Nitrogen and phosphorus co-doped solid luminescent carbon dots and preparation method thereof
The method of preparing nitrogen and phosphorus co-doped carbon dots by hydrothermal method solves the problem of aggregation-induced quenching of carbon dots under high concentration and solid state conditions, and achieves its wide application prospect in the fields of biology and photoelectricity.
Patent Information
- Application Number
- CN202411924207.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-25
- Publication Date
- 2025-05-06
AI Technical Summary
The existing carbon dots are prone to aggregation and induce quenching under high concentration and solid state conditions, which hinders its wide application in the fields of biological imaging, drug delivery, photoluminescent devices, etc.
The precursor of nitrogen and phosphorus co-doped carbon dots was prepared in a hydrothermal reaction by a mixed solution of 1,8-diaminonaphthalene and phosphorus acid. After purifying by column chromatography, a pure nitrogen and phosphorus co-doped carbon dots was obtained. Finally, the nitrogen and phosphorus co-doped solid-state luminescent carbon dots were obtained by thermal drying.
The good water solubility of nitrogen and phosphorus co-doped carbon dots and excellent liquid and solid-state fluorescence emission performance are achieved, and the problems of cumbersome preparation, high cost, difficult doping and poor solid-state luminescence performance in the existing methods are overcome.
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Figure CN119929780A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of luminescent carbon nanomaterial preparation, in particular to nitrogen and phosphorus co-doped solid luminescent carbon dots and a preparation method thereof. Background Art
[0002] Carbon dots are an emerging type of carbon-based nanomaterials. In terms of morphology and performance, carbon dots have both the size advantages and optical performance advantages of traditional quantum dots; in terms of elemental composition, carbon dots use carbon, which is abundant in nature, as the main element, which greatly reduces the cost of raw materials. In recent years, carbon dots have attracted the attention of countless researchers due to their excellent properties such as good water solubility, biocompatibility, photostability, low toxicity, adjustable luminescence, ultraviolet absorption and chemical inertness, and have become a research hotspot. Currently, carbon dots have been widely used in bioimaging, drug delivery, photoluminescent devices, electroluminescent devices, catalysis and energy storage.
[0003] Due to energy resonance transfer or π-π stacking, most carbon dots are prone to aggregation-induced quenching like organic molecules, which hinders the application of high-concentration and solid-state carbon dots. Common strategies for carbon dots to achieve solid-state fluorescence are: (1) dispersing carbon dots into appropriate matrices by means of adsorption, embedding, encapsulation, etc.; (2) surface engineering regulation, regulating the surface state of carbon dots, such as introducing long-chain blocking groups on the surface, manipulating surface charge distribution, and preventing aggregation. Compared with the rapid rise of liquid luminescent carbon dots, the research progress of solid-state luminescent carbon dots is still relatively slow. Therefore, the synthesis of high-performance solid-state luminescent carbon dots is in line with the current development needs. Summary of the invention
[0004] The purpose of the present invention is to provide a nitrogen-phosphorus co-doped solid-state luminescent carbon dot and a preparation method thereof. The nitrogen-phosphorus co-doped carbon dot prepared by the method of the present invention has good water solubility and excellent liquid and solid-state fluorescence emission properties.
[0005] The present invention is achieved in that:
[0006] The invention firstly utilizes a mixed solution of 1,8-diaminonaphthalene and phosphoric acid to perform a hydrothermal reaction in a reactor to obtain a precursor product of nitrogen-phosphorus co-doped carbon dots, then purifies the product by column chromatography to obtain a pure aqueous solution of nitrogen-phosphorus co-doped carbon dots, and finally obtains a nitrogen-phosphorus co-doped carbon dot solid by thermal drying.
[0007] The specific steps are: weigh 0.1-2.8g of 1,8-diaminonaphthalene solid and dissolve it in 20mL of phosphoric acid, and stir it magnetically to dissolve it; transfer the above solution to a hydrothermal kettle, and perform hydrothermal reaction at 120-300°C for 6-26 hours; after heating, cool the reactor to room temperature in a natural environment to obtain a precursor of nitrogen-phosphorus co-doped carbon dots; purify it by column chromatography, use deionized water as a washing solvent, and obtain a pure nitrogen-phosphorus co-doped carbon dot aqueous solution; finally, remove moisture with a rotary evaporator, and obtain solid luminescent carbon dots after drying.
[0008] In the above scheme, preferably, the concentration of phosphoric acid is 85%.
[0009] In the above scheme, preferably, the hydrothermal reaction conditions are: hydrothermal reaction at 240° C. for 16 to 26 hours.
[0010] In the above scheme, preferably, 1.2 to 2.8 g of 1,8-diaminonaphthalene solid is weighed and dissolved in 20 mL of phosphoric acid, and magnetic stirring is applied to dissolve the solid.
[0011] The nitrogen-phosphorus co-doped solid luminescent carbon dots prepared by the method of the present invention are orange-yellow in sunlight and green under ultraviolet light, which may be, for example, an ultraviolet light emitting at a wavelength of 365 nm or 395 nm.
[0012] The obtained nitrogen-phosphorus co-doped solid-state luminescent carbon dots form a carbon dot aqueous solution when in contact with water. The carbon dot aqueous solution is light green under sunlight and emits green fluorescence under ultraviolet light excitation.
[0013] The method of the present invention overcomes the drawbacks of the existing methods, such as cumbersome preparation, high cost, difficult doping, and difficulty in achieving solid-state luminescence of the prepared carbon dots. The precursor product of nitrogen and phosphorus doped carbon dots is prepared by a one-step hydrothermal method, and a pure aqueous solution of nitrogen and phosphorus doped carbon dots is obtained after purification by column chromatography, and finally a solid-state luminescent carbon dot is obtained by heat drying. The obtained nitrogen and phosphorus co-doped solid-state luminescent carbon dots have broad application prospects in the fields of ion detection, biological living body labeling, and light-emitting diode preparation. The method of the present invention is simple, easy to operate, low in cost, and high in output, and can achieve batch synthesis. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 These are the renderings of the nitrogen-phosphorus co-doped carbon dots prepared in Example 1 of the present invention under sunlight and ultraviolet light; wherein, (a) corresponds to the rendering of the liquid nitrogen-phosphorus co-doped carbon dots under sunlight and ultraviolet light; (b) corresponds to the rendering of the solid nitrogen-phosphorus co-doped carbon dots under sunlight and ultraviolet light.
[0015] Figure 2 1 is a transmission electron microscopy test result diagram of nitrogen-phosphorus co-doped carbon dots obtained in Example 1 of the present invention; wherein (a) is a transmission electron microscopy photograph of the carbon dots, and (b) is a particle size statistical distribution histogram of the carbon dots.
[0016] Figure 3 This is the X-ray dispersion spectrum of the nitrogen and phosphorus co-doped carbon dots obtained in Example 1 of the present invention.
[0017] Figure 4 It is an X-ray dispersion spectrum after surface scanning of two dispersed carbon dot particles selected from the nitrogen and phosphorus co-doped carbon dots obtained in Example 1 of the present invention.
[0018] Figure 5 1 is the X-ray photoelectron spectrum test result of the nitrogen-phosphorus co-doped carbon dots obtained in Example 1 of the present invention; wherein, (a) is the X-ray photoelectron spectrum of the carbon dots, and (b) is the proportion of each element of C, N, O, and P.
[0019] Figure 6 This is the fluorescence emission spectrum of the nitrogen and phosphorus co-doped carbon dot aqueous solution obtained in Example 1 of the present invention under 365nm ultraviolet light excitation.
[0020] Figure 7 1 and 2 are the absorption and excitation spectra of the nitrogen-phosphorus co-doped carbon dot aqueous solution obtained in Example 1 of the present invention.
[0021] Figure 8 This is the fluorescence emission spectrum of the nitrogen and phosphorus co-doped carbon dot solid powder obtained in Example 1 of the present invention under 365nm ultraviolet light excitation.
[0022] Fig. 9 It is the emission spectrum of the nitrogen and phosphorus co-doped carbon dot solid powder prepared in Examples 2 to 5 of the present invention under 395nm ultraviolet light excitation.
[0023] Fig.10 It is the emission spectrum of the nitrogen and phosphorus co-doped carbon dot solid powder prepared in Examples 6 to 12 of the present invention under 395nm ultraviolet light excitation. DETAILED DESCRIPTION
[0024] Example 1
[0025] Weigh 1.6 g of 1,8-diaminonaphthalene solid, dissolve it in 20 mL of 85% phosphoric acid, and stir it magnetically to dissolve it. Inject the above solution into a 25 mL polytetrafluoroethylene liner, then transfer it to a stainless steel reactor and hydrothermally react at 240 ° C for 16 hours. After heating, the reactor is cooled to room temperature under natural conditions to obtain the precursor of nitrogen-phosphorus co-doped carbon dots. Column chromatography is used for purification, and deionized water is used as the washing solvent to obtain a pure nitrogen-phosphorus co-doped carbon dot aqueous solution. Finally, a rotary evaporator is used to remove moisture, and an orange-yellow solid powder is obtained after drying.
[0026] Before removing water by rotary evaporator, the prepared nitrogen-phosphorus co-doped carbon dots aqueous solution was light green in sunlight. Figure 1(a) As shown in the glass bottle on the left; when the nitrogen-phosphorus co-doped carbon dots aqueous solution in the glass bottle is irradiated with a 365nm ultraviolet lamp, the nitrogen-phosphorus co-doped carbon dots emit bright green fluorescence, as shown in Figure 2. Figure 1 (a) Shown in the glass bottle on the right.
[0027] After removing the water by rotary evaporator and drying to obtain orange-yellow solid powder, the obtained orange-yellow solid powder is filled into two different logo grooves pre-engraved by laser, and the orange-yellow logo shape is displayed under sunlight, such as Figure 1 (b) As shown in the two figures above; when the two logos and the solid powder on them are irradiated with 365nm ultraviolet light, the solid powder emits green fluorescence, and the orange-yellow pattern turns green, as shown in the figure below. Figure 1 (b) As shown in the following two figures.
[0028] The orange-yellow solid powder was tested by transmission electron microscopy, and the results were as follows: Figure 2 shown. Figure 2 (a) shows that carbon dots are spherical nanoparticles observed under transmission electron microscopy. Figure 2 (b) shows that the diameters of the spherical nanoparticles range from 1.6 nm to 7.8 nm, with an average particle size of 3.0 nm.
[0029] The elemental composition of carbon dots was investigated using X-ray energy dispersive spectroscopy. Figure 3 As shown. Figure 3 It can be clearly observed that the four elements C, N, O, and P are evenly distributed, and the distribution profile coincides with the distribution of carbon dots. Compared with the distribution of C and O elements, the data points in the element distribution of N and P are relatively sparse, which indicates that the content of N and P elements in carbon dots is relatively low.
[0030] In order to verify that the N and P elements have been successfully doped into the carbon dots, rather than existing in the carbon dot sample in a free state, two dispersed carbon dot particles were selected and scanned. The results are as follows: Figure 4 As shown, Figure 4 It is clearly observed that the profiles of the data points of N and P elements collected are consistent with those of carbon dots, proving that N and P elements have been successfully doped into carbon dots.
[0031] The obtained orange-yellow solid powder was subjected to X-ray photoelectron spectroscopy (XPS) test, and the results were as follows: Figure 5 The full XPS spectrum shows that the carbon dots contain four elements: C, N, O, and P. The corresponding characteristic peaks are observed at 284.8 eV, 399.5 eV, 532.8 eV, and 133.9 eV (see Figure 5 (a)), and the proportions of the four elements are 79.4%, 2.7%, 15.7%, and 2.2% respectively (see Figure 5 (b)).
[0032] Before removing water by rotary evaporator, the optimal emission peak of the prepared nitrogen-phosphorus co-doped carbon dot aqueous solution was located at 525 nm under the excitation of 365 nm excitation light. Figure 6 shown.
[0033] like Figure 7 As shown, by comparing the excitation spectrum and absorption spectrum of nitrogen-phosphorus co-doped carbon dots aqueous solution, it can be found that they overlap in the range of 290nm to 490nm and the spectral shapes are basically the same. This phenomenon indicates that the fluorescence emission of carbon dots originates from n-π* transition.
[0034] Carbon dot solid powder has excellent fluorescence emission properties. Under the excitation of 365nm ultraviolet lamp, the presence of fluorescence peaks such as 460nm, 493nm and 530nm can be observed from the fluorescence emission spectrum. Figure 8 shown.
[0035] Example 2
[0036] Weigh 1.6 g of 1,8-diaminonaphthalene solid, dissolve it in 20 mL of 85% phosphoric acid, and stir it magnetically to dissolve it. Inject the above solution into a 25 mL polytetrafluoroethylene liner, then transfer it to a stainless steel reactor and hydrothermally react at 240 ° C for 6 hours. After heating, the reactor is cooled to room temperature under natural conditions to obtain the precursor of nitrogen-phosphorus co-doped carbon dots. Column chromatography is used for purification, and deionized water is used as the washing solvent to obtain a pure nitrogen-phosphorus co-doped carbon dot aqueous solution. Finally, a rotary evaporator is used to remove moisture, and an orange-yellow solid powder is obtained after drying.
[0037] Example 3
[0038] Compared with Example 2, the hydrothermal reaction in this example is carried out at 240° C. for 12 hours, and the rest is the same as Example 2.
[0039] Example 4
[0040] Compared with Example 2, the hydrothermal reaction in this example is carried out at 240° C. for 21 hours, and the rest is the same as Example 2.
[0041] Example 5
[0042] Compared with Example 2, the hydrothermal reaction in this example is carried out at 240° C. for 26 hours, and the rest is the same as Example 2.
[0043] The samples prepared in Examples 2 to 5 were irradiated with 395 nm ultraviolet light. Fig. 9 As shown. Fig. 9 It can be seen that the carbon dot solid powder has strong green fluorescence emission under 395nm ultraviolet light excitation.
[0044] Example 6
[0045] Weigh 0.1 g of 1,8-diaminonaphthalene solid in turn, dissolve it in 20 mL of 85% phosphoric acid, and stir it magnetically to dissolve it. Inject the above solution into a 25 mL polytetrafluoroethylene liner, then transfer it to a stainless steel reactor and hydrothermally react at 240°C for 16 hours. After heating, the reactor is cooled to room temperature under natural conditions to obtain the precursor of nitrogen-phosphorus co-doped carbon dots. Column chromatography is used for purification, and deionized water is used as the washing solvent to obtain a pure nitrogen-phosphorus co-doped carbon dot aqueous solution. Finally, a rotary evaporator is used to remove moisture, and an orange-yellow solid powder is obtained after drying.
[0046] Example 7
[0047] Compared with Example 6, 0.4 g of 1,8-diaminonaphthalene solid was weighed in this example, and the rest was the same as Example 6.
[0048] Example 8
[0049] Compared with Example 6, 0.8 g of 1,8-diaminonaphthalene solid was weighed in this example, and the rest was the same as Example 6.
[0050] Example 9
[0051] Compared with Example 6, 1.2 g of 1,8-diaminonaphthalene solid was weighed in this example, and the rest was the same as Example 6.
[0052] Example 10
[0053] Compared with Example 6, 2.0 g of 1,8-diaminonaphthalene solid was weighed in this example, and the rest was the same as Example 6.
[0054] Embodiment 11
[0055] Compared with Example 6, 2.4 g of 1,8-diaminonaphthalene solid was weighed in this example, and the rest was the same as Example 6.
[0056] Example 12
[0057] Compared with Example 6, 2.8 g of 1,8-diaminonaphthalene solid was weighed in this example, and the rest was the same as Example 6.
[0058] The samples prepared in Examples 6 to 12 were irradiated with 395 nm ultraviolet light. Fig.10 As shown. Fig.10 It can be seen that the carbon dot solid powders prepared in Examples 6 to 12 have strong green fluorescence emission under the excitation of 395 nm ultraviolet light.
[0059] It should be noted that the present invention uses 1,8-diaminonaphthalene and phosphoric acid to prepare nitrogen-phosphorus co-doped solid-state luminescent carbon dots. In the reaction product, in addition to nitrogen-phosphorus co-doped solid-state luminescent carbon dots, there are also red fluorescent carbon nanodots. After column chromatography is used to obtain a pure nitrogen-phosphorus co-doped carbon dot aqueous solution using deionized water as a washing solvent, dichloromethane is used as a solvent to remove impurities and other miscellaneous carbon dots in the precursor again until the outflowing dichloromethane has no obvious fluorescence under ultraviolet light irradiation, and finally anhydrous ethanol is added to the silica gel column, and the red fluorescent carbon nanodots are flowing out with the anhydrous ethanol. The obtained red fluorescent carbon nanodot solid powder does not have the property of fluorescence emission, but has strong red fluorescence emission after being dissolved in anhydrous ethanol, and has good solubility in anhydrous ethanol.
Claims
1. A method for preparing nitrogen-phosphorus co-doped solid-state luminescent carbon dots, characterized in that: The steps include: (1) Weigh 0.1-2.8 g of 1,8-diaminonaphthalene solid and dissolve it in 20 mL of phosphoric acid, stirring it magnetically to dissolve it; (2) transferring the dissolved solution in step (1) to a hydrothermal reactor and performing a hydrothermal reaction at 120 to 300° C. for 6 to 26 hours; (3) After the hydrothermal reaction is completed, the mixture is naturally cooled to room temperature to obtain a precursor of nitrogen-phosphorus co-doped carbon dots; (4) purifying the nitrogen-phosphorus co-doped carbon dot precursor by column chromatography, using deionized water as a washing solvent to obtain a nitrogen-phosphorus co-doped carbon dot aqueous solution; (5) The nitrogen-phosphorus co-doped carbon dots aqueous solution is subjected to thermal drying treatment to obtain nitrogen-phosphorus co-doped solid-state luminescent carbon dots.
2. The method for preparing nitrogen-phosphorus co-doped solid-state luminescent carbon dots according to claim 1, characterized in that: The phosphoric acid concentration in step (1) is 85%.
3. The method for preparing nitrogen and phosphorus co-doped solid-state luminescent carbon dots according to claim 1, characterized in that: The hydrothermal reaction conditions in step (2) are: hydrothermal reaction at 240° C. for 16 to 26 hours.
4. The method for preparing nitrogen and phosphorus co-doped solid-state luminescent carbon dots according to claim 1, characterized in that: Step (1) Weigh 1.2-2.8 g of 1,8-diaminonaphthalene solid and dissolve it in 20 mL of phosphoric acid, stirring it magnetically to dissolve it.
5. Nitrogen and phosphorus co-doped solid-state luminescent carbon dots prepared by the method according to any one of claims 1 to 4.
6. The nitrogen-phosphorus co-doped solid-state luminescent carbon dots according to claim 5, characterized in that: The nitrogen-phosphorus co-doped solid-state luminescent carbon dots are orange-yellow in sunlight and green in ultraviolet light.
7. The nitrogen-phosphorus co-doped solid-state luminescent carbon dots according to claim 6, characterized in that: The nitrogen and phosphorus co-doped solid-state luminescent carbon dots emit green fluorescence under the excitation of ultraviolet light of 365nm or 395nm.