阅读说明：本技术 一种多元素掺杂的石墨烯纤维、其制备和应用 (Multi-element doped graphene fiber, and preparation and application thereof ) 是由 肖菲 许云 张艳 赵安顺 于 2019-09-30 设计创作，主要内容包括：本发明属于纳米材料制备技术领域,更具体地,涉及一种多元素掺杂的石墨烯纤维、其制备和应用。本发明以离子液体作为氧化石墨烯的凝固浴,利用石墨烯表面的活性基团与离子液体成键来制备均匀负载的离子液体-石墨烯纤维,再经过热解制备非金属元素共掺杂石墨烯纤维,离子液体作为氮源、硼源、磷源,由此制备了导电性好、电化学活性高的石墨烯纤维,将其作为微电极用于电化学传感系统,能用于检测生物小分子,解决现有技术掺杂的多孔石墨烯纤维制备方法中掺杂源需求量大、工艺复杂、产生污染,成本高以及在实际检测中粉体需要涂覆在电极上的缺陷等问题。(The invention belongs to the technical field of nano material preparation, and particularly relates to a multi-element doped graphene fiber, and preparation and application thereof. According to the preparation method, the ionic liquid is used as a coagulation bath of graphene oxide, active groups on the surface of graphene and the ionic liquid are bonded to prepare uniformly-loaded ionic liquid-graphene fibers, the non-metallic element co-doped graphene fibers are prepared through pyrolysis, the ionic liquid is used as a nitrogen source, a boron source and a phosphorus source, so that the graphene fibers with good conductivity and high electrochemical activity are prepared, and the graphene fibers are used as microelectrodes for an electrochemical sensing system and can be used for detecting biological micromolecules.)

1. A preparation method of multi-element doped graphene fiber is characterized by comprising the following steps:

(1) injecting the graphene oxide solution into a coagulation bath by a wet spinning method to gelatinize and separate out the graphene oxide to obtain graphene oxide fibers, wherein the coagulation bath is an aqueous solution of an ionic liquid; the ionic liquid contains at least two elements of N, B, P, S and F;

(2) reducing the graphene oxide fiber obtained in the step (1) to reduce oxygen-containing functional groups on the surface of the graphene oxide, and drying to obtain the graphene fiber;

(3) and (3) calcining the graphene fiber obtained in the step (2) in an inert atmosphere to carbonize the graphene fiber, so as to obtain the multi-element doped graphene fiber.

2. The preparation method according to claim 1, wherein the concentration of graphene oxide in the graphene oxide solution in the step (1) is 10 to 30 mg/mL.

3. The production method according to claim 1 or 2, wherein the graphene oxide solution is obtained by:

s1: oxidizing and stripping expanded graphite to obtain an initial graphene oxide solution;

s2: repeatedly rinsing the graphene oxide initial solution to be neutral by using ultrapure water;

s3: and (3) uniformly mixing the rinsed neutral graphene oxide initial solution and centrifuging to obtain the graphene oxide solution in the step (1).

4. The method of claim 1, wherein the ionic liquid is one or more of 1-vinyl-3-ethylimidazole tetrafluoroborate, 1-butyl-3-methylimidazole tetrafluoroborate, and 1-butyl-3-methylimidazole hexafluorophosphoric acid.

5. The method according to claim 1, wherein the ionic liquid of step (1) has a concentration of 1 to 10 mg/L.

6. The method according to claim 1, wherein the reducing agent used in the reduction in the step (2) is hydroiodic acid and the reduction time is 12 to 24 hours.

7. The method according to claim 1, wherein the calcination in step (3) is carried out at a calcination temperature of 500-1000 ℃ for a calcination time of 1-3 hours.

8. The multi-element doped graphene fiber prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the multielement doped graphene fiber according to claim 8 as an electrochemical biosensor.

Technical Field

The invention belongs to the technical field of nano material preparation, and particularly relates to a multi-element doped graphene fiber, and preparation and application thereof.

Background

The excellent electrochemical behavior of the carbon material enables the carbon material to have wide application prospects in constructing portable and implantable electrochemical biosensors, and the main way for the carbon material to be practically applied is to assemble the carbon material into a macroscopic material. Since graphene, a perfect two-dimensional atomic crystal composed purely of a carbon skeleton, was successfully exfoliated for the first time in 2004, graphene has been widely used in many disciplines such as chemistry, materials, physics, biology, environment, energy and the like due to its excellent electrochemical properties, high surface area, mechanical strength, biocompatibility and the like. Currently, graphene has been assembled into fibers, paper, and some three-dimensional porous structures.

Since the first article on graphene fibers was published in Nature Communications in 2011 by the university of Zhejiang university super topic group, graphene fibers of various structures and composite types appeared. Wet spinning is also one of the main methods for preparing fibers, and graphene oxide is used as a precursor of graphene and is often considered as a spinning solution for preparing graphene fibers. Besides the spinning dope, the coagulation bath is the second important factor, whose principle is to gelate GO out by changing the Zeta potential of the GO surface.

Most of the existing methods for preparing graphene fibers are template methods or hydrothermal methods, and the preparation methods generally have the defects of large doping source requirement, complex process, incapability of large-scale production, pollution generation or high cost and the like.

Compared with the traditional annular disc electrode, the traditional disc electrode and the traditional columnar electrode, the graphene fiber electrode has the advantages of small size, flexibility and the like, can be inserted into tissues for detection when being used for the actual application of electrochemical biosensing, and the electrode system needs to be designed in the micrometer size range for the miniaturized electrochemical sensor. The low impedance and very fine microelectrode must be sufficiently rigid to penetrate soft neural tissue while being flexible or stretchable to minimize mechanical mismatch with the tissue and to accommodate minute movements after implantation. The prior art does not find the microelectrode as a microelectrode for selectively detecting the dopamine uric acid and the ascorbic acid at the same time.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides a multi-element doped graphene fiber, and preparation and application thereof.

To achieve the above object, according to one aspect of the present invention, there is provided a method for preparing a multi-element doped graphene fiber, including the steps of:

(1) injecting the graphene oxide solution into a coagulation bath by a wet spinning method to gelatinize and separate out the graphene oxide to obtain graphene oxide fibers, wherein the coagulation bath is an aqueous solution of an ionic liquid; the ionic liquid contains at least two elements of N, B, P, S and F;

(2) reducing the graphene oxide fiber obtained in the step (1) to reduce oxygen-containing functional groups on the surface of the graphene oxide, and drying to obtain the graphene fiber;

(3) and (3) calcining the graphene fiber obtained in the step (2) in an inert atmosphere to carbonize the graphene fiber, so as to obtain the multi-element doped graphene fiber.

Preferably, the concentration of the graphene oxide in the graphene oxide solution in the step (1) is 10-30 mg/mL.

Preferably, the graphene oxide solution is obtained by the following method:

s1: oxidizing and stripping expanded graphite to obtain an initial graphene oxide solution;

s2: repeatedly rinsing the graphene oxide initial solution to be neutral by using ultrapure water;

s3: and (3) uniformly mixing the rinsed neutral graphene oxide initial solution and centrifuging to obtain the graphene oxide solution in the step (1).

Preferably, the oxidation stripping is specifically activated by concentrated sulfuric acid and potassium permanganate, and the concentration of the obtained graphene oxide initial solution is 2-7 mg/mL.

Preferably, the concentration of the graphene oxide initial solution is 3-6 mg/mL.

Preferably, the ionic liquid in the step (1) is an ionic liquid containing at least two elements of N, B, P, S and F.

Preferably, the ionic liquid is one or more of 1-vinyl-3-ethylimidazole tetrafluoroborate, 1-butyl-3-methylimidazole tetrafluoroborate and 1-butyl-3-methylimidazole hexafluorophosphate.

Preferably, the concentration of the ionic liquid in the step (1) is 1-10 mg/L.

Preferably, the reducing agent used in the reduction in the step (2) is hydroiodic acid, and the reduction time is 12 to 24 hours.

Preferably, the calcination temperature in the step (3) is 500-1000 ℃, and the calcination time is 1-3 hours.

According to another aspect of the invention, the multi-element doped graphene fiber prepared by the preparation method is provided.

According to another aspect of the invention, there is provided a use of the multielement doped graphene fiber, characterized in that it is used as an electrochemical biosensor.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

(1) according to the invention, the ionic liquid is used as a solidification bath of graphene oxide, the porous graphene oxide fiber is obtained by solidification in the ionic liquid, the porous fiber structure is beneficial to subsequent application of materials, and the ionic liquid uniformly dispersed on the surface uniformly dopes nitrogen, boron and phosphorus elements carried by the ionic liquid into the graphene crystal structure after high-temperature reaction, so that the phenomenon that other substances containing elements to be doped are additionally added in the prior art is avoided, the preparation process is simplified, the preparation cost is reduced, and the yield is improved.

(2) According to the invention, the ionic liquid is used as a multi-element doping source, the graphene oxide is induced to self-assemble into a fiber structure at normal temperature by utilizing the electrostatic interaction between the positive charge of the molecular chain of the ionic liquid and the negative charge of the graphene oxide nanosheet, the reaction condition is mild, the required amount is small, and the attached pollutants are few.

(3) The processing amount of co-doping is large, the element content of nitrogen, boron and phosphorus elements can be adjusted, the large-scale production is easy, the method can be applied to the industrial production of nitrogen, phosphorus and boron co-doping graphene, and the output requirement of the method on element-doped graphene is met.

(4) The graphene fiber provided by the invention can be used as a self-supporting microelectrode, and can be inserted into cells or tissues for detection due to excellent mechanical property flexibility and electrochemical properties, so that an electrochemical biosensing device is hopefully and thoroughly changed. And the ionic liquid is adopted for multi-element doping, is a metal-free green solvent, has biocompatibility, and can realize one-step heteroatom doping on the fiber to increase the catalytic activity of the fiber. The multi-element doped one-dimensional porous graphite fiber prepared by the preparation method has large specific surface area and good application prospect.

Drawings

Fig. 1 is a scanning electron microscope image of the nitrogen and boron co-doped graphene fiber prepared in embodiment 1 of the present invention.

Fig. 2 is a transmission electron microscope image of the nitrogen and boron co-doped graphene fiber prepared in embodiment 1 of the present invention.

Fig. 3 is an X-ray photoelectron spectrum of C, N, O, B in the nitrogen and boron co-doped graphene fiber prepared in example 1 of the present invention.

Fig. 4 is an X-ray photoelectron spectrum of B1s in the nitrogen and boron co-doped graphene fiber prepared in example 1 of the present invention.

Fig. 5 is an X-ray photoelectron spectrum of N1s in the nitrogen and boron co-doped graphene fiber prepared in example 1 of the present invention.

Fig. 6 is an X-ray photoelectron spectrum of O1s in the nitrogen and boron co-doped graphene fiber prepared in example 1 of the present invention.

Fig. 7 is a raman spectrum analysis diagram of the nitrogen-boron co-doped graphene fiber prepared in embodiment 1 of the present invention.

Fig. 8 is a fourier transform infrared spectroscopy analysis diagram of the nitrogen and boron co-doped graphene fiber prepared in embodiment 1 of the present invention.

Fig. 9 is a DPV differential pulse voltammogram of dopamine with different concentrations in 0.1mol/L Phosphate Buffered Saline (PBS) of the nitrogen and boron co-doped graphene fiber prepared in example 1 of the present invention, and the scan rates are: 8 millivolts per second (mV/s).

Fig. 10 is a DPV differential pulse voltammogram of ascorbic acid with different concentrations in 0.1mol/L Phosphate Buffered Saline (PBS) for nitrogen and boron co-doped graphene fibers prepared in example 1 of the present invention, with scan rates: 8 millivolts per second (mV/s).

Fig. 11 is a DPV differential pulse voltammogram of uric acid with different concentrations in 0.1mol/L Phosphate Buffered Saline (PBS) of the nitrogen and boron co-doped graphene fiber prepared in example 1 of the present invention, and the scan rates are: 8 millivolts per second (mV/s).

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides a preparation method of multi-element doped graphene fiber, which comprises the following steps:

(1) injecting the graphene oxide solution into a coagulation bath by a wet spinning method to gelatinize and separate out the graphene oxide to obtain graphene oxide fibers, wherein the coagulation bath is an aqueous solution of an ionic liquid;

(2) reducing the graphene oxide fiber obtained in the step (1) to reduce oxygen-containing functional groups on the surface of the graphene oxide, and drying to obtain the graphene fiber;

(3) and (3) calcining the graphene fiber obtained in the step (2) in an inert atmosphere to carbonize the graphene fiber, so as to obtain the multi-element doped one-dimensional porous graphene fiber.

In order to be coagulated and precipitated into fibers in a coagulating bath, the concentration of the graphene oxide in the graphene oxide solution in the step (1) needs to reach a certain concentration, and in some embodiments, the concentration is 10-30 mg/mL.

In some embodiments, the graphene oxide solution is obtained by:

s1: oxidizing and stripping expanded graphite to obtain an initial graphene oxide solution;

s2: repeatedly rinsing the graphene oxide initial solution to be neutral by using ultrapure water;

s3: and (3) uniformly mixing the rinsed neutral graphene oxide initial solution and centrifuging to obtain the graphene oxide solution in the step (1).

In some embodiments, the oxidation stripping is specifically performed by activating with concentrated sulfuric acid and potassium permanganate, and the obtained graphene oxide initial solution is 2-7 mg/mL, preferably 3-6 mg/mL.

The ionic liquid in the step (1) of the invention is an ionic liquid containing at least two elements of N, B, P, S and F.

In some embodiments, the ionic liquid is one or more of 1-vinyl-3-ethylimidazole tetrafluoroborate, 1-butyl-3-methylimidazole tetrafluoroborate, and 1-butyl-3-methylimidazole hexafluorophosphate.

Experiments show that the ionic liquid directly used as the coagulating bath cannot be gelled and precipitated into fibers due to too large concentration of the ionic liquid, and the ionic liquid needs to be diluted with water, and in some embodiments, the concentration of the ionic liquid in the step (1) is 1-10 mg/L.

In some embodiments, the reducing agent used in the reduction of step (2) is hydroiodic acid and the reduction time is 12 to 24 hours.

The drying in the step (2) can be performed in various drying modes, such as freeze drying, vacuum drying or drying at a certain temperature, such as 60-80 ℃, and the like, and preferably freeze drying is performed, wherein the drying temperature ranges from-10 ℃ to-60 ℃, and the drying time is 12-24 hours.

In some embodiments, the calcination temperature in step (3) is 500-1000 ℃ and the calcination time is 1-3 hours.

In some embodiments, the inert atmosphere of step (3) is a nitrogen, argon or helium atmosphere.

The invention also provides the multi-element doped graphene fiber prepared by the preparation method, the graphene fiber is correspondingly doped with different elements according to different ionic liquid types, the length and the diameter of the graphene fiber prepared by the method are controllable, and the thickness of the fiber can be controlled by controlling the size of equipment during injection, such as the diameter of a spray head of an injector.

The multi-element doped one-dimensional porous graphene fiber provided by the invention is a self-supporting material, can be used as an electrochemical biosensor, such as can be used for detecting nerve cells, or can be used for selectively detecting the concentrations of dopamine, ascorbic acid and uric acid in Phosphate Buffered Saline (PBS) in a simulated human body environment.

In some embodiments of the invention, when the ionic liquid is 1-butyl-3 methylimidazolium tetrafluoroborate with a concentration of 6mg/L, which is simultaneously used as a nitrogen source and a boron source, the graphene is co-doped according to the preparation method of the invention, and the porous co-doped nitrogen-boron graphene fiber is prepared.

In some embodiments of the invention, the ionic liquid is 1-vinyl-3-ethylimidazole tetrafluoroborate, and when the concentration is 6mg/L, the ionic liquid is simultaneously used as a nitrogen source and a boron source, and the porous nitrogen-boron co-doped graphene fiber is prepared by co-doping graphene according to the preparation method of the invention.

In some embodiments of the invention, the ionic liquid is 1-butyl-3-methylimidazole hexafluorophosphate, and when the concentration of the ionic liquid is 6mg/L, the ionic liquid is simultaneously used as a nitrogen source and a phosphorus source, and the ionic liquid is co-doped into graphene according to the preparation method of the invention, so that the multielement co-doped nitrogen-phosphorus graphene fiber is prepared.

Two or more ionic liquids can be simultaneously adopted according to the requirement to prepare the multi-element doped one-dimensional graphene fiber. According to the invention, the ionic liquid and the graphene oxide fibers are solidified, the graphene oxide fibers are reduced into the graphene fibers by HI, and then nitrogen, boron and phosphorus are doped into the graphene crystals by calcination, so that the specific surface area is large, and more available active sites at the edges are exposed due to the existence of the sheet layer, thereby facilitating catalytic reaction.

According to the invention, the graphene oxide fibers are further induced to be solidified and formed in the ionic liquid under normal temperature and normal pressure through the electrostatic interaction between the molecular chain (positive electricity) of the ionic liquid and the graphene oxide nanosheets (negative electricity), the reaction condition is mild, and the graphene oxide fibers are reduced by hydroiodic acid and then are freeze-dried. The heteroatoms contained in the ionic liquid are then doped into the graphene by high-temperature calcination in an inert atmosphere. The ionic liquid contains different elements, so that multi-element doping can be realized. The multi-element co-doped graphene has a synergistic effect on catalysis, and different element dopings have different asymmetric spins and charge densities.

In view of the unique stretchability and electrochemical properties of graphene fibers, the invention provides a self-supporting microelectrode material for preparing an electric signal conduction substrate in an electrochemical biosensor from the graphene fibers, compared with a metal electrode and traditional carbon fibers, the flexible graphene microfibers prepared from a Liquid Crystal (LC) dispersion of Graphene Oxide (GO) have low impedance and excellent electrochemical properties, the preparation method is simple and efficient, and the graphene fiber microelectrode is expected to completely change an electrochemical device when being used as the electrochemical biosensor.

The invention takes the ionic liquid as a new coagulating bath, and the graphene oxide is coagulated, formed and precipitated in the ionic liquid through the electrostatic interaction between the molecular chain (positive electricity) of the ionic liquid and the abundant polar functional groups (carboxyl, hydroxyl and the like) (negative electricity) on the graphene oxide.

According to the invention, the graphene oxide spinning solution is injected into the ionic liquid, the fiber can be rapidly gelated and formed, the non-metallic elements in the ionic liquid are doped into the crystal of the graphene after reduction, drying and high-temperature calcination, the large specific surface area of the graphene and the strong synergistic effect between nitrogen, boron, phosphorus and other impurity elements form a stable and excellent mixed material, and the mixed material is used as a flexible self-supporting electrode and shows excellent performance when being used for selectively detecting electrochemically active biomolecules such as dopamine, ascorbic acid and uric acid in a simulated human body fluid environment-phosphate buffer salt solution.

The following are examples: