CN116103042A - A preparation method of fluorescent carbon quantum dots using castor seeds as carbon source - Google Patents

Abstract

The invention provides a method for preparing fluorescent carbon quantum dots using castor seeds as a carbon source. The method comprises the following steps: dispersing peeled castor seed powder into deionized water, stirring evenly, and putting it into a hydrothermal kettle The hydrothermal reaction is carried out in a drying oven; after the reaction, the product is taken out, filtered, centrifuged, and the supernatant is taken out and concentrated by rotary evaporation; the concentrated aqueous solution is added to a liquid chromatography column filled with silica gel powder, and washed off with dichloromethane Impurities, and then use deionized water to extract carbon quantum dots from castor seeds, and finally freeze-dry them into powder. The surface of the carbon quantum dot prepared by the method has no cohesive organic impurities, and lattice fringes are clearly visible. In addition, the preparation method has low cost and simple implementation, and the prepared carbon quantum dots have strong luminescence and good dispersibility, can emit light stably in different pH environments, and are expected to be widely used in chemical detection and biological imaging.

Description

A preparation method of fluorescent carbon quantum dots using castor seeds as carbon source

technical field

The invention relates to a method for preparing carbon quantum dots, in particular to a method for preparing fluorescent carbon quantum dots using castor seeds as carbon sources.

Background technique

Due to the advantages of high-efficiency fluorescence, stable performance, and strong adjustability, nano-fluorescent materials have great application prospects in optoelectronic devices and sensing and detection. Although the traditional inorganic semiconductor quantum dots (such as CdTe, CdSe) and inorganic perovskite quantum dots (such as CsPbI ₃ , CsPbBr ₃ ) have excellent luminous performance, they have relatively negative effects on organisms and the environment due to the heavy metals contained in them. The effect, and the general preparation is more complicated, and the raw materials are more expensive. In recent years, many high-performance and easily regulated carbon quantum dots have been reported by researchers at home and abroad. As a new type of fluorescent nanomaterial, carbon quantum dots have low or no toxicity, good biocompatibility and water solubility, and the preparation raw materials are cheap and easy to obtain. It has a very broad application space in light-emitting devices, sensing detection, biomedicine, etc.

The choice of carbon source is crucial for the in situ synthesis of carbon quantum dots, especially in the study of heteroatom doping and surface group regulation. Biomass carbon sources are abundant in nature and often contain elements such as nitrogen and phosphorus, so they have great potential for preparing excellent carbon dots. However, the carbon dots prepared from biological carbon sources are often not pure enough, and most of the fluorescence is not pH stable. Great significance.

Contents of the invention

The purpose of the present invention is to provide a method for preparing fluorescent carbon quantum dots using castor seeds as a carbon source, so as to obtain carbon quantum dots that emit light stably in different pH environments.

The present invention is achieved in that a kind of preparation method of the fluorescent carbon quantum dot that takes castor bean seeds as carbon source comprises the following steps:

a, disperse the peeled castor seed powder into deionized water, stir evenly, put into a hydrothermal kettle and carry out hydrothermal reaction in a drying box;

b. After the reaction is finished, the product is taken out, filtered, centrifuged, and the supernatant is taken out and concentrated by rotary evaporation;

c. Add the concentrated aqueous solution to a chromatographic column filled with silica gel powder, wash off impurities with dichloromethane, then extract castor seed carbon quantum dots with deionized water, and finally freeze-dry them into powder.

Preferably, in step a, the consumption ratio of castor seed powder and deionized water is 2 ~ 5g: 50ml.

Preferably, the peeled castor seed powder in step a is prepared by the following steps: soak the castor seeds in deionized water for 5-10 hours, peel off the skin, grind and sieve, and dry at 60-80°C for 15-30min .

Preferably, the sieve aperture after the castor seeds are ground is 100-200 mesh.

Preferably, the hydrothermal kettle in step a uses polytetrafluoroethylene as the liner.

Preferably, in step a, the temperature of the hydrothermal reaction is 150-180° C., and the reaction time is 4-8 hours.

Preferably, in step b, the pore size of the filter head is 0.22µm or 0.45µm, the centrifuge speed is 6000~8000rpm, the centrifugation time is 10~15min, the rotary evaporation temperature of the supernatant is 65~80°C, and the rotary evaporation concentration is up to 30~40mg/ml.

Preferably, in step c, the particle size of the silica gel powder is 100-200 mesh, the purity of dichloromethane is ≥99.0%, the pressure in the chamber of the freeze dryer is 30-100 Pa, and the freeze-drying time is 24-30 hours.

Beneficial effects of the present invention:

(1) Using natural carbon source castor seeds as a single carbon source, fluorescent carbon quantum dots with stable pH were obtained. The preparation method has low cost and simple implementation, and the prepared carbon quantum dots have high purity, strong luminescence and good dispersibility, can emit light stably in different pH environments, and are expected to be widely used in chemical detection and biological imaging.

(2) Unlike the traditional dialysis method commonly used in the preparation of biological carbon source carbon quantum dots, the present invention adopts a one-step hydrothermal method-column chromatography-freeze-drying combination preparation-purification system to obtain carbon quantum dots without organic impurities on the surface , the lattice fringes are clearly visible, which provides a new idea for the preparation of biological carbon source carbon quantum dots.

Description of drawings

Fig. 1 is the transmission electron microscope image of the castor seed carbon quantum dot prepared in embodiment 2.

Fig. 2 is the transmission electron microscope high-resolution image of the castor seed carbon quantum dot prepared in embodiment 2.

Fig. 3 is the X-ray photoelectron spectrometer spectrogram of the castor seed carbon quantum dot prepared in embodiment 2.

Fig. 4 is the infrared absorption spectrogram of the castor seed carbon quantum dot prepared in embodiment 2.

Fig. 5 is the ultraviolet-visible absorption spectrogram of castor seed carbon quantum dot prepared in embodiment 2.

Fig. 6 is the fluorescence excitation and emission light diagram of castor seed carbon quantum dots prepared in Example 2.

Fig. 7 is the emission spectrum diagram of castor seed carbon quantum dots prepared in Example 2 under different excitation light excitation.

Fig. 8 is the fluorescence lifetime diagram of castor seed carbon quantum dots prepared in Example 2.

Fig. 9 is a graph showing the changes in fluorescence intensity of castor seed carbon quantum dots prepared in Example 2 measured at different pHs.

Detailed ways

The present invention will be further elaborated below in conjunction with the examples, and the following examples are only for illustration and do not limit the protection scope of the present invention in any way.

The processes and methods not described in detail in the following examples are conventional methods well known in the art, and the reagents used in the examples are all analytically pure or chemically pure, and all of them are commercially available or prepared by methods well known to those of ordinary skill in the art.

Embodiment 1 prepares castor plant seed powder

Soak castor seeds in deionized water for 6 hours, take them out, peel them, grind them for 10 minutes, pass through a 200-mesh sieve, and dry them in a drying oven at 70°C for 20 minutes to obtain castor seeds powder.

Example 2 Preparation of fluorescent carbon quantum dots with castor seeds as carbon source (method 1)

Get the castor seed powder prepared in 2g embodiment 1 and be dispersed in 50ml deionized water, stir 10min, put into and carry out hydrothermal reaction in the hydrothermal still of liner with tetrafluoroethylene, the temperature of hydrothermal reaction is 150 ℃, The reaction time is 5 hours; after the reaction is completed, use a 0.45 μm filter head to filter, then put it in a centrifuge for 10 minutes at 7000 rpm, take the supernatant and place it in a rotary evaporator at 70 ° C to concentrate to 30 mg/ml; The concentrated aqueous solution was added to a column chromatography filled with 200 mesh silica gel powder, and the impurities were first washed away with dichloromethane with a purity of ≥99.0%, and then rinsed with deionized water to obtain a pure carbon quantum dot solution, and finally the pure carbon quantum dot solution was Place in a freeze dryer, dry at 50pa for 24h to obtain white castor seed carbon quantum dot powder.

Get 1g of carbon quantum dot powder and disperse it into 20ml deionized water, stir to obtain carbon quantum dot aqueous solution, measure the TEM particle size distribution of this carbon quantum dot aqueous solution, the measured results are shown in Figure 1, as can be seen from Figure 1, carbon quantum dots The average particle size of the dots was 15 nm. The high-resolution image of the carbon quantum dot aqueous solution was measured, and the measured results are shown in Figure 2. It can be seen from Figure 2 that the lattice fringes of the carbon quantum dots are clearly visible. The XPS elemental analysis data of the prepared carbon quantum dot aqueous solution were measured, and the results are shown in FIG. 3 . In addition, the infrared absorption, ultraviolet-visible, excitation emission, different excitation light, and fluorescence lifetime spectra of the prepared carbon quantum dot aqueous solution were measured, and the measured results are shown in Figures 4 to 8 in sequence. It can be seen from Fig. 3 and Fig. 4 that the surface of carbon quantum dots contains abundant functional groups related to nitrogen and oxygen. It can be seen from Figure 5 that there are photon energy absorptions of π-π ^* (at 282nm) and n-π ^* (at 328nm) in castor seed carbon quantum dots, that is, antibonding orbitals of conjugated π domains are generated; from As can be seen from Figure 6, the fluorescence of the carbon quantum dot aqueous solution under the excitation of ultraviolet light is blue; as can be seen from Figure 7, there is an excitation-dependent phenomenon in the carbon quantum dots obtained in this embodiment; as can be seen from Figure 8, this embodiment obtains The fluorescence lifetime of carbon quantum dots is nanoscale.

In addition, concentrated hydrochloric acid, solid sodium hydroxide and deionized water were used to prepare 10 ml of 11 samples each with a pH of 2 to 12, and 0.1 g of the carbon quantum dot powder prepared in this example was added to the 11 samples to measure The variation of the fluorescence intensity of the carbon quantum dots is shown in Figure 9. It can be seen from Figure 9 that the fluorescence intensity of the carbon quantum dots prepared in this embodiment does not change much at different pH values.

Example 3 Preparation of fluorescent carbon quantum dots with castor seeds as carbon source (method 2)

Get the castor seed powder prepared in 3g embodiment 1 and be dispersed in 50ml deionized water, stir 15min, put into and carry out hydrothermal reaction in the hydrothermal still of liner with tetrafluoroethylene, the temperature of hydrothermal reaction is 150 ℃, The reaction time is 7 hours; after the reaction is completed, use a 0.45 μm filter head to filter, then put it in a centrifuge for 15 minutes at 7000 rpm, take the supernatant and place it in a rotary evaporator at 70 ° C to concentrate to 35 mg/ml; The concentrated aqueous solution was added to a column chromatography filled with 200 mesh silica gel powder, and the impurities were first washed away with dichloromethane with a purity of ≥99.0%, and then rinsed with deionized water to obtain a pure carbon quantum dot solution, and finally the pure carbon quantum dot solution was Place in a freeze dryer, dry at 40pa for 24h to obtain white castor seed carbon quantum dot powder. The aqueous solution of carbon quantum dots prepared in this example and its characterization at different pHs are the same as in Example 2.

Example 4 Preparation of fluorescent carbon quantum dots using castor seeds as carbon source (method 3)

Get the castor seed powder prepared in 4g embodiment 1 and be dispersed in 50ml deionized water, stir 20min, put into and carry out hydrothermal reaction in the hydrothermal still of liner with tetrafluoroethylene, the temperature of hydrothermal reaction is 160 ℃, The reaction time is 6 hours; after the reaction is completed, use a 0.22 μm filter head to filter, then put it in a centrifuge for 10 minutes at 8000 rpm, take the supernatant and place it in a rotary evaporator at 75 ° C to concentrate to 30 mg/ml; The concentrated aqueous solution was added to a column chromatography filled with 200 mesh silica gel powder, and the impurities were first washed away with dichloromethane with a purity of ≥99.0%, and then rinsed with deionized water to obtain a pure carbon quantum dot solution, and finally the pure carbon quantum dot solution was Place in a freeze dryer, dry at 30pa for 30h to obtain white castor seed carbon quantum dot powder. The aqueous solution of carbon quantum dots prepared in this example and its characterization at different pHs are the same as in Example 2.

Example 5 Preparation of fluorescent carbon quantum dots with castor seeds as carbon source (method 4)

Get the castor seed powder prepared in 5g embodiment 1 and be dispersed in 50ml deionized water, stir 20min, put into and carry out hydrothermal reaction in the hydrothermal still of liner with tetrafluoroethylene, the temperature of hydrothermal reaction is 170 ℃, The reaction time is 8 hours; after the reaction is completed, use a 0.22 μm filter head to filter, then put it in a centrifuge for 20 minutes at 8000 rpm, take the supernatant and place it in a rotary evaporator at 80 ° C to concentrate to 40 mg/ml; The concentrated aqueous solution is added to a column chromatography filled with 100 mesh silica gel powder, and the impurities are first washed with dichloromethane with a purity of ≥99.0%, and then rinsed with deionized water to obtain a pure carbon quantum dot solution, and finally the pure carbon quantum dot solution is Place in a freeze dryer, dry at 30pa for 28h to obtain white castor seed carbon quantum dot powder. The aqueous solution of carbon quantum dots prepared in this example and its characterization at different pHs are the same as in Example 2.

Claims (8)

1. The preparation method of the fluorescent carbon quantum dot by taking castor seeds as a carbon source is characterized by comprising the following steps of:

a. dispersing peeled castor seed powder into deionized water, uniformly stirring, and placing into a hydrothermal kettle to perform hydrothermal reaction in a drying oven;

b. taking out the product after the reaction is finished, filtering and centrifuging, taking out the supernatant, and concentrating by rotary evaporation;

c. adding the concentrated aqueous solution into a column chromatography filled with silica gel powder, washing impurities with dichloromethane, extracting carbon quantum dots of castor seeds with deionized water, and freeze-drying to obtain powder.

2. The method for preparing fluorescent carbon quantum dots by taking castor seeds as a carbon source according to claim 1, wherein in the step a, the dosage ratio of castor seed powder to deionized water is 2-5 g:50ml.

3. The method for preparing fluorescent carbon quantum dots by using castor seeds as a carbon source according to claim 1, wherein the peeled castor seed powder in the step a is prepared by the following steps: and soaking the castor seeds in deionized water for 5-10 hours, peeling, grinding, sieving, and drying at 60-80 ℃ for 15-30 minutes.

4. The method for preparing the fluorescent carbon quantum dots by taking castor seeds as a carbon source according to claim 3, wherein the sieving aperture of the castor seeds after grinding is 100-200 meshes.

5. The method for preparing fluorescent carbon quantum dots by using castor seeds as a carbon source according to claim 1, wherein the hydrothermal kettle in the step a uses polytetrafluoroethylene as an inner container.

6. The method for preparing fluorescent carbon quantum dots by using castor seeds as a carbon source according to claim 5, wherein in the step a, the hydrothermal reaction temperature is 150-180 ℃ and the reaction time is 4-8 h.

7. The method for preparing the fluorescent carbon quantum dots by taking castor seeds as a carbon source according to claim 1, wherein in the step b, the aperture of a filter head is 0.22 mu m or 0.45 mu m, the rotation speed of a centrifugal machine is 6000-8000 rpm, the centrifugation time is 10-15 min, the rotary evaporation temperature of supernatant fluid is 65-80 ℃, and the rotary evaporation concentration is 30-40 mg/ml.

8. The method for preparing the fluorescent carbon quantum dots by taking castor seeds as a carbon source according to claim 1, wherein in the step c, the particle size of silica gel powder is 100-200 meshes, the purity of dichloromethane is more than or equal to 99.0%, the pressure in a freeze dryer cavity is 30-100pa, and the freeze drying time is 24-30 h.

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