A long-afterglow composite material based on excited state regulation of bromonaphthalimide structure carbon dots and a preparation method thereof

Abstract

The application discloses a long afterglow composite material based on excited state regulation of bromine-containing naphthalimide structure carbon dots, which comprises bromine-containing carbon dots and a matrix material; the bromine-containing carbon dots are carbon dots formed by carbonization of bromine-containing naphthalimide compounds and serve as single light-emitting centers; the matrix material is used for constructing a limited environment, regulating excited state kinetic behavior of the bromine-containing carbon dots and realizing long afterglow light emission; the large pi conjugated structure introduced into the carbon dots is beneficial to the formation of a stable excited state, the heavy atom effect of bromine atoms enhances spin-orbit coupling, promotes intersystem crossing and improves the generation efficiency of triplet excitons; different matrices regulate radiation and non-radiation processes of the triplet excitons through rigid confinement or intermolecular interaction, so that the long afterglow light emission performance is effectively regulated. The application can realize the regulatable output of light emission behavior without constructing a multi-light-emitting center or a complex doped system, and can be applied to the fields of information storage, anti-counterfeiting and optoelectronic devices.

Description

Technical Field

[0001] This invention relates to the field of luminescent nanomaterials and functional composite materials, and in particular to an excited-state regulated long afterglow composite material based on bromonaphthalimide structural carbon dots and its preparation method. Background Technology

[0002] Carbon dots, as a new type of carbon-based zero-dimensional luminescent nanomaterial, have shown broad application prospects in fields such as information security, bioimaging, and optoelectronic devices due to their low toxicity, excellent biocompatibility, simple preparation methods, and highly tunable surface and structure. In recent years, room-temperature long-afterglow luminescent systems based on carbon dots have attracted widespread attention. Compared with traditional inorganic long-afterglow materials, carbon dot materials have significant advantages in terms of flexible processing, environmental friendliness, and structural designability. However, existing carbon dot long-afterglow materials still face the following problems: On the one hand, in terms of emission wavelength control, achieving long-wavelength emission, especially in the red light region, is still relatively difficult for carbon dot systems. Due to the bandgap law, non-radiative transitions are significantly enhanced, leading to a decrease in luminescence efficiency. On the other hand, in terms of excited-state dynamics control, triplet excitons are easily quenched by molecular vibrations and environmental perturbations, making it difficult to achieve both long afterglow lifetime and luminescence intensity.

[0003] Furthermore, previous studies have shown that constructing a rigid matrix environment can stabilize triplet excitons to some extent, but existing systems mostly rely on defect states or the synergistic effect of multiple luminescent centers, resulting in complex luminescence mechanisms and limited controllability. Meanwhile, existing carbon dot precursors are mostly simple small molecule structures, lacking well-defined large π-conjugated luminescent units, which hinders precise control of excited-state behavior. Therefore, there is an urgent need to develop a carbon dot luminescence system with well-defined molecular structural characteristics, combining structural design with external matrix modulation to achieve effective control of long-afterglow luminescence performance. Summary of the Invention

[0004] The purpose of this invention is to provide a composite material with excited-state controlled long afterglow based on bromonaphthalene imide structural carbon dots; another purpose of this invention is to provide a method for preparing a composite material with excited-state controlled long afterglow based on bromonaphthalene imide structural carbon dots.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A composite material for long afterglow emission based on excited-state controlled carbon dots of bromonaphthalene imide structure, the composite material comprising bromonaphthalene-containing carbon dots and a matrix material; wherein, the bromonaphthalene-containing carbon dots are bromonaphthalene-containing imide-based carbon dots formed by carbonization of bromonaphthalene-containing imide compounds, serving as single luminescent centers; the matrix material is used to construct a confined environment, regulate the excited-state dynamics of the bromonaphthalene-containing carbon dots, and achieve long afterglow emission; the bromonaphthalene-containing imide-based carbon dots are formed by carbonization reaction of bromonaphthalene-containing anhydride compounds and amino-containing compounds, and the structural formula is selected from one of the following structural formulas:

[0007] .

[0008] Preferably, the amino-containing compound is selected from one or more of ethylenediamine, ethanolamine, and amino acids.

[0009] Preferably, the matrix material is selected from one or more of polymer matrices or small molecule rigid matrices.

[0010] Preferably, the polymer matrix is ​​selected from any one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polymethyl methacrylate, and cholic acid.

[0011] Preferably, when the matrix is ​​polyvinyl alcohol, the amount of bromine-containing carbon dots added is 0.1 to 2 wt% of the total mass of the composite material; when the matrix is ​​polyvinylpyrrolidone, the amount of bromine-containing carbon dots added is 0.1 to 1 wt% of the total mass of the composite material; when the matrix is ​​polymethyl methacrylate, the amount of bromine-containing carbon dots added is 0.1 to 2 wt% of the total mass of the composite material.

[0012] Preferably, the molecular weight of the polyvinyl alcohol is 80,000-1,000,000; the molecular weight of the polyvinylpyrrolidone is 10,000-360,000; the molecular weight of the polyacrylamide is 2,000,000-1,400,000; and the molecular weight of the polymethyl methacrylate is 50,000-350,000.

[0013] A method for preparing a composite material with excited-state controlled long afterglow based on bromonaphthalimide structural carbon dots includes the following steps:

[0014] (1) A bromine-containing naphthalene imide compound and an amino-containing compound are dissolved in an organic solvent and subjected to a solvothermal reaction. After purification, a bromine-containing carbon point is obtained.

[0015] (2) Disperse the bromine-containing carbon dots in a matrix material solution;

[0016] (3) The composite material is formed by solution casting, volatilization drying or melt cooling.

[0017] The design principle of this invention lies in the combination of molecular structure design and matrix confinement regulation to construct a long-afterglow system of carbon dots with a single luminescent center and a bromonaphthalene imide structure as the core luminescent unit, thereby achieving effective regulation of excited-state dynamics. Specifically, this invention selects bromonaphthalene imide compounds with large π-conjugated structures as carbon dot precursors, retaining part of their conjugated luminescent structure during carbonization, resulting in carbon dots forming stable and well-defined single luminescent centers. The large π-conjugated structure helps reduce excited-state energy level losses and enhances electron delocalization, thus improving excited-state stability. Simultaneously, the bromine atoms in the molecule can enhance spin-orbit coupling (SOC) through the heavy atom effect, promoting intersystem crossing (ISC) from singlet to triplet states, improving the production efficiency of triplet excitons, and providing a foundation for long-afterglow luminescence. Furthermore, this invention constructs confined environments by introducing different types of matrix materials. Different matrices can regulate the molecular motion and excited-state decay process of carbon dots through hydrogen bonding, rigid confinement effects, and intermolecular interactions, thereby effectively suppressing nonradiative transitions of triplet excitons and improving their stability and radiative recombination efficiency. Simultaneously, the differences in polarity, molecular stacking, and energy level interactions among different matrices can further regulate the excited-state energy level structure and luminescence transition paths, thus achieving tunable output of long-afterglow luminescence color and lifetime. This invention achieves long-afterglow luminescence behavior dominated by a single luminescent center without relying on traditional multi-luminescent-center, defect-state modulation, or complex doping systems, and features a clear luminescence mechanism, strong structural designability, and tunable luminescence behavior.

[0018] Beneficial Effects: Compared with existing technologies, this invention has significant advantages: By introducing bromonaphthaleneimide luminescent units with well-defined structural characteristics, this invention constructs a single luminescent center system. Compared with existing technologies that rely on multiple luminescent centers or defect states, it has the advantages of a clear luminescence mechanism and strong structural designability. Simultaneously, the introduction of bromine atoms enhances the spin-orbit coupling effect, promotes intersystem crossing, and improves the generation efficiency of triplet excitons. Furthermore, the confined environments constructed using different matrix materials effectively suppress molecular vibrational and non-radiative transitions of carbon dots, thereby significantly improving the intensity and duration of long-afterglow luminescence. This invention proposes a long-afterglow material construction strategy based on molecular structure design and matrix synergistic regulation, providing a new approach to the regulation of long-afterglow luminescence performance of carbon dots. Attached Figure Description

[0019] Figure 1 Transmission electron microscope (TEM) images and size distribution diagrams of the carbon dots BrNI-CDs prepared in Example 1 are shown; where (a) is a TEM image of the carbon dots BrNI-CDs and (b) is a size distribution diagram of the carbon dots BrNI-CDs.

[0020] Figure 2 The images shown are high-resolution XPS images of carbon dots BrNI-CDs prepared in Example 1; where (a) is the high-resolution C 1s spectrum of carbon dots BrNI-CDs, (b) is the high-resolution N 1s spectrum of carbon dots BrNI-CDs, (c) is the high-resolution O 1s spectrum of carbon dots BrNI-CDs, and (d) is the high-resolution Br 3d spectrum of carbon dots BrNI-CDs.

[0021] Figure 3 The image shows the luminescence behavior of the carbon dots BrNI-CDs prepared in Example 1 dispersed in THF; where (a) is the UV-Vis absorption spectrum and photoluminescence spectrum, and (b) is the fluorescence lifetime decay curve at the emission peak of 518 nm.

[0022] Figure 4 Steady-state photoluminescence spectra of carbon dots BrNI-CDs prepared in Example 1 at different excitation wavelengths (λex) in THF;

[0023] Figure 5 Normalized steady-state spectra and afterglow emission spectra of BrNI-CDs / PVA (a), BrNI-CDs / PVP (b), BrNI-CDs / CLA (c), and BrNI-CDs / PMMA (d) under 365 nm excitation. Detailed Implementation

[0024] Unless otherwise specified, the experimental methods described in the embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0025] Example 1

[0026] 0.40 g of 4-bromo-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-lined 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 the precipitate. 50 mL of deionized water was added to the supernatant (dark brown), and the solid was collected and dried in a 45 °C oven to obtain an orange-yellow solid. This solid was then dissolved in ethanol and dialyzed through a 1000 Da dialysis membrane for 24 hours to remove residual organic molecules. After freeze-drying, carbon dots (BrNI-CDs) were obtained.

[0027] like Figure 1As shown in (a) and (b), the prepared carbon dot BrNI-CDs exhibit uniformly distributed quasi-spherical nanoparticles with an average diameter of approximately 3.0 nm and a narrow particle size distribution, indicating that the synthesized CDs possess good monodispersity and high morphological consistency. Figure 2 As shown in (a), the high-resolution C 1s spectrum of BrNI-CDs can be decomposed into three peaks at 284.8, 286.7, and 289.6 eV, which are attributed to C=C / CC, CO / CN, and C=O / CN bonds, respectively; Figure 2 As shown in (b), the N 1s spectrum shows two peaks at 399.8 eV and 402.1 eV, corresponding to the CN and NH bonds, further proving that ethylenediamine successfully introduced nitrogen atoms and formed an amine structure in the reaction; as Figure 2 As shown in (c), the two peaks at 531.6 eV and 533.2 eV in the O 1s spectrum are attributed to C=O and CO bonds, respectively, indicating that the carbon dot surface contains carbonyl and hydroxyl functional groups; Figure 2 As shown in (d), the Br 3d spectrum consists of two sets of binding energies: one set belongs to the binding of peripheral Br with sp³ hybrid carbon, and the other set belongs to the binding with sp² hybrid carbon, indicating that Br exists in two different chemical environments on the carbon dot surface. Figure 3 As shown in (a) and (b) above, the luminescence behavior of carbon dots BrNI-CDs in tetrahydrofuran exhibits strong green photoluminescence emission at ~510 nm with a lifetime of approximately 6.5 ns. Figure 4 As shown, the maximum emission peak at 510 nm of carbon dot BrNI-CDs did not shift within the excitation wavelength range of 320-400 nm, indicating that BrNI-CDs exhibit excitation wavelength-independent behavior. Figure 5 As shown in (a), the BrNI-CDs / PVA composite material exhibits a green emission peak at 518 nm; however, after the UV excitation is removed, a significant phosphorescence signal is detected at 580 nm, and orange afterglow emission can be observed with the naked eye. Figure 5 As shown in (c), the BrNI-CDs / CLA composite also exhibits green emission and orange afterglow luminescence. Figure 5 (b) and such Figure 5 As shown in (d), BrNI-CDs / PVP and BrNI-CDs / PMMA exhibited steady-state green photoluminescence at 520 nm; while after the ultraviolet excitation source was removed, a phosphorescence signal dominated by the emission peak at 620 nm was detected, and a very obvious bright red afterglow emission was observed with the naked eye.

[0028] Example 2

[0029] 2.5 mg of BrNI-CDs was weighed and dissolved in 1 mL of ethanol solution. This solution was then rapidly added to 10 mL of an aqueous solution of polyvinylpyrrolidone (PVP, 0.5 g) and mixed thoroughly using a magnetic stirrer. Subsequently, 1 mL of this solution was coated onto a quartz plate. The solvent was allowed to evaporate naturally at room temperature, and then the plate was further dried in an oven at 55°C to obtain a BrNI-CDs / PVP composite film.

[0030] Example 3

[0031] Weigh 5 mg of BrNI-CDs and dissolve them in 1 mL of ethanol solution. Then, quickly add the solution to 5 mL of aqueous solution of polymethyl methacrylate (PMMA, 0.05 g / mL) and mix thoroughly using a magnetic stirrer. Subsequently, take 1 mL of this solution and coat it onto a quartz plate. Allow the solvent to evaporate naturally at room temperature, and then place it in an oven at 55°C for further drying to obtain the BrNI-CDs@PMMA composite film.

[0032] Example 4

[0033] 0.5 mg of BrNI-CDs was dissolved in 1 mL of ethanol solution, and then added to an aqueous solution of polyvinyl alcohol (PVA, 100 mg / mL). The mixture was stirred at 80°C for 30 min. Next, the solution was coated onto a quartz plate, and the solvent was allowed to evaporate naturally at room temperature before being further dried in an oven at 55°C to obtain a BrNI-CDs@PVA composite film.

[0034] Example 5

[0035] BrNI-CDs@CLA were prepared using a rapid melt-cooling method. 5 mg of BrNI-CDs were mixed with 1 g of cholic acid (CLA), vigorously ground for 15 min, and heated to 340°C using a heat gun until the solution was completely fluid. Subsequently, the mixture was cooled to room temperature to form a glassy composite, yielding the BrNI-CDs / CLA composite material.

Claims

1. A composite material with excited-state controlled long afterglow based on bromonaphthalimide structural carbon dots, characterized in that, The composite material comprises bromine-containing carbon dots and a matrix material; wherein, the bromine-containing carbon dots are bromine-containing naphthyl imide-structured carbon dots formed by carbonization of bromine-containing naphthyl imide compounds, serving as single luminescent centers; the matrix material is used to construct a confined environment, regulate the excited-state dynamics of the bromine-containing carbon dots, and achieve long afterglow luminescence; the bromine-containing naphthyl imide-structured carbon dots are formed by carbonization reaction of bromine-containing naphthyl anhydride compounds and amino-containing compounds, and the structural formula is selected from one of the following structural formulas: 。 2. The long afterglow composite material based on excited-state controlled carbon dots of bromonaphthalimide structure according to claim 1, characterized in that, The amino-containing compound is selected from one or more of ethylenediamine, ethanolamine, and amino acids.

3. The long afterglow composite material based on excited-state controlled carbon dots of bromonaphthalimide structure according to claim 1, characterized in that, The matrix material is selected from one or more of polymer matrices or small molecule rigid matrices.

4. The long afterglow composite material based on excited-state controlled carbon dots of bromonaphthalimide structure according to claim 3, characterized in that, The polymer matrix is ​​selected from any one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polymethyl methacrylate, and cholic acid.

5. The composite material according to claim 4, characterized in that, When the matrix is ​​polyvinyl alcohol, the amount of bromine-containing carbon dots added is 0.1 to 2 wt% of the total mass of the composite material; when the matrix is ​​polyvinylpyrrolidone, the amount of bromine-containing carbon dots added is 0.1 to 1 wt% of the total mass of the composite material; when the matrix is ​​polymethyl methacrylate, the amount of bromine-containing carbon dots added is 0.1 to 2 wt% of the total mass of the composite material.

6. The long afterglow composite material based on excited-state controlled carbon dots of bromonaphthalimide structure according to claim 4, characterized in that, The molecular weight of the polyvinyl alcohol is 80,000-1,000,000; the molecular weight of the polyvinylpyrrolidone is 10,000-360,000; the molecular weight of the polyacrylamide is 2,000,000-1,400,000; and the molecular weight of the polymethyl methacrylate is 50,000-350,000.

7. A method for preparing a long afterglow composite material based on excited-state controlled carbon dots of bromonaphthalimide structure as described in claim 1, characterized in that, The steps include the following: (1) Dissolve bromonaphthalimide-containing compounds and amino-containing compounds in an organic solvent, carry out a solvothermal reaction, and purify to obtain bromo-containing carbon dots; (2) Disperse the bromine-containing carbon dots in a matrix material solution; (3) The composite material is formed by solution casting, volatilization drying or melt cooling.

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