Synthetic method of visible light excited multicolor water-phase organic afterglow nano material

Abstract

The invention discloses a synthesis method of a visible light excited multicolor water-phase organic afterglow nanomaterial, which comprises the following steps: synthesizing carbon dots by using pure organic molecules as a raw material through a hydrothermal method, and then synthesizing silicon-coated carbon dots by using a reflux silicon coating method and a Stober silicon coating method; according to the invention, molecular engineering design is utilized to obtain the water-phase afterglow nano material excited by visible light, and broadband emission of color is realized by adjusting the proportion of the raw materials for the first time; according to the invention, the excitation and emission wave bands of the existing afterglow material are broadened, and an innovative idea is provided for the development of the visible light excitation nano afterglow material and the realization of multicolor by adjusting the proportion of the raw materials.

Description

Technical Field

[0001] This invention belongs to the field of organic afterglow materials technology, specifically relating to a method for synthesizing multicolor aqueous organic afterglow nanomaterials excited by visible light. Background Technology

[0002] Afterglow materials are materials that continue to emit light for a period of time after the excitation source is removed. Currently, most afterglow materials are inorganic, doped with inorganic metals. Compared to organic afterglow materials, they suffer from drawbacks such as high pollution levels, difficult preparation, and poor biocompatibility. This makes the development of organic molecular afterglow materials a hot research topic. However, generating afterglow with pure organic molecules is difficult due to the weak spin coupling from the excited singlet to the excited triplet state, low intersystem crossing (ISC) efficiency, the tendency of the excited triplet state to dissipate energy due to nonradiative transitions, and collisional quenching by water and oxygen. In the past, researchers have used methods such as introducing heavy, halogen, carbonyl, and nitrogen atoms as dopants to strengthen the ISC between the excited singlet and excited triplet states, and employing feasible strategies (such as crystallization induction) to construct a rigid environment to suppress nonradiative transitions. These methods, along with H-aggregation and host-guest doping, have led to the preparation of a series of long-lasting afterglow materials with long lifetimes and high quantum yields.

[0003] However, most existing organic afterglow materials are achieved under ultraviolet light excitation, which greatly limits their practical applications. Therefore, there is an urgent need for a visible light-excited long afterglow material and its preparation method to solve the above problems. Currently, most visible light-excited afterglow materials suffer from the drawback of a single emission color. This invention, however, can control different colors by adjusting the ratio of two reagent raw materials, achieving a wide range of multi-color tunability from blue to red, greatly enriching the emission wavelength of the system. Furthermore, most reported organic afterglow materials are mainly solid-phase because solid phases provide a relatively rigid environment, restricting molecular motion and suppressing nonradiative transitions of triplet excitons. However, solid phases have poor modifiability, which is not conducive to large-scale applications. Therefore, it is necessary to find an aqueous afterglow material that can produce afterglow effects under aqueous conditions.

[0004] In the prior art, CN 119351088 A obtained a mixed solution using m-phenylenediamine, boric acid, and silicic acid as precursors via a solvothermal method, and then mixed the dialyzed mixed solution with silicic acid and ammonia water by ultrasonication to obtain an aqueous afterglow material capable of white light excitation; CN 116217464 A used carbazole as a raw material and achieved the construction of phosphorescent materials through the organic synthesis of m-hydroxybenzoyl chloride, thereby shifting its excitation spectrum into the visible light region; CN 117903800A adjusted the Eu ion concentration in (Tb 1-x Eu xThe ratio of red and green light in the phosphor can be adjusted arbitrarily to achieve multicolor emission of the phosphor; the fluorescent molecules synthesized in CN 114957220 A achieve blue, white and yellow-green emission by adjusting the ratio of fluorescent molecules and cucurbituril.

[0005] Compared with existing technologies, this invention innovatively realizes the realization of multi-color aqueous afterglow nanomaterials that can be excited by visible light and whose raw material ratio can be adjusted. Summary of the Invention

[0006] The purpose of this invention is to provide a method for synthesizing multicolor aqueous organic afterglow nanomaterials excited by visible light.

[0007] Since conventional afterglow materials use ultraviolet excitation sources, which limits their application, this invention employs organic amino acids that can be excited by white light and fluorobenzaldehydes that reduce the band gap as dopants. By adjusting the ratio of raw materials, multicolor afterglow can be formed. This invention is simple to operate, uses reagents with low toxicity, is easy to synthesize, and can achieve multicolor without the need for dyes or other doping substances.

[0008] The technical solution of the present invention is as follows: A method for synthesizing visible light-excited multicolor aqueous organic afterglow nanomaterials includes: (1) At room temperature, reagent A, reagent B and deionized water are mixed evenly and subjected to hydrothermal reaction at 100~200℃ (preferably 200℃) for 8~12h (preferably 11h). After cooling to room temperature, the reaction solution is filtered using a 0.22μm filter membrane, and the filtrate is dialyzed using a 500D dialysis bag for 4~12h (preferably 12h) to obtain an organic fluorescent molecule solution. Reagent A is an amino acid selected from one or more of glycine, diglycine peptide, L-arginine, L-leucine, N-fluorenmethoxycarbonyl-glycine, N-fluorenmethoxycarbonyl-glycine, and N-fluorenmethoxycarbonyl-phenylpropionamide-glycine. Reagent B is a fluorobenzaldehyde compound selected from one or more of the following: benzaldehyde, o-fluorobenzaldehyde, m-fluorobenzaldehyde, p-fluorobenzaldehyde, 2,3-difluorobenzaldehyde, 2,4-difluorobenzaldehyde, 2,5-difluorobenzaldehyde, 3,4-difluorobenzaldehyde, 2,3,4-trifluorobenzaldehyde, 2,3,5-trifluorobenzaldehyde, 2,4,5-trifluorobenzaldehyde, and 3,4,5-trifluorobenzaldehyde. The preferred ratio of the total molar amount of reagent A and reagent B to the volume of deionized water is 13~32.5 mmol: 12 mL; The preferred reagent A is N-fluorenylmethoxycarbonyl-glycyl-glycine, and the preferred reagent B is 2,4,5-trifluorobenzaldehyde; and the molar ratio of N-fluorenylmethoxycarbonyl-glycyl-glycine to 2,4,5-trifluorobenzaldehyde is 1~2:4~1; By adjusting the ratio of reagent A and reagent B, organic fluorescent molecule solutions of different colors can be obtained; (2) Take the organic fluorescent molecule solution obtained in step (1), add tetraethyl silicate A, adjust the pH to 9 with ammonia A, heat to 60~120℃ (preferably 100℃) and reflux for 1~8h (preferably 5h), then cool naturally to room temperature, centrifuge, collect the solid material and redisperse it in ethanol A, add deionized water A and ammonia B, then add tetraethyl silicate B in batches under stirring, stir at room temperature for 5~10h (preferably 6h), centrifuge to collect the solid product, wash with ethanol B and disperse it in deionized water B to obtain multicolor aqueous organic afterglow nanomaterials; The preferred feeding ratio of organic fluorescent molecule solution, tetraethyl silicate A, ethanol A, deionized water A, and ammonia B is 5 mL: 0.8 mL: 10 mL: 2.5 mL: 312.5 μL; It is preferable to add 15µL, 30µL, 60µL, 90µL, and 120µL of tetraethyl orthosilicate B in batches every 1 hour. By adding it in batches, the material can be coated layer by layer, making the structure more compact. "Tetraethyl silicate A" and "Tetraethyl silicate B" have no special meaning. They are simply marked "A" and "B" to distinguish the tetraethyl silicate used in different operation steps. The same applies to "ammonia water A", "ammonia water B", "ethanol A", "ethanol B", "deionized water A", and "deionized water B".

[0009] The multicolor aqueous organic afterglow nanomaterials prepared by this invention can be centrifuged, precipitated, dried, and ground to obtain solid-phase multicolor organic afterglow nanomaterial powder.

[0010] The beneficial effects of this invention are reflected in: This invention utilizes molecular engineering design, using pure organic molecules as raw materials, to synthesize carbon dots via a hydrothermal method, followed by the synthesis of silicon-coated carbon dots using reflux silicon coating and Stober silicon coating methods. Compared to the complex synthesis, chromatographic purification, and inert gas protection steps in other methods, this invention is simple to operate, uses readily available reagents and raw materials, and can achieve visually observable blue afterglow of approximately 5 seconds, green afterglow of approximately 7 seconds, yellow afterglow of approximately 7 seconds, orange afterglow of approximately 7 seconds, and red afterglow of approximately 3 seconds simply by changing the ratio of different synthetic raw materials.

[0011] This invention not only broadens the excitation and emission bands of existing afterglow materials, but also provides innovative ideas for the development of visible light-excited nano-afterglow materials and the realization of multicolor through the adjustment of raw material ratios. Attached Figure Description

[0012] Figure 1 Schematic diagram of the process for preparing white light-excited multicolor afterglow materials.

[0013] Figure 2 Electron micrograph of the multicolor afterglow material prepared in Example 3.

[0014] Figure 3 UV-Vis absorption spectra of the multicolor afterglow materials prepared in Examples 1, 2, 3, 4, and 5.

[0015] Figure 4 Infrared spectra of the multicolor afterglow materials prepared in Examples 1, 2, 3, 4, and 5.

[0016] Figure 5 Sunlight and afterglow images of aqueous multicolor afterglow materials in Examples 1, 2, 3, 4, and 5.

[0017] Figure 6 Excitation and emission spectra of the fluorescence afterglow of the multicolor afterglow material prepared in Example 1.

[0018] Figure 7 The excitation and emission spectra of the fluorescence afterglow of the multicolor afterglow material prepared in Example 2.

[0019] Figure 8 The excitation and emission spectra of the fluorescence afterglow of the multicolor afterglow material prepared in Example 3.

[0020] Figure 9 The excitation and emission spectra of the fluorescence afterglow of the multicolor afterglow material prepared in Example 4.

[0021] Figure 10 The excitation and emission spectra of the fluorescence afterglow of the multicolor afterglow material prepared in Example 5. Detailed Implementation

[0022] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0023] Example 1: Blue organic aqueous afterglow nanomaterials

[0024] 1. The preparation steps are as follows: (1) Organic fluorescent molecule solution: At room temperature (25-30℃), reagent A (N-fluorenylmethoxycarbonyl-glycyl-glycine) and reagent B (2,4,5-trifluorobenzaldehyde) were added to 12 mL of deionized water at a stoichiometric ratio of 6.5 mmol:26.0 mmol. The mixture was stirred for 30 min to mix evenly, and then sonicated for 10 min to mix evenly. The mixture was then transferred to a 25 mL stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and hydrothermally heated at 200 ℃ for 11 h. After cooling to room temperature, the product solution was filtered using a commercially available 0.22 μm polyethersulfone (PES) membrane. The solution was then dialyzed using a dialysis bag (500D) for 12 h to obtain an organic fluorescent molecule solution, named b organic fluorescent molecule solution.

[0025] (2) Aqueous blue organic afterglow nanomaterials: Take 5 mL of the b organic fluorescent molecule solution obtained in step (1), add 0.8 mL of tetraethyl silicate (TEOS), adjust the pH to about 9.0 with ammonia (28% by mass), heat to reflux at 100 °C for 5 h to coat silicon; after reflux, cool naturally to room temperature to obtain a multi-colored afterglow nano-aqueous solution, centrifuge and redisperse the solid in 10 mL of ethanol. Add 2.5 mL of deionized water and 312.5 μL of ammonia, and then add 15 µL, 30 µL, 60 µL, 90 µL and 120 µL of TEOS every 1 h, respectively, and stir for a total of 6 h. Collect the obtained product by centrifugation, wash with ethanol three times, and finally disperse in deionized water to obtain blue aqueous organic afterglow nanomaterials b-CDs@SiO2.

[0026] 2. Structural identification

[0027] The UV-Vis absorption spectrum of the aqueous blue afterglow nanomaterial was detected using a UV-Vis spectrophotometer. Figure 3 As shown in the figure, a characteristic ultraviolet absorption peak is observed at 340 nm. These absorption peaks are mainly attributed to the π-π bonds of C=C. Leap forward.

[0028] Infrared spectra of aqueous blue afterglow nanomaterials were detected using an infrared spectrometer. Figure 4 As shown in the figure, 1600 cm -1 The strong absorption peaks on the left and right are attributed to the stretching vibration of C=O; 1360 cm⁻¹ -1 The relatively strong absorption peaks on the left and right are attributed to the CN stretching vibration; 1200 cm⁻¹ -1 The strong and broad absorption peak is attributed to the stretching vibration of Si-O.

[0029] Photos of sunlight and afterglow time of aqueous blue afterglow nanomaterials taken with a Canon camera, such as... Figure 5As shown in the figure, the blue afterglow lasts for 5 seconds and the color is pure and clear.

[0030] The fluorescence emission spectrum and phosphorescence-excited emission spectrum of the aqueous blue afterglow material in the 300-700 nm range were detected using a fluorescence spectroscopy instrument. (See [link to fluorescence spectroscopy description]). Figure 6 As shown, both blue fluorescence excitation and emission exhibit a maximum emission peak at 460 nm, which is standard for blue fluorescence and afterglow.

[0031] Example 2: Green organic aqueous afterglow nanomaterials

[0032] 1. The preparation steps are as follows: (1) Organic fluorescent molecule solution: At room temperature (25-30℃), reagent A (N-fluorenylmethoxycarbonyl-glycyl-glycine) and reagent B (2,4,5-trifluorobenzaldehyde) were mixed in a stoichiometric ratio of 6.5 mmol:19.5 mmol with 12 mL of deionized water. The mixture was stirred for 30 min to mix evenly, and then sonicated for 10 min to mix evenly. The mixture was then transferred to a 25 mL stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and hydrothermally heated at 200 ℃ for 11 h. After cooling to room temperature, the product solution was filtered using a commercially available 0.22 μm polyethersulfone (PES) membrane. The solution was then dialyzed using a dialysis bag (500D) for 12 h to obtain the organic fluorescent molecule solution, which was named g organic fluorescent molecule solution.

[0033] (2) Green aqueous organic afterglow nanomaterials: Take 5 mL of the organic fluorescent molecule solution obtained in step (1), add 0.8 mL of tetraethyl silicate (TEOS), adjust the pH to about 9.0 with ammonia (28% by mass), heat at 100 °C and reflux for 5 h to coat silicon; after reflux, cool naturally to room temperature to obtain a multicolor afterglow nano-aqueous solution, centrifuge and redisperse the solid in 10 mL of ethanol. Add 2.5 mL of deionized water and 312.5 μL of ammonia, and then add 15 µL, 30 µL, 60 µL, 90 µL and 120 µL of TEOS every 1 h, respectively, and stir for a total of 6 h. Collect the obtained product by centrifugation, wash with ethanol three times, and finally disperse in deionized water to obtain green aqueous organic afterglow nanomaterials g-CDs@SiO2.

[0034] 2. Structural identification

[0035] The UV-Vis absorption spectrum of the aqueous green afterglow nanomaterial was detected using a UV-Vis spectrophotometer. Figure 3 As shown in the figure, a characteristic ultraviolet absorption peak is observed at 340 nm. These absorption peaks are mainly attributed to the π-π bonds of C=C. Leap forward.

[0036] Infrared spectra of aqueous green afterglow nanomaterials were detected using an infrared spectrometer. Figure 4 As shown in the figure, 1600 cm -1 The strong absorption peaks on the left and right are attributed to the stretching vibration of C=O; 1360 cm⁻¹ -1 The relatively strong absorption peaks on the left and right are attributed to the CN stretching vibration; 1200 cm⁻¹ -1 The strong and broad absorption peak is attributed to the stretching vibration of Si-O. The significantly enhanced vibrational intensity of CN indicates that N-fluorenemethoxycarbonyl-glycyl-glycine participated in the formation of the carbon dot, and its intensity increased with increasing concentration.

[0037] Images of the afterglow time spectrum of the aqueous green afterglow nanomaterial excited by sunlight and visible light were captured using a Canon camera, as shown below. Figure 5 As shown in the figure, the green afterglow lasts for 7 seconds.

[0038] The fluorescence emission spectrum and phosphorescence excitation emission spectrum of the aqueous green afterglow material in the 300-700 nm range were detected using a fluorescence spectroscopy instrument. (See [link to fluorescence spectroscopy]). Figure 7 As shown, the maximum emission peak of green fluorescence is at 530 nm, while the maximum peak positions of the excitation and emission spectra of green phosphorescence are 460 nm and 530 and 570 nm, respectively. The phosphorescence emission peak exhibits dual emission characteristics, corresponding to the formation of different carbon nuclei and surface states emitting light, with two emission centers emitting different light. It is speculated that this is because the ratio of the two groups exactly matches the reaction between amino and aldehyde groups, resulting in the appearance of two afterglow emission peaks.

[0039] Example 3: Yellow aqueous organic afterglow nanomaterials

[0040] 1. The preparation steps are as follows: (1) Organic fluorescent molecule solution: At room temperature (25-30℃), reagent A (N-fluorenemethoxycarbonyl-glycyl-glycine) and reagent B (2,4,5-trifluorobenzaldehyde) were mixed in a stoichiometric ratio of 6.5 mmol:13.0 mmol with 12 mL of deionized water. The mixture was stirred for 30 min to mix evenly, and then sonicated for 10 min to mix evenly. The mixture was then transferred to a 25 mL stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and hydrothermally heated at 200 ℃ for 11 h. After cooling to room temperature, the product solution was filtered using a commercially available 0.22 μm polyethersulfone (PES) membrane. The solution was then dialyzed using a dialysis bag (500D) for 12 h to obtain an organic fluorescent molecule solution, named γ organic fluorescent molecule solution.

[0041] (2) Aqueous yellow organic afterglow nanomaterials: Take 5 mL of the y organic fluorescent molecule solution obtained in step (1), add 0.8 mL of tetraethyl silicate (TEOS), adjust the pH to about 9.0 with ammonia (28% by mass), heat to reflux at 100 °C for 5 h to coat silicon; after reflux, cool naturally to room temperature to obtain a multi-colored afterglow nano-aqueous solution, centrifuge and redisperse the solid in 10 mL of ethanol. Add 2.5 mL of deionized water and 312.5 μL of ammonia, and then add 15 µL, 30 µL, 60 µL, 90 µL and 120 µL of TEOS every 1 h, respectively, and stir for a total of 6 h. Collect the obtained product by centrifugation, wash three times with ethanol, and finally disperse in deionized water to obtain yellow aqueous organic afterglow nanomaterials y-CDs@SiO2.

[0042] 2. Structural identification

[0043] Electron micrograph of the aqueous yellow afterglow nanomaterial is shown below. Figure 2 As shown, the morphology was characterized by a 120 kV transmission electron microscope. The synthesized y-CDs@SiO2 has a spherical structure. The average particle size was statistically analyzed by silicon spheres of different sizes, 100 nm and 200 nm. The obtained size was 20.08 nm, which conformed to a normal distribution and had a relatively uniform and regular morphology.

[0044] The UV-Vis absorption spectrum of the aqueous yellow afterglow nanomaterial was detected using a UV-Vis spectrophotometer. Figure 3 As shown in the figure, characteristic ultraviolet absorption peaks are observed at 260 nm and 400 nm. These absorption peaks are mainly attributed to the π-π bonds of C=C. The transition and the n-π transition of C=N due to the increased ratio of N-fluorenemethyloxycarbonyl-glycyl-glycine Redshift in the transition.

[0045] The infrared spectrum of the aqueous yellow afterglow nanomaterial was detected using an infrared spectrometer. Figure 4 As shown in the figure, 1600 cm -1 The strong absorption peaks on the left and right are attributed to the stretching vibration of C=O; 1360 cm⁻¹ -1 The relatively strong absorption peaks on the left and right are attributed to the CN stretching vibration; 1200 cm⁻¹ -1 The strong and broad absorption peak is attributed to the stretching vibration of Si-O. The significantly enhanced vibrational intensity of CN indicates that N-fluorenemethoxycarbonyl-glycyl-glycine participated in the formation of the carbon dot, and the peak became stronger with increasing amounts of the corresponding compounds.

[0046] Afterglow time spectra of water-phase yellow afterglow nanomaterials excited by sunlight and visible light were captured using a Canon camera, as shown below. Figure 5As shown in the figure, the yellow afterglow lasts for 7 seconds.

[0047] The fluorescence emission spectrum and phosphorescence excitation emission spectrum of the aqueous yellow afterglow material at 300-700 nm were detected using a fluorescence spectroscopy instrument. (See [reference needed]). Figure 8 As shown, the maximum emission peak of yellow fluorescence is 570 nm, while the maximum peak positions of the excitation and emission spectra of yellow phosphorescence are 460 nm and 570 nm, respectively.

[0048] Example 4: Orange Aqueous Organic Afterglow Nanomaterials

[0049] 1. The preparation steps are as follows: (1) Organic fluorescent molecule solution: At room temperature (25-30℃), reagent A (N-fluorenylmethoxycarbonyl-glycyl-glycine) and reagent B (2,4,5-trifluorobenzaldehyde) were mixed in a stoichiometric ratio of 6.5 mmol:6.5 mmol with 12 mL of deionized water. The mixture was stirred for 30 min to mix evenly and then sonicated for 10 min to mix evenly. The mixture was then transferred to a 25 mL stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and hydrothermally heated at 200 ℃ for 11 h. After cooling to room temperature, the product solution was filtered using a commercially available 0.22 μm polyethersulfone (PES) membrane. The solution was then dialyzed using a dialysis bag (500D) for 12 h to obtain an organic fluorescent molecule solution, which was named o organic fluorescent molecule solution.

[0050] (2) Aqueous orange organic afterglow nanomaterials: Take 5 mL of the o organic fluorescent molecule solution obtained in step (1), add 0.8 mL of tetraethyl silicate (TEOS), adjust the pH to about 9.0 with ammonia (28% by mass), heat to reflux at 100 °C for 5 h to coat silicon; after reflux, cool naturally to room temperature to obtain a multi-colored afterglow nano-aqueous solution, centrifuge and redisperse the solid in 10 mL of ethanol. Add 2.5 mL of deionized water and 312.5 μL of ammonia, and then add 15 µL, 30 µL, 60 µL, 90 µL and 120 µL of TEOS every 1 h, respectively, and stir for a total of 6 h. Collect the obtained product by centrifugation, wash with ethanol three times, and finally disperse in deionized water to obtain orange aqueous organic afterglow nanomaterials o-CDs@SiO2.

[0051] 2. Structural identification

[0052] The UV-Vis absorption spectrum of the aqueous orange afterglow nanomaterial was detected using a UV-Vis spectrophotometer. Figure 3 As shown in the figure, characteristic ultraviolet absorption peaks are observed at 260 nm and 460 nm. These absorption peaks are mainly attributed to the π-π bonds of C=C. Transitions and n-π of C=N The transitions are more pronounced due to the increased proportion of N-fluorenemethyloxycarbonyl-glycyl-glycine.

[0053] Infrared spectra of aqueous orange afterglow nanomaterials were detected using an infrared spectrometer. Figure 4 As shown in the figure, 1600 cm -1 The strong absorption peaks on the left and right are attributed to the stretching vibration of C=O; 1360 cm⁻¹ -1 The relatively strong absorption peaks on the left and right are attributed to the CN stretching vibration; 1200 cm⁻¹ -1 The strong and broad absorption peak is attributed to the stretching vibration of Si-O. The significantly enhanced vibrational intensity of CN indicates that N-fluorenemethoxycarbonyl-glycyl-glycine participated in the formation of the carbon dot, and the peak became stronger with increasing concentration.

[0054] Images of the afterglow time spectrum of the water-phase orange afterglow nanomaterial excited by sunlight and visible light were captured using a Canon camera, as shown below. Figure 5 As shown in the figure, the orange afterglow lasts for 7 seconds.

[0055] The fluorescence emission spectrum and phosphorescence excitation emission spectrum of the aqueous orange afterglow material in the 300-700 nm range were detected using a fluorescence spectroscopy instrument. (See [reference needed]). Figure 9 As shown, the maximum emission peak of orange fluorescence is 600 nm, while the maximum peak positions of the excitation and emission spectra of orange phosphorescence are 460 nm and 610 nm, respectively.

[0056] Example 5: Red aqueous organic afterglow nanomaterials

[0057] 1. The preparation steps are as follows: (1) Organic fluorescent molecule solution: At room temperature (25-30℃), reagent A (N-fluorenylmethoxycarbonyl-glycyl-glycine) and reagent B (2,4,5-trifluorobenzaldehyde) were added to 12 mL of deionized water in a stoichiometric ratio of 13.0 mmol:6.5 mmol. The mixture was stirred for 30 min to mix evenly, and then sonicated for 10 min to mix evenly. The mixture was then transferred to a 25 mL stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and hydrothermally heated at 200 ℃ for 11 h. After cooling to room temperature, the product solution was filtered using a commercially available 0.22 μm polyethersulfone (PES) membrane. The solution was then dialyzed using a dialysis bag (500D) for 12 hours to obtain an organic fluorescent molecule solution, named r organic fluorescent molecule solution.

[0058] (2) Aqueous red organic afterglow nanomaterials: Take 5 mL of the o organic fluorescent molecule solution obtained in step (1), add 0.8 mL of tetraethyl silicate (TEOS), adjust the pH to about 9.0 with ammonia (28% by mass), heat at 100 °C and reflux for 5 h to coat silicon; after reflux, cool naturally to room temperature to obtain a multi-colored afterglow nano-aqueous solution, centrifuge and redisperse the solid in 10 mL of ethanol. Add 2.5 mL of deionized water and 312.5 μL of ammonia, and then add 15 µL, 30 µL, 60 µL, 90 µL and 120 µL of TEOS every 1 h, respectively, and stir for a total of 6 h. Collect the obtained product by centrifugation, wash with ethanol three times, and finally disperse in deionized water to obtain red aqueous organic afterglow nanomaterials r-CDs@SiO2.

[0059] 2. Structural identification

[0060] The UV-Vis absorption spectrum of the aqueous red afterglow nanomaterial was detected using a UV-Vis spectrophotometer. Figure 3 As shown in the figure, characteristic ultraviolet absorption peaks are observed at 260 nm and 460 nm. These absorption peaks are mainly attributed to the π-π bonds of C=C. Transitions and n-π of C=N The transition occurs, and with the increase of N-fluorenemethyloxycarbonyl-glycyl-glycine content, it exhibits a broad absorption range of 250-550 nm, demonstrating ultraviolet characteristics with visible light absorption.

[0061] Infrared spectra of aqueous red afterglow nanomaterials were detected using an infrared spectrometer. Figure 4 As shown in the figure, 1600 cm -1 The strong absorption peaks on the left and right are attributed to the stretching vibration of C=O; 1360 cm⁻¹ -1 The relatively strong absorption peaks on the left and right are attributed to the CN stretching vibration; 1200 cm⁻¹ -1 The strong and broad absorption peak is attributed to the stretching vibration of Si-O. The significantly enhanced vibrational intensity of CN indicates that N-fluorenemethoxycarbonyl-glycyl-glycine participated in the formation of the carbon dot, and the peak became stronger with increasing concentration.

[0062] Images of the afterglow time spectrum of water-phase red afterglow nanomaterials excited by sunlight and visible light were captured using a Canon camera, as shown below. Figure 5 As shown in the figure, the red afterglow lasts for 3 seconds.

[0063] The fluorescence emission spectrum and phosphorescence excitation emission spectrum of aqueous red afterglow material in the 300-700 nm range were detected using a fluorescence spectroscopy instrument. (See [reference needed]). Figure 10As shown, the maximum emission peak of red fluorescence is at 640 nm, while the maximum peak positions of the excitation and emission spectra of red phosphorescence are 460 nm and 640 nm, respectively. Furthermore, the red shift due to the increased ratio of N-fluorenemethyloxycarbonyl-glycyl-glycine is more pronounced. As the ratio of raw material A to raw material B gradually changes from 1:4 to 2:1, it can be seen that the optimal emission peak position of the phosphorescence spectrum gradually shifts to the red, achieving multi-color broadband modulation from blue to red.

[0064] Example 6: Optimization of preparation conditions for multicolor afterglow materials

[0065] Taking Example 3 as an example, the conditions are optimized as follows: (1) Reaction temperature: The hydrothermal reaction temperature in step (1) of Example 3 was increased from 160℃ to 220℃, with a temperature increase of 20℃. Other operations were the same. The afterglow intensity tended to increase, but after 200℃, the afterglow intensity tended to decrease. Since the fluorescence difference was not significant when the temperature changed, the afterglow intensity needed to be considered comprehensively. It first increased and then decreased with the increase of temperature, and was strongest at 200℃. Therefore, 200℃ was selected as the optimal reaction temperature.

[0066] (2) Reaction time: The hydrothermal reaction time in step (1) of Example 3 was changed to 9, 10, 11, 12 and 13 hours. Other operations were the same. The afterglow intensity first increased and then decreased with time. When the time was 11 hours, the afterglow intensity was the strongest. Taking into account the afterglow intensity, 11 hours was selected as the optimal reaction time.

[0067] (3) TEOS dosage: The amount of TEOS added for the first time in step (2) of Example 3 was changed to 0.4, 0.6, 0.8, 1.0 and 1.2 mL, and the other operations were the same. Since a small amount of TEOS is not enough to form silicon spheres of a suitable size to coat the organic fluorescent molecules, and too much TEOS will form silicon spheres that are too large, which will not only weaken the afterglow of the afterglow material, but also affect the dispersibility of y-CDs@SiO2 in water. Considering both the afterglow intensity of carbon dots and their dispersibility in water, 0.8 mL of TEOS was finally selected as the optimal dosage.

[0068] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A method for synthesizing visible light-excited multicolor aqueous organic afterglow nanomaterials, characterized in that, The synthesis method includes: (1) At room temperature, reagent A, reagent B and deionized water are mixed evenly and subjected to hydrothermal reaction at 100~200℃ for 8~12h. After cooling to room temperature, the reaction solution is filtered with a 0.22μm filter membrane and the filtrate is dialyzed with a 500D dialysis bag for 4~12h to obtain an organic fluorescent molecule solution. Reagent A is selected from one or more of glycine, diglycine peptide, L-arginine, L-leucine, N-fluorenylmethoxycarbonyl-glycine, N-fluorenylmethoxycarbonyl-glycine, and N-fluorenylmethoxycarbonyl-phenylpropionamide-glycine; Reagent B is selected from one or more of benzaldehyde, o-fluorobenzaldehyde, m-fluorobenzaldehyde, p-fluorobenzaldehyde, 2,3-difluorobenzaldehyde, 2,4-difluorobenzaldehyde, 2,5-difluorobenzaldehyde, 3,4-difluorobenzaldehyde, 2,3,4-trifluorobenzaldehyde, 2,3,5-trifluorobenzaldehyde, 2,4,5-trifluorobenzaldehyde, and 3,4,5-trifluorobenzaldehyde. (2) Take the organic fluorescent molecule solution obtained in step (1), add tetraethyl silicate A, adjust the pH to 9 with ammonia A, heat to 60~120℃ and reflux for 1~8h to coat with silicon, then cool naturally to room temperature, centrifuge, collect the solid material and redisperse it in ethanol A, add deionized water A and ammonia B, then add tetraethyl silicate B in batches under stirring, stir at room temperature for 5~10h, centrifuge to collect the solid product, wash with ethanol B and disperse it in deionized water B to obtain multicolor aqueous organic afterglow nanomaterials.

2. The method for synthesizing visible light-excited multicolor aqueous organic afterglow nanomaterials as described in claim 1, characterized in that, In step (1), the ratio of the total molar amount of reagent A and reagent B to the volume of deionized water is 13~32.5 mmol: 12 mL.

3. The method for synthesizing visible light-excited multicolor aqueous organic afterglow nanomaterials as described in claim 1, characterized in that, In step (1), reagent A is N-fluorenylmethoxycarbonyl-glycine, and reagent B is 2,4,5-trifluorobenzaldehyde; and the molar ratio of N-fluorenylmethoxycarbonyl-glycine and 2,4,5-trifluorobenzaldehyde is 1~2:4~1.

4. The method for synthesizing visible light-excited multicolor aqueous organic afterglow nanomaterials as described in claim 1, characterized in that, In step (1), a hydrothermal reaction is carried out at 200℃ for 11 hours.

5. The method for synthesizing visible light-excited multicolor aqueous organic afterglow nanomaterials as described in claim 1, characterized in that, In step (2), the ratio of organic fluorescent molecular solution, tetraethyl silicate A, ethanol A, deionized water A, and ammonia B is 5 mL: 0.8 mL: 10 mL: 2.5 mL: 312.5 μL; 15 µL, 30 µL, 60 µL, 90 µL, and 120 µL of tetraethyl silicate B are added in batches every 1 hour.

6. The method for synthesizing visible light-excited multicolor aqueous organic afterglow nanomaterials as described in claim 1, characterized in that, In step (2), the temperature of the reflow silicon coating is 100℃ and the time is 5h.

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