Manganese dioxide coated rare earth up-conversion nano fluorescent material, preparation method thereof and application of manganese dioxide coated rare earth up-conversion nano fluorescent material in glutathione detection

Abstract

The invention discloses a manganese dioxide coated rare earth up-conversion nano fluorescent material and a preparation method and application thereof in glutathione detection, and the preparation method comprises the following steps: mixing YbCl3, ErCl3 and YCl3, adding oleic acid and 1-octadecene, heating and stirring until chloride is completely dissolved; then adding NaOH and NH4F, heating and stirring to react to obtain Core NPs; the preparation method comprises the following steps: mixing YCl3 and NdCl3, adding oleic acid and 1-octadecene, and heating and stirring until chloride is completely dissolved; then adding NaOH, NH4F and Core NPs, and heating and stirring for reaction to obtain CS NPs; cS NPs is dried and ground into powder, the powder and potassium permanganate are mixed and ground, and then standing is carried out; and centrifugally washing with water, drying and grinding to obtain the fluorescent material. The material has higher sensitivity on glutathione detection, quantitative detection can be realized, and the detection limit is as low as 31.2 nM.

Description

Technical Field

[0001] The present invention relates to the technical fields of nanomaterial preparation and biological detection and analysis, and specifically relates to a synthesis method of a manganese dioxide-coated rare earth upconversion nanomaterial and its application in glutathione detection. Background Art

[0002] Glutathione (GSH), as a common non-protein thiol species in biological systems, is an important endogenous antioxidant and is crucial for maintaining the redox balance in organisms. Clinical studies have found that various diseases are closely related to abnormal GSH levels, such as Alzheimer's disease, Parkinson's disease, liver injury, various cancers, etc. Therefore, developing simple, rapid, and sensitive GSH detection methods is of great significance for life science research and clinical diagnosis.

[0003] Currently, traditional GSH detection techniques have many defects. Electrochemical detection methods are susceptible to working electrode contamination and interference from electrochemically active substances; high-performance liquid chromatography (HPLC) requires complex instruments and a long determination time; commonly used organic dye fluorescence detection materials are not suitable for long-term detection due to poor photostability and photobleaching problems; although quantum dots are used for GSH sensing detection, they generate downconversion luminescence when excited by ultraviolet or visible light and are easily interfered by autofluorescence.

[0004] Upconversion nanoparticles (UCNPs) doped with lanthanide elements can convert near-infrared light into visible light, and have advantages such as high photostability and thermal stability, large tissue penetration depth, and the ability to avoid autofluorescence interference, and are widely used in the biological field. Manganese dioxide (MnO2) has been used as a fluorescence quencher for UCNPs fluorescence detection of GSH, but the existing UCNPs modified with MnO2 nanosheets have the following problems: the surface energy of MnO2 nanosheets is large, and they are prone to aggregation under laser irradiation, the material stability is poor, and the dispersed MnO2 nanosheets reduce the fluorescence efficiency and sensitivity, resulting in the problem that the quantitative measurement of GSH using it has not been solved. Summary of the Invention

[0005] The present invention aims to design a manganese dioxide-modified rare earth upconversion nanomaterial to solve the deficiencies of existing GSH detection methods and related materials, and achieve highly sensitive, rapid, and simple detection of GSH.

[0006] The present invention is achieved through the following technical solutions:

[0007] A preparation method of a manganese dioxide-coated rare earth upconversion nanophosphor, comprising the following steps:

[0008] (1) Mix YbCl3, ErCl3, and YCl3, add oleic acid and 1-octadecene, heat and stir until the chlorides are completely dissolved; then add NaOH and NH4F, heat and stir to react to obtain Core NPs;

[0009] (2) Mix YCl3 and NdCl3, add oleic acid and 1-octadecene, heat and stir until the chlorides are completely dissolved; then add NaOH, NH4F, and the Core NPs obtained in step (1), heat and stir to react to obtain CS NPs;

[0010] (3) Dry the CS NPs and grind them into powder, then mix and grind with potassium permanganate, and then let stand; wash by centrifugation with water and dry, and finally grind to obtain the rare earth upconversion nanophosphor material coated with manganese dioxide;

[0011] The stirring speed during the reactions in steps (1) and (2) is 450 - 1950 rpm.

[0012] Preferably, the stirring speed during the reactions in steps (1) and (2) is 800 - 1500 rpm.

[0013] Preferably, the stirring speed during the reactions in steps (1) and (2) is 950 - 1250 rpm.

[0014] Preferably, the mass ratio of CS NPs to potassium permanganate in step (3) is 1:6, and the standing time is 7 - 9 hours.

[0015] Preferably, the molar ratio of rare earth ions of YbCl3, ErCl3, and YCl3 in step (1) is: Yb 3+ :Er 3+ :Y 3+ = 20:2:78.

[0016] Preferably, the molar ratio of rare earth ions of YCl3 and NdCl3 in step (2) is: Y 3+ :Nd 3+ = (100 - X):X, where X ranges from 5 to 40.

[0017] Preferably, the total molar amount ratio of rare earth ions in step (1) and step (2) is 1:(0.5 - 2).

[0018] Preferably, the value of X ranges from 25 to 35.

[0019] Preferably, the dissolution conditions in step (1) are: heat to 120 ± 10 °C and stir for 20 ± 10 min, then raise the temperature to 150 ± 10 °C and react for 60 min.

[0020] Preferably, the conditions for dissolution in step (2) are: heating to 120 ± 10 °C, stirring for 20 ± 10 min, and then raising the temperature to 180 ± 10 °C and reacting for 60 min.

[0021] Preferably, the reaction conditions for steps (1) and (2) are: heating to 70 ± 10 °C, stirring for 20 ± 10 min, then raising the temperature to 120 ± 10 °C and stirring for 30 ± 10 min, and then heating to 300 ± 10 °C and reacting for 75 min ± 10 min.

[0022] Preferably, in steps (1) and (2), the volume ratio of oleic acid to 1-octadecene is 6:(10 - 20), the mass ratio of NaOH to NH4F is 1:(1 - 2); the total molar amount of rare earth ions to the molar volume of oleic acid is 1:(4 - 8) mol / L; the total molar amount of rare earth ions to the molar mass of NaOH is 1:(50 - 200) mol / g.

[0023] Preferably, the CS NPs prepared in step (2) are cooled and washed with a mixed solution of cyclohexane and ethanol to obtain the product, and the volume ratio of the cyclohexane and ethanol solution is 1.5 ± 0.5:1.

[0024] Application of the manganese dioxide-coated rare earth upconversion nanophosphor in glutathione detection.

[0025] As a control group, hydrophilic rare earth upconversion nanomaterials were synthesized through the following steps:

[0026] (a) Mix the CS NPs cyclohexane dispersion with a hydrochloric acid solution and ultrasonicate, remove the upper layer solution, and centrifuge to collect the nanocrystals;

[0027] (b) Dry in a vacuum drying oven and grind to obtain a powdery solid product.

[0028] Preferably, the concentration of the hydrochloric acid solution in step (a) is 0.4 - 0.6 mol·L-1;

[0029] Preferably, the drying in step (b) is drying in a vacuum drying oven at 60 ± 5 °C for 8 - 12 h.

[0030] As a control group, the UCNPs / MnO2 nanosheet composite nanomaterials were synthesized through the following steps:

[0031] I. Take an appropriate amount of the above hydrophilic rare earth upconversion nanomaterials and mix them with a 2-morpholinoethanesulfonic acid (MES) solution, and place the mixture in an ultrasonic environment for treatment;

[0032] II. While continuously ultrasonically treating, slowly add a newly prepared potassium permanganate (KMnO4) solution to the mixture in which the nanoparticles are uniformly dispersed, and continue ultrasonication;

[0033] III. Let the reaction solution stand still to complete the reaction fully and allow the product to form stably. Wash the product after the reaction twice with deionized water, and collect the product by centrifugation and store it in deionized water.

[0034] Preferably, in step I, the concentration of the hydrophilic nanomaterial is 2 ± 0.2 g / L, the concentration of the 2-morpholinoethanesulfonic acid solution is 0.033 mol / L, and the ultrasonic time is 2 - 5 min;

[0035] Preferably, in step II, the concentration of the potassium permanganate solution is 5 ± 0.3 mmol / L, and the addition amount is 20 μL per 1 mL of the solution in step I.

[0036] The UCNPs@MnO2 composite nanomaterial is synthesized by the following steps:

[0037] S1. Mix and grind the dried powder product (with oleic acid ligands on the surface) of the CS NPs obtained in the above step (2) with potassium permanganate, and then let it stand still;

[0038] S2. Centrifuge and wash three times with deionized water, place the product in a vacuum drying oven to dry, and finally grind to obtain the UCNPs@MnO2 composite nanomaterial;

[0039] Preferably, in step S1, the mass ratio of the dried powder to potassium permanganate is 1:6, and the standing time is 7 - 9 hours.

[0040] A rare earth upconversion nanomaterial coated with manganese dioxide prepared by the method of the present invention.

[0041] Synthesize upconversion nanoparticles NaYF4:20% Yb, 2% Er@NaYF4:30% Nd (UCNPs) with a particle size of about 40 nm and uniform size by the thermal decomposition method. By optimizing the doping of the Nd 3+ sensitizer, the particle size of the nanoparticles is regulated, and the upconversion fluorescence intensity of the UCNPs is enhanced. Subsequently, MnO2 nanosheets are modified on the surface of the UCNPs as a contrast material for detecting GSH. The results show that the sensitivity for GSH detection is poor, and only qualitative detection of GSH can be achieved. Then, MnO2 is in-situ coated by a one-step redox method to prepare UCNPs@MnO2, realizing highly sensitive, rapid and simple detection of GSH. The detection range is 0.4 μM to 116.0 μM, and the detection limit is as low as 31.2 nM, providing a new method for quantitative detection of GSH.

[0042] The present invention rationally designs Nd 3+A composite nano-fluorescent material for sensitive detection of GSH was synthesized by doping regulation, nano-crystal particle size regulation, and optimization of the manganese dioxide coating route. Compared with the prior art, it has the following advantages:

[0043] (1) By optimizing the Nd 3+ doping to 30% and the UCNPs particle size to 40 nm, the up-conversion fluorescence intensity of UCNPs was increased. Compared with the core nano-particles, the fluorescence intensity was increased by about 63 times. The optimized fluorescence performance is beneficial to improving the detection sensitivity and detection range.

[0044] (2) The present invention uses Nd 3+ sensitization to generate up-conversion luminescence. Nd 3+ has a wide absorption at 808 nm. Compared with other down-conversion fluorescent materials for GSH detection, it can increase the tissue penetration depth. And the 808 nm nano-excitation avoids the thermal effect caused by traditional 980 nm excitation, making the present invention more suitable as a biosensor for developing more application functions, such as detecting cancer cells.

[0045] (3) The nano-composite material of the present invention has high sensitivity for GSH detection, with a detection range of 0.4 μM to 116.0 μM and a detection limit as low as 31.2 nM. The detection operation is simple and fast. Only need to mix the nano-material with the GSH solution for reaction, and use 808 nm near-infrared laser irradiation to detect the change in fluorescence intensity. Description of the Drawings

[0046] Figure 1 is the up-conversion fluorescence spectrum of NaYF4:20% Yb, 2% Er@NaYF4:X% Nd (CS NPs) under 808 nm laser.

[0047] Figure 2 (a) is the TEM image of NaYF4:20% Yb, 2% Er@NaYF4:30% Nd (UCNPs) synthesized using a polytetrafluoroethylene A-150 stir bar and (b) the corresponding particle size distribution diagram.

[0048] Figure 3 (a) is the TEM image of NaYF4:20% Yb, 2% Er@NaYF4:30% Nd (UCNPs) synthesized using a polytetrafluoroethylene A-200 stir bar and (b) the corresponding particle size distribution diagram.

[0049] Figure 4 (a) is the TEM image of NaYF4:20% Yb, 2% Er@NaYF4:30% Nd (UCNPs) synthesized using a polytetrafluoroethylene A-300 stir bar and (b) the corresponding particle size distribution diagram.

[0050] Figure 5 Upconversion fluorescence spectra of NaYF4:20% Yb, 2% Er@NaYF4:30% Nd (UCNPs) with different average particle sizes under 808 nm laser.

[0051] Figure 6 TEM image of NaYF4:20% Yb, 2% Er@NaYF4:30% Nd (UCNPs) with an average particle size of about 40 nm.

[0052] Figure 7 HRTEM image of NaYF4:20% Yb, 2% Er@NaYF4:30% Nd (UCNPs) with an average particle size of about 40 nm.

[0053] Figure 8 XRD pattern of NaYF4:20% Yb, 2% Er@NaYF4:30% Nd (UCNPs) with an average particle size of about 40 nm.

[0054] Figure 9 TEM image of UCNPs / MnO2.

[0055] Figure 10 TEM image of UCNPs@MnO2.

[0056] Figure 11 (a) Upconversion fluorescence spectra of UCNPs / MnO2 at different GSH solution concentrations and (b) linear fitting plot of fluorescence intensity at 541 nm.

[0057] Figure 12 (a) Upconversion fluorescence spectra of UCNPs@MnO2 at different GSH solution concentrations and (b) linear fitting plot of fluorescence intensity at 541 nm. Detailed implementation

[0058] In the following examples, unless otherwise specified, the technical means used in the examples are all conventional means in the technical field.

[0059] The reagents and instruments used in the present invention are described as follows:

[0060] Main reagents and instruments: Yttrium chloride (YCl3, 99.99%), ytterbium chloride (YbCl3, 99.99%), erbium chloride (ErCl3, 99.99%), neodymium chloride (NdCl3, 99.99%), oleic acid (C18H34O2, 90%), octadecene (C18H36, 90%), ammonium fluoride (NH4F, 97%), glutathione (GSH, 98%) were purchased from Energy Chemical (Shanghai, China). Absolute ethanol (C2H6O) and sodium hydroxide (NaOH, 97%) were purchased from Fuchen Chemical Reagent Co., Ltd. Hydrochloric acid (HCl, 38%), anhydrous methanol (CH3OH, 99.5%) were purchased from Guangzhou Chemical Reagent Factory. Potassium permanganate (KMnO4) was purchased from Tianjin Chemical Reagent Co., Ltd. 2-(N-Morpholino)ethanesulfonic acid (MES, 99%) was purchased from Shanghai Aladdin. All chemicals in the present invention are analytical grade reagents and can be used without further purification. The ultrapure water used in the experiment was purified by a Milli-Q purification system (Millipore, USA) with a resistivity of 18.2 MΩ.

[0061] Main characterization instruments: X-ray powder diffractometer (XRD, Bruker D8 Advance, Cu-Kα), transmission electron microscope (JEM-2100F, JEOL Ltd., Japan), fluorescence spectrometer (FluoroMax-4, HORIBA, USA), 808 nm laser (MDL-H-808nm-5W-ED42165, Changchun New Industries Optoelectronics Technology Co., Ltd.).

[0062] Example 1

[0063] The NaYF4:20% Yb, 2% Er@NaYF4:30% Nd core-shell nanoparticles (CSNPs) used in Example 1 below were prepared by the following method:

[0064] Synthesis of NaYF4:20% Yb, 2% Er nanoparticles (Core NPs):

[0065] Mix 1 mmol of RECl (78% YCl3, 20% YbCl3, 2% ErCl3) with 6 mL of oleic acid and 16 mL of octadecene, place them in a 100 mL three-necked round-bottom flask, heat to 120 °C under a nitrogen atmosphere, stir for 20 minutes, then heat to 150 °C and stir for 60 minutes to form a clear and transparent solution, and finally cool to room temperature. Then, add 10 mL of anhydrous methanol (dispersed with 0.1 g of NaOH and 0.148 g of NH4F) to the clear solution, heat to 70 °C under a nitrogen atmosphere, stir for 20 minutes, then raise the temperature to 120 °C and stir for 30 minutes, and finally quickly raise the temperature to 300 °C and stir for 75 minutes until the reaction ends, and then cool to room temperature. Collect the product and wash it three times with a solution of cyclohexane:ethanol = 1.5:1 (volume ratio), and then disperse the final product in 10 mL of cyclohexane for storage.

[0066] Synthesis of NaYF4:20% Yb, 2% Er@NaYF4:X% Nd core-shell nanoparticles (CS NPs):

[0067] Mix 1 mmol of RECl ((100 - X)% YCl3, X% NdCl3, where X = 5, 20, 30, 40, and NdCl3 has been dissolved in 200 μL of deionized water before addition) with 6 mL of oleic acid and 16 mL of octadecene, and place them in a 100 mL three-necked flask. Heat the mixture to 120 °C under a nitrogen atmosphere, stir for 20 minutes, then heat to 180 °C and stir for 60 minutes to form a clear and transparent solution, and then cool to room temperature. Then, disperse 0.1 g of NaOH and 0.148 g of NH4F in 10 mL of anhydrous methanol, and add the core nanoparticles retained in cyclohexane synthesized in the previous step to the clear solution. Slowly raise the temperature to 80 °C with stirring and stir for 20 minutes to remove the methanol and cyclohexane solution, then raise the temperature to 120 °C with stirring and stir for 30 minutes, and finally quickly raise the temperature to 300 °C with stirring and stir for 75 minutes. After the reaction ends, cool to room temperature. Collect the product and wash it three times with a solution of cyclohexane:ethanol = 1.5:1 (volume ratio), and finally vacuum-dry the core-shell nanoparticles into a white powder and store them.

[0068] Synthesis description of NaYF4:20% Yb, 2% Er@NaYF4:30% Nd core-shell nanoparticles (CS NPs) with a particle size of approximately 18.5 nm:

[0069] Consistent with the above steps, the specifications of the magnetic stir bar used in the synthesis of Core NPs and CS NPs are polytetrafluoroethylene magnetic stir bar A-150, and the stirring speed is 1550 - 1950 rmp.

[0070] Synthesis instructions for NaYF4:20% Yb, 2% Er@NaYF4:30% Nd core-shell nanoparticles (CS NPs) with a particle size of approximately 39 nm:

[0071] Consistent with the above steps, the specifications of the magnetic stir bar used in the synthesis of Core NPs and CS NPs are polytetrafluoroethylene magnetic stir bar A-200, and the stirring speed is 950 - 1250 rmp.

[0072] Synthesis instructions for NaYF4:20% Yb, 2% Er@NaYF4:30% Nd core-shell nanoparticles (CS NPs) with a particle size of approximately 86.5 nm:

[0073] Consistent with the above steps, the specifications of the magnetic stir bar used in the synthesis of Core NPs and CS NPs are polytetrafluoroethylene magnetic stir bar A-300, and the stirring speed is 450 - 500 rmp.

[0074] Synthesis of hydrophilic NaYF4:20% Yb, 2% Er@NaYF4:30% Nd nanoparticles:

[0075] Mix 2 mL of the cyclohexane dispersion of NaYF4:20% Yb, 2% Er@NaYF4:30% Nd nanocrystals with 2 mL of (0.5 mol·L -1 ) HCl solution, sonicate for 5 min, retain the lower layer solution, centrifuge to collect the nanocrystals, and dry them in a vacuum drying oven at 60 °C for 12 h to obtain a powdery product.

[0076] Example 2

[0077] The UCNPs / MnO2 nanosheets used in this example were prepared according to the following method:

[0078] Mix hydrophilic NaYF4:20% Yb, 2% Er@NaYF4:30% Nd nanoparticles (2 g / L) with MES solution (0.033 mol / L), and then sonicate for 2 minutes to uniformly disperse the nanoparticles in the MES solution. Subsequently, under sonication, slowly add the newly prepared potassium permanganate (KMnO4) solution (20 / 40 / 60 / 80 / 100 / 120 / 140 / 160 μL, 5 mmol / L) to it, continue to sonicate for 1 minute to fully mix the solution with the nanoparticles, and then let the solution stand for more than 1 hour to obtain a brown colloid. Subsequently, wash it twice with deionized water and centrifuge to collect the product, and disperse the final product in 2 mL of deionized water and store it.

[0079] Example 3

[0080] The UCNP@MnO2 used in this example was prepared according to the following method:

[0081] The untreated hydrophilic white powdery UCNPs (upconversion nanoparticles with 30% Nd doping content) and potassium permanganate (KMnO4) were thoroughly ground and mixed evenly at a mass ratio of 1:6, and then left standing for 8 hours. After that, the unreacted KMnO4 was washed away with deionized water and the product was collected by centrifugation until the supernatant changed from purple to colorless. Then, it was dried in a vacuum drying oven at 60 °C for 10 hours. Finally, the obtained product UCNP@MnO2 was ground into powder and stored at room temperature.

[0082] Example 4

[0083] This example illustrates the influence of the Nd 3+ doping concentration on the upconversion fluorescence intensity:

[0084] When the doping concentration of Nd 3+ in the core-shell nanocrystals increases from 5% to 30%, the emission intensity of the nanocrystals gradually increases. However, if the doping concentration of Nd 3+ is further increased, the emission intensity of the core-shell nanocrystals will gradually decrease. Under 808 nm laser irradiation, Nd 3+ absorbs energy, and an energy transfer process occurs between Nd 3+ →Yb 3+ →Er 3+ . Theoretically explained, increasing the concentration of Nd 3+ can increase the absorbance of the nanocrystals at 808 nm wavelength, promoting the energy transfer to Yb 3+ , thus promoting upconversion luminescence. However, a high doping concentration of Nd 3+ means that the distance between Nd 3+ -Nd 3+ is greatly shortened, thereby increasing the occurrence of harmful cross-relaxation processes between Nd 3+ -Nd 3+ ( 4 F 3 / 2 + 4 I 9 / 2 →2 4 I 15 / 2 ), resulting in a weakening of upconversion luminescence. According to the emission spectrum, the optimal doping concentration of Nd 3+ in the CS nanocrystals is 30%, at which the strongest fluorescence emission can be obtained. Compared with the core nanoparticles, the fluorescence intensity increases by about 63 times.

[0085] Example 5

[0086] This example illustrates the particle size of rare earth nanoparticles:

[0087] In the thermal decomposition synthesis method of rare earth upconversion nanoparticles, the stirring speed will affect the synthesized particle size. The slower the stirring speed, the larger the synthesized particle size. This is mainly because the stirring speed is related to the shear force, heat transfer, mass transfer, and nucleation growth kinetics of the reaction. In the present invention, three polytetrafluoroethylene stirrers of different sizes, with specifications A-150, A-200, and A-300 respectively; and the corresponding stirring speeds, with speed ranges of 1550 - 1950 rpm, 950 - 1250 rpm, and 450 - 500 rpm respectively. The average particle sizes of the synthesized rare earth nanoparticles are 18.5 nm, 39.0 nm, and 86.5 nm respectively. Their upconversion emission spectra show that when the particle size is about 39.0 nm, it has the strongest fluorescence emission. From the aspect of energy transfer efficiency, the nanoparticles undergo the Nd 3+ →Yb 3+ →Er 3+ energy transfer process to generate luminescence. When the nanoparticles are very small, the distance between ions is too close, and there may be a competitive process of energy migration, resulting in a decrease in energy transfer efficiency and thus weakened luminescence; while when the particle size is too large, the average distance of Nd 3+ →Yb 3+ →Er 3+ may also increase, reducing the energy transfer efficiency; when the particle size is 39 nm, the distance between ions reaches equilibrium, and a better luminescence state can be achieved.

[0088] Example 6

[0089] This example describes NaYF4:20% Yb, 2% Er@NaYF4:30% Nd (UCNPs) with an average particle size of 39 nm:

[0090] As can be seen, the UCNPs synthesized by the thermal decomposition method exhibit a hexagonal phase morphology with uniform particle size and regular morphology, and the average particle size is about 40 nm. As can be seen from Figure 6 , the nanoparticles show clear lattice fringes, and the measured lattice spacing is 0.30 nm, which matches the (110) crystal plane of Na(Y Figure 7 Yb 0.57 Yb 0.39 Er 0.04 )F4 PDF#28 - 1192 ( Figure 8 ). In addition, the XRD pattern shows that the diffraction peaks of UCNPs are highly consistent with the standard card spectrum, proving the successful synthesis of NaYF4:20% Yb, 2% Er@NaYF4:30% Nd (UCNPs).

[0091] Example 7

[0092] This example describes UCNPs / MnO2 nanosheets:

[0093] Figure 9 It can be observed that MnO2 nanosheets are dispersed on the carbon surface and some UCNPs are attached to the MnO2 nanosheets, demonstrating the successful preparation of UCNPs / MnO2 nanosheets.

[0094] Example 9

[0095] This example describes UCNPs@MnO2:

[0096] Figure 10 It can be observed that amorphous MnO2 closely coats the UCNPs, demonstrating the successful preparation of UCNPs@MnO2.

[0097] Example 10

[0098] This example describes the linear experiment of UCNPs / MnO2 nanosheets and UCNPs@MnO2 for GSH detection:

[0099] Figure 11 and Figure 12 shows the linear experiments of the two materials for GSH detection respectively. From Figure 11 it can be seen that as the GSH concentration increases, the fluorescence intensity of UCNPs / MnO2 nanosheets increases, but accurate and sensitive quantitative detection of GSH cannot be achieved, and only qualitative detection can be realized; from Figure 12 it can be seen that UCNPs@MnO2 has high sensitivity for GSH detection, with a detection range of 0.4 μM to 116.0 μM, a detection limit as low as 31.2 nM, and R 2 = 0.994, enabling quantitative detection of GSH.

[0100] Example 11

[0101] This example describes the detection mechanism: When irradiated with an 808 nm near-infrared laser, UCNPs absorb energy and are excited to an excited state, while MnO2 has a broad absorption band at 300 - 550 nm that overlaps with the emission band of UCNPs in the green spectral region ( 2 H 11 / 2 - 4 I 15 / 2 ) at approximately 541 nm, and part of the emitted light is absorbed by MnO2, resulting in fluorescence quenching of UCNPs. When GSH is added to the system, a redox reaction occurs between GSH and MnO2, and MnO2 is reduced to Mn 2+ , and the fluorescence of UCNPs is restored. The new route adopts an in-situ coating method, which significantly shortens the distance between the acceptor MnO2 and the donor UCNPs, facilitating the FRET effect and improving the sensitivity.

[0102] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of a manganese dioxide-coated rare earth upconversion nanophosphor, characterized in that, It includes the following steps: (1) After mixing YbCl3, ErCl3, and YCl3, add oleic acid and 1-octadecene, heat and stir until the chlorides are completely dissolved; then add NaOH and NH4F, heat and stir to react to obtain Core NPs; (2) After mixing YCl3 and NdCl3, add oleic acid and 1-octadecene, heat and stir until the chlorides are completely dissolved; then add NaOH, NH4F, and the Core NPs obtained in step (1), heat and stir to react to obtain CS NPs; (3) Dry the CS NPs and grind them into powder, then mix and grind with potassium permanganate, and then let it stand; wash with water by centrifugation and then dry, and finally grind to obtain the rare earth upconversion nanophosphor coated with manganese dioxide; The stirring speed during the reactions in steps (1) and (2) is 450 - 1950 rpm.

2. The preparation method according to claim 1, wherein The stirring speed during the reactions in steps (1) and (2) is 800 - 1500 rpm.

3. The preparation method according to claim 2, wherein The stirring speed during the reactions in steps (1) and (2) is 950 - 1250 rpm.

4. The preparation method according to claim 1 or 2 or 3, characterized in that, In step (3), the mass ratio of CS NPs to potassium permanganate is 1:6, and the standing time is 7 - 9 hours.

5. The preparation method according to claim 4, characterized in that, The molar ratio of rare earth ions of YbCl3, ErCl3, and YCl3 in step (1) is: Yb 3+ :Er 3+ :Y 3+ = 20:2:78; The molar ratio of rare earth ions of YCl3 and NdCl3 described in step (2) is: Y 3+ :Nd 3+ =(100 - X):X, where X ranges from 5 to 40; The molar amount ratio of the total rare earth ions in step (1) to that in step (2) is 1:(0.5 - 2).

6. The preparation method according to claim 5, characterized in that, The value of X is 25 - 35.

7. The preparation method according to claim 6, characterized in that, The dissolution conditions in step (1) are: heat to 120 ± 10 °C and stir for 20 ± 10 min, then raise the temperature to 150 ± 10 °C and react for 60 min; the dissolution conditions in step (2) are: heat to 120 ± 10 °C and stir for 20 ± 10 min, then raise the temperature to 180 ± 10 °C and react for 60 min; the reaction conditions in steps (1) and (2) are: heat to 70 ± 10 °C and stir for 20 ± 10 min, then raise the temperature to 120 ± 10 °C and stir for 30 ± 10 min, and then heat to 300 ± 10 °C and react for 75 min ± 10 min.

8. The preparation method according to claim 7, characterized in that, In steps (1) and (2), the volume ratio of oleic acid to 1-octadecene is 6:(10 - 20), the mass ratio of NaOH to NH4F is 1:(1 - 2); the molar volume ratio of the total molar amount of rare earth ions to oleic acid is 1:(4 - 8) mol / L; the molar mass ratio of the total molar amount of rare earth ions to NaOH is 1:(50 - 200) mol / g; After cooling, the CS NPs prepared in step (2) are washed with a mixed solution of cyclohexane and ethanol to obtain the product, and the volume ratio of the cyclohexane and ethanol solution is 1.5 ± 0.5:

1.

9. The rare earth upconversion nanophosphor coated with manganese dioxide prepared by the method according to any one of claims 1 - 8.

10. The application of the rare earth upconversion nanophosphor coated with manganese dioxide according to claim 9 in the detection of glutathione.

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