CN106497560B - The controllable carbon dots based compound nano material and the preparation method and application thereof of luminescent properties - Google Patents

Abstract

The invention provides a carbon point-based composite nanomaterial with controllable luminous performance, a preparation method and application thereof. By adding cyanuric acid or alkali metal hydroxide and cyanuric acid to the aqueous solution of carbon quantum dots modified with carboxyl groups on the surface, the resulting mixture is stirred and centrifuged, the precipitate is collected, and freeze-dried to obtain the luminescent properties Controllable carbon dot-based composite nanomaterials. The preparation process of the invention is simple, low in cost, non-toxic and environment-friendly. By adjusting the pH value, not only can the fluorescence luminescence efficiency of the material be greatly improved, but also the color and lifespan of the afterglow of the material can be changed, which has important application value in the fields of anti-counterfeiting, biosensing, display and lighting.

Description

Carbon-dot-based composite nanomaterials with controllable luminescent properties and their preparation methods and applications

technical field

The invention relates to the field of material engineering, in particular to a carbon-dot-based composite nanomaterial with controllable luminous performance, a preparation method and application thereof.

Background technique

Carbon quantum dots (CQDs) are luminescent carbon particles with a particle size below 10nm and composed of dispersed spherical particles discovered in recent years. Since its discovery, due to its unique properties, it has aroused great interest of researchers. Carbon quantum dots have excellent properties different from traditional quantum dots, such as photoluminescence, low toxicity, chemical inertness and good biocompatibility, and have broad application prospects in optoelectronic devices, biological detection, medicine and other fields. One of the most concerned is its photoluminescent properties. However, due to the influence of the inherent properties of carbon dots, the luminescent properties of the carbon dot-based composite nanomaterials prepared by them are uncontrollable. Therefore, realizing carbon dot-based composite nanomaterials with controllable luminescent properties through a simple method can greatly reduce the production cost.

Contents of the invention

Aiming at the problems in the prior art such as complex preparation process of optical materials, scarcity of preparation raw materials and uncontrollable optical properties, the invention provides a carbon dot-based composite nanomaterial with controllable luminescence performance and a preparation method thereof.

Another object of the present invention is to provide the application of the carbon dot-based composite nanomaterial with controllable luminescent properties.

In order to realize the object of the present invention, the present invention provides the preparation method of the carbon dot-based composite nanomaterial with controllable luminous performance, described method is to add cyanuric acid to the carbon quantum dot aqueous solution that surface is modified with carboxyl group, or add alkali Metal hydroxide and cyanuric acid, the obtained mixed solution is stirred and centrifuged, the precipitate is collected, and freeze-dried to obtain the carbon dot-based composite nanometer material with controllable luminescence performance.

The carbon quantum dot aqueous solution that the surface is modified with carboxyl groups can be prepared as follows:

(1) Folic acid and citric acid are dissolved in deionized water in a mass ratio of 1:0.1-10, and the mass ratio of folic acid and water is 1:50-1000 to obtain a mixed solution I;

(2) Put the mixed solution obtained in (1) in a polytetrafluoroethylene high-pressure sealed tank, heat or microwave reaction at 150-300°C for 1-5 hours, and obtain solution II;

(3) Centrifuge the solution II obtained in (2) at 3000-10000rpm for 5-30min, take the supernatant, and dialyze it with a dialysis bag with a molecular weight cut-off of 500-3500Da for 12-72h to obtain the fluorescent carbon quantum dot aqueous solution III;

(4) Freeze-dry the solution III obtained in (3) for 12 to 96 hours to obtain a carbon quantum dot powder with surface-modified carboxyl groups; the freeze-drying temperature is -44°C;

(5) Dissolving the powder obtained in (4) in deionized water to prepare a solution of 0.01-10 mg/L, which is an aqueous solution of carbon quantum dots modified with carboxyl groups on the surface.

The alkali metal hydroxide used in the present invention is sodium hydroxide and/or potassium hydroxide.

In the aforementioned method, 0.2-2 g of cyanuric acid and 0-8 g of alkali metal hydroxide are added to 8 mL of carbon quantum dot aqueous solution modified with carboxyl groups on the surface, and stirred for 2 to 24 hours to obtain an emulsion. Wherein, the molar ratio of cyanuric acid and alkali metal hydroxide is 1:0.01-6.

In the aforementioned method, the centrifugation condition is: 5000-10000 rpm for 5-20 minutes.

In the aforementioned method, the freeze-drying condition is: freeze-drying at -44°C for 12-96 hours.

The present invention also provides the carbon dot-based composite nanomaterial with controllable luminous performance prepared according to the above method. Wherein, the carbon quantum dot accounts for 0.01%-0.5% by weight of the composite nanomaterial.

The invention also provides the application of the carbon dot-based composite nanomaterial in the preparation of anti-counterfeiting materials, biological sensor materials, display materials and lighting materials.

The present invention further provides anti-counterfeiting materials, biosensing materials, display materials and lighting materials prepared from the carbon dot-based composite nanomaterials.

The present invention has the following advantages:

(1) The present invention uses carbon quantum dots and cyanuric acid as raw materials, adjusts the pH value of the mixed solution through alkali metal hydroxide (such as sodium hydroxide), and prepares carbon dot-based composite nanomaterials with controllable luminescent properties. When the molar ratio of cyanuric acid to sodium hydroxide is less than 3:1, the composite material emits blue fluorescence and blue afterglow under the irradiation of ultraviolet light with a wavelength of 365nm; when the molar ratio of sodium hydroxide to cyanuric acid is ≥ At the ratio of 3:1, the composite emits blue fluorescence and yellow afterglow under the irradiation of 365nm ultraviolet lamp, and the fluorescence quantum yield increases gradually with the increase of sodium hydroxide dosage.

(2) The preparation method of the present invention is simple, and the whole technological process is green and environment-friendly. Luminescent materials with different fluorescent and phosphorescent efficiencies, colorful and different lifespans can be prepared by adjusting the pH value of the solution only by adjusting the amount of sodium hydroxide added.

(3) The carbon dot-based composite nanomaterial with controllable luminescence performance prepared by the present invention has good stability, long life, and afterglow decay time of several seconds, and has important application value in the fields of information anti-counterfeiting and biomarking.

Description of drawings

Fig. 1 is the fluorescent photo (left) and the long afterglow photo (right) of the composite optical material prepared in Example 1 of the present invention under the irradiation of an ultraviolet lamp with a wavelength of 365nm;

Fig. 2 is the steady-state fluorescence spectrum diagram of the composite optical material prepared in Example 1 of the present invention;

Fig. 3 is the steady-state spectrogram measured in the phosphorescence mode of the composite optical material prepared in Example 1 of the present invention;

Fig. 4 is the afterglow attenuation curve at 520nm of the composite optical material prepared in Example 1 of the present invention under the excitation of 380nm wavelength;

Fig. 5 is a steady-state fluorescence spectrum diagram of the composite optical material prepared in Example 2 of the present invention under different excitation wavelengths;

Fig. 6 is a steady-state spectrogram measured in phosphorescence mode of the composite optical material prepared in Example 2 of the present invention;

Fig. 7 is the afterglow decay curve at 520nm of the composite optical material prepared in Example 2 of the present invention under the excitation of 380nm wavelength;

Fig. 8 is the fluorescent photo (left) and the long afterglow photo (right) of the composite optical material prepared in Example 3 of the present invention under the irradiation of an ultraviolet lamp with a wavelength of 365nm;

Fig. 9 is a steady-state fluorescence spectrum diagram of the composite optical material prepared in Example 3 of the present invention;

Fig. 10 is a steady-state spectrogram of the composite optical material prepared in Example 3 of the present invention measured in phosphorescence mode;

Fig. 11 is the afterglow attenuation curve at 520nm of the composite optical material prepared in Example 3 of the present invention under the excitation of 380nm wavelength;

Fig. 12 is a steady-state fluorescence spectrum diagram of the composite optical material prepared in Example 4 of the present invention under different excitation wavelengths;

Fig. 13 is a steady-state spectrum measured in phosphorescence mode of the composite optical material prepared in Example 4 of the present invention;

Figure 14 is the afterglow attenuation curve at 520nm of the composite optical material prepared in Example 4 of the present invention under excitation at a wavelength of 380nm;

Fig. 15 is a comparison chart of fluorescence quantum yields of composite optical materials prepared in Examples 1-4 of the present invention.

Detailed ways

The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available products.

The freeze-drying conditions in the following examples are: freeze-drying at -44°C for 12-96 hours.

Example 1 Carbon dot-based composite nanomaterial with controllable luminescence performance and its preparation method

(1) Preparation of aqueous solution of carbon quantum dots with carboxyl groups on the surface

1. Weigh 0.5g of folic acid and 1.0g of citric acid and dissolve them in 50ml of deionized water, stir thoroughly for 10 minutes, then place the obtained mixed solution in a polytetrafluoroethylene high-pressure sealed reaction kettle, and heat at 250°C for 4 hours. get the initial solution;

2. Centrifuge the initial solution obtained above at 10,000 rpm for 20 minutes to remove the black precipitate, take the upper layer of brownish-yellow clear liquid, use a dialysis bag with a molecular weight cut-off of 500Da, and dialyze for 24 hours to obtain a pure aqueous solution of fluorescent carbon quantum dots;

3. The carbon quantum dot aqueous solution obtained above was freeze-dried for 96 hours to obtain a fluorescent carbon quantum dot powder containing a large amount of carboxyl groups and amino groups on the surface;

4. Dissolve the powder obtained above in deionized water to prepare a 2 mg/L solution, which is an aqueous solution of carbon quantum dots modified with carboxyl groups on the surface.

(2) Preparation of carbon dot-based composite nanomaterials with controllable luminescence properties

Include the following steps:

(1) 8ml of surface-modified carbon quantum dot aqueous solution with carboxyl group is mixed with sodium hydroxide 0.62g and cyanuric acid powder 1g, then magnetically stirred for 10h to obtain emulsion;

(2) Centrifuge the emulsion obtained in (1) at a rotating speed of 10000rpm for 10min, discard the supernatant, and obtain a water-containing carbon dot-based composite nanomaterial;

(3) freeze-drying the water-containing carbon dot-based composite nanomaterial obtained in (2) for 24 hours to obtain a carbon-dot-based composite nanomaterial with controllable luminescent properties. Wherein the carbon quantum dot accounts for 0.02% by weight of the dry composite material.

The properties of the carbon dot-based composite nanomaterials prepared in this example are shown in Fig. 1 to Fig. 4 .

Figure 1 is the fluorescent photo and long afterglow photo of the composite optical material under the irradiation of a UV lamp with a wavelength of 365nm; A blue afterglow visible to the naked eye (right).

Figure 2 is the steady-state fluorescence spectrum diagram of the composite optical material at different excitation wavelengths; it can be seen from Figure 2 that the optimum excitation wavelength is 380nm and the maximum emission wavelength is 435nm.

Figure 3 is a steady-state spectrogram of the composite optical material measured in phosphorescence mode; Figure 3 shows that the composite material has a maximum emission wavelength of 435nm under excitation at 360nm, and a maximum emission wavelength of 525nm under excitation at 380nm.

Figure 4 is the afterglow decay curve of the composite optical material at 520nm under the excitation of 380nm wavelength; Figure 4 shows that the composite material has a long afterglow lifetime, and its average lifetime is 289ms.

Example 2 Carbon-dot-based composite nanomaterial with controllable luminescence performance and its preparation method

(1) Preparation of aqueous solution of carbon quantum dots with carboxyl groups on the surface

1. Weigh 0.5g of folic acid and 0.2g of citric acid and dissolve them in 50ml of deionized water, stir thoroughly for 10 minutes, then place the obtained mixed solution in a polytetrafluoroethylene high-pressure sealed tank, and heat it at 240°C with a power of 700w for 4 hours, the initial solution was obtained;

2. Centrifuge the initial solution obtained above at 10,000 rpm for 20 minutes to remove the black precipitate, take the upper layer of brownish-yellow clear liquid, use a dialysis bag with a molecular weight cut-off of 500Da, and dialyze for 24 hours to obtain a pure aqueous solution of fluorescent carbon quantum dots;

3. The carbon quantum dot aqueous solution obtained above was freeze-dried for 96 hours to obtain a fluorescent carbon quantum dot powder containing a large amount of carboxyl groups and amino groups on the surface;

4. Dissolve the powder obtained above in deionized water to prepare a 1 mg/L solution, which is an aqueous solution of carbon quantum dots modified with carboxyl groups on the surface.

(2) Preparation of carbon dot-based composite nanomaterials with controllable luminescence properties

Include the following steps:

(1) 8ml of surface-modified carbon quantum dot aqueous solution with carboxyl groups and 1g of cyanuric acid powder are mixed uniformly, then magnetically stirred for 10h to obtain emulsion;

(2) Centrifuge the emulsion obtained in (1) at a rotating speed of 10000rpm for 10min, discard the supernatant, and obtain a water-containing carbon dot-based composite nanomaterial;

(3) freeze-drying the water-containing carbon dot-based composite nanomaterial obtained in (2) for 24 hours to obtain a carbon-dot-based composite nanomaterial with controllable luminescent properties. Wherein the carbon quantum dot accounts for 0.02% by weight of the dry composite material.

The properties of the carbon dot-based composite nanomaterials prepared in this example are shown in FIGS. 5 to 7 .

The composite material emits blue fluorescence under the irradiation of a 365nm wavelength ultraviolet lamp, and has a blue afterglow visible to the naked eye after the ultraviolet lamp is extinguished.

Figure 5 is a steady-state fluorescence spectrum diagram of the composite optical material at different excitation wavelengths; it can be seen from Figure 5 that the optimum excitation wavelength is 380nm and the maximum emission wavelength is 475nm.

Fig. 6 is a steady-state spectrogram of the composite optical material measured in phosphorescence mode; Fig. 6 shows that the maximum emission wavelength of the composite material is at 475nm when excited at a wavelength of 340nm.

Figure 7 is the afterglow decay curve of the composite optical material at 520nm under the excitation of 380nm wavelength; Figure 7 shows that the composite material has a long afterglow lifetime, and its average lifetime is 120ms.

Example 3 Carbon dot-based composite nanomaterial with controllable luminescence performance and its preparation method

(1) Preparation of aqueous solution of carbon quantum dots with carboxyl groups on the surface

1. Weigh 0.5g of folic acid and 1.0g of citric acid and dissolve them in 50ml of deionized water, stir thoroughly for 10 minutes, then place the resulting mixed solution in a polytetrafluoroethylene high-pressure sealed reaction kettle, and heat at 240°C for 4 hours. get the initial solution;

2. Centrifuge the initial solution obtained above at 10,000 rpm for 20 minutes to remove the black precipitate, take the upper layer of brownish-yellow clear liquid, use a dialysis bag with a molecular weight cut-off of 500Da, and dialyze for 24 hours to obtain a pure aqueous solution of fluorescent carbon quantum dots;

3. The carbon quantum dot aqueous solution obtained above was freeze-dried for 96 hours to obtain a fluorescent carbon quantum dot powder containing a large amount of carboxyl groups and amino groups on the surface;

4. Dissolve the powder obtained above in deionized water to prepare a 2 mg/L solution, which is an aqueous solution of carbon quantum dots modified with carboxyl groups on the surface.

(2) Preparation of carbon dot-based composite nanomaterials with controllable luminescence properties

Include the following steps:

(1) 8 ml of surface-modified carbon quantum dot aqueous solution with carboxyl groups are mixed with 0.93 g of sodium hydroxide and 1 g of cyanuric acid powder, and then magnetically stirred for 10 h to obtain an emulsion;

(2) Centrifuge the emulsion obtained in (1) at a rotating speed of 10000rpm for 10min, discard the supernatant, and obtain a water-containing carbon dot-based composite nanomaterial;

(3) freeze-drying the water-containing carbon dot-based composite nanomaterial obtained in (2) for 24 hours to obtain a carbon-dot-based composite nanomaterial with controllable luminescent properties. Wherein the carbon quantum dot accounts for 0.02% by weight of the dry composite material.

The properties of the carbon dot-based composite nanomaterials prepared in this example are shown in FIGS. 8 to 11 .

Figure 8 is the fluorescent photo and long afterglow photo of the composite optical material under the irradiation of a 365nm wavelength ultraviolet lamp; Figure 8 shows that the composite material emits blue fluorescence (left figure) under the irradiation of a 365nm wavelength ultraviolet lamp, and there is Yellow-green afterglow visible to the naked eye (right).

Fig. 9 is a steady-state fluorescence spectrum diagram of the composite optical material at different excitation wavelengths; it can be seen from Fig. 9 that the optimum excitation wavelength is 380nm and the maximum emission wavelength is 435nm.

Fig. 10 is a steady-state spectrogram of the composite optical material measured in phosphorescence mode; Fig. 10 shows that the maximum emission wavelength of the composite material is at 525nm under the excitation of 360nm and 380nm wavelength.

Figure 11 is the afterglow attenuation curve of the composite optical material at 520nm under the excitation of 380nm wavelength; Figure 11 shows that the composite material has a long afterglow lifetime, and its average lifetime is 380ms.

Example 4 Carbon-dot-based composite nanomaterial with controllable luminescence performance and its preparation method

(1) Preparation of aqueous solution of carbon quantum dots with carboxyl groups on the surface

1. Weigh 0.5g of folic acid and 0.5g of citric acid and dissolve them in 50ml of deionized water, stir thoroughly for 10 minutes, then place the obtained mixed solution in a polytetrafluoroethylene high-pressure sealed reaction kettle, and heat at 300°C for 3 hours. get the initial solution;

2. Centrifuge the initial solution obtained above at 10,000 rpm for 20 minutes to remove the black precipitate, take the upper layer of brownish-yellow clear liquid, use a dialysis bag with a molecular weight cut-off of 500Da, and dialyze for 24 hours to obtain a pure aqueous solution of fluorescent carbon quantum dots;

3. The carbon quantum dot aqueous solution obtained above was freeze-dried for 96 hours to obtain a fluorescent carbon quantum dot powder containing a large amount of carboxyl groups and amino groups on the surface;

4. Dissolve the powder obtained above in deionized water to prepare a 1 mg/L solution, which is an aqueous solution of carbon quantum dots modified with carboxyl groups on the surface.

(2) Preparation of carbon dot-based composite nanomaterials with controllable luminescence properties

Include the following steps:

(1) 8ml of surface-modified carbon quantum dot aqueous solution with carboxyl group is mixed with sodium hydroxide 2g and cyanuric acid powder 1g, then magnetically stirred for 10h to obtain emulsion;

(2) Centrifuge the emulsion obtained in (1) at a rotating speed of 10000rpm for 10min, discard the supernatant, and obtain a water-containing carbon dot-based composite nanomaterial;

(3) freeze-drying the water-containing carbon dot-based composite nanomaterial obtained in (2) for 24 hours to obtain a carbon-dot-based composite nanomaterial with controllable luminescent properties. Wherein the carbon quantum dot accounts for 0.02% by weight of the dry composite material.

The properties of the carbon dot-based composite nanomaterials prepared in this example are shown in FIGS. 5 to 7 .

The composite material emits blue fluorescence under the irradiation of a 365nm wavelength ultraviolet lamp, and has a yellow-green afterglow visible to the naked eye after the ultraviolet lamp is extinguished.

Figure 12 is a steady-state fluorescence spectrum diagram of the composite optical material at different excitation wavelengths; it can be seen from Figure 12 that the optimum excitation wavelength is 380nm and the maximum emission wavelength is 435nm.

Fig. 13 is a steady-state spectrogram of the composite optical material measured in phosphorescence mode; Fig. 13 shows that the maximum emission wavelength of the composite material is at 525nm under the excitation of 360nm and 380nm wavelength.

Figure 14 is the afterglow attenuation curve of the composite optical material at 520nm under the excitation of 380nm wavelength; Figure 14 shows that the composite material has a long afterglow lifetime, and its average lifetime is 331ms.

The comparison results of the fluorescence quantum yields of the composite optical materials prepared in Examples 1-4 are shown in FIG. 15 .

Although the present invention has been described in detail with general descriptions and specific embodiments above, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (10)

1. The preparation method of the carbon-dot-based composite nanomaterial with controllable luminescence performance, is characterized in that, adding cyanuric acid to the carbon quantum dot aqueous solution that surface is modified with carboxyl groups, or adding alkali metal hydroxide and trimerization Cyanic acid, the resulting mixed solution is stirred and centrifuged, the precipitate is collected, and freeze-dried to obtain a carbon dot-based composite nanomaterial with controllable luminescent properties. 2. method according to claim 1, is characterized in that, the preparation method of the carbon quantum dot aqueous solution that described surface is modified with carboxyl group is as follows: (1) Folic acid and citric acid are dissolved in deionized water in a mass ratio of 1:0.1-10, and the mass ratio of folic acid and water is 1:50-1000 to obtain a mixed solution I; (2) Put the mixed solution I obtained in (1) in a polytetrafluoroethylene high-pressure sealed tank, and heat or react in microwave at 150-300° C. for 1-5 hours to obtain solution II; (3) Centrifuge the solution II obtained in (2) at 3000-10000rpm for 5-30min, take the supernatant, and dialyze it with a dialysis bag with a molecular weight cut-off of 500-3500Da for 12-72h to obtain the fluorescent carbon quantum dot aqueous solution III; (4) Freeze-dry the solution III obtained in (3) for 12 to 96 hours to obtain carbon quantum dot powder with carboxyl groups on the surface; (5) Dissolving the powder obtained in (4) in deionized water to prepare a solution of 0.01-10 mg/L, which is an aqueous solution of carbon quantum dots modified with carboxyl groups on the surface. 3. the method according to claim 2 is characterized in that, in the carbon quantum dot aqueous solution that 8mL surface is modified with carboxyl group, add 0.2-2g cyanuric acid and 0-8g alkali metal hydroxide, stir 2～ 24h to obtain emulsion. 4. The method according to any one of claims 1-3, characterized in that the centrifugation condition is: centrifugation at 5000-10000 rpm for 5-20 minutes. 5. The method according to any one of claims 1-3, characterized in that the freeze-drying condition is: freeze-drying at -44°C for 12-96 hours. 6. The method according to any one of claims 1-3, characterized in that, the alkali metal hydroxide is sodium hydroxide and/or potassium hydroxide. 7. The carbon dot-based composite nanomaterial with controllable luminescence properties prepared according to the method according to any one of claims 1-6. 8 . The carbon dot-based composite nanomaterial according to claim 7 , wherein the carbon quantum dots account for 0.01% to 0.5% by weight of the composite nanomaterial. 9. The application of the carbon dot-based composite nanomaterial according to claim 7 or 8 in the preparation of anti-counterfeiting materials, biosensing materials, display materials and lighting materials. 10. The anti-counterfeiting material, biosensing material, display material and lighting material prepared by the carbon dot-based composite nanomaterial according to claim 7 or 8.