A method for ultrasonic intensification of microfluidic synthesis of perovskite quantum dots at room temperature with high chemical yield

Abstract

The application provides a perovskite quantum dot room-temperature high-chemical-yield ultrasonic reinforcement droplet microfluidic synthesis method, which comprises the following steps: preparing a two-section series double-T structure droplet microfluidic reaction chip and coupling the droplet microfluidic reaction chip with an ultrasonic vibrator to form a reaction system; injecting precursor solution, ligand solution and acetonitrile solution into the droplet microfluidic reaction chip in proportion, and starting the ultrasonic vibrator to ultrasonically reinforce the reaction solution. After centrifugal drying of the product, perovskite quantum dots are prepared. Compared with the prior art, the application has the following beneficial effects: 1. Ultrasonic treatment accelerates the mass transfer between two phases, strengthens the reaction process, and improves the chemical yield and efficiency of the quantum dots; 2. The size of the quantum dots can be controlled by adjusting the flow rate ratio and the ultrasonic power; 3. The reaction system can be used to increase the specific surface area of the reactants and accurately control the reaction conditions; 4. The reaction system has high automation compatibility and is suitable for distributed continuous production.

Description

TECHNICAL FIELD

[0001] The application relates to a room-temperature high-chemical-yield ultrasonic reinforced droplet microfluidic synthesis method of perovskite quantum dots and belongs to the technical field of perovskite quantum dot preparation. BACKGROUND

[0002] Halide perovskite materials (such as CH3NH3PbX3, X = Cl, Br, I) have great potential in optoelectronic devices (such as LEDs, solar cells) due to their excellent photoelectric properties (such as high light absorption coefficient, tunable band gap and narrow emission line width). However, the synthesis of quantum dots (QDs) thereof mainly depends on high-temperature hot injection method and room-temperature reprecipitation method, which has the following problems: (1) low chemical yield (usually < 10%), resulting in waste of raw materials; (2) by-products (such as micron-sized crystals) need complex centrifugal purification, causing material loss; (3) sensitive to polar solvents (such as water, alcohol), easy to degrade; (4) difficult to control size, poor controllability of optical properties (such as emission wavelength). Therefore, it is crucial to develop new methods to simplify the process and improve the performance. Droplet microfluidic chip technology divides the reaction system into nanoliter- picoliter droplets as independent microreactors, realizing high-throughput, low-consumption precise reaction control. Its advantages include accurate control of droplet size and composition, providing uniform reaction environment and avoiding cross contamination, but there are still limitations in mass transfer efficiency in rapid mixing and high-viscosity systems. Ultrasonic treatment technology accelerates the mixing and diffusion of reactants through cavitation effect (local high temperature and high pressure and microjet generated by bubble collapse), promotes the activation of reactants, improves the reaction rate and efficiency, and increases the specific surface area and improves the system uniformity. It has been widely used in the field of nanomaterial synthesis. The combination of droplet microfluidic chip and ultrasonic treatment technology can build an efficient and controllable microreaction platform, providing a new way for the synthesis and performance optimization of perovskite quantum dots. SUMMARY

[0003] In view of the defects in the prior art, the purpose of the present application is to provide a method for preparing perovskite quantum dots.

[0004] The present application is realized by the following technical solutions:

[0005] The present application provides a room-temperature high-chemical-yield ultrasonic reinforced droplet microfluidic synthesis method of perovskite quantum dots, which comprises the following steps:

[0006] A two-section series double-T structure droplet microfluidic reaction chip is made and coupled with an ultrasonic vibrator to form a reaction system;

[0007] Dissolve PbBr2 and CH3NH3Br in DMF solvent to form a precursor solution, dissolve oleic acid and octylamine in n-hexane to form a ligand solution, inject the precursor solution, the ligand solution and acetonitrile solution into a droplet microfluidic reaction chip by a microsyringe in proportion, and start an ultrasonic vibrator to intensify the reaction solution and enhance the mass transfer of the reaction solution.

[0008] After centrifugal drying of the product, the perovskite quantum dots are prepared.

[0009] Preferably, the concentration of PbBr2 in the precursor solution is 200 mmol / L, the concentration of CH3NH3Br is 200 mmol / L, and the volume of DMF is 4 mL.

[0010] Preferably, the octylamine is 150 μL, and the oleic acid is 250 μL dissolved in 50 mL of n-hexane.

[0011] Preferably, the flow rate ratio of the precursor solution, the ligand solution and the acetonitrile solution is 1:20:10.

[0012] Preferably, the frequency of the ultrasonic treatment is 28 kHz, and the power is 60 W.

[0013] Preferably, the material of the micro-reaction chip is PMMA, and isopropanol is used for bonding of the micro-channel.

[0014] Preferably, the ultrasonic intensification is direct contact ultrasonic treatment.

[0015] Preferably, the centrifugal extraction is centrifugation at a speed of 6000 rpm for 5 minutes, and the drying is sufficient drying at 40℃ for 4 hours.

[0016] The implementation principle of the present application is as follows:

[0017] The present application injects the three-phase liquid of the precursor solution, the ligand solution and acetonitrile into a two-stage serial droplet microfluidic reaction chip with a double-T structure by a microsyringe, and the n-hexane solution of the ligand shears the acetonitrile solution to form a droplet multiphase flow at the first T structure of the first-stage droplet microfluidic reaction chip. When the multiphase flow passes through the second T structure, the acetonitrile droplets merge with the DMF droplets of the dissolved reaction precursor, acetonitrile as a poor solvent changes the solvent environment of the DMF solution when mixed with the DMF solution, provides a crystallization driving force, initiates a crystallization reaction, and starts the whole reaction process. When the mixed droplets flow through the second-stage droplet microfluidic reaction chip, the ultrasonic treatment is enabled to intensify the synthesis of quantum dots.

[0018] For the synthesis of quantum dots, on the one hand, in the nucleation stage of quantum dots, a larger interface reaction area means more nucleation sites, so that the nucleation process occurs more uniformly, and the increased droplet interface reaction area of ultrasonic cavitation also makes the interaction between the ligand and the crystal nucleus surface more sufficient, which helps to guide the crystal to grow along a specific orientation. The template effect of the ligand can be more efficiently exerted under the action of ultrasound, so that the quantum dots are more likely to form a consistent crystal orientation during crystallization, reducing the formation of defects such as vacancies, dislocations, and the like, thereby significantly improving the uniformity of the morphology of the quantum dots. On the other hand, in the precipitation-dissolution process, the precursor ions need to diffuse from the surface of the precipitate to the solution and then migrate to the interface to participate in the formation of quantum dots. A larger interface area provides more ion diffusion channels and exchange sites, greatly accelerating the diffusion rate of ions, and thus accelerating the movement of the precipitation-dissolution equilibrium to the dissolution direction. This means that the large block of perovskite quantum dot precipitate can be dissolved more quickly, releasing more ions for the generation of quantum dots, thereby improving the utilization rate of precursor substances and ultimately improving the chemical yield.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] 1. Ultrasonic treatment can accelerate the mass transfer between two phases, thereby strengthening the reaction process, shortening the reaction time, and thus improving the chemical yield and efficiency of quantum dots;

[0021] 2. The size of the quantum dots can be controlled by adjusting the flow rate ratio and the ultrasonic power;

[0022] 3. The microfluidic droplet reaction system constructed can increase the specific surface area of the reactants and accurately control the reaction conditions;

[0023] 4. The reaction system has high automation compatibility and is suitable for distributed continuous production;

[0024] 5. The phase transfer strategy allows the quantum dots to be transferred from a polar solvent to a non-polar solvent through spontaneous phase separation, simplifying the purification process and reducing material loss;

[0025] 6. The method is not only suitable for the synthesis of CH3NH3PbBr3 quantum dots, but also can be used for the preparation of other quantum dots based on the supersaturation recrystallization reaction. BRIEF DESCRIPTION OF DRAWINGS

[0026] Other features, objects, and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the accompanying drawings:

[0027] Figure 1 FIG. 1 is a schematic diagram of the overall structure of a droplet microfluidic reaction system in a room temperature high chemical yield ultrasonic enhanced droplet microfluidic synthesis method of perovskite quantum dots according to the present application.

[0028] Figure 2 For the room temperature high chemical yield ultrasonic enhanced droplet microfluidic synthesis method of perovskite quantum dots of the application, comparative parameters of perovskite quantum dots prepared under different ultrasonic enhancement powers.

[0029] Figure 3 For the room temperature high chemical yield ultrasonic enhanced droplet microfluidic synthesis method of perovskite quantum dots of the application, comparative parameters of perovskite quantum dots prepared under different flow rate ratios between precursors and ligands.

[0030] Figure 4 For the room temperature high chemical yield ultrasonic enhanced droplet microfluidic synthesis method of perovskite quantum dots of the application, a low-magnification transmission electron microscope morphology diagram of perovskite quantum dots obtained.

[0031] Figure 5 For the room temperature high chemical yield ultrasonic enhanced droplet microfluidic synthesis method of perovskite quantum dots of the application, a high-resolution transmission electron microscope morphology diagram of perovskite quantum dots obtained.

[0032] Figure 6 For the room temperature high chemical yield ultrasonic enhanced droplet microfluidic synthesis method of perovskite quantum dots of the application, an X-ray diffraction spectrum diagram of perovskite quantum dots obtained.

[0033] Figure 7 For the room temperature high chemical yield ultrasonic enhanced droplet microfluidic synthesis method of perovskite quantum dots of the application, an ultraviolet-visible absorption and fluorescence emission spectrum diagram of perovskite quantum dots obtained.

[0034] Figure 8 For the room temperature high chemical yield ultrasonic enhanced droplet microfluidic synthesis method of perovskite quantum dots of the application, a Fourier transform infrared spectrum diagram of perovskite quantum dots obtained. DETAILED DESCRIPTION

[0035] The application will be described in detail below with specific embodiments. The following examples will help those skilled in the art to further understand the application, but do not limit the application in any form. It should be noted that for those skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made. These all belong to the protection scope of the application.

[0036] Example 1

[0037] The embodiment provides a room temperature high chemical yield ultrasonic enhanced droplet microfluidic synthesis method of perovskite quantum dots, which specifically comprises the following steps:

[0038] PbBr2 and CH3NH3Br3 were dissolved in DMF solvent (the concentration of PbBr2 in the precursor solution was 200 mmol / L and the concentration of CH3NH3Br3 was 200 mmol / L, and the volume of polar solvent DMF was 4 mL) to form a precursor solution, and octylamine and oleic acid were dissolved in n-hexane to form a ligand solution (n-octylamine 150 μL, oleic acid 250 μL, hexane 50 mL). A two-stage tandem double-T structure droplet microfluidic reaction chip was prepared and coupled with an ultrasonic vibrator to form a reaction system. The precursor solution, ligand solution and acetonitrile solvent were injected into the micro-reaction system by a micro-injection pump at a ratio of 1:20:10, and direct contact ultrasonic (frequency 28 kHz, power 60 W) was started to intensify the reaction solution and enhance the mass transfer of the reaction solution. The CH3NH3PbBr3 quantum dots were transferred from the polar solvent phase to the non-polar solvent phase by phase transfer to obtain a quantum dot mixture. The product obtained at the outlet was centrifuged, extracted and dried to obtain clean perovskite quantum dots. The chemical yield of CH3NH3PbBr3 quantum dots produced in this embodiment was greater than 80%, which was much higher than the international standard.

[0039] Comparative Example 1

[0040] The other experimental parameters of this comparative example were the same as those of Example 1, except that the ultrasonic intensification power was different. The comparative parameters of the perovskite quantum dots prepared are shown in the accompanying drawings of the specification. Figure 2

[0041] Comparative Example 2

[0042] The other experimental parameters of this comparative example were the same as those of Example 1, except that the flow rate ratio between the precursor and the ligand was different. The comparative parameters of the perovskite quantum dots prepared are shown in the accompanying drawings of the specification. Figure 3

[0043] The above describes specific embodiments of the present application. It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various modifications or modifications within the scope of the claims, which does not affect the essential content of the present application.​​

Claims

1. A room-temperature ultrasonic-enhanced microfluidic synthesis method for perovskite quantum dots, characterized in that, The method comprises the following steps: A two-stage series double-T structure droplet microfluidic reaction chip is made and coupled with an ultrasonic vibrator to form a reaction system; PbBr2 and CH3NH3Br are dissolved in DMF solvent to form a precursor solution, oleic acid and octylamine are dissolved in n-hexane to form a ligand solution, the precursor solution, the ligand solution and acetonitrile solution are injected into the droplet microfluidic reaction chip by a micro-injection pump according to a proportion, and the ultrasonic vibrator is started to ultrasonically strengthen the reaction solution and enhance the mass transfer of the reaction solution, and after the product is centrifuged and dried, the perovskite quantum dots are prepared.

2. The method of claim 1, wherein, The chip is a two-stage series double-T structure micro-reaction chip, the two-stage chip comprises a droplet generation microfluidic chip and an ultrasonic droplet microfluidic chip, the two-stage chips are connected by a capillary hose to form a droplet microfluidic reaction chip, and the chip microchannels involved can be processed and prepared on a polymer, a silicon-based material or a glass substrate.

3. The method of claim 1, wherein, The frequency of the ultrasonic vibrator is 20-60 KHz, and the power is 20-100 W.

4. The method of claim 1, wherein, The flow rate ratio of the precursor solution to the ligand solution is 1:20-1:10, and the flow rate ratio of the ligand solution to the acetonitrile solution is constant at 2:

1.

5. The method of claim 1, wherein, The average diameter of the CH3NH3PbBr3 quantum dots is 2.20-3.10 nm.

6. The method of claim 1, wherein, The emission wavelength of the CH3NH3PbBr3 quantum dots is 380-700 nm, and the FWHM is 15-22 nm.

7. The method of claim 1, wherein, The chemical yield of the CH3NH3PbBr3 quantum dots reaches 80-95%.

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