A fluorescent composite nanomaterial, a preparation method and application thereof

Abstract

This invention discloses a fluorescent composite nanomaterial, its preparation method, and its application, belonging to the field of fluorescent materials technology. The fluorescent composite nanomaterial provided by this invention comprises carbon quantum dots with carboxyl groups on their surface and fluorescent nanoparticles with amino groups on their surface, in a mass ratio of (0.8–3):1; the carbon quantum dots with carboxyl groups and the fluorescent nanoparticles with amino groups are connected by amide bonds formed by the dehydration condensation of carboxyl and amino groups; the molecular formula of the fluorescent nanoparticles is Cs₂NaYCl₆:Yb. 3+ / Eu 3+ Among them, Yb 3+ The molar concentration of doping is 15–25%, Eu 3+ The molar concentration of the dopant is 8-12%. The fluorescent composite nanomaterials provided by this invention have the advantages of uniform particle size, high fluorescence emission intensity, and good fluorescence stability, and can be applied in fields such as humidity detection and fluorescence imaging.

Description

Technical Field

[0001] This invention relates to the field of fluorescent materials technology, and in particular to a fluorescent composite nanomaterial, its preparation method, and its application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Fluorescent nanomaterials have significant applications in biomedical imaging and environmental sensing. In biomedicine, fluorescent contrast agents are key materials for in vivo imaging, and their luminescence stability directly affects image quality and diagnostic reliability. Commonly used rare-earth materials in existing technologies suffer from insufficient luminescence efficiency due to their low absorption cross-sections and are prone to fluorescence quenching under prolonged illumination or complex physiological environments. While quantum dot materials possess high quantum yields, their poor chemical stability makes them susceptible to environmental oxidation or photobleaching, leading to rapid decay of luminescence performance. Furthermore, nanoparticles obtained through traditional preparation methods generally exhibit uneven particle size distribution, which not only affects the consistency of optical properties but also leads to non-specific aggregation within the body, reducing imaging resolution and potentially triggering toxic reactions.

[0004] In the field of humidity sensing, existing sensors based on organic fluorescent dyes face significant technological bottlenecks. The response of organic dye molecules to humidity changes is often accompanied by irreversible changes in their molecular structure, resulting in a continuous decay of the fluorescence signal and severely impacting the device's lifespan and measurement accuracy. Although recent studies have attempted to improve material stability through polymer coating or inorganic-organic composite structures, the improvements have consistently fallen short of expectations due to poor interfacial compatibility and low energy transfer efficiency. These inherent defects severely restrict the industrial application of fluorescent nanomaterials in precision medical detection and intelligent sensing devices. Summary of the Invention

[0005] In view of this, the present invention provides a fluorescent composite nanomaterial, its preparation method and application. The fluorescent composite nanomaterial provided by the present invention has the characteristics of uniform particle size and high fluorescence emission intensity, and its preparation method is simple and has good fluorescence stability. It is suitable for use as a fluorescent probe in humidity detection, bioimaging and other fields.

[0006] In a first aspect, the present invention provides a fluorescent composite nanomaterial comprising carbon quantum dots with carboxyl groups on their surface and fluorescent nanoparticles with amino groups on their surface in a mass ratio of (0.8 to 3):1.

[0007] The carbon quantum dots with carboxyl groups on their surface are connected to the fluorescent nanoparticles with amino groups on their surface through amide bonds formed by the dehydration condensation of carboxyl and amino groups.

[0008] The fluorescent nanoparticles have the molecular formula Cs2NaYCl6:Yb 3+ / Eu 3+ Among them, Yb 3+ The molar concentration of doping is 15-25%, Eu 3+ The molar concentration of doping is 8–12%.

[0009] Secondly, the present invention provides a method for preparing the above-mentioned fluorescent composite nanomaterials, comprising the following steps:

[0010] Fluorescent nanoparticles were reacted with polyethyleneimine to obtain fluorescent nanoparticles with amino-modified surfaces.

[0011] The product is obtained by performing a dehydration condensation reaction of carboxyl-modified carbon quantum dots and amino-modified fluorescent nanoparticles.

[0012] Thirdly, the present invention provides applications of the above-mentioned fluorescent composite nanomaterials or fluorescent composite nanomaterials prepared by the above-mentioned preparation method, wherein the fluorescent composite nanomaterials are used to prepare humidity sensors or fluorescent imaging contrast agents.

[0013] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0014] The fluorescent composite nanomaterials provided by this invention have the advantages of uniform particle size and high fluorescence emission intensity. They exhibit a blue light emission peak at 450–510 nm under excitation wavelengths of 360–400 nm and 250–260 nm, and the fluorescence shows good stability, remaining unchanged over long periods, which is beneficial for accurate imaging. Furthermore, the fluorescence intensity exhibits a strong humidity dependence, increasing with increasing humidity and showing a good linear relationship, thus enabling humidity measurement. It can be applied in humidity detection and fluorescence imaging. Moreover, the preparation method provided by this invention is relatively simple and low-cost. Attached Figure Description

[0015] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0016] Figure 1 This is a transmission electron microscope image of carbon quantum dots from Embodiment 1 of the present invention;

[0017] Figure 2 This is the emission spectrum of the carbon quantum dots in Embodiment 1 of the present invention;

[0018] Figure 3 This refers to Cs2NaYCl6:Yb prepared in Example 2 of the present invention. 3+ / Eu 3+ Transmission electron microscopy image of nanoparticles;

[0019] Figure 4 This refers to Cs2NaYCl6:Yb prepared in Example 2 of the present invention. 3+ / Eu 3+ X-ray diffraction pattern of nanoparticles;

[0020] Figure 5 This refers to Cs2NaYCl6:Yb prepared in Example 2 of this invention. 3+ / Eu 3+ Emission spectrum of nanoparticles;

[0021] Figure 6 This refers to CDs-Cs2NaYCl6:Yb prepared in Example 3 of this invention. 3+ / Eu 3+ Scanning electron microscope image;

[0022] Figure 7 The CDs and Cs2NaYCl6:Yb prepared in Examples 1 and 3 of this invention are 3+ / Eu 3+ -PEI、CDs-Cs2NaYCl6:Yb 3 + / Eu 3+ Fourier transform infrared absorption spectrum;

[0023] Figure 8 The carbon quantum dots of Example 1 and the Cs2NaYCl6:Yb prepared in Example 2 of this invention are examples of the present invention. 3+ / Eu 3+ Nanoparticles and CDs-Cs2NaYCl6:Yb prepared in Example 3 3+ / Eu 3+ Emission spectrum under 254nm laser excitation;

[0024] Figure 9 The carbon quantum dots of Example 1 and the Cs2NaYCl6:Yb prepared in Example 2 of this invention. 3+ / Eu 3+ Nanoparticles and CDs-Cs2NaYCl6:Yb prepared in Example 3 3+ / Eu 3+ Emission spectrum under 365nm laser excitation;

[0025] Figure 10 The carbon quantum dots of Example 1 and the Cs2NaYCl6:Yb prepared in Example 2 of this invention. 3+ / Eu 3+ Nanoparticles and CDs-Cs2NaYCl6:Yb prepared in Example 3 3+ / Eu 3+ Emission spectrum under 395nm laser excitation;

[0026] Figure 11 CDs-Cs2NaYCl6:Yb prepared in Example 3 of this invention 3+ / Eu 3+ Emission spectra of light emitted at different times under 365nm laser excitation;

[0027] Figure 12 CDs-Cs2NaYCl6:Yb prepared in Example 3 of this invention 3+ / Eu 3+ Emission spectra after irradiation with a 365nm laser at different humidity levels;

[0028] Figure 13 CDs-Cs2NaYCl6:Yb prepared in Example 3 of this invention 3+ / Eu 3+ Linear curve of emission intensity versus humidity under 365nm laser irradiation;

[0029] Figure 14 Cs2NaYCl6:Yb prepared in Example 2 of this invention 3+ / Eu 3+ The curve showing the relationship between emission intensity and humidity under 365nm laser irradiation;

[0030] Figure 15 CDs-Cs2NaYCl6:Yb prepared in Example 3 of this invention 3+ / Eu 3+ Fluorescence imaging within cells under 365nm laser irradiation. Detailed Implementation

[0031] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0032] As mentioned in the background section, the fluorescence stability of existing fluorescent nanomaterials is easily affected by environmental factors, making it difficult to maintain a stable fluorescence signal output.

[0033] In view of this, the present invention provides a fluorescent composite nanomaterial comprising carbon quantum dots with carboxyl groups on their surface and fluorescent nanoparticles with amino groups on their surface in a mass ratio of (0.8-3):1.

[0034] The carbon quantum dots with carboxyl groups on their surface are connected to the fluorescent nanoparticles with amino groups on their surface through amide bonds formed by the dehydration condensation of carboxyl and amino groups.

[0035] The fluorescent nanoparticles have the molecular formula Cs2NaYCl6:Yb 3+ / Eu 3+ Among them, Yb 3+ The molar concentration of doping is 15–25%, Eu 3+ The molar concentration of doping is 8–12%.

[0036] It is well known to those skilled in the art that not all rare earth ions possess excellent luminescent properties. Ineffective doping in the crystal lattice, insufficient energy transfer due to energy mismatch between rare earth ions, and concentration quenching can all lead to luminescence quenching. This invention uses Cs₂NaYCl₆:Yb 3+ / Eu 3+ Fluorescent nanoparticles, with Yb 3+ Eu 3+ As the doped ion replacement part Y 3+ It possesses high fluorescence efficiency, emitting visible light under 365nm laser excitation, exhibiting stable luminescence performance and good chemical stability. However, its quantum yield when used alone still needs improvement, and in complex biological systems and other practical application environments, it is easily affected by environmental factors, potentially leading to luminescence quenching. This invention discovers that combining carbon quantum dots with fluorescent nanoparticles Cs₂NaYCl₆:Yb... 3+ / Eu 3+ The two components are linked by chemical bonds, which enables them to have good bonding performance. The chemical bonding can improve the dispersibility and biocompatibility of the material in biological systems. The abundant functional groups on the surface of carbon quantum dots can reduce the aggregation of fluorescent nanoparticles in biological environments. Furthermore, its good biocompatibility can help the entire composite system to be used in fields such as biolabeling and imaging, and can also enhance fluorescence stability.

[0037] In this invention, the carbon quantum dots with carboxyl groups on their surface have a particle size of 2–5 nm; the fluorescent nanoparticles have a particle size of 20–60 nm. The fluorescent nanoparticles prepared by this invention exhibit a nano-tetragonal shape.

[0038] The fluorescent composite nanomaterials provided by this invention exhibit a blue light emission peak at 450–510 nm under excitation wavelengths of 360–400 nm and 250–260 nm.

[0039] This invention also provides a method for preparing the above-mentioned fluorescent composite nanomaterials, comprising the following steps:

[0040] Fluorescent nanoparticles were reacted with polyethyleneimine to obtain fluorescent nanoparticles with amino-modified surfaces.

[0041] The product is obtained by performing a dehydration condensation reaction of carboxyl-modified carbon quantum dots and amino-modified fluorescent nanoparticles.

[0042] In this invention, the specific steps for reacting fluorescent nanoparticles with polyethyleneimine are as follows: Fluorescent nanoparticles are mixed with nitrosyl tetrafluoroborate in solvent one, centrifuged, and the precipitate is dispersed in solvent two. Then, polyethyleneimine is added, and the mixture is stirred for 8–20 hours to obtain fluorescent nanoparticles with amino-modified surfaces. This invention first utilizes nitrosyl tetrafluoroborate to imbue the surface of fluorescent nanoparticles with BF4. - Polyethyleneimine (PEI) carries a positive charge, and the two are bound together by electrostatic adsorption. PEI is rich in amino groups, and when combined with BF4-containing compounds on its surface... - After the fluorescent nanoparticles are mixed, a large number of amino groups will be distributed on the surface of the fluorescent nanoparticles for subsequent connection with carbon quantum dots.

[0043] This invention does not impose special restrictions on the dehydration condensation reaction conditions and methods of carboxyl and amino groups; commonly used reaction conditions for carboxyl and amino groups in the art can be used. Preferably, this invention uses 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to activate the carboxyl groups on the surface of carbon quantum dots, and then the carboxyl groups react with the amino groups to form amide bonds. Preferably, the activation time is 1–3 hours.

[0044] In this invention, the mass ratio of the fluorescent nanoparticles, nitroso tetrafluoroborate, and polyethyleneimine is (1-1.5):(150-250):(80-120); the first solvent is selected from one or more of cyclohexane, toluene, or chloroform; the second solvent is N,N-dimethylformamide.

[0045] In this invention, the preparation method of the fluorescent nanoparticles includes the following steps: under an inert atmosphere, Yb salt, Eu salt, Y salt are mixed with oleic acid, oleylamine and 1-octadecene at 110-120°C, and then added to a methanol solution containing Na salt and Cs salt. After heating to remove the methanol, a thermal injection synthesis reaction is carried out, and the nanoparticles are purified to obtain the final product.

[0046] In this invention, the Yb salt is selected from the acetate or hydrochloride of Yb; the Eu salt is selected from the acetate or hydrochloride of Eu; the Y salt is selected from the acetate or hydrochloride of Y; the Na salt is selected from sodium acetate or sodium chloride; and the Cs salt is selected from the acetate or hydrochloride of Cs. The amount of the above compounds added is determined by the stoichiometric ratio of each element in the fluorescent nanoparticles, and no special limitation is made here.

[0047] This invention does not impose any special restrictions on the inert atmosphere; nitrogen or argon can be used.

[0048] The present invention does not impose any special restrictions on the amount of oleic acid, oleylamine and 1-octadecene. Preferably, the ratio of the total molar amount of Yb salt, Eu salt and Y salt to the amount of oleic acid, oleylamine and 1-octadecene is (0.4-0.6) mmol:(0.5-1) mL:(2-3) mL:(8-15) mL.

[0049] In this invention, the specific steps of the thermal injection synthesis reaction are as follows: the solution temperature is raised to 170–185°C, and trimethylchlorosilane is injected during the heating process, reacting for 5–20 seconds; then the temperature is rapidly lowered. The total molar ratio of trimethylchlorosilane to the Y salt, Yb salt, and Eu salt is (5–8):1, which serves to react with the metal ions (Y3+, Yb, etc.) in the reaction system. 3+ Eu 3+ (etc.) The role of ligands in coordination reactions.

[0050] In this invention, the preparation method of the carbon quantum dots with carboxyl groups on the surface is as follows: ethanolamine is added dropwise to an aqueous solution of citric acid, stirred vigorously until clear, and then subjected to a hydrothermal synthesis reaction at 170–200°C for 5–8 hours, followed by purification. In this invention, the molar ratio of ethanolamine to citric acid is (1.8–2.2):1, preferably 2:1. Using ethanolamine and citric acid in the above molar ratio as raw materials, the synthesized carbon quantum dots exhibit good luminescent properties. This invention does not impose special limitations on the purification process of the carbon quantum dots with carboxyl groups on the surface; for example, dialysis can be used to remove unreacted raw materials.

[0051] This invention provides applications for the aforementioned fluorescent composite nanomaterials or fluorescent composite nanomaterials prepared by the aforementioned method, specifically for the preparation of humidity sensors or fluorescent imaging contrast agents. The fluorescent composite nanomaterials provided by this invention exhibit increased fluorescence intensity with increasing humidity under 365nm laser excitation, demonstrating a good linear relationship between fluorescence intensity and humidity, thus enabling humidity measurement. Furthermore, they possess a small and uniform particle size, allowing them to enter cells after co-incubation, demonstrating promising application prospects.

[0052] The technical solution of the present invention will be further described below with reference to specific embodiments. The present invention does not impose any special restrictions on the source of reagents used in the following embodiments; commercially available products well known to those skilled in the art can be used.

[0053] Example 1

[0054] This embodiment provides a method for preparing carbon quantum dots (CDs) with carboxyl groups modified on the surface, including the following steps:

[0055] (1) Weigh 19.212g of citric acid and add it to 20mL of deionized water and stir until homogeneous to obtain a citric acid (0.1mol) aqueous solution. Then add 11.98mL of ethanolamine (0.2mol) aqueous solution to the citric acid aqueous solution and stir vigorously until the solution becomes clear.

[0056] (2) The above clear solution was sealed in a reaction vessel, heated to 180°C and kept for 6 hours, and then naturally cooled to room temperature to obtain a reddish-brown solution.

[0057] (3) Add the reddish-brown solution to a dialysis bag with a molecular weight cutoff of 3500 for dialysis. Change the water every 4 hours and dialyze for three days to remove excess small molecule products and impurities, and obtain purified CDs aqueous solution.

[0058] Transmission electron microscopy (TEM) images of the obtained carbon quantum dots are shown below. Figure 1 As shown, CDs are spherical with a size of about 3nm.

[0059] Take 0.25 mL of purified CDs aqueous solution, add 16 mL of deionized water to dilute the carbon dots, and measure the emission spectrum of the carbon quantum dots as shown below. Figure 2 As shown, the emission peak is at 519nm, the excitation source used is 254nm, and the power is 4W.

[0060] Example 2

[0061] This embodiment provides a fluorescent nanoparticle Cs2NaYCl6:Yb 3+ / Eu 3+ The preparation method includes the following steps:

[0062] (1) Add Yb(OAc)3·4H2O (0.1 mmol, 20%), EuCl3·6H2O (0.05 mmol, 10%), and Y(OAc)3·4H2O (0.35 mmol, 70%) to a four-necked flask, then add 2.8 mL of oleic acid, 0.7 mL of oleylamine, and 10 mL of octadecene. Heat the solution to 110 °C under nitrogen protection until a pale yellow transparent solution is formed. Then allow the solution to cool naturally to room temperature.

[0063] (2) Dissolve 1 mmol CsOAc and 2.7 mmol NaOAc·3H2O in 8 mL of methanol solution, add this solution to the above solution, heat the mixed solution to 70°C and maintain for 30 minutes, and remove the methanol.

[0064] (3) In a sealed four-necked flask, the above solution was heated under nitrogen protection. When the solution temperature reached 165°C, 0.4 mL of trimethylchlorosilane (TMS-Cl) was injected, and the temperature was raised to 180°C for 10 seconds. Then, it was quickly cooled to room temperature using an ice-water bath.

[0065] (4) The reacted solution was centrifuged at 9000 r / min for 20 min to obtain 1.2 mg of Cs2NaYCl6:Yb. 3+ / Eu 3+ The nanoparticles were washed and dispersed in 6 mL of cyclohexane for later use.

[0066] Figure 3 The Cs2NaYCl6:Yb prepared in this embodiment 3+ / Eu 3+ Scanning electron microscope (SEM) images of nanoparticles, showing that Cs₂NaYCl₆:Yb 3+ / Eu 3+ The nanoparticles are tetragonal in shape and about 30 nm in size.

[0067] Figure 4 The Cs2NaYCl6:Yb prepared in this embodiment 3+ / Eu 3+ X-ray diffraction (XRD) pattern of nanoparticles, Cs2NaYCl6:Yb 3+ / Eu 3+ The XRD pattern of the nanoparticles was completely consistent with the standard card (JCPDS#79-0772), indicating that the prepared Cs2NaYCl6:Yb 3+ / Eu 3+ Nanoparticles are a pure phase, free of impurities.

[0068] Figure 5 The Cs2NaYCl6:Yb prepared in this embodiment 3+ / Eu 3+ The emission spectrum of the nanoparticles shows characteristic emission peaks at 592 nm and 616 nm, corresponding to Eu values, respectively. 3+ of 5 D0→ 7 F1 and 5 D0→ 7 The F2 transition was performed using a 365nm excitation source with a power of 4W.

[0069] Example 3

[0070] This embodiment provides a fluorescent composite nanomaterial CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ The specific steps for preparing nanoparticles are as follows:

[0071] (1) Weigh 200 mg of nitrosotetrafluoroborate solid and dissolve it in a mixed solution containing 10 mL of N,N-dimethylformamide (DMF) and 6 mL of cyclohexane. Stir for 10 min. Add 6 mL of the fluorescent nanoparticles Cs₂NaYCl₆:Yb from Example 2. 3+ / Eu 3+ (Contains 1.2mg Cs2NaYCl6:Yb) 3+ / Eu 3+ Stir for 30 min. Centrifuge the reacted solution (12000 r / min × 10 min) and disperse in 5 ml DMF. Weigh 100 mg PEI and dissolve it in 10 mL DMF, then add it to the fluorescent nanomaterial (Cs2NaYCl6:Yb). 3+ / Eu 3+ The mixture was stirred in a DMF solution for 12 hours, centrifuged, and then dissolved in deionized water to obtain Cs2NaYCl6:Yb with an amino-modified surface. 3+ / Eu 3+ Fluorescent nanoparticles Cs2NaYCl6:Yb 3+ / Eu 3+ -PEI.

[0072] (2) Take 40 mg EDC and 20 mg NHS and dissolve them in the CDs aqueous solution (containing 1.2 mg CDs) of Example 1 and stir for 2 hours to activate the carboxyl groups on the surface of CDs to obtain the activated CDs aqueous solution.

[0073] (3) Take the activated CDs aqueous solution and the amino-modified Cs2NaYCl6:Yb from step (1). 3+ / Eu 3+ An aqueous solution containing 1.2 mg Cs2NaYCl6:Yb 3+ / Eu 3+ Mix and stir for 12 hours, centrifuge at 12000 rpm, wash once with water, and disperse a portion in 20 mL of water to obtain CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ The aqueous solution of the fluorescent composite nanomaterial was dried to obtain CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ Fluorescent composite nanomaterial powder.

[0074] Figure 6The CDs-Cs2NaYCl6:Yb prepared in this embodiment 3+ / Eu 3+ The scanning electron microscope image shows small spheres with rough surfaces, indicating that the surface roughness is due to the presence of microspheres in Cs2NaYCl6:Yb. 3+ / Eu 3+ The surface has a large number of carbon dots distributed, and the size of the nanoparticles is 30-40 nm.

[0075] Figure 7 CDs and Cs2NaYCl6:Yb prepared in Examples 1 and 3 3+ / Eu 3+ -PEI、CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ The Fourier transform infrared absorption spectrum is shown in the figure. As can be seen from the figure, the absorption peaks of the functional groups on the CDs surface are at 1315 cm⁻¹. -1 1700cm -1 Cs2NaYCl6:Yb 3+ / Eu 3+ The absorption peaks of the functional groups on the PEI surface are at 1639 cm⁻¹. -1 2953cm -1 CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ The absorption peaks of the surface functional groups are 2921 cm⁻¹. -1 1377cm -1 2921cm -1 The absorption peak at 1377 cm⁻¹ corresponds to the stretching vibration of the OH bond in the hydroxyl group -OH. -1 The absorption peak at this point is related to the bending vibration of the amide bond, and the presence of the amide bond indicates that Cs2NaYCl6:Yb 3+ / Eu 3+ It is bound to CDs through dehydration condensation between amino and carboxyl groups.

[0076] Figure 8 , Figure 9 and Figure 10 The CDs-Cs2NaYCl6:Yb prepared in this embodiment are respectively 3+ / Eu 3+ Fluorescent composite nanomaterials, CDs prepared in Example 1, and Cs2NaYCl6:Yb prepared in Example 2 3+ / Eu 3+The emission spectra obtained by excitation at 254 nm, 365 nm, and 395 nm with an excitation power of 4 W show that the main emission peak is 456 nm at excitation wavelengths of 254 nm and 395 nm, emitting blue light; and the main emission peak is 507 nm at excitation wavelength of 365 nm, indicating the fluorescent properties of the fluorescent composite nanomaterial prepared in this embodiment.

[0077] Figure 11 The CDs-Cs2NaYCl6:Yb prepared in this embodiment 3+ / Eu 3+ The fluorescence intensity histograms of the fluorescent composite nanomaterials after irradiation at 365 nm for 1 h, 10 h, 24 h, 48 h, and 72 h show that the fluorescence intensity of the fluorescent composite nanomaterials prepared in this embodiment does not change much, indicating that the material has excellent stability.

[0078] Application Example 1

[0079] The fluorescent composite nanomaterial CDs-Cs2NaYCl6:Yb from Example 3 was used. 3+ / Eu 3+ The specific steps for humidity sensing experiments are as follows:

[0080] Take 20 mg of CDs-Cs2NaYCl6:Yb prepared in Example 3 3+ / Eu 3+ The composite nanomaterial powder was dried and then placed in a constant temperature and humidity chamber with different humidity levels (30%RH, 40%RH, 50%RH, 60%RH, 70%RH, 80%RH, 90%RH) for 20 minutes. After stabilization, the CDs-Cs2NaYCl6:Yb composite nanomaterial powder was tested using a spectrometer under 365nm laser irradiation. 3+ / Eu 3+ Fluorescence spectra of composite nanomaterials, such as Figure 12 As shown, the fluorescence spectrum at 507 nm as a function of humidity is obtained as follows: Figure 13 As shown, this straight line can then be used to calculate the humidity of the environment in which the material is located. The excitation light source used is 365nm with a power of 4W. The fitted equation is y=13.77432x+1644.131514, and the goodness of fit R is . 2 =0.98363, indicating that CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ The fluorescence intensity of the composite nanomaterial gradually increases with increasing humidity, and the regression linear line fits the detection value well.

[0081] The Cs2NaYCl6:Yb of Example 2 was measured in the same manner. 3+ / Eu 3+The fluorescence properties of nanomaterials under different humidity levels were investigated. The fluorescence spectrum at 457 nm under 365 nm laser irradiation was shown as a function of reaction time with water, as illustrated below. Figure 14 As shown, this indicates that Cs2NaYCl6:Yb 3+ / Eu 3+ The fluorescence intensity of nanomaterials gradually decreases with increasing humidity, indicating that fluorescence quenching occurs in high-humidity environments.

[0082] Application Example 2

[0083] The materials from Example 3 were used in a fluorescence imaging experiment, and the specific steps are as follows:

[0084] (1) Using ultraviolet light to irradiate the prepared CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ The composite nanomaterials were sterilized in an aqueous solution (5 mL) and dispersed in 15 mL of Hela cell culture medium DMEM.

[0085] (2) HeLa cells were inoculated at 5 × 10 3 The cells were seeded at a density of 10 cells / well in 96-well plates and incubated overnight at 37°C with 5% CO2 to ensure cell adhesion. 200 μL of a solution containing CDs-Cs2NaYCl6:Yb was added to each well. 3+ / Eu 3+ The composite nanomaterials were incubated together in DMEM medium for 2 hours.

[0086] (3) Cells were fixed with 4% paraformaldehyde and observed using an inverted fluorescence microscope. 3 + / Eu 3+ Fluorescence imaging of composite nanomaterials in cells.

[0087] Cell bright-field and material fluorescence images were captured separately, and then the two images were combined to obtain a superimposed image, such as... Figure 15 As shown, Figure 15 CDs-Cs2NaYCl6:Yb prepared in Example 3 3+ / Eu 3+ Fluorescence imaging within HeLa cells was performed using a 365nm excitation source. To more clearly distinguish the fluorescence properties of the material, the blue emission was adjusted to green. Figure 15 This indicates that CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ Fluorescent properties of fluorescent composite nanomaterials in cell imaging.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fluorescent composite nanomaterial, characterized in that, The surface-modified carboxyl carbon quantum dots and the surface-modified amino fluorescent nanoparticles are in a mass ratio of (0.8-3):

1. The surface-modified carboxyl carbon quantum dots and the surface-modified amino fluorescent nanoparticles are connected through an amide bond formed by dehydration condensation between carboxyl and amino. The molecular formula of the fluorescent nanoparticles is Cs2NaYCl6: Yb 3+ / Eu 3+ Yb 3+ The doping molar concentration is 15-25%, Eu 3+ The doping molar concentration is 8-12%. The preparation method of the fluorescent composite nanomaterial comprises the following steps: The fluorescent nanoparticles are reacted with polyethyleneimine to obtain the surface-modified amino fluorescent nanoparticles. The surface-modified carboxyl carbon quantum dots and the surface-modified amino fluorescent nanoparticles are subjected to dehydration condensation reaction of carboxyl and amino, and thus the fluorescent composite nanomaterial is obtained. The specific steps of the reaction of the fluorescent nanoparticles with polyethyleneimine are as follows: The fluorescent nanoparticles are mixed with nitrous tetrafluoroborate in a solvent one, and after centrifugation, the precipitate is dispersed in a solvent two, then polyethyleneimine is added, and stirring is performed for 8-20 hours, so as to obtain the surface-modified amino fluorescent nanoparticles. The surface-modified carboxyl carbon quantum dots are prepared by the following method: ethanolamine is dropped into a citric acid solution, the solution is stirred until it is clear, and then a hydrothermal synthesis reaction is performed at 170-200 DEG C for 5-8 hours, and thus the surface-modified carboxyl carbon quantum dots are obtained after purification. 2.The fluorescent composite nanomaterial of claim 1, wherein, The particle size of the surface-modified carboxyl carbon quantum dots is 2-5 nm, and the particle size of the fluorescent nanoparticles is 20-60 nm.

3. The method for preparing fluorescent composite nanomaterials according to any one of claims 1-2, wherein, The preparation method of the fluorescent composite nanomaterial comprises the following steps: The fluorescent nanoparticles are reacted with polyethyleneimine to obtain the surface-modified amino fluorescent nanoparticles. The surface-modified carboxyl carbon quantum dots and the surface-modified amino fluorescent nanoparticles are subjected to dehydration condensation reaction of carboxyl and amino, and thus the fluorescent composite nanomaterial is obtained. The specific steps of the reaction of the fluorescent nanoparticles with polyethyleneimine are as follows: The fluorescent nanoparticles are mixed with nitrous tetrafluoroborate in a solvent one, and after centrifugation, the precipitate is dispersed in a solvent two, then polyethyleneimine is added, and stirring is performed for 8-20 hours, so as to obtain the surface-modified amino fluorescent nanoparticles. The surface-modified carboxyl carbon quantum dots are prepared by the following method: ethanolamine is dropped into a citric acid solution, the solution is stirred until it is clear, and then a hydrothermal synthesis reaction is performed at 170-200 DEG C for 5-8 hours, and thus the surface-modified carboxyl carbon quantum dots are obtained after purification.

4. The production method according to claim 3, wherein The mass ratio of the fluorescent nanoparticles, nitrous tetrafluoroborate and polyethyleneimine is (1-1.5):(150-250):(80-120), the solvent one is selected from one or more of cyclohexane, toluene or chloroform, and the solvent two is N, N-dimethylformamide. 5.The fluorescent composite nanomaterial of claim 1, wherein, The preparation method of the fluorescent nanoparticles comprises the following steps: under an inert atmosphere, Yb salt, Eu salt, Y salt are mixed with oleylamine, oleic acid and 1-octadecene and heated to 110-120 DEG C, then added to a methanol solution containing Na salt and Cs salt, and after removal of methanol by heating, a hot injection synthesis reaction is performed, and thus the fluorescent nanoparticles are obtained after purification. 6.The fluorescent composite nanomaterial of claim 5, wherein, The Yb salt is selected from Yb acetate, nitrate, sulfate or hydrochloride, the Eu salt is selected from Eu acetate, nitrate, sulfate or hydrochloride, the Y salt is selected from Y acetate, nitrate, sulfate or hydrochloride, the Na salt is selected from sodium acetate, sodium chloride or sodium sulfate, and the Cs salt is selected from Cs acetate, nitrate, sulfate or hydrochloride.

7. The fluorescent composite nanomaterial as described in claim 5, characterized in that, The specific steps of the hot injection synthesis reaction are as follows: the solution temperature is raised to 170-185 DEG C, the trimethylchlorosilane is injected during the temperature rising process, and the reaction is carried out for 5-20s; then the temperature is rapidly lowered.

8. The application of the fluorescent composite nanomaterial according to any one of claims 1-2, 5-7 or the fluorescent composite nanomaterial prepared by the preparation method according to any one of claims 3-4, characterized in that, The fluorescent composite nanomaterial is used for preparing a humidity sensor or a fluorescent imaging contrast agent.

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