CN116179198B - Method for preparing solid rare earth doped fluorescent carbon dots by one-step hydrothermal method - Google Patents

Abstract

The invention provides a method for preparing solid rare earth doped fluorescent carbon dots by a one-step hydrothermal method. The method comprises the following steps: firstly, dissolving naphthalene acetamide and terbium oxide in sulfuric acid aqueous solution, fully stirring, then carrying out hydrothermal reaction in a reaction kettle, and taking out after cooling to room temperature to obtain a primary product; and (3) performing centrifugal purification on the obtained initial product for a plurality of times, and drying the solid precipitate after centrifugal purification to obtain the solid rare earth doped carbon dot material with stable luminescence, wherein the characteristic emission peak of the rare earth terbium can be seen under the excitation of ultraviolet wavelength. The invention belongs to the field of luminescent material preparation, and the carbon dot product prepared by the method disclosed by the invention exists in a solid state, does not have solid state fluorescence quenching, and is stable in luminescence, and the fluorescent performance of the original material is improved by rare earth doping.

Description

One-step hydrothermal method for preparing solid rare earth-doped fluorescent carbon dots

Technical field

The invention relates to the technical field of carbon quantum dot preparation, specifically a one-step hydrothermal method for preparing solid rare earth doped fluorescent carbon dots.

Background technique

Carbon dots are new nanomaterials with carbon as the skeleton structure. Because the surface has rich functional groups, it facilitates further compounding. The doping of carbon dots can change the electronic chemical structure of carbon dots by regulating the energy band gap and charge density, thereby improving the optical properties of carbon dots. Expand the application of carbon dots in analytical detection and biomedicine through doping. The doping of carbon dots mainly includes non-metal doping, transition metal doping and rare earth doping. Luminescent rare earth complexes have the advantages of narrow fluorescence peaks, good monochromaticity, and high fluorescence efficiency. Through doping, the luminescence advantages of carbon dots and rare earths can be maintained and the weaknesses of the luminescence properties of the two can be compensated. However, rare earth metals themselves are highly toxic. At present, rare earth doping is mainly based on material compounding, and the preparation steps are relatively cumbersome. In detection applications using composite materials, the emission peaks of carbon dots are mostly used for detection. However, there are few reports on the red zone emission signals of rare earth metals, and their applications in the field of analytical sensing need to be expanded.

Contents of the invention

The purpose of the present invention is to provide a one-step hydrothermal method for preparing solid rare earth doped fluorescent carbon dots to overcome the shortcomings in the existing rare earth composite doped carbon dot preparation technology and avoid complicated purification steps.

The present invention is implemented as follows:

The one-step hydrothermal method prepares solid rare earth-doped fluorescent carbon dots, including the following steps: dissolve the carbon source in a sulfuric acid aqueous solution, then add the rare earth oxide to fully react, react at 200°C for 4 hours, and undergo centrifugation, drying and other steps to obtain a solution containing Rare earth doped solid carbon dots.

The carbon source is naphthyl acetamide; the rare earth oxide is terbium oxide. The mass ratio of terbium oxide and naphthylacetamide is 4:3-2:1.

The solid product containing rare earth doped carbon dots was purified by centrifugation in deionized water.

Through XPS spectrum detection, the XPS full spectrum and the high-resolution electronic spectrum of Tb are obtained, and the existence of the Tb peak can be clearly seen.

The research of this invention found that:

Using naphthyl acetamide as the carbon source and terbium oxide as the rare earth doped compound, a one-step preparation method for synthesizing solid rare earth doped carbon dots using a hydrothermal method specifically includes the following steps:

(1) Dissolve naphthyl acetamide in aqueous sulfuric acid solution, add rare earth compounds and stir until completely dissolved;

(2) Put the evenly stirred mixed solution into the reaction kettle, and put the reaction kettle into a drying box for heating;

(3) After cooling to room temperature, take it out and use deionized water for centrifugal purification;

(4) Dry the precipitate obtained after centrifugal purification.

In step (1), the mass of naphthaleneacetamide is 0.6g, the rare earth compound is terbium oxide, its mass is 0.8-1.2g, and the stirring time is 30-60min.

In step (2), the reaction temperature is 200°C and the reaction time is 4 hours.

In step (3), the centrifuge speed is 8000 rpm, the centrifugation time is 5 minutes, and the centrifugal purification operation is repeated 2-5 times.

In step (4), the drying oven is set to a temperature of 80°C and a time of 4 hours.

Beneficial effects of the present invention:

(1) The present invention uses naphthyl acetamide as a single carbon source and terbium oxide as a doping material to obtain solid rare earth doped carbon dots. This method is simple to prepare, and the selected rare earth compounds can be tested without further treatment. The prepared carbon dots exist in solid form, maintaining the luminescent properties of the rare earth and carbon dots.

(2) The solid rare earth-doped carbon dots do not require complicated purification steps and can be used for subsequent testing after centrifugation and drying.

(3) The carbon dot product prepared by the method of the present invention exists in a solid state, has no solid-state fluorescence quenching, and has stable luminescence. Rare earth doping improves the fluorescence performance of the original material.

Description of drawings

Figure 1 is an X-ray electron spectrometer spectrum of the solid rare earth doped carbon dots prepared in Example 1 of the present invention.

Figure 2 is a high-resolution electronic spectrum of Tb ³⁺ of solid rare earth-doped carbon dots prepared in Example 1 of the present invention.

Figure 3 is the infrared absorption spectrum of the solid rare earth doped carbon dots prepared in Example 1 of the present invention.

Figure 4 is the fluorescence excitation spectrum of the solid rare earth doped carbon dots prepared in Example 1 of the present invention.

Figure 5 shows the emission spectra at different excitation wavelengths of the solid rare earth doped carbon dots prepared in Example 1 of the present invention.

Figure 6 is the ultraviolet-visible absorption spectrum of the solid rare earth doped carbon dots prepared in Example 1 of the present invention.

Figure 7 shows the effects of different doping ratios on solid rare earth doped carbon dots in Examples 1-3 of the present invention.

Figure 8 is the fluorescence spectrum of the carbon dots prepared in Comparative Example 1.

Detailed ways

Example 1

Solid-state fluorescent carbon dots are prepared by a one-step hydrothermal method using naphthyl acetamide and terbium oxide, which specifically includes the following steps:

(1) Dissolve 0.6g naphthyl acetamide in 10mL sulfuric acid aqueous solution, stir for 0.5h until the solution is transparent and colorless, then add 0.8g terbium oxide and dissolve in it, stir for 0.5h, and fully react; wherein, the sulfuric acid aqueous solution is composed of 98% Concentrated sulfuric acid and deionized water are prepared at a volume ratio of 1:1.

(2) Place the mixed solution in a reaction kettle for hydrothermal reaction, stir magnetically for 30 minutes, and heat the reaction kettle in a drying oven at 200°C for 4 hours.

(3) After the reaction, take the precipitate, use deionized water as the extraction agent, put it into a centrifuge and centrifuge it at 8000 rpm for 5 minutes. Repeat the centrifugation operation four times to ensure that impurities are removed.

(4) Place the centrifuged solid precipitate in a drying oven at 80°C for 4 hours to obtain pure rare earth Tb-doped carbon dots (Tb-CDs/0.8).

Take an appropriate amount of rare earth Tb doped carbon dots and measure the XPS elemental analysis data of the solid powder, as shown in Figures 1 and 2. It can be seen that the prepared solid rare earth doped fluorescent carbon dots are successfully incorporated with Tb.

Mix the carbon dot powder and potassium bromide, press it into tablets through a tablet press, and perform infrared absorption spectrum testing, excitation emission, and fluorescence spectrum testing under different excitation lights. The results are shown in Figures 3 to 5 respectively. As can be seen from Figure 3, the solid rare earth-doped fluorescent carbon dots contain abundant N and O functional groups, and the existence of Tb-O bonds appears in the fingerprint area. It can be seen from Figure 5 that the solid rare earth-doped fluorescent carbon dots maintain the luminescence properties of the carbon dots and rare earth.

Disperse 1g of rare earth Tb doped carbon dot powder into 30 mL of deionized water and stir evenly to obtain a rare earth Tb doped carbon dot aqueous solution. Measure the UV-visible spectrum in the solution state. The results are shown in Figure 6.

Example 2

The preparation steps of solid rare earth doped fluorescent carbon dots are the same as in Example 1, except that the mass of terbium oxide is 1.0g:

(1) Dissolve 0.6g naphthyl acetamide in a sulfuric acid aqueous solution, and then add 0.8g terbium oxide to fully react. The sulfuric acid aqueous solution is prepared from 98% concentrated sulfuric acid and deionized water in a volume ratio of 1:1.

(2) Stir on a magnetic stirrer for 30 minutes and heat in a drying oven at 200°C for 4 hours.

(3) After the reaction, take the precipitate, use deionized water as the extraction agent, put it into a centrifuge and centrifuge it at 8000 rpm for 5 minutes. Repeat the centrifugation operation four times to ensure that impurities are removed.

(4) Place the centrifuged solid precipitate in a drying oven at 80°C for 4 hours to obtain pure rare earth Tb-doped carbon dots (Tb-CDs/1.0).

Example 3

The preparation steps of solid rare earth doped fluorescent carbon dots are the same as in Example 1, except that the mass of terbium oxide is 1.2g:

(1) Dissolve 0.6g naphthyl acetamide in a sulfuric acid aqueous solution, and then add 1.2g terbium oxide to fully react. The sulfuric acid aqueous solution is prepared from 98% concentrated sulfuric acid and deionized water in a volume ratio of 1:1.

(2) Stir on a magnetic stirrer for 30 minutes and heat in a drying oven at 200°C for 4 hours.

(3) After the reaction, take the precipitate, use deionized water as the extraction agent, put it into a centrifuge and centrifuge it at 8000 rpm for 5 minutes. Repeat the centrifugation operation four times to ensure that impurities are removed.

(4) Place the centrifuged solid precipitate in a drying oven at 80°C for 4 hours to obtain pure rare earth Tb-doped carbon dots (Tb-CDs/1.2).

The solid rare earth-doped fluorescent carbon dots prepared in Examples 1-3 were respectively excited using 360 nm laser, and the results obtained are shown in Figure 7. It can be seen from Figure 7 that solid rare earth-doped fluorescent carbon dots have concentration-dependent characteristics. As the amount of rare earth compounds increases, the rare earth luminescence gradually increases.

Comparative example 1

Dissolve 0.6g of naphthyl acetamide with sulfuric acid aqueous solution, transfer it to a polytetrafluoroethylene reactor, seal it and put it in a drying box for heating reaction. The reaction temperature is 200°C, react for 4 hours, and remove after cooling to room temperature. The solution is a carbon dot aqueous solution without rare earth doping.

The prepared aqueous solution of undoped rare earth carbon dots was tested for fluorescence spectrum, and the results are shown in Figure 8. It can be seen from Figure 8 that carbon dots without rare earth doping have excitation-dependent characteristics.

Claims (3)

1. A one-step hydrothermal method for preparing solid rare earth doped fluorescent carbon dots, which is characterized by including the following steps: a. Preparation of rare earth doped carbon dots by hydrothermal method: Dissolve naphthyl acetamide and terbium oxide in a sulfuric acid aqueous solution, stir thoroughly, and then perform a hydrothermal reaction in a reaction kettle. After the reaction is completed, cool to room temperature, and then take it out to obtain the initial product; b. Purify the initial product obtained in step a by several times of centrifugation, and dry the solid precipitate after centrifugation purification to obtain solid rare earth-doped fluorescent carbon dots; In step a, the mass ratio of terbium oxide and naphthylacetamide is 4:3-2:1; the temperature of the hydrothermal reaction is set to 200°C, and the reaction time is 4 h. 2. A method for preparing solid rare earth doped fluorescent carbon dots by a one-step hydrothermal method according to claim 1, wherein step a is specifically: weigh 0.6 g of naphthylacetamide and add it to 10 mL of sulfuric acid aqueous solution to dissolve and stir. 0.5 h until the solution is transparent and colorless, weigh 0.8-1.2 g of terbium oxide, dissolve it in it, and stir for 0.5 h to fully react; place the mixed solution in a reaction kettle for hydrothermal reaction, and take it out after cooling to room temperature. 3. The method for preparing solid rare earth-doped fluorescent carbon dots by a one-step hydrothermal method according to claim 1, characterized in that in step b, centrifuge at a speed of 8000 rpm for 5 min, and the number of centrifuges is 2-5 times, The drying temperature is 80°C, and the drying time is set to 4 h.