A bnqds / p (vdf-trfe) nanofiber membrane and a preparation method thereof

Abstract

The application provides a BNQDs / P(VDF-TrFE) nanofiber membrane and a preparation method thereof. The nanofiber membrane is composed of boron nitride quantum dots (BNQDs) and poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)). The preparation method comprises the following steps: synthesizing BNQDs with controllable size by adopting an ultrasonic-assisted liquid phase exfoliation method and a solvothermal method; and introducing the BNQDs with a large number of trap states into the P(VDF-TrFE) nanofiber membrane by using an electrospinning technology. In the application, the addition of the BNQDs makes the Young's modulus of the composite nanofiber membrane increase by 160.0% compared to the original composite, and the tensile property increases by 120%. This is mainly because the large number of trap states in the BNQDs makes the photoresponsivity increase by 847.8%. The prepared BNQDs / P(VDF-TrFE) nanofiber membrane can be used for manufacturing advanced stretchable optoelectronic devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optoelectronics, in particular to a BNQDs / P(VDF-TrFE) nanofiber membrane and a preparation method thereof. BACKGROUND

[0002] Wearable optoelectronics have attracted increasing attention due to their unprecedented application potential, such as stretchable light-emitting diodes, foldable batteries, twisted photodetectors, curved touch panels, portable solar cells, and soft electric skins, etc. Among them, photodetectors are electronic devices that convert light into electricity under light irradiation, which have been widely used in radiometric calibration, fire detection, satellite optical communication, and biosensing, etc. The most advanced photodetectors on the market are mainly based on silicon materials and wide-bandgap semiconductors. However, these materials have the disadvantages of high cost, slow response, poor flexibility, etc., which greatly limit their application range. Environmentally unfriendly, heavy metal pollution is a major problem. Recently, stretchable photodetectors based on ZnO and Zn2SnO4 nanowires and Ag nanowire electrodes have been prepared and shown good stretchability. However, such devices need to use elastomer matrix (polydimethylsiloxane, PDMS) or polyethylene terephthalate (PET) as a substrate, and their response speed is very slow. The rise time of the pulse response of the ZnO nanowire photodetector under 100% strain is 51.7 s, and the decay time is 12.2 s. Although the strain of the Zn2SnO4 nanowire photodetector is reduced to 50%, the rise time of the pulse response can be slightly reduced to 0.8 s, and the decay time is reduced to 3 s, but these values are still not comparable to the values of the single nanowire photodetector which is not stretchable within milliseconds. This is mainly due to the reduction of the Schottky barrier height induced by the nanowire junction and the narrowing of the width, which limits the transport of carriers. Therefore, there is an urgent need for simpler synthesis techniques and new methods to improve performance and reduce energy consumption.

[0003] P(VDF-TrFE) is a ferroelectric polymer with excellent piezoelectric and electro-optic properties, as well as excellent mechanical properties. However, it has poor photosensitivity. Based on this, in order to improve the light response of the ferroelectric polymer, BNQDs with numerous trap states are introduced into the ferroelectric polymer nanofiber in the range of 2.7-3.4 eV. BNQDs do not contain heavy metals and are environmentally friendly, and they have three effective luminescent centers: N vacancy point defects (3-3.4 eV), carbonene structures at sawtooth edges (2.9 eV), and BO x -(2.7-3.0 eV). The existence of these trap states in P(VDF-TrFE) can effectively reduce its lowest unoccupied molecular orbital (LUMO) and rearrange the interface Fermi level. In this case, the energy barrier of hole injection is reduced, thereby improving the external quantum efficiency (EQEs) of the photodetector prepared by the ferroelectric polymer P(VDF-TrFE). SUMMARY

[0004] (1) Technical problems to be solved

[0005] P(VDF-TrFE) is a ferroelectric polymer with excellent piezoelectric and electro-optic properties, as well as excellent mechanical properties. However, it has poor photosensitivity.

[0006] (2) Technical solutions

[0007] To solve the above technical problems, the present application specifically adopts the following scheme:

[0008] In this work, a BNQDs / P(VDF-TrFE) nanofiber membrane was first developed. BNQDs with controllable size were synthesized by ultrasonic-assisted liquid phase exfoliation and solvothermal method, and then BNQDs with a large number of trap states were introduced into the ferroelectric P(VDF-TrFE) nanofiber membrane by electrospinning technology. The method comprises the following steps:

[0009] S1, uniformly sized commercial boron nitride powder is dispersed in DMF, stirred, and after removing large BN particles by centrifugation, a BNNSs dispersion is obtained.

[0010] S2, the BNNSs dispersion is subjected to solvothermal treatment, the synthesized suspension is centrifuged and filtered through a microporous membrane to obtain a BNQDs solution.

[0011] S3, P(VDF-TrFE) powder is dissolved in DMF solvent, after stirring, BNQDs solution is added to the polymer solution as an electrospinning precursor solution.

[0012] S4, a BNQDs / P(VDF-TrFE) nanofiber membrane is prepared by electrospinning technology.

[0013] Preferably, the size of the commercial boron nitride powder in step S1 is 10 µm, the mass is 3-5 g, and the amount of DMF is 100-180 mL.

[0014] Preferably, the solvothermal treatment temperature in step S2 is 150-200°C, and the treatment time is 20-24 hours.

[0015] Preferably, the stirring time in step S3 is 4-6 hours.

[0016] Preferably, the BNQDs solution is added into the polymer solution in step S3, so that the final concentration of the BNQDs is 2wt%-4wt%.

[0017] Preferably, the precursor solution for electrospinning in step S4 is the BNQDs / P(VDF-TrFE) solution. The concentration of P(VDF-TrFE) in the BNQDs / P(VDF-TrFE) solution is between 8wt%-16wt%. During the electrospinning process, the distance between the spinneret and the collector is 100-110 cm; the flow rate in the syringe is 6-10 ml / h. The rotation speed of the collector is 1000-1200 rpm.

[0018] (III) Beneficial effects

[0019] The present application first successfully synthesizes the BNQDs modified P(VDF-TrFE) nanofiber membrane with controllable morphology by using the electrospinning technology. The BNQDs modified P(VDF-TrFE) nanofiber membrane has good hexagonal crystallinity, and rich B-O functional groups are introduced during the solvothermal process. The BNQDs modified P(VDF-TrFE) nanofiber membrane has pure beta phase, and the diameter can reach hundreds of nanometers, which can be adjusted by changing the concentration of P(VDF-TrFE).

[0020] In the present application, after being modified by the BNQDs, the Young's modulus of the P(VDF-TrFE) nanofiber membrane is increased by 160.0% than the original, and the tensile property is increased by 120%. The light detector made of the BNQDs / P(VDF-TrFE) nanofiber membrane has significantly improved light responsiveness.

[0021] The present application makes the photoelectric detector have good tensile property, and after being stretched to 100% strain, there is almost no obvious performance decline, and the fast rise time (15.6 ms) and the fast decay time (12.6 ms) are maintained. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Figure 1 is a schematic diagram of the synthesis steps of the BNQDs and the P(VDF-TrFE) nanofiber membrane in the present application. (a) is a schematic diagram of the two-step synthesis of the BNQDs. (b) is a device for electrospinning setting.

[0023] Figure 2 Figure 2 is the XPS spectra of (a) C 1s, (b) B 1s, and (c) N 1s in the BNQDs prepared in Example 1 of the present application.

[0024] Figure 3 Figure 3 is the XRD pattern of the pure, 2wt% and 4wt% BNQDs modified P(VDF-TrFE) nanofiber membrane in Examples 1-3 of the present application.

[0025] Figure 4Photoluminescence spectra and photo-current of the device for BNQDs of the present application embodiment 3. (a) Photoluminescence spectra and photoluminescence excitation spectra of the sample. The inset is the photo of the prepared BNQDs solution under visible and UV light. (b) I-V curves of BNQDs / P(VDF-TrFE) nanofiber film under irradiation. The inset describes the schematic diagram of the light detector structure measured. (c) Modulation of the photo-current of P(VDF-TrFE) and BNQDs / P(VDF-TrFE) at a bias of 2 V. (d) Photo-current of BNQDs / P(VDF-TrFE) nanofiber films with different diameters.

[0026] Figure 5 Modulation of the photo-current of the device for BNQDs of the present application embodiment 3 under different tensile strains.

[0027] Figure 6 Schematic diagram of the interaction between BNQDs and P(VDF-TrFE) chains for the BNQDs / P(VDF-TrFE) nanofiber film photodetector of the present application embodiment 3 in the relaxed state and the strained state. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0029] Embodiment 1

[0030] A preparation method of a BNQDs / P(VDF-TrFE) nanofiber film, comprising the following steps:

[0031] 1) BNNSs synthesis: 3 g of commercial boron nitride powder with uniform size of 10 µm is weighed using an electronic analytical balance, and the boron nitride powder is dispersed into 150 mL of DMF. The solution is stirred in a clockwise direction, and after stirring for 8 h, large BN particles are removed by centrifugal force to obtain a BNNSs dispersion.

[0032] 2) Synthesis of BNQDs: 5 μL of DMF solvent is sprayed on the bottom of a 50 mm petri dish using a spray pen, and the petri dish is inverted in a pre-formed closed space with a DMF solvent atmosphere on a 100°C heating table. The BNNSs dispersion is heat-treated in air at 150°C for 24 hours. After centrifugation and filtration through a microporous membrane, a BNQDs solution is obtained.

[0033] 3) Preparation of BNQDs / P(VDF-TrFE) solution: 25 g of P(VDF-TrFE) powder was weighed using an electronic analytical balance in a glass bottle, then 150 ml of DMF was added, and it was placed in a 60°C vacuum drying oven for 12 h to make P(VDF-TrFE) completely dissolved in the solvent, then it was taken out and stirred using a magnetic stirrer to remove bubbles in the solution, and a homogeneous and bubble-free solution was prepared to obtain pure P(VDF-TrFE) solution. The pure P(VDF-TrFE) solution was divided into three equal parts, and the first part was stirred using a magnetic stirrer to remove bubbles in the solution, and the obtained pure P(VDF-TrFE) solution was used as the precursor for electrospinning.

[0034] 4) Preparation of BNQDs / P(VDF-TrFE) nanofiber membrane by electrospinning technology: The pure P(VDF-TrFE) solution was poured into the syringe used for electrospinning, and the positive electrode of the high-voltage power supply was clamped on the needle, and the negative electrode was connected to the receiving drum device. The distance between the spinneret and the collector was set to 110 cm; the flow rate in the syringe was 6-10 mL / h; and the rotating speed of the collector was 1000 revolutions per second. After the spinning was completed, the aluminum foil used to receive the fibers was taken out and placed in a vacuum drying oven at 60°C for 12 h to obtain a pure P(VDF-TrFE) nanofiber membrane.

[0035] Example 2

[0036] 1) Synthesis of BNNSs: 3 g of commercial boron nitride powder with uniform size of 10 pm was weighed using an electronic analytical balance, and the boron nitride powder was dispersed in 150 mL of DMF, and the solution was stirred in a clockwise direction. After stirring for 8 h, the large BN particles were removed by centrifugal force to obtain a BNNSs dispersion.

[0037] 2) Synthesis of BNQDs: 5 pL of DMF solvent was sprayed on the bottom of a 50 mm petri dish using a spray pen, and the petri dish was inverted in a pre-formed closed space with a DMF solvent atmosphere on a 100°C heating table. The BNNSs dispersion was heat-treated at 150°C in air for 24 hours. The synthesized suspension was centrifuged and filtered through a microporous membrane to obtain a BNQDs solution.

[0038] 3) Preparation of BNQDs / P(VDF-TrFE) solution: 25 g of P(VDF-TrFE) powder was weighed in a glass bottle using an electronic analytical balance, then 150 ml of DMF was added, and it was placed in a 60°C vacuum drying oven for 12 h to make P(VDF-TrFE) completely dissolved in the solvent, then it was taken out and stirred with a magnetic stirrer to remove bubbles in the solution, and a homogeneous and bubble-free solution was obtained to obtain a pure P(VDF-TrFE) solution. The pure P(VDF-TrFE) solution was divided into three equal parts, and the second part was added to the final concentration of 2wt% BNQDs, and the magnetic stirrer was used to stir to remove bubbles in the solution, and the obtained 2wt% BNQDs / P(VDF-TrFE) solution was used as the precursor of electrospinning.

[0039] 4) Preparation of BNQDs / P(VDF-TrFE) nanofiber membrane by electrospinning technology: 2wt% BNQDs / P(VDF-TrFE) solution was poured into the syringe used for electrospinning, and the positive electrode of the high-voltage power supply was clamped on the needle, and the negative electrode was connected to the receiving drum device. The distance between the spinneret and the collector was set to 110 cm; the flow rate in the syringe was 6-10 mL / h; and the rotation speed of the collector was 1000 revolutions per second. After spinning, the aluminum foil for receiving the fibers was taken out and placed in a vacuum drying oven at 60°C for 12 h to obtain a BNQDs / P(VDF-TrFE) nanofiber membrane with a 2wt% BNQDs concentration.

[0040] Example 3

[0041] A method for preparing a BNQDs / P(VDF-TrFE) nanofiber membrane, comprising the following steps:

[0042] 1) Synthesis of BNNSs: 3 g of commercial boron nitride powder with uniform size of 10 pm was weighed using an electronic analytical balance, and the boron nitride powder was dispersed in 150 mL of DMF. The solution was stirred in a clockwise direction, and after 8 h of stirring, large BN particles were removed by centrifugal force to obtain a BNNSs dispersion.

[0043] 2) Synthesis of BNQDs: 5 μL of DMF solvent was sprayed on the bottom of a 50 mm petri dish using a spray pen, and the petri dish was inverted on a pre-formed closed space with a DMF solvent atmosphere in a 100°C heating table. The BNNSs dispersion was heat-treated at 150°C for 24 hours in air. The synthesized suspension was centrifuged and filtered through a microporous membrane to obtain a BNQDs solution.

[0044] 3) Preparation of BNQDs / P(VDF-TrFE) solution: 25 g of P(VDF-TrFE) powder was weighed in a glass bottle using an electronic analytical balance, then 150 ml of DMF was added, and it was placed in a 60°C vacuum drying oven for 12 h to make P(VDF-TrFE) completely dissolved in the solvent, then it was taken out and stirred using a magnetic stirrer to remove the bubbles in the solution, and a homogeneous and bubble-free solution was prepared to obtain a pure P(VDF-TrFE) solution. The pure P(VDF-TrFE) solution was divided into three equal parts, and the third part was taken and added with BNQDs at a final concentration of 4wt%, and a magnetic stirrer was used to stir to remove the bubbles in the solution, and the obtained 4wt% BNQDs / P(VDF-TrFE) solution was used as the precursor for electrospinning.

[0045] 4) Preparation of BNQDs / P(VDF-TrFE) nanofiber membrane by electrospinning technology: Pour the 4wt% BNQDs / P(VDF-TrFE) solution into the syringe used for electrospinning, and clamp the positive electrode of the high-voltage power supply on the needle, and the negative electrode is connected to the receiving drum device. The distance between the spinneret and the collector is set to 110 cm; the flow rate in the syringe is 6-10 mL / h; and the rotating speed of the collector is 1000 revolutions per second. After the spinning is completed, the aluminum foil used for receiving the fibers is taken out and placed in a vacuum drying oven at 60°C for 12 h to obtain a BNQDs / P(VDF-TrFE) nanofiber membrane with a BNQDs concentration of 4wt%.

[0046] Figure 1 Schematic diagram of the two-step synthesis of BNQDs in the present application and the electrospinning device used in the present application.

[0047] In the present application, the use of the multimodal Gaussian method, it is observed that Figure 2 In (a) of FIG. 6, the C 1s of BNQDs has three peaks at 285.0 eV, 286.7 eV and 289.0 eV, respectively, corresponding to the C-C / C=C, C-N and C-N / C-O-B bonds. It can be seen that, compared with BNNSs, the C-N and C-N / C-O-B bond strengths are significantly increased due to the solvothermal reaction of BNQDs. In addition, for Figure 2 In (b) of FIG. 6, two peaks near 190.8 eV and 192.3 eV are found in both BNNSs and BNQDs, revealing the existence of B-O and B-N bonds. Figure 2 In (c) of FIG. 6, the N 1s spectrum of BNQDs has two peaks at 398.3 eV and 399.5 eV, respectively, corresponding to B-N and N-C / N-O bonds. Two similar peaks are also found in the BNNS sample.

[0048] As shown in FIG. 7, the BNQDs / P(VDF-TrFE) nanofiber membrane has a smooth and uniform surface, and the BNQDs are uniformly dispersed in the P(VDF-TrFE) matrix. Figure 3As shown, there is pure β phase in both P(VDF-TrFE) nanofiber membrane and BNQDs loaded on P(VDF-TrFE) nanofiber membrane. With the increase of BNQDs concentration, the peak position slightly shifts to small angle.

[0049] Figure 4 The photoluminescence (PL) spectrum and excitation spectrum (PLE) of BNQDs were further studied in the middle (a), and the absorption peak appeared at 293.0 nm, which was related to the surface chemistry and effective size. Figure 4 The I-V curve of the tested BNQDs / P(VDF-TrFE) nanofiber membrane photodetector structure is shown in the middle (b), which shows that the BNQDs / P(VDF-TrFE) nanofiber membrane exhibits significant photoresponse under light. Figure 4 The photoelectric current modulation of P(VDF-TrFE) nanofiber membrane and BNQDs / P(VDF-TrFE) nanofiber membrane device is shown in the middle (c). Compared with P(VDF-TrFE) nanofiber membrane device, BNQDs loaded P(VDF-TrFE) nanofiber membrane exhibits stronger modulation. Under the condition of power density of 0.5 mW / cm 2 , bias voltage of 2 V, the photocurrent increases significantly from 67.1 Pa to 635.2 Pa. This huge enhancement of light responsiveness (increased by 847.8%). Figure 4 The middle (d) shows that when the diameter of BNQDs / P(VDF-TrFE) nanofiber membrane changes from 197.3 nm to 142.1 nm, the light responsiveness increases by 832.1%.

[0050] As Figure 5 shown, the on-off photocurrent performance of BNQDs / P(VDF-TrFE) nanofiber membrane photodetector under different strain ranges from 0% to 100% was further studied. The photocurrent slightly decreases with the increase of strain, but when the strain reaches 100%, the detector still exhibits stable periodic modulation response. Even under 100% strain, the photodetector can work well, which indicates that the flexibility of the detector is very high.

[0051] Finally, as Figure 6 shown, when there is no strain, the charge distribution on both sides is balanced. When there is strain, due to the piezoelectric effect, one side of the P(VDF-TrFE) NF has a higher potential than the other side, resulting in a stronger piezoelectric potential between the two sides of the BNQDs / P(VDF-TrFE) NF.

[0052] The embodiment develops a BNQDs modified P(VDF-TrFE) nanofiber membrane for the first time. The BNQDs have an average size of about 2.9 nm, have good hexagonal crystallinity, and introduce abundant B-O functional groups in the solvothermal process. The BNQDs / P(VDF-TrFE) nanofiber membrane obtained by electrospinning has a pure beta phase and a diameter of several hundred nanometers, which can be adjusted by changing the P(VDF-TrFE) concentration. After being modified by the BNQDs, the Young's modulus of the P(VDF-TrFE) nanofiber membrane is increased by 160.0%, and the tensile property is increased by 120%. The photo detector made of the BNQDs / P(VDF-TrFE) nanofiber membrane has a significantly improved photoresponsivity (increased by 847.8%), which is related to the large number of trap states of the BNQDs and the continuity of the nanofiber. In addition, the photoelectric detector has good tensile property and almost no obvious performance decline after being stretched to 100% strain, and maintains a fast rise time (15.6 ms) and a fast decay time (12.6 ms). Therefore, the photoelectric detector based on the BNQDs / P(VDF-TrFE) nanofiber membrane has great application prospects in emerging human-computer interaction devices and stretchable implantable electronic devices.

[0053] The present application modifies the P(VDF-TrFE) nanofiber membrane with BNQDs, which significantly improves the Young's modulus and tensile property of the P(VDF-TrFE) nanofiber membrane. The photo detector based on the BNQDs / P(VDF-TrFE) nanofiber membrane has a significantly improved photoresponsivity. The photoelectric detector based on the present application has great application prospects in emerging human-computer interaction devices and stretchable implantable electronic devices.

[0054] The above embodiments are only used to illustrate the present application, but not to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, all equivalent technical solutions belong to the scope of the present application, and the actual protection scope of the present application should be defined by the claims.

Claims

1. Use of BNQDs / P(VDF-TrFE) nanofiber membranes for the preparation of photodetectors, characterized by, The nanofiber membrane is composed of boron nitride quantum dots BNQDs and poly(vinylidene-fluoride-trifluoroethylene) P(VDF-TrFE), wherein the P(VDF-TrFE) nanofiber membrane is modified by the BNQDs, and the average size of the BNQDs is 2.9 nm. The preparation method of the nanofiber membrane comprises the following steps: an ultrasonic-assisted liquid phase exfoliation method and a solvothermal method are used to synthesize the BNQDs; and the BNQDs are introduced into the P(VDF-TrFE) nanofiber membrane by using an electrospinning technology.

2. Use according to claim 1, wherein The preparation method of the BNQDs / P(VDF-TrFE) nanofiber membrane comprises the following steps: 1) uniformly dispersing boron nitride powder into DMF, stirring, removing large-particle boron nitride by centrifugation, and obtaining a boron nitride nanosheet BNNSs dispersion; 2) performing solvothermal treatment on the BNNSs dispersion, centrifuging the synthesized suspension, and filtering the suspension through a microporous membrane to obtain a BNQDs solution; 3) dissolving P(VDF-TrFE) powder in a DMF solvent, stirring in a magnetic stirrer to fully dissolve the P(VDF-TrFE) powder, then adding BNQDs solution of different mass, and stirring to obtain a BNQDs / P(VDF-TrFE) solution; 4) using an electrospinning technology to prepare a BNQDs / P(VDF-TrFE) nanofiber membrane.

3. Use according to claim 2, characterized in that, In the step 1), the size of the commercial boron nitride powder is 10 µm, the amount is 3-5 g, and the amount of DMF is 100-180 mL.

4. Use according to claim 2, characterized in that, In the step 2), the solvothermal treatment temperature is 150-200 ℃, and the treatment time is 20-24 hours.

5. Use according to claim 2, characterized in that, In the step 3), the stirring time is 4-6 hours.

6. Use according to claim 2, characterized in that, In the step 3), the concentration of the BNQDs in the BNQDs / P(VDF-TrFE) solution is 2wt%-4wt%.

7. Use according to claim 2, characterized in that, In the step 4), the electrospinning precursor solution is the BNQDs / P(VDF-TrFE) solution.

8. The use according to claim 2, characterized in that, In the step 4), the concentration of P(VDF-TrFE) in the BNQDs / P(VDF-TrFE) solution is 8wt%-16wt%.

9. The use according to claim 2, characterized in that, In the step 4), the distance between the spinneret and the collector is 100-120 cm during the electrospinning process; the flow rate in the syringe is 6-10 mL / h; and the rotation speed of the collector is 1000-1200 revolutions / second.

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