CN104195642A - A kind of method for preparing single crystal BiFeO3 nano sheet - Google Patents

Abstract

The invention discloses a method for preparing single-crystal BiFeO ₃ nanosheets, comprising the following steps: dissolving Fe(NO ₃ ) ₃ 9H ₂ O and Bi(NO ₃ ) ₃ 5H ₂ O in nitric acid solution to form a matrix Salt solution; dissolve CTAB in an organic solvent to prepare two sets of CTAB solutions; add the mother salt solution dropwise to one set of CTAB solutions, and stir to obtain solution A; add dropwise KOH solution to another set of CTAB solutions, and stir to obtain a solution B: Add solution B dropwise to solution A, and stir to obtain a hydrothermal reaction precursor; put the hydrothermal reaction precursor and solvent into a hydrothermal kettle; seal the hydrothermal kettle, and react in an oven at 140-160°C for 12 After ~24h, the precipitate was obtained by filtration; the precipitate was washed and dried to obtain single crystal BiFeO ₃ nanosheets. The invention can synthesize pure-phase single _- crystal BiFeO nanosheets at low temperature, saves energy, has high product crystallinity, easy process control, and simple equipment required.

Description

A kind of method for preparing single crystal BiFeO3 nano sheet

technical field

The invention relates to a preparation method of _BiFeO3 nanometer powder, in particular to a method for preparing single crystal _BiFeO3 nanosheets.

Background technique

Due to their simultaneous ferroelectricity, ferromagnetism or ferroelasticity, multiferroic materials have broad application prospects in information storage devices, spintronic devices and sensors. Among the many multiferroic materials, BiFeO ₃ is special. It is one of the few single-phase multiferroic materials found to have both ferroelectric order and antiferromagnetic order at room temperature. Its Curie The temperature and the Neil temperature are relatively high, 1103K and 643K respectively, so they have been extensively studied in recent years. In addition, due to its narrow bandgap (~2.1eV) and good photoresponse in the visible light range, it has great application value in the field of photocatalysis. However, the excessive leakage current due to the existence of impurity phases seriously hinders the application of _BiFeO3 materials.

So far, there are many synthesis methods of BiFeO ₃ , mainly including chemical methods such as high-temperature solid-state sintering method, polymer precursor method, sol-gel method and co-precipitation method. The reproducibility of the high-temperature solid-state method is not good, and the impurity phases such as Bi ₂ Fe ₄ O ₉ and Bi ₂₅ FeO ₄₀ need to be washed with nitric acid after sintering, so that the surface of the synthesized powder is rough. However, chemical methods such as polymer precursor method, co-precipitation method, sol-gel method, microemulsion method, etc. still need to be sintered at a temperature higher than 400 ° C, which consumes a lot of energy and will lead to uneven particle size distribution. And the irregular shape of the powder will eventually affect the performance of the material.

The catalytic ability of photocatalyst is related to its purity, specific surface area, crystallization degree and so on. The higher the purity (no impurity phase), the higher the degree of crystallization, the larger the specific surface area, and the stronger the catalytic ability of the photocatalyst. Due to the large specific surface area of nanosheets, more reactive sites can be provided, and the quantum efficiency of interfacial charge transfer can be improved, so photocatalysts with nanosheet-like morphology have higher catalytic activity. So far, there are very few reports on the preparation of single crystal BiFeO ₃ nanosheets at home and abroad.

Contents of the invention

In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the object of the present invention is to provide a method for preparing single-crystal _BiFeO3 nanosheets, which can synthesize pure-phase single-crystal _BiFeO3 nanosheets at 140°C to 160°C, saving energy, Moreover, the single-crystal BiFeO ₃ nanosheet has high crystallinity, the process is easy to control, and the instruments and equipment required for the synthesis are simple.

The object of the present invention is achieved through the following technical solutions:

A method for preparing single crystal BiFeO ₃ nanosheets, comprising the following steps:

(1) Weigh analytically pure Fe(NO ₃ ) ₃ 9H ₂ O and Bi(NO ₃ ) ₃ 5H ₂ O in a molar ratio of 1:1, and dissolve them in nitric acid with a mass concentration of 8-10% In the solution, a uniform mother salt solution is prepared by magnetic stirring; the concentration of the mother salt solution is 0.05-0.15mol/L;

(2) Weigh CTAB and dissolve it in an organic solvent to prepare two groups of CTAB solutions with a concentration of 0.1-0.25mol/L;

(3) Add the mother salt solution dropwise to a group of CTAB solutions, and obtain solution A through magnetic stirring. The volume ratio of the mother salt solution to the CTAB solution is 1:5 to 1:2; Add 10-30mol/L KOH solution dropwise to another group of CTAB solution, and stir it magnetically to obtain solution B. The volume ratio of KOH solution to CTAB solution is 1:5-1:2;

(4) Add solution B dropwise to solution A, and obtain a precipitate after magnetic stirring to obtain a hydrothermal reaction precursor;

(5) Put the hydrothermal reaction precursor prepared in step (4) into a hydrothermal kettle, and add a solvent so that the filling degree of the hydrothermal kettle is 70% to 80%;

(6) Seal the hydrothermal kettle, place the hydrothermal kettle in an oven at 140°C to 160°C, take out the product in the hydrothermal kettle after reacting for 12 to 24 hours, and obtain a precipitate by filtration; the precipitate is washed and dried to obtain a single Crystalline BiFeO ₃ nanosheets.

The organic solvent described in step (2) is a mixed solution of cyclohexane and n-butanol.

In the mixed solution of cyclohexane and n-butanol, the volume ratio of cyclohexane and n-butanol is 3:1˜6:1.

Add solution B dropwise to solution A as described in step (4), specifically:

Add solution B dropwise to solution A at a titration rate of less than 5 mL/min.

The drying temperature is 80°C.

The solvent described in step (5) is cyclohexane.

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

(1) The BiFeO ₃ powder prepared by the present invention is a single crystal BiFeO ₃ nanosheet, with perfect crystallization and a single crystal phase. Due to the large specific surface area of single crystal BiFeO ₃ nanosheets, it can be used as a photocatalyst for degrading pollutants under visible light. In addition, it can also be used to make information storage devices, spintronic devices and sensors with good performance.

(2) The method for preparing single crystal _BiFeO3 nanosheets of the present invention, the preparation temperature is 140°C to 160°C, and the existing solid phase sintering method and polymer precursor method, sol-gel method and co-precipitation method, etc. Compared with the chemical method, the temperature is greatly reduced, saving energy.

(3) In the method for preparing single crystal BiFeO ₃ nanosheets of the present invention, the reaction product does not need subsequent sintering treatment, the process control and the equipment required for synthesis are simple, and the production cost is further reduced.

(4) In the method for preparing single crystal _BiFeO nanosheets of the present invention, the prepared reactant precursor solution does not need to be filtered, washed and dried, further shortening the process preparation cycle.

(5) In the method for preparing single-crystal _BiFeO3 nanosheets of the present invention, the raw materials are configured in a liquid phase, the content of each component can be precisely controlled and uniformly mixed at the molecular/atomic level, and the prepared single-crystal _BiFeO3 nanometer Tablets have the advantages of high purity and good dispersibility.

Description of drawings

Fig. 1 is a flow chart of the preparation of single crystal BiFeO ₃ nanosheets prepared in Example 1 of the present invention.

Fig. 2 is the x-ray diffraction pattern of the single crystal _BiFeO3 nanoplate prepared by the embodiment of the present invention 1

FIG. 3 is a transmission electron micrograph of the single crystal BiFeO ₃ nanosheet prepared in Example 1 of the present invention.

FIG. 4 is a high-resolution transmission electron micrograph of the single crystal BiFeO ₃ nanosheets prepared in Example 1 of the present invention.

FIG. 5 is a transmission electron microscope selected area electron diffraction pattern of single crystal BiFeO ₃ nanosheets prepared in Example 1 of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto.

Example 1

As shown in Figure 1, the _BiFeO3 nanosheet preparation process of the present embodiment comprises the following steps:

Weigh 1 mmol of analytically pure Fe(NO ₃ ) ₃ 9H ₂ O and 1 mmol Bi(NO ₃ ) ₃ 5H ₂ O, and dissolve them in 10 ml of 8% nitric acid solution with a mass concentration of 0.5 h, made into a uniform mother salt solution; two groups of CTAB solutions with the same concentration were prepared, and the preparation process of each group of CTAB solutions was as follows: Weigh 1gCTAB and dissolve it in a mixed solution of 20ml cyclohexane and 4ml n-butanol , by magnetically stirring for 0.5h to obtain a CTAB solution; add the mother salt solution dropwise to a group of CTAB solutions, and magnetically stir for 0.5h to obtain solution A; add 10ml of 10mol/L KOH solution dropwise to another group of CTAB solutions , and magnetically stirred for 0.5h to obtain solution B; then solution B was added dropwise to solution A at a titration rate of 4.5mL/min, and magnetically stirred for 0.5h to obtain a hydrothermal reaction precursor; the above hydrothermal reaction precursor Put it into a hydrothermal kettle, and add cyclohexane to make the filling degree 80%. Seal the hydrothermal kettle, place the hydrothermal kettle in an oven at 140°C, take out the product in the hydrothermal kettle after reacting for 16 hours, filter the precipitate, wash it, and dry it in an oven at 80°C to obtain single crystal BiFeO ₃ Nanosheets.

Fig. 2 is the x-ray diffraction pattern of the BiFeO ₃ nanopowder prepared in this example. It can be seen from Fig. 2 that the pure phase BiFeO ₃ nanopowder prepared in this example has high crystallinity.

Fig. 3 is the transmission electron micrograph of the _BiFeO3 nanopowder prepared in this embodiment, as can be seen from Fig. 3, the _BiFeO3 powder prepared in this embodiment is a rectangular nanosheet, and its edge size is (70～130)nm×( 90-200) nm.

4 is a high-resolution transmission electron microscope photo of _BiFeO3 nanosheets prepared in Example 1 of the present invention. As shown in the figure, the interplanar spacing is 0.39nm, corresponding to the (012) crystal plane of _BiFeO3 .

Fig. 5 is a transmission electron microscope selected area electron diffraction pattern of the BiFeO ₃ nanosheets prepared in Example 1 of the present invention. It can be seen from the figure that the BiFeO ₃ nanosheets are single crystals.

Example 2

Weigh 1 mmol of analytically pure Fe(NO ₃ ) ₃ 9H ₂ O and 1 mmol Bi(NO ₃ ) ₃ 5H ₂ O, and dissolve them in 8 ml of 9% nitric acid solution, stir for 0.5 h by magnetic force, and prepare into a uniform mother salt solution; prepare two groups of CTAB solutions with the same concentration, the preparation process of each group of CTAB solutions is as follows: weigh 1.5gCTAB, and dissolve it in the mixed solution of 20ml cyclohexane and 4ml n-butanol, pass Stir magnetically for 0.5h to obtain a CTAB solution; add the mother salt solution dropwise to a group of CTAB solutions, and magnetically stir for 0.5h to obtain solution A; add 8ml of 10mol/L KOH solution dropwise to another group of CTAB solutions, And magnetically stirred for 0.5h to obtain solution B; then solution B was added dropwise to solution A at a titration rate of 4mL/min, and magnetically stirred for 0.5h to obtain a hydrothermal reaction precursor; put the above hydrothermal reaction precursor into water Heat the kettle, and add cyclohexane to make the filling degree 70%. Seal the hydrothermal kettle, place the hydrothermal kettle in an oven at 140°C, take out the product in the hydrothermal kettle after reacting for 12 hours, filter the precipitate, wash it, and dry it in an oven at 80°C to obtain the edge size of (80-130)nm×(80-200)nm single crystal BiFeO ₃ nanosheets.

Example 3

Weigh 1 mmol of analytically pure Fe(NO ₃ ) ₃ 9H ₂ O and 1 mmol Bi(NO ₃ ) ₃ 5H ₂ O, and dissolve them in 10 ml of 9% nitric acid solution, stir for 0.5 h by magnetic force, and prepare into a uniform mother salt solution; prepare two groups of CTAB solutions with the same concentration, the preparation process of each group of CTAB solutions is as follows: weigh 2gCTAB, and dissolve it in a mixed solution of 24ml cyclohexane and 4ml n-butanol, Stir for 0.5h to obtain a CTAB solution; add the mother salt solution dropwise to a group of CTAB solutions, and magnetically stir for 0.5h to obtain solution A; add 10ml of 10mol/L KOH solution dropwise to another group of CTAB solutions, and Magnetically stirred for 0.5h to obtain solution B; then solution B was added dropwise to solution A at a titration rate of 4mL/min, and magnetically stirred for 0.5h to obtain a hydrothermal reaction precursor; the above hydrothermal reaction precursor was placed in a hydrothermal In the still, add cyclohexane to make the filling degree 80%. Seal the hydrothermal kettle, place the hydrothermal kettle in an oven at 160°C, take out the product in the hydrothermal kettle after reacting for 24 hours, filter to obtain a precipitate, wash it, and dry it in an oven at 80°C to obtain an edge size of ( 60~120)nm×(80~160)nm single crystal BiFeO ₃ nanosheets.

Example 4

Weigh 1mmol analytically pure Fe(NO ₃ ) ₃ 9H ₂ O and 1 mmol Bi(NO ₃ ) ₃ 5H ₂ O, and dissolve them in 8ml of 10% nitric acid solution, stir for 0.5h by magnetic force, and prepare into a uniform mother salt solution; two groups of CTAB solutions with the same concentration were prepared, and the preparation process of each group of CTAB solutions was as follows: Weigh 1.5g CTAB and dissolve it in a mixed solution of 22.5ml cyclohexane and 4.5ml n-butanol , by magnetically stirring for 0.5h to obtain a CTAB solution; add the mother salt solution dropwise to a group of CTAB solutions, and magnetically stir for 0.5h to obtain solution A; add 8ml of 20mol/L KOH solution dropwise to another group of CTAB solutions , and magnetically stirred for 0.5h to obtain solution B; then solution B was added dropwise to solution A at a titration rate of 4.5mL/min, and magnetically stirred for 0.5h to obtain a hydrothermal reaction precursor; the above hydrothermal reaction precursor Put it into a hydrothermal kettle, and add cyclohexane to make the filling degree 75%. Seal the hydrothermal kettle, place the hydrothermal kettle in an oven at 140°C, take out the product in the hydrothermal kettle after reacting for 16 hours, filter the precipitate, wash it, and dry it in an oven at 80°C to obtain the edge size of (80-140) nm×(80-180) nm single crystal BiFeO ₃ nanosheets.

Example 5

Weigh 1mmol analytically pure Fe(NO ₃ ) ₃ 9H ₂ O and 1 mmol Bi(NO ₃ ) ₃ 5H ₂ O, and dissolve them in 8ml of 10% nitric acid solution, stir for 0.5h by magnetic force, and prepare into a uniform mother salt solution; two groups of CTAB solutions with the same concentration were prepared, and the preparation process of each group of CTAB solutions was as follows: Weigh 1gCTAB and dissolve it in a mixed solution of 20ml cyclohexane and 4ml n-butanol, Stir for 0.5h to obtain a CTAB solution; add the mother salt solution dropwise to a group of CTAB solutions, and magnetically stir for 0.5h to obtain solution A; add 8ml of 30mol/L KOH solution dropwise to another group of CTAB solutions, and Magnetically stir for 0.5h to obtain solution B; then add solution B dropwise to solution A at a titration rate of 4.5mL/min, and magnetically stir for 0.5h to obtain a hydrothermal reaction precursor; put the above hydrothermal reaction precursor into water Heat the kettle, and add cyclohexane to make the filling degree 70%. Seal the hydrothermal kettle, place the hydrothermal kettle in an oven at 150°C, take out the product in the hydrothermal kettle after reacting for 16 hours, filter the precipitate, wash it, and dry it in an oven at 80°C to obtain the edge size of (70~120)nm×(80~190)nm single crystal BiFeO ₃ nanosheets.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the embodiment, and any other changes, modifications, substitutions and combinations made without departing from the spirit and principle of the present invention , simplification, all should be equivalent replacement methods, and are all included in the protection scope of the present invention.

Claims (6)

1. prepare monocrystalline BiFeO for one kind ₃the method of nanometer sheet, is characterized in that, comprises the following steps:

(1) 1:1 weighs analytically pure Fe (NO in molar ratio ₃) ₃9H ₂o and Bi (NO ₃) ₃5H ₂o, and to be dissolved in mass concentration be, in 8～10% salpeter solution, by magnetic agitation, to be made into uniform female salts solution; The concentration of described female salts solution is 0.05～0.15mol/L;

(2) weigh CTAB, and be dissolved in organic solvent, prepare two groups of CTAB solution that concentration is 0.1～0.25mol/L;

(3) female salts solution is added drop-wise in one group of CTAB solution, through magnetic agitation, obtains solution A, female salts solution is 1:5～1:2 with the ratio of the volume of CTAB solution; The KOH solution of 10～30mol/L with female salts solution same volume is added drop-wise in another group CTAB solution, through magnetic agitation, obtains solution B, KOH solution is 1:5～1:2 with the ratio of the volume of CTAB solution;

(4) solution B is added drop-wise in solution A, and is precipitated thing after magnetic agitation, make hydro-thermal reaction precursor;

(5) the hydro-thermal reaction precursor of being prepared by step (4) is put into water heating kettle, and adds solvent, and making water heating kettle compactedness is 70%～80%;

(6) sealing water heating kettle, is placed in water heating kettle in 140 ℃～160 ℃ baking ovens, after reaction 12～24h, takes out the product in water heating kettle, is precipitated after filtration thing; Throw out, through washing, obtains monocrystalline BiFeO after being dried ₃nanometer sheet.

2. the monocrystalline BiFeO for preparing according to claim 1 ₃the method of nanometer sheet, is characterized in that, the described organic solvent of step (2) is the mixing solutions of hexanaphthene and propyl carbinol.

3. the monocrystalline BiFeO for preparing according to claim 2 ₃the method of nanometer sheet, is characterized in that, in the mixing solutions of described hexanaphthene and propyl carbinol, the volume ratio of hexanaphthene and propyl carbinol is 3:1～6:1.

4. the monocrystalline BiFeO for preparing according to claim 1 ₃the method of nanometer sheet, is characterized in that, step (4) is described to be added drop-wise to solution B in solution A, is specially:

Solution B is added drop-wise in solution A to be less than the rate of titration of 5mL/min.

5. the monocrystalline BiFeO for preparing according to claim 1 ₃the method of nanometer sheet, is characterized in that, described dry temperature is 80 ℃.

6. the monocrystalline BiFeO for preparing according to claim 1 ₃the method of nanometer sheet, is characterized in that, the described solvent of step (5) is hexanaphthene.