Bilateral SiO2 coated CsPbX3 quantum dot, method and application

Abstract

The invention provides a bilateral SiO2-coated CsPbX3 quantum dot, a method and application, and relates to the field of nanomaterials and biosensing, Cs4PbX6 nanoparticles are added into an organic phase to obtain an organic phase dispersion liquid of the Cs4PbX6 nanoparticles; adding a silicon source into the dispersion liquid; adding an aqueous solution containing halide ions into the system, and then vigorously oscillating to initiate crystal phase transformation of Cs4PbX6 to CsPbX3 and react with the silicon source, so as to form CsPbX3 quantum dots coated with bilateral SiO2 in situ; and after standing, carrying out centrifugal separation to obtain a CsPbX3 quantum dot solution coated with bilateral SiO2. The obtained quantum dot has excellent water stability and efficient fast anion exchange (FAE) activity, the fluorescence lifetime of the quantum dot is as long as 46.44 ns, and the fluorescence intensity is only attenuated by 21.8% after the quantum dot is violently reacted with water for 60 minutes.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterials and biosensing, and in particular to CsPbX3 quantum dots with bilateral SiO2 coating, methods, and applications. Background Technology

[0002] All-inorganic perovskite quantum dots CsPbX3 (X=Cl, Br, I) have shown great potential in optoelectronic devices and biosensing due to their excellent optical properties, such as narrow emission half-width, high photoluminescence quantum yield, and tunable emission wavelength. However, the poor stability of CsPbX3 quantum dots in polar solvents (especially water) severely limits their practical applications.

[0003] To improve stability, researchers often coat quantum dots with SiO2. However, the traditional full coating strategy, while improving stability, severely suppresses the feasibility-exchange (FAE) activity of the quantum dots, making them unsuitable for ion exchange-based sensing. For example, the FAE reaction efficiency of fully coated CsPbX3 quantum dots may decrease by more than 99%, and the reaction time may be significantly prolonged. Therefore, developing a perovskite quantum dot structure that can significantly improve stability while effectively preserving FAE activity is a pressing technical challenge in this field.

[0004] A water-triggered sol-gel method has been proposed to synthesize CsPbX3 quantum dots with SiO2 coating on only one side. This structure improves water stability while retaining high FAE activity. However, there is still room for improvement in the stability of the single-sided coating structure. Therefore, further improvements should be made to the coating strategy of perovskite quantum dots to enhance their environmental stability while ensuring high FAE activity. Summary of the Invention

[0005] The purpose of this invention is to provide CsPbX3 quantum dots with double-sided SiO2 coating, methods and applications. The resulting quantum dots have both excellent water stability and efficient fast anion exchange (FAE) activity, with a fluorescence lifetime of up to 46.44 ns. After a violent reaction with water for 60 minutes, the fluorescence intensity only decreases by 21.8%.

[0006] To achieve the above objectives, this invention provides a method for preparing CsPbX3 quantum dots with bilateral SiO2 coating, comprising the following steps: Step 1: Add Cs4PbX6 nanoparticles to the organic phase to obtain an organic phase dispersion of Cs4PbX6 nanoparticles, wherein X is chlorine (Cl), bromine (Br), or iodine (I). Step 2: Add a silicon source to the dispersion described in Step 1; Step 3: After adding an aqueous solution containing halide ions to the system of Step 2, the mixture is violently shaken to induce a crystal phase transformation from Cs4PbX6 to CsPbX3 and react with the silicon source to form CsPbX3 quantum dots coated with bilateral SiO2 in situ. Step 4: After placement, centrifugation is performed to obtain the CsPbX3 quantum dot solution coated with bilateral SiO2.

[0007] Preferably, the organic phase is one or more selected from n-hexane, cyclohexane, and chlorobenzyl toluene; The silicon source is an organic phase solution of orthosilicate, wherein the concentration of the silicon source is 15%-25% v; preferably, the orthosilicate includes ethyl orthosilicate and methyl orthosilicate. The aqueous solution containing halide ions is a KX aqueous solution, wherein X is chlorine (Cl), bromine (Br), or iodine (I), and its concentration is 0.1-3.0 mol / L.

[0008] Preferably, the Cs4PbX6 nanoparticles are synthesized using a hot injection method or a ligand-assisted reprecipitation method.

[0009] Preferably, the ratio of Cs4PbX6 nanoparticles to organic phase is (0.05~0.1mol):(20-25mL).

[0010] Preferably, the ratio of silicon source to CsPbX3 nanoparticle dispersion is (4~6 mL): (80~120 μL).

[0011] Preferably, the ratio of the aqueous solution containing halide ions to the dispersion containing the silicon source is (4-6 mL): (150-250 μL).

[0012] Preferably, in step 3, the rotation speed of the violent oscillation is 1500-2000 rpm, and the oscillation time is 5-10 minutes; In step 4, the settling time is 10-12 hours, the centrifugation speed is 8000-10000 rpm, and the centrifugation time is 5-10 minutes.

[0013] A CsPbX3 quantum dot coated with bilateral SiO2 prepared by the above preparation method, wherein the quantum dot has a core-shell structure, the core being an orthorhombic CsPbX3 crystal, and the outer shell being a bilaterally coated amorphous SiO2 layer.

[0014] Application of a double-sided SiO2-coated CsPbX3 quantum dot in the fabrication of optoelectronic devices and biosensors.

[0015] Therefore, the present invention employs the above-mentioned bilateral SiO2-coated CsPbX3 quantum dots, method, and application, and the technical effects are as follows: (1) This invention effectively regulates the phase transformation process of Cs4PbX6 nanoparticles at the organic-water interface by utilizing KX aqueous solution to induce the phase transformation of Cs4PbX6 to CsPbX3. A higher concentration of KX aqueous solution provides external halide ions (X... - This controlled and relatively slow phase transition process slowed down the phase transition of Cs4PbX6 and the formation and growth rate of CsPbX3 nuclei. This provided a sufficient kinetic window for the hydrolysis of tetramethyl orthosilicate (TMOS) at the oil-water interface to generate SiO2, allowing SiO2 to be deposited in situ and directionally during the nucleation and growth of CsPbX3 quantum dots, rather than completely covering the already formed quantum dot surface. Transmission electron microscopy (TEM) characterization confirmed that the obtained quantum dots had a well-defined CsPbX3 crystal core surrounded by a symmetrically but incompletely amorphous SiO2 layer, exposing part of the CsPbX3 crystal surface, successfully constructing bilaterally SiO2-coated CsPbX3 quantum dots. This unique structure, while maintaining orthorhombic phase and high FAE activity, significantly improved the material's aqueous phase stability (fluorescence intensity decreased by only 21.8% after 60 minutes of water reaction) and extended the fluorescence lifetime to 46.44 ns.

[0016] (2) This invention ingeniously utilizes the interfacial oxidation reaction of OLAI under the action of H2O2 to regulate the degree of FAE reaction, and uses the fluorescence emission wavelength shift of CsPbX3@SiO2 quantum dots as a sensing signal to construct a sensing platform for H2O2. This method has strong anti-interference ability and a detection limit as low as the micromolar level.

[0017] (3) By combining the above-mentioned H2O2 sensing platform with the enzymatic reaction of pyruvate oxidase, the visualization and multicolor fluorescence detection of pyruvate, a key metabolite in serum, was realized. Attached Figure Description

[0018] Figure 1 XRD patterns of Cs4PbBr6 nanoparticles, CsPbBr3 quantum dots, and CsPbBr3@SiO2 quantum dots coated with bilateral SiO2 prepared in Example 1 of this invention. Figure 1 (A) represents Cs4PbBr6 nanoparticles; Figure 1 (B) is a CsPbBr3 quantum dot, with CsPbBr3@SiO2 coated on one side and CsPbBr3@SiO2 coated on both sides by SiO2; Figure 2 TEM images of Cs4PbBr6 nanoparticles, CsPbBr3 quantum dots, and CsPbBr3@SiO2 quantum dots coated with bilateral SiO2 prepared in Example 1 of the present invention. Figure 2(A) is a CsPbBr3 quantum dot; Figure 2 (B) represents Cs4PbBr6 nanoparticles; Figure 2 (C) represents CsPbBr3@SiO2 quantum dots with bilateral SiO2 coating; Figure 3 These are test images of the optical and water properties of the CsPbBr3@SiO2 quantum dots with bilateral SiO2 coating of the present invention; Figure 3 (A) shows the fluorescence emission and UV-Vis absorption spectra and Figure 3 (B) is a water stability test diagram; Figure 4 The above diagram shows the H2O2 sensing performance of the CsPbBr3@SiO2 quantum dots with double-sided SiO2 coating according to the present invention. Figure 4 (A) is the fluorescence spectrum response to different concentrations of H2O2; Figure 4 (B) is the calibration curve of H2O2 concentration versus emission wavelength; Figure 5 The graph shows the pyruvate sensing performance of the CsPbBr3@SiO2 quantum dots with double-sided SiO2 coating according to the present invention. Figure 5 (A) shows the changes in fluorescence emission spectra corresponding to different concentrations of pyruvate; Figure 5 (B) is the calibration curve of pyruvate concentration versus emission wavelength. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0021] Example 1 Synthesis of Cs4PbBr6 nanoparticles: A hot-injection method was used. 0.16 g of Cs2CO3, 0.5 mL of oleic acid (OA), and 8 mL of 1-octadecene (ODE) were dried under vacuum at 120 °C for 1 hour. The mixture was then stirred at 150 °C under nitrogen until the reaction was complete, yielding a Cs-oleate solution. Separately, 0.0734 g of PbBr2, 1 mL of oleylamine (OAm), 1 mL of OA, and 10 mL of LODE were dried under vacuum and stirred at 140 °C under nitrogen until the solid was completely dissolved. 2.2 mL of hot Cs-oleate solution was rapidly injected, and the mixture was reacted for 10 seconds before cooling in an ice bath. The precipitate was centrifuged and dispersed in 25 mL of n-hexane for later use.

[0022] Synthesis of bilaterally coated CsPbBr3@SiO2 quantum dots: Take 4 mL of the above Cs4PbBr6 n-hexane solution and add 100 μL of 20% (v / v) TMOS / n-hexane solution. Under vigorous shaking at 2000 rpm, quickly add 200 μL of 1 mol / L KBr aqueous solution and continue shaking for 5 minutes. After the mixed solution is allowed to stand in the dark for 12 hours, it is centrifuged at 9000 rpm for 5 minutes, and the supernatant is collected to obtain a green colloidal CsPbBr3@SiO2 quantum dot solution.

[0023] Performance Characterization The quantum dots prepared in Example 1 were characterized as follows: XRD ( Figure 1 The results confirmed that the products were pure phase Cs4PbBr6 and orthorhombic phase CsPbBr3.

[0024] TEM Figure 2 The results show that the bilaterally coated quantum dots have a distinct core-shell structure.

[0025] Optical testing ( Figure 3 (A)) and stability testing ( Figure 3 (B) indicates that the emission peak of the bilaterally coated quantum dots is located at 525 nm, with a full width at half maximum (FWHM) of 18 nm. The fluorescence intensity of the bilaterally coated quantum dots decreased by only 21.8% after 60 minutes of vigorous reaction with water.

[0026] Example 2 This example is used for comparison and illustration. When the KBr aqueous solution is replaced with pure deionized water, it is difficult to form a highly stable double-sided coating structure.

[0027] Preparation process: Except for replacing the 1 mol / L KBr aqueous solution with deionized water, all other steps, material types, and amounts are exactly the same as in Example 1. Specifically, 200 μL of deionized water is added to 4 mL of Cs4PbBr6 n-hexane solution (containing 100 μL of 20% TMOS / n-hexane solution), and the subsequent shaking, standing, and centrifugation steps are the same as in Example 1.

[0028] Product morphology: CsPbBr3@SiO2 quantum dots with single-sided coating were observed under transmission electron microscopy (TEM).

[0029] Stability test: The same concentration of quantum dot solution as in Example 1 was used for the same vigorous water reaction test (oscillation at 2000 rpm, water volume ratio 25%). After 60 minutes, the fluorescence intensity decreased by more than 50%. This indicates that the single-sided coated CsPbBr3@SiO2 quantum dots are less effective at blocking water molecules from attacking the quantum dot core than the double-sided coated CsPbBr3@SiO2 quantum dots, and their stability is significantly worse than that of Example 1 (decay of 21.8%).

[0030] Example 3 This example is used for comparison and illustration to show that when the KBr concentration is too high, it will seriously affect the optical performance of quantum dots.

[0031] Preparation process: Except for replacing the concentration of the KBr aqueous solution from 1 mol / L to 4 mol / L (i.e., the concentration is too high), all other steps, material types and amounts are exactly the same as in Example 1.

[0032] Specifically, in the bilateral coating synthesis step, 200 μL of 4 mol / L KBr aqueous solution was added to 4 mL of Cs4PbBr6 n-hexane solution (containing 100 μL of 20% TMOS / n-hexane solution), and the subsequent shaking, standing, and centrifugation steps were the same as in Example 1.

[0033] Optical performance comparison: extremely high external Br - Concentration can significantly delay or even inhibit the phase transition process of Cs4PbBr6. This leads to premature and excessive deposition of SiO2, which may form a thicker shell or even encapsulate multiple quantum dots, thus affecting the optical properties of the resulting CsPbBr3@SiO2 and causing a significant decrease in fluorescence intensity.

[0034] Example 4 This embodiment illustrates that when the target quantum dot is CsPbI3, a similar preparation can be achieved by replacing the halogen precursor.

[0035] In the synthesis of Cs4PbBr6 nanoparticles, the precursor PbBr2 was replaced with an equimolar amount of PbI2, while other steps, material types, and amounts remained unchanged, resulting in Cs4PbI6 nanoparticles, which were then dispersed in n-hexane for later use.

[0036] In the subsequent bilateral coating synthesis steps, the KBr aqueous solution was replaced with an equal volume of 0.2 mol / L KI aqueous solution, and the remaining steps were exactly the same as in Example 1 (using Cs4PbBr6 and KBr), which yielded CsPbI3@SiO2 quantum dots. These CsPbI3@SiO2 quantum dots are expected to have a similar bilateral coating structure and produce red fluorescence emission, while maintaining higher environmental stability compared to uncoated CsPbI3 quantum dots.

[0037] Example 5 This embodiment illustrates that when the target quantum dot is CsPbCl3, a similar preparation can be achieved by replacing the halogen precursor.

[0038] In the synthesis of Cs4PbCl6 nanoparticles, the precursor PbBr2 was replaced with an equimolar amount of PbCl2, while other steps, material types, and amounts remained unchanged. Cs4PbCl6 nanoparticles were obtained and dispersed in n-hexane for later use.

[0039] In the subsequent bilateral coating synthesis steps, the KBr aqueous solution was replaced with an equal volume of 3 mol / L KCl aqueous solution. The remaining steps were exactly the same as in Example 1 (using Cs4PbBr6 and KBr), which yielded CsPbCl3@SiO2 quantum dots. These CsPbCl3@SiO2 quantum dots are expected to have a similar bilateral coating structure and produce blue fluorescence emission, while maintaining higher environmental stability compared to uncoated CsPbCl3 quantum dots.

[0040] Application Example 1 H2O2 sensor based on CsPbBr3@SiO2 quantum dots CsPbBr3@SiO2 quantum dots, OLAI (n-hexane solution), and aqueous solutions of H2O2 at different concentrations (0-220 μmol / L) were mixed. The fluorescence emission spectra of the mixed systems were measured. Figure 4 (A)). The results showed that the fluorescence emission peak blue-shifted with increasing H2O2 concentration. A calibration curve was plotted using the emission wavelength as the signal. Figure 4 (B) shows a good linear relationship in the ranges of 1-160 μmol / L and 160-220 μmol / L.

[0041] Application Example 2 Pyruvate Sensing Based on CsPbBr3@SiO2 Quantum Dots Different concentrations of pyruvate solutions (0-220 μmol / L) were reacted with pyruvate oxidase in PBS buffer for a certain period of time to generate H₂O₂. The reaction solution was then mixed with CsPbBr₃@SiO₂ quantum dots and OLAI. Fluorescence emission spectra were measured. Figure 5 (A)) and observed the fluorescence color. The results showed that as the concentration of pyruvate increased, the fluorescence emission peak shifted to blue, and the fluorescence color of the solution changed from red through orange-yellow to green. A calibration curve was plotted using the emission wavelength as the signal. Figure 5 (B) shows a good linear relationship in the ranges of 0-140 μmol / L and 140-220 μmol / L.

[0042] Therefore, the present invention employs the above-mentioned double-sided SiO2-coated CsPbX3 quantum dots, methods and applications. The resulting quantum dots have both excellent water stability and efficient fast anion exchange (FAE) activity, with a fluorescence lifetime of up to 46.44 ns. After a violent reaction with water for 60 minutes, the fluorescence intensity only decreases by 21.8%.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing double-sided SiO 2-coated CsPbX 3 quantum dots, characterized in that, The method comprises the following steps: Step 1, adding Cs4PbX6 nanoparticles into an organic phase to obtain an organic phase dispersion of Cs4PbX6 nanoparticles, wherein X is chlorine Cl, bromine Br or iodine I; Step 2, adding a silicon source into the dispersion of step 1; Step 3, adding a halogen ion-containing aqueous solution into the system of step 2 and then violently shaking to induce a crystal phase transition of Cs4PbX6 to CsPbX3 and a reaction of the silicon source, thereby forming in-situ double-side SiO2-coated CsPbX3 quantum dots; Step 4, centrifuging after standing to obtain a solution of the double-side SiO2-coated CsPbX3 quantum dots. 2.The method of claim 1, wherein the method is characterized by, The organic phase is one or more of n-hexane, cyclohexane, chlorobenzene and toluene; The silicon source is an organic phase solution of orthosilicate, wherein the concentration of the silicon source is 15%-25v%; The halogen ion-containing aqueous solution is a KX aqueous solution, wherein X is chlorine Cl, bromine Br or iodine I, and the concentration is 0.1-3.0 mol / L. 3.The method of claim 1, wherein the method is characterized by, The Cs4PbX6 nanoparticles are synthesized by a hot injection method or a ligand-assisted reprecipitation method. 4.The method of claim 1, wherein the method is characterized by, The ratio of Cs4PbX6 nanoparticles to the organic phase is (0.05-0.1 mol):(20-25 mL).

5. The method of claim 1, wherein the method is characterized by: The ratio of the silicon source to the dispersion of CsPbX3 nanoparticles is (4-6 mL):(80-120 μL). 6.The method of claim 1, wherein the CsPbX 3 quantum dots are coated with SiO 2 on both sides. The ratio of the halogen ion-containing aqueous solution to the dispersion to which the silicon source is added is (4-6 mL):(150-250 μL).

7. The method of claim 1, wherein the method is characterized by: In step 3, the violent shaking is at a speed of 1500-2000 rpm for 5-10 minutes. In step 4, the standing time is 10-12 hours, the centrifuging speed is 8000-10000 rpm, and the centrifuging time is 5-10 minutes.

8. The double-side SiO2-coated CsPbX3 quantum dots prepared by the method of any one of claims 1-7, wherein, The quantum dots have a core-shell structure, wherein the inner core is a CsPbX3 crystal of an orthorhombic system, and the outer shell is a double-side coated amorphous SiO2 layer.

9. Use of the double-side SiO2-coated CsPbX3 quantum dots of claim 8 in the preparation of optoelectronic devices and biological sensing.

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