Method for recycling of mxene preparation residues and its application in biosensors

Abstract

The application discloses a recycling method of MXene preparation residues, comprising the following steps: recovering bottom layer residual precipitates obtained in the process of MXene preparation by MILD etching, mixing the bottom layer residual precipitates with a PVA molten liquid, drying the mixture, and preparing Ti3C2T x Ti3AlC2 / PVA composite film. The application realizes resource utilization of MXene process residues, effectively considers mechanical properties and conductive properties of the obtained composite film, has extremely high sensitivity to stress and strain and good stability, is suitable for flexible connection and sensing fields such as biosensors and robots, has significant economic benefits and environmental benefits, and is suitable for popularization and application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional materials, and particularly relates to a recycling method of MXene preparation residues and application thereof in biosensors. BACKGROUND

[0002] As a new type of two-dimensional material with stacked layers, MXene has the structural characteristics of traditional two-dimensional materials such as graphene, and excellent photoelectric performance. In addition, the interlayer spacing of MXene can be adjusted in a wide range, and the surface groups can be easily functionalized. Moreover, the elements constituting MXene are very rich, making it possible to design and control the physical and chemical properties of MXene at the molecular level. MXene has potential applications in supercapacitors, electromagnetic shielding, sensors, photocatalysis and many other fields. In particular, the electrical properties of MXene have ultra-high sensitivity to stress and strain response, making it a focus of attention in sensor applications. Currently, the strain sensitivity coefficient (gage factor, GF) of MXene used in piezoelectric sensors exceeds 180.

[0003] MXene is usually prepared by the minimum interlayer strength delamination method (MILD). However, after MXene is prepared by etching using the MILD method, a large amount of precipitate from the bottom layer is often discarded as waste due to the lack of proper recycling and utilization, resulting in a huge waste of materials and increasing the production and subsequent disposal costs of MXene.

[0004] The main components of the precipitate obtained by the MILD method are a blend of MXene (Ti3C2Tx) with different layers, a small amount of unetched MAX phase, and an incompletely etched MAX phase. Among them, the two-dimensional MXene has excellent electrical conductivity, and its outer layer contains rich termination groups that can form good interactions with polymer materials such as PVA, thereby forming a structurally stable composite material. The unetched and incompletely etched three-dimensional MAX phase has high mechanical strength, interlayer lubricity, and corrosion resistance, which can provide good mechanical properties and environmental stability to the composite material. Therefore, the residues from MXene preparation are not completely waste, and if they can be reasonably utilized, they can not only reduce the production cost of MXene, but also provide additional high-value new products, which undoubtedly has potential application prospects and environmental value. However, the residues from MXene preparation are a very viscous brown substance, which is difficult to separate, recycle and effectively utilize by conventional methods. SUMMARY

[0005] The application aims at the present situation of great material waste in MXene preparation and the problem of residue recycling, and provides a recycling method of MXene preparation residue and application thereof in biosensors; the residue in MXene preparation by MAX phase etching is compounded with polyvinyl alcohol (PVA), and the obtained composite film has very high sensitivity and good stability, and can be well applied to flexible connection and sensing of biosensors and robots; the application can effectively utilize MXene process residue, and effectively consider the mechanical properties and conductive properties of the obtained composite film, and has very high sensitivity and good stability to stress and strain; the application has significant economic benefits and good environmental benefits, effectively reduces solid waste emission, and provides a new product with high added value, and is suitable for popularization and application.

[0006] To achieve the above object, the technical scheme adopted by the application is:

[0007] A recycling method of MXene preparation residue, which recycles bottom layer residual precipitate obtained in the process of MILD etching for preparing MXene, mixes the residual precipitate with PVA molten liquid, and dries to prepare Ti3C2Tx-Ti3AlC2 / PVA composite film. x The bottom layer precipitate by-product is Ti3C2Tx-Ti3AlC2-based mixture (mainly a mixture of Ti3C2Tx and Ti3AlC2); and specifically includes the following steps:

[0008] 1) etching Ti3AlC2 powder by MILD method, adding water for multiple centrifugal separation, recycling and drying the bottom layer residual precipitate after centrifugal separation to obtain MXene preparation residue (Ti3C2Tx-Ti3AlC2 mixture);

[0009] 2) adding PVA particles into water, heating to a complete melting state of PVA to obtain PVA molten liquid; then adding MXene preparation residue into the PVA molten liquid in proportion, and stirring and mixing uniformly (heating temperature is 60-150 DEG C, stirring rate is 100-500 rpm, and time is 10-30 min), and then filtering and drying to obtain Ti3C2Tx-Ti3AlC2 / PVA composite film. x The Ti3C2Tx-Ti3AlC2 / PVA composite film.

[0010] In the above scheme, the etching step includes:

[0011] 1) adding MAX phase Ti3AlC2 powder into an etchant aqueous solution for stirring treatment, chemically etching the MAX phase, then adding water for centrifugal treatment, adjusting the pH value of the solution to 6-7, and washing away residual etchant to obtain a preliminary etched MXene primary product;

[0012] 2) adding intercalation agent to MXene primary product solution, stirring, ultrasonic treatment and centrifugal treatment;

[0013] 3) recovering the bottom precipitate after centrifugal treatment, vacuum drying to obtain MXene preparation residue (Ti3C2Tx-Ti3AlC2 mixture).

[0014] In the above scheme, the particle size of the MXene preparation residue is 100-400 μm.

[0015] In the above scheme, the etchant is HF, HCl / LiF, NaHF2, KHF2 or NH4HF2, etc., and the mass ratio of the etchant to Ti3AlC2 powder of MAX phase is 1:(0.5-3).

[0016] In the above scheme, the stirring treatment in step 1) is carried out at a speed of 400-1000 rpm for 48-72 h.

[0017] In the above scheme, the intercalation agent is one or more of ethanol, DMSO, TMAOH, TBAOH, etc., and the mass ratio of the intercalation agent to MAX phase is 1:(5-20).

[0018] In the above scheme, the stirring in step 2) is carried out at a speed of 100-1000 rpm for 1-8 h; the ultrasonic treatment is carried out at a power of 100-500 W for 0.5-5 h; the centrifugal treatment is carried out at a speed of 2000-12000 rpm for 1-6 times, each time for 10-60 min; the vacuum drying is carried out at a vacuum degree of 0.05-0.1 MPa and a temperature of 40-60℃ for 12-48 h.

[0019] In the above scheme, the solid-liquid ratio of PVA to water in the PVA melt solution is 1 g:0.02-1 ml.

[0020] In the above scheme, the amount of the Ti3C2Tx-Ti3AlC2 mixture accounts for 10-25% of the mass of the PVA particles, the heating temperature is 60-150℃, the stirring rate is 100-500 rpm, and the time is 10-30 min.

[0021] Preferably, the amount of the Ti3C2Tx-Ti3AlC2 mixture accounts for 8-18% of the mass of the PVA particles.

[0022] More preferably, the amount of the Ti3C2Tx-Ti3AlC2 mixture accounts for 10-15% of the mass of the PVA particles.

[0023] The Ti3C2Tx-Ti3AlC2 mixture prepared according to the above scheme has the following properties: x-Ti3AlC2 / PVA composite films, when applied to the fabrication of biosensors, exhibit excellent sensitivity (response time <100ms) and flexibility, and can quickly recover their original state after bending, demonstrating good stability.

[0024] The principle of this invention is as follows:

[0025] This invention utilizes the abundant residue (Ti3C2Tx-Ti3AlC2 mixture) generated during the MXene etching process, further combining it with PVA. The two-dimensional MXene exhibits excellent electrical conductivity, and its outer layer contains abundant terminating groups, which can form good interactions with polymer materials such as PVA, thereby forming a structurally stable composite material. In addition, the introduced unetched and incompletely etched three-dimensional MAX phase has high mechanical strength, interlayer lubrication, and corrosion resistance, providing the composite material with good mechanical properties and environmental stability. The resulting composite film has good mechanical and electrical properties.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1) This paper proposes for the first time to recycle and utilize a large amount of residue from the MXene etching process, and further combine it with PVA to prepare composite films, which can achieve a highly viscous Ti3C2T film that is difficult to separate. x The resource utilization of Ti3AlC2 mixture can simultaneously ensure the good mechanical and electrical properties of the resulting thin film, resulting in significant economic and environmental benefits.

[0028] 2) The obtained Ti3C2T x -Ti3AlC2 / PVA composite film, by tracking the change in resistance after bending, can be used as a flexible biosensor to monitor the activity of joints such as fingers and wrists. It has extremely high sensitivity and good flexibility. Moreover, the sensor can recover its original state in a short time after bending, and has good stability. It has potential applications in wearable electronics.

[0029] 3) Due to Ti3C2T x -Ti3AlC2 itself has good mechanical strength, and the resulting Ti3C2T x -Ti3AlC2 / PVA composite films possess high tensile strength, making them suitable for biosensing. Furthermore, due to the Ti3C2T... x -Ti3AlC2 / PVA composite films have high tensile strength and elongation, and are expected to be used in flexible connections and sensing in robots. Attached Figure Description

[0030] Figure 1 Schematic diagram of the recycling method of MXene preparation residues and the preparation process of Ti3C2Tx-Ti3AlC2 / PVA composite film in Example 1.

[0031] Figure 2 (a) X-ray diffraction (XRD) and (b) Fourier transform infrared absorption spectrum (FTIR) of Ti3C2Tx-Ti3AlC2used in Example 1.

[0032] Figure 3 Scanning electron microscope images (SEM) of composite films with different Ti3C2Tx-Ti3AlC2contents in Example 1; (a) 10%, (b) 20%, (c) 25%, (d) 30%.

[0033] Figure 4 Resistance change of 25% Ti3C2Tx-Ti3AlC2 / PVA composite film obtained in Example 2, (a) resistance change under different bending radii, (b) output current change of the film under a given 1V voltage at different bending radii, (c) change of film resistance with tensile strain. x Tensile stress-strain curve of Ti3C2Tx-Ti3AlC2 / PVA composite film and pure PVA film.

[0034] Figure 5 Resistance change of 25% Ti3C2Tx-Ti3AlC2 / PVA composite film obtained in Example 2, (a) resistance change under different bending radii, (b) output current change of the film under a given 1V voltage at different bending radii, (c) change of film resistance with tensile strain.

[0035] Figure 6 Application effect of composite film obtained in Example 2 for preparing biosensors, (a) index finger, (b) middle finger, (c) ring finger, (d) little finger, (e) wrist joint bending, (f) wrist joint twisting.

[0036] Figure 7 Scanning electron microscope images (SEM) of composite films with different Ti3C2Tx-Ti3AlC2contents in Example 3-5; (a) 10%, (b) 20%, (c) 25%, (d) 30%. x Tensile stress-strain curve of Ti3C2Tx-Ti3AlC2 / PVA composite film and pure PVA film.

[0037] Figure 8 Scanning electron microscope images (SEM) of composite films with different Ti3C2Tx-Ti3AlC2contents in Example 3-5; (a) 10%, (b) 20%, (c) 25%, (d) 30%. x Tensile stress-strain curve of Ti3C2Tx-Ti3AlC2 / PVA composite film and pure PVA film. DETAILED DESCRIPTION

[0038] In order to better understand the present application, the content of the present application will be further illustrated below in combination with specific examples, but the content of the present application is not limited to the following examples only.

[0039] In the following examples, Ti3C2Tx-Ti3AlC2was prepared according to the method of Example 1. xTi3AlC2 mixture is the bottom layer of residual precipitate collected in the process of preparing Ti3C2Tx filter membrane by etching MXene with MILD method, and the specific preparation method comprises the following steps:

[0040] 1) 2g LiF is stirred with 40ml 9M hydrochloric acid in a Teflon beaker for 30min; then the beaker is placed in ice water, and 2g Ti3AlC2 is slowly added into the beaker, and the reaction temperature is adjusted to 40℃ after the addition of Ti3AlC2 is completed, and the stirring is continued for 45h; after the reaction is completed, the obtained mixed solution is centrifuged, and the pH value of the solution is adjusted to 6-7, and then the obtained mixed solution is subjected to ultrasonic treatment, vacuum filtration and drying to obtain black MXene (Ti3C2Tx) primary product; x

[0041] 2) DMSO is added into the beaker containing the MXene primary product, and stirred for 4h, and then subjected to ultrasonic treatment (150W, 2h), and then deionized water is added for centrifugal treatment (speed 8000rpm, time 5min) to wash away the intercalating agent, and the main product is collected; deionized water is continuously added for centrifugal treatment (speed 3500rpm, time 30min), and finally the bottom layer of residual precipitate is dried under vacuum to obtain Ti3C2Tx-Ti3AlC2, which mainly comprises a mixture of Ti3C2Tx and Ti3AlC2 which is not completely etched.

[0042] Example 1

[0043] A recycling method of MXene preparation residue, and the preparation process thereof is shown in Figure 1 ; and the method comprises the following steps:

[0044] 1) The Ti3C2Tx-Ti3AlC2 mixture is ground into fine particles (100-400μm) for standby; 1g polyvinyl alcohol (PVA) is added into 50ml deionized water, and heated to completely become a molten state at 100℃ to obtain a PVA molten liquid;

[0045] 2) 20ml deionized water is added into the Ti3C2Tx-Ti3AlC2 mixture and ultrasonically dispersed, and then slowly poured into the obtained PVA molten liquid under stirring; different contents of PVA (Ti3C2Tx-Ti3AlC2 accounts for 10%, 20%, 25% and 30% of the mass of PVA, respectively) are selected, and the stirring and mixing are continued (temperature is 100℃, stirring rate is 120rpm, and time is 15min) before the PVA starts to solidify; the obtained blended liquid is filtered through gauze and poured into a standard Teflon mold with a size of 7.5×10×1cm 3 , and naturally dried for 48h to obtain a PVA / Ti3C2Tx-Ti3AlC2 composite film with good toughness.​

[0046] Figure 1 The MXene preparation residue recycling method and the Ti3C2Tx-Ti3AlC2 / PVA composite film preparation process described in Example 1. After etching and intercalation with DMSO, the layered MXene was obtained through repeated centrifugation (taking the supernatant), which can be used for other experiments, and the clay-like mixture precipitated at the bottom of the centrifuge tube was extracted by suction filtration and drying, etc. to obtain the MXene preparation residue (Ti3C2Tx-Ti3AlC2) used in the application; then the Ti3C2Tx-Ti3AlC2 of different proportions was ground into powder and blended with PVA, and finally the composite film was obtained by natural drying. Such a process can ensure that the obtained film has good flexibility and mechanical strength.

[0047] Figure 2 a is the XRD pattern of 25% Ti3C2Tx-Ti3AlC2 obtained in this example. It can be seen that: in addition to having the same (002) peak of 9.5° and the characteristic peak of Al (104) peak of 39.5° as MAX phase, there is a stronger peak at a low angle of 9.5° in the obtained bottom precipitate, which is located at 6.2°, which is the same angle as the (002) peak of DMSO-MXene. It can be seen that the obtained bottom precipitate is mainly a mixture of MAX and MXene.

[0048] Figure 2 b is the Fourier transform infrared absorption spectrum (FTIR) of the Ti3C2Tx-Ti3AlC2 / PVA (20%) composite film obtained in this example. The figure shows: in MXene-MAX, the O-H stretching vibration peak is at 3430 cm -1 -1, while in the Ti3C2Tx-Ti3AlC2 / PVA film sample, a significant red shift (3250 cm -1 -1) is produced, which proves that after adding Ti3C2Tx-Ti3AlC2, hydrogen bonding can be produced with the PVA molecular chain. The same red shift phenomenon is also observed at the O-H vibration peak of 1550 cm -1 -1.

[0049] Figure 3 SEM of the composite film obtained in Example 1 under different Ti3C2Tx-Ti3AlC2 content conditions. The figure shows: in the sample containing 10% Ti3C2Tx-Ti3AlC2 mixture, the blocky particles are scattered in the PVA ( Figure 3 a), and under a higher magnification, the layered structure is obviously stacked, but a continuous conductive network is not formed. After increasing the content of the mixture to 20% ( Figure 3b), the layers overlap each other, stacked together, but still have gaps. Further increase the ratio of the mixture to 25% Figure 3 c), the relatively flat surface can be seen and the uniform distribution of Ti3C2Tx-Ti3AlC2. After magnification 5000 times can be seen with two-dimensional layered structure of MXene stacked in which, which also proves that the main improvement for the conductivity is the Ti3C2Tx in it (Ti3AlC2 is not conductive).

[0050] Example 2

[0051] A recycling method of MXene preparation residue and its application in biosensor, comprising the following steps:

[0052] 1) Take 1g of PVA, add 50ml of deionized water, heat to 100℃ until completely melted into PVA melt;

[0053] 2) Add 20ml of deionized water to the Ti3C2Tx-Ti3AlC2 mixture and ultrasonic dispersion, slowly pour into the obtained PVA melt under stirring conditions, the mass content of Ti3C2Tx-Ti3AlC2 is 25% of the mass of PVA, continue to stir uniformly (temperature is 120℃, stirring rate is 80rpm, time is 20min), before the PVA begins to solidify, the obtained solution is filtered through gauze and poured into a standard polytetrafluoroethylene mold of 7.5x10x1cm 3 , and naturally dried for 48h to obtain a PVA / Ti3C2Tx-Ti3AlC2 composite film.

[0054] Figure 4 For example 2, 25% Ti3C2T x -Ti3AlC2 / PVA composite film and pure PVA film tensile stress strain curve. The addition of a small amount of Ti3C2Tx-Ti3AlC2 will produce hydrogen bond in PVA, which is beneficial to improve the tensile strength of the material, but with the increasing amount of Ti3C2Tx-Ti3AlC2, the improvement of the tensile strength of the material is limited, more Ti3C2Tx-Ti3AlC2 will destroy the hydrogen bond between PVA, so that the strength of the material is weakened, as Figure 4 shown, the addition of 25% Ti3C2T x -Ti3AlC2 significantly reduces the tensile strength of PVA. When the content of Ti3C2Tx-Ti3AlC2 is 25%, the elongation at break is 78.9%, the tensile strength is 17.6MPa, and the Young's modulus is 1.1GPa. In addition, its resistance is 1.25x10 6 Ω.

[0055] Figure 5 The resistance change of the 25% Ti3C2Tx-Ti3AlC2 / PVA composite film in Example 2 is shown in the following table, wherein Figure 5 a is the change in resistance at different bending radii. As the bending radius gradually decreases, the change in film resistance is more obvious. When the bending radius is only 1 cm, the resistance increases by 17%, when the bending radius reaches 0.8 cm, the resistance increases by about 60%, and when the bending radius reaches 0.5 cm, the resistance changes by 80%. Moreover, the resistance of the film can recover to the initial value after the bending process, which proves that the composite film has good flexibility and stability. Figure 5 b is the output current change of the film at different bending radii under a given voltage of 1 V. When the bending radius is greater than 1, the output current changes little, and as the bending degree increases, the resistance increases and the output current correspondingly decreases. When the bending radius is less than 0.4 cm, the current change is relatively stable, because an effective connection is established inside the material, and even if the film is completely folded, it still has conductivity. Figure 5 c is the change of film resistance with strain. When the tensile strain is less than 10%, GF is 533, showing very high sensitivity, and when the strain exceeds 10%, GF still reaches 290. When the tensile strain exceeds 52%, the internal connection of the film breaks, and the film has basically no conductivity. Through the determination of the material GF, it can be seen that Ti3C2Tx-Ti3AlC2 / PVA has high sensitivity in detecting small range of activity changes, and can be used for various types of sensors.

[0056] Figure 6 The bending resistance change of the composite film obtained in Example 2 applied to different active parts is shown in the following table, wherein (a) is the index, (b) is the middle finger, (c) is the ring finger, (d) is the little finger, (e) is the wrist joint bending, and (f) is the wrist joint. Figure 6 a-d show that after bending the fingers, the resistance increases obviously, and the response time is extremely short (<100 ms), showing extremely high sensitivity (due to the difference in flexibility of the test personnel's finger joints, the resistance change obtained by the test will be slightly different). It takes a certain time to restore the resistance to the initial value after bending, because the internal connection of the film is broken to a certain extent after bending, so it takes a certain time to rebuild the internal connection during the recovery process. Figure 6The results show that the wrist joint also exhibits excellent response speed and sensitivity. The resistance increases significantly after bending, but the recovery time is longer compared to finger joint movements. Larger ranges of motion have a greater impact on the material's internal structure, thus requiring more recovery time. The resistance changes after wrist twisting and bending are significantly different; after twisting, the resistance decreases significantly instead of increasing. This is likely because twisting causes unconnected Ti3C2Tx MXene within the film to cross-stack, resulting in a significant reduction in film resistance. The response time for wrist twisting is also very short, with a 50% reduction in resistance after twisting. After recovery from twisting, the resistance slightly increases and then decreases again. This is because the internal MXene undergoes misalignment and reconnection during film recovery, but the recovery time for twisting is shorter than that for bending. These results indicate that the Ti3C2Tx-Ti3AlC2 / PVA composite film is fully capable of being used in biosensors.

[0057] Example 3

[0058] A method for recycling residues from MXene preparation includes the following steps:

[0059] 1) Take 1g of PVA, add it to 50ml of deionized water, and heat it at 100℃ until it is completely melted to obtain PVA melt liquid;

[0060] 2) Add 20 ml of deionized water to the Ti3C2Tx-Ti3AlC2 mixture and ultrasonically disperse until homogeneous. Slowly pour this mixture into the resulting PVA melt while stirring. The Ti3C2Tx-Ti3AlC2 should account for 10% of the PVA volume. Continue stirring until homogeneous (temperature 120℃, stirring speed 80 rpm, time 20 min), before the PVA begins to solidify. Then filter the resulting solution through gauze and pour it into a 7.5×10×1 cm... 3 The film was naturally dried in a standard polytetrafluoroethylene mold for 48 hours to obtain a PVA / Ti3C2Tx-Ti3AlC2 composite film.

[0061] Figure 7 Example 3 shows 10% Ti3C2T x Tensile stress-strain curves of Ti3AlC2 / PVA composite film and pure PVA film; the resulting composite film has an elongation at break of 147.0%, a tensile strength of 29.0 MPa, a Young's modulus of 2.1 GPa, and a resistivity of 8.5 × 10⁻⁶. 6 Ω.

[0062] Tests showed that the resulting composite film exhibits high sensitivity (response time < 100 ms) in detecting small-scale changes in activity, while also possessing excellent mechanical properties, making it suitable for use in various types of sensors.

[0063] Example 4

[0064] A method for recycling residues from MXene preparation includes the following steps:

[0065] 1) Take 1g of PVA, add it to 50ml of deionized water, and heat it at 100℃ until it is completely melted to obtain PVA melt liquid;

[0066] 2) Add 20 ml of deionized water to the Ti3C2Tx-Ti3AlC2 mixture and ultrasonically disperse until homogeneous. Slowly pour this mixture into the resulting PVA melt while stirring. The Ti3C2Tx-Ti3AlC2 should account for 15% of the PVA mass. Continue stirring until homogeneous (temperature 120℃, stirring speed 80 rpm, time 20 min). Before the PVA begins to solidify, filter the resulting solution through gauze and pour it into a 7.5×10×1 cm... 3 The film was naturally dried in a standard polytetrafluoroethylene mold for 48 hours to obtain a PVA / Ti3C2Tx-Ti3AlC2 composite film.

[0067] Figure 7 Example 4 shows 15% Ti3C2T x Tensile stress-strain curves of Ti3AlC2 / PVA composite film and pure PVA film; the obtained composite film has an elongation at break of 145.2%, a tensile strength of 29.2 MPa, a Young's modulus of 3.5 GPa, and a resistivity of 6.5 × 10⁻⁶. 6 Ω.

[0068] Tests showed that the resulting composite film exhibits high sensitivity (response time < 100 ms) in detecting small-scale changes in activity, while also possessing excellent mechanical properties, making it suitable for use in various types of sensors.

[0069] Example 5

[0070] A method for recycling residues from MXene preparation includes the following steps:

[0071] 1) Take 1g of PVA, add it to 50ml of deionized water, and heat it at 100℃ until it is completely melted to obtain PVA melt liquid;

[0072] 2) To the Ti3C2Tx-Ti3AlC2 mixture, 20 ml of deionized water was added and uniformly dispersed by ultrasonic, and slowly poured into the obtained PVA melt under stirring conditions, wherein Ti3C2Tx-Ti3AlC2 accounted for 20% of the mass of PVA, and continue to stir uniformly (temperature 120℃, stirring rate 80rpm, time 20min), before the PVA began to solidify, the obtained solution was filtered through gauze and poured into a standard polytetrafluoroethylene mold of 7.5x10x1cm 3 , and naturally dried for 48h to obtain a PVA / Ti3C2Tx-Ti3AlC2 composite film.

[0073] Figure 7 For Example 5, 20% Ti3C2T x -Ti3AlC2 / PVA composite film and pure PVA film tensile stress-strain curve; the elongation at break of the obtained composite film was 109.7%, the tensile strength was 19.9MPa, and the Young's modulus was 1.1GPa; its resistance was 3.4x10 6 Ω.

[0074] Comparative Example 1

[0075] A method for recycling MXene preparation residues, comprising the following steps:

[0076] 1) Take 1g of PVA, add 50ml of deionized water, heat to completely melt at 100℃ to obtain a PVA melt;

[0077] 2) To the Ti3C2Tx-Ti3AlC2 mixture, 20 ml of deionized water was added and uniformly dispersed by ultrasonic, and slowly poured into the obtained PVA melt under stirring conditions, wherein Ti3C2Tx-Ti3AlC2 accounted for 20% of the mass of PVA, and continue to stir uniformly (temperature 120℃, stirring rate 80rpm, time 20min), before the PVA began to solidify, the obtained solution was filtered through gauze and poured into a standard polytetrafluoroethylene mold of 7.5x10x1cm 3 , and naturally dried for 48h to obtain a PVA / Ti3C2Tx-Ti3AlC2 composite film.

[0078] Figure 8 For Example 5, 20% Ti3C2T x -Ti3AlC2 / PVA composite film and pure PVA film tensile stress-strain curve; the elongation at break of the obtained composite film was 109.7%, the tensile strength was 19.9MPa, and the Young's modulus was 1.1GPa; its resistance was 3.4x10

[0079] Comparative Example 2

[0080] A recycling method of MXene preparation residue, comprising the following steps:

[0081] 1) Take 1g of PVA, add 50ml of deionized water, heat to 100℃ until completely melted to obtain a PVA melt;

[0082] 2) Add 20ml of deionized water to the Ti3C2Tx-Ti3AlC2 mixture and ultrasonically disperse uniformly, slowly pour into the obtained PVA melt under stirring conditions, wherein the mass content of Ti3C2Tx-Ti3AlC2 is 30%, continue to stir uniformly (temperature is 120℃, stirring rate is 80rpm, time is 20min); then filter the obtained solution through gauze and pour into a standard polytetrafluoroethylene mold of 7.5x10x1cm 3 , and naturally dry for 48h to obtain a PVA / Ti3C2Tx-Ti3AlC2 composite film.

[0083] Figure 8 For the 30% Ti3C2T x -Ti3AlC2 / PVA composite film in Comparative Example 2, the tensile stress-strain curve of the film is shown in the figure; the obtained film has good electrical conductivity, and the resistance is 1x10 6 Ω, but the addition of too much Ti3C2T x -Ti3AlC2 significantly reduces the elongation and tensile strength of PVA; the elongation at break is only 24%, the tensile strength is 10.9MPa, and the Young's modulus is 2.0GPa, which is not suitable for stress-strain sensors.

[0084] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A method for recycling MXene preparation residues, characterized by, The application relates to a Ti3C2T x -Ti3AlC2 / PVA composite film; wherein the bottom layer residual precipitate is Ti3C2T x -Ti3AlC2-based mixture; The solid-liquid ratio of PVA to water in the PVA melt solution is 1g:0.02-1ml; the heating melting temperature is 60-150 DEG C; The Ti3C2T x The amount of Ti3AlC2 mixture is 10-25% of the mass of PVA particles. 2.The method of recycling MXene preparation residue according to claim 1, characterized in that, The etching step comprises: 1) adding MAX phase powder into an aqueous etchant solution, and stirring and heating, then adding water to centrifugal treatment, while adjusting the pH value of the solution to 6-7, and then ultrasonic, suction filtration, drying to obtain a preliminary etched MXene primary product; 2) adding an intercalation agent to the MXene primary product solution, and stirring, ultrasonic and centrifugal treatment; 3) recovering the bottom precipitate after centrifugation, and vacuum drying to constant weight to obtain an MXene preparation residue. 3.The method of recycling MXene preparation residue according to claim 2, characterized in that, The etchant is HCl / LiF; the mass ratio of the introduced etchant to the MAX phase powder is 1:(0.5-3). 4.The method of recycling MXene preparation residue according to claim 2, characterized in that, The temperature for the heating and stirring reaction in step 1) is 40-80 DEG C, and the time is 12-96h. 5.The recycling method of MXene preparation residue according to claim 2, characterized in that, The intercalation agent is one or several of ethanol, DMSO, TMAOH, TBAOH, wherein the mass ratio of the intercalation agent to the MAX phase powder is 1:(5-20).

6. Ti3C2T prepared by the recycling method of MXene preparation residues according to any one of claims 1 to 5 x - Ti3AlC2 / PVA composite film.

7. The Ti3C2T of claim 6 x Use of the Ti3AlC2 / PVA composite film in the field of biosensors, characterized in that, When the strain is below 10%, the GF is as high as 533, and when the strain is greater than 10%, the GF is 299.

Images