CN114479833A - A kind of carbon dot room temperature phosphorescent material and preparation method and application thereof - Google Patents

Abstract

The invention discloses a carbon dot room temperature phosphorescent material and a preparation method and application thereof. The synthesis method is simple and convenient, and is easy to synthesize and apply in large-scale production, and the phosphorescence service life of the prepared three room temperature phosphorescent materials is 300 milliseconds to 1.5 seconds. The series of carbon point room temperature phosphorescent materials have long-life room temperature phosphorescent properties, and the series of materials are applied to multicolor and time-resolved anti-counterfeiting materials. The anti-counterfeiting ink is uniformly mixed with aloe gel to obtain the anti-counterfeiting ink, so that multiple colors and time-related multiple anti-counterfeiting can be effectively realized, the anti-counterfeiting grade is improved, and counterfeiting is difficult.

Description

A kind of carbon dot room temperature phosphorescent material and preparation method and application thereof

technical field

The invention belongs to the technical field of material synthesis, relates to a carbon dot room temperature phosphorescent material, a preparation method and application thereof, and in particular relates to a series of preparation methods and applications of carbon dot room temperature phosphorescent materials with multicolor and time-resolved multiple anti-counterfeiting functions.

Background technique

Counterfeiting and counterfeiting are widespread all over the world, and despite many efforts by governments and businesses to prevent counterfeiting through enacting laws, a large number of counterfeit products in the fields of food, medicine, clothing and electronics are still spreading in our daily lives, seriously affecting property security, social stability, and even threaten human health. To prevent counterfeiting, various anti-counterfeiting strategies have been explored, including watermarks, holograms, lighting, barcodes, and QR codes.

However, traditional anti-counterfeiting strategies are easy to replicate and difficult to effectively prevent counterfeiting. At present, the technology based on optical anti-counterfeiting is mostly a single mode, which can only be simply anti-counterfeiting through different patterns displayed under sunlight and ultraviolet light. Therefore, it is easy to counterfeit and forgery, and it is difficult to achieve advanced anti-counterfeiting.

Although anti-counterfeiting technology based on room temperature phosphorescence has been reported, such as the room temperature phosphorescent material based on organic small molecules reported in the journal Nature Photonics in 2019, this method is difficult to synthesize, and it is difficult to produce and use on a large scale.

SUMMARY OF THE INVENTION

Objective: In order to overcome the deficiencies in the prior art, the present invention provides a room temperature phosphorescent material of carbon dots, and a preparation method of a room temperature phosphorescent material with multicolor and time-resolved multiple anti-counterfeiting functions based on carbon dots. The method is simple, convenient, easy to synthesize and apply in large-scale production, and can effectively realize multiple anti-counterfeiting of commodities, which is difficult to forge.

Technical scheme: In order to solve the above-mentioned technical problems, the preferred technical scheme adopted in the present invention is:

In a first aspect, a method for preparing a carbon dot room temperature phosphorescent material is provided, comprising:

Step (1), mix citric acid and urea in deionized water, react under 600-750 W microwave for 2-10 minutes, cool, filter, dialyze, freeze-dry to obtain nitrogen-doped carbon dots NCD;

In step (2), the nitrogen-doped carbon dots NCD obtained in step (1) is uniformly mixed with the solid matrix source and water to obtain a mixed solution of NCD and solid matrix source; The reaction or calcination is carried out at a fixed temperature to obtain an NCD/solid matrix composite material, that is, a carbon dot room temperature phosphorescent material, and the solid matrix is one or more of urea, boric acid or silicon dioxide.

In some embodiments, the carbon dot room temperature phosphorescent material is NCD/urea composite material, NCD/boric acid composite material or NCD/silica composite material.

The preparation method of NCD/urea composite material includes:

The nitrogen-doped carbon dots NCD is added to deionized water and uniformly mixed with urea and stirred for 5-30 minutes to obtain a mixed solution of NCD/urea. Urea composite.

Further, the mass ratio of NCD to urea is 1:(300-500), and the mass-to-volume ratio of NCD to deionized water is 1 mg:2-4 ml.

The preparation method of NCD/boric acid composite material includes: adding the nitrogen-doped carbon dots NCD into deionized water and uniformly mixing and stirring with boric acid for 5-30 minutes to obtain a NCD/boric acid mixed solution, and heating the mixed solution at 120-200° C. The reaction was carried out for 4-10 hours, and the NCD/boric acid composite material was obtained by cooling.

Further, the mass ratio of NCD to boric acid is 1:100-300, and the mass-to-volume ratio of NCD to deionized water is 1 mg:15-25 ml.

The preparation method of NCD/silica composite material includes:

React tetraethyl orthosilicate, ethanol, water and pH=2 hydrochloric acid at 75-100°C for 110-150 minutes to obtain a mixed solution;

The nitrogen-doped carbon dot NCD is added to the mixed solution, stirred at room temperature until a uniform gel is formed, and dried to obtain a gel powder; the dried gel powder is calcined at 400-650° C. for 1-3 hours, An NCD/silica composite material was obtained.

Further, the molar ratio of tetraethyl orthosilicate, ethanol, water and hydrochloric acid is 1:(3-5):(4-6):(0.1-0.3); the mass volume ratio of NCD and the mixed solution is 1 mg:10 -15 ml.

In a second aspect, a carbon dot room temperature phosphorescent material is provided, and the carbon dot room temperature phosphorescent material is at least one of NCD/urea composite material, NCD/boric acid composite material or NCD/silica composite material; prepared by the above method produced.

In a third aspect, an application of the carbon dot room temperature phosphorescent material in multicolor and time-resolved multiple anti-counterfeiting is provided.

The application includes: uniformly mixing the carbon dot room temperature phosphorescent material and aloe vera gel to prepare an anti-counterfeiting ink.

Further, the anti-counterfeiting ink is screen printed to print the anti-counterfeiting pattern.

In some embodiments, the mass ratio of the carbon dot room temperature phosphorescent material to the aloe vera gel is preferably 1:(3-5).

Beneficial effects: The present invention uses citric acid and urea as starting materials, prepares nitrogen-doped carbon dots (NCDs) by microwave method, and prepares three room temperature phosphorescent materials by combining NCDs with solid substrates. This series of carbon dot room temperature phosphorescent materials have long-lived room temperature phosphorescence properties, and this series of materials is applied to multicolor and time-resolved anti-counterfeiting materials. The above synthesis method is simple, convenient and easy to synthesize and apply in large-scale production. The anti-counterfeiting ink is obtained by uniformly mixing it with aloe vera gel, which can effectively realize multi-color and time-related multiple anti-counterfeiting, improve the anti-counterfeiting level, and is difficult to counterfeit. In addition, the preparation method provided by the present invention is energy-saving, environmentally friendly, non-toxic, not affected by water and oxygen in the air, and has excellent stability.

Description of drawings

Fig. 1 is the high-resolution transmission electron microscope of NCD carbon dots prepared in Example 1;

Fig. 2 is the X-ray photoelectron spectroscopy (XPS) analysis figure of the NCD carbon dots prepared in Example 1;

Fig. 3 is the XPS analysis figure of the NCD/urea composite material prepared in Example 2;

Fig. 4 is the fluorescence and phosphorescence emission spectrum of the NCD/urea composite material prepared in Example 2;

Fig. 5 is the attenuation curve of the NCD/urea composite material prepared in Example 2;

Fig. 6 is the XPS analysis chart of the NCD/boric acid composite material prepared in Example 3;

Fig. 7 is the fluorescence and phosphorescence emission spectrum of NCD/boric acid composite material prepared in Example 3;

Fig. 8 is the attenuation curve of the NCD/boric acid composite material prepared in Example 3;

Fig. 9 is the XPS analysis diagram of the NCD/silica composite material prepared in Example 4;

Figure 10 is the fluorescence and phosphorescence emission spectra of the NCD/silica composite material prepared in Example 4;

Figure 11 is the attenuation curve of the NCD/silica composite material prepared in Example 4;

Figure 12 and Figure 13 are the effect diagrams of the patterns printed by screen using fluorescent dyes and NCD/silica composites as inks before and after the 254 nm UV lamp is turned off;

Figure 14 and Figure 15 are the effect diagrams of the pattern printed by screen using NCD/urea composite material as the ink before and after the 254 nm UV lamp is turned off; Figure 16 is the 365 nm UV lamp in Figure 14 after the 365 nm UV lamp is irradiated, and the 365 nm UV lamp is turned off. the pattern shown later;

Figure 17 and Figure 18 are the effect diagrams of the patterns printed by screen using NCD/urea composite material and NCD/boric acid composite material as inks before and after the 254 nm UV lamp is turned off; Figure 19 is the UV lamp in Figure 18 when the UV lamp is turned off for 1 second Figure 20 shows the pattern shown in Figure 18 after the UV lamp is turned off for 2 seconds.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

The endpoints of ranges and any values disclosed herein are not limited to the precise ranges or values, which are to be understood to encompass values proximate to those ranges or values. For ranges of values, the endpoints of each range, the endpoints of each range and the individual point values, and the individual point values can be combined with each other to yield one or more new ranges of values that Ranges should be considered as specifically disclosed herein.

For the purposes of this specification and the appended claims, unless stated otherwise, all figures expressing quantities, percentages or ratios and other numerical values used in this specification and the appended claims are to be understood in all cases as Modified by the term "about". Furthermore, all ranges disclosed herein are inclusive of the endpoints and independently combinable.

Example 1

(1) The preparation method of carbon dots is:

Mix 3 g of citric acid and 6 g of urea in 20 ml of deionized water, react under 650 W microwave for 5 minutes, cool to room temperature, filter with filter paper, and then centrifuge the obtained liquid at 8000 rpm for three times to remove large particles. The particles were dialyzed with a dialysis bag with a molecular weight cut-off of 3500 for 2 days, and the obtained liquid was then freeze-dried to obtain nitrogen-doped carbon dots (NCD) powder.

(2) Characterization of NCD:

The high-resolution transmission electron microscope is shown in Figure 1. The NCD carbon dots have good uniformity and quasi-spherical morphology, with an average diameter of about 2.8 nm, and lattice fringes can be seen. To further understand the composition of NCDs, X-ray photoelectron spectroscopy (XPS) analysis was performed. The XPS results (Fig. 2) showed that the NCD was mainly composed of carbon, nitrogen, and oxygen.

Example 2

(1) The preparation method of NCD/urea composite material is:

The synthesized NCD (20 mg) was added to 60 ml of deionized water and uniformly mixed with 8 g of urea for 20 minutes to obtain a mixed solution of NCD/urea. The NCD/urea composite was obtained at room temperature.

(2) Characterization of NCD/urea composites:

To further understand the composition of the NCD/urea composite, X-ray photoelectron spectroscopy (XPS) analysis was performed. The XPS results (Fig. 3) show that the NCD/urea composites are mainly composed of carbon, nitrogen, and oxygen.

(3) Photoluminescence properties of NCD/urea composites:

The fluorescence and phosphorescence emission spectra of the NCD/urea composite were obtained by excitation at 373 nm at room temperature, respectively. The results are shown in Figure 4. It can be seen from Figure 4 that the fluorescence emission peak of NCD/urea composite material is at 436 nm, and the phosphorescence emission peak is at 501 nm.

The decay curve of the NCD/urea composite was obtained by excitation with a wavelength of 373 nm at room temperature (Fig. 5), and the average lifetime was calculated to be 332.26 ms.

Example 3

(1) The preparation method of NCD/boric acid composite material is:

The synthesized NCD (10 mg) was added to 160 ml of deionized water and uniformly mixed with 2 g of boric acid for 20 minutes to obtain a mixed solution of NCD/boric acid. The NCD/boric acid composite was obtained at room temperature.

(2) Characterization of NCD/boric acid composites

To further understand the composition of the NCD/boric acid composite, X-ray photoelectron spectroscopy (XPS) analysis was performed. The XPS results (Fig. 6) show that the NCD/boronic acid is mainly composed of carbon, nitrogen, oxygen, and boron.

(3) Photoluminescence properties of NCD/boric acid composites:

The fluorescence and phosphorescence emission spectra of NCD/boronic acid composites were obtained by excitation at 273 nm wavelength at room temperature, respectively. The results are shown in Figure 7. It can be seen from Figure 7 that the fluorescence emission peak of the NCD/boric acid composite material is at 408 nm, and the phosphorescence emission peak is at 453 nm.

The decay curve of the NCD/boric acid composite was obtained by excitation with a wavelength of 273 nm at room temperature (Fig. 8), and the average lifetime was calculated to be 652.05 ms.

Example 4

(1) The preparation method of NCD/silica composite material is:

Tetraethyl orthosilicate, ethanol, water and hydrochloric acid (pH = 2) were uniformly mixed in a molar ratio of 1:4:5:0.2 and reacted at 80 °C for 120 minutes. The synthesized NCD (10 mg) was added to 100 mL of the mixed solution and stirred at room temperature until a homogeneous gel was formed. The dried gel powder was calcined at 600°C for 90 minutes to obtain the final NCD/silica composite material.

(2) Characterization of NCD/silica composites:

To further understand the composition of the NCD/silica composite, X-ray photoelectron spectroscopy (XPS) analysis was performed. The XPS results (Fig. 9) show that the NCD/silica composites are mainly composed of carbon, nitrogen, oxygen, and silicon.

(3) Photoluminescence properties of NCD/silica composites:

The fluorescence and phosphorescence emission spectra of NCD/silica composites were obtained by excitation at a wavelength of 290 nm at room temperature, respectively. The results are shown in Figure 10. It can be seen from Figure 10 that the fluorescence emission peak of the NCD/silica composite material is at 400 nm, and the phosphorescence emission peak is at 474 nm.

The decay curve of the NCD/silica composite was obtained by excitation with a wavelength of 290 nm at room temperature (Fig. 11), and the average lifetime was calculated to be 1587.22 ms.

Example 5

The preparation method of the anti-counterfeiting ink is as follows:

The NCD/urea composite material, the NCD/boric acid composite material, the NCD/silica composite material and the aloe vera gel were uniformly mixed in a mass ratio of 1 g: 3 g respectively to prepare an anti-counterfeiting ink.

Example 6

The numbers "2" and "3" printed by screen, in which the ink of "2" is fluorescent dye, and the ink of "3" is NCD/silica composite material, as shown in Figure 12. Figure 13 is a photo of the pattern shown in Figure 12 after the 254 nm UV lamp is turned off. Since the NCD/silica composite has room temperature phosphorescence properties, the number "3" can still be seen after the UV lamp is turned off.

Example 7

A bouquet of flower patterns obtained by screen printing of NCD/urea composite as ink is shown in Figure 14. Figure 15 shows the pattern after the 254 nm UV lamp in Figure 14 is turned off. Since the NCD/urea composite has room temperature phosphorescence, the flower pattern can still be seen after turning off the UV lamp; Figure 16 is the 365 nm UV lamp in Figure 14. After the lamp is irradiated, the pattern displayed after the 365 nm UV lamp is turned off, compared with the pattern after the 254 nm UV lamp is turned off, the color of the flower changes from blue to green, so multi-color anti-counterfeiting can be achieved.

Example 8

NCD/urea composite material and NCD/boric acid composite material are two numbers "8" obtained by screen printing as ink, the ink of the first "8" from the left is carbon dots/urea, and the ink of the second "8" is carbon dots/urea. The ink is NCD/boric acid, as shown in Figure 17; Figure 18 is a photo of the pattern after the 254 nm UV lamp in Figure 17 is turned off. Since both the NCD/urea composite material and the NCD/boric acid composite material have room temperature phosphorescence properties, they are turned off. Two numbers "8" can still be seen after the UV lamp; Figure 19 shows the pattern after the UV lamp is turned off for 1 second in Figure 18. Due to the different phosphorescence lifetimes of NCD/urea and NCD/boric acid, the first number "8" ” gradually dimmed; Figure 20 shows the pattern shown in Figure 18 after the UV lamp was turned off for 2 seconds. Due to the different phosphorescence lifetimes of NCD/urea composite and NCD/boric acid composite, the first number “8” disappeared, and only visible to the second number "8", thus enabling time-dependent multiple anti-counterfeiting.

The above examples provide experiments to prove that the three composite materials prepared in the embodiments of the present invention have long-life room temperature phosphorescence properties, and this series of materials can be applied to multicolor and time-resolved anti-counterfeiting materials. The above synthesis method is simple, convenient and easy to synthesize and apply in large-scale production. The anti-counterfeiting ink is obtained by uniformly mixing it with aloe vera gel, which can effectively realize multi-color and time-related multiple anti-counterfeiting, improve the anti-counterfeiting level, and is difficult to counterfeit. In addition, the preparation method provided by the present invention is energy-saving, environmentally friendly, non-toxic, not affected by water and oxygen in the air, and has excellent stability.

Claims (10)

1. A preparation method of a carbon dot room temperature phosphorescent material is characterized by comprising the following steps:

mixing citric acid and urea in deionized water, reacting for 2-10 minutes under 600-750W microwave, cooling, filtering, dialyzing, and freeze-drying to obtain nitrogen-doped carbon point NCD;

step (2), uniformly mixing the nitrogen-doped carbon point NCD prepared in the step (1) with a solid matrix source and water to obtain a mixed solution of the NCD and the solid matrix source; and reacting or calcining the mixed solution of the NCD and the solid matrix source at a set temperature to obtain the NCD/solid matrix composite material, namely the carbon dot room temperature phosphorescent material, wherein the solid matrix is one or more of urea, boric acid or silicon dioxide.

2. The method according to claim 1, wherein the carbon dot phosphorescent material at room temperature is an NCD/urea composite material, an NCD/boric acid composite material, or an NCD/silica composite material.

3. The method according to claim 2, wherein the NCD/urea composite is prepared by a method comprising:

and adding the nitrogen-doped carbon point NCD into deionized water, uniformly mixing and stirring with urea for 5-30 minutes to obtain an NCD/urea mixed solution, reacting the mixed solution at the temperature of 120-180 ℃ for 4-10 hours, and cooling to obtain the NCD/urea composite material.

4. The method according to claim 3, wherein the mass ratio of NCD to urea is 1 (300-500), and the mass-to-volume ratio of NCD to deionized water is 1 mg: 2-4 ml.

5. The method according to claim 2, wherein the NCD/boric acid composite is prepared by a method comprising: and adding the nitrogen-doped carbon point NCD into deionized water, uniformly mixing and stirring with boric acid for 5-30 minutes to obtain an NCD/boric acid mixed solution, reacting the mixed solution at the temperature of 120-200 ℃ for 4-10 hours, and cooling to obtain the NCD/boric acid composite material.

6. The method according to claim 5, wherein the mass ratio of NCD to boric acid is 1:100-300, and the mass-to-volume ratio of NCD to deionized water is 1 mg: 15-25 ml.

7. The method of claim 2, wherein the NCD/silica composite is prepared by a method comprising:

tetraethyl orthosilicate, ethanol, water and hydrochloric acid with pH = 2 are reacted for 110-100 ℃ for 150 minutes to obtain a mixed solution;

adding the nitrogen-doped carbon point NCD into the mixed solution, stirring at room temperature until uniform gel is formed, and drying to obtain gel powder; and calcining the dried gel powder at the temperature of 400-650 ℃ for 1-3 hours to obtain the NCD/silicon dioxide composite material.

8. The method according to claim 7, wherein the molar ratio of tetraethyl orthosilicate, ethanol, water and hydrochloric acid is 1 (3-5) to (4-6) to (0.1-0.3);

and/or the mass volume ratio of the NCD to the mixed solution is 1 mg: 10-15 ml.

9. The carbon dot room temperature phosphorescent material is characterized in that the carbon dot room temperature phosphorescent material is at least one of an NCD/urea composite material, an NCD/boric acid composite material or an NCD/silicon dioxide composite material; prepared by the preparation method of any one of claims 1 to 8.

10. Use of the carbon dot room temperature phosphorescent material of claim 9 in multicolor and time-resolved multiplexed security.

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