CN111718713A - Carbon dots, preparation method and application thereof, solid luminescent excipient material - Google Patents

Abstract

The invention discloses a carbon dot, a preparation method and application thereof, and a solid luminescent excipient material. The preparation method of the carbon dots includes: dissolving and mixing the raw materials for preparing the carbon dots in a solvent, and then removing the solvent capable of reacting with the dehydrating agent. In the homogeneous mixture, a dehydrating agent is added, and the reaction is carried out at a temperature of 80 to 200 °C; wherein, the raw materials for preparing carbon dots contain hydrophilic groups, and the raw materials for preparing carbon dots are fully and uniformly mixed by dissolving to provide the reaction effect. The basic conditions are met, and in the reaction process, the hydrophilic groups contained in the raw materials are polycondensed under the action of the dehydrating agent, so that the reaction process can generate water-soluble and hydrophobic carbon dots at the same time. Achieve the ratio of water-soluble and hydrophobic Cdot synthesis. In addition, the entire preparation process is simple to operate, the synthesized hydrophobic carbon dots have long wavelengths and are adjustable, and the carbon dots have a high fluorescence quantum yield.

Description

Carbon dots, preparation method and application thereof, solid luminescent excipient material

technical field

The invention relates to the technical field of nanomaterials, in particular, to a carbon dot, a preparation method and application thereof, and a solid luminescent excipient material.

Background technique

Carbon dots (CDs) are a new class of fluorescent nanomaterials, which have attracted extensive attention of researchers due to their easy functionalization, good biocompatibility, stable chemical properties, strong resistance to photobleaching, abundant raw materials and easy preparation. . Carbon dots have gradually shown the potential to replace conventional quantum dots in applications in drug delivery, medical diagnosis, two-photon imaging, ion detection, and catalysis.

So far, the synthesized CDs are mostly water-soluble CDs. However, due to the limitation of their surface groups, such CDs are prone to the phenomenon of fluorescence quenching after aggregation (ACQ phenomenon), which is difficult to apply to organic electronics, thin film applications, or sensors in hydrophobic environments. Therefore, hydrophobic carbon dots (HCDs) have become a new research object for researchers.

At present, the methods for synthesizing carbon dots mainly include arc discharge, laser ablation, chemical oxidation in strong acid, and electrochemical synthesis, pulverizing carbon allotropes, such as carbon nanotubes, nanodiamonds or graphite until the product produces fluorescent nanoparticles. characteristic. Among them, the methods for preparing hydrophobic Cdots mainly include: firstly synthesizing water-soluble CDs (WCDs), and then converting them into HCDs through surface modification, or preparing HCDs by one-step reaction at high temperature in strong acids, strong bases or organic reagents. However, these preparation methods have the disadvantages of complicated operation steps, long time-consuming, reduced quantum yield, or strong toxicity and corrosiveness of the solvent selected. In addition, the prior art also lacks a method for preparing carbon dots that can simultaneously prepare water-soluble and hydrophobic carbon dots.

In view of this, the present invention is proposed.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a carbon dot, a preparation method and application thereof, and a solid luminescent excipient material to improve the above problems.

The present invention is realized in this way:

In a first aspect, an embodiment of the present invention provides a method for preparing carbon dots, comprising:

A dehydrating agent is added to the homogeneous mixture of the raw materials for the preparation of carbon dots, and the reaction is carried out at a temperature of 100-200 °C; wherein the raw materials for the preparation of carbon dots contain hydrophilic groups, and the homogeneous mixture is mainly obtained by the following preparation steps: The raw materials for point preparation are dissolved and mixed in a solvent, and then the solvent that can react with the dehydrating agent is removed.

In the second aspect, the embodiment of the present invention also provides a carbon dot, which is prepared by the above preparation method. Optionally, the carbon dot is a hydrophobic carbon dot obtained by separation after the reaction.

In a third aspect, the embodiments of the present invention also provide the application of the above carbon dots in the preparation of fluorescent materials.

In a fourth aspect, the present invention also provides the application of the above-mentioned carbon dots in the preparation of solid-state lighting devices, displays or solid luminescent excipient materials, where the carbon dots are hydrophobic carbon dots obtained by separation after the reaction, optionally, the hydrophobicity The carbon dots are N, S co-doped hydrophobic carbon dots with a fluorescence emission wavelength of 450-580 nm.

In a fifth aspect, an embodiment of the present invention further provides a solid light-emitting excipient material, the raw material component of which contains the above-mentioned hydrophobic carbon dots.

The invention has the following beneficial effects: by first dissolving the carbon dots preparation raw materials and then removing the solvent capable of reacting with the dehydrating agent, the carbon dots preparation raw materials can be fully and uniformly mixed, providing basic conditions for the reaction effect of the carbon dots generation, Then a dehydrating agent is added to the homogeneous mixture, and in the process of reacting to generate carbon dots, the hydrophilic groups such as carboxyl groups, amino groups or hydroxyl groups contained in the raw materials for preparing carbon dots can be polycondensed under the action of the dehydrating agent, so that the reaction The process can generate both water-soluble Cdots and hydrophobic Cdots at the same time. And by controlling the amount and type of dehydrating agent, the synthesis ratio of water-soluble carbon dots and hydrophobic carbon dots can be achieved. In addition, the whole preparation process is simple to operate, the synthesized hydrophobic carbon dots have a long wavelength and are adjustable, and the fluorescent quantum yield of the carbon dots is high.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation of the scope, and for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without any creative effort.

1 is a photo of the solid product synthesized in the second step of Example 1 of the present invention (a mixture of hydrophilic and hydrophobic carbon dots);

2 is a photo of the solid product synthesized in the second step of Example 2 of the present invention (a mixture of hydrophilic and hydrophobic carbon dots);

3 is a photo of the solid product synthesized in the second step of Example 3 of the present invention (a mixture of hydrophilic and hydrophobic carbon dots);

4 is a photo of the hydrophobic carbon dot solution of Example 1 of the present invention under 365nm ultraviolet light irradiation;

5 is a fluorescence emission diagram of the hydrophobic carbon dots synthesized in Example 1 of the present invention;

Fig. 6 is the ultraviolet-visible absorption spectrogram of the hydrophobic carbon dots synthesized in Example 1 of the present invention;

Fig. 7 is the XPS scanning pattern (i) of the hydrophobic carbon dots synthesized in Example 1 of the present invention, the peak-splitting pattern of C1s XPS (ii), the peak-splitting pattern of N1s XPS (iii), and the peak-splitting pattern of O1s XPS (iV ) Peak-splitting spectrum of S2p XPS (V);

8 is a photo of the hydrophilic carbon dot solution synthesized in Example 1 of the present invention under the irradiation of 365 nm ultraviolet light;

9 is a fluorescence emission diagram of the hydrophilic carbon dots synthesized in Example 1 of the present invention;

Fig. 10 is the ultraviolet-visible absorption spectrogram of the hydrophilic carbon dots synthesized in Example 1 of the present invention;

11 is a photo of the hydrophobic carbon dot solution in Comparative Example 1 of the present invention under the irradiation of 365 nm ultraviolet light;

Figure 12 is a fluorescence emission diagram of the hydrophobic carbon dots synthesized in Comparative Example 1 of the present invention;

13 is a photo of the hydrophilic carbon dot solution synthesized in Comparative Example 1 of the present invention under the irradiation of 365 nm ultraviolet light;

Figure 14 is a fluorescence emission diagram of the hydrophilic carbon dots synthesized in Comparative Example 1 of the present invention;

Figure 15 is a white light illumination LED lamp constructed with the hydrophobic carbon dots synthesized in Example 1 of the present invention as one of the light source components;

FIG. 16 is an electroluminescence spectrum diagram of the white light-emitting LED lamp in FIG. 12;

Figure 17 is a picture of the solid epoxy resin device loaded with the hydrophobic carbon dots of Example 1 under natural light;

18 is a picture of the solid epoxy resin device encapsulated with the hydrophobic carbon dots of Example 1 under the irradiation of 365 nm ultraviolet light;

Figure 19 is a comparative photo of the hydrophilic carbon dot solution in Example 2 of the present invention under natural light and 365nm ultraviolet light irradiation;

Figure 20 is the fluorescence emission spectrum of the hydrophobic carbon dots synthesized in Example 2 of the present invention;

Figure 21 is a comparative photograph of the hydrophobic carbon dot solution of Example 3 of the present invention under natural light and 365 nm ultraviolet light irradiation.

Detailed ways

In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not indicated in the examples, it is carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used without the manufacturer's indication are conventional products that can be purchased from the market.

The carbon dots provided by the present invention, the preparation method and application thereof, and the solid luminescent excipient material are specifically described below.

By analyzing the preparation methods of carbon dots in the prior art, the inventor found that there is a lack of a synthetic method that can easily generate water-soluble carbon dots and hydrophobic carbon dots at the same time. There are two main methods for the preparation of hydrophobic Cdots. One is to synthesize hydrophilic CDs (WCDs) first, and then convert them into HCDs through surface modification. For example, Shang and his colleagues dissolved WCDs in toluene and oleyl amine and heated them to reflux in an oil bath at 130 °C. After 6 h, orange HCDs were obtained, and their emission wavelength (λem) was red-shifted by 20 nm compared to WCDs; , and then add ethylenediamine or dodecylamine, and stir at 115 °C for 4 h to obtain HCDs with unchanged wavelength. Such methods have complicated operation steps, take a long time, and reduce the quantum yield. Another category is the preparation of HCDs by one-step reaction at high temperature in strong acids, strong bases or organic reagents. Commonly used reagents include strong acids and bases such as phosphoric acid, nitric acid, and sodium hydroxide, or organic reagents such as toluene and 1-octadecene as solvents. And the reaction temperature of most experiments was between 160-280℃, and the reaction time was between 20min and 12h. However, due to the characteristics of toxicity and corrosiveness of the solvent selected in this method, it is not friendly to the environment and does not meet the characteristics of green synthesis.

Therefore, it is one of the main purposes of the present invention to develop a solid-phase synthesis method that is simple, quick, and environmentally friendly (reduces or does not use strong acids, strong bases and organic reagents) to obtain long-wavelength luminescent HCDs. Therefore, based on the defects existing in the preparation of carbon dots at present, the inventor creatively proposes the following technical solutions through a lot of research and practice on the basis of the prior art.

Some embodiments of the present invention provide a method for preparing carbon dots, which includes: adding a dehydrating agent to a uniform mixture of raw materials for preparing carbon dots, and performing a reaction at a temperature of 100-200°C. Wherein, the raw materials for preparing carbon dots contain hydrophilic groups, and the homogeneous mixture is mainly obtained by the following preparation steps: dissolving and mixing the raw materials for preparing carbon dots in a solvent, and then removing the solvent capable of reacting with the dehydrating agent.

By dissolving the raw materials for the preparation of carbon dots first, and then removing the solvent that can react with the dehydrating agent, the raw materials for preparing the carbon dots can be fully mixed evenly, and the solvent will not react with the dehydrating agent to affect the synthesis of the carbon dots. process. It should be noted that, in the embodiment of the present invention, the removal of the solvent can also be basically removed, and it should be ensured that a small amount of residual solvent will not affect the carbon dot synthesis process, and the preferred way is to completely remove it. When the solvent is not reacted with the dehydrating agent, the step of removing the solvent is not an essential step.

Further, in the process of reacting to generate carbon dots, the dehydrating agent can promote the polycondensation of hydrophilic groups such as carboxyl groups, amino groups or hydroxyl groups contained in the raw material for carbon dot preparation itself, promote the synthesis of carbon dots, and realize water-soluble carbon dots. and the preparation of hydrophobic Cdots, and in the synthesis process, the water-soluble Cdots and the hydrophobic Cdots are synthesized at the same time, but the main body is the hydrophobic Cdots. The ratio of water-soluble and hydrophobic C-dot synthesis and the wavelength of hydrophobic C-dots can be achieved by adjusting the amount and type of dehydrating agent. That is, the more dehydrating agent is used, the less water-soluble carbon dots are synthesized, the proportion of hydrophobic carbon dots increases, and the wavelength is red-shifted.

The longer the reaction time and the higher the reaction temperature, the better the preparation of long-wavelength hydrophobic carbon dots.

Specifically, some embodiments of the present invention provide a method for preparing carbon dots, comprising the following steps:

S1. Dissolving and mixing the raw materials for carbon dot preparation in a solvent, and then removing the solvent capable of reacting with the dehydrating agent.

In some embodiments, carbon dots preparation feedstocks include, but are not limited to, carbon sources and nitrogen and sulfur co-doping agents. Further, the carbon source includes, but is not limited to, at least one of citric acid, oxalic acid, sodium citrate, sodium oxalate, and glucose. Nitrogen, sulfur co-incorporators include but are not limited to D,L-homocysteine, L-methionine, L-cysteine, L-cysteine hydrochloride, D-cysteine at least one of acid, glutathione, N-acetyl-L-cysteine, beta-mercaptoethylamine and thioacetamide.

In some preferred embodiments, the nitrogen and sulfur co-incorporators include at least one of L-cysteine, L-cysteine hydrochloride, and N-acetyl-L-cysteine. In some preferred embodiments, the mass ratio of the carbon source to the nitrogen and sulfur co-doping agents is 1:0.5-10.

Or, the raw materials for preparing carbon dots include ethylenediamine, polyethyleneimine, phenol and the like.

In some embodiments, the solvent used for dissolving the carbon dots preparation raw materials is water, and dissolving and mixing the carbon dot preparation raw materials in the solvent and then removing the solvent includes: co-dissolving the carbon dot preparation raw materials in water, and then at 60-80 The reaction is carried out at ℃ for 6-15 h, preferably, the water is ultrapure water. That is, after completely dissolving the carbon dot preparation raw material in water, wherein the carbon dot preparation raw material is preferably powder, the water is evaporated by heating to obtain a solid homogeneous mixture without water or a slurry homogeneous mixture containing a small amount of water.

In some embodiments, the vessel for dissolving and removing the solvent is selected from any one of a Teflon reaction liner, a beaker, and a round bottom flask. Preferably, the vessel is a polytetrafluoroethylene reaction liner.

S2, adding a dehydrating agent to the uniform mixture of the raw materials for preparing carbon dots, and performing the reaction at a temperature of 80-200°C.

In some embodiments, the reaction time is 10-360 min, preferably 20-200 min, more preferably 20-80 min. By controlling the above reaction time, the raw materials can be fully reacted to obtain carbon dots with better quality.

Further, according to the ratio and quality requirements of the hydrophobic carbon dots, in some embodiments, the amount of the dehydrating agent can be 0.1-1 g.

Further, in some embodiments, the dehydrating agent includes but is not limited to polyphosphoric acid, N,N'-dicyclohexylcarbonimide (DCC), 1-(3-dimethylaminopropyl)-3-ethyl Ethyl carbonimide (EDC), 1-(3-dimethylaminopropyl)-3-ethylcarbonimide hydrochloride (EDCI), N,N-dimethylformamide, 2,2 -Dichloro-5-(2-phenethyl)-4-(trimethylsilyl)-3-furanone (DPTF), 1,3-dimethyl-2-imidazolidinone (P-DMI), Bis(trichloromethyl)carbonate (BTC), thionyl chloride-dimethylformamide (SOCl ₂ -DMF), 2-chloro-1,3 dimethyl imidazolium chloride (DMC), pentachloro At least one of phosphorus oxychloride, phosphorus oxychloride and phosphorus pentoxide.

In some preferred embodiments, the dehydrating agent is N,N'-dicyclohexylcarbonimide, 1-(3-dimethylaminopropyl)-3-ethylcarbonimide or 1-(3 - Dimethylaminopropyl)-3-ethylcarbonimide hydrochloride.

Specifically, most of the dehydrating agents are solid. Therefore, in order to enable the dehydrating agent to fully contact the raw materials for preparing carbon dots, in some embodiments, the dehydrating agent is added in the form of an organic solution. The organic solvent for dissolving the dehydrating agent is acetonitrile, but the amount of the organic solvent used for dissolving the dehydrating agent is very small, only 100-1000uL, which will not substantially affect the reaction system. After the removal, the process of adding a dehydrating agent to carry out the reaction is not carried out in an organic solvent as a whole. In addition, when the dehydrating agent is a liquid dehydrating agent, it is not necessary to add an organic solvent to dissolve the dehydrating agent.

Further, in some embodiments, the reaction vessel used for preparing carbon dots is selected from any one of a hydrothermal reactor, a beaker and a round-bottomed flask. In a preferred embodiment, the reaction vessel is a hydrothermal reactor.

In some embodiments, the heating vessel for heating and maintaining the reaction temperature is selected from any one of a water bath, an oil bath and an electric heating constant temperature blast drying oven. In a preferred embodiment, the heating container is an electric heating constant temperature blast drying oven.

Further, since the carbon dots directly generated by the synthesis reaction are solids in a consolidated state in which water-soluble carbon dots and hydrophobic carbon dots are mixed, in some embodiments, the following optional steps may also be included:

S3. The carbon dot solids obtained by the reaction are dissolved in a solvent to obtain a carbon dot solution.

In some embodiments, since the Cdot solids include both water-soluble Cdots and hydrophobic Cdots, the Cdots are dissolved in a water-soluble solvent and a hydrophobic solvent, respectively, to obtain a water-soluble Cdot solution and a hydrophobic Cdot solution. , and then the solvent was removed to obtain water-soluble Cdots and hydrophobic Cdots. That is, when the solvent is water, the carbon dots in the carbon dot solution are hydrophilic carbon dots, and the remaining solids can be extracted by the corresponding solvent to obtain hydrophobic carbon dots; When the hydrophobic solvent is dissolved, the obtained carbon dot solution is the hydrophobic carbon dot solution, and the remaining solid can be extracted by pure water to obtain water-soluble carbon dots. Therefore, the water-soluble carbon dots and the hydrophobic carbon dots can be separated by solvent dissolution and extraction to obtain separate water-soluble carbon dots and hydrophobic carbon dots.

It should be noted that the method of removing the solvent from the carbon dot solution to obtain the carbon dots includes, but is not limited to, rotary evaporation or freeze-drying.

Specifically, in some embodiments, the water-soluble solvent is water, the hydrophobic solvent is an organic solvent, and the organic solvent includes but is not limited to at least one of cyclohexane, carbon tetrachloride, chloroform, tetrahydrofuran and methanol. Preferably, the hydrophobic solvent is chloroform.

It should be noted that, when water is used as the solvent to prepare the raw materials for carbon dots in the embodiment, the use of organic solvents is avoided in the entire synthesis process, which is environmentally friendly and green. In contrast, in other existing synthesis methods, organic solutions are used and need to be heated, and the organic solutions are volatile when heated, and there is a potential safety hazard. The embodiment of the present invention needs to use an organic solvent for extraction and dissolution in the separation stage, but does not require heating.

Some embodiments of the present invention also provide a carbon dot, which is prepared by the preparation method of a carbon dot according to any of the foregoing embodiments. In some preferred embodiments, the carbon dots are hydrophobic carbon dots separated after the reaction. Further, the hydrophobic carbon dots can also be N, S co-doped hydrophobic carbon dots with a fluorescence emission wavelength of 450-540 nm.

Some embodiments of the present invention also provide applications of the above carbon dots in the preparation of fluorescent materials.

Some embodiments of the present invention also provide the application of carbon dots in the preparation of solid-state lighting devices, displays or solid luminescent excipient materials, where the carbon dots are hydrophobic carbon dots separated after the reaction.

Some embodiments of the present invention also provide a solid light-emitting excipient material, the raw material component of which contains the above-mentioned hydrophobic carbon dots.

The features and performances of the present invention will be further described in detail below in conjunction with the embodiments.

Example 1

(1) Place citric acid and L-cysteine hydrochloride in a polytetrafluoroethylene lining, add 2 mL of ultrapure water to the lining to dissolve and mix evenly, and the amount of citric acid is 0.4 mmol, and the amount of L-cysteine hydrochloride is 0.5 mmol. The lining was placed in an electric heating constant temperature blast drying oven at 70°C for reaction for 12h.

(2) add 0.3g N,N'-dicyclohexyl carbonimide (DCC) to the inner lining of step (1), put the inner lining into the hydrothermal reaction kettle and place it in the electric heating constant temperature blast drying oven The reaction was carried out at 180° C. for 40 min to obtain a dark brown solid product (as shown in Figure 1).

(3) Dissolving the solid product with chloroform ultrasonically to obtain a hydrophobic carbon dot solution, and then rotary evaporation to obtain a hydrophobic carbon dot solid. The solid insoluble in chloroform is extracted with 10 ml of pure water by ultrasonic for many times to obtain the aqueous solution of hydrophilic carbon dots, and the solid of hydrophilic carbon dots can be obtained by freeze-drying.

Example 2

(1) Place sodium citrate and D,L-homocysteine in a beaker, add 2 mL of ultrapure water to the beaker to dissolve and mix evenly, the amount of sodium citrate is 0.6 mmol, D , The amount of L-homocysteine is 1 mmol. The beaker was placed in an electric heating constant temperature blast drying oven at 70°C for 6h reaction.

(2) in the beaker of step (1), add 0.5g 1-(3-dimethylaminopropyl)-3-ethyl carbonimide (EDC), continue to be placed in the electric heating constant temperature blast drying oven for 200 The reaction was carried out at °C for 10 min to obtain a yellow solid (as shown in Figure 2). The yellow solid was dissolved by ultrasonic in pure water in multiple steps to obtain a blue luminescent hydrophilic carbon dot solution, and the hydrophilic carbon dot solid can be obtained by freeze-drying. Part of the product that cannot be dissolved in pure water is completely dissolved in methanol to obtain a hydrophobic carbon dot solution, and a hydrophobic carbon dot solid is obtained by rotary evaporation.

Example 3

(1) place oxalic acid and N-acetyl-L-cysteine in a round-bottomed flask, add 2 mL of ultrapure water to the round-bottomed flask to dissolve and mix uniformly, the amount of oxalic acid is 1.2 mmol, The amount of the substance of N-acetyl-L-cysteine was 1 mmol. The beaker was placed in an electric heating constant temperature blast drying oven for 10h at 70°C.

(2) Add 0.5g of 1,3-dimethyl-2-imidazolidinone to the round-bottomed flask of step (1), place it in a water bath and react at 100°C for 5h to obtain a brownish-yellow solid (as shown in Figure 3) ). The solid was dissolved with chloroform for multiple times by ultrasonic to obtain a solution of hydrophobic carbon dots. After adding methanol to the solution and centrifuging, a solid of hydrophobic carbon dots could be obtained. The solid insoluble in chloroform solution was dissolved in pure water to obtain a hydrophilic carbon dot aqueous solution. After adding isopropanol to the aqueous solution, centrifuge at 8000 rpm to obtain a hydrophilic carbon dot solid.

Example 4

(1) Place citric acid and polyethyleneimine in a round-bottomed flask, add 2 mL of ultrapure water and a one-to-one mixing reagent of ethanol to the round-bottomed flask, dissolve the raw materials and mix them evenly, and the citric acid The amount of substance was 1.0 mmoL, and the amount of substance of polyethyleneimine was 2.8 mmoL. The round-bottomed flask was placed in an electric heating constant temperature blast drying oven at 70°C for reaction for 3h.

(2) add 0.2g bis (trichloromethyl) carbonate (BTC) to the round-bottomed flask of step (1), place the round-bottomed flask in a medium oil bath at 170° C. for 2h to react to obtain a dark brown solid, Dissolve with chloroform to obtain a hydrophobic carbon dot solution, add acetonitrile and centrifuge to obtain a hydrophobic carbon dot solid. The carbon dots emit yellow light, the optimal emission wavelength is 543 nm, and the quantum yield is 18%. The remaining insoluble solid was dissolved in pure aqueous solution to obtain an aqueous solution of blue luminescent hydrophilic carbon dots. After adding acetonitrile to the aqueous solution and centrifuging and drying, a hydrophilic carbon dot solid was obtained. The optimal emission wavelength was 431 nm and the quantum yield was 22 %.

Comparative Example 1

(1) Place citric acid and L-cysteine hydrochloride in a polytetrafluoroethylene liner, and stir and mix thoroughly with a glass rod. The amount of citric acid is 0.4 mmol, and L-cysteine salt is The amount of the acid salt was 0.5 mmol.

(2) add 0.3g N,N'-dicyclohexyl carbonimide (DCC) to the inner lining of step (1), put the inner lining into the hydrothermal reaction kettle and place it in the electric heating constant temperature blast drying oven The reaction was carried out at 180°C for 40min to obtain a pale yellow solid product. The solid product was dissolved by ultrasonication with chloroform to obtain a hydrophobic carbon dot solution, which was then rotary evaporated to obtain a hydrophobic carbon dot solid. The remaining insoluble solid is dissolved with water to obtain a blue luminescent water-soluble carbon dot solution, which is freeze-dried to obtain a water-soluble carbon dot solid.

Comparative Example 2

The difference between this comparative example and Example 1 is that the reaction temperature of step (2) is 60 degrees, and the reaction time is 30 minutes, and a light yellow solid product can be prepared. color fluorescence, that is, only hydrophilic carbon dots can be prepared.

It should be noted that, in the above examples and comparative examples, when the dehydrating agent is solid, it is first dissolved in 200uL of acetonitrile, and then added to the reaction kettle.

Comparative Example 3

The only difference between this comparative example and Example 1 is that, in step (2), the reaction is carried out directly without adding a dehydrating agent. The product is a brownish-yellow solid, and the carbon dots are only blue-emitting hydrophilic carbon dots.

Test Example 1

The hydrophobic carbon dot solution in Example 1 was irradiated under 365nm ultraviolet light, as shown in Figure 4, it was yellow light emission, and the fluorescence emission map and UV-Vis absorption spectrum of the hydrophobic carbon dots in Example 1 were obtained. , as shown in Figure 5 and Figure 6 in turn, the results show that the optimal emission wavelength of the hydrophobic carbon dots is 540 nm, and the maximum absorption wavelength is 352 nm, but there is a broad absorption between 400 nm and 500 nm, and the fluorescence quantum yield is 30%. Then, elemental analysis was performed on the hydrophobic carbon dots in Example 1 by X-ray photoelectron spectroscopy (XPS). The results are shown in Figure 7. The results show that the carbon dots contain four elements: C, N, O, S , belonging to the N, S co-doped hydrophobic carbon dots. The hydrophilic carbon dot solution in Example 1 was irradiated under 365 nm ultraviolet light, as shown in FIG. 8 , it emitted blue light. Its fluorescence spectrum and ultraviolet-visible absorption spectrum are shown in Figure 9 and Figure 10, the optimal emission wavelength is 450 nm, the maximum absorption wavelength is 352 nm, and the quantum yield is 34%.

The carbon dots of Comparative Example 1 are analyzed. As shown in Figure 11, the hydrophobic carbon dots emit blue light. The fluorescence emission spectrum of the hydrophobic carbon dots of Comparative Example 1 shown in Figure 12 shows that the maximum The emission wavelength is 440 nm, and the quantum yield is 11%. As shown in Figure 13 and Figure 14, the photo and fluorescence emission spectrum of the hydrophilic carbon dot solution of the water-soluble carbon dots of Comparative Example 1 under the irradiation of 365 nm ultraviolet light can be known. , which emits blue light with a maximum emission wavelength of 448 nm and a quantum yield of 14%.

From the comparison between Example 1 and Comparative Example 1, it can be seen that if the carbon source and the N, S doping reagent are fully dissolved and mixed evenly without adding a solvent in the first step, when the dehydrating agent is directly added for the reaction, it is not conducive to N, S co-doping In the synthesis of carbon dots (most of the dehydrating agents only react with one raw material), the synthesis efficiency is low, the emission wavelength of the prepared hydrophobic carbon dots is obviously shortened, and the quantum yield is low.

Test Example 2

The hydrophobic carbon dots obtained in Example 1 showed excellent fluorescence and were used in solid-state lighting and displays. As shown in Figure 15, a white light-illuminating LED lamp was constructed with hydrophobic carbon dots as one of the light source components. FIG. 16 is an electroluminescence spectrum diagram of the fabricated white LED device. Consists of two emission bands: blue λ at 450 nm, from blue GaN-based chips, and broad yellow emission from hydrophobic carbon dots at 575 nm. The two emission bands mix to produce white light. The CIE of the prepared white light LED is (0.2637, 0.2255), which falls within the white light region. These results demonstrate the successful fabrication of white LEDs based on yellow-emitting hydrophobic carbon dots.

Test Example 3

The application of the hydrophobic carbon dots of Example 1 in the production of solid luminescent excipients. Mix the transparent epoxy resin A and the epoxy resin B in a mass ratio of 3:1, add an appropriate amount of hydrophobic carbon dot solution, and mix it evenly again, pour it into the mold, and let it stand at room temperature for 24 hours, as shown in Figure 17 and The solid luminescent excipient material shown in FIG. 18 . The material is a hard solid material with a brownish color observed in sunlight (as shown in Figure 17). Under the irradiation of 365 nm UV light, the solid emits yellow fluorescence (as shown in Figure 18).

Test Example 4

The hydrophilic carbon dot solution in Example 2 was irradiated under 365 nm ultraviolet light, as shown in FIG. 19 , it emitted blue light. A fluorescence emission spectrum was obtained from the hydrophobic carbon dot solid in Example 2, as shown in FIG. 20 , the fluorescence emission wavelength was 490 nm, and the fluorescence quantum yield was 19%. The hydrophobic carbon dot solution in Example 3 was irradiated under 365 nm ultraviolet light, as shown in FIG. 21 , it was green luminescence, the optimal emission wavelength was 530 nm, and the quantum yield was 21%. Similarly, the hydrophilic carbon dots obtained in Example 3 emit blue light, the optimal emission wavelength is 426 nm, and the quantum yield is 33%.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A method for producing a carbon dot, comprising:

adding a dehydrating agent into a uniform mixture of the carbon dot preparation raw materials, and reacting at the temperature of 100-200 ℃;

wherein the carbon dot preparation raw material contains hydrophilic groups, and the uniform mixture is mainly prepared by the following preparation steps: dissolving and mixing the carbon dot preparation raw materials in a solvent, and removing the solvent capable of reacting with the dehydrating agent.

2. The method according to claim 1, wherein the reaction is carried out for 10 to 360min, preferably 20 to 200min, and more preferably 20 to 80 min;

preferably, the dehydrating agent is used in an amount of 0.1 to 1 g;

preferably, the dehydrating agent comprises at least one of polyphosphoric acid, N' -dicyclohexylcarbodiimide, 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride, N-dimethylformamide, 2-dichloro-5- (2-phenylethyl) -4- (trimethylsilyl) -3-furanone, 1, 3-dimethyl-2-imidazolidinone, bis (trichloromethyl) carbonate, thionyl chloride-dimethylformamide and 2-chloro-1, 3-dimethylimidazolium chloride, phosphorus pentachloride, phosphorus oxychloride and phosphorus pentoxide; more preferably, the dehydrating agent is N, N' -dicyclohexylcarbodiimide, 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide or 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride;

preferably, the dehydrating agent is added in the form of an organic solution, more preferably, the organic solvent used to dissolve the dehydrating agent is acetonitrile;

preferably, the reaction vessel for preparing the carbon dots is selected from any one of a hydrothermal reaction kettle, a beaker and a round-bottom flask, and more preferably, the reaction vessel is a hydrothermal reaction kettle;

preferably, the heating vessel for heating to maintain the reaction temperature is selected from any one of a water bath, an oil bath, and an electrically heated constant temperature forced air drying oven.

3. The preparation method according to claim 1, wherein the carbon point preparation raw material comprises a carbon source and a nitrogen and sulfur co-doping agent, preferably, the carbon source comprises at least one of citric acid, oxalic acid, sodium citrate, sodium oxalate and glucose; preferably, the nitrogen, sulfur co-dopant comprises at least one of D, L-homocysteine, L-methionine, L-cysteine hydrochloride, D-cysteine, glutathione, N-acetyl-L-cysteine, beta-mercaptoethylamine, and thioacetamide; more preferably, the nitrogen, sulfur co-dopant comprises at least one of L-cysteine, L-cysteine hydrochloride, and N-acetyl-L-cysteine; preferably, the mass ratio of the carbon source to the nitrogen and sulfur codoping agent is 1: 0.5 to 10;

or the carbon dot preparation raw material comprises at least one of ethylenediamine, polyethyleneimine, aniline and phenol.

4. The preparation method according to any one of claims 1 to 3, wherein the solvent is water, and the step of removing the solvent after dissolving and mixing the carbon dot preparation raw material in the solvent comprises: dissolving carbon dot preparation raw materials into water, and reacting at 60-80 ℃ for 6-15 h, wherein the water is preferably ultrapure water;

preferably, the vessel for dissolving and removing the solvent is selected from any one of a polytetrafluoroethylene reaction lining, a beaker, and a round-bottom flask.

5. The production method according to any one of claims 1 to 3, characterized by further comprising dissolving the carbon dot solid obtained by the reaction with a solvent to obtain a carbon dot solution.

6. The production method according to claim 5, further comprising removing the solvent from the carbon dot solution to obtain a carbon dot powder;

preferably, the carbon dot solid is dissolved with a water-soluble solvent and a hydrophobic solvent, respectively, to obtain a solution of water-soluble carbon dots and a solution of hydrophobic carbon dots, and then the solvents are removed to obtain water-soluble carbon dots and hydrophobic carbon dots, respectively;

preferably, the water-soluble solvent is pure water and a buffer solution, the hydrophobic solvent is an organic solvent, and the organic solvent comprises at least one of cyclohexane, carbon tetrachloride, chloroform, tetrahydrofuran and methanol; more preferably, the organic solvent is chloroform.

7. A carbon dot prepared by the preparation method of any one of claims 1 to 6, preferably, the carbon dot is a hydrophobic carbon dot separated after reaction, and more preferably, the hydrophobic carbon dot is an N, S co-doped hydrophobic carbon dot with a fluorescence emission wavelength of 450 to 580 nm.

8. Use of the carbon dot according to claim 7 for the preparation of a fluorescent material.

9. Use of the carbon dot according to claim 7 for producing a solid illumination device, a display, or a solid luminescent excipient, wherein the carbon dot is a hydrophobic carbon dot separated after reaction.

10. A solid luminescent excipient characterized in that the hydrophobic carbon dots according to claim 7 are contained in the raw material components.

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