A kind of quantum clipping material based on triplet ligand sensitized nanocrystal and its preparation method and application

Abstract

The present application relates to the technical field of light conversion materials, and particularly relates to a quantum cutting material based on a triplet ligand sensitized nanocrystal and a preparation method and application thereof. The quantum cutting material comprises a nanocrystal core and a surface ligand layer. The nanocrystal core is NaYF4 or NaGdF4, doped with Yb 3+ and Tb 3+ . The surface ligand layer comprises a triplet sensitized ligand capable of generating triplet excitons through an inverse intersystem crossing process. The triplet sensitized ligand is pyridine-2,6-dicarboxylic acid, 1,2,4,5-benzene tetracarboxylic acid or 1,3,5-benzene tricarboxylic acid, and a carboxylic acid group at a molecular end of the triplet sensitized ligand forms a coordination bond with Yb 3+ and Tb 3+ on the surface of the nanocrystal core. After the triplet sensitized ligand absorbs excitation light, the triplet exciton energy generated by the triplet sensitized ligand is transferred to the quantum cutting center. The present application provides strong support for solar cells, biological imaging and light emitting devices.

Description

Technical Field

[0001] This invention relates to the field of light conversion materials technology, specifically to a quantum tailoring material based on triplet ligand-sensitized nanocrystals, its preparation method, and its application. Background Technology

[0002] With the continuous growth of global energy demand and the increasing depletion of traditional fossil fuels, solar energy, as a clean, renewable, and widely distributed energy form, has received widespread attention. Photovoltaic cells are the core devices that directly convert solar energy into electricity, and improving their energy conversion efficiency has always been a research hotspot and challenge. In single-junction solar cells, there is a significant spectral mismatch loss: photons with energy below the semiconductor bandgap cannot be absorbed and utilized, while photons with energy above the bandgap dissipate their excess energy as heat, resulting in energy loss. Taking silicon-based solar cells, which dominate the photovoltaic market, as an example, their bandgap is approximately 1.12 eV, corresponding to an intrinsic absorption edge at approximately 1100 nm, exhibiting good response to the visible-near-infrared region with energy above the bandgap. However, the ultraviolet region (300-400 nm), which occupies a considerable proportion of the solar spectrum, accounts for about 6% of the total energy of the Earth's solar spectrum. Although the energy of these high-energy photons is much higher than the bandgap of silicon, their excess energy is mainly dissipated as heat, failing to be effectively converted into electrical energy, severely limiting the full utilization of solar photons by silicon-based solar cells. Therefore, reducing thermal losses in the ultraviolet region and improving the photoelectric conversion efficiency of silicon-based solar cells have become important research directions in the photovoltaic field.

[0003] Quantum shaving technology, as a photon management method capable of converting a high-energy photon into two or more low-energy photons, can theoretically achieve a quantum efficiency exceeding 100% (Non-Patent Document 1), providing a novel solution for effectively reducing thermal losses in solar cells and significantly improving their photoelectric conversion efficiency. By converting ultraviolet photons into near-infrared photons that match the bandgap of silicon, quantum shaving materials allow energy that would otherwise be dissipated as heat to be reused, thus overcoming the physical limit of traditional downconversion materials (Non-Patent Document 2) that are constrained by energy conservation and cannot achieve a quantum efficiency exceeding 100%.

[0004] Currently, research on quantum trimming materials mainly focuses on lanthanide rare-earth ion-doped inorganic nanocrystalline systems (non-patent literature 3), primarily due to their unique luminescence mechanism and excellent optical properties. Rare-earth ions possess abundant energy level structures and 4f electronic transition characteristics. Although their ff transitions are parity-forbidden, once excited, they can produce narrow-band emission, long luminescence lifetime, and high stability, making them an ideal system for quantum trimming research. Compared to the singlet splitting of organic molecules, the physical mechanisms by which they achieve quantum efficiencies exceeding 100% are fundamentally different: singlet splitting refers to the splitting of a high-energy singlet exciton into two triplet excitons through a spin-allowed process in organic semiconductor materials (patent literature 1), thereby generating two low-energy photons. This process mainly occurs in organic conjugated molecular systems and is strictly limited by molecular packing and energy level matching; while rare-earth quantum trimming is achieved through energy transfer processes between rare-earth ions, such as Tb 3+ After absorbing a high-energy ultraviolet photon, the excitation energy is simultaneously transferred to two Yb cells through cooperative energy transfer. 3+ Ions, thereby emitting two near-infrared photons (Non-Patent Document 4). In contrast, rare-earth quantum-tailored materials have the following significant advantages: First, narrow emission bands and high color purity, which are conducive to accurately matching the application requirements of specific wavelengths; second, long luminescence lifetime (microseconds to milliseconds), which facilitates time-resolved detection and avoids autofluorescence interference; third, excellent thermal and chemical stability, suitable for long-term use in harsh environments; fourth, by selecting different combinations of rare-earth ions, quantum-tailored emission over a wide spectral range from ultraviolet to infrared can be achieved, with high tunability. These advantages make rare-earth-doped inorganic nanocrystal systems show broad application prospects in photovoltaic enhancement, bioimaging, optoelectronic devices and other fields. Among the many rare-earth quantum-tailored systems, Yb 3+ Ions as acceptors, with Tb 3+ or Pr 3+ Co-doped NaYF4 or NaGdF4 nanocrystals with donor ions (Non-Patent Document 5) have become a research hotspot in this field because they can convert ultraviolet-visible photons into near-infrared photons (approximately 980 nm) that match the bandgap of silicon-based solar cells. For example, the NaYF4:Tb / Yb system reported in the prior art (Non-Patent Document 6), Tb 3+ After absorbing a high-energy ultraviolet photon, the excitation energy is simultaneously transferred to two Yb cells through cooperative energy transfer. 3+ This allows the emission of two low-energy near-infrared photons, achieving a quantum cutting efficiency of over 100%.

[0005] Although rare-earth-doped quantum-tailored materials can theoretically achieve quantum efficiencies exceeding 100%, they still face an inherent key bottleneck in practical applications: the ff transitions of rare-earth ions are parity-selection-forbidden transitions, with extremely small absorption cross-sections, typically less than 10. -20 cm 2 This inherent defect results in the material having extremely weak absorption capacity for the ultraviolet-visible light, which constitutes the largest proportion of the solar spectrum. A large number of photons cannot be effectively captured and utilized, which severely restricts the overall quantum cutting efficiency and energy conversion performance.

[0006] The problem of small absorption cross-section of rare earth ions is widely recognized from existing patent technologies. Existing technologies disclose a method based on Yb... 3+ The method for preparing downconversion fluorescent materials (Patent Document 2), while achieving quantum trimming and claiming a quantum efficiency exceeding 100%, is still limited to the traditional rare-earth ion co-doping strategy, relying solely on energy transfer between rare-earth ions and failing to fundamentally solve the problem of a small absorption cross-section. Another method concerning rare-earth ion Er... 3+ Existing technologies for doped upconversion luminescent materials (Patent Document 3) also clearly point out that the major challenges faced by existing upconversion materials stem primarily from their small absorption cross-section and the parity-forbidden transition characteristics of the ff electric dipole transition, resulting in a narrow excitation band and less than ideal luminescence efficiency. The technical background analysis of these patents and research further confirms that simply relying on energy transfer between rare-earth ions is insufficient to overcome the physical limitation of a small absorption cross-section; therefore, new sensitization mechanisms need to be introduced to enhance the material's ability to capture excitation light.

[0007] To address these bottlenecks, researchers have attempted various improvement strategies. One such strategy involves introducing wide bandgap sensitizers such as Ce. 3+ Eu 2+ Ce ions enhance absorption through their allowed fd transitions. 3+ Eu 2+ While the absorption coefficient of rare earth ions is higher than that of ordinary rare earth ions, it is still more than an order of magnitude lower than that of organic dyes and quantum dots, and the absorption range is limited, making it difficult to achieve broad-spectrum, high-efficiency absorption (Non-Patent Literature 7). Secondly, a semiconductor quantum dot shell is constructed, utilizing the high absorption cross-section of the quantum dots to capture photons and then transfer energy to rare earth ions. However, quantum dots face problems such as severe self-absorption, small Stokes shift leading to easy reabsorption, difficulty in matching energy levels with rare earth ions, and low energy transfer efficiency, making it difficult to achieve efficient and stable energy transfer. Furthermore, perovskite quantum dots based on rare earth ion doping reported in recent years also face shortcomings such as being susceptible to water and heat, easily damaged structures, and poor material stability (Non-Patent Literature 8). Thirdly, organic dye molecules are used as antenna sensitizers. Although organic dyes have extremely high molar extinction coefficients (up to 10), they are still limited in their application. 5 L·mol -1·cm -1 There have been reports of attempts to improve light absorption efficiency by using fluorescent dyes to transfer energy to rare earth ions through the singlet states generated after excitation (non-patent literature 9). However, the exciton lifetime of the singlet state is extremely short (picosecond level), which does not match the energy transfer window of the long-lived excited state of rare earth ions (microsecond to millisecond level). Furthermore, the efficiency of singlet-to-singlet Förster resonance energy transfer (FRET) is strictly limited by the donor-acceptor distance and coupling strength, making it difficult to achieve efficient and stable energy transfer.

[0008] In summary, existing rare-earth quantum tailoring materials have the following main drawbacks: First, the intrinsic absorption cross-section of rare-earth ions is small, resulting in insufficient ability to capture excitation light; second, existing sensitization strategies (Ce... 3+ / Eu 2+ Doping, quantum dot composites, and organic dye sensitization all have their own limitations, making it difficult to simultaneously achieve broad-spectrum high-efficiency absorption, high-efficiency energy transfer, and excellent stability. Thirdly, no technical solution has yet been able to fundamentally overcome the inherent advantages of rare-earth quantum-cut materials (narrow-band emission, long lifetime, and high stability) while retaining their fundamental defects of small absorption cross-section and low energy utilization.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Chinese Patent Document CN111433317A, Publication Date July 17, 2020.

[0012] Patent Document 2: Chinese Patent Document CN102977880A, Publication Date December 4, 2012.

[0013] Patent Document 3: Chinese Patent Document CN116445163B, Publication Date: February 27, 2024.

[0014] Non-patent literature

[0015] Non-patent literature 1: Progress in Materials Science, DOI: 10.1016 / j.pmatsci.2009.10.001.

[0016] Non-patent literature 2: Journal of Luminescence, DOI: 10.1016 / j.jlumin.2017.11.024.

[0017] Non-patent literature 3: Science, DOI: 10.1126 / science.283.5402.663.

[0018] Non-patent literature 4: Results in Physics, DOI: 10.1016 / j.rinp.2021.104595.

[0019] Non-patent literature 5: Advanced Materials, DOI: 10.1002 / adma.200803854.

[0020] Non-patent document 6: Optical Materials Express, DOI: 10.1364 / OME.7.000224.

[0021] Non-patent literature 7: Journal of Fluorescence, DOI: 10.1007 / s10895-024-04019-7.

[0022] Non-patent literature 8: Advanced Optical Materials, DOI: 10.1002 / adom.202500123.

[0023] Non-patent literature 9: J. Phys. Chem. Lett., DOI: 10.1021 / acs.jpclett.8b00516. Summary of the Invention

[0024] The purpose of this invention is to overcome the shortcomings of the prior art and provide a quantum tailoring material based on triplet ligand-sensitized nanocrystals, its preparation method and application. By using triplet organic ligands with high molar extinction coefficients as antenna sensitizers, which are bonded to the surface of rare earth-doped fluoride nanocrystals, the efficient absorption of the ligands enhances the material's ability to capture excitation light, and the long-lived triplet excitons of the ligands transfer energy to rare earth ions through the Dexter electron exchange mechanism, thereby significantly improving the quantum tailoring efficiency.

[0025] According to a first aspect of the present invention, a quantum tailoring material based on triplet ligand-sensitized nanocrystals is proposed, comprising a nanocrystal nucleus and a surface ligand layer, wherein the nanocrystal nucleus is NaYF4 or NaGdF4 and is doped with Yb. 3+ and Tb 3+ The surface ligand layer includes a triplet-sensitized ligand capable of generating triplet excitons through an anti-system crossing process; the triplet-sensitized ligand is pyridine-2,6-dicarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, or 1,3,5-benzenetricarboxylic acid, and interacts with the Yb on the surface of the nanocrystal core through the carboxylic acid group at its molecular end. 3+ and the Tb 3+ Forming coordinate bonds; the Yb3+ and the Tb 3+ This constitutes a quantum tailoring center. The quantum tailoring material is constructed by bonding organic ligands with high molar extinction coefficients to the surface of rare-earth-doped nanocrystal nuclei, utilizing the efficient absorption of the organic ligands to enhance the material's ability to capture excitation light.

[0026] Furthermore, the triplet-sensitized ligand absorbs excitation light and transfers the energy of the generated triplet excitons to the quantum trimming center. Utilizing the long-lived triplet excitons of the organic ligands, efficient energy transfer to rare-earth ions is achieved through the Dexter electron exchange mechanism. This significantly improves the photon conversion efficiency of the material while retaining the inherent advantages of rare-earth nanocrystals, such as quantum trimming capabilities, narrow emission bandgap, high stability, and long luminescence lifetime.

[0027] According to a second aspect of the present invention, a method for preparing the quantum tailoring material is provided, comprising the following steps:

[0028] S1. Rare earth acetate, oleic acid and 1-octadecene are mixed and heated to form a rare earth oleate complex. After cooling, a solution containing a sodium source and a fluorine source is added to obtain a mixed solution. The solvent in the solution is methanol or ethanol.

[0029] S2. The mixture is heated under vacuum to remove the methanol or ethanol, and then heated under inert gas protection. After cooling, it is centrifuged and washed, and dispersed in cyclohexane to obtain oleic acid-encapsulated nanocrystals.

[0030] S3. The oleic acid-coated nanocrystal nuclei are mixed with hydrochloric acid and ultrasonically treated to remove the oleic acid on the surface. After centrifugation and washing, they are dispersed in anhydrous ethanol to obtain ligand-free nanocrystal nuclei.

[0031] S4. Dissolve the triplet-state sensitized ligand in a solvent and mix it with the ligand-free nanocrystal nucleus for an ultrasonic reaction. The triplet-state sensitized ligand forms a coordination bond with the surface of the nanocrystal nucleus to obtain the quantum tailoring material.

[0032] The preparation method synthesizes uniformly sized and highly crystalline nanocrystal nuclei through a high-temperature hot-injection method, and then effectively removes surface oleic acid by hydrochloric acid ultrasonic treatment to expose rare earth ion active sites. Finally, triplet-state sensitized ligands are stably anchored on the surface of the nanocrystal nuclei through ultrasonic-assisted ligand exchange to form a compact hybrid structure.

[0033] Further, in step S1, the rare earth acetate includes yttrium acetate or gadolinium acetate, ytterbium acetate and terbium acetate, wherein the amount of yttrium acetate or gadolinium acetate is 0.076~0.152 mmol, the amount of ytterbium acetate is 0.1~0.2 mmol, and the amount of terbium acetate is 0.024~0.048 mmol; the amount of oleic acid is 3~7 mL, and the amount of 1-octadecene is 7~14 mL.

[0034] Further, in step S1, the sodium source is sodium hydroxide, the fluorine source is ammonium fluoride, the heating temperature is 110–170°C, and the heating time is 0.5–1.5 h. These heating conditions effectively remove oxygen and moisture from the reaction system, avoid oxidation side reactions, and ensure the purity and crystallization quality of the nanocrystal nuclei.

[0035] Further, in step S2, the heating temperature is 100~130℃, and the time is 20~40 min; the temperature rise is 250~320℃, and the time is 1.5~3 h. The vacuum heating condition effectively removes residual low-boiling-point solvents such as methanol or ethanol, and the high-temperature reaction condition promotes the full growth of nanocrystal nuclei, resulting in nanocrystal nuclei with uniform size and high crystallinity.

[0036] Furthermore, in step S3, the concentration of hydrochloric acid is 1 M, and the ultrasonic treatment time is 30-120 s. The hydrochloric acid ultrasonic treatment conditions are mild and efficient, and can remove oleic acid without damaging the crystal structure and surface active sites of the nanocrystal nuclei.

[0037] Further, in step S4, the triplet-state sensitizing ligand is pyridine-2,6-dicarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, or 1,3,5-benzenetricarboxylic acid, and the ultrasonic reaction time is 30-90 min. The ultrasonic reaction conditions enable the ligand to form stable coordination bonds with the rare earth ions on the surface of the nanocrystal nucleus through the carboxylic acid group, ensuring a strong bond between the triplet-state ligand and the nanocrystal nucleus, thereby achieving efficient energy transfer.

[0038] According to a third aspect of the present invention, a photovoltaic panel is provided, comprising the quantum-cutting material as described above. The quantum-cutting material is disposed on the light-receiving surface of the photovoltaic panel, thereby improving the photoelectric conversion efficiency of the photovoltaic panel.

[0039] According to a fourth aspect of the present invention, an application of the quantum-tailored material as described herein is proposed in the fabrication of photovoltaic devices, bioimaging reagents, or light-emitting devices. The quantum-tailored material can efficiently convert ultraviolet light into near-infrared light, which is beneficial for improving the spectral response range of silicon-based solar cells; the near-infrared II emission of the material has the advantages of deep tissue penetration and low background noise, making it suitable for high signal-to-noise ratio bioimaging; at the same time, the thermal stability and photostability of the material ensure its long-term stable operation in the field of light-emitting devices.

[0040] The beneficial effects of this invention are:

[0041] First, this invention utilizes organic ligands with high molar extinction coefficients as antenna sensitizers. The efficient absorption of the ligands significantly enhances the material's ability to capture excitation light, enabling more ultraviolet photons to be effectively utilized, thus overcoming the fundamental defect of small intrinsic absorption cross-section of rare earth ions from the source.

[0042] Second, this invention employs organic ligands with long-lived triplet excitons to efficiently convert singlet excitons into long-lived triplet excitons through intersystem crossing, matching their lifetimes with the excited states of rare earth ions. This allows for efficient energy transfer through the Dexter electron exchange mechanism, avoiding energy loss due to lifetime mismatch in the singlet FRET mechanism.

[0043] Third, this invention constructs a triplet organic ligand-rare earth nanocrystal hybrid structure by bonding organic ligands to the surface of rare earth doped nanocrystal nuclei. This structure not only leverages the efficient antenna effect of organic ligands but also retains the inherent advantages of rare earth nanocrystals, such as narrow emission band, high stability, and long luminescence lifetime, thus achieving complementary advantages between the two.

[0044] Fourth, this invention significantly enhances the absorption and utilization of ultraviolet light energy, improves the near-infrared luminescence intensity, and the material has excellent thermal and light stability. The preparation process is stable and reliable, and it has broad application prospects in fields such as improving solar cell efficiency, near-infrared II bioimaging, photocatalysis, and light-emitting devices. Attached Figure Description

[0045] Figure 1 A schematic diagram illustrating the working principle of the quantum tailoring material based on triplet ligand-sensitized nanocrystals provided by this invention;

[0046] Figure 2 The flowchart below shows the preparation method of the quantum cutting material provided by the present invention.

[0047] Figure 3 The NaYF4:50% Yb provided for this invention 3+ / 12% Tb 3+ X-ray powder diffraction pattern of quantum-tailored nanocrystals;

[0048] Figure 4 The NaYF4:50% Yb provided for this invention 3+ / 12% Tb 3+ Transmission electron microscopy morphology and size distribution of quantum-tailored nanocrystals;

[0049] Figure 5 The ultraviolet absorption spectra of the triplet ligands DPA, PMA, and TMA in DMF solution provided by this invention;

[0050] Figure 6 Fourier transform infrared spectra of ligand-free nanocrystals and nanocrystals modified with DPA, PMA, and TMA respectively, prepared according to the present invention.

[0051] Figure 7 The ultraviolet absorption spectra of the ligand-free nanocrystals and the nanocrystals modified with DPA, PMA and TMA respectively provided by the present invention in DMF solution;

[0052] Figure 8 Near-infrared emission spectra of ligand-free nanocrystals and nanocrystals modified with DPA, PMA, and TMA respectively in DMF solution provided by the present invention;

[0053] Figure 9 The DPA ligand solution and DPA-modified NaYF4:50% Yb provided by this invention 3+ / 12% Tb 3+ Nanosecond transient absorption spectrum of nanocrystals in DMF solution;

[0054] Figure 10 The DPA ligand solution and DPA-modified NaYF4:50% Yb provided by this invention 3+ / 12% Tb 3+ Triplet decay kinetics diagram of nanocrystals;

[0055] Figure 11 The ligand-free nanocrystals and DPA-modified NaYF4:50% Yb prepared according to the present invention 3+ / 12% Tb 3+ Thermal stability test results for nanocrystalline powder;

[0056] Figure 12 The DPA-modified NaYF4:50% Yb prepared for this invention 3+ / 12% Tb 3+ Photostability test results of nanocrystals in DMF solution;

[0057] In the attached diagram, QCNP stands for Quantum Cutting Nanoparticles; DPA, PMA, and TMA are abbreviations for the triplet ligands pyridine-2,6-dicarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, and 1,3,5-benzenetricarboxylic acid, respectively; and DMF stands for N,N-dimethylformamide. Detailed Implementation

[0058] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0059] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0060] Given the current limitations of quantum tailoring materials in achieving broad-band strong light absorption while maintaining efficient quantum tailoring, the limited increase in absorption cross-section due to inorganic sensitizers, and the fact that organic dyes, while exhibiting strong absorption, suffer from short singlet lifetimes and ineffective energy transfer to the nanocrystal nucleus, the first objective of this invention is to propose a quantum tailoring material based on triplet ligand-sensitized nanocrystals. This quantum tailoring material significantly enhances the absorption of ultraviolet-visible light by coordinating and bonding triplet-sensitized ligands with large conjugated planar structures to the surface of the nanocrystal nucleus. Furthermore, it utilizes long-lived triplet excitons and the Dexter energy transfer mechanism to achieve efficient energy transfer to the quantum tailoring center, effectively overcoming the bottlenecks of weak light absorption and difficult energy transfer in traditional rare-earth materials, and significantly improving near-infrared luminescence intensity while maintaining efficient quantum tailoring.

[0061] The second objective of this invention is to provide a method for preparing the quantum cutting material, wherein the preparation method is simple, mild, and reproducible, and can achieve efficient and uniform assembly of ligands on the surface of nanocrystals to form a stable energy transfer interface. Furthermore, the resulting material has excellent thermal and optical stability and is suitable for large-scale preparation and application.

[0062] The third objective of this invention is to provide a photovoltaic panel in which the quantum cutting material is disposed on the light-receiving surface of the photovoltaic panel to improve the photoelectric conversion efficiency of the photovoltaic panel.

[0063] The fourth objective of this invention is to propose the application of the quantum-cutting material as described above in the fabrication of photovoltaic devices, bioimaging reagents, or light-emitting devices. The near-infrared luminescence intensity of the quantum-cutting material is significantly enhanced, meeting the requirements for long-term stable operation of light-emitting devices and possessing broad application prospects.

[0064] The abbreviations used in the following examples are explained as follows: the triplet ligands pyridine-2,6-dicarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid and 1,3,5-benzenetricarboxylic acid are abbreviated as DPA, PMA and TMA, respectively; 1-octadecene is abbreviated as ODE, oleic acid is abbreviated as OA, N,N-dimethylformamide is abbreviated as DMF, and QCNP is an abbreviation for quantum tailored nanoparticles.

[0065] This invention provides a quantum tailoring material based on triplet ligand-sensitized nanocrystals, comprising a nanocrystal core and a surface ligand layer, wherein the nanocrystal core is NaYF4 or NaGdF4 and is doped with Yb. 3+ and Tb 3+ The surface ligand layer includes a triplet-state sensitizing ligand with a large conjugated planar structure; the triplet-state sensitizing ligand is pyridine-2,6-dicarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, or 1,3,5-benzenetricarboxylic acid, and interacts with the Yb on the surface of the nanocrystal core through the carboxylic acid group at its molecular end. 3+ and the Tb 3+ Forming coordinate bonds; the Yb 3+ and the Tb 3+ The triplet-state sensitized ligand, constituting a quantum trimming center, absorbs excitation light, generates a triplet-state exciton through an antisystem crossing process, and transfers energy to the quantum trimming center. The Yb 3+ and the Tb 3+ Through a cooperative quantum cutting process, one ultraviolet photon can be converted into two near-infrared photons. The triplet-state sensitized ligand has a large conjugated planar structure and high intersystem crossing efficiency, which can efficiently absorb ultraviolet-visible light and rapidly convert it into a long-lived triplet exciton, providing a sufficient time window for energy transfer. This significantly enhances the utilization of excitation light by the nanocrystal nucleus and greatly improves the near-infrared luminescence intensity.

[0066] The preparation method of the quantum cutting material includes the following steps:

[0067] (1) At room temperature, terbium acetate, ytterbium acetate, yttrium acetate or gadolinium acetate, 1-octadecene (ODE), and oleic acid (OA) are placed in a round-bottom flask. The mixture is heated and maintained at a certain temperature to remove oxygen and water, and then cooled to room temperature for subsequent experiments. The amount of yttrium acetate or gadolinium acetate is 0.076~0.152 mmol, the amount of terbium acetate is 0.024~0.048 mmol, and the amount of ytterbium acetate is 0.1~0.2 mmol; the amount of ODE is 7~14 mL, and the amount of OA is 3~7 mL; the heating temperature is 110~170℃, and the heating time is 0.5~1.5 h, preferably 160℃ and 1 h, respectively.

[0068] (2) Weigh out the sodium source and fluorine source separately, dissolve them in a polar organic solvent, and sonicate them to obtain a transparent and clear pre-prepared solution. Then add the prepared sodium source and fluorine source solutions to the mixed solution in step (1), stir thoroughly to ensure the ions are fully mixed, and increase the reaction temperature to allow the reaction to proceed for a certain period of time to obtain a homogeneous mixed solution. The sodium source is selected from at least one of sodium hydroxide, sodium carbonate, or sodium fluoride, preferably sodium hydroxide; the fluorine source is selected from at least one of ammonium fluoride, sodium fluoride, or ammonium trifluoroacetate, preferably ammonium fluoride; the polar organic solvent is methanol or ethanol, preferably methanol; the heating temperature is 40~60℃, and the reaction time is 30~60 min, preferably 50℃ and 30 min.

[0069] (3) The mixed solution obtained in step (2) is heated under vacuum and kept at a certain reaction time to remove low-boiling-point impurity solvents such as methanol or ethanol, and to enhance the stability of the complex. Then, under the protection of an inert gas, the temperature is raised to a high temperature for a certain time to promote the formation of crystal nuclei and crystal growth. Finally, the system after the reaction is completed is naturally cooled to room temperature, and after centrifugation and repeated washing with washing solvent, unreacted substances and by-products are removed. Finally, the obtained solid is dispersed in cyclohexane to obtain the nanocrystalline nuclei. Among them, the vacuum heating temperature is 100~130℃, the reaction time is 20~40 min, the vacuum degree is 10~100 Pa, the vacuum heating temperature is preferably 120℃, the reaction time is preferably 30 min, and the vacuum degree is preferably 50 Pa; the high temperature reaction temperature is 250~320℃, the reaction time is 1.5~3 h, the high temperature reaction temperature is preferably 290℃, and the reaction time is preferably 2 h.

[0070] (4) The nanocrystal nuclei obtained in step (3) are mixed with hydrochloric acid and ultrasonically treated to remove the oleic acid on the surface. After centrifugation and repeated washing with a washing solvent, unreacted hydrochloric acid and nanocrystals are removed. Finally, the obtained solid is dispersed in ethanol to obtain the ligand-free nanocrystals. The concentration of the nanocrystal nuclei is 5~20 mg / mL, the amount used is 1 mL, the concentration of hydrochloric acid is 1M, the amount used is 1 mL, the ultrasonic time is 30~120 s, the washing solvent is anhydrous ethanol, and the number of washing times is 1~2.

[0071] (5) Weigh sodium hydroxide and triplet ligand, dissolve them in a polar solvent, and sonicate to obtain a transparent and clear pre-prepared solution for later use; then mix the obtained nanocrystals with the ligand solution and sonicate for a certain time to promote the coupling of ligand and nanocrystals. After centrifugation and repeated washing with washing solvent to remove unreacted substances, the obtained solid is finally dispersed in DMF to obtain the quantum tailoring material. Among them, the triplet ligand is selected from pyridine-2,6-dicarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid or 1,3,5-benzenetricarboxylic acid, preferably pyridine-2,6-dicarboxylic acid. The ligand concentration is 5~50 μmol / mL, and the ligand volume is 100 μL; the nanocrystal concentration is 5~20 mg / mL, the nanocrystal volume is 1~2 mL, the sonication time is 30~90 min, the washing solvent is anhydrous ethanol, and the number of washings is 1~2 times.

[0072] Example 1

[0073] Figure 1 This diagram illustrates the working principle of efficient quantum tailoring of nanocrystals through the triplet state energy transfer of ultraviolet light absorbed by ligands. Specifically, after an ion is excited to a higher energy level through excited-state absorption, it can transfer its energy to another ion in the ground state through an efficient cross-relaxation process, causing the ion to transition to an intermediate state, while the ion itself returns to the intermediate state. This newly excited ion can then absorb another photon, triggering a new round of energy transfer. This chain reaction ensures that the absorption of a single photon ultimately excites multiple ions to the luminescent energy level, resulting in significant optical gain.

[0074] This embodiment prepares nanomaterials with ultra-high quantum cutting efficiency based on triplet ligand sensitization. Figure 2 The preparation method flowchart shows the specific steps as follows:

[0075] 1. NaYF4: 50% Yb 3+ / 12% Tb 3+ Preparation of nanocrystals:

[0076] Typically, an aqueous solution containing (2 mL, 0.2 M) Ln(CH3COO)3 (Ln = Y / Yb / Tb) is added to a 50 mL flask containing oleic acid (3 mL) and 1-octadecene (7 mL). The mixture is heated to 150 °C and magnetically stirred for 60 min to form a lanthanide oleate complex. After cooling to room temperature, a methanol solution of NH4F (4 mL, 0.5 M) and NaOH (2 mL, 0.4 M) is added dropwise at 50 °C, and the mixture is stirred for 30 min. The reaction mixture is heated to 100 °C for 30 min under a vacuum of 50 Pa to remove residual methanol, and then heated to 290 °C for 120 min under nitrogen to promote crystal growth. After cooling, the reaction mixture is treated with excess ethanol, centrifuged at 6000 rpm for 5 min to collect the product, thoroughly washed with cyclohexane and ethanol to remove residual impurities, and finally redispersed in 4.0 mL of cyclohexane for storage and subsequent characterization.

[0077] 2. NaYF4 based on triplet ligand sensitization: 50% Yb 3+ / 12% Tb 3+ Preparation of nanocrystals:

[0078] Typically, nanocrystals dissolved in 1 mL of cyclohexane (10 mg / mL) are mixed with 1 mL of 1 M hydrochloric acid-ethanol solution and sonicated at room temperature for 1 minute. The nanocrystals are collected by centrifugation at 15,000 rpm for 10 min, and washed with ethanol to remove residual impurities. The hydrochloric acid-treated nanocrystals are then weighed and dissolved in 2 mL of ethanol for subsequent ligand sensitization experiments. The ethanol solution (2.0 mL) containing the ligand-free nanocrystal nuclei is divided into two equal portions (1.0 mL each). Triplet ligands pyridine-2,6-dicarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, and 1,3,5-benzenetricarboxylic acid are prepared into solutions with a concentration of 50 μmol / mL. 1.0 mL of the ligand-free nanocrystal nuclei ethanol solution is added to 100 μL of the ligand solution, and the mixture is sonicated for 1 hour to ensure coordination between the ligands and the nanoparticle surface. Excess ligands are then removed by centrifugation. Finally, the product was dispersed in 2 mL of DMF to obtain DPA-modified, PMA-modified, and TMA-modified quantum tailored materials, which were then preserved and further characterized.

[0079] Figure 3 The NaYF4 prepared for this embodiment: 50% Yb 3+ / 12% Tb 3+ X-ray powder diffraction pattern of quantum-tailored nanocrystals indicates that NaYF4: 50% Yb 3+ / 12% Tb 3+The quantum-cut nanocrystals exhibit good crystallinity, and their diffraction peaks correspond to those of the standard card (PDF: 75-0411) for hexagonal phase crystals. No impurity phases were observed, indicating that the synthesized nanocrystals are all pure phases.

[0080] Figure 4 The NaYF4 prepared for this embodiment: 50% Yb 3+ / 12% Tb 3+ Transmission electron microscopy morphology and size distribution of quantum-tailored nanocrystals, where (a) shows oleic acid-coated NaYF4: 50% Yb 3+ / 12% Tb 3+ (a) Quantum-cut nanocrystals; (b) NaYF4 after surface oleic acid removal: 50% Yb 3+ / 12% Tb 3+ Quantum-cut nanocrystals. (From...) Figure 4 It can be seen that the obtained NaYF4: 50% Yb 3+ / 12% Tb 3+ The nanocrystals have a uniform morphology. After removing the surface oleic acid with hydrochloric acid, the particle size of the nanocrystals decreased, indicating that the surface structure of the nanocrystals was exposed after the oleic acid was removed by hydrochloric acid.

[0081] Figure 5 This embodiment compares the UV absorption intensities of the triplet ligands TMA, PMA, and DPA in DMF solution. PMA exhibits the highest absorption in the UV region, followed by DPA, and then TMA.

[0082] Figure 6 The ligand-free and triplet ligand-modified NaYF4: 50% Yb prepared as described in this embodiment 3+ / 12% Tb 3+ Comparison of Fourier transform infrared spectra of nanoparticles. Figure 6 The characteristic peak shifts of the ligand-sensitized nanoparticle samples confirmed that the carboxylic acid groups on the surface of the triplet molecules participated in the coordination with the surface lanthanide ions. Among them, the characteristic peak shifts of the DPA-modified nanoparticles were the most obvious, followed by those of the PMA-modified nanoparticles.

[0083] Figure 7 The ligand-free and triplet ligand-modified NaYF4: 50% Yb prepared for this embodiment 3+ / 12% Tb 3+ Comparison of UV absorption intensity of nanoparticles in DMF solution. Quantum-tailored nanocrystals, after coupling with triplet ligands, exhibit a significant increase in UV absorption, indicating that the triplet ligands are well anchored on the surface of the quantum-tailored nanocrystals and effectively enhance their energy utilization in the UV region.

[0084] Figure 8 The ligand-free and triplet ligand-modified NaYF4: 50% Yb prepared for this embodiment 3+ / 12% Tb 3+ Comparison of near-infrared luminescence intensity of nanoparticles in DMF solution. Quantum-tailored nanocrystals, after coupling with triplet ligands, exhibit a significant increase in near-infrared luminescence intensity, indicating that the triplet ligands effectively utilize energy in the ultraviolet region. The triplet state transfers energy to the nanocrystals, enabling efficient quantum tailoring and thus significantly enhancing the near-infrared luminescence intensity. Specifically, the near-infrared luminescence intensity of DPA-sensitized nanoparticles is 1084 times higher than that of unliganded nanoparticles.

[0085] Example 2

[0086] Triplet-state ligand-sensitized quantum cutting is a technique that utilizes organic ligands to efficiently absorb ultraviolet-visible light and achieves quantum cutting luminescence within rare-earth or doped ions via energy transfer. The triplet state of the ligand transfers energy to the nanocrystals for quantum cutting, thereby significantly enhancing the luminescence intensity in the near-infrared region. The mechanism lies in the fact that after the ligand coordinates with rare-earth ions, the heavy atom effect significantly accelerates the intersystem crossing process, drastically shortening the triplet state lifetime and achieving ultrafast energy transfer efficiency. Simultaneously, the effective passivation of the nanocrystal surface by the ligand limits the formation of defect states, significantly enhancing the luminescence stability of the material under thermal fields, suppressing non-radiative energy dissipation, and endowing it with excellent photostability, maintaining extremely high luminescence intensity even under continuous ultraviolet irradiation. This embodiment utilizes DPA and DPA-modified NaYF4:12% Tb, which exhibit the best near-infrared luminescence enhancement effect. 3+ 50% Yb 3+ Taking nanoparticles as an example, we will perform characterization.

[0087] Figure 9 The DPA and DPA-modified NaYF4:12% Tb prepared in DMF solution according to Example 1 of this invention 3+ 50% Yb 3+ Nanosecond transient absorption spectra of nanoparticles. Figure 9 (a) and (b) are the nanosecond transient absorption spectra of the DPA. Figure 9 (c) and (d) are DPA-modified NaYF4:12% Tb 3+ 50% Yb 3+ The nanosecond transient absorption spectrum of the nanoparticles shows that the spectral lifetime of the DPA-modified nanoparticles is significantly reduced.

[0088] Figure 10 The DPA and DPA-modified NaYF4:12% Tb prepared in DMF solution according to Example 1 of this invention 3+ 50% Yb3+ The triplet decay kinetics obtained from nanosecond transient absorption spectroscopy of nanoparticles shows that the triplet decay time for the obtained single ligand is 6.9 μs, while the decay time for the lanthanide ion coordinated with the ligand is 943 ns. This is because the introduction of rare earth heavy atoms enhances the utilization of triplet excitons and accelerates the S1-T1 gap crossing, indicating effective ligand-ion triplet energy transfer. The formula for triplet energy transfer efficiency is:

[0089] ;

[0090] in, For energy transfer efficiency. The decay rate of lanthanide ions coordinated with ligands. The decay rate of the ligand. The lifetime of lanthanide ions coordinated with ligands, Let be the lifetime of the ligand. Substituting the lifetimes of both into the formula, the calculated energy transfer efficiency of the DPA ligand to the nanoparticle is close to 100%.

[0091] Figure 11 The ligand-free and DPA-modified NaYF4: 50% Yb prepared in Example 1 of this invention 3+ / 12% Tb 3+ The thermal stability of the nanoparticle powder in visible light emission after complete dehydration in dry argon gas indicates that, under the same conditions, the visible light emission of DPA-modified particles exhibits significantly enhanced heat resistance to temperature changes compared to ligand-free nanoparticles. This is attributed to the fact that DPA coordinates and restricts the formation of defects in the surface layer, thereby effectively suppressing the nonradiative dissipation of excitation energy under thermal field.

[0092] Figure 12 The preparation of DPA-modified NaYF4: 50% Yb in Example 1 of this invention 3+ / 12% Tb 3+ The curve showing the change in near-infrared luminescence intensity of nanoparticles under continuous irradiation with a 270 nm laser (100 mW / cm²) in DMF solution indicates that the luminescence intensity of the material can still be maintained above 85% after 2 h of ultraviolet light irradiation. This shows that DPA-modified quantum-cut nanocrystals have good photostability and can greatly expand their practical potential in advanced photonics applications.

[0093] The above results demonstrate that the introduction of triplet ligands effectively enhances the utilization of ultraviolet energy by quantum-tailored nanocrystals, and the triplet state of the ligands transfers energy to the nanocrystals for quantum tailoring, thereby significantly improving their near-infrared luminescence intensity. Meanwhile, the excellent thermal and photostability indicate that the preparation method is stable and reliable, providing strong support for the material's application in improving solar cell efficiency, near-infrared II bioimaging, photocatalysis, and light-emitting devices.

[0094] The specific embodiments of this application have been described above, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A quantum tailoring material based on triplet ligand-sensitized nanocrystals, characterized in that, It includes a nanocrystalline core and a surface ligand layer, wherein the nanocrystalline core is NaYF4 or NaGdF4 and is doped with Yb. 3+ and Tb 3+ The surface ligand layer includes a triplet-sensitized ligand capable of generating triplet excitons through an anti-system crossing process; the triplet-sensitized ligand is pyridine-2,6-dicarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, or 1,3,5-benzenetricarboxylic acid, and interacts with the Yb on the surface of the nanocrystal core through the carboxylic acid group at its molecular end. 3+ and the Tb 3+ Forming coordinate bonds; the Yb 3+ and the Tb 3+ It constitutes the center of quantum cutting.

2. The quantum tailoring material according to claim 1, characterized in that, The triplet-state sensitized ligand absorbs the excitation light and then transfers the energy of the generated triplet-state exciton to the quantum trimming center.

3. A method for preparing a quantum tailoring material as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Rare earth acetate, oleic acid and 1-octadecene are mixed and heated to form a rare earth oleate complex. After cooling, a solution containing a sodium source and a fluorine source is added to obtain a mixed solution. The solvent in the solution is methanol or ethanol. S2. The mixture is heated under vacuum to remove the methanol or ethanol, and then heated under inert gas protection. After cooling, it is centrifuged and washed, and dispersed in cyclohexane to obtain oleic acid-encapsulated nanocrystals. S3. The oleic acid-coated nanocrystal nuclei are mixed with hydrochloric acid and ultrasonically treated to remove the oleic acid on the surface. After centrifugation and washing, they are dispersed in anhydrous ethanol to obtain ligand-free nanocrystal nuclei. S4. Dissolve the triplet-state sensitized ligand in a solvent and mix it with the ligand-free nanocrystal nucleus for an ultrasonic reaction. The triplet-state sensitized ligand forms a coordination bond with the surface of the nanocrystal nucleus to obtain the quantum tailoring material.

4. The method for preparing the quantum tailoring material according to claim 3, characterized in that, In step S1, the rare earth acetate includes yttrium acetate or gadolinium acetate, as well as ytterbium acetate and terbium acetate. The amount of yttrium acetate or gadolinium acetate is 0.076~0.152 mmol, the amount of ytterbium acetate is 0.1~0.2 mmol, and the amount of terbium acetate is 0.024~0.048 mmol. The amount of oleic acid is 3~7 mL, and the amount of 1-octadecene is 7~14 mL.

5. The method for preparing the quantum tailoring material according to claim 3, characterized in that, In step S1, the sodium source is sodium hydroxide, the fluorine source is ammonium fluoride, the heating temperature is 110–170°C, and the heating time is 0.5–1.5 h.

6. The method for preparing the quantum tailoring material according to claim 3, characterized in that, In step S2, the heating temperature is 100~130℃ and the time is 20~40 min; the temperature rise is 250~320℃ and the time is 1.5~3 h.

7. The method for preparing the quantum tailoring material according to claim 3, characterized in that, In step S3, the concentration of hydrochloric acid is 1 M, and the ultrasonic treatment time is 30~120 s.

8. The method for preparing the quantum tailoring material according to claim 3, characterized in that, In step S4, the ultrasonic reaction time is 30~90 min.

9. A photovoltaic panel, characterized in that, Includes quantum-cut materials as described in any one of claims 1-2.

10. The application of a quantum-cutting material as described in any one of claims 1-2 in the fabrication of photovoltaic devices, bioimaging reagents, or light-emitting devices.

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