Preparation method of long-life yellow-green room-temperature phosphorescent carbon dot-silicon dioxide-aluminum oxide composite material

Abstract

The preparation method comprises the following steps: adding 2-methylimidazole, urea and aluminum isopropoxide into absolute ethyl alcohol, stirring to obtain a milky white solution, then adding solid silicon dioxide, stirring, drying, and calcining by a muffle furnace to obtain the long-life yellow-green room-temperature phosphorescent carbon dot-silicon dioxide-aluminum oxide composite material. The yellow green room temperature phosphorescent carbon dot-silicon dioxide-aluminum oxide composite material is obtained. The composite material is characterized in that the composite material is directly obtained through a one-step calcination method. Besides, a novel double-matrix structure and a nitrogen element synergistic doping strategy are used in a room-temperature phosphorescent material, so that 1.6-second long-life phosphorescence is realized, and yellow-green room-temperature phosphorescence visible to naked eyes can reach 16 seconds after an ultraviolet lamp is turned off. The medicines used for preparation are nontoxic, harmless and low in price, the preparation is simple, and the used time is short. The prepared long-life yellow-green room-temperature phosphorescent carbon dot-silicon dioxide-aluminum oxide composite material can be successfully applied to the fields of information encryption and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon dot material preparation, and in particular relates to a method for preparing a long-life yellow-green room-temperature phosphorescent carbon dot@silicon dioxide@alumina composite material. Background Art

[0002] In the research of room-temperature phosphorescent carbon dots (RTP) (Cds), color modulation is a current research focus, with the yellow-green wavelength range (approximately 500–600 nm) attracting significant attention due to its unique advantages. Yellow-green emission lies within the human visual sensitivity region, offering higher visual brightness and suitable for applications such as luminous displays and anti-counterfeiting labels. Furthermore, this wavelength range offers excellent tissue penetration and low background noise in bioimaging, holding great potential for application. However, the preparation of high-efficiency, long-lived, and color-pure yellow-green RTP Cds faces numerous challenges. Firstly, the narrow energy gap associated with yellow-green emission makes it prone to nonradiative relaxation, resulting in a short luminescence lifetime and low quantum yield. Secondly, factors such as multimodal emission and defect-state clutter within the Cd material make it difficult to effectively capture and stabilize triplet excited states. Furthermore, yellow-green RTP Cds are extremely sensitive to environmental conditions and surface state changes; improper handling can lead to phosphorescence quenching or shifts in the emission peak position. Therefore, the development of long-lived, high-brightness yellow-green RTP Cds remains a critical challenge in this field, which urgently needs to be overcome.

[0003] To solve the problems of low brightness, short lifespan and poor color purity of yellow-green room temperature phosphorescent carbon dots. The present invention adopts a dual-matrix collaborative confinement strategy. Through an organic-inorganic dual-matrix system, the molecular motion of carbon dots is doubly restricted at the physical space and molecular level, the rigid environment is enhanced, and the non-radiative relaxation of the triplet energy level is reduced, thereby significantly extending the phosphorescence lifetime. At the same time, the dual-matrix system helps to reduce the penetration of quenching factors such as oxygen, further improving the stability of room temperature phosphorescence. In addition, this paper adopts a combined strategy of N self-doping and exogenous N doping to regulate the energy level. N self-doping comes from the skeleton nitrogen source in 2-methylimidazole, which helps to form a stable triplet excited state. Exogenous N doping further regulates the surface state and electronic energy level structure of the carbon dots, promotes the intersystem crossing process, and improves the triplet generation efficiency. The present invention, through the combined strategy of dual-matrix confinement and N self-doping and exogenous N doping, not only helps to improve the triplet capture efficiency of carbon dots, but also effectively regulates their luminescence energy level, red-shifts their emission wavelength to the yellow-green region, while significantly improving the phosphorescence lifetime and luminescence intensity. Therefore, this synergistic regulation mechanism provides a feasible and effective material design method for achieving high efficiency, long life, and excellent color purity yellow-green room temperature phosphorescent carbon dots. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention provides a long-life yellow-green room temperature phosphorescent carbon dot@silicon dioxide@alumina composite material and a preparation method thereof.

[0005] One of the objectives of the present invention is to provide a novel matrix structure.

[0006] A second object of the present invention is to provide a new nitrogen doping strategy.

[0007] A third object of the present invention is to provide a long-life yellow-green room temperature phosphorescent carbon dot@silica@alumina composite material.

[0008] The long-life yellow-green room-temperature phosphorescent carbon dot@silica@alumina composite material prepared by the present invention is prepared using 2-methylimidazole, urea, aluminum isopropoxide, ethanol and solid silica as raw materials through a one-step calcination method. The preparation process includes the following specific steps: 1. First, dissolve 0.02-0.1 g of 2-methylimidazole, 0-0.1 g of urea, and 0.1-0.4 g of aluminum isopropoxide in 1 mL of anhydrous ethanol and stir to obtain a milky white solution. 2. Add 0.1-0.7 g of solid silica to the white solution obtained in step 1 and stir evenly to obtain a milky white precipitate; 3. Dry the milky white precipitate obtained in step 2 in an oven at 60°C for 12-24 hours to obtain a white solid; 4. The white solid obtained in step 3 was placed in a crucible with a lid and calcined in a muffle furnace at 400-700° C. for 2 hours to obtain a yellow-green room temperature phosphorescent carbon dot@silica@alumina composite material.

[0009] Beneficial effects of the present invention: 1. The present invention provides a method for preparing a long-life yellow-green room-temperature phosphorescent carbon dot@silica@alumina composite material, which is characterized by using 2-methylimidazole, urea, aluminum isopropoxide, ethanol and solid silica as raw materials and preparing it through a one-step calcination method. The raw material cost is low, only common laboratory equipment is required, and no special equipment is required. The preparation process is simple to operate; 2. This method synthesized a molecule with a dual-matrix structure and, through a nitrogen co-doping strategy, prepared a long-life yellow-green room-temperature phosphorescent carbon dot@silica@alumina composite material, achieving a red shift in room-temperature phosphorescence emission; 3. The long-life yellow-green room-temperature phosphorescent carbon dot@silica@alumina composite material obtained by this method has a phosphorescence lifetime of 1.6 seconds. After turning off the UV light, the bright yellow-green afterglow visible to the naked eye lasts for up to 16 seconds. 4. The drug used in this invention is green, safe, inexpensive, and has a simple and rapid preparation and operation process, without requiring any subsequent complex processing. Therefore, this preparation process has excellent scalability and cost-effectiveness, demonstrating significant industrial compatibility and commercial potential. 5. The long-life yellow-green room-temperature phosphorescent carbon dot@silicon dioxide@aluminum oxide composite material provided by the present invention can be used for information protection and encryption. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction to the drawings will be given below in the description of the embodiments or the prior art. However, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0011] Figure 1 Transmission electron microscopy and high-resolution transmission electron microscopy of the long-life yellow-green room-temperature phosphorescent carbon dot@silica@alumina composite material prepared in Example 1 of the present invention.

[0012] Figure 2 This is the X-ray diffraction pattern of the long-life yellow-green room-temperature phosphorescent carbon dot@silica@alumina composite material prepared in Example 1 of the present invention.

[0013] Figure 3 This is a phosphorescence spectrum of the long-life yellow-green room-temperature phosphorescent carbon dot@silica@alumina composite material prepared in Example 1 of the present invention.

[0014] Figure 4 This is a phosphorescence lifetime diagram of the long-life yellow-green room-temperature phosphorescent carbon dot@silica@alumina composite material prepared in Example 1 of the present invention.

[0015] Figure 5 Graphs showing the yellow-green room temperature phosphorescent carbon dot@silica@alumina composite materials prepared in Examples 1-3 and Comparative Examples 1-2 under 365 nm ultraviolet light irradiation and after the light is turned off.

[0016] Figure 6 This is a photo of the application of the long-life yellow-green room-temperature phosphorescent carbon dot@silicon dioxide@alumina composite material prepared in Example 1 of the present invention in information encryption. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0019] Unless otherwise specified, the experimental methods described in the following examples are all conventional methods; the reagents and materials described are all commercially available unless otherwise specified.

[0020] Example 1: First, 0.05 g of 2-methylimidazole, 0.05 g of urea, and 0.2 g of aluminum isopropoxide were weighed and dissolved in 1 mL of anhydrous ethanol and ultrasonically stirred to obtain a milky white solution. Then, 0.3 g of solid silica was weighed and added to the above solution and ultrasonic stirring was continued. The white solution and white precipitate were placed in a 60°C oven and dried for 24 hours to obtain a white solid. The white solid was placed in a covered crucible and calcined at 600°C in a muffle furnace for 2 hours to obtain a long-life yellow-green room-temperature phosphorescent carbon dot@silica@alumina composite material.

[0021] Example 2: First, about 0.02 g of 2-methylimidazole and 0.1 g of aluminum isopropoxide were weighed and dissolved in 1 mL of anhydrous ethanol and ultrasonically stirred to obtain a milky white solution. Then, 0.1 g of solid silica was weighed and added to the above solution and ultrasonic stirring was continued. The white solution and white precipitate were placed in a 60°C oven and dried for 12 hours to obtain a white solid. The white solid was placed in a covered crucible and calcined at 400°C in a muffle furnace for 2 hours to obtain a yellow-green room-temperature phosphorescent carbon dot@silica@alumina composite material.

[0022] Example 3: First, 0.1 g of 2-methylimidazole, 0.1 g of urea, and 0.4 g of aluminum isopropoxide were weighed and dissolved in 1 mL of anhydrous ethanol and ultrasonically stirred to obtain a milky white solution. Then, 0.7 g of solid silica was weighed and added to the above solution, and ultrasonic stirring was continued. The white solution and white precipitate were placed in an 80°C oven and dried for 24 hours to obtain a white solid. The white solid was placed in a covered crucible and calcined at 700°C in a muffle furnace for 2 hours to obtain a yellow-green room-temperature phosphorescent carbon dot@silica@alumina composite material.

[0023] Comparative Example 1: First, 0.05 g of 2-methylimidazole, 0.05 g of urea, and 0.2 g of aluminum isopropoxide were weighed and dissolved in 1 mL of anhydrous ethanol and ultrasonically stirred to obtain a milky white solution. The above solution was placed in a 60°C oven and dried for 24 hours to obtain a white solid. The white solid was placed in a covered crucible and calcined at 600°C in a muffle furnace for 2 hours to obtain a yellow-green room-temperature phosphorescent carbon dot@alumina composite material.

[0024] Comparative Example 2: First, 0.05 g of 2-methylimidazole, 0.05 g of urea, and 0.3 g of solid silica were weighed and dissolved in 1 mL of anhydrous ethanol and ultrasonically stirred to obtain a milky white solution. The above solution was placed in a 60°C oven and dried for 24 hours to obtain a white solid. The white solid was placed in a covered crucible and calcined at 600°C in a muffle furnace for 2 hours to obtain a yellow-green room-temperature phosphorescent carbon dot@silica composite material.

[0025] Figure 1 Transmission electron microscopy and high-resolution transmission electron microscopy of the long-life yellow-green room temperature phosphorescent carbon dot@silicon dioxide@alumina composite material prepared in Example 1. Figure 1 It can be seen from the figure that the carbon dots generated by 2-methylimidazole are evenly distributed in the silica and alumina dual matrices.

[0026] Figure 2 This is the X-ray diffraction pattern of the long-life yellow-green room temperature phosphorescent carbon dot@silicon dioxide@alumina composite material prepared in Example 1. Figure 2 It can be seen that the diffraction peak at 21° is consistent with the characteristic peak of amorphous SiO2, and the broad reflections around 42° and 63° are typical amorphous aluminum oxide structures.

[0027] Figure 3 This is the phosphorescence spectrum of the long-life yellow-green room temperature phosphorescent carbon dot@silicon dioxide@alumina composite material prepared in Example 1. Figure 3 As can be seen in Figure 3, upon excitation at 365 nm, phosphorescence is detected with an emission band centered around 537 nm.

[0028] Figure 4 This is the phosphorescence lifetime diagram of the long-life yellow-green room temperature phosphorescent carbon dot@silicon dioxide@alumina composite material prepared in Example 1. Figure 4 It can be seen that the time-resolved decay spectrum is fitted with a three-exponential function according to the following formula: avg =∑α i τ i 2 / ∑α i τ i The phosphorescence lifetime was calculated to be 1.6 s at room temperature.

[0029] Figure 5 The yellow-green room temperature phosphorescent carbon dot@silica@alumina composite material prepared in Example 1-3 and Comparative Example 1-2 is shown under 365 nm ultraviolet light and after the light is turned off. Figure 5 It can be seen that Example 1 exhibits the longest visible time to the naked eye, which is as long as 16 seconds. The yellow-green room temperature phosphorescent carbon dot@silica@alumina composite materials prepared in other Examples 2-3 and Comparative Examples 1-2 have relatively short visible time to the naked eye.

[0030] Figure 6 This is a photo of the application of the long-life yellow-green room temperature phosphorescent carbon dot@silicon dioxide@alumina composite material prepared in Example 1 in information encryption and anti-counterfeiting. Figure 6 It can be seen that under 365 nm ultraviolet light, “I The results show that the prepared long-life yellow-green room-temperature phosphorescent carbon dots@silica@alumina phosphor powder can be successfully used in time encryption anti-counterfeiting applications.

[0031] Obviously, those skilled in the art may make various modifications and variations to the long-life yellow-green room-temperature phosphorescent carbon dot@silica@alumina composite material and its preparation method described herein without departing from the spirit and scope of the present invention. Thus, to the extent such modifications and variations fall within the scope of the claims and their equivalents, the present invention is intended to encompass such modifications and variations.

Claims

1. A method for preparing a long-life yellow-green room temperature phosphorescent carbon dot@silicon dioxide@alumina composite material, comprising the following steps: First, weigh 0.02-0.1 g of 2-methylimidazole, 0-0.1 g of urea, and 0-0.4 g of aluminum isopropoxide and dissolve them in 1 mL of anhydrous ethanol, stirring to obtain a milky white solution; then add 0.1-0.7 g of solid silica and stir evenly to obtain a milky white precipitate; the milky white precipitate is placed in a 60°C oven and dried for 12-24 hours to obtain a white solid; the white solid is placed in a covered crucible and calcined in a muffle furnace at 400-700°C for 2 hours to obtain a dynamic yellow room temperature phosphorescent carbon dot@silica@alumina composite material.

2. The method for preparing the long-life yellow-green room temperature phosphorescent carbon dot@silicon dioxide@alumina composite material according to claim 1, characterized in that: The amount of 2-methylimidazole used was 0.05 g, and the amount of urea used was 0.05 g.

3. The method for preparing the long-life yellow-green room temperature phosphorescent carbon dot@silicon dioxide@alumina composite material according to claim 1, characterized in that: The amount of aluminum isopropoxide used was 0.3 g, and the amount of solid silica used was 0.5 g.

4. Application of the long-life yellow-green room temperature phosphorescent carbon dot@silicon dioxide@alumina composite material obtained by the preparation method according to claim 1, characterized in that: The long-life yellow-green room-temperature phosphorescent carbon dot@silicon dioxide@aluminum oxide composite material is used for information encryption.

Images