Carbon quantum dot fluorescent ink, preparation method and application thereof

Abstract

The application provides a carbon quantum dot fluorescent ink as well as a preparation method and application thereof, and relates to the technical field of anti-fake materials.The preparation method of the carbon quantum dot fluorescent ink provided by the application comprises the following steps: mixing an alcohol compound, water and an oxidizing agent, and performing a hydrothermal reaction to obtain a mixed dispersion liquid; and performing drying treatment on the mixed dispersion liquid to obtain the carbon quantum dot fluorescent ink.The entire preparation process is simple, fast and low in cost; the prepared carbon quantum dot fluorescent ink is stable in chemical properties, colorless under natural light after writing, can emit strong fluorescence under ultraviolet light irradiation, has an anti-fake effect, and solves the problems of complex purification steps, long time and high cost of the carbon quantum dot fluorescent ink.

Description

Technical Field

[0001] This invention relates to the field of anti-counterfeiting materials technology, specifically to a carbon quantum dot fluorescent ink, its preparation method, and its application. Background Technology

[0002] Anti-counterfeiting fluorescent inks are widely used in the field of anti-counterfeiting technology. Common fluorescent materials include organic luminescent dyes, semiconductor quantum dots, and rare earth quantum dots. However, these materials are complex to prepare and require cumbersome post-processing. Furthermore, semiconductor quantum dots contain heavy metals such as lead and cadmium, which have a significant environmental impact, and rare earth quantum dots are a non-renewable resource, thus limiting their application. Carbon quantum dots are a class of luminescent nanomaterials with optical properties discovered in recent years. They can emit visible light under ultraviolet light excitation and have advantages such as being harmless to the environment and organisms, having readily available raw materials, and exhibiting stable luminescent properties.

[0003] Most methods for synthesizing carbon quantum dots require processes such as dialysis, column chromatography, freeze-drying, and centrifugation. The purification process takes 2 to 5 days, resulting in limited yields and consuming significant amounts of materials and manpower. Chinese patent CN114752257A discloses a method for preparing carbon quantum dot fluorescent anti-counterfeiting ink, but it requires post-processing steps such as centrifugation, dialysis, and freeze-drying, which severely limits its production and application. Summary of the Invention

[0004] The purpose of this invention is to provide a carbon quantum dot fluorescent ink, its preparation method, and its application. The preparation method provided by this invention is fast, low-cost, and requires no complex post-processing.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing carbon quantum dot fluorescent ink, comprising the following steps:

[0007] An alcohol compound, water, and an oxidizing agent are mixed and subjected to a hydrothermal reaction to obtain a mixed dispersion.

[0008] The mixed dispersion was dried to obtain carbon quantum dot fluorescent ink.

[0009] Preferably, the alcohol compound includes one or more of ethanol, isopropanol, triethanolamine, ethylene glycol, and glycerol.

[0010] Preferably, the ratio of the alcohol compound to water is 1g:1-5mL.

[0011] Preferably, the oxidant includes one of hydrogen peroxide, potassium peroxide, and peracetic acid.

[0012] Preferably, the ratio of the oxidant to water is 1g:6-15mL.

[0013] Preferably, the temperature of the hydrothermal reaction is 160–200°C, and the time of the hydrothermal reaction is 2–6 hours.

[0014] Preferably, the drying process includes baking or rotary evaporation;

[0015] The drying temperature is 60–90°C, and the drying time is 2–8 hours.

[0016] The rotary evaporation temperature is 40–80°C, and the rotary evaporation time is 5–20 min.

[0017] Preferably, the solid content of the carbon quantum dot fluorescent ink is 30-70%.

[0018] The present invention provides a carbon quantum dot fluorescent ink prepared by the preparation method described above, comprising carbon quantum dots and a polymer; the size of the carbon quantum dots is 2-5 nm; and the number average molecular weight of the polymer is 40,000-350,000.

[0019] This invention provides the application of the carbon quantum dot fluorescent ink described in the above technical solution in anti-counterfeiting materials.

[0020] This invention provides a method for preparing carbon quantum dot fluorescent ink, comprising the following steps: mixing an alcohol compound, water, and an oxidant, and carrying out a hydrothermal reaction to obtain a mixed dispersion; drying the mixed dispersion to obtain the carbon quantum dot fluorescent ink. The preparation method of this invention employs a one-step synthesis, and the entire preparation process is simple, rapid, and low-cost. The resulting carbon quantum dot fluorescent ink has stable chemical properties, is colorless under natural light after writing, and emits strong fluorescence under ultraviolet light, exhibiting anti-counterfeiting effects. This method solves the problems of complex purification steps, long processing time, and high cost associated with carbon quantum dot fluorescent ink.

[0021] This invention selects alcohol compounds as carbon sources, which are more suitable for the reaction system of this invention compared with raw materials such as citric acid. In the hydrothermal process, the oxidant oxidizes the alcohol compounds to carboxylic acids. Subsequently, the carboxylic acids and alcohol compounds undergo dehydration polymerization under high temperature and high pressure to generate polyester polymers, and carbonization also occurs to obtain carbon quantum dots.

[0022] This invention eliminates the need for any thickeners or lubricants. The viscosity and lubricity of the carbon quantum dot fluorescent ink can be controlled simply by adjusting the feeding ratio, hydrothermal reaction time, and drying time. Therefore, the resulting system can be used directly as fluorescent ink without further purification, greatly saving costs.

[0023] The carbon quantum dot fluorescent ink prepared by this invention has excellent fluorescence properties. The test results show that its ultraviolet absorption spectrum has an absorption peak at 363 nm, indicating that the carbon quantum dot fluorescent ink has undergone a band gap transition at this point. Furthermore, the fluorescence emission spectrum shows an emission peak at 450 nm, indicating that it emits blue-green fluorescence.

[0024] The carbon quantum dot fluorescent ink prepared by this invention has adjustable viscosity. By adjusting different feeding ratios and drying times, ink solutions with different viscosities can be obtained. The adjustable polymer molecular weight was further demonstrated in gel permeation chromatography.

[0025] The preparation method of the present invention can prepare carbon quantum dot fluorescent ink in as little as 3 hours, and has the advantages of short preparation cycle, low cost, environmental friendliness and obvious fluorescence effect. Attached Figure Description

[0026] Figure 1 The transmission electron microscopy (TEM) scan results are shown for the carbon quantum dot fluorescent ink prepared in Example 1 of this invention.

[0027] Figure 2 The results of high-magnification transmission electron microscopy scans of the carbon quantum dots prepared in Example 1 of this invention;

[0028] Figure 3 The fluorescence spectrum of the carbon quantum dot fluorescent ink prepared in Example 1 of this invention;

[0029] Figure 4 Image of the carbon quantum dot fluorescent ink prepared in Example 1 of this invention;

[0030] Figure 5 The images are photographs taken under natural light (a) and ultraviolet light (b) after a pattern is written on paper without fluorescent powder using the carbon quantum dot fluorescent ink prepared in Example 1 of this invention.

[0031] Figure 6 The gel permeation chromatography elution curve and molecular weight statistics of the carbon quantum dot fluorescent ink prepared in Example 1 are shown. Detailed Implementation

[0032] This invention provides a method for preparing carbon quantum dot fluorescent ink, comprising the following steps:

[0033] An alcohol compound, water, and an oxidizing agent are mixed and subjected to a hydrothermal reaction to obtain a mixed dispersion.

[0034] The mixed dispersion was dried to obtain carbon quantum dot fluorescent ink.

[0035] This invention involves mixing an alcohol compound, water, and an oxidizing agent, followed by a hydrothermal reaction to obtain a mixed dispersion. In this invention, the alcohol compound preferably includes one or more of ethanol, isopropanol, triethanolamine, ethylene glycol, and glycerol. In this invention, the preferred ratio of the alcohol compound to water is 1 g: 1–5 mL, more preferably 1 g: 3.3–4.2 mL.

[0036] In this invention, the oxidant preferably includes one of hydrogen peroxide, potassium peroxide, and peracetic acid. In this invention, the ratio of the oxidant to water is preferably 1g:6-15mL, more preferably 1g:10-12.5mL. In this invention, the hydrogen peroxide is preferably added in the form of a hydrogen peroxide solution; the mass concentration of the hydrogen peroxide solution is preferably 30%.

[0037] In this invention, the water is preferably deionized water.

[0038] In this invention, the mixing of the alcohol compound, water and oxidant preferably includes: first mixing the alcohol compound and water, and then adding the oxidant.

[0039] In this invention, the temperature of the hydrothermal reaction is preferably 160-200°C, more preferably 170-180°C; the time of the hydrothermal reaction is preferably 2-6 hours, more preferably 3-5 hours.

[0040] Preferably, after the hydrothermal reaction, the resulting reaction system is naturally cooled to room temperature to obtain a mixed dispersion.

[0041] In a specific embodiment of the present invention, the mixed dispersion is a clear yellow dispersion.

[0042] After obtaining the mixed dispersion, the present invention performs a drying treatment on the mixed dispersion to obtain carbon quantum dot fluorescent ink. In the present invention, the drying treatment preferably includes baking or rotary evaporation. In the present invention, the baking temperature is preferably 60–90°C, more preferably 70–80°C; the baking time is preferably 2–8 hours, more preferably 4–6 hours. In the present invention, the rotary evaporation temperature is preferably 40–80°C, more preferably 60–70°C; the rotary evaporation time is preferably 5–20 minutes, more preferably 10–15 minutes.

[0043] In this invention, the solid content of the carbon quantum dot fluorescent ink is preferably 30-70%, more preferably 40-60%. In this invention, the carbon quantum dot fluorescent ink is a clear yellow dispersion.

[0044] This invention provides a carbon quantum dot fluorescent ink prepared by the method described above, comprising carbon quantum dots and a polymer; the size of the carbon quantum dots is 2-5 nm; the number-average molecular weight of the polymer is 40,000-350,000. In this invention, the carbon quantum dot fluorescent ink exhibits fluidity and lubricity; the carbon quantum dot fluorescent ink emits blue-green fluorescence under ultraviolet light irradiation.

[0045] This invention provides the application of the carbon quantum dot fluorescent ink described in the above technical solution in anti-counterfeiting materials.

[0046] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0047] Example 1

[0048] (1) Mix 4g glycerol, 20mL deionized water and 3mL hydrogen peroxide solution (mass concentration of 30%) to obtain a mixture;

[0049] (2) The mixture was transferred to a hydrothermal reactor, sealed, and reacted at 180°C for 2 hours. After natural cooling to room temperature, a clear yellow dispersion was obtained.

[0050] (3) The clear yellow dispersion was dried at 80°C in air for 6 hours to obtain carbon quantum dot fluorescent ink.

[0051] The number-average molecular weight of the polymer in the carbon quantum dot fluorescent ink prepared in this embodiment is 341,448.

[0052] Example 2

[0053] (1) Mix 6g of ethylene glycol, 25mL of deionized water and 2mL of hydrogen peroxide solution (mass concentration of 30%) to obtain a mixture;

[0054] (2) The mixture was transferred to a hydrothermal reactor, sealed, and reacted at 160°C for 6 hours. After natural cooling to room temperature, a clear yellow dispersion was obtained.

[0055] (3) The clear yellow dispersion was rotary evaporated at 60°C for 20 min to obtain carbon quantum dot fluorescent ink.

[0056] The number-average molecular weight of the polymer in the carbon quantum dot fluorescent ink prepared in this embodiment is 334532.

[0057] Example 3

[0058] (1) Mix 3g glycerol, 3g ethylene glycol, 20mL deionized water and 2g potassium peroxide to obtain a mixture;

[0059] (2) The mixture was transferred to a hydrothermal reactor, sealed, and reacted at 200°C for 2 hours. After natural cooling to room temperature, a clear yellow dispersion was obtained.

[0060] (3) The clear yellow dispersion was dried at 80°C in air for 6 hours to obtain carbon quantum dot fluorescent ink.

[0061] The number-average molecular weight of the polymer in the carbon quantum dot fluorescent ink prepared in this embodiment is 407,355.

[0062] Example 4

[0063] (1) Mix 2g ethanol, 2g isopropanol, 2g ethylene glycol, 25mL deionized water and 3g peracetic acid to obtain a mixture;

[0064] (2) The mixture was transferred to a hydrothermal reactor, sealed and reacted at 170°C for 3 hours, and then naturally cooled to room temperature to obtain a clear yellow dispersion.

[0065] (3) The clear yellow dispersion was dried at 60°C in air for 8 hours to obtain carbon quantum dot fluorescent ink.

[0066] The number-average molecular weight of the polymer in the carbon quantum dot fluorescent ink prepared in this embodiment is 173302.

[0067] Test case

[0068] Figure 1 The above are transmission electron microscopy (TEM) scans of the carbon quantum dot fluorescent ink prepared in Example 1 of this invention. Figure 1 The dark-colored dots are carbon quantum dots, while the other irregular parts are polymers.

[0069] Figure 2 The high-magnification transmission electron microscopy scanning results of the carbon quantum dots prepared in Example 1 of this invention are shown below. Figure 1 When magnified, the darker areas show distinct lattice fringes with a spacing of approximately 0.28 nm, consistent with the structure of carbon quantum dots.

[0070] Figure 3 The fluorescence spectrum of the carbon quantum dot fluorescent ink prepared in Example 1 of this invention shows that after ultraviolet light irradiation, the emission range of the carbon quantum dot fluorescent ink is in the blue-green light range.

[0071] Figure 4 Images of the carbon quantum dot fluorescent ink prepared in Example 1 of this invention are provided by [the relevant authority / organization]. Figure 4It can be seen that the carbon quantum dot fluorescent ink is a clear yellow dispersion with good dispersibility.

[0072] The carbon quantum dot fluorescent ink prepared in Example 1 of this invention was used to write patterns on phosphorless paper. The photographs under natural light (a) and ultraviolet light (b) are shown below. Figure 5 As shown, by Figure 5 As can be seen, the carbon quantum dot fluorescent ink provided by this invention, after being written and dried, leaves no obvious traces under natural light, but displays the written pattern under ultraviolet light, thus achieving an effective anti-counterfeiting effect.

[0073] The test results of Examples 2 to 4 are similar to those of Example 1.

[0074] Figure 6 The gel permeation chromatography elution curve and molecular weight statistics of the carbon quantum dot fluorescent ink prepared in Example 1 show that its number-average molecular weight is 341448.

[0075] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon quantum dot fluorescent ink, comprising the following steps: An alcohol compound, water, and an oxidizing agent are mixed and subjected to a hydrothermal reaction to obtain a mixed dispersion. The mixed dispersion was dried to obtain carbon quantum dot fluorescent ink; The ratio of the alcohol compound to water is 1g:1~5mL; The ratio of the oxidant to water is 1g:6~15mL; The carbon quantum dot fluorescent ink comprises carbon quantum dots and a polymer; the size of the carbon quantum dots is 2-5 nm; and the number-average molecular weight of the polymer is 40,000-350,000.

2. The preparation method according to claim 1, characterized in that, The alcohol compounds include one or more of ethanol, isopropanol, triethanolamine, ethylene glycol, and glycerol.

3. The preparation method according to claim 1, characterized in that, The oxidant includes one of hydrogen peroxide, potassium peroxide, and peracetic acid.

4. The preparation method according to claim 1, characterized in that, The hydrothermal reaction temperature is 160~200℃, and the hydrothermal reaction time is 2~6h.

5. The preparation method according to claim 1, characterized in that, The drying process includes drying or rotary evaporation; The drying temperature is 60~90℃, and the drying time is 2~8h; The rotary evaporation temperature is 40~80℃, and the rotary evaporation time is 5~20min.

6. The preparation method according to claim 1 or 5, characterized in that, The solid content of the carbon quantum dot fluorescent ink is 30-70%.

7. The carbon quantum dot fluorescent ink prepared by the preparation method according to any one of claims 1 to 6 comprises carbon quantum dots and a polymer; the size of the carbon quantum dots is 2 to 5 nm; and the number average molecular weight of the polymer is 40,000 to 350,000.

8. The application of the carbon quantum dot fluorescent ink according to claim 7 in anti-counterfeiting materials.

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