阅读说明：本技术 一种水分散性碳纳米材料的高效纯化方法 (Efficient purification method of water-dispersible carbon nano material ) 是由 胡成国 杨佳 于 2019-07-25 设计创作，主要内容包括：本发明提供一种水分散性碳纳米材料的高效纯化方法。将碳纳米材料、水溶性偶氮染料分子和可衍生修饰分子的球磨混合物用水溶解,然后将其与无机盐/碱水溶液混合均匀,在3000～10000转/分钟的离心速度下离心1～30分钟,将上层染料水溶液吸出,然后加入水超声溶解底部沉淀；重复上述盐析辅助离心纯化过程至洗净,得到分散于水中的碳纳米材料。本发明的突出特点是：使用常见的碱及盐作为辅助沉降剂,可在较短时间和较低离心速度下,实现游离态染料分子与水分散性碳纳米材料的高效分离,其纯化过程中碳纳米材料损失小、纯化试剂绿色环保、成本低,而且纯化过程对碳纳米材料的水分散性和光电性能等各方面的物理化学性能无影响。(The invention provides a high-efficiency purification method of a water-dispersible carbon nano material. Dissolving a ball-milled mixture of a carbon nano material, water-soluble azo dye molecules and derivatizable modification molecules with water, then uniformly mixing the ball-milled mixture with an inorganic salt/alkali aqueous solution, centrifuging the mixture at a centrifugal speed of 3000-10000 r/min for 1-30 min, sucking out an upper-layer dye aqueous solution, and then adding water to dissolve a bottom precipitate by ultrasonic wave; repeating the salting-out assisted centrifugal purification process to clean to obtain the carbon nano-material dispersed in water. The invention has the outstanding characteristics that: common alkali and salt are used as auxiliary settling agents, the high-efficiency separation of free dye molecules and the water-dispersible carbon nano material can be realized in a short time at a low centrifugal speed, the loss of the carbon nano material in the purification process is small, a purification reagent is green and environment-friendly, the cost is low, and the purification process has no influence on the physical and chemical properties of the carbon nano material in all aspects such as water dispersibility, photoelectric property and the like.)

1. A high-efficiency purification method of a water-dispersible carbon nanomaterial is characterized in that a ball-milling mixture of the carbon nanomaterial, water-soluble azo dye molecules and derivatizable modification molecules is fully dissolved by water to obtain a ball-milling mixture aqueous solution, the ball-milling mixture aqueous solution is uniformly mixed with at least two inorganic salt/alkali aqueous solutions with certain concentrations, the mixture is centrifuged for 1 to 30 minutes at a centrifugal speed of 3000 to 10000 revolutions per minute, the clear dye aqueous solution on the upper layer is sucked out, and then a certain volume of water is added to dissolve bottom sediment by ultrasonic waves; repeating the salting-out assisted centrifugal purification process until the carbon nano-material is cleaned to obtain the carbon nano-material dispersed in water.

2. A high-efficiency purification method of a water-dispersible carbon nanomaterial is characterized in that a binary ball-milling mixture consisting of the carbon nanomaterial and a water-soluble azo dye is fully dissolved by water to obtain a binary ball-milling mixture aqueous solution, the binary ball-milling mixture aqueous solution is uniformly mixed with a single salt or an alkali solution with a certain concentration, the mixture is centrifuged for 1 to 30 minutes at a centrifugal speed of 3000 to 10000 r/min, the clear dye aqueous solution on the upper layer is sucked out, and then a certain volume of water is added to dissolve the bottom sediment by ultrasonic wave; repeating the salting-out assisted centrifugal purification process until the carbon nano-material is cleaned to obtain the carbon nano-material dispersed in water.

3. A high-efficiency purification method of a water-dispersible carbon nanomaterial is characterized in that a ball-milled mixture of the carbon nanomaterial, water-soluble azo dye molecules and non-aminocaproic acid modified molecules is fully dissolved by water to obtain a non-amino ball-milled mixture aqueous solution, the non-amino ball-milled mixture aqueous solution is uniformly mixed with a single inorganic salt/alkali aqueous solution with a certain concentration, the mixture is centrifuged for 1 to 30 minutes at a centrifugal speed of 3000 to 10000 r/min, the clear dye aqueous solution on the upper layer is sucked out, and then a certain volume of water is added to dissolve bottom sediment by ultrasonic wave; repeating the salting-out assisted centrifugal purification process until the carbon nano-material is cleaned to obtain the carbon nano-material dispersed in water.

4. The method for efficiently purifying a water-dispersible carbon nanomaterial according to any one of claims 1 to 3, wherein the carbon nanomaterial is one or more of carbon nanotube, graphene oxide, fullerene, and carbon nitride.

5. The efficient purification method for the water-dispersible carbon nanomaterial according to any one of claims 1 to 3, wherein the water-soluble azo dye molecule is a water-soluble anionic azo dye molecule containing a sulfonate group and an azo group.

6. The method for efficiently purifying the water-dispersible carbon nanomaterial according to claim 1, wherein the derivatizable modifying molecule is a bifunctional molecule containing an amino group and a carboxyl group or a borate group, and capable of performing a ball milling reaction with the carbon nanomaterial.

7. The method for purifying a water-dispersible carbon nanomaterial with high efficiency according to any one of claims 1 to 3, wherein the high-concentration inorganic salt/alkali aqueous solution is an aqueous solution of sulfate, phosphate, chloride, nitrate, acetate, or hydroxide of sodium ions, potassium ions, ammonium ions, magnesium ions, or calcium ions.

8. The method for efficiently purifying a water-dispersible carbon nanomaterial according to claim 1, wherein an aqueous solution of the ball-milled mixture is uniformly mixed with an equal volume of a high-concentration inorganic salt/alkaline aqueous solution.

9. The method for purifying a water-dispersible carbon nanomaterial with high efficiency of claim 5, wherein the water-soluble azo dye molecule is either a bright red or a direct yellow 50.

10. The method for efficiently purifying the water-dispersible carbon nanomaterial of claim 6, wherein the derivatizable modification molecule is one or more of p-aminobenzoic acid, aminocaproic acid and 3-aminophenylboronic acid.

Technical Field

The invention belongs to the field of material synthesis, and particularly relates to a high-efficiency purification method of a water-dispersible carbon nano material.

Background

The carbon nano material represented by fullerene, carbon nano tube and graphene has unique physical and chemical properties such as structure, photoelectricity, machinery and the like, leads multiple revolution in the field of materials science, and has wide application prospect in various fields such as materials, energy, environmental protection, biomedicine and the like. However, a key factor limiting the large-scale application of these materials is how to achieve their efficient dispersion in various solvents, which is an important prerequisite for the construction of large quantities of carbon-based functional materials, thin films and devices. Compared with organic solvents, the aqueous solvent has the characteristics of environmental protection, low cost, good biocompatibility and the like, and the preparation of the carbon nano-material aqueous solution is also very important for the application in the fields of biomedicine and the like.

Due to the lack of solvating groups on the surface, the solubility or dispersibility of carbon nanomaterials in most solvents is poor. To solve this problem, various covalent and non-covalent means are applied to surface modification of the carbon nanomaterial, thereby significantly improving its dispersibility in various solvents. For example, based on pi-pi and charge transfer non-covalent interaction between a water-soluble anionic azo dye and a Carbon nano material, azo dyes such as Congo red and direct yellow 50 can realize high-efficiency dispersion of Carbon nanotubes (Carbon 2006, 44 and 428; invention patent 200410060849.4), fullerenes (Analytical Chemistry 2013, 85 and 10612; invention patent 201310367405.4) and graphene nanosheets (Carbon 2017, 120 and 411; invention patent 201310434073.7) in water through simple manual grinding or mechanical ball milling treatment. Among them, the water-dispersible Carbon nanotube shows a strong sensitization effect on electrochemical detection of various organic small molecules (electrochemistry communications 2007, 9, 128), and the water-dispersible fullerene is proved to be an excellent photoelectric biosensing material (Analytical Chemistry 2015, 87, 9368), and the dispersible graphene nanosheet prepared by the method has a potential application prospect in the fields of conductive and heating functional coatings and the like (Carbon 2017, 120, 411).

Although azo dyes such as congo red and direct yellow 50 can be used for preparing high-dispersity carbon nano materials in a large scale in ball milling and other modes, the prepared functional materials also have good application prospects in various fields, however, the removal of free dye molecules in ball milling mixing is a huge technical problem: (1) due to the high water dispersibility of the ball-milled carbon nano-material, partial ball-milled carbon nano-material can not be completely settled at the high-speed centrifugal speed of 15000 r/min, so that the centrifugal separation efficiency is low, and the loss of a high-dispersibility product is large; (2) as azo dyes such as Congo red can be firmly combined with some polysaccharides, free azo dye molecules in the ball milling mixture cannot be removed through dialysis by a dialysis bag; (3) the carbon nano material after ball milling has small particle size, good dispersibility, slow filtering and washing speed and large loss. For example, for a ball-milled product of fullerenes, a 0.1 micron pore size mixed cellulose membrane also does not retain a portion of the water-dispersible fullerene material having a size less than 100 nm. Therefore, the high-efficiency purification of the ball-milling mixture of the water-soluble azo dye and the carbon nano material becomes a key limiting factor for the scale synthesis of the water-soluble carbon nano material.

Disclosure of Invention

The invention provides a high-efficiency purification method of a water-dispersible carbon nano material, aiming at a mixture of a high-dispersibility azo dye carbon nano material obtained by ball milling, common low-cost environment-friendly inorganic salt/alkaline water solution can be used, and the high-efficiency auxiliary centrifugal separation purification of the carbon nano material is realized without influencing the physical and chemical properties such as dispersibility, photoelectrochemical properties and the like of the carbon nano material, so that the problem that the azo dye ball-milled carbon nano material mixture cannot be purified at high yield and low cost by the schemes such as simple centrifugation, dialysis, filtration and the like is effectively solved, and a road is paved for the large-scale preparation of the high-dispersibility and surface-derivatizable carbon nano material.

A high-efficiency purification method of a water-dispersible carbon nano material is disclosed, which has the following basic principle: under the action of mechanical force in the ball milling process, azo dyes such as Congo red and the like can be fixed on the surface of the carbon nano material through pi-pi and charge transfer non-covalent action to form a stable adsorption layer, so that the high-efficiency stripping of the carbon material and the high-efficiency dispersion in solvents such as water and the like can be realized; meanwhile, in the ball milling process, free amino in some amino-containing double-functional group molecules (such as aminocaproic acid, p-aminobenzoic acid and 3-aminophenylboronic acid) can be bonded to the surface of the carbon nano material through a special addition reaction, so that carboxyl, phenylboronic acid and other derivable groups are introduced to the surface of the carbon nano material; the water-soluble azo dye aggregates combined with the carbon nanomaterial have a stronger salting-out effect than the free dye molecules. Therefore, the ball-milling mixture can be purified by centrifugal separation assisted by a high-concentration salt solution with a proper pH value, and in the process, the water-dispersible carbon nano material is completely settled while the free dye molecules are still remained in the solution, so that the high-efficiency purification of the water-soluble azo dye-dispersed carbon nano material is realized.

The technical scheme is as follows:

a high-efficiency purification method of a water-dispersible carbon nanomaterial comprises the following steps:

(1) fully dissolving a ball-milling mixture of a carbon nano material, water-soluble azo dye molecules and derivatizable modification molecules with water to obtain a ball-milling mixture aqueous solution, uniformly mixing the ball-milling mixture aqueous solution with at least two inorganic salt or alkaline aqueous solutions with certain concentrations, centrifuging for 1 ~ 30 minutes at a centrifugal speed of 3000 ~ 10000 rpm, sucking out the upper clear dye aqueous solution, and adding a certain volume of water to ultrasonically dissolve a bottom precipitate;

(2) repeating the salting-out centrifugation-assisted purification washing process for 4 ~ 5 times, carefully washing the carbon nano-material precipitate obtained by the last centrifugation for 1 ~ 2 times with pure water, retaining the supernatant to remove impurities insoluble in water, and ultrasonically dispersing the precipitate in water to form a carbon nano-material aqueous dispersion solution with a specific concentration for storage.

In the above method for efficiently purifying a water-dispersible carbon nanomaterial, the carbon nanomaterial in step (1) is carbon nanotube, graphene oxide, fullerene, carbon nitride, or a derivative thereof;

according to the efficient purification method of the water-dispersible carbon nanomaterial, the water-soluble azo dye molecules in the step (1) are water-soluble anionic azo dye molecules containing sulfonate groups and azo groups, such as Congo red, direct yellow 50 and the like;

in the above method for efficiently purifying a water-dispersible carbon nanomaterial, the derivatizable modified molecule in step (1) is a bifunctional molecule containing carboxyl, amino and borate, which can perform a ball-milling reaction with the carbon nanomaterial, and comprises p-aminobenzoic acid, aminocaproic acid, p-aminobenzoic acid and isomers thereof;

the method for efficiently purifying the water-dispersible carbon nanomaterial comprises the steps of (1) adding an inorganic salt/alkaline water solution, sulfate, phosphate, chloride, nitrate, acetate, hydroxide of sodium ions, potassium ions, ammonium ions, magnesium ions and calcium ions, and a mixture water solution thereof.

The method for efficiently purifying the water-dispersible carbon nanomaterial comprises the steps of (1) enabling the concentration of the carbon nanomaterial in a ball-milling mixture water solution to be 2 mg/mL, mixing the carbon nanomaterial with at least two inorganic salt/alkali water solutions with certain concentrations in an equal volume uniformly, centrifuging at a centrifugal speed of 3000 ~ 10000 rpm for 1 ~ 30 minutes, sucking out the upper clear dye water solution, adding a certain volume of water to dissolve bottom sediment by ultrasonic waves, enabling the concentration of the carbon nanomaterial to be 2 mg/mL, and repeating the salting-out centrifugation-assisted purification process for 4 ~ 5 times.

The invention also provides two specific embodiments for different ball milling mixtures:

(1) a binary ball-milling mixture consisting of a carbon nano material and a water-soluble azo dye or a ternary ball-milling mixture consisting of the carbon nano material, the water-soluble azo dye and a non-aminocaproic acid modified molecule can be subjected to salting-out assisted centrifugal separation by adopting a single high-concentration salt or alkali solution, preferably, after a 20 ~ 60% ammonium sulfate aqueous solution or a sodium hydroxide aqueous solution with the molar concentration of 2 ~ 6mol/L and the ball-milling mixture are uniformly mixed in equal volume, centrifugal separation is carried out, wherein the 100% ammonium sulfate aqueous solution is a solution obtained by adding 767 g of ammonium sulfate solid into 1 liter of water for full dissolution and adjusting the pH of the solution to 7.0 by using ammonia water or sulfuric acid.

In the method for efficiently purifying the water-dispersible carbon nanomaterial, the non-aminocaproic acid is heptanoic acid, phenylboronic acid or other molecules which do not contain amino groups and contain other oxygen-containing functional groups.

(2) Aiming at carbon nano material, water-soluble azo dye and aminoThe ternary ball-milled mixture of hexanoic acid, for its excellent water-dispersing properties, the salting-out formulation used in scheme (1) is not suitable, preferably consisting of 1 ~ 5mol/L NaH₂PO₄And 2 ~ 10mol/L NaOH according to the volume ratio of 5:1 ~ 1:5, and the mixed salt solution and the ball milling mixture solution are mixed in equal volume, and can be used for salting out assisted centrifugal separation and purification of the ternary ball milling mixture.

As a simple and easy scheme, the method can realize high-concentration and high-stability dispersion of the carbon nano material in solvents such as water with one-step ball milling treatment of azo dyes such as Congo red, and the prepared carbon nano material has excellent photoelectric properties and is widely applied in the fields of functional coatings, electronic devices, biosensing and the like. However, the removal of free dye molecules in the ball-milled mixture of azo dye and carbon nanomaterial is a key factor that restricts the preparation and application of the material. By using the principle of protein fractional salting-out, separation and purification, the invention adopts high-concentration salt/alkali aqueous solution to assist the centrifugal separation of a ball-milling mixture of the carbon nano material, can use common inorganic salt or alkali aqueous solution, realizes the high-efficiency separation of free dye molecules and the water-dispersible carbon nano material in lower centrifugal speed and shorter centrifugal time, and has the characteristics of high yield, low cost, easy operation, easy scale amplification, green and environment-friendly separation process and the like.

Detailed Description