Water-dispersible red light carbon quantum dots and preparation method thereof

Abstract

The application discloses a kind of water-dispersible red light carbon quantum dots and preparation method thereof, belong to carbon quantum dots preparation technical field.The method includes the following steps: (1) 1, 2-diaminobenzene and / or 1, 2-diaminobenzene derivative and concentrated sulfuric acid are placed in container and mixed and stirred uniformly, and the reaction is carried out at 80~100 ℃ for 3~10 h, after the reaction is completed, ice water mixture is added to the reaction mixture to adjust the concentration of concentrated sulfuric acid to 30~50%, and then the intermediate A is obtained by filtration;(2) intermediate A of step (1) is placed in container with catechol and / or catechol derivative and deionized water is added, and stirred to dissolve completely, then the reaction is carried out at 30~90 ℃ under normal pressure for 12~24 h, after the reaction is completed, the carbon quantum dots crude product is obtained by suction filtration;(3) the carbon quantum dots crude product of step (2) is purified to obtain water-dispersible red light carbon quantum dots.The water-dispersible red light carbon quantum dots are prepared by low temperature and normal pressure, and the preparation process is simple and easy to mass production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon quantum dot preparation, in particular to a water-dispersible red light carbon quantum dot and a preparation method thereof. BACKGROUND

[0002] Quantum dots are semiconductor nanocrystals with a size less than 20 nanometers. Due to the quantum confinement effect, the optical properties of quantum dots can be controlled by changing the size and shape. Compared with inorganic quantum dots containing heavy metals, carbon quantum dots are composed of a highly carbonized core and surface-like molecular functional groups, and their emission wavelength can be adjusted from blue to infrared. Compared with blue and green light carbon quantum dots, red light carbon quantum dots have the advantages of wide absorption range, deep tissue penetration, and small tissue light damage, and are expected to be used in light solar concentrators (LSC), photocatalysis, biological imaging and other fields. However, so far most of the reported carbon quantum dots emit blue or green light. Although there are some studies on orange or red light carbon quantum dots, their photoluminescence quantum yields are generally low, which limits their application range. In addition, the synthesis method of carbon quantum dots is usually high-temperature hydrothermal method, that is, the precursor is added to the reaction kettle, and the reaction is carried out at high temperature and high pressure. This method is difficult to realize large-scale preparation of carbon quantum dots. At present, low-temperature and normal-pressure method for preparing carbon quantum dots has attracted attention. This method is conducive to scale-up, but the technology for preparing carbon quantum dots by low-temperature and normal-pressure method is not mature, the quantum yield is low, and the prepared carbon quantum dots are mainly blue and green light carbon quantum dots, and there are few reports on red light carbon quantum dots. In addition, due to the larger conjugated structure of red light carbon quantum dots, their water dispersibility is poor, which limits their application in the field of biomedicine. Therefore, it is necessary to prepare a water-dispersible red light carbon quantum dot with high quantum yield. SUMMARY

[0003] To solve the above technical problems, the present application provides a water-dispersible red light carbon quantum dot and a preparation method thereof. The water-dispersible red light carbon quantum dot is prepared by using a low-temperature and normal-pressure method, and the preparation process is simple and easy to mass-produce.

[0004] The technical scheme adopted by the present application is as follows:

[0005] The present application provides a water-dispersible red light carbon quantum dot and a preparation method thereof. The preparation method comprises the following steps:

[0006] (1) Put 1,2-diaminobenzene and / or 1,2-diaminobenzene derivative and concentrated sulfuric acid into a container and stir uniformly, heat to 80-100℃ and react for 3-10h. After the reaction is completed, add ice water mixture to the reaction mixture to adjust the concentration of concentrated sulfuric acid to 30-50%, and then filter to obtain intermediate A;

[0007] (2) placing the intermediate A of step (1) and catechol and / or catechol derivative into a container, adding deionized water, stirring to fully dissolve, then reacting at 30-90 DEG C under normal pressure for 12-24 hours, after the reaction is completed, performing suction filtration to obtain a carbon quantum dot crude product;

[0008] (3) purifying the carbon quantum dot crude product of step (2) by column chromatography to obtain water-dispersible red light carbon quantum dots.

[0009] Further, the molar ratio of 1,2-diaminobenzene and / or 1,2-diaminobenzene derivative to concentrated sulfuric acid in step (1) is 1:5-8.

[0010] Further, the 1,2-diaminobenzene derivative in step (1) is at least one of 3-bromo-1,2-diaminobenzene, 3-chloro-1,2-diaminobenzene, 3-iodo-1,2-diaminobenzene, 3-methyl-1,2-diaminobenzene, and 3-ethyl-1,2-diaminobenzene.

[0011] Further, the molar ratio of intermediate A to catechol and / or catechol derivative in step (2) is 0.5-2:1.

[0012] Further, the catechol derivative in step (2) is at least one of 3-bromocatechol, 3-chlorocatechol, 3-iodocatechol, 3-methylcatechol, and 3-ethylcatechol.

[0013] Further, the reaction temperature in step (2) is 60-90 DEG C, and the reaction is performed under normal pressure for 12-15 hours.

[0014] Further, the purification process in step (3) is:

[0015] First, the carbon quantum dot crude product obtained in step (2) is suction filtered to obtain a blue-black carbon quantum dot powder; then the blue-black carbon quantum dot powder is washed with ethanol to obtain a clean black powder; then the black powder is dispersed in an ethanol aqueous solution, and silica gel powder is weighed and added to a 5 cm x 35 cm chromatography column; the chromatography column is used, and the ethanol aqueous solution is used as an eluent to perform chromatographic separation; the obtained product is freeze-dried to obtain red light carbon quantum dots.

[0016] Further, the volume ratio of ethanol to water in the ethanol aqueous solution used in the purification process in step (3) is 1:3-5.

[0017] The beneficial effects of the present application are:

[0018] (1) The application provides a preparation method of water-dispersible red-light carbon quantum dots, which uses 1,2-diaminobenzene and derivatives thereof and o-dihydroxybenzene and derivatives thereof as precursors, controls the polymerization of free radical conjugated structures of in-situ formed carbon quantum dots at a low temperature and under normal pressure to control the structure and surface groups of the carbon quantum dots, thereby regulating the energy band structure of the carbon quantum dots, obtaining the carbon quantum dots emitting red light, and the obtained carbon quantum dots have water dispersibility, can be used in fields of light-emitting solar concentrators (LSC), photocatalysis and the like, can be used in the biomedical field, and have wide application prospects.

[0019] (2) The application provides a preparation method of water-dispersible red-light carbon quantum dots, which adopts a low-temperature and normal-pressure mode, has simple preparation process and is easy to mass produce, and the hydrophilic groups do not fall off in the reaction by adopting the low-temperature and normal-pressure mode, so that the carbon quantum dots can maintain good water dispersibility.

[0020] (3) The water-dispersible red-light carbon quantum dots prepared by the application present double-band emission wavelengths, have high fluorescence quantum yield, and the emission wavelength does not shift depending on the excitation wavelength and is more than 35%. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0022] Figure 1 TEM and HRTEM diagrams of the red-light carbon quantum dots prepared in the embodiment 1 of the application;

[0023] Figure 2 Fluorescence quantum yield diagram of the red-light carbon quantum dots prepared in the embodiment 1 of the application;

[0024] Figure 3 PL spectrum diagram of the red-light carbon quantum dots prepared in the embodiment 1 of the application under different excitation wavelengths;

[0025] Figure 4 Fluorescence emission spectrum diagram and ultraviolet-visible absorption spectrum diagram of the red-light carbon quantum dots prepared in the embodiment 1 of the application;

[0026] Figure 5 Photo of the red-light carbon quantum dots prepared in the embodiment 1 of the application under irradiation of a 395 nm wavelength ultraviolet lamp. DETAILED DESCRIPTION

[0027] The application provides a water-dispersible red-light carbon quantum dot and a preparation method thereof.

[0028] The application will be described in detail below with reference to the drawings.

[0029] Embodiment 1

[0030] The embodiment provides a water-dispersible red-light carbon quantum dot, and a preparation process thereof is as follows:

[0031] (1) 0.2 mol of 1,2-diaminobenzene and 1.3 mol of concentrated sulfuric acid are added into a 500 mL beaker and stirred uniformly, and the temperature is increased to 90 DEG C and reacted for 5 h; after the reaction is completed, an ice water mixture is added into the reaction mixture to adjust the concentration of the concentrated sulfuric acid to 40%, and then the intermediate A is obtained through filtration;

[0032] (2) 0.1 mol of the intermediate A in step (1) and 0.1 mol of catechol are added into an 800 mL beaker, and 300 mL of deionized water is added, and stirred to dissolve completely, and then reacted at 90 DEG C and normal pressure for 12 h; after the reaction is completed, the carbon quantum dot crude product is obtained through filtration;

[0033] (3) the carbon quantum dot crude product obtained in step (2) is filtered, and the blue-black carbon quantum dot powder is obtained; then the black powder is washed with ethanol through filtration, and the clean black powder is obtained; then the black powder is dispersed into an ethanol water solution with a volume ratio of 1:4, and silica gel powder is weighed and added into a chromatographic column with a size of 5 cm*35 cm; the chromatographic column is used, and the ethanol water solution with a volume ratio of 1:4 is used as an eluent to perform chromatographic separation; the obtained product is freeze-dried to obtain the red-light carbon quantum dot.

[0034] Embodiment 2

[0035] The embodiment provides a water-dispersible red-light carbon quantum dot, and a preparation process thereof is as follows:

[0036] (1) 0.2 mol of 1,2-diaminobenzene and 1.3 mol of concentrated sulfuric acid are added into a 500 mL beaker and stirred uniformly, and the temperature is increased to 90 DEG C and reacted for 5 h; after the reaction is completed, an ice water mixture is added into the reaction mixture to adjust the concentration of the concentrated sulfuric acid to 40%, and then the intermediate A is obtained through filtration;

[0037] (2) 0.1 mol of the intermediate A of step (1) and 0.05 mol of 3-methyl catechol were added into a 800 mL beaker, 300 mL of deionized water was added, and it was stirred to be fully dissolved, then it was reacted at 60°C under normal pressure for 15 h, after the reaction was completed, it was filtered to obtain a carbon quantum dot crude product;

[0038] (3) The carbon quantum dot crude product obtained in step (2) was filtered to obtain a blue-black carbon quantum dot powder; then it was washed with ethanol to obtain a clean black powder; then the black powder was dispersed into an ethanol aqueous solution with a volume ratio of ethanol to water of 1:4, and silica gel powder was weighed and added into a chromatographic column with a size of 5 cm x 35 cm, the chromatographic column was used, and an ethanol aqueous solution with a volume ratio of ethanol to water of 1:4 was used as an eluent to perform chromatographic separation, and the obtained product was freeze-dried to obtain red light carbon quantum dots.

[0039] Example 3

[0040] The present embodiment provides a water-dispersible red light carbon quantum dot, and the preparation process is as follows:

[0041] (1) 0.1 mol of 3-methyl-1,2-diaminobenzene, 0.1 mol of 3-chloro-1,2-diaminobenzene and 1.5 mol of concentrated sulfuric acid were added into a 500 mL beaker and stirred uniformly, and the temperature was raised to 90°C to react for 5 h, after the reaction was completed, an ice water mixture was added to the reaction mixture to adjust the concentration of sulfuric acid to 50%, and then the intermediate A was obtained by filtration;

[0042] (2) 0.1 mol of the intermediate A of step (1) and 0.2 mol of catechol and 3-methyl catechol were added into a 800 mL beaker, 300 mL of deionized water was added, and it was stirred to be fully dissolved, then it was reacted at 30°C under normal pressure for 24 h, after the reaction was completed, it was filtered to obtain a carbon quantum dot crude product;

[0043] (3) The carbon quantum dot crude product obtained in step (2) was filtered to obtain a blue-black carbon quantum dot powder; then it was washed with ethanol to obtain a clean black powder; then the black powder was dispersed into an ethanol aqueous solution with a volume ratio of ethanol to water of 1:5, and silica gel powder was weighed and added into a chromatographic column with a size of 5 cm x 35 cm, the chromatographic column was used, and an ethanol aqueous solution with a volume ratio of ethanol to water of 1:5 was used as an eluent to perform chromatographic separation, and the obtained product was freeze-dried to obtain red light carbon quantum dots.

[0044] Comparative Example 1

[0045] The difference between the present comparative example and Example 1 is that the present comparative example does not add catechol in the preparation process of carbon quantum dots.

[0046] The comparative example cannot obtain carbon quantum dots.

[0047] Comparative Example 2

[0048] The present comparative example is different from Example 1 in that the present comparative example does not add catechol in the preparation of carbon quantum dots, and is subjected to hydrothermal reaction at 180℃ for 12h.

[0049] The comparative example can obtain red light carbon quantum dots, but the water dispersibility is poor. The reason is that the hydrophilic group is easy to fall off under the high temperature and high pressure conditions in the hydrothermal process, resulting in that the obtained carbon quantum dots do not have water dispersibility. In the present example, the hydrophilic group does not fall off in the reaction due to the use of low temperature and normal pressure, so that the carbon quantum dots can maintain water dispersibility.

[0050] Reference Figures 1-5 The red light carbon quantum dots prepared in Example 1 are subjected to the following detection.

[0051] Figure 1 The low resolution transmission electron microscopy image and the high resolution transmission electron microscopy image of the red light carbon quantum dots prepared in Example 1 can be seen from FIG. 1 and FIG. 2, respectively. Figure 1 It can be seen that the size of the red light carbon quantum dots is uniform, and the particle size is about 3.3nm, and the interplanar spacing is 0.21nm, corresponding to the (100) plane of graphite.

[0052] Figure 2 The quantum yield diagram of the red light carbon quantum dots prepared in Example 1 can be seen from FIG. 3. Figure 2 It can be calculated that the quantum yield of the red light carbon quantum dots is 35.7%.

[0053] Figure 3 The PL spectrum diagram of the red light carbon quantum dots prepared in Example 1 under different excitation wavelengths can be seen from FIG. 4. Figure 3 It can be seen that the emission wavelength of the red light carbon quantum dots does not shift with the excitation wavelength, and presents double-band emission wavelength, which is 610nm and 660nm, respectively.

[0054] Figure 4 The fluorescence emission spectrum and the ultraviolet-visible absorption spectrum of the red light carbon quantum dots prepared in Example 1 can be seen from FIG. 5, wherein the absorption at 300nm is the absorption of carbon nucleus, and the absorption at 420-620nm is the absorption of fluorophore; the red light carbon quantum dots have double fluorescence peaks, which are 610nm and 660nm, respectively.

[0055] Figure 5 The photo of the red light carbon quantum dots prepared in Example 1 under the irradiation of 395nm wavelength ultraviolet lamp can be seen from FIG. 6. The red light carbon quantum dots present red light under the irradiation of ultraviolet lamp, and have good water dispersibility.

[0056] It should be noted that the parts not described in the present application can be realized by using or referring to the existing technology.

[0057] Of course, the above description is not a limitation of the present application, and the present application is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present application should also be within the scope of the present application.

Claims

1. A method for preparing water-dispersible red light-emitting carbon quantum dots, characterized in that, The method comprises the steps of: (1) placing 1,2-diaminobenzene and / or 1,2-diaminobenzene derivative and concentrated sulfuric acid into a container and stirring to be uniform, and then reacting at 80-100 ℃ for 3-10 h, after the reaction is completed, adding an ice water mixture to adjust the concentration of the concentrated sulfuric acid to 30-50%, and then filtering to obtain intermediate A; (2) placing intermediate A of step (1) and catechol and / or catechol derivative into a container and adding deionized water, stirring to fully dissolve, and then reacting at 30-90 ℃ under normal pressure for 12-24 h, after the reaction is completed, performing suction filtration to obtain a carbon quantum dot crude product; (3) purifying the carbon quantum dot crude product of step (2) by column chromatography to obtain water-dispersible red light carbon quantum dots; In step (1), the molar ratio of 1,2-diaminobenzene and / or 1,2-diaminobenzene derivative to concentrated sulfuric acid is 1:5-8; In step (1), the 1,2-diaminobenzene derivative is at least one of 3-bromo-1,2-diaminobenzene, 3-chloro-1,2-diaminobenzene, 3-iodo-1,2-diaminobenzene, 3-methyl-1,2-diaminobenzene and 3-ethyl-1,2-diaminobenzene; In step (2), the catechol derivative is at least one of 3-bromocatechol, 3-chlorocatechol, 3-iodocatechol, 3-methylcatechol and 3-ethylcatechol.

2. The method for preparing water-dispersible red carbon quantum dots according to claim 1, characterized in that, In step (2), the molar ratio of intermediate A to catechol and / or catechol derivative is 1:0.5-2.

3. The method for preparing water-dispersible red carbon quantum dots according to claim 1, characterized in that, In step (2), the reaction temperature is 60-90 ℃, and the reaction is performed under normal pressure for 12-15 h.

4. The method for preparing water-dispersible red carbon quantum dots according to claim 1, characterized in that, In step (3), the purification process is as follows: First, the carbon quantum dot crude product obtained in step (2) is suction filtered to obtain blue-black carbon quantum dot powder; then the blue-black carbon quantum dot powder is washed with ethanol to obtain clean black powder; then the black powder is dispersed in an ethanol aqueous solution, silica gel powder is weighed, and a chromatographic column with a size of 5 cm×35 cm is added, the chromatographic column is used, and the ethanol aqueous solution is used as an eluent for chromatographic separation, and the obtained product is freeze-dried to obtain red light carbon quantum dots.

5. The method for preparing water-dispersible red carbon quantum dots according to claim 1, characterized in that, In step (3), the volume ratio of ethanol to water in the ethanol aqueous solution used in the purification process is 1:3-5.

6. A water-dispersible red light carbon quantum dot prepared by the method of any one of claims 1-5.

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