SiO2 nanomaterials activated in situ for room temperature long afterglow luminescence, preparation method and application thereof

Abstract

The application provides a SiO2 nanomaterial capable of activating room-temperature long-afterglow luminescence in situ, a preparation method and application thereof, and solves the technical problem of uncontrolled morphology in the preparation method of the current SiO2 long-afterglow luminescent material. The application directly selects a SiO2 nanomaterial with uniform morphology as a carrier, and uses a high-pressure hydrothermal method to treat the carrier and a luminescent material, so that the luminescent material is in-situ encapsulated, that is, the in-situ encapsulation of the luminescent material is realized through the process of hydrolysis of the carrier surface SiO2 into silicic acid and polymerization of the silicic acid into SiO2, and the long-afterglow emission of the luminescent body itself or the defect luminescence of the SiO2 itself sensitized by the molecules is realized by the strong hydrogen bond interaction between the luminescent body and the SiO2. In the whole process, the luminescent material does not participate in the synthesis process of the SiO2 nanomaterial, and therefore does not affect the nucleation process of the SiO2 nanomaterial. Finally, the morphology of the SiO2 long-afterglow luminescent material completely depends on the morphology of the selected carrier, and an ideal current SiO2 long-afterglow luminescent material can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials technology, specifically relating to an in-situ activated SiO2 nanomaterial with room temperature long afterglow luminescence, its preparation method, and its application. Background Technology

[0002] Silica (SiO2), as one of the most common compounds, appears in a variety of ways in daily industrial production, machinery manufacturing, food, daily chemicals, and agricultural production. The optical transparency, thermodynamics, and chemical stability of SiO2 make it a widely studied matrix for composite materials. Furthermore, SiO2 offers advantages such as simple preparation, tunable particle size, low cytotoxicity, and high biocompatibility. The surface of SiO2 can also be easily modified, allowing for further functionalization with various functional groups to meet different requirements. These numerous advantages make SiO2 an ideal matrix for preparing luminescent composite materials.

[0003] Multifunctional SiO2 composite materials are formed by assembling, coating, or integrating one or more different luminescent materials into SiO2 nanoparticles through various methods. SiO2 nanomaterials are an important component of nanotechnology, and currently, various SiO2 nanomaterials such as nanowires, mesoporous nanoparticles, hollow nanoparticles, and thin films can be prepared through precise process control.

[0004] Current research and applications of SiO2 long-afterglow luminescent materials mainly rely on incorporating luminescent materials during SiO2 synthesis and encapsulating these materials through hydrolysis. However, the addition of luminescent molecules often affects the nucleation process of SiO2 nanoparticles, ultimately resulting in nanoparticles with irregular morphology and poor dispersibility. Furthermore, the complexity of the preparation process remains a pressing issue.

[0005] Given the broad application prospects of SiO2 long afterglow luminescent materials, the research team of this invention believes it is necessary to explore a new preparation method. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problem of uncontrollable morphology in the current preparation methods of SiO2 long afterglow luminescent materials, and to provide in-situ activated room temperature long afterglow luminescent SiO2 nanomaterials, preparation methods and applications.

[0007] To achieve the above objectives, the technical solution provided by this invention is:

[0008] A novel in-situ activated, room-temperature long-afterglow luminescence SiO2 nanomaterial is characterized by the following: it uses uniformly morphological SiO2 nanomaterial as a carrier, and achieves in-situ encapsulation of luminescent molecules and carbon dots with long-afterglow luminescence potential through the process of SiO2 on the carrier surface hydrolyzing into silicic acid and then polymerizing back into SiO2. The outer layer is a dense, secondary hydrolyzed SiO2, which provides a rigid environment, suppresses nonradiative transitions of triplet excitons, protects the internal luminescent molecules, and prevents them from being quenched by reactive oxygen species in the air.

[0009] Furthermore, the carrier is a monodisperse SiO2 nanoparticle, SiO2 nanowire, or irregularly shaped silica nanomaterial with a particle size of 199-298 nm.

[0010] The luminescent molecules with long afterglow luminescence potential are carbon dots (CDs) or organic luminescent molecules.

[0011] The organic light-emitting molecule is 4,4'-bipyridine, 1,8-naphthalenediamine, 1,8-naphthalenedicarboxylic anhydride, 4-phenylpyridine, 2-phenylpyridine, 3-phenylpyridine, 4-phenylquinoline, or 9-phenylacridine;

[0012] The aforementioned in-situ activated room temperature long-afterglow luminescent SiO2 nanomaterials can be classified according to different carrier morphologies into nanowires with long-afterglow luminescence, nanopowders with long-afterglow luminescence, and nanoparticles with long-afterglow luminescence; and according to different in-situ encapsulated luminescent materials, they can be classified into carbon dot@SiO2 nanomaterials and organic luminescent molecule@SiO2 nanomaterials.

[0013] This invention also provides a method for preparing the above-mentioned in-situ activated room temperature long afterglow luminescence SiO2 nanomaterials, which is characterized by including the following steps:

[0014] 1) Deionized water containing dispersed SiO2 nanomaterials and luminescent molecules with long afterglow luminescence potential is placed in a pressure-resistant reaction vessel and heated to 100-200℃ to carry out a high-pressure hydrothermal reaction;

[0015] 2) After the reaction is complete and cooled to room temperature, the precipitate is collected by centrifugation (12000 rpm). The precipitate is washed and centrifuged multiple times to obtain SiO2 nanomaterials with in-situ activated room temperature long afterglow luminescence.

[0016] Furthermore, step 1) specifically involves:

[0017] 1.1) SiO2 nanomaterials and luminescent molecules with long afterglow luminescence potential are simultaneously dispersed in deionized water to form a dispersion;

[0018] Or perhaps,

[0019] First, SiO2 nanomaterials are uniformly dispersed in deionized water, and then luminescent molecules with long afterglow luminescence potential are dissolved in the uniformly dispersed SiO2 nanomaterials to form a reaction dispersion.

[0020] 1.2) Place the dispersion obtained in step 1.1) in a pressure tube, heat it to 100-200℃ in a sand bath or water bath, and stir it at 200-500 rpm (preferably 300 rpm) for 3-60 hours;

[0021] Or perhaps,

[0022] Place the dispersion obtained in step 1.1) into a reaction flask, and place the reaction flask into a polytetrafluoroethylene hydrothermal reactor. Add water around the flask until it is level with the liquid level in the reaction flask. Seal the hydrothermal reactor and heat it at 100-200℃ for 0.5-5 hours.

[0023] Furthermore, in step 1), the luminescent molecule with long afterglow luminescence potential is a carbon dot or an organic luminescent molecule;

[0024] The organic light-emitting molecule is 4,4'-bipyridine, 1,8-naphthalenediamine, 1,8-naphthalenediic anhydride, 4-phenylpyridine, 2-phenylpyridine, 3-phenylpyridine, 4-phenylquinoline, or 9-phenylacridine;

[0025] The carbon dots and organic light-emitting molecules can be added according to the required luminescence lifetime and intensity. In this invention, the carbon dots, SiO2 nanomaterials and water are added in a mass ratio of 9:250:25000, and the organic light-emitting molecules, SiO2 nanomaterials and water are added in a mass ratio of 0.1-4:10:1000, depending on the requirements.

[0026] Furthermore, the carbon dots are synthesized using ethanolamine and phosphoric acid via microwave, then adjusted to neutral (pH=7) with NaHCO3 solution and filtered through a 0.22μm aqueous microporous membrane. After filtration, they are decolorized using activated carbon.

[0027] Further, in step 1), the carrier is SiO2 nanowires, silica gel, or monodisperse SiO2 nanoparticles with a particle size of 199-298 nm.

[0028] The method for preparing the monodisperse SiO2 nanoparticles with a particle size of 199-298 nm is as follows:

[0029] S1 prepares "seed" stock solution

[0030] Ethanol, deionized water and ammonia are mixed and slowly stirred at 200-500 rpm and heated to 60-70℃. Then, tetraethyl orthosilicate (TEOS, as a silicon source, is added dropwise at a constant rate) is added to the reaction system at a rate of 0.2 mL / min. The reaction is carried out for at least 10 h. The resulting colloidal solution is used as the "seed" stock solution.

[0031] The volume ratio of ethanol, deionized water, ammonia, and tetraethyl orthosilicate is 160:33:3.5:4.4.

[0032] S2 Preparation of Monodisperse SiO2 Nanoparticles

[0033] S2.1 Mix ethanol, deionized water and ammonia water evenly at room temperature (200 rpm), add the "seed" stock solution obtained in S1 to the reaction system to obtain mixture 1;

[0034] The volume ratio of ethanol, deionized water, ammonia, and the "seed" stock solution is 160:40:40:0.4-1.5.

[0035] S2.2 Ethanol, deionized water and ammonia are mixed evenly to obtain mixture 2. Tetraethyl orthosilicate and mixture 2 are added to mixture 1 obtained in S2.1 at a rate of 0.2 mL / min. The reaction is carried out for at least 2 hours to obtain the reaction product.

[0036] The volume ratio of ethanol, deionized water, ammonia, tetraethyl orthosilicate, and mixture 1 is 10:3:7:20:120.2-120.75.

[0037] S2.3 The reaction product obtained in S2.2 was washed repeatedly by alternating centrifugation with ethanol and water, and then dried in an oven to obtain monodisperse SiO2 nanoparticles with a particle size of 199-298 nm. The entire preparation process involves the growth of SiO2 nanoparticles of different sizes through seed nucleation; the amount of seeds used determines the final diameter of the SiO2 nanoparticles, and generally, the more seeds added, the smaller the particle size.

[0038] Furthermore, in S1, tetraethyl orthosilicate is added to the reaction system using a syringe;

[0039] In S2.1, a three-necked flask is used as the reaction vessel;

[0040] The "seed" stock solution obtained in S1 was added to the reaction system using a pipette;

[0041] In S2.2, when adding tetraethyl orthosilicate and mixture 2 to mixture 1 using a syringe, they are added from different ports of a three-necked flask, ensuring that the injection port does not come into contact with the interface of mixture 1.

[0042] This invention also provides the application of the nanoparticles in the above-mentioned in-situ activated room temperature long afterglow luminescence SiO2 nanomaterials in the preparation of photonic crystals or multiple anti-counterfeiting measures.

[0043] Based on the above applications, a photonic crystal is provided, characterized in that: the aforementioned in-situ activated room-temperature long afterglow luminescence SiO2 nanomaterials are dispersed as raw materials in anhydrous ethanol with a mass fraction of 6-10 wt% (preferably 8 wt%) to form a dispersion, and then the dispersion is refluxed at 2 μm s⁻¹. -1 The rate is obtained by dip-coating the substrate multiple times (e.g., 1-10 times, preferably 6 times).

[0044] The principle of this invention:

[0045] This invention changes the preparation strategy by directly selecting uniformly morphological SiO2 nanomaterials as a carrier. High-pressure hydrothermal treatment is used to process the carrier and luminescent material, thus encapsulating the luminescent material in situ. Specifically, the luminescent material is encapsulated in situ through the hydrolysis of SiO2 on the carrier surface into silicic acid, which is then polymerized back into SiO2. The strong hydrogen bonding between the luminescent material and SiO2 enables either long-afterglow emission from the luminescent material itself or defect luminescence from the molecularly sensitized SiO2. Throughout this process, the luminescent material no longer participates in the synthesis of SiO2 nanomaterials, thus not affecting the nucleation process of SiO2 nanomaterials. The final morphology of the long-afterglow SiO2 luminescent material depends entirely on the morphology of the selected carrier, resulting in ideal SiO2 long-afterglow luminescent nanomaterials.

[0046] Advantages of this invention:

[0047] 1. This invention possesses the characteristic of long afterglow luminescence that universally activates luminescent materials and molecules. The preparation method fundamentally avoids the problem of uncontrollable morphology in current SiO2 long afterglow luminescent material preparation methods. The entire preparation process is simpler, directly using SiO2 nanomaterials with excellent morphology as carriers. Through in-situ sensitization, SiO2 nanomaterials with regular morphology, good dispersion, and ultra-long lifetime afterglow emission can be prepared, thereby improving the luminescent performance of the material.

[0048] 2. This invention utilizes SiO2 nanomaterials with excellent morphology to achieve in-situ encapsulation of luminescent materials through high-pressure hydrothermal treatment. Based on the achievement of the initial objective, it discloses two types of SiO2 nanomaterials that can be in-situ activated for long-afterglow luminescence via high-pressure hydrothermal methods, along with their preparation methods. Nine material molecules capable of emitting long-afterglow luminescence are involved: carbon dots (CDs) prepared from phosphoric acid and ethanolamine via microwave method; tetraphenylpyridine (4PP), diphenylpyridine (2PP), triphenylpyridine (3PP), 4,4'-dipyridyl (4PP), 9-phenylacridine (PL), 1H-Benz[de]isoquinoline-1,3(2H)-dione (BD), and 1,8-naphthalic anhydride (1,8-naphthalic anhydride). Anhydride (NA) and tetraphenylquinoline (4-Phenylquinoline). Two hydrothermal methods are provided: a simple preparation process for synthesizing SiO2 long-afterglow luminescent nanomaterials via a pressure-resistant tube, and a simple preparation process for synthesizing SiO2 long-afterglow luminescent nanomaterials via a hydrothermal reactor. The hydrothermal reaction temperature and time involved in this invention affect the lifetime of the final long-afterglow luminescent nanoparticles without changing the fluorescence and phosphorescence emission positions. The long-afterglow luminescent SiO2 nanomaterials prepared using monodisperse SiO2 nanoparticles as a carrier can stably emit light in aqueous solution. After hydrothermal heating, the particles do not agglomerate or stick together, maintaining their initial monodispersity characteristics, such as: a monodisperse, uniform 4,4'- Bipyridine-SiO2 nanoparticles with blue long-afterglow luminescence; two monodisperse uniform 1,8-naphthalenediamine-SiO2 and 1,8-naphthalenediamide-SiO2 nanoparticles with orange long-afterglow luminescence; five monodisperse uniform 4-phenylpyridine, 2-phenylpyridine, 3-phenylpyridine, 4-phenylquinoline and 9-phenylacridine nanoparticles in situ embedded in SiO2 with cyan long-afterglow luminescence; one monodisperse uniform 4-phenylpyridine nanowire in situ embedded in SiO2 with cyan long-afterglow luminescence; and one monodisperse uniform 4-phenylpyridine nanowire in situ embedded in silica gel with cyan long-afterglow luminescence.These SiO2 nanoparticles with long afterglow emission have long afterglow emission wavelengths ranging from 434 to 593 nm and lifetimes ranging from 0.31 to 3.77 s. The most efficient luminescence is achieved by 4PP-loaded SiO2 nanoparticles, which, after being excited at the optimal excitation wavelength of 292 nm, can emit fluorescence at 348 nm (lifetime of 5.76 ns) and phosphorescence at 472 nm (lifetime of 3.77 s).

[0049] 3. The monodisperse SiO2 nanoparticles used in this invention are optimized... The method produces uniformly shaped nanoparticle spheres by adjusting the amount of "seed". The entire preparation process is simple, low-cost, environmentally stable, green and environmentally friendly, highly operable and widely applicable. It can serve as an important system for achieving in-situ activated, efficient and long-afterglow luminescence, and has broad practical application prospects.

[0050] 4. In this invention, the surface hydrolysis of SiO2 under hydrothermal conditions is used to encapsulate the sensitized molecules. Under 292 nm ultraviolet excitation, the 4PP-loaded SiO2 nanoparticles emit blue light under ultraviolet irradiation, and emit cyan phosphorescence after emission is turned off. The SiO2 nanoparticles and sensitization process involved in this invention are simple, the materials are readily available, and the processing cycle is short. Furthermore, due to the low cost and wide availability of SiO2 nanoparticles, the preparation process of this invention has economic and environmental advantages, and can achieve large-scale production for application in multiple fields such as chemical catalysis and information encryption.

[0051] 5. The SiO2 nanomaterials with long afterglow luminescence obtained by this invention, the photonic crystals prepared based on long afterglow nanoparticles, and their preparation process have the following beneficial effects:

[0052] 5.1 The SiO2 nanomaterials with long afterglow luminescence obtained by in-situ hydrothermal treatment retain the morphology and dispersibility of the precursor nanomaterials (i.e., the carrier). Therefore, the morphology of the final product can be adjusted by controlling the preparation process of the precursor.

[0053] 5.2 The highest efficiency of this invention is that a long afterglow emission with a lifespan of up to 3.5 seconds can be obtained by high-temperature hydrothermal treatment at 180°C for 3 hours.

[0054] 5.3 The photonic crystal obtained by impregnation and pulling self-assembly of uniform SiO2 nanoparticles with long afterglow luminescence not only has the angle-dependent different reflection luminescence properties of photonic crystals, but also the time-dependent long afterglow luminescence properties.

[0055] 5.4 The long afterglow nanomaterials obtained by this invention still retain the functions and roles of the main material, and have great development potential in the fields of bioimaging, anti-counterfeiting encryption, chemical catalysis, and intelligent sensing. Attached Figure Description

[0056] Figure 1 In Example 1, the optimized version was used Transmission electron microscopy images and dynamic light scattering particle size distribution diagrams of SiO2 nanoparticles with different particle sizes prepared by the method are shown. The ae correspond to SiO2 nanoparticles with particle sizes of 199 nm, 221 nm, 262 nm, 277 nm and 298 nm respectively.

[0057] Figure 2 Morphological structure and luminescence characterization of carbon dot@SiO2 composite nanoparticles in Example 2;

[0058] a represents the excitation-dependent emission spectrum of the carbon dot@SiO2 composite nanoparticles;

[0059] b shows the photoluminescence spectrum and its image under UV light in an aqueous dispersion (top), the transient emission spectrum (gated time 1 ms) and its emission spectrum after the UV lamp is turned off (bottom);

[0060] c represents the fluorescence lifetime at 415 nm;

[0061] d represents the luminescence lifetime at 527 nm;

[0062] Figure 3 Comparison of lifetime and quantum yield of carbon dot@SiO2 composite nanoparticles synthesized at different temperatures and times

[0063] a shows the comparison of phosphorescence lifetime at 527 nm for carbon dot@SiO2 composite nanoparticles obtained by hydrothermal treatment at different temperatures for 48 hours.

[0064] b shows the comparison of phosphorescence lifetime at 527 nm for carbon dot@SiO2 composite nanoparticles obtained by hydrothermal treatment at 175℃ for different times.

[0065] c represents a comparison of the fluorescence quantum yield (red line) and phosphorescence quantum yield (blue line) of carbon dot @SiO2 composite nanoparticles obtained at different temperatures after 48 hours of hydrothermal treatment.

[0066] d represents the comparison of fluorescence quantum yield (red line) and phosphorescence quantum yield (blue line) of carbon dot@SiO2 composite nanoparticles obtained by hydrothermal treatment at 175℃ for different times;

[0067] Figure 4 Transmission electron microscopy images and dynamic light scattering particle size distribution diagrams of 277, 262, 221 and 199 nm SiO2 nanoparticles and carbon dots after hydrothermal treatment.

[0068] Figure 5Comparison of attenuation curves at 527 nm for 277, 262, 221, and 199 nm SiO2 nanoparticles and carbon dots after hydrothermal treatment;

[0069] Figure 6 The image shows the display effect of the photonic crystal under different light sources (fluorescent lamp, ultraviolet lamp, and ultraviolet lamp turned off). Image a is a schematic diagram of the photonic crystal structure.

[0070] b shows the light reflection images of the 285nm carbon dot@SiO2 composite nanoparticle self-assembled photonic crystal at different angles;

[0071] c shows photoluminescence images under 365nm ultraviolet light illumination at different angles;

[0072] d is the image of the green afterglow emission after the UV lamp is turned off;

[0073] Figure 7 Comparison of color coordinates and images of the emission spectra of carbon dots@SiO2 composite nanoparticles of different sizes at 10°;

[0074] Figure 8 Basic morphology and luminescence characterization of 4-phenylpyridine-SiO2 composite nanoparticles

[0075] a is a TEM image of 4-phenylpyridine-SiO2 after reacting at 180℃ for 3 hours in a high-temperature reactor. The image shows a high-resolution image of a single particle inside (scale bar is 50 nm).

[0076] b shows the photoluminescence spectrum and its image under UV light in an aqueous dispersion (top), the transient emission spectrum (gated time 1ms) and its emission spectrum after the UV lamp is turned off;

[0077] c represents the excitation-dependent transient emission spectrum (gating time: 1 ms);

[0078] d represents the long afterglow emission lifetime at 472 nm (fluorescence lifetime at 415 nm).

[0079] Figure 9 Comparison of the lifetimes of 4-phenylpyridine@SiO2 composite nanoparticles under different hydrothermal conditions;

[0080] a shows the comparison of the lifetimes of 4-phenylpyridine@SiO2 composite nanoparticles under different hydrothermal temperatures;

[0081] b shows the lifetime comparison of 4-phenylpyridine@SiO2 composite nanoparticles under different hydrothermal times;

[0082] Figure 10 TEM images and delayed emission spectra of SiO2 nanomaterials with different morphologies;

[0083] a shows the TEM image and delayed emission spectrum of the nanowires after hydrothermal treatment (gating time: 1ms);

[0084] b shows the TEM image and delayed emission spectrum of the nanopowder after hydrothermal treatment (gating time: 1ms);

[0085] Figure 11 These are the excitation spectra, photoluminescence spectra, and transient emission spectra of different molecules after hydrothermal treatment in a reactor. Detailed Implementation

[0086] The following detailed description, in conjunction with specific embodiments, illustrates the SiO2 composite nanoparticles with long afterglow luminescence involved in this invention and the photonic crystals prepared based thereon.

[0087] The preparation method of monodisperse SiO2 nanoparticles with a particle size of 199-298 nm includes the following steps:

[0088] S1 prepares "seed" stock solution

[0089] Mix ethanol, deionized water and ammonia, stir slowly at 200-500 rpm and heat to 60-70℃. Then use a syringe to add tetraethyl orthosilicate (TEOS, as a silicon source, added dropwise at a uniform rate) to the reaction system at a rate of 0.2 mL / min. React for at least 10 hours and use the resulting colloidal solution as the "seed" stock solution.

[0090] The volume ratio of ethanol, deionized water, ammonia, and tetraethyl orthosilicate is 160:33:3.5:4.4.

[0091] S2 Preparation of Monodisperse SiO2 Nanoparticles

[0092] S2.1 Ethanol, deionized water and ammonia were mixed evenly in a three-necked flask at room temperature (200-500 rpm). The "seed" stock solution obtained in S1 was added to the reaction system using a pipette to obtain mixture 1.

[0093] The volume ratio of ethanol, deionized water, ammonia, and the "seed" stock solution is 160:40:40:0.4-1.5.

[0094] S2.2 Mix ethanol, deionized water and ammonia water evenly to obtain mixture 2. Use a syringe to add tetraethyl orthosilicate and mixture 2 into mixture 1 obtained in S2.1 from different openings of a three-necked flask at a rate of 0.2 mL / min. React for at least 2 hours to obtain the reaction product.

[0095] The volume ratio of ethanol, deionized water, ammonia, and tetraethyl orthosilicate is 10:3:7:20.

[0096] S2.3 The reaction product obtained from S2.2 was washed by alternating centrifugation with ethanol and water multiple times, and then dried in an oven to obtain monodisperse SiO2 nanoparticles with a particle size of 199-298 nm.

[0097] Example 1

[0098] Morphology, structure, and luminescence characterization of SiO2 nanoparticles in this invention:

[0099] Following the aforementioned method, in S1, 160 mL of ethanol, 33 mL of deionized water, and 3.5 mL of ammonia were measured into a single-necked flask. The mixture was heated to 60 °C with slow stirring. Then, 4.4 mL of tetraethyl orthosilicate (TEOS) was measured using a 5 mL medical syringe and added to the reaction system at a rate of 0.2 mL / min. The reaction was carried out for 10 hours to obtain the "seed" stock solution for later use.

[0100] In S2.1, five groups of 160 mL ethanol, 40 mL deionized water and 40 mL ammonia water were measured into three-necked flasks and mixed evenly at room temperature at 300 rpm. 1.5 mL, 1.2 mL, 1 mL, 0.8 mL and 0.4 mL of the "seed" stock solution were transferred into each flask respectively.

[0101] In step S2.2, five groups of 10 mL ethanol, 3 mL deionized water, and 7 mL ammonia solution were measured and mixed thoroughly in beakers. Using a 20 mL medical syringe, the mixture and the five groups of tetraethyl orthosilicate (TEOS) were respectively measured and injected into the reaction system of S2.1 through different openings of a three-necked flask. After injection, the reaction was allowed to proceed for 2 hours to prepare SiO2 nanoparticles. The particles were then uniformly dispersed in anhydrous ethanol solution and dropped onto a 3 mm diameter 200-mesh copper screen for transmission electron microscopy imaging. Figure 1 The TEM analysis results show that the obtained nanoparticles are 199nm, 221nm, 262nm, 277nm and 298nm, respectively; they show a trend of decreasing size with increasing content of "seed" stock solution, and the figure shows that the particles all maintain monodisperse characteristics.

[0102] Example 2

[0103] Morphology and luminescence characterization of carbon dot@SiO2 nanoparticles in this invention:

[0104] The 298 nm SiO2 nanoparticles (50 mg) obtained in Example 1 were dispersed in 5 mL of deionized water along with carbon dots (1.8 mg) synthesized by microwave with ethanolamine and phosphoric acid. The mixture was heated to 175 °C and stirred at 300 rpm for 48 h in a 15 mL pressure-resistant tube. After cooling to room temperature, the nanoparticles were washed three times with deionized water and centrifuged (12000 rpm for 5 min) to obtain the desired carbon dot@SiO2 composite nanoparticles. Optical characterization of the carbon dot@SiO2 composite nanoparticles dispersed in ethanol revealed the following:

[0105] like Figure 2 As shown, under 350 nm excitation, in addition to blue photoluminescence at 415 nm, a gated spectrum with a delay time of 1.0 ms also exhibits green phosphorescence concentrated at 527 nm. After excitation ceases, a green afterglow can be directly observed with the naked eye from the aqueous dispersive liquid. Under optimal excitation, the average lifetime of green phosphorescence at 527 nm is 1.50 s. Furthermore, due to the SiO2 matrix encapsulation, the blue fluorescence lifetime of CDs at 415 nm is 9.56 ns. The fluorescence quantum yield is 11.16%, and the phosphorescence quantum yield is 5.47%.

[0106] Example 2-1

[0107] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the hydrothermal reaction temperature in the preparation of carbon dot@SiO2 composite nanoparticles by hydrothermal method is 100℃.

[0108] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0109] The phosphorescence emission lifetime at 527 nm is 1.16 s, the fluorescence quantum yield at 415 nm is 7.37%, and the phosphorescence quantum yield is 4.38%.

[0110] Example 2-2

[0111] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the hydrothermal reaction temperature in the preparation of carbon dot@SiO2 composite nanoparticles by hydrothermal method is 125℃.

[0112] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0113] The phosphorescence emission lifetime at 527 nm is 1.39 s, the fluorescence quantum yield at 415 nm is 8.36%, and the phosphorescence quantum yield is 4.29%.

[0114] Example 2-3

[0115] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the hydrothermal reaction temperature in the preparation of carbon dot@SiO2 composite nanoparticles by hydrothermal method is 150℃.

[0116] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0117] The phosphorescence emission lifetime at 527 nm is 1.44 s, the fluorescence quantum yield at 415 nm is 11.09%, and the phosphorescence quantum yield is 5.35%.

[0118] Examples 2-4

[0119] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the hydrothermal reaction temperature in the preparation of carbon dot@SiO2 composite nanoparticles by hydrothermal method is 200℃.

[0120] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0121] The phosphorescence emission lifetime at 527 nm is 1.48 s, the fluorescence quantum yield at 415 nm is 12.62%, and the phosphorescence quantum yield is 5.77%.

[0122] The lifetime comparison diagram of carbon dot@SiO2 composite nanoparticles obtained at different hydrothermal temperatures for the same hydrothermal time is shown below. Figure 3 As shown in a and c.

[0123] Examples 2-5

[0124] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the hydrothermal reaction time in the preparation of carbon dot@SiO2 composite nanoparticles by hydrothermal method is 3h.

[0125] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0126] The phosphorescence emission lifetime at 527 nm is 1.18 s, the fluorescence quantum yield at 415 nm is 6.89%, and the phosphorescence quantum yield is 3.84%.

[0127] Examples 2-6

[0128] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the hydrothermal reaction time in the preparation of carbon dot@SiO2 composite nanoparticles by hydrothermal method is 6 hours.

[0129] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0130] The phosphorescence emission lifetime at 527 nm is 1.21 s, the fluorescence quantum yield at 415 nm is 7.01%, and the phosphorescence quantum yield is 3.80%.

[0131] Examples 2-7

[0132] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the hydrothermal reaction time in the preparation of carbon dot@SiO2 composite nanoparticles by hydrothermal method is 12h.

[0133] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0134] The phosphorescence emission lifetime at 527 nm is 1.33 s, the fluorescence quantum yield at 415 nm is 7.93%, and the phosphorescence quantum yield is 3.85%.

[0135] Examples 2-8

[0136] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the hydrothermal reaction time in the preparation of carbon dot@SiO2 composite nanoparticles by hydrothermal method is 24h.

[0137] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0138] The phosphorescence emission lifetime at 527 nm is 1.37 s, the fluorescence quantum yield at 415 nm is 7.89%, and the phosphorescence quantum yield is 3.83%.

[0139] Examples 2-9

[0140] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the hydrothermal reaction time in the preparation of carbon dot@SiO2 composite nanoparticles by hydrothermal method is 36h.

[0141] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0142] The phosphorescence emission lifetime at 527 nm is 1.48 s, the fluorescence quantum yield at 415 nm is 8.84%, and the phosphorescence quantum yield is 4.35%.

[0143] Example 2-10

[0144] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the hydrothermal reaction time in the preparation of carbon dot@SiO2 composite nanoparticles by hydrothermal method is 60h.

[0145] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0146] The phosphorescence emission lifetime at 527 nm is 1.44 s, the fluorescence quantum yield at 415 nm is 10.34%, and the phosphorescence quantum yield is 4.79%.

[0147] Comparison of lifetime and quantum yield of carbon dot@SiO2 composite nanoparticles obtained at the same hydrothermal temperature but with different hydrothermal times is shown in the figure. Figure 3 As shown, with increasing temperature and reaction time, the luminescence lifetime reaches its maximum value of 1.50 s at 175℃ and 48 h, corresponding to a quantum yield of 11.16%. Increasing the hydrothermal temperature and extending the lifetime will improve the hydrolysis degree of SiO2 nanoparticles, thereby enhancing their ability to coat carbon dots. However, excessively high temperatures and times, such as the 200℃ and 60h reaction conditions in the examples, will lead to over-hydrolysis, affecting the final luminescence effect.

[0148] Example 2-11

[0149] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the size of the SiO2 nanoparticles in the hydrothermal preparation of carbon dot@SiO2 composite nanoparticles is changed to 277nm.

[0150] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0151] The phosphorescence emission lifetime at 527 nm is 1.43 s, and the size of the carbon dot@SiO2 composite nanoparticles is reduced by 19 nm compared to the original particle size.

[0152] Example 2-12

[0153] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the size of the nanoparticles in the hydrothermal preparation of carbon dot@SiO2 composite nanoparticles is changed to 262nm.

[0154] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0155] The phosphorescence emission lifetime at 527 nm is 1.37 s. The nanoparticle size is reduced by 14 nm compared to the original particle size.

[0156] Example 2-13

[0157] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the size of the nanoparticles in the hydrothermal preparation of carbon dot@SiO2 composite nanoparticles is changed to 221 nm.

[0158] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0159] The phosphorescence emission lifetime at 527 nm is 1.34 s. The nanoparticle size is reduced by 21 nm compared to the original particle size.

[0160] Example 2-14

[0161] The difference between the preparation of carbon dot@SiO2 composite nanoparticles involved in this invention and Example 2 is that the size of the nanoparticles in the hydrothermal preparation of carbon dot@SiO2 composite nanoparticles is changed to 199 nm.

[0162] Excitation at 350 nm showed blue photoluminescence at 415 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 527 nm.

[0163] The phosphorescence emission lifetime at 527 nm is 1.33 s. The nanoparticle size is 4 nm smaller than the original particle size.

[0164] TEM results of carbon dot@SiO2 composite nanoparticles of different sizes obtained in Examples 2-11 to 2-14, and particle size distribution diagrams are shown below. Figure 4 As shown, after in-situ encapsulation of the luminescent material and molecules, the size of SiO2 nanoparticles is reduced to within 20 nm, and the lifetime is compared to... Figure 5As shown, for SiO2 nanoparticles of the same mass but different sizes, the smaller the size, the greater the quantity, and the larger the specific surface area. The smaller the size and the greater the quantity of these small particles, the shorter their lifetime.

[0165] As can be seen from the comparison, the carbon dots prepared by the microwave method have photoluminescence with a peak value of 415nm and phosphorescence emission with a peak value of 527nm. The longest phosphorescence lifetime is 1.5s, corresponding to a hydrothermal temperature of 175℃ and a hydrothermal time of 48h.

[0166] Meanwhile, within the aforementioned process range (heating temperature 100-200℃, reaction time 3-60h), the present invention also conducted verification experiments by adjusting the heating temperature and reaction time, and similarly obtained carbon dot @SiO2 nanoparticles with long afterglow luminescence.

[0167] Example 3

[0168] The uniform carbon dot @SiO2 composite nanoparticles with long afterglow luminescence obtained in Example 2 were dispersed in ethanol to prepare an 8 wt% nanoparticle ethanol dispersion. The resulting dispersion was then loaded into an dip-coating machine and dipped at 2 μms. -1 The photonic crystal is obtained by dipping and coating an aluminum substrate and a steel plate six times at a certain rate. This photonic crystal is produced according to... Figure 6 The image shows the luminescence of a precision displacement platform with a resolution of α under fluorescent light and after ultraviolet light is turned on and off. Figure 6 As shown in b, c, and d, it can be seen that when the ultraviolet lamp is turned on, the fluorescence weakens as the incident angle increases, while the long afterglow exhibits time-resolved at a fixed angle.

[0169] Example 3-1

[0170] The nanoparticles in the ethanol dispersion in Example 3 were replaced with particles of different sizes from those in Examples 2-11 to 2-14. The resulting image of the photonic crystal at an observation angle of 10° is shown below. Figure 7 As shown, it can be seen that as the particle size decreases, the emitted light exhibits a blue shift according to Bragg's equation. Furthermore, by assembling particles of different sizes with average particle diameters of 195 nm, 207 nm, 241 nm, 258 nm, and 285 nm, photonic crystals in violet, blue, green, yellow, and orange hues can be prepared at an observation angle of 10°, and these photonic crystals exhibit long afterglow luminescence.

[0171] Example 4

[0172] Morphology and luminescence characterization of organic light-emitting molecule @SiO2 composite nanoparticles in this invention:

[0173] 50 mg of SiO2 nanoparticles and 5 mg of 4-phenylpyridine obtained in Example 1 were ultrasonically dispersed in 4 mL of deionized water. The resulting mixture was transferred to a 5 mL reaction glass bottle, which was then placed in a 20 mL polytetrafluoroethylene (PTFE) reaction vessel. 4 mL of deionized water was added around the outside of the vessel until the water level was level with the liquid in the reaction bottle. The reaction vessel was sealed and heated at 180 °C for 3 h. After the reaction was complete and cooled to room temperature, the resulting mixture was centrifuged at 12000 rpm for 5 min. The precipitate was alternately centrifuged and dispersed three times with deionized water (or anhydrous ethanol), finally dispersing the precipitate in 3 mL of aqueous solution.

[0174] Under excitation at 292 nm, in addition to blue photoluminescence at 350 nm, gated spectra with a delay time of 1.0 ms show that green phosphorescence is also emitted, concentrated at 472 nm. After excitation is stopped, a green afterglow can be directly observed with the naked eye from the water dispersion. Under optimal excitation, the average lifetime of the green phosphorescence at 472 nm is 3.77 s. The TEM imaging results of the obtained particles are compared with the photoluminescence, delayed emission spectra, and corresponding lifetimes as follows: Figure 8 As shown.

[0175] Example 4-1

[0176] The preparation of 4-phenylpyridine@SiO2 composite nanoparticles involved in this invention differs from that in Example 4 in that the hydrothermal reaction temperature in the preparation of 4-phenylpyridine@SiO2 composite nanoparticles by hydrothermal method is 100℃.

[0177] Excitation at 292 nm showed blue photoluminescence at 350 nm, and a gated spectrum with a delay of 1.0 ms also showed green phosphorescence emission concentrated at 472 nm, with a phosphorescence emission lifetime of 3.18 s at 472 nm.

[0178] Example 4-2

[0179] The preparation of 4-phenylpyridine@SiO2 composite nanoparticles involved in this invention differs from that in Example 4 in that the hydrothermal reaction temperature in the preparation of 4-phenylpyridine@SiO2 composite nanoparticles by hydrothermal method is 120℃.

[0180] Excitation at 292 nm showed blue photoluminescence at 350 nm, and a gated spectrum with a delay of 1.0 ms also showed green phosphorescence emission concentrated at 472 nm, with a phosphorescence emission lifetime of 3.20 s at 472 nm.

[0181] Example 4-3

[0182] The preparation of 4-phenylpyridine@SiO2 composite nanoparticles involved in this invention differs from that in Example 4 in that the hydrothermal reaction temperature in the preparation of 4-phenylpyridine@SiO2 composite nanoparticles by hydrothermal method is 140℃.

[0183] Excitation at 292 nm showed blue photoluminescence at 350 nm, and a gated spectrum with a delay of 1.0 ms also showed green phosphorescence emission concentrated at 472 nm, with a phosphorescence emission lifetime of 3.37 s at 472 nm.

[0184] Example 4-4

[0185] The preparation of 4-phenylpyridine@SiO2 composite nanoparticles involved in this invention differs from that in Example 4 in that the hydrothermal reaction temperature in the preparation of 4-phenylpyridine@SiO2 composite nanoparticles by hydrothermal method is 160℃.

[0186] Excitation at 292 nm showed blue photoluminescence at 350 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 472 nm, with a phosphorescence emission lifetime of 3.43 s at 472 nm.

[0187] Examples 4-5

[0188] The preparation of 4-phenylpyridine@SiO2 composite nanoparticles involved in this invention differs from that in Example 4 in that the hydrothermal reaction temperature in the preparation of 4-phenylpyridine@SiO2 composite nanoparticles by hydrothermal method is 200℃.

[0189] Excitation at 292 nm showed blue photoluminescence at 350 nm, and a gated spectrum with a delay of 1.0 ms also showed green phosphorescence emission concentrated at 472 nm, with a phosphorescence emission lifetime of 3.53 s at 472 nm.

[0190] The lifetimes of 4-phenylpyridine@SiO2 composite nanoparticles obtained at different hydrothermal temperatures for the same hydrothermal time are compared to... Figure 9 As shown in Figure a, similar to the trend of carbon dots in pressure-resistant tubes, the lifespan increases with increasing hydrothermal temperature, reaching a maximum of 3.77 seconds when the hydrothermal temperature reaches 180℃.

[0191] Examples 4-6

[0192] The preparation of 4-phenylpyridine@SiO2 composite nanoparticles involved in this invention differs from that in Example 4 in that the hydrothermal reaction temperature in the preparation of 4-phenylpyridine@SiO2 composite nanoparticles by hydrothermal method is 0.5 h.

[0193] Excitation at 292 nm showed blue photoluminescence at 350 nm, and a gated spectrum with a delay of 1.0 ms also revealed green phosphorescence concentrated at 472 nm, with a phosphorescence emission lifetime of 3.36 s at 472 nm.

[0194] Examples 4-7

[0195] The preparation of 4-phenylpyridine@SiO2 composite nanoparticles involved in this invention differs from that in Example 4 in that the hydrothermal reaction temperature in the preparation of 4-phenylpyridine@SiO2 composite nanoparticles by hydrothermal method is 1 h.

[0196] Excitation at 292 nm showed blue photoluminescence at 350 nm, and a gated spectrum with a delay of 1.0 ms also showed green phosphorescence emission concentrated at 472 nm, with a phosphorescence emission lifetime of 3.54 s at 472 nm.

[0197] Examples 4-8

[0198] The preparation of 4-phenylpyridine@SiO2 composite nanoparticles involved in this invention differs from that in Example 4 in that the hydrothermal reaction temperature in the preparation of 4-phenylpyridine@SiO2 composite nanoparticles by hydrothermal method is 2h.

[0199] Excitation at 292 nm showed blue photoluminescence at 350 nm, and a gated spectrum with a delay of 1.0 ms also showed green phosphorescence emission concentrated at 472 nm, with a phosphorescence emission lifetime of 3.58 s at 472 nm.

[0200] Examples 4-9

[0201] The preparation of 4-phenylpyridine@SiO2 composite nanoparticles involved in this invention differs from that in Example 4 in that the hydrothermal reaction temperature in the preparation of 4-phenylpyridine@SiO2 composite nanoparticles by hydrothermal method is 4h.

[0202] Excitation at 292 nm showed blue photoluminescence at 350 nm, and a gated spectrum with a delay of 1.0 ms also showed green phosphorescence emission concentrated at 472 nm, with a phosphorescence emission lifetime of 3.75 s at 472 nm.

[0203] Examples 4-10

[0204] The preparation of 4-phenylpyridine@SiO2 composite nanoparticles involved in this invention differs from that in Example 4 in that the hydrothermal reaction temperature in the preparation of 4-phenylpyridine@SiO2 composite nanoparticles by hydrothermal method is 5h.

[0205] Excitation at 292 nm showed blue photoluminescence at 350 nm, and a gated spectrum with a delay of 1.0 ms revealed green phosphorescence concentrated at 472 nm with a phosphorescence emission lifetime of 3.73 s at 472 nm.

[0206] The lifetimes of 4-phenylpyridine@SiO2 composite nanoparticles obtained at the same hydrothermal temperature but with different hydrothermal times are compared, for example... Figure 9 As shown in b. Similar to the trend of carbon dots in the pressure-resistant tube, the lifespan increases with the length of the hydrothermal time, reaching a maximum of 3.77 seconds when the hydrothermal temperature reaches 3 hours.

[0207] In summary, the long-afterglow SiO2 nanoparticles obtained by encapsulating 4-phenylpyridine (4PP) molecules exhibit photoluminescence with a peak at 350 nm and phosphorescence emission with a peak at 472 nm, with a phosphorescence lifetime of 3.18-3.77 s.

[0208] Example 4-11

[0209] The preparation of 4-phenylpyridine@SiO2 composite nanoparticles involved in this invention differs from that in Example 4 in that the SiO2 nanomaterial used is SiO2 nanowires.

[0210] Under excitation at 292 nm, in addition to blue photoluminescence at 350 nm, a gated spectrum with a delay time of 1.0 ms shows that it also exhibits green phosphorescence emission concentrated at 472 nm, with a phosphorescence emission lifetime of 3.54 s at 472 nm. Figure 10 As shown in a.

[0211] Example 4-12

[0212] The preparation of 4-phenylpyridine@SiO2 composite nanoparticles involved in this invention differs from that in Example 4 in that the SiO2 nanomaterial used is SiO2 nanopowder.

[0213] Under excitation at 292 nm, in addition to blue photoluminescence at 350 nm, a gated spectrum with a delay time of 1.0 ms shows that it also exhibits green phosphorescence emission concentrated at 472 nm, with a phosphorescence emission lifetime of 3.44 s at 472 nm. Figure 10 As shown in b.

[0214] Under the same hydrothermal conditions, SiO2 nanomaterials with different morphologies can achieve in-situ long afterglow activation of molecules without significantly altering the morphology and dispersibility of the SiO2 material itself.

[0215] Example 4-13

[0216] Preparation of 2-phenylpyridine@SiO2 composite nanoparticles involved in this invention:

[0217] The difference from Example 4 is that 5 mg of the luminescent molecule 2-phenylpyridine was weighed and subjected to the same hydrothermal treatment as in Example 4.

[0218] Excitation at 305 nm showed blue photoluminescence at 355 nm, and a gated spectrum with a delay of 1.0 ms also showed green phosphorescence emission concentrated at 482 nm, with a phosphorescence emission lifetime of 2.91 s at 482 nm.

[0219] Example 4-14

[0220] Preparation of 3-phenylpyridine@SiO2 composite nanoparticles involved in this invention:

[0221] The difference from Example 4 is that 5 mg of the luminescent molecule 3-phenylpyridine was weighed and subjected to the same hydrothermal treatment as in Example 4.

[0222] Excitation at 292 nm showed blue photoluminescence at 368 nm, and a gated spectrum with a delay of 1.0 ms also showed green phosphorescence emission concentrated at 485 nm, with a phosphorescence emission lifetime of 1.93 s at 485 nm.

[0223] Examples 4-15

[0224] Preparation of 4,4'-bipyridine@SiO2 composite nanoparticles involved in this invention:

[0225] The difference from Example 4 is that 5 mg of the luminescent molecule 4,4'-bipyridine was weighed and subjected to the same hydrothermal treatment as in Example 4.

[0226] Excitation at 277 nm showed blue photoluminescence at 434 nm, and a gated spectrum with a delay of 1.0 ms revealed phosphorescence with emission concentrated at 434 nm and a lifetime of 0.86 s.

[0227] Example 4-16

[0228] Preparation of 9-phenylacridine@SiO2 composite nanoparticles involved in this invention:

[0229] The difference from Example 4 is that 5 mg of the luminescent molecule 9-phenylacridine was weighed and subjected to the same hydrothermal treatment as in Example 4.

[0230] Excitation at 272 nm showed blue photoluminescence at 368 nm, and a gated spectrum with a delay of 1.0 ms revealed green phosphorescence concentrated at 485 nm with a phosphorescence lifetime of 1.96 s at 485 nm.

[0231] Example 4-17

[0232] Preparation of 4-phenylquinoline@SiO2 composite nanoparticles involved in this invention:

[0233] The difference from Example 4 is that 5 mg of the luminescent molecule 4-phenylquinoline was weighed and subjected to the same hydrothermal treatment as in Example 4.

[0234] Excitation at 336 nm showed blue photoluminescence at 412 nm, and a gated spectrum with a delay of 1.0 ms revealed green phosphorescence emission concentrated at 455 nm with a phosphorescence emission lifetime of 2.54 s at 455 nm.

[0235] Example 4-18

[0236] Preparation of 1,8-naphthalenedicarboxylic anhydride@SiO2 composite nanoparticles involved in this invention:

[0237] The difference from Example 4 is that 5 mg of the luminescent molecule 1,8-naphthalenedicarboxylic anhydride was weighed and subjected to the same hydrothermal treatment as in Example 4.

[0238] Excitation at 344 nm showed blue photoluminescence at 328 nm. A gated spectrum with a delay of 1.0 ms revealed phosphorescence concentrated at 546 nm and 594 nm, with emission lifetimes of 0.32 s and 0.31 s, respectively.

[0239] Example 4-19

[0240] Preparation of 1,8-naphthalenediamide@SiO2 composite nanoparticles involved in this invention:

[0241] The difference from Example 4 is that 5 mg of the luminescent molecule 1,8-naphthalenediamide was weighed and subjected to the same hydrothermal treatment as in Example 4.

[0242] Excitation at 343 nm showed blue photoluminescence at 328 nm. Gated spectra with a delay of 1.0 ms also showed phosphorescence concentrated at 546 nm and 594 nm, with phosphorescence emission lifetimes of 1.62 s and 0.56 s at 596 nm.

[0243] Photoluminescence spectra, phosphorescence emission spectra, and lifetimes of SiO2 nanoparticles with different luminescent molecules intercalated are compared. Figure 11 As shown.

[0244] The above implementation examples demonstrate that the in-situ activated SiO2 composite nanoparticles obtained by this invention have good monodispersity and stable long afterglow luminescence characteristics. Furthermore, the method for achieving long afterglow by encapsulating luminescent materials with SiO2 used in this invention is simple, easy to operate, and has the advantage of being commercially viable for large-scale processing. For production and daily life that require room temperature long afterglow luminescent materials, the processing source can be controlled. The hydrothermal treatment has the advantage of not significantly affecting the morphology, and materials with ideal size and morphology can be obtained.

[0245] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. Si02 nanomaterials that activate room temperature long afterglow luminescence in situ, characterized in that: Using uniformly shaped SiO2 nanomaterials as a carrier, the in-situ encapsulation of luminescent molecules with long afterglow luminescence potential is achieved through the process of SiO2 on the carrier surface hydrolyzing into silicic acid and then polymerizing back into SiO2. The outer layer is dense secondary hydrolyzed SiO2.

2. The in-situ activated room-temperature long afterglow luminescence SiO2 nanomaterial according to claim 1, characterized in that: The carrier is made of SiO2 nanowires, silica gel, or monodisperse SiO2 nanoparticles with a particle size of 199-298 nm. The luminescent molecules with long afterglow luminescence potential are carbon dots or organic luminescent molecules; The organic light-emitting molecule is 4,4'-bipyridine, 1,8-naphthalenedimide, 1,8-naphthalenedicarboxylic anhydride, 4-phenylpyridine, 2-phenylpyridine, 3-phenylpyridine, 4-phenylquinoline, or 9-phenylacridine.

3. The method for preparing in-situ activated room-temperature long afterglow luminescence SiO2 nanomaterials according to claim 1, characterized in that, Includes the following steps: 1) An aqueous solution containing dispersed SiO2 nanomaterials and luminescent molecules with long afterglow luminescence potential is placed in a pressure-resistant reaction vessel and heated to 100-200℃ to carry out a high-pressure hydrothermal reaction; 2) After the reaction is complete and cooled to room temperature, the precipitate is collected by centrifugation. The precipitate is washed and centrifuged multiple times to obtain SiO2 nanomaterials with in-situ activated room temperature long afterglow luminescence.

4. The preparation method according to claim 3, characterized in that, Step 1) Specifically: 1.1) SiO2 nanomaterials and luminescent molecules with long afterglow luminescence potential are simultaneously dispersed in deionized water to form a dispersion; or, First, SiO2 nanomaterials are uniformly dispersed in deionized water, and then luminescent molecules with long afterglow luminescence potential are dissolved in the uniformly dispersed SiO2 nanomaterials to form a reaction dispersion. 1.2) Place the dispersion obtained in step 1.1) in a pressure tube, heat to 100-200℃, and stir at 200-500 rpm for 3-60 h; or, Place the dispersion obtained in step 1.1) into a reaction flask, and then place the reaction flask into a hydrothermal reactor. Add water around the flask until it is level with the liquid level in the reaction flask. Seal the hydrothermal reactor and heat it at 100-200℃ for 0.5-5 h.

5. The preparation method according to claim 4, characterized in that: In step 1), the luminescent molecule with long afterglow luminescence potential is a carbon dot or an organic luminescent molecule; The organic light-emitting molecule is 4,4'-bipyridine, 1,8-naphthalenedimide, 1,8-naphthalenedian anhydride, 4-phenylpyridine, 2-phenylpyridine, 3-phenylpyridine, 4-phenylquinoline, or 9-phenylacridine.

6. The preparation method according to claim 5, characterized in that: The carbon dots were synthesized using ethanolamine and phosphoric acid via microwave, then adjusted to neutral with NaHCO3 solution and filtered through an aqueous microporous membrane. After filtration, they were decolorized.

7. The preparation method according to claim 6, characterized in that: In step 1), the carrier is SiO2 nanowires, silica gel, or monodisperse SiO2 nanoparticles with a particle size of 199-298 nm. The method for preparing the monodisperse SiO2 nanoparticles with a particle size of 199-298 nm is as follows: S1 Preparation of "Seed" Stock Solution Ethanol, deionized water and ammonia were mixed and heated to 60-70℃ with stirring at 200-500 rpm. Then, tetraethyl orthosilicate was added to the reaction system at a rate of 0.2 mL / min and the reaction was carried out for at least 10 h to obtain the "seed" stock solution. The volume ratio of ethanol, deionized water, ammonia, and tetraethyl orthosilicate is 160:33:3.5:4.

4. S2 Preparation of monodisperse SiO2 nanoparticles S2.1 Ethanol, deionized water and ammonia are mixed evenly at room temperature. The "seed" stock solution obtained in S1 is added to the reaction system to obtain mixture 1. The volume ratio of ethanol, deionized water, ammonia, and the "seed" stock solution is 160:40:40:0.4-1.

5. S2.2 Ethanol, deionized water and ammonia are mixed evenly to obtain mixture 2. Tetraethyl orthosilicate and mixture 2 are added to mixture 1 obtained in S2.1 at a rate of 0.2 mL / min. The reaction is carried out for at least 2 h to obtain the reaction product. The volume ratio of ethanol, deionized water, ammonia, tetraethyl orthosilicate, and mixture 1 is 10:3:7:20:120.2-120.

75. S2.3 The reaction product obtained from S2.2 was washed three times by alternating centrifugation with ethanol and water, and after drying, monodisperse SiO2 nanoparticles with a particle size of 199-298 nm were obtained.

8. The preparation method according to claim 7, characterized in that: In S2.2, when injecting mixture 2 and tetraethyl orthosilicate into mixture 1, it must be ensured that the injection port does not come into contact with the interface of mixture 1.

9. The application of nanoparticles in the in-situ activated room temperature long afterglow luminescence SiO2 nanomaterial of claim 1 in the preparation of photonic crystals or multiple anti-counterfeiting measures.

10. A photonic crystal, characterized by: The SiO2nanomaterials in situ activated room temperature long afterglow luminescence of claim 1 are dispersed in anhydrous ethanol with a mass fraction of 6-10wt% to form a dispersion liquid, and then the dispersion liquid is dip-coated on a substrate at a rate of 2 μm s -1 for 6 times.

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