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CN-121991691-A - Method for enhancing rare earth up-conversion nanocrystalline ultraviolet fluorescence through local structure regulation and control and local structure measurement method

CN121991691ACN 121991691 ACN121991691 ACN 121991691ACN-121991691-A

Abstract

The invention discloses a method for enhancing rare earth up-conversion nanocrystalline ultraviolet fluorescence through local structure regulation and control and a local structure measurement method, and belongs to the field of rare earth luminescent nanomaterials. According to the method, in the process of synthesizing LiREF 4 :@LiREF 4 core-shell structures, the stoichiometric ratio of LiOH and NH 4 F in a core layer and/or the dosage of lithium trifluoroacetate in a shell layer are precisely regulated, and the selective regulation and control of a luminous transition path of the lithium trifluoroacetate are realized by changing the local crystal field environment around activated ions, so that the emission intensity of multi-photon ultraviolet up-conversion luminescence is improved. The method can obviously enhance the high-order multiphoton up-conversion process of rare earth ions, inhibit low-order emission, improve the luminescence selectivity of the up-conversion nano material, enable the same matrix material to synthesize the emitted light with corresponding wavelength according to the needs of synthesizers, be applicable to various rare earth activated ions and matrix materials, and have application potential in the fields of nano photonics and biomedicine.

Inventors

  • LIU SONGBIN
  • PENG YUSHUANG
  • YE XINYU
  • QIU YUXUAN
  • WANG JUNJIE
  • Fei Hongyuan
  • YU YUTIAN
  • YANG FENGLI
  • PENG JIAQING

Assignees

  • 国瑞科创稀土功能材料(赣州)有限公司
  • 江西理工大学

Dates

Publication Date
20260508
Application Date
20260202

Claims (9)

  1. 1. The method for enhancing the ultraviolet fluorescence of the rare earth up-conversion nanocrystalline by local structure regulation and control is characterized in that the local structure microenvironment of activated ions is changed by regulating and controlling the stoichiometric ratio of precursors in the synthesis process, and at least one of the following modes is adopted for regulation and control: (a) In the synthesis of the nuclear layer, the molar ratio RE of rare earth ions RE 3+ to LiOH is regulated to be 1:1.25-1:3.75; (b) In the nuclear layer synthesis, the molar ratio of RE 3+ to NH 4 F is regulated to be RE, NH 4 F is 1:3-1:5; (c) In the shell synthesis, the molar ratio CF 3 COORE：CF 3 COOLi of the rare earth trifluoroacetate to the lithium trifluoroacetate is regulated to be 1:0.5-1:2.5.
  2. 2. The method for enhancing rare earth up-conversion nanocrystalline ultraviolet fluorescence by local structure regulation according to claim 1, wherein the regulation modes (a), (b) and (c) can be used singly or in any combination.
  3. 3. The method for enhancing rare earth up-conversion nanocrystalline ultraviolet fluorescence according to claim 1, wherein RE in the core layer matrix is selected from one or more of Y, gd, lu, yb and doped with rare earth activating ions and sensitizing ions.
  4. 4. A method of enhancing rare earth upconversion nanocrystalline uv fluorescence according to claim 3, wherein said rare earth activating ion is selected from at least one of Tm 3+ 、Er 3+ 、Ho 3+ 、Eu 3+ 、Tb 3+ .
  5. 5. A method of enhancing rare earth upconversion nanocrystalline uv fluorescence according to claim 3, wherein the sensitizing ion is selected from at least one of Yb 3+ 、Nd 3+ .
  6. 6. The method for enhancing rare earth up-conversion nanocrystalline ultraviolet fluorescence according to claim 1, wherein in the LiREF 4 @LiREF 4 core-shell structure, RE in the shell matrix is one or more selected from Y, gd and Lu.
  7. 7. A method for measuring the local structure of the rare earth up-conversion nanocrystalline prepared by the method according to any one of claims 1 to 6, wherein the local structure is measured by measuring the local crystal field environment around rare earth ions and obtaining the lattice parameter by combining with XRD structural refinement or X-ray absorption fine structure spectrum.
  8. 8. A method for measuring the local structure of the rare earth up-conversion nanocrystalline prepared by the method according to any one of claims 1-6 is characterized in that a series of LiYF 4 ：Eu@LiYF 4 is synthesized by using the same stoichiometric ratio regulation means, and then the sensitivity characteristic of red orange ratio of an optical probe Eu 3+ to local symmetry is utilized to measure the local symmetry of a local lattice around rare earth ions, so that the local structure measurement is realized, and the method can be used for revealing photoluminescence behavior relatively sensitive to the local symmetry.
  9. 9. A method for measuring the local structure of the rare earth up-conversion nanocrystalline prepared by the method according to any one of claims 1 to 6, which is characterized in that a series of LiYF 4 ：Ce@LiYF 4 is synthesized by using the same stoichiometric ratio regulation means, and then the sensitive characteristic of 4 f-5 d transition of an optical probe Ce 3+ to local symmetry is utilized, so that the local symmetry of the local lattice around rare earth ions is measured, the local structure measurement is realized, and the method can also be used for revealing photoluminescence behavior relatively sensitive to the local symmetry.

Description

Method for enhancing rare earth up-conversion nanocrystalline ultraviolet fluorescence through local structure regulation and control and local structure measurement method Technical Field The invention belongs to the field of rare earth luminescent nano materials, and particularly relates to a method for enhancing multi-photon up-conversion luminescence of a rare earth core-shell structure nanocrystalline. Background Rare earth element doped up-conversion nano particles (UCNPs) are functional materials capable of converting low-energy near infrared light into high-energy visible light or ultraviolet light through a multiphoton absorption process, and have wide application prospects in the front-edge fields of biological imaging, drug release, photodynamic therapy, three-dimensional display, micro-nano lasers and the like. The multi-photon ultraviolet up-conversion luminescence has unique advantages in the aspects of photoetching, spectrum analysis, photocatalysis and the like due to the short emission wavelength and high photon energy. However, ultraviolet up-conversion typically involves a higher order multiphoton process (n≥4), which has large energy loss and extremely low luminous efficiency compared to the usual lower order visible up-conversion (n≥3). In addition, rare earth ions have rich electron energy level structures, so that a phenomenon that a plurality of emission peaks coexist in the up-conversion luminescence process is caused, the emission intensity of target wavelength is reduced, and the application of the material in a selective luminescent device requiring single color or multiple colors is limited. Therefore, how to effectively regulate the selectivity of up-conversion luminescence, especially to enhance the luminescence intensity of ultraviolet band, becomes the research difficulty in the field at present. At present, common strategies for enhancing up-conversion luminescence mainly comprise matrix material optimization, core-shell structure construction, doping ion species and concentration regulation and the like. In the selection of matrix materials, the NaREF 4 (re=y, lu, gd, etc.) series is recognized as the preferred matrix for up-conversion luminescence due to low phonon energy characteristics, with NaYF 4 becoming the most widely studied classical system by virtue of excellent photon conduction efficiency and structural stability. A number of studies have shown that increasing the relative content of Na + ions (i.e., na-rich + design deviating from the ideal stoichiometric ratio) in NaYF 4 matrix is a key means to enhance the upconversion luminous efficiency, e.g., by Xiao et al, the red-green visible upconversion luminous intensity of Er 3+ ions is increased by 2.5 and 3.2 times, respectively, by controlling the Na +/rare earth ion (Yb 3+) feed ratio to 2.0:1 (higher than the ideal stoichiometric ratio 1:1), with the core mechanism that excess Na + relieves lattice strain, and, The NaYF 4 core-shell structure designed by rich Na + can reduce cation mixing at the core-shell interface, promote energy transfer between Yb 3+ sensitized ions and Tm 3+ activated ions, improve the five-photon ultraviolet up-conversion luminous intensity at 345nm by 210 times, and directly support the traditional cognition that the higher the Na + content is in a NaYF 4 system, the better the high-order multiphoton luminous performance is. In addition, by adopting methods such as surface quenching effect inhibition through core-shell structure design, the whole luminous intensity of the material can be mostly only improved, the selective enhancement of specific wavelength (especially ultraviolet band) is difficult to realize, the synthesis process is complex, the regulation and control means are limited, and particularly, the precise control of the activated ion local structure is realized through simple chemical synthesis parameter regulation and control, so that the selective enhancement of high-order multiphoton ultraviolet up-conversion luminescence is still a great challenge. In recent years, li-based substrates (e.g., liREF 4 (re=y, gd, lu, yb, etc.), abbreviated as Li-based substrates), have become new research systems for up-conversion materials, which exhibit potential advantages in terms of ultraviolet band luminescence modulation, due to unique crystal structures and low phonon energy characteristics. However, the existing researches directly follow the traditional design logic of the NaYF 4 system, and defaults to 'improving the content of alkali metal ions (Li +) can optimize the luminous performance', but no ideal effect is obtained in the related attempts, and even the luminous efficiency is reduced. Therefore, the Li-based UCNPs local structure regulation method which is simple and convenient to operate, obvious in effect and universal is developed, the traditional limitation of a NaYF 4 system is broken, the high-efficiency regulation and control on the ultraviolet multiphoton