Preparation method for improving yield of nitrogen-doped carbon quantum dots

Abstract

The invention discloses a method for rapidly depolymerizing and carbonizing a carbon-based material through electron beam (EB) pre-irradiation at room temperature and combining with a hydrothermal reaction to improve the synthesis yield of carbon quantum dots (CDs), the action mechanism is that a large amount of stable free radicals are introduced into a reaction system through EB irradiation, the free radicals accelerate depolymerization and carbonization of the carbon-based material, and the synthesis yield of the CDs is improved. Then, smaller segments of carbon compounds are more rapidly polymerized in a closed system of hydrothermal reaction to form a large number of CDs. The technical scheme provided by the invention is simple to operate, is an effective method convenient for large-scale production of the CDs, can adjust the yield of the synthesized CDs by adjusting the radiation dose, and has potential application value in the technical field of industrial production of the CDs.

Description

Technical Field

[0001] The present invention relates to the field of new material preparation, and in particular to a preparation method for increasing the yield of nitrogen-doped carbon quantum dots based on electron beam irradiation. Background Art

[0002] Carbon quantum dots (CDs), as a new member of the nanomaterial family, have attracted widespread attention in recent years. To date, the vast majority of CDs are synthesized by hydrothermal methods. In the hydrothermal reaction, hydrogen ions dissociated from water first attack the carbon-based skeleton, forming a large number of small molecular carbon fragments composed of hydrophobic or hydrophilic groups. These fragments condense to form primary clusters, which are then converted into primary clusters through dehydration, polymerization, and condensation reactions. As the reaction time increases at high temperatures, the accumulation of π-π bonds, sp 2 Hybridization, and finally polymerization to form CDs. It can be seen that the depolymerization of macromolecules is the key step in the formation of CDs. However, the commonly used hydrothermal synthesis of CDs usually requires a long time of more than 24 hours, high temperature, closed system and high pressure, and low yield, which creates obstacles for large-scale production. Although scientists have extensively studied new methods for synthesizing CDs in the past decade, such as laser ablation, chemical oxidation, and electrochemical oxidation, the search for environmentally friendly and highly efficient CDs synthesis methods (with advantages in saving time, energy and yield) remains a research goal in this field.

[0003] Electron beam (EB) irradiation is a unique energy source. The energy of EB is significantly higher than that of any chemical bond, making it highly effective in activating all species involved in a chemical reaction. Using EB as a pretreatment for CDs synthesis to increase CD yield is promising. Theoretically, EB utilizes its high energy to generate free radical sites on substrates, which in turn trigger the depolymerization of monomers at these sites into short chains. This approach offers advantages such as ultrafast material synthesis, ease of operation, high energy efficiency, and wide applicability. However, there are currently no reports on using EB irradiation to depolymerize macromolecules to aid in improving CDs synthesis yield. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing nitrogen-doped carbon quantum dots with high yield, in order to solve the problem of low yield in the existing carbon quantum dot preparation, increase the yield of carbon quantum dots, and promote the development of industrial production of carbon quantum dots.

[0005] In order to achieve the above object, the present invention provides a preparation method for improving the yield of nitrogen-doped carbon quantum dots, comprising the following steps:

[0006] (1) After dissolving the carbon-based material, the dissolved solution is irradiated with an electron beam;

[0007] (2) performing a hydrothermal reaction on the irradiated solution;

[0008] (3) The hydrothermal reaction solution is cooled, centrifuged, and the supernatant is filtered. The filtrate is dialyzed and then freeze-dried to obtain nitrogen-doped carbon quantum dots CDs.

[0009] Preferably, the carbon-based material in the above preparation method is selected from any one or more of urea and citric acid, more preferably urea and citric acid, and urea and citric acid are dissolved in distilled water at a mass fraction of 10% and 30% respectively to obtain a solution after the carbon-based material is dissolved.

[0010] Preferably, the dose of electron beam irradiation is 50-400 kGy, and the irradiation dose is proportional to the yield of carbon quantum dots CDs.

[0011] Preferably, the hydrothermal reaction is carried out at 180° C. for 3 to 10 hours.

[0012] Preferably, the centrifugation is carried out at 10,000 rpm for 30 min, the supernatant after centrifugation is filtered with a 0.22 μm filter membrane, and the filtered filtrate is dialyzed in a dialysis bag with a molecular weight of 3,500 Da for 24 h, and the dialysate is selected from distilled water.

[0013] The above-mentioned preparation method can significantly increase the yield of carbon quantum dots and has potential value in the industrial production of carbon quantum dots.

[0014] The present invention has the following advantages:

[0015] The present invention discloses for the first time a method for increasing the yield of carbon quantum dots by combining electron beam irradiation and hydrothermal reaction. The yield of CDs synthesized by the preparation method provided by the present invention can be increased by electron beam irradiation, the operation is simple, and the industrial production development of carbon quantum dots is accelerated.

[0016] The present invention introduces nitrogen into the preparation of carbon quantum dots, so that the electron transition rate after nitrogen doping is increased, the CDS fluorescence is enhanced, and the nitrogen doped carbon quantum dots have more significant application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 TEM morphologies of CDs synthesized with different irradiation doses in the present invention.

[0018] Figure 2 The yields of CDs synthesized with different irradiation doses in the present invention are shown. DETAILED DESCRIPTION

[0019] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0020] Note: Unless otherwise noted, the experimental methods in the following examples are conventional methods, performed according to the techniques and conditions described in literature in the field or according to product specifications. Materials and reagents used in the following examples, unless otherwise noted, are commercially available.

[0021] Example

[0022] This embodiment provides a method for increasing the yield of nitrogen-doped carbon quantum dots (CDs) by electron beam (EB) irradiation, which is prepared by the following steps:

[0023] (1) Weigh 10 g of urea and 30 g of citric acid and dissolve them in 100 mL of distilled water. Spread the mixture flat and irradiate with EB at doses of 50, 100, 150, 200, 250, 300, 350, and 400 kGy, respectively.

[0024] (2) The irradiated solution was placed in a 250 mL reactor and subjected to hydrothermal reaction at 180°C for 3 h;

[0025] (3) The solution after the hydrothermal reaction was cooled and then centrifuged at 10,000 rpm for 30 min. The supernatant was filtered through a 0.22 μm filter membrane. The filtrate was then transferred to a dialysis bag with a molecular weight of 3,500 Da and dialyzed in distilled water for 24 h. The solution in the dialysis bag was collected and freeze-dried to obtain CDs.

[0026] At the same time, CDs prepared by the same preparation method as above but without EB irradiation were set as controls. TEM morphologies of all synthesized CDs are shown in Figure 1 The yield of each group of products is shown in Figure 2 As shown, the yield of the product in each treatment group was: 1.21±0.21 g for the non-EB irradiated group, and 6.05±0.32, 6.89±0.25, 7.36±0.24, 8.32±0.31, 9.64±0.26, 9.78±0.24, 10.23±0.26, and 12.10±0.21 g for the irradiated groups with doses of 50, 100, 150, 200, 250, 300, 350, and 400 kGy, respectively. Figure 1 Figure 2It can be seen that both the hydrothermal synthesis method and EB pre-irradiation followed by hydrothermal treatment can successfully synthesize CDs materials; and compared with the CDs in the control group, the EB pre-irradiation method can significantly increase the yield of CDs synthesis, and the yield increases with the increase of irradiation dose.

[0027] In summary, the present invention provides a simple method for increasing the yield of carbon quantum dots by combining electron beam irradiation and a hydrothermal reaction. The yield of CDs is positively correlated with the irradiation dose. The preparation method provided by the present invention has potential application value in the field of industrialized CD production technology, helping to accelerate the development of industrialized production of carbon quantum dots.

[0028] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing nitrogen-doped carbon quantum dots to improve yield, characterized in that: The following steps are included: (1) after dissolving the carbon-based material, irradiating the dissolved solution with an electron beam; (2) performing a hydrothermal reaction on the irradiated solution; (3) The hydrothermal reaction solution is cooled, centrifuged, and the supernatant is filtered. The filtrate is dialyzed and then freeze-dried to obtain nitrogen-doped carbon quantum dots.

2. The preparation method according to claim 1, characterized in that: The carbon-based material in step (1) is selected from any one or more of urea and citric acid.

3. The preparation method according to claim 1, characterized in that: The carbon-based materials are urea and citric acid, and the solution is obtained by dissolving urea and citric acid in distilled water at a mass fraction of 10% and 30% respectively.

4. The preparation method according to claim 1, characterized in that: The dosage of the electron beam irradiation is 50-400 kGy.

5. The preparation method according to claim 1, characterized in that: The hydrothermal reaction is carried out at 180° C. for 3 to 10 hours.

6. The preparation method according to claim 1, characterized in that: The centrifugation is performed at 10000 rpm for 30 min.

7. The preparation method according to claim 1, characterized in that: The filtration is 0.22 μm filter membrane filtration.

8. The preparation method according to claim 1, characterized in that: The dialysis was performed for 24 hours in a dialysis bag with a molecular weight of 3500Da, and the dialysis fluid was distilled water.

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