Method for realizing room-temperature phosphorescence emission of silicon dioxide microspheres through molecular doping

Abstract

The invention relates to a molecule-doped silicon dioxide microsphere and a preparation method thereof. The preparation method comprises the following steps: adding ammonia water into a mixed solution of ethanol and water, stirring TEOS, and carrying out hydrothermal treatment, centrifugation and drying to obtain white powder as a precursor; and mixing the obtained white powder with doped molecules, dispersing the mixture into water again, carrying out secondary hydrothermal treatment, centrifuging and drying to obtain the molecule doped silicon dioxide microspheres. The preparation method is characterized in that the molecule-doped silicon dioxide microspheres are obtained by a two-step hydrothermal method. Besides, the synthesized molecule-doped silicon dioxide microspheres have bright green phosphorescence and good dispersibility, the average phosphorescence lifetime of the obtained molecule-doped silicon dioxide microspheres is 0.85 s, and phosphorescence with dynamic color change from yellow to green can be seen for 10 s by naked eyes after an ultraviolet lamp is turned off. The medicines used for preparation are cheap and easy to obtain, the preparation process is simple and convenient, and complicated and tedious post-treatment steps are not needed.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of room temperature phosphorescent materials, and particularly relates to a method for preparing silica microspheres with room temperature phosphorescent emission by molecular doping. Background Art

[0002] As a typical emerging luminescent material, room temperature phosphorescent materials exhibit important application values in multiple fields such as optoelectronic devices, chemical sensing, bioimaging, and information encryption due to their advantages of large Stokes shift, high signal-to-noise ratio, long luminescence lifetime, etc. Currently, matrix assistance (such as polymers, boric acid, urea, etc.) is the main strategy to achieve room temperature phosphorescent emission of materials. The triplet excitons generated are stabilized and protected through the restrictive effects of the rigid matrix, strong covalent bonds, or hydrogen bonds formed during the synthesis process to achieve room temperature phosphorescent emission. However, these materials generally do not have specific morphologies and are difficult to surface modify, which greatly limits their potential applications. In addition, under the synthesis conditions of high temperature and high pressure, the structural integrity of room temperature phosphorescent materials is easily damaged, resulting in quenching of triplet excitons and a decrease in the room temperature phosphorescent emission efficiency.

[0003] In contrast, silica microspheres stand out due to their regular morphologies, high specific surface areas and porosities, high chemical stabilities, high temperature resistance, good biocompatibilities, and ease of surface functionalization. In addition, the rigid network structure constructed by Si-O bonds can effectively reduce the loss of triplet excitons, thereby obtaining long-lived phosphorescence. However, since traditional room temperature phosphorescent materials often have complex surface chemical structures, which can interfere with the condensation kinetics of tetraethyl orthosilicate (TEOS) and affect the formation of uniform and well-dispersed silica microspheres, the method of directly doping to obtain silica microspheres with room temperature phosphorescent emission has little effect. On the contrary, small molecule substances can not only be embedded in silica microspheres through the hydrothermal process, but also, due to their simple chemical structures, will not damage the morphology of silica microspheres. More surprisingly, appropriate doping molecules can establish a strong covalent bond or hydrogen bond crosslinking network with the silica microsphere matrix, thereby making the triplet excitons of the doping molecules more stable and realizing the room temperature phosphorescent emission of silica microspheres. Based on the above analysis, it is highly desirable to design and develop a simple and economical method to achieve the room temperature phosphorescent emission of silica microspheres through molecular doping. Summary of the Invention

[0004] In order to avoid the deficiencies of the prior art, the present invention provides a method for preparing silica microspheres with room temperature phosphorescent emission by molecular doping.

[0005] One of the purposes of the present invention is to provide a simple and feasible two-step hydrothermal method.

[0006] The second object of the present invention is to provide a silica microsphere with room temperature phosphorescence emission.

[0007] The room temperature phosphorescent silica microspheres prepared by the present invention are prepared by a two-step hydrothermal method using tetraethyl orthosilicate (TEOS), ammonia water, and glucose as raw materials. The preparation process includes the following specific steps: 1. First, add 2 - 8 mL of ammonia water to a mixed solution of 7 mL of ethanol and 2 mL of water to obtain a transparent solution; 2. Add 1 - 5 mL of TEOS to the transparent solution obtained in step 1 and stir for 6 - 24 hours to obtain a white solution; 3. Transfer the white solution obtained in step 2 to a reaction kettle lined with polytetrafluoroethylene and react at 160 - 200 °C for 12 hours to obtain a white solution; 4. Centrifuge the white solution obtained in step 3 at a speed of 8000 revolutions per minute for 5 minutes using a high-speed centrifuge, remove the supernatant in the centrifuge tube, and obtain a white precipitate; 5. Place the white precipitate obtained in step 4 in an oven at 60 - 100 °C and dry for 6 - 24 hours to obtain a white powder as a precursor; 6. Disperse 0.3 - 0.7 g of the white powder obtained in step 5 and 0.1 - 0.6 g of a doping molecule (glucose) in 10 mL of water to obtain a white solution; 7. Transfer the white solution obtained in step 6 to a reaction kettle and react at 160 - 200 °C for 1 - 5 hours to obtain a brown solution; 8. Centrifuge the brown solution obtained in step 7 at a speed of 8000 revolutions per minute for 5 minutes using a high-speed centrifuge, remove the supernatant in the centrifuge tube, and obtain a brown precipitate; 9. Place the brown precipitate obtained in step 8 in an oven at 60 - 100 °C and dry for 6 - 24 hours to obtain a molecularly doped silica composite material.

[0008] Advantages of the present invention: 1. The present invention provides a method for preparing silica microspheres with room temperature phosphorescence emission by molecular doping. The method is characterized by using TEOS, ammonia water, and glucose as raw materials and preparing them by a two-step hydrothermal method. It only requires ordinary equipment commonly used in laboratories and does not require special equipment. The process is simple and easy to operate; 2. The phosphorescence lifetime of the molecularly doped silica microspheres obtained by this method is 0.85 s, and long-lived phosphorescence lasting for 10 s can be observed with the naked eye after turning off the ultraviolet lamp; 3. The drugs used in the present invention are cheap and easily available, and the preparation process is simple. There is no need for complex and cumbersome post-treatment steps, which is particularly suitable for batch and low-cost preparation and is suitable for industrial-scale production and commercial applications. Brief Description of the Drawings

[0009] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings 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 those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0010] Figure 1 Transmission electron microscope image of the molecular-doped silica microspheres prepared in Example 1 of the present invention.

[0011] Figure 2 X-ray diffraction pattern of the molecular-doped silica microspheres prepared in Example 1 of the present invention.

[0012] Figure 3 Phosphorescence spectrum of the molecular-doped silica microspheres prepared in Example 1 of the present invention.

[0013] Figure 4 Phosphorescence lifetime diagram of the molecular-doped silica microspheres prepared in Example 1 of the present invention.

[0014] Figure 5 Diagrams of the states of the molecular-doped silica microspheres prepared in Examples 1-3 and Comparative Examples 1-2 under sunlight, under irradiation with a 365 nm ultraviolet lamp, and after the ultraviolet lamp is turned off. Detailed Description of the Embodiments

[0015] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further details the present invention in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0016] All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0017] Unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods; unless otherwise specified, the reagents and materials can all be obtained in the market.

[0018] Example 1: First, 6 mL of ammonia water was added to a mixed solution of 7 mL of ethanol and 2 mL of water. Then, 3 mL of TEOS was added and the mixture was stirred for 12 hours to obtain a white solution. The obtained solution was transferred to a reaction kettle with a polytetrafluoroethylene liner and reacted at 180 °C for 12 hours to obtain a white solution. It was centrifuged at a speed of 8000 revolutions per minute for 5 minutes using a high-speed centrifuge, and the supernatant in the centrifuge tube was removed to obtain a white precipitate. The white precipitate was dried in an oven at 80 °C for 24 hours to obtain a white powder. 0.5 g of the obtained white powder and 0.3 g of glucose were dispersed in 10 mL of water to obtain a white solution. The obtained solution was transferred to a reaction kettle with a polytetrafluoroethylene liner and reacted at 180 °C for 3 hours. It was centrifuged at a speed of 8000 revolutions per minute for 5 minutes using a high-speed centrifuge, and the supernatant in the centrifuge tube was removed to obtain a brown precipitate. The brown precipitate was dried in an oven at 80 °C for 12 hours to obtain molecularly doped silica microspheres.

[0019] Example 2: First, 2 mL of ammonia water was added to a mixed solution of 7 mL of ethanol and 2 mL of water. Then, 1 mL of TEOS was added and the mixture was stirred for 6 hours to obtain a white solution. The obtained solution was transferred to a reaction kettle with a polytetrafluoroethylene liner and reacted at 160 °C for 12 hours to obtain a white solution. It was centrifuged at a speed of 8000 revolutions per minute for 5 minutes using a high-speed centrifuge, and the supernatant in the centrifuge tube was removed to obtain a white precipitate. The white precipitate was dried in an oven at 60 °C for 24 hours to obtain a white powder. 0.3 g of the obtained white powder and 0.1 g of glucose were dispersed in 10 mL of water to obtain a white solution. The obtained solution was transferred to a reaction kettle with a polytetrafluoroethylene liner and reacted at 160 °C for 1 hour. It was centrifuged at a speed of 8000 revolutions per minute for 5 minutes using a high-speed centrifuge, and the supernatant in the centrifuge tube was removed to obtain a brown precipitate. The brown precipitate was dried in an oven at 60 °C for 24 hours to obtain molecularly doped silica microspheres.

[0020] Example 3: First, 8 mL of ammonia water was added to a mixed solution of 7 mL of ethanol and 2 mL of water. Then, 5 mL of TEOS was added and the mixture was stirred for 24 hours to obtain a white solution. The obtained solution was transferred to a reaction kettle with a polytetrafluoroethylene inner lining and reacted at 200 °C for 12 hours to obtain a white solution. It was centrifuged at a speed of 8000 revolutions per minute for 5 minutes using a high-speed centrifuge, and the supernatant in the centrifuge tube was removed to obtain a white precipitate. The white precipitate was dried in an oven at 100 °C for 6 hours to obtain a white powder. 0.7 g of the obtained white powder and 0.6 g of glucose were dispersed in 10 mL of water to obtain a white solution. The obtained solution was transferred to a reaction kettle with a polytetrafluoroethylene inner lining and reacted at 200 °C for 5 hours. It was centrifuged at a speed of 8000 revolutions per minute for 5 minutes using a high-speed centrifuge, and the supernatant in the centrifuge tube was removed to obtain a brown precipitate. The brown precipitate was dried in an oven at 100 °C for 6 hours to obtain molecularly doped silica microspheres.

[0021] Comparative Example 1: First, 6 mL of ammonia water was added to a mixed solution of 7 mL of ethanol and 2 mL of water. Then, 3 mL of TEOS was added and the mixture was stirred for 12 hours to obtain a white solution. The obtained solution was transferred to a reaction kettle with a polytetrafluoroethylene inner lining and reacted at 180 °C for 12 hours to obtain a white solution. It was centrifuged at a speed of 8000 revolutions per minute for 5 minutes using a high-speed centrifuge, and the supernatant in the centrifuge tube was removed to obtain a white precipitate. The white precipitate was dried in an oven at 80 °C for 12 hours to obtain a white powder. 0.5 g of the obtained white powder was dissolved in 10 mL of water to obtain a white solution. The obtained solution was transferred to a reaction kettle with a polytetrafluoroethylene inner lining and reacted at 180 °C for 3 hours. It was centrifuged at a speed of 8000 revolutions per minute for 5 minutes using a high-speed centrifuge, and the supernatant in the centrifuge tube was removed to obtain a white precipitate. The white precipitate was dried in an oven at 80 °C for 12 hours to obtain molecularly doped silica microspheres.

[0022] Comparative Example 2: First, 6 mL of ammonia water was added to a mixed solution of 7 mL of ethanol and 2 mL of water. Then, 3 mL of TEOS and 0.3 g of glucose were added and stirred for 12 hours to obtain a white solution. The obtained solution was transferred to a reaction kettle lined with polytetrafluoroethylene and reacted at 180 °C for 12 hours to obtain a brown solution. It was centrifuged at a speed of 8000 revolutions per minute for 5 minutes using a high-speed centrifuge, and the supernatant in the centrifuge tube was removed to obtain a brown precipitate. The white precipitate was dried in an oven at 80 °C for 12 hours to obtain a brown powder. 0.5 g of the obtained brown powder was dissolved in 10 mL of water to obtain a white solution. The obtained solution was transferred to a reaction kettle lined with polytetrafluoroethylene and reacted at 180 °C for 3 hours. It was centrifuged at a speed of 8000 revolutions per minute for 5 minutes using a high-speed centrifuge, and the supernatant in the centrifuge tube was removed to obtain a white precipitate. The white precipitate was dried in an oven at 80 °C for 12 hours to obtain molecularly doped silica microspheres.

[0023] Figure 1 It is the transmission electron microscope image of the molecularly doped silica microspheres prepared in Example 1. From Figure 1 it can be seen that the average diameter of the molecularly doped silica microspheres is about 390 nm, and the sample has very good dispersibility.

[0024] Figure 2 It is the X-ray diffraction image of the molecularly doped silica microspheres prepared in Example 1. From Figure 2 it can be seen that the molecularly doped silica microspheres show an amorphous structure.

[0025] Figure 3 It is the phosphorescence spectrum of the molecularly doped silica composite prepared in Example 1. From Figure 3 it can be seen that when the excitation wavelength is 365 nm, the center of its phosphorescence emission band is located at about 500 nm.

[0026] Figure 4 It is the phosphorescence lifetime image of the molecularly doped silica microspheres prepared in Example 1. From Figure 4 it can be seen that the time-resolved decay spectrum was fitted using a tri-exponential function according to the following formula: τ avg =∑α i τ i 2 / ∑α i τ i . The average phosphorescence lifetime at room temperature was calculated to be 0.85 s, indicating that the prepared molecularly doped silica microspheres have excellent long phosphorescence lifetimes.

[0027] Figure 5 It is the state diagram of the molecularly doped silica microspheres prepared in Examples 1 - 3 and Comparative Examples 1 - 2 under sunlight, under irradiation with a 365 nm ultraviolet lamp, and after turning off the light. FromFigure 5 It can be seen that the prepared Example 1 exhibits the longest visible phosphorescence duration of 10 s; for the other Examples 2-3 and Comparative Examples 1-2, the visible phosphorescence time of the prepared molecularly doped silica microspheres is relatively short.

[0028] Obviously, those skilled in the art can make various changes and modifications to a molecularly doped silica microsphere and its preparation method described in the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. A method for preparing molecularly doped silica microspheres, comprising the following steps: First, 2-8 mL of ammonia water is added to a mixed solution of 7 mL of ethanol and 2 mL of water, 1-5 mL of TEOS is added, and the mixture is stirred for 6-24 hours to obtain a white solution; the obtained solution is transferred to a polytetrafluoroethylene-lined reactor, and reacted at 160-200°C for 6-24 hours. The solution after the reaction is centrifuged at a speed of 8000 rpm for 5 minutes in a high-speed centrifuge, and the supernatant in the centrifuge tube is removed to obtain a white precipitate; the solution is placed in a 60-100°C oven and dried for 6-24 hours to obtain a white powder as a precursor; 0.3-0.7 g of the obtained white powder and 0.1-0.6 g of the doping molecule are dispersed in 10 mL of water, and reacted at 160-200°C for 1-5 hours. The solution after the reaction is centrifuged at a speed of 8000 rpm for 5 minutes in a high-speed centrifuge, and the supernatant in the centrifuge tube is removed to obtain a brown precipitate; the solution is placed in a 60-100°C oven and dried for 6-24 hours to obtain molecularly doped silica microspheres.

2. The method for preparing molecularly doped silica microspheres according to claim 1, characterized in that: The amount of ammonia water used was 6 mL, and the amount of TEOS used was 3 mL.

3. The method for preparing molecularly doped silica microspheres according to claim 1, characterized in that: In the second hydrothermal step, the amount of precursor used was 0.5 g, and the amount of doping molecule (glucose) used was 0.3 g.

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