Composite superlattice nanosphere with adjustable fluorescence lifetime as well as preparation method and application of composite superlattice nanosphere

Abstract

The invention discloses a composite superlattice nanosphere with adjustable fluorescence lifetime and a preparation method and application thereof, and belongs to the technical field of nano luminescent materials. Quantum dots with band gaps smaller than the transition energy level difference of a rare earth nanocrystalline luminescent material are selected, the quantum dots and the rare earth nanocrystalline luminescent material are self-assembled to form composite superlattice nanospheres, and energy transfer between the quantum dots and the rare earth nanocrystalline luminescent material is realized based on the composite superlattice nanosphere structure, so that the luminescent efficiency is improved. Further, the transition probability of rare earth ions in the composite superlattice nanospheres is changed; by selecting quantum dots with different band gaps, the fluorescence lifetime of the composite superlattice nanosphere can be regulated and controlled, the operation is simple, the cost is low, the composite superlattice nanosphere is expected to replace the existing rare earth nanocrystalline luminescent material, the problem of trailing caused by overlong fluorescence lifetime in stimulated radiation super-resolution imaging is solved, and the imaging resolution is improved.

Description

Technical Field

[0001] The present invention specifically relates to a composite superlattice nanosphere with adjustable fluorescence lifetime and a preparation method and application thereof, belonging to the technical field of nano luminescent materials. Background Art

[0002] Rare earth ions have a rich electronic energy level structure, can produce up to millions of intrastate transitions, and can emit light in various bands from ultraviolet to visible and near-infrared, and are known as a treasure trove of luminescence. Rare earth nanocrystal luminescent materials obtained by doping rare earth ions into rare earth nanocrystal matrices have now become a functional material with great development potential and application prospects. They have significant characteristics such as good stability, narrow emission band, strong penetration, and low toxicity. They have attracted much attention in the fields of micro-nano optical devices, biodiagnosis and treatment, and super-resolution imaging. Especially for the stimulated emission depletion imaging mode in super-resolution imaging, due to the advantages of rare earth nanocrystal luminescent materials such as large Stokes-like shifts, narrow emission spectrum peaks, and good biocompatibility, they show great potential as super-resolution imaging probes.

[0003] The inert rare earth nanocrystal matrix of rare earth nanocrystal luminescent materials does not emit light itself, and its luminescence comes from the doped active rare earth ions. However, due to the parity forbidden transition between the 4f electronic configurations of rare earth ions, the forbidden transition is partially lifted under the low-symmetry local crystal field, which in turn leads to the rare earth ions having a long fluorescence lifetime. When performing stimulated emission super-resolution imaging, the excessively long fluorescence lifetime will not only slow down the scanning imaging speed, but also cause the image tailing effect and affect the imaging resolution, which restricts the application of existing rare earth nanocrystal luminescent materials in stimulated emission super-resolution imaging. Summary of the invention

[0004] In view of the problem of too long fluorescence lifetime of rare earth nanocrystal luminescent materials in the prior art, the present invention proposes a composite superlattice nanosphere with adjustable fluorescence lifetime and a preparation method and application thereof; the present invention selects quantum dots with a band gap smaller than the transition energy level difference of the rare earth nanocrystal luminescent materials, so that they self-assemble with the rare earth nanocrystal luminescent materials to form a composite superlattice nanosphere, and based on the composite superlattice nanosphere structure, realizes energy transfer between the two, thereby changing the transition probability of rare earth ions in the composite superlattice nanosphere; by selecting quantum dots with different band gaps, the fluorescence lifetime of the composite superlattice nanosphere can be regulated, and the operation is simple and the cost is low; the composite superlattice nanosphere is expected to replace the existing rare earth nanocrystal luminescent materials, solve the tailing problem caused by the excessively long fluorescence lifetime in stimulated emission super-resolution imaging, and improve the imaging resolution.

[0005] The technical solution of the present invention is as follows:

[0006] The present invention provides a composite superlattice nanosphere with adjustable fluorescence lifetime. The composite superlattice nanosphere is formed by self-assembly of quantum dots with different band gaps and rare earth nanocrystal luminescent materials; the rare earth nanocrystal luminescent materials are rare earth nanocrystals doped with rare earth ions; the rare earth ions are +3 valence rare earth ions; the band gap of the quantum dots is smaller than one or more transition energy level differences of the rare earth ions.

[0007] Furthermore, the rare earth nanocrystal luminescent material is one of hexagonal rare earth ion-doped NaLuF4 nanocrystals, rare earth ion-doped NaGdF4 nanocrystals or rare earth ion-doped NaYF4; the chemical formula of the rare earth ion-doped NaLuF4 nanocrystals is NaLuF4:Ln 3+ The chemical formula of the rare earth ion doped NaGdF4 nanocrystal is NaGdF4:Ln 3+ The chemical formula of the rare earth ion doped NaYF4 nanocrystal is NaYF4:Ln 3+ , Ln 3+ For rare earth ions, Ln 3+ Including Ce 3+ , Yb 3+ , Er 3+ 、Tm 3+ 、Ho 3+ , Tb 3+ 、Dy 3+ 、Sm 3+ 、Nd 3+ and Pr 3+ One or more of .

[0008] Furthermore, the rare earth nanocrystal luminescent material is a rare earth nanocrystal luminescent material with a core-shell structure formed on the basis of hexagonal rare earth ion-doped NaLuF4 nanocrystals and / or rare earth ion-doped NaGdF4 nanocrystals and / or rare earth ion-doped NaYF4 nanocrystals.

[0009] Furthermore, the chemical formula of the rare earth nanocrystal luminescent material with core-shell structure is NaLuF4:Yb 3+ @NaLuF4:Er 3+ .

[0010] Furthermore, the quantum dots are one of the II-VI group quantum dots.

[0011] Furthermore, the quantum dots are CdSe@CdS@ZnS.

[0012] The existing rare earth luminescent materials emit light from the doped rare earth ions. The present invention is based on the composite superlattice nanosphere structure to achieve energy transfer between quantum dots and existing rare earth nanocrystal luminescent materials, thereby regulating the fluorescence lifetime of rare earth ions; when the selected quantum dot band gap is smaller than one or more transition energy level differences of rare earth ions, in the composite superlattice nanosphere structure, The principle of resonant energy transfer can realize energy transfer from rare earth ions as donors to quantum dots as acceptors, effectively reducing the lifetime of fluorescence emitted by electron radiation transitions with transition energy level differences greater than the band gap of quantum dots; since different quantum dots have different band gaps, by selecting different types of quantum dots, the controllable reduction of the fluorescence lifetime of multi-level radiation transitions of composite superlattice nanospheres can be achieved.

[0013] The present invention also provides a method for preparing the composite superlattice nanosphere with adjustable fluorescence lifetime, comprising the following steps:

[0014] S1. Dissolve sodium dodecyl sulfate in ultrapure water to obtain solution 1;

[0015] S2, mixing the oil-soluble rare earth nanocrystal luminescent material and quantum dots in cyclohexane, and then adding the mixed solution dropwise into solution one under ultrasonic conditions to obtain solution two;

[0016] S3. Heat and stir the second solution in an inert gas atmosphere until the cyclohexane is completely evaporated. After the solution is cooled to room temperature, the product is separated by centrifugation and washed with deionized water to obtain water-soluble composite superlattice nanospheres.

[0017] Furthermore, in step S1, the mass ratio of the dosage of sodium dodecyl sulfate to ultrapure water is 1.5 mg / g.

[0018] Furthermore, in step S2, the molar ratio of the added amount of rare earth nanocrystal luminescent material to the quantum dots is 1:100.

[0019] Furthermore, in step S3, heating is performed to 60°C.

[0020] The composite superlattice nanosphere with adjustable fluorescence lifetime provided by the present invention can be applied to the preparation of a rare earth nanocrystal luminescent probe with a short fluorescence lifetime.

[0021] Different from the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention provides a composite superlattice nanosphere with adjustable fluorescence lifetime, which has good dispersibility and repeatability, high order, and its interference image after long-order arrangement can be observed under a transmission electron microscope. It can be applied to the preparation of short fluorescence lifetime rare earth nanoluminescent probes, and has good practical application prospects.

[0023] 2. Compared with the existing rare earth nanocrystal luminescent materials, the fluorescence lifetime of the composite superlattice nanosphere is significantly reduced. The composite superlattice nanosphere uses the rare earth nanocrystal luminescent material as a donor to the quantum dot as an acceptor. Resonant energy transfer effectively reduces the lifetime of fluorescence emitted by electrons with a transition energy level difference greater than the band gap of quantum dots when they transition from an excited state back to a ground state. In addition, by selecting quantum dots with different band gaps, the fluorescence lifetime of the composite superlattice nanospheres can be controllably reduced. The operation is simple and the cost is low. The composite superlattice nanospheres are expected to solve the tailing problem caused by the long fluorescence lifetime of existing rare earth nanocrystal luminescent materials in stimulated emission super-resolution imaging, thereby improving imaging resolution.

[0024] 3. The present invention self-assembles quantum dots and rare earth nanocrystal luminescent materials to obtain composite superlattice nanospheres with adjustable fluorescence lifetime, which has simple preparation steps and low cost; the quantum dots can be any of the II-VI group quantum dots, and thanks to the close stacking of rare earth nanocrystals and quantum dots in the composite superlattice nanosphere structure, the distance between the two is within Within the effective distance of resonant energy transfer (1-10nm), the energy transfer can be completed through long-range electric dipole-electric dipole interaction as long as the fluorescence emission spectrum of the selected donor (rare earth nanocrystal) overlaps with the absorption spectrum of the acceptor (quantum dot). Under the premise of resonant energy transfer, the preparation method can use rare earth nanocrystal luminescent materials prepared by any method as preparation raw materials, and has relatively broad applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the self-assembly of rare earth nanocrystal luminescent materials and quantum dots to form superlattice nanospheres in the present invention.

[0026] Figure 2 It is NaLuF4:50%Yb in the embodiment of the present invention. 3+ @NaLuF4:10%Er 3+ Transmission electron microscopy image of nanocrystalline luminescent materials.

[0027] Figure 3 This is a transmission electron microscope image of CdSe@CdS@ZnS quantum dots in an embodiment of the present invention.

[0028] Figure 4 It is NaLuF4:50%Yb in the embodiment of the present invention. 3+ @NaLuF4:10%Er 3+ Composite superlattice nanospheres formed by self-assembly of nanocrystalline luminescent materials and CdSe@CdS@ZnS quantum dots.

[0029] Figure 5 NaLuF4:50%Yb in the comparative example of the present invention 3+ @NaLuF4:10%Er 3+ Transmission electron microscopy image of self-assembled nanospheres of rare earth nanocrystals.

[0030] Figure 6 Graph showing the emission spectrum of the composite superlattice nanospheres in an embodiment of the present invention, wherein the inset is a photograph of a sample of the composite superlattice nanosphere solution.

[0031] Figure 7 The rare earth nanocrystal luminescent material and the composite superlattice nanosphere in the embodiment of the present invention are 3+ ion 4 F 9 / 2 Comparison of fluorescence lifetimes of energy levels.

[0032] Figure 8 The rare earth nanocrystal luminescent material and the composite superlattice nanosphere in the embodiment of the present invention are 3+ ion 4 S 3 / 2 Comparison of fluorescence lifetimes of energy levels.

[0033] Fig. 9 is the Er in the composite superlattice nanosphere in the embodiment of the present invention. 3+ ion 4 S 3 / 2 Comparison of energy levels and fluorescence lifetime of quantum dot band edges excitons.

[0034] Fig.10 Schematic diagram of energy transfer between rare earth nanocrystal luminescent material and quantum dots in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments. The given embodiments are only for illustrating the present invention, rather than for limiting the scope of the present invention.

[0036] Unless otherwise specified, the materials, reagents, etc. used in the following examples can be obtained from commercial sources; the methods in the following examples are conventional methods unless otherwise specified.

[0037] The present invention provides a composite superlattice nanosphere with adjustable fluorescence lifetime. The composite superlattice nanosphere is formed by self-assembly of quantum dots with different band gaps and rare earth nanocrystal luminescent materials; the rare earth nanocrystal luminescent materials are rare earth nanocrystals doped with rare earth ions; the rare earth ions are +3 valence rare earth ions; the band gap of the quantum dots is smaller than one or more transition energy level differences of the rare earth ions.

[0038] In some preferred embodiments, the rare earth nanocrystal luminescent material may be one of hexagonal rare earth ion-doped NaLuF4 nanocrystals, rare earth ion-doped NaGdF4 nanocrystals or rare earth ion-doped NaYF4 nanocrystals; the chemical formula of the rare earth ion-doped NaLuF4 nanocrystals is NaLuF4:Ln 3+ The chemical formula of the rare earth ion doped NaGdF4 nanocrystal is NaGdF4:Ln 3+ The chemical formula of the rare earth ion doped NaYF4 nanocrystal is NaGdF4:Ln 3+ , Ln 3+ For rare earth ions, Ln 3+ Including Ce 3+ , Yb 3+ , Er 3+ 、Tm 3+ 、Ho 3+ , Tb 3+ 、Dy 3+ 、Sm 3+ 、Nd 3+ and Pr 3+ One or more of .

[0039] In some preferred embodiments, the rare earth nanocrystal luminescent material may be a rare earth nanocrystal luminescent material with a core-shell structure formed on the basis of rare earth ion-doped NaLuF4 nanocrystals and / or rare earth ion-doped NaGdF4 nanocrystals and / or rare earth ion-doped NaYF4 nanocrystals.

[0040] In some preferred embodiments, the chemical formula of the rare earth nanocrystal luminescent material with core-shell structure is NaLuF4:Yb 3+ @NaLuF4:Er 3+ .

[0041] In some preferred embodiments, the quantum dots may be one of the group II-VI quantum dots.

[0042] In some preferred embodiments, the quantum dots are CdSe@CdS@ZnS.

[0043] The present invention also provides a method for preparing composite superlattice nanospheres with adjustable fluorescence lifetime, comprising the following steps:

[0044] S1. Dissolve sodium dodecyl sulfate in ultrapure water to obtain solution 1;

[0045] S2, mixing the oil-soluble rare earth nanocrystal luminescent material and quantum dots in cyclohexane, and then adding the mixed solution dropwise into solution one under ultrasonic conditions to obtain solution two;

[0046] S3. Heat and stir the second solution in an inert gas atmosphere until the cyclohexane is completely evaporated. After the solution is cooled to room temperature, the product is separated by centrifugation and washed with deionized water to obtain water-soluble composite superlattice nanospheres.

[0047] In some preferred embodiments, the mass ratio of the dosage of sodium dodecyl sulfate to ultrapure water in step S1 is 1.5 mg / g.

[0048] In some preferred embodiments, the molar ratio of the rare earth nanocrystal luminescent material added to the quantum dots in step S2 is 1:100.

[0049] In some preferred embodiments, the heating is performed to 60° C. in step S3 .

[0050] The composite superlattice nanosphere with adjustable fluorescence lifetime provided by the present invention can be applied to the preparation of a rare earth nanocrystal luminescent probe with a short fluorescence lifetime.

[0051] The composite superlattice nanosphere with adjustable fluorescence lifetime of the present invention is further described below in conjunction with specific embodiments:

[0052] Example 1

[0053] This embodiment provides a composite superlattice nanosphere with adjustable fluorescence lifetime (schematic diagram as shown in FIG. Figure 1 As shown), the composite superlattice nanosphere is formed by self-assembly of quantum dots and rare earth nanocrystal luminescent materials; the rare earth nanocrystal luminescent materials are rare earth nanocrystals doped with rare earth ions; the rare earth ions are +3 valence rare earth ions; the band gap of the quantum dots is smaller than one or more transition energy level differences of the rare earth ions.

[0054] The rare earth nanocrystal luminescent material in this embodiment is NaLuF4:Yb 3+ @NaLuF4:Er 3+ , Yb 3+ The doping amount is 50%, Er 3+ The doping amount is 10%, and the chemical formula of the rare earth nanocrystal luminescent material can be expressed as NaLuF4:50%Yb 3+ @NaLuF4:10%Er 3+ .

[0055] The quantum dots used in this embodiment are CdSe@CdS@ZnS, and the band gap of the quantum dots used is smaller than that of Er doped in the rare earth nanocrystal luminescent material. 3+ 4S 3 / 2 The transition energy level difference of the energy level is used to adjust the Er 3+ 4S 3 / 2 The lifetime of fluorescence generated by energy level transition.

[0056] The method for preparing the composite superlattice nanosphere with adjustable fluorescence lifetime comprises the following steps:

[0057] S1. Under room temperature, weigh 15 mg of sodium dodecyl sulfate and ultrasonically disperse it in 10 g of ultrapure water to obtain solution 1;

[0058] S2. Figure 2 NaLuF4:50%Yb shown in the transmission electron microscope image 3+ @NaLuF4:10%Er 3+ Rare earth nanocrystal luminescent materials and Figure 3 The CdSe@CdS@ZnS quantum dots shown in the transmission electron microscopy image were mixed in a cyclohexane solution at a molar ratio of 1:100, and then the mixed solution was added dropwise into solution 1 under the assistance of ultrasound to obtain solution 2;

[0059] S3, the second solution is transferred to a flask, heated to 60° C. in an inert gas atmosphere, and stirred at a constant temperature for 0.5 to 1 hour. After the cyclohexane is completely evaporated, the solution is cooled to room temperature, the product is separated by centrifugation, and washed with deionized water to obtain composite superlattice nanospheres;

[0060] like Figure 4 As shown, in the transmission electron microscope image of the composite superlattice nanosphere, the interference image that appears inside the superlattice nanosphere due to the long-range arrangement of particles can be observed.

[0061] Comparative Example 1

[0062] This comparative example provides a self-assembled nanosphere of a rare earth nanocrystal luminescent material, which is different from Example 1 in that:

[0063] The nanosphere is formed by self-assembly of rare earth nanocrystal luminescent material under the action of amphiphilic molecules without the addition of quantum dots.

[0064] The method for preparing the self-assembled nanospheres of rare earth nanocrystal luminescent material is different from that of Example 1 in that:

[0065] In step S2, no CdSe@CdS@ZnS quantum dots were added;

[0066] The remaining steps are the same as those in Example 1 and will not be described in detail here. The transmission electron microscope image of the self-assembled nanospheres of the rare earth nanocrystal luminescent material prepared in this comparative example is as follows: Figure 5 shown.

[0067] Optical performance characterization

[0068] The optical performance test of the composite superlattice nanosphere with adjustable fluorescence lifetime described in Example 1 is studied:

[0069] The composite superlattice nanospheres were dispersed in deionized water (such as Figure 6 The upconversion emission spectrum of the composite superlattice nanospheres under the excitation of 980nm near-infrared laser was monitored by FLS980 fluorescence spectrometer (see the inset photo). Figure 6 As shown in Figure 1, the composite material combines the luminescence characteristics of rare earth ions and quantum dots: it has green light (520-570nm) and red light (640-670nm) upconversion narrow-band emission peaks, which come from Er 3+ Ionic 2 H 11 / 2 / 4 S 3 / 2 arrive 4 I 15 / 2 energy level, and 4 F 9 / 2 arrive 4 I 15 / 2 Intraconfigurational transitions of energy levels; and a broadband emission peak at 600nm, which belongs to the band-edge exciton radiative recombination luminescence of CdSe@CdS@ZnS quantum dots.

[0070] Furthermore, in order to verify the energy transfer process between the rare earth nanocrystal luminescent material and the quantum dots in the composite superlattice nanospheres, the excited state dynamics of the composite superlattice nanospheres was studied to compare the changes in their fluorescence lifetimes. The FLS980 fluorescence spectrometer was connected to an external OPO laser to monitor the sample under the excitation of a 980nm near-infrared pulsed laser. 4 S 3 / 2 , 4 F 9 / 2 The fluorescence lifetime of the energy level band edge exciton. Figure 7 As shown in the figure, the composite superlattice nanospheres formed by self-assembly of rare earth nanocrystals and quantum dots 4 F 9 / 2 The energy level lifetime is basically the same as that of the rare earth nanocrystal self-assembled nanospheres in Comparative Example 1 without self-assembly with quantum dots, both of which are 450 μs, indicating that the band gap of the quantum dots does not match 4 F 9 / 2 Energy levels do not undergo energy transfer processes; e.g. Figure 8 As shown, before and after the composite 4 S 3 / 2 The fluorescence lifetime of the energy level is shortened from 340μs to 270μs, and the fluorescence lifetime of the quantum dot band edge exciton in the composite superlattice nanosphere is 4 S 3 / 2 The energy levels are all in the μs range (e.g. Fig. 9 ); The above results show that the band gap of quantum dots matches 4 S 3 / 2 In addition to the radiation reabsorption process (PR), there is also a The resonance energy transfer process (FRET) is shown in the schematic diagram of the energy transfer process between the two. Fig.10 shown.

[0071] Therefore, based on the composite superlattice structure proposed in this patent, energy transfer between rare earth nanocrystal luminescent materials and quantum dots can be realized, and its fluorescence lifetime is significantly shortened. It is expected to replace existing rare earth nanocrystal luminescent materials and be used in the preparation of various types of short fluorescence lifetime rare earth nanocrystal luminescent probes.

Claims

1. A composite superlattice nanosphere with adjustable fluorescence lifetime, characterized in that: The composite superlattice nanospheres are formed by self-assembly of quantum dots with different band gaps and rare earth nanocrystal luminescent materials; The rare earth nanocrystal luminescent material is a nanocrystal doped with rare earth ions; the rare earth ions are +3 valence rare earth ions; and the band gap of the quantum dots is smaller than one or more transition energy level differences of the rare earth ions.

2. The composite superlattice nanosphere with adjustable fluorescence lifetime according to claim 1, characterized in that: The rare earth nanocrystal luminescent material is one of hexagonal rare earth ion doped NaLuF4 nanocrystal, rare earth ion doped NaGdF4 nanocrystal or rare earth ion doped NaYF4 nanocrystal; the chemical formula of the rare earth ion doped NaLuF4 nanocrystal is NaLuF4:Ln 3+ The chemical formula of the rare earth ion doped NaGdF4 nanocrystal is NaGdF4:Ln 3+ The chemical formula of the rare earth ion doped NaYF4 nanocrystal is NaYF4:Ln 3+ , Ln 3+ For rare earth ions, Ln 3+ Including Ce 3+ , Yb 3+ , Er 3+ 、Tm 3+ 、Ho 3+ , Tb 3+ 、Dy 3+ 、Sm 3+ 、Nd 3+ and Pr 3+ One or more of .

3. The composite superlattice nanosphere with adjustable fluorescence lifetime according to claim 2, characterized in that: The rare earth nanocrystal luminescent material is a rare earth nanocrystal luminescent material with a core-shell structure formed on the basis of hexagonal rare earth ion-doped NaLuF4 nanocrystals and / or rare earth ion-doped NaGdF4 nanocrystals and / or rare earth ion-doped NaYF4 nanocrystals.

4. The composite superlattice nanosphere with adjustable fluorescence lifetime according to claim 3, characterized in that: The chemical formula of the rare earth nanocrystalline luminescent material with core-shell structure is NaLuF4:Yb 3+ @NaLuF4:Er 3+ .

5. The composite superlattice nanosphere with adjustable fluorescence lifetime according to claim 1, characterized in that: The quantum dots are one of the II-VI group quantum dots.

6. The composite superlattice nanosphere with adjustable fluorescence lifetime according to claim 5, characterized in that: The quantum dots are CdSe@CdS@ZnS.

7. A method for preparing composite superlattice nanospheres with adjustable fluorescence lifetime as claimed in claim 1, characterized in that: The steps include: S1. Dissolve sodium dodecyl sulfate in ultrapure water to obtain solution 1; S2, mixing the oil-soluble rare earth nanocrystal luminescent material and quantum dots in cyclohexane, and then adding the mixed solution dropwise into solution one under ultrasonic conditions to obtain solution two; S3. Heat and stir the second solution in an inert gas atmosphere until the cyclohexane is completely evaporated. After the solution is cooled to room temperature, the product is separated by centrifugation and washed with deionized water to obtain water-soluble composite superlattice nanospheres.

8. The method for preparing a composite superlattice nanosphere with adjustable fluorescence lifetime according to claim 7, characterized in that: The mass ratio of the added amount of sodium dodecyl sulfate to the ultrapure water in step S1 is 1.5 mg / g; the molar ratio of the added amount of rare earth nanocrystalline luminescent material to the quantum dots in step S2 is 1:

100.

9. The method for preparing a composite superlattice nanosphere with adjustable fluorescence lifetime according to claim 7, characterized in that: In step S3, the mixture is heated to 60°C.

10. Use the composite superlattice nanosphere with adjustable fluorescence lifetime as claimed in any one of claims 1 to 6 in the preparation of a short fluorescence lifetime rare earth nanocrystal luminescent probe.

Images