Flexible rare earth nanocrystalline composite luminescent film and preparation process thereof
By employing a composite of core-shell structured rare-earth nanocrystals and modified carbon quantum dots in a flexible polymer matrix, the problems of rare-earth nanocrystal aggregation and weak interfacial bonding in the flexible polymer matrix are solved, resulting in a highly efficient and flexible composite luminescent film suitable for precise spectral biomedicine and high color gamut flexible displays.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI ALPHA LIGHTING EQUIP TESTING
- Filing Date
- 2026-02-12
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies struggle to efficiently integrate rare-earth nanocrystals into flexible polymer matrices, leading to nanoparticle aggregation, optical scattering, and weak inorganic-organic interface bonding. High luminescence efficiency requires high filler loading, but this reduces flexibility.
Rare earth nanocrystals with core-shell structure and modified carbon quantum dots are used to synthesize modified carbon quantum dots via a hydrothermal method. The rare earth nanocrystals are then uniformly dispersed in a flexible polymer matrix. The surfactant effect of the modified carbon quantum dots is used to prevent agglomeration, and glycerol is added to form a hydrogen bond network, which enhances the dispersion stability and flexibility.
A composite luminescent film with high luminous efficiency, excellent flexibility and optical transparency has been achieved, which is suitable for precise spectral biomedicine and high color gamut flexible display.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of rare earth luminescent display technology, and relates to a flexible rare earth nanocrystalline composite luminescent film and its preparation process. Background Technology
[0002] With the rapid development of wearable devices, flexible displays, biomedical sensing, and smart camouflage, there is an urgent need for flexible light source materials that combine excellent luminescence performance, mechanical flexibility, and environmental stability. Rare earth nanocrystals, especially upconversion luminescent nanocrystals, are considered ideal light-emitting centers for constructing next-generation flexible optoelectronic devices due to their unique narrow-band emission, long fluorescence lifetime, excellent photochemical stability, and near-infrared light excitation characteristics. However, efficiently integrating them into flexible polymer matrices to prepare high-performance composite luminescent films still faces a series of severe scientific and technological challenges.
[0003] Currently, the mainstream technical approach in this field typically employs a simple physical blending method, which involves mixing surface-modified rare-earth nanocrystals with polymer solutions (such as polydimethylsiloxane PDMS and polyurethane PU) and then curing the mixture. However, this method has the following inherent drawbacks: 1. Nanoparticle aggregation and optical scattering issues; 2. Weak inorganic-organic interface bonding; 3. High luminescence efficiency often requires high filler loading, which leads to reduced flexibility.
[0004] Therefore, there is an urgent need to develop a flexible rare-earth nanocrystalline composite luminescent film that combines high luminous efficiency and excellent flexibility. Summary of the Invention
[0005] The purpose of this invention is to provide a flexible rare-earth nanocrystalline composite luminescent film and its preparation process. The resulting film has excellent optical transparency, flexibility and luminous efficiency.
[0006] The objective of this invention can be achieved through the following technical solutions: A flexible rare-earth nanocrystal composite luminescent film, the composite luminescent film comprising a flexible polymer matrix and rare-earth nanocrystals and modified carbon quantum dots uniformly dispersed in the flexible polymer matrix; The rare earth nanocrystals have a core-shell structure, with the core being doped with Yb. 3+ and Tm 3+ The rare earth nanocrystals are hexagonal NaYF4 with an undoped NaYF4 shell and a nanoparticle size of 5~50nm.
[0007] As a preferred embodiment of the present invention, the preparation process of the modified carbon quantum dots is as follows: The modified carbon quantum dots were prepared by hydrothermal reaction of citric acid, aspartic acid, 3-aminophenylboronic acid and deionized water. The hydrothermal reaction was carried out at 180-200℃ for 6-10 hours. After the hydrothermal reaction, the product was purified by dialysis with a molecular weight cutoff of 1000-3000 Da to obtain modified carbon quantum dots.
[0008] As a preferred embodiment of the present invention, the preparation process of the rare earth nanocrystals is as follows: Yttrium chloride, TmCl3, and ytterbium trichloride were mixed with oleic acid and octadecene and heated to form a transparent solution of rare earth precursors. Ammonium fluoride and sodium hydroxide were dissolved in methanol to obtain a mixed solution. The mixed solution was added to the transparent solution of rare earth precursors, and the reaction yielded rare earth nanocrystal nuclei. Yttrium chloride and sodium fluoride were added to methanol to obtain a shell precursor solution. The shell precursor solution was mixed with the rare earth nanocrystal nuclei, and the reaction yielded the rare earth nanocrystals.
[0009] As a preferred embodiment of the present invention, the mass-to-volume ratio (g / g / g / mL) of citric acid, aspartic acid, 3-aminophenylboronic acid and deionized water is (0.1~0.5):(2~3):(0.6~1):(50~70).
[0010] A process for preparing a flexible rare-earth nanocrystalline composite luminescent film includes the following steps: S1. Disperse rare earth nanocrystals in chloroform to obtain dispersion A, disperse modified carbon quantum dots in N,N-dimethylformamide to obtain dispersion B, mix dispersion A and dispersion B at a mass ratio of 1:(5~10) to obtain a mixture, add glycerol, stir at 500~600 rpm for 1~2 h at 40~50℃, add ethanol after stirring to produce a precipitate, collect the solid by centrifugation, wash with ethanol 2~3 times, disperse in a solvent to obtain a composite rare earth nanocrystal dispersion with a mass fraction of 10~15%. S2. According to the mass fraction, 3-7 parts of composite rare earth nanocrystal dispersion, 25-30 parts of polyol compound and 1-2 parts of crosslinking agent are mixed to obtain a premix. Then, 70-90 parts of isocyanate-terminated prepolymer are added, mixed evenly and cast into a mold, and then cured to form the flexible composite light-emitting film.
[0011] As a preferred embodiment of the present invention, the concentration of dispersion A is 5~10 mg / mL, and the concentration of dispersion B is 1~2 mg / mL.
[0012] In a preferred embodiment of the present invention, the volume of glycerol is 1 to 2% of the total volume of the mixture.
[0013] As a preferred embodiment of the present invention, the method for preparing the isocyanate-terminated prepolymer is as follows: Under nitrogen atmosphere at 40-100°C, the diol polymer is mixed with polytetrahydrofuran, heated to 100-120°C and stirred for 2-3 hours, then cooled to 45-90°C, and diisocyanate monomer and dibutyltin dilaurate are added. The mixture is stirred at 50-90°C for 2-6 hours and then cooled to 35-65°C to obtain the isocyanate-terminated prepolymer.
[0014] As a preferred embodiment of the present invention, the crosslinking agent is one of trimethylolpropane, glycerol, 1,2,6-hexanetriol, 1,2,4-butanetriol, triethanolamine, and pentaerythritol.
[0015] As a preferred embodiment of the present invention, the diol polymer is polytetrahydrofuran or polycaprolactone diol.
[0016] This invention enhances the optical properties of a film by incorporating rare-earth nanocrystals and carbon quantum dots into a flexible polymer matrix. The rare-earth nanocrystals have a core-shell structure, and the NaYF4 matrix nanocrystals are synthesized using an oleic acid / octadecene system. NaYF4 is chosen as the matrix to ensure luminescence efficiency. The rare-earth nanocrystal cores are doped with Yb and Tm. 3+ As a sensitizer, Tm 3+ As an activator, it further enhances luminescence efficiency. In this core-shell structure, the shell is an undoped inert shell layer, which can effectively isolate the luminescent ions inside the core from the non-radiative quenching centers of the external environment, thereby improving luminescence efficiency; at the same time, it ensures the particle size, so that it can be well dispersed in the polymer without affecting the light transmittance of the film.
[0017] The carbon quantum dots used in this invention are prepared by a one-pot hydrothermal method using citric acid, aspartic acid and 3-aminophenylboronic acid as precursors. 3-aminophenylboronic acid is introduced to covalently bond phenylboronic acid groups to the surface of the generated carbon quantum dots.
[0018] In preparing the composite luminescent film, this invention first combines rare earth nanocrystals with carbon quantum dots. During the composite process, glycerol is added, and its polyhydroxyl groups are simultaneously adsorbed onto the surfaces of both through interactions such as hydrogen bonds, helping to achieve uniform mixing and preventing agglomeration. When modified carbon quantum dots are combined with rare earth nanocrystals, the modified carbon quantum dots, with their hydrophilic phenylboronic acid groups and lipophilic carbon core structure on the surface of the rare earth nanocrystals, act as a kind of "surfactant," greatly improving the dispersion stability of the composite nanounits in solvents and prepolymers.
[0019] After the addition of glycerol, the phenylboronic acid groups of the modified carbon quantum dots can form a strong hydrogen bond network with the free hydroxyl groups of glycerol, and interact with the oleic acid carboxyl groups on the surface of rare earth nanocrystals and the carboxyl / hydroxyl groups of the modified carbon quantum dots themselves. Therefore, the modified carbon quantum dots are more evenly distributed on the surface of rare earth nanocrystals through the bridging effect of glycerol, while isolating the surface defects of rare earth nanocrystals and helping to improve luminescence efficiency. At the same time, the carbon quantum dots themselves have good flexibility, which can help buffer stress when the film is subjected to force and avoid stress concentration that leads to interface debonding or cracking of rare earth nanocrystals.
[0020] Therefore, the phenylboronic acid groups abundant on the surface of modified carbon quantum dots provide rich active sites for dynamic covalent cross-linking with the flexible polymer matrix in subsequent steps, which can be used for subsequent cross-linking with the polymer matrix. Thus, rare earth nanocrystals, as luminescent centers, are integrated with carbon quantum dots and flexible polymer matrix to form a strong, tough, and stable composite luminescent film.
[0021] The beneficial effects of this invention are: This invention provides a composite luminescent film in which rare earth nanocrystals with a core-shell structure are incorporated, which can generate high-intensity characteristic visible light emission with a narrow half-maximum width (<20 nm) and extremely high color purity, making it suitable for biomedical applications and flexible displays requiring precise spectra. At the same time, through the interface modification and dispersion of phenylboronic acid-functionalized carbon quantum dots, the aggregation of nanofillers is effectively suppressed, and the resulting film has excellent optical transparency, flexibility and luminous efficiency. Detailed Implementation
[0022] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.
[0023] It should be noted that, unless otherwise specified, the present invention does not specifically limit the source of the raw materials used in the following embodiments. Commercially available products or products prepared by conventional preparation methods that are well known to those skilled in the art can be used. Experimental methods that do not specify specific conditions are all conventional methods and conventional conditions well known in the art.
[0024] The preparation process of rare earth nanocrystals in this invention is as follows: 0.79 mmol of YCl3, 0.01 mmol of TmCl3, and 0.20 mmol of ytterbium trichloride were mixed with 6 mL of oleic acid and 15 mL of octadecene. The mixture was heated to 150 °C under an argon atmosphere and stirred for 40 min to form a transparent solution. The transparent solution was cooled to 40 °C to obtain mixture A. 5 mmol of NH4F and 3.6 mmol of NaOH were dissolved in 8 mL of methanol to obtain mixture B. Mixture B was added to mixture A, and the mixture was heated to 90 °C and held for 30 min to remove methanol. Then, the mixture was evacuated for 10 min. The mixture was heated to 300 °C under an argon atmosphere and held for 60 min. The temperature was then lowered to 280 °C. A solution of 0.4 mmol of YCl3 and 0.4 mmol of NaF dissolved in 1.5 mL of methanol was added to the above solution. The mixture was held at 280 °C for 40 min and stirred. After stirring, the mixture was allowed to cool to room temperature. 20 mL of ethanol was added, and the solid was collected by centrifugation. The solid was washed with a cyclohexane / ethanol mixed solvent with a volume ratio of 1:3 to obtain rare earth nanocrystals.
[0025] Example 1 S1. Citric acid, aspartic acid, 3-aminophenylboronic acid and deionized water were prepared by hydrothermal reaction at a mass-to-volume ratio of 0.3:5:0.8:60 (g / g / g / mL). The hydrothermal reaction was carried out at 190℃ for 8 hours. After the hydrothermal reaction, the product was purified by dialysis. The molecular weight cutoff for dialysis was 1000 Da, and modified carbon quantum dots were obtained. Rare earth nanocrystals were dispersed in chloroform to obtain dispersion A, and modified carbon quantum dots were dispersed in N,N-dimethylformamide to obtain dispersion B. Dispersion A and dispersion B were mixed at a mass ratio of 1:8 to obtain a mixture. Then, 1.5% of glycerol (by volume of the total mixture) was added, and the mixture was stirred at 550 rpm for 2 hours at 45°C. After stirring, ethanol was added to produce a precipitate. The solid was collected by centrifugation and washed three times with ethanol. The precipitate was then dispersed in a solvent to obtain a composite rare earth nanocrystal dispersion with a mass fraction of 13%. The concentration of dispersion A was 8 mg / mL, and the concentration of dispersion B was 1.5 mg / mL. S2. According to the mass fraction, under nitrogen conditions at 60°C, 60 parts of polycaprolactone diol and 40 parts of polytetrahydrofuran are mixed, heated to 110°C and stirred for 2 hours, then cooled to 70°C, 25 parts of isophorone diisocyanate and 0.05 parts of dibutyltin dilaurate are added, stirred at 70°C for 5 hours, and then cooled to 55°C to obtain the isocyanate-terminated prepolymer. Six parts of composite rare earth nanocrystal dispersion, 28 parts of polyol compound and 1.5 parts of trimethylolpropane were mixed to obtain a premix, and then 80 parts of isocyanate-terminated prepolymer were added. After mixing evenly, the mixture was cast into a mold and cured to form the flexible composite luminescent film.
[0026] Example 2 S1. Citric acid, aspartic acid, 3-aminophenylboronic acid and deionized water were prepared by hydrothermal reaction at a mass-to-volume ratio of 0.1:2:0.6:50 (g / g / g / mL). The hydrothermal reaction was carried out at 190°C for 8 hours. After the hydrothermal reaction, the product was purified by dialysis. The molecular weight cutoff for dialysis was 1000 Da, and modified carbon quantum dots were obtained. Rare earth nanocrystals were dispersed in chloroform to obtain dispersion A, and modified carbon quantum dots were dispersed in N,N-dimethylformamide to obtain dispersion B. Dispersion A and dispersion B were mixed at a mass ratio of 1:5 to obtain a mixture. Then, 1% of glycerol (by volume of the total mixture) was added, and the mixture was stirred at 550 rpm for 2 hours at 45°C. After stirring, ethanol was added to produce a precipitate. The solid was collected by centrifugation and washed three times with ethanol. The precipitate was then dispersed in a solvent to obtain a composite rare earth nanocrystal dispersion with a mass fraction of 15%. The concentration of dispersion A was 8 mg / mL, and the concentration of dispersion B was 2 mg / mL. S2. According to the mass fraction, under nitrogen conditions at 60°C, 60 parts of polycaprolactone diol and 40 parts of polytetrahydrofuran are mixed, heated to 110°C and stirred for 2 hours, then cooled to 70°C, 25 parts of isophorone diisocyanate and 0.05 parts of dibutyltin dilaurate are added, stirred at 70°C for 5 hours, and then cooled to 55°C to obtain the isocyanate-terminated prepolymer. Three parts of composite rare earth nanocrystal dispersion, 25 parts of polyol compound and 1 part of trimethylolpropane were mixed to obtain a premix, and then 70 parts of isocyanate-terminated prepolymer were added. After mixing evenly, the mixture was cast into a mold and cured to form the flexible composite light-emitting film.
[0027] Example 3 S1. Citric acid, aspartic acid, 3-aminophenylboronic acid and deionized water were prepared by hydrothermal reaction at a mass-to-volume ratio of 0.5:3:1:70 (g / g / g / mL). The hydrothermal reaction was carried out at 200°C for 10 hours. After the hydrothermal reaction, the product was purified by dialysis. The molecular weight cutoff for dialysis was 1000 Da, and modified carbon quantum dots were obtained. Rare earth nanocrystals were dispersed in chloroform to obtain dispersion A, and modified carbon quantum dots were dispersed in N,N-dimethylformamide to obtain dispersion B. Dispersion A and dispersion B were mixed at a mass ratio of 1:10 to obtain a mixture. Then, 2% glycerol (by volume of the total mixture) was added, and the mixture was stirred at 600 rpm for 2 hours at 45°C. After stirring, ethanol was added to produce a precipitate. The solid was collected by centrifugation and washed three times with ethanol. The precipitate was then dispersed in a solvent to obtain a composite rare earth nanocrystal dispersion with a mass fraction of 15%. The concentration of dispersion A was 10 mg / mL, and the concentration of dispersion B was 2 mg / mL. S2. According to the mass fraction, under nitrogen conditions at 60°C, 60 parts of polycaprolactone diol and 40 parts of polytetrahydrofuran are mixed, heated to 110°C and stirred for 2 hours, then cooled to 70°C, 25 parts of isophorone diisocyanate and 0.05 parts of dibutyltin dilaurate are added, stirred at 70°C for 5 hours, and then cooled to 55°C to obtain the isocyanate-terminated prepolymer. Seven parts of composite rare earth nanocrystal dispersion, 30 parts of polyol compound and 2 parts of trimethylolpropane were mixed to obtain a premix. Then, 90 parts of isocyanate-terminated prepolymer were added, mixed evenly and cast into a mold for curing reaction to form the flexible composite light-emitting film.
[0028] Comparative Example 1 This comparative example is basically the same as Example 1, except that in step S1 of this comparative example, rare earth nanocrystals and modified carbon quantum dots are directly physically mixed.
[0029] Comparative Example 2 This comparative example is basically the same as Example 1, except that no modified carbon quantum dots were added during the preparation of the flexible composite light-emitting film in this comparative example.
[0030] Comparative Example 3 This comparative example is basically the same as Example 1, except that 3-aminophenylboronic acid was not added during the preparation of the modified carbon quantum dots in this comparative example.
[0031] Comparative Example 4 This comparative example is basically the same as Example 1, except that the rare earth nanocrystals in this comparative example are only bare core rare earth nanocrystals.
[0032] Performance testing: 1. The total transmitted light flux was measured at a wavelength of 550 nm using a UV-Vis spectrophotometer; 2. Bending resistance: The film was cut into strips 70 mm long and 10 mm wide, and fixed on a bending tester. The middle 40 mm section of the sample was repeatedly bent (0 to 180°) around a cylindrical mandrel with a radius of 3 mm at a bending frequency of 1 Hz. The number of bending cycles required for the luminous intensity to decrease to 80% of its initial value was recorded as the bending fatigue life of the sample. The results are shown in the table below: Based on the above data, it can be seen that the membrane prepared by the present invention has excellent light transmittance and flexibility.
[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A flexible rare-earth nanocrystalline composite luminescent film, characterized in that, The composite luminescent film comprises a flexible polymer matrix and rare earth nanocrystals and modified carbon quantum dots uniformly dispersed in the flexible polymer matrix; The rare earth nanocrystals have a core-shell structure, with the core being doped with Yb. 3+ and Tm 3+ The rare earth nanocrystals are hexagonal NaYF4 with an undoped NaYF4 shell and a nanoparticle size of 5~50nm.
2. The flexible rare-earth nanocrystalline composite luminescent film according to claim 1, characterized in that, The preparation process of the modified carbon quantum dots is as follows: The modified carbon quantum dots were prepared by hydrothermal reaction of citric acid, aspartic acid, 3-aminophenylboronic acid and deionized water. The hydrothermal reaction was carried out at 180-200℃ for 6-10 hours. After the hydrothermal reaction, the product was purified by dialysis with a molecular weight cutoff of 1000-3000 Da to obtain modified carbon quantum dots.
3. The flexible rare-earth nanocrystalline composite luminescent film according to claim 1, characterized in that, The preparation process of the rare earth nanocrystals is as follows: Yttrium chloride, TmCl3, and ytterbium trichloride were mixed with oleic acid and octadecene and heated to form a transparent solution of rare earth precursors. Ammonium fluoride and sodium hydroxide were dissolved in methanol to obtain a mixed solution. The mixed solution was added to the transparent solution of rare earth precursors, and the reaction yielded rare earth nanocrystals. Yttrium chloride and sodium fluoride were added to methanol to obtain a shell precursor solution. The shell precursor solution is mixed with rare earth nanocrystal nuclei, and the reaction yields the rare earth nanocrystals.
4. The flexible rare-earth nanocrystalline composite luminescent film according to claim 2, characterized in that, The mass-to-volume ratio (g / g / g / mL) of citric acid, aspartic acid, 3-aminophenylboronic acid, and deionized water is (0.1~0.5):(2~3):(0.6~1):(50~70).
5. A preparation process for a flexible rare-earth nanocrystalline composite luminescent film as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Disperse rare earth nanocrystals in chloroform to obtain dispersion A, disperse modified carbon quantum dots in N,N-dimethylformamide to obtain dispersion B, mix dispersion A and dispersion B at a mass ratio of 1:(5~10) to obtain a mixture, add glycerol, stir at 500~600 rpm for 1~2 h at 40~50℃, add ethanol after stirring to produce a precipitate, collect the solid by centrifugation, wash with ethanol 2~3 times, disperse in a solvent to obtain a composite rare earth nanocrystal dispersion with a mass fraction of 10~15%. S2. According to the mass fraction, 3-7 parts of composite rare earth nanocrystal dispersion, 25-30 parts of polyol compound and 1-2 parts of crosslinking agent are mixed to obtain a premix. Then, 70-90 parts of isocyanate-terminated prepolymer are added, mixed evenly and cast into a mold, and then cured to form the flexible composite light-emitting film.
6. The preparation process of the flexible rare-earth nanocrystalline composite luminescent film according to claim 5, characterized in that, The concentration of dispersion A is 5~10 mg / mL, and the concentration of dispersion B is 1~2 mg / mL.
7. The preparation process of the flexible rare-earth nanocrystalline composite luminescent film according to claim 5, characterized in that, The volume of glycerol is 1 to 2% of the total volume of the mixture.
8. The preparation process of the flexible rare-earth nanocrystalline composite luminescent film according to claim 5, characterized in that, The method for preparing the isocyanate-terminated prepolymer is as follows: Under nitrogen atmosphere at 40-100°C, the diol polymer is mixed with polytetrahydrofuran, heated to 100-120°C and stirred for 2-3 hours, then cooled to 45-90°C, and diisocyanate monomer and dibutyltin dilaurate are added. The mixture is stirred at 50-90°C for 2-6 hours and then cooled to 35-65°C to obtain the isocyanate-terminated prepolymer.
9. The preparation process of the flexible rare-earth nanocrystalline composite luminescent film according to claim 5, characterized in that, The crosslinking agent is one of trimethylolpropane, glycerol, 1,2,6-hexanetriol, 1,2,4-butanetriol, triethanolamine, and pentaerythritol.
10. The preparation process of the flexible rare-earth nanocrystalline composite luminescent film according to claim 8, characterized in that, The diol polymer is polytetrahydrofuran or polycaprolactone diol.