Preparation method of InP quantum dot based on silicon-based phosphine salt and InP quantum dot prepared by same

Abstract

The invention discloses a preparation method of an InP quantum dot based on silicon-based phosphine salt and the InP quantum dot prepared by the preparation method. The preparation method comprises the following steps: stirring and reacting an indium precursor, silicon-based phosphonium salt MP (TMS) 2 and a selectively added first zinc precursor in a solvent in an inert atmosphere at 150-220 DEG C to obtain a solution containing an InP nanocrystal nucleus, then heating to 240-310 DEG C, adding one or more of a second zinc precursor, a selenium precursor and a sulfur precursor, coating the InP nanocrystal nucleus with a shell layer, and carrying out vacuum drying to obtain the indium-selenium-sulfur-doped InP nanocrystal. The shell layer contains one or more of a zinc element, a selenium element and a sulfur element; m in the silicon-based phosphine salt MP (TMS) 2 is K, Na or Li, and TMS is [-Si (CH3) 3].

Description

A method for preparing InP quantum dots based on silicon-based phosphine salts and the InP quantum dots prepared therefrom Technical Field

[0001] This invention relates to the field of nanomaterials, specifically to an indium phosphide (InP) quantum dot and its preparation method. Background Technology

[0002] Quantum dots, also known as nanocrystals, are an important low-dimensional semiconductor material. When a certain voltage or light pressure is applied, they emit fluorescence at a specific frequency, and the frequency changes with the size of the nanocrystals.

[0003] Traditional cadmium and lead-based quantum dot materials face limitations in application due to their bandgap, difficulties in post-processing, and the presence of toxic heavy metals.

[0004] In recent years, InP quantum dots have attracted much attention as a very promising nanomaterial. With a band gap of 1.35 eV, high covalent bond content, and a large Bohr exciton radius (9.6 nm), their fluorescence emission peak is tunable in the visible to near-infrared range and has good stability. In addition, their low toxicity makes InP quantum dots a promising candidate for a wide range of applications in light emission, display, photodetector devices, and fluorescence imaging.

[0005] InP quantum dots are based on certain phosphorus precursors (phosphorus sources), and their molecular structure and reactivity are important factors affecting the growth of InP nanocrystals and the final material properties.

[0006] Currently reported phosphorus sources mainly include PH3, aminophosphine (P(NR2)3, where R is alkyl), silylphosphine (P(SiR3)3, where R is alkyl or aromatic), as well as solid P4 and sodium phosphine alcohol NaOCP. For example, the patent specification with publication number CN106701076A discloses a method for preparing InP quantum dots. This method uses PH3 as the phosphorus source and, by alternately adding raw materials, the growth of quantum dots becomes more uniform, and it is easier to prepare InP quantum dots with larger particle sizes.

[0007] However: (1) PH3 and P4 can react directly with indium fatty acid precursors to prepare InP quantum dots under high temperature solution conditions, but both are highly toxic, have poor reaction controllability, and are highly dangerous to operate; (2) Liquid aminophosphine P(NR2)3 (R=Me, Et) can react with indium precursors to prepare InP quantum dots with good performance. Although it is economical, it still has certain volatility and toxicity. The amount of phosphorus source required for the quantum dots prepared by it is relatively large and the fluorescence modulation range is limited; (3) NaOCP (sodium phosphine alkoxide) is a solid with a low coordination P molecule structure developed in recent years. Phosphorus source can be used to prepare high-performance InP quantum dots from blue light to red light and is safe to operate. However, it has poor solubility in high-boiling-point long-chain alkanes, alkenes or amine solvents, which is not conducive to the stable control of the reaction at high temperature and large-scale production. (4) Tris(trimethylsilyl)phosphine P(TMS)3 (TMS=-Si(CH3)3) is the most widely used liquid phosphorus source for InP quantum dots. Although the performance of InP quantum dots prepared by it has been continuously improved in recent years, it still has the problems of high price, poor safety (flammability) and rapid consumption in the reaction, which leads to harsh requirements for the preparation process. Summary of the Invention

[0008] To address the aforementioned technical problems and shortcomings in the field, this invention provides a method for preparing InP quantum dots based on silicon-based phosphine salts, and the InP quantum dots prepared therefrom.

[0009] This invention employs a novel solid phosphorus source, MP(TMS)2, as one of the reaction precursors, where M is an alkali metal (K, Na, or Li), and TMS is [-Si(CH3)3]. This new phosphorus source combines the advantages and disadvantages of both P(TMS)3 and NaOCP, specifically: 1) Compared to the highly reactive liquid phosphorus source P(TMS)3, the number of active Si-P bonds in the molecular structure of this new phosphorus source is reduced, resulting in moderate reactivity, and its solid powder form makes it safer and more convenient to store and use; 2) Compared to the poor solubility of the solid phosphorus source NaOCP in high-boiling-point long-chain alkyl hydroxyl, alkenyl hydroxyl, or amine solvents, the new phosphorus source of this invention exhibits good solubility in the above solvents, which is beneficial for controlling reaction stability at high temperatures and for large-scale production. The InP quantum dots prepared by the new phosphorus source of this invention have an adjustable emission wavelength range (e.g., adjustable from blue to red light), especially exhibiting a narrow fluorescence half-width and high quantum yield in the green light range, demonstrating excellent luminescence performance. Furthermore, the preparation process of InP quantum dots in this invention is simple and controllable, making it suitable for large-scale production.

[0010] The specific technical solution is as follows: In the first aspect, the present invention provides a method for preparing InP quantum dots, comprising: under an inert atmosphere, in a solvent, an indium precursor, a silicon-based phosphine salt MP(TMS)2 and a first zinc precursor that may or may not be added are stirred and reacted at 150~220℃ (e.g., 160℃, 180℃, 200℃, etc.) to obtain a solution containing InP nanocrystal nuclei, and then the temperature is raised to 240~310℃ (e.g., 280℃, 300℃, etc.), and one or more of a second zinc precursor, a selenium precursor, and a sulfur precursor are added to coat the InP nanocrystal nuclei with a shell layer containing one or more of zinc, selenium, and sulfur elements to obtain InP quantum dots; in the silicon-based phosphine salt MP(TMS)2, M is K, Na or Li, and TMS is [-Si(CH3)3].

[0011] In this invention, the inert atmosphere refers to an atmosphere that does not participate in the reaction, and can be, for example, one or more of nitrogen, argon, etc.

[0012] It should be understood that, unless otherwise specified, the entire reaction process of the preparation method of the present invention is carried out in an inert atmosphere.

[0013] In this invention, the silicon-based phosphine salt MP(TMS)2 is prior art and can be obtained through known means, such as references Inorg. Chem. 1998, 37, 3532-3537, J. Organomet. Chem. 1993, 452, C9, etc.

[0014] The solvent used in the preparation method of InP quantum dots preferably includes one or more of long-chain alkanes, long-chain alkenes, long-chain amines, and long-chain fatty acids with a chain length of not less than 14 carbon atoms, and more preferably includes one or more of octadecane, hexadecane, 1-octadecene, 1-hexadecene, 1-tetradecene, oleylamine, hexadeceneamine, and octadeceneamine.

[0015] The method for preparing InP quantum dots, wherein the indium precursor preferably includes one or more of indium fluoride, indium chloride, indium bromide, indium iodide, indium acetate, indium stearate, and indium tetradecanoate.

[0016] The method for preparing InP quantum dots, wherein the first zinc precursor preferably includes one or more of zinc fluoride, zinc chloride, zinc bromide, zinc iodide, zinc acetate, zinc carbonate, basic zinc carbonate, zinc oleate, zinc stearate, and diethyl zinc.

[0017] In the method for preparing InP quantum dots, the second zinc precursor preferably includes one or more of zinc fluoride, zinc chloride, zinc bromide, zinc iodide, zinc acetate, zinc carbonate, basic zinc carbonate, zinc oleate, zinc stearate, and diethyl zinc.

[0018] In the method for preparing InP quantum dots, the second zinc precursor can be added in solution form. Further, the solvent in the second zinc precursor solution preferably includes one or more of long-chain alkanes, long-chain alkenes, long-chain amines, and long-chain fatty acids with a chain length of not less than 14 carbon atoms, and more preferably includes one or more of octadecane, hexadecane, 1-octadecene, 1-hexadecene, 1-tetradecene, oleylamine, hexadeceneamine, and octadeceneamine.

[0019] In the method for preparing InP quantum dots, the selenium precursor may include a trioctylphosphine solution of selenium.

[0020] The method for preparing InP quantum dots may include one or more of the following: a solution of sulfur trioctylphosphine and dodecathiol.

[0021] Preferably, the method for preparing InP quantum dots incorporates one or more of a selenium precursor and a sulfur precursor, as well as a second zinc precursor, and the shell contains one or two of selenium and sulfur elements, as well as zinc element.

[0022] The method for preparing InP quantum dots may also include steps such as cooling, separation, and purification after the InP quantum dots are generated. These are well known in the art and will not be specifically described here.

[0023] Secondly, the present invention provides InP quantum dots prepared by the preparation method described in the first aspect.

[0024] Compared with existing technologies, the advantages of this invention are as follows: The phosphorus source MP(TMS)2 used in this invention is solid, where M is an alkali metal K, Na, or Li, and TMS is [-Si(CH3)3]. Compared with the traditional liquid phosphorus source P(TMS)3, the number of active Si-P bonds in the molecular structure of this new phosphorus source is reduced, resulting in moderate reactivity; at the same time, its solid powder form makes storage and use safer and more convenient. Furthermore, this novel phosphorus source exhibits good solubility in solvents such as high-boiling-point long-chain alkanes, long-chain alkenes, and long-chain amines. In summary, this phosphorus source can serve as an excellent precursor for the preparation of InP quantum dots. When using the above-mentioned phosphorus source to prepare InP quantum dots, the reaction process is safe and controllable, and the process is relatively simple, making it suitable for large-scale production.

[0025] The phosphorus source MP(TMS)2 used in this invention has moderate reactivity and is suitable for preparing InP quantum dots with good luminescence performance. The InP quantum dots prepared by it have an adjustable emission wavelength range (e.g., adjustable from blue light to red light), and in particular, they can exhibit a narrow fluorescence half-width and a high quantum yield in the green light range, with excellent luminescence performance. Detailed Implementation

[0026] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0027] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0028] Example 1: ① Under an inert atmosphere, 5 mL of oleylamine was added to a solid mixture containing 0.2 mmol indium chloride and 0.34 mmol KP(TMS)₂. After stirring at 220 °C for 30 min, a solution containing InP nanocrystal nuclei was obtained. ② The temperature was raised to 310 °C, and within 40 min, a solution of 3 mmol zinc oleate in oleylamine, a solution of 0.8 mmol selenium in trioctylphosphine, and a solution of 1.6 mmol sulfur in trioctylphosphine were added. After cooling, separation, and purification, InP quantum dots were obtained.

[0029] Example 2: ① Under an inert atmosphere, 5 mL of oleylamine was added to a solid mixture containing 0.2 mmol indium chloride, 1.6 mmol zinc chloride, and 0.34 mmol LKP(TMS)2. The mixture was stirred at 220 °C for 30 min to obtain a solution containing InP nanocrystal nuclei. ② The temperature was raised to 310 °C, and 3 mmol of oleylamine solution containing zinc stearate, 0.8 mmol of trioctylphosphine solution containing selenium, and 1.6 mmol of trioctylphosphine solution containing sulfur were added over 40 min. After cooling, separation, and purification, InP quantum dots were obtained.

[0030] Example 3: ① Under an inert atmosphere, 11.8 mL of oleylamine was added to a solid mixture containing 0.2 mmol indium chloride, 1.6 mmol zinc iodide, and 0.34 mmol NaP(TMS)₂, and the mixture was stirred at 200 °C for 30 min to obtain a solution containing InP nanocrystal nuclei; ② The temperature was raised to 240 °C, and 1 mmol of oleylamine solution containing zinc oleate and 0.8 mmol of trioctylphosphine solution containing selenium were added over 15 min; ③ The temperature was raised to 310 °C, and 3 mmol of oleylamine solution containing zinc oleate, 1.2 mmol of trioctylphosphine solution containing selenium, and 1.8 mmol of trioctylphosphine solution containing sulfur were added over 40 min. After cooling, separation, and purification, InP quantum dots were obtained.

[0031] Example 4: ① Under an inert atmosphere, 1.8 mL of oleylamine was added to a solid mixture containing 0.2 mmol indium chloride, 1.6 mmol zinc bromide, and 0.34 mmol NaP(TMS)₂, and the mixture was stirred at 180 °C for 30 min to obtain a solution containing InP nanocrystal nuclei; ② The temperature was raised to 280 °C, and 1 mmol of oleylamine solution containing zinc oleate and 0.8 mmol of trioctylphosphine solution containing selenium were added over 30 min; ③ The temperature was raised to 310 °C, and 3 mmol of oleylamine solution containing zinc acetate and 5 mL of dodecanethiol were added over 30 min. After cooling, separation, and purification, InP quantum dots were obtained.

[0032] Example 5: ① Under an inert atmosphere, 1.8 mL of oleylamine was added to a solid mixture containing 0.2 mmol indium chloride, 1.6 mmol zinc fluoride, and 0.34 mmol NaP(TMS)₂. The mixture was stirred at 160 °C for 30 min to obtain a solution containing InP nanocrystal nuclei. ② The temperature was raised to 310 °C, and a solution of 3 mmol diethylzinc, 0.8 mmol selenium in trioctylphosphine, and 5 mL dodecyl mercaptan were added over 40 min. After cooling, separation, and purification, InP quantum dots were obtained.

[0033] Example 6: ① Under an inert atmosphere, 1.8 mL of 1-octadecene was added to a solid mixture containing 0.2 mmol indium iodide, 1.6 mmol zinc iodide, and 0.34 mmol LiP(TMS)₂. The mixture was stirred at 150 °C for 30 min to obtain a solution containing InP nanocrystal nuclei; ② The temperature was raised to 300 °C, and 3 mmol of a 1-octadecene solution of zinc oleate and 3 mmol of a trioctylphosphine solution of sulfur were added over 30 min. After cooling, separation, and purification, InP quantum dots were obtained.

[0034] The InP quantum dots prepared in Examples 1-6 were dispersed in n-hexane and subjected to fluorescence spectroscopy and fluorescence quantum yield tests. The results are shown in Table 1 below.

[0035] Table 1 As shown in the table above, the InP quantum dots prepared using MP(TMS)2 as the phosphorus source have tunable fluorescence emission peaks from blue to red light, and exhibit narrow fluorescence half-width and high quantum yield, especially in the green light range, demonstrating good luminescence performance.

[0036] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing InP quantum dots, characterized in that, include: In an inert atmosphere, in a solvent, an indium precursor, a silicon-based phosphine salt MP(TMS)2, and a selectively added first zinc precursor are stirred and reacted at 150-220°C to obtain a solution containing InP nanocrystal nuclei. Then, the temperature is raised to 240-310°C, and one or more of a second zinc precursor, a selenium precursor, and a sulfur precursor are added to coat the InP nanocrystal nuclei with a shell containing one or more of zinc, selenium, and sulfur elements to obtain InP quantum dots. In the silicon-based phosphine salt MP(TMS)2, M is K, Na, or Li, and TMS is [-Si(CH3)3].

2. The method for preparing InP quantum dots according to claim 1, characterized in that, The solvent includes one or more of long-chain alkanes, long-chain alkenes, long-chain amines, and long-chain fatty acids with a chain length of not less than 14 carbon atoms, preferably including one or more of octadecane, hexadecane, 1-octadecene, 1-hexadecene, 1-tetradecene, oleylamine, hexadeceneamine, and octadeceneamine.

3. The method for preparing InP quantum dots according to claim 1, characterized in that, The indium precursor includes one or more of indium fluoride, indium chloride, indium bromide, indium iodide, indium acetate, indium stearate, and indium tetradecanoate.

4. The method for preparing InP quantum dots according to claim 1, characterized in that, The first zinc precursor includes one or more of zinc fluoride, zinc chloride, zinc bromide, zinc iodide, zinc acetate, zinc carbonate, basic zinc carbonate, zinc oleate, zinc stearate, and diethyl zinc.

5. The method for preparing InP quantum dots according to claim 1, characterized in that, The second zinc precursor includes one or more of zinc fluoride, zinc chloride, zinc bromide, zinc iodide, zinc acetate, zinc carbonate, basic zinc carbonate, zinc oleate, zinc stearate, and diethyl zinc.

6. The method for preparing InP quantum dots according to claim 1 or 4, characterized in that, The second zinc precursor is added in solution form. The solvent in the second zinc precursor solution includes one or more of long-chain alkanes, long-chain alkenes, long-chain amines, and long-chain fatty acids with a chain length of not less than 14 carbon atoms, preferably including one or more of octadecane, hexadecane, 1-octadecene, 1-hexadecene, 1-tetradecene, oleylamine, hexadeceneamine, and octadeceneamine.

7. The method for preparing InP quantum dots according to claim 1, characterized in that, The selenium precursor comprises a trioctylphosphine solution of selenium.

8. The method for preparing InP quantum dots according to claim 1, characterized in that, The sulfur precursor includes one or more of trioctylphosphine solution of sulfur and dodecyl mercaptan.

9. The method for preparing InP quantum dots according to claim 1, characterized in that, The preparation method incorporates one or more of a selenium precursor and a sulfur precursor, as well as a second zinc precursor, and the shell contains one or two of selenium and sulfur elements, as well as zinc elements.

10. InP quantum dots prepared by the preparation method according to any one of claims 1 to 9.

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