Method, system and application of rare earth nanoparticles inducing long lifetime charge transfer excited state of organic molecules

Abstract

The application provides a method, a system and an application of a rare earth nanoparticle-induced long-life charge transfer excited state of an organic molecule. The application is a long-life charge transfer excited state system of a rare earth nanoparticle-induced organic molecule, in which a lanthanide rare earth nanoparticle and an organic molecule are compounded; the diameter of the rare earth nanoparticle is between 10 nm and 20 nm, and the surface is exposed to a dangling bond and a rare earth cation through acid washing. Under the irradiation of an excitation light, the organic molecule produces an exciton between molecules and undergoes charge separation under the effect of a spin-orbit coupling, the separated exciton recombines to generate long-life charge transfer state luminescence, and can be applied to the fields of organic molecule life control, trace water molecule sensing, trace solvent sensing, trace water dose detection and the like.

Description

Technical Field

[0001] This invention relates to the coupling of lanthanide rare earth nanoparticles with organic molecules to alter the exciton radiation pathway in organic molecules, and particularly to a method, system, and application of rare earth nanoparticles inducing long-lived charge transfer excited states in organic molecules. Background Technology

[0002] Organic molecular materials with long-lived excited-state properties have attracted much attention in fields such as bioimaging, photocatalysis, photovoltaic cells, sensing, and organic light-emitting diodes. Traditional organic phosphors mainly exhibit singlet excitations at room temperature, with very short lifetimes of only 10 nanoseconds. Long-lived materials can be obtained by converting singlet excitons into spin triplet or charge-separated excitons. However, these long-lived organic molecules are mainly limited to noble metal complexes or a few types of molecules with special structures. Noble metals are expensive, while metal-free long-lived organic materials require strict molecular structure design, limiting the wide-ranging applications of these materials.

[0003] If the properties of excited states of molecules can be modulated through certain external conditions, the intrinsic properties of molecules can be altered, leading to the development of material systems with multiple functions. Therefore, there is an urgent need to develop new strategies to construct a composite system that is both simple, fast, and efficient in converting singlet excitons in organic materials into long-lived excitons. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a novel method for efficiently altering the radiative deactivation pathway of excited states of organic molecules by surface states of rare earth particles, thereby constructing a long-lived molecular luminescence system and providing its applications.

[0005] The present invention adopts the following technical solution:

[0006] A method for directly converting a molecular singlet excited state to a charge-transfer excited state (CT state) from the surface state of rare-earth particles is disclosed. The method involves using lanthanide rare-earth nanoparticles with exposed rare-earth cations to form a strong spin-orbit coupling effect with the organic molecules. Under photoexcitation, excitons are generated between the organic molecules, and charge separation occurs under the spin-orbit coupling effect. The separated excitons recombine, producing long-lifetime luminescence. The organic molecules possess strong electron-donating capabilities, such as nitrogen-oxygen functional group molecules with lone pairs of electrons.

[0007] Furthermore, the diameter of the lanthanide rare earth nanoparticles is between 10 nm and 20 nm.

[0008] Furthermore, the organic molecules include compounds such as N,N,N',N'-tetramethylbenzidine and N,N,N',N'-tetraphenylbenzidine.

[0009] The wavelength of the light used for excitation is related to the charge separation state generated between rare earth nanoparticles and organic molecules, and is generally 250–450 nm.

[0010] In certain specific embodiments of the present invention, the rare earth cation is: Ce 3+ Pr 3+ 、Nd 3+ 、Sm 3+ Eu 3+ Gd 3 + 、Tb 3+ Dy 3+ Ho 3+ Er 3+ Tm 3+ Yb 3+ .

[0011] Another objective of this invention is to provide a rare-earth nanoparticle-induced long-lifetime charge transfer excited-state system for organic molecules, which is composed of lanthanide rare-earth nanoparticles and organic molecules. The organic molecules have strong electron-donating capabilities, such as nitrogen-oxygen functional group molecules with lone pairs of electrons, and the rare-earth cations of the lanthanide rare-earth nanoparticles are exposed on their surfaces.

[0012] The lanthanide rare earth nanoparticles are nanoparticles with the following composition: LnF3 or BLnF4, wherein Ln is selected from Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb, and B is selected from Na, K, and Li.

[0013] Preferably, the nanoparticle component is BLnF4.

[0014] Preferably, Ln is Gd.

[0015] Preferably, the B is Na.

[0016] In some specific embodiments of the present invention, the mass ratio of the organic molecule to the nanoparticle is 1:(25-200).

[0017] In all embodiments of the present invention, the system is water-soluble.

[0018] In certain specific embodiments of the present invention, the preparation method of the system includes:

[0019] (1) Preparation of oil-soluble rare earth-doped nanoparticles based on co-precipitation method;

[0020] (2) The nanoparticles obtained in step (1) are acid-washed to remove the surface oleic acid ligands, and water-soluble nanoparticles are obtained.

[0021] (3) The water-soluble nanoparticles obtained in step (2) are combined with the target organic molecules to obtain a water-soluble composite material.

[0022] (4) The water-soluble composite material obtained in step (3) is evaporated in a glove box to obtain a solid composite material, which is the rare earth nanoparticle-induced organic molecule long-lifetime charge transfer excited state system of the present invention.

[0023] Preferably, step (1) above specifically includes:

[0024] (a) Add 4 mL of 0.2 M Ln(CH3COO)3 aqueous solution, 8 mL of oleic acid, and 12 mL of 1-octadecene to a 50 mL two-necked flask and mix at room temperature. Then heat the mixture in an oil bath to 110 °C to remove water, and maintain the temperature at 110 °C for 1 h.

[0025] (b) Cool the mixture to room temperature, add a well-mixed methanol solution containing 2 mmol NaOH and 2.72 mmol NH4F to a two-necked flask, stir at 50°C for 30 min, and then heat to 130°C to remove methanol and water.

[0026] (c) Connect the adapter and vacuum pump and degas for 20 min to further remove moisture and air from the solution. Then, purge with nitrogen and evacuate again, repeating this process three times. Continue purging with nitrogen and rapidly heat to 290℃ under nitrogen atmosphere, holding for 1.5 h. After the reaction is complete, cool the reactants to room temperature and add anhydrous ethanol to the reaction solution to precipitate the product. Centrifuge for 5–20 min at 5000–6000 r / min. Wash three times with a mixed solvent of cyclohexane and anhydrous ethanol to obtain oil-soluble NaLnF4 nanoparticles, which are dispersed in 4 mL of cyclohexane for later use.

[0027] In certain specific embodiments of the present invention, step (2) specifically includes:

[0028] Take 1 mL of the NaLnF4 cyclohexane solution obtained in step (1), add 4 mL of acetone, centrifuge to precipitate, redisperse the precipitate in 4 mL of acetone, add 0.5 mL of hydrochloric acid, sonicate for 30 min, let stand for 1–6 h, centrifuge at 20000 r / min, and wash three times with acetone to obtain water-soluble NaLnF4 nanoparticles.

[0029] In certain specific embodiments of the present invention, step (3) specifically includes:

[0030] The water-soluble NaLnF4 nanoparticle methanol solution obtained in step (2) was mixed with the toluene solution of the organic target molecule and sonicated for 10 min.

[0031] In certain specific embodiments of the present invention, step (4) specifically includes:

[0032] The mixed solution is placed in a glove box to remove oxygen, and then the mixed solution is dropped onto a quartz plate. The solvent is removed by heating at 75°C and a uniform mixed film is formed, thus obtaining the rare earth nanoparticle-induced organic molecule long-lifetime charge transfer excited state system of the present invention.

[0033] According to the present invention, the organic molecules in the system have an extremely long CT state lifetime.

[0034] This invention also provides an application of the rare earth nanoparticle-induced long-lifetime charge transfer excited-state system of organic molecules, including:

[0035] (1) Ultrasensitive cyclic detection and dosage determination of various solvents;

[0036] The system of this invention removes surface oleic acid ligands by acid washing, exposing surface dangling bonds and rare earth cations. The rare earth nanoparticles are positively charged, enabling ultrasensitive solvent detection. This application cleverly utilizes the cyclic adsorption performance of rare earth particles on various solvents and the sensitivity of the spin coupling effect to solvents. By quenching CT state luminescence, ultrasensitive detection of various solvents is achieved.

[0037] The above applications include: using water molecules to quench N,N,N',N'-tetramethylbenzidine CT-state luminescence to achieve water molecule ppm detection and dosage determination.

[0038] The above applications include: using organic solvents to quench the CT state luminescence of N,N,N',N'-tetramethylbenzidine, achieving ppm-level detection of organic solvents.

[0039] The above applications include: using the non-immobilized binding of N,N,N',N'-tetraphenylbenzidine and rare earth particles, and the CT-state luminescence of N,N,N',N'-tetraphenylbenzidine quenched by water molecules to achieve ultra-low limit detection of water molecules.

[0040] (2) Regulation of the CT state lifetime of organic molecules. The CT state lifetime of organic molecules can be regulated by adjusting the ratio of lanthanide rare earth nanoparticles to organic molecules in the system. Generally, the CT state luminescence lifetime increases with the increase of the doping amount of lanthanide rare earth nanoparticles.

[0041] Compared with the prior art, the advantages of the present invention are as follows:

[0042] This invention provides a method for effectively inducing long-lived charge-transfer excited states of organic molecules using rare-earth nanoparticles. Compared with traditional techniques, it eliminates the need for expensive precious metals, the requirement to consider whether the molecule possesses functional groups for coordination, and the need for complex crystallization induction engineering, metal-organic framework construction, and molecular H-state aggregation. Simply mixing and evaporating rare-earth nanoparticles with a small organic molecule solvent can induce long-lived CT-state luminescence. Furthermore, by cleverly utilizing the adsorption properties of nanoparticles and the disruption of coupling by the solvent, a dose detection platform at the ppm level for various solvents is constructed. Attached Figure Description

[0043] Figure 1 This diagram illustrates the method of altering the exciton radiation path in organic molecules through coupling lanthanide rare-earth nanoparticles with organic molecules, as described in this invention, and shows the structures of the target organic molecules used in certain specific embodiments. Figure a is a schematic diagram showing the spin-orbit coupling effect between the lanthanide rare-earth nanoparticles and the organic molecules. Under photoexcitation, excitons are generated between the organic molecules and undergo charge separation under the spin-orbit coupling effect. The separated excitons recombine, producing long-lifetime luminescence. Trace amounts of water molecules affect the coupling effect, quenching the CT-state green light. Figure b shows the chemical structures of N,N,N',N'-tetramethylbenzidine (TMB) and N,N,N',N'-tetraphenylbenzidine (TPB).

[0044] Figure 2 This figure shows the changes in HOMO and LUMO of the organic molecular dimer and the coupling of lanthanide metal atoms with the organic molecule, calculated using first-principles calculations in this invention. An open-shell calculation was used to calculate the energy levels of the lanthanide metal atom-organic molecule. As can be seen from the figure, the energy level difference of the molecular dimer is 4.36 eV. When the organic molecule and the lanthanide metal molecule are coupled, the energy level difference decreases, indicating a redshift of the emission peak, which is consistent with the CT state emission peak in this example.

[0045] Figure 3 Transmission electron microscopy image (a) and particle size distribution diagram (b) of NaGdF4 nanoparticles prepared in Example 1.

[0046] Figure 4 The image shows the X-ray powder diffraction pattern of the NaGdF4 nanomaterials prepared in Example 1.

[0047] Figure 5 Thermogravimetric analysis and in-situ Fourier transform infrared spectra of NaGdF4 nanoparticles in Example 1 are shown in Figure a. Figure a shows the thermogravimetric analysis. Figure b shows the in-situ Fourier transform infrared spectra.

[0048] Figure 6The images show the spectral properties of NaGdF4 nanoparticles and organic TMB composites in Example 2. a) shows the emission spectrum changes of TMB after adding nanoparticles of different masses while keeping the TMB mass constant; b) shows the absorption spectrum changes of TMB after adding nanoparticles of different masses while keeping the TMB mass constant; c) is a comparison of the absorption spectra of NaGdF4 nanoparticles and TMB composites in the presence and absence of water molecules in Example 2.

[0049] Figure 7 The figures show the lifetime changes after NaGdF4 nanoparticles and the target organic molecule were combined in the examples. a) is the lifetime at 410 nm under 365 nm excitation, which, after fitting, is approximately 2 ns. The addition of NaGdF4 nanoparticles did not alter the singlet emission properties. b) is the lifetime at 530 nm under 365 nm excitation. With increasing NaGdF4 nanoparticle doping, the CT state emission lifetime of TMB significantly increased, eventually reaching 1.28 ms, while the CT state emission lifetime of TPB reached 1 ms.

[0050] Figure 8 The excitation-fluorescence / phosphorescence spectra of NaGdF4 nanoparticles and organic molecule TMB after composite formation in Example 2 are shown. a) Excitation-fluorescence spectrum when the mass ratio of NaGdF4 nanoparticles to organic molecule TMB is 200:1; b) Excitation-phosphorescence spectrum collected after 100 μs excitation decay.

[0051] Figure 9 The image shows the changes in CT-state luminescence under the influence of trace amounts of water molecules after NaGdF4 nanoparticles and organic molecule TMB are combined in Example 4.

[0052] Figure 10 The results of the moisture absorption-heating cycle test are shown in Example 4 after NaGdF4 nanoparticles and organic molecule TMB are combined.

[0053] Figure 11 The results show the effects of different solvent vapors on the composite of NaGdF4 nanoparticles and organic molecule TMB in Example 5.

[0054] Figure 12 The image shows the changes in CT-state luminescence under the influence of trace amounts of water molecules after NaGdF4 nanoparticles and organic molecule TPB are combined in Example 6. Detailed Implementation

[0055] This invention provides a method, system, and application for inducing long-lived charge transfer excited states of organic molecules using rare-earth nanoparticles. Figure 2This figure shows the changes in HOMO and LUMO of organic molecular dimers and lanthanide metal atoms coupled with organic molecules, calculated using first-principles calculations in this invention. An open-shell calculation was used to calculate the energy levels of the lanthanide metal atom-organic molecule pair. As can be seen from the figure, the energy level difference of the molecular dimer is 4.36 eV. When the organic molecule and the lanthanide metal molecule are coupled, the energy level difference decreases, indicating a redshift of the emission peak, consistent with the CT state emission peak. Therefore, by utilizing lanthanide metal nanoparticles that can couple with organic molecules, a strong spin-orbit coupling effect can be formed, thereby enhancing the induction of long-lived charge-transfer excited states in organic molecules. Generally, organic molecules have strong electron-donating capabilities, such as nitrogen-oxygen functional group molecules with lone pairs of electrons. Lanthanide rare-earth nanoparticles expose dangling bonds and rare-earth cations on their surface to achieve coupling between the two.

[0056] Figure 1 a is a schematic diagram of the method for altering the exciton radiation path in organic molecules by coupling lanthanide rare earth nanoparticles with organic molecules in this invention, as shown in Figure 1. Figure 1 As shown in a, this method utilizes the strong spin-orbit coupling effect formed by lanthanide rare earth nanoparticles and organic molecules. Under photoexcitation, excitons are generated between organic molecules and undergo charge separation under the spin-orbit coupling effect. The separated excitons recombine to produce long-lifetime luminescence.

[0057] The following is Figure 1 Taking the two organic molecules shown in Figure b as examples, and in conjunction with specific embodiments and accompanying drawings, the present invention will be further described in detail. The scope of protection of the present invention is not limited to the following embodiments. After reading this invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope defined by the appended claims.

[0058] Example 1: Preparation of acid-washed NaGdF4 nanoparticles and their application in cyclic adsorption-desorption of water

[0059] Add 4 mL of 0.2 M Gd(CH3COO)3 aqueous solution, 8 mL of oleic acid, and 12 mL of 1-octadecene to a 50 mL two-necked flask and mix at room temperature. Then heat the mixture in an oil bath to 110 °C to remove water, and maintain the temperature at 110 °C for 1 h. Afterward, cool the mixture to room temperature, add a well-mixed methanol solution containing 2 mmol NaOH and 2.72 mmol NH4F to the two-necked flask, stir at 50 °C for 30 min, and then heat to 130 °C to remove methanol and water. Connect an adapter and a vacuum pump and degas for 20 min to further remove water and air from the solution. Then purge with nitrogen and evacuate again, repeating this process three times. Continue purging with nitrogen, and rapidly heat to 290 °C under nitrogen atmosphere, maintaining the temperature for 1.5 h. After the reaction is complete, cool the reactants to room temperature, add anhydrous ethanol to the reaction solution to precipitate the product, and centrifuge for 5–20 min at 5000–6000 rpm. Oil-soluble NaGdF4 nanoparticles were obtained by washing three times with a mixed solvent of cyclohexane and anhydrous ethanol and dispersing them in 4 mL of cyclohexane for later use. 1 mL of the NaGdF4 cyclohexane solution was taken, 4 mL of acetone was added, and the mixture was centrifuged. The nanoparticles were then redispersed in 4 mL of acetone, 0.5 mL of hydrochloric acid was added, and the mixture was sonicated for 30 min. After standing for 1–6 h, the nanoparticles were centrifuged at 20,000 r / min and washed three times with acetone to obtain water-soluble NaGdF4 nanoparticles.

[0060] Figure 3 The image shows a transmission electron microscope (TEM) image of NaGdF4 nanoparticles prepared in Example 1. Figure 3 As can be seen, the nanoparticles have a uniform size distribution with an average particle size of 9.8 nm.

[0061] Figure 4 The X-ray powder diffraction pattern of the NaGdF4 nanomaterials prepared in Example 1 is shown below. Figure 4 It can be seen that the nanoparticles are pure hexagonal NaGdF4 crystal phase.

[0062] Figure 5 Thermogravimetric analysis and in-situ Fourier transform infrared spectroscopy of NaGdF4 nanoparticles. Figure 5 For thermogravimetric analysis (TGA), NaGdF4 nanoparticles were heated to 140°C and then placed in air. After removing the oleic acid ligands on the surface of the NaGdF4 nanoparticles with hydrochloric acid, the dangling bonds and rare earth cations on the nanoparticle surface were exposed. These cations may adsorb water molecules from the air and release them upon heating, resulting in a decrease in mass during TGA. Thermogravimetric analysis showed that the exposed NaGdF4 nanoparticles possessed a certain adsorption capacity and good cyclic adsorption-desorption performance. Figure 5 b is the in-situ Fourier transform infrared spectrum; the vibrational peaks at wavenumbers 1629 and 3367 in the figure represent the absorption peaks of the bending and stretching vibrations of water molecules. From Figure 5b indicates that the NaGdF4 nanoparticles adsorb water molecules in the air, and verifies their excellent cyclic adsorption-desorption performance.

[0063] Example 2: Preparation and lifetime regulation of TMB-coupled NaGdF4 nanomaterials

[0064] The water-soluble NaGdF4 nanoparticles obtained in Example 1 were dissolved in 1 mL of methanol to prepare a 50 mg / mL NaGdF4 nanoparticle methanol solution. 10–100 μL of the NaGdF4 methanol solution was mixed thoroughly with 50 μL of 0.5 mg / mL TMB toluene. The mixture was dropped onto a quartz plate, placed in a glove box, and heated at 75°C to remove the solvent and form a uniform mixed film.

[0065] The nanoparticles prepared in this embodiment have uniform morphology and size, and are hexagonal NaGdF4 crystal phase. The lanthanide rare earth nanoparticles and TMB form a strong spin-orbit coupling effect. Under photoexcitation, excitons are generated between TMB molecules and undergo charge separation under the spin-orbit coupling effect. The separated excitons recombine, producing long-lifetime luminescence.

[0066] Figure 6 The figures show the spectral properties of NaGdF4 nanoparticles and organic TMB composites in Example 2. a) Changes in the emission spectrum of organic TMB after adding nanoparticles of different masses with a fixed organic TMB mass. The figure shows that the singlet emission of organic TMB occurs at 410 nm. As the amount of nanoparticles added gradually increases, the green emission intensity at 530 nm gradually increases, and the ratio of green to blue emission intensities gradually increases, indicating that the excited singlet energy gradually transfers to the CT state energy level of green emission. b) Changes in the absorption spectrum of organic TMB after adding nanoparticles of different masses with a fixed organic TMB mass. When the mass ratio of nanoparticles to organic TMB reaches 200:1, new absorption peaks appear at 380 nm and 475 nm compared to lower doping levels. The 380 nm absorption peak is inferred to be the absorption of the CT state; while the 475 nm absorption peak, according to literature reports, is due to the formation of cationic TMB. + This leads to absorption.

[0067] Figure 7 The change in lifetime after NaGdF4 nanoparticles and organic molecule TMB were combined in Example 2. Figure 7 a represents the lifetime at 410 nm under 365 nm excitation, and the fitted lifetime is approximately 2 ns. The addition of NaGdF4 nanoparticles did not alter the singlet luminescence properties. Figure 7b represents the lifetime at 530 nm under 365 nm excitation. With increasing NaGdF4 nanoparticle doping, the CT state luminescence lifetime increases, eventually reaching 1.28 ms, achieving the goal of transferring energy from the short-lived singlet state to the long-lived CT state. Furthermore, when the NaGdF4 nanoparticle doping mass is relatively low, due to the concentration quenching effect of organic molecules, the CT state lifetime is only 0.28 ms, thus also achieving the modulation of the CT state lifetime.

[0068] Figure 8 The excitation-fluorescence / phosphorescence spectroscopic properties of NaGdF4 nanoparticles and organic molecule TMB after composite formation in Example 2 are shown. Figure 8 a represents the excitation-fluorescence spectrum when the mass ratio of NaGdF4 nanoparticles to organic molecule TMB is 200:1. The figure shows that when excited by a high-energy excitation source below 350 nm, fluorescence emission occurs at 380 nm. Figure 6 The absorption at 380 nm is shown in Figure b. When excited by an excitation source of 360–425 nm, CT state emission with a peak at 530 nm is observed. Figure 8 b is the excitation-phosphorescence spectrum collected after 100 μs of excitation decay; after 100 μs decay, the short-lived singlet state emission disappears, and the remaining emission is the long-lived CT state emission. The spectrum is relatively symmetrical, which is consistent with the CT state emission characteristics.

[0069] Example 3: Preparation and lifetime regulation of TPB-coupled NaGdF4 nanomaterials

[0070] The water-soluble NaGdF4 nanoparticles obtained in Example 1 were dissolved in 1 mL of methanol to prepare a 50 mg / mL NaGdF4 nanoparticle methanol solution. 100 μL of the NaGdF4 methanol solution was mixed thoroughly with 50 μL of 0.5 mg / mL TPB toluene. The mixture was dropped onto a quartz plate, placed in a glove box, and heated at 75°C to remove the solvent and form a uniform mixed film.

[0071] The nanoparticles prepared in this embodiment have uniform morphology and size, and are hexagonal NaGdF4 crystal phase. The lanthanide rare earth nanoparticles and TPB molecules form a strong spin-orbit coupling effect. Under photoexcitation, excitons are generated between TPB molecules and undergo charge separation under the spin-orbit coupling effect. The separated excitons recombine, producing long-lifetime luminescence. Figure 7 b shows the lifetime change after NaGdF4 nanoparticles and organic molecule TPB are combined. The CT state emission lifetime reached 1 ms under 365 nm excitation, achieving the goal of transferring energy from the short-lived singlet state to the long-lived CT state.

[0072] Example 4: Preparation of TMB-coupled NaGdF4 nanomaterials and their application in water sensing and water dosing detectors

[0073] The hybrid membrane prepared in Example 2 was placed in different water molecule environments (10 min) to test the effect of trace water molecules on the coupling effect. It was found that trace water molecules affect the coupling effect and quench the TMB green light. Figure 6 c represents the spectral change of NaGdF4 nanoparticles and organic molecule TMB after contacting water for 10 minutes following a 200:1 mass ratio composite. When the composite comes into contact with water molecules, the green emission at 530 nm disappears, leaving only blue emission at 410 nm, and the spectrum broadens. The significant color change from bright green to blue emission indicates that the composite membrane of this invention can be used as a water sensor.

[0074] In addition, the quenching strength is positively correlated with the water molecule dose, and the dose of trace water molecules can be calculated through spectroscopy.

[0075] Figure 9 The figure shows the changes in CT-state luminescence of NaGdF4 nanoparticles and organic molecule TMB under the influence of trace water molecules. The blue luminescence remains essentially unchanged, while the green luminescence undergoes strong quenching. When the water molecule content changes from 0.1 ppm to 400 ppm, the composite changes from green to white luminescence. The Langmuir equation shows that the ratio of green to blue luminescence intensity decreases exponentially with changing water content, indicating static fluorescence quenching. The figure suggests that the NaGdF4 nanoparticles adsorb a certain amount of water molecules on their surface monolayer, and the water molecules influence the coupling, quenching the green TMB light. Based on the exponential decay equation, the composite material can be used to prepare a trace water molecule dosimeter.

[0076] Figure 10 A moisture absorption-heating cycle test was conducted on the composite of NaGdF4 nanoparticles and organic molecule TMB. The moisture absorption method involved directly adding 10 μl of water to the composite membrane, followed by heating at 65°C for 10 min. The results show that after dozens of cycles of severe disruption of the coupling effect by water molecules, the green luminescence of TMB could be restored by heating, demonstrating the excellent cyclic detection capability of the composite material.

[0077] Example 5: Preparation of TMB-coupled NaGdF4 nanomaterials and their application in organic solvent sensing

[0078] The hybrid membrane prepared in Example 2 was placed in a saturated vapor environment of different organic solvents (10 min) to test the effect of organic solvents on the coupling effect. It was found that trace amounts of solvents affected the coupling effect and quenched the TMB green light. Figure 11This section describes the effect of different solvent vapors (ethanol, cyclohexane, acetone, tetrahydrofuran, etc.) on the NaGdF4 nanoparticles and the organic molecule TMB composite in Example 5. Because the surface of the NaGdF4 nanoparticles is exposed with dangling bonds and rare earth cations after acid washing, their adsorption capacity for different solvents varies, leading to different luminescence decays. Therefore, the NaGdF4-TMB composite system, as a solvent indicator, can be used to determine the type of solvent by observing the luminescence of the composite.

[0079] Example 6: Preparation of TPB-coupled NaGdF4 nanomaterials and their application in a water dosing detector

[0080] The hybrid membrane prepared in Example 3 was placed in different water molecule environments to test the effect of trace water molecules on the coupling effect. It was found that trace water molecules affect the coupling effect and quench the TPB green light. The quenching strength is positively correlated with the water molecule dose. The trace water molecule dose can be calculated by spectroscopy.

[0081] Figure 12 This figure shows the changes in CT-state luminescence of NaGdF4 nanoparticles and organic molecule TPB after composite formation under the influence of trace water molecules in Example 6. Since TPB has benzene rings at both ends and is relatively far from the NaGdF4 nanoparticles, the coupling effect is weak. The NaGdF4-TPB composite system exhibits a strong response to trace water molecules, filling the response gap of the NaGdF4-TMB composite system in the range of less than 30 ppm.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this invention, based on the technical solution and inventive concept of the present invention, should be within the protection scope of this invention.

Claims

1. A method for inducing long-lived charge-transfer excited states of organic molecules using rare-earth nanoparticles, characterized in that, The method is as follows: the organic molecule is an organic compound with electron-donating ability. The lanthanide rare earth nanoparticles with exposed rare earth cations form a spin-orbit coupling effect with the organic molecule. Under photoexcitation, excitons are generated between the organic molecules and charge separation occurs under the spin-orbit coupling effect. The separated excitons recombine to generate long-lived charge-transfer excited state luminescence. The organic molecule is a nitrogen-oxygen functional group molecule with lone pair electrons.

2. The method according to claim 1, characterized in that, The organic molecules include: N,N,N',N'-tetramethylbenzidine and N,N,N',N'-tetraphenylbenzidine.

3. The method according to claim 1, characterized in that, The rare earth cation is: Ce 3+ Pr 3+ 、Nd 3+ 、Sm 3+ Eu 3+ Gd 3+ 、Tb 3+ Dy 3+ Ho 3+ Er 3+ Tm 3+ Yb 3+ .

4. The method according to claim 1, characterized in that, The wavelength of the light used for excitation is 250~450 nm.

5. A rare-earth nanoparticle-induced long-lived charge transfer excited-state system for organic molecules, characterized in that, It is composed of lanthanide rare earth nanoparticles and organic molecules. The organic molecules are organic compounds with strong electron-donating ability. The lanthanide rare earth nanoparticles have rare earth cations exposed on their surface. The organic molecules are nitrogen and oxygen functional group molecules with lone pairs of electrons.

6. The system according to claim 5, characterized in that, The organic molecules include: N,N,N',N'-tetramethylbenzidine and N,N,N',N'-tetraphenylbenzidine.

7. An application of the rare earth nanoparticle-induced long-lived charge transfer excited-state system of organic molecules according to any one of claims 5-6, characterized in that, include: (1) Ultrasensitive cyclic detection and dosage determination of various solvents; (2) Regulation of the lifetime of the excited state of charge transfer in organic molecules.

8. The application according to claim 7, characterized in that, The solvents include water, ethanol, cyclohexane, acetone, and tetrahydrofuran.

Images