CN115125001B - A kind of preparation method of green luminescent carbon dot - Google Patents

Abstract

The invention discloses a method for preparing green luminescent carbon dots. Using coffee grounds as raw materials, the raw materials are first subjected to high-temperature carbonization, and then the raw materials after high-temperature carbonization are subjected to hydrothermal treatment under acidic conditions, and then carried out under alkaline conditions. Hydrothermal treatment to obtain green luminescent carbon dots. The carbon dots of the present invention can be directly photographed under ordinary lighting conditions in the laboratory to observe a bright, single green color without photographing under ultraviolet light, and have high luminous efficiency and high luminous brightness, which solves the problem of the single The problems of poor color, low luminous efficiency, and low luminous brightness. The preparation method of the present invention is simple and easy to implement, the carbon dots have high brightness, good monochromaticity, and excellent luminescent performance, which can help the carbon dots to obtain better luminescent properties, and show strong performance in the fields of imaging probes, fluorescent tracers, and luminescence. application potential.

Description

A kind of preparation method of green luminescent carbon dot

technical field

The invention relates to a preparation method of carbon dots, in particular to a preparation method of N-P co-doped green light-emitting carbon dots with high luminous efficiency, and belongs to the technical field of luminescent materials and applications.

Background technique

Carbon dots, also known as carbon nanoparticles, carbon nanodots, and nanoscale graphite phase carbon particles, refer to a carbon core structure with a single layer or less than 5 layers of graphene, and its size is usually less than 100 nanometers. The layered structure determines the carbon dots. The size of carbon dots has typical anisotropy, and the lateral size is greater than the vertical height. The size of the so-called carbon dots is its lateral size, which has a typical carbon lattice structure.

Carbon dots have important applications in the fields of biosensors, medical imaging devices, and light-emitting diodes. Carbon dots as luminescent materials Carbon nanodots are usually spherical structures, which can be divided into carbon nanodots with obvious lattice and carbon nanodots without lattice. Due to the diversity of carbon nanodot structures, the luminescent centers, luminescent mechanisms and luminous efficiencies of carbon nanodots prepared in different ways are quite different. Generally, the luminescence peak of luminescent carbon dots is relatively broad, and the luminous efficiency is not high, which limits its application. The luminous efficiency of carbon dots is not controlled by the carbon core, and the surface groups of carbon dots have a non-negligible impact on the luminous efficiency.

Contents of the invention

The purpose of the present invention is to provide a method for preparing green luminescent carbon dots with high brightness and good monochromaticity. The method has simple operation process, good repeatability, and is convenient for industrial production. The obtained carbon dots can emit a single green light, and The luminous brightness is high, the luminous efficiency is high, and the application potential is stronger.

In the present invention, coffee grounds are used as raw materials. First, the raw materials are subjected to high-temperature carbonization, and then special acid-base hydrothermal treatment is performed on the high-temperature carbonized raw materials to obtain green luminescent carbon dots. The combination of the two steps of high-temperature carbonization and acid-base hydrothermal treatment is closely related.

The coffee grounds used in the present invention refer to the residue remaining on the filter paper after brewing coffee. The coffee grounds contain elements such as carbon, nitrogen, and phosphorus, which can be used as raw materials for nitrogen and phosphorus doped carbon dots, thereby improving the luminescent properties of the carbon dots.

Further, the high-temperature carbonization in the present invention refers to high-temperature calcination of coffee grounds containing nitrogen and phosphorus in an inert atmosphere to carbonize them. The inert atmosphere can be an inert gas such as nitrogen or argon. The purpose of calcination is to fully carbonize the coffee grounds, and the selection of its temperature and time only needs to meet this requirement. For example, the conventional carbonization temperature is generally 600-800°C. At this high temperature, coffee grounds can be rapidly transformed into highly crystalline nitrogen and phosphorus co-doped graphite phase carbon, and the calcination time is generally 0.5-2 hours. The presence of nitrogen and phosphorus in coffee grounds is beneficial to improve the luminescence brightness of carbon dots, and the obtained carbon dots have narrow spectrum and good monochromaticity.

Further, the special acid-base hydrothermal treatment referred to in the present invention is as follows: first, the raw material after high-temperature carbonization is subjected to hydrothermal treatment under acidic conditions (acid treatment for short), and then hydrothermal treatment is performed under alkaline conditions (alkaline treatment for short). . The specific operation method of hydrothermal treatment under acidic conditions is: co-grinding the raw material obtained by high-temperature carbonization with oleic acid, and then dispersing the ground mixture into hydrochloric acid solution for hydrothermal treatment. The purpose of co-grinding the raw materials obtained by high-temperature carbonization with oleic acid is to increase the dispersion of raw materials. The dosage relationship between raw materials and oleic acid after high-temperature carbonization is 2-10g: 0.5-3 mL. The purpose of acid treatment is to reduce the particle size of larger carbon particles and provide prerequisites for the next step of alkali treatment. The concentration of hydrochloric acid solution is 0.05-0.15mol/L, the temperature of acid treatment is 50-80°C, and the treatment time is 0.5 -1 hour. During the acid treatment, there is no special requirement on the amount of the sample and the hydrochloric acid solution, as long as the sample can be completely immersed in the hydrochloric acid solution. In order to fully react the sample with the acid, the entire acid treatment process can be carried out under ultrasonic.

Further, the high-temperature carbonized sample is first ground into fine powder, and then mixed with oleic acid. After acid treatment, the treated samples were washed to neutral, dried, and then subjected to alkali treatment.

Further, the specific operation method of hydrothermal treatment under alkaline conditions is: adding the acid-treated sample into sodium hydroxide solution for hydrothermal treatment. The purpose of alkali treatment is to make sodium ions and hydroxide ions enter the interlayer through intercalation, reduce the number of layers of carbon dots, hydrothermal treatment can increase the crystallinity and dispersibility of carbon dots, and obtain high-brightness luminescence. NaOH solution The concentration of the alkali is 0.05-0.15mol/L, the temperature of the alkali treatment is 120-200°C, and the treatment time is 1-5 hours. During alkali treatment, there is no special requirement on the amount of sample and sodium hydroxide solution, as long as the sample can be completely immersed in the sodium hydroxide solution.

Further, after the alkali treatment, the sample is washed to neutrality, then dried, and dispersed in an aqueous solution of thioglycolic acid to obtain green luminescent carbon dots with good dispersibility. The aqueous solution of thioglycolic acid can better disperse the carbon dots and prevent the agglomeration of carbon dots. The concentration of thioglycolic acid is generally 0.5-2wt%.

In a specific embodiment of the present invention, a specific method for preparing green luminescent carbon dots is provided, comprising the following steps:

(1) Calcining 10g of nitrogen- and phosphorus-containing coffee grounds at 600-800°C for 0.5-2 hours under inert conditions, and grinding them into fine powder for later use;

(2) Take 2-10 grams of fine powder in step (1), drop 0.5-3 mL of oleic acid, grind in an agate mortar, then disperse into 0.1M hydrochloric acid solution, and disperse ultrasonically at 50-80°C for 0.5 hours , followed by centrifugation, washing to neutrality, and drying;

(3) Take 2-10 grams of fine powder from step (2), put it into 0.1M NaOH solution, react at 120-200°C for 1-5 hours, then centrifuge, wash until neutral, and dry. The dried powder was dispersed into an aqueous solution containing 1wt% thioglycolic acid to obtain green luminescent carbon dots.

The invention adopts a special method to prepare carbon dots. The particle size of the obtained carbon dots is less than 20 nanometers, and can emit a single green light with high luminous brightness and high luminous efficiency. Bright green can be observed under ordinary photo conditions, which can help Carbon dots have better luminescent properties, showing strong application potential in the field of imaging probes and luminescence.

The present invention utilizes the high-temperature carbonization method for the first time to obtain highly crystalline graphite-phase carbon by using nitrogen- and phosphorus-containing coffee grounds as raw materials, which strengthens the crystallinity of the graphite-phase carbon, and then undergoes acid-base hydrothermal treatment to obtain high-luminescence brightness. Green luminescent carbon dots, the carbon dots can be directly photographed under ordinary lighting conditions in the laboratory to observe bright, single green, without the need to photograph under ultraviolet light, with high luminous efficiency and high luminous brightness, which solves the problem of Ordinary carbon dots have poor luminous monochromaticity, low luminous efficiency, and low luminous brightness. The preparation method of the present invention is simple and easy to implement, the carbon dots have high brightness, good monochromaticity, and excellent luminescent performance, which can help the carbon dots to obtain better luminescent properties, and show strong performance in the fields of imaging probes, fluorescent tracers, and luminescence. application potential.

Description of drawings

Fig. 1 is the photoluminescence spectrogram of the product obtained in Example 1 of the present invention and pictures under ordinary lighting conditions.

Detailed ways

The present invention will be further elaborated by the following examples. It should be understood that the following descriptions are only for explaining the present invention, and the content thereof is not limited.

Example 1

1.1 Calcinate 10g of nitrogen- and phosphorus-containing coffee grounds at 700 degrees Celsius for 1 hour under inert conditions, and then grind them into fine powder for later use;

1.2 Take 5 grams of the fine powder in step 1.1, drop 1 mL of oleic acid, grind in an agate mortar for 10 minutes, then disperse into 0.1M (mol/L, the same below) hydrochloric acid solution, and disperse ultrasonically at 60 degrees Celsius for 0.5 hours , followed by centrifugation, washing to neutrality, and drying;

1.3 Take 5 grams of fine powder from step 1.2, disperse it into 0.1M NaOH solution, react at 150 degrees Celsius for 3 hours, then centrifuge, wash until neutral, then dry, and disperse the dried powder to a concentration of 1wt% In the aqueous solution of thioglycolic acid, the powder is well dispersed in the aqueous solution of thioglycolic acid without agglomeration, that is, a solution containing green luminescent carbon dots is obtained. The solution containing carbon dots was directly photographed under normal lighting conditions in the laboratory, as shown in the photo in Figure 1, and the solution was bright green. The solution was photographed under ordinary lighting in the laboratory, and the resulting photoluminescence spectrum is shown in Figure 1. It can be seen from the figure that the sample shows very bright green fluorescence, indicating that the sample can be excited under ordinary lighting. , and the brightness is very high, which further shows that the carbon dots synthesized by this method have good luminescent properties.

Example 2

2.1 Calcinate 10g of nitrogen and phosphorus-containing coffee grounds at 600 degrees Celsius for 1 hour under inert conditions, and then grind them into fine powder for later use;

2.2 Take 2 grams of the fine powder in step 1.1, drop 1 mL of oleic acid, grind in an agate mortar for 10 minutes, then disperse into 0.1M (mol/L, the same below) hydrochloric acid solution, and disperse ultrasonically at 60 degrees Celsius for 0.5 hours , followed by centrifugation, washing to neutrality, and drying;

2.3 Take 4 grams of the fine powder in step 1.2, disperse it into 0.1M NaOH solution, react at 150 degrees Celsius for 3 hours, then centrifuge, wash until neutral, then dry, and disperse the dried powder to a concentration of 1wt% In the aqueous solution of thioglycolic acid, the powder is well dispersed in the aqueous solution of thioglycolic acid without agglomeration, that is, a solution containing green luminescent carbon dots is obtained. The performance of the carbon dots is similar to that of Example 1, and its solution also presents the same green color as that shown in Figure 1 directly under ordinary lighting conditions in the laboratory.

Example 3

3.1 Calcinate 10g of nitrogen- and phosphorus-containing coffee grounds at 600°C for 2 hours under inert conditions, and then grind them into fine powder for later use;

3.2 Take 2 grams of the fine powder in step 3.1, drop 0.5 mL of oleic acid, grind in an agate mortar for 10 minutes, then disperse into 0.1M hydrochloric acid solution, ultrasonically disperse at 50 degrees Celsius for 0.5 hours, then centrifuge and wash to medium sexual, dry;

3.3 Take 2 grams of fine powder from step 3.2, disperse it into 0.1M NaOH solution, react at 120 degrees Celsius for 1 hour, then centrifuge, wash until neutral, then dry, and disperse the dried powder to a concentration of 1wt% mercapto In the aqueous solution of acetic acid, the powder is well dispersed in the aqueous solution of thioglycolic acid without agglomeration, that is, green luminescent carbon dots are obtained. The performance of the carbon dots is similar to that of Example 1, and its solution also presents the same green color as that shown in Figure 1 directly under ordinary lighting conditions in the laboratory.

Example 4

4.1 Calcinate 10g of nitrogen- and phosphorus-containing coffee grounds at 800 degrees Celsius for 0.5 hours under inert conditions, and then grind them into fine powder for later use;

4.2 Take 10 grams of the fine powder in step 4.1, drop 3 mL of oleic acid, grind it in an agate mortar for 10 minutes, then disperse it into a 0.05M hydrochloric acid solution, disperse it ultrasonically at 80 degrees Celsius for 0.5 hours, then centrifuge and wash until medium sexual, dry;

4.3 Take 10 grams of the fine powder in step 4.2, disperse it into 0.1M NaOH solution, react at 200 degrees Celsius for 5 hours, then centrifuge, wash until neutral, then dry, and disperse the dried powder to a concentration of 1wt% mercapto In the aqueous solution of acetic acid, green luminescent carbon dots were obtained. The performance of the carbon dots is similar to that of Example 1, and its solution also presents the same green color as that shown in Figure 1 directly under ordinary lighting conditions in the laboratory.

Example 5

5.1 Calcinate 10g of nitrogen- and phosphorus-containing coffee grounds at 750 degrees Celsius for 1 hour under inert conditions, and then grind them into fine powder for later use;

5.2 Take 6 grams of the fine powder in step 5.1, drop 2 mL of oleic acid, grind it in an agate mortar for 10 minutes, then disperse it into a 0.15M hydrochloric acid solution, disperse it ultrasonically at 75 degrees Celsius for 0.5 hours, then centrifuge and wash until medium sexual, dry;

5.3 Take 6 grams of fine powder from step 5.2, disperse it into 0.1M NaOH solution, react at 180 degrees Celsius for 3 hours, then centrifuge, wash until neutral, and then dry, and disperse the dried powder to a concentration of 1wt% In the aqueous solution of thioglycolic acid, green luminescent carbon dots can be obtained. The performance of the carbon dots is similar to that of Example 1, and its solution also presents the same green color as that shown in Figure 1 directly under ordinary lighting conditions in the laboratory.

Comparative example 1

Carbon dots are prepared according to the method of Example 1, the difference is: the fine powder after high-temperature carbonization is directly subjected to alkali treatment, and the specific operations are as follows:

Calcining 10 g of nitrogen- and phosphorus-containing coffee grounds at 700 degrees Celsius for 1 hour under inert conditions, and then grinding them into fine powder for later use;

Take 5 grams of the above-mentioned fine powder, disperse it in 0.1M NaOH solution, react at 150 degrees Celsius for 3 hours, then centrifuge, wash until neutral, then dry, and disperse the dried powder into a solution containing 1wt% mercaptoacetic acid In the aqueous solution, the powder is well dispersed in the aqueous solution of thioglycolic acid without agglomeration, and the solution is dark blue-green under ordinary lighting conditions in the laboratory, and does not show high-brightness green.

Comparative example 2

The carbon dots were prepared according to the method of Example 1, except that the high-temperature calcination temperature in step 1.1 was 500 degrees Celsius, the carbonization of the product was incomplete, and the final product obtained did not emit light under the irradiation of a strong ultraviolet lamp.

Comparative example 3

Prepare carbon dots according to the method of Example 1, the difference is: no NaOH is added in the hydrothermal process of step 1.3, and the specific operations are as follows:

Calcining 10 g of nitrogen- and phosphorus-containing coffee grounds at 700 degrees Celsius for 1 hour under inert conditions, and then grinding them into fine powder for later use;

Take 5 grams of the above fine powder, drop 1 mL of oleic acid, grind in an agate mortar for 10 minutes, then disperse into 0.1M (mol/L, the same below) hydrochloric acid solution, ultrasonically disperse at 60 degrees Celsius for 0.5 hours, and then centrifuge Separation, washing to neutrality and drying;

Take 5 grams of the above-mentioned acid-treated fine powder, disperse it in water, react at 150 degrees Celsius for 3 hours, then centrifuge and dry, and disperse the dried powder into an aqueous solution containing 1wt% thioglycolic acid. Reunited together in the middle, does not emit light under strong ultraviolet light.

Comparative example 4

Prepare carbon dots according to the method of Example 1, the difference is: the acid-base treatment sequence of steps 1.2 and 1.3 is replaced, and the specific operations are as follows:

Calcining 10 g of nitrogen- and phosphorus-containing coffee grounds at 700 degrees Celsius for 1 hour under inert conditions, and then grinding them into fine powder for later use;

Take 5 grams of the above fine powder, disperse it into 0.1M NaOH solution, react at 150 degrees Celsius for 3 hours, then centrifuge, wash until neutral, and then dry;

Take 5 grams of the above alkali-treated fine powder, drop 1 mL of oleic acid, grind in an agate mortar for 10 minutes, then disperse into 0.1M (mol/L, the same below) hydrochloric acid solution, and disperse ultrasonically at 60 degrees Celsius for 0.5 hours , followed by centrifugation, washing to neutrality, and drying;

Disperse the dried powder into an aqueous solution containing 1wt% thioglycolic acid. The dispersion of the powder in the aqueous solution of thioglycolic acid is not good, and the sample does not emit light under the irradiation of an ultraviolet lamp.

Claims (3)

1. A preparation method for green luminescent carbon dots, characterized in that: use coffee grounds as raw material, first carry out high-temperature carbonization of raw materials, then carry out hydrothermal treatment under acidic conditions with the raw materials after high-temperature carbonization, and then under alkaline conditions Under hydrothermal treatment, green luminescent carbon dots are obtained; High-temperature carbonization is carried out under an inert atmosphere, and the temperature of high-temperature carbonization is 600-800°C; The specific operation method of hydrothermal treatment under acidic conditions is: co-grind the raw material obtained by high-temperature carbonization with oleic acid, and then disperse the ground mixture into hydrochloric acid solution for hydrothermal treatment. The concentration of hydrochloric acid solution is 0.05-0.15mol/L, The treatment temperature is 50-80°C, and the treatment time is 0.5-1 hour; The specific operation method of hydrothermal treatment under alkaline conditions is: add the sample after hydrothermal treatment under acidic conditions into sodium hydroxide solution for hydrothermal treatment, the concentration of NaOH solution is 0.05-0.15mol/L, the treatment temperature is 120-200 °C The time is 1-5 hours; The samples after hydrothermal treatment under alkaline conditions were washed to neutrality, and then dispersed in aqueous thioglycolic acid solution. 2. The preparation method according to claim 1, characterized in that: during hydrothermal treatment under acidic conditions, the dosage relationship between raw material and oleic acid after high-temperature carbonization is 2-10g: 0.5-3 mL. 3. The preparation method according to claim 1, characterized in that: after hydrothermal treatment under acidic conditions, the sample is first washed to neutrality, and then hydrothermal treatment is carried out under alkaline conditions.

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