Method for preparing single-crystal-phase intermediate infrared band gap indium antimonide colloidal quantum dots through gradual crystallization and product

Abstract

The invention discloses a method for preparing single-crystal-phase intermediate infrared band gap indium antimonide colloidal quantum dots through gradual crystallization, which comprises the following steps: (1) preparing a precursor solution containing an indium precursor and an antimony precursor, and heating at 100-300 DEG C for 10-180 minutes; (2) in an inert atmosphere, heating a solvent to a reduction temperature, adding a reducing agent and the heated precursor solution, and maintaining a reaction system at the reduction temperature for 5-60 minutes; and heating the system to a reaction temperature, keeping the temperature for 1-180 minutes, and stopping the reaction to obtain the single-crystal-phase intermediate infrared band gap indium antimonide colloidal quantum dots. The invention also discloses the intermediate infrared band gap indium antimonide colloidal quantum dot prepared by the preparation method. According to the preparation method disclosed by the invention, complicated post-treatment is not needed, the prepared intermediate infrared band gap indium antimonide colloidal quantum dots are in a single crystal phase, the size is large, the spectral response range is relatively wide, and the prepared indium antimonide colloidal quantum dots are good in repeatability.

Description

Technical Field

[0001] The invention relates to the technical field of nano material synthesis, and in particular to a method and product for preparing single-crystal mid-infrared band gap indium antimonide colloidal quantum dots by gradual crystallization. Background Art

[0002] Infrared detectors are widely used in night vision, industrial detection, scientific instruments and other fields. InSb (indium antimony) colloidal quantum dots (CQDs) are a "green" semiconductor material with unique optoelectronic properties. They are considered to be a promising mid-infrared (MIR) light detection material due to their non-toxicity, low cost, and excellent optical and electronic properties.

[0003] However, existing InSb quantum dot synthesis methods have many limitations, such as short absorption wavelength, wide size distribution, and complex size-selective precipitation. In 2012, the Talapin team developed the first successful synthesis of InSb colloidal quantum dots with size tunability (3.4-6.5nm) and narrow polydispersity (reduced to about 15% by post-synthesis size-selective precipitation technology) by using lithium triethylborohydride (LiEt 3 BH, also known as superhydride), silyl amide antimony (Sb[N(Si(Me) 3 ) 2 ] 3 ) and InCl 3 Co-reduction at room temperature, and then heated to the growth temperature (240-260°C) (Liu, W.; Chang, AY; Schaller, RD; Talapin, DV, Colloidal InSb Nanocrystals. Journal of the American Chemical Society 2012, 134 (50), 20258-20261.). However, on the one hand, the size range of the obtained quantum dot product is small, which cannot meet the needs of longer wavelength response; on the other hand, the monodispersity of the obtained quantum dot product is extremely poor, and complex size-selective precipitation technology is required before it can be used. These limitations seriously affect the application of InSb quantum dots in mid-infrared optoelectronic devices.

[0004] A Chinese patent document with the publication number CN119430279A discloses a method for preparing size - controllable monodisperse indium antimonide colloidal quantum dots, which includes the following steps: (1) Prepare a precursor solution containing an indium precursor and an antimony precursor, and heat the precursor solution at 50 - 300 °C for 1 - 20 min; (2) Under an inert atmosphere, heat the solvent to the reaction temperature, inject a reducing agent, and then inject the heated precursor solution. After maintaining the reaction temperature for 10 s - 30 min, stop the reaction to obtain monodisperse indium antimonide colloidal quantum dots; the reaction temperature is 250 - 300 °C. The preparation method of this invention can achieve precise control of the size of indium antimonide colloidal quantum dots without relying on complex size - selective precipitation techniques. However, the size of the quantum dots prepared needs to be further improved. In addition, the quantum dots prepared are a mixed phase of the zinc blende phase and the wurtzite phase.

[0005] The crystal phases of indium antimonide (InSb) colloidal quantum dots mainly include the thermodynamically stable zinc blende phase (ZB) and the metastable wurtzite phase (WZ). The ZB phase has a cubic structure, which is common in natural bulk materials. Its direct bandgap is relatively small (about 0.17 eV), and in quantum dots, the optical response can be extended to the near - infrared to mid - infrared band through the quantum confinement effect; the WZ phase has a hexagonal structure and is usually generated along with the ZB phase during the rapid - growth reaction process. Its bandgap is slightly larger than that of the ZB phase. Currently, indium antimonide colloidal quantum dots prepared by the preparation methods of large - size indium antimonide (InSb) colloidal quantum dots are all a mixed phase of the zinc blende phase (ZB) and the wurtzite phase (WZ).

[0006] The core advantage of single - crystal - phase quantum dots lies in their structural uniformity. The single crystal phase avoids interface defects and energy - band disorders caused by the mixed phase, thus ensuring the coherence of the carrier migration path, the narrow - band characteristic of the spectrum, and the long - term stability of the material in the device. In addition, in the mixed - phase system, the lattice mismatch at the ZB / WZ interface will introduce stress and recombination centers, which not only reduce the carrier lifetime and quantum yield but also cause the broadening of the absorption / emission spectrum, limiting its application in optoelectronic devices (such as infrared detection).

[0007] Therefore, achieving single - crystal - phase control through a new synthesis strategy is the top priority for improving the performance of InSb quantum dots. Summary of the Invention

[0008] The present invention provides a method for gradually crystallizing to prepare single - crystal - phase mid - infrared - bandgap indium antimonide colloidal quantum dots, which does not require complex post - treatment. The prepared mid - infrared - bandgap indium antimonide colloidal quantum dots are in a single zinc blende phase (ZB), with large size and uniform size distribution.

[0009] The technical solution of the present invention is as follows:

[0010] A method for gradually crystallizing to prepare single - crystal - phase mid - infrared - bandgap indium antimonide colloidal quantum dots, including:

[0011] (1) Prepare a precursor solution containing an indium precursor and an antimony precursor, and heat it at 100 - 300 °C for 10 - 180 min;

[0012] (2) In an inert atmosphere, first heat the solvent to the reduction temperature, add a reducing agent and the heated precursor solution, and maintain the reaction system at the reduction temperature for 5 - 60 min;

[0013] Then heat the system to the reaction temperature and hold for 1 - 180 min, stop the reaction, and obtain single-crystalline-phase indium antimonide colloidal quantum dots.

[0014] Preferably, before adding the precursor solution, first heat the precursor solution at 60 - 100 °C for 5 - 15 min.

[0015] Before injecting the precursor solution, the present invention first performs a heat treatment on the precursor solution to enhance its reaction activity, which helps the formation of amorphous intermediates, so that the obtained indium antimonide colloidal quantum dots have a larger size and good monodispersity. The size and distribution of the quantum dot products synthesized after heat-treating the precursor solution at a high temperature of 60 - 120 °C are significantly better than those obtained by heat-treating the precursor solution below 60 °C.

[0016] Preferably, the reduction temperature is 200 - 230 °C, and it is maintained at the reduction temperature for 5 - 20 min.

[0017] Preferably, the reaction temperature is 250 - 320 °C, and it is held at the reaction temperature for 1 - 30 min.

[0018] Preferably, in the reaction system of step (2), the concentrations of the indium precursor and the antimony precursor are independently 3.6 - 28.8 mmol / L.

[0019] More preferably, in step (2), the reducing agent is added in excess, so that the molar ratio of the amount of the reducing agent added to the amount of the precursor added is above 40:1.

[0020] By regulating the concentration of the precursor (high concentration), the amount of the reducing agent (added in excess), two-step temperature rise, and growth time in the reaction system, the synthesis of indium antimonide colloidal quantum dots with a larger size and single-crystalline phase can be achieved.

[0021] More preferably, in the reaction system of step (2), the molar ratio of the reducing agent to the precursor is above 40:1. In the case of a high ratio of the reducing agent, the reduction kinetics can be accelerated, and large-sized intermediates can be rapidly formed, so that the finally obtained quantum dots have a larger size and better monodispersity.

[0022] In the present invention, the method of stepwise heating makes the reaction process easier to control, the growth is relatively mild, so that while the size of the obtained indium antimonide colloidal quantum dots breaks through the current maximum size record of indium antimonide colloidal quantum dots, the formation of a mixed phase is avoided.

[0023] The present invention also provides a single-crystalline mid-infrared bandgap indium antimonide colloidal quantum dot prepared by the above preparation method.

[0024] The size range of the single-crystalline mid-infrared bandgap indium antimonide colloidal quantum dots of the present invention is about 20 nm - 24 nm, and it is a single-crystalline sphalerite phase.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] The present invention provides a method for preparing single-crystalline mid-infrared bandgap indium antimonide colloidal quantum dots by stepwise crystallization, realizing the controllable synthesis of mid-infrared bandgap indium antimonide colloidal quantum dots. This method synthesizes large-sized and single-crystalline sphalerite-phase InSb colloidal quantum dots, achieving the control of large-sized single crystal phases, filling the gap of environmentally friendly quantum dots in the mid-infrared field, and providing new possibilities for the application of InSb quantum dots in mid-infrared optoelectronic devices. Description of the Drawings

[0027] Figure 1 In-situ XRD pattern of InSb colloidal quantum dots in Comparative Example 1;

[0028] Figure 2 XRD pattern (a) and TEM image (b) of the amorphous intermediate, and XRD pattern (c) and TEM image (d) of InSb colloidal quantum dots in Example 1;

[0029] Figure 3 EDS elemental analysis spectrum of InSb colloidal quantum dots prepared in Example 1;

[0030] Figure 4 Fourier infrared absorption spectrum of InSb colloidal quantum dots prepared in Example 1;

[0031] Figure 5 TEM image of InSb colloidal quantum dots prepared in Example 2;

[0032] Figure 6 TEM image of InSb colloidal quantum dots prepared in Example 3. Detailed Description of the Embodiments

[0033] The present invention will be further described in detail below with reference to the drawings and embodiments. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0034] Comparative Example 1:

[0035] A method for preparing mid-infrared bandgap indium antimonide colloidal quantum dots:

[0036] (1) Prepare the reducing agent solution: Measure 6 mL of lithium triethylborohydride (LiEt3BH) solution and 6 mL of n-octyl ether solvent, mix them in a pre-prepared container, and ensure thorough and uniform mixing of the solution by stirring.

[0037] (2) Prepare the precursor solution: Accurately weigh 0.78 mmol of indium chloride (InCl3) and antimony chloride (SbCl3) powders respectively, add them to a mixed solution of 2 mL of toluene and 0.6 mL of oleylamine (or other fatty amine), and make the mixture uniform by stirring.

[0038] (3) Dissolve the precursor: Heat the precursor solution prepared in step 2 to 75 °C, continue heating and stirring until the precursor powder is completely dissolved to form a clear and transparent solution.

[0039] (4) Reaction process: Add 5 mL of oleylamine to a 25 mL three-necked flask, introduce argon and keep stirring. After exhausting the air in the flask, heat the flask to 270 °C. Subsequently, inject 1.5 mL of the lithium triethylborohydride solution prepared in step 1 into the flask. Heat the precursor solution obtained in step 3 to 100 °C and keep it for 10 minutes, then quickly inject 100 μL of the heated precursor solution into the flask within the shortest possible time, and maintain the reaction temperature for growth.

[0040] (5) Grow for 10 minutes, quickly stop the reaction of the reaction solution with cold water, cool it to room temperature, purify it using toluene and methanol solvents, and disperse and store it with toluene or tetrachloroethylene solution to obtain InSb colloidal quantum dots.

[0041] The in-situ XRD pattern of the InSb colloidal quantum dots obtained in Comparative Example 1 is as Figure 1 shown. The XRD pattern shows that the InSb colloidal quantum dots obtained in Comparative Example 1 are a mixed-phase crystal form of zinc blende phase (ZB) and wurtzite phase (WZ).

[0042] Example 1:

[0043] A method for preparing mid-infrared bandgap indium antimonide colloidal quantum dots by stepwise crystallization:

[0044] (1) Prepare the reducing agent solution: Measure 6 mL of lithium triethylborohydride (LiEt3BH) solution and 6 mL of n-octyl ether solvent, mix them in a pre-prepared container, and ensure thorough and uniform mixing of the solution by stirring.

[0045] (2) Preparation of the precursor solution: Weigh accurately 0.78 mmol of indium chloride (InCl3) and antimony chloride (SbCl3) powders respectively, add them to a mixed solution of 2 mL of toluene and 0.6 mL of oleylamine (or other fatty amines), and make the mixture homogeneous by stirring.

[0046] (3) Dissolution of the precursor: Heat the precursor solution prepared in step (2) to 75 °C, continuously heat and stir until the precursor powder is completely dissolved to form a clear and transparent solution.

[0047] (4) Reaction process: Add 5 mL of oleylamine to a 25 mL three-necked flask, introduce argon and continuously stir. After exhausting the air in the flask, heat the flask to the reduction temperature of 230 °C. Heat the precursor solution obtained in step (3) to 100 °C and keep it for 10 minutes, and then quickly inject 100 μL of the heated precursor solution into the flask in the shortest possible time. Subsequently, inject 1.5 mL of the lithium triethylborohydride solution prepared in step (1) into the flask, maintain it for 10 minutes at the reduction temperature, and then heat to 270 °C. Keep the reaction temperature for growth.

[0048] (5) After growing for 10 minutes, when the target growth time is reached, quickly stop the reaction of the reaction solution with cold water, cool it to room temperature, purify it using toluene and methanol solvents, and disperse and store it with toluene or tetrachloroethylene solution.

[0049] The reaction process of the preparation method described in the present invention is characterized in that it includes the following steps:

[0050] (1) In Example 1, at the reduction temperature, uniform amorphous nanoparticles with an average particle size of about 16 nm are generated, and the amorphous structural characteristics are confirmed by the XRD image in (a) of Figure 2 , and the size distribution characteristics are confirmed by the TEM analysis in (b) of Figure 2 ;

[0051] (2) In Example 1, when the temperature is raised to the growth temperature for 10 minutes, uniform crystalline nanoparticles with an average particle size of about 23.7 nm, that is, InSb colloidal quantum dots, are generated. The crystalline structural characteristics are confirmed by the XRD image in (c) of Figure 2 , and the size distribution characteristics are confirmed by the TEM analysis in (d) of Figure 2 .

[0052] It should be noted that according to the XRD image in (c) of Figure 2 , the InSb colloidal quantum dots obtained by the stepwise temperature raising method only show a single crystal phase of the zinc blende (ZB) structure, and the single crystal synthesis of large-size InSb colloidal quantum dots is realized for the first time.

[0053] (3) EDS elemental analysis of the final product( Figure 3 ) shows that the stoichiometric ratio of the constituent elements of the prepared quantum dots is close to 1:1, proving that this method has the ability of precise composition control at the same time.

[0054] (4) Fourier transform infrared absorption spectrum( Figure 4 ) proves that the samples synthesized by this method have good absorption in the near-infrared to mid-infrared range.

[0055] Example 2:

[0056] A method for preparing mid-infrared bandgap indium antimonide colloidal quantum dots by stepwise crystallization:

[0057] (1) Prepare a reducing agent solution: Measure 6 mL of lithium triethylborohydride (LiEt3BH) solution and 6 mL of n-octyl ether solvent, mix them in a pre-prepared container, and ensure thorough and uniform mixing of the solution by stirring.

[0058] (2) Prepare a precursor solution: Weigh accurately 0.78 mmol of indium chloride (InCl3) and antimony chloride (SbCl3) powders respectively, add them to a mixed solution of 2 mL of toluene and 0.6 mL of oleylamine (or other fatty amine), and make the mixture uniform by stirring.

[0059] (3) Dissolve the precursor: Heat the precursor solution prepared in step 2 to 75 °C, continue heating and stirring until the precursor powder is completely dissolved to form a clear and transparent solution.

[0060] (4) Reaction process: Add 5 mL of oleylamine to a 25 mL three-necked flask, introduce argon and stir continuously. After exhausting the air in the flask, heat the flask to the reduction temperature of 230 °C. Heat the precursor solution obtained in step 3 to 100 °C and keep it for 10 minutes, and then quickly inject 100 μL of the heated precursor solution into the flask in the shortest possible time. Subsequently, inject 1.5 mL of the lithium triethylborohydride solution prepared in step 1 into the flask, maintain it at the reduction temperature for 5 minutes, and then heat it to 250 °C. Keep the reaction temperature for growth.

[0061] (5) Grow for 30 minutes. After reaching the target growth time, quickly stop the reaction of the reaction solution with cold water, cool it to room temperature, purify it with toluene and methanol solvents, and disperse and store it with toluene or tetrachloroethylene solution.

[0062] The TEM image of the InSb colloidal quantum dots prepared in Example 2 is as Figure 5 shown, and the average particle size is 22.7 nm. The InSb colloidal quantum dots prepared in Example 2 are single crystal phases with a zinc blende (ZB) structure.

[0063] Example 3:

[0064] A method for preparing mid-infrared bandgap indium antimonide colloidal quantum dots by stepwise crystallization:

[0065] (1) Prepare a reducing agent solution: Measure 6 mL of lithium triethylborohydride (LiEt3BH) solution and 6 mL of octyl ether solvent, mix them in a pre-prepared container, and ensure thorough and uniform mixing of the solution by stirring.

[0066] (2) Prepare a precursor solution: Weigh accurately 0.78 mmol of indium chloride (InCl3) and antimony chloride (SbCl3) powders respectively, add them to a mixed solution of 2 mL of toluene and 0.6 mL of oleylamine (or other fatty amine), and make the mixture uniform by stirring.

[0067] (3) Dissolve the precursor: Heat the precursor solution prepared in step 2 to 75 °C, continue heating and stirring until the precursor powder is completely dissolved to form a clear and transparent solution.

[0068] (4) Reaction process: Add 5 mL of oleylamine to a 25 mL three-necked flask, introduce argon and keep stirring. After exhausting the air in the flask, heat the flask to the reduction temperature of 230 °C. Heat the precursor solution obtained in step 3 to 100 °C and keep it for 10 minutes, then quickly inject 100 μL of the heated precursor solution into the flask in the shortest possible time. Subsequently, inject 1.5 mL of the lithium triethylborohydride solution prepared in step 1 into the flask, maintain it at the reduction temperature for 5 minutes, and then heat to 250 °C. Keep the reaction temperature for growth.

[0069] (5) Grow for 5 minutes. After reaching the target growth time, quickly stop the reaction of the reaction solution with cold water, cool it to room temperature, purify it using toluene and methanol solvents, and disperse and store it with toluene or tetrachloroethylene solution.

[0070] The TEM image of the InSb colloidal quantum dots prepared in Example 3 is as Figure 6 shown, and the average particle size is 20.8 nm. The InSb colloidal quantum dots prepared in Example 3 are single crystal phases of the zinc blende (ZB) structure. The above-described embodiments have elaborated on the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, supplements, equivalent replacements, etc. made within the scope of the principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing single-crystalline mid-infrared bandgap indium antimonide colloidal quantum dots by stepwise crystallization, characterized in that: include: (1) preparing a precursor solution containing an indium precursor and an antimony precursor, and heating the solution at 100 to 300° C. for 10 to 180 minutes; (2) In an inert atmosphere, the solvent is first heated to the reduction temperature, a reducing agent and the heated precursor solution are added, and the reaction system is maintained at the reduction temperature for 5 to 60 minutes; Then the system is heated to a reaction temperature and maintained for 1 to 180 minutes, the reaction is stopped, and single crystal mid-infrared band gap indium antimonide colloidal quantum dots are obtained.

2. The method for preparing single-crystalline mid-infrared bandgap indium antimonide colloidal quantum dots by stepwise crystallization according to claim 1, characterized in that: Before adding the precursor solution, the precursor solution is heated at 60-100° C. for 5-15 minutes.

3. The method for preparing single-crystalline mid-infrared bandgap indium antimonide colloidal quantum dots by stepwise crystallization according to claim 1, characterized in that: The reduction temperature is 200-230° C. and is maintained at the reduction temperature for 5-20 minutes.

4. The method for preparing single-crystalline mid-infrared bandgap indium antimonide colloidal quantum dots by stepwise crystallization according to claim 1 or 3, characterized in that: The reaction temperature is 250-320°C, and the reaction temperature is maintained for 1-30 minutes.

5. The method for preparing single-crystalline mid-infrared bandgap indium antimonide colloidal quantum dots by stepwise crystallization according to claim 1, characterized in that: In the reaction system of step (2), the concentrations of the indium precursor and the antimony precursor are independently 3.6 to 28.8 mmol / L.

6. The method for preparing single-crystalline mid-infrared bandgap indium antimonide colloidal quantum dots by stepwise crystallization according to claim 1, characterized in that: In step (2), the reducing agent is added in excess.

7. The method for preparing single-crystalline mid-infrared bandgap indium antimonide colloidal quantum dots by stepwise crystallization according to claim 1 or 6, characterized in that: In the reaction system of step (2), the molar ratio of the reducing agent to the precursor is greater than 40:

1.

8. A single crystal mid-infrared band gap indium antimonide colloidal quantum dot, characterized in that: The preparation method is described in any one of claims 1 to 7.

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