Color-tunable room temperature phosphorescent material, preparation method and application thereof

Abstract

The present application relates to phosphorescent material technical field, specifically to a kind of color-adjustable room temperature phosphorescent material and its preparation method and application.Room temperature phosphorescent material preparation method includes: carbon black particles are added to nitric acid and refluxed, then cooled, centrifuged in turn.Supernatant after centrifugation is collected and evaporated to dryness, to obtain carbon dots.Carbon dots and boric acid are mixed and then dispersed uniformly in deionized water to obtain transparent liquid.The transparent liquid is heated and then cooled to room temperature to obtain room temperature phosphorescent material.Room temperature phosphorescent material is continuously red-shifted from 464nm to 553nm and phosphorescent color is continuously transitioned from blue to orange when excitation light wavelength increases from 254nm to 520nm.Room temperature phosphorescent material prepared by the present application can change its phosphorescent color based on adjusting excitation light wavelength, and through the special response relationship between excitation light wavelength and phosphorescent color, it can be used as dynamic anti-counterfeiting material.

Description

Technical Field

[0001] This invention relates to the field of phosphorescent materials technology, specifically to a room-temperature phosphorescent material with tunable color, its preparation method, and its application. Background Technology

[0002] Room-temperature phosphorescence (RTP) materials have significant advantages over fluorescent materials in areas such as next-generation optoelectronic devices, time-resolved bioimaging, and multimodal anti-counterfeiting, and have attracted considerable attention in recent years. Traditional organic RTP materials are synthesized by creating specific structures, such as molecular clusters and host-guest systems, or by adding special photogroups, including heavy halogens and aromatic aldehydes. However, most of these RTP materials suffer from limitations such as short afterglow lifetime, poor photostability, and complex synthesis processes, which greatly restrict their practical applications. Furthermore, most existing pure organic phosphorescent materials require relatively complex synthesis processes and exhibit limited room-temperature phosphorescence colors, further limiting their applications. Summary of the Invention

[0003] To address the technical problems of complex preparation processes and limited color options in existing room-temperature phosphorescent materials, this invention provides a room-temperature phosphorescent material with adjustable color, its preparation method, and its applications.

[0004] This invention employs the following technical solution: a method for preparing a color-tunable room-temperature phosphorescent material, comprising: adding carbon black particles to nitric acid at a mass-to-volume ratio of 0.1 g:25 mL for reflux reaction, and sequentially cooling and centrifuging after the reflux reaction. Collecting the supernatant after centrifugation and evaporating it to dryness to obtain carbon dots containing carboxyl groups on the surface. Mixing the carbon dots and boric acid at a mass ratio of 1-4:80, and then dispersing them evenly in deionized water at a mass-to-volume ratio of 1 g:20 mL to obtain a transparent liquid. Heating the transparent liquid and then cooling it to room temperature yields the color-tunable room-temperature phosphorescent material. When the excitation wavelength of the prepared room-temperature phosphorescent material increases from 254 nm to 520 nm, its phosphorescence emission peak position continuously red-shifts from 464 nm to 553 nm, and the phosphorescence color continuously transitions from blue to orange.

[0005] As a further improvement of the present invention, the room temperature phosphorescent material exhibits the following phosphorescence colors: blue when the excitation wavelength range is 254nm to 290nm; green when the excitation wavelength range is 290nm to 365nm; yellow-green when the excitation wavelength range is 365nm to 405nm; yellow when the excitation wavelength range is 405nm to 420nm; and orange when the excitation wavelength range is 420nm to 440nm.

[0006] As a further improvement of the present invention, the concentration of nitric acid is 6 mol / L.

[0007] As a further improvement of the present invention, the reflux reaction time is 24 to 28 hours.

[0008] As a further improvement of the present invention, the temperature range during the evaporation process is 150~200℃.

[0009] As a further improvement of the present invention, the temperature of the heating reaction is 150℃~200℃, and the heating time is 2~10 hours.

[0010] As a further improvement of the present invention, the carbon dots are reddish-brown solids.

[0011] As a further improvement of the present invention, the device used for heating the reaction is an oven; the operation of heating the transparent liquid in the oven is as follows: first place the transparent liquid in a beaker and cover the beaker with aluminum foil, then place the beaker in the oven and adjust the oven temperature to 180°C for 5 hours.

[0012] The present invention also includes a color-tunable room temperature phosphorescent material, which is prepared by the method described above for preparing color-tunable room temperature phosphorescent materials.

[0013] As a further improvement of the present invention, the room temperature phosphorescent material produces visible phosphorescence when excited by sunlight.

[0014] As a further improvement of the present invention, the room temperature phosphorescent material is in an amorphous glass state, which can be ground into powder during use.

[0015] The present invention also includes the application of a room temperature phosphorescent material with adjustable color as described above in information anti-counterfeiting or multi-color display.

[0016] The technical solution provided by this invention has the following beneficial effects: (1) The method for preparing color-tunable room temperature phosphorescent materials provided by this invention uses low-cost carbon black as a precursor and boric acid as a matrix, and is prepared in a simple and easy manner. The preparation process requires only common laboratory equipment and no special equipment, making the entire process simple and easy to operate. Simultaneously, the phosphorescent color of the prepared room temperature phosphorescent material can gradually change from blue to orange under different excitation wavelengths. This allows the phosphorescent color of the prepared room temperature phosphorescent material to be changed by adjusting the excitation wavelength. Through this special response relationship between the excitation wavelength and the phosphorescent color, the room temperature phosphorescent material prepared by this method can be used as a dynamic anti-counterfeiting material. Furthermore, when applied as a dynamic anti-counterfeiting material in the field of information anti-counterfeiting, this dual anti-counterfeiting mechanism makes the anti-counterfeiting code difficult to forge, and verification can be achieved through the excitation wavelength and phosphorescent color. Therefore, when the room temperature phosphorescent material of this method is used as an anti-counterfeiting code, it can simultaneously satisfy the requirements of the anti-counterfeiting code being difficult to forge and the verification process being simple.

[0017] (2) The method for preparing room temperature phosphorescent materials with adjustable color provided by the present invention uses non-toxic and harmless raw materials with low price in the preparation process. The preparation is simple and takes a short time. After preparation, no complicated and cumbersome steps are required. It is particularly suitable for batch and low-cost preparation and is suitable for industrial-scale production and commercial application.

[0018] (3) The room-temperature phosphorescent material with adjustable color provided by this invention can produce visible phosphorescence when excited by sunlight. This gives our room-temperature phosphorescent material excellent sunlight-responsive phosphorescence characteristics, allowing it to use natural sunlight as an excitation source without the need for high-energy deep ultraviolet irradiation, thus producing clearly visible phosphorescence emission. Overcoming the limitation of traditional phosphorescent materials that can only be observed in a dark room under ultraviolet light, the room-temperature phosphorescent material of this invention can be directly observed for afterglow under natural light, making it suitable for direct application as an anti-counterfeiting material in outdoor or everyday environments. Furthermore, with the increase of the excitation wavelength, its phosphorescence emission peak exhibits a continuous redshift, enabling dynamic control of the phosphorescence color. Attached Figure Description

[0019] Figure 1 The present invention provides a flowchart of the preparation method of a room-temperature phosphorescent material with adjustable color.

[0020] Figure 2 This is a transmission electron microscope image of the room-temperature phosphorescent material prepared in Test Example 2 of the present invention.

[0021] Figure 3 The X-ray diffraction pattern is shown for the room-temperature phosphorescent material prepared in Test Example 2 of this invention.

[0022] Figure 4 The phosphorescence spectrum of the room-temperature phosphorescent material prepared in Test Example 2 of this invention is shown.

[0023] Figure 5 The above are comparison diagrams of the phosphorescence spectra of the room-temperature phosphorescent materials in the three sets of test examples 2, 4 and 5 of this invention.

[0024] Figure 6 This is a comparison chart of the phosphorescence lifetime of the room-temperature phosphorescent materials in the three sets of test examples 2, 4 and 5 of this invention.

[0025] Figure 7 The phosphorescence spectra of the room-temperature phosphorescent materials prepared by the three schemes of Test Example 2, Test Example 6 and Test Example 7 of this invention are compared.

[0026] Figure 8 This is a comparison chart of the phosphorescence lifetime of the room-temperature phosphorescent materials prepared by the three schemes of Test Example 2, Test Example 6 and Test Example 7 of the present invention.

[0027] Figure 9 This is a comparison of the phosphorescence spectra of the room-temperature phosphorescent materials prepared under the three schemes of Test Example 1, Test Example 2 and Test Example 3 of the present invention.

[0028] Figure 10 This is a comparison chart of the phosphorescence lifetime of the room-temperature phosphorescent materials prepared under the three schemes of Test Example 1, Test Example 2 and Test Example 3 of the present invention.

[0029] Figure 11 This is a phosphorescence lifetime curve of the room-temperature phosphorescent material prepared in Test Example 2 of the present invention.

[0030] Figure 12 This is a comparison diagram of the phosphorescence color of the room temperature phosphorescent material prepared in Test Example 2 of the present invention after being irradiated with different excitation wavelengths and then turned off.

[0031] Figure 13 This is a diagram showing the application of the room-temperature phosphorescent material prepared in Test Example 2 of the present invention in an information anti-counterfeiting demonstration experiment. Detailed Implementation

[0032] The present invention will now be further described in conjunction with specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0033] In the description of this invention, it should be noted that directional terms such as "center," "lateral," "longitudinal," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limiting the specific scope of protection of this invention. The terms "first," "second," etc., in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. The terms "comprising" and "having," and any variations thereof, in the specification and claims of this invention, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or devices.

[0034] This embodiment provides a color-tunable room-temperature phosphorescent material (referred to as C-CDs@BA), whose raw materials include carbon black particles, nitric acid, boric acid (BA), and deionized water. Please refer to... Figure 1 As shown, the preparation process of room temperature phosphorescent materials is as follows: (a) Preparation of carbon dots Carbon black particles are added to nitric acid and refluxed for 24 hours. After the reflux reaction is completed, the mixture is cooled and centrifuged. The reddish-brown supernatant is collected and evaporated to dryness at 150-200℃ to obtain reddish-brown carbon dots (C-CDs) with many carboxyl groups on their surface.

[0035] The mass-to-volume ratio of carbon black particles to nitric acid can be 0.1g to 25mL, and the concentration of nitric acid can be 6mol / L.

[0036] (II) Preparation of room temperature phosphorescent materials Carbon dots (C-CDs) and boric acid (BA) are mixed uniformly at a mass ratio of 1-4:80, and then dispersed uniformly in deionized water at a mass-to-volume ratio of 1g:20mL to obtain a transparent liquid. The transparent liquid is heated and then cooled to room temperature to obtain a room-temperature phosphorescent material with tunable color (C-CDs@BA). The obtained room-temperature phosphorescent material is in an amorphous glassy state and can be ground into powder before use. In this method, the rigid framework of boric acid effectively suppresses the movement of carbon dot molecules and inhibits the depletion of non-radiative energy, thereby significantly improving the stability of phosphorescence emission. Simultaneously, the continuously distributed energy level structure of the carbon dots endows the room-temperature phosphorescent material with wavelength-dependent continuous redshift phosphorescence characteristics, and the material can be excited by sunlight.

[0037] The heating reaction can be performed using an oven, with a temperature of 160-200℃ and a reaction time of 2-10 hours. The specific operation is as follows: first, place the transparent liquid in a beaker and cover it with aluminum foil. Then, place the beaker in an oven and adjust the oven temperature to 180℃ for 5 hours. Covering the beaker with aluminum foil prevents excessive water evaporation. It is understandable that in practical applications, if the amount of transparent liquid is large, other commonly available large-capacity heating devices can be used, and the beaker can be replaced with a larger-capacity container that can be placed in the heating device for heating.

[0038] Since the reflux reaction, cooling, centrifugation, and heating reactions in this scheme are all routine operations, these operations and the specific equipment involved will not be described in detail. The main purpose of this scheme is to prepare room temperature phosphorescent materials using the specific raw materials described above in a specific ratio and through common operations. Because the preparation process described above is very simple, the preparation process of the color-tunable room temperature phosphorescent material provided by this scheme is simple, effectively solving the technical problem of cumbersome preparation processes in existing room temperature phosphorescent materials, and facilitating the promotion and production of the room temperature phosphorescent materials of this scheme in practical applications.

[0039] The specific mechanism by which the room-temperature phosphorescent material formed by combining carbon dots with boric acid exhibits tunable color is as follows: Under ultraviolet light excitation, electrons of carbon dots containing carboxyl groups on their surface absorb energy and transition from the ground state (S0) to the excited singlet state (S1). Since the S1 state electrons are unstable, some return to S0 via radiative transitions, producing yellow fluorescence; others dissipate energy through non-radiative pathways such as vibration and rotation, returning to the ground state. Although some electrons successfully transition to the triplet state (T1) via the ISC process, the chromophores on the carbon dot surface are easily quenched by oxygen in the air, causing the triplet excitons to return to S0 via non-radiative relaxation, thus resulting in no phosphorescence emission. However, in our scheme, by embedding the carbon dots into boric acid through the CB covalent bond, the rigid structure of boric acid effectively suppresses the intramolecular rotation and vibration of the carbon dots, significantly suppressing the non-radiative transition from T1 to S0. Combined with the dense band structure of the carbon dots themselves, this scheme's room-temperature phosphorescent material exhibits unique wavelength-dependent excitation light emission behavior.

[0040] This method leverages the excellent photophysical properties of carbon dots, embedding them tightly within a boric acid matrix as luminescent centers. Boric acid possesses a polycrystalline network structure, providing highly rigid three-dimensional spatial confinement to the embedded carbon dots. This restricts the stretching, rotation, and other movements of the carbon dot molecular structure, effectively suppressing nonradiative T1 transitions and stabilizing the triplet excited states of the carbon dots. Furthermore, the polycrystalline network structure of boric acid effectively isolates environmental quenchers, protecting the phosphorescence properties of the carbon dots. The resulting room-temperature phosphorescent material exhibits excitation-dependent phosphorescence emission characteristics within the excitation wavelength range of 254 nm to 520 nm, with the phosphorescence emission peak continuously red-shifting with increasing excitation wavelength. When the excitation wavelength increases from 254 nm to 520 nm, the phosphorescence emission peak continuously red-shifts from 464 nm to 553 nm, and the phosphorescence color continuously transitions from blue to orange. Specifically, the resulting room-temperature phosphorescent material exhibits a blue phosphorescence color within the excitation wavelength range of 254 nm to 290 nm. Room-temperature phosphorescent materials exhibit a green phosphorescence color when the excitation wavelength range is 290nm–365nm. When the excitation wavelength range is 365nm–405nm, the phosphorescence color is yellowish-green. When the excitation wavelength range is 405nm–420nm, the phosphorescence color is yellow. When the excitation wavelength range is 420nm–440nm, the phosphorescence color is orange. It can be understood that the phosphorescence color of the room-temperature phosphorescent material provided in this solution changes with the excitation wavelength. Furthermore, if the excitation wavelength gradually increases from 254nm, the phosphorescence color gradually changes from blue to orange, and this gradual increase in wavelength results in a gradual change in phosphorescence color. Because the phosphorescence color of the room-temperature phosphorescent material based on this solution can change with the excitation wavelength, it can be used as a dynamic anti-counterfeiting label or a multi-level encryption key. This principle of changing color response based on excitation wavelength effectively enhances anti-counterfeiting security.

[0041] In this scheme, the prepared room-temperature phosphorescent material can produce visible phosphorescence under sunlight excitation. This gives our room-temperature phosphorescent material excellent sunlight-responsive phosphorescence characteristics, allowing the use of natural sunlight as an excitation source without the need for high-energy deep ultraviolet irradiation, producing clearly discernible phosphorescence emission. Overcoming the limitation of traditional phosphorescent materials that can only be observed in a dark room under ultraviolet light, the room-temperature phosphorescent material of this scheme allows for direct observation of afterglow under natural light, making it suitable for direct application as an anti-counterfeiting material in outdoor or everyday environments. Furthermore, with increasing excitation wavelength, the phosphorescence emission peak exhibits a continuous redshift, enabling dynamic control of the phosphorescence color.

[0042] The above preparation method can produce room-temperature phosphorescent materials with tunable colors. Because the color of the prepared room-temperature phosphorescent material is tunable and the color change responds to changes in the excitation wavelength, this method allows the room-temperature phosphorescent material to be applied in the fields of information anti-counterfeiting technology or multi-color display technology. In the field of information anti-counterfeiting technology, the room-temperature phosphorescent material prepared in this method can achieve dynamic anti-counterfeiting through a dual anti-counterfeiting mechanism based on a dynamic code of one-to-one correspondence between the excitation wavelength and the phosphorescent color response, thereby improving the security of anti-counterfeiting. Furthermore, when applied as a dynamic anti-counterfeiting material in the field of information anti-counterfeiting, this dual anti-counterfeiting mechanism makes the anti-counterfeiting code difficult to forge, and verification can be achieved through the excitation wavelength and phosphorescent color. Therefore, when using the room-temperature phosphorescent material of this method as an anti-counterfeiting code, it can simultaneously satisfy the requirements of difficult-to-forge anti-counterfeiting code and simple verification process. In the field of multicolor display technology, the room-temperature phosphorescent material of this solution can achieve phosphorescence color changes of blue, green, yellow-green, yellow, and orange simply by changing the excitation wavelength. It enables multicolor emission using a single-structure room-temperature phosphorescent material, overcoming the shortcomings of existing technologies that require the combination of multiple luminescent materials, pixel array color matching, and complex processes. Furthermore, the room-temperature phosphorescent material of this solution allows for the following operation: by fabricating the same pattern or sign using the room-temperature phosphorescent material, the emission color of the pattern or sign can be changed simply by switching the excitation wavelength during actual use. This makes it applicable to dynamic signs in shopping malls, color-changing display screens in subways or other transportation systems, etc.

[0043] Performance testing To verify the performance of the color-tunable room temperature phosphorescent material provided in this embodiment, the following performance study experiments were also conducted.

[0044] Test Example 1 First, weigh 0.2 g of carbon black granules and add them to 50 mL of 6 mol / L nitric acid under stirring. Then, reflux the mixture for 24 hours. After the reflux reaction is complete, cool the mixture to room temperature, centrifuge it, and collect the reddish-brown supernatant. Dry the supernatant at 180 °C to obtain a reddish-brown solid, i.e., carbon dots.

[0045] Weigh 25 mg of the carbon dots and 2 g of boric acid obtained above; add the weighed carbon dots and boric acid to 40 mL of deionized water and mix well to obtain a reddish-brown solution. Place the obtained reddish-brown solution in a beaker and cover the beaker with aluminum foil to prevent water from evaporating too quickly. Then place the beaker in an oven at 180°C for 5 hours and finally cool it naturally to room temperature to obtain an amorphous glassy room-temperature phosphorescent material.

[0046] Test Example 2 First, weigh 0.2 g of carbon black granules and add them to 50 mL of 6 mol / L nitric acid under stirring. Then, reflux the mixture for 24 hours. After the reflux reaction is complete, cool the mixture to room temperature, centrifuge it, and collect the reddish-brown supernatant. Dry the supernatant at 180 °C to obtain a reddish-brown solid, i.e., carbon dots.

[0047] Weigh 50 mg of the prepared carbon dots and 2 g of boric acid. Add the weighed carbon dots and boric acid to 40 mL of deionized water and mix well to obtain a reddish-brown solution. Place the obtained reddish-brown solution in a beaker and cover the beaker with aluminum foil to prevent water from evaporating too quickly. Then place the beaker in an oven at 180°C for 5 hours and let it cool naturally to room temperature to obtain an amorphous glassy room-temperature phosphorescent material.

[0048] Test Example 3 First, weigh 0.2 g of carbon black granules and add them to 50 mL of 6 mol / L nitric acid under stirring. Then, reflux the mixture for 24 hours. After the reflux reaction is complete, cool the mixture to room temperature, centrifuge it, and collect the reddish-brown supernatant. Dry the supernatant at 180 °C to obtain a reddish-brown solid, i.e., carbon dots.

[0049] Weigh 100 mg of the carbon dots and 2 g of boric acid obtained above; add the weighed carbon dots and boric acid to 40 mL of deionized water and mix well to obtain a reddish-brown solution. Place the obtained reddish-brown solution in a beaker and cover the beaker with aluminum foil to prevent water from evaporating too quickly. Then place the beaker in an oven at 180°C for 5 hours and finally cool it naturally to room temperature to obtain an amorphous glassy room-temperature phosphorescent material.

[0050] Test Example 4 First, weigh 0.2 g of carbon black granules and add them to 50 mL of 6 mol / L nitric acid under stirring. Then, reflux the mixture for 24 hours. After the reflux reaction is complete, cool the mixture to room temperature, centrifuge it, and collect the reddish-brown supernatant. Dry the supernatant at 180 °C to obtain a reddish-brown solid, i.e., carbon dots.

[0051] Weigh 50 mg of the prepared carbon dots and 2 g of boric acid. Add the weighed carbon dots and boric acid to 40 mL of deionized water and mix well to obtain a reddish-brown solution. Place the obtained reddish-brown solution in a beaker and cover the beaker with aluminum foil to prevent water from evaporating too quickly. Then place the beaker in an oven at 150°C for 5 hours and finally allow it to cool naturally to room temperature to obtain an amorphous glassy room-temperature phosphorescent material.

[0052] Test Example 5 First, weigh 0.2 g of carbon black granules and add them to 50 mL of 6 mol / L nitric acid under stirring. Then, reflux the mixture for 24 hours. After the reflux reaction is complete, cool the mixture to room temperature, centrifuge it, and collect the reddish-brown supernatant. Dry the supernatant at 180 °C to obtain a reddish-brown solid, i.e., carbon dots.

[0053] Weigh 50 mg of the prepared carbon dots and 2 g of boric acid; add the weighed carbon dots and boric acid to 40 mL of deionized water and mix well to obtain a reddish-brown solution. Place the obtained reddish-brown solution in a beaker and cover the beaker with aluminum foil to prevent water from evaporating too quickly. Then place the beaker in an oven at 200°C for 5 hours and finally cool it naturally to room temperature to obtain an amorphous glassy room-temperature phosphorescent material.

[0054] Test Example 6 First, weigh 0.2 g of carbon black granules and add them to 50 mL of 6 mol / L nitric acid under stirring. Then, reflux the mixture for 24 hours. After the reflux reaction is complete, cool the mixture to room temperature, centrifuge it, and collect the reddish-brown supernatant. Dry the supernatant at 180 °C to obtain a reddish-brown solid, i.e., carbon dots.

[0055] Weigh 50 mg of the prepared carbon dots and 2 g of boric acid. Add the weighed carbon dots and boric acid to 40 mL of deionized water and mix well to obtain a reddish-brown solution. Place the obtained reddish-brown solution in a beaker and cover the beaker with aluminum foil to prevent water from evaporating too quickly. Then place the beaker in an oven at 180°C and react for 2 hours. Finally, allow it to cool naturally to room temperature to obtain an amorphous glassy room-temperature phosphorescent material.

[0056] Test Example 7 First, weigh 0.2 g of carbon black granules and add them to 50 mL of 6 mol / L nitric acid under stirring. Then, reflux the mixture for 24 hours. After the reflux reaction is complete, cool the mixture to room temperature, centrifuge it, and collect the reddish-brown supernatant. Dry the supernatant at 180 °C to obtain a reddish-brown solid, i.e., carbon dots.

[0057] Weigh 50 mg of the prepared carbon dots and 2 g of boric acid. Add the weighed carbon dots and boric acid to 40 mL of deionized water and mix well to obtain a reddish-brown solution. Place the obtained reddish-brown solution in a beaker and cover the beaker with aluminum foil to prevent water from evaporating too quickly. Then place the beaker in an oven at 180°C for 10 hours and finally allow it to cool naturally to room temperature to obtain an amorphous glassy room-temperature phosphorescent material.

[0058] (I) Transmission electron microscopy (TEM) analysis The room-temperature phosphorescent material prepared in Test Example 2 was ground into powder and analyzed under a transmission electron microscope to obtain... Figure 2 . Figure 2The transmission electron microscope (TEM) image of the room-temperature phosphorescent material prepared in Test Example 2 is obtained by analyzing... Figure 2 Analysis revealed that the carbon dots in the room-temperature phosphorescent material are spherical particles with good dispersion.

[0059] (II) X-ray diffraction analysis The room-temperature phosphorescent material prepared in Test Example 2 was ground into powder and analyzed under an X-ray diffractometer to obtain... Figure 3 . Figure 3 The X-ray diffraction pattern of the room-temperature phosphorescent material prepared in Test Example 2 was obtained by analyzing... Figure 3 Analysis revealed that the room-temperature phosphorescent material of Test Example 2 exhibited significantly identical characteristic peaks to molten boric acid at 2θ = 14.56°, 23.2°, 27.96°, and 43.4°. This indicates that the carbon dots and boric acid were successfully composited, meaning that the carbon dots were embedded in the boric acid matrix.

[0060] (III) Phosphorescence Spectroscopy Analysis The room-temperature phosphorescent material prepared in Test Example 2 was ground into powder and analyzed using an ultrafast time-resolved fluorescence spectrometer. Figure 4 . Figure 4 The phosphorescence spectrum of the room-temperature phosphorescent material prepared in Test Example 2 was obtained by... Figure 4 Analysis shows that when the excitation wavelength changes from 290 nm to 460 nm, the emission peak of the room-temperature phosphorescent material shifts from about 460 nm to 575 nm. This indicates that the room-temperature phosphorescent material prepared in Test Example 2 exhibits excitation-dependent phosphorescence emission characteristics, and the phosphorescence emission peak position continuously redshifts with the increase of the excitation wavelength.

[0061] (IV) Investigating the effect of heating temperature on heating reactions To determine the optimal heating temperature for the heating reaction between carbon dots and boric acid during the preparation of room-temperature phosphorescent materials, this study also investigated the performance of room-temperature phosphorescent materials prepared under three sets of methods: Test Example 2, Test Example 4, and Test Example 5. The purpose of selecting these three sets of room-temperature phosphorescent materials was to examine the effects of heating temperatures of 150℃, 180℃, and 200℃ on the performance of the prepared room-temperature phosphorescent materials, under the conditions of a fixed heating reaction time of 5 h and a carbon dot dosage of 50 mg. The three sets of room-temperature phosphorescent materials were ground into powder, and their corresponding phosphorescence spectra and phosphorescence lifetimes were obtained using an ultrafast time-resolved fluorescence spectrometer. Figure 5 The phosphorescence spectra of the room-temperature phosphorescent materials in the three test examples 2, 4 and 5 are compared. Figure 6 This is a comparison of the phosphorescence lifetime of the room-temperature phosphorescent materials in Test Example 2, Test Example 4, and Test Example 5. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) Figure 5 and Figure 6Analysis shows that the phosphorescence intensity is strongest and the phosphorescence lifetime reaches its maximum when the heating reaction temperature is 180℃. Therefore, it can be determined that the optimal temperature for the heating reaction between carbon dots and boric acid is 180℃.

[0062] (V) Investigating the effect of heating time on the heating reaction To determine the optimal heating time for the heating reaction between carbon dots and boric acid during the preparation of room-temperature phosphorescent materials, this study also investigated the performance of room-temperature phosphorescent materials prepared under three sets of methods: Test Example 2, Test Example 6, and Test Example 7. The purpose of selecting these three sets of room-temperature phosphorescent materials was to examine the effects of heating times of 2 h, 5 h, and 10 h on the performance of the prepared room-temperature phosphorescent materials, under the condition of a fixed heating reaction temperature of 180 °C and a carbon dot dosage of 50 mg. The three sets of room-temperature phosphorescent materials were ground into powder, and their corresponding phosphorescence spectra and phosphorescence lifetimes were obtained using an ultrafast time-resolved fluorescence spectrometer. Figure 7 The image shows a comparison of the phosphorescence spectra of the room-temperature phosphorescent materials prepared under the three test schemes: Test Example 2, Test Example 6, and Test Example 7. Figure 8 This is a comparison of the phosphorescence lifetimes of the room-temperature phosphorescent materials prepared under the three schemes of Test Example 2, Test Example 6, and Test Example 7. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) Figure 7 and Figure 8 Analysis reveals that different heating reaction times significantly affect the phosphorescence properties of room-temperature phosphorescent materials. When the heating reaction time is 5 hours, the prepared room-temperature phosphorescent material exhibits the highest phosphorescence intensity. Simultaneously, the phosphorescence lifetime curve obtained by fitting the phosphorescence decay curve also indicates that the prepared room-temperature phosphorescent material has the longest phosphorescence lifetime when the heating reaction time is 5 hours. Therefore, the optimal reaction time for the heating reaction between carbon dots and boric acid can be determined to be 5 hours.

[0063] (VI) Investigating the effect of carbon dot dosage This scheme also investigates the phosphorescence properties of room-temperature phosphorescent materials prepared under three sets of schemes: Test Example 1, Test Example 2, and Test Example 3. The aim is to examine the effect of the amount of carbon dots used as a precursor on the phosphorescence properties of the prepared room-temperature phosphorescent materials, given an optimal reaction time of 5 hours. The three sets of room-temperature phosphorescent materials were ground into powder, and their corresponding phosphorescence spectra and lifetimes were obtained using an ultrafast time-resolved fluorescence spectrometer. Figure 9 The phosphorescence spectra of the room-temperature phosphorescent materials prepared under the three schemes of Test Example 1, Test Example 2 and Test Example 3 are compared. Figure 10 This is a comparison of the phosphorescence lifetimes of the room-temperature phosphorescent materials prepared under three different test schemes: Test Example 1, Test Example 2, and Test Example 3. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) Figure 9 and Figure 10Analysis shows that the amount of carbon dots used has a significant impact on the phosphorescence performance of the prepared room-temperature phosphorescent material. Figure 9 It can be seen that when the amount of carbon dots is 50 mg, the room-temperature phosphorescent material prepared exhibits the highest room-temperature phosphorescence intensity. From Figure 10 Analysis shows that when the amount of carbon dots is 50 mg, the room temperature phosphorescent material produced exhibits the longest phosphorescence lifetime, which proves that 50 mg of carbon dots is the optimal match between carbon dots and boric acid.

[0064] (VII) Phosphorescence lifetime decay analysis The room-temperature phosphorescent material prepared in Test Example 2 was ground into powder. Using an ultrafast time-resolved fluorescence spectrometer with a fixed excitation wavelength of 365 nm, the room-temperature phosphorescent material of Test Example 2 was excited by a pulsed laser. The dynamic change of phosphorescence emission intensity over time was monitored in real time. The signal was collected and subjected to exponential fitting to obtain the phosphorescence lifetime decay curve. Figure 11 .from Figure 11 It can be seen that the time-resolved decay spectrum of the room-temperature phosphorescent material in Test Example 2 was fitted using a triple exponential function, and the phosphorescence lifetime was calculated to be approximately 714 ms based on the existing phosphorescence lifetime calculation formula: In the phosphorescence lifetime calculation formula, represents the lifetime of the i-th decaying component. is the pre-exponential factor for the corresponding component, i.e., the initial amplitude, reflecting the intensity proportion of that component. is the weighted average phosphorescence lifetime, which reflects the overall average behavior of signal intensity decay over time. The phosphorescence lifetime of common room-temperature phosphorescent materials is approximately 130 ms to 540 ms, thus demonstrating that the room-temperature phosphorescent material prepared in Test Example 2 possesses excellent phosphorescence lifetime.

[0065] (VIII) Phosphorescence color analysis under different excitation wavelengths The test example was prepared by grinding the room-temperature phosphorescent material obtained in Test Example 2 into powder. Ultrafast time-resolved fluorescence spectroscopy was used to obtain the phosphorescence color maps of Test Example 2 after irradiation with different excitation wavelengths and subsequent irradiation. Figure 12 . Figure 12 This is a comparison of the phosphorescence colors of the room-temperature phosphorescent material prepared in Test Example 2 after irradiation with different excitation wavelengths and subsequent shutdown. This was achieved through... Figure 12Analysis shows that the room-temperature phosphorescent material in Test Example 2 exhibits a blue phosphorescence color after being irradiated with a 254nm excitation wavelength and then turned off, lasting approximately 1 second; a green phosphorescence color after being irradiated with a 365nm excitation wavelength and then turned off, lasting approximately 6 seconds; a yellowish-green phosphorescence color after being irradiated with a 405nm excitation wavelength and then turned off, lasting approximately 3 seconds; a yellow phosphorescence color after being irradiated with a 420nm excitation wavelength and then turned off, lasting approximately 2 seconds; and an orange phosphorescence color after being irradiated with a 440nm excitation wavelength and then turned off, lasting approximately 1.5 seconds. It also exhibits visible phosphorescence after being irradiated with sunlight and then turned off, lasting approximately 1.5 seconds. As described above, the room-temperature phosphorescent material in Test Example 2 exhibits a significant change in phosphorescence color with varying excitation wavelengths. This demonstrates that the room-temperature phosphorescent material provided by this solution possesses the advantage of multicolor emission, and its color change depends on the change in excitation wavelength. Based on the one-to-one correspondence between excitation wavelength, phosphorescent color, and emission time, the room-temperature phosphorescent material of this solution can be used as a dynamic anti-counterfeiting material. When used as a dynamic anti-counterfeiting material, it has a good anti-counterfeiting effect and is not easily counterfeited, thus improving its anti-counterfeiting effectiveness. In addition, the room-temperature phosphorescent material of this solution can continue to be observed for several seconds after the excitation light source is turned off, which proves that the room-temperature phosphorescent material of this solution has long lifespan and high-intensity room-temperature phosphorescence characteristics.

[0066] (IX) Application in information anti-counterfeiting To verify the application of the room-temperature phosphorescent material provided in our solution for information anti-counterfeiting, this solution also includes a simple patterning demonstration experiment. The specific operation is as follows: The room-temperature phosphorescent material from Test Example 2 of this solution is filled into a petal pattern mold. The mold is then irradiated for several seconds under natural light, a 254nm ultraviolet lamp, a 365nm ultraviolet lamp, a 405nm ultraviolet lamp, and a 440nm ultraviolet lamp, respectively, and then the irradiation is turned off. The changes in the petal pattern during this process are observed. Figure 13 . Figure 13 This image shows the application of the room-temperature phosphorescent material prepared in Test Example 2 in an information anti-counterfeiting demonstration experiment. After irradiation with a 254nm UV lamp for several seconds and then turning it off, the previously hidden petal pattern appeared bright blue; after irradiation with a 365nm UV lamp for several seconds and then turning it off, the previously hidden petal pattern appeared bright green; after irradiation with a 405nm UV lamp for several seconds and then turning it off, the previously hidden petal pattern appeared yellowish-green; after irradiation with a 440nm UV lamp for several seconds and then turning it off, the previously hidden petal pattern appeared bright orange; and the phosphorescent colors of the petal pattern were clearly distinguishable after excitation with different wavelengths. This simple and easy-to-implement demonstration experiment fully demonstrates that the room-temperature phosphorescent material provided in this scheme has significant application prospects in information anti-counterfeiting.

[0067] The basic principles, main features, and advantages of this invention have been described above. Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made without departing from the spirit and scope of the invention, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection claimed by this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a room-temperature phosphorescent material with tunable color, characterized in that, It includes: Carbon black particles were added to nitric acid at a mass-to-volume ratio of 0.1 g: 25 mL and refluxed. After the reflux reaction was completed, the mixture was cooled and centrifuged. The supernatant after centrifugation was collected and evaporated to dryness to obtain carbon dots with carboxyl groups on the surface. Carbon dots and boric acid are mixed at a mass ratio of 1~4:80, and then dispersed evenly in deionized water at a mass-volume ratio of 1g:20mL to obtain a transparent liquid. A room-temperature phosphorescent material with adjustable color is obtained by heating and reacting a transparent liquid and then cooling it to room temperature. When the excitation wavelength of the prepared room-temperature phosphorescent material is increased from 254 nm to 520 nm, its phosphorescence emission peak position continuously redshifts from 464 nm to 553 nm and the phosphorescence color continuously transitions from blue to orange.

2. The method for preparing the color-tunable room-temperature phosphorescent material as described in claim 1, characterized in that, The room-temperature phosphorescent material exhibits the following phosphorescence colors: blue when the excitation wavelength range is 254 nm to 290 nm; green when the excitation wavelength range is 290 nm to 365 nm; yellow-green when the excitation wavelength range is 365 nm to 405 nm; yellow when the excitation wavelength range is 405 nm to 420 nm; and orange when the excitation wavelength range is 420 nm to 440 nm.

3. The method for preparing the color-tunable room-temperature phosphorescent material as described in claim 1, characterized in that, The concentration of the nitric acid is 6 mol / L; And / or, the reflux reaction time is 24 to 28 hours; And / or, the temperature range during the evaporation process is 150~200℃.

4. The method for preparing the color-tunable room-temperature phosphorescent material as described in claim 1, characterized in that, The heating reaction is carried out at a temperature of 150℃ to 200℃ for 2 to 10 hours.

5. The method for preparing the color-tunable room-temperature phosphorescent material as described in claim 1, characterized in that, The carbon dots are reddish-brown solids.

6. The method for preparing the color-tunable room-temperature phosphorescent material as described in claim 1, characterized in that, The device used for the heating reaction is an oven; the operation of the transparent liquid heating reaction in the oven is as follows: first place the transparent liquid in a beaker and cover the beaker with aluminum foil, then place the beaker in the oven and adjust the oven temperature to 180°C for 5 hours.

7. A color-tunable room temperature phosphorescent material, which is prepared by the method for preparing a color-tunable room temperature phosphorescent material as described in any one of claims 1-6.

8. The color-tunable room-temperature phosphorescent material as described in claim 7, characterized in that, The room-temperature phosphorescent material produces visible phosphorescence when excited by sunlight.

9. The color-tunable room-temperature phosphorescent material as described in claim 7, characterized in that, The room-temperature phosphorescent material is in an amorphous glass state and can be ground into powder during use.

10. The application of a color-tunable room-temperature phosphorescent material as described in any one of claims 7-9 in information anti-counterfeiting or multi-color display.

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