Fluorescent composite nano material as well as preparation method and application thereof

Abstract

The invention discloses a fluorescent composite nano material as well as a preparation method and application thereof, and belongs to the technical field of fluorescent materials. The fluorescent composite nano-material provided by the invention comprises carbon quantum dots with carboxyl modified surfaces and fluorescent nano-particles with amino modified surfaces, wherein the mass ratio of the carbon quantum dots to the fluorescent nano-particles is (0.8-3): 1; the carbon quantum dots of which the surfaces are modified with carboxyl groups are connected with the fluorescent nanoparticles of which the surfaces are modified with amino groups through amido bonds formed by dehydration condensation of carboxyl groups and amino groups; the molecular formula of the fluorescent nanoparticles is Cs2NaYCl6: Yb < 3 + > / Eu < 3 + >, the molar concentration of doped Yb < 3 + > is 15-25%, and the molar concentration of doped Eu < 3 + > is 8-12%. The fluorescent composite nanomaterial provided by the invention has the advantages of uniform particle size and high fluorescence emission intensity, has good fluorescence stability, and can be applied to the fields of humidity detection, fluorescence imaging and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescent materials, and particularly relates to a fluorescent composite nanomaterial, a preparation method thereof, and an application thereof. Background Art

[0002] The information disclosed in the background art of the present invention is only intended to enhance the overall understanding of the present invention, and is not necessarily regarded as an admission or an indication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Fluorescent nanomaterials have important application values in the fields of biomedical imaging and environmental sensing. In the biomedical field, as a key material for in vivo imaging, the luminescence stability of fluorescent contrast agents directly affects the imaging quality and diagnostic reliability. The rare earth materials commonly used in the prior art are limited by the insufficient luminescence efficiency caused by the low absorption cross section, and are prone to fluorescence quenching under long-term illumination or complex physiological environments; although quantum dot materials have relatively high quantum yields, their chemical stability is poor and they are easily affected by environmental oxidation or photobleaching, resulting in rapid attenuation of the luminescence performance. At the same time, the nanoparticles obtained by traditional preparation methods generally have the problem of uneven particle size distribution, which not only affects the consistency of the optical properties of the materials, but also leads to non-specific aggregation in the body, reducing the imaging resolution and possibly causing toxic reactions.

[0004] In the field of humidity sensing, the existing sensor devices based on organic fluorescent dyes face greater technical bottlenecks. The response of organic dye molecules to humidity changes is often accompanied by irreversible molecular structure changes, resulting in continuous attenuation of the fluorescence signal, seriously affecting the service life and measurement accuracy of the devices. Although in recent years, research has attempted to improve the material stability through polymer coating or inorganic-organic composite structures, due to problems such as poor interfacial compatibility and low energy transfer efficiency, the improvement effect has not reached the expected level. These inherent defects severely restrict the industrial application process 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, a preparation method thereof, and an application thereof. 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, with good fluorescence stability, and is suitable for use as a fluorescent probe in applications such as humidity detection and biological imaging.

[0006] In a first aspect, the present invention provides a fluorescent composite nanomaterial, comprising carboxyl group-modified carbon quantum dots and amino group-modified fluorescent nanoparticles with a mass ratio of (0.8 - 3):1;

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

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

[0009] In a second aspect, the present invention provides a method for preparing the above fluorescent composite nanomaterial, including the following steps:

[0010] React the fluorescent nanoparticles with polyethyleneimine to obtain fluorescent nanoparticles with amino groups on the surface;

[0011] Perform a dehydration condensation reaction of carboxyl groups and amino groups between the carbon quantum dots with carboxyl groups on the surface and the fluorescent nanoparticles with amino groups on the surface, and that's it.

[0012] In a third aspect, the present invention provides an application of the above fluorescent composite nanomaterial or the fluorescent composite nanomaterial prepared by the above preparation method, and uses the fluorescent composite nanomaterial to prepare a humidity sensor or a fluorescence imaging contrast agent.

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

[0014] The fluorescent composite nanomaterial provided by the present invention has the advantages of uniform particle size and high fluorescence emission intensity. It can have a blue light emission peak at 450-510 nm under excitation wavelengths of 360-400 nm and 250-260 nm, and the fluorescence has good stability, and the emission peak does not change for a long time, which is conducive to realizing accurate imaging; at the same time, its fluorescence intensity has strong humidity dependence, can increase with the increase of humidity, and has a good linear relationship, so that the determination of humidity can be realized; it can be applied in the fields of humidity detection and fluorescence imaging, etc.; at the same time, the preparation method provided by the present invention is relatively simple and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The specification drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work.

[0016] Figure 1 It is a transmission electron microscope image of the carbon quantum dots in Example 1 of the present invention;

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

[0018] Figure 3 is Cs2NaYCl6:Yb prepared in Example 2 of the present invention 3+ / Eu 3+ transmission electron microscopy image of the nanoparticles;

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

[0020] Figure 5 is Cs2NaYCl6:Yb prepared in Example 2 of the present invention 3+ / Eu 3+ emission spectrum of the nanoparticles;

[0021] Figure 6 is the scanning electron microscopy image of CDs-Cs2NaYCl6:Yb prepared in Example 3 of the present invention 3+ / Eu 3+ ;

[0022] Figure 7 are the Fourier transform infrared absorption spectra of CDs, Cs2NaYCl6:Yb 3+ / Eu 3+ -PEI, CDs-Cs2NaYCl6:Yb prepared in Examples 1 and 3 of the present invention 3 + / Eu 3+ ;

[0023] Figure 8 are the emission spectra of the carbon quantum dots of Example 1 of the present invention, Cs2NaYCl6:Yb 3+ / Eu 3+ nanoparticles prepared in Example 2 and CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ under 254 nm laser excitation;

[0024] Figure 9 are the carbon quantum dots of Example 1 of the present invention, Cs2NaYCl6:Yb prepared in Example 2 3+ / Eu 3+ nanoparticles and CDs-Cs2NaYCl6:Yb prepared in Example 3 3+ / Eu 3+ under 365 nm laser excitation;

[0025] Figure 10 For the carbon quantum dots of Example 1 of the present invention, the Cs2NaYCl6:Yb prepared in Example 2 3+ / Eu 3+ nanoparticles, and the CDs-Cs2NaYCl6:Yb prepared in Example 3 3+ / Eu 3+ Emission spectrogram under 395 nm laser excitation;

[0026] Figure 11 For the CDs-Cs2NaYCl6:Yb prepared in Example 3 of the present invention 3+ / Eu 3+ Emission spectrogram irradiated for different times under 365 nm laser excitation;

[0027] Figure 12 For the CDs-Cs2NaYCl6:Yb prepared in Example 3 of the present invention 3+ / Eu 3+ Emission spectrum irradiated by 365 nm laser at different humidities;

[0028] Figure 13 For the CDs-Cs2NaYCl6:Yb prepared in Example 3 of the present invention 3+ / Eu 3+ Linear curve of the relationship between the emission intensity and humidity under 365 nm laser irradiation;

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

[0030] Figure 15 For the CDs-Cs2NaYCl6:Yb prepared in Example 3 of the present invention 3+ / Eu 3+ , fluorescence imaging map in cells under 365 nm laser irradiation. Detailed implementation manners

[0031] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

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

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

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

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

[0036] As is well known to those skilled in the art, not all rare earth ions have excellent luminescence properties. Due to reasons such as ineffective doping in the lattice, insufficient energy transfer caused by energy mismatch between rare earth ions, and concentration quenching, luminescence quenching may occur. The present invention selects Cs2NaYCl6:Yb 3+ / Eu 3+ fluorescent nanoparticles, with Yb 3+ , Eu 3+ as doping ions to replace part of Y 3+ . It has a high fluorescence emission efficiency, can emit visible light under the excitation of a 365 nm laser, has stable luminescence performance, and good chemical stability. However, when used alone, its quantum yield still needs to be improved, and in practical application environments such as complex biological systems, it is easily interfered by environmental factors and may exhibit luminescence quenching phenomena. The present invention discovers that by combining carbon quantum dots and fluorescent nanoparticles Cs2NaYCl6:Yb 3+ / Eu 3+ in a way of chemical bond connection, this method can enable good binding performance between the two. The chemical bonding of the two can improve the dispersibility and biocompatibility of the material in the biological system. The abundant functional groups on the surface of carbon quantum dots can reduce the aggregation of fluorescent nanoparticles in the biological environment, and its good biocompatibility itself contributes to the application of the entire composite system in the fields of biological labeling, imaging, etc., and can enhance fluorescence stability.

[0037] In the present invention, the particle size of the carbon quantum dots modified with carboxyl groups is 2 to 5 nm; the particle size of the fluorescent nanoparticles is 20 to 60 nm. The fluorescent nanoparticles prepared by the present invention present a nano-tetragonal shape.

[0038] The fluorescent composite nanomaterial provided by the present invention has a blue light emission peak at 450 - 510 nm under excitation wavelengths of 360 - 400 nm and 250 - 260 nm.

[0039] The present invention also provides a preparation method of the above fluorescent composite nanomaterial, which includes the following steps:

[0040] React the fluorescent nanoparticles with polyethyleneimine to obtain fluorescent nanoparticles with amino groups on the surface;

[0041] Perform a dehydration condensation reaction between the carboxyl group and the amino group of the carbon quantum dots with carboxyl groups on the surface and the fluorescent nanoparticles with amino groups on the surface to obtain the product.

[0042] In the present invention, the specific steps of reacting the fluorescent nanoparticles with polyethyleneimine are as follows: Mix and react the fluorescent nanoparticles with nitrous acid tetrafluoroborate in solvent one, after centrifugation, disperse the precipitate in solvent two, and then add polyethyleneimine and stir for 8 - 20 h to obtain fluorescent nanoparticles with amino groups on the surface. In the present invention, first, nitrous acid tetrafluoroborate is used to make the surface of the fluorescent nanoparticles carry BF4 - , and polyethyleneimine (PEI) has a positive charge, and the two are combined together through electrostatic adsorption. PEI has abundant amino groups. When it is mixed with the fluorescent nanoparticles with BF4 - on the surface, a large number of amino groups on it will be distributed on the surface of the fluorescent nanoparticles for subsequent connection with carbon quantum dots.

[0043] The present invention does not impose special restrictions on the conditions and methods of the dehydration condensation reaction between the carboxyl group and the amino group. The reaction conditions commonly used in the art for the reaction between the carboxyl group and the amino group can be adopted. The present invention preferably uses 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to activate the carboxyl groups on the surface of the carbon quantum dots, and then the carboxyl group and the amino group react to form an amide bond. Preferably, the activation time is 1 - 3 h in the present invention.

[0044] In the present invention, the mass ratio of the fluorescent nanoparticles, nitrous acid 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; the solvent two is N,N-dimethylformamide.

[0045] In the present invention, the preparation method of the fluorescent nanoparticles includes the following steps: Under an inert atmosphere condition, heat Yb salt, Eu salt, Y salt, oleic acid, oleylamine, and 1-octadecene to 110 - 120 °C for mixing and reacting, then add them to a methanol solution containing Na salt and Cs salt, heat to remove methanol and then perform a thermal injection synthesis reaction, and purify to obtain the product.

[0046] In the present invention, the Yb salt is selected from ytterbium acetate or ytterbium hydrochloride; the Eu salt is selected from europium acetate or europium hydrochloride; the Y salt is selected from yttrium acetate or yttrium hydrochloride; the Na salt is selected from sodium acetate or sodium chloride; the Cs salt is selected from cesium acetate or cesium hydrochloride. The addition amounts of the above compounds are determined by the stoichiometric ratios of the elements in the fluorescent nanoparticles, and no special limitation is imposed herein in the present invention.

[0047] No special limitation is imposed on the inert atmosphere in the present invention, and nitrogen or argon can be used.

[0048] No special limitation is imposed on the amounts of oleic acid, oleylamine and 1-octadecene in the present invention. Preferably, the molar ratio of the total molar amounts of the Yb salt, Eu salt and Y salt to the amounts 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 the present invention, the specific steps of the thermal injection synthesis reaction are as follows: raise the temperature of the solution to 170 - 185 °C, inject trimethylchlorosilane during the heating process, and react for 5 - 20 s; then rapidly cool down. The molar ratio of trimethylchlorosilane to the total molar amounts of the Y salt, Yb salt and Eu salt is (5 - 8) : 1, which functions to coordinate with the metal ions (Y3+, Yb 3+ , Eu 3+ etc.) in the reaction system.

[0050] In the present invention, the preparation method of the carbon quantum dots modified with carboxyl groups on the surface is as follows: drop ethanolamine into the aqueous solution containing citric acid, stir vigorously until it becomes clear, and carry out a hydrothermal synthesis reaction at 170 - 200 °C for 5 - 8 h, and then purify to obtain. In the present invention, the molar ratio of ethanolamine to citric acid is (1.8 - 2.2) : 1, preferably 2 : 1. Using ethanolamine and citric acid with the above molar ratio as raw materials, the synthesized carbon quantum dots have good luminescence properties. No special limitation is imposed on the purification process of the carbon quantum dots modified with carboxyl groups on the surface in the present invention. For example, dialysis can be used to remove the unreacted raw materials.

[0051] The present invention provides the application of the above fluorescent composite nanoparticles or the fluorescent composite nanoparticles prepared by the above preparation method, and uses the fluorescent composite nanoparticles to prepare a humidity sensor or a fluorescence imaging contrast agent. Under the excitation of a 365 nm laser, the fluorescence intensity of the fluorescent composite nanoparticles provided by the present invention increases with the increase of humidity, and there is a good linear relationship between the fluorescence intensity and humidity, enabling humidity measurement. At the same time, it has a small and uniform particle size, and can enter cells after co-incubation with cells, having good application prospects.

[0052] The technical solution of the present invention will be further described below in conjunction with specific embodiments. The present invention has no special restrictions on the sources of the reagents used in the following embodiments, and commercially available products well-known to those skilled in the art can be used.

[0053] Example 1

[0054] This example provides a preparation method of carbon quantum dots (CDs) surface-modified with carboxyl groups, including the following steps:

[0055] (1) Weigh 19.212 g of citric acid and add it to 20 mL of deionized water, stir evenly to obtain an aqueous solution of citric acid (0.1 mol), and then drop 11.98 mL of an aqueous solution of ethanolamine (0.2 mol) into the aqueous solution of citric acid, and stir vigorously until the solution becomes clear.

[0056] (2) Seal the above clear solution in a reaction kettle, heat it to 180 °C and keep it for 6 h, then naturally cool it to room temperature to obtain a reddish-brown solution.

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

[0058] The transmission electron microscope (TEM) image of the obtained carbon quantum dots is as Figure 1 shown. It can be seen therefrom that the CDs are spherical and the size is about 3 nm.

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

[0060] Example 2

[0061] This example provides a preparation method of fluorescent nanoparticles Cs2NaYCl6:Yb 3+ / Eu 3+ , including the following steps:

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

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

[0064] (3) In a sealed four-necked flask, heat the above solution under nitrogen protection. When the solution temperature reaches 165 °C, inject 0.4 mL of trimethylchlorosilane (TMS-Cl), raise the temperature to 180 °C and react for 10 s, then quickly cool it to room temperature with an ice-water bath.

[0065] (4) Centrifuge the reacted solution at 9000 r / min for 20 min to obtain 1.2 mg of Cs₂NaYCl₆:Yb 3+ / Eu 3+ nanoparticles, wash them and disperse them in 6 mL of cyclohexane for standby.

[0066] Figure 3 This is the scanning electron microscope image of the Cs₂NaYCl₆:Yb 3+ / Eu 3+ nanoparticles prepared in this example. As can be seen from the figure, the Cs₂NaYCl₆:Yb 3+ / Eu 3+ nanoparticles are tetragonal in shape, and the particle size is about 30 nm.

[0067] Figure 4 This is the X-ray diffraction (XRD) pattern of the Cs₂NaYCl₆:Yb 3+ / Eu 3+ nanoparticles prepared in this example. The XRD pattern of the Cs₂NaYCl₆:Yb 3+ / Eu 3+ nanoparticles is completely consistent with the standard card (JCPDS#79-0772), indicating that the prepared Cs₂NaYCl₆:Yb 3+ / Eu 3+ nanoparticles are pure phase without impurities.

[0068] Figure 5 This is the emission spectrum of the Cs₂NaYCl₆:Yb 3+ / Eu 3+ nanoparticles prepared in this example. The characteristic emission peaks are at 592 nm and 616 nm, corresponding to the 3+ of 5 D₀→ 7 F₁ and 5 D₀→ 7 F₂ transitions respectively. The excitation light source used is 365 nm and the power is 4 W.

[0069] Example 3

[0070] This embodiment provides a preparation method for fluorescent composite nanomaterials CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ nanoparticles, and the specific steps are as follows:

[0071] (1) Weigh 200 mg of nitrous acid tetrafluoroborate solid and dissolve it in a mixed solution of 10 mL of N-N dimethylformamide (DMF) and 6 mL of cyclohexane, and stir for 10 min. Add 6 mL of the fluorescent nanoparticles Cs2NaYCl6:Yb 3+ / Eu 3+ (containing 1.2 mg of Cs2NaYCl6:Yb 3+ / Eu 3+ ) in Example 2, and stir for 30 min. Centrifuge the reacted solution (12000 r / min × 10 min) and disperse it in 5 ml of DMF. Weigh 100 mg of PEI and dissolve it in 10 mL of DMF, and add it to the DMF solution of the fluorescent nanomaterial (Cs2NaYCl6:Yb 3+ / Eu 3+ ), stir for 12 h, and after centrifugation, dissolve it in deionized water to obtain Cs2NaYCl6:Yb 3+ / Eu 3+ fluorescent nanoparticles Cs2NaYCl6:Yb 3+ / Eu 3+ -PEI with surface-modified amino groups.

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

[0073] (3) Take the activated aqueous solution of CDs and mix it with the aqueous solution of the Cs2NaYCl6:Yb 3+ / Eu 3+ modified with amino groups in step (1) (containing 1.2 mg of Cs2NaYCl6:Yb 3+ / Eu 3+ ), stir for 12 h, centrifuge at 12000 r / min, wash with water once, take a part and disperse it in 20 mL of water to obtain an aqueous solution of the CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ fluorescent composite nanomaterial, and dry the other part to obtain the CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ fluorescent composite nanomaterial powder.

[0074] Figure 6The CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ scanning electron micrograph prepared in this example shows small balls with rough surfaces, indicating that a large number of carbon dots are distributed on the surface of Cs2NaYCl6:Yb 3+ / Eu 3+ , and the size of the nanoparticles is in the range of 30-40 nm.

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

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

[0077] Figure 11 For the CDs-Cs2NaYCl6:Yb prepared in this example 3+ / Eu 3+ Bar chart of fluorescence intensity of the fluorescent composite nanomaterial irradiated for 1 h, 10 h, 24 h, 48 h, and 72 h under 365 nm excitation. It can be seen that the fluorescence intensity of the fluorescent composite nanomaterial prepared in this example changes little, indicating excellent material stability.

[0078] Application Example 1

[0079] The fluorescent composite nanomaterial CDs-Cs2NaYCl6:Yb in Example 3 3+ / Eu 3+ was used for the humidity sensing experiment, and the specific steps are as follows:

[0080] Take 20 mg of the powder of the composite nanomaterial CDs-Cs2NaYCl6:Yb prepared in Example 3 3+ / Eu 3+ After drying, place it in a thermostatic and humidistatic chamber with different humidities (30% RH, 40% RH, 50% RH, 60% RH, 70% RH, 80% RH, 90% RH). After stabilizing for 20 min, under 365 nm laser irradiation, use a spectrometer to measure the fluorescence spectrum of CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ The fluorescence spectrum of the composite nanomaterial is as Figure 12 shown. The change curve of the fluorescence spectrum at 507 nm with humidity is as Figure 13 shown. Furthermore, the humidity in the environment where the material is located can be calculated using this straight line. The excitation light source used is 365 nm, and the power is 4 W. The fitted equation is y = 13.77432x + 1644.131514, and the goodness of fit R 2 = 0.98363, indicating that the fluorescence intensity of the CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ composite nanomaterial gradually increases with the increase of humidity, and the regression linear line has a good fitting degree for the measured values.

[0081] The Cs2NaYCl6:Yb in Example 2 was measured in the same way 3+ / Eu 3+The fluorescence properties of the nanomaterials at different humidities. Under the irradiation of a 365 nm laser, the change curve of the fluorescence spectrum at 457 nm with the reaction time with water is as Figure 14 shown, indicating that Cs2NaYCl6:Yb 3+ / Eu 3+ nanomaterials show a gradual decrease in fluorescence intensity with the increase in humidity, indicating that there is fluorescence quenching in a humid environment.

[0082] Application Example 2

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

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

[0085] (2) Hela cells were seeded in a 96-well plate at a density of 5×10 3 cells / well and incubated overnight in an environment of 5% CO2 and 37 °C to ensure cell adhesion. 200 μL of DMEM medium containing CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ composite nanomaterials was added to each well and co-incubated for 2 h.

[0086] (3) The cells were fixed with 4% paraformaldehyde, and the fluorescence imaging of CDs-Cs2NaYCl6:Yb 3 + / Eu 3+ composite nanomaterials in the cells was observed using an inverted fluorescence microscope.

[0087] The bright-field image of the cells and the fluorescence image of the material were taken separately, and finally the two were combined to obtain a superimposed image, as Figure 15 shown, Figure 15 which is the fluorescence imaging diagram of CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ prepared in Example 3 in Hela cells. The excitation light source used was 365 nm. In order to more clearly distinguish the fluorescence properties of the material, the blue luminescence of the material was adjusted to green, Figure 15 indicating the fluorescence properties of CDs-Cs2NaYCl6:Yb 3+ / Eu 3+ fluorescent composite nanomaterials in cell imaging.

[0088] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A fluorescent composite nanomaterial, characterized in that, It includes carbon quantum dots modified with carboxyl groups and fluorescent nanoparticles modified with amino groups with a mass ratio of (0.8 - 3):1; The carbon quantum dots modified with carboxyl groups and the fluorescent nanoparticles modified with amino groups are connected by amide bonds formed through dehydration condensation between carboxyl groups and amino groups; The molecular formula of the fluorescent nanoparticles is Cs2NaYCl6:Yb 3+ / Eu 3+ , where the doping molar concentration of Yb 3+ is 15-25%, and the doping molar concentration of Eu 3+ is 8-12%.

2. The fluorescent composite nanomaterial according to claim 1, wherein The particle size of the carbon quantum dots modified with carboxyl groups is 2 - 5 nm; the particle size of the fluorescent nanoparticles is 20 - 60 nm.

3. The preparation method of the fluorescent composite nanomaterial according to any one of claims 1 to 2, characterized in that, It includes the following steps: React the fluorescent nanoparticles with polyethyleneimine to obtain fluorescent nanoparticles modified with amino groups; Perform a dehydration condensation reaction between the carboxyl groups and amino groups of the carbon quantum dots modified with carboxyl groups and the fluorescent nanoparticles modified with amino groups to obtain the product.

4. The preparation method according to claim 3, wherein, The specific steps of reacting the fluorescent nanoparticles with polyethyleneimine are as follows: Mix and react the fluorescent nanoparticles with nitrous acid tetrafluoroborate in Solvent 1, after centrifugation, disperse the precipitate in Solvent 2, then add polyethyleneimine and stir for 8 - 20 h to obtain fluorescent nanoparticles modified with amino groups.

5. The preparation method according to claim 4, characterized in that The mass ratio of the fluorescent nanoparticles, nitrous acid tetrafluoroborate, and polyethyleneimine is (1 - 1.5):(150 - 250):(80 - 120); Solvent 1 is selected from one or more of cyclohexane, toluene, or chloroform; Solvent 2 is N,N - dimethylformamide.

6. The preparation method according to claim 1, characterized in that, The preparation method of the fluorescent nanoparticles includes the following steps: Under an inert atmosphere condition, heat Yb salt, Eu salt, Y salt, oleylamine, oleic acid, and 1 - octadecene to 110 - 120 °C for mixing and reacting, then add them to a methanol solution containing Na salt and Cs salt, heat to remove methanol and then carry out a hot - injection synthesis reaction, and purify to obtain the product.

7. The preparation method according to claim 6, characterized in that, The Yb salt is selected from acetate, nitrate, sulfate, or hydrochloride of Yb; the Eu salt is selected from acetate, nitrate, sulfate, or hydrochloride of Eu; the Y salt is selected from acetate, nitrate, sulfate, or hydrochloride of Y; the Na salt is selected from sodium acetate, sodium chloride, or sodium sulfate; the Cs salt is selected from acetate, nitrate, sulfate, or hydrochloride of Cs.

8. The preparation method according to claim 6, characterized in that, The specific steps of the hot - injection synthesis reaction are as follows: Raise the temperature of the solution to 170 - 185 °C, inject trimethylchlorosilane during the heating process, react for 5 - 20 s; then quickly cool down.

9. The preparation method according to claim 3, characterized in that, The preparation method of the carbon quantum dots modified with carboxyl groups is as follows: Drop ethanolamine into an aqueous solution containing citric acid, stir vigorously until it becomes clear, carry out a hydrothermal synthesis reaction at 170 - 200 °C for 5 - 8 h, and purify to obtain the product.

10. Use of the fluorescent composite nanomaterial according to any one of claims 1 to 2 or the fluorescent composite nanomaterial prepared by the preparation method according to any one of claims 3 to 9, characterized in that, Use the fluorescent composite nanomaterial to prepare a humidity sensor or a fluorescent imaging contrast agent.

Images