阅读说明：本技术 一种氧化石墨烯表面官能团的定性定量分析方法 (Qualitative and quantitative analysis method for graphene oxide surface functional groups ) 是由 宋肖肖 刘太峥 王文文 马乐 于 2021-08-04 设计创作，主要内容包括：本发明涉及一种氧化石墨烯表面官能团的定性定量分析方法,属于石墨烯理化分析领域,其基于Boehm滴定法,在反应前将氧化石墨烯加入至滤袋中再置于反应液中进行反应并滴定；采用该方法无需过滤或离心进行固液分离,尤其适用于水溶性较好的材料如氧化石墨烯的检测,而且全程利于通入惰性气体保护的实施,避免了空气中CO-(2)的干扰,测定分析结果更准确。(The invention relates to a qualitative and quantitative analysis method for graphene oxide surface functional groups, belonging to the field of physical and chemical analysis of graphene, wherein based on a Boehm titration method, graphene oxide is added into a filter bag before reaction and then placed into reaction liquid for reaction and titration; the method does not need filtration or centrifugation for solid-liquid separation, is particularly suitable for detecting materials with good water solubility, such as graphene oxide, is beneficial to the implementation of inert gas protection in the whole process, and avoids CO in the air 2 The interference is avoided, and the measurement and analysis result is more accurate.)

1. A qualitative and quantitative analysis method for graphene oxide surface functional groups is characterized by comprising the following steps:

preparing required alkali liquor and HCl standard solution according to the requirements of a Boehm titration method, and sealing for later use;

2) taking 4 clean containers, respectively pouring a certain amount of 4 kinds of alkali liquor with certain concentration, marked as A, B, C, D, and respectively connecting into inert gas for protection;

3) respectively suspending filter bags in the 4 containers;

4) weighing 0.5-1g of 4 parts of graphene oxide to be detected with the particle size of more than 8 mu m, respectively adding the graphene oxide to be detected into the filter bag in the step 3), and sealing the filter bag;

5) transferring the 4 containers in the step 4) to a constant temperature oscillator, inserting an ultrasonic rod, and carrying out ultrasonic vibration and reaction for a certain time;

6) after the reaction is finished, washing and taking out the ultrasonic bar, adding the magneton, transferring the container to a stirring table, and titrating to the end point by using HCl by using methyl red as an indicator under continuous magnetic stirring;

wherein, nitrogen is continuously introduced for protection in the processes of the steps 2) to 6).

2. The qualitative and quantitative analysis method for graphene oxide surface functional groups according to claim 1, wherein the diameter of the filter bag in the step 3) is not more than 1/3 of the diameter of the container.

3. The method for qualitatively and quantitatively analyzing the graphene oxide surface functional groups according to claim 1 or 2, wherein the filter bag in the step 3) is 2000-5000 mesh.

4. The method for qualitatively and quantitatively analyzing the graphene oxide surface functional groups according to claim 1 or 2, wherein the ultrasonic frequency in the step 5) is 10 to 30 HZ.

5. The method for qualitative and quantitative analysis of graphene oxide surface functional groups according to claim 1 or 2, wherein the reaction time in step 5) is 10-24 h.

Technical Field

The invention relates to the field of physical and chemical analysis of graphene, in particular to a qualitative and quantitative analysis method for graphene oxide surface functional groups.

Background

Carbon materials such as activated carbon, carbon fiber, graphene oxide and the like are more or less introduced with some oxygen-containing functional groups such as carboxyl, lactone group, phenolic hydroxyl, carbonyl and the like in the preparation or application modification process. These oxygen-containing functional groups have an important influence on the properties of the carbon material, such as electronic properties, wettability, electrical conductivity, thermal conductivity, and chemical reactivity. Therefore, the measurement of the type and the content of the oxygen-containing functional groups on the surface of the carbon material has important significance for the quality control and the application of the carbon material. Typical analytical measurement methods include fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), Electron Energy Loss Spectroscopy (EELS), fluorescence labeling, and Boehm titration. Among them, Boehm titration has the characteristics of low cost, good repeatability, simple operation and the like, and is widely used.

The principle of Boehm's titration is the qualitative and quantitative analysis of oxides based on the possibility of alkali reaction with acidic surface oxides of different strengths, NaHCO₃Only the carboxyl group, Na, on the carbon surface is neutralized₂CO₃The carboxyl and lactone groups on the carbon surface can be neutralized, the carboxyl, lactone groups and phenolic hydroxyl groups on the carbon surface can be neutralized by NaOH, and the amount of the corresponding functional groups can be calculated according to different alkali consumption. The conventional operation process (see GB/T38114-2019) comprises the following steps: preparing an alkaline standard solution (comprising sodium bicarbonate, sodium carbonate, sodium hydroxide and sodium ethoxide) with a certain concentration, weighing 4 parts of a certain amount of a sample to be detected in a container, weighing a certain volume of standard alkali liquor, respectively adding the standard alkali liquor into the 4 parts of the sample to be detected, carrying out oscillation reaction for 24 hours, filtering or centrifuging, washing, collecting all filtrate, and titrating unreacted alkali liquor to an end point by using an HCL standard solution with a fixed concentration by using methyl red as an indicator. Two important points are that nitrogen or argon is generally introduced into the whole reaction and titration process to avoid CO in air₂The second is that filtration or centrifugation is an essential step, because the carbon material is black, if solid-liquid separation is not performed, color change in the late titration process will be interfered, resulting in titration error. The method has the following defects: 1) the solid-liquid separation can be realized by filtering and centrifuging materials with poor water solubility, such as activated carbon, carbon fiber, carbon black and the like, but the solid-liquid separation cannot be realized by filtering and centrifuging carbon materials which are very soluble in water, such as graphene oxide and the like, so that the application range of the method is limited; 2) the centrifugal or suction filtration process can not be generally used for protecting gas and CO in the air₂Will have certain influence on the experimental result and cause inaccurate result. In view of the above problems, it is highly desirable to find a method that is suitable for detecting materials with good water solubility, such as graphene oxide, and that can ensure the accuracy of the detection resultAnd (5) determining.

Disclosure of Invention

The invention aims to solve the technical problem of the prior art, and provides a qualitative and quantitative analysis method of graphene oxide surface functional groups, which is suitable for detecting materials with better water solubility, such as graphene oxide, and can ensure the accuracy of detection results.

The technical scheme for solving the technical problems is as follows: a qualitative and quantitative analysis method for graphene oxide surface functional groups is characterized by comprising the following steps:

1) preparing required alkali liquor and HCl standard solution according to the requirements of a Boehm titration method, and sealing for later use;

2) taking 4 clean containers, respectively pouring a certain amount of 4 kinds of alkali liquor with certain concentration, marked as A, B, C, D, and respectively connecting into inert gas for protection;

3) respectively suspending filter bags in the 4 containers;

4) weighing 0.5-1g of 4 parts of graphene oxide to be detected with the particle size of more than 8 mu m, respectively adding the graphene oxide to be detected into the filter bag in the step 3), and sealing the filter bag;

5) transferring the 4 containers in the step 4) to a constant temperature oscillator, inserting an ultrasonic rod, and carrying out ultrasonic vibration and reaction for a certain time;

the purpose of adding ultrasound is to further promote water circulation inside and outside the filter bag, so that the reaction is more thorough, the ultrasonic frequency is not easy to be too high, and the carbon material can be crushed if the ultrasonic frequency is too high, so that the carbon material is seeped out of the filter bag;

6) after the reaction is finished, washing and taking out the ultrasonic bar, adding magnetons, transferring the container to a stirring table, continuously stirring by the magnetons, taking methyl red as an indicator, and titrating to the end point by using HCl;

wherein, inert gas is continuously introduced for protection in the processes of the steps 2) to 6).

Further, the diameter of the filter bag in the step 3) is not more than 1/3 of the diameter of the container. The bag mouth of the filter bag is hermetically suspended in the container, the height of the filter bag is higher than that of the container, and the bottom of the filter bag is contacted with the bottom of the container.

Further, the filter bag in the step 3) is 2000-5000 meshes. The excessive mesh number of the filter bag influences water circulation and reaction efficiency, and the excessive mesh number of the filter bag is easy to leak substances to be detected, so that the mesh number needs to be matched with the particle size of the carbon material to be detected; reasons for limiting the diameter of the filter bag: the diameter is too large, and the ultrasound and titration in the later steps cannot be carried out; too small is not favorable for dispersion and reaction of the carbon material.

Further, the ultrasonic frequency in the step 5) is 10-30HZ, and the reaction time is 10-24 h.

The invention has the beneficial effects that: the method changes the thought of fully dispersing reactants for good contact in the prior art, adopts the reverse thought, and directly adds the material to be detected into the reaction liquid by adding the filter bag (the means or the sufficiency of the contact between the reactants influenced under the traditional thought) before the reaction instead of the existing standard Boehm titration method, so that the solid-liquid separation is not needed to be carried out by filtering or centrifuging after the reaction is finished, the application range is wider, the method is particularly suitable for the qualitative and quantitative determination and analysis of the surface functional group of the carbon material with excellent water solubility, namely the graphene oxide, and the graphene oxide is prevented from being easily dispersed in water and being incapable of being separated from the water; meanwhile, the method is beneficial to the implementation of whole-course inert gas protection, and avoids CO in the air₂The interference is avoided, and the measurement and analysis result is more accurate.

Drawings

FIG. 1 is a schematic view of the construction of a titration apparatus used in the present invention;

in the figure: 1. the device comprises a reaction container, 2, a first support, 3, a second support, 4, a magnetic stirrer, 5, a magneton, 6, a filter bag, 7, an ultrasonic bar, 8, an inert gas pipe, 9, an inert gas bottle, 10, a burette and 11, wherein the reaction container is provided with a hole.

Detailed Description

The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.

Example 1

The qualitative and quantitative analysis method for the graphene oxide surface functional group in the embodiment is based on a Boehm titration method in national standard GB/T38114-2019, and specifically includes the following steps:

1) according toPreparing required alkali liquor and HCl standard liquor according to the requirements of a Boehm titration method, specifically C with standard concentration of 0.05mol/L₂H₅ONa、NaOH、HCl、Na₂CO₃And NaHCO₃Each solution was 1L. In addition, potassium hydrogen phthalate, methyl red, bromocresol green, phenolphthalein and anhydrous sodium carbonate-reference solution for calibrating concentration and titration are prepared. Calibrating the prepared alkali liquor and HCl standard liquor and then sealing for later use;

2) taking 4 clean 150ml beakers, respectively pouring 100ml of 4 alkali liquids with certain concentration, marking as A, B, C, D, and respectively connecting in nitrogen protection;

3) respectively suspending 2000-mesh filter bags in the 4 beakers, wherein the diameters of the filter bags are not more than 1/3 of the diameters of the beakers, the bag openings of the filter bags are hermetically suspended in the beakers, the filter bags are higher than the beakers, the bottoms of the filter bags are in contact with the bottoms of the beakers, and the bag openings are hermetically suspended;

4) weighing 4 parts of graphene oxide to be detected with the particle size of more than 8 mu m 0.5, respectively adding the graphene oxide to be detected into 4 filter bags in 3), and sealing the filter bags;

5) transferring the 4 beakers in the step 4) to a constant-temperature oscillator, inserting an ultrasonic rod, and reacting for 10 hours at an ultrasonic frequency of 10 while vibrating and ultrasonic;

6) after the reaction is finished, washing and taking out the ultrasonic bar, adding the magnetons, slightly increasing the positions of the filter bags, reserving a magneton rotating space between the filter bags and the bottom of the beaker, transferring the beaker to a stirring table, and titrating to a terminal point by using HCl with the concentration of 0.05mol/L and taking methyl red as an indicator under continuous magneton stirring;

wherein, nitrogen is continuously introduced for protection in the processes of the steps 2) to 6).

Example 2

The qualitative and quantitative analysis method for the graphene oxide surface functional group in the embodiment is based on a Boehm titration method in national standard GB/T38114-2019, and specifically includes the following steps:

1) preparing required alkali liquor and HCl standard solution according to the requirement of a Boehm titration method, specifically C with standard concentration of 0.05mol/L₂H₅ONa、NaOH、HCl、Na₂CO₃And NaHCO₃Each solution was 1L. In additionPotassium hydrogen phthalate, methyl red, bromocresol green, phenolphthalein and anhydrous sodium carbonate-reference solution for calibrating concentration and titration are prepared externally. Calibrating the prepared alkali liquor and HCl standard liquor and then sealing for later use;

2) taking 4 clean 150ml beakers, respectively pouring 100ml of 4 alkali liquids with certain concentration, marking as A, B, C, D, and respectively connecting in nitrogen protection;

3) respectively suspending 3000-mesh filter bags in the 4 beakers, wherein the diameters of the filter bags are not more than 1/3 of the diameters of the beakers, the bag openings of the filter bags are hermetically suspended in the beakers, the filter bags are higher than the beakers, the bottoms of the filter bags are in contact with the bottoms of the beakers, and the bag openings are hermetically suspended;

4) weighing 0.7g of 4 parts of graphene oxide to be detected with the particle size of more than 8 mu m, respectively adding the graphene oxide to be detected into 4 filter bags in 3), and sealing the filter bags;

5) transferring the 4 beakers in the step 4) to a constant-temperature oscillator, inserting an ultrasonic rod, vibrating while performing ultrasonic treatment, wherein the ultrasonic frequency is 20HZ, and reacting for 16 hours;

6) after the reaction is finished, washing and taking out the ultrasonic bar, adding the magnetons, slightly increasing the positions of the filter bags, reserving a magneton rotating space between the filter bags and the bottom of the beaker, transferring the beaker to a stirring table, and titrating to a terminal point by using HCl with the concentration of 0.05mol/L and taking methyl red as an indicator under continuous magneton stirring;

wherein, nitrogen is continuously introduced for protection in the processes of the steps 2) to 6).

Example 3

The qualitative and quantitative analysis method for the graphene oxide surface functional group in the embodiment is based on a Boehm titration method in national standard GB/T38114-2019, and specifically includes the following steps:

1) preparing required alkali liquor and HCl standard solution according to the requirement of a Boehm titration method, specifically C with standard concentration of 0.05mol/L₂H₅ONa、NaOH、HCl、Na₂CO₃And NaHCO₃Each solution was 1L. In addition, potassium hydrogen phthalate, methyl red, bromocresol green, phenolphthalein and anhydrous sodium carbonate-reference solution for calibrating concentration and titration are prepared. Calibrating the prepared alkali liquor and HCl standard liquor and then sealing for later use;

2) taking 4 clean 150ml beakers, respectively pouring 100ml of 4 alkali liquids with certain concentration, marking as A, B, C, D, and respectively connecting in nitrogen protection;

3) respectively suspending 5000-mesh filter bags in the 4 beakers, wherein the diameters of the filter bags are not more than 1/3 of the diameters of the beakers, the bag openings of the filter bags are hermetically suspended in the beakers, the filter bags are higher than the beakers, the bottoms of the filter bags are in contact with the bottoms of the beakers, and the bag openings are hermetically suspended;

4) weighing 4 parts of graphene oxide to be detected with the particle size of more than 8 microns, 1g, respectively adding into 4 filter bags in 3), and sealing the filter bags;

5) transferring the 4 beakers in the step 4) to a constant-temperature oscillator, inserting an ultrasonic rod, vibrating while performing ultrasonic treatment, wherein the ultrasonic frequency is 30HZ, and reacting for 24 hours;

6) after the reaction is finished, washing and taking out the ultrasonic bar, adding the magnetons, slightly increasing the positions of the filter bags, reserving a magneton rotating space between the filter bags and the bottom of the beaker, transferring the beaker to a stirring table, and titrating to a terminal point by using HCl with the concentration of 0.05mol/L and taking methyl red as an indicator under continuous magneton stirring;

wherein, nitrogen is continuously introduced for protection in the processes of the steps 2) to 6).

The titration apparatus adopted in the above embodiment is shown in fig. 1, and comprises a reaction container 1, a first support 2, a second support 3, and a magnetic stirrer 4, wherein the reaction container 1 is placed on the magnetic stirrer 4, a magneton 5 matched with the magnetic stirrer 4 is installed in the reaction container 1, a filter bag 6 is arranged in the reaction container 1 and used for containing graphene oxide to be measured, the upper end of the filter bag 6 is of a sealable structure, the diameter of the filter bag 6 is not more than 1/3 of the diameter of the reaction container 1, the filter bag 6 is suspended in the reaction container 1 and connected to the first support 2 through the upper part, an ultrasonic rod 7 is further arranged in the reaction container 1, and the ultrasonic rod 7 is fixedly connected to the first support 2; a hole 11 is arranged on the side wall of the reaction container 1 and used for placing an inert gas tube 8, one end of the inert gas tube 8 is communicated below the liquid level in the reaction container 1, the other end of the inert gas tube 8 is externally connected with an inert gas bottle 9, a burette 10 is further arranged above the reaction container 1, and the burette 10 is suspended above the liquid level of the reaction container 1 and connected to the second support 3.

Comparative example 1

The qualitative and quantitative analysis method for the graphene oxide surface functional group in the comparative example specifically comprises the following steps according to a Boehm titration method in the national standard GB/T38114-2019:

1) preparing required alkali liquor and HCl standard solution according to the requirement of a Boehm titration method, specifically C with standard concentration of 0.05mol/L₂H₅ONa、NaOH、HCl、Na₂CO₃And NaHCO₃Each solution was 1L. In addition, potassium hydrogen phthalate, methyl red, bromocresol green, phenolphthalein and anhydrous sodium carbonate-reference solution for calibrating concentration and titration are prepared. Calibrating the prepared alkali liquor and HCl standard liquor and then sealing for later use;

2) taking 4 clean 150ml beakers, respectively pouring 100ml of 4 alkali liquids with certain concentration, marking as A, B, C, D, and respectively connecting in nitrogen protection;

3) weighing 1g of 4 parts of graphene oxide to be detected with the particle size of more than 8 microns, and respectively adding the graphene oxide to be detected into 4 beakers in the step 2);

4) transferring the 4 beakers in the step 3) to a constant-temperature oscillator, inserting an ultrasonic rod, vibrating while performing ultrasonic treatment, wherein the ultrasonic frequency is 30HZ, and reacting for 24 hours;

5) after the reaction is finished, centrifuging and collecting all filtrate, taking methyl red as an indicator, and titrating with HCl with the concentration of 0.05mol/L to the end point;

wherein, nitrogen is continuously introduced for protection in the processes of the steps 2) to 5).

The filter bag structure of the example was not used in this comparative example.

The experimental data for the above examples and comparative examples are shown in table 1:

table 1 results of determination of respective functional groups of GO in examples and comparative examples

	Carboxyl group mmoL/g	Lactone group mmoL/g	Phenolic hydroxyl group mmoL/g	Carbonyl group mmoL/g
					Example 1	0.149	0.238	0.205	0.291
Example 2	0.150	0.238	0.207	0.293
					Example 3	0.151	0.240	0.209	0.294
Comparative example 1	0.155	0.243	0.212	0.296

As can be seen from the detection data in Table 1, the test results of the examples and the comparative examples have better parallelism, and the surface of the method for determining the graphene oxide concentration has the advantages that the graphene oxide is filled in the filter bag and placed in the reaction solution for titration before the reaction, the reaction sufficiency of the graphene oxide is not reacted by the method, the steps of centrifugal separation and the like are saved, and the operation is simpler and faster; the comparative example not only needs centrifugal separation, but also easily causes the loss of the graphene oxide in the process.