Preparation Method of Watermelon-shaped Structural Nanoparticles with Piezo-phototronic Effect

Abstract

A preparation method of watermelon-shaped structure nanoparticles with piezoelectric optoelectronic effect, which relates to a preparation method of nanoparticles with piezoelectric optoelectronic effect. The present invention aims to solve the problem that existing ZnSnO3 QDs can only be excited by ultraviolet or short-wavelength visible light. Method: First, preparation of metal oleate complex precursors; second, preparation of ZnSnO3 QDs; third, synthesis of ZnSnO3 QDs@UCNPs nanoparticles; fourth, synthesis of water-soluble ZnSnO3 QDs@UCNPs-PEI. The present invention is used for the preparation of watermelon-shaped structure nanoparticles with piezoelectric optoelectronic effect.

Description

Technical Field

[0001] The present invention relates to a method for preparing nanoparticles with piezoelectric optoelectronic effect. Background Art

[0002] One of the most important problems hindering photocatalytic applications is the low photocatalytic activity caused by the recombination of photoinduced carriers in semiconductor photocatalysts, resulting in the neutralization of photoinduced electrons and holes before initiating the photocatalytic process. Although some heterostructure-based measures have been proposed and practiced to solve this problem, the efficiency is still too low to completely separate electron-hole pairs during the photocatalytic process. Recently, a new concept of introducing an internal electric field (internal field) into photocatalyst particles has been proposed to enhance the separation of photo-generated charge carriers. The presence of the internal electric field provides a driving force for the transport of photo-generated charge carriers, thereby enhancing their separability. Although the internal electric field can separate photoinduced carriers, the static field is easily saturated by free carriers, so the enhancement of photocatalysis is stopped. Updating the internal electric field during the photocatalytic process and maintaining the continuous separation of photoinduced carriers are the greatest challenges for maintaining the high performance of internal electric field photocatalysts.

[0003] It is well known that piezoelectricity can change the potential by applying stress to a crystal, and the piezoelectric potential can effectively affect charge transport, thus significantly enhancing optoelectronic performance. This is called the piezoelectric optoelectronic effect existing in piezoelectric semiconductor materials. Different from the internal fields in other nanoparticles, the internal potential of piezoelectric materials can be alternately amplified and reduced by applying stress driven by mechanical vibration or ultrasonic waves. Some studies have proposed the concept that ultrasonic waves can be used as an irradiation energy source to enhance photocatalysis and achieve sono-catalysis. Methods for sono-photocatalytic treatment of chemical reactions and cancer treatment have been proposed and discussed. The enhanced catalytic performance is attributed to the possible increase in the catalyst surface area, sonoluminescence, ultrasonic cavitation effect, and sono-chemical and sono-electrochemical effects, resulting in ultrasonic-induced particle depolymerization.

[0004] Among numerous inorganic piezoelectric materials, lead-free perovskite oxides have attracted a great deal of research due to their excellent piezoelectric response, low toxicity, high thermal stability, and structural stability. In particular, piezoelectric-phase perovskite quantum dots (QDs), such as ZnSnO3, have drawn great interest because of their unique semiconductor, piezoelectric, and optoelectronic properties, which form the basis for their applications in electronics, optoelectronics, biology, environmental science, and energy fields. At the same time, these characteristics also enable ZnSnO3 to meet the triggering conditions for the piezo-phototronic effect and can be applied to improve the piezo-photocatalytic efficiency. More specifically, ZnSnO3 has a piezoelectric effect due to its non-centrosymmetric crystal structure. By applying an external mechanical stress, a piezoelectric polarization across the piezoelectric domains is generated. This built-in electric field not only provides a long-range driving force for the separation and diffusion of photo-generated electron-hole pairs, suppressing their recombination, but also changes the band structure and surface charge energy of the applied semiconductor, providing new ideas for improving the charge transfer efficiency. However, ZnSnO3 generally has the problem of a relatively wide bandgap and can usually only be excited by ultraviolet or short-wavelength visible light, not by near-infrared light. The penetration depth of ultraviolet or visible light in biological tissues is relatively low, so the application of ZnSnO3 in biocatalysis and the medical field is limited. Summary of the Invention

[0005] The present invention aims to solve the problem that existing ZnSnO3 QDs can only be excited by ultraviolet or short-wavelength visible light, and further provides a preparation method for watermelon-shaped structure nanoparticles with a piezo-phototronic effect.

[0006] A preparation method for watermelon-shaped structure nanoparticles with a piezo-phototronic effect is carried out according to the following steps:

[0007] I. Preparation of metal oleate complex precursors:

[0008] Mix a tetramethylammonium hydroxide methanol solution, methanol, and oleic acid to obtain a mixed solution. Under the condition of a temperature of 40 °C to 60 °C, dropwise add a metal salt methanol solution to the mixed solution and stir for 1 h to 2 h. After the reaction, cool to room temperature, and finally wash and dry to obtain tin oleate or zinc oleate.

[0009] II. Preparation of ZnSnO3 QDs:

[0010] ① Mix zinc oleate, oleic acid, and octadecene to obtain a zinc oleate solution;

[0011] ② Mix tin oleate and oleylamine to obtain a tin oleate solution;

[0012] ③Under the conditions of a nitrogen atmosphere and a temperature of 70 °C to 90 °C, heat the zinc oleate solution for 15 min to 30 min, then increase the temperature to 100 °C to 300 °C at a heating rate of 10 °C / min to 15 °C / min, maintain nitrogen purging for 5 min to 10 min, and then, under the conditions of a nitrogen atmosphere and a temperature of 100 °C to 300 °C, add the tin oleate solution at an addition rate of 2 mL / min to 20 mL / min and heat for 30 min to 60 min. After the reaction is completed, cool to room temperature and purify to obtain ZnSnO3 QDs nanoparticles. Disperse the ZnSnO3 QDs nanoparticles in cyclohexane to obtain a ZnSnO3 QDs solution;

[0013] III. Synthesis of ZnSnO3 QDs@UCNPs nanoparticles:

[0014] ①Mix (CH3CO2)3Y, (CH3CO2)3Yb, (CH3CO2)3Tm, (CH3CO2)3Er, oleic acid and octadecene to obtain a reaction system. Under the conditions of vacuum and a temperature of 100 °C to 130 °C, keep the reaction system warm for 0.5 h to 1 h, and then, under the conditions of a nitrogen atmosphere and a temperature of 150 °C to 160 °C, keep warm for 0.2 h to 0.5 h until the solid is completely dissolved. Finally, cool to room temperature to obtain the reaction system after the solid is dissolved;

[0015] ②Under the conditions of a nitrogen atmosphere and room temperature, add the methanol solution of NaOH / NH4F to the reaction system after the solid is dissolved at an addition rate of 2 mL / min to 20 mL / min, stir for 5 min to 10 min, add the ZnSnO3 QDs solution after stirring, and successively carry out methanol removal and degassing treatments. Then, under the conditions of a nitrogen atmosphere and a temperature of 250 °C to 300 °C, keep warm for 0 min to 80 min. Finally, cool to room temperature, wash and disperse in cyclohexane to obtain a watermelon-shaped structure ZnSnO3QDs@UCNPs nanoparticle solution;

[0016] IV. Synthesis of water-soluble ZnSnO3 QDs@UCNPs-PEI:

[0017] ①Mix the watermelon-shaped structure ZnSnO3 QDs@UCNPs nanoparticle solution, NOBF4 and DMF, oscillate for 5 min to 10 min to obtain a solution after ligand exchange. Centrifuge the solution after ligand exchange and disperse it in DMF to obtain a ZnSnO3QDs@UCNPs-NOBF4 solution;

[0018] ② Add PEI to the ZnSnO3 QDs@UCNPs-NOBF4 solution, stir at a temperature of 50 °C to 100 °C for 0.3 h to 0.5 h, add acetone for precipitation after cooling, and finally disperse in water to obtain watermelon-like structured ZnSnO3 QDs@UCNPs with piezoelectric optoelectronic effect.

[0019] The beneficial effects of the present invention are as follows:

[0020] 1. The present invention prepares tetragonal ZnSnO3 ultra-small nanoparticles with uniform size distribution and piezoelectric optoelectronic effect, which are successfully encapsulated in hexagonal upconversion nanoparticles (UCNPs) by a one-pot high-temperature pyrolysis method to form an integrated watermelon-like structured sonosensitizer (ZnSnO3 QDs@UCNPs).

[0021] 2. The watermelon-like structure hinders the degradation of ZnSnO3 and avoids the loss of catalytic performance.

[0022] 3. The near-infrared light excited by UCNPs has a high penetration depth. The watermelon-like structure realizes the close contact between UCNPs and ZnSnO3, and the efficiency of resonance energy transfer (FRET) is increased to 80.30%.

[0023] 4. Under the action of ultrasonic cavitation, UCNPs are deformed along the direction with the weakest lattice, thereby driving the deformation of all ZnSnO3 ultra-small nanoparticles inside UCNPs, and forming many small internal electric fields similar to isotropic electric domains based on the piezoelectric effect of ZnSnO3. This piezoelectric effect not only increases the internal electric field strength of the whole material, but also prevents the random movement and rapid recombination of charge carriers, achieving a satisfactory catalytic effect.

[0024] Therefore, the preparation method of the watermelon-like structured ZnSnO3 QDs@UCNPs nanomaterials with piezoelectric optoelectronic effect prepared by the present invention is simple, has a uniform size distribution, good catalytic performance, and has characteristics such as high electron-hole separation ability.

[0025] Description of the drawings

[0026] Figure 1 Schematic diagram of the formation process of watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1;

[0027] Figure 2 Transmission electron microscope (TEM) imaging diagram of ZnSnO3 QDs nanoparticles prepared in Step 2③ of Example 1;

[0028] Figure 3XRD pattern of the ZnSnO3 QDs nanoparticles prepared in Step 2 ③ of Example 1. 1 is ZnSnO3 QDs, and 2 is PDF#28-1486;

[0029] Figure 4 XRD pattern of the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles. 1 is Example 2, 2 is Example 3, 3 is Example 4, 4 is Example 5, 5 is Example 1, a is the characteristic peak position of PDF#28-1486, b is the characteristic peak position of PDF#77-2042, and c is the characteristic peak position of PDF#16-0334;

[0030] Figure 5 TEM images of the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles. a is Example 2, b is Example 3, c is Example 4, d is Example 5, and e is Example 1;

[0031] Figure 6 Elemental mapping of the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1;

[0032] Figure 7 X-ray photoelectron spectroscopy. 1 is the full spectrum of the ZnSnO3 QDs nanoparticles prepared in Step 2 ③ of Example 1, and 2 is the full spectrum of the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1;

[0033] Figure 8 Fourier transform infrared spectroscopy. 1 is the ZnSnO3 QDs nanoparticles prepared in Step 2 ③ of Example 1, 2 is the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1, 3 is ZnSnO3 QDs@UCNPs-NOBF4 prepared in Step 4 ① of Example 1, 4 is ZnSnO3 QDs@UCNPs-PEI prepared in Step 4 ② of Example 1, a is the -OH characteristic peak, b is the -COOH characteristic peak, c is the C=O characteristic peak, d is the BF4 characteristic peak, e is the N-H characteristic peak, and f is the C-N characteristic peak;

[0034] Figure 9 UV and fluorescence spectra. 1 is the UV absorption spectrum of the ZnSnO3 QDs nanoparticles prepared in Step 2 ③ of Example 1, and 2 is the fluorescence spectrum of the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1;

[0035] Figure 10Digital photos of the ZnSnO3 QDs nanoparticles prepared in Step 2③ of Example 1 at different times under neutral and acidic conditions;

[0036] Figure 11 Degradation experiment of ZnSnO3 QDs@UCNPs-PEI prepared in Step 4② of Example 1 under acidic (pH = 6.0) conditions. a is the digital photo at different times, and b is the fluorescence spectrum at different times. 1 is 0 h, 2 is 1 h, 3 is 2 h, 4 is 4 h, 5 is 6 h, 6 is 12 h, and 7 is 24 h;

[0037] Figure 12 Schematic diagram of energy transfer from UCNPs to QDs in ZnSnO3 QDs@UCNPs-PEI prepared in Step 4② of Example 1 and the subsequent ROS generation mechanism diagram;

[0038] Figure 13 Fluorescence spectrum of watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles. 1 is UCNPs prepared without adding ZnSnO3 QDs in Comparative Experiment 1, 2 is Example 6, 3 is Example 7, 4 is Example 1, and 5 is Example 8;

[0039] Figure 14 Fluorescence lifetime of watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles. a is the lifetime of ZnSnO3 QDs@UCNPs excited at 362 nm, b is the lifetime of ZnSnO3 QDs@UCNPs excited at 450 nm, c is the lifetime of ZnSnO3 QDs@UCNPs excited at 540 nm. 1 is UCNPs prepared without adding ZnSnO3 QDs in Comparative Experiment 1, 2 is Example 6, 3 is Example 7s, 4 is Example 1, and 5 is Example 8;

[0040] Figure 15 Piezoelectric response amplitude curve and phase curve diagram of watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1. 1 is the piezoelectric response amplitude curve, and 2 is the phase curve diagram;

[0041] Figure 16 Ultrasonic current test spectrum. a is the current test comparison under the combined action of ultrasound and 980 nm laser. 1 is the ZnSnO3 QDs nanoparticles prepared in Step 2③ of Example 1, and 2 is the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1; b is the current test comparison of the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under different conditions. 3 is 980 nm laser, 4 is ultrasound, and 5 is the combined action of ultrasound and 980 nm laser;

[0042] Figure 17 For the degradation efficiency of DPBF solution under different conditions, 1 is the change in the degradation efficiency of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under 980 nm light irradiation, 2 is the change in the degradation efficiency of the ZnSnO3 QDs nanoparticles prepared in Step 2③ of Example 1 under 980 nm light irradiation and ultrasonic action, 3 is the change in the degradation efficiency of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under ultrasonic action, and 4 is the change in the degradation efficiency of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under 980 nm light irradiation and ultrasonic action;

[0043] Figure 18 For the change in the absorbance of TMB solution with time under different conditions, 1 is the change in the absorbance of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under 980 nm light irradiation, 2 is the change in the absorbance of the ZnSnO3 QDs nanoparticles prepared in Step 2③ of Example 1 under 980 nm light irradiation and ultrasonic action, 3 is the change in the absorbance of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under ultrasonic action, and 4 is the change in the absorbance rate of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under 980 nm light irradiation and ultrasonic action. Detailed implementation mode

[0044] Detailed implementation mode 1: This implementation mode is a preparation method of watermelon-like structure nanoparticles with piezoelectric optoelectronic effect, and it is carried out according to the following steps:

[0045] I. Preparation of metal oleate complex precursor:

[0046] Mix the tetramethylammonium hydroxide methanol solution, methanol and oleic acid to obtain a mixed solution. Under the condition of a temperature of 40 °C to 60 °C, dropwise add the metal salt methanol solution to the mixed solution and stir for 1 h to 2 h. After the reaction is completed, cool to room temperature, and finally wash and dry to obtain tin oleate or zinc oleate;

[0047] II. Preparation of ZnSnO3 QDs:

[0048] ① Mix zinc oleate, oleic acid and octadecene to obtain a zinc oleate solution;

[0049] ② Mix tin oleate and oleylamine to obtain a tin oleate solution;

[0050] ③Under the conditions of a nitrogen atmosphere and a temperature of 70 °C to 90 °C, heat the zinc oleate solution for 15 min to 30 min, then increase the temperature to 100 °C to 300 °C at a heating rate of 10 °C / min to 15 °C / min, maintain nitrogen purging for 5 min to 10 min, and then add the tin oleate solution at an addition rate of 2 mL / min to 20 mL / min under the conditions of a nitrogen atmosphere and a temperature of 100 °C to 300 °C and heat for 30 min to 60 min. After the reaction is completed, cool to room temperature and purify to obtain ZnSnO3 QDs nanoparticles. Disperse the ZnSnO3 QDs nanoparticles in cyclohexane to obtain a ZnSnO3 QDs solution;

[0051] III. Synthesis of ZnSnO3 QDs@UCNPs nanoparticles:

[0052] ①Mix (CH3CO2)3Y, (CH3CO2)3Yb, (CH3CO2)3Tm, (CH3CO2)3Er, oleic acid and octadecene to obtain a reaction system. Under the conditions of vacuum and a temperature of 100 °C to 130 °C, keep the reaction system warm for 0.5 h to 1 h, and then under the conditions of a nitrogen atmosphere and a temperature of 150 °C to 160 °C, keep warm for 0.2 h to 0.5 h until the solid is completely dissolved. Finally, cool to room temperature to obtain the reaction system after the solid is dissolved;

[0053] ②Under the conditions of a nitrogen atmosphere and room temperature, add the methanol solution of NaOH / NH4F to the reaction system after the solid is dissolved at an addition rate of 2 mL / min to 20 mL / min, stir for 5 min to 10 min, add the ZnSnO3 QDs solution after stirring, and successively carry out methanol removal and degassing treatments. Then, under the conditions of a nitrogen atmosphere and a temperature of 250 °C to 300 °C, keep warm for 0 min to 80 min. Finally, cool to room temperature, wash and disperse in cyclohexane to obtain a watermelon-shaped structure ZnSnO3QDs@UCNPs nanoparticle solution;

[0054] IV. Synthesis of water-soluble ZnSnO3 QDs@UCNPs-PEI:

[0055] ①Mix the watermelon-shaped structure ZnSnO3 QDs@UCNPs nanoparticle solution, NOBF4 and DMF, oscillate for 5 min to 10 min to obtain a solution after ligand exchange. Centrifuge the solution after ligand exchange and disperse it in DMF to obtain a ZnSnO3QDs@UCNPs-NOBF4 solution;

[0056] ② Add PEI to the ZnSnO3 QDs@UCNPs-NOBF4 solution, stir for 0.3 h to 0.5 h under the condition that the temperature is 50 °C to 100 °C, add acetone precipitation after cooling, and finally disperse in water to obtain watermelon-shaped structure ZnSnO3 QDs@UCNPs with piezoelectric optoelectronic effect.

[0057] The beneficial effects of this embodiment are as follows:

[0058] 1. In this embodiment, a kind of tetragonal ZnSnO3 ultra-small nanoparticles with uniform size distribution and piezoelectric optoelectronic effect are prepared, and are successfully encapsulated in hexagonal upconversion nanoparticles (UCNPs) by one-pot high-temperature pyrolysis method to form an integrated watermelon-shaped structure sonosensitizer (ZnSnO3 QDs@UCNPs).

[0059] 2. The watermelon-shaped structure hinders the degradation of ZnSnO3 and avoids the loss of catalytic performance.

[0060] 3. The near-infrared light excited by UCNPs has a higher penetration depth. The watermelon-shaped structure realizes the close contact between UCNPs and ZnSnO3, and the efficiency of resonance energy transfer (FRET) is increased to 80.30%.

[0061] 4. Under the action of ultrasonic cavitation, UCNPs are deformed along the direction with the weakest lattice, thereby driving the deformation of all ZnSnO3 ultra-small nanoparticles inside UCNPs, and forming many small internal electric fields similar to isotropic electric domains based on the piezoelectric effect of ZnSnO3. This piezoelectric effect not only increases the internal electric field strength of the whole material, but also prevents the random movement and rapid recombination of charge carriers, and realizes a satisfactory catalytic effect.

[0062] Therefore, the preparation method of the watermelon-shaped structure ZnSnO3 QDs@UCNPs nanomaterial with piezoelectric optoelectronic effect prepared in this embodiment is simple, has a uniform size distribution, good catalytic performance, and has characteristics such as high electron-hole separation ability.

[0063] Embodiment 2: The difference between this embodiment and Embodiment 1 is as follows: The metal salt methanol solution in Step 1 is tin chloride methanol solution or zinc acetate methanol solution; the concentration of the metal salt methanol solution in Step 1 is 4 mg / mL to 10 mg / mL; the mass percentage of tetramethylammonium hydroxide in the tetramethylammonium hydroxide methanol solution in Step 1 is 25%; the volume ratio of the tetramethylammonium hydroxide methanol solution to methanol in Step 1 is 1:(25 - 50); the volume ratio of the tetramethylammonium hydroxide methanol solution to oleic acid in Step 1 is 1:(0.5 - 1); the volume ratio of the tetramethylammonium hydroxide methanol solution to the metal salt methanol solution in Step 1 is 1:(0.5 - 2.5). Others are the same as Embodiment 1.

[0064] Embodiment 3: The difference between this embodiment and either Embodiment 1 or Embodiment 2 is as follows: In Step 2①, the mass - to - volume ratio of zinc oleate to oleic acid is 1 g:(12.5 - 20) mL; the mass - to - volume ratio of zinc oleate to octadecene in Step 2① is 1 g:(87.5 - 140) mL; in Step 2②, the mass - to - volume ratio of tin oleate to oleylamine is 1 g:(15 - 40) mL; in Step 2③, the volume ratio of the zinc oleate solution to the tin oleate solution is 1:(0.25 - 2); the concentration of ZnSnO3 QDs nanoparticles in the ZnSnO3 QDs solution in Step 2③ is 10 mg / mL to 50 mg / mL. Others are the same as either Embodiment 1 or Embodiment 2.

[0065] Embodiment 4: The difference between this embodiment and any one of Embodiments 1 to 3 is as follows: In Step 3①, the total molar amount of (CH3CO2)3Y, (CH3CO2)3Yb, (CH3CO2)3Tm, and (CH3CO2)3Er to the volume of oleic acid is 1 mmol:(5 - 10) mL; the total molar amount of (CH3CO2)3Y, (CH3CO2)3Yb, (CH3CO2)3Tm, and (CH3CO2)3Er to the volume of octadecene in Step 3① is 1 mmol:(10 - 20) mL; the molar ratio of (CH3CO2)3Y to (CH3CO2)3Yb in Step 3① is 1:(0.25 - 0.3); the molar ratio of (CH3CO2)3Y to (CH3CO2)3Tm in Step 3① is 1:(0.06 - 0.07); the molar ratio of (CH3CO2)3Y to (CH3CO2)3Er is 1:(0.015 - 0.02). Others are the same as any one of Embodiments 1 to 3.

[0066] Embodiment 5: The difference between this embodiment and any one of Embodiments 1 to 4 is as follows: In the NaOH / NH4F methanol solution described in Step 3②, the concentration of NaOH is 5 mg / mL to 15 mg / mL, and the concentration of NH4F is 7.5 mg / mL to 22.5 mg / mL; the volume ratio of the reaction system after the solid is dissolved to the NaOH / NH4F methanol solution in Step 3② is 1:(0.25 to 2); the volume ratio of the reaction system after the solid is dissolved to the ZnSnO3 QDs solution in Step 3② is 1:(0.02 to 0.15); the concentration of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles in the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticle solution described in Step 3② is 5 mg / mL to 20 mg / mL. Others are the same as those in Embodiments 1 to 4.

[0067] Embodiment 6: The difference between this embodiment and any one of Embodiments 1 to 5 is as follows: In Step 3②, the removal of methanol is carried out successively under the conditions of vacuum and a temperature of 60 °C to 120 °C, and the methanol is removed by heating for 0.5 h to 1 h. Others are the same as those in Embodiments 1 to 5.

[0068] Embodiment 7: The difference between this embodiment and any one of Embodiments 1 to 6 is as follows: In Step 4①, the volume ratio of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticle solution to the mass of NOBF4 is 1 mL:(20 to 50) mg; the volume ratio of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticle solution to DMF in Step 4① is 1:(1 to 5). Others are the same as those in Embodiments 1 to 6.

[0069] Embodiment 8: The difference between this embodiment and any one of Embodiments 1 to 7 is as follows: In Step 4①, the centrifugation is specifically to add the ligand-exchanged solution to toluene and cyclohexane, and under the condition of a rotation speed of 8000 rpm to 12000 rpm, centrifugation is carried out for 5 min to 10 min; the concentration of ZnSnO3 QDs@UCNPs-NOBF4 in the ZnSnO3 QDs@UCNPs-NOBF4 solution in Step 4① is 5 mg / mL to 20 mg / mL. Others are the same as those in Embodiments 1 to 7.

[0070] Embodiment 9: The difference between this embodiment and any one of Embodiments 1 to 8 is as follows: In Step 4②, the volume ratio of the ZnSnO3 QDs@UCNPs-NOBF4 solution to the mass of PEI is 1 mL:(0.1 to 0.5) g. Others are the same as those in Embodiments 1 to 8.

[0071] Embodiment 10: The difference between this embodiment and any one of Embodiments 1 to 9 is as follows: In Step 1, the washing and drying are specifically carried out by washing with methanol 3 to 5 times and then drying under vacuum; in Step 2③, the purification is specifically carried out according to the following steps: centrifuging with acetone to obtain a precipitate, dispersing the precipitate in chloroform, and then centrifuging again with ethanol; in Step 3②, the cleaning is specifically carried out by alternately cleaning with ethanol and cyclohexane 3 to 5 times. Others are the same as those in Embodiments 1 to 9.

[0072] The following examples are used to verify the beneficial effects of the present invention:

[0073] Example 1:

[0074] A preparation method of watermelon-shaped structural nanoparticles with piezoelectric optoelectronic effect is carried out according to the following steps:

[0075] I. Preparation of metal oleate complex precursors:

[0076] ① Mix 6.7 mL of tetramethylammonium hydroxide methanol solution, 245 mL of methanol, and 5 mL of oleic acid to obtain a mixed solution. Under the condition of a temperature of 50 °C, add 15 mL of metal salt methanol solution dropwise to the mixed solution and stir for reaction for 2 h. After the reaction is completed, cool to room temperature, and finally wash and dry to obtain tin oleate;

[0077] The metal salt methanol solution is a tin chloride methanol solution with a concentration of 4.25 mg / mL; the mass percentage of tetramethylammonium hydroxide in the tetramethylammonium hydroxide methanol solution is 25%;

[0078] ② Mix 6.7 mL of tetramethylammonium hydroxide methanol solution, 195 mL of methanol, and 5 mL of oleic acid to obtain a mixed solution. Under the condition of a temperature of 50 °C, add 20 mL of metal salt methanol solution dropwise to the mixed solution and stir for reaction for 1 h. After the reaction is completed, cool to room temperature, and finally wash and dry to obtain zinc oleate;

[0079] The metal salt methanol solution is zinc acetate methanol with a concentration of 6.22 mg / mL; the mass percentage of tetramethylammonium hydroxide in the tetramethylammonium hydroxide methanol solution is 25%;

[0080] II. Preparation of ZnSnO3 QDs:

[0081] ① Mix 62.8 mg of zinc oleate, 1 mL of oleic acid, and 7 mL of octadecene to obtain a zinc oleate solution;

[0082] ② Mix 124.4 mg of tin oleate with 2 mL of oleylamine to obtain a tin oleate solution;

[0083] ③ Under the conditions of a nitrogen atmosphere and a temperature of 80 °C, heat 8 mL of zinc oleate solution for 30 min, then increase the temperature to 280 °C at a heating rate of 10 °C / min, blow nitrogen for 10 min. Under the conditions of a nitrogen atmosphere and a temperature of 280 °C, add 2 mL of tin oleate solution at an addition rate of 5 mL / min and heat for 60 min. After the reaction is completed, cool to room temperature and purify to obtain ZnSnO3 QDs nanoparticles. Disperse the ZnSnO3 QDs nanoparticles in cyclohexane to obtain a ZnSnO3 QDs solution;

[0084] The concentration of ZnSnO3 QDs nanoparticles in the ZnSnO3 QDs solution is 20 mg / mL;

[0085] III. Synthesis of ZnSnO3 QDs@UCNPs nanoparticles:

[0086] ① Mix 0.75 mmol (CH3CO2)3Y, 0.19 mmol (CH3CO2)3Yb, 0.048 mmol (CH3CO2)3Tm, 0.012 mmol (CH3CO2)3Er, 6 mL of oleic acid and 15 mL of octadecene to obtain a reaction system. Under the conditions of vacuum and a temperature of 110 °C, keep the reaction system at this temperature for 1 h. Then, under the conditions of a nitrogen atmosphere and a temperature of 156 °C, keep it at this temperature for 0.5 h until the solid is completely dissolved. Finally, cool to room temperature to obtain the reaction system after the solid is dissolved;

[0087] ② Under the conditions of a nitrogen atmosphere and room temperature, add 15 mL of a methanol solution of NaOH / NH4F to 21 mL of the reaction system after the solid is dissolved at an addition rate of 5 mL / min, stir for 10 min. After stirring, add 2 mL of ZnSnO3 QDs solution, and successively carry out methanol removal and degassing treatments. Then, under the conditions of a nitrogen atmosphere and a temperature of 300 °C, keep it at this temperature for 80 min. Finally, cool to room temperature, wash and disperse in cyclohexane to obtain a solution of watermelon-shaped ZnSnO3 QDs@UCNPs nanoparticles;

[0088] The concentration of NaOH in the methanol solution of NaOH / NH4F is 10 mg / mL, and the concentration of NH4F is 15 mg / mL; The concentration of watermelon-shaped ZnSnO3 QDs@UCNPs nanoparticles in the solution of watermelon-shaped ZnSnO3 QDs@UCNPs nanoparticles is 10 mg / mL;

[0089] IV. Synthesis of water-soluble ZnSnO3 QDs@UCNPs-PEI:

[0090] ① Mix 1 mL of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticle solution, 20 mg of NOBF4, and 1 mL of DMF, and oscillate for 10 min to obtain the ligand-exchanged solution. Centrifuge the ligand-exchanged solution and disperse it in DMF to obtain the ZnSnO3 QDs@UCNPs-NOBF4 solution;

[0091] The concentration of ZnSnO3 QDs@UCNPs-NOBF4 in the ZnSnO3 QDs@UCNPs-NOBF4 solution described above is 2 mg / mL;

[0092] ② Add 0.2 g of PEI to 1 mL of the ZnSnO3 QDs@UCNPs-NOBF4 solution, stir at 80 °C for 0.5 h, add acetone for precipitation after cooling, and finally disperse it in water to obtain the watermelon-like structure ZnSnO3 QDs@UCNPs with piezoelectric optoelectronic effect, that is, the ZnSnO3 QDs@UCNPs-PEI solution.

[0093] In step three ②, the removal of methanol is specifically carried out by heating to remove methanol for 1 h under vacuum and at a temperature of 110 °C.

[0094] In step four ①, the centrifugation is specifically to add the ligand-exchanged solution to 5 mL of toluene and 5 mL of cyclohexane, and centrifuge for 5 min at a rotation speed of 10,000 rpm;

[0095] The washing and drying in step one are specifically to wash 3 times with methanol and then dry under vacuum; the purification in step two ③ is carried out as follows: centrifuge with acetone to obtain a precipitate, disperse the precipitate in chloroform, and then centrifuge again with ethanol; the cleaning in step three ② is specifically to alternately wash 3 times with ethanol and cyclohexane.

[0096] Example two: The difference between the example and example one is that in step three ②, it is kept warm for 80 min under a nitrogen atmosphere and at a temperature of 250 °C. Others are the same as example one.

[0097] Example three: The difference between the example and example one is that in step three ②, it is kept warm for 0 min under a nitrogen atmosphere and at a temperature of 300 °C. Others are the same as example one.

[0098] Example four: The difference between the example and example one is that in step three ②, it is kept warm for 40 min under a nitrogen atmosphere and at a temperature of 300 °C. Others are the same as example one.

[0099] Example five: The difference between the example and example one is that in step three ②, it is kept warm for 60 min under a nitrogen atmosphere and at a temperature of 300 °C. Others are the same as example one.

[0100] Example 6: The difference between this example and Example 1 is that: after stirring in Step 3②, 0.5 mL of ZnSnO3 QDs solution was added. Others are the same as in Example 1.

[0101] Example 7: The difference between this example and Example 1 is that: after stirring in Step 3②, 1 mL of ZnSnO3 QDs solution was added. Others are the same as in Example 1.

[0102] Example 8: The difference between this example and Example 1 is that: after stirring in Step 3②, 3 mL of ZnSnO3 QDs solution was added. Others are the same as in Example 1.

[0103] Comparative experiment: The difference between this comparative experiment and Example 1 is that: the addition of ZnSnO3 QDs in Step 3② was cancelled. Others are the same as in Example 1.

[0104] Figure 1 Schematic diagram of the formation process of watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1; It can be seen from the figure that as the temperature gradually increases, the tetragonal upconversion gradually coats the periphery of ZnSnO3 QDs. When the temperature rises to 300 °C, as time increases, the tetragonal upconversion gradually transforms into the hexagonal phase.

[0105] Figure 2 Transmission electron microscope (TEM) imaging diagram of ZnSnO3 QDs nanoparticles prepared in Step 2③ of Example 1; It can be seen from the figure that ZnSnO3 QDs show uniform small sizes, and the average size is 2 nm - 3 nm.

[0106] Figure 3 X-ray diffractometer (XRD) diagram of ZnSnO3 QDs nanoparticles prepared in Step 2③ of Example 1. 1 is ZnSnO3 QDs, and 2 is PDF#28-1486; The XRD diffraction peaks of ZnSnO3 QDs are highly consistent with those of PDF#28-1486. Broad diffraction peaks are shown at 26.5°, 33.7° and 51.5°, corresponding to the (012), (110) and (116) planes of the material respectively. The appearance of the broad diffraction peaks is due to the extremely small size of the QDs.

[0107] Figure 4XRD pattern of watermelon-shaped ZnSnO3 QDs@UCNPs nanoparticles. 1 represents Example 2, 2 represents Example 3, 3 represents Example 4, 4 represents Example 5, 5 represents Example 1, a represents the characteristic peak position of PDF#28-1486, b represents the characteristic peak position of PDF#77-2042, and c represents the characteristic peak position of PDF#16-0334. As shown in the figure, for Example 2, the reaction temperature of 250 °C was maintained for 80 min, and the obtained product was tetragonal UCNPs. When the temperature was increased to 300 °C, the tetragonal phase gradually transformed into the hexagonal phase as the reaction time increased. When Example 1 was maintained at 300 °C for 80 min, the information of tetragonal UCNPs (PDF#77-2042) disappeared in the XRD diffraction peaks of the obtained sample, and only the characteristic peaks of hexagonal UCNPs (PDF#16-0334) and ZnSnO3 remained, and the crystallinity was also significantly improved.

[0108] Figure 5 TEM imaging of watermelon-shaped ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1. a represents Example 2, b represents Example 3, c represents Example 4, d represents Example 5, and e represents Example 1. As shown in the figure, in the transmission image of Example 2 with a reaction temperature of 250 °C for 80 min, there are many small particles spreading in the field of view of the transmission image. When the temperature of Example 4 rose to 300 °C and the reaction continued for 40 min, small-sized tetragonal UCNPs that were not completely reacted and were in the initial nucleation stage were clearly visible in the TEM image, as well as the already formed large-sized ZnSnO3 QDs@UCNPs. In the result of Example 5 with a reaction time of 60 minutes, the only different phenomenon was that the number of large-sized particles increased significantly. After 300 °C, as the reaction time was extended from 60 min to 80 min, the thickness of UCNPs on the surface of ZnSnO3 QDs@UCNPs increased from 3 nm to 6 nm. This is caused by Ostwald ripening, in which small particles with high energy dissolve and aggregate on the surface of larger particles.

[0109] Figure 6 Elemental mapping of watermelon-shaped ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1; it can be intuitively observed from the elemental mapping results that Zn, Sn, and O elements are concentrated in ZnSnO3 QDs@UCNPs, which further proves the successful formation of ZnSnO3 QDs@UCNPs.

[0110] Figure 7It is an X-ray photoelectron spectroscopy diagram. 1 is the full-spectrum diagram of the ZnSnO3 QDs nanoparticles prepared in Step 2③ of Example 1, and 2 is the full-spectrum diagram of the watermelon-shaped ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1. Almost no Zn and Sn elements were detected in ZnSnO3 QDs@UCNPs. Since the XPS test depth of inorganic materials is generally about 5 nm to 10 nm, it further proves that ZnSnO3 QDs are indeed completely wrapped inside the UCNP.

[0111] Figure 8 It is a Fourier transform infrared spectroscopy diagram. 1 is the ZnSnO3 QDs nanoparticles prepared in Step 2③ of Example 1, 2 is the watermelon-shaped ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1, 3 is ZnSnO3 QDs@UCNPs-NOBF4 prepared in Step 4① of Example 1, 4 is ZnSnO3QDs@UCNPs-PEI prepared in Step 4② of Example 1. a is the characteristic peak of -OH, b is the characteristic peak of -COOH, c is the characteristic peak of C=O, d is the characteristic peak of BF4, e is the characteristic peak of N-H, f is the characteristic peak of C-N. Fourier transform infrared spectroscopy proves that the OA groups (COOH corresponding to 920 cm -1 and 1466 cm -1 , OH corresponding to 2850 cm -1 and 2920 cm -1 ) on the surface of ZnSnO3 QDs@UCNPs are successfully replaced by PEI (NH2 corresponding to 1655 cm -1 ).

[0112] Figure 9 It is an ultraviolet spectrum diagram and a fluorescence spectrum diagram. 1 is the ultraviolet absorption spectrum diagram of the ZnSnO3 QDs nanoparticles prepared in Step 2③ of Example 1, and 2 is the fluorescence spectrum diagram of the watermelon-shaped ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1. It can be seen from the figure that ZnSnO3 QDs have a wide absorption in the ultraviolet and visible light ranges, which is matched with the emission of the designed Er, Tm-sensitized UCNPs for promoting FRET.

[0113] Figure 10 They are digital photos of the ZnSnO3 QDs nanoparticles prepared in Step 2③ of Example 1 at different times under neutral and acidic conditions. As the placement time in the weak acid solution prolongs, the ZnSnO3 QDs nanoparticle solution quickly changes from milky white to transparent. The results show that the ZnSnO3 QDs nanoparticles have a degradation phenomenon in solutions with pH = 7.4 and pH = 6.0.

[0114] Figure 11Degradation experiment of ZnSnO3 QDs@UCNPs-PEI prepared in Step 4② of Example 1 under acidic (pH = 6.0) conditions. a is the digital photo at different times, and b is the fluorescence spectrum at different times. 1 is 0 h, 2 is 1 h, 3 is 2 h, 4 is 4 h, 5 is 6 h, 6 is 12 h, and 7 is 24 h. As the placement time in the weak acid solution prolongs, there are almost no changes in the digital photo image and fluorescence spectrum of ZnSnO3 QDs@UCNPs-PEI. It is proved that the watermelon-like structure can effectively hinder the degradation of ZnSnO3 QDs and avoid the loss of catalytic performance.

[0115] Figure 12 Schematic diagram of energy transfer from UCNPs to QDs and subsequent ROS generation mechanism diagram of ZnSnO3 QDs@UCNPs prepared in Step 4② of Example 1; Er- and Tm-sensitized UCNPs respectively undergo corresponding radiative transition processes. Then, ZnSnO3 absorbs photon energy as the acceptor and generates ROS based on the photodynamic and semiconductor photocatalytic processes. Under ultrasonic irradiation, ZnSnO3 QDs generate ROS due to the sonodynamic process.

[0116] Figure 13 Fluorescence spectrum diagram of watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles. 1 is UCNPs prepared without adding ZnSnO3 QDs in Comparative Experiment 1, 2 is Example 6, 3 is Example 7, 4 is Example 1, and 5 is Example 8. As can be seen from the figure, almost no UCL emission intensity between 300 nm and 500 nm of ZnSnO3 QDs@UCNPs with different QD contents is observed, indicating good FRET conversion efficiency between the UCNPs donor and the ZnSnO3 QDs acceptor.

[0117] Figure 14For the fluorescence lifetime of watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles, a is the lifetime of ZnSnO3 QDs@UCNPs excited at 362 nm, b is the lifetime of ZnSnO3 QDs@UCNPs excited at 450 nm, c is the lifetime of ZnSnO3 QDs@UCNPs excited at 540 nm, 1 is the UCNPs prepared without adding ZnSnO3 QDs in Comparative Experiment 1, 2 is Example VI, 3 is Example VII, 4 is Example I, 5 is Example VIII; as shown in the figure, due to the gradual increase in the FRET conversion efficiency and the increase in the content of ZnSnO3 QDs, the fluorescence lifetime at 362 nm decreased from 24.9 ns to 13.1 ns. The fluorescence lifetime of ZnSnO3 QDs@UCNPs at 450 nm first increased from 30.84 ns to 31.17 ns and then decreased to 20.75 ns, and the fluorescence lifetime at 540 nm first increased from 47.76 μs to 55.18 μs and then decreased to 42.50 μs. This is because ZnSnO3 QDs itself is a fluorescent nanomaterial and the Stokes shift phenomenon occurred. The results show that the watermelon-like structure realizes the close contact between UCNPs and ZnSnO3. By calculating the lifetime at 362 nm in the comparative experiment and Example 1, the efficiency of FRET is 80.30%.

[0118] Figure 15 For the piezoelectric response amplitude curve and phase curve diagram of the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example I, 1 is the piezoelectric response amplitude curve, 2 is the phase curve diagram; the amplitude and phase images show a clear and distinct contraction, confirming an obvious piezoelectric response. By applying a ramp bias in the range of -10 V to +10 V, a characteristic amplitude voltage butterfly loop and a phase change close to 180° were found, indicating that ZnSnO3 QDs has traditional piezoelectric ability. By calculating the slope of the displacement-voltage curve, the d 33 value was determined to be 30.44 pm / V, indicating that ZnSnO3 QDs can generate a large piezoelectric potential through force-induced deformation. This piezoelectric potential can sufficiently change the energy band structure of the material, thereby determining the carrier migration behavior in the optoelectronic process.

[0119] The ZnSnO3 QDs nanoparticles prepared in Step 2(3) of Example 1 and the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 were electrochemically tested using an electrochemical workstation. A 0.5 M Na2SO4 solution was used as the electrolyte, Ag / AgCl as the reference electrode, and a platinum wire as the counter electrode. 10 mg of the ZnSnO3 QDs nanoparticles prepared in Step 2(3) of Example 1 or the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 were dispersed in 0.5 mL of H2O, 0.5 mL of ethanol, and 32 μL of 10 mM Nafion, and coated on nickel foam to form a working electrode. Under the intermittent action of US (1 MHz; 0.96 W / cm 2 ; 40% duty cycle), 980 nm laser (power of 0.4 W / cm 2 ), or the combined action of ultrasound and 980 nm laser, the response of the instantaneous current over time was measured. Figure 16 Fig. is the ultrasonic current test spectrogram. a is the current test comparison under the combined action of ultrasound and 980 nm laser. 1 is the ZnSnO3 QDs nanoparticles prepared in Step 2(3) of Example 1, and 2 is the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1; b is the current test comparison of the watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under different conditions. 3 is the 980 nm laser, 4 is ultrasound, and 5 is the combined action of ultrasound and 980 nm laser. Under the action of US, the electronic conductivity and transient voltage current were significantly enhanced. When the near-infrared light and US were irradiated simultaneously, the current intensity was further enhanced, demonstrating the existence of a synergistic enhancement effect. In addition, the transient current generated by ZnSnO3 QDs@UCNPs (0.42 mA / cm 2 ) was higher than that of ZnSnO3 QDs (0.16 mA / cm 2 ), which proved that the piezoelectric effect not only increased the internal electric field strength of the whole material but also prevented the random movement and rapid recombination of charge carriers.

[0120] 0.1 mL of a 33 μg / mL DPBF solution and 0.1 mL of a 100 μg / mL watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticle solution were mixed in 2.8 mL of a PBS solution with pH = 5.5. The absorbance at 420 nm was measured using a UV-visible spectrophotometer under ultrasound (1 MHz; 0.96 W / cm 2 ; 40% duty cycle) or / and 980 nm laser irradiation (0.4 W / cm 2 ). Figure 17Degradation efficiency of DPBF solution under different conditions. 1 is the change in degradation efficiency of watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under 980 nm light irradiation. 2 is the change in degradation efficiency of ZnSnO3 QDs nanoparticles prepared in Step 2③ of Example 1 under 980 nm light irradiation and ultrasonic treatment. 3 is the change in degradation efficiency of watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under ultrasonic treatment. 4 is the change in degradation efficiency of watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under 980 nm light irradiation and ultrasonic treatment. Under 980 nm light irradiation or ultrasonic treatment, the degradation efficiencies calculated from the ultraviolet-visible spectral intensity of the DPBF solution treated with ZnSnO3QDs@UCNPs at approximately 420 nm are 27.23% and 86.57% respectively. With the extension of time, the decreasing trend of the ultraviolet-visible spectral intensity of the DPBF solution at approximately 420 nm proves that the material generates a large amount of ROS( 1 O2 and O2 ·- ). For ZnSnO3 QDs nanoparticles, under dual stimuli, a limited amount of ROS is also generated, which may be due to the instability of ZnSnO3 QDs in aqueous solution. The watermelon-like structured ZnSnO3 QDs@UCNPs nanoparticles achieved a satisfactory catalytic effect under the combined action of 980 nm light irradiation and ultrasonic treatment, with a degradation rate of 88.55%.

[0121] Mix 0.1 mL of TMB solution with a concentration of 300 μg / mL and 0.1 mL of watermelon-like structured ZnSnO3QDs@UCNPs nanoparticle solution with a concentration of 100 μg / mL in 2.8 mL of PBS solution with pH = 5.5. Use an ultraviolet-visible spectrophotometer to measure the absorbance at 420 nm under ultrasonic (1 MHz; 0.96 W / cm 2 ; 40% duty cycle) or / and 980 nm laser irradiation (0.4 W / cm 2 ). Figure 18The absorbance of the TMB solution changes with time under different conditions. 1 is the absorbance change of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under 980 nm light irradiation. 2 is the absorbance change of the ZnSnO3 QDs nanoparticles prepared in Step 2 ③ of Example 1 under 980 nm light irradiation and ultrasonic treatment. 3 is the absorbance change of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under ultrasonic treatment. 4 is the absorbance rate change of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles prepared in Step 3 of Example 1 under 980 nm light irradiation and ultrasonic treatment. Using TMB as a probe, the ability of ZnSnO3 QDs@UCNPs to generate ·OH was studied. TMB can be oxidized by ·OH to form light blue. After NIR+US treatment, the UV-vis absorption intensity of the solution increased significantly, indicating the generation of a large amount of ·OH and achieving a satisfactory catalytic effect.

Claims

1. A preparation method of watermelon-shaped structural nanoparticles with a piezoelectric optoelectronic effect, characterized in that It is carried out according to the following steps: I. Preparation of metal oleate complex precursors: Mix a tetramethylammonium hydroxide methanol solution, methanol, and oleic acid to obtain a mixed solution. Under the condition of a temperature of 40°C to 60°C, dropwise add a metal salt methanol solution to the mixed solution and stir for 1 h to 2 h. After the reaction ends, cool to room temperature, and finally wash and dry to obtain tin oleate or zinc oleate; II. Preparation of ZnSnO3 QDs: ① Mix zinc oleate, oleic acid, and octadecene to obtain a zinc oleate solution; ② Mix tin oleate and oleylamine to obtain a tin oleate solution; ③ Under a nitrogen atmosphere and at a temperature of 70°C to 90°C, heat the zinc oleate solution for 15 min to 30 min, then increase the temperature to 100°C to 300°C at a heating rate of 10°C / min to 15°C / min, maintain nitrogen purging for 5 min to 10 min, and then under a nitrogen atmosphere and at a temperature of 100°C to 300°C, add the tin oleate solution at an addition rate of 2 mL / min to 20 mL / min and heat for 30 min to 60 min. After the reaction ends, cool to room temperature and purify to obtain ZnSnO3 QDs nanoparticles. Disperse the ZnSnO3 QDs nanoparticles in cyclohexane to obtain a ZnSnO3 QDs solution; III. Synthesis of ZnSnO3 QDs@UCNPs nanoparticles: ① Mix (CH3CO2)3Y, (CH3CO2)3Yb, (CH3CO2)3Tm, (CH3CO2)3Er, oleic acid, and octadecene to obtain a reaction system. Under vacuum and at a temperature of 100°C to 130°C, keep the reaction system warm for 0.5 h to 1 h, and then under a nitrogen atmosphere and at a temperature of 150°C to 160°C, keep it warm for 0.2 h to 0.5 h until the solid is completely dissolved. Finally, cool to room temperature to obtain the reaction system after the solid is dissolved; ② Under a nitrogen atmosphere and at room temperature, add a NaOH / NH4F methanol solution to the reaction system after the solid is dissolved at an addition rate of 2 mL / min to 20 mL / min, stir for 5 min to 10 min, add the ZnSnO3 QDs solution after stirring, successively carry out methanol removal and degassing treatments, and then under a nitrogen atmosphere and at a temperature of 250°C to 300°C, keep it warm for 0 min to 80 min. Finally, cool to room temperature, wash, and disperse in cyclohexane to obtain a watermelon-shaped structure ZnSnO3 QDs@UCNPs nanoparticle solution; IV. Synthesis of water-soluble ZnSnO3 QDs@UCNPs-PEI: ① Mix the watermelon-shaped structure ZnSnO3 QDs@UCNPs nanoparticle solution, NOBF4, and DMF, and oscillate for 5 min to 10 min to obtain a solution after ligand exchange. Centrifuge the solution after ligand exchange and disperse it in DMF to obtain a ZnSnO3 QDs@UCNPs-NOBF4 solution; ② Add PEI to the ZnSnO3 QDs@UCNPs-NOBF4 solution, stir at a temperature of 50 °C to 100 °C for 0.3 h to 0.5 h, add acetone for precipitation after cooling, and finally disperse in water to obtain watermelon-shaped ZnSnO3 QDs@UCNPs with piezoelectric optoelectronic effect.

2. The preparation method of a watermelon-shaped structural nanoparticle having a piezoelectric optoelectronic effect according to claim 1, characterized in that The metal salt methanol solution described in Step 1 is tin chloride methanol solution or zinc acetate methanol solution; the concentration of the metal salt methanol solution described in Step 1 is 4 mg / mL to 10 mg / mL; the mass percentage of tetramethylammonium hydroxide in the tetramethylammonium hydroxide methanol solution described in Step 1 is 25%; the volume ratio of the tetramethylammonium hydroxide methanol solution to methanol in Step 1 is 1:(25 to 50); the volume ratio of the tetramethylammonium hydroxide methanol solution to oleic acid in Step 1 is 1:(0.5 to 1); the volume ratio of the tetramethylammonium hydroxide methanol solution to the metal salt methanol solution in Step 1 is 1:(0.5 to 2.5).

3. The preparation method of a watermelon-shaped structural nanoparticle with a piezoelectric optoelectronic effect according to claim 1, characterized in that The mass-to-volume ratio of zinc oleate to oleic acid described in Step 2① is 1 g:(12.5 to 20) mL; the mass-to-volume ratio of zinc oleate to octadecene described in Step 2① is 1 g:(87.5 to 140) mL; the mass-to-volume ratio of tin oleate to oleylamine described in Step 2② is 1 g:(15 to 40) mL; the volume ratio of the zinc oleate solution to the tin oleate solution described in Step 2③ is 1:(0.25 to 2); the concentration of ZnSnO3 QDs nanoparticles in the ZnSnO3 QDs solution described in Step 2③ is 10 mg / mL to 50 mg / mL.

4. The preparation method of a watermelon-shaped structural nanoparticle with piezoelectric optoelectronic effect according to claim 1, characterized in that The total molar amount of (CH3CO2)3Y, (CH3CO2)3Yb, (CH3CO2)3Tm, and (CH3CO2)3Er described in Step 3① has a volume ratio to oleic acid of 1 mmol:(5 to 10) mL; the total molar amount of (CH3CO2)3Y, (CH3CO2)3Yb, (CH3CO2)3Tm, and (CH3CO2)3Er described in Step 3① has a volume ratio to octadecene of 1 mmol:(10 to 20) mL; the molar ratio of (CH3CO2)3Y to (CH3CO2)3Yb described in Step 3① is 1:(0.25 to 0.3); the molar ratio of (CH3CO2)3Y to (CH3CO2)3Tm described in Step 3① is 1:(0.06 to 0.07); the molar ratio of (CH3CO2)3Y to (CH3CO2)3Er is 1:(0.015 to 0.02).

5. The preparation method of a watermelon-shaped structure nanoparticle with a piezoelectric optoelectronic effect according to claim 1, characterized in that In the NaOH / NH4F methanol solution described in Step 3②, the concentration of NaOH is 5 mg / mL to 15 mg / mL, and the concentration of NH4F is 7.5 mg / mL to 22.5 mg / mL; the volume ratio of the reaction system after the solid is dissolved to the NaOH / NH4F methanol solution is 1:(0.25 - 2); the volume ratio of the reaction system after the solid is dissolved to the ZnSnO3 QDs solution is 1:(0.02 - 0.15); the concentration of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticles in the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticle solution described in Step 3② is 5 mg / mL to 20 mg / mL.

6. The preparation method of a watermelon-shaped structural nanoparticle having a piezoelectric optoelectronic effect according to claim 1, characterized in that In Step 3②, the methanol is removed successively under vacuum and at a temperature of 60 °C to 120 °C, and the methanol is removed by heating for 0.5 h to 1 h.

7. The preparation method of a watermelon-shaped structural nanoparticle having a piezoelectric optoelectronic effect according to claim 1, characterized in that In Step 4①, the volume ratio of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticle solution to the mass of NOBF4 is 1 mL:(20 - 50) mg; the volume ratio of the watermelon-like structure ZnSnO3 QDs@UCNPs nanoparticle solution to DMF is 1:(1 - 5).

8. The preparation method of a watermelon-shaped structural nanoparticle with piezoelectric optoelectronic effect according to claim 1, characterized in that In Step 4①, the centrifugation is specifically to add the ligand-exchanged solution to toluene and cyclohexane, and centrifuge for 5 min to 10 min under the condition of a rotation speed of 8000 rpm to 12000 rpm; the concentration of ZnSnO3 QDs@UCNPs-NOBF4 in the ZnSnO3 QDs@UCNPs-NOBF4 solution described in Step 4① is 5 mg / mL to 20 mg / mL.

9. The preparation method of a watermelon-shaped structural nanoparticle with a piezoelectric optoelectronic effect according to claim 1, characterized in that In Step 4②, the volume ratio of the ZnSnO3 QDs@UCNPs-NOBF4 solution to the mass of PEI is 1 mL:(0.1 - 0.5) g.

10. The preparation method of a watermelon-shaped structural nanoparticle with a piezoelectric optoelectronic effect according to claim 1, characterized in that The washing and drying described in Step 1 is specifically to wash with methanol 3 to 5 times and then dry under vacuum; the purification described in Step 2③ is carried out according to the following steps: centrifuge with acetone to obtain a precipitate, disperse the precipitate in chloroform, and then centrifuge again with ethanol; the cleaning described in Step 3② is to alternately wash with ethanol and cyclohexane 3 to 5 times.

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