A high-efficiency circularly polarized luminescence and phosphorescence emitting carbonized polymer / cellulose nanocrystal composite material and preparation and application thereof

Abstract

The application provides a carbonized polymer / cellulose nanocrystal composite material with efficient circularly polarized luminescence and phosphorescence emission and a preparation method and application thereof.The preparation method of the composite material comprises the following steps: dispersing polyethylene glycol, rhodamine B and hydrochloric acid aqueous solution in water, performing hydrothermal reaction, and then performing filtration, dialysis, concentration and freeze-drying to obtain red light carbonized polymer; and dispersing the red light carbonized polymer in a cellulose nanocrystal aqueous solution and drying to obtain the carbonized polymer / cellulose nanocrystal composite material with efficient circularly polarized luminescence and phosphorescence emission.The preparation method is simple, raw materials are cheap and easy to obtain, and the method is green and environment-friendly; the composite material obtained by the application is a composite film, the mechanical strength of which is greatly improved, the composite film exhibits efficient red circularly polarized luminescence and has a very high asymmetric factor value; meanwhile, the composite film realizes room temperature phosphorescence emission, the fluorescence lifetime is greatly increased, and obvious long afterglow emission is observed under room temperature conditions.

Description

A carbonized polymer / cellulose nanocrystal composite material with high efficiency in circularly polarized luminescence and phosphorescence emission, its preparation and application Technical Field

[0001] This invention belongs to the field of fluorescent and phosphorescent materials technology, specifically relating to a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission, and its preparation and application. Background Technology

[0002] Circularly polarized emission (CPL) possesses irreplaceable advantages in 3D imaging, information encryption, and biological probes due to its asymmetric emission characteristics. Generally, the production of CPL materials involves two main approaches: using building blocks with chiral and fluorescent emission capabilities, and co-assembling achiral fluorescent emitters with chiral materials. Among various chiral luminescent molecular systems, inorganic lanthanide complexes tend to yield high asymmetry factor values, with the highest reported asymmetry factor value coming from Eu(III) complexes. Compared to inorganic complexes, organic systems can regulate their emission by adjusting the excited-state electron levels, but their low asymmetry factor value limits their practical application.

[0003] Carbonized polymers are a novel type of bottom-up fabricated carbon nanomaterial. They not only possess tunable optical properties but also inherit the characteristics of polymers. Their highly cross-linked network structure also makes room-temperature phosphorescence possible, thus offering broad application prospects as functional light-emitting units. However, significant breakthroughs have not yet been achieved in the research of chiral luminescence using carbonized polymers. Because chiral precursors are easily destroyed under high-temperature conditions, the preparation of high-performance chiral circularly polarized luminescent carbonized polymers is challenging. Currently, one development approach is to select a suitable chiral template to induce non-chiral carbonized polymer dots to generate circularly polarized luminescence.

[0004] Composite materials using cellulose nanocrystals as chiral templates show feasibility in inducing circularly polarized emission from chiral light sources. Cellulose nanocrystals are a class of natural materials with chiral structures that can generate chiral liquid crystal phases under concentration induction. However, currently, almost all circularly polarized emission generated based on carbon nanomaterials is blue, and reports of long-wavelength emission such as red circularly polarized emission are extremely rare. Furthermore, research on phosphorescence emission based on cellulose nanocrystals is also relatively lacking.

[0005] Chinese patent document CN 110540666 A discloses a crystalline nanocellulose-based dual-circularly polarized / fluorescent thin film material, its preparation method, and its application in anti-counterfeiting labels. This invention employs a one-step method to capture the metastable crystalline nanocellulose nematic phase in situ by changing two self-assembly conditions: the evaporation temperature and the initial concentration of the crystalline nanocellulose colloidal solution. This results in a fully crystalline nanocellulose thin film with a left-handed chiral nematic structure containing embedded nematic phase defects. This nematic phase defect structure exhibits a half-wavelength blocking effect, leading to chiral reversal of circularly polarized light to selectively reflect left-handed and right-handed dual-circularly polarized light. Furthermore, by embedding a fluorescent guest, it obtains a dual-circularly polarized fluorescence signal regulated by the optical bandgap in the near-ultraviolet to near-infrared wavelength range. However, the thin film material of this invention suffers from poor toughness and fragility, and its luminescence is limited to fluorescence emission. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a carbonized polymer / cellulose nanocrystal composite material with high-efficiency circularly polarized luminescence and phosphorescence emission, as well as its preparation and application. The preparation method of this invention is simple, uses inexpensive and readily available raw materials, and is environmentally friendly. The composite material obtained by this invention is a composite film with significantly improved mechanical strength, exhibits highly efficient red circularly polarized luminescence, and possesses an extremely high asymmetry factor value (g). lum Meanwhile, the composite film achieved room temperature phosphorescence emission, greatly increased fluorescence lifetime, and observed significant long afterglow emission at room temperature.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a carbonized polymer / cellulose nanocrystal composite material with high efficiency in circularly polarized luminescence and phosphorescence emission includes the following steps:

[0009] (1) Polyethylene glycol (PEG), rhodamine B and hydrochloric acid aqueous solution are fully dispersed in water, and then subjected to hydrothermal reaction. After filtration, dialysis, concentration and freeze drying, red light carbonized polymer is obtained.

[0010] (2) The red light carbonized polymer is fully dispersed in an aqueous solution of cellulose nanocrystals and dried to obtain a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circular polarization emission and phosphorescence emission.

[0011] According to a preferred embodiment of the present invention, in step (1), the mass-average molecular weight of the polyethylene glycol is 1,000 to 200,000, preferably 5,000 to 20,000.

[0012] According to a preferred embodiment of the present invention, in step (1), the mass concentration of the hydrochloric acid aqueous solution is 30%-37%.

[0013] According to a preferred embodiment of the present invention, in step (1), the mass ratio of polyethylene glycol to rhodamine B is 8-12:1; the mass ratio of polyethylene glycol to the volume ratio of hydrochloric acid aqueous solution is 8-15 g / mL; and the mass ratio of polyethylene glycol (PEG) to water is 1:60-70.

[0014] According to a preferred embodiment of the present invention, in step (1), polyethylene glycol is first dissolved in water, then hydrochloric acid aqueous solution is added, and finally rhodamine B is added, and mechanical stirring is performed to mix and disperse it evenly.

[0015] According to a preferred embodiment of the present invention, in step (1), the hydrothermal reaction temperature is 200℃~250℃, preferably 220℃~230℃, and the hydrothermal reaction time is 1~5h, preferably 2~3h.

[0016] According to a preferred embodiment of the present invention, in step (1), the molecular weight cutoff of the dialysis bag used for dialysis is 1000-30000 Da, preferably 10000-15000 Da. The dialysis bag is filled with the filtered filtrate, and the outside of the dialysis bag is deionized water.

[0017] According to a preferred embodiment of the present invention, in step (1), the dialysis time is 5 to 12 days, preferably 7 to 10 days. After the dialysis is completed, the solution in the dialysis bag is concentrated and freeze-dried to obtain red light carbonized polymer powder.

[0018] According to a preferred embodiment of the present invention, in step (2), the concentration of the aqueous solution of cellulose nanocrystals is 10-50 mg / mL, preferably 30-40 mg / mL.

[0019] According to a preferred embodiment of the present invention, the method for preparing the aqueous solution of cellulose nanocrystals in step (2) includes the following steps: mixing paper scraps with an aqueous solution of sulfuric acid with a concentration of 60-70 wt%, stirring and reacting, then adding water to stop the acid hydrolysis reaction, letting it stand, centrifuging to take the supernatant, and then dialysis, diluting or concentrating the supernatant to obtain the aqueous solution of cellulose nanocrystals.

[0020] Preferably, the mass ratio of paper scraps to the volume of sulfuric acid solution is 1:5-15 g / mL; the stirring reaction temperature is 45-55℃; the stirring reaction time is 20-40 minutes; and the standing time is 10-20 hours.

[0021] According to a preferred embodiment of the present invention, in step (2), the mass ratio of the red light carbonized polymer to the cellulose nanocrystals is 1:3.3-100.

[0022] According to a preferred embodiment of the present invention, in step (2), the mixed solution of red light carbonized polymer and cellulose nanocrystal aqueous solution is transferred to a petri dish and dried at 20-30°C to obtain a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission; the drying time is 2-5 days, preferably 3-4 days.

[0023] A carbonized polymer / cellulose nanocrystal composite material with high efficiency in circularly polarized light emission and phosphorescence emission was prepared by the above method.

[0024] According to a preferred embodiment of the present invention, the carbonized polymer / cellulose nanocrystal composite material is a composite film of red-light carbonized polymer and cellulose nanocrystals.

[0025] Application of the aforementioned high-efficiency circularly polarized light emission and phosphorescence emission carbonized polymer / cellulose nanocrystal composite material in red circularly polarized light emission and / or long-afterglow phosphorescence emission devices.

[0026] The technical features and beneficial effects of this invention are as follows:

[0027] 1. The carbonized polymer prepared by this invention using PEG and Rhodamine B as raw materials is simple, and the raw materials are environmentally friendly, inexpensive, and readily available. The resulting red-light carbonized polymer inherits the structure of the polymer PEG, has good solubility in water, and can produce orange-red fluorescence under 365nm ultraviolet light irradiation, but its fluorescence lifetime is relatively short.

[0028] 2. The carbonized polymer of this invention is prepared based on the dehydration condensation between the terminal hydroxyl groups of polyethylene glycol and the carboxyl groups of Rhodamine B, and the polymerization and carbonization process of the two. Hydrochloric acid, as a small molecule acid, plays a catalytic role in the formation of the carbonized polymer because although Rhodamine B contains carboxyl groups, it does not readily react with hydroxyl or amino groups. The addition of hydrochloric acid promotes the grafting of the carbon dots onto the polymer surface. Without the addition of hydrochloric acid aqueous solution, the solid-state luminescence intensity of the resulting carbonized polymer will be significantly reduced. In addition, this invention uses ultra-high molecular weight PEG. Rhodamine B, as a dye, exhibits significant aggregation quenching behavior. The long molecular chains of high molecular weight PEG can effectively disperse the fluorophores, resist the aggregation-induced quenching effect, and achieve efficient solid-state luminescence of the carbon dots.

[0029] 3. In the composite film of this invention, the red-light carbonized polymer and cellulose nanocrystals are uniformly dispersed due to electrostatic interactions. The composite film of this invention exhibits a bright structural color. The addition of the red-light carbonized polymer significantly improves the mechanical strength of the cellulose nanocrystal film, giving it the toughness to bend without breaking. The composite film of this invention achieves room-temperature phosphorescence emission, with the phosphorescence emission peak located at approximately 570 nm. Its fluorescence lifetime increases from 3.35 nanoseconds for the red-light carbonized polymer to 27.14 milliseconds, and a significant long afterglow phenomenon of phosphorescence is observed.

[0030] 4. The principle of this invention is based on the chiral liquid crystal phase formed by the concentration-driven formation of cellulose nanocrystals. After the film dries, the internal chiral structure is preserved. This internal chiral structure induces the achiral red-light carbonized polymer to produce highly efficient red circularly polarized luminescence. The fluorescence emission peak is around 570 nm. By adjusting the preparation conditions, the circularly polarized luminescence can be controlled, with the highest asymmetry factor value of the film sample reaching 0.6.

[0031] 5. The carbonized polymer of this invention retains the basic structure of high molecular weight PEG. Cellulose films themselves have poor mechanical strength and are fragile. The mixing of long-chain polymers with cellulose nanocrystals significantly enhances the mechanical strength of the film. Simultaneously, the addition of the carbonized polymer alters the interlayer spacing of the film, further affecting its optical properties and changing its structural color. Therefore, it is possible to control the circularly polarized emission of the composite film. Finally, in addition to circularly polarized fluorescence, visible phosphorescent long-afterglow emission is also achieved. Attached Figure Description

[0032] Figure 1 is an X-ray diffraction pattern of the red light carbonized polymer powder obtained in Example 1.

[0033] Figure 2 shows the Fourier transform infrared spectra of the red-light carbonized polymer obtained in Example 1 and the raw materials Rhodamine B and PEG.

[0034] Figure 3 shows the fluorescence emission spectrum of the red light carbonized polymer powder obtained in Example 1 at excitation wavelengths of 500 nm to 560 nm.

[0035] Figure 4 shows the fluorescence emission spectrum of the red light carbonized polymer aqueous solution obtained in Example 1 at excitation wavelengths of 500 nm to 560 nm.

[0036] Figure 5 shows the fluorescence emission spectra of the carbonized polymers obtained in Examples 1 and 6-10 at an excitation wavelength of 550 nm.

[0037] Figure 6 shows the UV-Vis absorption spectra of the aqueous solution of the red light carbonized polymer obtained in Example 1 with a concentration of 0.5–5 mg / mL.

[0038] Figure 7 shows photographs of the thin film samples obtained in Examples 1-5 under natural light (top) and 365nm ultraviolet light (bottom).

[0039] Figure 8 shows the ultraviolet absorption spectra of the films obtained in Comparative Example 1 and Examples 1-5.

[0040] Figure 9 shows the reflection spectra of the thin films obtained in Comparative Example 1 and Examples 1-5.

[0041] Figure 10 shows the fluorescence spectrum of the thin film sample obtained in Example 1.

[0042] Figure 11 shows the fluorescence spectrum of the thin film sample obtained in Example 2.

[0043] Figure 12 shows the fluorescence spectrum of the thin film sample obtained in Example 3.

[0044] Figure 13 shows the fluorescence spectrum of the thin film sample obtained in Example 4.

[0045] Figure 14 shows the fluorescence spectrum of the thin film sample obtained in Example 5.

[0046] Figure 15 shows the fluorescence lifetime of the red carbonized polymer powder obtained in Example 1 at 570 nm.

[0047] Figure 16 shows the phosphorescence spectrum of the thin film sample obtained in Example 5.

[0048] Figure 17 shows the fluorescence lifetime of the thin film sample obtained in Example 5 at 570 nm.

[0049] Figure 18 shows the afterglow of phosphorescence on the thin film sample obtained in Example 5 after the ultraviolet lamp was removed.

[0050] Figure 19 shows the circularly polarized emission spectra of the thin film samples obtained in Examples 1-5.

[0051] Figure 20 shows a comparison photograph of the mechanical strength of the thin film samples obtained in Comparative Example 1 and Example 5.

[0052] Figure 21 shows the stress-strain curves of the thin film samples obtained in Comparative Example 1 and Examples 1-5. Detailed Implementation

[0053] To better understand the present invention, specific embodiments are described below.

[0054] Unless otherwise specified, the experimental methods used in the examples are conventional methods.

[0055] Unless otherwise specified, all materials and reagents used in the examples are commercially available.

[0056] The cellulose nanocrystals used in this example were obtained by hydrolyzing cellulose with sulfuric acid. The specific steps are as follows: First, 1g of paper scraps were stirred with 10mL of a 64wt% sulfuric acid aqueous solution at 50°C for 30 minutes. After that, 100mL of deionized water was added to stop the acid hydrolysis reaction. After standing for 12 hours, the mixture was centrifuged, and the supernatant was dialyzed (the dialysis bag had a molecular weight cutoff of 10000 Da, and dialysis was performed at room temperature for 7 days) to obtain an aqueous solution of cellulose nanocrystals. The obtained aqueous solution of cellulose nanocrystals can be diluted or concentrated as needed.

[0057] Example 1

[0058] A method for preparing a carbonized polymer / cellulose nanocrystal composite material with high efficiency in circularly polarized luminescence and phosphorescence emission includes the following steps:

[0059] 0.1544 g of PEG (weight-average molecular weight approximately 8000) was placed in a beaker and dissolved in 10.125 mL of water. Then, 13 μL of a 37% hydrochloric acid aqueous solution was added, followed by 0.0154 g of Rhodamine B. The mixture was mechanically stirred until homogeneous and then transferred to a reaction vessel. The reaction vessel was placed in an oven for hydrothermal reaction at 230°C. The hydrothermal reaction was carried out for 2 hours. After the sample cooled naturally to room temperature, it was filtered, and the filtrate was transferred to a 10000 Da dialysis bag. The dialysis bag was immersed in deionized water and dialyzed at room temperature for 7 days. After dialysis, most of the water in the solution in the dialysis bag was removed by rotary evaporation to obtain a concentrated solution. The concentrated solution was then freeze-dried to obtain the red-light carbonized polymer powder.

[0060] Weigh 1.2 mg of red-light carbonized polymer powder and add it to 3 mL of a 40 mg / mL cellulose nanocrystal aqueous solution (the mass ratio of red-light carbonized polymer to cellulose nanocrystals is 1:100). Mix thoroughly by mechanical stirring. Transfer the mixture to a 30 mm diameter plastic petri dish and dry it at 25 °C for 3 days to obtain the final red-light carbonized polymer / cellulose nanocrystal composite film.

[0061] Example 2

[0062] A method for preparing a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission is as described in Example 1, except that: the red light carbonized polymer powder is changed to 6 mg (the mass ratio of red light carbonized polymer to cellulose nanocrystals is 1:20); other steps and conditions are the same as in Example 1.

[0063] Example 3

[0064] A method for preparing a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission is as described in Example 1, except that: the red light carbonized polymer powder is changed to 12 mg (the mass ratio of red light carbonized polymer to cellulose nanocrystals is 1:10); other steps and conditions are the same as in Example 1.

[0065] Example 4

[0066] A method for preparing a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission is as described in Example 1, except that: the red light carbonized polymer powder is changed to 24 mg (the mass ratio of red light carbonized polymer to cellulose nanocrystals is 1:5); other steps and conditions are the same as in Example 1.

[0067] Example 5

[0068] A method for preparing a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission is as described in Example 1, except that: the red light carbonized polymer powder is changed to 36 mg (the mass ratio of red light carbonized polymer to cellulose nanocrystals is 1:3.3); other steps and conditions are the same as in Example 1.

[0069] Example 6

[0070] A method for preparing a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission is as described in Example 1, except that the hydrothermal reaction temperature is changed from 230℃ to 200℃; the other steps and conditions are the same as in Example 1.

[0071] Example 7

[0072] A method for preparing a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission is as described in Example 1, except that the hydrothermal reaction temperature is changed from 230℃ to 210℃; the other steps and conditions are the same as in Example 1.

[0073] Example 8

[0074] A method for preparing a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission is as described in Example 1, except that the hydrothermal reaction temperature is changed from 230℃ to 220℃; the other steps and conditions are the same as in Example 1.

[0075] Example 9

[0076] A method for preparing a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission is as described in Example 1, except that the hydrothermal reaction temperature is changed from 230℃ to 240℃; the other steps and conditions are the same as in Example 1.

[0077] Example 10

[0078] A method for preparing a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission is as described in Example 1, except that the hydrothermal reaction temperature is changed from 230℃ to 250℃; the other steps and conditions are the same as in Example 1.

[0079] Comparative Example 1

[0080] A method for preparing a cellulose nanocrystalline thin film includes the following steps:

[0081] Take 3 mL of 40 mg / mL cellulose nanocrystal aqueous solution and transfer it to a 30 mm diameter plastic petri dish. Dry it at 25 °C for 3 days to obtain a cellulose nanocrystal film.

[0082] Experimental Example 1

[0083] The X-ray diffraction and Fourier transform infrared spectra of the red-light carbonized polymer obtained in Example 1 are shown in Figure 1 and Figure 2, respectively. The sharp diffraction peaks in the X-ray diffraction correspond to the folding and crystallization of the polyoxyethylene ether chain. Analysis of the absorption peaks in the infrared spectrum shows that the absorption peaks of the product are basically consistent with those of PEG, indicating that the carbonized polymer retains the basic structure of PEG.

[0084] Experimental Example 2

[0085] The red-light carbonized polymer obtained in Example 1 emitted orange-red fluorescence under ultraviolet light irradiation. The emission spectrum of the carbonized polymer powder is shown in Figure 3, with the emission peak around 570 nm. The powder has good water solubility; the emission spectrum of a 10 mg / mL aqueous solution is shown in Figure 4, with the emission peak also around 570 nm, and the optimal excitation wavelength appearing at 550 nm. Furthermore, the emission peak position remained essentially unchanged with changes in excitation wavelength, indicating the presence of a specific luminescent center. Figure 5 shows the fluorescence emission changes of the carbonized polymer at different temperatures ranging from 200 to 250 °C. The degree of carbonization continuously increases with increasing reaction temperature, with the best effect observed at a reaction temperature of 230 °C.

[0086] Experimental Example 3

[0087] The aqueous solutions of the red-light carbonized polymer obtained in Example 1 (concentrations of 0.5, 1, 2, 3, 4, and 5 mg / mL) -1 The ultraviolet absorption spectra are shown in Figure 6. The absorbance increases with increasing concentration, and a distinct absorption peak exists at 550 nm. Figure 7 shows photographs of the film samples obtained in Examples 1-5 under natural light and 365 nm ultraviolet light. When the amount of carbonized polymer added is small, the film exhibits a bright structural color and shows weak orange fluorescence under ultraviolet light. As the amount of carbonized polymer added increases, the structural color of the film weakens, and the red color imparted by the carbonized polymer dominates, indicating that the addition of carbonized polymer gradually changes the internal structure of the film. The absorption and reflection spectra of the composite films prepared in Examples 1-5 and Comparative Example 1 are shown in Figures 8 and 9. It can be seen from the figures that as the amount of carbonized polymer added increases, the composite film gradually shows an absorption peak at 550 nm, further proving the successful incorporation of carbonized polymer. Furthermore, with the increase of the amount added, the positions of the absorption and reflection peaks of the cellulose nanocrystals themselves shift towards larger wavelengths, indicating that the addition of carbonized polymer gradually increases the interlayer spacing inside the film.

[0088] Test Example 4

[0089] The fluorescence emission spectra of the films obtained in Examples 1-5 are shown in Figures 10-14, respectively. The fluorescence emission peak of the film samples is around 570 nm. The fluorescence intensity increases with the amount of carbonized polymer added. The film obtained in Example 5, with the highest fluorescence intensity, has a fluorescence quantum yield of 41.72%, while the fluorescence quantum yield of the carbonized polymer powder is only 6.42%. This indicates that encapsulating the carbonized polymer into a cellulose film can significantly improve the fluorescence capability of the carbonized polymer.

[0090] Experimental Example 5

[0091] The fluorescence lifetime of the carbonized polymer powder prepared in Example 1 at 570 nm is shown in Figure 15, which is only 3.35 nanoseconds. Encapsulating the carbonized polymer into a thin film (the film prepared in Example 5) using the preparation method described in this invention resulted in phosphorescence emission, as shown in Figure 16. The emission peak at 480 nm corresponds to the phosphorescence peak of the cellulose nanocrystals themselves, and the emission peak at 570 nm is the red phosphorescence emission generated by the carbonized polymer. The phosphorescence lifetime is as long as 27.14 milliseconds (as shown in Figure 17), and a significant yellow phosphorescence emission was observed after the UV lamp irradiation was removed, as shown in Figure 18.

[0092] Experimental Example 6

[0093] Thanks to its internal chiral nematic structure, the cellulose-based composite film can selectively reflect natural light of specific wavelengths and convert it into right-handed circularly polarized light. The films obtained in Examples 1-5 induced strong circularly polarized luminescence by the non-chiral carbonized polymer, and the circularly polarized spectrum under 500 nm excitation is shown in Figure 19. The internal structure of the composite film maintains the chiral nematic structure. The addition of the carbonized polymer affects the interlayer spacing of the chiral structure, thereby achieving the control of its optical properties. The asymmetry factor value of the film samples showed a trend of first increasing and then decreasing with the amount of carbonized polymer added. The maximum asymmetry factor value appeared in the film sample of Example 2, reaching as high as 0.6.

[0094] Experimental Example 7

[0095] Cellulose nanocrystal-based films have extremely low mechanical strength and are prone to breakage. However, the film samples obtained using this method exhibit significantly improved mechanical strength and can be bent repeatedly without breaking. Figure 20 shows photographs of a film made from pure cellulose (Comparative Example 1) and a composite film with added carbonized polymer (Example 5). The cellulose film, due to its inherent poor mechanical strength, cracked during preparation. The addition of long-chain carbonized polymer, while making the composite film softer, increases energy dissipation during movement, thus resulting in higher mechanical strength and toughness, allowing for repeated bending. The stress-strain curves of the films obtained in Examples 1-5 and Comparative Example 1 are shown in Figure 21.

Claims

1. A method for preparing a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission, comprising the following steps: (1) dispersing polyethylene glycol, rhodamine B, and hydrochloric acid aqueous solution fully in water, subjecting the mixture to a hydrothermal reaction, and then filtering, dialysis, concentration, and freeze-drying to obtain a red-light carbonized polymer; the hydrothermal reaction temperature is 220℃~230℃, and the hydrothermal reaction time is 2~3h; the weight-average molecular weight of the polyethylene glycol is 5000~20000; the molecular weight cutoff of the dialysis bag used for dialysis is 1000~30000 Da; (2) The red-light carbonized polymer is fully dispersed in an aqueous solution of cellulose nanocrystals and dried to obtain a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission; the preparation method of the aqueous solution of cellulose nanocrystals includes the following steps: paper scraps are mixed with an aqueous solution of sulfuric acid with a concentration of 60-70wt%, stirred and reacted, then water is added to stop the acid hydrolysis reaction, allowed to stand, centrifuged and the supernatant is taken, and the supernatant is dialyzed, diluted or concentrated to obtain an aqueous solution of cellulose nanocrystals; the mass ratio of red-light carbonized polymer to cellulose nanocrystals is 1:3.3-100.

2. The method for preparing the high-efficiency circularly polarized luminescence and phosphorescence emission carbonized polymer / cellulose nanocrystal composite material according to claim 1, characterized in that, Step (1) includes one or more of the following conditions: i. the mass concentration of hydrochloric acid aqueous solution is 30%-37%; ii. the mass ratio of polyethylene glycol to rhodamine B is 8-12:1; the mass ratio of polyethylene glycol to the volume ratio of hydrochloric acid aqueous solution is 8-15 g / mL; the mass ratio of polyethylene glycol to water is 1:60-70; iii. the dialysis time is 5-12 days.

3. The method for preparing the high-efficiency circularly polarized light emission and phosphorescent emission carbonized polymer / cellulose nanocrystal composite material according to claim 1, characterized in that, Step (1) includes one or more of the following conditions: i. The molecular weight cutoff of the dialysis bag used for dialysis is 10,000 to 15,000 Da; ii. The dialysis time is 7 to 10 days.

4. The method for preparing the high-efficiency circularly polarized luminescence and phosphorescence emission carbonized polymer / cellulose nanocrystal composite material according to claim 1, characterized in that, In step (2), the concentration of the aqueous solution of cellulose nanocrystals is 10–50 mg / mL.

5. The method for preparing the high-efficiency circularly polarized luminescence and phosphorescence emission carbonized polymer / cellulose nanocrystal composite material according to claim 1, characterized in that, In step (2), in the preparation method of cellulose nanocrystal aqueous solution, the mass ratio of paper scraps to sulfuric acid water solution is 1:5-15 g / mL; the stirring reaction temperature is 45-55℃, the stirring reaction time is 20-40 minutes, and the standing time is 10-20 h.

6. The method for preparing the high-efficiency circularly polarized luminescence and phosphorescence emission carbonized polymer / cellulose nanocrystal composite material according to claim 1, characterized in that, In step (2), the mixed solution of red light carbonized polymer and cellulose nanocrystal aqueous solution is transferred to a petri dish and dried at 20-30℃ to obtain a carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission; the drying time is 2-5 days.

7. A carbonized polymer / cellulose nanocrystal composite material with high efficiency of circularly polarized light emission and phosphorescence emission, prepared by the method described in any one of claims 1-6.

8. The carbonized polymer / cellulose nanocrystal composite material with high-efficiency circularly polarized light emission and phosphorescence emission according to claim 7, characterized in that, The carbonized polymer / cellulose nanocrystal composite material is a composite film of red-light carbonized polymer and cellulose nanocrystals.

9. The application of the carbonized polymer / cellulose nanocrystal composite material with high efficiency circularly polarized light emission and phosphorescence emission as described in any one of claims 7-8 in red circularly polarized light emission and / or long-afterglow phosphorescence emission devices.

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