A solvothermal method for the synthesis of dye-based full-color fluorescent carbon dots

Abstract

The present invention discloses a solvent-thermal method for synthesizing dye-based full-color fluorescent carbon dots, relating to the technical field of carbon dot materials. The present invention comprises at least the following steps: S1: mixing a certain amount of 2-aminoterephthalic acid and Nile Blue A, dissolving them in ethanol, and ultrasonically treating them at room temperature for 5 minutes to mix them evenly; S2: transferring the mixture to a 25mL polytetrafluoroethylene-lined reactor and heating it in a stainless steel autoclave. The present invention selects 2-aminoterephthalic acid and Nile Blue A as precursors, avoiding tedious debugging processes during the process. Multicolor fluorescent carbon dots are successfully prepared through a one-step solvent-thermal method without adjusting other steps. Studies have found that the fluorescence emission peak exhibits a continuous red shift from 440nm deep blue to 628nm red, achieving wide color gamut coverage. In addition, based on their excellent optical properties, the prepared blue, cyan, and red carbon dots are used as fluorescent inks and carbon dot / polyvinyl alcohol composites, which have been successfully used in information encryption and anti-counterfeiting fields.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dot materials, in particular to a solvent thermal method for synthesizing dye-based full-color fluorescent carbon dots. Background Art

[0002] As a new type of photoluminescent carbon-based nanomaterial with an average size of less than 10nm, carbon dots (Cdots) have ideal properties such as abundant raw materials, low toxicity, long life, high photostability and biocompatibility. These unique properties have attracted scientists to conduct in-depth research on the formation process and optical and biological applications of Cdots. They have great potential in the fields of light-emitting devices, anti-counterfeiting, biosensors, photocatalysis, therapy and bioimaging. Since the first discovery of Cdots in 2004, their optical properties and applications have been widely studied. To date, researchers have explored the preparation of tunable multicolor Cdots and related luminescence mechanisms through a large number of studies, such as by changing the synthesis method, carbon source, reaction temperature, reaction solvent, reaction time and pH. The most common raw materials are citric acid and phenylenediamine substances, which have been widely used in the preparation of Cdots.

[0003] Currently, most multi-color carbon dots are prepared by hydrothermal / solvothermal methods, which makes it difficult to precisely control the synthesis process, resulting in mostly monochromatic luminescence.

[0004] At the same time, in most cases, the emission wavelength of carbon dots is mainly concentrated in the blue to yellow fluorescence emission region, and generally has a relatively low fluorescence quantum yield, which greatly limits their practical applications in light-emitting devices, information encryption and bioimaging.

[0005] In addition, the fluorescence properties of carbon dots are affected by many factors, such as the choice of reactant types, raw material ratios, time, solvents, temperature, and acidity and alkalinity. Therefore, continuous attempts and repetitions are required to achieve tunable emission, and the steps are cumbersome. In summary, designing a controllable synthesis strategy for tunable carbon dots with full spectrum coverage, achieving high quantum yields of multicolor carbon dots, and having broad and innovative applications remains an important challenge. Summary of the Invention

[0006] The purpose of the present invention is to provide a solvent-thermal method for synthesizing dye-based full-color fluorescent carbon dots to solve the existing problem: the existing methods for preparing carbon dots are often relatively complicated, and the raw materials used are mostly common substances such as citric acid and phenylenediamine, and the obtained carbon dots cannot cover a wide color gamut.

[0007] To achieve the above object, the present invention provides the following technical solution: a solvothermal method for synthesizing dye-based full-color fluorescent carbon dots, comprising at least the following steps:

[0008] S1: A certain amount of 2-aminoterephthalic acid and Nile Blue A were mixed and dissolved in ethanol, and then ultrasonicated at room temperature for 5 minutes to mix them evenly;

[0009] S2: The mixture was transferred to a 25 mL polytetrafluoroethylene-lined reactor and heated in a stainless steel autoclave;

[0010] S3: Purification pretreatment: After the product is naturally cooled to room temperature, centrifuge it, collect the supernatant and filter it;

[0011] S4: dichloromethane and methanol as eluents;

[0012] S5: Thin-layer chromatography (TLC) was used to separate the carbon dots of different polarities in the red supernatant, and six types of carbon dots were obtained: blue, cyan, yellow-green, orange, red, and dark red.

[0013] S6: Finally, the obtained carbon dot samples with different fluorescence are redispersed in ethanol.

[0014] Preferably, the amount of 2-aminoterephthalic acid in S1 is 0.3 mmol, and the amount of Nile Blue A in S1 is 0.025 mmol.

[0015] Preferably, the amount of ethanol in S1 is 5 ml.

[0016] Preferably, the heating temperature in the stainless steel autoclave in S2 is 160° C. for 8 hours.

[0017] Preferably, the rotation speed of the centrifugal treatment in S3 is 10000 rpm and the time is 10 min.

[0018] Preferably, the filtration device used for collecting and filtering the supernatant in S3 is a microporous membrane with a pore size of 0.22 μm.

[0019] Preferably, the volume ratio of dichloromethane to methanol in S4 is 80:1.

[0020] The preparation of the carbon dot / polyvinyl alcohol composite material comprises at least the following steps:

[0021] Dissolve 3 g of polyvinyl alcohol solid in 10 mL of ultrapure water, heat with an electric stove and continue stirring until the solid is completely dissolved;

[0022] A certain amount of carbon dots were added to the polyvinyl alcohol solution and stirred continuously to form a homogeneous mixture;

[0023] The mixture is used to coat different shapes and allowed to stand for more than 6 hours in a natural environment for curing to obtain carbon dot / polyvinyl alcohol composite materials of different colors.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention uses 2-aminoterephthalic acid and Nile Blue A as precursors, avoiding tedious debugging processes. Multicolor fluorescent carbon dots are successfully prepared through a one-step solvothermal method without adjusting other steps (solvent, temperature, time, acidity and alkalinity). Studies have found that the fluorescence emission peak exhibits a continuous red shift from 440nm (deep blue) to 628nm (red), achieving wide color gamut coverage.

[0026] 2. The raw materials used in this invention are no longer common substances such as citric acid and phenylenediamine, but 2-aminoterephthalic acid and dye-based Nile Blue A, which provides a new idea for the preparation of luminescent tunable carbon dot materials;

[0027] 3. Based on their excellent optical properties, the blue, cyan and red carbon dots prepared in the present invention are used as fluorescent inks and carbon dot / polyvinyl alcohol composite materials, which can be better applied in the fields of information encryption and anti-counterfeiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 Schematic diagram of the synthesis of tunable multicolor carbon dots of the present invention and their applications in information encryption and anti-counterfeiting;

[0030] Figure 2 is the fluorescence quantum yield of the multicolor carbon dots of the present invention. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0032] Example 1:

[0033] A solvothermal method for synthesizing dye-based full-color fluorescent carbon dots comprises at least the following steps:

[0034] The target carbon dots were synthesized by a one-step solvothermal method using 2-aminoterephthalic acid and Nile Blue A as the precursors, respectively.

[0035] The steps are as follows: 2-aminoterephthalic acid (0.3 mmol) and Nile Blue A (0.025 mmol) were mixed and dissolved in ethanol (5 mL). The mixture was then ultrasonically mixed at room temperature for 5 minutes to achieve uniform mixing. The mixture was then transferred to a 25 mL polytetrafluoroethylene-lined reactor and heated at 160°C in a stainless steel autoclave for 8 hours. For purification, the product was allowed to cool naturally to room temperature and then centrifuged (10,000 rpm for 10 minutes). The supernatant was collected and filtered (through a 0.22 μm microporous membrane). The resulting red supernatant was then separated by thin-layer chromatography (TLC) using dichloromethane and methanol (80:1 by volume) as eluents to yield six different carbon dot colors: blue, cyan, yellow-green, orange, red, and deep red. Finally, the resulting fluorescent carbon dot samples were redispersed in ethanol.

[0036] 2-aminoterephthalic acid (2-ATA) and Nile Blue A (Nile Blue A) were selected as precursors, and the tedious debugging process was avoided during the process. Multi-color fluorescent carbon dots were successfully prepared through a one-step solvothermal method without adjusting other steps (solvent, temperature, time, acidity and alkalinity, etc.). The study found that the fluorescence emission peak showed a continuous red shift from 440nm (deep blue) to 628nm (red), achieving a rare wide color gamut coverage (such as Figure 1 ).

[0037] The prepared carbon dots have good photostability and high quantum yield, among which the quantum yields of blue carbon dots (B-carbon dots), cyan carbon dots (G-carbon dots) and red carbon dots (R-carbon dots) are 22.71%, 9.59% and 18.77%, respectively ( Figure 2 ).

[0038] Example 2:

[0039] This embodiment is used in the above embodiment 1, and the carbon dots prepared in embodiment 1 are compounded with polyvinyl alcohol to prepare a carbon dot / polyvinyl alcohol composite material.

[0040] The preparation of the carbon dot / polyvinyl alcohol composite material comprises at least the following steps:

[0041] Dissolve 3 g of polyvinyl alcohol solid in 10 mL of ultrapure water, heat with an electric stove and continue stirring until the solid is completely dissolved;

[0042] A certain amount of carbon dots were added to the polyvinyl alcohol solution and stirred continuously to form a homogeneous mixture;

[0043] The mixture is used to coat different shapes and allowed to stand for more than 6 hours in a natural environment for curing to obtain carbon dot / polyvinyl alcohol composite materials of different colors.

[0044] Based on their excellent optical properties, the prepared blue, cyan and red carbon dots are used as fluorescent inks and carbon dot / polyvinyl alcohol composites for use in information encryption and anti-counterfeiting.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for synthesizing dye-based full-color fluorescent carbon dots by a solvothermal method, characterized in that: At least the following steps are included: S1: A certain amount of 2-aminoterephthalic acid and Nile Blue A are mixed and dissolved in ethanol, and then ultrasonically treated at room temperature for 5 minutes to mix uniformly. The amount of 2-aminoterephthalic acid in S1 is 0.3 mmol, the amount of Nile Blue A in S1 is 0.025 mmol, and the amount of ethanol in S1 is 5 ml; S2: The mixture was transferred to a 25 mL polytetrafluoroethylene-lined reactor and heated in a stainless steel autoclave. The heating temperature in the stainless steel autoclave in S2 was 160° C. for 8 h. S3: Purification pretreatment: After the product is naturally cooled to room temperature, centrifuge it, collect the supernatant and filter it; S4: using dichloromethane and methanol as eluents, wherein the volume ratio of dichloromethane to methanol in S4 is 80:1; S5: Thin-layer chromatography was used to separate the carbon dots of different polarities in the red supernatant, and six types of carbon dots were obtained: blue, cyan, yellow-green, orange, red, and dark red. S6: Finally, the obtained carbon dot samples with different fluorescence are redispersed in ethanol.

2. The method for synthesizing dye-based full-color fluorescent carbon dots by a solvothermal method according to claim 1, wherein: The centrifugal treatment in S3 is performed at a rotation speed of 10,000 rpm for 10 minutes.

3. The method for synthesizing dye-based full-color fluorescent carbon dots by a solvothermal method according to claim 1, wherein: The filtration device used for collecting the supernatant and filtering in S3 is a microporous membrane with a pore size of 0.22 μm.

4. The method for synthesizing dye-based full-color fluorescent carbon dots by a solvothermal method according to claim 1, wherein: The preparation of the carbon dot / polyvinyl alcohol composite material comprises at least the following steps: Dissolve 3 g of polyvinyl alcohol solid in 10 mL of ultrapure water, heat with an electric stove and continue stirring until the solid is completely dissolved; A certain amount of carbon dots were added to the polyvinyl alcohol solution and stirred continuously to form a homogeneous mixture; The mixture is used to coat different shapes and allowed to stand for more than 6 hours in a natural environment for curing to obtain carbon dot / polyvinyl alcohol composite materials of different colors.

Images