Preparation method of bismuth oxygen selenium nanosheet

Abstract

The invention belongs to the technical field of bismuth oxygen selenium nanosheets, and particularly relates to a preparation method of a Bi3O2.5 Se2 nanosheet. According to the preparation method, a chemical vapor deposition method is adopted, Bi2Se3 and KI containing crystal water are respectively used as a precursor and an oxygen supply source to form a mixture, a substrate is placed above the mixture, the mixture is heated under the condition that a carrier gas is introduced for reaction, and the Bi3O2.5 Se2 nanosheet grows on the surface of the substrate to obtain the Bi3O2.5 Se2 nanosheet. According to the preparation method provided by the invention, the uniformity and the crystallization quality of the Bi3O2.5 Se2 nanosheet are remarkably improved, the roughness of a crystal domain combination interface is effectively reduced, and the quality of the crystal domain combination interface is improved; meanwhile, the growth temperature is low, energy consumption and equipment loss are reduced, and the method is more suitable for industrial application.

Description

Technical Field

[0001] The present invention belongs to the technical field of bismuth oxy selenide nanosheets, and specifically relates to a preparation method of Bi 3 O 2.5 Se 2 nanosheets. Background Art

[0002] High-performance photodetectors are widely used in the fields of communication, imaging, and medicine. In recent years, photodetectors based on low-dimensional materials have attracted extensive attention. Low-dimensional Bi 2 O 2 Se has been widely studied due to its excellent air stability and optical properties. Similarly, Bi 3 O 2.5 Se 2 also has these advantages and has a higher responsivity (8×10 4 A / W).

[0003] Currently, the chemical vapor deposition (CVD) process for preparing Bi 3 O 2.5 Se 2 usually uses O 2 or Bi 2 O 3 as the oxygen supply source in the precursor, but this method has certain defects. First, the volatilization and reaction of Bi 2 O 3 require a relatively high temperature (usually exceeding 650 °C) in a tube furnace, which not only increases energy consumption but also may lead to the accumulation of epitaxial thermal stress in the Bi 3 O 2.5 Se 2 nanosheet material, affecting the crystallization quality of the material, especially the interface quality during grain boundary merging. Second, when Bi 2 O 3 participates in the reaction in powder form, it is difficult to achieve uniform volatilization and deposition during the reaction, easily resulting in uneven growth of the thin film or nanostructure, thus affecting the electrical and thermal properties of the material and its application performance in devices. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of Bi 3 O 2.5 Se 2 nanosheets. The preparation method provided by the present invention significantly improves Bi 3 O 2.5 Se 2The uniformity and crystallization quality of the nanosheets are improved, and the roughness of the interface for grain boundary merging is effectively reduced, improving the quality of the interface for grain boundary merging. At the same time, the growth temperature of the present invention is low, reducing energy consumption and equipment loss, and being more suitable for industrial applications.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing Bi 3 O 2.5 Se 2 nanosheets, comprising the following steps:

[0007] Using chemical vapor deposition, Bi 2 Se 3 and KI containing crystal water are used as a precursor and an oxygen supply source respectively to form a mixture. A substrate is placed above the mixture, and the mixture is heated under the condition of introducing a carrier gas for reaction to grow the Bi 3 O 2.5 Se 2 nanosheets on the surface of the substrate.

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

[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 5-60 min.

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

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

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

[0015] Preferably, the heating rate of temperature rise is 30-80 °C / min.

[0016] Preferably, the Bi 3 O 2.5 Se 2 nanosheets are single-crystal nanosheets.

[0017] The present invention provides a Bi 3 O 2.5 Se2 Method for preparing nanosheets, comprising the following steps: using chemical vapor deposition method, with Bi 2 Se 3 and KI containing crystal water as precursor and oxygen supply source respectively to form a mixture, placing a substrate above the mixture, heating the mixture under the condition of introducing carrier gas for reaction, and growing the Bi 3 O 2.5 Se 2 nanosheets on the surface of the substrate. Through the salt-assisted inverted growth chemical vapor deposition (CVD) method of the present invention, bismuth selenide (Bi 2 Se 3 ) is used as the precursor, and KI containing crystal water is introduced as the oxygen supply source and catalyst for the growth of Bi 3 O 2.5 Se 2 nanosheets. First, the volatilization temperature of Bi 2 Se 3 is relatively low, which can effectively reduce the heating requirement for growth compared with the growth process of bismuth oxide, reducing energy consumption; secondly, KI containing crystal water can regulate the proportion of oxygen element participating in the reaction, and can uniformly supply oxygen element during the reaction to achieve more stable growth of Bi 3 O 2.5 Se 2 nanosheets, thereby significantly improving the growth uniformity and crystallization quality of Bi 3 O 2.5 Se 2 , and effectively reducing the roughness of the interface of grain boundary merging and improving the quality of the interface of grain boundary merging.

[0018] Furthermore, in the present invention, the mass ratio of the precursor to the oxygen source is (1 - 4):1. By controlling the mass ratio relationship between the precursor and the oxygen source, the present invention realizes the regulation of the nucleation-growth kinetics of Bi 3 O 2.5 Se 2 crystals, which can significantly improve the quality of the interface of grain boundary merging during the crystal growth process of Bi 3 O 2.5 Se 2 crystals, and at the same time improve the crystallization quality of Bi 3 O 2.5 Se 2 nanosheets. Thus, the present invention effectively solves the common grain boundary defect problem in the polycrystalline domain fusion process of Bi 3 O 2.5 Se 2 , and thus prepares large-sized Bi 3 O 2.5 Se 2 single-crystal nanosheets. Description of the Drawings

[0019] Figure 1 HRTEM image of the Bi 3 O 2.5 Se 2 nanosheets prepared according to the present invention;

[0020] Figure 2 HRTEM image of the Bi 3 O 2.5 Se 2 selected area electron diffraction (SAED) image of the nanosheets prepared according to the present invention;

[0021] Figure 3 Element mapping diagrams of Bi, O, and Se in the Bi 3 O 2.5 Se 2 nanosheets prepared according to the present invention;

[0022] Figure 4 XPS spectrum of the Bi 3 O 2.5 Se 2 nanosheets prepared according to the present invention;

[0023] Figure 5 AFM image of the Bi 3 O 2.5 Se 2 nanosheets prepared according to the present invention;

[0024] Figure 6 Experimental setup diagram provided by the present invention;

[0025] Figure 7 Optical microscope photographs of the influence of reaction raw materials with different mass ratios at 600 °C on the growth of Bi 3 O 2.5 Se 2 nanosheets in the examples of the present invention;

[0026] Figure 8 Optical microscope photographs of the influence of reaction raw materials with different mass ratios at 600 °C on the domain merging of Bi 3 O 2.5 Se 2 nanosheets in the examples of the present invention;

[0027] Figure 9 Optical microscope photographs of the influence of reaction raw materials with different mass ratios at 600 °C on the domain coverage rate of Bi 3 O 2.5 Se 2 nanosheets in the examples of the present invention;

[0028] Figure 10The Bi prepared for the examples 3 O 2.5 Se 2 Optical microscope photograph showing the merging of two nanosheets in the Bi 3 O 2.5 Se 2 nanosheet product;

[0029] Figure 11 For Figure 10 High-angle annular dark-field image of the material surface in the region where the two marked nanosheets merge. Detailed implementation manners

[0030] The present invention provides a method for preparing Bi 3 O 2.5 Se 2 nanosheets, comprising the following steps:

[0031] Using chemical vapor deposition, taking Bi 2 Se 3 and KI containing crystal water as a precursor and an oxygen supply source respectively to form a mixture, placing a substrate above the mixture, heating the mixture under the condition of introducing a carrier gas for reaction, and growing the Bi 3 O 2.5 Se 2 nanosheets on the surface of the substrate.

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

[0034] The present invention studies and finds that the mass ratio of the KI containing crystal water to the Bi 2 Se 3 precursor has an impact on the Bi 3 O 2.5 Se 2 ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​The crystal nucleation-growth kinetics has a significant regulatory effect. By controlling the mass ratio of the precursor and the oxygen source in the present invention, the interfacial quality of domain merging during the growth of Bi 3 O 2.5 Se 2 crystals can be significantly improved, and meanwhile, the crystallization quality of Bi 3 O 2.5 Se 2 nanosheets can be enhanced. Thus, the present invention effectively solves the problem of grain boundary defects commonly found in the polycrystalline domain fusion process of Bi 3 O 2.5 Se 2 and can thereby prepare large-sized Bi 3 O 2.5 Se 2 single-crystal nanosheets.

[0035] In the present invention, the material of the substrate is preferably mica. The substrate is more preferably fluorophlogopite (f-mica), and the fluorophlogopite is preferably atomically flat fluorophlogopite. The surface of the atomically flat fluorophlogopite has no dangling bonds, and the strong electrostatic interaction and low diffusion barrier between Bi 3 O 2.5 Se 2 and the substrate promote the in-plane lateral growth mode of Bi 3 O 2.5 Se 2 nanosheets.

[0036] In the present invention, the distance between the substrate and the mixture is preferably 0.4 - 0.8 cm, more preferably 0.4 - 0.6 cm, and can be 0.4 cm in the examples. By controlling the distance between the substrate and the mixture to be preferably 0.4 - 0.8 cm in the present invention, it can ensure that the precursor can be uniformly transported 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 - 8%, and can be 5% in the examples. The flow rate of the carrier gas is preferably 30 - 100 sccm, more preferably 30 - 80 sccm, and can be 30 sccm in the examples. In the present invention, the hydrogen in the carrier gas is beneficial to the in-plane lateral growth of Bi 3 O 2.5 Se 2 nanosheets to obtain large-sized Bi 3 O 2.5 Se 2 nanosheets.

[0038] In the present invention, the heating rate of temperature rise is preferably 30 - 80 °C / min, more preferably 30 - 50 °C / min, and it can be 30 °C / min in the examples.

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

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

[0041] The preparation method provided by the present invention is preferably carried out under the environmental pressure condition of 760 torr. The preparation method provided by the present invention is preferably carried out in a tube furnace. The device diagram used in the preparation method provided by the present invention is as Figure 6 shown. The preparation method provided by the present invention preferably includes the following steps: forming a mixture of the precursor and the oxygen supply source in a quartz boat; placing the quartz boat containing the mixture at the central position of the quartz tube in the tube furnace; placing the substrate in the quartz tube and above the mixture; before the heating, the present invention preferably seals and washes the quartz tube, and the washing gas used is preferably hydrogen and an inert gas, and the inert gas is preferably argon. The flow rate of the washing gas is preferably 200 - 300 sccm. The washing time is preferably 5 - 10 min. The composition of the washing gas is preferably the same as the composition of the carrier gas. The present invention removes the impurity gas in the quartz tube through the 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 Bi 3 O 2.5 Se 2 nanosheets on the surface of the substrate; 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 introducing the carrier gas.

[0042] The present invention obtains the Bi 3 O 2.5 Se 2 nanosheets on the surface of the substrate. The Bi 3 O 2.5 Se 2 nanosheets are preferably single-crystal nanosheets. The morphology of the Bi 3 O 2.5 Se 2 nanosheets is preferably a hexagonal morphology.

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

[0044] In the following embodiments, the Figure 6 shown experimental device is used to prepare Bi 3 O 2.5 Se 2 nanosheets.

[0045] Example 1

[0046] KI powder is evenly spread on dust-free paper, then placed in an environment with a relative humidity of 35%, placed at room temperature for 10 h, and finally KI . 2H 2 O is collected.

[0047] 200 mg (99.99%) of Bi 2 Se 3 powder and 50 mg of KI . 2H 2 O are used as the precursor and the oxygen supply source (mKI . 2H 2 O:mBi 2 Se 3 = 1:4) and placed in a quartz boat in the center of the quartz tube of a tube furnace. Subsequently, an atomically flat fluorophlogopite (f-mica) substrate is precisely placed upside down on the quartz boat, 0.4 cm above the mixture powder formed by Bi 2 Se 3 and KI . 2H 2 O, so as to ensure that the precursor can be evenly transported to the substrate surface along with the carrier gas. Before the growth starts, the sealed quartz tube is purged with an Ar / H 2 mixed gas (the volume content of hydrogen is 5%) at a flow rate of 200 sccm as the purge gas (i.e., the carrier gas) for 5 min to remove the impurity gas in the tube. Next, the carrier gas flow rate is adjusted to 30 sccm, and at the same time, the quartz tube is heated at a heating rate of 30 °C / min. When the furnace center temperature reaches 600 °C, it is maintained at 600 °C for 5 min to ensure that Bi 2 Se 3 fully reacts with the supplied oxygen and generates Bi 3 O 2.5 Se 2 nanosheets. 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 Bi 3 O 2.5 Se is grown on the surface of the atomically flat fluorophlogopite (f-mica) substrate.2 Nanosheets.

[0048] The Bi 3 O 2.5 Se 2 single-crystalline nanosheets prepared in this example have a hexagonal morphology. The Bi 3 O 2.5 Se 2 optical photograph of the single-crystalline nanosheets is as shown in Figure 7 d.

[0049] Figure 1 For the Bi 3 O 2.5 Se 2 single-crystalline nanosheets prepared in Example 1; Figure 2 For the Bi 3 O 2.5 Se 2 selected area electron diffraction (SAED) pattern of the nanosheets; Figure 3 For the Bi 3 O 2.5 Se 2 elemental mapping of Bi, O, and Se in the nanosheets; Figure 4 For the Bi 3 O 2.5 Se 2 XPS spectrum of the nanosheets; Figure 5 For the Bi 3 O 2.5 Se 2 AFM image of the nanosheets. As can be seen from Figures 1 to 5 the Bi 3 O 2.5 Se 2 single-crystalline nanosheets prepared in Example 1 have a lattice structure belonging to the monoclinic system with lattice parameters of β = 102.91°. The structure of Bi 3 O 2.5 Se 2 is characterized by a layered arrangement where the positively charged [Bi 2 O 2.5 n n+ layers and the negatively charged [BiSe 2 n n- layers are stacked alternately along the crystallographic c-axis. The Bi 3 O 2.5 Se 2 nanosheets exhibit excellent uniformity in optical contrast and show an obvious hexagonal morphology. ​​

[0050] Example 2

[0051] The preparation method is basically the same as that of Example 1, except that the mass of KI . 2H 2 O powder is 200 mg (mKI . 2H 2 O:mBi 2 Se 3 =1:1). The optical photograph of the Bi 3 O 2.5 Se 2 single crystal nanosheets obtained in Example 2 is as shown in Figure 7 a in.

[0052] Example 3

[0053] The preparation method is basically the same as that of Example 1, except that the mass of KI . 2H 2 O powder is 100 mg (mKI . 2H 2 O:mBi 2 Se 3 =1:2). The optical photograph of the Bi 3 O 2.5 Se 2 single crystal nanosheets obtained in Example 3 is as shown in Figure 7 b in.

[0054] Example 4

[0055] The preparation method is basically the same as that of Example 1, except that the mass of KI . 2H 2 O powder is 66.67 mg (mKI . 2H 2 O:mBi 2 Se 3 =1:3). The optical photograph of the Bi 3 O 2.5 Se 2 single crystal nanosheets obtained in Example 4 is as shown in Figure 7 c in.

[0056] Figure 7 This shows the influence of reaction raw materials with different mass ratios at 600 °C on the growth of Bi 3 O 2.5 Se 2 nanosheets in Examples 1-4 of the present invention; Figure 7 The scale bar in is 100 μm. Figure 7 a in is the Bi prepared in Example 2 3 O 2.5 Se2 Nanosheets. Figure 7 In which, b is Bi prepared in Example 3 3 O 2.5 Se 2 Nanosheets. Figure 7 In which, c is Bi prepared in Example 4 3 O 2.5 Se 2 Nanosheets. Figure 7 In which, d is Bi prepared in Example 1 3 O 2.5 Se 2 Nanosheets.

[0057] Figure 8 For the influence of reaction raw materials with different mass ratios at 600 °C in Examples 1 - 4 of the present invention on the 3 O 2.5 Se 2 merging of nanosheet crystal domains of Bi; Figure 8 The scale bar in it is 20 μm. Figure 8 In which, a is Bi prepared in Example 2 3 O 2.5 Se 2 Nanosheets. Figure 8 In which, b is Bi prepared in Example 4 3 O 2.5 Se 2 Nanosheets. Figure 8 In which, c is Bi prepared in Example 1 3 O 2.5 Se 2 Nanosheets.

[0058] Figure 9 For the influence of reaction raw materials with different mass ratios at 600 °C in Examples 1 - 4 of the present invention on the 3 O 2.5 Se 2 coverage rate of nanosheet crystal domains of Bi; Figure 9 The scale bar in it is 250 μm. Figure 9 In which, a is Bi prepared in Example 2 3 O 2.5 Se 2 Nanosheets. Figure 9 In which, b is Bi prepared in Example 4 3 O 2.5 Se 2 Nanosheets. Figure 9 In which, c is Bi prepared in Example 1 3 O 2.5 Se 2 Nanosheets.

[0059] Composed of Figure 7 ,Figure 8 and Figure 9 it can be seen that when the mass ratios of KI . 2H 2 O powder and Bi 2 Se 3 powder are 1:3 and 1:4 respectively, especially 1:4, the obtained Bi 3 O 2.5 Se 2 nanosheet crystal domains are effectively improved in interface quality when merging, solving the grain boundary defect problem during the polycrystalline domain fusion process, and obtaining large-size Bi 3 O 2.5 Se 2 single-crystal nanosheets.

[0060] Figure 10 The optical microscope photo showing the merging of two nanosheets in the Bi 3 O 2.5 Se 2 nanosheet product prepared in Example 1. Figure 11 For Figure 10 the high-angle annular dark-field image of the material surface in the region where two nanosheets merge marked in Figure 11 a in Figure 11 is shown in Figure b in Figure 11 a in Figure 11 is shown in Figure c in Figure 11 a in Figure 11 is shown in Figure d in Figure 11 . From Figure b, Figure c and Figure d in 3 O 2.5 Se 2 it can be seen that the two Bi

[0061] nanosheets prepared in Example 1 are single crystals after merging. . 2H 2 O auxiliary agent and the mass ratio of the bismuth selenide precursor to Bi 3 O 2.5 Se 2 crystal nucleation-growth kinetics form are effectively regulated. By systematically regulating the mass ratio of KI . 2H 2 O to Bi 2 Se 3 precursor (mKI . 2H 2 O:mBi 2 Se 3), the products were characterized and analyzed by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). It was found in the research of this invention that when the mass ratio of mKI . 2H 2 O:mBi 2 Se 3 is at an appropriate mass ratio (preferably 1:3 - 4) (the reaction temperature is 600 °C, the flow rate of the carrier gas is 30 sccm, and the volume content of hydrogen in the carrier gas is 5%), it can significantly improve the interfacial quality of domain merging during the crystal growth of Bi 3 O 2.5 Se 2 , and at the same time improve the crystallization quality of single crystal nanosheets. This invention effectively solves the common grain boundary defect problem in the process of polycrystalline domain fusion, and can prepare large-size Bi 3 O 2.5 Se 2 single crystals.

[0062] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all embodiments. Other embodiments can be obtained according to these embodiments without creative efforts, and these embodiments all fall within the protection scope 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 adopted 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 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 crystalline nanosheets.

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