Solid-state luminous magnetic carbon dot fluorescent material as well as preparation method and application thereof

Abstract

The invention provides a solid-state luminous magnetic carbon dot fluorescent material as well as a preparation method and application thereof. Ammonium ferric citrate is taken as an iron source, basic fuchsin is taken as a carbon source, polyethyleneimine is taken as a cross-linking agent, and magnetic Fe3O4 is formed through reaction of polyethyleneimine and ammonium ferric citrate; magnetic Fe3O4 and carbon dots formed by a carbon source are connected through dehydration condensation of amino of polyethyleneimine and carboxyl on the surface of basic fuchsin, the solid-state light-emitting magnetic carbon dot fluorescent material in which the carbon dots and the magnetic Fe3O4 are dispersed and are not in contact is obtained, AIQ does not occur in the aggregate, solid-state light emitting of the magnetic carbon dot fluorescent material can be achieved, and the magnetic carbon dot fluorescent material has good application prospects. The magnetic carbon dot fluorescent material can be applied to fingerprint extraction.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fluorescent carbon dots, and particularly relates to a solid-state luminescent magnetic carbon dot fluorescent material and a preparation method and application thereof. BACKGROUND

[0002] Carbon dots (CDs) are a new quasi-zero-dimensional luminescent carbon nanomaterial, and are regarded as a potential substitute for organic dyes and semiconductor quantum dots due to good chemical stability, light stability, water solubility and excellent biocompatibility. Based on the above advantages, carbon dot fluorescent powder has wide application prospects in the fields of biosensing, photocatalysis, luminescent devices, anti-counterfeiting encryption and the like.

[0003] In recent years, as a kind of high-efficiency solid-state luminescent fluorescent powder, the most important problem to be solved for carbon dots is low fluorescence quantum efficiency caused by aggregation-induced quenching (AIQ) of carbon dots in solid or high concentration. A common method to overcome this adverse effect is to disperse carbon dots in a dispersion medium such as inorganic salt which does not absorb or less absorbs carbon dot fluorescence, and this method can realize solid-state luminescence of carbon dots at low concentration. However, the medium used in this method will have different degrees of absorption of carbon dot fluorescence. Therefore, the solid-state luminescence efficiency of carbon dots is usually low.

[0004] At present, the method used for commercial fingerprint extraction is a magnetic brush developing method, and the developing powder used is magnetic iron powder, cobalt powder, nickel powder and the like metal powder, which does not have fluorescent properties and is difficult to be used again in a relatively dark or black object. The introduction of fluorescent properties will greatly improve the resolution of fingerprint extraction on dark and black objects. There are relevant reports showing the potential of carbon dot fluorescent powder for fingerprint extraction. However, carbon dots without magnetic field guidance have certain degree of limitation in the application of fingerprint extraction. Fe3O4 is a commonly used green and safe magnetic nanomaterial which is easy to be synthesized. However, Fe3O4 has strong absorption in the visible light region, and Fe3O4 usually quenches the luminescence of carbon dots, so that the synthesis of magnetic fluorescent dual-functional composite materials cannot be realized.

[0005] Therefore, the effective synthesis of magnetic fluorescent dual-functional composite materials has become an important problem to be solved in the field of fingerprint extraction on dark and black objects. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings and deficiencies of the prior art, and to provide a solid-state luminescent magnetic carbon dot fluorescent material and a preparation method and application thereof.

[0007] The technical scheme adopted by the present application is as follows: The first aspect of the present application provides a preparation method of a solid-state luminescent magnetic carbon dot fluorescent material, which uses ammonium ferric citrate (AFC) as an iron source, basic fuchsin (BasF) as a carbon source, and polyethyleneimine (PEI) as a crosslinking agent, and forms magnetic Fe3O4 by the reaction of polyethyleneimine and ammonium ferric citrate, and connects the carbon dots formed by the magnetic Fe3O4 and the carbon source by the dehydration condensation of the amino group of polyethyleneimine and the carboxyl group on the surface of basic fuchsin, to obtain a solid-state luminescent magnetic carbon dot fluorescent material in which the carbon dots and the magnetic Fe3O4 are dispersed and do not contact.

[0008] Preferably, it comprises the following steps: S1, dissolving ammonium ferric citrate, basic fuchsin and polyethyleneimine in water to form a uniform solution, and heating and reacting; S2, drying the mixed solution obtained by heating and reacting in step S1 after magnetic separation and water washing to obtain a solid-state luminescent magnetic carbon dot fluorescent powder.

[0009] Preferably, in step S1, the mass ratio of ammonium ferric citrate to basic fuchsin is (1-2):1, and the mass-volume ratio of the ammonium ferric citrate to polyethyleneimine is (1-2):1 g / mL.

[0010] Preferably, in step S1, the heating reaction is carried out at a temperature of 160-200℃ for 1-3 h.

[0011] Preferably, in step S1, the heating reaction is carried out under microwave conditions, and the microwave power is 500-1000 W.

[0012] Preferably, in step S2, the drying temperature is -100--60℃.

[0013] The second aspect of the present application provides a solid-state luminescent magnetic carbon dot fluorescent material, which is prepared according to the preparation method described above.

[0014] The third aspect of the present application provides an application of the solid-state luminescent magnetic carbon dot fluorescent material prepared according to the preparation method described above, which is used for fingerprint detection.

[0015] Preferably, it comprises the following steps: using a magnetic brush to absorb the magnetic carbon dot fluorescent material, brushing the potential fingerprint on the surface of the object after the magnetic powder bushing is formed, removing the magnetic carbon dot fluorescent material not combined with the fingerprint, making the magnetic fluorescent nanoparticles uniformly distributed on the potential fingerprint, under the ultraviolet light source, exciting the green fingerprint to appear, and using a camera to take a picture and record.

[0016] The present application has the following beneficial effects: 1. The magnetic carbon dot fluorescent material of the present application is prepared by one-step microwave hydrothermal method with AFC, BasF and PEI as raw materials. AFC provides magnetic iron source, BasF provides carbon source for the formation of carbon dots, and PEI is a crosslinking agent and a surface modifier. Among them, PEI plays an important role in realizing the magnetic and fluorescent properties of the composite material. It can promote the stable formation of magnetic Fe3O4, and through the dehydration condensation of its amino group and the carboxyl group on the surface of the carbon dots, it can connect magnetic Fe3O4 and carbon dots, so that the carbon dots are dispersed at a relatively far distance on the surface of magnetic Fe3O4. Therefore, the AIQ does not occur, and the magnetic carbon dot fluorescent material can realize solid-state light emission.

[0017] 2. The magnetic carbon dot fluorescent material of the present application can be applied to fingerprint extraction: the magnetic carbon dot fluorescent powder is absorbed with a magnetic brush, after a good magnetic fringe is formed, gently brush along the direction of the fingerprint for one or two times, blow off the magnetic fluorescent powder which is not firm with an ear ball, irradiate the fingerprint fluorescent image of the part with an ultraviolet lamp, and take a photo for preservation. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings obtained according to these drawings without creative labor still belong to the scope of the present application.

[0019] Figure 1 Preparation flow chart of the magnetic carbon dot fluorescent powder solid powder of the present application; Figure 2 Excitation-emission three-dimensional fluorescence spectrum of the magnetic carbon dot fluorescent powder solid powder provided in Example 1 of the present application; Figure 3 Visible light and fluorescence photos of the magnetic carbon dot fluorescent powder solid powder provided in Example 1 of the present application; Figure 4 Visible light and fluorescence photos of the magnetic carbon dot fluorescent powder aqueous solution according to Example 1 of the present application under the action of magnetic field and without magnetic field under 365nm ultraviolet light Figure 5 Absorption spectrum comparison chart of the magnetic carbon dot fluorescent powder according to Example 1 of the present application and the products under different reaction raw materials of the same reaction conditions of Comparative Examples 1-4; Figure 6 High-resolution transmission electron microscope picture of the magnetic carbon dot fluorescent powder according to Example 1 of the present application; Figure 7 Fourier transform infrared spectrum chart of the magnetic carbon dot fluorescent powder according to Example 1 of the present application and magnetic Fe3O4 of Comparative Example 1; Figure 8 X-ray diffraction pattern of magnetic carbon dot fluorescent powder and magnetic Fe3O4 according to Example 1 and Comparative Example 1 of the present application; Figure 9 Solid powder UV-Vis absorption spectrum of magnetic carbon dot fluorescent powder and magnetic Fe3O4 according to Example 1 and Comparative Example 1 of the present application; Figure 10 High-resolution X-ray photoelectron spectroscopy of C1s of magnetic carbon dot fluorescent powder according to Example 1 of the present application; Figure 11 High-resolution X-ray photoelectron spectroscopy of N1s of magnetic carbon dot fluorescent powder according to Example 1 of the present application; Figure 12 High-resolution X-ray photoelectron spectroscopy of O1s of magnetic carbon dot fluorescent powder according to Example 1 of the present application; Figure 13 High-resolution X-ray photoelectron spectroscopy of Fe2p of magnetic carbon dot fluorescent powder according to Example 1 of the present application; Figure 14 Hysteresis curve of magnetic carbon dot fluorescent powder and magnetic Fe3O4 according to Example 1 and Comparative Example 1 of the present application; Figure 15 Schematic diagram of magnetic carbon dot fluorescent powder magnetic brush method for developing latent fingerprints according to Example 1 of the present application; Figure 16 AI processing process diagram of fingerprint extraction after magnetic carbon dot fluorescent powder in Example 1 of the present application; Figure 17 Fingerprint detail feature diagram under microscope after fingerprint development of magnetic carbon dot fluorescent powder in Example 1 of the present application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings.

[0021] Example 1 The present embodiment provides a kind of magnetic carbon dot fluorescent powder, which is prepared by one-step microwave hydrothermal method and magnetic separation purification using AFC, BasF and PEI as raw materials.

[0022] As shown in Figure 1 The preparation method of the above-mentioned magnetic carbon dot fluorescent powder comprises the following steps: S1, 1.5 g of AFC, 1 g of BasF and 1 mL of PEI solution were dispersed in a beaker containing 15 ml of ultrapure water, stirred and shaken to a uniform solution, then the mixed solution was transferred to a polytetrafluoroethylene lined reaction kettle, and microwave hydrothermal reaction was carried out in an intelligent microwave digestion instrument, the reaction conditions were set as follows: microwave power 700 W, reaction temperature 180℃, reaction time 2 hours; S2, the mixed solution after reaction in S1 was transferred to a beaker for magnetic separation, and after the supernatant was discarded, appropriate amount of ultrapure water was added, ultrasonic mixing was carried out, and magnetic separation was continued, and the above process was repeated for 5 cycles or more until the supernatant had almost no fluorescence. The obtained substrate was freeze-dried at -80℃ to obtain magnetic carbon dot fluorescent powder CDs@Fe3O4; S3, the magnetic carbon dot fluorescent powder was absorbed with a magnetic brush, and after a good magnetic fringe was formed, the magnetic brush was gently brushed along the direction of the fingerprint for one or two times, the magnetic fluorescent powder which was not firm was blown off with an ear bulb, the number of magnetic brush was determined according to the adhesion of the magnetic powder, the fingerprint fluorescence image of the part was irradiated with an ultraviolet lamp, and photographed and saved, and the fluorescence photos of the fingerprint detail characteristics were taken with a fluorescence microscope.

[0023] Comparative Example 1 S1, 1.5 g of AFC and 1 mL of PEI solution were dispersed in a beaker containing 15 ml of ultrapure water, stirred and shaken to a uniform solution, then the mixed solution was transferred to a polytetrafluoroethylene lined reaction kettle, and microwave hydrothermal reaction was carried out in an intelligent microwave digestion instrument, the reaction conditions were set as follows: microwave power 700 W, reaction temperature 180℃, reaction time 2 hours; S2, the mixed solution after reaction in S1 was transferred to a beaker for magnetic separation, and after the supernatant was discarded, appropriate amount of ultrapure water was added, ultrasonic mixing was carried out, and magnetic separation was continued, and the above process was repeated for 5 cycles or more until the supernatant had almost no fluorescence. The obtained substrate was freeze-dried at -80℃ to obtain magnetic carbon dot fluorescent powder CDs@Fe3O4; Comparative Example 2 S1, 1.5 g of AFC was dispersed in a beaker containing 15 ml of ultrapure water, stirred and shaken to a uniform solution, then the mixed solution was transferred to a polytetrafluoroethylene lined reaction kettle, and microwave hydrothermal reaction was carried out in an intelligent microwave digestion instrument, the reaction conditions were set as follows: microwave power 700 W, reaction temperature 180℃, reaction time 2 hours; S2, the mixed solution after reaction in S1 was transferred to a beaker for magnetic separation, and after the supernatant was discarded, appropriate amount of ultrapure water was added, ultrasonic mixing was carried out, and magnetic separation was continued, and the above process was repeated for 5 cycles or more until the supernatant had almost no fluorescence. The obtained substrate was freeze-dried at -80℃ to obtain magnetic carbon dot fluorescent powder CDs@Fe3O4;

[0024] Comparative Example 3 S1, 1.0 g of BasF was dispersed in a beaker containing 15 ml of ultrapure water, and stirred and shaken to form a uniform solution, then the mixed solution was transferred to a polytetrafluoroethylene lined reaction kettle, and a microwave hydrothermal reaction was carried out in an intelligent microwave digestion instrument, the reaction conditions were set as follows: microwave power 700 W, reaction temperature 180℃, reaction time 2 hours; S2, the mixed solution after reaction in S1 was transferred to a beaker for magnetic separation, and no magnetic nanomaterials or fluorescent materials were generated.

[0025] Comparative Example 4 S1, 1.5 g of AFC and 1.0 g of BasF were dispersed in a beaker containing 15 ml of ultrapure water, and stirred and shaken to form a uniform solution, then the mixed solution was transferred to a polytetrafluoroethylene lined reaction kettle, and a microwave hydrothermal reaction was carried out in an intelligent microwave digestion instrument, the reaction conditions were set as follows: microwave power 700 W, reaction temperature 180℃, reaction time 2 hours; S2, the mixed solution after reaction in S1 was transferred to a beaker for magnetic separation, and no magnetic nanomaterials or fluorescent materials were generated.

[0026] Characterization Results As shown in Figure 2 is the excitation-emission three-dimensional fluorescence spectrum of the solid powder of the magnetic carbon dot fluorescent powder prepared in Example 1, Figure 3 is the visible light and fluorescence photos of the solid powder of the magnetic carbon dot fluorescent powder prepared in Example 1, Figure 4 is the visible light and fluorescence photos under 365 nm ultraviolet light in the aqueous solution of the magnetic carbon dot fluorescent powder of Example 1 under the action of a magnetic field or not, as can be seen from the figure, the aqueous solution of the prepared magnetic carbon dot fluorescent powder emits green light (520 nm) in the visible light region, and has the dual characteristics of magnetism and solid-state light emission.

[0027] Figure 5 is the absorption spectrum comparison chart of the products prepared under the same reaction conditions and different reaction raw materials of the magnetic carbon dot fluorescent powder prepared in Example 1 and Comparative Examples 1-4, as can be seen from the figure, the main absorption peak is located in the ultraviolet light region, and only when AFC, BasF and PEI are all present can the magnetic carbon dot fluorescent powder be obtained.

[0028] As shown in Figure 6 is the high-resolution transmission electron microscope picture of the magnetic carbon dot fluorescent powder prepared in Example 1, as can be seen from the figure, the particle size distribution of the magnetic carbon dot fluorescent powder is between 5-10 nm, and the lattice spacing is 0.21-0.24 nm (carbon dot) and 0.26 nm (Fe3O4).

[0029] Figure 7The Fourier transform infrared spectrograms of the magnetic carbon dot fluorescent powder and magnetic Fe3O4 of Example 1 and Comparative Example 1 show that the carbon dot fluorescent powder prepared in Example 1 contains N-H functional groups, proving that PEI plays a crucial role in the formation of magnetic materials and connecting the magnetic materials and fluorescent carbon dots.

[0030] Figure 8 The X-ray diffraction patterns of the magnetic carbon dot fluorescent powder and magnetic Fe3O4 of Example 1 and Comparative Example 1 show that not only Fe3O4 crystals are formed in the magnetic fluorescent powder, but also new crystals are formed due to the carbon dots, so as to achieve solid-state light emission.

[0031] Figure 9 The solid-state powder ultraviolet-visible absorption spectrograms of the magnetic carbon dot fluorescent powder and magnetic Fe3O4 of Example 1 and Comparative Example 1 show that the carbon dots account for a large proportion in the magnetic fluorescent powder.

[0032] Figure 10-13 The high-resolution X-ray photoelectron spectrograms of C1s, N1s, O1s and Fe2p of the magnetic carbon dot fluorescent powder of Example 1 show that the carbon dot fluorescent powder prepared in Example 1 contains carbon, nitrogen, oxygen and iron elements, and shows that the magnetic carbon dot fluorescent powder contains N-H bonds, proving the important role of PEI.

[0033] Figure 14 The hysteresis curve graphs of the magnetic carbon dot fluorescent powder and magnetic Fe3O4 of Example 1 and Comparative Example 1 further prove that the carbon dots account for a dominant position in the magnetic fluorescent powder while retaining strong magnetism.

[0034] Figure 15 The schematic diagram of the magnetic brush method of the magnetic carbon dot fluorescent powder of Example 1 for developing latent fingerprints, Figure 16 The AI processing process diagram of the picture after fingerprint extraction of the magnetic carbon dot fluorescent powder in Example 1, Figure 17 The fingerprint detail feature diagram under the microscope after the fingerprint development of the magnetic carbon dot fluorescent powder in Example 1, showing the potential and advantages of the magnetic carbon dot fluorescent powder prepared in Example 1 in extracting fingerprints on dark black objects.

[0035] The above disclosure is only the preferred embodiments of the present application, and of course cannot limit the scope of the rights of the present application, so the equivalent changes made according to the claims of the present application still fall within the scope covered by the present application.

Claims

1. A method for preparing a solid-state luminescent magnetic carbon dot fluorescent material, characterized in that, Using ferric ammonium citrate as the iron source, basic fuchsin as the carbon source, and polyethyleneimine as the crosslinking agent, magnetic Fe3O4 is formed by the reaction of polyethyleneimine and ferric ammonium citrate. The magnetic Fe3O4 is then connected to the carbon dots formed by the carbon source through the dehydration condensation of the amino groups of polyethyleneimine and the carboxyl groups on the surface of basic fuchsin. This results in a solid-state luminescent magnetic carbon dot fluorescent material in which the carbon dots and magnetic Fe3O4 are dispersed and do not come into contact.

2. The method for preparing a solid-state luminescent magnetic carbon dot fluorescent material according to claim 1, characterized in that, It includes the following steps: S1. Dissolve ferric ammonium citrate, basic fuchsin, and polyethyleneimine in water, mix them into a homogeneous solution, and heat to react; S2. The mixture obtained from the heating reaction in step S1 is washed with water by magnetic separation and then dried to obtain solid-state luminescent magnetic carbon dot phosphor.

3. The method for preparing a solid-state luminescent magnetic carbon dot fluorescent material according to claim 2, characterized in that: In step S1, the mass ratio of ferric ammonium citrate to basic fuchsin is (1~2):1, and the mass-volume ratio of ferric ammonium citrate to polyethyleneimine is (1~2):1 g / mL.

4. The method for preparing a solid-state luminescent magnetic carbon dot fluorescent material according to claim 2, characterized in that: In step S1, the heating reaction is carried out at a temperature of 160℃ to 200℃ for a time of 1 to 3 hours.

5. The method for preparing a solid-state luminescent magnetic carbon dot fluorescent material according to claim 2, characterized in that: In step S1, the heating reaction is carried out under microwave conditions with a microwave power of 500~1000W.

6. The method for preparing a solid-state luminescent magnetic carbon dot fluorescent material according to claim 2, characterized in that: In step S2, the drying temperature is -100~-60℃.

7. A solid-state luminescent magnetic carbon dot fluorescent material, characterized in that, It is prepared according to any one of claims 1-6.

8. An application of a solid-state luminescent magnetic carbon dot fluorescent material prepared by any one of the preparation methods of claims 1-6, characterized in that: It is used for fingerprint detection.

9. The application according to claim 8, characterized in that... The process includes the following steps: using a magnetic brush to pick up the magnetic carbon dot fluorescent material, and after forming magnetic powder spikes, brushing the latent fingerprint on the surface of the object to remove the magnetic carbon dot fluorescent material that has not been bound to the fingerprint, so that the magnetic fluorescent nanoparticles are evenly distributed on the texture of the latent fingerprint. Under ultraviolet light, the green fingerprint is excited and displayed, and then photographed and recorded with a camera.

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