CN115386973A - A method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning - Google Patents

Abstract

The invention relates to a method for preparing side-by-side heterojunction nano-fibers by single-source double-field electrostatic spinning, which comprises the steps of firstly, respectively preparing a precursor solution I containing indium nitrate pentahydrate/polyvinylpyrrolidone and a precursor solution II containing stannous chloride dihydrate/polyvinylpyrrolidone; then respectively injecting the precursor solution I and the precursor solution II into a glass injector I and a glass injector II which are arranged in a single-source double-field electrostatic spinning device in parallel, and adjustingSpinning is carried out by the voltage of a direct-current high-voltage power supply, taylor cones ejected by a needle head I and a needle head II are entangled, and a nano-fiber membrane is obtained on a stainless steel collecting plate; finally, annealing the nanofiber membrane to obtain SnO ₂ /In ₂ O ₃ Side-by-side heterojunction nanofiber materials. The method is convenient to operate, easy to popularize and apply in a large scale, stable in filament output state in the electrostatic spinning process, good in spinning effect and suitable for preparing the heterojunction nano-fiber of any combination of MOS materials such as NiO, znO and the like.

Description

A method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning

technical field

The invention relates to the technical field of preparation of one-dimensional nanomaterials, in particular to a method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning.

Background technique

One-dimensional nanomaterials (nanofibers, nanobelts, nanotubes, nanorods, and various one-dimensional nanostructure arrays) have large specific surface area, high crystallinity, low defect level, easy size control, small size and surface effects, etc. advantages have received extensive attention. Metal-oxide-semiconductor (MOS) materials have the advantages of tunable bandgap, easy preparation, low cost, and easy doping and modification. One-dimensional nano-MOS materials have been widely used in research fields such as gas sensors, photodetectors, supercapacitors, and ion batteries due to the advantages of both. The adsorption and reaction provides a large number of active sites, effectively improving the efficiency of adsorption and reaction. In addition, the nonwoven two-dimensional sheet structure interwoven by one-dimensional nano-MOS materials has certain mechanical flexibility and mechanical strength, which can be applied to flexible wearable electronic devices.

Although one-dimensional nano-MOS materials have the above-mentioned advantages, in many application fields, due to the characteristics of the material itself, it is difficult for a single MOS material to meet the requirements of various performance indicators at the same time, and there will be certain defects in some performances. Therefore, many studies have used the strategy of combining two MOS materials to form a heterogeneous structure to make up for performance defects and improve the overall performance of the material. The formation of the heterostructure can transfer electrons from high-energy states to unoccupied low-energy states, separate electrons from holes, effectively inhibit the recombination of electron-hole pairs, and prolong the lifetime of carriers. At the same time, the combination of two MOS materials with their own advantages can make the composite material have the advantages of both, thus effectively improving the overall performance of the device.

At present, the preparation methods of MOS-based heterojunction nanofiber materials mainly include: (1) Single MOS nanofibers are prepared by electrospinning method, molecular technology preparation method, etc., and then hydrothermal method, solvothermal method and chemical vapor deposition method are used. and other methods to post-treat the prepared MOS nanofiber precursor, and modify another MOS material on the surface of the precursor fiber to prepare a heterogeneous structure; (2) prepare a precursor solution containing two or more precursor metal salts at the same time, Then, the electrospinning method was used to prepare heterojunction nanofibers; (3) the precursor solutions of two MOS materials were prepared respectively, and the core-shell nanofibers coated with one material and another material were prepared by coaxial electrospinning; (4) Precursor solutions of two MOS materials were prepared respectively, and side-by-side nanofibers were prepared by double-power and double-electrode spinning technology. However, the above method still has the following problems: i) post-processing the prepared nanofiber monofilament can only modify the surface of the fiber with tiny particles, and it is difficult to form a large-area heterogeneous structure. However, excessive density of particle modification will cause the fiber to be covered by particles, which hinders the exposure of the fiber material, reduces the number of active sites, and has a negative impact on the improvement of performance. ii) In the heterojunction materials prepared by electrospinning using spinning solutions containing different material precursor metal salts, grains of multiple MOS materials co-exist in a single nanofiber. Due to the different energy level structures of different semiconductor materials, potential barriers will be formed at the grain boundaries, which will cause the bending of the energy band of the semiconductor material and hinder the transmission of electrons between the grains of different materials. iii) The core-shell heterostructure prepared by the coaxial electrospinning method, although the two materials produced a large area of bonding, the core layer material was completely or mostly covered by the shell material, which hindered the core The exposure of the layer material prevents the active sites on the surface of the core layer material from being exposed and then reacts with the target substance, thereby affecting the further improvement of the performance. iv) Dual-power dual-electrode spinning technology requires two power devices to work at the same time, which increases the energy consumption of the preparation process.

Contents of the invention

The technical problem to be solved by the present invention is to provide a simple and scalable single-source double-field electrospinning method for preparing side-by-side heterojunction nanofibers.

In order to solve _the above problems, a method for preparing side-by-side heterojunction nanofibers by single- _source double-field electrospinning according to the present invention is characterized in that: the method refers to firstly preparing ·5H ₂ O)/polyvinylpyrrolidone (PVP) precursor solution Ⅰ, containing dihydrate stannous chloride (SnCl ₂ ·2H ₂ O)/polyvinylpyrrolidone (PVP) precursor solution II; then the precursor Solution Ⅰ and precursor solution Ⅱ were respectively injected into the glass syringe Ⅰ and glass syringe Ⅱ placed in parallel in the single-source double-field electrospinning device, and the voltage of the DC high-voltage power supply was adjusted for spinning, and the needles Ⅰ and Ⅱ were ejected The Taylor cones of the SnO ₂ /In ₂ O ₃ side-by-side heterojunction nanofibrous material are obtained by entanglement to obtain a nanofiber film on a stainless steel collecting plate; finally, the nanofiber film is annealed.

The weight average molecular weight of the polyvinylpyrrolidone is 1,300,000.

The precursor solution I refers to the solution A obtained by dissolving 1.5 mmol (0.5864g) InN ₃ O ₉ 5H ₂ O in 5 ml of absolute ethanol and stirring evenly; then dissolving 0.75 g of PVP powder in 5 ml of N , in the N-dimethylformamide solution, stir the obtained solution B; finally, mix the solution A and the solution B and stir for 12 h to obtain.

The precursor solution II refers to the solution C obtained by dissolving 0.15 mmol (0.0338g) SnCl ₂ ·2H ₂ O in 5 ml of absolute ethanol and stirring evenly; then dissolving 0.75 g of PVP powder in 5 ml of N,N - In the dimethylformamide solution, stir the obtained solution D; finally, mix the solution C and the solution D, and stir for 12 h to obtain.

The single-source double-field electrospinning device includes a DC high-voltage power supply, a stainless steel collecting plate, and two iron stands; the two iron stands are placed opposite each other, and a glass syringe I with a needle I is fixed on one of the iron stands A glass syringe II with a needle II is fixed on the other iron stand; the needle I is connected to the positive pole of the DC high-voltage power supply through a wire I; the needle II is grounded through a wire III; The stainless steel collecting plate is arranged between the iron frames, and the stainless steel collecting plate is connected to the negative pole of the DC high voltage power supply through the wire II.

Both the glass syringe I and the glass syringe II were perpendicular to the stainless steel collecting plate.

The voltage of the DC high-voltage power supply is 8-14 kV.

The distance between the needle I and the needle II is 3-5 cm.

The distances between the needle I and the needle II and the stainless steel collecting plate are both 10-15 cm.

The conditions for the annealing treatment refer to using a tube furnace, annealing in an air atmosphere, raising the temperature to 300°C, holding it for 60 minutes, then raising the temperature to 500°C, holding it for 120 minutes, and cooling to room temperature with the furnace.

Compared with the prior art, the present invention has the following advantages:

1. The present invention utilizes a single-source double-field electrospinning device to construct an electric field between two needles and between two needles and a collecting plate through a DC high-voltage power supply, so that two different MOS nanofibers are in the dual electric field. Under the combined action, they are adsorbed together by electrostatic adsorption force to form a long-range and large-area heterostructure, thus effectively exerting the positive role of the heterojunction in the working process of the device.

2. In the side-by-side heterostructure constructed in the present invention, two kinds of MOS nanofibers are combined side by side. Except for the bonding interface of the two materials, most of the surfaces of the two materials are exposed, allowing more surface active sites to participate in the reaction. At the same time, this side-by-side heterostructure effectively avoids the loss of the number of active sites caused by mutual coating of two different materials.

3. The single-source double-field electrospinning device in the present invention has simple structure, convenient operation, and easy large-scale popularization and application.

4. By adopting the method of the present invention, the state of filament output during the electrospinning process is stable, and the spinning effect is good. At the same time, the side-by-side heterojunction material constructed by the present invention does not simply blend the two materials together, but makes the two materials maintain the microstructure of nanofibers, that is, retains the advantages of the one-dimensional nanostructure of the two materials. At the same time, in a single nanofiber, there are only crystal grains of a certain kind of MOS material, and no potential barrier between different kinds of grains is formed, which effectively ensures the integrity of the carrier transport channel.

5. The present invention utilizes a single-source double-field electrospinning device to prepare a SnO ₂ /In ₂ O ₃ heterojunction nanofiber material in one step, which can be applied to any combination of NiO, ZnO and other MOS materials. The preparation method is simple and suitable for mass production.

Description of drawings

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Fig. 1 is a schematic diagram of a single-source double-field electrospinning device of the present invention.

In the figure: 1—DC high-voltage power supply; 2—glass syringe Ⅰ; 3—glass syringe Ⅱ; 4—needle Ⅰ; 5—needle II; 6—iron stand; 7—stainless steel collecting plate; II; 10—wire III.

Figure 2 shows the DC voltage values for stable spinning under different _d1 distances (the distance between the needle head I and the needle head II) and different _d2 distances (the distance between the needle head I and the stainless steel collecting plate) of the present invention.

Figure 3 is a diagram of the stable spinning state of needle I and needle II at different d ₁ under the condition of d ₂ = 15 cm according to the present invention: (a) 3 cm, (b) 4 cm and (c) 5 cm.

Figure 4 shows the SnO ₂ /In ₂ O ₃ side-by-side heterojunction nanofibers ((a) 3 cm, (b) 4 cm and (c) 5 cm prepared under the condition of d ₂ = 15 cm and different d ₁ cm) and SEM images of indium oxide nanofibers (d).

Fig. 5 is an XRD pattern of SnO ₂ /In ₂ O ₃ heterostructure nanofibers prepared in the present invention.

Detailed ways

A method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning: the method refers to the preparation of precursors containing indium nitrate pentahydrate (InN ₃ O ₉ 5H ₂ O)/polyvinylpyrrolidone (PVP) respectively Precursor solution I, precursor solution II containing stannous chloride dihydrate (SnCl ₂ 2H ₂ O)/polyvinylpyrrolidone (PVP); In the glass syringe Ⅰ2 and glass syringe Ⅱ3 placed in parallel in the electrospinning device, the voltage of the DC high-voltage power supply 1 was adjusted to 8-14 kV for spinning, and the Taylor cones ejected from the needles Ⅰ4 and Ⅱ5 were entangled together. The nanofiber membrane was obtained on the stainless steel collecting plate 7; finally, the nanofiber membrane was annealed in an air atmosphere in a tube furnace, heated to 300 °C, kept for 60 min, then raised to 500 °C, kept for 120 min, and then cooled to room temperature with the furnace , that is, the SnO ₂ /In ₂ O ₃ side-by-side heterojunction nanofibrous material.

Wherein: the weight average molecular weight of polyvinylpyrrolidone is 1,300,000.

Precursor solution I refers to the solution A obtained by dissolving 1.5 mmol (0.5864g) InN ₃ O ₉ 5H ₂ O in 5 ml of absolute ethanol and stirring evenly; then dissolving 0.75 g of PVP powder in 5 ml of N,N - In the dimethylformamide solution, stir the obtained solution B; finally, mix solution A and solution B and stir for 12 h to obtain a colorless and transparent clear solution.

Precursor solution II refers to solution C obtained by first dissolving 0.15 mmol (0.0338g) SnCl ₂ ·2H ₂ O in 5 ml of absolute ethanol and stirring evenly; then dissolving 0.75 g of PVP powder in 5 ml of N,N-di In the methylformamide solution, stir the obtained solution D; finally, mix the solution C and solution D and stir for 12 h to obtain a colorless and transparent clear solution.

As shown in FIG. 1 , the single-source double-field electrospinning device includes a DC high-voltage power supply 1 , a stainless steel collecting plate 7 and two iron stands 6 . Two iron stands 6 are placed opposite each other, and one of the iron stands 6 is fixed with a glass syringe I2 with a needle I4, and the other iron stand 6 is fixed with a glass syringe II3 with a needle II5; the needle I4 is connected to the DC high-voltage power supply through the wire I8 The positive pole of 1 is connected; the needle II5 is grounded through the wire III10; the stainless steel collecting plate 7 is arranged between the two iron frames 6, and the stainless steel collecting plate 7 is connected with the negative pole of the DC high voltage power supply 1 through the wire II9. Both the glass syringe I2 and the glass syringe II3 are perpendicular to the stainless steel collecting plate 7 . The distance between needle I4 and needle II5 was 3-5 cm; the distances between needle I4 and needle II5 and the stainless steel collecting plate 7 were both 10-15 cm.

[Working principle] Using a single DC high-voltage power supply 1, two electric fields are respectively constructed between the needle head I4 and the stainless steel collecting plate 7, and between the needle head I4 and the needle head II5. The stainless steel collecting plate 7 is connected to the negative pole of the power supply and placed directly below the middle of the needles I4 and II5. When the circuit is connected, under the action of the double electric field, needles I4 and needles II5 can simultaneously spray, and the two kinds of nanofibers that are sprayed are adsorbed together due to electrostatic interaction to form heterojunction nanofibers arranged side by side. , and are deposited together on the stainless steel collecting plate 7 under the action of gravity and electric field. This method constructs a long-range, large-area heterogeneous structure and the two materials do not wrap each other, while maintaining the microscopic morphology of one-dimensional nanomaterials and maintaining the integrity of the conductive channel.

Example 1 A method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning:

The precursor solution I was injected into the glass syringe I2 in the single-source double-field electrospinning device, and the precursor solution II was injected into the glass syringe II3 of the device. The needle I4 is connected to the positive pole of the DC high voltage power supply 1 through the wire I8; the needle II5 is grounded through the wire III10; the stainless steel collecting plate 7 is connected to the negative pole of the DC high voltage power supply 1 through the wire II9.

Adjust d ₁ within the range of 3-5 cm, adjust d ₂ within the range of 10-15 cm, adjust the voltage value of the DC high-voltage power supply 1, so that both the needles I4 and II5 of the spinning device have silk ejected, and A stable spinning state is reached (Figure 2). At the same time, the Taylor cones ejected from the two needles are entangled together under the action of the electric field between the two needles in the spinning device, and the positively charged nanofibers containing InN ₃ O ₉ 5H ₂ O generate an induced negative charge on the surface. Nanofibers containing SnCl ₂ 2H ₂ O attract each other to form a side-by-side heterostructure material (Fig. 3). Under certain d ₁ and d ₂ values, it is difficult to reach a stable Taylor cone entanglement state below or above the stable spinning voltage. The material falls onto the stainless steel collecting plate 7 under the action of the electric field between the needle and the stainless steel collecting plate 7 and gravity to obtain a nanofibrous film.

The obtained nanofibrous membrane was removed with tweezers and annealed in a tube furnace. The annealing heating program is as follows: the heating rate is 2 ℃min ^-1 , the temperature is raised to 300 ℃, and the temperature is kept for 60 minutes, and then the temperature is raised to 500℃ at a heating rate of 2 ℃min ^-1 , and the temperature is kept for 120 minutes, and then cooled to room temperature with the furnace, and the obtained SnO ₂ /In ₂ O ₃ heterojunction nanofibers (Fig. 4).

Since the atomic ratio of In and Sn in precursor solution I and precursor solution II is 10:1, the diameter of obtained SnO ₂ nanofibers is smaller than that of In ₂ O ₃ nanofibers. The SnO ₂ nanofibers are entangled on the In ₂ O ₃ nanofibers, forming a SnO ₂ /In ₂ O ₃ heterostructure (Fig. 4).

Claims (10)

1. A method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning, characterized in that: the method firstly prepares precursor solution I containing indium nitrate pentahydrate/polyvinylpyrrolidone, containing dihydrate Precursor solution II of stannous chloride/polyvinylpyrrolidone; then inject precursor solution I and precursor solution II into the glass syringe I (2) and glass syringe II placed in parallel in the single-source double-field electrospinning device In (3), adjust the voltage of the DC high-voltage power supply (1) for spinning, and entangle the Taylor cones ejected from needles I (4) and II (5), and obtain nano Fiber membrane; finally, the nanofiber membrane is annealed to obtain a SnO ₂ /In ₂ O ₃ side-by-side heterojunction nanofiber material. 2 . The method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning as claimed in claim 1 , wherein the polyvinylpyrrolidone has a weight-average molecular weight of 1,300,000. 3. A method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning as claimed in claim 1 or 2, characterized in that: the precursor solution I refers to first dissolving 1.5 mmol indium nitrate pentahydrate In 5 ml absolute ethanol, stir the obtained solution A; then dissolve 0.75 g polyvinylpyrrolidone powder in 5 ml N,N-dimethylformamide solution, stir the obtained solution B; finally, the obtained The solution A was mixed with the solution B and then stirred for 12 h. 4. A method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning as claimed in claim 1 or 2, characterized in that: the precursor solution II refers to first dissolving 0.15 mmol chlorinated chlorinated dihydrate Dissolve tin in 5 ml of absolute ethanol, and stir to obtain solution C; then dissolve 0.75 g of polyvinylpyrrolidone powder in 5 ml of N,N-dimethylformamide solution, and stir to obtain solution D; finally, The solution C was mixed with the solution D and stirred for 12 h to obtain the obtained solution. 5. A method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning according to claim 1, characterized in that: the single-source double-field electrospinning device includes a DC high-voltage power supply (1), A stainless steel collection plate (7) and two iron stands (6); the two iron stands (6) are placed opposite each other, and a glass syringe I with a needle I (4) is fixed on one of the iron stands (6) (2), the other iron stand (6) is fixed with a glass syringe II (3) with a needle II (5); the needle I (4) is connected to the DC high voltage power supply ( 1) is connected to the positive pole; the needle II (5) is grounded through the wire III (10); the stainless steel collecting plate (7) is provided between the two iron frames (6), and the stainless steel collecting plate ( 7) Connect to the negative pole of the DC high-voltage power supply (1) through wire II (9). 6. A method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning as claimed in claim 5, characterized in that: the glass syringe I (2) and the glass syringe II (3) are both perpendicular to the stainless steel collecting plate (7). 7. The method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning according to claim 1, characterized in that: the voltage of the DC high-voltage power supply (1) is 8-14 kV. 8. A method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning according to claim 1 or 5, characterized in that: the needle I (4) and the needle II (5) The distance between them is 3-5 cm. 9. A method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning according to claim 1 or 5, characterized in that: the needles I (4) and the needles II (5) are respectively The distance from the stainless steel collecting plate (7) is 10-15 cm. 10. A method for preparing side-by-side heterojunction nanofibers by single-source double-field electrospinning as claimed in claim 1, characterized in that: the conditions of the annealing treatment refer to adopting a tube furnace and annealing in an air atmosphere , heat up to 300 °C, keep warm for 60 minutes, then heat up to 500 °C, keep warm for 120 minutes, and then cool to room temperature with the furnace.

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