Method for preparing high-stability cellulose acetate perovskite quantum dot material in one step

Abstract

The application relates to the technical field of semiconductor materials, and provides a method for preparing high-stability cellulose acetate perovskite quantum dot materials in one step, which adopts cellulose acetate (CA) as an inorganic matrix, generates and encapsulates CsPbBr3 PQDs in one step through improved ligand-assisted precipitation, and forms a CA-CsPbBr3 PQDs composite film with a chrysalis-shaped void network structure. The composite film not only prepares high-quality PQDs (uniform size 5.7 nm, narrow FWHM=20.6 nm and high quantum lifetime 16.9 ns), but also significantly enhances the environmental stability of the PQDs, and the optical performance of the PQDs does not obviously decrease after 60 days of water immersion and 100 days of UV resistance experiments, so that the PQDs have excellent extreme environmental adaptability.

Description

Technical Field

[0001] This invention relates to the field of quantum dot materials technology, and in particular to a one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials. Background Technology

[0002] Quantum dots are tiny semiconductor particles, ranging in size from a few nanometers. They exhibit unique electronic and optical properties that differ from bulk semiconductor materials, and their electronic wavefunctions resemble the discrete electronic states of real atoms. Therefore, they are often referred to as artificial atoms. Quantum dots have been applied in various modern technologies, including solar cells, photodetectors, field-effect transistors, biomedicine, and light-emitting diodes. Perovskite quantum dots (PQDs) are novel optoelectronic nanomaterials developed in recent years. Among them, oil-soluble inorganic perovskite CsPbX3 (X = Cl, Br, I) is inexpensive, color-tunable, has a narrow maximum half-width (FWHM < 40 nm), is cadmium-free, and has a high photoluminescence quantum yield (PLQY > 95%). Current methods for preparing perovskite quantum dots generally include porous template synthesis, hot-injection (HI) method, ligand-assisted precipitation (LARP) method, ultrasonic synthesis, microwave radiation synthesis, ball milling, and laser-assisted in-situ synthesis. These methods effectively prepare PQDs with uniform distribution, stronger luminescence intensity, and better stability. Currently, the mainstream methods for preparing PODs are mainly hot injection and ligand-assisted reprecipitation.

[0003] Perovskite quantum dots exhibit superior optical properties compared to traditional quantum dots and rare-earth fluorescent materials, and their preparation methods are simple and inexpensive. However, the poor stability of both metal-organic hybrid perovskite quantum dots and all-inorganic perovskite quantum dots remains a significant problem, limiting their application in complex environments. Due to their ionic compound nature, perovskites are prone to ion migration in natural environments, continuous irradiation, and polar solvents such as water. Ion exchange facilitates spectral tuning of perovskites but also leads to the inherent instability of mixed-halogen perovskites. Existing techniques employ ligands of different chain lengths, such as alkanes, conjugated structures, silanes, and inorganic ligands, to address issues related to crystal defects, stability, optical control, charge transport, and film growth. However, the addition of ligands often introduces complex synthetic steps and chemical environments, increasing the difficulty and cost of the synthesis process and potentially affecting the optical properties and subsequent processing applications of quantum dots. Against this backdrop, the synthesis of high-quality quantum dots using simplified methods has become an important research direction.

[0004] Numerous research achievements have been made in the application of cellulose and its derivatives in perovskite materials, mainly in their roles as substrate films, reinforcing materials, and auxiliary agents in crystal growth. In existing technologies, cellulose nanocrystal (CNC) colloidal materials can be effectively mixed with the CH3NH3PbBr3 precursor, spontaneously forming perovskite crystals during film formation. This film exhibits a light absorption efficiency of 91% and strong green light emission (518 nm).

[0005] Cellulose acetate (CA), a natural polymer with good biodegradability and film-forming properties, has been widely used in perovskite solar cells in recent years due to its moisture resistance, heat resistance, good optical transparency, and UV shielding potential. However, a technique for improving the stability of perovskite quantum dots by directly combining cellulose acetate with perovskite quantum dots in a one-step film-forming method has not yet been reported. Summary of the Invention

[0006] To address the problems of non-renewable raw materials and cumbersome synthesis conditions and high costs associated with existing technologies that enhance the stability of PQDs by treating surface defects through organic ligand design, polymer and molecular organic framework (MOF) encapsulation, this invention aims to provide a one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials. Using cellulose acetate (CA) as the inorganic matrix, a modified ligand-assisted precipitation method is employed to generate and encapsulate CsPbBr3 PQDs in one step, forming a CA-CsPbBr3 PQDs composite film with a pupa-like porous network structure. This composite film not only produces high-quality PQDs (uniform size 5.7 nm, narrow FWHM = 20.6 nm and a high quantum lifetime of 16.9 ns), but also significantly enhances their environmental stability. After 60 days of water immersion and 100 days of UV resistance testing, their optical performance showed no significant decline, demonstrating excellent adaptability to extreme environments.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] This invention provides a one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials, comprising the following steps:

[0009] (1) Synthesis of precursor solution: CsBr and PbBr2 were dissolved in DMF and magnetically stirred at room temperature until the solution was completely transparent. The solution was then sealed for later use.

[0010] (2) Preparation of CA solution: Dissolve cellulose acetate powder in DMF and seal for later use;

[0011] (3) Preparation of CA-CsPbBr3-PQDs composite membrane: The precursor solution in step (1) is added to the CA solution in step (2), magnetically stirred at room temperature, vacuum filtered and then vacuum dried to obtain CA-CsPbBr3-PQDs composite membrane.

[0012] A schematic diagram of the synthesis of the one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials according to the present invention is shown below. Figure 1 As shown.

[0013] Furthermore, the molar ratio of CsBr and PbBr2 in step (1) is 1:1.

[0014] Furthermore, the solid-liquid ratio of the precursor solution in step (1) is 14-15 g / L.

[0015] Furthermore, the magnetic stirring speed in step (1) is 600 rpm, and the magnetic stirring time is 3 hours.

[0016] Furthermore, the concentration of the CA solution in step (2) is 2 wt%.

[0017] Further, the volume ratio of the precursor solution and the CA solution in step (3) is (1-5):10.

[0018] Furthermore, the volume ratio of the precursor solution and the CA solution in step (3) is 2.5:10.

[0019] Furthermore, the magnetic stirring speed in step (3) is 600 rpm, and the magnetic stirring time is 3 hours.

[0020] Furthermore, the vacuum filtration time in step (3) is 24 hours.

[0021] Furthermore, the vacuum degree of the vacuum drying in step (3) is 0.1 atmospheres.

[0022] Furthermore, the vacuum drying temperature in step (3) is 45°C, and the vacuum drying time is 24 hours.

[0023] Furthermore, the size of the cellulose acetate perovskite quantum dots is 5-6.5 nm.

[0024] Furthermore, the size of the cellulose acetate perovskite quantum dots is 5.7 nm.

[0025] The beneficial effects of this application are as follows:

[0026] (1) This invention prepares a CA-CsPbBr3-PQDs membrane with excellent luminescence performance in one step. The ligand-assisted precipitation method is simplified by mixing the additive-free precursor solution into the CA solution, and the PQDs are generated in one step and encapsulated inside the CA to prepare a CA-CsPbBr3-PQDs composite membrane with excellent luminescence performance.

[0027] (2) The CA-CsPbBr3-PQDs film exhibits excellent optical properties and stability. The composite film also possesses a long quantum lifetime (τ). ave =16.895ns) and a narrower FWHM (20.6nm) and a more uniform quantum dot size (5.7nm), exhibiting good crystal structure retention at low temperatures (E b =80.74 meV, FWHM peak position unchanged).

[0028] (3) It exhibited excellent stability in humid and ultraviolet environment stability tests. The PL strength was not lost after immersion in water for 60 days, and the PL performance was still 86.2% of the original after 100 days of 16W ultraviolet light irradiation, which greatly reduced the susceptibility of PODs to extreme environments such as water and ultraviolet light. Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating the one-step synthesis method for preparing highly stable cellulose acetate perovskite quantum dot materials according to the present invention.

[0030] Figure 2 The image shows the X-ray diffraction spectrum of the CA-CsPbBr3-PQDs composite film prepared in Example 1. The inset on the left is a photograph taken under 365nm ultraviolet light excitation, and the image on the right is a high-resolution TEM photograph.

[0031] Figure 3 The optical performance analysis diagrams of the CA-CsPbBr3-PQDs composite film prepared in Example 1 are shown in (ac), which shows the TEM image of CA-CsPbBr3-PQDs, and the inset is a statistical diagram of the distribution of quantum dot size under the 20nm TEM image; (de) shows the CA-CsPbBr3-PQDs quantum dot film under environmental conditions and POM photographs; and (fg) shows photographs taken under 360nm ultraviolet light and POM in UV mode.

[0032] Figure 4The temperature dependence test graphs of the CA-CsPbBr3-PQDs composite film prepared in Example 1 are shown. (a) is the PL spectrum of CA-CsPbBr3-PQDs as a function of temperature in the range of 80-300K; (b) is the calculation of exciton binding energy: 1 / PL and 1 / T of CA-CsPbBr3-PQDs. The solid line is best suited to a model assuming the existence of free excitons and self-captured excitons; (c) is the temperature dependence of the emission peak energy; and (d) is the FWHM of the steady-state PL spectrum as a function of temperature.

[0033] Figure 5 The images show cross-sectional SEM images of the CA-CsPbBr3-PQDs composite film prepared in Example 5 and the CA film prepared in Comparative Example 2. (ac) shows a cross-sectional SEM image of the pure CA film prepared in Comparative Example 2; (df) shows a cross-sectional SEM image of the CA-CsPbBr3-PQDs composite film prepared in Example 5.

[0034] Figure 6 The PL spectra of the CA-CsPbBr3-PQDs composite films prepared in Examples 1-10 are shown, where (a) the photoluminescence spectra of CA-CsPbBr3-PQDs with different doping volumes are shown in the form of three-dimensional spectra; (b) the PL peak intensity of CA-CsPbBr3-PQDs and (c) the dependence of the emission peak position on the doping volume.

[0035] Figure 7 The images show the PL spectra of the CA-CsPbBr3-PQDs composite film prepared in Example 1 and the CsPbBr3PQDs prepared in Comparative Example 1 under 360 nm ultraviolet light excitation.

[0036] Figure 8 The image shows the PL spectrum obtained by immersing the CA-CsPbBr3-PQDs composite membrane prepared in Example 1 in pure water. The inset shows its contact angle test, natural light and 360nm ultraviolet photograph.

[0037] Figure 9To compare the UV tolerance of the CA-CsPbBr3-PQDs composite film prepared in Example 1 and the CsPbBr3 PQDs prepared in Comparative Example 1, the following graphs are provided: (a) PL spectrum of the CsPbBr3 PQDs prepared in Comparative Example 1 under continuous 16W UV; (b) PL intensity and emission peak position of the CsPbBr3 PQDs prepared in Comparative Example 1 over time; (c) PL spectrum of the CA-CsPbBr3-PQDs composite film prepared in Example 1 under continuous 16W UV; and (d) PL intensity and emission peak position of the CA-CsPbBr3-PQDs composite film prepared in Example 1 over time. Detailed Implementation

[0038] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] In the following examples and comparative examples, the cellulose acetate powder was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., and contained 9.8 wt% acetyl groups and 3.5 wt% hydroxyl groups.

[0040] Example 1

[0041] A one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials includes the following steps:

[0042] (1) Synthesis of precursor solution: Dissolve 0.5 mmol CsBr and 0.5 mmol PbBr2 in 20 mL DMF respectively, set the magnetic stirrer to 600 rpm, stir at room temperature for 3 hours until the solution is completely transparent, seal and store in sample vials for later use.

[0043] (2) Preparation of CA solution: Under normal temperature conditions, cellulose acetate powder is dissolved in DMF to prepare a CA solution with a concentration of 2wt%. The prepared CA solution is sealed with sealant for later use.

[0044] (3) Preparation of CA-CsPbBr3-PQDs composite membrane: 2.5 mL of the precursor solution in step (1) was added to 10 mL of the CA solution in step (2), and the mixture was magnetically stirred at 600 rpm for 3 hours at room temperature. After vacuum filtration for 24 hours, the mixture was dried at 45°C in a vacuum drying oven at 0.1 atm for 24 hours to obtain the CA-CsPbBr3-PQDs composite membrane.

[0045] The X-ray diffraction spectrum of the CA-CsPbBr3-PQDs composite film prepared in this embodiment is shown below. Figure 2 As shown, the left inset is a photograph taken under 365nm ultraviolet light excitation, while the right side is a high-resolution TEM image. The quantum dot liquid in the cuvette emits bright green light, and this strong luminescence performance proves the successful preparation of PQDs. The characteristic peaks 15.21°, 21.50°, 30.70°, 34.20°, 37.60°, and 43.69° in the XRD pattern correspond to the cubic crystal planes (100), (110), (200), (210), (211), and (202) of the perovskite structure, respectively, which correspond to the PDF card of cesium lead bromide perovskite. The TEM image on the right further confirms the formation of CsPbBr3 PQDs.

[0046] The optical performance analysis diagram of the CA-CsPbBr3-PQDs composite film prepared in this embodiment is shown in the figure below. Figure 3 As shown, (ac) presents a TEM image of CA-CsPbBr3-PQDs, with the inset showing a statistical distribution of quantum dot size under a 20nm TEM image; (de) shows the prepared CA-CsPbBr3-PQDs quantum dot film under environmental conditions and POM photographs; (fg) shows photographs taken under 360nm ultraviolet light and POM in UV mode. (a) shows that PQDs are uniformly dispersed on the surface of CA, and the average size of the generated quantum dots is statistically determined to be 5.7nm, mainly concentrated in the range of 5nm and 6.5nm. The synthesized PQDs have a narrow size distribution and uniform size. Figure (c) shows the structure of a single PQD and a lattice spacing of 0.205nm, corresponding to the (200) plane, which is consistent with the previously reported lattice parameters of CsPbBr3 PQDs. (de) shows that the CA-CsPbBr3-PQDs film appears pale yellow under natural light. POM observation reveals that the surface of CA is not smooth. During solvent evaporation and water molecule precipitation, the CA molecular chains easily contract and attract each other, providing a strong coating and spatial confinement effect for PQDs formation. (f) shows that the film exhibits bright pure green fluorescence under 360 nm UV excitation. POM observation of the CA-G-PQDs film under UV excitation, as shown in (g), reveals the uniformity of PQD luminescence on the film surface at the microscale. This indicates that there are no local quenching or strong absorption regions, suggesting that the quantum dots are relatively uniformly dispersed within the film.

[0047] The temperature dependence test graph of the CA-CsPbBr3-PQDs composite membrane prepared in this embodiment is shown in the figure below. Figure 4As shown, (a) is the pulse intensity (PL) spectrum of CA-CsPbBr3-PQDs as a function of temperature in the range of 80–300 K; (b) is the calculation of the exciton binding energy: a function of 1 / PL and 1 / T for CA-CsPbBr3-PQDs, with the solid line best suited to a model assuming the existence of free excitons and self-captured excitons; (c) is the temperature dependence of the emission peak energy; and (d) is the FWHM of the steady-state PL spectrum as a function of temperature. In (a), the PL intensity of CA-CsPbBr3-PQDs gradually increases from 80 K to 140 K, and then continuously decreases after 140 K. The exciton binding energy E of CA-CsPbBr3-PQDs was calculated. b = 80.74 meV; As shown in (c), under the coordination and space-confined chelation, the CA-assisted PQDs have a stable lattice structure. The energy change caused by electron-phonon interactions is small with temperature variations, meaning that the PQDs can maintain relatively stable photoelectric properties at different temperatures. As shown in (d), when the temperature increases from 80 K to 140 K, the FWHM of CA-CsPbBr3-PQDs decreases from 55.35 meV to 44.46 meV. This is because the increase in exciton binding energy at low temperatures means that electrons and holes are more tightly bound together, reducing interactions with the lattice and thus reducing phonon-induced scattering events.

[0048] Example 2

[0049] A one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials includes the following steps:

[0050] (1) Synthesis of precursor solution: Dissolve 0.5 mmol CsBr and 0.5 mmol PbBr2 in 20 mL DMF respectively, set the magnetic stirrer to 600 rpm, stir at room temperature for 3 hours until the solution is completely transparent, seal and store in sample vials for later use.

[0051] (2) Preparation of CA solution: Under normal temperature conditions, cellulose acetate powder is dissolved in DMF to prepare a CA solution with a concentration of 2wt%. The prepared CA solution is sealed with sealant for later use.

[0052] (3) Preparation of CA-CsPbBr3-PQDs composite membrane: Take 0.5 mL of the precursor solution in step (1) and add it to 10 mL of the CA solution in step (2). Stir magnetically at 600 rpm for 3 hours at room temperature, filter under vacuum for 24 hours, and dry at 45°C in a vacuum drying oven at 0.1 atm for 24 hours to obtain CA-CsPbBr3-PQDs composite membrane.

[0053] Example 3

[0054] A one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials includes the following steps:

[0055] (1) Synthesis of precursor solution: Dissolve 0.5 mmol CsBr and 0.5 mmol PbBr2 in 20 mL DMF respectively, set the magnetic stirrer to 600 rpm, stir at room temperature for 3 hours until the solution is completely transparent, seal and store in sample vials for later use.

[0056] (2) Preparation of CA solution: Under normal temperature conditions, cellulose acetate powder is dissolved in DMF to prepare a CA solution with a concentration of 2wt%. The prepared CA solution is sealed with sealant for later use.

[0057] (3) Preparation of CA-CsPbBr3-PQDs composite membrane: Take 1 mL of the precursor solution in step (1) and add it to 10 mL of CA solution in step (2). Stir magnetically at 600 rpm for 3 hours at room temperature, filter under vacuum for 24 hours, and dry at 45°C in a vacuum drying oven at 0.1 atm for 24 hours to obtain CA-CsPbBr3-PQDs composite membrane.

[0058] Example 4

[0059] A one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials includes the following steps:

[0060] (1) Synthesis of precursor solution: Dissolve 0.5 mmol CsBr and 0.5 mmol PbBr2 in 20 mL DMF respectively, set the magnetic stirrer to 600 rpm, stir at room temperature for 3 hours until the solution is completely transparent, seal and store in sample vials for later use.

[0061] (2) Preparation of CA solution: Under normal temperature conditions, cellulose acetate powder is dissolved in DMF to prepare a CA solution with a concentration of 2wt%. The prepared CA solution is sealed with sealant for later use.

[0062] (3) Preparation of CA-CsPbBr3-PQDs composite membrane: 1.5 mL of the precursor solution in step (1) was added to 10 mL of the CA solution in step (2), and the mixture was magnetically stirred at 600 rpm for 3 hours at room temperature. After vacuum filtration for 24 hours, the mixture was dried at 45°C in a vacuum drying oven at 0.1 atm for 24 hours to obtain the CA-CsPbBr3-PQDs composite membrane.

[0063] Example 5

[0064] A one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials includes the following steps:

[0065] (1) Synthesis of precursor solution: Dissolve 0.5 mmol CsBr and 0.5 mmol PbBr2 in 20 mL DMF respectively, set the magnetic stirrer to 600 rpm, stir at room temperature for 3 hours until the solution is completely transparent, seal and store in sample vials for later use.

[0066] (2) Preparation of CA solution: Under normal temperature conditions, cellulose acetate powder is dissolved in DMF to prepare a CA solution with a concentration of 2wt%. The prepared CA solution is sealed with sealant for later use.

[0067] (3) Preparation of CA-CsPbBr3-PQDs composite membrane: Take 2 mL of the precursor solution in step (1) and add it to 10 mL of CA solution in step (2). Stir magnetically at 600 rpm for 3 hours at room temperature, filter under vacuum for 24 hours, and dry at 45°C in a vacuum drying oven at 0.1 atm for 24 hours to obtain CA-CsPbBr3-PQDs composite membrane.

[0068] Example 6

[0069] A one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials includes the following steps:

[0070] (1) Synthesis of precursor solution: Dissolve 0.5 mmol CsBr and 0.5 mmol PbBr2 in 20 mL DMF respectively, set the magnetic stirrer to 600 rpm, stir at room temperature for 3 hours until the solution is completely transparent, seal and store in sample vials for later use.

[0071] (2) Preparation of CA solution: Under normal temperature conditions, cellulose acetate powder is dissolved in DMF to prepare a CA solution with a concentration of 2wt%. The prepared CA solution is sealed with sealant for later use.

[0072] (3) Preparation of CA-CsPbBr3-PQDs composite membrane: Take 3 mL of the precursor solution in step (1) and add it to 10 mL of CA solution in step (2). Stir magnetically at 600 rpm for 3 hours at room temperature, filter under vacuum for 24 hours, and dry at 45°C in a vacuum drying oven at 0.1 atm for 24 hours to obtain CA-CsPbBr3-PQDs composite membrane.

[0073] Example 7

[0074] A one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials includes the following steps:

[0075] (1) Synthesis of precursor solution: Dissolve 0.5 mmol CsBr and 0.5 mmol PbBr2 in 20 mL DMF respectively, set the magnetic stirrer to 600 rpm, stir at room temperature for 3 hours until the solution is completely transparent, seal and store in sample vials for later use.

[0076] (2) Preparation of CA solution: Under normal temperature conditions, cellulose acetate powder is dissolved in DMF to prepare a CA solution with a concentration of 2wt%. The prepared CA solution is sealed with sealant for later use.

[0077] (3) Preparation of CA-CsPbBr3-PQDs composite membrane: Take 3.5 mL of the precursor solution in step (1) and add it to 10 mL of CA solution in step (2). Stir magnetically at 600 rpm for 3 hours at room temperature, filter under vacuum for 24 hours, and dry at 45°C in a vacuum drying oven at 0.1 atm for 24 hours to obtain CA-CsPbBr3-PQDs composite membrane.

[0078] Example 8

[0079] A one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials includes the following steps:

[0080] (1) Synthesis of precursor solution: Dissolve 0.5 mmol CsBr and 0.5 mmol PbBr2 in 20 mL DMF respectively, set the magnetic stirrer to 600 rpm, stir at room temperature for 3 hours until the solution is completely transparent, seal and store in sample vials for later use.

[0081] (2) Preparation of CA solution: Under normal temperature conditions, cellulose acetate powder is dissolved in DMF to prepare a CA solution with a concentration of 2wt%. The prepared CA solution is sealed with sealant for later use.

[0082] (3) Preparation of CA-CsPbBr3-PQDs composite membrane: Take 4 mL of the precursor solution in step (1) and add it to 10 mL of the CA solution in step (2). Stir magnetically at 600 rpm for 3 hours at room temperature, filter under vacuum for 24 hours, and dry at 45°C in a vacuum drying oven at 0.1 atm for 24 hours to obtain CA-CsPbBr3-PQDs composite membrane.

[0083] Example 9

[0084] A one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials includes the following steps:

[0085] (1) Synthesis of precursor solution: Dissolve 0.5 mmol CsBr and 0.5 mmol PbBr2 in 20 mL DMF respectively, set the magnetic stirrer to 600 rpm, stir at room temperature for 3 hours until the solution is completely transparent, seal and store in sample vials for later use.

[0086] (2) Preparation of CA solution: Under normal temperature conditions, cellulose acetate powder is dissolved in DMF to prepare a CA solution with a concentration of 2wt%. The prepared CA solution is sealed with sealant for later use.

[0087] (3) Preparation of CA-CsPbBr3-PQDs composite membrane: 4.5 mL of the precursor solution in step (1) was added to 10 mL of the CA solution in step (2), and the mixture was magnetically stirred at 600 rpm for 3 hours at room temperature. After vacuum filtration for 24 hours, the mixture was dried at 45°C in a vacuum drying oven at 0.1 atm for 24 hours to obtain the CA-CsPbBr3-PQDs composite membrane.

[0088] Example 10

[0089] A one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials includes the following steps:

[0090] (1) Synthesis of precursor solution: Dissolve 0.5 mmol CsBr and 0.5 mmol PbBr2 in 20 mL DMF respectively, set the magnetic stirrer to 600 rpm, stir at room temperature for 3 hours until the solution is completely transparent, seal and store in sample vials for later use.

[0091] (2) Preparation of CA solution: Under normal temperature conditions, cellulose acetate powder is dissolved in DMF to prepare a CA solution with a concentration of 2wt%. The prepared CA solution is sealed with sealant for later use.

[0092] (3) Preparation of CA-CsPbBr3-PQDs composite membrane: 4.5 mL of the precursor solution in step (1) was added to 10 mL of the CA solution in step (2), and the mixture was magnetically stirred at 600 rpm for 3 hours at room temperature. After vacuum filtration for 24 hours, the mixture was dried at 45°C in a vacuum drying oven at 0.1 atm for 24 hours to obtain the CA-CsPbBr3-PQDs composite membrane.

[0093] Comparative Example 1

[0094] A method for preparing CsPbBr3 PQDs by ligand-assisted precipitation includes the following steps:

[0095] 1) Synthesis of precursor solution: Dissolve 0.5 mmol CsBr and 0.5 mmol PbBr2 in 20 mL DMF, respectively. Set the magnetic stirrer to 600 rpm and stir at room temperature for 3 hours until the solution is completely transparent. Seal and store it in a sample vial for later use.

[0096] (2) Preparation of PQDs colloidal solution using ligand-assisted precipitation (LARP): Take 5 mL of precursor solution in a beaker, add 200 μL of oleic acid (OA) and 70 μL of oleylamine (OLA), and stir for 3 minutes under magnetic stirring to ensure that the ligands are fully dissolved. Then, quickly add the above 200 μL solution dropwise to 10 mL of toluene and continue stirring for 5 minutes to promote the reaction. After the reaction is completed, separate the coarse particles by high-speed centrifugation (7000 rpm, 5 minutes), collect the supernatant and store it at room temperature for subsequent use.

[0097] (3) Preparation of CsPbBr3 PQDs: After vacuum filtering the supernatant in step (2) for 24 hours, it was dried in a vacuum drying oven at 0.1 atmospheres at 45°C for 24 hours to obtain CsPbBr3 PQDs.

[0098] Comparative Example 2

[0099] A method for preparing a CA membrane includes the following steps:

[0100] At room temperature, cellulose acetate powder was dissolved in DMF to prepare a CA solution with a concentration of 2wt%. After vacuum filtration for 24 hours, the solution was dried in a vacuum drying oven at 0.1 atm at 45°C for 24 hours to obtain a CA membrane.

[0101] Cross-sectional SEM images of the CA-CsPbBr3-PQDs composite membrane prepared in Example 5 and the CA membrane prepared in Comparative Example 2 are shown below. Figure 5As shown, (ac) is a scanning electron microscope (SEM) image of the cross-section of the pure CA film prepared in Comparative Example 2; (df) is a scanning electron microscope (SEM) image of the cross-section of the CA-CsPbBr3-PQDs composite film prepared in Example 5; (b) shows a very obvious hierarchical structure in the cross-section. This hierarchical structure is related not only to uneven solvent evaporation and the interaction between CA molecules, but also to the interaction between the solvent and water. Especially during the filtration process, the upper membrane is exposed to the environment and inevitably comes into contact with moisture in the air, resulting in phase separation. A distinct porous structure appears in the upper layer. Further magnification reveals details (c) showing large, "pupa-like" particles with a network structure of small particles at the openings. This phenomenon is caused by water entering the surface of the membrane, especially the upper layer, and interacting with molecules in the CA solution, promoting the formation of a gel-like structure in the upper layer and accelerating phase separation. The formation of the gel makes the upper layer structure more loose and porous, consistent with the porosity characteristics caused by the rapid solvent evaporation rate. The lower layer (a) forms a denser film due to less contact with water, slower solvent evaporation, molecular stacking, and thermal conduction. This layered structure reflects the film's self-assembly process, differences in solvent evaporation rates, and the deposition and solidification characteristics of the material.

[0102] The presence of PQDs grown within the film exhibits significant differences compared to pure CA: (d) shows a rougher and more irregular surface. This is because the addition of perovskite quantum dots triggers new self-assembly behavior on the film surface, resulting in a looser network structure. The small size of the perovskite quantum dots themselves allows for easy dispersion in the matrix material, and the network structure provides a growth environment for the PQDs, contributing to their uniform formation. In (f), the quantum dots are encapsulated in "pupa-like" particles. The PQDs can be distributed relatively uniformly within the CA film. The CA matrix, through its spatial structure, provides support and an attachment environment for the quantum dot growth, preventing excessive aggregation or crystallization, thus maintaining the optical activity of the quantum dots. This stability explains the retention of photoluminescence intensity; even without ligands, the chemical and physical environment of the matrix itself may play a partial stabilizing role, enabling the quantum dots to maintain their optical properties.

[0103] The PL spectra of the CA-CsPbBr3-PQDs composite films prepared in Examples 1-10 are as follows: Figure 6As shown, (a) the photoluminescence spectra of CA-CsPbBr3-PQDs with different doping volumes are presented in three-dimensional form; (b) the intensity of the PL peak of CA-CsPbBr3-PQDs and (c) the dependence of the emission peak position on the doping volume are shown. It can be seen that the emission peaks of the prepared CA-CsPbBr3-PQDs composite films with different doping volumes are mainly located between 510 and 525 nm, exhibiting green fluorescence emission characteristics. Meanwhile, the intensity and position of the PL peak change with the increase of the precursor volume.

[0104] The average carrier lifetime of the CA-CsPbBr3-PQDs composite membranes in Examples 1-10 was fitted using the TRPL decay exponential function, and the results are shown in Table 1 below.

[0105] Table 1

[0106]

[0107] As shown in Table 1, the average quantum dot lifetime of the CA-CsPbBr3-PQDs composite film of this invention can reach up to 16.895 ns. This is higher than that of CsPbBr3 QDs synthesized by the oleic acid / oleylamine ligand-assisted precipitation method in the prior art. ave =7~8ns) twice.

[0108] The PL spectra of the CA-CsPbBr3-PQDs composite film prepared in Example 1 and the CsPbBr3 PQDs prepared in Comparative Example 1 under 360 nm UV excitation are shown below. Figure 7 As shown, under the same excitation test conditions, CA-CsPbBr3-PQDs can still maintain a green light emission intensity that is not much different from that of CsPbBr3 PQDs. At the same time, CA-CsPbBr3-PQDs has a narrow FWHM of 20.6nm (close to 19.6nm of CsPbBr3 PQDs), which means better monochromaticity and higher color purity.

[0109] Stability test

[0110] The CA-CsPbBr3-PQDs composite membrane prepared in Example 1 was immersed in pure water, and the resulting PL spectrum is shown below. Figure 8As shown in the illustration, the contact angle test, under natural light and 360nm UV images, reveals that the emission wavelength of the quantum dots did not change significantly over time (black data in the figure), remaining at approximately 527nm. Such a change typically indicates that the optical band gap of the quantum dots has not changed significantly. This is because CA has good water resistance and non-swelling properties. The hydroxyl groups (-OH) in the cellulose of the CA molecule are replaced by acetate groups (-OCOCH3), resulting in overall hydrophobicity (contact angle of 94.3°). This characteristic allows the CA-CsPbBr3-PQDs composite film to maintain a good basic morphology without swelling in water (shown in the lower right illustration). Simultaneously, the pupae-like protective layer and dense pores formed by CA prevent direct contact between water and water-soluble impurities and the quantum dots. Water molecules on the CA surface, through hydrogen bonds, make the film more flat, which also explains the PL intensity (yellow-green data in the figure), although fluctuating over time, even showing an overall increasing trend. This implies that CA-G-PQDs have strong water stability.

[0111] The CA-CsPbBr3-PQDs composite film prepared in Example 1 and the CsPbBr3PQDs prepared in Comparative Example 1 were subjected to continuous UV (RH=60%, RT, 16WUV) tolerance tests under ambient humidity of 60% and room temperature. The results are shown in the figure. Figure 9As shown, (a) the PL spectrum of CsPbBr3 PQDs prepared in Comparative Example 1 under continuous 16W UV, (b) the changes in PL intensity and emission peak position of CsPbBr3 PQDs prepared in Comparative Example 1 over time, (c) the PL spectrum of the CA-CsPbBr3-PQDs composite film prepared in Example 1 under continuous 16W UV, and (d) the changes in PL intensity and emission peak position of the CA-CsPbBr3-PQDs composite film prepared in Example 1 over time. It can be seen that the PL intensity of the CA-CsPbBr3-PQDs composite film decreased by only 13.8% after 100 days of UV irradiation, exhibiting stronger UV stability than CsPbBr3 PQDs. The emission spectrum of CsPbBr3 PQDs showed that as time increased (from 1 to 8 days), the intensity of the emission peak gradually decreased, reaching zero on the eighth day, and the peak position also exhibited a redshift. The CA-CsPbBr3-PQDs composite film showed a slight increase in luminescence intensity during the first 20 days, followed by a stable decrease. The increase is likely due to the rapid generation of electrons and holes in the quantum dots during the initial stages of UV irradiation, leading to a redistribution of photogenerated carriers on or within the quantum dots, resulting in a small-scale increase in luminescence intensity (PL). This process is typically related to the accumulation of photogenerated carriers in localized areas. Simultaneously, the passivation effect on the PQDs surface may gradually intensify. With continued radiation irradiation, the molecular chains in cellulose acetate may interact more effectively with photogenerated carriers, reducing defect state generation and temporarily increasing exciton recombination efficiency, thus boosting PL intensity. The decrease is likely due to the increasing UV irradiation time. UV light may induce more surface defects or lattice disruption, leading to a decline in the material's optical properties. Some exciton recombination pathways may transform into non-radiative recombination pathways. These defect states consume photogenerated carriers, resulting in decreased luminescence efficiency and ultimately a weakening of PL intensity. In addition, CA also has ultraviolet absorption capabilities, which can greatly alleviate the weakening process of PL intensity and improve the stability of PQDs under UV.

[0112] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A one-step method for preparing highly stable cellulose acetate perovskite quantum dot materials, characterized in that, Includes the following steps: (1) Synthesis of precursor solution: CsBr and PbBr2 were dissolved in DMF and magnetically stirred at room temperature until the solution was completely transparent and sealed for later use; the solid-liquid ratio of the precursor solution was 14-15 g / L. (2) Preparation of CA solution: Dissolve cellulose acetate powder in DMF and seal for later use; the cellulose acetate contains 9.8 wt% acetyl groups and 3.5 wt% hydroxyl groups; the concentration of the CA solution is 2 wt%. (3) Preparation of CA-CsPbBr3-PQDs composite membrane: The precursor solution in step (1) is added to the CA solution in step (2), and the volume ratio of the precursor solution to the CA solution is (1-5):

10. The membrane is magnetically stirred at room temperature, vacuum filtered for 24 h, and then vacuum dried for 24 h at a vacuum pressure of 0.1 atm and a temperature of 45°C to obtain the CA-CsPbBr3-PQDs composite membrane.

2. The method for preparing highly stable cellulose acetate perovskite quantum dot materials in one step according to claim 1, characterized in that, The molar ratio of CsBr and PbBr2 in step (1) is 1:

1.

3. The method for preparing highly stable cellulose acetate perovskite quantum dot materials in one step according to claim 1, characterized in that, The magnetic stirring speed in step (1) is 600 rpm, and the magnetic stirring time is 3 hours.

4. The method for preparing highly stable cellulose acetate perovskite quantum dot materials in one step according to claim 1, characterized in that, The magnetic stirring speed in step (3) is 600 rpm, and the magnetic stirring time is 3 hours.

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