A synthesis method of self-assembled growth of monodisperse HgTe quantum dots

Abstract

The present invention provides a method for synthesizing self-assembled monodisperse HgTe quantum dots, belonging to the technical field of short-wave infrared optoelectronic materials. Specifically, a TOPTe precursor solution and a Hg precursor solution are prepared. The TOPTe precursor solution is injected into the Hg precursor solution, and stirred at 35-50 °C for 8-10 min to obtain a HgTe quantum dot seed crystal solution. The oleylamine solution is degassed, and the HgTe quantum dot seed crystal solution is injected into the oleylamine solution, and self-assembled and grown at 70-90 °C for 3-5 min. A quenching agent is added, and after cooling, a HgTe quantum dot solution to be filtered is obtained. It is centrifugally washed with an anti-solvent multiple times and dried to obtain self-assembled monodisperse HgTe quantum dots. The HgTe quantum dots obtained by the present invention have high shape and size uniformity, can achieve short-wave light absorption of 1400-2500 nm, and have the advantages of controllable size and low cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of short-wave infrared optoelectronic materials, and particularly relates to a method for synthesizing self-assembled growth monodisperse HgTe quantum dots. Background Art

[0002] As a low-dimensional semiconductor material, quantum dots have a size range between a few nanometers and dozens of nanometers, and have excellent optoelectronic properties, and are widely used in the fields of light emission, solar cells, and photodetectors. Quantum dots can be synthesized by simple and low-cost chemical methods, with high process controllability and good repeatability, and can be compatible with different substrate materials. Different from traditional bulk semiconductor materials, due to the quantum size effect of quantum dots, the bandgap of quantum dots can be continuously adjusted by precisely controlling their size range, and it has a very wide application prospect in the fields of light-emitting display and micro-spectrometer.

[0003] Bulk HgTe is a negative bandgap semiconductor material. Due to the large exciton Bohr radius (40 nm) of HgTe quantum dots, it has an obvious quantum confinement effect and exhibits a narrow bandgap characteristic, and its light absorption range can be extended to the entire infrared band. By using HgTe quantum dots to prepare colloidal inks, low-cost, large-area, and highly uniform thin films can be prepared through spin coating, drop coating, and spraying processes. Compared with the current use of molecular epitaxial growth of InSb, InGaAs, or HgCdTe, the material usage cost can be greatly reduced, and the device preparation process can be simplified, which is a very promising infrared optoelectronic material in the future.

[0004] In recent years, HgTe has been widely used in the fields of short-wave and mid-wave infrared detection. The room-temperature short-wave specific detectivity of HgTe detectors can reach up to 1×10 11 Jones, comparable to current InSb and InGaAs short-wave infrared detectors, while the room-temperature mid-wave specific detectivity can reach 8×10 9 Jones, not inferior to the performance of amorphous Si and VO x photothermal detectors.

[0005] Due to the small size and large surface energy of quantum dots, agglomeration is likely to occur between them, resulting in poor stability of the quantum dot solution and attenuation of optoelectronic properties. Currently, traditional hot injection methods are generally used to synthesize HgTe quantum dots, and there are two specific methods: the first uses low-activity TOPTe as the tellurium precursor solution. Due to its low activity, the nucleation rate is slow, resulting in uneven size distribution of HgTe quantum dots synthesized by the traditional hot injection method; the second uses highly active bis(trimethylsilyl) telluride (TMSTe) as the tellurium precursor solution, which has a fast nucleation rate and uniform size distribution. However, it has a long absorption band tail, and TMSTe has a high cost, which is not conducive to the industrialization of HgTe quantum dots. Therefore, it is urgent to optimize the process of synthesizing HgTe quantum dots by the hot injection method to prepare monodisperse, process-controllable, and low-cost HgTe quantum dots.

[0006] In view of this, overcoming this technical problem has become an urgent problem to be solved in this field. Summary of the Invention

[0007] In view of the above technical problems existing in the prior art, the present invention proposes a synthesis method for self-aggregation growth of monodisperse HgTe quantum dots. Using low-cost TOPTe as the tellurium precursor solution, by first synthesizing the HgTe quantum dot seed crystal solution and then synthesizing the HgTe quantum dots, the problem of uneven size distribution of quantum dots caused by the low activity of TOPTe is improved.

[0008] The specific technical solution of the present invention is as follows:

[0009] A synthesis method for self-aggregation growth of monodisperse HgTe quantum dots, comprising the following steps:

[0010] Step 1: Based on trioctylphosphine (TOP) solution, prepare a TOPTe precursor solution with a Te concentration of 1M;

[0011] Step 2: Prepare a Hg precursor solution with a Hg concentration of 0.12 - 0.36 mmol / mL;

[0012] Step 3: Inject the TOPTe precursor solution into the Hg precursor solution, and continuously stir at 35 - 50 °C for 8 - 10 min under an inert gas or nitrogen to obtain a HgTe quantum dot seed crystal solution with a concentration of 0.08 - 0.24 mmol / mL; wherein, the molar ratio of Te in the TOPTe precursor solution to Hg in the Hg precursor solution is 3:2;

[0013] Step 4: Pour the oleylamine solution into a three-necked flask, perform degassing treatment at 80-100 °C. After washing with an inert gas or nitrogen multiple times, inject the HgTe quantum dot seed crystal solution into the oleylamine solution, and perform self-assembly growth at 70-90 °C for 3-5 min. Add a quenching agent, and after cooling with ice water, obtain the HgTe quantum dot solution to be filtered; wherein, the volume ratio of the oleylamine solution to the HgTe quantum dot seed crystal solution is 10:(1-2);

[0014] Step 5: Pour the HgTe quantum dot solution to be filtered into a centrifuge tube, perform centrifugal washing multiple times with an anti-solvent, and obtain self-assembled monodisperse HgTe quantum dots after drying.

[0015] Further, the size of the self-assembled monodisperse HgTe quantum dots is 8-10 nm, realizing light absorption in the 1400-2500 nm wavelength band.

[0016] Further, the specific process of Step 1 is: Add tellurium powder to the TOP solution, perform ultrasonic treatment, then perform degassing treatment at 80-100 °C. After washing with an inert gas or nitrogen multiple times, continuously stir at 180-200 °C for 3-5 h until the tellurium powder is completely dissolved, and naturally cool to room temperature to obtain a TOPTe precursor solution with a Te concentration of 1 M.

[0017] Further, the temperature of the ultrasonic treatment is 20-25 °C, the power is 80-100 W, and the duration is 20-30 min.

[0018] Further, the specific process of Step 2 is: Add a mercury halide to the oleylamine solution, perform degassing treatment at 80-100 °C. After washing with an inert gas or nitrogen multiple times, continuously stir at 100 °C for 30-40 min until the mercury halide is fully dissolved, to obtain a Hg precursor solution with a Hg concentration of 0.12-0.36 mmol / mL.

[0019] Further, the mercury halide is one of mercury chloride, mercury bromide, and mercury iodide.

[0020] Further, the duration of the degassing treatment is 30-50 min.

[0021] Further, the number of times of washing with an inert gas or nitrogen is 3-4 times.

[0022] Further, the volume ratio of the quenching agent to the oleylamine solution is 1:1. The quenching agent is composed of n-dodecyl mercaptan (DDT), a TOP long-chain ligand, and a non-polar solvent. The non-polar solvent is tetrachloroethylene (TCE) or toluene.

[0023] Further, the specific process of centrifugal cleaning in step 5 is as follows: Add an anti-solvent to the centrifuge tube containing the HgTe quantum dot solution to be filtered, causing the HgTe quantum dots to precipitate. After centrifugation and drying, black powder of HgTe quantum dots is obtained, which is dissolved in a non-polar solvent, and then the anti-solvent is added again; repeat the above process 2 to 3 times to obtain HgTe quantum dots dissolved in the non-polar solution, that is, the HgTe quantum dot solution.

[0024] Further, before drying in step 5, it is also necessary to filter the HgTe quantum dot solution using a 100 nm filter tip, add the anti-solvent again, and after centrifugation and drying, self-assembled growth monodisperse HgTe quantum dots are obtained.

[0025] Further, the anti-solvent is methanol or isopropanol, and the non-polar solvent is toluene or tetrachloroethylene.

[0026] Further, the specific process of centrifugation is: Centrifuge at a speed of 7000 rpm for 3 min.

[0027] In summary, the beneficial effects of the present invention are as follows:

[0028] The present invention provides a method for synthesizing self-assembled growth monodisperse HgTe quantum dots. Based on the TOPTe precursor solution, the thermal injection method is adopted. First, the HgTe quantum dot seed crystal solution is injected, and then it is self-assembled and grown in the oleylamine solution to obtain monodisperse HgTe quantum dots with high shape and size uniformity; by controlling the concentration, growth time and temperature of the HgTe quantum dot seed crystal solution, as well as the time and temperature of self-assembled growth, the size of the obtained HgTe quantum dots is controlled, so as to achieve short-wavelength light absorption of 1400 - 2500 nm; compared with the traditional method for synthesizing HgTe quantum dots by thermal injection, the present invention has the advantages of uniform size distribution, controllable size and low cost. Description of the Drawings

[0029] Figure 1 It is the TEM (transmission electron microscope) image of the HgTe quantum dot seeds obtained in Example 1 of the present invention;

[0030] Figure 2 It is the flow chart of the method for synthesizing self-assembled growth monodisperse HgTe quantum dots proposed in Example 4 of the present invention;

[0031] Figure 3 It is the schematic diagram of the method for synthesizing self-assembled growth monodisperse HgTe quantum dots proposed in Example 4 of the present invention;

[0032] Figure 4 It is the TEM image of the HgTe quantum dots obtained in Example 4 of the present invention;

[0033] Figure 5TEM image of the HgTe quantum dots obtained in Comparative Example 1;

[0034] Figure 6 XRD (X-ray diffraction) comparison chart of the HgTe quantum dot seeds obtained in Example 1 of the present invention, the HgTe quantum dots obtained in Example 4, and the HgTe quantum dots obtained in Comparative Example 1;

[0035] Figure 7 Absorption spectrum comparison chart of the HgTe quantum dot seeds obtained in Example 1 of the present invention, the HgTe quantum dots obtained in Example 4, and the HgTe quantum dots obtained in Comparative Example 1. Detailed implementation manners

[0036] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described below in conjunction with the following specific examples and comparative examples, and with reference to the accompanying drawings.

[0037] Example 1

[0038] In this example, a solution of HgTe quantum dot seeds (Seed) was prepared, which specifically included the following steps:

[0039] Step A1: Add 0.3828 g of tellurium powder to 3 mL of TOP solution, perform ultrasonic treatment at 25°C for 30 min, with an ultrasonic power of 80 W, until it becomes a suspension state, perform degassing treatment at 100°C for 30 min, wash with nitrogen gas 3 times, ensure a nitrogen atmosphere in the synthesis environment, continuously stir at 200°C for 3 h until the tellurium powder is completely dissolved, the solution becomes orange, and naturally cool to room temperature to obtain a clear and transparent yellow TOPTe precursor solution, which is sealed and stored in a vacuum;

[0040] Step A2: Add 0.246 g of mercury chloride to 5 mL of oleylamine solution, perform degassing treatment at 100°C for 60 min, wash with nitrogen gas 3 times, ensure a nitrogen atmosphere in the synthesis environment, continuously stir at 100°C for 30 min until the mercury chloride is fully dissolved to obtain a Hg precursor solution;

[0041] Step A3: Inject 0.6 mL of the TOPTe precursor solution into the Hg precursor solution, continuously stir at 35°C for 10 min under nitrogen, and cool with ice water to obtain a HgTe quantum dot seed solution to be filtered with a concentration of 0.12 mmol / mL; wherein, the molar ratio of Te in the TOPTe precursor solution to Hg in the Hg precursor solution is 3:2;

[0042] Step A4: Pour the HgTe quantum dot seed crystal solution to be filtered into a centrifuge tube, add a methanol antisolvent, with the volume ratio of the two being 1:1, to precipitate the HgTe quantum dot seeds, centrifuge at a speed of 7000 rpm for 3 min, dry to obtain HgTe quantum dot seeds, dissolve them in toluene, and add the methanol antisolvent again; repeat the above process 3 times to obtain HgTe quantum dot seeds dissolved in toluene, i.e., the HgTe quantum dot seed crystal solution;

[0043] Step A5: Pour the HgTe quantum dot seed crystal solution into a centrifuge tube for centrifugation to remove lamellar and massive quantum dots. After filtering through a 100 nm filter tip, add a methanol antisolvent, and after centrifugation and drying, obtain HgTe quantum dot seed crystal powder, dissolve it in a n-octane solution to prepare a HgTe quantum dot seed crystal with a concentration of 100 mg / mL.

[0044] Perform TEM testing on the HgTe quantum dot seed crystal dissolved in the n-octane solution obtained in this example, and obtain the TEM image as shown in Figure 1 It can be seen that the size of the HgTe quantum dot seed crystal is relatively small, only about 3 nm.

[0045] Example 2

[0046] In this example, a kind of HgTe quantum dot seed crystal was prepared. Compared with Example 1, the only differences are: adjust the addition amount of mercury chloride in Step A2 to 0.164 g; adjust the stirring temperature in Step A3 to 50 °C, and then obtain a HgTe quantum dot seed crystal solution with a concentration of 0.08 mmol / mL; the remaining steps are the same.

[0047] Example 3

[0048] In this example, a kind of HgTe quantum dot seed crystal was prepared. Compared with Example 1, the only differences are: adjust the addition amount of mercury chloride in Step A2 to 0.492 g; adjust the stirring duration in Step A3 to 8 min, and then obtain a HgTe quantum dot seed crystal solution with a concentration of 0.24 mmol / mL; the remaining steps are the same.

[0049] Example 4

[0050] Based on the HgTe quantum dot seed crystal solution to be filtered obtained in Step A3 of Example 1, in this example, a kind of HgTe quantum dot (HgTe CQDs) was prepared. The process flow and growth principle are respectively as shown in Figure 2 and Figure 3 as follows, and specifically include the following steps:

[0051] Step B1: Pour 5 mL of oleylamine solution into a three-necked flask, perform degassing treatment at 100 °C for 60 min, and after purging with nitrogen 3 times, ensure a nitrogen atmosphere in the synthesis environment;

[0052] Step B2, injecting 1 mL of the HgTe quantum dot seed solution with a concentration of 0.12 mmol / mL obtained in Step A3 of Example 1 into the oleylamine solution, self-aggregating and growing at 80° C. for 3 min, adding 5 mL of a quencher (composed of TOP, DDT and TCE in a volume ratio of 1:2:20), and cooling with ice water to obtain a HgTe quantum dot solution to be filtered;

[0053] Step B3, pour the HgTe quantum dot solution to be filtered into a centrifuge tube, add methanol anti-solvent, the volume ratio of the two is 1:1, precipitate the HgTe quantum dots, centrifuge at 7000 rpm for 3 minutes, dry to obtain HgTe quantum dot black powder, dissolve in toluene, add methanol anti-solvent again; repeat the above process 3 times to obtain HgTe quantum dots dissolved in toluene, that is, HgTe quantum dot solution;

[0054] Step B4: Pour the HgTe quantum dot solution into a centrifuge tube and centrifuge to remove the flaky and blocky quantum dots. After filtering through a 100 nm filter, add methanol antisolvent, centrifuge and dry to obtain HgTe quantum dot powder, which is dissolved in n-octane solution to prepare self-aggregated monodisperse HgTe quantum dots with a concentration of 100 mg / mL.

[0055] Figure 4 This is a TEM image of the HgTe quantum dots obtained in this example. It can be seen that after the HgTe quantum dot seed crystals self-aggregate and grow at 80° C., circular HgTe quantum dots with a size of 8 to 10 nm are formed. The shape and size are uniform and monodispersed.

[0056] Example 5

[0057] Based on the HgTe quantum dot seed crystal solution to be filtered obtained in step A3 of Example 1, this example prepared a HgTe quantum dot. The preparation process was different from that in Example 4, except that the self-aggregation growth temperature in step B2 was adjusted to 70°C and the duration was adjusted to 5 minutes. The remaining steps were the same.

[0058] Example 6

[0059] Based on the HgTe quantum dot seed crystal solution to be filtered obtained in step A3 of Example 1, this example prepared a HgTe quantum dot. The preparation process was different from that of Example 4 only in that the self-aggregation growth temperature in step B2 was adjusted to 90°C; the remaining steps were the same.

[0060] Comparative Example 1

[0061] Based on the HgTe quantum dot seed crystal solution obtained in step A3 of Example 1, this comparative example prepared a kind of HgTe quantum dots. Compared with Example 2 in the preparation process, the only difference is that the self-aggregation growth temperature in step B2 was adjusted to 100 °C; the remaining steps were the same.

[0062] Figure 5 This is the TEM image of the HgTe quantum dots obtained in this comparative example. It can be seen that after the self-aggregation growth temperature is increased to 100 °C, due to the increase in the nucleation driving force, the HgTe quantum dots further aggregate and grow, and a chain-like structure of HgTe quantum dots appears, lacking the monodisperse characteristic.

[0063] The HgTe quantum dot seeds dissolved in n-octane solution obtained in Example 1, the HgTe quantum dot solution obtained in Example 4, and the HgTe quantum dot solution obtained in Comparative Example 1 were respectively drop-coated on glass slides to prepare the corresponding HgTe quantum dot seed crystal thin films and HgTe quantum dot thin films. After XRD testing, the XRD comparative diagram as shown in Figure 6 was obtained. It can be seen that the obtained HgTe quantum dot seed crystal thin film and the HgTe quantum dot thin film are consistent with the HgTe PDF standard card, indicating that the obtained product is pure and there are no other impurity phases.

[0064] The absorption spectra of the HgTe quantum dot seeds obtained in Example 1, the HgTe quantum dots obtained in Example 4, and the HgTe quantum dots obtained in Comparative Example 1 were respectively tested, and the absorption spectrum comparative diagram as shown in Figure 7 was obtained. It can be seen that the absorption peak position of the small-sized HgTe quantum dot seeds is at 1400 nm; as the HgTe seeds self-aggregate and grow, the quantum dot size increases, and the best absorption peak position of the obtained HgTe quantum dots redshifts to 1800 nm; under the condition of 100 °C, due to aggregation to form a chain-like structure, two size distributions are formed, showing dual-band light absorption, with strong light absorption at 1400 nm and 2560 nm.

[0065] As mentioned above, the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for synthesizing self-assembled and growing monodisperse HgTe quantum dots, characterized in that, It includes the following steps: Step 1: Based on the TOP solution, prepare a TOPTe precursor solution with a Te concentration of 1 M. Step 2: Prepare a Hg precursor solution with a Hg concentration of 0.12 - 0.36 mmol / mL. Step 3: Inject the TOPTe precursor solution into the Hg precursor solution, and continuously stir at 35 - 50 °C for 8 - 10 min under an inert gas or nitrogen to obtain a HgTe quantum dot seed crystal solution with a concentration of 0.08 - 0.24 mmol / mL. Among them, the molar ratio of Te in the TOPTe precursor solution to Hg in the Hg precursor solution is 3:

2. Step 4: Pour the oleylamine solution into a three-necked flask, perform degassing treatment at 80 - 100 °C, and after washing with an inert gas or nitrogen multiple times, inject the HgTe quantum dot seed crystal solution into the oleylamine solution, and perform self-assembly growth at 70 - 90 °C for 3 - 5 min. Add a quenching agent, and after cooling with ice water, obtain a HgTe quantum dot solution to be filtered. Among them, the volume ratio of the oleylamine solution to the HgTe quantum dot seed crystal solution is 10:(1 - 2). Step 5: Pour the HgTe quantum dot solution to be filtered into a centrifuge tube, perform centrifugal cleaning multiple times with an anti-solvent, and after drying, obtain self-assembled monodisperse HgTe quantum dots.

2. The synthesis method of self-assembled growth of monodisperse HgTe quantum dots according to claim 1, characterized in that, The size of the self-assembled monodisperse HgTe quantum dots is 8 - 10 nm, achieving light absorption in the wavelength range of 1400 - 2500 nm.

3. The synthesis method of self-assembled growth of monodisperse HgTe quantum dots according to claim 1, characterized in that, The specific process of Step 1 is as follows: Add tellurium powder to the TOP solution, perform ultrasonic treatment, then perform degassing treatment at 80 - 100 °C, and after washing with an inert gas or nitrogen multiple times, continuously stir at 180 - 200 °C for 3 - 5 h until the tellurium powder is completely dissolved, and naturally cool to room temperature to obtain a TOPTe precursor solution with a Te concentration of 1 M.

4. The synthesis method of self - aggregating and growing monodisperse HgTe quantum dots according to claim 1, characterized in that, The specific process of Step 2 is as follows: Add a mercury halide to the oleylamine solution, perform degassing treatment at 80 - 100 °C, and after washing with an inert gas or nitrogen multiple times, continuously stir at 100 °C for 30 - 40 min until the mercury halide is fully dissolved to obtain a Hg precursor solution with a Hg concentration of 0.12 - 0.36 mmol / mL.

5. The synthesis method of self - aggregating and growing monodisperse HgTe quantum dots according to claim 1, wherein, The specific process of centrifugal cleaning in Step 5 is as follows: Add an anti-solvent to the centrifuge tube containing the HgTe quantum dot solution to be filtered to precipitate the HgTe quantum dots. After centrifugation and drying, obtain black HgTe quantum dot powder, dissolve it in a non-polar solvent, and then add the anti-solvent again; repeat the above process 2 - 3 times to obtain a HgTe quantum dot dissolved in a non-polar solution, that is, a HgTe quantum dot solution.

6. The synthesis method of self - aggregating and growing monodisperse HgTe quantum dots according to claim 5, characterized in that, Before drying in Step 5, the HgTe quantum dot solution is also filtered using a 100 nm filter tip, and then the anti-solvent is added again. After centrifugation and drying, self-assembled monodisperse HgTe quantum dots are obtained.

7. The synthesis method of self-assembled growth of monodisperse HgTe quantum dots according to claim 6, characterized in that, The anti-solvent is methanol or isopropyl alcohol, and the non-polar solvent is toluene or tetrachloroethylene.

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