A method for preparing a multi-color carbon dot solution on a large scale at normal temperature and pressure and application thereof

Abstract

The application discloses a method for preparing multicolor carbon dot solution on a large scale under normal temperature and pressure and application thereof. The method uses o-phenylenediamine and polyhydric alcohol or polybasic acid as raw materials, N,N-dimethylformamide as a solvent, and an oxidant is added and stirred under normal temperature and pressure to obtain blue, green, yellow and red carbon dot solutions respectively. Compared with traditional carbon dot preparation methods which need high temperature, high pressure and other external energy, the method can realize the preparation of multicolor carbon dot solution under normal temperature and pressure, and does not need separation and purification, and can be used for large-scale preparation of multicolor carbon dot solution. The prepared multicolor carbon dot solution has the advantages of color adjustability and excellent optical performance, and can be used in the field of LED lighting.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of material preparation, and particularly relates to a method for large-scale preparation of multi-color carbon dot solution at normal temperature and pressure and application. BACKGROUND

[0002] Carbon dots are a new type of fluorescent carbon nanomaterial, which has been widely used in optoelectronic devices, sensing, biological imaging and catalysis due to its excellent optical properties. Among them, multi-color carbon dots are concerned because of their coordinated emission wavelengths. In particular, the emergence of long-wavelength fluorescent carbon dots greatly expands the application range of carbon dots.

[0003] At present, many preparation methods of carbon dots have been developed, which can be divided into top-down and bottom-up methods according to the characteristics of the precursor itself. Among them, the most commonly used methods are solvothermal / hydrothermal method and microwave method. However, these methods generally involve high temperature, high pressure and other external energy, which not only goes against the concept of "green and environmental protection", but also has complicated preparation method and high requirement for equipment, thereby limiting its large-scale production. In addition, Chinese invention patent 202310138053.9 discloses a method for large-scale preparation of multi-color carbon dots under normal temperature and pressure, which uses o-phenylenediamine as raw material, carbonizes the raw material under normal temperature and pressure to prepare a crude product of carbon dots, and then purifies the blue, yellow and red emitting carbon dots by column chromatography. The multi-color carbon dots of the patent are obtained by separating and purifying the crude product, which not only increases the complexity of the preparation process, but also causes large solvent consumption, long time consumption and low yield, etc. It is not suitable for large-scale production. Therefore, it is of great significance to develop a multi-color carbon dot solution which is large-scale prepared without separation and purification under simple equipment and mild reaction conditions. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a method for large-scale preparation of multi-color carbon dot solution based on normal temperature and pressure and application. The present application can realize the synthesis of multi-color carbon dot solution at normal temperature and pressure, and the multi-color carbon dot solution can be obtained without separation and purification. The preparation method is simple, energy-saving, environmentally friendly, low-cost and high-production-efficiency. The fluorescent carbon dot solution prepared by the present application has adjustable color and excellent optical performance, and can be applied in the field of LED lighting.

[0005] The technical scheme of the present application is as follows:

[0006] A method for large-scale preparation of multi-color carbon dot solution based on normal temperature and pressure, the processing method comprises the following steps:

[0007] (1) mixing a carbon source, a polyol or a polyacid, adding a solvent, and stirring to obtain a clear solution;

[0008] (2) adding an acid oxidant and stirring to react to obtain a multi-color carbon dot solution;

[0009] The carbon source is o-phenylenediamine.

[0010] Further, in step (1), the polyol includes one of glucose and ascorbic acid; and the polyacid includes one of malic acid and citric acid.

[0011] Further, in step (1), the solvent is N,N-dimethylformamide.

[0012] Further, in step (1), the molar ratio of the carbon source to the polyol or the polyacid is 1:0.3-3; and the molar volume ratio of the carbon source to the solvent is 1 mol:1.5-15 L.

[0013] Further, in step (1), the stirring speed is 200-300 r / min, and the stirring time is 30-60 s.

[0014] Further, in step (2), the acid oxidant includes one of concentrated nitric acid, concentrated sulfuric acid, concentrated hydrochloric acid, and hydrogen peroxide; the mass fraction of the concentrated nitric acid is 65-70%, the mass fraction of the concentrated sulfuric acid is 70-98%, the mass fraction of the concentrated hydrochloric acid is 36-40%, and the mass fraction of the hydrogen peroxide is 30-35%; and the molar volume ratio of the carbon source in step (1) to the acid oxidant in step (2) is 1 mol:0.2-1 L.

[0015] Further, in step (2), the stirring speed is 200-300 r / min, and the stirring time is 0.5-6 h.

[0016] Further, in step (2), the multi-color carbon dot solution includes one of a blue fluorescent carbon dot solution, a green fluorescent carbon dot solution, a yellow fluorescent carbon dot solution, and a red fluorescent carbon dot solution.

[0017] Further, the multi-color carbon dot solution is used for preparing a multi-color LED lamp; the fluorescent carbon dot solution is compounded with polyvinylpyrrolidone to form a film, and the film is used for preparing the multi-color LED lamp; and the volume-mass ratio of the fluorescent carbon dot solution to the polyvinylpyrrolidone is 1 mL:1-1.5 g.

[0018] The present application has the beneficial technical effects that:

[0019] The synthetic method of the present application can make more kinds of precursors be dissolved in the system to participate in the reaction, greatly broaden the selection range of raw material precursors, and be more conducive to enrich the types of carbon dots. The specific method is that the present application takes o-phenylenediamine as a carbon source and glucose, ascorbic acid as a polyhydric alcohol or malic acid, citric acid as a polyacid, N,N-dimethylformamide as a solvent, and after adding an acidic oxidant, the system generates a large amount of heat due to the occurrence of a severe redox reaction, so that the temperature of the reaction system is as high as 97℃, the released heat further accelerates the oxidation and self-polymerization of o-phenylenediamine in the system, and at the same time, the o-phenylenediamine polymer reacts with N,N-dimethylformamide and polyhydric alcohol / acid to generate Schiff base and amide reaction, and the heat released promotes the carbonization of the carbon source.

[0020] In addition, the synthetic method of the present application can also adjust the carbon core size and surface state by adding different precursors, such as glucose, malic acid, ascorbic acid, and citric acid, to prepare a multi-color carbon dot solution. Compared with the prior art, the present application provides a simple, universal and large-scale preparation method for preparing a multi-color carbon dot solution, takes o-phenylenediamine as a carbon source, changes the carbon core structure of the carbon dots by adding different polyhydric alcohols or polybasic acids, thereby changing the carbonization degree and adjusting the size of the carbon dots, and finally obtaining multi-color carbon dots, which avoids the disadvantages of column chromatography separation and purification.

[0021] The multi-color carbon dot solution prepared by the present application is prepared in a normal temperature and pressure environment, so the reaction method is simple, without the need to provide external energy and complex equipment, the reaction conditions are mild and controllable, the side reactions are less, the experimental progress can be monitored at any time, the process flow is more mature, the standard flow preparation of the multi-color carbon dot solution can be realized, the components of the prepared multi-color carbon dot solution are more single, without the need for further separation and purification, and it is more conducive to production. Compared with the conventional hydrothermal / solvothermal method, the main advantage of the synthetic method of the present application is that it is carried out at normal pressure without the need to use a pressure reaction kettle, the operation is simpler, and the reactants can be added at any time during the reaction process to monitor the reaction process, which is more conducive to perfecting the preparation process of the multi-color carbon dot solution; compared with the microwave method, the synthetic method of the present application can use a beaker as a reaction device to prepare carbon dots in a normal temperature and pressure environment, which overcomes the difficulty of the microwave reaction kettle as a device that is not conducive to operation and control, and is more conducive to large-scale industrial production.

[0022] The multi-color carbon dot solution prepared by the present application has stable optical properties, a single emission peak, and high fluorescence quantum yield, and the fluorescence intensity fluctuates little under continuous ultraviolet light irradiation, has the advantages of color controllability and excellent optical performance, high experimental repeatability, and large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The transmission electron microscope image of the blue carbon dot solution prepared in Example 1 of the present application.

[0024] Figure 2 Size distribution graph of the blue carbon dot solution prepared in Example 1 of the present application.

[0025] Figure 3 Fluorescence and absorption spectra of the blue carbon dot solution prepared in Example 1 of the present application.

[0026] Figure 4 Transmission electron microscope graph of the green carbon dot solution prepared in Example 2 of the present application.

[0027] Figure 5 Size distribution graph of the green carbon dot solution prepared in Example 2 of the present application.

[0028] Figure 6 Fluorescence and absorption spectra of the green carbon dot solution prepared in Example 2 of the present application.

[0029] Figure 7 Transmission electron microscope graph of the yellow carbon dot solution prepared in Example 3 of the present application.

[0030] Figure 8 Size distribution graph of the yellow carbon dot solution prepared in Example 3 of the present application.

[0031] Figure 9 Fluorescence and absorption spectra of the yellow carbon dot solution prepared in Example 3 of the present application.

[0032] Figure 10 Transmission electron microscope graph of the red carbon dot solution prepared in Example 4 of the present application.

[0033] Figure 11 Size distribution graph of the red carbon dot solution prepared in Example 4 of the present application.

[0034] Figure 12 Fluorescence and absorption spectra of the red carbon dot solution prepared in Example 4 of the present application.

[0035] Figure 13 Color coordinate graph of the LED prepared using the blue carbon dot solution prepared in Example 1 of the present application.

[0036] Figure 14 Spectrum graph of the LED prepared using the blue carbon dot solution prepared in Example 1 of the present application.

[0037] Figure 15 Color coordinate graph of the LED prepared using the green carbon dot solution prepared in Example 2 of the present application.

[0038] Figure 16 Spectrum graph of the LED prepared using the green carbon dot solution prepared in Example 2 of the present application.

[0039] Figure 17 Color coordinate diagram of LED prepared by yellow carbon dots solution prepared in embodiment 3 of the present application.

[0040] Figure 18 Spectrum diagram of LED prepared by yellow carbon dots solution prepared in embodiment 3 of the present application.

[0041] Figure 19 Color coordinate diagram of LED prepared by red carbon dots solution prepared in embodiment 4 of the present application.

[0042] Figure 20 Spectrum diagram of LED prepared by red carbon dots solution prepared in embodiment 4 of the present application.

[0043] Figure 21 Fluorescence stability diagram of multicolor carbon dots solution prepared in embodiments 1-4 of the present application and light stability diagram of multicolor carbon dots / polyvinylpyrrolidone film prepared in embodiments 1-4 of the present application under 365nm excitation ultraviolet lamp and thermogravimetric analysis diagram.

[0044] In the figure: (a), fluorescence stability diagram; (b), light stability diagram under 365nm excitation ultraviolet lamp; (c), thermogravimetric analysis diagram. DETAILED DESCRIPTION

[0045] The present application will be described in detail below in combination with the drawings and embodiments.

[0046] Embodiment 1

[0047] A method for preparing a multicolor carbon dots solution on a large scale at normal temperature and pressure, specifically comprising the following steps:

[0048] (1) 108g (1mol) of o-phenylenediamine and 180g (1mol) of glucose were weighed and placed in a beaker, 5L of N,N-dimethylformamide was added, stirred at 300r / min for 30s, and a clear solution was obtained;

[0049] (2) 0.4L of concentrated nitric acid (mass fraction of 68%) was added to the clear solution, and the reaction was stirred at 300r / min for 0.5h at normal temperature and pressure to obtain a blue carbon dots solution.

[0050] 5g of polyvinylpyrrolidone was dissolved in 5mL of the blue carbon dots solution to prepare a blue carbon dots / polyvinylpyrrolidone film, and then the obtained film was peeled off and prepared into an LED lamp to obtain an LED lamp prepared by the blue carbon dots solution.

[0051] Embodiment 2

[0052] A method for preparing a multicolor carbon dots solution on a large scale at normal temperature and pressure, specifically comprising the following steps:

[0053] (1) 108 g (1 mol) of o-phenylenediamine and 134 g (1 mol) of malic acid were weighed into a beaker, 5 L of N,N-dimethylformamide was added, stirred at 200 r / min for 60 s to obtain a clear solution;

[0054] (2) 0.4 L of concentrated nitric acid (mass fraction of 68%) was added to the clear solution, stirred at 200 r / min for 0.5 h at room temperature and normal pressure to obtain a green carbon dot solution.

[0055] 5 g of polyvinylpyrrolidone was dissolved in 5 mL of the green carbon dot solution to prepare a green carbon dot / polyvinylpyrrolidone film, and then the obtained film was peeled off and prepared into an LED lamp to obtain the LED lamp prepared from the green carbon dot solution.

[0056] Example 3

[0057] A method for preparing a multi-color carbon dot solution on a large scale at room temperature and normal pressure, specifically comprising the following steps:

[0058] (1) 108 g (1 mol) of o-phenylenediamine and 176 g (1 mol) of ascorbic acid were weighed into a beaker, 5 L of N,N-dimethylformamide was added, stirred at 250 r / min for 45 s to obtain a clear solution;

[0059] (2) 0.4 L of concentrated nitric acid (mass fraction of 68%) was added to the clear solution, stirred at 250 r / min for 0.5 h at room temperature and normal pressure to obtain a yellow carbon dot solution.

[0060] 5 g of polyvinylpyrrolidone was dissolved in 5 mL of the yellow carbon dot solution to prepare a yellow carbon dot / polyvinylpyrrolidone film, and then the obtained film was peeled off and prepared into an LED lamp to obtain the LED lamp prepared from the yellow carbon dot solution.

[0061] Example 4

[0062] A method for preparing a multi-color carbon dot solution on a large scale at room temperature and normal pressure, specifically comprising the following steps:

[0063] (1) 108 g (1 mol) of o-phenylenediamine and 192 g (1 mol) of citric acid were weighed into a beaker, 5 L of N,N-dimethylformamide was added, stirred at 300 r / min for 30 s to obtain a clear solution;

[0064] (2) 0.4 L of concentrated nitric acid (mass fraction of 68%) was added to the clear solution, stirred at 300 r / min for 6 h at room temperature and normal pressure to obtain a red carbon dot solution.

[0065] 5g of polyvinylpyrrolidone is dissolved in 5mL of red carbon dot solution to prepare a red carbon dot / polyvinylpyrrolidone film, and then the obtained film is peeled off and prepared into an LED lamp to obtain the LED lamp prepared from the red carbon dot solution.

[0066] Example 5

[0067] A method for preparing a multi-color carbon dot solution on a large scale at normal temperature and pressure, specifically comprising the following steps:

[0068] (1) 108g (1mol) of o-phenylenediamine and 54g (0.3mol) of glucose are weighed into a beaker, 1.5L of N,N-dimethylformamide is added, and stirred at 300r / min for 30s to obtain a clear solution;

[0069] (2) 0.6L of concentrated sulfuric acid (mass fraction of 70%) is added to the clear solution, and stirred at 300r / min for 3h at normal temperature and pressure to obtain a blue carbon dot solution.

[0070] 6g of polyvinylpyrrolidone is dissolved in 5mL of blue carbon dot solution to prepare a blue carbon dot / polyvinylpyrrolidone film, and then the obtained film is peeled off and prepared into an LED lamp to obtain the LED lamp prepared from the blue carbon dot solution.

[0071] Example 6

[0072] A method for preparing a multi-color carbon dot solution on a large scale at normal temperature and pressure, specifically comprising the following steps:

[0073] (1) 108g (1mol) of o-phenylenediamine and 540g (3mol) of glucose are weighed into a beaker, 15L of N,N-dimethylformamide is added, and stirred at 300r / min for 30s to obtain a clear solution;

[0074] (2) 1L of concentrated hydrochloric acid (mass fraction of 36%) is added to the clear solution, and stirred at 300r / min for 6h at normal temperature and pressure to obtain a blue carbon dot solution.

[0075] 7.5g of polyvinylpyrrolidone is dissolved in 5mL of blue carbon dot solution to prepare a blue carbon dot / polyvinylpyrrolidone film, and then the obtained film is peeled off and prepared into an LED lamp to obtain the LED lamp prepared from the blue carbon dot solution.

[0076] Example 7

[0077] A method for preparing a multi-color carbon dot solution on a large scale at normal temperature and pressure, specifically comprising the following steps:

[0078] (1) 108 g (1 mol) of o-phenylenediamine and 268 g (2 mol) of malic acid were weighed into a beaker, 10 L of N,N-dimethylformamide was added, stirred at 300 r / min for 30 s, and a clear solution was obtained;

[0079] (2) 0.2 L of hydrogen peroxide (30% by mass) was added to the clear solution, stirred at 300 r / min for 3 h at room temperature and normal pressure, and a green carbon dot solution was obtained.

[0080] 5 g of polyvinylpyrrolidone was dissolved in 5 mL of the green carbon dot solution to prepare a green carbon dot / polyvinylpyrrolidone film, and then the obtained film was peeled off and prepared into an LED lamp to obtain the LED lamp prepared from the green carbon dot solution.

[0081] Example 8

[0082] A method for preparing a multi-color carbon dot solution on a large scale at room temperature and normal pressure, specifically comprising the following steps:

[0083] (1) 108 g (1 mol) of o-phenylenediamine and 268 g (2 mol) of malic acid were weighed into a beaker, 10 L of N,N-dimethylformamide was added, stirred at 300 r / min for 30 s, and a clear solution was obtained;

[0084] (2) 0.2 L of concentrated sulfuric acid (98% by mass) was added to the clear solution, stirred at 300 r / min for 6 h at room temperature and normal pressure, and a green carbon dot solution was obtained.

[0085] 5 g of polyvinylpyrrolidone was dissolved in 5 mL of the green carbon dot solution to prepare a green carbon dot / polyvinylpyrrolidone film, and then the obtained film was peeled off and prepared into an LED lamp to obtain the LED lamp prepared from the green carbon dot solution.

[0086] Example 9

[0087] A method for preparing a multi-color carbon dot solution on a large scale at room temperature and normal pressure, specifically comprising the following steps:

[0088] (1) 108 g (1 mol) of o-phenylenediamine and 268 g (2 mol) of malic acid were weighed into a beaker, 10 L of N,N-dimethylformamide was added, stirred at 300 r / min for 30 s, and a clear solution was obtained;

[0089] (2) 0.2 L of concentrated sulfuric acid (98% by mass) was added to the clear solution, stirred at 300 r / min for 6 h at room temperature and normal pressure, and a green carbon dot solution was obtained.

[0090] The 5g polyvinylpyrrolidone is dissolved in 5mL yellow carbon dots solution to prepare a yellow carbon dots / polyvinylpyrrolidone film, and then the obtained film is peeled off and prepared into an LED lamp to obtain the LED lamp prepared by the yellow carbon dots solution.

[0091] Example 10

[0092] A method for preparing a multi-color carbon dot solution on a large scale at normal temperature and pressure, specifically comprising the following steps:

[0093] (1) 108g (1mol) of o-phenylenediamine and 352g (2mol) of ascorbic acid are weighed into a beaker, 15L of N,N-dimethylformamide is added, stirred at 300r / min for 30s, and a clear solution is obtained;

[0094] (2) 1L of hydrogen peroxide (mass fraction 35%) is added to the clear solution, stirred at 300r / min for 6h at normal temperature and pressure, and a yellow carbon dot solution is obtained.

[0095] The 5g polyvinylpyrrolidone is dissolved in 5mL yellow carbon dots solution to prepare a yellow carbon dots / polyvinylpyrrolidone film, and then the obtained film is peeled off and prepared into an LED lamp to obtain the LED lamp prepared by the yellow carbon dots solution.

[0096] Example 11

[0097] A method for preparing a multi-color carbon dot solution on a large scale at normal temperature and pressure, specifically comprising the following steps:

[0098] (1) 216g (2mol) of o-phenylenediamine and 384g (2mol) of citric acid are weighed into a beaker, 10L of N,N-dimethylformamide is added, stirred at 300r / min for 30s, and a clear solution is obtained;

[0099] (2) 0.6L of concentrated nitric acid (mass fraction 65%) is added to the clear solution, stirred at 300r / min for 3h at normal temperature and pressure, and a red carbon dot solution is obtained.

[0100] The 5g polyvinylpyrrolidone is dissolved in 5mL red carbon dots solution to prepare a red carbon dots / polyvinylpyrrolidone film, and then the obtained film is peeled off and prepared into an LED lamp to obtain the LED lamp prepared by the red carbon dots solution.

[0101] Example 12

[0102] A method for preparing a multi-color carbon dot solution on a large scale at normal temperature and pressure, specifically comprising the following steps:

[0103] (1) Take 324 g (3 mol) of o-phenylenediamine and 576 g (3 mol) of ascorbic acid into a beaker, add 15 L of N,N-dimethylformamide, stir at 300 r / min for 30 s to obtain a clear solution;

[0104] (2) Add 1 L of concentrated nitric acid (mass fraction of 70%) to the clear solution, stir at 300 r / min at room temperature and normal pressure for 6 h to obtain a red carbon dot solution.

[0105] 5 g of polyvinylpyrrolidone is dissolved in 5 mL of the red carbon dot solution to prepare a red carbon dot / polyvinylpyrrolidone film, and then the obtained film is peeled off and prepared into an LED lamp to obtain the LED lamp prepared from the red carbon dot solution.

[0106] Comparative Examples 1-15:

[0107] On the basis of Examples 1-4, the carbon source is replaced by m-phenylenediamine, and the remaining conditions are unchanged, to set up Comparative Examples 1-4; on the basis of Examples 1-4, the carbon source is replaced by p-phenylenediamine, and the remaining conditions are unchanged, to set up Comparative Examples 5-8; on the basis of Example 1, the polyol or polyacid is replaced by mannitol, sorbitol, or sorbic acid, and the remaining contents are unchanged, to set up Comparative Examples 9-11; on the basis of Example 1, the acidic oxidant is replaced by 0.1 mol / L of sodium hydroxide, and the remaining contents are unchanged, to set up Comparative Examples 12-15; the specific conditions are shown in Table 1:

[0108] Table 1

[0109]

[0110]

[0111] Test Example 1

[0112] (1) Carbon dot distribution, size, emission wavelength, and relative quantum yield test:

[0113] Take the blue carbon dot solution prepared in Example 1 of the present application, observe the carbon dot distribution and size by transmission electron microscopy, and detect the emission wavelength by a fluorescence spectrophotometer, and the results are shown in Figures 1-3 From the figure, it can be seen that the carbon dots have good dispersibility, the particles are uniformly distributed, the average particle size is 2.86 nm, and the emission wavelength of the carbon dots is 490 nm.

[0114] Take the blue carbon dot solution prepared in Example 1 of the present application, and detect the relative quantum yield with 0.05 mol / L of quinine sulfate ethanol solution as a reference (quantum yield of 55%). The relative quantum yield of the blue carbon dot solution is 31.5%.

[0115] (2) Fluorescence stability test and luminous efficiency test:

[0116] The blue carbon dots solution prepared in Example 1 of the present application was taken, and the fluorescence intensity was monitored for 30 consecutive days, and the results are shown in Figure (a) of Figure 21 From the figure, it can be seen that the fluorescence intensity of the blue carbon dots fluctuates slightly, indicating that they have good optical stability.

[0117] The blue carbon dots / polyvinylpyrrolidone film prepared in Example 1 of the present application was taken, and the fluorescence intensity was monitored for 30 hours under continuous ultraviolet light of 365 nm, and the results are shown in Figure (b) of Figure 21 From the figure, it can be seen that the fluorescence intensity of the blue carbon dots / polyvinylpyrrolidone film is almost unchanged, indicating that it has high resistance to photobleaching.

[0118] The blue carbon dots / polyvinylpyrrolidone film prepared in Example 1 of the present application was taken, and thermogravimetric analysis was performed, and the results are shown in Figure (c) of Figure 21 The mass of the blue carbon dots / polyvinylpyrrolidone film decreased slightly at 105°C, which may be due to the evaporation of residual solvent in the blue carbon dots / polyvinylpyrrolidone film. When the temperature increased to 394°C, the mass decreased sharply and eventually stabilized, indicating that the blue carbon dots / polyvinylpyrrolidone film was completely decomposed above 394°C. Thus, it can be concluded that the blue carbon dots / polyvinylpyrrolidone film has considerable thermal stability.

[0119] Based on the above findings, it can be concluded that the blue carbon dots / polyvinylpyrrolidone film exhibits excellent fluorescence stability. Considering that the working temperature and working time of most LEDs are below 80°C and 24 hours, respectively, the blue carbon dots / polyvinylpyrrolidone film has great potential in LED applications. The blue LED prepared is shown in Figures 13-14 The color coordinates CIE and correlated color temperature CCT of the International Commission on Illumination are characterized by blue light (0.17, 0.14) and 7402 K, and the color rendering index CRI is 88.3, with ideal luminous efficiency.

[0120] Test Example 2

[0121] (1) Carbon dot distribution, size, emission wavelength, and relative quantum yield test:

[0122] The green carbon dot solution prepared in Example 2 of the present application was taken, and the carbon dot distribution and size were observed by transmission electron microscopy, and the emission wavelength was detected by a fluorescence spectrophotometer, and the results are shown in Figure Figures 4-6 From the figure, it can be seen that the carbon dots have good dispersibility, uniform particle distribution, and an average particle size of 3.27 nm, and the emission wavelength of the carbon dots is 530 nm.

[0123] The green carbon dots solution prepared in Example 2 of the present application was taken as a sample, and a 0.05 mol / L quinine sulfate ethanol solution was taken as a reference sample (quantum yield 55%), and the relative quantum yield was detected. The relative quantum yield of the green carbon dots solution was 26.4%.

[0124] (2) Fluorescence stability test and luminous efficiency test:

[0125] The green carbon dots solution prepared in Example 2 of the present application was taken, and the fluorescence intensity was monitored for 30 consecutive days, and the results are shown in Fig. (a) of Figure 21 From the figure, it can be seen that the fluorescence intensity of the green carbon dots fluctuates slightly, indicating that they have good optical stability.

[0126] The green carbon dots / polyvinylpyrrolidone film prepared in Example 2 of the present application was taken, and exposed to 365 nm continuous ultraviolet light for 30 hours, and the results are shown in Fig. (b) of Figure 21 From the figure, it can be seen that the fluorescence intensity of the green carbon dots / polyvinylpyrrolidone film is almost unchanged, indicating that it has high resistance to photobleaching.

[0127] The green carbon dots / polyvinylpyrrolidone film prepared in Example 2 of the present application was taken, and thermogravimetric analysis was performed, and the results are shown in Fig. (c) of Figure 21 The mass of the green carbon dots / polyvinylpyrrolidone film decreased slightly at 105°C, which may be due to the evaporation of residual solvent in the green carbon dots / polyvinylpyrrolidone film. When the temperature increased to 394°C, the mass decreased sharply and eventually stabilized, indicating that the green carbon dots / polyvinylpyrrolidone film was completely decomposed above 394°C. Thus, it can be concluded that the green carbon dots / polyvinylpyrrolidone film has considerable thermal stability.

[0128] Based on the above findings, it can be concluded that the green carbon dots / polyvinylpyrrolidone film exhibits excellent fluorescence stability. Considering that the working temperature and working time of most LEDs are below 80°C and 24 hours, respectively, the green carbon dots / polyvinylpyrrolidone film has great potential in LED applications. The green LED prepared is shown in Figures 15-16 The color coordinates CIE and the correlated color temperature CCT of the International Commission on Illumination are characterized by green light (0.18, 0.35) and 5853 K, and the color rendering index CRI is 87.2, having ideal luminous efficiency.

[0129] Test Example 3

[0130] (1) Carbon dots distribution, size, emission wavelength and relative quantum yield test:

[0131] The yellow carbon dots solution prepared in Example 3 of the present application was taken, and the carbon dot distribution and size were observed by transmission electron microscopy, and the emission wavelength was detected by fluorescence spectrophotometer, and the results are shown in Figures 7-9 From the figure, it can be seen that the carbon dots have good dispersity, the particles are uniformly distributed, the average particle size is 4.22 nm, and the emission wavelength of the carbon dots is 570 nm.

[0132] The yellow carbon dots solution prepared in Example 3 of the present application was taken, and the relative quantum yield was detected with 0.05 μg / mL rhodamine B ethanol solution as a reference (quantum yield is 82%). The relative quantum yield of the yellow carbon dots solution is 21.8%.

[0133] (2) Fluorescence stability test and luminescence efficiency test:

[0134] The yellow carbon dots solution prepared in Example 3 of the present application was taken, and the fluorescence intensity was monitored for 30 consecutive days, and the results are shown in Figure 21 (a) of the figure. From the figure, it can be seen that the fluorescence intensity of the yellow carbon dots fluctuates slightly, indicating that they have good optical stability.

[0135] The yellow carbon dots / polyvinylpyrrolidone film prepared in Example 3 of the present application was taken, and exposed to 365 nm continuous ultraviolet light for 30 hours, and the results are shown in Figure 21 (b) of the figure. From the figure, it can be seen that the fluorescence intensity of the yellow carbon dots / polyvinylpyrrolidone film is almost unchanged, indicating that it has high anti-photobleaching property.

[0136] The yellow carbon dots / polyvinylpyrrolidone film prepared in Example 3 of the present application was taken, and thermogravimetric analysis was performed, and the results are shown in Figure 21 (c) of the figure, the mass of the yellow carbon dots / polyvinylpyrrolidone film decreases slightly at 105℃, which may be due to the evaporation of residual solvent in the yellow carbon dots / polyvinylpyrrolidone film. When the temperature rises to 394℃, the mass decreases sharply and finally tends to be stable, indicating that the yellow carbon dots / polyvinylpyrrolidone film is completely decomposed above 394℃. Thus, it can be concluded that the yellow carbon dots / polyvinylpyrrolidone film has considerable thermal stability.

[0137] Based on the above findings, it can be concluded that the yellow carbon dots / polyvinylpyrrolidone film all exhibit excellent fluorescence stability. Considering that the working temperature and working time of most LEDs are lower than 80℃ and 24 hours respectively, the yellow carbon dots / polyvinylpyrrolidone film has great potential in LED applications. The yellow LED prepared is shown in Figures 17-18 The color coordinates CIE and the related color temperature CCT of the International Commission on Illumination are characterized as follows: yellow light is (0.50, 0.49) and 3901 K, the color rendering index CRI is 90.2, and it has ideal luminescence efficiency.

[0138] Test Example 4

[0139] (1) Testing of carbon dot distribution, size, emission wavelength, and relative quantum yield:

[0140] The red carbon dot solution prepared in Example 4 of this invention was used to observe the distribution and size of the carbon dots using a transmission electron microscope, and the emission wavelength was detected using a fluorescence spectrophotometer. The results are as follows: Figures 10-12 As shown in the figure, the carbon dots are well dispersed, with a uniform particle distribution, an average particle size of 4.96 nm, and an emission wavelength of 615 nm.

[0141] The red carbon dot solution prepared in Example 4 of this invention was used, and the relative quantum yield was determined using a 0.05 μg / mL ethanol solution of Rhodamine B as a reference (quantum yield 82%). The relative quantum yield of the red carbon dot solution was 17.2%.

[0142] (2) Fluorescence stability test and luminescence efficiency test:

[0143] The red carbon dot solution prepared in Example 4 of this invention was used to monitor fluorescence intensity for 30 consecutive days, and the results are as follows. Figure 21 As shown in Figure (a), the fluorescence intensity of the red carbon dots fluctuates slightly, indicating that they have good optical stability.

[0144] The red carbon dot / polyvinylpyrrolidone film prepared in Example 4 of this invention was exposed to continuous ultraviolet light at 365 nm for 30 hours, and the results were as follows. Figure 21 As shown in Figure (b), the fluorescence intensity of the red carbon dot / polyvinylpyrrolidone film remains almost unchanged, indicating its high resistance to photobleaching.

[0145] The red carbon dot / polyvinylpyrrolidone film prepared in Example 4 of this invention was subjected to thermogravimetric analysis, and the results are as follows: Figure 21 As shown in Figure (c), the mass of the red carbon dot / polyvinylpyrrolidone film decreases slightly at 105 °C, which may be due to the evaporation of residual solvent in the film. When the temperature rises to 394 °C, the mass decreases sharply and eventually stabilizes, indicating that the red carbon dot / polyvinylpyrrolidone film completely decomposes above 394 °C. Therefore, the red carbon dot / polyvinylpyrrolidone film has considerable thermal stability.

[0146] Based on the above findings, it can be concluded that the red carbon dot / polyvinylpyrrolidone films exhibit excellent fluorescence stability. Considering that most LEDs operate at temperatures below 80°C and for a duration of 24 hours, the red carbon dot / polyvinylpyrrolidone films hold great potential for LED applications. The resulting red LEDs, such as...Figures 19-20 As shown, the color coordinates CIE and the correlated color temperature CCT of the international lighting committee are characterized by red light (0.61, 0.33) and 1936K, the color rendering index CRI is 93.2, and the luminous efficiency is ideal.

[0147] Test Example 5

[0148] The carbon dot solution prepared in Comparative Example 1-15 was detected by a fluorescence spectrophotometer for the emission wavelength, and the relative quantum yield was detected with 0.05 μg / mL of a rhodamine B ethanol solution as a reference (quantum yield 82%), and the results are shown in Table 2.

[0149] Table 2

[0150] Comparative Example Emission wavelength of synthesized carbon dot solution Relative quantum yield (%) 1 Not luminescent - 2 Not luminescent - 3 Not luminescent - 4 Not luminescent - 5 Not luminescent - 6 Not luminescent - 7 Not luminescent - 8 Not luminescent - 9 602 nm 6.2 10 602 nm 8.7 11 580 nm 6.9 12 570 nm 3.2 13 572 nm 4.1 14 570 nm 3.6 15 550 nm 5.7

[0151] As can be seen from Table 2, the carbon source is changed to m-phenylenediamine and p-phenylenediamine, and the carbon dots are not prepared at normal temperature and pressure, which indicates that o-phenylenediamine has higher reactivity and plays an important role in the generation of carbon dots; the polyhydric alcohol or polybasic acid is changed, and the fluorescent carbon dot solution can be prepared at normal temperature and pressure, but the emission wavelength of the fluorescent carbon dot solution is concentrated in 580-602 nm, and the quantum yield is low, which is not conducive to the preparation of multi-color LED lamps; the acidic oxidant is changed to sodium hydroxide, and the prepared solution has an emission wavelength concentrated in 550-572 nm, and the multi-color carbon dot solution cannot be prepared.

[0152] The above description is only preferred embodiments of the present application, and the present application is not limited to the above examples. It can be understood that other improvements and changes directly derived or thought by those skilled in the art without departing from the spirit and concept of the present application should be considered to be included in the protection scope of the present application.

Claims

1. A method for large-scale preparation of multicolor carbon dot solutions at room temperature and pressure, characterized in that, The method includes the following steps: (1) Mix the carbon source, polyol or polyacid, add solvent, and stir to obtain a clear solution; (2) Add an acidic oxidant and stir the reaction to obtain a multicolor carbon dot solution; The carbon source is o-phenylenediamine; the polyol includes glucose and ascorbic acid; the polyacid includes malic acid and citric acid; and the solvent is N,N-dimethylformamide.

2. The method according to claim 1, characterized in that, In step (1), the molar ratio of the carbon source to the polyol or polyacid is 1:0.3-3; the molar volume ratio of the carbon source to the solvent is 1mol:1.5-15L.

3. The method according to claim 1, characterized in that, In step (1), the stirring speed is 200-300 r / min and the stirring time is 30-60 s.

4. The method according to claim 1, characterized in that, In step (2), the acidic oxidant includes one of concentrated nitric acid, concentrated sulfuric acid, concentrated hydrochloric acid, and hydrogen peroxide; the mass fraction of the concentrated nitric acid is 65-70%, the mass fraction of the concentrated sulfuric acid is 70-98%, the mass fraction of the concentrated hydrochloric acid is 36%-40%, and the mass fraction of the hydrogen peroxide is 30%-35%; the molar volume ratio of the carbon source in step (1) to the acidic oxidant in step (2) is 1 mol: 0.2-1 L.

5. The method according to claim 1, characterized in that, In step (2), the stirring speed is 200-300 r / min and the time is 0.5-6 h.

6. The method according to claim 1, characterized in that, In step (2), the multicolor carbon dot solution includes blue fluorescent carbon dot solution, green fluorescent carbon dot solution, yellow fluorescent carbon dot solution, and red fluorescent carbon dot solution.

7. A multicolor carbon dot solution prepared by the method of any one of claims 1-6.

8. An application of the multicolor carbon dot solution according to claim 7, characterized in that, The multicolor carbon dot solution is used to prepare multicolor LED lamps. The multicolor carbon dot solution is compounded with polyvinylpyrrolidone to form a thin film, which is then used to prepare multicolor LED lamps. The volume-to-mass ratio of the multicolor carbon dot solution to polyvinylpyrrolidone is 1 mL: 1-1.5 g.

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