A preparation method of dendritic two-dimensional palladium diselenide

Abstract

The present invention discloses a preparation method of dendritic two-dimensional PdSe2, belonging to the field of preparation of nonlinear materials. Using KCl as a transport agent, PdCl2 and Se are added into a quartz tube with a specific structure according to the atomic ratio of Pd / Se of 1:1, and the quartz tube is evacuated to 10 ‑3 Pa and then flame-sealed to form a high-vacuum environment inside the quartz tube. The dendritic two-dimensional PdSe2 is obtained through heating reaction. The preparation process of the present invention is simple, the product is dendritic, with a small thickness and large size, and the surface of the product is rich in a large number of defects, which is of great significance for promoting the development of optoelectronics.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of nonlinear optical materials, and particularly relates to a method for preparing dendritic two-dimensional PdSe2. Background Art

[0002] Due to its excellent air stability, high carrier mobility, and wide-band response, two-dimensional PdSe2 has attracted the attention of researchers. At the same time, its unique pentagonal structure endows its surface with abundant active sites, and atomic defects are easily generated at the active sites. The defects enable two-dimensional PdSe2 to be used as a highly active electrocatalyst for hydrogen evolution reaction, and the defects can also regulate the carrier relaxation process of PdSe2, giving it greater advantages in the field of optoelectronic devices.

[0003] The key to promoting the practical application of two-dimensional PdSe2 in ultrafast dynamics lies in realizing the controllable preparation of large-size and defect-rich two-dimensional PdSe2. Currently, the methods for preparing two-dimensional PdSe2 mainly include crystal exfoliation method, chemical vapor deposition method, palladium selenide film method, etc. However, the two-dimensional PdSe2 prepared by the above methods has few defects and is difficult to provide sufficient active sites. If more defects are to be obtained, subsequent means need to be adopted, and the operation is cumbersome. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing dendritic two-dimensional PdSe2, which can directly synthesize dendritic two-dimensional PdSe2 with rich defects in one step. The obtained dendritic two-dimensional PdSe2 has a large size and many defects.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A method for preparing dendritic two-dimensional PdSe2 includes the following steps:

[0007] (1) Weigh a certain amount of PdCl2 powder, Se powder, and KCl respectively, and place each raw material at the bottom of a quartz tube with one end sealed;

[0008] (2) Use mica as a growth substrate, put it into the quartz tube, and separate the mica from the raw materials by the constriction of the quartz tube;

[0009] (3) Place a quartz column with a diameter slightly smaller than that of the quartz tube on the mica, evacuate with a molecular pump, and then aim a flame gun at the position of the quartz column for heating to fuse the quartz tube and the quartz column by high temperature to seal the mouth, thereby forming a high-vacuum growth environment inside the quartz tube;

[0010] (4) Horizontally place the flame-sealed quartz tube in a single-temperature zone tube furnace, align the bottom of the quartz tube with the center of the tube furnace, and make the mica close to the end of the quartz column. After heating and reacting, the dendritic two-dimensional PdSe2 is obtained.

[0011] Further, the molar ratio of PdCl2 powder, Se powder, and KCl used in step (1) is 1:1:(3.5 - 5.6).

[0012] Further, in step (2), the mica is placed 17 cm away from the bottom of the quartz tube.

[0013] Further, in step (3), the vacuum is pumped to 10 -3 Pa.

[0014] Further, in step (4), the temperature of the heating reaction is 800 - 900 °C, the heating rate is 10 - 20 °C / min, the heating time is 30 - 45 min, and the holding time is 5 - 30 min.

[0015] The dendritic two-dimensional PdSe2 prepared by the above method has an ultrafast relaxation time, making it suitable for the fabrication of pulsed lasers, photodetectors, solar cells, light-emitting diodes, and phototransistors, etc.

[0016] The significant advantages of the present invention are as follows:

[0017] (1) The present invention adopts the chemical vapor transport (CVT) method to control the growth temperature by regulating the Pd / Se atomic ratio and the distance between the growth substrate and the bottom of the quartz tube, and prepares large-sized dendritic two-dimensional PdSe2, greatly improving its defect density.

[0018] (2) The dendritic two-dimensional PdSe2 prepared by the present invention has an ultrafast carrier relaxation time, which is of great significance for promoting the development of photonics and optoelectronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a reaction device diagram for preparing dendritic PdSe2 of the present invention.

[0020] Figure 2 It is an optical microscope image of the two-dimensional PdSe2 prepared in Example 1 at 100 times magnification. It can be seen from the optical microscope image that the obtained material is dendritic.

[0021] Figure 3 It is a Raman spectrum of the dendritic PdSe2 prepared in Example 1. It can be seen from the figure that the peak positions of its Raman peaks are at 146 cm -1 、208 cm -1 、224 cm -1 、258 cm -1 , which is basically consistent with the literature reports, indicating that PdSe2 has been successfully synthesized.

[0022] Figure 4This is the Raman mapping image of the dendritic PdSe2 obtained in Example 1. It can be seen from the Raman mapping image that the obtained dendritic PdSe2 is relatively uniform.

[0023] Figure 5 This is a steady-state absorption spectrum of the dendritic PdSe2 prepared in Example 1. As can be seen from the figure, the material has good absorption of light in the 530-1600 nm region.

[0024] Figure 6 The carrier dynamics curves of the dendritic PdSe2 prepared in Example 1 were detected at three wavelengths under a pump light of 400 nm. Further analysis confirmed that it had an ultrafast carrier relaxation time.

[0025] Figure 7 The sample image (a) of the rectangular PdSe2 prepared in Example 3 and its carrier dynamics curves detected at three wavelengths under a pump light of 400 nm (b). Further analysis shows that its carrier relaxation time is much longer than that of the dendritic PdSe2 with more defects. DETAILED DESCRIPTION

[0026] A dendritic two-dimensional PdSe2, the preparation method of which comprises the following steps:

[0027] (1) Weigh a certain amount of PdCl2 powder, Se powder and KCl in a molar ratio of 1:1:(3.5-5.6) and place each raw material at the bottom of a quartz tube sealed at one end;

[0028] (2) Using mica as the growth substrate, place it in a quartz tube so that the mica and the raw material are separated by the neck of the quartz tube and the distance between the mica and the bottom of the quartz tube is 17 cm;

[0029] (3) Place a quartz column with a diameter slightly smaller than the quartz tube on the mica and use a molecular pump to evacuate to 10 -3 Pa, and then use a flame gun to aim at the position of the quartz column for flame sealing, so that a high vacuum growth environment is formed inside the quartz tube;

[0030] (4) Place the flame-sealed quartz tube horizontally in a single-temperature zone tubular furnace, with the bottom of the quartz tube aligned with the center of the tubular furnace and the mica close to the end of the quartz column. Heat the tube to 800-900°C at a rate of 10-20°C / min (the heating time is controlled within 30-45min), then keep the temperature for 5-30min, and then cool naturally to room temperature to obtain dendritic two-dimensional PdSe2.

[0031] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0032] Example 1

[0033] (1)Weigh 3.5 mg of PdCl2, 1.5 mg of Se powder (the atomic ratio of Pd to Se is 1:1), and 5 mg of KCl in sequence. Transport them to the bottom of the quartz tube through a transfer tube. Then, add a clean mica substrate 17 cm away from the bottom of the quartz tube, separate the mica from the raw materials by the necking of the quartz tube, and put a quartz column with a diameter slightly smaller than that of the quartz tube;

[0034] (2)Use a molecular pump to evacuate to 10 -3 Pa, and then use a hydrogen-oxygen machine flame gun to seal the quartz column, creating a high-vacuum growth environment inside the quartz tube;

[0035] (3)Place the sealed quartz tube horizontally in a single-zone tube furnace, align the bottom of the quartz tube with the center of the tube furnace, and make the mica substrate close to the end of the quartz column, that is, the sealed part;

[0036] (4)Heat it to 900 °C at a rate of 20 °C / min (control the heating time within 44 min), then keep it warm for 10 min, and then cool it naturally. The obtained two-dimensional PdSe2 is dendritic, and its lateral size is 80 - 100 μm.

[0037] Example 2

[0038] (1)Weigh 2.6 mg of PdCl2, 2.4 mg of Se powder (the atomic ratio of Pd to Se is 1:2), and 5 mg of KCl in sequence. Transport them to the bottom of the quartz tube through a transfer tube. Then, add a clean mica substrate 17 cm away from the bottom of the quartz tube, separate the mica from the raw materials by the necking of the quartz tube, and put a quartz column with a diameter slightly smaller than that of the quartz tube;

[0039] (2)Use a molecular pump to evacuate to 10 -3 Pa, and then use a hydrogen-oxygen machine flame gun to seal the quartz column, creating a high-vacuum growth environment inside the quartz tube;

[0040] (3)Place the sealed quartz tube horizontally in a single-zone tube furnace, align the bottom of the quartz tube with the center of the tube furnace, and make the mica substrate close to the end of the quartz column, that is, the sealed part;

[0041] (4)Heat it to 900 °C at a rate of 20 °C / min (control the heating time within 44 min), then keep it warm for 10 min, and then cool it naturally. The obtained two-dimensional PdSe2 is rectangular, and its lateral size is 10 - 15 μm.

[0042] Example 3

[0043] (1)Weigh 1.8 mg of PdCl2, 3.2 mg of Se powder (the atomic ratio of Pd to Se is 1:4), and 5 mg of KCl in sequence. Transport them to the bottom of the quartz tube through a transfer tube. Subsequently, add a clean mica substrate 17 cm away from the bottom of the quartz tube, separate the mica from the raw materials by the necking of the quartz tube, and then place a quartz column with a diameter slightly smaller than that of the quartz tube;

[0044] (2)Use a molecular pump to evacuate to 10 -3 Pa, and then use a hydrogen-oxygen machine flame gun to seal the quartz column, creating a high-vacuum growth environment inside the quartz tube;

[0045] (3)Place the sealed quartz tube horizontally in a single-zone tube furnace, align the bottom of the quartz tube with the center of the tube furnace, and make the mica substrate close to the end of the quartz column, i.e., the sealed part;

[0046] (4)Heat it to 900 °C at a rate of 20 °C / min (control the heating time within 44 min), then keep it warm for 10 min, and then cool it naturally. The obtained two-dimensional PdSe2 is rectangular, and its lateral size is 10 - 20 μm.

[0047] Optical property test

[0048] Perform pump-probe characterization on the two-dimensional PdSe2 obtained in Examples 1 and 3. In the pump-probe test, a femtosecond laser with a wavelength of 400 nm is used as the pump beam, and the probe light is supercontinuum white light. Analyze the kinetic curves at probe light wavelengths of 569.5 nm, 600.7 nm, and 630.4 nm respectively, and fit the carrier kinetic curve at 600.7 nm.

[0049] The results show that the values of the two time constants obtained for the two-dimensional PdSe2 in Example 1 are τ1 = 1.00 ps and τ2 = 65.72 ps respectively, while the relaxation time τ2 obtained for the two-dimensional PdSe2 in Example 3 is 120 ps, which is twice that of the dendritic two-dimensional PdSe2 in Example 1. This indicates that the dendritic PdSe2 with rich defects can effectively reduce the carrier relaxation time, and the relaxation time of the dendritic PdSe2 is ultrafast, suggesting its potential for constructing high-performance optical modulation devices with ultrafast response (such as ultrafast lasers, etc.).

[0050] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A preparation method of dendritic two-dimensional PdSe2, characterized in that, It includes the following steps: (1) Weigh a certain amount of PdCl2 powder, Se powder and KCl respectively, and place each raw material at the bottom of a quartz tube with one end sealed; (2) Use mica as the growth substrate, put it into the quartz tube, and separate the mica from the raw materials by the necking of the quartz tube; (3) Place a quartz column with a diameter slightly smaller than that of the quartz tube on the mica, evacuate and then perform flame sealing to create a high-vacuum growth environment inside the quartz tube; (4) Horizontally place the flame-sealed quartz tube in a single-temperature-zone tube furnace, align the bottom of the quartz tube with the center of the tube furnace, and make the mica close to the end of the quartz column. After heating and reaction, the dendritic two-dimensional PdSe2 is obtained.

2. The preparation method according to claim 1, wherein: In step (1), the molar ratio of the PdCl2 powder, Se powder and KCl used is 1:1:(3.5 - 5.6).

3. The preparation method according to claim 1, wherein: In step (2), the mica is placed at a position 17 cm away from the bottom of the quartz tube.

4. The preparation method according to claim 1, characterized in that: In step (3), evacuate to 10 -3 Pa.

5. The preparation method according to claim 1, characterized in that: In step (4), the temperature of the heating reaction is 800 - 900 °C, the heating rate is 10 - 20 °C / min, and the heat preservation time is 5 - 30 min.

6. A dendritic two-dimensional PdSe2 prepared by the method according to any one of claims 1 - 5.

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