阅读说明：本技术 一种磁性碳量子点的制备方法 (Preparation method of magnetic carbon quantum dots ) 是由 张现峰 芦静波 沈雪梅 李宗群 姜凤 于 2020-10-30 设计创作，主要内容包括：本发明涉及功能纳米材料制备的技术领域,具体涉及一种磁性碳量子点的制备方法,步骤如下：首先称取柠檬酸铁作为铁前驱体和碳源,将还原剂溶于适量的水配制还原剂溶液；然后将柠檬酸铁溶于所配制的还原剂溶液中,将混合溶液转移到高压釜中,密封并加热,反应一段时间,使得3价的铁还原成Fe-3O-4,同时,柠檬酸盐和还原剂碳化成氮掺杂的碳量子点(CQDs)；接下来将高压釜自然冷却至室温,反应所得产物离心得到固相A；然后,将固相A分散在分散剂中,超声、分离得到固相B；接下来,洗涤固相B多次；最后干燥洗涤后的产物,即得磁性碳量子点。本发明制备方法简单,所制备的磁性碳量子点具有优异的磁性和荧光性能,无毒且成本较低。(The invention relates to the technical field of functional nano material preparation, in particular to a preparation method of magnetic carbon quantum dots, which comprises the following steps: firstly, weighing ferric citrate as an iron precursor and a carbon source, and dissolving a reducing agent in a proper amount of water to prepare a reducing agent solution; dissolving ferric citrate in the prepared reducing agent solution, transferring the mixed solution into a high-pressure autoclave, sealing and heating, and reacting for a period of time to reduce the 3-valent iron into Fe 3 O 4 Simultaneous citrate and reductionCarbonizing the agent into nitrogen-doped Carbon Quantum Dots (CQDs); then, naturally cooling the autoclave to room temperature, and centrifuging a product obtained by the reaction to obtain a solid phase A; then, dispersing the solid phase A in a dispersing agent, and carrying out ultrasonic treatment and separation to obtain a solid phase B; next, the solid phase B was washed several times; and finally, drying the washed product to obtain the magnetic carbon quantum dot. The preparation method is simple, and the prepared magnetic carbon quantum dot has excellent magnetism and fluorescence property, is nontoxic and has low cost.)

1. A preparation method of magnetic carbon quantum dots is characterized by comprising the following steps: the method comprises the following steps:

step S1: weighing: weighing a certain mass of ferric citrate as an iron precursor and a carbon source;

step S2: preparing a reducing agent solution: mixing a quantity of reducing agent with water;

step S3: mixing and reacting: dissolving the ferric citrate of step S1 in a certain volume of the reducing agent solution prepared in step S2, transferring the mixed solution into an autoclave, sealing and heating to a certain temperature, and reacting for a period of time to reduce the iron with 3 valence into Fe₃O₄Simultaneously, the citrate and the reducing agent are carbonized into nitrogen-doped carbon quantum dots;

step S4: magnetic separation: naturally cooling the high-pressure kettle in the step S3 to room temperature, and centrifugally separating a product obtained by the reaction to obtain a solid phase A;

step S5: ultrasonic dispersion: dispersing the solid phase A obtained in the step S4 in a dispersing agent with a certain volume, ultrasonically dispersing for a certain time, and then centrifugally separating to obtain a solid phase B;

step S6: washing: washing the solid phase B obtained in the step S5 for multiple times by using a cleaning agent;

step S7: and (3) drying: and (5) transferring the product washed in the step (S6) to an oven, and drying for a certain time at a certain temperature to obtain the magnetic carbon quantum dots.

2. The method for preparing the magnetic carbon quantum dot according to claim 1, wherein: in the step S2, the reducing agent is one of triethanolamine, triethylene tetramine, or diethylene triamine.

3. The method for preparing the magnetic carbon quantum dot according to claim 1 or 2, wherein: the volume ratio of the reducing agent to the water in the step S2 is 1: (8-12).

4. The method for preparing the magnetic carbon quantum dot according to claim 3, wherein: in step S1, the weight of ferric citrate is 0.12-0.15 g.

5. The method for preparing the magnetic carbon quantum dot according to claim 4, wherein: the volume of the reducing agent solution in the step S3 is 8-15mL, the heating temperature is 150-250 ℃, and the reaction time is 2-6 hours.

6. The method for preparing the magnetic carbon quantum dot according to claim 1, wherein: the speed of the centrifugation in step S4 and step S5 is 8000-.

7. The method for preparing the magnetic carbon quantum dot according to claim 5, wherein: the dispersant in the step S5 is acetone, the volume of the dispersant is 10-15mL, the ultrasonic power is 100-500w, and the ultrasonic time is 3-10 minutes.

8. The method for preparing the magnetic carbon quantum dot according to claim 1, wherein: in the step S6, the cleaning agent is a mixed solution of n-hexane and ethanol, and the volume ratio of the n-hexane to the ethanol is (2-6): 1.

9. The method for preparing the magnetic carbon quantum dot according to claim 1, wherein: in the step S7, the drying temperature is 60-100 ℃, and the drying time is 24-36 hours.

Technical Field

The invention relates to the technical field of functional nano material preparation, in particular to a preparation method of magnetic carbon quantum dots.

Background

Since the advent, magnetic nanomaterials have received much attention from people, and nanomaterials are widely used in many disciplinary fields such as biomedicine and the like due to their unique properties. The main properties are as follows: superparamagnetic nanoparticles, especially superparamagnetic nanoparticles, have fluorescence properties, and can be used in various biomedicines, such as Magnetic Resonance Imaging (MRI), fluorescence imaging, drug carriers, and photothermal therapy. Therefore, much interest has been generated in it.

In order to construct magnetic-fluorescent composite Nanoparticles (NPs), great efforts have been made to incorporate composite nanofunctional materials in combination with magnetic and fluorescent properties, demonstrating that materials of both component properties can exist simultaneously. However, the conventional magnetic-fluorescent composite nanoparticles have some limitations in many practical applications, such as the disadvantages of poor light stability, poor biocompatibility, high toxicity, high cost, etc. of the noble metal nanoparticles and some rare earth metal nanoparticles. In addition, the complicated multi-step synthesis method for preparing the magnetic fluorescent composite nano-particles also hinders the practical application thereof.

A new type of fluorescent material has emerged in recent years: the Carbon Quantum Dots (CQDs) have the particle size of less than 10nm, are spherical carbon particles and are novel nano materials consisting of a carbon skeleton and surface groups. Compared with metal quantum dot materials, CQDs have the advantage of low toxicity, so that the CQDs have less harm to the environment; CQDs also have the characteristics of good biocompatibility, easy functionalization and the like, and are one of the most popular carbon nano materials after fullerene, carbon nano tube and graphene.

Due to the fact thatCQDs have optical properties superior to other fluorescent materials, and are more suitable for optical bioimaging in vitro and in vivo than conventional fluorescent materials. In addition, CQDs can be easily obtained by various low-cost and multi-material synthesis methods. The invention relates to the preparation of Fe by solvothermal method₃O₄And (4) CQDs composite nano particles to obtain the magnetic carbon quantum dots with good performance.

Disclosure of Invention

Aiming at the problems, the invention provides the preparation method of the magnetic carbon quantum dot, which has simple process and excellent product performance, by taking ferric citrate as an iron precursor and a carbon source and taking triethylene tetramine (triethanolamine and diethylenetriamine) as a reducing agent and a nitrogen source in a reaction medium. In order to realize the purpose of the invention, the following technical scheme is adopted:

a preparation method of magnetic carbon quantum dots comprises the following steps:

step S1: weighing: weighing a certain mass of ferric citrate as an iron precursor and a carbon source;

step S2: preparing a reducing agent solution: mixing a quantity of reducing agent with water;

step S3: mixing and reacting: dissolving the ferric citrate of step S1 in a certain volume of the reducing agent solution prepared in step S2, transferring the mixed solution into an autoclave, sealing and heating to a certain temperature, and reacting for a period of time to reduce the iron with 3 valence into Fe₃O₄Simultaneously, the citrate and the reducing agent are carbonized into nitrogen-doped carbon quantum dots;

step S4: magnetic separation: naturally cooling the high-pressure kettle in the step S3 to room temperature, and centrifugally separating a product obtained by the reaction to obtain a solid phase A;

step S5: ultrasonic dispersion: dispersing the solid phase A obtained in the step S4 in a dispersing agent with a certain volume, ultrasonically dispersing for a certain time, and then centrifugally separating to obtain a solid phase B;

step S6: washing: washing the solid phase B obtained in the step S5 for multiple times by using a cleaning agent;

step S7: and (3) drying: and (5) transferring the product washed in the step (S6) to an oven, and drying for a certain time at a certain temperature to obtain the magnetic carbon quantum dots.

Preferably, the reducing agent in step S2 is one of triethanolamine, triethylene tetramine, or diethylene triamine.

Preferably, the volume ratio of the reducing agent to the water in step S2 is 1: (8-12).

Preferably, the ferric citrate in the step S1 has a mass of 0.12-0.15 g.

Preferably, the volume of the reducing agent solution in the step S3 is 8-15mL, the heating temperature is 150-250 ℃, and the reaction time is 2-6 hours.

Preferably, the centrifugation speed in step S4 and step S5 is 8000-15000rpm, and the centrifugation time is 10-20 minutes.

Preferably, the dispersant in step S5 is acetone, the volume of the dispersant is 10-15mL, the power of the ultrasonic treatment is 100-500w, and the ultrasonic treatment time is 3-10 minutes.

Preferably, the cleaning agent in the step S6 is a mixed solution of n-hexane and ethanol, and the volume ratio of the n-hexane to the ethanol is (2-6): 1.

Preferably, the drying temperature in step S7 is 60-100 ℃, and the drying time is 24-36 hours.

Compared with the prior art, the invention has the beneficial effects that:

the invention adopts a solvothermal method to prepare Fe₃O₄The CQDs composite nano-particles have simple preparation method, avoid the complicated preparation of the magnetic fluorescent composite nano-particles, and in addition, the prepared Fe₃O₄the-CQDs composite nano particles have excellent magnetism and fluorescence performance, are non-toxic and low in cost, are beneficial to mass production and application, and have practical value.

Drawings

FIG. 1 is an infrared spectrum of the synthesized magnetic carbon quantum dots;

FIG. 2 is a diagram of the synthesized UV-VIS absorption spectrum of the magnetic carbon quantum dot;

FIG. 3 shows the fluorescence emission spectrum of the synthesized magnetic carbon quantum dots;

FIG. 4 Fe prepared at different hydrothermal times₃O₄Room temperature magnetic behavior of CQDs composite nanoparticles;

FIG. 5 Fe prepared at different hydrothermal temperatures₃O₄Fluorescence intensity profile of CQDs composite nanoparticles.

Fig. 6 is an overall flowchart of a method for preparing magnetic carbon quantum dots according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Detailed description of the preferred embodiment 1

A preparation method of magnetic carbon quantum dots comprises the following steps:

(1) weighing: 0.12g of ferric citrate was weighed as a cheap, non-toxic iron precursor and carbon source.

(2) Preparing a reducing agent solution: mixing triethanolamine and water according to a volume ratio of 1: 8 and mixing.

(3) Mixing and reacting: dissolving ferric citrate in the step (1) in 8mL of the reducing agent solution obtained in the step (2), transferring the mixed solution into a polytetrafluoroethylene autoclave, sealing and heating to 150 ℃, and reacting for 2 hours to reduce 3-valent iron into Fe₃O₄(ii) a At the same time, citrate and reducing agents are carbonized to nitrogen-doped CQDs.

(4) Magnetic separation: and (3) naturally cooling the high-pressure kettle to room temperature in the step (3), then carrying out centrifugal separation for 10 minutes at 8000rpm, and discarding the liquid to obtain a solid phase A.

(5) Ultrasonic dispersion: and (3) dispersing the solid phase A obtained in the step (4) in 10mL of acetone by ultrasonic dispersion for 3 minutes at the ultrasonic power of 100w, and then centrifuging at 8000rpm for 10 minutes to obtain a solid phase B.

(6) Washing: and (3) washing the solid phase B obtained in the step (5) for three times by using a cleaning agent, wherein the cleaning agent is a mixed solution of n-hexane and ethanol, and the volume ratio of the n-hexane to the ethanol is 2: 1.

(7) And (3) drying: and (4) transferring the product washed in the step (6) to an oven, and drying at 60 ℃ for 24 hours to obtain the magnetic carbon quantum dots.

Specific example 2

A preparation method of magnetic carbon quantum dots comprises the following steps:

(1) weighing: 0.15g of ferric citrate was weighed as a cheap, non-toxic iron precursor and carbon source.

(2) Preparing a reducing agent solution: triethylene tetramine and water are mixed according to the volume ratio of 1: 12 and mixing.

(3) Mixing and reacting: dissolving ferric citrate in the step (1) in 15mL of reducing agent solution obtained in the step (2), transferring the mixed solution into a polytetrafluoroethylene autoclave, sealing and heating to 250 ℃, and reacting for 6 hours to reduce 3-valent iron into Fe₃O₄(ii) a At the same time, citrate and reducing agents are carbonized to nitrogen-doped CQDs.

(4) Magnetic separation: and (4) naturally cooling the high-pressure kettle in the step (3) to room temperature, then carrying out centrifugal separation at 15000rpm for 20 minutes, and discarding liquid to obtain a solid phase A.

(5) Ultrasonic dispersion: and (3) dispersing the solid phase A obtained in the step (4) in 15mL of acetone, performing ultrasonic dispersion for 10 minutes at the ultrasonic power of 500w, and then performing centrifugal separation for 20 minutes at 15000rpm to obtain a solid phase B.

(6) Washing: and (3) washing the solid phase B obtained in the step (5) for three times by using a cleaning agent, wherein the cleaning agent is a mixed solution of n-hexane and ethanol, and the volume ratio of the n-hexane to the ethanol is 6: 1.

(7) And (3) drying: and (4) transferring the product washed in the step (6) into an oven, and drying at 100 ℃ for 36 hours to obtain the magnetic carbon quantum dots.

Specific example 3

A preparation method of magnetic carbon quantum dots comprises the following steps:

(1) weighing: 0.13g of ferric citrate was weighed as a cheap, non-toxic iron precursor and carbon source.

(2) Preparing a reducing agent solution: mixing diethylenetriamine and water according to a volume ratio of 1: 9 and mixing.

(3) Mixing and reacting: dissolving ferric citrate in the step (1) in 10mL of reducing agent solution obtained in the step (2), transferring the mixed solution into a polytetrafluoroethylene autoclave, sealing and heating to 200 ℃, and reacting for 4 hours to reduce 3-valent iron into Fe₃O₄(ii) a At the same time, citrate and reducing agents are carbonized to nitrogen-doped CQDs.

(4) Magnetic separation: and (4) naturally cooling the high-pressure kettle in the step (3) to room temperature, then performing centrifugal separation for 15 minutes at 10000rpm, and discarding liquid to obtain a solid phase A.

(5) Ultrasonic dispersion: and (3) dispersing the solid phase A obtained in the step (4) in 10mL of acetone for 3 minutes by ultrasonic dispersion with the ultrasonic power of 300w, and then centrifuging for 15 minutes at 10000rpm to obtain a solid phase B.

(6) Washing: and (3) washing the solid phase B obtained in the step (5) for three times by using a cleaning agent, wherein the cleaning agent is a mixed solution of n-hexane and ethanol, and the volume ratio of the n-hexane to the ethanol is 4: 1.

(7) And (3) drying: and (4) transferring the product washed in the step (6) to an oven, and drying at 80 ℃ for 24 hours to obtain the magnetic carbon quantum dots.

As can be seen from the drawings: FIG. 1 is an infrared spectrum of synthesized magnetic carbon quantum dots to identify Fe₃O₄CQDs functional groups, as shown in FIG. 1. For Fe₃O₄-CQDs，3393cm^-1The band at (A) can indicate the presence of O-H and N-H, 1561cm^-1Broadband sum of (A) 1637cm^-1The broad band at (a) may be due to bending vibration of N-H and amide I C ═ O stretching vibration. 1310cm^-1The weak band at (a) may be due to C-N stretching vibrations. 1400cm^-1And 577cm^-1The bands at (A) are respectively Fe₃O₄C-O bond and Fe-O bond in (1). The result of the infrared spectrogram of the magnetic carbon quantum dot shows that the prepared N-doped CQDs are attached to Fe₃O₄On the surface of the nanoparticles.

FIG. 2 shows the resultant magnetThe ultraviolet-visible absorption spectrum of the sex carbon quantum in the aqueous solution is shown as Fe₃O₄CQDs show two typical absorption peaks at 242nm and 354nm, the peak at 242nm being attributed to the pi-pi of the C ═ C bond^*The transition, and another peak at about 354nm is due to the n-pi of the C ═ O bond^*And (4) transition. The results show that CQDs maintain a good light effect area in the ultraviolet visible absorption spectrum and are not influenced by iron ions in the synthesis process. Moreover, the introduction of triethylene tetramine (triethanolamine or diethylenetriamine) well improves Fe₃O₄And CQDs.

FIG. 3 is a fluorescent emission spectrum of the synthesized magnetic carbon quantum dots. Performing spectrum scanning with the excitation wavelength between 310 nm and 400nm, wherein the result shows that the excitation wavelength is 370nm and the strongest fluorescence emission peak exists at 448nm in the fluorescence emission spectrum; and with the increase of the excitation wavelength, the position of the fluorescence emission peak generates red shift, the fluorescence intensity is increased firstly and then reduced, and the obvious dependence of the fluorescence intensity and wavelength on the excitation wavelength is shown.

Fig. 4 shows the magnetic behavior of magnetic carbon quantum dots prepared under different hydrothermal time conditions. Fe with hydrothermal time of 2h, 4h and 6h₃O₄The saturation magnetization of CQDs is 33.5emug, respectively^-1、45.8emug^-1And 55.7emug^-1Triethylene tetramine (triethanolamine or diethylenetriamine) provides a reducing environment, reduces iron precursors and promotes nucleation and subsequent growth phase, and increases Fe due to increase of hydrothermal time₃O₄Crystallinity of CQDs, facilitating Fe₃O₄Improvement of the magnetic properties of CQDs.

Fig. 5 shows fluorescence intensities of magnetic carbon quantum dots prepared at different hydrothermal temperatures. The reaction temperature is very important for the carbonization process for forming the carbon quantum dots. The reaction temperature is increased from 150 ℃ to 200 ℃, carbon dots with a similar polymer structure are changed into carbon quantum dots, and the fluorescence intensity is gradually enhanced; however, as the temperature continues to increase to 250 ℃, higher temperatures result in carbon quantum dots with higher graphitization and larger particle sizes, and the fluorescence intensity decreases.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can understand that the changes or modifications within the technical scope of the present invention are included in the scope of the present invention, and therefore, the scope of the present invention should be subject to the protection scope of the claims.