A photochromic circularly polarized luminescent carbon dot long afterglow composite material and a preparation method thereof
By constructing a composite system of photochromic carbon dots and cellulose nanocrystals, the multifunctional integration of photochromism, circularly polarized luminescence, and long afterglow luminescence of carbon dot materials was achieved. This solves the problems of single function and structural instability in existing technologies, provides a simple preparation method, and has broad application potential.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV OF POSTS & TELECOMM
- Filing Date
- 2026-04-29
- Publication Date
- 2026-07-28
AI Technical Summary
Existing carbon dot materials are difficult to integrate multiple functions such as photochromism, circularly polarized emission, and long afterglow emission, and they also suffer from structural instability and complex preparation methods.
By constructing a composite system consisting of photochromic carbon dots, a polymer matrix, and cellulose nanocrystals, the self-assembly of cellulose nanocrystals forms a cholesteric chiral ordered structure, modulating the luminescence of the carbon dots. Combined with the hydrogen bonding and rigid confinement effect of the polymer matrix, a synergistic integration of multiple functions is achieved.
The synergistic integration of photochromism, circularly polarized luminescence, and long afterglow luminescence in a single material system has been achieved, improving the stability and ease of preparation of the material and showing broad application prospects.
Smart Images
Figure CN122465584A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of luminescent materials and chiral photonic materials; specifically, it relates to a photochromic circularly polarized luminescent carbon dot long afterglow composite material and its preparation method. Background Technology
[0002] Circularly polarized luminescent materials, capable of emitting polarized light with a specific rotational direction, hold significant application value in fields such as information storage, 3D display, optical encryption, and chiral optoelectronic devices. In recent years, with the development of optoelectronic information technology, functional materials possessing multiple optical response characteristics have gradually become a research hotspot. Among these, integrating circularly polarized luminescence with other optical functions (such as photochromism and long-afterglow luminescence) holds promise for achieving multi-dimensional information control and higher levels of optical encryption performance.
[0003] Carbon dots, as a novel zero-dimensional carbon-based nanomaterial, possess advantages such as simple preparation methods, tunable luminescence properties, good biocompatibility, and high stability, attracting widespread attention in fields such as fluorescence imaging, optoelectronic devices, and information anti-counterfeiting. Through molecular design or surface manipulation, carbon dots can be endowed with photochromic luminescence and long-afterglow luminescence, demonstrating promising application potential in stimulus-responsive luminescent materials. However, since carbon dots are typically isotropic, their emitted light lacks chiral modulation capabilities, making it difficult to directly generate circularly polarized luminescence. To achieve circularly polarized luminescence in carbon dot systems, researchers usually need to introduce chiral structures or chiral matrices to regulate luminescence. However, existing research mostly focuses on achieving single circularly polarized luminescence or ordinary fluorescence modulation; material systems integrating multiple optical functions such as photochromism, circularly polarized luminescence, and long-afterglow luminescence are still relatively rare. Furthermore, existing materials still face certain limitations in terms of functional coupling, structural stability, and preparation methods. Therefore, developing a composite material system that is structurally stable, easy to prepare, and capable of simultaneously achieving photochromism, circularly polarized luminescence, and long afterglow luminescence is of great significance for expanding the application of multifunctional luminescent materials in fields such as information anti-counterfeiting, optical encryption, and intelligent optoelectronic devices. Summary of the Invention
[0004] The purpose of this invention is to provide a photochromic circularly polarized luminescent carbon dot long afterglow composite material; another purpose of this invention is to provide a method for preparing the photochromic circularly polarized luminescent carbon dot long afterglow composite material.
[0005] To achieve the above objectives, the present invention provides the following technical solution: a photochromic circularly polarized luminescent carbon dot long-afterglow composite material, the composite material comprising photochromic carbon dots, a polymer matrix, and cellulose nanocrystals; wherein the photochromic carbon dots are dispersed in the polymer matrix to form a luminescent phase; the cellulose nanocrystals form a cholesteric chiral ordered structure through self-assembly; the cholesteric chiral ordered structure selectively modulates the luminescence of the photochromic carbon dots, causing the composite material to exhibit circularly polarized luminescence characteristics; and the composite material exhibits photochromic luminescence properties under photoexcitation and produces long-afterglow luminescence after excitation stops.
[0006] Furthermore, the photochromic carbon dots are prepared by reacting an organic precursor containing an aromatic imide structure with an amino-containing compound.
[0007] Furthermore, the organic precursor containing the aromatic imide structure is selected from one or more of 1,8-naphthalenedicarboxylic anhydride and 1,4,5,8-naphthalenetetracarboxylic dianhydride;
[0008] The structural formula of 1,8-naphthalenedicarboxylic anhydride is as follows:
[0009] ;
[0010] The structural formula of 1,4,5,8-naphthalenetetracarboxylic dianhydride is as follows:
[0011] .
[0012] Furthermore, the amino-containing compound is selected from one or more of ethylenediamine, ethanolamine, lysine, and arginine;
[0013] The structural formula of ethylenediamine is as follows:
[0014] ;
[0015] The structural formula of ethanolamine is as follows:
[0016] ;
[0017] The structural formula of arginine is as follows:
[0018] ;
[0019] The structural formula of lysine is as follows:
[0020] .
[0021] Preferably, the polymer matrix is polyvinylpyrrolidone or polyvinyl alcohol. The molecular weight of the polyvinylpyrrolidone is 10,000-360,000; the molecular weight of the polyvinyl alcohol is 80,000-1,000,000.
[0022] Preferably, the photochromic carbon dots have a mass fraction of 0.05–2 wt% in the polymer matrix.
[0023] Preferably, the photochromic carbon dots, polymer matrix, and cellulose nanocrystals are compositely assembled through hydrogen bonding, electrostatic interaction, or intermolecular interaction.
[0024] This invention also provides a method for preparing a photochromic circularly polarized luminescent carbon dot long afterglow composite material, comprising the following steps:
[0025] (1) Dissolve the organic precursor and the amino-containing compound in an organic solvent;
[0026] (2) A solvothermal reaction was carried out in a reactor to obtain photochromic carbon dots;
[0027] (3) The obtained photochromic carbon dots were centrifuged, dialyzed and dried;
[0028] (4) Disperse the photochromic carbon dots in a polymer solution and dry them to obtain a photochromic carbon dot polymer;
[0029] (5) The obtained photochromic carbon dot polymer is mixed with cellulose nanocrystal dispersion and self-assembly is induced by solvent evaporation to obtain the composite material.
[0030] Preferably, in step (2), the thermal reaction temperature is 120–180°C and the reaction time is 6–24 h.
[0031] The design principle of this invention is as follows: The composite system of this invention uses photochromic carbon dots as a single luminescent center. Through molecular structure design and interface modulation, multi-channel luminescence output is achieved without introducing multiple luminescent components or rare earth doping, thereby improving the material's consistency and stability. Cellulose nanocrystals form a cholesteric chiral ordered structure through self-assembly, selectively modulating the carbon dot luminescence and enabling the material to exhibit stable circularly polarized luminescence characteristics, providing an effective strategy for achieving chiral luminescence in carbon dot systems. Simultaneously, the polymer matrix suppresses nonradiative transitions through hydrogen bonding and rigid confinement effects, enhancing the stability of triplet excitons and significantly improving the material's long-afterglow luminescence performance.
[0032] Beneficial Effects: Compared with existing technologies, this invention has significant advantages: By constructing a composite system composed of photochromic carbon dots, a polymer matrix, and cellulose nanocrystals, this invention achieves the synergistic integration of multiple functions such as photochromic luminescence, circularly polarized luminescence, and long-afterglow luminescence in a single material system, avoiding the problems of complex structure and difficult functional coupling in traditional multi-component systems. The preparation method of this composite material is simple, mild, and highly reproducible, with good scalability, and has broad application prospects in fields such as information anti-counterfeiting, optical encryption, multi-dimensional information storage, and chiral optoelectronic devices. Attached Figure Description
[0033] Figure 1 The images show transmission electron microscope (TEM) images and size distribution diagrams of NICDs; where a is a TEM image of the carbon dot NICDs prepared in Example 1, and b is a particle size distribution diagram of the carbon dot NICDs prepared in Example 1.
[0034] Figure 2 X-ray diffraction spectra of NICDs-PVP / CNC1 and cellulose nanocrystalline CNC materials;
[0035] Figure 3 Cross-sectional scanning electron microscope image of the NICDs-PVP / CNC1 composite material;
[0036] Figure 4 Polarized light microscope images of CNC and NICDs-PVP / CNC1 films;
[0037] Figure 5 The absorption spectra of the NICDs-PVP / CNC1 composite material after initial and photoactivation are shown.
[0038] Figure 6 For the NICDs-PVP / CNC1 composite material in its initial and photoactivated states, (a) is the steady-state photoluminescence spectrum; (b) is the CIE coordinate.
[0039] Figure 7 (a) Phosphorescence spectra and (b) phosphorescence lifetime decay curves of NICDs-PVP / CNC1, NICDs-PVP / CNC2, NICDs-PVP / CNC3 and NICDs-PVP / CNC4 composite materials after a delay of 10 ms;
[0040] Figure 8 Circular polarization spectra of NICDs-PVP / CNC1, NICDs-PVP / CNC2, NICDs-PVP / CNC3 and NICDs-PVP / CNC4 composite materials;
[0041] Figure 9Photographs of NICDs-PVP / CNC1, NICDs-PVP / CNC2, NICDs-PVP / CNC3, and NICDs-PVP / CNC4 composites under sunlight, UV-on, photoactivated, and UV-off conditions. Detailed Implementation
[0042] The specific preparation process of cellulose nanocrystals (CNC) in this invention is as follows: 2.74 g of cellulose was weighed and added to 24 mL of 64% sulfuric acid solution. The mixture was stirred at 45ºC for 1 h, and then 240 mL of deionized water was added to dilute the suspension and stop the hydrolysis reaction. After standing for 24 h, the turbid suspension at the bottom was centrifuged, the precipitate was collected, washed three times with deionized water, and dialyzed using a dialysis membrane (8000-14000 molecular weight) for 7 days. The resulting aqueous solution of cellulose nanocrystals was concentrated to 3 wt% at 60ºC.
[0043] Example 1
[0044] 0.40 g of 1,8-naphthalenedicarboxylic anhydride and 0.12 g of ethylenediamine were dissolved in 10 mL of N,N-dimethylformamide to form a homogeneous solution. This solution was then transferred to a 25 mL polytetrafluoroethylene autoclave and reacted at 180ºC for 10 h. After the reaction, the solution was allowed to cool naturally to room temperature and centrifuged at 10,000 rpm for 15 min to remove unreacted precipitate. The dark brown supernatant was diluted with deionized water at a volume ratio of 1:2 and dialyzed through a dialysis membrane with a molecular weight of 1000 Da for 24 h to remove residual organic molecules. Finally, the dialyzed solution was freeze-dried to obtain light yellow solid carbon dots (NICDs). Figure 1 As shown in a, the prepared carbon dots (NICDs) have a quasi-spherical morphology, such as... Figure 1 As shown in b, the average diameter of carbon dots (NICDs) is approximately 2.89 nm.
[0045] Example 2
[0046] 0.40 g of 1,8-naphthalenedicarboxylic anhydride and 0.12 g of ethanolamine were dissolved in 10 mL of N,N-dimethylformamide to form a homogeneous solution. This solution was then transferred to a 25 mL polytetrafluoroethylene autoclave and reacted at 180ºC for 6 h. After the reaction, the solution was allowed to cool naturally to room temperature and centrifuged at 10,000 rpm for 15 min to remove unreacted precipitate. The dark brown supernatant was diluted with deionized water at a volume ratio of 1:2 and dialyzed through a 1000 Da dialysis membrane for 24 h to remove residual organic molecules. Finally, the dialyzed solution was freeze-dried to obtain pale yellow solid carbon dots (NICDs).
[0047] Example 3
[0048] 0.40 g of 1,4,5,8-tetracarboxylic dianhydride and 0.12 g of ethylenediamine were dissolved in 10 mL of N,N-dimethylformamide to form a homogeneous solution. This solution was then transferred to a 25 mL polytetrafluoroethylene autoclave and reacted at 180ºC for 24 h. After the reaction, the solution was allowed to cool naturally to room temperature and centrifuged at 10,000 rpm for 15 min to remove unreacted precipitate. The dark brown supernatant was diluted with deionized water at a volume ratio of 1:2 and dialyzed through a 1000 Da dialysis membrane for 24 h to remove residual organic molecules. Finally, the dialyzed solution was freeze-dried to obtain light yellow solid carbon dots (NICDs).
[0049] Example 4
[0050] 0.40 g of 1,8-naphthalenedicarboxylic anhydride and 0.12 g of ethylenediamine were dissolved in 10 mL of N,N-dimethylformamide to form a homogeneous solution. This solution was then transferred to a 25 mL polytetrafluoroethylene autoclave and reacted at 120ºC for 10 h. After the reaction, the solution was allowed to cool naturally to room temperature and centrifuged at 10,000 rpm for 15 min to remove unreacted precipitate. The dark brown supernatant was diluted with deionized water at a volume ratio of 1:2 and dialyzed through a 1000 Da dialysis membrane for 24 h to remove residual organic molecules. Finally, the dialyzed solution was freeze-dried to obtain light yellow solid carbon dots (NICDs).
[0051] Example 5
[0052] 0.40 g of 1,8-naphthalenedicarboxylic anhydride and 0.12 g of ethylenediamine were dissolved in 10 mL of N,N-dimethylformamide to form a homogeneous solution. This solution was then transferred to a 25 mL polytetrafluoroethylene autoclave and reacted at 140ºC for 10 h. After the reaction, the solution was allowed to cool naturally to room temperature and centrifuged at 10,000 rpm for 15 min to remove unreacted precipitate. The dark brown supernatant was diluted with deionized water at a volume ratio of 1:2 and dialyzed through a 1000 Da dialysis membrane for 24 h to remove residual organic molecules. Finally, the dialyzed solution was freeze-dried to obtain light yellow solid carbon dots (NICDs).
[0053] Example 6
[0054] 0.40 g of 1,8-naphthalenedicarboxylic anhydride and 0.12 g of ethylenediamine were dissolved in 10 mL of N,N-dimethylformamide to form a homogeneous solution. This solution was then transferred to a 25 mL polytetrafluoroethylene autoclave and reacted at 160ºC for 10 h. After the reaction, the solution was allowed to cool naturally to room temperature and centrifuged at 10,000 rpm for 15 min to remove unreacted precipitate. The dark brown supernatant was diluted with deionized water at a volume ratio of 1:2 and dialyzed through a 1000 Da dialysis membrane for 24 h to remove residual organic molecules. Finally, the dialyzed solution was freeze-dried to obtain light yellow solid carbon dots (NICDs).
[0055] Example 7
[0056] Weigh 5 mg of the carbon dots (NICDs) prepared in Example 1 and dissolve them in 1 g of polyvinylpyrrolidone (PVP) ethanol solution. Stir continuously to form a homogeneous solution and pour it into a petri dish to form a NICDs-PVP composite material.
[0057] Example 8
[0058] 0.1 g of the NICDs-PVP composite material prepared in Example 7 was weighed and added to 3 mL of cellulose nanocrystal (CNC) suspension, and then stirred vigorously to obtain a homogeneous composite suspension. This suspension was then placed in a plastic petri dish (30 mm × 30 mm) and dried at room temperature to obtain the NICDs-PVP / CNC1 composite material. Figure 2 As shown, the X-ray diffraction patterns of the NICDs-PVP / CNC1 composite material and the cellulose nanocrystals (CNC) prepared above correspond to the characteristic diffraction peaks of cellulose type I (101, 002, 040), indicating that the introduction of NICDs does not destroy the original crystal structure of the material. Figure 3 As shown, the cross-sectional scanning electron microscope image of NICDs-PVP / CNC1 clearly reveals a periodic and ordered helical arrangement with a helical pitch of 252 nm, exhibiting a uniform and regular layered structure. Figure 4 As shown, polarized light microscopy images of the NICDs-PVP / CNC1 composite material and the aforementioned prepared cellulose nanocrystals (CNCs) reveal clear birefringence and fingerprint-like textures, forming an ordered chiral nematic liquid crystal structure. Figure 5 As shown, the NICDs-PVP / CNC1 composite material exhibits a maximum absorption band at ~350 nm in its initial state. When photoactivated using a 365 nm UV lamp, a new absorption band appeared at ~450 nm in the UV-Vis absorption spectrum. Figure 6As shown in Figure a, the NICDs-PVP / CNC1 composite material exhibits a clear steady-state emission at 430 nm in its initial state, with an emission color of blue. With prolonged irradiation time under 365 nm ultraviolet light, the photoluminescence spectrum shows a significant redshift to 550 nm, and the emission color transitions from blue to yellow, demonstrating obvious photochromic behavior. Figure 6 As shown in b, a clear transition from the blue to the yellow region can be observed using the CIE color coordinates. Figure 7 As shown in a, the NICDs-PVP / CNC1 composite material exhibits strong phosphorescence emission peaks dominated by 550 and 590 nm under 365 nm excitation, and a distinct orange afterglow is clearly visible to the naked eye, lasting for more than 2 s. Figure 7 As shown in b, the emission peak at 550 nm was monitored after the ultraviolet excitation was turned off, and the afterglow lifetime was as long as 220 ms, indicating its long afterglow properties.
[0059] Example 9
[0060] 5 mg of the carbon dots (NICDs) prepared in Example 1 were weighed and dissolved in 1 g of polyvinylpyrrolidone (PVP) ethanol solution. The solution was stirred continuously to form a homogeneous solution, which was then poured into a petri dish to form a NICDs-PVP composite material. 0.2 g of NICDs-PVP was weighed and added to 3 mL of cellulose nanocrystal (CNC) suspension, and then stirred vigorously to obtain a homogeneous composite suspension. These were then placed in plastic petri dishes (30 mm × 30 mm) and dried at room temperature to obtain the NICDs-PVP / CNC2 composite material.
[0061] Example 10
[0062] 5 mg of the carbon dots (NICDs) prepared in Example 1 were weighed and dissolved in 1 g of polyvinylpyrrolidone (PVP) ethanol solution. The solution was stirred continuously to form a homogeneous solution, which was then poured into a petri dish to form a NICDs-PVP composite material. 0.3 g of NICDs-PVP was weighed and added to 3 mL of cellulose nanocrystal (CNC) suspension, and then stirred vigorously to obtain a homogeneous composite suspension. These were then placed in plastic petri dishes (30 mm × 30 mm) and dried at room temperature to obtain the NICDs-PVP / CNC3 composite material.
[0063] Example 11
[0064] 5 mg of the carbon dots (NICDs) prepared in Example 1 were weighed and dissolved in 1 g of polyvinylpyrrolidone (PVP) ethanol solution. The solution was stirred continuously to form a homogeneous solution, which was then poured into a petri dish to form a NICDs-PVP composite material. 0.5 g of NICDs-PVP was weighed and added to 3 mL of cellulose nanocrystal (CNC) suspension, and then stirred vigorously to obtain a homogeneous composite suspension. These were then placed in plastic petri dishes (30 mm × 30 mm) and dried at room temperature to obtain the NICDs-PVP / CNC4 composite material.
[0065] like Figure 8 As shown, the circularly polarized (CPL) spectra of NICDs-PVP / CNC1, NICDs-PVP / CNC2, NICDs-PVP / CNC3, and NICDs-PVP / CNC4 composites are presented. All composites exhibit right-handed (R-CPL) emission at different wavelengths, with varying CPL intensities. With increasing NICDs-PVP content, the CPL signal gradually redshifts and weakens. This is because excessive NICDs induce aggregation-induced quenching and reduce luminescence intensity. Simultaneously, doping with different amounts of NICDs-PVP can modulate the asymmetry factor (g). lum The change from -0.35 to -0.12.
[0066] like Figure 9 The images shown are photographs of the NICDs-PVP / CNC1 composite material, NICDs-PVP / CNC2 composite material, NICDs-PVP / CNC3 composite material, and NICDs-PVP / CNC4 composite material under daylight, UV-on, photoactivated, and UV-off conditions, demonstrating their distinct structural colors, photochromic properties, and long afterglow characteristics.
Claims
1. A photochromic circularly polarized luminescent carbon dot long afterglow composite material, characterized in that, The composite material comprises photochromic carbon dots, a polymer matrix, and cellulose nanocrystals; wherein the photochromic carbon dots are dispersed in the polymer matrix to form a luminescent phase; the cellulose nanocrystals form a cholesteric chiral ordered structure through self-assembly; the cholesteric chiral ordered structure selectively modulates the luminescence of the photochromic carbon dots, causing the composite material to exhibit circularly polarized luminescence characteristics; and the composite material exhibits photochromic luminescence properties under photoexcitation and produces long afterglow luminescence after excitation stops.
2. The photochromic circularly polarized luminescent carbon dot long afterglow composite material according to claim 1, characterized in that, The photochromic carbon dots are prepared by reacting an organic precursor containing an aromatic imide structure with an amino-containing compound.
3. The photochromic circularly polarized luminescent carbon dot long afterglow composite material according to claim 2, characterized in that, The organic precursor containing the aromatic imide structure is selected from one or more of 1,8-naphthalenedicarboxylic anhydride and 1,4,5,8-naphthalenetetracarboxylic dianhydride; The structural formula of 1,8-naphthalenedicarboxylic anhydride is as follows: ； The structural formula of 1,4,5,8-naphthalenetetracarboxylic dianhydride is as follows: 。 4. The photochromic circularly polarized luminescent carbon dot long afterglow composite material according to claim 2, characterized in that, The amino-containing compound is selected from one or more of ethylenediamine, ethanolamine, lysine, and arginine; The structural formula of ethylenediamine is as follows: ； The structural formula of ethanolamine is as follows: ； The structural formula of arginine is as follows: ； The structural formula of lysine is as follows: 。 5. The photochromic circularly polarized luminescent carbon dot long afterglow composite material according to claim 1, characterized in that, The polymer matrix is polyvinylpyrrolidone or polyvinyl alcohol; the molecular weight of polyvinylpyrrolidone is 10,000-360,000; the molecular weight of polyvinyl alcohol is 80,000-1,000,000.
6. The photochromic circularly polarized luminescent carbon dot long afterglow composite material according to claim 1, characterized in that, The mass fraction of the photochromic carbon dots in the polymer matrix is 0.05–2 wt%.
7. The photochromic circularly polarized luminescent carbon dot long afterglow composite material according to claim 1, characterized in that, The photochromic carbon dots, polymer matrix, and cellulose nanocrystals are compositely assembled through hydrogen bonding, electrostatic interaction, or intermolecular interaction.
8. The method for preparing the photochromic circularly polarized luminescent carbon dot long afterglow composite material according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Dissolve the organic precursor and the amino-containing compound in an organic solvent; (2) A solvothermal reaction was carried out in a reactor to obtain photochromic carbon dots; (3) The obtained photochromic carbon dots were centrifuged, dialyzed and dried; (4) Disperse the photochromic carbon dots in a polymer solution and dry them to obtain a photochromic carbon dot polymer; (5) The obtained photochromic carbon dot polymer is mixed with cellulose nanocrystal dispersion and self-assembly is induced by solvent evaporation to obtain the composite material.
9. The preparation method according to claim 8, characterized in that, In step (2), the thermal reaction temperature is 120–180℃; the reaction time is 6–24 h.