CN115386361B - A method for realizing multi-ion nanophoton avalanche luminescence using interface energy transfer - Google Patents

Abstract

The invention discloses a method for realizing multi-ion nano photon avalanche luminescence by utilizing interface energy transfer, wherein the multi-ion nano photon avalanche based on the interface energy transfer is realized by constructing a multi-layer core-shell nano structure, isolating a photon avalanche engine and receptor ions from each other and completing energy transfer at a core-shell interface. The energy level transition of the donor ion is carried out under the irradiation of laser with specific wavelength, and the photon avalanche fluorescence with high efficiency and stability is radiated. Compared to the case of co-doping of both ions, excessive interactions between donor and acceptor ions are avoided. Meanwhile, the invention also enables more rare earth ions which can not generate photon avalanche effect to realize high-order nonlinear photon avalanche fluorescent radiation.

Description

A method for realizing multi-ion nanophoton avalanche luminescence using interface energy transfer

Technical Field

The invention relates to the technical field of nonlinear optics and nanophotonics, and in particular to a method of multi-ion nanophoton avalanche luminescence based on interface energy transfer.

Background technique

Rare earth doped upconversion nanoparticles are an emerging nonlinear fluorescent medium. Compared with traditional luminescent materials, rare earth doped upconversion nanoparticles have the advantages of extremely high photostability, long intermediate excited state lifetime, large anti-Stokes shift, narrow emission band and low photochemical toxicity, and have broad application prospects in super-resolution imaging, biomedicine, single particle tracking, sensing and detection, anti-counterfeiting printing, etc. Due to the unique 4f electronic configuration, lanthanide ions have rich energy levels, so the spectral range of their upconversion emission band can cover from near-infrared light to ultraviolet light.

Photon avalanche is an important mechanism of upconversion luminescence and was first discovered in 1979. As a special positive feedback upconversion mechanism, photon avalanche can provide efficient upconversion luminescence. However, at present, it is very difficult to realize the photon avalanche phenomenon at the nanoscale due to the decrease of the absorption and emission interface of nanoparticles with increasing temperature, as well as its obvious surface quenching effect. The research on photon avalanche is mainly concentrated in bulk solid materials and polymers, and most of the research is carried out in low temperature environments. More importantly, the photon avalanche effect can only be realized in single rare earth ions such as Tm ³⁺ and Er ³⁺ . If it is necessary to realize the photon avalanche fluorescence of different ions, multiple complex excitation mechanisms are required, which hinders the popularization and application of the photon avalanche effect in the field of nonlinear optics.

In order to make the photon avalanche mechanism more universal, in addition to the avalanche of a single nanoparticle, it is also necessary to realize the avalanche mechanism of a multi-nanoparticle system in more particle systems. However, in the traditional photon avalanche system, the donor ion (A ³⁺ ) and the acceptor ion (X ³⁺ ) are co-doped in the same area. Due to the close distance between the two, more cross-relaxation and energy reflux processes occur between the donor ion and the acceptor ion, which hinders the photon avalanche process of A ³⁺ .

In order to solve the above problems, a strategy to effectively control ion interactions, interfacial energy transfer (IET), has been proposed. IET usually occurs in a series of lanthanide nanoparticles with a short spatial distance, and each lanthanide particle needs to be separated to a different spatial position. Therefore, it often occurs in nanoparticles with a multilayer core-shell structure. By taking advantage of the combination of the IET principle and nanostructure design, the interactions between various lanthanide ions can be studied in depth, and the upconversion luminescence in different bands can be regulated. However, there is no research showing that the IET mechanism can be used to separate two different ions into different regions of the same nanoparticle, so that the nanoparticle that has already avalanched can transfer energy to other nanoparticles that have not avalanched, thereby causing the nanoparticle to avalanche cascade nanoparticles.

Summary of the invention

In view of the deficiencies of the prior art, the present invention aims to provide a method and detection device for realizing multi-ion nanophoton avalanche based on interface energy transfer, breaking the principle limitation that photon avalanche is only for a single type of ion in traditional research, so that more rare earth ions that cannot produce photon avalanche effect by themselves can achieve high-order nonlinear photon avalanche fluorescence radiation. The inventor establishes a cascade photon avalanche network, distributes cascade ions of different concentrations in the isolated space of nanoparticles with core-shell structure, uses a single photon avalanche engine as the core, and drives other ions in the core-shell structure to produce photon avalanche fluorescence radiation under the drive of the engine, thus realizing cascade avalanche of multiple different ions under the condition of single wavelength excitation light.

In order to achieve the above object, the technical solution adopted by the present invention is as follows:

A method for realizing multi-ion nanophoton avalanche based on interface energy transfer, the method comprising the following steps:

S1 separates the photon avalanche donor ions and acceptor ions in different structural layers by constructing a multilayer core-shell nanostructure, where the donor ions are in the core layer and the acceptor ions are in the shell layer;

S2 constructs a nanostructure core layer, selects Tm ³⁺ ions that can produce photon avalanche effect as photon avalanche engine ions in the core-shell structure system, namely donor ions, and dopes them into nanocrystals; donor ions undergo energy level transitions under the irradiation of lasers with a wavelength of 1064nm or 1470nm, and after a certain amount of energy cycle conduction, the number of particles in the excited state energy level of the avalanche ions shows an avalanche growth, radiating highly efficient and stable photon avalanche fluorescence with a high-order nonlinear dependence on the intensity of the excitation light;

S3 constructs the nanoparticle intermediate shell, which is composed of acceptor ions X ³⁺ doped in the nanocrystal, and the acceptor ions include but are not limited to Er ³⁺ and Ho ³⁺ ions; when the near-infrared light beam excites the donor ions to produce photon avalanche fluorescence, the energy is transferred from the donor avalanche engine body ions to the acceptor ions X ³⁺ located in the shell through the interface energy transfer, and the acceptor ions Er ³⁺ , Ho ³⁺ and other ions receive the avalanche energy and then undergo step-by-step up-conversion to a high energy level, and then radiate photon avalanche fluorescence;

After achieving the avalanche of the middle shell nano ions, S4 constructs more shells and transfers the avalanche energy of the middle shell nano ions to the third cascade ions other than the avalanche engine and the middle layer ions in the form of interface energy transfer. The cascade ions include but are not limited to Ce ³⁺ and Yb ³⁺ ions. After receiving the avalanche energy, the cascade ions undergo step-by-step up-conversion transitions to high energy levels and radiate up-conversion photon avalanche fluorescence, thus realizing the multi-ion cascade photon avalanche effect under a single excitation wavelength condition.

It should be noted that the near-infrared laser is a continuous near-infrared steady-state laser beam with a wavelength of 1064nm or 1470nm.

It should be noted that Tm ³⁺ is selected as the photon avalanche engine, that is, as the donor ion A ³⁺ , and is excited by a beam of near-infrared laser. The photon energy of the laser does not completely match the ground state absorption of Tm ³⁺ from ³ H ₆ to ³ H ₅ , but can match the excited state absorption of Tm ³⁺ from ³ F ₄ to ³ F ₂ ; at the same time, cross relaxation occurs between two adjacent Tm ³⁺ ions, and the generated photon avalanche fluorescence radiation; when the near-infrared light beam excites the donor ion to produce photon avalanche fluorescence, part of the energy is transferred from Tm ³⁺ to the acceptor ion X ³⁺ located in the shell. After receiving the avalanche energy, the acceptor ion undergoes step-by-step up-conversion transition to a high energy level and radiates up-conversion photon avalanche fluorescence.

It should be noted that the photon avalanche engine is composed of avalanche ions Tm ³⁺ doped in fluoride nanocrystals, the intermediate shell structure where the acceptor ions are located is composed of acceptor ions X ³⁺ doped in fluoride nanocrystals, and the outer shell structure can be composed of inert fluoride nanocrystals or other cascade ions except avalanche engine ions and acceptor ions.

It should be noted that the acceptor ions include but are not limited to Er ³⁺ and Ho ³⁺ ions, and the cascade ions include but are not limited to Ce ³⁺ and Yb ³⁺ ions.

It should be noted that the nanoparticles with multilayer core-shell nanostructures spatially separate donor ions and acceptor ions; dope the core region with donor ions A ³⁺ , and dope the shell region with acceptor ions X ³⁺ ; so that the energy transfer process mainly occurs at the interface region of adjacent core-shell structures.

The present invention also provides a device for detecting nanophoton avalanche of multi-ions based on interface energy transfer, the device comprising an excitation light generation module, a multiphoton microscopy module, a photoelectric detection module and photon avalanche nanoparticles; wherein the near-infrared continuous light laser beam generated by the excitation light generation module is reflected by a vertical reflector into the multiphoton microscopy module. The near-infrared continuous light laser beam entering the multiphoton microscopy module is reflected by a high-reflection and low-transmittance dichroic mirror and irradiated onto the photon avalanche fluorescent nanoparticles located on the stage. The photoelectric detection module detects the photon avalanche fluorescent signal.

It should be noted that the excitation light generating module includes a single-mode semiconductor laser and a half-wave plate, a polarization beam splitter, a 980nm long-pass filter, and a neutral attenuation plate placed in sequence along the optical axis direction of the single-mode semiconductor laser; wherein the single-mode semiconductor laser emits a 1064nm near-infrared continuous steady-state laser beam, the power of which is adjusted by the half-wave plate, and then the 980nm component in the excitation light beam is removed by the polarization beam splitter and the 980nm long-pass filter to prevent each layer of ions from being directly excited by 980nm, and then the laser power is reduced by the neutral attenuation plate.

It should be noted that the multiphoton microscopy module includes a vertical reflector, a focusing lens, a high-reflection and low-transmittance dichroic mirror and an objective lens in sequence along the advancing direction of the near-infrared continuous steady-state laser beam; wherein the vertical reflector collimates the near-infrared continuous steady-state laser beam into the focusing lens, and after being focused by the focusing lens, it is reflected by the high-reflection and low-transmittance dichroic mirror into the objective lens and focused on the photon avalanche nanoparticles.

It should be noted that the photoelectric detection module includes a visible light detection module and a near-infrared light detection module; wherein the visible light detection module includes a short-pass filter, a vertical reflector, a focusing lens, and a visible light spectrometer; when the objective lens receives the visible photon avalanche fluorescence emitted by the nanoparticles, it is filtered by the short-pass filter, then passes through the vertical reflector, is focused by the focusing lens, and then is detected by the visible light spectrometer to obtain a photon avalanche fluorescence signal.

It should be noted that the near-infrared light detection module includes a long-pass filter, a focusing lens, and a near-infrared spectrometer; the continuous near-infrared steady-state laser beam is received by the objective lens, filtered by the long-pass filter, and then focused by the focusing lens and received by the near-infrared spectrometer.

The beneficial effects of the present invention are:

1. By constructing upconversion nanoparticles with a core-shell structure, the core layer is doped with donor ions (A ³⁺ ) and the intermediate shell layer is doped with acceptor ions (X ³⁺ ). The energy transfer between the donor and acceptor ions only occurs in the interface region, thereby preventing the photon avalanche process in A ³⁺ from being interrupted by the cross relaxation and energy reflux process between A ³⁺ and X ³⁺ , and also promoting the photon avalanche of X ³⁺ .

2. Compared with traditional photon avalanche fluorescence, the present invention only requires a single beam of 1064nm or 1470nm continuous near-infrared laser and a single photon avalanche engine ion to stimulate multiple ions such as Er ³⁺ , Ho ³⁺ , Yb ³⁺ , Ce ³⁺ to simultaneously produce photon avalanche fluorescence emission, allowing more rare earth ions that cannot produce photon avalanche effect by themselves to achieve high-order nonlinear photon avalanche fluorescence radiation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram showing a method for realizing multi-ion nanophoton avalanche based on interface energy transfer.

FIG. 2 is a schematic diagram of a multi-ion nanophoton avalanche fluorescence detection device based on interface energy transfer.

FIG3 is a schematic diagram of the principle of a multi-ion nanophoton avalanche system based on interface energy transfer in Example 1, with Tm ³⁺ as the donor ion and Er ³⁺ as the acceptor ion.

FIG. 4 is a graph showing the logarithmic relationship between the excitation power and the emission intensity of the avalanche process of NaYF ₄ :Tm(8%)@NaYF ₄ :Er(1%)@NaYF ₄ in Example 1. FIG.

5 is a schematic diagram of the principle of a multi-ion nanophoton avalanche system based on interface energy transfer in Example 2, with Tm ³⁺ as the donor ion and Er ³⁺ and Yb ³⁺ as the acceptor ions.

6 is a graph showing the logarithmic relationship between the excitation power and the emission intensity of the avalanche process of NaYF ₄ :Tm(8%)@NaYF ₄ :Er(1%)@NaYF ₄ :Yb(10%) in Example 2. FIG.

7 is a schematic diagram of the principle of a multi-ion nanophoton avalanche system based on interface energy transfer in Example 3, with Tm ³⁺ as donor ions and Er ³⁺ and Ce ³⁺ as acceptor ions.

8 is a graph showing the logarithmic relationship between the excitation power and the emission intensity of the avalanche process of NaYF ₄ :Tm(8%)@NaYF ₄ :Er(1%)@NaYF ₄ :Er/Ce(5%/5%) in Example 3. FIG.

9 is a transmission electron micrograph of the multi-layer core-shell structured multi-ion photon avalanche nanoparticles NaYF ₄ :Tm(8%)@NaYF ₄ :Er(1%)@NaYF ₄ :Er/Ce(5%/5%) synthesized in Example 4. FIG.

The reference numerals in FIG2 are as follows: 1, single-mode semiconductor laser; 2, half-wave plate; 3, polarization beam splitter; 4, 980nm long-pass filter; 5, neutral attenuation plate; 6, vertical reflector; 7, vertical reflector; 8, focusing lens; 9, focusing lens; 10, visible light spectrometer; 11, focusing lens; 12, vertical reflector; 13, 842nm short-pass filter; 14, 950nm high-reflection and low-transmittance dichroic mirror; 15, objective lens; 16, photon avalanche nanoparticles; 17, objective lens; 18, 937nm short-pass filter; 19, focusing lens; 20, near-infrared spectrometer

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to this embodiment.

The present invention is a method for realizing multi-ion nanophoton avalanche based on interface energy transfer. The basic principle of the method is shown in FIG1 , and comprises the following steps:

S1 separates the photon avalanche donor ions and acceptor ions in different structural layers by constructing a multilayer core-shell nanostructure, where the donor ions are in the core layer and the acceptor ions are in the shell layer;

S2 constructs a nanostructure core layer, selects Tm ³⁺ ions that can produce photon avalanche effect as photon avalanche engine ions in the core-shell structure system, namely donor ions, and dopes them into nanocrystals; donor ions undergo energy level transitions under the irradiation of lasers with a wavelength of 1064nm or 1470nm, and after a certain amount of energy cycle conduction, the number of particles in the excited state energy level of the avalanche ions shows an avalanche growth, radiating highly efficient and stable photon avalanche fluorescence with a high-order nonlinear dependence on the intensity of the excitation light;

S3 constructs the nanoparticle intermediate shell, which is composed of acceptor ions X ³⁺ doped in the nanocrystal, and the acceptor ions include but are not limited to Er ³⁺ and Ho ³⁺ ions; when the near-infrared light beam excites the donor ions to produce photon avalanche fluorescence, the energy is transferred from the donor avalanche engine body ions to the acceptor ions X ³⁺ located in the shell through the interface energy transfer, and the acceptor ions Er ³⁺ , Ho ³⁺ and other ions receive the avalanche energy and then undergo step-by-step up-conversion to a high energy level, and then radiate photon avalanche fluorescence;

After achieving the avalanche of the middle shell nano ions, S4 constructs more shells and transfers the avalanche energy of the middle shell nano ions to the third cascade ions other than the avalanche engine and the middle layer ions in the form of interface energy transfer. The cascade ions include but are not limited to Ce ³⁺ and Yb ³⁺ ions. After receiving the avalanche energy, the cascade ions undergo step-by-step up-conversion transitions to high energy levels and radiate up-conversion photon avalanche fluorescence, thus realizing the multi-ion cascade photon avalanche effect under a single excitation wavelength condition.

Furthermore, the present invention selects Tm ³⁺ as a photon avalanche engine, that is, as a donor ion A ³⁺ , and uses a beam of 1064nm single-wavelength near-infrared laser for excitation. The photon energy of the laser does not completely match the ground state absorption of Tm ³⁺ from ³ H ₆ to ³ H ₅ , but can match the excited state absorption of Tm ³⁺ from ³ F ₄ to ³ F ₂ ; at the same time, cross relaxation occurs between two adjacent Tm ³⁺ ions, generating photon avalanche fluorescence radiation; when the near-infrared light beam excites the donor ion to generate photon avalanche fluorescence, part of the energy is transferred from Tm ³⁺ to the acceptor ion X ³⁺ located in the shell layer. After receiving the avalanche energy, the acceptor ion undergoes step-by-step up-conversion transition to a high energy level and radiates up-conversion photon avalanche fluorescence.

Furthermore, the photon avalanche engine of the present invention is composed of avalanche ions Tm ³⁺ doped in fluoride nanocrystals, the intermediate shell structure where the acceptor ions are located is composed of acceptor ions X ³⁺ doped in fluoride nanocrystals, and the outer shell structure can be composed of inert fluoride nanocrystals or other cascade ions except avalanche engine ions and acceptor ions.

Furthermore, the acceptor ions of the present invention include but are not limited to Er ³⁺ and Ho ³⁺ ions, and the cascade ions include but are not limited to Ce ³⁺ and Yb ³⁺ ions.

Furthermore, the nanoparticles with multilayer core-shell nanostructures of the present invention spatially separate donor ions and acceptor ions; dope the core region with donor ions A ³⁺ , and dope the shell region with acceptor ions X ³⁺ ; so that the energy transfer process mainly occurs at the interface region of adjacent core-shell structures.

The present invention also provides a device for detecting nanophoton avalanches of multi-ions based on interface energy transfer. The specific device is shown in FIG2 and includes an excitation light generation module, a multiphoton microscopy module, a photoelectric detection module, and photon avalanche nanoparticles; wherein the near-infrared continuous light laser beam generated by the excitation light generation module is reflected by a vertical reflector into the multiphoton microscopy module. The near-infrared continuous light laser beam entering the multiphoton microscopy module is reflected by a high-reflection and low-transmittance dichroic mirror and irradiated onto the photon avalanche fluorescent nanoparticles located on the stage. The photoelectric detection module detects the photon avalanche fluorescent signal.

Furthermore, the excitation light generating module of the present invention comprises a single-mode semiconductor laser and a half-wave plate, a polarization beam splitter, a 980nm long-pass filter, and a neutral attenuation plate which are sequentially placed along the optical axis direction of the single-mode semiconductor laser; wherein the single-mode semiconductor laser emits a 1064nm near-infrared continuous steady-state laser beam, the power of which is adjusted by the half-wave plate, and then the 980nm component in the excitation light beam is removed by the polarization beam splitter and the 980nm long-pass filter to prevent each layer of ions from being directly excited by 980nm, and then the laser power is reduced by the neutral attenuation plate.

Furthermore, the multiphoton microscopy module of the present invention comprises a vertical reflector, a focusing lens, a high-reflection and low-transmittance dichroic mirror and an objective lens in sequence along the advancing direction of the near-infrared continuous steady-state laser beam; wherein the vertical reflector collimates the near-infrared continuous steady-state laser beam into the focusing lens, and after being focused by the focusing lens, it is reflected by the high-reflection and low-transmittance dichroic mirror into the objective lens and focused on the photon avalanche nanoparticles.

Furthermore, the photoelectric detection module of the present invention includes a visible light detection module and a near-infrared light detection module; wherein, the visible light detection module includes a short-pass filter, a vertical reflector, a focusing lens, and a visible light spectrometer; when the objective lens receives the visible photon avalanche fluorescence emitted by the nanoparticles, it is filtered by the short-pass filter, then focused by the focusing lens, and detected by the visible light spectrometer to obtain a photon avalanche fluorescence signal.

Furthermore, the near-infrared light detection module of the present invention includes a long-pass filter, a focusing lens, and a near-infrared spectrometer; the continuous near-infrared steady-state laser beam is received by the objective lens and then filtered by the long-pass filter, and then passed through the vertical reflector and focused by the focusing lens before being received by the near-infrared spectrometer.

Example

Example 1

This embodiment provides a method for realizing multi-ion nanophoton avalanche based on interface energy transfer with Tm ³⁺ as donor ion and Er ³⁺ as acceptor ion. The multilayer core-shell structure upconversion nanoparticles constructed in this embodiment, the core of the nanoparticle is a photon avalanche engine, composed of Tm ³⁺ doped NaYF ₄ nanocrystals, Tm ³⁺ doping concentration is 8%; the middle shell layer is composed of acceptor ion Er ³⁺ doped in NaYF ₄ nanocrystals, Er ³⁺ doping concentration is 1%; the outer shell layer is inert NaYF ₄ nanocrystals, that is, NaYF ₄ :Tm(8%)@NaYF ₄ :Er(1%)@NaYF ₄ .

The avalanche process of Tm ³⁺ —Er ³⁺ system through interfacial energy transfer is shown in Figure 3. Under the excitation of a near-infrared steady-state laser beam, the photon energy of the laser does not completely match the ground state absorption of Tm ³⁺ from ³ H ₆ to ³ H ₅ , but can match the excited state absorption of Tm ³⁺ from ³ F ₄ to ³ F _2. At the same time, Tm ³⁺ itself produces cross relaxation ( ³ H ₄ + ³ H ₆ → ³ F ₄ + ³ F ₄ ), generating 800nm photon avalanche fluorescence radiation. Subsequently, part of the photon avalanche energy is transferred from the energy level ³ H ₄ of Tm ³⁺ to the ⁴ I _9/2 state of Er ³⁺ through interface energy transfer ( ³ H ₄ → ⁴ I _9/2 ), causing cross relaxation between Tm ³⁺ and Er ³⁺ ( ⁴ I _13/2 + ³ H ₆ → ³ F ₄ + ⁴ I _15/2 ). Then another cross relaxation between Tm ³⁺ and Er ³⁺ ( ⁴ I _15/2 + ³ H ₄ → ³ F ₄ + ⁴ I _13/2 ) brings all the energy back to the ³ F ₄ state of Tm ³⁺ and the ground state of Er ³⁺ . This promotes the self-cross relaxation and ground state absorption and excited state absorption of Er ³⁺ , thereby forming an energy cycle between Tm ³⁺ and Er ³⁺ and within Er ³⁺ , causing Er ³⁺ to produce 542nm and 656nm photon avalanche fluorescence, and it is a positive feedback process for the avalanche of Tm ³⁺ .

It should be noted that only Er ³⁺ ions located near Tm ³⁺ ions can be excited through this mechanism. Therefore, the continuation of the avalanche process of Tm ³⁺ can trigger the avalanche process of Er ³⁺ . The logarithmic relationship curve of the excitation power dependence of NaYF ₄ :Tm(8%)@NaYF ₄ :Er(1%)@NaYF ₄ on the emission intensity is shown in Figure 4. An obvious power threshold appears when the excitation power is around 5mw. When approaching the power threshold, the upconversion luminescence intensity of Tm/Er shows a nonlinear dependence on the excitation power, among which the 542nm and 656nm upconversion emission intensities of Er ³⁺ increase sharply after exceeding the power threshold, which proves that ^the Tm ³⁺ —Er ³⁺ system has undergone a photon avalanche process.

Example 2

This embodiment provides a method for realizing multi-ion nanophoton avalanche based on interface energy transfer, using Tm ³⁺ as donor ions, Er ³⁺ as acceptor ions, and Yb ³⁺ as cascade ions. The multilayer core-shell structure upconversion nanoparticles constructed in this embodiment, the core of the nanoparticle is a photon avalanche engine, composed of Tm ³⁺ doped NaYF ₄ nanocrystals, Tm ³⁺ doping concentration is 8%; the inner shell layer is composed of acceptor ions Er ³⁺ doped in NaYF ₄ nanocrystals, Er ³⁺ doping concentration is 5%; the outer shell layer is composed of cascade ions Yb ³⁺ doped in NaYF ₄ nanocrystals, and the doping concentration is 10%, that is, NaYF ₄ :Tm (8%) @NaYF ₄ :Er (1%) @NaYF ₄ :Yb (10%).

The avalanche process of Tm ³⁺ —Er ³⁺ —Yb ³⁺ system through interfacial energy transfer is shown in Figure 5. Under the excitation of a near-infrared steady-state laser beam, the photon energy of the laser does not completely match the ground state absorption of Tm ³⁺ from ³ H ₆ to ³ H ₅ , but can match the excited state absorption of Tm ³⁺ from ³ F ₄ to ³ F _2. At the same time, Tm ³⁺ itself produces cross relaxation ( ³ H ₄ + ³ H ₆ → ³ F ₄ + ³ F ₄ ), generating 800nm photon avalanche fluorescence radiation. Subsequently, part of the photon avalanche energy is transferred from the energy level ³ H ₄ of Tm ³⁺ to the ⁴ I _9/2 state of Er ³⁺ through interface energy transfer ( ³ H ₄ → ⁴ I _9/2 ), causing cross relaxation between Tm ³⁺ and Er ³⁺ ( ⁴ I _13/2 + ³ H ₆ → ³ F ₄ + ⁴ I _15/2 ). Then another cross relaxation between Tm ³⁺ and Er ³⁺ ( ⁴ I _15/2 + ³ H ₄ → ³ F ₄ + ⁴ I _13/2 ) brings all the energy back to the ³ F ₄ state of Tm ³⁺ and the ground state of Er ³⁺ . This promotes the self-cross relaxation and ground state absorption and excited state absorption of Er ³⁺ , thereby forming an energy cycle between Tm ³⁺ and Er ³⁺ and within Er ³⁺ , causing Er ³⁺ to produce 542nm and 656nm photon avalanche fluorescence, and it is a positive feedback process for the avalanche of Tm ³⁺ . At the same time, Er ³⁺ transfers part of its energy to the outer shell Yb ³⁺ through the direct energy transfer process ( ⁴ I _11/2 → ² F _5/2 ), causing Yb ³⁺ and Er ³⁺ to undergo a cross-relaxation process ( ⁴ I _11/2 + ² F _7/2 → ² F _5/2 + ⁴ I _15/2 ). One Er ³⁺ ion returns to the ground state, while one Yb ³⁺ ion is excited from the ground state to the excited state, thereby forming an energy cycle between Er ³⁺ and Yb ³⁺ , allowing the avalanche energy of Er ³⁺ to be transferred to Yb ³⁺ , generating 980nm photon avalanche fluorescence radiation.

The emission intensity curve of NaYF ₄ :Tm(8%)@NaYF ₄ :Er(1%)@NaYF ₄ :Yb(10%) excitation power dependence is shown in Figure 6. An obvious power threshold appears at an excitation power of about 5 mW. The upconversion emission intensity of Yb ³⁺ at 980 nm increases sharply after exceeding the power threshold, indicating that Yb ³⁺ can achieve a photon avalanche process through the sensitization of Er ³⁺ .

Example 3

This embodiment provides a method for realizing multi-ion nanophoton avalanche based on interface energy transfer, using Tm ³⁺ as donor ions, Er ³⁺ as acceptor ions, and Ce ³⁺ as cascade ions. In this embodiment, a multilayer core-shell structure upconversion nanoparticle is constructed, the core of which is a photon avalanche engine, composed of Tm ³⁺ doped NaYF ₄ nanocrystals, with a Tm ³⁺ doping concentration of 8%; the inner shell layer is composed of acceptor ions Er ³⁺ doped in NaYF ₄ nanocrystals, with an Er ³⁺ doping concentration of 5%; the outer shell layer is composed of cascade ions Er ³⁺ and cascade ions Ce ³⁺ doped in NaYF ₄ nanocrystals, with doping concentrations of 5% and 5%, respectively, that is, NaYF ₄ :Tm(8%)@NaYF ₄ :Er(1%)@NaYF ₄ :Er/Ce(5%/5%).

The avalanche process of the Tm ³⁺ —Er ³⁺ —Ce ³⁺ system through interfacial energy transfer is shown in Figure 7. Under the excitation of a near-infrared steady-state laser beam, the photon energy of the laser does not completely match the ground state absorption of Tm ³⁺ from ³ H ₆ to ³ H ₅ , but can match the excited state absorption of Tm ³⁺ from ³ F ₄ to ³ F _2. At the same time, Tm ³⁺ itself produces cross relaxation ( ³ H ₄ + ³ H ₆ → ³ F ₄ + ³ F ₄ ), generating 800nm photon avalanche fluorescence radiation. Subsequently, part of the photon avalanche energy is transferred from the energy level ³ H ₄ of Tm ³⁺ to the ⁴ I _9/2 state of Er ³⁺ through interface energy transfer ( ³ H ₄ → ⁴ I _9/2 ), causing cross relaxation between Tm ³⁺ and Er ³⁺ ( ⁴ I _13/2 + ³ H ₆ → ³ F ₄ + ⁴ I _15/2 ). Then another cross relaxation between Tm ³⁺ and Er ³⁺ ( ⁴ I _15/2 + ³ H ₄ → ³ F ₄ + ⁴ I _13/2 ) brings all the energy back to the ³ F ₄ state of Tm ³⁺ and the ground state of Er ³⁺ . This promotes the self-cross relaxation and ground state absorption and excited state absorption of Er ³⁺ , thereby forming an energy cycle between Tm ³⁺ and Er ³⁺ and within Er ³⁺ , causing Er ³⁺ to produce 542nm and 656nm photon avalanche fluorescence, and it is a positive feedback process for the avalanche of Tm ³⁺ . At the same time, by doping Er ³⁺ in both the middle shell and the outer shell, the avalanche energy of Er ³⁺ in the middle shell is transferred to Er ³⁺ in the outer shell. Er ³⁺ in the outer shell then transfers part of its energy to Ce ³⁺ in the outer shell through the cross-relaxation process with Ce ³⁺ . At the same time, the electrons in the higher excited state of Er ³⁺ are transferred to the lower ⁴ I _13/2 state through step-by-step energy level transition, which promotes the energy cycle inside Er ³⁺ . A Ce ³⁺ ion receives the energy of Er ³⁺ and is excited from the ground state to the excited state ( ² F _5/2 → ² F _7/2 ), thereby forming an energy cycle between Er ³⁺ and Ce ³⁺ , so that the avalanche energy of Er ³⁺ is transferred to Ce ³⁺ , thereby realizing the avalanche of Ce ³⁺ .

The logarithmic curve of the emission intensity of NaYF ₄ :Tm(8%)@NaYF ₄ :Er(1%)@NaYF ₄ :Er/Ce(5%/5%) excitation power is shown in Figure 8. The upconversion emission intensity of Er ³⁺ at 656nm and 542nm increases sharply after exceeding the power threshold, and the nonlinear order of photon avalanche luminescence can reach 40 and 37, respectively. This shows that Ce ³⁺ can greatly enhance the photon avalanche process of Er ³⁺ .

Example 4

Based on the method for realizing multi-ion photon avalanche rare earth doped nanoparticles based on interface energy transfer in Example 3, this example illustrates the specific synthesis steps:

The first step is to synthesize the core structure of the photon avalanche engine: at room temperature (23-25°C), add 5mL of RECl ₃ (0.2M, RE＝Y, Tm) solution to a 100mL round-bottom flask, then add 7.5mL of oleic acid and 17.5mL of 1-octadecene in sequence, and react at 150°C for 50 minutes to form a precursor. Remove the heating jacket and allow the reaction mixture to cool to 40°C while stirring, quickly add a mixture of 10mL of NH ₄ F-methanol solution (0.4mmol/mL) and 2.5mL of NaOH-methanol solution (1mmol/mL), and then react at 40°C for at least 2 hours, then react at 100°C under vacuum for 30 minutes to remove methanol. Then, heat to 300°C under argon atmosphere and react at this temperature for 1.5 hours. Remove the heating jacket and cool the system to room temperature while stirring. Then add 10 mL of anhydrous ethanol to the product and centrifuge at 7500 rpm for 5 minutes. Remove the supernatant to collect the product and repeat the above steps with a mixture of ethanol and cyclohexane to obtain the core _NaYF4 :Tm (8%) of the upconversion nanoparticles, which is dispersed in 8 mL of cyclohexane.

The second step is to synthesize the intermediate shell structure where the acceptor ion Er ³⁺ ion is located: at room temperature (23-25°C), add 5mL RECl ₃ (0.2M, RE＝Y, Er) solution to a 100mL round-bottom flask, then add 7.5mL oleic acid and 17.5mL 1-octadecene in sequence, and react at 150°C for 50 minutes to form a precursor. Remove the heating mantle and allow the reaction mixture to cool to 95°C while stirring, then add 4mL of the photon avalanche nanoparticle solution of the core structure NaYF ₄ :Tm (8%) synthesized in the previous step, wait for the solution to cool to 40°C, quickly add a mixture of 10mL NH ₄ F-methanol solution (0.4mmol/mL) and 2.5mL NaOH-methanol solution (1mmol/mL), then react at 40°C for at least 2 hours, then react at 100°C under vacuum for 30 minutes to remove methanol. Then, heat to 300°C in an argon atmosphere and react at this temperature for 1.5 hours. The heating jacket was removed and the system was allowed to cool to room temperature while stirring. Then 10 mL of anhydrous ethanol was added to the product. The mixture was centrifuged at 7500 rpm for 5 minutes. The supernatant was removed to collect the product. The product was washed with a mixture of ethanol and cyclohexane and the above steps were repeated to obtain upconversion nanoparticles _NaYF4 : Tm (8%) @ _NaYF4 : Er (5%), which were dispersed in 4 mL of cyclohexane.

Finally, the outer shell structure composed of Er ³⁺ and Ce ³⁺ fluoride nanocrystals was synthesized: at room temperature (23-25°C), 5 mL of RECl ₃ (0.2 M, RE = Er ³⁺ , Ce ³⁺ ) solution was added to a 100 mL round-bottom flask, and then 7.5 mL of oleic acid and 17.5 mL of 1-octadecene were added in sequence, and the reaction was carried out at 150°C for 50 minutes to form a precursor. Remove the heating jacket and allow the reaction mixture to cool to 95°C while stirring, then add 2.67 mL of the core-shell photon avalanche nanoparticle NaYF ₄ :Tm (8%) @NaYF ₄ :Er (5%) solution synthesized in the previous step, and quickly add a mixture of 10 mL of NH ₄ F-methanol solution (0.4 mmol/mL) and 2.5 mL of NaOH-methanol solution (1 mmol/mL) after the solution cools to 40°C, and then react at 40°C for at least 2 hours, and then react at 100°C under vacuum for 30 minutes to remove methanol. Then, heat to 300°C in an argon atmosphere and keep the reaction at this temperature for 1.5 hours. The heating jacket was removed and the system was allowed to cool to room temperature while stirring. Then 10 mL of anhydrous ethanol was added to the product and centrifuged at 7500 rpm for 5 minutes. The supernatant was removed to collect the product and the product was washed repeatedly with a mixture of ethanol and cyclohexane to obtain upconversion nanoparticles _NaYF4 : Tm (8%) @ _NaYF4 : Er (1%) @ _NaYF4 : Er/Ce (5%/5%), which were dispersed in 2.67 mL of cyclohexane.

The transmission electron microscopy image of the successfully synthesized multi-layer core-shell structured multi-ion photon avalanche nanoparticles NaYF ₄ :Tm(8%)@NaYF ₄ :Er(1%)@NaYF ₄ :Er/Ce(5%/5%) is shown in FIG9 .

For those skilled in the art, various other corresponding changes and modifications can be made according to the technical solutions and concepts described above, and all of these changes and modifications should fall within the protection scope of the claims of the present invention.

Claims (5)

1. A method for realizing multi-ion nanophotonic avalanche luminescence by using interface energy transfer, which is characterized by comprising the following steps:

S1, separating photon avalanche donor ions and acceptor ions in different structural layers by constructing a multi-layer core-shell nano structure, wherein the donor ions are positioned in a core layer, and the acceptor ions are positioned in a shell layer;

s2, constructing a nano-structure nuclear layer, selecting an ion Tm ³⁺ capable of generating photon avalanche effect as a photon avalanche engine ion in a nuclear shell structure system, namely a donor ion A ³⁺, and doping the ion Tm ³⁺ into nanocrystals; the donor ion A ³⁺ is subjected to energy level transition under the irradiation of laser with the wavelength of 1064nm or 1470nm, and the energy level particle number of an avalanche ion excited state is increased in an avalanche mode through certain energy circulation conduction, so that photon avalanche fluorescence which is efficient and stable and has a high-order nonlinear dependency relationship on the excitation light intensity is radiated;

S3, constructing a nano particle intermediate shell layer, wherein the nano particle intermediate shell layer is formed by doping acceptor ions X ³⁺ into nano crystals, and the acceptor ions comprise Er ³⁺、Ho³⁺ ions; when the near infrared light beam excites the donor ion to generate photon avalanche fluorescence, energy is transferred from the donor avalanche engine body ion to the acceptor ion X ³⁺ positioned on the shell layer through interfacial energy transfer, and the acceptor ion Er ³⁺、Ho³⁺ receives the avalanche energy and then is transferred to a high energy level through gradual up-conversion, so that photon avalanche fluorescence is radiated;

S4, after realizing avalanche of the intermediate shell nano-ions, constructing more shells, and transmitting avalanche energy of the intermediate shell nano-ions to a third cascade ion except an avalanche engine and intermediate layer ions in an interface energy transmission mode, wherein the cascade ion comprises Ce ³⁺、Yb³⁺ ions; after receiving avalanche energy, the cascade ions are converted to a high energy level by step up-conversion, and up-conversion photon avalanche fluorescence is radiated, so that the multi-ion cascade photon avalanche effect under the condition of single excitation wavelength is realized.

2. A detection device for implementing a multi-ion nano-photon avalanche lighting method using interface energy according to claim 1, wherein the device comprises an excitation light generation module, a multi-photon microscopy module, a photoelectric detection module and photon avalanche nanoparticles; the continuous near-infrared steady laser beam generated by the excitation light generation module is reflected by the vertical reflecting mirror to enter the multiphoton microscopic module; the continuous near-infrared steady laser beam entering the multiphoton microscopic module is reflected by the high-reflection low-transmission dichroic mirror and irradiates on the photon avalanche fluorescent nanoparticle positioned on the objective table; the photoelectric detection module detects photon avalanche fluorescence signals; the excitation light generation module comprises a single-mode semiconductor laser, and a half wave plate, a polarization beam splitter, a 980nm long-pass filter and a neutral attenuation sheet are sequentially arranged along the optical axis direction of the single-mode semiconductor laser; the single-mode semiconductor laser emits 1064nm continuous near-infrared steady laser beams, the power of the laser beams is adjusted through the half-wave plate, 980nm components in the continuous near-infrared steady-state laser beams are removed through the polarization beam splitter and the 980nm long-pass filter, ions in each layer are prevented from being directly excited by 980nm, and then the laser power is reduced through the neutral attenuation plate.

3. The detection apparatus for implementing a multi-ion nanophotonic avalanche process using interfacial energy according to claim 2, wherein the multi-photon microscopy module comprises a vertical mirror, a focusing lens, a high-reflection low-transmittance dichroic mirror, and an objective lens in this order along a continuous near-infrared steady laser beam advancing direction; the vertical reflecting mirror collimates the 1064nm continuous near-infrared steady laser beam regulated by the excitation light generating module into a focusing lens, and the laser beam is focused by the focusing lens, reflected by the high-reflection low-transmission dichroic mirror into an objective lens and focused on photon avalanche nanoparticles.

4. The detection apparatus for implementing a multi-ion nanophotonic avalanche lighting method using interface transduction of claim 3, wherein said photodetection module comprises a visible light detection module and a near-red light detection module; the visible light detection module comprises a short-pass filter, a vertical reflecting mirror, a focusing lens and a visible light spectrometer; when the objective lens receives the visible photon avalanche fluorescence emitted by the nano particles, the visible photon avalanche fluorescence is filtered by a short-pass filter, then is focused by the focusing lens after passing through the vertical reflecting mirror, and then is detected by the visible light spectrometer to obtain photon avalanche fluorescence signals.

5. The detection apparatus for implementing a multi-ion nanophotonic avalanche lighting method using interface transduction of claim 4, wherein the near infrared light detection module comprises a long pass filter, a focusing lens, a near infrared spectrometer; the continuous near-infrared steady laser beam is received by the objective lens, filtered by the long-pass filter, focused by the focusing lens and received by the near-infrared spectrometer.