Preparation method of red fluorescent carbon quantum dot material
Red fluorescent carbon quantum dots were prepared by a solvothermal reaction of organic small molecules with boric acid and subsequent purification steps, which solved the problems of insufficient fluorescence emission and complex preparation in the existing technology, and achieved efficient and low-cost preparation of red carbon quantum dots.
Patent Information
- Application Number
- CN202410138289.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-31
- Publication Date
- 2025-11-18
- Estimated Expiration
- 2044-01-31
AI Technical Summary
Existing methods for preparing red carbon quantum dots suffer from problems such as insufficient fluorescence emission wavelength, low fluorescence quantum yield, complex preparation process, and the use of expensive and toxic small molecules with fused ring structures.
Red fluorescent carbon quantum dots are prepared by solvothermal reaction of small organic molecules such as citric acid and urea with boric acid in an organic solvent, combined with membrane filtration, dialysis and centrifugation, avoiding the use of small molecules with fused ring structures.
It achieves efficient fluorescence emission in the red and near-infrared light range, improves fluorescence quantum yield, simplifies the preparation process, reduces costs, and uses non-toxic raw materials.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of nano-fluorescent materials technology, specifically relating to a method for preparing red fluorescent carbon quantum dot materials. Background Technology
[0002] Semiconductor quantum dots are a novel type of nanomaterial that has attracted widespread attention due to their excellent fluorescence quantum yield. Binary non-oxide quantum dots (cadmium selenide, indium phosphide, etc.) have already been commercially used in the semiconductor display field, while perovskite quantum dots have also been extensively studied. However, these two types of quantum dot materials contain heavy metals (cadmium, lead, etc.) and large amounts of halogens (chlorine, bromine, iodine), which can have serious environmental impacts during equipment manufacturing and after disposal, thereby posing a threat to water and soil resources and human health.
[0003] Carbon quantum dots (CQDs) have attracted widespread attention as a stable and non-toxic material due to their high fluorescence quantum yield, well-coordinated fluorescence emission range, and stable chemical properties. Their synthesis raw materials are widely available, are renewable resources, and are inexpensive. Furthermore, CQDs exhibit low toxicity and good biocompatibility. Therefore, CQDs have significant potential applications in displays, lighting, bioimaging, and catalysis. Red CQDs are one of the three primary colors for display, and red is also the best color for bioimaging, as it does not conflict with the fluorescence of biological organisms. Currently, the preparation of red CQDs faces the following challenges: most prepared CQDs emit blue-green light, and very few emit wavelengths exceeding 630 nm; the few CQDs with long-wavelength fluorescence emission have very low fluorescence quantum yields; the preparation of red CQDs generally requires column chromatography, which is time-consuming, complex, and yields low results. The preparation of red fluorescent CQDs requires the use of small molecules with fused-ring structures, which are extremely scarce, expensive, and toxic. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for preparing red fluorescent carbon quantum dot materials.
[0005] The technical solution of the present invention is as follows:
[0006] A method for preparing a red fluorescent carbon quantum dot material includes placing an organic small molecule compound and boric acid in an organic solvent for a solvothermal reaction, followed by separation and purification; the organic small molecule compound is at least one selected from citric acid, urea, thiourea, o-phenylenediamine, p-phenylenediamine and melamine.
[0007] In a preferred embodiment of the present invention, the organic solvent is N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, or N-methylpyrrolidone.
[0008] More preferably, the ratio of the organic small molecule compound, boric acid and organic solvent is 1-3g:0.5-2g:20-30mL.
[0009] More preferably, the ratio of the organic small molecule compound, boric acid and organic solvent is 1-2.7g:0.5-1.8g:25mL.
[0010] In a preferred embodiment of the present invention, the temperature of the solvothermal reaction is 180°C and the time is 12 hours.
[0011] In a preferred embodiment of the present invention, the separation and purification process includes, in sequence, membrane filtration, dialysis, centrifugation, and ultrapure water washing.
[0012] More preferably, the pore size of the filter membrane is 0.22 μm.
[0013] More preferably, the dialysis is performed by dialysis in ultrapure water for 2-3 days using a dialysis bag with a molecular weight cutoff of 500-2000D.
[0014] More preferably, the centrifugation is performed at 10,000 rpm for 30-90 minutes.
[0015] More preferably, the pore size of the filter membrane is 0.22 μm; the dialysis is performed by dialyzing in ultrapure water for 2-3 days using a dialysis bag with a molecular weight cutoff of 500-2000D; and the centrifugation is performed by centrifugation at 10000 rpm for 30-90 min.
[0016] The beneficial effects of this invention are:
[0017] 1. The carbon quantum dot material prepared by this invention has a size of 2-6 nm and an average size of 4.134 nm. Obvious 0.212 nm lattice fringes can be observed. Its XRD image has an obvious peak at 26°, indicating that it has a graphite structure with small sheets. The peak at around 21° indicates that it has a graphene-like structure inside, which belongs to the structure of carbon quantum dots.
[0018] 2. This invention involves the bottom-up synthesis of small organic molecule compounds in an organic solvent using boric acid as a catalyst. Boric acid, acting as a catalyst, promotes the dehydration and carbonization of the small organic molecule compounds, thereby promoting the formation and growth of carbon quantum dots and increasing the sp(s) content of the carbon quantum dots. 2 The increased area of the carbon core enhances the area of the π-π conjugated region, reduces the energy level difference of the carbon quantum dot, and effectively reduces the optical bandgap of the hybrid orbitals of the carbon quantum dot molecules. Combined with the quantum size effect, this causes the carbon quantum dot to emit red light.
[0019] 3. This invention does not use rare and expensive precursors with complex fused ring structures to synthesize red fluorescent carbon quantum dots. Instead, it uses inexpensive, non-toxic and common organic small molecule compounds as raw materials for carbon quantum dot preparation, such as citric acid and urea. Furthermore, the catalyst boric acid can be reused after filtration.
[0020] 4. The preparation and purification process of this invention is efficient and convenient, and does not require the use of time-consuming and low-yield purification methods such as column chromatography. The yield of red carbon quantum dots is high and the production volume is large. Attached Figure Description
[0021] Figure 1 The image shows the XRD pattern of the red fluorescent carbon quantum dot material prepared in Example 1 of this invention.
[0022] Figure 2 This is a transmission electron microscope image of the red fluorescent carbon quantum dot material prepared in Example 1 of the present invention.
[0023] Figure 3 This is the XPS full spectrum of the red fluorescent carbon quantum dot material prepared in Example 1 of this invention.
[0024] Figure 4 This is an image of the red fluorescent carbon quantum dot material prepared in Example 1 of the present invention under 365nm ultraviolet light.
[0025] Figure 5 This is a TEM image of the red fluorescent carbon quantum dot material prepared in Example 1 of the present invention. Detailed Implementation
[0026] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.
[0027] Example 1
[0028] (1) Weigh 1.93g of anhydrous citric acid, 0.6g of urea and 1.8g of boric acid, dissolve them in 25mL of N,N-dimethylformamide, transfer them to a 50mL polytetrafluoroethylene-lined reaction vessel, and solvothermal reaction at 180℃ for 12h to obtain a mixture containing carbon quantum dots.
[0029] (2) Filter 50 mL of the carbon quantum dot mixture described in step (1) through a 0.22 μm filter membrane to remove the catalyst boric acid and obtain a carbon quantum dot mixed solution.
[0030] (3) The carbon quantum dot mixed solution described in step (2) is dialyzed in ultrapure water for 3 days using a dialysis bag with a molecular weight cutoff of 1000D to obtain an aqueous solution of carbon quantum dots.
[0031] (4) Centrifuge the carbon quantum dot aqueous solution from step (3) at 10000 rpm for 90 min, wash the precipitate with ultrapure water and centrifuge twice, and finally take the precipitate to obtain the following: Figures 1 to 5 The red fluorescent carbon quantum dot material shown has a size of 2-6 nm and an average size of 4.134 nm. It exhibits obvious 0.212 nm lattice fringes. Its XRD image shows a distinct peak at 26°, indicating the presence of a small graphite structure. The peak at around 21° indicates the presence of a graphene-like structure inside, which belongs to the structure of carbon quantum dots.
[0032] The red fluorescent carbon quantum dot material prepared using this embodiment has a fluorescence emission wavelength range of 600-800 nm, covering the range of red and near-infrared light, with the optimal emission peak at 675 nm. Compared with the carbon quantum dot fluorescence emission peak wavelength prepared without using boric acid as a catalyst, it is red-shifted by 207 nm.
[0033] Example 2
[0034] (1) Weigh 1.08g of p-phenylenediamine and 1.6g of boric acid, dissolve them in 25mL of N,N-dimethylformamide, transfer them to a 50mL polytetrafluoroethylene-lined reaction vessel, and solvothermal reaction at 180℃ for 12h to obtain a mixture containing carbon quantum dots.
[0035] (2) Filter 50 mL of the carbon quantum dot mixture described in step (1) through a 0.22 μm filter membrane to remove the catalyst boric acid and obtain a carbon quantum dot mixed solution.
[0036] (3) The carbon quantum dot mixed solution described in step (2) is dialyzed in ultrapure water for 3 days using a dialysis bag with a molecular weight cutoff of 1000D to obtain an aqueous solution of carbon quantum dots.
[0037] (4) Centrifuge the carbon quantum dot aqueous solution in step (3) at 10,000 rpm for 90 min, wash the precipitate with ultrapure water and centrifuge twice, and finally take the precipitate to obtain red fluorescent carbon quantum dot material.
[0038] The red fluorescent carbon quantum dot material prepared using this embodiment has a fluorescence emission wavelength range of 590-740 nm, covering the range of red and near-infrared light, with the optimal emission peak at 640 nm. Compared with the carbon quantum dot fluorescence emission peak wavelength prepared without using boric acid as a catalyst, it is red-shifted by 131 nm.
[0039] Example 3
[0040] (1) Weigh 1.93g of anhydrous citric acid, 0.76g of thiourea and 0.6g of boric acid, dissolve them in 25mL of N,N-dimethylformamide, transfer them to a 50mL polytetrafluoroethylene-lined reaction vessel, and solvothermal reaction at 180℃ for 12h to obtain a mixture containing carbon quantum dots.
[0041] (2) Filter 50 mL of the carbon quantum dot mixture described in step (1) through a 0.22 μm filter membrane to remove the catalyst boric acid and obtain a carbon quantum dot mixed solution.
[0042] (3) The carbon quantum dot mixed solution described in step (2) is dialyzed in ultrapure water for 3 days using a dialysis bag with a molecular weight cutoff of 1000D to obtain an aqueous solution of carbon quantum dots.
[0043] (4) Centrifuge the carbon quantum dot aqueous solution in step (3) at 10,000 rpm for 90 min, wash the precipitate with ultrapure water and centrifuge twice, and finally take the precipitate to obtain red fluorescent carbon quantum dot material.
[0044] The red fluorescent carbon quantum dot material prepared using this embodiment has a fluorescence emission wavelength range of 590-780 nm, covering the range of red and near-infrared light, with the optimal emission peak at 641.5 nm. Compared with the carbon quantum dot fluorescence emission peak wavelength prepared without using boric acid as a catalyst, it is redshifted by 166 nm.
[0045] Table 1
[0046]
[0047]
[0048] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.
Claims
1. A method for preparing a red fluorescent carbon quantum dot material, characterized in that: Comprising the following steps: (1) Take 1.93 g of anhydrous citric acid, 0.6 g of urea, 1.8 g of boric acid, dissolve in 25 mL of N,N-dimethylformamide, transfer to a 50 mL polytetrafluoroethylene lined reaction tank, solvent thermal reaction at 180 ℃ for 12 h to obtain a mixture containing carbon quantum dots; (2) Filter the catalyst boric acid from the 50 mL mixture containing carbon quantum dots in step (1) with a filter membrane of 0.22 μm to obtain a carbon quantum dot mixed solution; (3) The carbon quantum dot mixed solution in step (2) is dialyzed in ultrapure water using a dialysis bag with a molecular weight cut-off of 1000 D for 3 d to obtain a carbon quantum dot aqueous solution; (4) The carbon quantum dot aqueous solution in step (3) is centrifuged at a speed of 10000 rpm for 90 min, the precipitate is washed twice by centrifugation with ultrapure water, and finally the precipitate is taken to obtain the red fluorescent carbon quantum dot material.