A method for rapidly synthesizing RGB room-temperature phosphorescent carbon dots by microwave heating
RGB room-temperature phosphorescent carbon dots were synthesized by microwave heating. The intersystem crossing was promoted by the cyclodextrin cavity structure and urea carbonyl group, which solved the problem of synthesizing long-lifetime and high-quantum-yield RGB carbon dots in the existing technology. A rapid and simple preparation method was realized, which improved the stability and application range of carbon dots.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN UNIV OF TECH
- Filing Date
- 2024-04-22
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies make it difficult to rapidly synthesize long-lifetime, high-quantum-yield, long-wavelength RGB room-temperature phosphorescent carbon dots, and the synthesis methods are cumbersome and have long reaction times.
RGB room temperature phosphorescent carbon dots were synthesized by microwave heating. By introducing cyclodextrin cavity structure and covalent bonds, nonradiative transitions of molecules were suppressed, and carbonyl groups were introduced by urea to promote intersystem crossing, thereby enhancing the lifetime and quantum yield of carbon dots.
The rapid synthesis of room-temperature phosphorescent carbon dots in red, green, and blue colors within 90 seconds has been achieved, with extended lifetime, improved quantum yield, and wider application range.
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Figure CN118387860B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for rapidly synthesizing RGB room temperature phosphorescent carbon dots by microwave heating, belonging to the field of phosphorescent nanomaterial preparation technology. Background Technology
[0002] Carbon dots are based on sp 2 Carbon-based, heavy metal-free nanomaterials with a size less than 10 nm are used as the luminescent center. Due to the strong quantum size effect, they exhibit excellent photoluminescence properties, enabling room-temperature phosphorescence (RTP). Their good photostability, water solubility, and low toxicity make them widely applicable in optoelectronic devices, information encryption, bioimaging, catalysis, and chemical sensing. However, most currently obtained RTP carbon dots have short lifetimes and relatively low quantum yields (QY).
[0003] Currently, the phosphorescence emission of carbon dots is mainly concentrated in the short wavelength region, such as blue phosphorescence. Although there are many reports on carbon dots with green and red phosphorescence in the long wavelength region, their lifetimes are relatively short, their quantum yield (QY) is relatively low, and their synthesis methods are complicated, often accompanied by high temperature and high pressure, and long reaction time. Therefore, the rapid preparation of long-wavelength phosphorescent carbon dots with long lifetime and high quantum yield has attracted the attention of researchers.
[0004] Microwave synthesis is often used as a convenient method for synthesizing carbon dots. Qu synthesized a series of green afterglow carbon dots using microwave urea. While this method eliminates many harsh experimental conditions, complex procedures, and tedious purification processes, the longest phosphorescence lifetime of the synthesized carbon dots was 532 ms, and the highest fluorescence quantum yield was 27%, both relatively low. This invention introduces a cavity structure and covalent bonds through cyclodextrin to suppress nonradiative transitions in molecules, and introduces carbonyl groups through urea to promote intersystem crossing (ISC), thereby enhancing the lifetime and quantum yield of the carbon dots. Summary of the Invention
[0005] This invention enables the rapid synthesis of RGB room temperature phosphorescent carbon dots via microwave heating, thus broadening their application areas.
[0006] The technical solution of this invention:
[0007] A method for rapidly synthesizing RGB room temperature phosphorescent carbon dots via microwave heating, comprising the following steps:
[0008] Step 1: Dissolve sodium carbonate and sodium bicarbonate in ultrapure water and stir until completely dissolved to prepare a buffer solution;
[0009] Step 2: Add α-cyclodextrin and urea to a buffer solution and stir until completely dissolved. Then add 1-pyreneboronic acid, 9-phenanthrolineboronic acid, and 4-methyl phenylboronic acid respectively. Microwave the mixture in a microwave oven for 50-200 seconds. After cooling to room temperature, red, green, and blue room temperature phosphorescent carbon dots are obtained respectively.
[0010] In step 1, the concentration of sodium carbonate in the buffer solution is 10 mmol / L, the concentration of sodium bicarbonate is 90 mmol / L, and the pH is 9–10.
[0011] In step 2, the mass ratio of α-cyclodextrin to 1-pyreneboronic acid (9-phenanthroline boric acid, 4-methyl phenylboronic acid) is 20:1 to 100:1, preferably 50:1.
[0012] In step 2, the mass ratio of urea to 1-pyreneboronic acid (9-phenanthreneboronic acid, 4-methyl phenylboronic acid) is 5:1 to 20:1, preferably 10:1, 20:1, or 5:1.
[0013] Microwave reaction for 90 seconds.
[0014] The beneficial effects of this invention are as follows: This invention synthesizes RGB room-temperature phosphorescent carbon dots by microwave heating. Using the microwave method, stable red, green, and blue room-temperature phosphorescent carbon dots can be synthesized in just 90 seconds using the same synthesis method. By introducing a cavity structure and covalent bonds through cyclodextrin, non-radiative transitions of molecules are suppressed. By introducing carbonyl groups through urea, intersystem crossing (ISC) of molecules is promoted, thereby enhancing the lifetime and quantum yield of carbon dots. The synthesized RGB room-temperature phosphorescent carbon dots have strong stability, long phosphorescence lifetime, and high quantum yield, and are simpler and more widely applicable. Attached Figure Description
[0015] Figure 1 The phosphorescence excitation spectrum of the carbon dots synthesized in Example 2 at 600 nm is shown.
[0016] Figure 2 The fluorescence and phosphorescence spectra of the carbon dots synthesized in Example 2 under 340 nm excitation are shown.
[0017] Figure 3 The image shows the afterglow decay curve of the carbon dots synthesized in Example 2 at 600 nm under 340 nm excitation.
[0018] Figure 4 The phosphorescence intensity spectra of the synthesized carbon dots in Example 8 under different excitation wavelengths are shown.
[0019] Figure 5 The fluorescence phosphorescence spectrum of the carbon dots synthesized in Example 8 under 275 nm excitation.
[0020] Figure 6The image shows the afterglow decay curve of the carbon dots synthesized in Example 8 at 505 nm under 275 nm excitation.
[0021] Figure 7 The phosphorescence intensity spectra of the synthesized carbon dots in Example 9 under different excitation wavelengths are shown.
[0022] Figure 8 The fluorescence phosphorescence spectrum of the carbon dots synthesized in Example 9 under 280 nm excitation.
[0023] Figure 9 The image shows the afterglow decay curve of the carbon dots synthesized in Example 9 at 410 nm under 280 nm excitation.
[0024] Figure 10 The image shows the afterglow visible to the naked eye after the excitation light is turned off for the carbon dots synthesized in Examples 2, 8, and 9, where a, b, and c are Examples 2, 8, and 9, respectively.
[0025] Figure 11 The flowers made from the carbon dots synthesized in Examples 2, 8, and 9 show the afterglow visible to the naked eye after the excitation light at 254 nm and 365 nm is turned off, where a and b are the states after the excitation light at 254 nm and 365 nm is turned off, respectively. Detailed Implementation
[0026] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.
[0027] Comparative Examples 1-12
[0028] A method for rapidly synthesizing RGB room temperature phosphorescent carbon dots by microwave heating, the method comprising the following steps:
[0029] (1) Dissolve sodium carbonate and sodium bicarbonate in ultrapure water and stir until completely dissolved to obtain 100 mL, 10 mmol / L sodium carbonate and 90 mmol / L sodium bicarbonate buffer solution.
[0030] (2) Different masses of α-cyclodextrin were dissolved in 5 ml of the buffer solution obtained in step (1), and stirred until completely dissolved. Then, 10 mg of 1-pyreneboronic acid, 9-phenanthrolineboronic acid, and 4-methyl phenylboronic acid were added respectively, and stirred thoroughly. The mixture was then microwaved for 90 s. After the reaction was completed, the mixture was cooled to room temperature and thoroughly ground to obtain red, green, and blue phosphorescent carbon dot powders, respectively. The comparative proportions were 1–4, 5–8, and 9–12, respectively, as shown in Tables 1, 3, and 5.
[0031] Table 1 compares different proportions of Examples 1-4.
[0032] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 mass ratio 20:1 50:1 70:1 100:1
[0033] 10 mg of the red afterglow carbon dots from Comparative Examples 1–4 were taken respectively, and their visible afterglow times at 254 nm were observed in a dark room. The visible afterglow times of Comparative Examples 1–4 are shown in Table 2.
[0034] Table 2 Comparative Examples 1-4: Naked-eye visible afterglow time
[0035] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Afterglow duration (s) 1.0 1.5 1.0 0.5
[0036] Table 2 shows that when the mass ratio of α-cyclodextrin to 1-pyreneboronic acid is 50:1, the time of the red visible afterglow in Comparative Example 2 reaches 1.5s, which is an improvement compared to Comparative Example 1, Comparative Example 3, and Comparative Example 4. Therefore, the optimal mass ratio of α-cyclodextrin to 1-pyreneboronic acid for red afterglow carbon dots is 50:1.
[0037] Table 3 compares different proportions of Examples 5–8.
[0038] Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 mass ratio 20:1 50:1 70:1 100:1
[0039] Ten mg of each of the green afterglow carbon dots from Comparative Examples 5–8 were taken, and their visible afterglow times at 254 nm were observed in a dark room. The visible afterglow times of Comparative Examples 5–8 are shown in Table 4.
[0040] Table 4 Comparative Examples 5-8: Naked-eye visible afterglow time
[0041] Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Afterglow duration (s) 10 15 12 10
[0042] Table 4 shows that when the mass ratio of α-cyclodextrin to 9-phenanthroline boric acid is 50:1, the green afterglow time of Comparative Example 6 reaches 15s, which is an improvement compared to Comparative Examples 5, 7, and 8. Therefore, the optimal mass ratio of α-cyclodextrin to 9-phenanthroline boric acid for green afterglow carbon dots is 50:1.
[0043] Table 5 compares different proportions of Examples 9–12.
[0044] Comparative Example 9 Comparative Example 10 Comparative Example 11 Comparative Example 12 mass ratio 20:1 50:1 70:1 100:1
[0045] Ten mg of each of the blue afterglow carbon dots from Comparative Examples 9–12 were taken and their visible afterglow time at 254 nm was observed in a dark room. The visible afterglow times of Comparative Examples 9–12 are shown in Table 6.
[0046] Table 6 Comparative Examples 9-12: Naked-eye visible afterglow time
[0047] Comparative Example 9 Comparative Example 10 Comparative Example 11 Comparative Example 12 Afterglow duration (s) 9 12 10 7
[0048] As shown in Figure 6, when the mass ratio of α-cyclodextrin to 4-methyl phenylboronic acid is 50:1, the blue afterglow time of Comparative Example 10 reaches 12 seconds, which is an improvement compared to Comparative Examples 9, 11, and 12. Therefore, the optimal mass ratio of α-cyclodextrin to 4-methyl phenylboronic acid for blue afterglow carbon dots is 50:1.
[0049] Examples 1-4
[0050] A method for rapidly synthesizing RGB room temperature phosphorescent carbon dots by microwave heating, the method comprising the following steps:
[0051] (1) Dissolve sodium carbonate and sodium bicarbonate in ultrapure water and stir until completely dissolved to obtain 100 mL, 10 mmol / L sodium carbonate and 90 mmol / L sodium bicarbonate buffer solution.
[0052] (2) Dissolve 50 mg of α-cyclodextrin and different masses of urea in 5 ml of the buffer solution obtained in step (1), stir until completely dissolved, then add 10 mg of 1-pyreneboric acid, stir thoroughly, microwave for 90 s, and after the reaction is complete, cool to room temperature and grind thoroughly to obtain red phosphorescent carbon dot powder. The different urea doping ratios in Examples 1 to 4 are shown in Table 7.
[0053] Table 7 Different urea blending ratios in Examples 1-4
[0054] Example 1 Example 2 Example 3 Example 4 Doping ratio 5:1 10:1 15:1 20:1
[0055] 10 mg of the red afterglow carbon dots from Examples 1-4 were taken respectively, and the visible afterglow time of Examples 1-4 at 254 nm was observed in a dark room. The visible afterglow time of Examples 1-4 is shown in Table 8.
[0056] Table 8. Afterglow time visible to the naked eye in Examples 1-4
[0057] Example 1 Example 2 Example 3 Example 4 Afterglow duration (s) 1.5 2 1.5 1
[0058] As shown in Table 8, when the urea doping ratio is 10:1, the red afterglow time visible to the naked eye in Example 2 reaches 2 seconds, which is an improvement compared to Example 1, Example 3 and Example 4. Therefore, the optimal urea doping ratio for red afterglow carbon dots is 10:1.
[0059] Depend on Figure 1 The optimal excitation wavelength for the carbon dots was found to be 340 nm, and the maximum emission wavelength was 600 nm, indicating that the synthesized carbon dots exhibited red afterglow. Figure 2It can be seen that at the optimal excitation wavelength of 340nm, the maximum emission wavelength of fluorescence in Example 2 is 400nm, and the maximum emission wavelength of phosphorescence in Example 2 is 600nm. This is different from the maximum emission wavelength of fluorescence, so the red afterglow of Example 2 is phosphorescence.
[0060] Depend on Figure 3 As can be seen from the afterglow lifetime decay diagram, in Example 2, the lifetime at the maximum emission wavelength of 600nm is 216.30ms under the optimal excitation wavelength of 340nm.
[0061] Examples 5-8
[0062] A method for rapidly synthesizing RGB room temperature phosphorescent carbon dots by microwave heating, the method comprising the following steps:
[0063] (1) Dissolve sodium carbonate and sodium bicarbonate in ultrapure water and stir until completely dissolved to obtain 100 mL, 10 mmol / L sodium carbonate and 90 mmol / L sodium bicarbonate buffer solution.
[0064] (2) Dissolve 50 mg of α-cyclodextrin and different masses of urea in 5 ml of the buffer solution obtained in step (1), stir until completely dissolved, then add 10 mg of 9-phenanthroline boric acid, stir thoroughly, microwave for 90 s, and after the reaction is complete, cool to room temperature and grind thoroughly to obtain green phosphorescent carbon dot powder. The different urea doping ratios in Examples 5 to 8 are shown in Table 9.
[0065] Table 9 shows the different urea doping ratios in Examples 5-8.
[0066]
[0067]
[0068] Ten mg of the green afterglow carbon dots from Examples 5-8 were taken respectively, and the afterglow time of Examples 5-8 at 254 nm was observed in a dark room. The afterglow time of Examples 5-8 is shown in Table 10.
[0069] Table 10 Afterglow time as seen by the naked eye in Examples 5-8
[0070] Example 5 Example 6 Example 7 Example 8 Afterglow duration (s) 17 20 22 28
[0071] As shown in Table 10, when the urea doping ratio is 20:1, the green afterglow visible to the naked eye in Example 8 reaches 28s, which is a significant improvement compared to Examples 5-7. Therefore, the optimal urea doping ratio for green afterglow carbon dots is 20:1.
[0072] Depend on Figure 4The optimal excitation wavelength for the carbon dots was found to be 275 nm, and the maximum emission wavelength was 505 nm, indicating that the synthesized carbon dots exhibited green afterglow. Figure 5 It can be seen that the maximum emission wavelength of fluorescence in Example 8 is 370 nm and the maximum emission wavelength of phosphorescence in Example 8 is 505 nm at the optimal excitation wavelength of 275 nm. This is different from the maximum emission wavelength of fluorescence, so the green afterglow of Example 8 is phosphorescence.
[0073] Depend on Figure 6 As can be seen from the afterglow lifetime decay diagram, in Example 8, the lifetime at the maximum phosphorescence emission wavelength of 505nm is 1.53s under the optimal excitation wavelength of 275nm.
[0074] Examples 9-12
[0075] A method for rapidly synthesizing RGB room temperature phosphorescent carbon dots by microwave heating, the method comprising the following steps:
[0076] (1) Dissolve sodium carbonate and sodium bicarbonate in ultrapure water and stir until completely dissolved to obtain 100 mL, 10 mmol / L sodium carbonate and 90 mmol / L sodium bicarbonate buffer solution.
[0077] (2) Dissolve 50 mg of α-cyclodextrin and different masses of urea in 5 ml of the buffer solution obtained in step (1), stir until completely dissolved, then add 10 mg of 4-methyl phenylboronic acid, stir thoroughly, microwave for 90 s, and after the reaction is complete, cool to room temperature and grind thoroughly to obtain blue afterglow carbon dot powder. The different urea doping ratios in Examples 9 to 12 are shown in Table 11.
[0078] Table 11 Different urea doping ratios in Examples 9-12
[0079] Example 9 Example 10 Example 11 Example 12 Doping ratio 5:1 10:1 15:1 20:1
[0080] Ten mg of the blue afterglow carbon dots from Examples 9-12 were taken respectively, and the afterglow time of Examples 9-12 at 254 nm was observed in a dark room. The afterglow time of Examples 9-12 is shown in Table 12.
[0081] Table 12 Afterglow time as seen by the naked eye in Examples 9-12
[0082] Example 9 Example 10 Example 11 Example 12 Afterglow duration (s) 15 10 8 5
[0083] As shown in Table 12, when the urea doping ratio is 5:1, the blue afterglow time visible to the naked eye in Example 9 reaches 15s, which is a significant improvement compared to Examples 10-12. Therefore, the optimal urea doping ratio for blue afterglow carbon dots is 5:1.
[0084] Depend on Figure 7The optimal excitation wavelength for the carbon dots was found to be 280 nm, and the maximum emission wavelength was 410 nm, indicating that the synthesized carbon dots exhibited blue afterglow. Figure 8 It can be seen that the maximum emission wavelength of fluorescence in Example 9 is 410 nm at the optimal excitation wavelength of 280 nm for carbon dots, and the maximum emission wavelength of phosphorescence in Example 9 is also 410 nm. This is the same as the maximum emission wavelength of fluorescence, so the blue afterglow of Example 9 is delayed fluorescence.
[0085] Depend on Figure 9 As can be seen from the afterglow lifetime decay diagram, in Example 9, the lifetime at the maximum afterglow emission wavelength of 410nm is 962.98ms under the optimal excitation wavelength of 280nm.
[0086] The fluorescence quantum yield and phosphorescence quantum yield of Example 2 at 340 nm, Example 8 at 275 nm, and Example 9 at 280 nm are shown in Table 13.
[0087] Table 13 Photoluminescence and phosphorescence quantum yields of Examples 2, 8, and 9
[0088] Example 2 Example 8 Example 9 PLQY (%) 59.7 51.5 86.1 PhQY(%) 0.72 6.4 60.7
[0089] Figure 10 From top to bottom, these are Examples 2, 8, and 9. Example 2, under 254nm excitation, has a red afterglow visible to the naked eye for 2 seconds. Example 8, under 254nm excitation, has a green afterglow visible to the naked eye for 28 seconds. Example 9, under 254nm excitation, has a blue afterglow visible to the naked eye for 15 seconds. This demonstrates the preparation of RGB room temperature phosphorescent carbon dots.
[0090] Figure 11 The flowers, leaves, and stems were fabricated using methods from Examples 2, 8, and 9, respectively. It can be observed that after the 254nm excitation light was turned off for 1 second, the flowers appeared red, the leaves green, and the stems blue. After the 254nm excitation light was turned off for 10 seconds, the red flowers disappeared, while the green leaves and blue stems remained. After the 254nm excitation light was turned off for 15 seconds, the red flowers and blue stems disappeared, leaving only the green leaves. After the 365nm excitation light was turned off for 1 second, red flowers and green leaves appeared. After the 365nm excitation light was turned off for 5 seconds, the red flowers disappeared, leaving only the green leaves.
[0091] Example 2 exhibits red phosphorescence emission and a long afterglow lifetime of 216.30 ms, demonstrating both a long lifetime and a long phosphorescence emission wavelength. Example 8 has a long afterglow lifetime of 1.53 s and a phosphorescence quantum yield of 6.4%, also exhibiting a long lifetime. Example 9 has a long afterglow lifetime of 962.98 ms and a phosphorescence quantum yield of 60.7%, demonstrating both a long lifetime and a high phosphorescence quantum yield.
Claims
1. A method for rapidly synthesizing RGB room temperature phosphorescent carbon dots by microwave heating, characterized in that, The steps are as follows: Step 1: Dissolve sodium carbonate and sodium bicarbonate in ultrapure water and stir until completely dissolved to prepare a buffer solution; Step 2: Add α-cyclodextrin and urea to the buffer solution and stir until completely dissolved. Then add 1-pyreneboronic acid, 9-phenanthrolineboronic acid and 4-methyl phenylboronic acid respectively. Microwave the mixture in a microwave oven for 50-200 seconds. After cooling to room temperature, red, green and blue room temperature phosphorescent carbon dots are obtained respectively. In step 2, the mass ratios of urea to 1-pyreneboronic acid, urea to 9-phenanthreneboronic acid, and urea to 4-methylphenylboronic acid are all 5:1 to 20:
1. The mass ratios of α-cyclodextrin to 1-pyreneboronic acid, α-cyclodextrin to 9-phenanthrolineboronic acid, and α-cyclodextrin to 4-methyl phenylboronic acid were all 20:1 to 100:
1.
2. The method according to claim 1, characterized in that, In step 1, the concentration of sodium carbonate in the buffer solution is 10 mmol / L, the concentration of sodium bicarbonate is 90 mmol / L, and the pH is 9-10.
3. The method according to claim 1, characterized in that, In step 2, the microwave reaction time is 90 s.