strong selectivity, high sensitivity, low power consumption and fast recovery.

[0005] In order to achieve the above-mentioned purposes, the technical scheme adopted by the present application is:

[0006] The present application provides a hemin nanosphere-graphene composite material. The composite material is a composite material formed by graphene coating hemin nanospheres.

[0007] Preferably, the hemocrystallin nanospheres are nanospheres with a core-shell structure, and the graphene is sheet-shaped graphene oxide.

[0008] Preferably, the hemocrystallin nanospheres exist in an amorphous structure, and have an average particle size of about 50 nm.

[0009] The application also provides a preparation method of the hemocrystallin nanosphere-graphene composite material.

[0010] S1, heat-treating hemocrystallin after dissolving the hemocrystallin in a ketone solvent, and preparing hemocrystallin nanospheres after purification and drying;

[0011] S2, preparing the hemocrystallin nanosphere-graphene composite material by alcohol thermal reaction of the hemocrystallin nanospheres and graphene oxide.

[0012] Preferably, in step 1, the ketone solvent is one of acetone, butanone and methyl ethyl ketone, and the solid-liquid ratio of the hemocrystallin to the ketone solvent is 3-5 mg / mL.

[0013] More preferably, in step 1, the ketone solvent is acetone.

[0014] Preferably, in step 1, the heat treatment is heating reaction at 180-200℃ for more than 24 hours.

[0015] Preferably, in step 1, the purification is filtering out impurity particles by using a microporous filter membrane after heat treatment, and then placing the obtained filtrate in a dialysis bag for purification.

[0016] Preferably, in step 2, the mass ratio of the hemocrystallin nanospheres to the graphene oxide is (1-3):1.

[0017] Preferably, in step 2, the alcohol solvent for the alcohol thermal reaction is ethanol or isopropyl alcohol, and the solid-liquid ratio of the graphene oxide to the alcohol solvent is 0.5-1 mg / mL.

[0018] Preferably, in step 2, the alcohol thermal reaction is stirring reaction at 70-80℃ for 10-12 hours, and then reaction at 120-160℃ for 3-5 hours under a closed condition.

[0019] The application also provides application of the hemocrystallin nanosphere-graphene composite material in detecting nitric oxide.

[0020] The application also provides a gas-sensitive electrode for detecting nitric oxide gas, which is prepared by using the hemocrystallin nanosphere-graphene composite material.

[0021] Preferably, the preparation method of the gas sensitive electrode is: dispersing the hematin nanospheres-graphene composite material in a solvent, then dropping the obtained solution on a commercial ceramic substrate interdigital electrode, and finally evaporating the solvent to obtain the gas sensitive electrode.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] The present application provides a preparation method of hematin nanospheres-graphene composite material, which comprises the following steps: dissolving hematin in a ketone solvent, then heat treating to obtain hematin nanospheres, and then performing alcohol thermal reaction between the hematin nanospheres and graphene oxide to obtain the hematin nanospheres-graphene composite material. The synthesis steps of the composite material are simple, the amorphous form of hematin is used to improve the detection capability of nitric oxide, the material can be applied to prepare a gas sensitive electrode for detecting NO at room temperature, the response value is as high as 5.8 when detecting 20 ppm nitric oxide, and the material has high sensitivity; the resistance of the electrode increases when detecting common gases, but decreases when detecting NO, and the electrode has strong selectivity and high resolution; after the detection is completed, the resistance of the electrode can quickly recover to the original value when the electrode is placed in air, and the electrode has fast recovery; the electrode can work at room temperature, has the characteristics of low power consumption, and the recovery and responsiveness are basically unchanged after long-time work, and the electrode has long-term stability. Therefore, the gas sensitive electrode based on the composite material can quickly and accurately detect NO molecules in gas phase according to the change of resistance, has the characteristics of strong selectivity, high sensitivity, low power consumption, high stability and fast recovery, and can realize trace detection of NO in gas phase. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a synthesis route diagram of hematin nanospheres-graphene composite material;

[0025] Figure 2 It is the morphology characterization of hematin nanospheres of Example 1, wherein (a) and (c) are SEM micro-morphology diagrams, (b) is a selected area electron diffraction diagram, and (d) is a high-resolution TEM diagram;

[0026] Figure 3 It is an argon ion etching combined with X-ray photoelectron spectroscopy analysis diagram of hematin nanospheres of Example 1;

[0027] Figure 4 It is an X-ray diffraction analysis diagram of hematin nanospheres of Example 1;

[0028] Figure 5 It is a SEM micro-morphology diagram of hematin nanospheres-graphene composite material of Example 1;

[0029] Figure 6SEM micrographs of the composite materials of the respective comparative examples, wherein (a) is the composite material of Comparative Example 1, (b) is the composite material of Comparative Example 2, (c) is the composite material of Comparative Example 3, and (d) is the composite material of Comparative Example 4;

[0030] Figure 7 Response curve of gas sensitive electrode (I) to 20 ppm of nitric oxide;

[0031] Figure 8 Response curve of gas sensitive electrode (I) to different gradients of nitric oxide concentration;

[0032] Figure 9 Linear fitting of the response of gas sensitive electrode (I) to the concentration of nitric oxide;

[0033] Figure 10 Response comparison chart of gas sensitive electrode (I) to different gases (20 ppm of nitric oxide, 20 ppm of ammonia, and 1000 ppm of ethanol, 1000 ppm of acetone, 1000 ppm of benzene, 1000 ppm of hexane and 1000 ppm of methanol);

[0034] Figure 11 Response-time chart of gas sensitive electrode (I) for long-term detection of 20 ppm of nitric oxide;

[0035] Figure 12 Response curve of gas sensitive electrode (II) to 20 ppm of nitric oxide;

[0036] Figure 13 Response curve of gas sensitive electrodes based on different comparative examples to 20 ppm of nitric oxide, wherein a is gas sensitive electrode (III), b is gas sensitive electrode (IV), c is gas sensitive electrode (V), and d is gas sensitive electrode (VI). DETAILED DESCRIPTION

[0037] The specific embodiments of the present application will be described further in the following. It should be noted that the description of the embodiments is used to help understand the present application, but does not constitute a limitation of the present application. In addition, the technical features involved in each of the embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0038] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials used in the following examples are all commercially available unless otherwise specified.

[0039] Example 1 Preparation of hemin nanospheres-graphene composite material

[0040] The process diagram for preparing the hemin nanospheres-graphene composite material is as followsFigure 1 The specific steps are as follows:

[0041] (1) Synthesis of hematin nanospheres:

[0042] First, 30 mg of hematin was weighed and dissolved in 10 mL of acetone, and then ultrasonic dispersion was performed. Subsequently, the solution was poured into a polytetrafluoroethylene liner with a volume of 25 mL and transferred to a stainless steel reaction kettle. The reaction was heated at 180°C for 24 h under airtight conditions. After the reaction was completed, the black solution obtained was cooled to room temperature, and then filtered through a 0.22 μm microporous filter membrane to remove impurity particles. Subsequently, the filtrate was placed in a dialysis bag (1000 molecular weight) for purification for 3 days, and finally the dialysate was freeze-dried to obtain pure hematin nanospheres.

[0043] Morphology characterization of hematin nanosphere powder: The hematin nanosphere powder was subjected to scanning electron microscopy (SEM) analysis, and the results are shown in Figure 2 (a) and (c), and the average particle size of the nanospheres was about 50 nm. The hematin nanosphere powder was subjected to selected area electron diffraction and high-resolution TEM analysis, and the results are shown in Figure 2 (b) and (d), and the hematin core in the nanospheres existed in an amorphous form.

[0044] The composition of the nanospheres was analyzed by argon ion etching combined with X-ray photoelectron spectroscopy. The composition analysis was performed every 10 nm of etching, and the results of the composition of the nanospheres from the outside to the inside are shown in Figure 3 The chemical composition of the surface of the nanospheres was similar to that of acetone, and the internal composition was similar to that of hematin, indicating that the hematin nanospheres were a kind of nanospheres with a core-shell structure, with an acetone shell layer on the outside and a hematin core on the inside. The acetone shell layer was beneficial to the formation of the amorphous hematin core and also provided a physical protection effect for the nanospheres, so that the sensing material exhibited good long-term stability.

[0045] X-ray diffraction analysis of the hematin core in the hematin nanospheres was performed, and the results are shown in Figure 4 The results were consistent with the crystal analysis results of SAE D and TEM, and the hematin core existed in an amorphous form. The Fe-N4 active site in the amorphous hematin had better adsorption capacity for NO.

[0046] (2) Preparation of hematin nanosphere-graphene composite material:

[0047] Take 1 mL of graphene oxide aqueous solution (5 mg / mL), pour into a 100 mL flask, add 10 mL of anhydrous ethanol, ultrasonic for 10 min, add 10 mg of hematin nanospheres and ultrasonic for another 5 min, then transfer the flask to an oil bath, and then raise the temperature of the oil bath to 80℃, and reflux and stir for 10 h. After stirring, pour the mixed solution into a polytetrafluoroethylene liner with a volume of 25 mL and transfer it to a stainless steel reactor, heat at 120℃ for 3 h under sealed conditions. After the reaction, cool to room temperature, and then use vacuum filtration to wash the resulting mixed solution with anhydrous ethanol 3 times under a hydrophobic polytetrafluoroethylene filter membrane with a pore size of 220 nm to obtain a hematin nanosphere-graphene composite material. SEM analysis of the hematin nanosphere-graphene composite material is shown in Figure 5 Fig. 1 (a), which is a composite material formed by sheet-shaped graphene coating hematin nanospheres.

[0048] Example 2 Preparation of hematin nanosphere-graphene composite material

[0049] The preparation method is the same as that of Example 1, except that the "heating reaction for 24 h" in step (1) is adjusted to a heating reaction for 8 h to obtain a hematin nanosphere-graphene composite material.

[0050] Preparation of hematin nanosphere-graphene composite material

[0051] The preparation method is the same as that of Example 1, except that the acetone in step (1) is replaced by pure water to obtain a hematin nanosphere-graphene composite material. The SEM result of the material is shown in Figure 6 Fig. 1 (a), which is a composite material formed by sheet-shaped graphene coating hematin nanospheres.

[0052] Preparation of hematin nanosphere-graphene composite material

[0053] The preparation method is the same as that of Example 1, except that the acetone in step (1) is replaced by anhydrous ethanol to obtain a hematin nanosphere-graphene composite material. The SEM result of the material is shown in Figure 6 Fig. 1 (b), which only shows sheet-shaped graphene and a small number of nanospheres.

[0054] Preparation of composite material

[0055] The preparation method is the same as that of Example 1, except that the hematin in step (1) is replaced by ferriphthalocyanine to obtain a composite material. The SEM result of the material is shown in Figure 6 Fig. 1 (c), which shows sheet-shaped graphene and ferriphthalocyanine crystals.

[0056] Preparation of hematin nanosphere-graphene composite material

[0057] The preparation method is the same as that of Example 1, except that the hematin in step (1) is replaced by protoporphyrin, to prepare a composite material, the SEM result of which is shown in Figure 6 (d), flaky graphene and protoporphyrin crystals are observed.

[0058] Performance characterization of the hematin nanospheres-graphene composite material of Example 1

[0059] The commercial ceramic substrate interdigital electrode used in this example is a silver-palladium electrode substrate, which is purchased from Beijing Ailite Technology Co., Ltd., and the standard gas bottles used are all with nitrogen as the background gas.

[0060] Preparation of the gas-sensitive electrode: the composite material (6 mg) of Example 1, Example 2, Comparative Examples 1 to 4 is dispersed into 10 mL of anhydrous ethanol, respectively, 10 μL of the obtained solution is dropped on the commercial ceramic substrate interdigital electrode, the interdigital electrode is placed on a hot stage at 50°C and heated for 10 minutes, and the gas-sensitive electrode is prepared after the complete evaporation of the ethanol solvent. The electrode of Example 1 is recorded as gas-sensitive electrode (I), the electrode of Example 2 is recorded as gas-sensitive electrode (II), and the electrodes of Comparative Examples 1 to 4 are recorded as gas-sensitive electrode (III), gas-sensitive electrode (IV), gas-sensitive electrode (V), and gas-sensitive electrode (VI), respectively.

[0061] 1. Response characterization of the gas-sensitive electrode (I) to nitrogen monoxide

[0062] The gas-sensing performance of the gas-sensitive electrode (I) is tested by using a test system with the model of Keithley 2450. During the test, the gas-sensitive electrode (I) is placed in a 1L glass bottle filled with nitrogen, connected to Keithley 2450, and a direct current voltage of 20V is applied. After 10 minutes, the current is stabilized, and the resistance of the electrode in nitrogen (Ra) is detected. Then, the gas-sensitive electrode (I) is transferred to a standard gas bottle with a concentration of 20 ppm of nitrogen monoxide, and the response curve of the gas-sensitive electrode (I) to 20 ppm of nitrogen monoxide is shown in Figure 7 The resistance of the electrode in the nitrogen monoxide environment is significantly reduced, and the rate of resistance reduction starts to decrease over time. The ratio of the resistance of the electrode in nitrogen (Ra) to the resistance of the electrode in nitrogen monoxide (Rg) is defined as the response value, which is 5.8 at 500 seconds. Then, the electrode is transferred to a 1L glass bottle with dry air (25% RH), and the resistance gradually recovers, reaching 90% of the resistance change value after 585 seconds. The above results show that the electrode has high response to nitrogen monoxide and fast recovery.

[0063] 2. Sensitivity characterization of the gas-sensitive electrode (I) to nitrogen monoxide

[0064] The gas sensing performance of the gas sensitive electrode (I) in different gradient concentrations (0.1 ppm, 0.3 ppm, 0.5 ppm, 1 ppm, 2 ppm, 5 ppm, 10 ppm, 20 ppm) of the standard gas of nitric oxide was tested by the method of characterization 1, and the gradient response curve of nitric oxide is shown in Figure 8 The experimental results show that the hemin nanospheres-graphene composite material provided by the embodiment of the application has good responsiveness to nitric oxide, and the resistance change of the gas sensitive electrode increases with the increase of the concentration of the contacted nitric oxide.

[0065] The linear fitting of different gradient concentrations of nitric oxide and response values (as shown in Figure 9 The resistance response of the gas sensitive electrode (I) to NO and the concentration of NO have a good linear relationship in a certain concentration range, the linear equation is y = 0.25x + 1.06, R 2 = 0.97748, the sensitivity is 0.25, indicating that the gas sensitive electrode (I) has high sensitivity for NO detection.

[0066] 3. Selectivity characterization of the gas sensitive electrode (I) to nitric oxide

[0067] The gas sensing performance of the gas sensitive electrode (I) in different standard gases (20 ppm of nitric oxide, 20 ppm of ammonia, and 1000 ppm of ethanol, 1000 ppm of acetone, 1000 ppm of benzene, 1000 ppm of hexane and 1000 ppm of methanol) was tested by the method of characterization 1, the resistance of the electrode in nitrogen is Ra, and the resistance (Rg) of the electrode in the standard gas is converted into the response value (Response) as follows:

[0068]

[0069] Ra: the resistance of the electrode in nitrogen;

[0070] Rg: the resistance of the electrode in nitric oxide.

[0071] The results are shown in Figure 10 It is found that the response values of the electrode in different standard gases (ammonia, ethanol, acetone, benzene, hexane and methanol) are -20.0%, -16.0%, -9.8%, -9.7%, -8.2% and -3.0% respectively, compared with the response value (83%) of NO, the resistance of the electrode increases when detecting the remaining gases, and the resistance decreases when detecting NO, which has strong selectivity and high resolution, indicating that the hemin nanospheres-graphene composite material provided by the embodiment 1 of the application has good selectivity for nitric oxide detection.

[0072] 4. Stability characterization of the gas sensitive electrode (I) for long-term detection of nitric oxide

[0073] The gas sensing performance of the gas sensitive electrode (I) was tested by the method of Characterization 1. The response of the gas sensitive electrode to 20 ppm of nitric oxide was tested multiple times a day, and the response performance after different days was recorded. The response-time analysis of the gas sensitive electrode (I) for detecting 20 ppm of nitric oxide for 120 days is shown in FIG. 1. The response value of the gas sensitive electrode (I) is basically unchanged, and the response speed and recovery speed performance remain good, indicating that the hematin nanosphere-graphene composite provided in Example 1 of the present application has good stability for detecting nitric oxide, and the acetone shell provides physical protection for the hematin core, ensuring the long-term stability of the hematin core. Figure 11

[0074] 5. Response characterization of gas sensitive electrodes (II) to (VI)

[0075] The gas sensing performance of the gas sensitive electrodes (II) to (VI) was tested by the method of Characterization 1. The ratio of the resistance of the electrode in nitrogen (Ra) to the resistance of the electrode in nitric oxide (Rg) was defined as the response value. The test results of each electrode are as follows:

[0076] (1) The response-recovery curve of the gas sensitive electrode (II) to 20 ppm of nitric oxide is shown in FIG. 2a. The response value of the gas sensitive electrode (II) in nitric oxide gas is 4.6. The resistance of the gas sensitive electrode (II) gradually recovers when placed in air, indicating that the heat treatment time of hematin nanospheres is less than 24 h, which cannot completely prepare hematin into nanospheres, resulting in a reduced response value. Figure 12

[0077] (2) The response-recovery curve of the gas sensitive electrode (III) to 20 ppm of nitric oxide is shown in FIG. 2b. The response value of the gas sensitive electrode (III) in nitric oxide gas is 1.8, and the recovery is poor. The response-recovery curve of the gas sensitive electrode (IV) to 20 ppm of nitric oxide is shown in FIG. 2c. The response value of the gas sensitive electrode (IV) in nitric oxide gas is 2, and the recovery rate is slow, indicating that acetone is necessary for the preparation of hematin nanospheres. Hematin is insoluble in water and slightly soluble in anhydrous ethanol. The use of only water and ethanol as solvents greatly affects the preparation of nanospheres, thereby greatly reducing the response value and the recovery performance is poor. Figure 13 Figure 13 (3) The response-recovery curves of the gas sensitive electrodes (V) and (VI) to 20 ppm of nitric oxide are shown in FIGS. 2d and 2e, respectively. The response values of the gas sensitive electrodes (V) and (VI) are 2 and 1.1, respectively. The recovery of the gas sensitive electrode (V) is poor, and the gas sensitive electrode (VI) has no recovery performance.

[0078] Figure 13

[0079] ​​​​​In summary, the application uses the heat reaction of hematin nanospheres and graphene alcohol to obtain a composite material, uses the amorphous form of hematin core to improve the adsorption capacity of NO, thereby improving the detection effect, and the gas sensitive electrode prepared from the composite material can quickly and accurately detect the NO molecules in the gas phase according to the change of resistance, has the characteristics of strong selectivity, high sensitivity, low power consumption, high stability and fast recovery, and can realize the trace detection of the gas phase NO.

[0080] The embodiments of the application are described in detail above, but the application is not limited to the described embodiments. For those skilled in the art, various changes, modifications, replacements and variations of the embodiments can be made without departing from the principles and spirits of the application, and still fall within the protection scope of the application.

Claims

1. A method for preparing a hematin nanosphere-graphene composite material, characterized in that: The hematin nanosphere-graphene composite material is a composite material formed by graphene coating hematin nanospheres, and is used for detecting nitric oxide. The preparation method thereof comprises the following steps: S1, dissolving hemin in a ketone solvent and then heat-treating it, purifying it, and drying it to obtain hemin nanospheres; the hemin nanospheres are nanospheres with a core-shell structure, with an amorphous hemin core inside; S2. The hematin nanospheres and graphene oxide are subjected to an alcohol-thermal reaction to obtain a hematin nanosphere-graphene composite material.

2. The method for preparing the hematin nanosphere-graphene composite material according to claim 1, wherein In step 1, the ketone solvent is one of acetone, butanone, and methyl ethyl ketone, and the solid-to-liquid ratio of hemin to the ketone solvent is 3-5 mg / mL.

3. The method for preparing the hematin nanosphere-graphene composite material according to claim 1, wherein: In step 1, the heat treatment is a heating reaction at 180-200° C. for more than 24 hours.

4. The method for preparing the hematin nanosphere-graphene composite material according to claim 1, wherein In step 2, the mass ratio of the hematin nanospheres to the graphene oxide is (1-3):

1.

5. The method for preparing the hematin nanosphere-graphene composite material according to claim 1, wherein: In step 2, the alcohol solvent for the alcohol thermal reaction is ethanol or isopropanol, and the solid-liquid ratio of the graphene oxide to the alcohol solvent is 0.5-1 mg / mL.

6. The method for preparing the hematin nanosphere-graphene composite material according to claim 1, wherein: In step 2, the alcohol thermal reaction is first stirred at 70-80° C. for 10-12 hours, and then reacted at 120-160° C. under closed conditions for 3-5 hours.

7. A hematin nanosphere-graphene composite material prepared by the preparation method according to any one of claims 1 to 6.

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