Preparation method of ultrahigh-stability patterned array based on laser-induced dehalogenation LH PQDs

Abstract

The invention discloses a preparation method of an ultrahigh-stability patterned array based on laser-induced dehalogenation (LH) PQDs. The preparation method comprises the following steps: dissolving a polymer matrix, a halogen source, a cesium source and a lead source in an organic solvent, spin-coating a glass substrate with the obtained solution, and heating and drying to obtain a precursor compound film; and carrying out laser direct writing on the film by adopting an ultraviolet nanosecond laser with the central wavelength of 355 nm, and carrying out patterning manufacturing. According to the preparation method, a halogenated organic matter R-X is taken as a precursor, 355 nm nanosecond with high photon energy is taken as a laser source, R-X dehalogenation is induced, X <-> is released, so that nucleation growth of the LH PQDs is further induced, and efficient preparation of the LH PQDs multicolor light-emitting patterned microarray in a common polymer matrix can be realized. The prepared LH PQDs patterned microarray shows quite excellent light, heat and water stability, and can be applied to the field of fluorescent falsification prevention.

Description

Technical Field

[0001] The present invention relates to the field of anti-counterfeiting technology, and in particular to a method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation. Background Art

[0002] Lead halide perovskite quantum dots (LH PQDs) have rapidly sparked a wave of research interest due to their low generation energy, high fluorescence quantum yield, narrow emission half-width (FWHM), tunable emission peak position, and excellent defect tolerance. Leveraging these advantages and precisely arranging LH PQDs at the micro- and nanoscale to achieve patterned arrays and the coordinated optimization of function and structure has important theoretical and practical implications for fields such as micro-LEDs, optoelectronic sensing, medical testing, information storage, and anti-counterfeiting.

[0003] Currently, the main methods for preparing LH PQDs patterned arrays are direct photolithography, inkjet printing, [] , nanoimprinting and laser direct writing, etc. Among them, direct laser writing (DLW) technology does not require a mask and has a simple operation process. It only needs to mix the LH PQDs precursor salt AX and PbX2 (A=Cs + 、MA + , FA + , X=Cl - Br - , I -) is mixed with a glass or polymer matrix to form a pre-film, which is then irradiated by laser. The irradiated area generates ultra-strong heat accumulation and ultra-high pressure, which induces the nucleation and growth of LH PQDs. This allows for large-scale production of high-resolution LH PQD patterned arrays with high manufacturing efficiency, making this method extremely promising. For example, Dong et al. used an 800nm ​​femtosecond (fs) laser to directly write three-dimensional patterns of LH PQDs into oxide glass containing perovskite precursor ions, and also controlled direct writing and erasing by laser. Thanks to the formation of the LH PQD patterned array inside the glass, the resulting array showed good stability and could be used in storage, three-dimensional commercial art, and information security, showing good application prospects. Qiu's research group used fs laser to treat the perovskite precursor glass in borophosphate glass containing perovskite precursor ions, successfully obtaining a three-dimensional pattern of perovskite nanocrystals (PNCs) with tunable fluorescence emission between 480-700nm, which was applied to micro-LEDs. These forward-looking works have aroused widespread interest and research enthusiasm among scientific researchers, and the preparation of LH PQDs strong luminescent patterned arrays based on glass substrate DLW has developed rapidly. Compared with glass substrates, polymer substrates have stronger processability, so people think about whether it is possible to extend the method of preparing PQDs arrays with DLW technology to polymer matrices. Based on this, Zhong's research group successfully obtained a pattern with a minimum line width of 900nm by using a nanosecond laser to directly laser write patterned γ-CsPbI3PQDs on PMMA films. Subsequently, in order to avoid the excessive thermal effects that may be caused by nanosecond lasers, Xu's research group used a 405nm continuous wave (CW) laser to in situ prepare multi-color luminescent LH PQDs (from green to red) in PVDF films. However, compared with the glass substrate DLW preparation technology, the preparation of polymer substrates still faces huge challenges. The reason is that the LH PQDs generation energy is low, which causes the precursor ion salts of LH PQDs (AX and PbX2) to crystallize into LH PQDs when the solvent is removed by heating during the preparation of the film, resulting in the failure of the laser direct writing patterned array preparation process. To address this problem, Zhang et al. cleverly used polyacrylonitrile (PAN) as the polymer matrix. Compared with other polymer matrix materials (PMMA or PVDF), the cyano group (C≡N) in PAN has stronger coordination ability and can react with PbX2 to form LH PQDs. 2+The coordination enhances the ion migration barrier and, through freeze-drying film formation, suppresses the spontaneous crystallization of LH PQDs within the film during the solvent removal process of the PQDs precursor ion salt. Using fs laser direct writing technology, they successfully achieved the efficient preparation of highly luminescent patterned arrays of blue, green, and red primary color LH PQDs. Similarly, Zeng's group recently used a non-heating film formation method to avoid the spontaneous nucleation and growth of LH PQDs caused by precursor precipitation in the film.

[0004] While the aforementioned strategy addresses the nucleation and growth issues of the precursor within the prefabricated film, after laser direct writing, the precursors will still nucleate and grow into LH PQDs within the film when the temperature rises in the areas not subjected to laser-induced reaction, leading to thermal extinction of the prepared patterned microarray. Therefore, developing novel chemical strategies to address the inherent contradictions in laser direct writing caused by the thermally induced nucleation and growth of traditional precursor ionic salts (AX and PbX2), thereby enabling the controllable preparation of thermally stable multicolor luminescent LH PQD patterned arrays within different polymer matrices, has important theoretical significance and application value. Summary of the Invention

[0005] Laser direct writing technology, due to its mask-free and simple operation, has great potential for efficiently fabricating high-resolution, highly luminescent microarrays of lead halide perovskite quantum dots (LH PQDs) in polymer films. However, due to the low formation energy of LH PQDs' intrinsic ionic salts, microarray polymer films prepared using halide salt precursors face the challenge of thermally induced array loss, severely restricting their practical application.

[0006] In order to solve the above problems, the present invention provides a method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation.

[0007] The technical solution adopted in the present invention is as follows:

[0008] The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation comprises the following steps:

[0009] 1) fully dissolving the polymer matrix and the halogen source, the cesium source, and the lead source in an organic solvent to obtain a mixed solution, then spin-coating the mixed solution on a glass substrate, and heating and drying to obtain a precursor composite film;

[0010] 2) The precursor composite film is patterned by laser direct writing using an ultraviolet nanosecond laser with a central wavelength of 355 nm.

[0011] Furthermore, the polymer matrix is ​​polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polystyrene (PS), thermoplastic polyurethane elastomer (TPU), etc.

[0012] Furthermore, the cesium source is a neutral non-halogenated cesium salt, and the neutral non-halogenated cesium salt is at least one of cesium hexafluoroglutarate (HFG-Cs), cesium trifluoroacetate (CF3COOCs), and cesium trifluoromethanesulfonate (CsOTf).

[0013] Furthermore, the lead source is an organic acid lead salt, and the organic acid lead salt is one of lead oleate and perfluorolead glutarate.

[0014] Furthermore, the halogen source is solid at room temperature and stable under normal light, and can be at least one of hexabromocyclododecane (HBCD), brominated butadiene / vinyl aromatic copolymer (Br-SBS), tetrabromobisphenol A bis(2,3-dibromopropyl) ether (BDDP), 3,5-dichloro-1-bromobenzene, and 1,3,5-trifluoro-2,4,6-triiodobenzene.

[0015] Furthermore, the precursor composite film prepared in step 1) is a CsPbBr3 PQDs film, a CsPbCl x Br 3-x PQDs film or CsPbI3 PQDs film.

[0016] Furthermore, the usage ratio of the polymer matrix, the halogen source, the cesium source and the lead source is 0.5 g: 0.1 mmol: 0.06 mmol: 0.06 mmol.

[0017] Furthermore, the organic solvent is N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), etc.

[0018] Furthermore, the heating and drying conditions are: 50-120° C., 0.1 MPa.

[0019] Furthermore, the pulse width of the laser direct writing is 10ns, the laser power is controlled by software, and the field mirror is used for focusing, F=11cm, and the patterning is performed in combination with the laser built-in laser galvanometer and software program control.

[0020] The present invention uses thermally stable organic halides (RX, R is a hydrocarbon group; X = Cl, Br, I) to replace traditional halide salts, and combines a 355nm ultraviolet nanosecond laser with high single-photon energy as a DLW light source (single-photon energy is about 3.49eV) to develop a new strategy for the preparation of laser-induced dehalogenation of halogenated organic LH PQDs patterned arrays. When the 355nm ultraviolet laser acts on RX, its carbon-halogen bond CX is broken and X is released. - , since the formation of LH PQDs is relatively low energy, X - A in the precursor film + and Pb 2+ Ions are combined in situ to generate LH PQDs. This strategy has the following advantages: (1) CX has strong tunability. By changing the type, number and substitution position of X in CX, the luminescence of CsPbX3 PQDs can be precisely adjusted; (2) Due to the good interfacial compatibility of CX intrinsic organic molecules with common polymers, efficient preparation under common different polymer matrices is achieved; and because 355nm ultraviolet light is a cold light source, it reduces the thermal defects and deficiencies caused by laser energy on the polymer matrix, greatly reducing the impact of the thermal effect generated by the laser on the resolution of PQDs, and maintaining the original physical and chemical properties of the polymer (such as transmittance and tensile properties), which can meet the application requirements of different scenarios. Based on this strategy, the present invention successfully achieved the efficient preparation of CsPbX3 PQDs arrays in different polymer matrices (the minimum dot size is about 20μm). The prepared patterned arrays exhibited good light, heat, and water stability. They can withstand high temperatures of 120°C, continuous irradiation of 365nm for 6 hours, and immersion in water for 30 days, while still maintaining their original luminescent arrays. They were ultimately applied to mesoscopic fluorescence anti-counterfeiting, showing good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the preparation of CsPbX3 PQDs patterned arrays based on laser-induced dehalogenation.

[0022] Figure 2 , a is a schematic diagram of the laser direct writing principle; b is a fluorescence image of the CsPbBr3PQDs circular dot pattern prepared by laser direct writing technology (scale bar: 100μm); c is a 3D fluorescence image of the CsPbBr3PQDs pattern prepared by laser direct writing technology; d is a transmission electron microscopy (TEM) image (scale bar: 10nm) and HRTEM image (scale bar: 2nm) of CsPbBr3 PQDs prepared by laser direct writing technology; e is the XRD characterization of the thin film before and after laser direct writing; f is the fluorescence emission spectrum and ultraviolet absorption spectrum of the synthesized CsPbBr3 PQDs; g is the hydrothermal stability test.

[0023] Figure 3 , a is the fluorescence image of CsPbBr3 PQDs dot matrix prepared with different laser direct writing parameters (scale bar: 200μm); b is the visible light image of CsPbBr3 PQDs dot matrix prepared with different laser direct writing parameters (scale bar: 200μm); c is the scanning electron microscope image of CsPbBr3 PQDs dot matrix prepared with different laser direct writing parameters (scale bar: 500μm); d is the fine spectrum of element Br in the XPS characterization of the film before and after CsPbBr3 PQD generation; e is the fine spectrum of element Cs in the XPS characterization of the film before and after CsPbBr3 PQD generation; f is the fine spectrum of element Pb in the XPS characterization of the film before and after CsPbBr3 PQD generation; g is the change in fluorescence intensity of CsPbBr3 PQDs with and without adding TEMPO; h is the infrared spectrum of the film before and after laser direct writing; i is the comparison of transmittance of the film before and after laser direct writing.

[0024] Figure 4 This is a comparison of the thermal stability of patterned lattices based on the traditional laser direct writing method of CsX and PbX2 precursors and the present method.

[0025] Figure 5 , ae are actual pictures of different polymer films after laser direct writing under visible light and fluorescence photos under 365nm ultraviolet light; f is a photo of patterned perovskite film under different elongation of TPU polymer film; g is ice flower, h is leaf, i is lantern; j is a fluorescence photo of the copy of "Shenlong Edition of Lanting Preface" (excerpt) under 365nm ultraviolet light (scale: 1cm).

[0026] Figure 6 It is based on laser-induced dehalogenation of CsPbCl 3-x Br x PQDs and CsPbI 3-x Br x Preparation of PQDs patterned arrays and their related PL and XRD characterization; a is CsPbCl generated by laser direct writing 3-x Br x Lattice morphology of PQDs; b is CsPbCl generated by laser direct writing 3-x Br x Photoluminescence spectra of PQDs; c is CsPbCl 3-x Br x XRD characterization of PQDs thin films before and after laser direct writing; d is CsPbI generated by laser direct writing 3-x Br x The lattice morphology of PQDs; e is CsPbI generated by laser direct writing 3-x Br x Photoluminescence spectrum of PQDs; f is CsPbI 3-xBr x XRD characterization of PQDs thin films before and after laser direct writing.

[0027] Figure 7 Industrial preparation of laser-induced dehalogenated LH PQDs patterned arrays and their anti-counterfeiting application scenarios DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to specific embodiments.

[0029] Some of the experimental materials used in the following examples are as follows:

[0030] Hexafluoroglutaric acid (HFG, ≥97%, Energy Chemical), N,N-dimethylformamide (DMF, 99.8%, Energy Chemical), 3,5-dichloro-1-bromobenzene (C6H3BrCl2, 98%, Energy Chemical), 1,3,5-trifluoro-2,4,6-triiodobenzene (C6H3BrCl2, 98%, Energy Chemical), polymethyl methacrylate (PMMA) (Energy Chemical), lead oleate (Pb(OA)2, C 36 H 66 O4Pb, 99%, Macklin), hexabromocyclododecane (HBCD, 95%, Rhawn), and cesium hydroxide solution (CsOH, 50 wt% aqueous solution, Energy Chemical). Isopropyl alcohol and anhydrous ether were purchased from Shantou Xilong Technology Co., Ltd. All reagents were used directly without further purification.

[0031] Example 1

[0032] The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation comprises the following steps:

[0033] 1. Preparation of CsPbBr3 PQDs polymer films

[0034] HFG-Cs (0.06 mmol), Pb(OA)2 (0.06 mmol), and HBCD (0.1 mmol) were dissolved in 2 mL of DMF to prepare a perovskite precursor solution. 0.5 g of PMMA was added to the precursor solution and heated at 60°C with stirring until completely dissolved. The solution was drop-coated onto a glass substrate and then transferred to a vacuum oven. Drying was performed at 60°C under low pressure (0.1 MPa) for 120 minutes to completely remove the polar solvent and form a precursor polymer film.

[0035] 2. Preparation of ultra-high stability patterned arrays of CsPbX3 PQDs based on laser-induced dehalogenation

[0036] like Figure 1 As shown, the precursor polymer film obtained above was subjected to a laser direct writing process using a laser beam with a central wavelength of 355nm and a pulse width of 10ns. The laser power was controlled by software and focused using a field lens (F = 11cm). Patterning was performed using a laser built-in galvanometer and software program control.

[0037] Example 2

[0038] The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation comprises the following steps:

[0039] 1. CsPbCl x Br 3-x Preparation of PQDs polymer films:

[0040] HFG-Cs (0.06 mmol), Pb(OA)2 (0.06 mmol), and 3,5-dichloro-1-bromobenzene (C6H3BrCl2) (0.1 mmol) were dissolved in DMF (2 mL) to prepare a perovskite precursor solution. 0.5 g of PMMA was added to the precursor solution and heated at 60°C with stirring until completely dissolved. The solution was drop-coated onto a glass substrate and then transferred to a vacuum oven. Drying was performed at 60°C under low pressure (0.1 MPa) for 120 minutes to completely remove the polar solvent and form a precursor polymer film.

[0041] 2. Preparation of ultra-high stability patterned arrays of CsPbX3 PQDs based on laser-induced dehalogenation

[0042] The precursor polymer film obtained above was subjected to a laser direct writing process using a laser beam with a central wavelength of 355nm and a pulse width of 10ns. The laser power was controlled by software and focused using a field lens (F = 11cm). Patterning was performed using a laser built-in galvanometer and software program control.

[0043] Example 3

[0044] The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation comprises the following steps:

[0045] 1. Preparation of CsPbI3 PQDs polymer films

[0046] HFG-Cs (0.06 mmol), Pb(OA)2 (0.06 mmol), and 1,3,5-trifluoro-2,4,6-triiodobenzene (C6H3BrCl2) (0.2 mmol) were dissolved in DMF (2 mL) to prepare a perovskite precursor solution. 0.5 g of PMMA was added to the precursor solution and heated at 60°C with stirring until completely dissolved. The solution was drop-coated onto a glass substrate and then transferred to a vacuum oven. Drying was performed at 60°C under low pressure (0.1 MPa) for 120 minutes to completely remove the polar solvent and form a precursor polymer film.

[0047] 2. Preparation of ultra-high stability patterned arrays of CsPbX3 PQDs based on laser-induced dehalogenation

[0048] The precursor polymer film obtained above was subjected to a laser direct writing process using a laser beam with a central wavelength of 355nm and a pulse width of 10ns. The laser power was controlled by software and focused using a field lens (F = 11cm). Patterning was performed using a laser built-in galvanometer and software program control.

[0049] Example 4

[0050] The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation comprises the following steps:

[0051] 1. Preparation of CsPbBr3 PQDs polymer films

[0052] CF3COOCs (0.06 mmol), Pb(OA)2 (0.06 mmol), and BDDP (0.1 mmol) were dissolved in 2 mL of DMF to prepare a perovskite precursor solution. 0.5 g of PAN was added to the precursor solution and heated at 60°C with stirring until completely dissolved. The solution was drop-coated onto a glass substrate and then transferred to a vacuum oven. Drying was performed at 60°C under low pressure (0.1 MPa) for 120 minutes to completely remove the polar solvent and form a precursor polymer film.

[0053] 2. Preparation of ultra-high stability patterned arrays of CsPbBr3 PQDs based on laser-induced dehalogenation

[0054] like Figure 1 As shown, the precursor polymer film obtained above was subjected to a laser direct writing process using a laser beam with a central wavelength of 355nm and a pulse width of 10ns. The laser power was controlled by software and focused using a field lens (F = 11cm). Patterning was performed using a laser built-in galvanometer and software program control.

[0055] Example 5

[0056] The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation comprises the following steps:

[0057] 1. Preparation of CsPbBr3 PQDs polymer films

[0058] CsOTf (0.06 mmol), Pb(OA)2 (0.06 mmol), and 0.5 g of Br-SBS were dissolved in 2 mL of DMF to prepare a perovskite precursor solution. This solution was drop-coated onto a glass substrate and then transferred to a vacuum oven and dried at 120°C and low pressure (0.1 MPa) for 120 minutes to completely remove the polar solvent and form a precursor polymer film.

[0059] 2. Preparation of ultra-high stability patterned arrays of CsPbBr3 PQDs based on laser-induced dehalogenation

[0060] like Figure 1 As shown, the precursor polymer film obtained above was subjected to a laser direct writing process using a laser beam with a central wavelength of 355nm and a pulse width of 10ns. The laser power was controlled by software and focused using a field lens (F = 11cm). Patterning was performed using a laser built-in galvanometer and software program control.

[0061] For Examples 1-5, the present invention uses the preparation of CsPbBr3 PQDs as a model to illustrate the preparation of laser-induced dehalogenated CsPbX3 PQDs patterned arrays. HBCD, HFG-Cs, and Pb(OA)2 were used as bromine, cesium, and lead sources, and PMMA polymer was used as a matrix. After being fully dissolved in DMF, it was directly spin-coated on a glass slide and vacuum-heated to dry into a prefabricated film. Subsequently, a 355nm ultraviolet nanosecond laser was used for laser direct writing. After the C-Br in the HBCD was irradiated by the laser, the bonds were broken to generate free Br. - Since the formation energy of CsPbBr3PQDs is very low, the released Br - Cs in the membrane + and Pb 2+ Combined with the rapid nucleation and growth of CsPbBr3PQDs, a CsPbBr3PQDs lattice with a diameter of about 20μm was prepared, which showed bright green fluorescence (PLQY of 40%) under 365nm ultraviolet light, and the lattice was further characterized by three-dimensional fluorescence imaging. Figure 2c The results show that the prepared lattice is uniform and the lattice depth is about 40μm. TEM and HRTEM results show that the size of the CsPbBr3PQDs in the array is nm and has good crystallinity, and the corresponding lattice fringe spacing is 0.31nm, which is slightly larger than the lattice spacing of the (200) crystal plane. It was further verified by X-ray diffraction (XRD). Before laser direct writing, there was no obvious characteristic peak. However, after laser irradiation, characteristic peaks appeared at 2θ = 15°, 21°, 29°, 33°, 38°, and 43°, which can be attributed to the (100), (110), (200), (210), (211), and (220) crystal planes, respectively, indicating that cubic phase CsPbBr3 PQDs were generated at this time, and the diffraction peak corresponding to its (200) was offset relative to the standard colorimetric card of cubic phase CsPbBr3 PQDs. This may be because the PMMA coating slightly reduced its crystallinity, which is consistent with the above HRTEM results. In addition, the present invention further conducted a thermal stability test on the prepared CsPbBr3 PQDs patterned array film. The results showed that compared with the traditional CsBr and PbBr2 thermally induced patterned arrays that disappeared, the preparation strategy based on laser-induced RX dehalogenation showed good thermal stability. It was found that even when heated to 100°C, the CsPbBr3 PQDs patterned array did not disappear and was still clearly visible, laying a good foundation for subsequent practical applications.

[0062] In order to explore the mechanism of this reaction model, the present invention deeply studies the effect of laser power on the prepared CsPbBr3PQDs patterned array film. Figure 3 a. Figure 3 b shows the microscope images of the dot matrix under natural light and 365nm ultraviolet light with different laser power and laser irradiation time. Figure 3 As can be seen in a, when the laser power continues to increase, the spot size continues to increase; similarly, when the irradiation time increases, it can be clearly observed that the spot continues to grow. The area irradiated by the laser generates a dot pattern of CsPbBr3PQDs with clear edges and very complete. At the same time, we also noticed that when the laser power is large and the irradiation time is long, the film has more serious thermal ablation marks. From the optical microscope image, the film in the laser irradiated area becomes no longer transparent. And from the scanning electron microscope image ( Figure 3c) shows that there are pits left by ablation in the central area of ​​the laser action. At this time, the nucleation and crystallization reaction of LH PQDs is induced by both thermal and optical effects. When the laser power is low and the irradiation time is short, we noticed that the laser-written area emits green fluorescence under ultraviolet light. However, in the optical microscope image, a different phenomenon was observed. The transmittance of the film did not change significantly. The transmittance of the film before and after DLW and the actual image are shown in the figure. Figure 3 i. At the same time, no damage to the film was observed in the corresponding laser irradiation area in the SEM image. This proves that when the laser energy is reduced and the action time is shortened, the single photon energy of 355nm is sufficient to destroy the CX bond in the organic halide and trigger the nucleation and crystallization process of LH PQDs by photon effect. In order to verify the mechanism of the reaction, we added the free radical scavenging agent 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) to the precursor solution. Compared with the control group, TEMPO has an inhibitory effect on the reaction at low pulse energy ( Figure 3 d), this is because TEMPO reacts with the free radical intermediate of HBCD, hindering the electron transfer of the free radical intermediate of HBCD to Br·, thereby inhibiting the Br - This observation indicates that photoradicals mainly release Br - To promote the formation of LHPQDs, this experiment proves that when the laser energy is low, the laser light effect plays a dominant role in the nucleation and crystallization process of LHPQDs. At the same time, we also noticed that when the laser energy increases, the inhibitory effect of TEMPO on the reaction is not obvious. This is because when the energy increases, the dominant role of the reaction gradually changes from the light effect to the laser thermal effect. High-resolution X-ray electron spectroscopy (XPS) data of Br 3d orbitals are Figure 3 As shown in Figure e, before laser direct writing, the fitting peak of the XPS spectrum is located at 70.1eV, which is attributed to the C-Br bond in HBCD. After laser direct writing, the signal of the fitting peak at 68.2eV becomes significantly stronger, which is attributed to the Br released by the destruction of the C-Br bond in the organic halide after laser direct writing. - The infrared spectrum of the film before and after laser direct writing is Figure 3 The infrared data shown in Figure 5 shows that the infrared spectrum of the film does not change significantly before and after laser direct writing, proving that the damage caused by the 355nm UV laser to the PMMA matrix is ​​very small. At the same time, the laser beam can be regarded as a Gaussian beam, so the focal spot diameter of the laser can be calculated using the following formula:

[0063]

[0064] Where d is the focal spot diameter, M is the beam quality factor, D is the incident beam diameter, f is the lens focal length, and λ is the central wavelength of the laser beam. The calculated laser focal diameter is 106.5 μm, much larger than the lattice radius of the resulting LH PQDs (40 μm). Therefore, it can be assumed that the reaction that induces the formation of LH PQDs at low power is photoinduced.

[0065] like Figure 4 As shown in the figure, after the traditional halide precursors CsBr and PbBr2 are dissolved with the polymer to form a film, when irradiated by laser, the nucleation and growth of CsPbX3 PQDs in the film are induced, and a clear fluorescent patterned array is displayed under ultraviolet light; however, when the prepared CsPbX3 PQDs patterned array film is heated to 60°C, the CsX and PbX2 in the film in the non-laser irradiated area will also nucleate and grow as the temperature rises, causing the thermally induced patterned array to disappear, directly affecting its practical use. The array prepared by this method based on laser-induced RX dehalogenation to drive the nucleation and growth of LH PQDs shows thermal quenching during the heating process, but the dot pattern remains clear. This is because heating is difficult to destroy the CX bond in the organic halide, so the film does not undergo spontaneous crystallization. This proves that the film of the present invention has very reliable thermal stability.

[0066] Because organic halides are difficult to break bonds under heating conditions. Therefore, the present invention has strong universality and good interface compatibility, and can be applied to various common polymer matrices such as polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polystyrene (PS) and thermoplastic polyurethane elastomer (TPU). The present invention uses laser direct writing technology to present the Chinese character "Fu" symbolizing happiness in five classic Chinese calligraphy fonts, and combines it with traditional Chinese window patterns to exquisitely engrave it on the above-mentioned polymer films, creating a unique cultural charm LH PQDs art pattern. There is no self-crystallization in various films ( Figure 5 ae). The present invention makes a pattern on the TPU film and performs a stretch test on it. The pattern on the TPU film is still clear. After stretching, its fluorescence intensity does not change significantly. The film shows elasticity and mechanical stability ( Figure 5 f). To expand the application of the method of the present invention, the fluorescence emission wavelength of the generated LH PQDs can be adjusted by adjusting the ratio of halogen in the organic halide. Then, by using the excellent pattern preparation ability of laser direct writing technology, the present invention prepared ice flowers ( Figure 5 g), leaves ( Figure 5 h) Lanterns ( Figure 5 i) At the same time, with the powerful patterning capability of laser direct writing technology, it is relatively easy to produce patterns of larger areas. Figure 5j is an excerpt from the traditional Chinese calligraphy work "Lanting Xu" prepared by laser direct writing technology. The pattern is about 9 cm long.

[0067] Similarly, by changing the composition of the halogenated hydrocarbon, CsPbCl 3-x Br x PQDs,CsPbI 3-x Br x PQDs lattice, its related PL spectrum and XRD pattern are as follows Figure 6 shown.

[0068] Example 6

[0069] In view of the fact that the strategy of the present invention can keep the transmittance of the LH PQDs film basically unchanged after the DLW process, the present invention applies it to the field of anti-counterfeiting technology. The present invention prepares a perovskite anti-counterfeiting label and constructs a composite anti-counterfeiting system that integrates macroscopic and microscopic features. The anti-counterfeiting label has unique optical response characteristics: under visible light conditions, the internal information of the film is difficult to identify; however, under 365nm ultraviolet light excitation, the hidden information can be clearly read. Thanks to the excellent patterning capability of laser direct writing technology, the present invention realizes the precise integration of macroscopic and microscopic structures. Specifically, the anti-counterfeiting label adopts a three-level structural design: one is the macroscopic hollow letters; the second is the microscopic letter patterns embedded in the letters; and the third is the microscopic letter details composed of precise dot matrices. This multi-level structure significantly improves the security and recognizability of the anti-counterfeiting label. As Figure 7 As shown, the present invention has designed an industrial production application scenario for this anti-counterfeiting mode, applying it to express packaging production lines. After DLW, the packaging shell is coated with a UV-responsive, dot-matrix QR code, which can be read by the user's mobile phone to obtain relevant product information. This mesoscopic anti-counterfeiting method not only has a high information encoding capacity but also has strong compatibility with industrial manufacturing.

[0070] In summary, the present invention adds organic halides instead of traditional halide salts as halogen sources to the precursor, effectively suppressing the spontaneous crystallization problem that may exist in traditional precursor films. At the same time, the 355nm ultraviolet laser is selected as the laser source. While effectively suppressing the thermal effect, its large single-photon energy can directly break the C-X bond of the organic halide, triggering a chemical reaction to make X - is released and reacts in situ with A site ions and Pb 2+Combined with the generation of LH PQDs, this strategy not only effectively solves the problem of film self-crystallization but also avoids the thermal effects of the laser. This expands the application range of DLW and makes this strategy adaptable to a wider range of polymer matrices. More importantly, the films prepared by this invention have excellent thermal stability. Even at a high temperature of 120°C, the films do not spontaneously crystallize, and the lattice morphology remains clear. Therefore, in addition to anti-counterfeiting, this method also has broad application prospects in fields such as micro-LEDs, solar cells, and laser devices.

Claims

1. A method for preparing ultra-high stability patterned arrays of LH PQDs based on laser-induced dehalogenation, characterized in that: The following steps are involved: 1) dissolving a polymer matrix and a halogen source, a cesium source, and a lead source in an organic solvent to obtain a mixed solution, then spin-coating the mixed solution on a glass substrate, and heating and drying to obtain a precursor composite film; 2) The precursor composite film is patterned by laser direct writing using an ultraviolet nanosecond laser with a central wavelength of 355 nm.

2. The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation according to claim 1, wherein: The polymer matrix is ​​at least one of polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, polystyrene, and thermoplastic polyurethane elastomer.

3. The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation according to claim 1, wherein: The cesium source is a neutral non-halogenated cesium salt, and the lead source is an organic acid lead salt.

4. The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation according to claim 3, wherein: The neutral non-halogenated cesium salt is at least one of cesium hexafluoroglutarate, cesium trifluoroacetate, and cesium trifluoromethanesulfonate, and the organic acid lead salt is at least one of lead oleate and perfluorolead glutarate.

5. The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation according to claim 1, wherein: The halogen source is at least one of hexabromocyclododecane, brominated butadiene / vinyl aromatic copolymer, tetrabromobisphenol A bis(2,3-dibromopropyl) ether, 3,5-dichloro-1-bromobenzene, and 1,3,5-trifluoro-2,4,6-triiodobenzene.

6. The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation according to claim 1, wherein: The usage ratio of the polymer matrix, halogen source, cesium source and lead source is 0.5 g: 0.1 mmol: 0.06 mmol: 0.06 mmol.

7. The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation according to claim 1, wherein: The organic solvent is N, N-dimethylformamide, dimethyl sulfoxide or N-methylpyrrolidone.

8. The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation according to claim 1, wherein: The heating and drying conditions are: 50-120° C., 0.1 MPa.

9. The method for preparing an ultra-high stability patterned array of LH PQDs based on laser-induced dehalogenation according to claim 1, wherein: The pulse width of the laser direct writing is 10 ns.

10. Application of the method for preparing ultra-high stability patterned arrays of LH PQDs based on laser-induced dehalogenation according to any one of claims 1 to 9 in fluorescent anti-counterfeiting labels.

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