Preparation method of composite functionalized carbon nanotube fiber based on polypyrrole and nanogold

Abstract

The invention belongs to the field of nano materials and bioelectronics, and particularly relates to a preparation method of composite functionalized carbon nanotube fibers based on polypyrrole and nanogold. The method comprises the following steps: preparing carbon nanotube fibers; carrying out polypyrrole electrochemical polymerization functionalization on the carbon nanotube fiber to obtain a polypyrrole functionalized CNT fiber; the surface of polypyrrole is modified with gold nanoparticles, and the gold nanoparticle-polypyrrole composite functional fiber (as an electrode) is obtained. Or the method comprises the following steps: preparing nanofibers; preparing nanogold composite nanofibers; and preparing the polypyrrole / nanogold composite functionalized nanofiber (as an electrode). Polypyrrole (PPy) and nanogold (Au NPs) are adopted for composite modification, so that the electrochemical performance of the product is improved.

Description

Technical Field

[0001] The invention belongs to the field of nanomaterials and bioelectronics, and particularly relates to a preparation method of functionalized carbon nanotube fibers based on polypyrrole and nano-gold composites. Background Art

[0002] Carbon nanotube fibers, with their excellent conductivity, flexibility, and mechanical properties, show broad application prospects in fields such as flexible electronic devices and biosensors. However, in biomedical scenarios such as brain-machine interfaces (BMIs), when carbon nanotube fibers come into direct contact with biological tissue, their high interfacial impedance and poor biocompatibility significantly affect the stability and long-term reliability of signal transmission. To overcome this challenge, researchers are committed to optimizing and modifying carbon nanotube fibers through surface functionalization technology to reduce interfacial impedance and enhance biocompatibility, thereby improving their performance in biomedical applications.

[0003] Polypyrrole (PPy), as a conductive polymer, is widely used in biosensors and electrode modification due to its conductivity, biocompatibility and chemical stability. In the prior art, some patents have involved the functionalization of nanomaterials. For example, CN102345678A describes the application of polypyrrole electrochemical polymerization technology in flexible electrodes, and the polypyrrole layer improves the electrochemical stability and biocompatibility. However, the conductivity and stability of the polypyrrole film still have room for improvement, especially in implantable brain-computer interface devices. In order to further improve the conductivity and biocompatibility of the functionalized layer, the composite functionalization of gold nanoparticles (Au NPs) and polypyrrole has become an effective strategy. CN103456789B uses nanogold to modify the carbon electrode structure. Although the conductivity is enhanced, it lacks the long-term stability applicable to flexible devices. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method of carbon nanotube fibers functionalized with polypyrrole (PPy) and gold nanoparticles (AuNPs) to improve their electrochemical properties.

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a carbon nanotube fiber electrode based on polypyrrole and nano-gold composite functionalization, comprising the following steps:

[0006] 1) Preparation of carbon nanotube fibers;

[0007] 2) functionalizing carbon nanotube fibers (CNT fibers) with polypyrrole (PPy) electrochemically to obtain polypyrrole-functionalized CNT fibers;

[0008] 3) Composite modification of gold nanoparticles

[0009] Gold nanoparticles are modified onto the surface of polypyrrole to obtain gold nanoparticle-polypyrrole composite functionalized fibers (as electrodes).

[0010] The present invention also provides another method for preparing a carbon nanotube fiber electrode based on polypyrrole and nano-gold composite functionalization, comprising the following steps:

[0011] 1) Preparation of nanofibers;

[0012] 2) Preparation of nano-gold composite nanofibers;

[0013] 3) Preparation of polypyrrole / nano-gold composite functionalized nanofibers (as electrodes).

[0014] As an improvement to the preparation method of the carbon nanotube fiber electrode based on polypyrrole and nano-gold composite functionalization of the present invention, the method further includes the following step 4):

[0015] performing high-temperature stabilization treatment on the gold nanoparticle-polypyrrole composite functionalized fibers or the polypyrrole / nano-gold composite functionalized nanofibers;

[0016] The high temperature stabilization treatment is: stabilization treatment at 200±20° C. for 1±0.1 hours under the protection of an inert gas (including N 2 ).

[0017] The purpose of high temperature stabilization treatment is to improve conductivity (optimize crystallinity) and structural stability (remove residual solvent).

[0018] As a further improvement to the preparation method of the carbon nanotube fiber electrode based on polypyrrole and nano-gold composite functionalization of the present invention, step 1) includes any of the following methods:

[0019] Method 1:

[0020] 1.1) Acidification treatment:

[0021] Mix concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3 to 1:1 to 5 (preferably 1:1) to obtain a mixed acid;

[0022] Immersing carbon nanotubes (CNTs) in mixed acid at 50-70° C. (preferably 60° C.) for 2-4 hours (to increase the active sites on the surface of the carbon nanotubes);

[0023] Then, the mixture was washed with deionized water until neutral and dried (at 60-80°C for 60 minutes) to obtain acidified carbon nanotubes.

[0024] Description: The purpose of this step is to introduce hydroxyl / carboxyl groups to enhance surface activity;

[0025] During the acidification process of carbon nanotubes (CNTs), the formation of carboxyl groups (-COOH) involves an oxidation reaction mechanism in a strong acid environment; although concentrated sulfuric acid (H2SO4) and concentrated nitric acid (HNO3) molecules themselves do not contain carboxyl groups, they act as strong oxidants and proton sources, which can trigger the oxidation of carbon atoms on the CNT surface and ultimately generate carboxyl groups.

[0026] 1.2) Fiber molding:

[0027] The acidified carbon nanotubes are dispersed in a (1±0.05) mol / L polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP) aqueous solution, the resulting dispersion is wet-spun, and then dried to obtain CNT fibers;

[0028] Carbon nanotubes: polyvinyl alcohol or polyvinyl pyrrolidone = 1-5 wt% (preferably 3 wt%);

[0029] Method 2:

[0030] A DWCNT array was prepared using a single-crystal silicon wafer; then, a DWCNT strip was pulled out from the DWCNT array and a torsional force was applied to produce DWCNT fibers (diameter 10±0.5μm, torsion angle 18±2°).

[0031] As a further improvement to the method for preparing the carbon nanotube fiber electrode based on polypyrrole and nano-gold composite functionalization of the present invention, step 2) includes the following steps:

[0032] 2.1) Electrolyte configuration

[0033] Dissolving a pyrrole monomer and a fluorine-containing lithium salt in a solvent to prepare an electrolyte; in the electrolyte, the concentration of the pyrrole monomer is 0.01 to 0.05 mol / L, and the concentration of the fluorine-containing lithium salt is 0.1 to 1 mol / L;

[0034] The fluorine-containing lithium salt is LiBF4 (lithium tetrafluoroborate) or LiPF6 (lithium hexafluorophosphate);

[0035] The solvent is water, acetonitrile or acetone;

[0036] 2.2) Polymerization process

[0037] Electrode system: The carbon nanotube fiber obtained in step 1) is used as the working electrode, the platinum sheet is used as the counter electrode, and the Ag / AgCl is used as the reference electrode; polymerization is carried out using a constant potential method;

[0038] 2.3) Post-processing

[0039] The resulting product was rinsed with deionized water and dried in vacuum (60±10° C., 2±0.5 hours) to obtain polypyrrole-functionalized CNT fibers.

[0040] As a further improvement to the preparation method of the carbon nanotube fiber electrode based on polypyrrole and nano-gold composite functionalization of the present invention, step 3) is to select any of the following methods:

[0041] Method 1: Chemical adsorption method

[0042] A gold nanoparticle suspension (particle size 20 ± 5 nm, prepared by sodium citrate reduction method) was used;

[0043] Immersing the polypyrrole-functionalized CNT fibers obtained in step 2) in the gold nanoparticle suspension for 30 to 60 minutes under stirring;

[0044] Then washed (rinsed with deionized water), dried, and the gold nanoparticle-polypyrrole composite functionalized fiber was prepared;

[0045] Method 2: Electrochemical deposition

[0046] Prepare 0.01 mol / L HAuCl4 solution; immerse the DWCNT@PPy fiber obtained in step 2 in the HAuCl4 solution;

[0047] Deposition conditions: Current density: 0.1 mA / cm 2 , time: 3 to 5 minutes (control the gold particle size to 10 to 30 nm); temperature: room temperature (to avoid nano-gold agglomeration).

[0048] As a further improvement of the preparation method of the carbon nanotube fiber electrode based on polypyrrole and nano-gold composite functionalization of the present invention,

[0049] In step 1.1) of method 1 of step 1), the acidification treatment can be performed under conventional ultrasound assistance (ultrasonic power 200W);

[0050] The parameters of the wet spinning (electrospinning) in step 1.2) of the method 1 of step 1) are:

[0051] The spinning temperature is 55-75°C.

[0052] Voltage: 15~20kV,

[0053] Needle-collection plate distance: 15-20 cm.

[0054] As a further improvement to the preparation method of the carbon nanotube fiber electrode based on polypyrrole and nano-gold composite functionalization of the present invention, the constant potential polymerization in step 2.2) is as follows:

[0055] Voltage: 0.6~0.7V;

[0056] Time: 5 to 30 minutes;

[0057] Current density: 0.1~1mA / cm 2 ;

[0058] Environmental control: Temperature: 20-25°C (water bath temperature control);

[0059] Stirring: magnetic stirring (to avoid local uneven concentration);

[0060] The electrolyte must completely immerse the fiber electrode.

[0061] As a further improvement of the preparation method of the carbon nanotube fiber electrode based on polypyrrole and nano-gold composite functionalization of the present invention, the step 1) is:

[0062] First, a composite emulsion system was prepared using polystyrene-N,N-dimethylformamide solution and HauCl4 / vinyl acetate / polyvinylpyrrolidone-DMF mixture;

[0063] The composite emulsion system is then formed by electrospinning to obtain nanofibers;

[0064] The step 2) is:

[0065] The nanofibers were sintered at 430±30° C. for 0.5±0.1 hours to convert HAuCl4 into Au; and the gold nanoparticles were obtained.

[0066] The step 3) is to prepare polypyrrole / nano-gold composite functionalized nanofibers by in-situ gas phase polymerization.

[0067] As a further improvement to the preparation method of the carbon nanotube fiber electrode based on polypyrrole and nano-gold composite functionalization of the present invention, step 3) is:

[0068] The nano-gold composite nanofibers were first pretreated with concentrated hydrochloric acid, and then pyrrole monomer was added for vacuum treatment.

[0069] This invention specifically involves functionalizing carbon nanotube fibers with polypyrrole and gold nanoparticles to enhance electrochemical performance. This technology is suitable for biomedical devices with high conductivity, low impedance, and long-term stability, particularly flexible brain-computer interface devices. By combining polypyrrole and gold nanoparticles for composite functionalization, this invention addresses the challenges of both conductivity and long-term biostability.

[0070] The acidification treatment method of the present invention can achieve efficient functionalization and reduce CNT structural damage compared to traditional methods (the Raman ID / IG ratio can be reduced by about 30%). The present invention reduces the concentration of pyrrole monomers to reduce side reactions (such as excessive cross-linking) and improve polymerization uniformity; the Li+ salt used can improve ionic conductivity and effectively inhibit by-products. The polymerization process of the present invention can utilize the high specific surface area of ​​CNT fibers to increase the PPy loading (theoretically increase 3 to 5 times); and avoid the interface impedance problem of traditional electrodes. Low voltage / current reduces the risk of overoxidation, thereby improving the conductivity of PPy films.

[0071] The beneficial effects of the present invention are mainly reflected in:

[0072] The method of the present invention can significantly reduce the interface impedance from 1MΩ·cm to 2MΩ·cm. 2 (Untreated) reduced to ~10 kΩ·cm 2 , enhance electrical conductivity, the electrical conductivity of carbon-based fibers can reach ~10 4 S / cm, which is 10 times higher than that of traditional metal electrodes (such as platinum, 3 S / cm) by an order of magnitude, and improves the long-term electrochemical, structural, and biological stability of the fiber. In accelerated aging tests (0.9% NaCl solution, 37°C), the charge storage capacity (CSC) of the functionalized electrode decayed by only 5% after 30 days, while the untreated electrode decayed by over 50%. In animal experiments, the expression of inflammatory factors (such as TNF-α) around the coated electrode decreased by 70%. After 12 weeks of implantation, the thickness of the glial scar around the fiber was <50μm (>200μm in the control group). It is particularly suitable for bioelectronic devices such as flexible brain-computer interfaces. This functionalization treatment helps improve the transmission efficiency of neural signals and extend the service life of the device. After dynamic bending testing (100,000 cycles, curvature radius of 1mm), the resistance change of the functionalized fiber was <10%, and biological rejection reactions were reduced.

[0073] In summary, this paper proposes a method for functionalizing carbon nanotube (CNT) fibers, using a composite modification of polypyrrole (PPy) and gold nanoparticles (Au NPs) to enhance their electrochemical performance. Polypyrrole is deposited on the surface of the CNT fibers via electrochemical polymerization, followed by the introduction of gold nanoparticles via electrodeposition to form functionalized CNT fibers. These CNT fibers, functionalized with a composite of polypyrrole and gold nanoparticles, exhibit excellent electrical conductivity and stability, making them particularly suitable for flexible bioelectronic devices, such as neural signal transmission and interfacial impedance optimization in brain-computer interfaces. DETAILED DESCRIPTION

[0074] The present invention is further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto:

[0075] Example 1: Preparation of carbon nanotube fiber electrodes based on polypyrrole and nano-gold composite functionalization, the following steps are performed in sequence:

[0076] 1. Preparation of Carbon Nanotube Fibers

[0077] 1.1) Acidification treatment:

[0078] Concentrated sulfuric acid (98%, ρ = 1.84 g / cm 3 ) and concentrated nitric acid (65%, ρ = 1.40 g / cm 3 ) are mixed in a volume ratio of 1:1 (v / v) to obtain a mixed acid;

[0079] Multi-walled carbon nanotubes (MWCNTs) were immersed in mixed acid at 60°C for 2 hours. Conventional ultrasound assistance (ultrasonic power 200W) was used during the acidification process to increase the active sites on the surface of the carbon nanotubes.

[0080] Then, the mixture was washed with deionized water until neutral and dried (at 60-80° C. for 60 minutes) to obtain acidified carbon nanotubes.

[0081] 1.2) Fiber molding:

[0082] Multi-walled carbon nanotubes (MWCNTs): polyvinyl alcohol (PVA) = 3 wt%; the degree of polymerization of polyvinyl alcohol (PVA) is 1700-1800;

[0083] The acidified carbon nanotubes obtained in step 1) are dispersed in a 1 mol / L polyvinyl alcohol (PVA) solution and ultrasonically treated for 40 minutes to obtain a uniform dispersion. Subsequently, a continuous fiber structure is prepared by wet spinning technology. The wet spinning technology used is a conventional technology, for example, reference can be made to CN103668528B "A carbon nanotube / polyvinyl alcohol composite fiber and its preparation method".

[0084] The parameters of wet spinning (electrospinning) can also be set as follows: spinning temperature of 55-75°C, voltage of 15-20 kV, needle-collecting plate distance of 15-20 cm, coagulation bath of methanol or saturated sodium sulfate solution, coagulation bath temperature of -20--30°C, and winding speed of 20-40 m / min.

[0085] The obtained fibers with a diameter of ∼50 μm were dried in a conventional manner (90° C., 1 hour) and named CNT fibers.

[0086] 2. Electrochemical polymerization of polypyrrole (PPy)

[0087] A polypyrrole film was deposited on the surface of the CNT fibers obtained in step 1.2) by electrochemical polymerization as follows:

[0088] 2.1) Preparation of electrolyte:

[0089] Pyrrole monomer and lithium tetrafluoroborate were dissolved in deionized water to prepare an electrolyte. In the electrolyte, the concentration of pyrrole monomer was 0.05M (ie, 0.05 mol / L), and the concentration of lithium tetrafluoroborate was 0.5M.

[0090] 2.2) Electrode configuration and polymerization conditions:

[0091] The CNT fiber obtained in step 1.2) was used as the working electrode, the platinum sheet was used as the counter electrode, and the Ag / AgCl was used as the reference electrode. The three-electrode system was placed in an electrolytic cell.

[0092] The working electrode (CNT fiber) was placed in the electrolyte obtained in step 2.1) and electropolymerized at 0.7 V (vs. Ag / AgCl) for 8 minutes at room temperature and magnetic stirring using a constant potential method with a current density of 0.5 mA / cm 2 ; The formed polypyrrole is uniformly deposited on the fiber surface to form a conductive film with a thickness of about 80±10nm (which can be measured by SEM).

[0093] During the polymerization process, the working electrode (CNT fiber) must always be immersed in the electrolyte.

[0094] 2.3) After the polymerization is completed, the unreacted monomers and oligomers are removed by ultrasonic cleaning with deionized water (cleaning time is about 30 seconds), and then vacuum drying is performed at 60° C. for 30 minutes to obtain polypyrrole-functionalized CNT fibers.

[0095] 3. Modification of gold nanoparticles:

[0096] After the polypyrrole film is formed, gold nanoparticles are modified onto the polypyrrole surface; specifically, as follows:

[0097] 3.1) Using a gold nanoparticle suspension with a diameter of about 20 nm;

[0098] It can be prepared by conventional citric acid reduction method: 10mL sodium citrate solution (38.8mM) is quickly added to 100mL boiling HAuCl4 solution (1mM), stirring is maintained at 800rpm and boiling is continued for 15 minutes. The color of the solution gradually changes from light yellow to wine red. After cooling to room temperature, a gold nanoparticle suspension with a diameter of about 20nm is obtained.

[0099] 3.2) Gold nanoparticle modification:

[0100] The polypyrrole-functionalized CNT fibers obtained in step 2) were immersed in a gold nanoparticle suspension and stirred continuously at room temperature for 1 hour to allow the gold nanoparticles to evenly and firmly bind to the polypyrrole surface through physical adsorption and electrostatic interactions. After modification, the fibers were thoroughly rinsed with deionized water to remove unbound gold nanoparticles and residual reagents, and then vacuum-dried at 60°C for 30 minutes to obtain gold nanoparticle-polypyrrole composite functionalized fibers.

[0101] 4. High temperature stabilization treatment

[0102] The gold nanoparticle-polypyrrole composite functionalized fiber obtained in step 3 was placed in a tube furnace and stabilized at 200°C for 1 hour under the protection of high-purity argon or nitrogen (oxygen content <0.1 ppm). The obtained product was named a gold nanoparticle-polypyrrole composite functionalized electrode (hereinafter referred to as the functionalized electrode).

[0103] As a control, the polypyrrole-functionalized CNT fibers obtained in step 2 were also subjected to the above high-temperature stabilization treatment, and the obtained electrode was named as an unfunctionalized electrode.

[0104] Note: The protection of high-purity argon or nitrogen (oxygen content <0.1ppm) is set to prevent material oxidation; the temperature of 200°C is set to avoid excessive temperature causing decomposition of polypyrrole or agglomeration of nano-gold.

[0105] 5. Characterization of Functionalized Electrodes

[0106] Surface morphology characterization: The surface morphology of the gold nanoparticle-polypyrrole composite functionalized electrode obtained in step 4 was observed using a scanning electron microscope (SEM). It was found that the gold nanoparticles were evenly distributed on the surface of the polypyrrole film, and the thickness of the polypyrrole layer was about 200 nm.

[0107] Electrochemical impedance spectroscopy (EIS) testing was conducted in a simulated physiological solution (0.01M PBS, pH 7.4) according to the test method specified in GB / T 39482.3-2020. The test results showed that the interfacial impedance of the functionalized electrode (modified with gold nanoparticles and polypyrrole) was 5Ω at 100Hz, while the interfacial impedance of the unfunctionalized electrode (not treated with gold nanoparticles) was 10Ω at the same frequency. A comparative analysis showed that the interfacial impedance of the functionalized electrode was 50% lower than that of the unfunctionalized electrode.

[0108] Cyclic voltammetry (CV) test: In 0.01M PBS (pH 7.4) electrolyte, a three-electrode system (functionalized electrode as working electrode, Ag / AgCl as reference electrode, platinum wire as counter electrode) was used to test within a voltage range of ±0.8V at a scan rate of 50mV / s. The test data showed that:

[0109] 1) The functionalized electrode exhibited obvious redox peaks at +0.35 V and -0.25 V, with peak currents of (25.6±1.2) μA and (-23.8±1.1) μA, respectively (n=3);

[0110] 2) After 20 consecutive CV scans, the redox peak potential shift is less than 15 mV and the peak current decay rate is less than 5%;

[0111] 3) Compared with the unfunctionalized electrode, the oxidation peak current of the functionalized electrode increased by 3.2 times (the peak current of the unfunctionalized electrode was 8.0±0.5μA).

[0112] The above results show that within the voltage range of ±0.8V, the redox reaction of the functionalized electrode has good reversibility and high electrochemical response sensitivity.

[0113] 6. Performance testing of brain-computer interfaces

[0114] In vitro testing: According to the test method of GB / T 26124-201, functionalized and non-functionalized electrodes were integrated into the flexible brain-computer interface device for comparative testing. The experimental data showed:

[0115] 1) When transmitting at 1 kHz, the signal attenuation rate of the functionalized electrode was (12.5±1.8)%, while that of the unfunctionalized electrode was (42.3±2.6)%.

[0116] 2) Signal stability (measured by the standard deviation of the signal-to-noise ratio): (3.2±0.5) dB for the functionalized electrode and (10.1±1.2) dB for the unfunctionalized electrode;

[0117] 3) Calculations show that the signal stability of the functionalized electrode is improved by (68±7)% compared to the non-functionalized electrode (n=5).

[0118] In vivo implantation experiment: According to the test method of GB / T 16886.1, functionalized electrodes were implanted into the cerebral cortex (primary motor area) of 5 SD rats, and the control group was implanted with non-functionalized electrodes. The experimental data showed that:

[0119] 1) Initial implantation (1 week): interface impedance of the functionalized electrode was (25.3±3.1) kΩ, and that of the non-functionalized electrode was (28.7±4.2) kΩ;

[0120] 2) 2 months after implantation: the impedance change rate of the functionalized electrode was (12.5±2.8)%, while that of the non-functionalized electrode was (58.3±6.7)%;

[0121] 3) Tissue section analysis showed that the thickness of glial cell proliferation around the functionalized electrodes was (35.2±5.6) μm, which was significantly lower than that of the non-functionalized electrode group (82.4±9.3) μm (p<0.01).

[0122] After two months of experimental observation, it was found that the electrodes were able to stably record neural discharge signals, and the interface impedance changes were small, without triggering obvious biological rejection reactions.

[0123] Example 2: Preparation of Au nanoparticle-reinforced carbon nanotube fiber heat-resistant electrode

[0124] 1. Preparation of Carbon Nanotube Fibers

[0125] The pristine vertically aligned DWCNT arrays for fiber preparation were synthesized by a continuous chemical vapor deposition (CVD) method.

[0126] The details are as follows:

[0127] A single crystal silicon wafer with a crystal orientation of <100> or <111> was placed in a quartz boat and placed in a tube furnace (volume of approximately 1L). The temperature was first raised to 700±10°C under an Ar flow (200sccm); then an Ar / H2 mixed gas (volume ratio 9:1, total flow rate 300sccm) was introduced and maintained for 10 minutes to reduce the surface of the single crystal silicon wafer; then C2H4 (20sccm) was introduced as a carbon source and grown for 8 minutes to obtain a vertically aligned DWCNT array (height ~500μm).

[0128] Using a spinning machine, DWCNT ribbons were pulled out from the DWCNT array at a speed of 0.5 m / min. A torsional force was applied by rotating the take-up spindle (300 rpm) to produce DWCNT fibers (diameter 10±0.5 μm, torsion angle 18±2°).

[0129] 2. Preparation of DWCNT@PPy Fibers

[0130] The DWCNT fiber (length 5 cm) obtained in step 1 above was used as a working electrode, and the rest was the same as step 2 of Example 1 to obtain DWCNT@PPy fiber.

[0131] 3. Preparation of Gold Nanoparticle-Modified DWCNT@PPy Fibers

[0132] Dissolve HauCl4·4H2O in deionized water and store in the dark to obtain a 10mM chloroauric acid solution. Immerse the DWCNT@PPy fiber obtained in step 2 above in a 10mM HAuCl4 solution at room temperature with a current density of 0.1mA / cm 2 , electrochemical reaction time 5min. The reducing property of PPy makes Au 3+ In situ reduction to Au 0, and Au NP-PPy-DWCNT composite fibers (DWCNT@PPy@Au) were prepared.

[0133] 4. High temperature stabilization treatment

[0134] The DWCNT@PPy@Au obtained in step 3 was placed in a high-temperature muffle furnace and stabilized at 200°C for 1 hour under nitrogen protection.

[0135] The unmodified DWCNT@PPy fiber obtained in step 2 was subjected to the above high-temperature stabilization treatment as a control.

[0136] 5. Performance testing for brain-computer interfaces:

[0137] 5.1 Physical property characterization

[0138] The conductivity of the DWCNT@PPy@Au fiber after high-temperature stabilization treatment obtained in step 4 was measured by the four-probe method to be 560±15S / cm.

[0139] The thermal conductivity was measured by laser flash method and was 150±5 W / m·K.

[0140] 5.2 Signal transmission test

[0141] The DWCNT@PPy@Au fibers obtained in step 4 after high-temperature stabilization were integrated onto a flexible PCB and packaged into an electrode array. Tested in 0.9% NaCl solution:

[0142] 1kHz signal attenuation rate: 9.5±0.8% (unmodified fiber DWCNT@PPy treated with high temperature stabilization as a control: 38.2±2.1%).

[0143] Signal-to-noise ratio: 25.6±1.2dB.

[0144] Example 3: Preparation of carbon nanotube fiber electrodes based on polypyrrole and nano-gold composite functionalization

[0145] 1. Preparation of Emulsion Solution

[0146] 4 mL of polystyrene (average MW ≈ 50,000 g / mol)-N,N-dimethylformamide solution (PS-DMF, 0.15 g mL -1) was slowly added dropwise to a 6 mL HauCl4 / vinyl acetate / polyvinyl pyrrolidone (average MW ≈ 40,000 g / mol)-DMF mixed solution containing 0.20 g mL⁻¹ of PVP (polyvinyl pyrrolidone), 0.25 M VA (vinyl acetate, MW = 86.09 g / mol), and a ratio of n(VA):n(Au) = 95:5. The mixture was stirred at 800 ± 50 rpm for 12 hours to produce a gold precursor / polymer composite emulsion (Au / VA / PVP-PS). Dynamic light scattering (DLS) analysis revealed a particle size distribution of 120 ± 25 nm (PDI = 0.18) and a zeta potential of -35.2 ± 2.1 mV, confirming the formation of a stable composite emulsion system.

[0147] 2. Fiber molding

[0148] The composite emulsion was electrospun to form nanofibers. Electrospinning was performed in air at 25 ± 5°C. The voltage between the needle tip and the collector (aluminum foil) was 18 cm. The flow rate was fixed at 1.2 mL h⁻¹ and the voltage was 18 kV to obtain nanofibers.

[0149] 3. Preparation of Gold Nanoparticles

[0150] The nanofibers obtained in step 2 were heated to 430° C. in air at a heating rate of 1° C. / min and sintered for 0.5 hours to degrade the polymer from the fibers and convert VA into V 2 O 5 and HAuCl 4 into Au; thereby obtaining nano-gold composite nanofibers.

[0151] 4. In situ gas phase polymerization

[0152] The gold nanofibers obtained in step 3 were placed in a desiccator containing 5 mL of concentrated hydrochloric acid (37 wt%) and treated under a vacuum condition of -0.1 MPa for 10 minutes. They were then transferred to a desiccator containing 2 mL of pyrrole monomer and continued to be vacuum treated for 1 hour. After repeating the hydrochloric acid / pyrrole cycle (repeated 4 to 5 times), they were soaked in a 1 M hydrochloric acid solution for 24 hours to completely remove unreacted V2O5. After washing with deionized water and ethanol three times each, they were vacuum dried at 40°C for 48 hours to finally obtain polypyrrole / gold nanocomposite functionalized hollow nanofibers (Au / PPy NM). XPS analysis showed that the Au content in the product was 12.3 ± 0.8 wt%, and the thickness of the PPy coating layer was 50 ± 5 nm (TEM measurement).

[0153] 5. High temperature stabilization treatment

[0154] The fiber obtained in step 4 was placed in a high-temperature muffle furnace and reacted at 200° C. for 1 hour (under argon protection) to remove the residual solvent. The obtained product was named Au / PPy NM.

[0155] Step 3 was omitted, and the product obtained in step 2) was directly subjected to steps 4 and 5. The product was named original PPy NM and used as a control.

[0156] 6. Electrochemical Performance Characterization

[0157] Surface morphology characteristics: Using scanning electron microscopy (SEM), it can be seen that after in situ polymerization of the rough surface with Au nanoparticles, white spots are scattered on the inner and outer surfaces of the Au / PPy nanotubes, maintaining a hollow structure.

[0158] Cyclic voltammetry (CV) tests: The CV curves in the potential from 0 to 0.8 V were approximately rectangular in shape by changing the scan rate from 5 mV s-1 to 1 V s-1, indicating the good capacitive behavior of PPy and Au / PPy NMs.

[0159] The performance comparison between pristine PPy NM and Au / PPy NM is shown in Table 1.

[0160] Table 1

[0161]

[0162]

[0163] 7. Performance test of carbon nanotube fiber electrodes

[0164] The conductivity is enhanced after doping with Au nanoparticles. At a scan rate of 5 mV s-1, Au doping increases the specific capacitance of the electrode from 193.7 to 455.3 F g-1, and the conductivity of Au / PPy NM (8.4×10-5 Sm-1) is higher than that of the original ppy NM (2.2×10-6 Sm-1).

[0165] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples and is subject to numerous variations. All variations that can be directly derived or conceived by a person of ordinary skill in the art from the disclosure of the present invention are considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing carbon nanotube fibers based on polypyrrole and nano-gold composite functionalization, characterized in that The following steps are involved: 1) Preparation of carbon nanotube fibers; 2) functionalizing the carbon nanotube fibers by electrochemical polymerization of polypyrrole to obtain polypyrrole functionalized CNT fibers; 3) Composite modification of gold nanoparticles: Gold nanoparticles are modified onto the surface of polypyrrole to obtain gold nanoparticle-polypyrrole composite functionalized fibers.

2. A method for preparing carbon nanotube fibers based on polypyrrole and nano-gold composite functionalization, characterized in that The following steps are involved: 1) Preparation of nanofibers; 2) Preparation of nano-gold composite nanofibers; 3) Preparation of polypyrrole / nano-gold composite functionalized nanofibers.

3. The method for preparing carbon nanotube fibers based on polypyrrole and nano-gold composite functionalization according to claim 1 or 2, characterized in that It also includes the following step 4): performing high-temperature stabilization treatment on the gold nanoparticle-polypyrrole composite functionalized fibers or the polypyrrole / nano-gold composite functionalized nanofibers; The high temperature stabilization treatment is: stabilization treatment at 200±20° C. for 1±0.1 hour under the protection of inert gas.

4. The method for preparing carbon nanotube fibers based on polypyrrole and nano-gold composite functionalization according to claim 1, characterized in that The step 1) includes any of the following methods: Method 1: 1.1) Acidification treatment: Mix concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3-1:1-5 to obtain a mixed acid; Immersing the carbon nanotubes in mixed acid at 50-70° C. for 2-4 hours; Then washing and drying to obtain acidified carbon nanotubes; 1.2) Fiber molding: The acidified carbon nanotubes are dispersed in a (1±0.05) mol / L polyvinyl alcohol or polyvinyl pyrrolidone aqueous solution, the resulting dispersion is wet-spun, and then dried to obtain CNT fibers; Carbon nanotubes: polyvinyl alcohol or polyvinyl pyrrolidone = 1-5 wt%; Method 2: DWCNT arrays were prepared using single crystal silicon wafers; Then, DWCNT strips are pulled out from the DWCNT array and a torsional force is applied to produce DWCNT fibers.

5. The method for preparing carbon nanotube fibers based on polypyrrole and nano-gold composite functionalization according to claim 1, characterized in that Step 2) includes the following steps: 2.1) Electrolyte configuration Dissolving a pyrrole monomer and a fluorine-containing lithium salt in a solvent to prepare an electrolyte; in the electrolyte, the concentration of the pyrrole monomer is 0.01 to 0.05 mol / L, and the concentration of the fluorine-containing lithium salt is 0.1 to 1 mol / L; The fluorine-containing lithium salt is LiBF4 or LiPF6; The solvent is water, acetonitrile or acetone; 2.2) Polymerization process Electrode system: The carbon nanotube fiber obtained in step 1) is used as the working electrode, the platinum sheet is used as the counter electrode, and the Ag / AgCl is used as the reference electrode; polymerization is carried out using a constant potential method; 2.3) Post-processing The product was rinsed with deionized water and dried in vacuum to obtain polypyrrole functionalized CNT fibers.

6. The method for preparing carbon nanotube fibers based on polypyrrole and nano-gold composite functionalization according to claim 1, characterized in that The step 3) is to select any of the following methods: Method 1: Chemical adsorption method Immersing the polypyrrole-functionalized CNT fibers obtained in step 2) in the gold nanoparticle suspension for 30 to 60 minutes under stirring; Then washing and drying are performed to obtain gold nanoparticle-polypyrrole composite functionalized fibers; Method 2: Electrochemical deposition Prepare a 0.01 mol / L HAuCl4 solution; immerse the polypyrrole-functionalized CNT fiber obtained in step 2) in the HAuCl4 solution; Deposition conditions: Current density: 0.1 mA / cm 2 , time: 3 to 5 minutes; temperature: room temperature.

7. The method for preparing carbon nanotube fibers based on polypyrrole and nano-gold composite functionalization according to claim 6, characterized in that: In step 1.1) of the method 1 of step 1), the acidification treatment may be performed with the assistance of conventional ultrasound; The parameters of the wet spinning in step 1.2) of the method 1 of step 1) are: The spinning temperature is 55-75°C. Voltage: 15~20kV, Needle-collection plate distance: 15-20 cm.

8. The method for preparing carbon nanotube fibers based on polypyrrole and nano-gold composite functionalization according to claim 7, characterized in that The constant potential polymerization in step 2.2) is as follows: Voltage: 0.6~0.7V; Time: 5 to 30 minutes; Current density: 0.1~1mA / cm 2 ; Environmental control: Temperature: 20~25℃.

9. The method for preparing carbon nanotube fibers based on polypyrrole and nano-gold composite functionalization according to claim 2, characterized in that: The step 1) is: First, a composite emulsion system was prepared using polystyrene-N,N-dimethylformamide solution and HauCl4 / vinyl acetate / polyvinylpyrrolidone-DMF mixture; The composite emulsion system is then formed by electrospinning to obtain nanofibers; The step 2) is: The nanofibers were sintered at 430±30° C. for 0.5±0.1 hours to convert HAuCl4 into Au; and the gold nanoparticles were obtained. The step 3) is to prepare polypyrrole / nano-gold composite functionalized nanofibers by in-situ gas phase polymerization.

10. The method for preparing carbon nanotube fibers based on polypyrrole and nano-gold composite functionalization according to claim 9, characterized in that The step 3) is: The nano-gold composite nanofibers were first pretreated with concentrated hydrochloric acid, and then pyrrole monomer was added for vacuum treatment.

Images