Preparation method of rhodamine b derivative full-color laser carbon dots
By synthesizing panchromatic laser carbon dots using a solvothermal method with Rhodamine B as a precursor, the problem of insufficient gain performance of existing carbon dots has been solved, achieving higher fluorescence quantum yield, radiative transition rate and lower laser threshold, thus expanding the application of carbon dots in the field of laser technology.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHENGZHOU UNIV
- Filing Date
- 2024-05-21
- Publication Date
- 2026-05-19
AI Technical Summary
The low fluorescence quantum yield, radiative transition rate, and gain coefficient of existing carbon dots result in a high lasing threshold, which is not conducive to expanding and promoting their practical application in the field of laser technology.
Using Rhodamine B as a precursor, carbon dots were synthesized via a solvothermal method, and cross-linking enhancement luminescence was achieved through chemical cross-linking or physical confinement of polymer chains to prepare full-color laser carbon dots, including blue, green, yellow, red, and near-infrared carbon dots.
It improves the fluorescence quantum yield, radiative transition rate and laser stability of carbon dots, and lowers the laser threshold, making its gain performance superior to that of Rhodamine B.
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Figure CN118652683B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of luminescent material preparation, specifically relating to a method for preparing rhodamine B-derived panchromatic laser carbon dots.
[0002] This invention belongs to the strategic emerging industries catalogue, specifically to the next-generation information technology industry, under the key direction of the core electronics industry, specifically to the following sub-directions: 1.3.2 Novel display devices, novel display materials, and quantum dot materials. Background Technology
[0003] The development of novel optical gain materials is a major driving force behind laser technology innovation, making miniaturized lasers, localized in space, a cornerstone of modern information technology. Solution-processable gain materials, represented by organic semiconductors, colloidal quantum dots, and perovskites, are leading the research frontier in the field of micro-nano laser technology. Due to their advantages such as material diversity, easily tunable emission, ease of processing, and ease of integration, they show great application potential in flexible wearable devices, panel displays, smart interconnects, and information security. As the laser performance of these materials continues to achieve breakthroughs, the issues of cost, toxicity, and stability become increasingly prominent, making the further development of low-cost, non-toxic, and stable novel nano-laser materials an urgent need.
[0004] Against this backdrop, fluorescent carbon dots, as a novel solution-processable zero-dimensional carbon-based nanomaterial, have abundant raw material sources and simple preparation methods, which greatly reduce production costs; these advantages make carbon dots a strong competitor to solution-processable gain materials.
[0005] However, compared with commonly used commercial laser dyes, current carbon dots (CDs) generally have lower fluorescence quantum yields, radiative transition rates, and gain coefficients, resulting in higher lasing thresholds. This hinders the expansion and promotion of their practical applications. Therefore, improving the gain performance of carbon dots is of great significance for advancing carbon dot-based micro / nano lasers.
[0006] The cross-linking-enhanced luminescence properties of carbon dots are ideal for constructing high-gain performance. The cross-linking-enhanced luminescence effect allows non-luminescent or weakly luminescent carbonized polymer dots to effectively suppress nonradiative transitions and improve their fluorescence quantum yield through covalent bonds, supramolecular interactions, ionic bonds, or confinement. Cross-linking-enhanced luminescence can be achieved through chemical cross-linking or physical confinement of polymer chains to enhance gain performance.
[0007] Rhodamine B, as a mature commercial fluorescent dye, boasts high fluorescence quantum efficiency, excellent gain performance, and good resistance to photobleaching, making it widely applicable in many fields such as biology, physiology, pharmacology, molecular sensors, and laser dyes. Therefore, we plan to conduct experiments to synthesize carbon dots using Rhodamine B as a precursor, providing a universal method for developing high-gain carbon dots, which can expand and promote the practical application of carbon dot lasers. Summary of the Invention
[0008] To address the aforementioned problems in existing technologies, this invention provides a method for preparing panchromatic laser carbon dots based on Rhodamine B derivatives. Using Rhodamine B as a precursor, carbon dots are synthesized via a solvothermal method, extending the excellent gain performance of Rhodamine B from orange and red to the entire visible and near-infrared light regions.
[0009] The objective of this invention is achieved through the following method: a method for preparing rhodamine B-derived panchromatic laser carbon dots, comprising the following steps:
[0010] (1) When Rhodamine B is ultrasonically dispersed in a liquid solvent, it is transferred to a high-pressure autoclave lined with polytetrafluoroethylene and heated at 140-240℃ for 6-10 hours, and then naturally cooled to room temperature to obtain a carbon dot solution; when Rhodamine B is mixed evenly with the solid, it is transferred to a beaker and heated at 180-240℃ for 6-10 hours, and then naturally cooled to room temperature to obtain a crude solid carbon dot product. The crude solid carbon dot product is dissolved in ethanol to obtain a carbon dot solution.
[0011] (2) The carbon dot solution was filtered through a microporous membrane to remove trace amounts of insoluble impurities, and then eluted or dialyzed, purified, and freeze-dried to obtain solid carbon dot powder.
[0012] When the solid is NaOH or KOH, blue carbon dots are prepared.
[0013] When the solvent is NaOH or KOH solution, green carbon dots are prepared.
[0014] When the solvent is Na2CO3 or K2CO3 solution, yellowish carbon dots are obtained;
[0015] When ethanol is used as the solvent, red carbon dots are obtained;
[0016] Near-infrared carbon dots are prepared when the solvent is a mixture of ethanol and concentrated sulfuric acid.
[0017] The preparation method of blue carbon dots includes the following steps: 0.02-1g of Rhodamine B and 0.1-1g of NaOH or KOH solid are mixed evenly, transferred to a beaker, and heated continuously at 180-240℃ for 6-10h. After natural cooling to room temperature, a crude blue carbon dot product solid is obtained; the obtained crude blue carbon dot product solid is dissolved in ethanol to obtain a crude blue carbon dot product solution; the obtained blue carbon dot suspension is filtered through a microporous membrane to remove trace amounts of insoluble impurities, and then the crude product is purified by column chromatography using a mixture of ethyl acetate and petroleum ether as eluent. After lyophilization, a blue carbon dot solid powder is obtained.
[0018] A method for preparing green carbon dots, characterized by the following steps: 0.02-1g of Rhodamine B is ultrasonically dispersed in 10-20mL of 1M NaOH or KOH solution, then transferred to a high-pressure reactor lined with polytetrafluoroethylene, and heated continuously at 160-240℃ for 6-10h, then naturally cooled to room temperature to obtain a green carbon dot suspension; the obtained green carbon dot suspension is filtered through a microporous membrane to remove trace amounts of insoluble impurities, then dialyzed with a dialysis bag for 5-8h to remove unreacted raw materials and purify the sample, and finally freeze-dried to obtain green carbon dot solid powder.
[0019] A method for preparing yellow carbon dots, characterized by the following steps: 0.02-1g of Rhodamine B is ultrasonically dispersed in 10-20mL of 0.36M K2CO3 or Na2CO3 solution, then transferred to a high-pressure reactor lined with polytetrafluoroethylene, and heated continuously at 140-240℃ for 6-10h, and then naturally cooled to room temperature to obtain a yellow carbon dot suspension; the obtained yellow carbon dot suspension is filtered through a microporous membrane to remove trace amounts of insoluble impurities, then dialyzed with a dialysis bag for 5-8h to remove unreacted raw materials and purify the sample, and then freeze-dried to obtain yellow carbon dot solid powder.
[0020] The method for preparing red-light carbon dots is characterized by the following steps: 0.02-1g of Rhodamine B is ultrasonically dispersed in 10-20mL of ethanol, then transferred to a high-pressure reactor lined with polytetrafluoroethylene, and heated continuously at 160-240℃ for 6-10h, and then naturally cooled to room temperature to obtain a crude red-light carbon dot product solution; the obtained red-light carbon dot suspension is filtered through a microporous membrane to remove trace amounts of insoluble impurities, and then dialyzed with a dialysis bag for 5-8h to remove unreacted raw materials and purify the sample, and then freeze-dried to obtain a solid powder of red-light carbon dots.
[0021] A method for preparing near-infrared photocarbon dots, characterized by the following steps: 0.02-1g of Rhodamine B is ultrasonically dispersed in a mixed solution of 10-20mL ethanol and 100-1000μL concentrated sulfuric acid, then transferred to a high-pressure reactor lined with polytetrafluoroethylene, and heated continuously at 160-240℃ for 6-10h, and naturally cooled to room temperature to obtain a crude near-infrared photocarbon dot product solution; the obtained near-infrared photocarbon dot suspension is filtered through a microporous membrane to remove trace amounts of insoluble impurities, then dialyzed with a dialysis bag for 5-8h to remove unreacted raw materials and purify the sample, and then freeze-dried to obtain near-infrared photocarbon dot solid powder.
[0022] The microporous membrane used for filtration has a pore size of 0.22 μm.
[0023] The molecular weight cutoff of the dialysis bag is 1000 Da.
[0024] Compared with existing technologies, this invention uses Rhodamine B as a precursor and synthesizes carbon dots by a solvothermal method, extending the excellent gain performance of Rhodamine B from orange and red to the entire visible and near-infrared light regions. It can even enhance the emission effect through crosslinking. The gain performance of carbon dots exceeds that of Rhodamine B, with higher fluorescence quantum yield, higher radiative transition rate, lower laser threshold, and better laser stability. Attached Figure Description
[0025] Figure 1 This is a flowchart of the preparation process for multicolor laser carbon dots.
[0026] Figure 2 This is a transmission electron microscope image of the blue carbon dot B-CDs prepared in Example 1.
[0027] Figure 3 This is a transmission electron microscope image of the green carbon dots G-CDs prepared in Example 2.
[0028] Figure 4 This is a transmission electron microscope image of the yellow carbon dots Y-CDs prepared in Example 3.
[0029] Figure 5 This is a transmission electron microscope image of the red carbon dot R-CDs prepared in Example 4.
[0030] Figure 6 This is a transmission electron microscope image of the near-infrared carbon dots (NIR-CDs) prepared in Example 5.
[0031] Figure 7 This is an XRD image of the blue carbon dot B-CDs prepared in Example 1.
[0032] Figure 8 This is an XRD image of the green carbon dots G-CDs prepared in Example 2.
[0033] Figure 9 This is an XRD image of the yellow carbon dots Y-CDs prepared in Example 3.
[0034] Figure 10 This is an XRD image of the red carbon dot R-CDs prepared in Example 4.
[0035] Figure 11 This is an XRD image of the near-infrared carbon dot NIR-CDs prepared in Example 5.
[0036] Figure 12 This is the infrared spectrum of the blue carbon dots B-CDs prepared in Example 1.
[0037] Figure 13 This is the infrared spectrum of the green carbon dots G-CDs prepared in Example 2.
[0038] Figure 14 This is the infrared spectrum of the yellow carbon dots Y-CDs prepared in Example 3.
[0039] Figure 15 This is the infrared spectrum of the red carbon dot R-CDs prepared in Example 4.
[0040] Figure 16 This is the infrared spectrum of the near-infrared carbon dots (NIR-CDs) prepared in Example 5.
[0041] Figure 17 The absorption and fluorescence emission spectra of the blue carbon dot B-CDs prepared in Example 1 are shown.
[0042] Figure 18 The quantum yield of the blue carbon dot B-CDs prepared in Example 1 is shown.
[0043] Figure 19 This refers to the lifetime of the blue carbon dot B-CDs prepared in Example 1.
[0044] Figure 20 The absorption and fluorescence emission spectra of the green carbon dots G-CDs prepared in Example 2 are shown.
[0045] Figure 21 The quantum yield of the green carbon dots G-CDs prepared in Example 2 is shown.
[0046] Figure 22 This is the lifetime of the green carbon dots G-CDs prepared in Example 2.
[0047] Figure 23 The absorption and fluorescence emission spectra of the yellow carbon dots Y-CDs prepared in Example 3 are shown.
[0048] Figure 24The quantum yield of the yellow carbon dots Y-CDs prepared in Example 3 is shown.
[0049] Figure 25 This refers to the lifetime of the yellow light carbon dots Y-CDs prepared in Example 3.
[0050] Figure 26 The absorption and fluorescence emission spectra of the red carbon dot R-CDs prepared in Example 4 are shown.
[0051] Figure 27 The quantum yield of the red carbon dot R-CDs prepared in Example 4 is shown.
[0052] Figure 28 This refers to the lifetime of the red carbon dot R-CDs prepared in Example 4.
[0053] Figure 29 The absorption and fluorescence emission spectra of near-infrared carbon dots (NIR-CDs) prepared in Example 5 are shown.
[0054] Figure 30 The quantum yield of the near-infrared carbon dots (NIR-CDs) prepared in Example 5 is shown.
[0055] Figure 31 This refers to the lifetime of the near-infrared carbon dot NIR-CDs prepared in Example 5.
[0056] Figure 32 The radiative transition rates are those of blue carbon dots B-CDs, green carbon dots G-CDs, yellow carbon dots Y-CDs, red carbon dots R-CDs, near-infrared carbon dots NIR-CDs, and rhodamine B prepared in Examples 1-5, respectively.
[0057] Figure 33 The maximum stimulated emission cross sections are those of blue carbon dots B-CDs, green carbon dots G-CDs, yellow carbon dots Y-CDs, red carbon dots R-CDs, near-infrared carbon dots NIR-CDs, and rhodamine B prepared in Examples 1-5, respectively.
[0058] Figure 34 This is the laser emission spectrum of the blue carbon dot B-CDs prepared in Example 1.
[0059] Figure 35 This is a laser spot photograph of the blue carbon dot B-CDs prepared in Example 1.
[0060] Figure 36 This is the high-resolution spectrum of the blue carbon dot B-CDs prepared in Example 1.
[0061] Figure 37 This is a threshold curve of the blue carbon dot B-CDs prepared in Example 1.
[0062] Figure 38This is a stability curve of the blue carbon dot B-CDs prepared in Example 1.
[0063] Figure 39 This is the laser emission spectrum of the green carbon dots G-CDs prepared in Example 2.
[0064] Figure 40 This is a laser spot photograph of the green carbon dots G-CDs prepared in Example 2.
[0065] Figure 41 This is the high-resolution spectrum of the green carbon dot G-CDs prepared in Example 2.
[0066] Figure 42 This is a threshold curve of the green carbon dots G-CDs prepared in Example 2.
[0067] Figure 43 This is a stability curve of the green carbon dots G-CDs prepared in Example 2.
[0068] Figure 44 This is the laser emission spectrum of the yellow carbon dots Y-CDs prepared in Example 3.
[0069] Figure 45 This is a laser spot photograph of the yellow carbon dots Y-CDs prepared in Example 3.
[0070] Figure 46 This is the high-resolution spectrum of the yellow carbon dot Y-CDs prepared in Example 3.
[0071] Figure 47 This is a threshold curve of the yellow carbon dots Y-CDs prepared in Example 3.
[0072] Figure 48 This is a stability curve of the yellow carbon dots Y-CDs prepared in Example 3.
[0073] Figure 49 This is the laser emission spectrum of the red carbon dot R-CDs prepared in Example 4.
[0074] Figure 50 This is a laser spot photograph of the red carbon dot R-CDs prepared in Example 4.
[0075] Figure 51 This is the high-resolution spectrum of the red carbon dot R-CDs prepared in Example 4.
[0076] Figure 52 This is a threshold curve of the red carbon dot R-CDs prepared in Example 4.
[0077] Figure 53 This is a stability curve of the red carbon dots R-CDs prepared in Example 4.
[0078] Figure 54 This is the laser emission spectrum of the near-infrared carbon dots (NIR-CDs) prepared in Example 5.
[0079] Figure 55 This is a laser spot photograph of the near-infrared carbon dots (NIR-CDs) prepared in Example 5.
[0080] Figure 56 This is the high-resolution spectrum of the near-infrared carbon dot NIR-CDs prepared in Example 5.
[0081] Figure 57 This is a threshold curve of the near-infrared carbon dots (NIR-CDs) prepared in Example 5.
[0082] Figure 58 This is a stability curve of the near-infrared carbon dots (NIR-CDs) prepared in Example 5.
[0083] Figure 59 This is the absorption and fluorescence emission spectrum of Rhodamine B, with an absorption peak at 544 nm and an emission peak at 597 nm.
[0084] Figure 60 The quantum yield of Rhodamine B is 45.19%.
[0085] Figure 61 The lifetime of Rhodamine B is 3.32 ns.
[0086] Figure 62 This is the laser emission spectrum of Rhodamine B, with a laser emission peak at 592 nm.
[0087] Figure 63 This is the threshold curve of Rhodamine B. The laser threshold of Rhodamine B is 45.6 mJ / cm². -2 .
[0088] Figure 64 This is the stability curve of Rhodamine B. After continuously pumping the Rhodamine B laser for 6 hours at twice the laser threshold, the laser intensity of Rhodamine B becomes 0.61 times the initial laser intensity. Detailed Implementation
[0089] To more clearly illustrate the technical solutions in this invention or the prior art, the invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0090] Example 1
[0091] 0.5 g of Rhodamine B and 0.8 g of NaOH solid were mixed evenly and transferred to a beaker. The mixture was heated at 200 °C for 8 h and then naturally cooled to room temperature to obtain a crude blue carbon dot product solid. The crude blue carbon dot product solid was dissolved in ethanol to obtain a crude blue carbon dot product solution. The obtained blue carbon dot suspension was filtered through a microporous membrane with a pore size of 0.22 μm to remove trace amounts of insoluble impurities. Then, the crude product was purified by column chromatography using a mixture of ethyl acetate and petroleum ether as eluent. After lyophilization, a solid blue carbon dot powder was obtained.
[0092] Figure 2 This is a transmission electron microscope (TEM) image of the blue carbon dots prepared in Example 1. From... Figure 2 It can be seen that the blue carbon dots are spherical or quasi-spherical in shape. The average particle size of the blue carbon dots B-CDs is 3.7 nm. The high-resolution transmission electron microscope image shows that the blue carbon dots have a crystal plane spacing of 0.21 nm, which corresponds to the graphite (100) crystal plane, meaning that the blue carbon dots have a graphitized structure.
[0093] Figure 7 This is the XRD pattern of the blue carbon dots prepared in Example 1. The diffraction peak at 25.4° corresponds to the interlayer spacing of the (002) plane of graphite.
[0094] Figure 12 This is the infrared spectrum of the blue carbon dots prepared in Example 1. (1387 cm⁻¹) -1 Attributable to CN tensile vibration, 3702cm -1 Attributable to -OH tensile vibration, 1740 cm -1 Attributable to C=O tensile vibration, 1134 cm -1 This is attributed to CO stretching vibrations. This indicates that the surface of CDs contains abundant polar functional groups, such as -OH and -COOH, which gives CDs good solubility in polar solvents. This is beneficial for increasing the absorption cross-section of pump light by increasing the concentration of carbon dots in optical pumping experiments, thus helping to increase laser emission efficiency.
[0095] Figure 17 These are the absorption and emission spectra of blue carbon dot B-CDs, with the absorption peak at 385 nm and the emission peak at 434 nm.
[0096] Figure 18 The fluorescence quantum yield of blue carbon dot B-CDs was 49.94%.
[0097] Figure 19 The lifetime of the blue carbon dot B-CDs is shown to be 2.13 ns.
[0098] Figure 34The laser spectrum of blue carbon dots B-CDs is shown, with a laser emission peak at 450 nm.
[0099] Figure 35 This is a laser spot photograph of blue carbon dots (B-CDs), indicating the occurrence of stimulated emission.
[0100] Figure 36 This is a high-resolution spectrum of blue carbon dot B-CDs. The high-resolution laser spectrum shows numerous fine longitudinal modes, which are characteristic of random lasers.
[0101] Figure 37 This is a threshold curve of blue carbon dot (B-CDs). The laser threshold of B-CDs is 31.24 mJ / cm². -2 .
[0102] Figure 38 This is a stability curve of blue carbon dot lasers (B-CDs). After continuous pumping of the B-CD laser at twice the laser threshold for 6 hours, the laser intensity of the B-CDs became 0.92 times the initial laser intensity, indicating that B-CDs have excellent stability.
[0103] Example 2
[0104] Dissolve 4g of NaOH in 10mL of distilled water. After cooling to room temperature, transfer the solution to a 100mL volumetric flask, make up to volume, and shake well to obtain a 1M NaOH solution. The preparation method for KOH solution is the same.
[0105] 0.5 g of Rhodamine B was ultrasonically dispersed in 20 mL of 1 M NaOH solution, then transferred to a high-pressure autoclave lined with polytetrafluoroethylene (PTFE), and heated at 220 °C for 8 h. After natural cooling to room temperature, a green carbon dot suspension was obtained. The green carbon dot suspension was filtered through a microporous membrane with a pore size of 0.22 μm to remove trace amounts of insoluble impurities. Then, it was dialyzed for 8 h using a dialysis bag with a molecular weight cutoff of 1000 Da to remove unreacted raw materials and purify the sample. After lyophilization, a green carbon dot solid powder was obtained.
[0106] Figure 3 This is a transmission electron microscope (TEM) image of the green carbon dots prepared in Example 2. From... Figure 3 It can be seen that the green carbon dots are spherical or quasi-spherical in shape. The average particle size of the green carbon dots G-CDs is 3.6 nm. The high-resolution transmission electron microscope image shows that the green carbon dots have a crystal plane spacing of 0.21 nm, which corresponds to the graphite (100) crystal plane, meaning that the green carbon dots have a graphitized structure.
[0107] Figure 8 This is the XRD pattern of the green carbon dots prepared in Example 2. The diffraction peak at 23.8° corresponds to the interlayer spacing of the (002) plane of graphite.
[0108] Figure 13 This is the infrared spectrum of the green carbon dots prepared in Example 2. (3418 cm⁻¹) -1 Attributable to the -NH / OH tensile vibration, 1614 cm -1 Attributable to C=O tensile vibration and 1387cm -1 The presence of abundant polar functional groups, such as -NH2, -OH, and -COOH, on the surface of G-CDs, as attributed to CN stretching vibrations, gives G-CDs good solubility in polar solvents. This, in turn, facilitates increasing the absorption cross-section of pump light by increasing the carbon dot concentration in optical pumping experiments, thereby contributing to increased laser emission efficiency.
[0109] Figure 20 These are the absorption and emission spectra of green carbon dots (G-CDs), with the absorption peak at 490 nm and the emission peak at 532 nm.
[0110] Figure 21 The fluorescence quantum yield of green carbon dots G-CDs was 96.84%.
[0111] Figure 22 The lifetime of the green carbon dots G-CDs is shown to be 4.50 ns.
[0112] Figure 39 The laser spectrum of green carbon dots G-CDs is shown, with a laser emission peak at 531.6 nm.
[0113] Figure 40 This is a laser spot photograph of green carbon dots (G-CDs), indicating the occurrence of stimulated emission.
[0114] Figure 41 This is a high-resolution spectrum of green carbon dots (G-CDs). The high-resolution laser spectrum shows numerous fine longitudinal modes, which are characteristic of random lasers.
[0115] Figure 42 This is the threshold curve of green carbon dots (G-CDs). The laser threshold of G-CDs is 34.5 mJ / cm². -2 .
[0116] Figure 43 This is a stability curve of green carbon dots (G-CDs). After continuous pumping of the G-CD laser at twice the laser threshold for 6 hours, the laser intensity of the G-CDs became 0.93 times the initial laser intensity, indicating that G-CDs have excellent stability.
[0117] Example 3
[0118] 5g of K2CO3 was dissolved in 10mL of distilled water. After cooling to room temperature, the solution was transferred to a 100mL volumetric flask, diluted to volume, and shaken well to obtain a 0.36M NaOH solution. The preparation method for Na2CO3 solution is the same.
[0119] 0.04 g of Rhodamine B was ultrasonically dispersed in 20 mL of 0.36 M K2CO3 solution, and then transferred to a high-pressure autoclave lined with polytetrafluoroethylene. The autoclave was heated at 180 °C for 6 h and then naturally cooled to room temperature to obtain a yellow carbon dot suspension. The yellow carbon dot suspension was filtered through a 0.22 μm microporous membrane to remove trace amounts of insoluble impurities. The suspension was then dialyzed for 8 h using a dialysis bag to remove unreacted raw materials and purify the sample. After lyophilization, the yellow carbon dot solid powder was obtained.
[0120] Figure 4 This is a transmission electron microscope (TEM) image of the yellowish carbon dots prepared in Example 3. From... Figure 4 It can be seen that the yellow carbon dots are spherical or quasi-spherical in shape. The average particle size of the yellow carbon dots Y-CDs is 2.3 nm. The high-resolution transmission electron microscope image shows that the yellow carbon dots have a crystal plane spacing of 0.21 nm, which corresponds to the graphite (100) crystal plane, meaning that the yellow carbon dots have a graphitized structure.
[0121] Figure 9 This is the XRD pattern of the yellow carbon dots prepared in Example 3. The diffraction peak at 24.1° corresponds to the interlayer spacing of the (002) plane of graphite.
[0122] Figure 14 This is the infrared spectrum of the yellow carbon dots prepared in Example 3. (3418 cm⁻¹) -1 Attributable to the -NH / OH tensile vibration, 1614 cm -1 Attributable to C=O tensile vibration and 1387cm -1 The presence of abundant polar functional groups, such as -NH2, -OH, and -COOH, on the surface of Y-CDs, as attributed to CN stretching vibrations, gives Y-CDs good solubility in polar solvents. This is beneficial for increasing the absorption cross-section of pump light by increasing the carbon dot concentration in optical pumping experiments, which helps to increase laser emission efficiency.
[0123] Figure 23 These are the absorption and emission spectra of yellow carbon dots Y-CDs, with the absorption peak at 491 nm and the emission peak at 557 nm.
[0124] Figure 24 The fluorescence quantum yield of the yellow carbon dots Y-CDs was shown to be 58.02%.
[0125] Figure 25The lifetime of the yellow carbon dots Y-CDs is shown to be 4.31 ns.
[0126] Figure 44 The laser spectrum of yellow carbon dots Y-CDs is shown, with a laser emission peak at 561.4 nm.
[0127] Figure 45 The image shows a laser spot photograph of yellow carbon dots Y-CDs, indicating the occurrence of stimulated emission.
[0128] Figure 46 This is a high-resolution spectrum of yellow carbon Y-CDs. The high-resolution laser spectrum shows numerous fine longitudinal modes, which are characteristic of random lasers.
[0129] Figure 47 This is the threshold curve of yellow-light carbon dots Y-CDs. The laser threshold of Y-CDs is 15.1 mJ / cm². -2 .
[0130] Figure 48 The graph shows the stability of the yellow carbon dot Y-CDs. After continuous pumping of the Y-CDs laser for 6 hours at twice the laser threshold, the laser intensity of the Y-CDs became 0.91 times the initial laser intensity, indicating that the Y-CDs have excellent stability.
[0131] Example 4
[0132] 0.5 g of Rhodamine B was ultrasonically dispersed in 20 mL of ethanol, then transferred to a high-pressure autoclave lined with polytetrafluoroethylene, and heated at 220 °C for 8 h. After natural cooling to room temperature, a crude red carbon dot product solution was obtained. The obtained red carbon dot suspension was filtered through a microporous membrane with a pore size of 0.22 μm to remove trace amounts of insoluble impurities. Then, it was dialyzed for 8 h using a dialysis bag with a molecular weight cutoff of 1000 Da to remove unreacted raw materials. The sample was purified and lyophilized to obtain a solid red carbon dot powder.
[0133] Figure 5 This is a transmission electron microscope (TEM) image of the red-light carbon dots prepared in Example 4. From... Figure 5 It can be seen that the red carbon dots are spherical or quasi-spherical in shape. The average particle size of the red carbon dots R-CDs is 2.4 nm. The high-resolution transmission electron microscope image shows that the red carbon dots have a crystal plane spacing of 0.21 nm, which corresponds to the graphite (100) crystal plane, meaning that the red carbon dots have a graphitized structure.
[0134] Figure 10 This is the XRD pattern of the red carbon dots prepared in Example 4. The diffraction peak at 23.2° corresponds to the interlayer spacing of the (002) plane of graphite.
[0135] Figure 15This is the infrared spectrum of the red carbon dots prepared in Example 4. (3418 cm⁻¹) -1 Attributable to the -NH / OH tensile vibration, 1614 cm -1 Attributable to C=O tensile vibration and 1387cm -1 The presence of abundant polar functional groups, such as -NH2, -OH, and -COOH, on the surface of R-CDs, as attributed to CN stretching vibrations, gives R-CDs good solubility in polar solvents. This is beneficial for increasing the absorption cross-section of pump light by increasing the carbon dot concentration in optical pumping experiments, which helps to increase laser emission efficiency.
[0136] Figure 26 These are the absorption and emission spectra of red carbon dot R-CDs, with the absorption peak at 546 nm and the emission peak at 628 nm.
[0137] Figure 27 The fluorescence quantum yield of red carbon dot R-CDs was shown to be 57.19%.
[0138] Figure 28 The lifetime of the red carbon dot R-CDs is shown to be 3.21 ns.
[0139] Figure 49 The laser spectrum of red carbon dots (R-CDs) is shown, with a laser emission peak at 631.6 nm.
[0140] Figure 50 This is a laser spot photograph of red carbon dots (R-CDs), indicating the occurrence of stimulated emission.
[0141] Figure 51 This is a high-resolution spectrum of red carbon dot R-CDs. The high-resolution laser spectrum shows numerous fine longitudinal modes, which are characteristic of random lasers.
[0142] Figure 52 This is a threshold curve of red carbon dot (R-CDs). The laser threshold of R-CDs is 15.8 mJ / cm². -2 .
[0143] Figure 53 This is a stability curve of red carbon dot R-CDs. After continuous pumping of the R-CDs laser at twice the laser threshold for 6 hours, the laser intensity of the R-CDs became 0.96 of the initial laser intensity, indicating that the R-CDs have excellent stability.
[0144] Example 5
[0145] 0.5 g of Rhodamine B was ultrasonically dispersed in a mixed solution of 20 mL ethanol and 600 μL concentrated sulfuric acid, and then transferred to a high-pressure autoclave lined with polytetrafluoroethylene. The autoclave was heated at 210 °C for 8 h and then naturally cooled to room temperature to obtain a crude near-infrared carbon dot product solution. The obtained near-infrared carbon dot suspension was filtered through a microporous membrane with a pore size of 0.22 μm to remove trace amounts of insoluble impurities. The solution was then dialyzed for 8 h using a dialysis bag with a molecular weight cutoff of 1000 Da to remove unreacted raw materials and purify the sample. After lyophilization, a near-infrared carbon dot solid powder was obtained.
[0146] Figure 6 This is a transmission electron microscope (TEM) image of the near-infrared carbon dots prepared in Example 5. From... Figure 6 It can be seen that the near-infrared carbon dots have a spherical or quasi-spherical structure. The average particle size of the near-infrared carbon dots NIR-CDs is 6.7 nm. The high-resolution transmission electron microscope image shows that the near-infrared carbon dots have a crystal plane spacing of 0.21 nm, which corresponds to the graphite (100) crystal plane, meaning that the near-infrared carbon dots have a graphitized structure.
[0147] Figure 11 This is the XRD pattern of the near-infrared carbon dots prepared in Example 5. The diffraction peak at 22.2° corresponds to the interlayer spacing of the (002) plane of graphite.
[0148] Figure 16 This is the infrared spectrum of the near-infrared carbon dots prepared in Example 5. (3418 cm⁻¹) -1 Attributable to the -NH / OH tensile vibration, 1614 cm -1 Attributable to C=O tensile vibration and 1387cm -1 The presence of abundant polar functional groups, such as -NH2, -OH, and -COOH, on the surface of NIR-CDs, due to the CN stretching vibration, gives NIR-CDs good solubility in polar solvents. This is beneficial for increasing the absorption cross-section of pump light by increasing the carbon point concentration in optical pumping experiments, which helps to increase laser emission efficiency.
[0149] Figure 29 These are the absorption and emission spectra of near-infrared carbon dots (NIR-CDs), with the absorption peak at 545 nm and the emission peak at 703 nm.
[0150] Figure 30 The fluorescence quantum yield of near-infrared carbon dots (NIR-CDs) was 14.69%.
[0151] Figure 31 The lifetime of the near-infrared carbon dot NIR-CDs is shown to be 2.81 ns.
[0152] Figure 54The laser spectrum of near-infrared carbon dots (NIR-CDs) is shown, with a laser emission peak at 705.1 nm.
[0153] Figure 55 The image shows a laser spot photograph of near-infrared carbon dots (NIR-CDs), indicating the occurrence of stimulated emission.
[0154] Figure 56 It is a high-resolution spectrum of near-infrared carbon dots (NIR-CDs). The high-resolution laser spectrum shows numerous fine longitudinal modes, which are characteristic of random lasers.
[0155] Figure 57 This is a threshold curve of near-infrared carbon dots (NIR-CDs). The laser threshold of NIR-CDs is 126.8 mJ / cm². -2 .
[0156] Figure 58 This is a stability curve of near-infrared carbon dot (NIR-CDs). After continuous pumping of the NIR-CDs laser for 6 hours at twice the laser threshold, the laser intensity of the NIR-CDs became 0.93 times the initial laser intensity, indicating that NIR-CDs have excellent stability.
[0157] like Figure 32 As shown, the radiative transition rates of blue carbon dots B-CDs, green carbon dots G-CDs, yellow carbon dots Y-CDs, red carbon dots R-CDs, near-infrared carbon dots NIR-CDs, and rhodamine B prepared in Examples 1-5 are 2.34*10⁻⁶, respectively. 8 2.15*10 8 1.35*10 8 1.78*10 8 0.52*10 8 and 1.33*10 8 s -1 This indicates that, except for the near-infrared carbon dots, the radiative transition rates of the other carbon dots are all higher than those of Rhodamine B.
[0158] like Figure 33 As shown, the maximum stimulated emission cross sections of blue carbon dots B-CDs, green carbon dots G-CDs, yellow carbon dots Y-CDs, red carbon dots R-CDs, near-infrared carbon dots NIR-CDs, and Rhodamine B prepared in Examples 1-5 are 2.25*10⁻⁶, respectively. -16 2.6*10 -16 1.92*10 -16 3.00*10 -16 1.23*10 -16 and 1.61*10 -16 cm 2This indicates that, except for near-infrared carbon dots, the maximum stimulated emission cross-section of the other carbon dots is greater than that of Rhodamine B.
[0159] Except for near-infrared (NIR) carbon dots (NIR-CDs), the fluorescence quantum yield, radiative transition rate, and stimulated emission cross section of other visible light carbon dots are higher than those of Rhodamine B, while their threshold emission is lower. This is because our near-infrared emitting carbon dots were prepared using a method that increases particle size. This method has some drawbacks, such as a low fluorescence quantum yield, which leads to a low radiative transition rate and a small maximum stimulated emission cross section in the NIR-CDs. Although the fluorescence quantum yield, radiative transition rate, maximum stimulated emission cross section, and threshold emission of NIR-CDs are inferior to those of Rhodamine B, this method represents a novel approach for preparing near-infrared laser carbon dots. Our future goal is to further optimize the preparation method of NIR-CDs, improve their performance, and enable them to achieve fluorescence quantum yield, radiative transition rate, and maximum stimulated emission cross section comparable to, or even surpass, that of Rhodamine B.
[0160] The parameters for Examples 6-20 are shown in Table 1. The preparation methods for Examples 6-8 are the same as those for Example 1. The preparation methods for Examples 9-11 are the same as those for Example 2. The preparation methods for Examples 12-14 are the same as those for Example 3. The preparation methods for Examples 15-17 are the same as those for Example 4. The preparation methods for Examples 18-20 are the same as those for Example 5.
[0161] Table 1
[0162]
[0163] This invention utilizes low-cost Rhodamine B as a raw material, employing a one-step solvothermal treatment to obtain a crude product. After dialysis purification, multi-colored carbon dot materials in blue, green, yellow, red, and near-infrared spectroscopy are obtained. This invention enhances the emission effect through cross-linking, resulting in carbon dots with gain performance exceeding that of Rhodamine B, exhibiting higher fluorescence quantum yield, higher radiative transition rate, lower laser threshold, and superior laser stability. This invention provides a universal method for developing high-gain carbon dots, which can expand and promote the practical application of carbon dot lasers.
[0164] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several changes and improvements without departing from the overall concept of the present invention, and these should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing rhodamine B-derived panchromatic laser carbon dots, characterized in that: Includes the following steps, 0.02-1g of Rhodamine B was mixed with 0.1-1g of NaOH or KOH solid, transferred to a beaker, and heated at 180-240℃ for 6-10 h. After natural cooling to room temperature, a crude blue carbon dot product solid was obtained. The crude blue carbon dot product solid was dissolved in ethanol to obtain a crude blue carbon dot product solution. The obtained blue carbon dot suspension was filtered through a microporous membrane to remove trace amounts of insoluble impurities. Then, the crude product was purified by column chromatography using a mixture of ethyl acetate and petroleum ether as eluent. After lyophilization, a blue carbon dot solid powder was obtained. 0.02-1 g of Rhodamine B was ultrasonically dispersed in 10-20 mL of 0.36 M K2CO3 or Na2CO3 solution, and then transferred to a polytetrafluoroethylene-lined autoclave. The autoclave was heated at 140-240 °C for 6-10 h and then naturally cooled to room temperature to obtain a yellow carbon dot suspension. The yellow carbon dot suspension was filtered through a microporous membrane to remove trace amounts of insoluble impurities, and then dialyzed through a dialysis bag for 5-8 h to remove unreacted raw materials and purify the sample. After lyophilization, the yellow carbon dot solid powder was obtained. 0.02-1 g of Rhodamine B was ultrasonically dispersed in 10-20 mL of ethanol, then transferred to a high-pressure autoclave lined with polytetrafluoroethylene, and heated continuously at 160-240 °C for 6-10 h. After natural cooling to room temperature, a crude red carbon dot product solution was obtained. The obtained red carbon dot suspension was filtered through a microporous membrane to remove trace amounts of insoluble impurities, and then dialyzed with a dialysis bag for 5-8 h to remove unreacted raw materials and purify the sample. After lyophilization, a solid powder of red carbon dots was obtained.
2. The method for preparing rhodamine B-derived panchromatic laser carbon dots according to claim 1, characterized in that: The microporous membrane used for filtration has a pore size of 0.22 μm.
3. The method for preparing rhodamine B-derived panchromatic laser carbon dots according to claim 1, characterized in that: The molecular weight cutoff of the dialysis bag is 1000 Da.