Method for regulating carbon dot multicolor luminescence by chemical oxidation, prepared multicolor carbon dots and application thereof

Abstract

The application discloses a kind of chemical oxidation regulation carbon dot multicolor luminescence method, prepared multicolor carbon dot and its application, belong to nanometer material technical field, the hydrophobic fluorescent carbon dot prepared by melamine and dithiosalicylic acid and oxidizing agent are dispersed in organic solvent, and pre-reaction liquid is obtained;Pre-reaction liquid is transferred to container, and stirring is dispersed uniformly, is condensed under 40~100 ℃ and refluxed 10min~10h, and is cooled to room temperature naturally, and product is obtained;Further centrifugation is carried out to the product, and the precipitate is collected, washed, centrifuged, dried, and multicolor carbon dot is obtained;The method of the application is simple, easy to operate, does not need expensive preparation instrument, reaction condition is mild, and the action of catalyst is not needed, by regulating the surface oxidation degree of hydrophobic fluorescent carbon dot, the preparation of multicolor luminescence carbon dot is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and in particular to a method for regulating the multicolor luminescence of carbon dots through chemical oxidation, the prepared multicolor carbon dots and applications thereof. Background Art

[0002] Fluorescent carbon dots (CFDs) are a class of zero-dimensional carbon nanomaterials with remarkable fluorescent properties. Compared to traditional fluorescent materials such as rare earth phosphors, fluorescent proteins, and quantum dots, they offer advantages such as diverse synthesis methods, excellent stability, low toxicity, and good biocompatibility. Their unique properties include tunable light absorption and emission properties, making them excellent light-conversion materials. These characteristics give CFDs broad application prospects, encompassing diverse fields such as sensing, display lighting, catalysis, energy, and biomedicine.

[0003] In recent years, fluorescent carbon dots (Cdots) with multicolor tunable luminescence have attracted considerable attention in the fields of bioimaging, optoelectronics, and sensors. By manipulating reaction conditions, optimizing raw material ratios, and introducing external stimuli, researchers have strived to precisely control Cdot particle size, surface modification, solvent environment, and excitation light source to achieve multicolor luminescence.

[0004] Chinese patent document CN110885680A discloses a solvent-free method for preparing multicolor fluorescent carbon dots. The invention mixes different types of aniline derivatives with inorganic metal salts in proportion and grinds them into powder. The mixed powder is then transferred to the lining of a reactor and kept warm at 140-200°C for 5-10 hours. After the reaction is completed, it is naturally cooled to room temperature and washed and dried to obtain blue, green, and red fluorescent carbon dots.

[0005] Chinese patent document CN111662713A discloses a method for preparing multicolor fluorescent carbon dots with dual carbon and nitrogen sources. The experimental raw materials in this invention are sunflower stem pith and urea, and the experimental solvents are deionized water, anhydrous ethanol, and N,N-dimethylformamide, respectively. By adjusting the mass percentage of the raw materials, the type of solvent, the reaction time, and the reaction temperature, multicolor fluorescent carbon dots are synthesized through a one-step hydrothermal method. The synthesized carbon dots have bright green, yellow, and red fluorescence, respectively.

[0006] Chinese patent publication CN114591737A discloses multicolor fluorescent carbon dots, their preparation method, and applications. The invention involves mixing a nitrogen-containing precursor, a hydroxyl-containing carbon precursor, and a catalyst in a solvent for reaction, followed by separation and purification to produce the multicolor fluorescent carbon dots. The nitrogen-containing precursor is selected from one or more of o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine; the hydroxyl-containing carbon precursor is selected from one or more of o-phthalic acid, m-phenylenediamine, p-phenylenediamine, catechol, resorcinol, hydroquinone, and 4-dimethylaminophenol; and the mass ratio of the nitrogen-containing precursor to the hydroxyl-containing carbon precursor is (1-3):(1-3). Different organic solutions of the multicolor fluorescent carbon dots can produce red, orange, yellow, and green fluorescence under ultraviolet light excitation.

[0007] Chinese patent publication CN118406488A discloses xylan-based carbon dots with multicolor fluorescence and a method for their preparation. The invention uses xylan and p-phenylenediamine as precursors, which are dissolved in different solvents at specific ratios, mixed evenly, and reacted in a hydrothermal reactor. After cooling to room temperature, the mixture is purified by extraction, separation, and drying to yield four powdered carbon dots. These four fluorescent carbon dots, dispersed in an ethanol solution, emit blue, green, yellow, and red fluorescence under 365nm ultraviolet light.

[0008] Although a variety of preparation methods for multicolor fluorescent carbon dots have been reported, achieving controllable multicolor fluorescent carbon dot preparation still faces challenges. Research in this field is of great significance for deepening the understanding of the luminescence mechanism of carbon dots and expanding their potential in applications. Summary of the Invention

[0009] The present invention provides a method for regulating the multicolor luminescence of carbon dots by chemical oxidation. The invention regulates the surface oxidation degree of hydrophobic fluorescent carbon dots by chemical oxidation, thereby preparing multicolor carbon dots with an emission spectrum peak wavelength between 420 and 620 nm under an excitation wavelength of 365 nm and colors ranging from blue to red.

[0010] The specific technical solutions adopted are as follows:

[0011] A method for regulating carbon dot multicolor luminescence by chemical oxidation, comprising the following steps:

[0012] (1) dispersing hydrophobic fluorescent carbon dots prepared from melamine and dithiosalicylic acid and an oxidant in an organic solvent to obtain a pre-reaction solution; the oxidant is at least one of ammonium persulfate, sodium hypochlorite, sulfuric acid, sodium ferrate, or azobisisobutyronitrile;

[0013] (2) Transfer the pre-reaction solution in step (1) to a container, stir until uniformly dispersed, reflux under condensation at 40-100° C. for 10 min-10 h, and naturally cool to room temperature to obtain the product;

[0014] (3) The product obtained in step (2) is centrifuged and the precipitate is collected, washed, centrifuged, and dried to obtain multi-color carbon dots.

[0015] The present invention performs oxidation etching on the surface of hydrophobic fluorescent carbon dots prepared with melamine and dithiosalicylic acid. By adjusting the type and amount of the oxidant, oxidation time, etc., carbon dots capable of emitting blue, red, and green fluorescence at 365 nm can be prepared.

[0016] The organic solvent is at least one of ethanol, acetic acid, dimethyl sulfoxide and formamide.

[0017] Preferably, the particle size of the hydrophobic fluorescent carbon dots is 1 to 100 nm.

[0018] In the pre-reaction solution, the mass concentration of the hydrophobic fluorescent carbon dots is 0.01-1 g / mL, and the mass concentration of the oxidant is 0.1-100 mg / mL.

[0019] The oxidant is preferably ammonium persulfate, which has high oxidation efficiency, wide sources, and is economical and practical.

[0020] Preferably, the product obtained in step (2) is centrifuged at 3000-50000 rpm for 1-100 min and the precipitate is collected.

[0021] Specifically, when the excitation wavelength is 365 nm, the peak wavelength of the emission spectrum of the multi-color carbon dots is between 420 and 620 nm.

[0022] The yield of the multi-color carbon dots is 10% to 80%, and the quantum efficiency is 1% to 20%.

[0023] The present invention also provides multi-color carbon dots prepared by the method of regulating the multi-color luminescence of carbon dots through chemical oxidation.

[0024] The present invention also provides applications of the multi-color carbon dots in the fields of fluorescent anti-counterfeiting and / or LED lighting.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention provides a method for regulating the multicolor luminescence of carbon dots by chemical oxidation. Hydrophobic fluorescent carbon dots prepared by melamine and dithiosalicylic acid are used as raw materials. By regulating the degree of surface oxidation, the multicolor luminescent carbon dots (with an emission spectrum peak wavelength between 420 and 620 nm at an excitation wavelength of 365 nm and colors ranging from blue to red) are prepared. The method of the present invention has a simple process, is easy to operate, does not require expensive preparation equipment, has mild reaction conditions, does not require the action of a catalyst, and is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the process of oxidation etching of hydrophobic fluorescent carbon dots in the embodiment.

[0028] Figure 2 These are optical images of the carbon dots prepared in Example 1 under sunlight and 365 nm ultraviolet light.

[0029] Figure 3 1 is the fluorescence spectrum of the carbon dots prepared in Example 1.

[0030] Figure 4 These are optical images of the carbon dots prepared in Example 3 under sunlight and 365 nm ultraviolet light.

[0031] Figure 5 3 is the fluorescence spectrum of the carbon dots prepared in Example 3. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the examples and accompanying drawings. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. The operating methods in the following examples where specific conditions are not specified are generally performed under conventional conditions or as recommended by the manufacturer. Contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0033] In the following examples, hydrophobic fluorescent carbon dots were prepared using melamine and dithiosalicylic acid as raw materials according to the description in Chinese patent document CN109825288A. The particle size of the hydrophobic fluorescent carbon dots was 1 to 100 nm. The sources of the remaining raw materials were not particularly limited and could be commercially available.

[0034] Example 1

[0035] This embodiment illustrates a method for regulating the multi-color luminescence of carbon dots through chemical oxidation. The schematic diagram of the oxidation etching process is shown in FIG. Figure 1 The specific control methods are as follows:

[0036] 0.01 g of hydrophobic fluorescent carbon dots prepared with melamine and dithiosalicylic acid was added to 1 mL of dimethyl sulfoxide and dispersed evenly. 0.1 mg of ammonium persulfate was then added and mixed thoroughly to obtain a pre-reaction solution. The pre-reaction solution was transferred to a three-necked flask and stirred until evenly dispersed. The solution was then heated to 40°C under reflux for 20 minutes for oxidation, and then naturally cooled to room temperature to obtain the product. The product was centrifuged at 3000 rpm for 30 minutes, and the precipitate was collected. The product was then washed with water and centrifuged multiple times, and the precipitate was collected and dried to obtain the carbon dots. The yield of the carbon dots was 51%, and the quantum efficiency was 3%.

[0037] The optical images of the carbon dots prepared in this example under sunlight and 365nm ultraviolet light are as follows: Figure 2 As shown, after further testing, the fluorescence spectrum of the carbon dots is shown in Figure 3 As shown, when the excitation wavelength is 365 nm, the peak wavelengths of its emission spectrum are located at 450 nm and 611 nm, appearing blue in ethanol and red in water.

[0038] Example 2

[0039] This example illustrates a method for regulating the multi-color luminescence of carbon dots through chemical oxidation, focusing on the effect of the fluorescent carbon dot content on the fluorescence properties of the carbon dots, as shown below:

[0040] 1g of hydrophobic fluorescent carbon dots prepared with melamine and dithiosalicylic acid was added to 1mL of dimethyl sulfoxide and dispersed evenly. 0.1mg of ammonium persulfate was then added and mixed thoroughly to obtain a pre-reaction solution. The pre-reaction solution was transferred to a three-necked flask and stirred until evenly dispersed. The solution was then heated to 40°C under reflux for 20 minutes for oxidation, and then cooled naturally to room temperature to obtain the product. The product was centrifuged at 3000 rpm for 30 minutes, and the precipitate was collected. The product was then washed with water and centrifuged multiple times, and the precipitate was collected and dried to obtain the carbon dots. The yield of the carbon dots was 65%, and the quantum efficiency was 4.2%.

[0041] The results of the test showed that when the excitation wavelength of the carbon dots was 365 nm, the peak wavelengths of their emission spectrum were located at 460 nm and 618 nm. They appeared blue in ethanol and red in water.

[0042] Example 3

[0043] This example illustrates a method for regulating the multi-color luminescence of carbon dots through chemical oxidation, focusing on the effect of the oxidant content on the fluorescence properties of the carbon dots, as shown below:

[0044] 0.01 g of hydrophobic fluorescent carbon dots prepared with melamine and dithiosalicylic acid was added to 1 mL of dimethyl sulfoxide and dispersed evenly. 100 mg of ammonium persulfate was then added and mixed thoroughly to obtain a pre-reaction solution. The pre-reaction solution was transferred to a three-necked flask and stirred until evenly dispersed. The solution was then heated to 40°C under reflux for 20 minutes for oxidation, and then cooled naturally to room temperature to obtain the product. The product was centrifuged at 3000 rpm for 30 minutes, and the precipitate was collected. The product was then washed with water and centrifuged multiple times, and the precipitate was collected and dried to obtain the carbon dots. The yield of the carbon dots was 25%, and the quantum efficiency was 2.3%.

[0045] The optical images of the carbon dots prepared in this example under sunlight and 365nm ultraviolet light are as follows: Figure 4 As shown, after further testing, the fluorescence spectrum of the carbon dots is shown in Figure 5As shown, the test results show that when the excitation wavelength of the carbon dots is 365 nm, the peak wavelengths of the emission spectrum are located at 480 nm and 580 nm, and the carbon dots appear blue in ethanol and green in water.

[0046] Example 4

[0047] This example illustrates a method for regulating the multi-color luminescence of carbon dots through chemical oxidation, focusing on the effect of oxidation temperature on the fluorescence properties of carbon dots, as shown below:

[0048] 0.01 g of hydrophobic fluorescent carbon dots prepared with melamine and dithiosalicylic acid was added to 1 mL of dimethyl sulfoxide and dispersed evenly. 0.1 mg of ammonium persulfate was then added and mixed thoroughly to obtain a pre-reaction solution. The pre-reaction solution was transferred to a three-necked flask and stirred until evenly dispersed. The solution was then heated to 100°C under reflux for 20 minutes for oxidation, and then naturally cooled to room temperature to obtain the product. The product was centrifuged at 3000 rpm for 60 minutes, and the precipitate was collected. The product was then washed with water and centrifuged multiple times, and the precipitate was collected and dried to obtain the carbon dots. The yield of the carbon dots was 37%, and the quantum efficiency was 3.8%.

[0049] The results of the test showed that when the excitation wavelength of the carbon dots was 365 nm, the peak wavelengths of their emission spectrum were located at 470 nm and 598 nm. They appeared blue in ethanol and red in water.

[0050] Example 5

[0051] This example illustrates a method for regulating the multi-color luminescence of carbon dots through chemical oxidation, focusing on the effect of oxidation time on the fluorescence properties of carbon dots, as shown below:

[0052] 0.01 g of hydrophobic fluorescent carbon dots prepared with melamine and dithiosalicylic acid was added to 1 mL of dimethyl sulfoxide and dispersed evenly. 0.1 mg of ammonium persulfate was then added and mixed thoroughly to obtain a pre-reaction solution. The pre-reaction solution was transferred to a three-necked flask and stirred until evenly dispersed. The solution was then heated to 40°C and refluxed for 10 hours for oxidation, followed by natural cooling to room temperature to obtain the product. The product was centrifuged at 3000 rpm for 60 minutes, and the precipitate was collected. The product was then washed with water and centrifuged multiple times, and the precipitate was collected and dried to obtain the carbon dots. The yield of the carbon dots was 41%, and the quantum efficiency was 3.5%.

[0053] The results of the test showed that when the excitation wavelength of the carbon dots was 365 nm, the peak wavelengths of their emission spectrum were located at 460 nm and 605 nm. They appeared blue in ethanol and red in water.

[0054] Sample analysis

[0055] The stronger the oxidizing agent, the greater the amount used, and the longer the oxidation time, the shorter the emission spectrum of the resulting carbon dots. Therefore, by adjusting the oxidation conditions, the emission spectrum of the carbon dots can be varied from red to blue.

[0056] Based on the above results, it can be clearly seen that the method provided by the present invention is a method for regulating the multicolor luminescence of carbon dots by chemical oxidation, which regulates the surface oxidation degree of hydrophobic fluorescent carbon dots by chemical oxidation to achieve the preparation of multicolor luminescent carbon dots; and the preparation method provided by the present invention is simple and easy to operate, and does not require expensive preparation instruments, high temperature and catalysts.

[0057] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for regulating carbon dot multicolor luminescence by chemical oxidation, characterized in that: The following steps are involved: (1) dispersing hydrophobic fluorescent carbon dots prepared from melamine and dithiosalicylic acid and an oxidant in an organic solvent to obtain a pre-reaction solution; the oxidant is at least one of ammonium persulfate, sodium hypochlorite, sulfuric acid, sodium ferrate, or azobisisobutyronitrile; (2) Transfer the pre-reaction solution in step (1) to a container, stir until uniformly dispersed, reflux under condensation at 40-100° C. for 10 min-10 h, and naturally cool to room temperature to obtain the product; (3) The product obtained in step (2) is centrifuged and the precipitate is collected, washed, centrifuged, and dried to obtain multi-color carbon dots.

2. The method for regulating carbon dot multicolor luminescence by chemical oxidation according to claim 1, characterized in that: The organic solvent is at least one of ethanol, acetic acid, dimethyl sulfoxide and formamide.

3. The method for regulating carbon dot multicolor luminescence by chemical oxidation according to claim 1, characterized in that: The particle size of the hydrophobic fluorescent carbon dots is 1-100 nm, and the oxidant is ammonium persulfate.

4. The method for regulating carbon dot multicolor luminescence by chemical oxidation according to claim 1, characterized in that: In the pre-reaction solution, the mass concentration of the hydrophobic fluorescent carbon dots is 0.01-1 g / mL, and the mass concentration of the oxidant is 0.1-100 mg / mL.

5. The method for regulating carbon dot multicolor luminescence by chemical oxidation according to claim 1, characterized in that: The product obtained in step (2) is centrifuged at 3000-50000 rpm for 1-100 min and the precipitate is collected.

6. The method for regulating carbon dot multicolor luminescence by chemical oxidation according to claim 1, characterized in that: When the excitation wavelength is 365 nm, the peak wavelength of the emission spectrum of the multi-color carbon dots is between 420 and 620 nm.

7. The method for regulating carbon dot multicolor luminescence by chemical oxidation according to claim 1, characterized in that: The yield of the multi-color carbon dots is 10% to 80%, and the quantum efficiency is 1% to 20%.

8. Multicolor carbon dots prepared by the method for regulating carbon dot multicolor luminescence by chemical oxidation according to any one of claims 1 to 7.

9. Use of the multicolor carbon dots according to claim 8 in the fields of fluorescent anti-counterfeiting and / or LED lighting.

Images