CN102897818A - A kind of preparation method of Sm2O3 semiconductor nanocrystal with hexagonal sheet structure - Google Patents

Abstract

A preparation method of hexagonal sheet-like structure Sm ₂ O ₃ semiconductor nanocrystals, adding analytically pure SmCl ₃ 6H ₂ O to isopropanol to prepare solution A; using NaOH solution to adjust the pH value of solution A to 7-12 Form a precursor solution, add CTAB to the precursor solution; pour the precursor solution into the hydrothermal kettle, seal the hydrothermal kettle, control the hydrothermal temperature to 120-200°C, and the pressure to 2-20MPa, react for 6-60 hours, and the reaction ends After cooling to room temperature naturally; the product was taken out, washed with absolute ethanol, centrifuged and separated several times, and then dried to obtain Sm ₂ O ₃ semiconductor nanocrystals with a hexagonal sheet structure. Since the present invention prepares hexagonal sheet-like structure Sm ₂ O ₃ nanocrystals, the reaction is completed once in the liquid phase, and does not require subsequent crystallization heat treatment, thereby avoiding possible agglomeration, crystal grains, etc. of Sm ₂ O ₃ nanocrystals during heat treatment. Coarsening and atmospheric reactions introduce defects such as impurities.

Description

A kind of preparation method of Sm2O3 semiconductor nanocrystal with hexagonal sheet structure

technical field

The invention relates to a method for _{preparing Sm2O3} nanocrystals, in particular to a method for preparing _Sm2O3 semiconductor nanocrystals with a hexagonal sheet structure by a _solvothermal method.

Background technique

Sm ₂ O ₃ is a light yellow powder, easy to deliquescence, insoluble in water, soluble in inorganic acid. Sm ₂ O ₃ is a new generation of energy conversion materials, semiconductor materials and high-performance catalyst materials. Nano Sm ₂ O ₃ can also be used in ceramic capacitors. In terms of magnetic materials, nano Sm ₂ O ₃ is mainly used to prepare rare earth permanent magnet materials; in addition, Sm ₂ O ₃ thin films can also be used in electronic devices, magnetic materials and optical filters of special glasses, which has broad development prospects .

Sm ₂ O ₃ crystals have three crystal forms, which belong to polycrystalline phase transformation oxides. It is a monoclinic crystal phase at room temperature, and it is a light yellow semiconductor at room temperature and pressure. Its melting point is 2269°C and boiling point is 3507°C. When the temperature is higher than 850°C, the monoclinic crystal phase transforms into a cubic crystal phase, and it transforms into a hexagonal crystal phase around 2000°C. With the transformation of the crystal form, the ground state of Sm ³⁺ changes to a certain extent, which leads to the change of the properties of samarium oxide. These special structures will produce some novel characteristics in the aspects of magnetism, electricity and optics, and thus arouse people's great enthusiasm for research.

The currently reported method for preparing Sm ₂ O ₃ is mainly low-temperature self-propagating combustion method [Bo Lili, Yang Wu, Ni Gang, He Xiaoyan, Lv Weilian. Preparation of nano-Sm ₂ O ₃ by low-temperature self-propagating combustion method, Journal of Northwest Normal University, 2005, 41(5):40-42]; Sol-gel method [Deng Gengfeng. 42] and microemulsion method [Geng Shouhua, Zhu Wenqing, Chang Pengmei, Chen Yashao. Preparation of nanometer Sm ₂ O ₃ in inverse microemulsion medium, 2008, 24(9): 1609-1614]; and solid phase sintering method [Yanglong Hou, Zhichuan Xu, Sheng Peng, Chuanbing Rong, J.Ping Liu, Shouheng Sun, A Facile Synthesis of SmCo ₅ Magnets from Core/Shell Co/Sm ₂ O ₃ Nanoparticles, Advanced Materials 2007,19:3349-3352] . The low-temperature self-propagating combustion method and the sol-gel method synthesize Sm ₂ O ₃ at high temperature under an oxygen atmosphere, the powder is easy to agglomerate and the sol-gel process cycle is long, and the utilization rate of the Sm ₂ O ₃ raw material is very small; and Sintering in a reducing atmosphere by the solid phase sintering method will also cause the agglomeration of nanocrystals, and the particles will grow abnormally. At the same time, the precursor prepared by the microemulsion method also needs high-temperature heat treatment to obtain Sm ₂ O ₃ nanocrystals, which is easy to introduce impurities and the powder is easy to agglomerate. In order to achieve the purpose of practical application, it is necessary to develop a low-cost, convenient and feasible preparation process for Sm ₂ O ₃ nanocrystals.

Contents of the invention

The object of the present invention is to provide a hexagonal sheet structure with simple equipment, easy control, lower temperature than microwave hydrothermal method and ordinary hydrothermal method, easier to obtain the required pressure, and can control the formation of specific morphology. A method for preparing Sm ₂ O ₃ semiconductor nanocrystals. The Sm ₂ O ₃ nano crystal prepared by the preparation method of the invention has high purity, good dispersibility, single crystal form and controllable grain growth.

In order to achieve the above object, the technical scheme adopted in the present invention is:

1) Add analytically pure SmCl ₃ 6H ₂ O into isopropanol and stir to obtain a solution A with a Sm ³⁺ concentration of 0.2-1.5 mol/L;

2) Heat and stir solution A at 45~55°C, use NaOH solution to adjust the pH value of solution A to 7~12, continue to stir to form a precursor solution, and then add CTAB to the precursor solution, the amount of which is equal to the theoretical yield of the product The ratio of the amount is n=0.5~2.5; the pH value of the precursor solution is determined again to be 7~12;

3) Pour the precursor solution into the hydrothermal kettle, control the filling degree at 50-60%, then seal the hydrothermal kettle, put it into the electric blast drying oven, control the hydrothermal temperature to 120-200℃, and the pressure to be 2~20MPa, react for 6~60 hours, cool to room temperature naturally after the reaction;

4) Open the hydrothermal kettle, take out the product, wash with absolute ethanol and centrifuge, repeat the washing with absolute ethanol and centrifuge for 4 to 6 times, and then dry it in an electric vacuum drying oven at 45 to 65°C to obtain the hexagonal sheet structure Sm ₂ O ₃ semiconductor nanocrystals.

The stirring in the step 1) adopts a magnetic stirrer to stir.

The concentration of the NaOH solution is 1-5 mol/L.

The electric blast drying oven adopts DHG-9075A type electric blast drying oven.

The electric heating vacuum drying oven adopts the ZKF030 electric heating vacuum drying oven.

Since the present invention prepares hexagonal sheet-like structure Sm ₂ O ₃ nanocrystals, the reaction is completed once in the liquid phase, and does not require subsequent crystallization heat treatment, thereby avoiding possible agglomeration, crystal grains, etc. of Sm ₂ O ₃ nanocrystals during heat treatment. Coarsening and atmospheric reaction introduce defects such as impurities, and the process equipment is simple. The degree of agglomeration is relatively light, and it is easy to obtain a suitable stoichiometric ratio, and the hexagonal sheet structure Sm ₂ O ₃ nanocrystals with a single grain shape; cheaper raw materials can be used; high-temperature calcination and ball milling are omitted, and the introduction of impurities and Structural defects. More importantly, the equipment and instruments required by the solvothermal method are relatively simple. The use of organic solvents is beneficial to obtain the required pressure and the template agent is easily soluble in organic solvents, which is more conducive to the growth of Sm ₂ O ₃ nanocrystals with specific shapes, reducing Agglomeration of nanocrystals. The prepared hexagonal flake Sm ₂ O ₃ has complete grain development, single shape, small particle size and uniform distribution, and high purity. The prepared nano crystals have a strong absorption effect on ultraviolet rays and a strong anti-reflection effect on visible light. Moreover, a variety of template agents can be added by using the solvothermal method, and nanocrystals with different shapes can be controlled and generated simply and conveniently, so as to realize the application of nanocrystals with different structures.

Description of drawings

Fig. 1 is the XRD pattern of the hexagonal sheet structure Sm _{O nanocrystal} prepared by the present invention;

Fig. 2 is an SEM image of Sm ₂ O ₃ nanocrystals with hexagonal sheet structure prepared in the present invention.

Detailed ways

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

Example 1:

1) Add analytically pure SmCl ₃ 6H ₂ O into isopropanol and stir with a magnetic stirrer to prepare a solution A with a Sm ³⁺ concentration of 0.5 mol/L;

2) Heat and stir solution A at 45°C, adjust the pH value of solution A to 9 with NaOH solution with a concentration of 1mol/L, continue stirring for 1 hour to form a precursor solution, and then add hexadecyltri Methyl ammonium bromide (CTAB), the ratio of the amount of substance of its add-on and product theoretical output is n=0.5, confirms again that the pH value of precursor solution is 9;

3) Pour the precursor solution into the hydrothermal kettle, the filling degree is controlled at 50%, then seal the hydrothermal kettle, put it into a DHG-9075A electric blast drying oven, and control the hydrothermal temperature to 120°C. The pressure is 8MPa, react for 48 hours, and naturally cool to room temperature after the reaction;

4) Turn on the hydrothermal kettle, take out the product, wash it with absolute ethanol and centrifuge it, repeat the washing with absolute ethanol and centrifuge it for 6 times, then place it in a ZKF030 electric vacuum drying oven at 50°C to obtain the hexagonal sheet structure Sm ₂ O ₃ semiconductor nanocrystals.

Example 2:

1) Add analytically pure SmCl ₃ 6H ₂ O into isopropanol and stir with a magnetic stirrer to prepare a solution A with a Sm ³⁺ concentration of 0.2 mol/L;

2) Heat and stir solution A at 50°C, use NaOH solution with a concentration of 2mol/L to adjust the pH value of solution A to 10, continue stirring for 1.5 hours to form a precursor solution, and then add hexadecyltri Methyl ammonium bromide (CTAB), the ratio of the amount of substance of its add-on and product theoretical output is n=1; Confirm again that the pH value of precursor solution is 10;

3) Pour the precursor solution into the hydrothermal kettle, the filling degree is controlled at 55%, then seal the hydrothermal kettle, put it into a DHG-9075A electric blast drying oven, and control the hydrothermal temperature to 150°C. The pressure is 15MPa, react for 60 hours, and naturally cool to room temperature after the reaction;

4) Open the hydrothermal kettle, take out the product, wash with absolute ethanol and centrifuge, repeat the washing with absolute ethanol and centrifuge for 4 times, and then dry it in a ZKF030 electric vacuum drying oven at 55°C to obtain the hexagonal sheet structure Sm ₂ O ₃ Semiconductor nanocrystals.

Example 3:

1) Add analytically pure SmCl ₃ 6H ₂ O into isopropanol and stir with a magnetic stirrer to prepare a solution A with a Sm ³⁺ concentration of 0.1mol/L;

2) Heat and stir solution A at 48°C, adjust the pH value of solution A to 11 with NaOH solution with a concentration of 2mol/L, continue stirring for 2 hours to form a precursor solution, and then add hexadecyltri Methyl ammonium bromide (CTAB), the ratio of the amount of substance of its add-on and product theoretical output is n=2; Confirm again that the pH value of precursor solution is 11;

3) Pour the precursor solution into the hydrothermal kettle, the filling degree is controlled at 50%, then seal the hydrothermal kettle, put it into the DHG-9075A type electric blast drying oven, control the hydrothermal temperature to 180°C, The pressure is 20MPa, react for 72 hours, and naturally cool to room temperature after the reaction;

4) Open the hydrothermal kettle, take out the product, wash it with absolute ethanol and centrifuge it, repeat the washing with absolute ethanol and centrifuge it for 5 times, and then dry it in a ZKF030 electric vacuum drying oven at 45°C to obtain the hexagonal sheet structure Sm ₂ O ₃ Semiconductor nanocrystals.

Example 4:

1) Add analytically pure SmCl ₃ 6H ₂ O into isopropanol and stir with a magnetic stirrer to prepare a solution A with a Sm ³⁺ concentration of 1mol/L;

2) Heat and stir solution A at 52°C, adjust the pH value of solution A to 12 with NaOH solution with a concentration of 4mol/L, continue stirring for 2.5 hours to form a precursor solution, and then add hexadecyltri Methyl ammonium bromide (CTAB), the ratio of the amount of substance of its add-on and product theoretical output is n=1.5; Confirm again that the pH value of precursor solution is 12;

3) Pour the precursor solution into the hydrothermal kettle, the filling degree is controlled at 50%, then seal the hydrothermal kettle, put it into a DHG-9075A type electric blast drying oven, control the hydrothermal temperature to 140 °C, The pressure is 18MPa, react for 36 hours, and naturally cool to room temperature after the reaction;

4) Open the hydrothermal kettle, take out the product, wash it with absolute ethanol and centrifuge it, repeat the washing with absolute ethanol and centrifuge it for 6 times, and then dry it in a ZKF030 electric vacuum drying oven at 50°C to obtain the hexagonal sheet structure Sm ₂ O ₃ Semiconductor nanocrystals.

Example 5:

1) Add analytically pure SmCl ₃ 6H ₂ O into isopropanol and stir with a magnetic stirrer to prepare a solution A with a Sm ³⁺ concentration of 0.8mol/L;

2) Heat and stir solution A at 55°C, use 4.5mol/L NaOH solution to adjust the pH value of solution A to 7, continue stirring for 3 hours to form a precursor solution, and then add hexadecyl to the precursor solution Trimethylammonium bromide (CTAB), the ratio of the amount of substance of its add-on and product theoretical output is n=2.5; Confirm again that the pH value of precursor solution is 7;

3) Pour the precursor solution into the hydrothermal kettle, the filling degree is controlled at 60%, then seal the hydrothermal kettle, put it into a DHG-9075A type electric blast drying oven, control the hydrothermal temperature to 200 °C, The pressure is 10MPa, react for 24 hours, and naturally cool to room temperature after the reaction;

4) Open the hydrothermal kettle, take out the product, wash it with absolute ethanol and centrifuge it, repeat the washing with absolute ethanol and centrifuge it for 6 times, and then dry it in a ZKF030 electric vacuum drying oven at 60°C to obtain the hexagonal sheet-like structure Sm ₂ O ₃ Semiconductor nanocrystals.

Embodiment 6:

1) Add analytically pure SmCl ₃ 6H ₂ O into isopropanol and stir with a magnetic stirrer to prepare a solution A with a Sm ³⁺ concentration of 1.5mol/L;

2) Heat and stir solution A at 53°C, adjust the pH value of solution A to 8 with NaOH solution with a concentration of 5mol/L, continue stirring for 1.5 hours to form a precursor solution, and then add hexadecyltri Methyl ammonium bromide (CTAB), the ratio of the amount of substance of its add-on and product theoretical output is n=2; Confirm again that the pH value of precursor solution is 8;

3) Pour the precursor solution into the hydrothermal kettle, the filling degree is controlled at 55%, then seal the hydrothermal kettle, put it into a DHG-9075A electric blast drying oven, and control the hydrothermal temperature to 160°C. The pressure is 2MPa, react for 6 hours, and naturally cool to room temperature after the reaction;

4) Open the hydrothermal kettle, take out the product, wash with absolute ethanol and centrifuge, repeat the washing with absolute ethanol and centrifuge for 6 times, and then dry it in a ZKF030 electric vacuum drying oven at 65°C to obtain the hexagonal sheet structure Sm ₂ O ₃ Semiconductor nanocrystals.

It can be seen from Figure 1 that the Sm ₂ O ₃ nanocrystals prepared by the present invention have high purity, sharper diffraction peaks, and a single monoclinic phase Sm ₂ O ₃ , which is consistent with the standard JCPDS 42-1464Sm ₂ O ₃ card .

It can be seen from Fig. 2 that the monoclinic phase Sm ₂ O ₃ nanocrystals prepared by the present invention have small and evenly distributed particles, light agglomeration, and a hexagonal sheet structure.

Claims (5)

1. a hexagonal sheet structure Sm ₂ O ₃ preparation method of semiconductor nanocrystal, it is characterized in that comprising the following steps: 1) Add analytically pure SmCl ₃ 6H ₂ O into isopropanol and stir to obtain a solution A with a Sm ³⁺ concentration of 0.2-1.5 mol/L; 2) Heat and stir solution A at 45~55°C, use NaOH solution to adjust the pH value of solution A to 7~12, continue to stir to form a precursor solution, and then add CTAB to the precursor solution, the amount of which is equal to the theoretical yield of the product The ratio of the amount is n=0.5~2.5; the pH value of the precursor solution is determined again to be 7~12; 3) Pour the precursor solution into the hydrothermal kettle, control the filling degree at 50-60%, then seal the hydrothermal kettle, put it into the electric blast drying oven, control the hydrothermal temperature to 120-200℃, and the pressure to be 2~20MPa, react for 6~60 hours, cool to room temperature naturally after the reaction; 4) Open the hydrothermal kettle, take out the product, wash with absolute ethanol and centrifuge, repeat the washing with absolute ethanol and centrifuge for 4 to 6 times, and then dry it in an electric vacuum drying oven at 45 to 65°C to obtain the hexagonal sheet structure Sm ₂ O ₃ semiconductor nanocrystals. 2 . The method for preparing hexagonal sheet-like structure Sm ₂ O ₃ semiconductor nanocrystals according to claim 1 , characterized in that: the stirring in step 1) is stirred by a magnetic stirrer. 3 . The method for preparing hexagonal sheet-like structure Sm ₂ O ₃ semiconductor nanocrystals according to claim 1 , wherein the concentration of the NaOH solution is 1˜5 mol/L. 4 . 4 . The method for preparing hexagonal sheet-like structure Sm ₂ O ₃ semiconductor nanocrystals according to claim 1 , characterized in that: the electric blast drying oven adopts a DHG-9075A type electric blast drying oven. 5 . The method for preparing hexagonal sheet-like structure Sm ₂ O ₃ semiconductor nanocrystals according to claim 1 , wherein the electrothermal vacuum drying oven adopts a ZKF030 electric heating vacuum drying oven. 6 .

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