CN109970896B - Method for constructing temperature-sensitive carbon nanotube composite material based on carbon dot modification - Google Patents

Method for constructing temperature-sensitive carbon nanotube composite material based on carbon dot modification Download PDF

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CN109970896B
CN109970896B CN201910276019.1A CN201910276019A CN109970896B CN 109970896 B CN109970896 B CN 109970896B CN 201910276019 A CN201910276019 A CN 201910276019A CN 109970896 B CN109970896 B CN 109970896B
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pnipam
carbon
temperature
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CN109970896A (en
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张谦
解晓妍
夏立新
田慧
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Liaoning University
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F120/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
    • C08F120/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F120/52—Amides or imides
    • C08F120/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/44—Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/04—Carbon
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/04—Carbon
    • C08K3/041—Carbon nanotubes

Abstract

The invention relates to a method for constructing a temperature-sensitive carbon nano tube composite material based on carbon dot modification. The technical scheme is as follows: adding carbon dots CDs into carbon nano tube CNT as a substrate, and obtaining a compound CNT-CDs through ultrasonic treatment, stirring and centrifugation; and (2) adjusting the system to be alkaline, adding purified NIPAM (N-isopropylacrylamide) and an initiator into the CNT-CDs under the protection of nitrogen, reacting for 2-3 h at 35-40 ℃, reacting for 4-6 h at 80-90 ℃, and centrifugally washing to obtain the temperature-sensitive carbon nanotube composite material CNT-CDs-PNIPAM constructed based on carbon dot modification. The temperature-sensitive composite material CNT-CDs-PNIPAM prepared by the method realizes nondestructive modification, and the prepared temperature-sensitive intelligent responsive material not only keeps the properties and the appearance of CNTs, but also has the temperature sensitivity of PNIPAM.

Description

Method for constructing temperature-sensitive carbon nanotube composite material based on carbon dot modification
Technical Field
The invention belongs to the field of chemical synthesis, and particularly relates to a carbon-point-based assembly method, which is characterized in that CNTs and PNIPAM are connected through CDs to realize nondestructive modification, and the prepared temperature-sensitive intelligent responsive material not only keeps the properties and the appearance of the CNTs, but also has the temperature sensitivity of the PNIPAM.
Background
The performance (e.g., volume change) of the smart device may change significantly due to small changes in the external environment, such as external temperature, pH, light, zoom, salts, electric field, and pressure. They have potential application prospect in the fields of tissue engineering, drug controlled release carriers, regeneration reaction and the like. Researchers in materials science and polymer science have been concerned about their intrinsic response characteristics for decades. Among them, the temperature-sensitive materials are most studied, however, their inability to bind to inorganic substances has restricted their wide use.
Carbon, one of the well-known inorganic substances, has shown great potential in various studies on the basis of its unique one-dimensional properties, with excellent mechanical, optical and electronic properties and high chemical stability. The characteristics have wide application prospects in the aspects of composite materials, field emission display, energy storage, sensors, scanning probes, drug-loaded carriers and the like. However, separation and uniform dispersion are fundamental prerequisites to achieve their full promise for developing new functional high quality products in a variety of applications. The multi-wall carbon is stabilized in an aqueous medium through non-supercritical interaction, and has potential advantages for the material in practical application.
Carbon dots are an emerging carbon material due to their excellent emission properties, good water solubility and energy conversion capability. The simple method of low-cost carbon source synthesis and the surface reprocessing are adopted, so that the carbon dots are widely applied to the fields of sensors, imaging and the like. Doping of heteroatoms and introducing different surface functionalities using different precursors during synthesis can directly adjust the physicochemical properties. Likewise, the carbon dots can interact with hydrophobic materials such that the hydrophobic core, together with the hydrophilic functional groups on the surface of the carbon dots, imparts to them surfactant, e.g., amphiphilic properties. In recent years, carbon dot composites have been developed and widely used in devices. In these methods, either chemical or polymer embedding, are used for dispersion in water, the surfactant-like behavior of the carbon dots results in the carbon dots forming a stable carbon dot complex in water.
PNIPAM has a fully reversible low critical solution temperature (around 32 ℃) in water, which is between room and body temperature, making PNIPAM interesting for biological applications. Above the critical temperature, the polymer phase separates from the solution, while polymers below the critical temperature are soluble. PNIPAM is a novel polymer with a typical low critical solution temperature (32 ℃). It transforms from random neutrality at the immediate vicinity to tightly packed neutrals in height. Such reaction sensitive polymers have been explored for modification and membrane applications. Dry-based materials with highly reactive polymers can be combined with composite/hybrid materials. Studies have been conducted with high performance reactive polymers by chemical or in situ atom transfer radical polymerization. Among these randomization strategies, they have received much attention because they are easy to acquire, highly scalable, relatively stable, reversible, and do not affect the structural integrity of the carbon network. However, at present, the combination with inorganic substances usually needs to be at the cost of destroying the surface of the inorganic substances, and the inorganic substances cannot be directly combined or modified, so that the structure and the property of the inorganic substances are destroyed, and the application of the inorganic substances is limited, therefore, a connection mode which can carry out nondestructive modification on the inorganic substances and the inorganic substances is required to be developed.
Therefore, the invention provides a technical scheme which can be combined with the inorganic substance on the premise of keeping the temperature-sensitive property and can also keep the property of the inorganic substance.
Disclosure of Invention
The invention aims to provide a method for constructing a temperature-sensitive carbon nanotube composite material based on carbon dot modification. The temperature-sensitive composite material CNT-CDs-PNIPAM prepared by the method realizes nondestructive modification, and the prepared temperature-sensitive intelligent responsive material not only keeps the properties and the appearance of CNTs, but also has the temperature sensitivity of PNIPAM.
The technical scheme adopted by the invention is as follows: a method for constructing a temperature-sensitive carbon nanotube composite material based on carbon dot modification comprises the following steps:
1) adding carbon dots CDs into carbon nano tube CNT as a substrate, and obtaining a compound CNT-CDs through ultrasonic treatment, stirring and centrifugation;
2) and (2) adjusting the system to be alkaline, adding purified NIPAM (N-isopropylacrylamide) and an initiator into the CNT-CDs under the protection of nitrogen, reacting for 2-3 h at 35-40 ℃, reacting for 4-6 h at 80-90 ℃, and centrifugally washing to obtain the temperature-sensitive carbon nanotube composite material CNT-CDs-PNIPAM constructed based on carbon dot modification.
Preferably, step 1) is specifically: adding carbon nanotube CNT (carbon nano tube) as a substrate, adding carbon dot CDs, performing ultrasonic treatment for 3-4 h, stirring for 3-4 h, repeating the ultrasonic treatment and stirring for 3-5 times, pouring the mixed solution into a centrifuge tube, centrifuging at 11000r for 30min to leave black matters on the wall of the centrifuge tube, adding deionized water to dissolve the black matters, centrifuging at 11000r for 30min, adding water to the black matters on the wall of the centrifuge tube repeatedly, and centrifuging for 4-5 times to obtain the compound CNT-CDs.
Preferably, the preparation method of the carbon dot CDs comprises the following steps: adding water into citric acid and glycine, performing ultrasonic treatment until the citric acid and the glycine are dissolved, putting the mixture into a reaction kettle, reacting for 6-7 hours at the temperature of 170-190 ℃, standing, cooling and filtering to obtain carbon dots CDs.
More preferably, the ratio by mass of citric acid to glycine is 1: 1.
Preferably, in the step 2), the pH value of the CNT-CDs is adjusted to 9-10.
Preferably, the purified NIPAM is obtained by purifying NIPAM sequentially with acetone and n-hexane.
Preferably, the initiator is azobisisobutyronitrile (AIBA).
Preferably, the centrifugal washing in step 2) is: and (4) centrifugally washing with distilled water at the temperature of 60-70 ℃.
The invention has the beneficial effects that:
1) the invention adopts multi-wall carbon nano-tubes as a carbon source to prepare CNT-CDs, and combines the CNT with the CDs through ultrasound and stirring. Due to the hydrophilicity of the carbon dots, the CNT-CDs have obvious hydrophilicity compared with the CNT, so that the CDs are subjected to nondestructive modification on the surface of the CNT. CNT-CDs are used as a substrate, and a CNT-CDs-PNIPAM compound is prepared through a functional group reaction to form a carbon-point-assembly-based intelligent carbon tube with temperature-sensitive property. The CNT modified by CDs and PNIPAM has hydrophilicity and temperature sensitivity, and retains the performance of the CNT.
2) The invention introduces the simple preparation method of the one-step method into the design and synthesis of the CNT-CDs-PNIPAM, successfully prepares the intelligent carbon nano tube of the novel intelligent material based on carbon point assembly, and establishes a novel method for nondestructively modifying the CNTs.
3) The invention considers the CNT-CDs nondestructive modification, and the modification of CNTs in the prior art is mostly modified by acid damage, and the invention utilizes the pi-pi action of CDs and CNTs, so that the modified CNTs can show the hydrophilic performance and can keep the good performance of the CNTs, thereby reflecting the great advantages which cannot be compared with the conventional CNTs modification and leading the CNTs to be put into subsequent application with high quality in a real sense.
4) The CNT-CDs nano material is prepared and used as a material for CNT-CDs-PNIPAM reaction, the preparation is simple, the cost is low, the yield is high, the prepared CNT-CDs nano material can completely remove unreacted CDs, and the interference of the CDs on the reaction is reduced.
5) The novel intelligent material designed and synthesized by the invention is based on the intelligent carbon nano tube CNT-CDs-PNIPAM assembled by carbon points, and the CNT-CDs and the PNIPAM are connected together in a lossless manner through the function of functional groups, so that the assembled intelligent carbon nano tube CNT-CDs-PNIPAM not only has the intelligent responsiveness of the temperature sensitive material PNIPAM, but also considers the property of CNTs, and the CDs are used as the connection to really realize lossless modification.
Drawings
FIG. 1 is a TEM image of CDs, CNTs, CNT-CDs, CNT-PNIPAM and CNT-CDs-PNIPAM;
wherein the content of the first and second substances,
CDs (Inset: I is a partial enlarged view of CDs, and II is a digital photograph);
CNTs (Inset: I is a partial enlarged view of CNTs, and II is a digital photograph);
CNT-CDs (Inset: I is a partial enlarged view of CNT-CDs, and II is a digital photograph);
CNT-PNIPAM (Inset: I is a partial enlarged view of CNT-PNIPAM, and II is a digital photograph);
e, CNT-CDs-PNIPAM (Inset: I is a partial enlarged view of CNT-CDs-PNIPAM, and II is a digital photograph).
FIG. 2 shows the emission spectra of CDs (a) and CNT-CDs (b) (Inset: digital photographs under UV irradiation with CDs for I and CNT-CDs for II).
FIG. 3 is a UV-Vis of CNT-CDs (a), CNT-CDs-PNIPAM (b), and CDs (c).
FIG. 4 is an IR chart of CNTs (a), CNT-CDs (b), CNT-CDs-PNIPAM (c), PNIPAM (d), and CDs (e).
FIG. 5 is a TGA plot of CNTs (a), CNT-CDs (b), CDs (c), CNT-CDs-PNIPAM (d), and PNIPAM (e).
FIG. 6 is a Raman diagram of CNT-CDs (a), PNIPAM (b), CNT-CDs-PNIPAM (c), and CNTs (d).
FIG. 7 is a graph of UV-Vis (Inset: temperature cycling of CNT-CDs-PNIPAM versus UV-V is absorption peak) for CNT-CDs-PNIPAM at 20 deg.C (a) and 40 deg.C (b).
FIG. 8a is a digital photograph of CNTs (a), CNT-PNIPAM (b), PNIPAM (c), and CNT-CDs-PNIPAM (d) at 20 ℃.
FIG. 8b is a digital photograph of CNTs (a), CNT-PNIPAM (b), PNIPAM (c), and CNT-CDs-PNIPAM (d) at 40 ℃.
FIG. 9a is a Zeta potential diagram of CNTs in aqueous solution.
FIG. 9b is a Zeta potential diagram of CNT-CDs in aqueous solution.
Detailed Description
For better understanding of the technical solution of the present invention, specific examples are described in further detail, but the solution is not limited thereto.
Embodiment 1 method for constructing temperature-sensitive carbon nanotube composite material based on carbon dot modification
(I) preparation method
1. Preparation of CDs
Adding 5g of citric acid and 5g of glycine into a beaker, adding 20ml of water, carrying out ultrasonic treatment until the citric acid and the glycine are dissolved, putting the mixture into a reaction kettle, reacting for 6 hours at 180 ℃, standing, cooling to room temperature, and filtering to obtain filtrate to obtain CDs.
2. Preparation of CNT-CDs
0.5g of carbon nanotube CNTs and 60ml of CDs are added to a round bottom flask, the mixture is subjected to sonication for 3 hours and then stirred for 3 hours, and the sonication and stirring steps are repeated 3 times until the CNTs are completely dissolved, and the round bottom flask is shaken to have no obvious black particles. Pouring the mixed solution into a centrifuge tube, centrifuging for 30min at 11000r, removing the yellow-green CDs solution to leave black matters on the wall of the centrifuge tube, performing centrifugal washing, namely adding a proper amount of deionized water, dissolving the black matters, centrifuging for 30min at 11000r, removing the yellow-green CDs solution to leave the black matters on the wall of the centrifuge tube, repeatedly adding water, centrifuging for 4-5 times until no residual CDs exist, leaving the black matters on the wall of the centrifuge tube as compound CNT-CDs, diluting to 140mL with deionized water, and collecting for later use. The yield after drying is 0.5279 g.
3. Preparation of CNT-CDs-PNIPAM
Purification of NIPAM: adding 10g NIPAM monomer into a two-neck round-bottom flask, dripping acetone at 50 deg.C until the NIPAM is completely dissolved, cooling and refluxing, dripping n-hexane until white substance appears after n-hexane is added (V)Acetone (II)：VN-hexane1:6), stopping heating, cooling to room temperature, transferring to 0 ℃ and standing for 10 DEG Ch, transferring the mixture to-10 ℃ and standing for 20 h. After the crystal is separated out, the crystal is taken out for suction filtration and washed by normal hexane. Drying in vacuum at room temperature.
A round-bottomed flask was charged with 10ml of an aqueous solution of CNT-CDs (about 0.03g of CNT-CDs), adjusted to pH 9 to 10 with ammonia, and then charged with 1.000g of purified NIPAM and 0.017g of AIBA in the presence of N2Under protection, the reaction is carried out for 2h at 35 ℃ and then for 3h at 80 ℃ to obtain a mixed solution of CNT-CDs-PNIPAM and PNIPAM. And (3) centrifugally washing until no PNIPAM exists in the solution, namely, centrifugally washing, namely, adding deionized water at about 60 ℃ into the mixed solution, removing the solution to leave a hydrophobic block, cooling to room temperature to enable the block to become hydrophilic and loose, repeatedly adding deionized water at about 60 ℃, filtering, cooling for 4-5 times, obtaining the block which is the CNT-CDs-PNIPAM, drying the yield to 0.1257g, and collecting a sample.
(II) correlation detection
1. FIG. 1 is a TEM image of CDs (Inset: partial magnified view I and digital photograph II of CDs), CNTs (B) (Inset: partial magnified view I and digital photograph II of CNTs), CNT-CDs (C) (Inset: partial magnified view I and digital photograph II of CNT-CDs), CNT-PNIPAM (D) (Inset: partial magnified view I and digital photograph II of CNT-PNIPAM), and CNT-CDs-PNIPAM (E) (Inset: partial magnified view I and digital photograph II of CNT-CDs-PNIPAM).
As can be seen from A-I in FIG. 1, it can be seen that many black dots are uniformly dispersed on the copper grid without significant aggregation, indicating that the CDs prepared are uniform spherical nanoparticles. In FIG. 1, A-II are digital photographs of CDs under fluorescent light, and it can be seen from the photographs that the CDs are uniformly distributed in the solution in yellow-green color.
As can be seen in FIG. 1B, CNTs are arranged randomly on the copper mesh and have a large number of nodes. As can be seen from B-I in FIG. 1, CNTs are intact on the surface and hollow in the middle. In FIG. 1, B-II are digital photographs of CNTs under a fluorescent lamp, from which it can be seen that CNTs are insoluble in water and exhibit hydrophobicity.
As can be seen from C-I in FIG. 1, CNT-CDs have better dispersibility and reduced junctions compared with CNTs, and the carbon tubes have perfect surface and hollow middle, similar morphology to CNTs, indicating that the structure of the carbon tubes is complete and CDs and CNTs are successfully compounded. As can be seen from the digital photograph of C-II CNT-CDs in FIG. 1, the CNT-CDs are uniformly dispersed in water and appear black under daylight lamps, also indicating successful complexation of CDs with CNTs.
As can be seen by D-I in FIG. 1, the PNIPAM hash was scattered over the surface of the CNTs, rather than grown on the CNTs. As can be seen from D-II in FIG. 1, CNT-PNIPAM exhibits hydrophobicity, which also demonstrates that CNTs cannot directly form a complex with PNIPAM.
As shown by E-I in FIG. 1, PNIPAM was successfully grown on the disordered carbon tube surface without damaging the CNTs surface. The CNTs modified by CDs can not only be successfully compounded with PNIPAM, but also can retain the properties of the CNTs. As can be seen from the digital photograph of E-II CNT-CDs-PNIPAM in FIG. 1, FIGS. 1E-II appear uniformly black compared to FIGS. 1D-II, demonstrating the successful complexation of CNT-CDs with PNIPAM.
2. FIG. 2 shows the emission spectra of CDs (a) and CNT-CDs (b) (Inset: digital photographs under UV lamp irradiation of CDs (I) and CNT-CDs (II)). The interaction between carbon dots and carbon nanotubes is studied by fluorescence spectroscopy, fig. 2 is an emission spectrogram of CDs (a) and CNT-CDs (b) with excitation wavelength of 368nm and emission wavelength of 448nm, inset is a digital photo under ultraviolet lamp irradiation of CDs (I) and CNT-CDs (II), the fluorescence intensity after interaction between carbon dots and carbon nanotubes is studied, CNT-CDs fluorescence quenching is seen from fig. 2, CNT-CDs are successfully compounded and then are uniformly dispersed in water without fluorescence under ultraviolet lamp irradiation, and the successful compounding of CNT-CDs is confirmed.
3. FIG. 3 shows UV-Vis for CNT-CDs (a), CNT-CDs-PNIPAM (b), and CDs (c). As can be seen from fig. 3: CNT-CD has an absorption peak at 260 nm; CDs have an absorption peak at 348 nm; the CNT-CDs-PNIPAM has an absorption peak at 258nm, and the absorption peak of the CNT-CDs-PNIPAM is blue-shifted, which proves that the CNT-CDs-PNIPAM is successfully compounded.
4. FIG. 4 is an IR chart of CNTs (a), CNT-CDs (b), CNT-CDs-PNIPAM (c), PNIPAM (d), and CDs (e). FT-IR of CNT (a) at 3427cm-1，1631cm-1And 1107cm-1Several peaks corresponding to O-H, C ═ O and C — O functional groups, respectively, appear at the site, but the intensity is weak. CNT-CDs (b) at 3409cm-1，1634cm-1And 1125cm-1There appear several peaks corresponding to O-H, C ═ O and C — O functional groups, respectively. This is probably due to the presence of oxygenated function of CDs in the CNT-CDs composite, indicating the immobilization of CDs on the CNT surface. It can be seen from the fact that the CNT-CDs-PNIPAM (c) shows that the CNT-CDs-PNIPAM is 3435cm-1And 2923cm-1A plurality of vibration peaks exist, belonging to stretching vibration of-OH and C-H. Furthermore, at 1631cm-1Is related to C ═ O stretching vibration, and C-O (1033 cm)-1) Related to stretching vibrations and bone vibrations of the aromatic ring and other characteristic vibrations. As can be seen, the surface of CNT-CDs-PNIPAM (b) not only contains the characteristic peaks of CNTs-CDs corresponding to O-H, C-O and C-O, but also contains the characteristic peaks of PNIPAM corresponding to C-H, so that the successful combination of CNT-CDs and PNIPAM can be proved. 3434cm, as seen by PNIPAM (d)-1The peak of (A) represents the complex-OH, 2973cm-1Corresponds to the stretching vibration of C-H at 1037cm-1A peak was observed due to the C-O oxygen-containing group, and the absorption peak was 1657-1605cm-1And in the range stands for C ═ O stretching. From FT-IR of CDs (e), CDs were found at 3413cm-1、2950cm-1And 1386cm-1There are several vibration peaks, belonging to the stretching vibration of-OH/-NH, C-H and C-NH-C. Furthermore, at 1606cm-1Is related to C ═ O stretching vibration, and C-O (1137 cm)-1) And C-H (759 cm)-1) Related to stretching vibrations and bone vibrations of the aromatic ring and other characteristic vibrations. CDs are seen to be composed of aromatic structures with a large number of organic groups, such as amino and phenolic hydroxyl groups, on the surface.
5. FIG. 5 shows TGA curves for CNTs (a), CNT-CDs (b), CDs (c), CNT-CDs-PNIPAM (d) and PNIPAM (e). From a and b, it can be seen that the thermal stability of CNT and CNT-CDs is good and that CNT-CDs are similar to CNT, indicating that weight loss of CNT-CDs is due to CNT. After the CNT-CDs-PNIPAM is compounded with PNIPAM to form the CNT-CDs-PNIPAM, it can be seen from (d) in FIG. 5 that the CNT-CDs-PNIPAM has 85% weight loss at 800 ℃, which is similar to the PNIPAM, indicating that the weight loss of the CNT-CDs-PNIPAM is caused by the PNIPAM.
6. FIG. 6 shows Raman spectra of CNT-CDs (a), PNIPAM (b), CNT-CDs-PNIPAM (c), and CNTs (d). As can be seen in FIG. 6, CNT-CDs (a) are at 1309cm-1And 1568cm-1Is present atTwo characteristic peaks, which can be assigned to the D band and the G band of CNT-CDs (a), respectively. In the composite CNT-CDs (a), the intensity ratio of D and G bands is 1.13, and in the composite CNT-CDs-PNIPAM (c), 1395cm-1And 1558cm-1Two characteristic peaks appear, which can be assigned to the D band and G band of CNT-CDs-PNIPAM (c), respectively. The strength ratio of the D and G bands is 1.35, the ratio becomes large, and the defects increase.
7. FIG. 7 is a graph of UV-Vis of CNT-CDs-PNIPAM at 20 deg.C (a) and 40 deg.C (b) (Inset: temperature cycling of CNT-CDs-PNIPAM versus UV-Vis absorption peaks). The effect of temperature on CNT-CDs-PNIPAM was examined using UV-visible absorption spectroscopy. As can be seen from FIG. 7, at 20 deg.C, CNT-CDs-PNIPAM has an absorption peak at 258nm, and no significant absorption peak is observed when heated to 40 deg.C, which indicates that CNT-CDs-PNIPAM precipitates from the solution at 40 deg.C and sinks to the bottom of the sample cell, so no absorption peak is detected, and heating again restores to the original state, and the hydrophilic-hydrophobic transition is presented repeatedly.
8. FIG. 8a is a digital photograph of CNTs (a), CNT-PNIPAM (b), PNIPAM (c), and CNT-CDs-PNIPAM (d) at 20 ℃. As can be seen from FIG. 8a (a), CNTs are not uniformly dispersed in water and exhibit hydrophobicity. As can be seen in FIG. 8a (b), CNTs are hydrophobic in PNIPAM solution and are clearly separated from PNIPAM and do not form a complex with PNIPAM. As can be seen from (c) of fig. 8a, PNIPAM is uniformly dispersed in the aqueous solution and is transparent. As can be seen from (d) in FIG. 8a, CNT-CDs-PNIPAM can be well dispersed in water, showing hydrophilicity, indicating effective de-agglomeration of the modified carbon nanotubes, and the solution is black.
FIG. 8b shows digital photographs of CNTs (a), CNT-PNIPAM (b), PNIPAM (c), and CNT-CDs-PNIPAM (d) at 40 ℃. As can be seen from FIG. 8b (a), CNTs are not uniformly dispersed in water and exhibit hydrophobicity. As can be seen from (b) in FIG. 8b, it can be seen that CNTs are not well dispersed in the PNIPAM solution, and CNTs in black are floated on the transparent PNIPAM solution. As can be seen from (c) of fig. 8b, PNIPAM was uniformly dispersed in the aqueous solution and was milky white at 40 ℃. As can be seen from (d) in FIG. 8b, CNT-CDs-PNIPAM aggregates at high temperature and curls, which is due to the temperature sensitivity of PNIPAM, the composite appears black.
9. FIG. 9a is a Zeta potential diagram of CNTs in aqueous solution. FIG. 9b is a Zeta potential diagram of CNT-CDs in aqueous solution. As a result of the test, FIG. 9a shows that CNTs exhibit a strong electronegativity in aqueous solution with a value of Zate potential of about-12.9 mV, and FIG. 9b shows that CNT-CDs also exhibit a strong electronegativity in aqueous solution with a value of Zeta potential of about-23.7 mV. The absolute value of the complex is changed from +/-26.35 mV to +/-29.5 mV, and the absolute value is increased, so that the stability of the CNT-CDs is increased, and the potentials before and after the recombination are negative values, which shows that the electronegativity of the electrons on the surface of the CNT-CDs is unchanged after the recombination.

Claims (5)

1. A method for constructing a temperature-sensitive carbon nanotube composite material based on carbon dot modification is characterized by comprising the following steps:
1) adding carbon dots CDs into carbon nano tube CNT as a substrate, and obtaining a compound CNT-CDs through ultrasonic treatment, stirring and centrifugation;
the method specifically comprises the following steps: adding carbon nanotube CNT (carbon nano tube) as a substrate, adding carbon dot CDs (carbon nano tube), performing ultrasonic treatment for 3-4 h, then stirring for 3-4 h, repeating the ultrasonic treatment and the stirring for 3-5 times, pouring the mixed solution into a centrifuge tube, centrifuging at 11000r for 30min to leave black matters on the wall of the centrifuge tube, adding deionized water to dissolve the black matters, then centrifuging at 11000r for 30min, adding water repeatedly to centrifuge the black matters on the wall of the centrifuge tube for 4-5 times, and obtaining a compound CNT-CDs;
the preparation method of the carbon dot CDs comprises the following steps: adding water into citric acid and glycine, performing ultrasonic treatment until the citric acid and the glycine are dissolved, putting the mixture into a reaction kettle, reacting for 6-7 hours at the temperature of 170-190 ℃, standing, cooling and filtering to obtain carbon spots CDs;
2) the adjusting system is alkaline until the pH value is 9-10, under the protection of nitrogen, purified NIPAM and an initiator azobisisobutyronitrile are added into the CNT-CDs, the mixture is reacted for 2-3 hours at the temperature of 35-40 ℃, then reacted for 4-6 hours at the temperature of 80-90 ℃, and centrifugally washed, so that the temperature-sensitive carbon nanotube composite material CNT-CDs-PNIPAM constructed based on carbon dot modification is obtained.
2. The method of claim 1, wherein citric acid to glycine =1 to 1 by mass ratio.
3. The method of claim 1, wherein the purified NIPAM is obtained by subjecting NIPAM to a purification treatment with acetone and n-hexane in this order.
4. The method of claim 1, wherein the centrifugal washing of step 2) is: and (4) centrifugally washing with deionized water at the temperature of 60-70 ℃.
5. Use of the carbon nanotube composite material CNT-CDs-PNIPAM prepared according to the method of any one of claims 1 to 4 as a temperature sensitive material.
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