Preparation method of rare earth ion doped carbon quantum dot fluorescent material

Abstract

The invention provides a preparation method of a rare earth ion doped carbon quantum dot fluorescent material, the chemical structural formula of the fluorescent material is CQDs: x% Eu, and x is equal to 1-30. The fluorescent material has the characteristics of efficient and stable luminous efficiency, wide excitation / emission spectrum range and tunability, can be excited by a commercial near ultraviolet chip or blue light chip, can be used for manufacturing an energy-saving white light LED with high luminous efficiency, is expected to save more than 70% of energy compared with a conventional LED, can be widely applied to urban illumination, plant light supplement and the like, and has wide application prospects. And support is provided for saving urban power consumption. Besides, the emission spectrum of the fluorescent material can shift along with the change of the pH value of a solution or the change of the concentration of heavy metal ions contained in the fluorescent material, so that the fluorescent material can be used for high-sensitivity and repeatable visual fluorescence detection, such as food safety, water quality detection, biological imaging and the like; the preparation method fully achieves the technical purposes of high efficiency and economy on the premise of ensuring the product performance, and is high in practicability.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorescent materials, and in particular relates to a method for preparing a rare earth ion-doped carbon quantum dot fluorescent material. Background Art

[0002] Carbon quantum dots are new nanomaterials with carbon as the skeleton structure. They are dispersed, spherical nanoparticles with a size of less than 10nm and a large number of reactive functional groups on the surface. In addition to the characteristics similar to traditional semiconductor quantum dots, carbon quantum dots also have adjustable excitation / emission characteristics, easy functionalization, high stability, water solubility and a wide range of raw material sources. The materials for preparing carbon dots are very simple and easy to obtain. For example, bananas, orange juice, sweet potatoes, watermelon rinds, poplar leaves, wheat straw, carbon nanotubes, graphite and other carbon-containing materials can be used as raw materials for preparing carbon dots. However, the current preparation cycle of carbon quantum dots is relatively long, the reaction efficiency is low, the reaction time is usually more than 20 hours, and the prepared carbon quantum dots are uneven in size and have poor reproducibility, making it difficult to fully reflect the excellent optical properties of carbon quantum dots.

[0003] As important strategic elements, rare earth elements have been widely used in the field of high-tech, and have shown an increasingly prominent position in the process of economic, scientific and technological construction. Rare earth elements have very rich energy level structures and special optical properties. The special electronic structure and energy level transition of rare earth ions can give carbon quantum dots new fluorescent properties and functions. When rare earth ions are combined with fluorescent carbon quantum dots, the fluorescence intensity of fluorescent carbon quantum dots can be significantly enhanced and their emission color can be regulated through energy transfer and synergistic effects. Rare earth-doped carbon quantum dots combine the advantages of quantum dots and rare earth metals, retaining the good biocompatibility and easy functionalization of carbon quantum dots, and achieving wide-spectrum emission and fluorescence performance through the doping of rare earth metals. This new type of nanomaterial has broad application prospects in the fields of bioanalysis, bioimaging, optoelectronic devices, etc.

[0004] In the prior art, there are few studies on rare earth ion doped carbon quantum dot fluorescent materials:

[0005] Application number: CN202410950287.8 discloses a quantum dot-doped lanthanide covalent organic framework hybrid material, a preparation method thereof, and an application in the detection of 2-aminoacetophenone. It mainly prepares CQDs and Eu synthetic dust in different steps. The preparation of CQDs uses silane coupling agent KH550 as raw material, the reaction cycle is more than 12 hours, the raw materials are expensive and the preparation cycle is long.

[0006] Based on this, the preparation of a rare earth ion doped carbon quantum dot fluorescent material with short cycle, strong performance, low cost and high practicality has become a new goal. Those skilled in the art It is of utmost importance. Summary of the invention

[0007] The purpose of the present invention is to propose a method for preparing rare earth ion-doped carbon quantum dots with short preparation time and tunable spectrum. The fluorescent material can be combined with commercial near-ultraviolet / blue light chips to produce efficient and energy-saving white light LEDs, and can also be used for visualized pH value and heavy metal ion fluorescence detection.

[0008] To achieve the above object, the present invention proposes a method for preparing a rare earth ion doped carbon quantum dot fluorescent material, wherein the chemical structural formula of the fluorescent material is: CQDs: x% Eu, wherein x=1-30; characterized in that the method comprises the following steps:

[0009] S1: weigh raw materials: oleic acid, oleylamine, EuCl3·6H2O and dimethylformamide solution;

[0010] S2: Place the above raw materials in a beaker and stir to dissolve them evenly;

[0011] S3: adding the uniformly mixed solution into a reaction kettle and heating it for reaction;

[0012] S4: refrigerate the solution after the reaction is completed;

[0013] S5: centrifuge the refrigerated solution to remove the supernatant;

[0014] S6: dissolving the precipitate after centrifugation in n-hexane;

[0015] S7: After centrifuging the mixed solution in S6, the supernatant extracted is CQDs: x% Eu.

[0016] Furthermore, the amounts of the raw materials are: oleic acid 1-2.5 ml, oleylamine 1-2.5 ml, EuCl3·6H2O 1-2 mmol and dimethylformamide solution 5-20 ml.

[0017] Furthermore, in S3, the temperature of the reactor is 100-160° C., and the heating reaction time is 1-4 hours.

[0018] Furthermore, in S4, the completely reacted solution is placed in a refrigerator for refrigeration.

[0019] Furthermore, in S5, the centrifugal speed is 5000-11000 rpm / min, and the centrifugal time is 1-5 min.

[0020] Furthermore, in S7, the centrifugal speed is 1000-5000 rpm / min, and the centrifugation time is 1-5 min.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] 1. CQDs prepared by the present invention: x% Eu fluorescent material, rare earth Eu 3+ The size of doped carbon quantum dots can be evenly distributed at 1.72±0.29nm, and the excitation spectrum can be continuously controlled from 300 to 400nm, covering the wavelength of commercial ultraviolet excitation chips and providing a basis for commercial applications.

[0023] 2. The method for preparing CQDs: x% Eu fluorescent material of the present invention adopts a one-step preparation method based on the selection of raw materials while ensuring product performance. The reaction time can be controlled within 6 hours, which is much lower than the existing preparation method.

[0024] 3. The preparation method of the present invention abandons the cumbersome preparation process of traditional carbon quantum dot synthesis, and innovatively uses oleic acid, oleylamine, EuCl3·6H2O and dimethylformamide as precursors of carbon dots and rare earth ions, and prepares CQDs with a size of less than 10nm and uniform distribution in a shorter reaction time: x% Eu. This efficient hydrothermal reaction preparation method has a lower precursor cost, and the preparation process is simpler and more efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Undoped carbon quantum dots and rare earth ions Eu 3+ Preparation flow chart of doped carbon quantum dots and fluorescence spectral characteristics.

[0026] Figure 2 For rare earth ion Eu 3+ X-ray diffraction pattern of doped carbon quantum dots.

[0027] Figure 3 For rare earth ion Eu 3+ Emission spectrum of doped carbon quantum dots under 300-400nm excitation light.

[0028] Figure 4 For rare earth ion Eu 3+ Fluorescence quenching spectra of doped carbon quantum dots to heavy metal Co ions of different concentrations. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be further described below.

[0030] Comparative Example 1:

[0031] like Figure 1As shown, the synthesis scheme of undoped carbon quantum dots is as follows: 2.5 ml of oleic acid and 2.5 ml of oleylamine are dissolved in 20 ml of dimethylformamide, and then the mixed solution is added to the reactor and heated at 160°C for 4 hours. After the reaction, the extracted solution is refrigerated in a refrigerator for 3 hours, and the refrigeration temperature is controlled at 5°C. After refrigeration, the resulting solution is placed in a centrifuge and centrifuged at a speed of 11000 rpm / min for 5 minutes, the supernatant is removed, and the precipitate is dissolved in n-hexane.

[0032] Embodiment 1:

[0033] Synthesis scheme of rare earth ion Eu3+ doped carbon quantum dots: Take 2mmol EuCl3·6H2O, 2.5ml oleic acid, 2.5ml oleylamine and dissolve in 20ml dimethylformamide, then add the mixed solution into the reactor and heat at 140℃ for 3 hours. After the reaction, the extracted solution was refrigerated in the refrigerator for 1 hour, and the refrigeration temperature was controlled at 5℃. After refrigeration, the resulting solution was placed in a centrifuge at a speed of 8000rpm / min, centrifuged for 5min, the supernatant was removed, the precipitate was dissolved in n-hexane, and then placed in a centrifuge at a speed of 4000rpm / min, centrifuged for 5min, and the supernatant was extracted, i.e. CQDs: 4% Eu 3+ , placed in a vial and refrigerated.

[0034] Embodiment 2:

[0035] Synthesis scheme of rare earth ion Eu3+ doped carbon quantum dots: Take 2mmol EuCl3·6H2O, 2.5ml oleic acid, 2.5ml oleylamine and dissolve in 20ml dimethylformamide, and then add the above mixed solution to the reactor and heat it at 160℃ for 4 hours. After the reaction, the extracted solution was refrigerated in the refrigerator for 1 hour, and the refrigeration temperature was controlled at 5℃. After refrigeration, the resulting solution was placed in a centrifuge at an optimal speed of 11000rpm / min, centrifuged for 5min, the supernatant was removed, the precipitate was dissolved in n-hexane, and then placed in a centrifuge at an optimal speed of 5000rpm / min, centrifuged for 5min, and the supernatant was extracted, which is the preferred CQDs: 20% Eu 3+ , placed in a vial and refrigerated.

[0036] Experimental comparison:

[0037] like Figure 4 As shown, the rare earth ion Eu in Example 1 3+ Fluorescence quenching spectra of doped carbon quantum dots to heavy metal Co ions of different concentrations. A 1 mmol CoCl2 solution was prepared and dripped into Eu 3+Doped carbon quantum dot solution. Prepare samples with different Co ion contents (0-61.2μL). Set the excitation light to 360nm, test the emission spectra and fluorescence intensity of the above samples respectively, and calculate the fluorescence quenching efficiency by the spectrum integral area method; in this scheme, the rare earth Eu 3+ The fluorescence quenching efficiency of doped carbon quantum dots for Co ions can reach 96.3%, and the detection limit is 0.139 μM, which is much lower than the Co ion concentration limit in domestic drinking water specified by the WHO.

[0038] Comprehensive comparative examples 1-3 and attached Figure 1-4 The rare earth ion doped carbon quantum dot fluorescent material prepared by the present invention can greatly reduce the synthesis cycle and show a more uniform morphology and size. The excitation spectrum can be continuously adjusted in the range of 300-400nm, covering the wavelength of commercial ultraviolet excitation chips. In addition, the fluorescent material also shows a specific fluorescence quenching effect on the pH of the solution and the heavy metal ion Co, and can be widely used in smart lighting, food safety, biological imaging and other fields.

[0039] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A method for preparing a highly efficient rare earth ion doped carbon quantum dot fluorescent material (CQDs: x% Eu, where x=1-30), wherein the method comprises the following steps: S1: weigh raw materials: oleic acid, oleylamine, EuCl3·6H2O and dimethylformamide solution; S2: Place the above raw materials in a beaker and stir to dissolve them evenly; S3: adding the uniformly mixed solution into a reaction kettle and heating it for reaction; S4: refrigerate the solution after the reaction is completed; S5: centrifuge the refrigerated solution to remove the supernatant; S6: dissolving the precipitate after centrifugation in n-hexane; S7: After centrifuging the mixed solution in S6, the supernatant extracted is CQDs: x% Eu.

2. The method for preparing the rare earth ion doped carbon quantum dot fluorescent material according to claim 1, characterized in that: The amounts of the raw materials are: 1-2.5 ml of oleic acid, 1-2.5 ml of oleylamine, 1-2 mmol of EuCl3·6H2O and 5-20 ml of dimethylformamide solution.

3. The method for preparing the rare earth ion doped carbon quantum dot fluorescent material according to claim 1, characterized in that: In S3, the temperature of the reactor is 100-160° C., and the heating reaction time is 1-4 hours.

4. The method for preparing the rare earth ion doped carbon quantum dot fluorescent material according to claim 1, characterized in that: In S4, the solution after the reaction is completely completed is placed in a refrigerator for refrigeration.

5. The method for preparing the rare earth ion doped carbon quantum dot fluorescent material according to claim 1, characterized in that: In S5, the centrifugal speed is 5000-11000 rpm / min, and the centrifugal time is 1-5 min.

6. The method for preparing the rare earth ion doped carbon quantum dot fluorescent material according to claim 1, characterized in that: In the S7, the centrifugal speed is 1000-5000 rpm / min, and the centrifugation time is 1-5 min.

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