A preparation method of bismuth oxide selenium nanosheets

Abstract

The present invention belongs to the technical field of bismuth oxide selenium nanosheets, and specifically relates to a Bi3O 2.5 Preparation method of Se2 nanosheets. The present invention adopts a chemical vapor deposition method, using Bi2Se3 and KI containing crystal water as a precursor and an oxygen source respectively to form a mixture, placing a substrate above the mixture, heating the mixture under the condition of passing a carrier gas to react, and growing the Bi3O on the surface of the substrate. 2.5 Se2 nanosheets. The preparation method provided by the present invention significantly improves Bi3O 2.5 The uniformity and crystal quality of Se2 nanosheets are improved, and the roughness of the interface of crystal domain merging is effectively reduced, thereby improving the quality of the interface of crystal domain merging; at the same time, the growth temperature of the present invention is low, which reduces energy consumption and equipment loss, and is more suitable for industrial application.

Description

Technical Field

[0001] The present invention belongs to the technical field of bismuth oxide selenium nanosheets, and specifically relates to a Bi3O 2.5 Preparation method of Se2 nanosheets. Background Art

[0002] High-performance photodetectors are widely used in communications, imaging, and medical fields. In recent years, photodetectors based on low-dimensional materials have attracted widespread attention. Low-dimensional Bi2O2Se has been widely studied due to its excellent air stability and optical properties. Similarly, Bi3O 2.5 Se2 also has these advantages and has a higher responsivity (8×10 4 A / W).

[0003] Currently, the preparation of Bi3O 2.5 The chemical vapor deposition (CVD) process of Se2 usually uses O2 or Bi2O3 as the oxygen source in the precursor, but this method has certain defects. First, the volatilization and reaction of Bi2O3 require a high temperature (usually over 650℃) in the tube furnace, which not only increases energy consumption but also may cause Bi3O 2.5 Epitaxial thermal stress accumulation in Se2 nanosheets affects the material's crystallization quality, particularly the interface quality during crystal domain merging. Furthermore, when Bi2O3 is reacted in powder form, uniform volatilization and deposition are difficult to achieve, leading to uneven growth of thin films or nanostructures, thus affecting the material's electrical and thermal properties and its application in devices. Summary of the Invention

[0004] The purpose of the present invention is to provide a Bi3O 2.5 Preparation method of Se2 nanosheets. The preparation method provided by the present invention significantly improves the 2.5 The uniformity and crystal quality of Se2 nanosheets are improved, and the roughness of the interface of crystal domain merging is effectively reduced, thereby improving the quality of the interface of crystal domain merging; at the same time, the growth temperature of the present invention is low, which reduces energy consumption and equipment loss, and is more suitable for industrial application.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a Bi3O 2.5 The preparation method of Se2 nanosheets comprises the following steps:

[0007] The chemical vapor deposition method is used to form a mixture with Bi2Se3 and KI containing crystal water as a precursor and an oxygen source, respectively. A substrate is placed above the mixture, and the mixture is heated under the condition of passing a carrier gas to react, and the Bi3O is grown on the surface of the substrate.2.5 Se2 nanosheets.

[0008] Preferably, the KI containing crystal water is KI·2H2O.

[0009] Preferably, the mass ratio of the precursor to the oxygen source is (1-4):1.

[0010] Preferably, the heating temperature is 550-600°C.

[0011] Preferably, the growth time is 5 to 60 minutes.

[0012] Preferably, the carrier gas includes an inert gas and hydrogen; the volume content of hydrogen in the carrier gas is 2 to 8%.

[0013] Preferably, the flow rate of the carrier gas is 30-100 sccm.

[0014] Preferably, the material of the substrate is mica; and the distance between the substrate and the mixture is 0.4 to 0.8 cm.

[0015] Preferably, the heating rate is 30 to 80° C. / min.

[0016] Preferably, the Bi3O 2.5 Se2 nanosheets are single crystal nanosheets.

[0017] The present invention provides a Bi3O 2.5 The preparation method of Se2 nanosheets comprises the following steps: using a chemical vapor deposition method to form a mixture with Bi2Se3 and KI containing crystal water as a precursor and an oxygen source, respectively; placing a substrate on the mixture; heating the mixture under the condition of passing a carrier gas to react; and growing the Bi3O on the surface of the substrate. 2.5 The present invention adopts a salt-assisted inverted growth chemical vapor deposition (CVD) method, uses bismuth selenide (Bi2Se3) as a precursor, and introduces KI containing crystal water as an oxygen source and catalyst to carry out Bi3O 2.5 First, the volatilization temperature of Bi2Se3 is relatively low, which can effectively reduce the growth temperature requirement and energy consumption compared with the growth process of bismuth oxide; secondly, KI containing crystal water can regulate the proportion of oxygen elements participating in the reaction and can evenly supply oxygen elements during the reaction to achieve Bi3O 2.5 Se2 nanosheets grow more stably, thus significantly improving the 2.5 The growth uniformity and crystal quality of Se2 are improved, and the roughness of the interface of crystal domain merging is effectively reduced, thereby improving the quality of the interface of crystal domain merging.

[0018] Furthermore, in the present invention, the mass ratio of the precursor to the oxygen source is (1-4):1. The present invention achieves the Bi3O 2.5 The regulation of Se2 crystal nucleation-growth kinetics can significantly improve the performance of Bi3O 2.5 The interface quality of crystal domain merging during Se2 crystal growth is improved, while Bi3O 2.5 The crystal quality of Se2 nanosheets. Therefore, the present invention effectively solves the problem of Bi3O 2.5 The common grain boundary defects in the process of Se2 multi-domain fusion are used to prepare large-sized Bi3O 2.5 Se2 single crystal nanosheets. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Bi3O prepared by the present invention 2.5 HRTEM image of Se2 nanosheets;

[0020] Figure 2 Bi3O prepared by the present invention 2.5 Selected area electron diffraction (SAED) images of Se2 nanosheets;

[0021] Figure 3 Bi3O prepared by the present invention 2.5 Elemental mapping of Bi, O, and Se in Se2 nanosheets;

[0022] Figure 4 Bi3O prepared by the present invention 2.5 XPS spectrum of Se2 nanosheets;

[0023] Figure 5 Bi3O prepared by the present invention 2.5 AFM images of Se2 nanosheets;

[0024] Figure 6 A diagram of the experimental device provided by the present invention;

[0025] Figure 7 The reaction materials of Bi3O in different mass ratios at 600°C in the embodiment of the present invention are shown in FIG. 2.5 Optical microscope photos of the effects of Se2 nanosheet growth;

[0026] Figure 8 The reaction materials of Bi3O in different mass ratios at 600°C in the embodiment of the present invention are shown in FIG. 2.5 Optical microscopy images of Se2 nanosheet domain merging effects;

[0027] Figure 9 The reaction materials of Bi3O in different mass ratios at 600°C in the embodiment of the present invention are shown in FIG.2.5 Optical microscopy images of the effect of Se2 nanosheet domain coverage;

[0028] Figure 10 The Bi3O prepared in this example 2.5 An optical microscope photo of two merging nanosheets shown in a Se2 nanosheet product.

[0029] Figure 11 for Figure 10 A high-angle annular dark-field image of the material surface showing the region where the two nanosheets merge. DETAILED DESCRIPTION

[0030] The present invention provides a Bi3O 2.5 The preparation method of Se2 nanosheets comprises the following steps:

[0031] The chemical vapor deposition method is used to form a mixture with Bi2Se3 and KI containing crystal water as a precursor and an oxygen source, respectively. A substrate is placed above the mixture, and the mixture is heated under the condition of passing a carrier gas to react, and the Bi3O is grown on the surface of the substrate. 2.5 Se2 nanosheets.

[0032] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0033] In the present invention, the form of the Bi2Se3 is preferably powdery. The purity of the Bi2Se3 is preferably ≥99.99%. The form of the KI containing crystalline water is preferably powdery. The KI containing crystalline water is KI·2H2O. The mass ratio of the precursor and the oxygen source is preferably (1 to 4): 1, and in the embodiment it can be 1:1, 2:1, 3:1 or 4:1. In the present invention, the preparation method of the KI containing crystalline water preferably includes: subjecting the KI powder to a moisture absorption treatment to obtain the KI containing crystalline water. The specific method of the moisture absorption treatment preferably includes: evenly spreading the KI powder on dust-free paper, and then placing it in an environment with a relative humidity of 30 to 35% for 10 to 12 hours, and finally collecting the KI containing crystalline water.

[0034] The present invention found that the mass ratio of KI containing crystal water to Bi2Se3 precursor has a significant effect on the Bi3O 2.5 The present invention can significantly improve the Bi3O 2.5 The interface quality of crystal domain merging during Se2 crystal growth is improved, while Bi3O 2.5 The crystal quality of Se2 nanosheets.2.5 The common grain boundary defect problem in the process of Se2 multi-domain fusion can be prepared to obtain large-sized Bi3O 2.5 Se2 single crystal nanosheets.

[0035] In the present invention, the material of the substrate is preferably mica. The substrate is more preferably fluorphlogopite (f-mica), and the fluorphlogopite is preferably atomically flat fluorphlogopite. The surface of the atomically flat fluorphlogopite has no dangling bonds, and Bi3O 2.5 The strong electrostatic interaction between Se2 and the substrate and the low diffusion barrier promote the 2.5 In-plane lateral growth mode of Se2 nanosheets.

[0036] In the present invention, the distance between the substrate and the mixture is preferably 0.4 to 0.8 cm, more preferably 0.4 to 0.6 cm, and in an embodiment, may be 0.4 cm. The present invention controls the distance between the substrate and the mixture to be preferably 0.4 to 0.8 cm to ensure that the precursor can be uniformly transferred to the substrate surface along with the carrier gas.

[0037] In the present invention, the carrier gas preferably includes an inert gas and hydrogen. The inert gas is preferably argon. The volume content of hydrogen in the carrier gas is preferably 2 to 8%, and in the embodiment it can be 5%. The flow rate of the carrier gas is preferably 30 to 100 sccm, more preferably 30 to 80 sccm, and in the embodiment it can be 30 sccm. In the present invention, the hydrogen in the carrier gas is beneficial to the Bi3O 2.5 The in-plane lateral growth of Se2 nanosheets resulted in large-sized Bi3O 2.5 Se2 nanosheets.

[0038] In the present invention, the heating rate is preferably 30 to 80° C. / min, more preferably 30 to 50° C. / min, and in the embodiment, it can be 30° C. / min.

[0039] In the present invention, the heating temperature (ie, the reaction temperature, the growth temperature) is preferably 550-600°C, and in the embodiment, it can be 600°C.

[0040] In the present invention, the growth time is preferably 5 to 60 minutes, and in embodiments it can be 5 minutes, 10 minutes, 20 minutes, 40 minutes or 60 minutes.

[0041] The preparation method provided by the present invention is preferably carried out under an ambient pressure of 760 torr. The preparation method provided by the present invention is preferably carried out in a tube furnace. Figure 6As shown. The preparation method provided by the present invention preferably includes the following steps: placing the precursor and the oxygen source in a quartz boat to form a mixture; placing the quartz boat containing the mixture in the center of the quartz tube of the tube furnace; placing the substrate in the quartz tube, and above the mixture; before the heating, the present invention preferably seals the quartz tube and washes it, and the washing gas used for the washing is preferably hydrogen and inert gas, and the inert gas is preferably argon. The flow rate of the washing gas is preferably 200-300sccm. The washing time is preferably 5-10min. The composition of the washing gas is preferably the same as that of the carrier gas. The present invention removes the impurity gas in the quartz tube by washing. After the washing is completed, the present invention adjusts the flow rate of the washing gas to the flow rate of the carrier gas, and at the same time turns on the heating system to heat the mixture for reaction, and grows the Bi3O on the surface of the substrate. 2.5 Se2 nanosheets; after the growth is completed, the heating system is turned off and the quartz tube is naturally cooled to room temperature under the condition of passing carrier gas.

[0042] The present invention obtains the Bi3O 2.5 Se2 nanosheets. 2.5 Se2 nanosheets are preferably single crystal nanosheets. 2.5 The morphology of Se2 nanosheets is preferably hexagonal.

[0043] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0044] In the following embodiments, Figure 6 The experimental setup shown is for preparing Bi3O 2.5 Se2 nanosheets.

[0045] Example 1

[0046] The KI powder was evenly spread on a dust-free paper, and then placed in an environment with a relative humidity of 35% and placed at room temperature for 10 hours. Finally, the KI was collected. . 2H2O.

[0047] 200 mg Bi2Se3 powder (99.99%) and 50 mg KI . 2H2O as precursor and oxygen source (mKI . 2H2O:mBi2Se3=1:4) is placed in a quartz boat in the center of the quartz tube of the tube furnace. Then, an atomically flat fluorphlogopite (f-mica) substrate is precisely placed upside down on the quartz boat, at a distance of 1 / 4 from Bi2Se3 and KI. .2H2O to ensure that the precursor can be evenly transferred to the substrate surface with the carrier gas. Before the growth begins, the sealed quartz tube is passed through an Ar\H2 mixed gas (wherein the volume content of hydrogen is 5%) at a flow rate of 200sccm as a wash gas (i.e., carrier gas) for 5 minutes to remove the impurity gas in the tube. Next, the carrier gas flow rate is adjusted to 30sccm, and the quartz tube is heated at a heating rate of 30°C / min. When the furnace center temperature reaches 600°C, maintain 600°C for 5 minutes to ensure that Bi2Se3 fully reacts with the supplied oxygen and generates Bi3O 2.5 After the reaction is completed, the heating system is turned off and the temperature in the quartz tube is allowed to cool naturally to room temperature. Finally, high-quality Bi3O is grown on the surface of the atomically flat fluorphlogopite (f-mica) substrate. 2.5 Se2 nanosheets.

[0048] The Bi3O prepared in this example 2.5 The morphology of the Se2 single crystal nanosheets is hexagonal. 2.5 Optical photographs of Se2 single crystal nanosheets Figure 7 As shown in d.

[0049] Figure 1 Bi3O prepared in Example 1 2.5 HRTEM image of Se2 single crystal nanosheets; Figure 2 Bi3O prepared in Example 1 2.5 Selected area electron diffraction (SAED) images of Se2 nanosheets; Figure 3 Bi3O prepared in Example 1 2.5 Elemental mapping of Bi, O, and Se in Se2 nanosheets; Figure 4 Bi3O prepared in Example 1 2.5 XPS spectrum of Se2 nanosheets; Figure 5 Bi3O prepared in Example 1 2.5 AFM images of Se2 nanosheets, Figures 1 to 5 It can be seen that the Bi3O prepared in Example 1 2.5 The lattice structure of Se2 single crystal nanosheets belongs to the monoclinic system, and the lattice parameters are β=102.91°. Bi3O 2.5 The structural characteristics of Se2 are layered arrangement, positively charged [Bi2O 2.5 ] n n+ layer and negatively charged [BiSe2] n n- The layers are stacked alternately along the crystallographic c-axis. 2.5The Se2 nanosheets exhibit excellent uniformity in optical contrast and display a distinct hexagonal morphology.

[0050] Example 2

[0051] The preparation method is basically the same as that of Example 1, except that KI . The mass of 2H2O powder is 200mg(mKI . 2H2O:mBi2Se3=1:1). Bi3O obtained in Example 2 2.5 Optical photographs of Se2 single crystal nanosheets Figure 7 As shown in a in .

[0052] Example 3

[0053] The preparation method is basically the same as that of Example 1, except that KI . The mass of 2H2O powder is 100mg(mKI . 2H2O:mBi2Se3=1:2). Bi3O obtained in Example 3 2.5 Optical photographs of Se2 single crystal nanosheets Figure 7 As shown in b.

[0054] Example 4

[0055] The preparation method is basically the same as that of Example 1, except that KI . The mass of 2H2O powder is 66.67 mg (mKI . 2H2O:mBi2Se3=1:3). Bi3O obtained in Example 4 2.5 Optical photographs of Se2 single crystal nanosheets Figure 7 As shown in c.

[0056] Figure 7 The reaction raw materials of different mass ratios at 600°C in Examples 1 to 4 of the present invention are Bi3O 2.5 The effect of Se2 nanosheet growth; Figure 7 The scale bar in the figure is 100 μm. Figure 7 a is Bi3O prepared in Example 2 2.5 Se2 nanosheets. Figure 7 b is Bi3O prepared in Example 3 2.5 Se2 nanosheets. Figure 7 c is Bi3O prepared in Example 4 2.5 Se2 nanosheets. Figure 7 Where d is the Bi3O prepared in Example 1 2.5 Se2 nanosheets.

[0057] Figure 8The reaction raw materials of different mass ratios at 600°C in Examples 1 to 4 of the present invention are Bi3O 2.5 The influence of Se2 nanosheet domain merging; Figure 8 The scale bar in the figure is 20 μm. Figure 8 a is Bi3O prepared in Example 2 2.5 Se2 nanosheets. Figure 8 b is Bi3O prepared in Example 4 2.5 Se2 nanosheets. Figure 8 c is Bi3O prepared in Example 1 2.5 Se2 nanosheets.

[0058] Figure 9 The reaction raw materials of different mass ratios at 600°C in Examples 1 to 4 of the present invention are Bi3O 2.5 The influence of Se2 nanosheet domain coverage; Figure 9 The scale bar in the figure is 250 μm. Figure 9 a is Bi3O prepared in Example 2 2.5 Se2 nanosheets. Figure 9 b is Bi3O prepared in Example 4 2.5 Se2 nanosheets. Figure 9 c is Bi3O prepared in Example 1 2.5 Se2 nanosheets.

[0059] Depend on Figure 7 、 Figure 8 and Figure 9 It can be seen that KI . When the mass ratio of 2H2O powder to Bi2Se3 powder is 1:3 and 1:4 respectively, especially when it is 1:4, the obtained Bi3O 2.5 The interface quality was effectively improved when the Se2 nanosheet domains merged, and the grain boundary defect problem in the multi-domain fusion process was solved, resulting in the large-size Bi3O 2.5 Se2 single crystal nanosheets.

[0060] Figure 10 The Bi3O prepared in Example 1 2.5 Optical microscope image of two merging nanosheets shown in the Se2 nanosheet product. Figure 11 for Figure 10 High-angle annular dark-field image of the material surface at the region where the two nanosheets merge, as marked in the figure. Figure 11 The surface high-angle annular dark field image of area ① in a is as follows Figure 11 As shown in Figure b, Figure 11 The high-angle annular dark field image of the surface of area ② in a is as follows Figure 11 As shown in Figure c, Figure 11The high-angle annular dark field image of the surface of area ③ in a is as follows: Figure 11 As shown in Figure d. Figure 11 As shown in Figures b, c and d, the two Bi3O 2.5 The Se2 nanosheets merged into a single crystal.

[0061] From the above examples, it can be seen that the present invention uses chemical vapor deposition (CVD) method to adopt KI . Effect of mass ratio of 2H2O auxiliary agent and bismuth selenide precursor on the performance of Bi3O 2.5 Se2 crystal nucleation-growth kinetics dosage form is effectively regulated by systematically regulating KI . The mass ratio of 2H2O to Bi2Se3 precursor (mKI . 2H2O:mBi2Se3), and the product was characterized and analyzed by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). . When the mass ratio of 2H2O:mBi2Se3 is appropriate (preferably 1:3-4) (reaction temperature is 600℃, carrier gas flow rate is 30sccm, and the volume content of hydrogen in the carrier gas is 5%), the Bi3O 2.5 The interface quality of Se2 crystal domain merging during crystal growth is improved, and the crystallization quality of single crystal nanosheets is improved. This invention effectively solves the common grain boundary defect problem in the process of multi-domain fusion, and can prepare large-sized Bi3O 2.5 Se2 single crystal.

[0062] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A Bi3O 2.5 The method for preparing Se2 nanosheets is characterized in that: The following steps are involved: The chemical vapor deposition method is used to form a mixture with Bi2Se3 and KI containing crystal water as a precursor and an oxygen source, respectively. A substrate is placed above the mixture, and the mixture is heated under the condition of passing a carrier gas to react, and the Bi3O is grown on the surface of the substrate. 2.5 Se2 nanosheets.

2. The preparation method according to claim 1, characterized in that The KI containing crystal water is KI·2H2O.

3. The preparation method according to claim 1 or 2, characterized in that The mass ratio of the precursor to the oxygen source is (1-4):

1.

4. The preparation method according to claim 1, characterized in that The heating temperature is 550-600°C.

5. The preparation method according to claim 1 or 4, characterized in that The growth time is 5 to 60 minutes.

6. The preparation method according to claim 1, characterized in that The carrier gas includes inert gas and hydrogen; the volume content of hydrogen in the carrier gas is 2-8%.

7. The preparation method according to claim 1 or 6, characterized in that The flow rate of the carrier gas is 30-100 sccm.

8. The preparation method according to claim 1, characterized in that The material of the substrate is mica; the distance between the substrate and the mixture is 0.4-0.8 cm.

9. The preparation method according to claim 1, characterized in that The heating rate is 30-80°C / min.

10. The preparation method according to claim 1, characterized in that The Bi3O 2.5 Se2 nanosheets are single crystal nanosheets.

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