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

Abstract

The invention discloses a water-dispersible red light carbon quantum dot and a preparation method thereof, and belongs to the technical field of carbon quantum dot preparation. The method comprises the following steps: (1) putting 1, 2-diaminobenzene and / or a 1, 2-diaminobenzene derivative and concentrated sulfuric acid into a container, mixing and uniformly stirring, heating to 80-100 DEG C, reacting for 3-10 hours, after the reaction is completed, adding an ice-water mixture into a reaction mixture to adjust the concentration of the concentrated sulfuric acid to 30-50%, and then filtering to obtain an intermediate A; (2) putting the intermediate A in the step (1) and catechol and / or a catechol derivative into a container, adding deionized water, stirring to fully dissolve, then reacting for 12-24 hours at 30-90 DEG C and normal pressure, and performing suction filtration after the reaction is completed to obtain a carbon quantum dot crude product; and (3) purifying the carbon quantum dot crude product in the step (2) to obtain the water-dispersible red light carbon quantum dot. The water-dispersible red light carbon quantum dots are prepared in a medium-low temperature and normal pressure mode, the preparation process is simple, and batch production is easy.

Description

Technical Field

[0001] The invention relates to the technical field of carbon quantum dot preparation, and in particular to water-dispersible red light carbon quantum dots and a preparation method thereof. Background Art

[0002] Quantum dots are semiconductor nanocrystals with a size of less than 20 nanometers. Thanks to their quantum confinement effect, the optical properties of quantum dots can be controlled by changing their size and shape. Compared with inorganic quantum dots containing heavy metals, carbon quantum dots are composed of a highly carbonized core and surface molecule-like functional groups, and their emission wavelength can be adjusted from blue to infrared. Compared with blue and green carbon quantum dots, red carbon quantum dots have the advantages of wide absorption range, deep tissue penetration, and little photodamage to tissues, and are expected to be used in luminescent solar concentrators (LSCs), photocatalysis, bioimaging and other fields. However, most of the carbon quantum dots reported so far emit blue or green light. Although there are some studies on orange or red 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 a high-temperature hydrothermal method, that is, the precursor is added to the reactor and the reaction is carried out under high temperature and high pressure. This method is difficult to achieve large-scale preparation of carbon quantum dots. At present, the preparation of carbon quantum dots by low temperature and normal pressure method has attracted attention. This method is conducive to achieving scale, but the technology of preparing carbon quantum dots by low temperature and normal pressure method is immature, the quantum yield is low, and the prepared carbon quantum dots are concentrated in blue and green carbon quantum dots, and there are few reports on red carbon quantum dots. In addition, due to the large conjugated structure of red carbon quantum dots, their water dispersibility is poor, which limits their application in the biomedical field. Therefore, it is very necessary to prepare a water-dispersible red carbon quantum dot with high quantum yield. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a water-dispersible red light carbon quantum dots and a preparation method thereof. The water-dispersible red light carbon quantum dots are prepared by medium-low temperature and normal pressure. The preparation process is simple and easy to mass produce.

[0004] The technical solution adopted by the present invention is:

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

[0006] (1) placing 1,2-diaminobenzene and / or 1,2-diaminobenzene derivatives and concentrated sulfuric acid in a container and stirring them uniformly, heating to 80-100° C. and reacting for 3-10 hours. After the reaction is completed, adding an ice-water mixture to the reaction mixture to adjust the concentrated sulfuric acid concentration to 30-50%, and then filtering to obtain an intermediate A;

[0007] (2) placing the intermediate A of step (1) and catechol and / or catechol derivatives into a container and adding deionized water, stirring to fully dissolve them, and then reacting at 30 to 90° C. and normal pressure for 12 to 24 hours. After the reaction is completed, filtering is performed to obtain a crude carbon quantum dot product;

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

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

[0010] Furthermore, in the 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.

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

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

[0013] Furthermore, in the step (2), the reaction temperature is 60 to 90° C., and the reaction is carried out at normal pressure for 12 to 15 hours.

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

[0015] First, the crude carbon quantum dot product obtained in step (2) is filtered to obtain a blue-black carbon quantum dot powder; then it is filtered and rinsed 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 5cm×35cm chromatographic column, and the chromatographic column is used with the ethanol aqueous solution as an eluent for chromatographic separation, and the obtained product is freeze-dried to obtain red light carbon quantum dots.

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

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

[0018] (1) The present invention provides a method for preparing water-dispersible red light-emitting carbon quantum dots, using 1,2-diaminobenzene and its derivatives and catechol and its derivatives as precursors, and controlling the polymerization of the free radical conjugated structure of the carbon quantum dots formed in situ at a relatively low temperature and normal pressure to control its structure and surface groups, thereby regulating the energy band structure of the carbon quantum dots, and obtaining red light-emitting carbon quantum dots. The obtained carbon quantum dots are water-dispersible and can be used not only in luminescent solar concentrators (LSCs), photocatalysis and other fields, but also in the biomedical field, and have broad application prospects;

[0019] (2) The present invention provides a method for preparing water-dispersible red light carbon quantum dots, which adopts a medium-low temperature and normal pressure method. The preparation process is simple and easy to mass produce. In addition, the hydrophilic groups will not fall off during the reaction, so that the carbon quantum dots can maintain good water dispersibility.

[0020] (3) The water-dispersible red carbon quantum dots prepared by the present invention exhibit dual-band emission wavelengths, a high fluorescence quantum yield of more than 35%, and the emission wavelength does not shift depending on the excitation wavelength. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 TEM and HRTEM images of red light carbon quantum dots prepared in Example 1 of the present invention;

[0023] Figure 2 This is a graph of the fluorescence quantum yield of red light carbon quantum dots prepared in Example 1 of the present invention;

[0024] Figure 3 PL spectra of red light carbon quantum dots prepared in Example 1 of the present invention at different excitation wavelengths;

[0025] Figure 4 The fluorescence emission spectrum and ultraviolet-visible absorption spectrum of the red light carbon quantum dots prepared in Example 1 of the present invention;

[0026] Figure 5 This is a photograph of the red light carbon quantum dots prepared in Example 1 of the present invention under irradiation with a 395nm wavelength ultraviolet lamp. DETAILED DESCRIPTION

[0027] The present invention provides a water-dispersible red light carbon quantum dot and a preparation method thereof. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] The present invention is described in detail below with reference to the accompanying drawings.

[0029] Example 1

[0030] This embodiment provides a water-dispersible red light-emitting carbon quantum dots, and the preparation process thereof is as follows:

[0031] (1) 0.2 mol of 1,2-diaminobenzene and 1.3 mol of concentrated sulfuric acid were added to a 500 mL beaker and stirred evenly, and the temperature was raised to 90° C. for reaction for 5 h. After the reaction was completed, an ice-water mixture was added to the reaction mixture to adjust the concentration of concentrated sulfuric acid to 40%, and then filtered to obtain intermediate A;

[0032] (2) 0.1 mol of the intermediate A of step (1) and 0.1 mol of catechol were added into a 800 mL beaker, and 300 mL of deionized water was added, stirred to fully dissolve, and then reacted at 90° C. and normal pressure for 12 h. After the reaction was completed, suction filtration was performed to obtain a crude carbon quantum dot product;

[0033] (3) Filter the crude carbon quantum dot product obtained in step (2) to obtain a blue-black carbon quantum dot powder; then filter and rinse with ethanol to obtain a clean black powder; then disperse the black powder in an ethanol aqueous solution with a volume ratio of ethanol to water of 1:4, weigh silica gel powder, add it to a 5cm×35cm chromatographic column, use the chromatographic column, and use the ethanol aqueous solution with a volume ratio of ethanol to water of 1:4 as an eluent to perform chromatographic separation, and freeze-dry the obtained product to obtain red light carbon quantum dots.

[0034] Example 2

[0035] This embodiment provides a water-dispersible red light-emitting carbon quantum dots, and the preparation process thereof is as follows:

[0036] (1) 0.2 mol of 3-bromo-1,2-diaminobenzene and 1.2 mol of concentrated sulfuric acid were added into a 500 mL beaker and stirred evenly, and the temperature was raised to 100° C. to react for 4 h. After the reaction was completed, an ice-water mixture was added to the reaction mixture to adjust the concentration of concentrated sulfuric acid to 30%, and then filtered to obtain intermediate A;

[0037] (2) 0.1 mol of the intermediate A of step (1) and 0.05 mol of 3-methylcatechol were added to a 800 mL beaker, and 300 mL of deionized water was added, stirred to fully dissolve, and then reacted at 60° C. and normal pressure for 15 h. After the reaction was completed, suction filtration was performed to obtain a crude carbon quantum dot product;

[0038] (3) Filter the crude carbon quantum dot product obtained in step (2) to obtain a blue-black carbon quantum dot powder; then filter and rinse with ethanol to obtain a clean black powder; then disperse the black powder in an ethanol aqueous solution with a volume ratio of ethanol to water of 1:4, weigh silica gel powder, add it to a 5cm×35cm chromatographic column, use the chromatographic column, and use the ethanol aqueous solution with a volume ratio of ethanol to water of 1:4 as an eluent to perform chromatographic separation, and freeze-dry the obtained product to obtain red light carbon quantum dots.

[0039] Example 3

[0040] This embodiment provides a water-dispersible red light-emitting carbon quantum dots, and the preparation process thereof 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 evenly, 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 concentrated sulfuric acid concentration to 50%, and then filtered to obtain intermediate A;

[0042] (2) 0.1 mol of the intermediate A of step (1) and 0.2 mol of catechol and 3-methylcatechol were added into a 800 mL beaker, and 300 mL of deionized water was added, stirred to fully dissolve, and then reacted at 30° C. and normal pressure for 24 h. After the reaction was completed, suction filtration was performed to obtain a crude carbon quantum dot product;

[0043] (3) Filter the crude carbon quantum dot product obtained in step (2) to obtain a blue-black carbon quantum dot powder; then filter and rinse with ethanol to obtain a clean black powder; then disperse the black powder in an ethanol aqueous solution with a volume ratio of ethanol to water of 1:5, weigh silica gel powder, add it to a 5cm×35cm chromatographic column, use the chromatographic column, and use the ethanol aqueous solution with a volume ratio of ethanol to water of 1:5 as an eluent to perform chromatographic separation, and freeze-dry the obtained product to obtain red light carbon quantum dots.

[0044] Comparative Example 1

[0045] The difference between this comparative example and Example 1 is that in this comparative example, no catechol is added during the preparation of carbon quantum dots.

[0046] After testing, it was found that no carbon quantum dots could be obtained in this comparative example.

[0047] Comparative Example 2

[0048] The difference between this comparative example and Example 1 is that in this comparative example, no catechol was added during the preparation of carbon quantum dots, and the hydrothermal reaction was carried out at 180° C. for 12 h.

[0049] After testing, it was found that the comparative example was able to obtain red light carbon quantum dots, but its water dispersibility was poor. The possible reason for this is that during the hydrothermal process, due to the presence of high temperature and high pressure conditions, the hydrophilic groups were easily detached, resulting in the obtained carbon quantum dots not having water dispersibility. However, since this embodiment adopts medium to low temperature and normal pressure, the hydrophilic groups will not fall off during the reaction, so that the carbon quantum dots can maintain water dispersibility.

[0050] Reference Figure 1-5 , the red light carbon quantum dots prepared in the above Example 1 were tested as follows:

[0051] Figure 1 The low-resolution transmission electron microscopy images and high-resolution transmission electron microscopy images of the red light carbon quantum dots prepared in Example 1 are shown in FIG. Figure 1 It can be seen that the red light carbon quantum dots are uniform in size, with a particle size of about 3.3nm and a crystal plane spacing of 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 is shown in FIG. Figure 2 It can be calculated that the quantum yield of red light carbon quantum dots is 35.7%.

[0053] Figure 3 The PL spectra of the red light carbon quantum dots prepared in Example 1 at different excitation wavelengths are shown in Figure 1. Figure 3 It can be seen that the emission wavelength of red light carbon quantum dots does not shift depending on the excitation wavelength, and exhibits a dual-band emission wavelength of 610nm and 660nm respectively.

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

[0055] Figure 5 This is a photograph of the red light carbon quantum dots prepared in Example 1 of the present invention under irradiation with a 395nm wavelength ultraviolet lamp. Under the irradiation with the ultraviolet lamp, the dots emit red light and have good water dispersibility.

[0056] It should be noted that some parts not described in the present invention can be implemented by adopting or drawing on existing technologies.

[0057] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing water-dispersible red light-emitting carbon quantum dots, characterized in that: Includes steps: (1) placing 1,2-diaminobenzene and / or 1,2-diaminobenzene derivatives and concentrated sulfuric acid in a container and stirring them uniformly, heating to 80-100° C. and reacting for 3-10 hours. After the reaction is completed, adding an ice-water mixture to the reaction mixture to adjust the concentrated sulfuric acid concentration to 30-50%, and then filtering to obtain an intermediate A; (2) placing the intermediate A of step (1) and catechol and / or catechol derivatives into a container and adding deionized water, stirring to fully dissolve them, and then reacting at 30 to 90° C. and normal pressure for 12 to 24 hours. After the reaction is completed, filtering is performed to obtain a crude carbon quantum dot product; (3) Purifying the crude carbon quantum dot product of step (2) by column chromatography to obtain water-dispersible red light-emitting carbon quantum dots.

2. The method for preparing water-dispersible red light-emitting carbon quantum dots according to claim 1, characterized in that: In the step (1), the molar ratio of 1,2-diaminobenzene and / or 1,2-diaminobenzene derivative to concentrated sulfuric acid is 1:5-8.

3. The method for preparing water-dispersible red light-emitting carbon quantum dots according to claim 1, characterized in that: In the 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.

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

5. The method for preparing water-dispersible red light-emitting carbon quantum dots according to claim 1, characterized in that: The catechol derivative in step (2) is at least one of 3-bromocatechol, 3-chlorocatechol, 3-iodocatechol, 3-methylcatechol and 3-ethylcatechol.

6. The method for preparing water-dispersible red light-emitting carbon quantum dots according to claim 1, characterized in that: In the step (2), the reaction temperature is 60 to 90° C. and the reaction is carried out at normal pressure for 12 to 15 hours.

7. The method for preparing water-dispersible red light-emitting carbon quantum dots according to claim 1, characterized in that: The purification process in step (3) is as follows: First, the crude carbon quantum dot product obtained in step (2) is filtered to obtain a blue-black carbon quantum dot powder; then it is filtered and rinsed 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 5cm×35cm chromatographic column, and the chromatographic column is used with the ethanol aqueous solution as an eluent for chromatographic separation, and the obtained product is freeze-dried to obtain red light carbon quantum dots.

8. The method for preparing water-dispersible red light-emitting carbon quantum dots according to claim 8, characterized in that: The volume ratio of ethanol to water in the ethanol aqueous solution used in the purification process of step (3) is 1:3-5.

9. A water-dispersible red light-emitting carbon quantum dot prepared by the preparation method according to any one of claims 1 to 8.

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