Preparation method of red-light and yellow-light carbon dots with aggregation-induced emission characteristic

Abstract

The invention relates to the technical field of preparation of novel functional materials, and particularly discloses a preparation method of red-light and yellow-light carbon dots with aggregation-induced emission characteristics, which comprises the following steps of: 1, mixing absolute ethyl alcohol and deionized water according to the ratio of 1: 1 to obtain a mixed solvent; step 2, respectively adding sodium chloride, o-phenylenediamine and D-arginine into the mixed solvent obtained in the step 1, and stirring for 10 minutes by using a magnetic stirrer to ensure that solutes are fully dissolved and uniformly mixed; 3, the prepared solution is poured into a discrete electrode container, positive and negative electrode carbon rods are placed close to each other, voltage and current are applied to the carbon rods, and electrochemical synthesis of carbon quantum dots is carried out; step 4, filtering the carbon quantum dot solution obtained after electrochemical synthesis through filter paper, and then standing the filtered solution for 36 hours to further purify the carbon quantum dots; and step 5, putting the solution after standing into a drying oven, and drying for 8-12 hours at the temperature of 80-120 DEG C until the solution is completely dried.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of novel functional materials, and specifically to a method for preparing red and yellow carbon dots with aggregation-induced emission characteristics. Background Art

[0002] As a class of highly regarded luminescent nanomaterials, carbon dots (CDs) have significant advantages such as easy preparation and purification, low cost, excellent biocompatibility, and flexible adjustment of optical and surface properties, showing broad application prospects in many fields. However, the current carbon dot technology still faces many challenges on the road to large-scale industrial production and practical applications. Most carbon dots are easily interfered by polymerization in practical applications, excessive resonance energy transfer or direct π-π stacking effects, resulting in the aggregation-induced quenching (ACQ) phenomenon like organic molecules, greatly limiting the effective application of carbon dots in high-concentration or solid-state environments and significantly reducing their application scope.

[0003] Currently, to achieve the solid-state emission of carbon dots, it is a relatively common method to disperse carbon dots in other matrix materials (such as transparent polymers, silica xerogels, starches, etc.) to prepare composite materials. However, while solving problems, this method also introduces new troubles. On the one hand, the use of additional matrix materials will inevitably lead to an increase in preparation costs; on the other hand, the formation process of composite materials may have an adverse impact on some properties of the carbon dots themselves. For example, when increasing the carbon dot loading rate, it often inevitably causes a serious decrease in the photoluminescence quantum yield (PLQY), which significantly hinders the commercial development of carbon dot-based white light-emitting diodes (WLEDs) and weakens the competitiveness of carbon dots in actual market applications; therefore, a method for preparing red and yellow carbon dots with aggregation-induced emission characteristics is provided.

[0004] The present invention uses a relatively simple and efficient one-step electrochemical method to synthesize red and yellow carbon dots that can exhibit aggregation-induced emission characteristics. Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies of the prior art by providing a method for preparing red and yellow carbon dots with aggregation-induced emission characteristics to solve the problems raised in the above background art. Specifically, a relatively simple and efficient one-step electrochemical method is used to synthesize red and yellow carbon dots that can exhibit aggregation-induced emission characteristics, providing a new and reliable synthesis route and application for red and yellow carbon dots. This method applies positive and negative voltages to two carbon rods, and uses the redox reactions at the cathode and anode to construct the differentiation of surface state modulation, introduce new functional groups on the surface of carbon quantum dots, and directly synthesize carbon quantum dots with both red and yellow light. The present invention is a one-step preparation method, which is fast, efficient, and simple.

[0006] To achieve the above object, the present invention provides the following technical solution: A preparation method of red and yellow carbon dots with aggregation-induced emission characteristics, the method comprising the following steps:

[0007] Step 1: Put anhydrous ethanol and deionized water into a beaker in a ratio of 1:1 and mix to obtain a mixed solvent;

[0008] Step 2: Add sodium chloride, o-phenylenediamine and D-arginine into the mixed solvent obtained in Step 1 respectively, and stir with a magnetic stirrer for 10 minutes to ensure that the solutes are fully dissolved and mixed evenly;

[0009] Step 3: Pour the prepared solution into a discrete electrode container, place the positive and negative carbon rods close to each other, apply voltage and current to the carbon rods, and perform electrochemical synthesis of carbon quantum dots;

[0010] Step 4: Filter the carbon quantum dot solution obtained after electrochemical synthesis through a filter paper with a pore size of 3-6 μm to remove impurities and unreacted raw materials, and then let the filtered solution stand for 36 hours to further purify the carbon quantum dots;

[0011] Step 5: Put the standing solution into an oven and dry it at a temperature of 80-120 °C for 8-12 hours until the solution is completely dry; Subsequently, grind the dried carbon quantum dots into powder to obtain red and yellow carbon quantum dot powder with aggregation-induced emission characteristics.

[0012] As a preferred technical solution of the present invention, the mass ratio of the addition amounts of sodium chloride, o-phenylenediamine and D-arginine in Step 2 is 2:0.09:0.5.

[0013] As a preferred technical solution of the present invention, the electrochemical etching conditions in Step 3 are: voltage 40-60V, current 0.2-0.4A, electrolysis time 1-3h, room temperature condition.

[0014] As a preferred technical solution of the present invention, the particle size of the ground carbon quantum dot powder in Step 5 is 2-4nm.

[0015] Red and yellow carbon dots with aggregation-induced emission characteristics prepared by the above preparation method are used to manufacture yellow and white LED light-emitting diodes.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] The carbon quantum dots obtained by one-step electrochemical synthesis employed in the present invention have many remarkable advantages. Different from traditional electrochemical methods, this method utilizes the redox reactions of the anode and cathode to construct a differential strategy for surface state modulation, thereby obtaining CDs with controllable emission on separate electrodes simultaneously. First, positive and negative voltages are applied to two carbon rods, and the redox reactions of the cathode and anode are used to construct the differential of surface state modulation. A quantitative amount of D-amino acid is added to introduce new functional groups onto the surface of the carbon quantum dots, directly synthesizing carbon quantum dots that emit both red and yellow light. It is found that the tunable emission of CDs mainly stems from the different bombardment effects of active free radicals (hydroxyl radicals, oxygen radicals, and ionic radicals), while phenylenediamine tends to introduce amino groups onto the surface of CD-, and at the same time introduce nitrogen atoms into the carbon nuclear framework, resulting in different sizes and formations of graphitic N in CD- and CD+. Among them, the addition of D-arginine is the key to achieving solid-state luminescence. Functional groups in arginine (such as amino groups, etc.) may form specific interactions with the surface of the carbon dots, thereby adjusting the surface state of the carbon dots and achieving fine tuning of the luminescence performance. Its addition may improve the stacking mode of the carbon dots in the solid state and reduce the luminescence quenching phenomenon caused by factors such as aggregation, thus achieving effective solid-state luminescence. Based on the one-step electrochemical method for synthesizing aggregation-induced emission red and yellow light carbon quantum dots, we fabricated light-emitting diodes of different colors. The improved electrochemical method is of great significance for fine spectral modulation and efficient synthesis, providing a new and reliable synthesis route and application for red and yellow light carbon dots.

[0018] The carbon quantum dots prepared by the technical solution of the present invention have a fixed-form graphite phase structure. The morphology of the sample is granular, the size of the quantum dots is several nanometers, and it contains chemical bonds such as C-O, C-N, C═C / C═N, and O-H / N-H. The prepared carbon quantum dots can be applied to the manufacture of yellow and white light LED light-emitting diodes. Description of the Drawings

[0019] Figure 1 It is a high-magnification transmission electron microscope image of red and yellow emission carbon quantum dots prepared by the one-step electrochemical method of the present invention; in the figure, A is the high-magnification transmission electron microscope image of red emission carbon quantum dots; B is the high-magnification transmission electron microscope image of yellow emission carbon quantum dots;

[0020] Figure 2 It is the solution excitation-emission spectrum of red and yellow light emission carbon quantum dots prepared by the one-step electrochemical method of the present invention;

[0021] In the figure, A is the solution emission spectrum of the carbon quantum dots; B is the solution excitation spectrum of the carbon quantum dots;

[0022] Figure 3 It is the powder excitation-emission spectrum of red and yellow light emission carbon quantum dots prepared by the one-step electrochemical method of the present invention;

[0023] In the figure, A is the powder emission spectrum of carbon quantum dots; B is the powder excitation spectrum of carbon quantum dots;

[0024] Figure 4 is the UV-absorption spectrum of red- and yellow-emitting carbon quantum dots prepared by the one-step electrochemical method of the present invention;

[0025] Figure 5 is the FTIR spectrum of red- and yellow-emitting carbon quantum dots prepared by the one-step electrochemical method of the present invention;

[0026] Figure 6 is the powder diagram of carbon quantum dots after drying the solution of red- and yellow-emitting carbon quantum dots prepared by the one-step electrochemical method of the present invention;

[0027] Figure 7 is the fingerprint recognition application of red- and yellow-emitting carbon quantum dots prepared by the one-step electrochemical method of the present invention. Detailed implementation mode

[0028] The following elaborates on the preferred embodiments of the present invention in conjunction with the attached drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making the protection scope of the present invention more clearly defined.

[0029] Example: Please refer to Figure 1 , the present invention provides a technical solution: a preparation method of red- and yellow-emitting carbon quantum dots with aggregation-induced emission, and the specific steps are as follows:

[0030] Step 1: Put absolute ethanol and deionized water into a beaker in a ratio of 1:1 and mix to obtain a mixed solvent;

[0031] Step 2: Add sodium chloride, o-phenylenediamine, and D-arginine to the mixed solvent obtained in Step 1 respectively, and stir with a magnetic stirrer for 10 minutes to ensure that the solutes are fully dissolved and mixed evenly;

[0032] Step 3: Pour the prepared solution into a discrete electrode container, place the positive and negative carbon rods close to each other, apply voltage and current to the carbon rods, and perform electrochemical synthesis of carbon quantum dots;

[0033] Step 4: Filter the carbon quantum dot solution obtained after electrochemical synthesis through a 3-6 μm filter paper to remove impurities and unreacted raw materials, and then let the filtered solution stand for 36 hours to further purify the carbon quantum dots;

[0034] Step 5: Put the standing solution into an oven and dry it at a temperature of 80-120 °C for 8-12 hours until the solution is completely dry; subsequently, grind the dried carbon quantum dots into powder to obtain red- and yellow-emitting carbon quantum dot powder with aggregation-induced luminescence characteristics.

[0035] The core of the present invention lies in the synthesis of red and yellow carbon quantum dots with aggregation-induced emission by a one-step electrochemical method. Compared with some preparation methods under high temperature and high pressure (such as hydrothermal method, solvothermal method, etc.), the electrochemical method can usually be carried out at normal temperature and pressure without extreme temperature and pressure conditions. In this way, the experimental operation is safer and simpler. This method applies positive and negative voltages to two carbon rods, and constructs the differentiation of surface state modulation through the redox reactions of the cathode and anode, introduces new functional groups on the surface of the carbon quantum dots, and directly synthesizes carbon quantum dots with both red and yellow light. At the same time, this method can precisely control the reaction process, promote the full conversion of the carbon source into carbon quantum dots, thereby improving the utilization rate of raw materials and reducing production costs.

[0036] The present invention conducts the following testing means on the prepared carbon quantum dots: transmission electron microscopy (transmission electron microscope (JEOL, 2100)), infrared spectroscopy (Fourier transform infrared spectroscopy (Bruker, WQF-410), the testing range is 500 to 3000 wavenumbers), ultraviolet-visible absorption spectroscopy (Hitachi, U-3900H), the testing range is 200 - 800 nm, excitation and emission spectra (fluorescence spectrometer (Hitachi, F-7000), the emission spectrum testing range is 350 - 700 nm, using monochromatic light with an excitation light of 365 nm, the excitation spectrum range is 230 - 420 nm).

[0037] Test results:

[0038] As Figure 1 shown, Figure 1 A in Figure 1 is a high-magnification transmission electron micrograph of red-emitting carbon quantum dots;

[0039] As Figure 2 shown, it is the solution excitation and emission spectrum diagram of red and yellow light-emitting carbon quantum dots prepared by the one-step electrochemical method of the present invention. From Figure 2It can be seen from A in [reference] that they all have excitation independence. Y-CD has a single emission peak at around 580 nm, and the excitation wavelength is in the range of 420 nm to 500 nm. R-CD has dual emission peaks at 605 nm and 645 nm, and the excitation wavelength is in the range of 540 nm to 620 nm. This can be attributed to different surface states formed by phenylenediamine. From Figure 2 It can be seen from B in [reference] that R-CD and Y-CD have multiple excitation peaks, which can confirm that functional groups containing oxygen, nitrogen, etc. (such as carboxyl groups and amino groups) will introduce surface states and form additional excitation channels, resulting in multiple excitation peaks.

[0040] Such as Figure 3 As shown, it is the powder excitation-emission spectrogram of red and yellow emission carbon quantum dots prepared by the one-step electrochemical method of the present invention. Compared with the spectrogram of the solution, it can be seen that the overall change in the emission spectrum is not significant, and the position and width of the excitation spectrum peaks have changed. This is because in the solution, the molecules are surrounded by solvent molecules, and the intermolecular interaction is mainly with the solvent. In the powder state, the direct intermolecular interaction is enhanced, and different aggregated state structures may be formed. This change in intermolecular force will affect the electron cloud distribution and energy level structure of the molecules, and thus affect the excitation spectrum.

[0041] Such as Figure 4 As shown, it is the UV-absorption spectrogram of red and yellow emission carbon quantum dots prepared by the one-step electrochemical method of the present invention. The absorption band shown in the figure at 233 - 450 nm belongs to the n-π* transition of the aromatic sp2 system containing C=O and C=N bonds. This confirms that different energy states are the result of the formation of functional surface states by redox reactions.

[0042] Such as Figure 5 As shown, it is the FTIR spectrogram of red and yellow emission carbon quantum dots prepared by the one-step electrochemical method. The FTIR peaks of CD at 1080 cm-1, 1402 cm-1, 1550 - 1600 cm-1, and 3320 - 3510 cm-1 are identified as C-O, C-N, C=C / C=N, and O-H / N-H, which confirms the existence of conjugated aromatic structures and groups containing O and N.

[0043] Such as Figure 6 As shown, it is the powder diagram after the carbon quantum dots are prepared by drying the solution of red and yellow emission carbon quantum dots prepared by the one-step electrochemical method. The left figure is irradiated by a fluorescent lamp at 365 nm, showing red and yellow emissions respectively; the right figure is to dissolve the carbon quantum dot powder in absolute ethanol to remove NaCl, and then put it in an oven to dry. After being irradiated by the fluorescent lamp, it still shows red and yellow emissions, confirming that NaCl does not damage the core structure of the carbon quantum dots and is not the factor causing a fundamental change in their fluorescence properties, so it can still maintain the original luminescence characteristics.

[0044] Such as Figure 7As shown, it is the fingerprint recognition application of red and yellow emissive carbon quantum dots prepared by the one-step electrochemical method of the present invention. The prepared CDs have strong solid-state and lipophilic fluorescence characteristics and are excellent powder phosphors. Different potential fingerprints can be detected by the powder detection method. The prepared red and yellow carbon quantum dot powders are respectively used for fingerprint detection. After development on a glass slide, due to the high contrast of the fluorescence signal, not only can the fingerprint image be clearly observed, but also the characteristics of the fingerprint such as bifurcations, islands, endings, loops, cores, ridges, intersections, etc. can be clearly observed. This indicates that the CDs with aggregation-induced emission prepared by the present invention can clearly display the fine structure of fingerprints in fingerprint detection.

[0045] Based on the above results, it can be seen that the method for synthesizing red and yellow carbon quantum dots with aggregation-induced emission by the one-step electrochemical method proposed by the present invention is extremely simple, efficient, convenient and fast, and has great potential for industrial production. In addition, the surface of the quantum dots has rich chemical bonds and surface functional groups (such as amino groups), which is very conducive to surface functionalization and also has broad application prospects in the fields of optoelectronic devices, information anti-counterfeiting, etc.

[0046] The above embodiments only express the implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for preparing red and yellow carbon dots with aggregation-induced emission characteristics, characterized in that: The method comprises the following steps: Step 1: Put anhydrous ethanol and deionized water into a beaker in a ratio of 1:1 to obtain a mixed solvent; Step 2: Sodium chloride, o-phenylenediamine and D-arginine are added to the mixed solvent obtained in step 1, and stirred for 10 minutes using a magnetic stirrer to ensure that the solutes are fully dissolved and mixed evenly; Step 3: Pour the prepared solution into a separate electrode container, place the positive and negative carbon rods close to each other, apply voltage and current to the carbon rods, and perform electrochemical synthesis of carbon quantum dots; Step 4: Filter the carbon quantum dot solution obtained after electrochemical synthesis through a 3-6 um filter paper to remove impurities and unreacted raw materials, and then let the filtered solution stand for 36 hours to further purify the carbon quantum dots; Step 5: Place the static solution into an oven and dry it at 80-120°C for 8-12 hours until the solution is completely dry; then, grind the dried carbon quantum dots into powder to obtain red and yellow carbon quantum dot powders with aggregation-induced emission properties.

2. The method for preparing red and yellow carbon dots with aggregation-induced emission characteristics according to claim 1, characterized in that: In step 2, the mass ratio of the added amounts of sodium chloride, o-phenylenediamine and D-arginine is 2:0.09:0.

5.

3. The method for preparing red and yellow carbon dots with aggregation-induced emission characteristics according to claim 1, characterized in that: The electrochemical etching conditions in step 3 are: voltage 40-60 V, current 0.2-0.4 A, electrolysis time 1-3 h, and room temperature.

4. The method for preparing red and yellow carbon dots with aggregation-induced emission characteristics according to claim 1, characterized in that: The particle size of the carbon quantum dot powder after grinding in step 5 is 2-4 nm.

5. Red and yellow carbon dots with aggregation-induced emission characteristics prepared by the preparation method according to any one of claims 1 to 4 are used to manufacture yellow and white LED light-emitting diodes.

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