Preparation of subject-object doped TADF nanoparticles and application of subject-object doped TADF nanoparticles in STED imaging

Abstract

The invention relates to the technical field of stimulated emission depletion (STED) super-resolution imaging probes, in particular to design synthesis based on curcumin compound molecules containing a beta-dicarbonyl fluorine boron skeleton and a preparation method of a low-power STED nano-particle probe. According to the invention, the curcumin derivative compound with the beta-dicarbonyl fluorine boron skeleton is synthesized, and the constructed host and guest body type TADF nanoparticles realize low-power STED biological imaging. The preparation method of the host-guest doped nanoparticles is simple and economical, and the host-guest doped nanoparticles have high luminance and TADF characteristics. As an STED nano-particle probe, the material has the advantages of high optical stability and low saturation power, so that ultrahigh-resolution imaging is realized.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of stimulated emission depletion (STED) super-resolution imaging probes, and in particular to a method for designing and synthesizing a curcumin compound molecule containing a β-dicarbonyl fluoroboron skeleton and preparing a low-power STED nanoparticle probe. Background Art

[0002] With the development of modern biology and micro-nanotechnology, traditional optical microscopes can no longer meet the imaging resolution requirements of researchers. As one of the super-resolution imaging methods, stimulated emission depletion (STED) technology has the advantages of fast imaging speed, no need for complex image post-processing, and simple sample preparation.

[0003] The principle of STED super-resolution imaging technology is to use stimulated radiation to selectively consume excited atoms at the edge of the excitation spot, so that the excited atoms at the edge of the spot return to the ground state through the stimulated emission (SE) process, thereby reducing the luminescence range and obtaining a resolution less than the diffraction limit. According to the STED imaging resolution formula: R = λ / [2NA(1+I STED / I sat ) 1 / 2 ], where NA is the numerical aperture of the objective lens, I STED is the loss light intensity, I sat is the saturation power. Therefore, a high intensity I STED To improve the imaging resolution, it will also lead to photobleaching of fluorophores and damage to biological samples. In addition, low saturation power can ensure high resolution at low power loss. sat =hc / (τλ STED σ STED ) we can see that, among them, STED is the stimulated emission cross section, λ STED is the wavelength of the lost light, and τ is the fluorescence lifetime. Therefore, the development of new STED probe materials with low saturation power and suitable fluorescence lifetime has important practical application value and realistic significance.

[0004] In recent years, thermally activated delayed fluorescence (TADF) materials have attracted extensive attention in the field of organic light-emitting diodes (OLEDs) and time-resolved imaging due to their advantages such as high exciton utilization efficiency and long luminescence time. Therefore, TADF molecules usually exhibit a large stimulated emission cross section and a long fluorescence lifetime, which is very beneficial for achieving low saturation power. However, there are few reports on the use of TADF compounds as STED imaging probes. There are mainly the following reasons: (i) Most TADF molecules rely on the highest occupied molecular orbital

[0005] (i) The spatial separation between the HOMO and the lowest unoccupied molecular orbital (LUMO) can reduce the singlet-triplet splitting, thereby realizing the RISC process. However, spatial charge separation usually leads to low excited state oscillator strength and weak luminescence, which is not conducive to obtaining a large stimulated emission cross section; (ii) In the aggregated state, the DA molecular system with a conjugated planar structure can easily produce a strong π-π interaction, resulting in fluorescence quenching, thereby affecting the stimulated emission loss efficiency and reducing the imaging resolution; (iii) The long-lived triplet excited state of TADF is usually relaxed due to intramolecular vibration or quenched by oxygen in the environment. Therefore, it is of great significance to design a TADF material system with a large stimulated emission cross section and a long fluorescence lifetime, which is conducive to providing new insights and new perspectives for exploring new STED probes. Summary of the invention

[0006] The development of new STED probe materials has important practical application value and realistic significance. TADF molecules usually exhibit a large stimulated emission cross section and a long fluorescence lifetime, which is very conducive to achieving low saturation power. However, the charge separation in most TADF molecules currently usually leads to low excited state oscillator intensity and weak aggregated state luminescence, which is not conducive to obtaining a large stimulated emission cross section. In addition, in the aggregated state, strong π-π interactions can lead to fluorescence quenching, thereby affecting the stimulated emission loss efficiency and reducing imaging resolution. Finally, the long-lived triplet excited state of TADF usually relaxes due to intramolecular vibrations or is quenched by oxygen in the water environment. Therefore, there are few reports on the use of TADF materials as STED imaging probes.

[0007] This patent mainly designs and synthesizes curcumin derivatives with β-dicarbonyl fluoroborane skeleton, and constructs host-guest TADF nanoparticles to achieve low-power STED imaging:

[0008] A curcumin compound containing a β-dicarbonyl fluoroboron skeleton, wherein the structure of formula I is as follows:

[0009]

[0010] Wherein, R is selected from thiophene groups, preferably thiophene alkyl groups, more preferably 2-thiophene-methyl, 5-bromothiophene-2-methyl or dibenzothiophene-2-methyl.

[0011] In some preferred embodiments, the specific structure of the compound represented by formula I is as follows:

[0012]

[0013] In some preferred embodiments, the compound shown in formula I is obtained according to the following reaction scheme:

[0014]

[0015] Step 1, adding ethyl acetate EtOAc to a mixture of ethyl diacetoacetate of compound 1 and boron trifluoride ether BF3·Et2O, and heating to perform a first contact reaction;

[0016] Step 2, adding compound 2 and tri-tert-butyl borate B(n-OBu)3 to step 1, and then adding n-butylamine BuNH2 to carry out a second contact reaction;

[0017] Step 3, cooling and purifying the crude product to obtain a curcumin compound with a β-dicarbonyl fluoroborane skeleton.

[0018] In some preferred embodiments, in step 2, compound 2 is selected from any one of the following groups: 2-thiophenecarboxaldehyde, 5-bromothiophene-2-methyl and dibenzothiophene-2-carboxaldehyde.

[0019] In some preferred embodiments, in step 1, the conditions for the first contact reaction include: reaction time of 0.5 to 1 h; reaction temperature of 50 to 60 ° C; preferably, the reaction time is 0.5 h and the reaction temperature is 55 ° C; more preferably, compound 1 and boron trifluoride ether BF3·Et2O are weighed in a branch tube reactor, ethyl acetate is added as a solvent, and the reaction is carried out under heating in an oil bath at 55 ° C for 0.5 hours;

[0020] and / or

[0021] The conditions for the second contact reaction include: reaction time of 8 to 12 hours; reaction temperature of 50 to 60°C; preferably, the reaction time is 12 hours and the reaction temperature is 55°C; more preferably, compound 2 and tri-tert-butyl borate B(n-OBu)3 are added to the reaction solution, and n-butylamine BuNH2 is added to the reaction system after 0.5 to 1 hour, and n-butylamine BuNH2 is added to the reaction system again after 5 to 7 hours.

[0022] In some preferred embodiments, the molar equivalent ratio of compound 1 ethyl diacetoacetate, boron trifluoride ether BF3·Et2O, compound 2, tri-tert-butyl borate B(n-OBu)3 and n-butylamine BuNH2 in the reaction system is 1-1.2:1.1-1.3:2.5-3:2.5-3:0.6-0.8.

[0023] In some preferred embodiments, in step 3, purification is performed using a silica gel column; preferably, the elution reagent for purification is petroleum ether / V: dichloromethane / V=1-1.2:1; more preferably, the product is dark red, and the yield is 50-60%.

[0024] In a second aspect, the present invention provides a method for preparing host-guest doped TADF nanoparticles using the curcumin derivative containing a β-dicarbonyl fluoroboron skeleton, comprising the following steps:

[0025] Step a, using the curcumin derivative containing a β-dicarbonyl fluoroborane skeleton as claimed in claim 1 or 2 as a host molecule, and dissolving a guest molecule, poloxamer F127 and tetrahydrofuran solvent to obtain a mixed solution;

[0026] Step b, rapidly injecting the mixed solution into deionized water, allowing it to stand at room temperature after ultrasonication; repeatedly centrifuging the system and washing it with deionized water to obtain a host-guest doped TADF nanoparticle solution.

[0027] In step a, the host molecule is selected from any one of the following groups: BDSF, BRSF and BBSF;

[0028] The guest molecule is selected from any one of the following groups: 4,4'-di(9-carbazole)biphenyl (CBP), 1,3-dicarbazole-9-ylbenzene (mCP), and 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi);

[0029] The molar equivalent ratio of the host molecule to the guest molecule is 2-5:1, and 10-11 mg of poloxamer F127 is added to every 1 mL of tetrahydrofuran solvent.

[0030] In the step b, the volume ratio of the mixed solution to deionized water is 1:9-10, the ultrasonic time is 1-2 minutes, the frequency is 20-25 MHz, and after standing for 12-24 hours, centrifugation is performed at a speed of 9000-10000 rpm.

[0031] In a third aspect, the present invention provides a low-power host-guest doped TADF nanoparticle.

[0032] In a fourth aspect, the present invention also provides an application of the low-power host-guest doped TADF nanoparticles in STED imaging.

[0033] The beneficial effects of the present invention are:

[0034] 1. The present invention selects β-dicarbonyl fluoroboron as an electron acceptor and groups containing different thiophene structures as electron donors. The designed and synthesized compounds have obvious charge transfer characteristics, and the molecular aggregation state exhibits bright deep red light emission.

[0035] 2. The present invention utilizes the host-guest doping method to improve the luminescence intensity, optical stability and fluorescence lifetime of nanoparticles in aqueous solution.

[0036] 3. The host-guest doped TADF nanoparticles of the present invention achieve a relatively low saturation power (150.46 mW) and high-resolution STED imaging (122.5 nm).

[0037] 4. The synthetic route of the curcumin derivative of the β-dicarbonyl fluoroborane skeleton of the present invention is efficient and has a high reaction yield. The preparation method of the host-guest doped nanoparticles is simple and economical, with high luminescence brightness and TADF characteristics. As a STED nanoparticle probe, it exhibits the advantages of strong optical stability and low saturation power, thereby achieving ultra-high resolution imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the synthesis process of curcumin compounds with a β-dicarbonyl fluoroborane skeleton.

[0039] Figure 2 The chemical structure of the curcumin compound with a β-dicarbonyl fluoroborane skeleton.

[0040] Figure 3 Characterization of TADF properties of curcumin compounds with β-dicarbonyl fluoroborane skeleton.

[0041] Figure 4 Schematic diagram of the preparation process of host-guest doped nanoparticles.

[0042] Figure 5 Transmission electron microscopy image of host-guest doped nanoparticles, scale bar is 500 nm.

[0043] Figure 6 (a) Absorption / emission spectra of BRSF@CBP nanoparticles.

[0044] Figure 7 (a) Fluorescence intensity of BRSF@CBP nanoparticles at different excitation powers and (b) loss efficiency at different times.

[0045] Figure 8 (a) Confocal and (b) STED images of BRSF@CBP nanoparticles, (c, d)

[0046] Magnified image at the yellow dashed line, scale bar is 3000 nm, (e) Resolution in confocal and super-resolution modes, scale bar is 500 nm. DETAILED DESCRIPTION

[0047] This patent mainly provides a method for synthesizing a curcumin compound containing a β-dicarbonyl fluoroborane skeleton, prepares a TADF-type nanoparticle probe by host-guest doping, and finally achieves high-resolution STED imaging at low power. The experimental plan is mainly divided into the following 6 parts:

[0048] Example 1 Synthesis of curcumin compounds containing β-dicarbonyl fluoroborane skeleton

[0049] In this embodiment 1, a method for synthesizing a curcumin compound containing a β-dicarbonyl fluoroborane skeleton is provided ( Figure 1 and Figure 2 ). The β-dicarbonyl fluoroboron skeleton has a strong electron-withdrawing effect, and the photophysical properties under different molecular stacking states vary greatly. Compounds based on this skeleton are generally reported to have good stimulated radiation properties, showing excellent photophysical properties and assembly performance. Based on this, β-dicarbonyl fluoroboron was selected as an electron acceptor, and a curcumin compound containing a β-dicarbonyl fluoroboron skeleton was designed and synthesized. Curcumin derivatives containing a β-dicarbonyl fluoroboron skeleton have the advantages of simple synthesis steps, cheap and easy-to-obtain raw materials, simple purification methods, and high yields. The following compound was obtained according to the reaction route:

[0050] Step 1: Compound 1 is subjected to a first contact reaction with BF3·Et2O in the presence of ethyl acetate EtOAc.

[0051] In step 1, compound 1 and boron trifluoride ether BF3·Et2O are weighed into a branch tube reactor, ethyl acetate EtOAc is added as a solvent, and the mixture is heated in an oil bath at 50-60° C. for 0.5-1 hour.

[0052] Step 2: Add compound 2 and tri-tert-butyl borate B(n-OBu)3 to the above reaction system to carry out a second contact reaction in the presence of n-butylamine BuNH2.

[0053] In step 2, compound 2 includes but is not limited to 2-thiophenecarboxaldehyde, 5-bromothiophene-2-carboxaldehyde and dibenzothiophene-2-carboxaldehyde. Compound 2 and tri-tert-butyl borate are added to the reaction solution, and n-butylamine is added to the reaction system after 0.5 to 1 hour, and n-butylamine is added to the reaction system again after 5 to 7 hours. The reaction time is 8 to 12 hours, and the oil bath heating temperature is 50 to 60°C. The molar equivalent ratio of compound 1, boron trifluoride etherate, compound 2, tri-tert-butyl borate and n-butylamine is 1 to 1.2: 1.1 to 1.3: 2.5 to 3: 2.5 to 3: 0.6 to 0.8.

[0054] Step 3, after cooling, the crude product is purified by silica gel column chromatography.

[0055] In step 3, the elution reagent is a mixed solution of petroleum ether: dichloromethane with a volume ratio of 1 to 1.2:1, and a dark red product is finally obtained with a yield of 50 to 60%.

[0056] 1H NMR spectrum data are as follows:

[0057] BDSF: 1H NMR (600MHz, Chloroform-d) δ8.33(s,2H),7.60(s,2H),7.48(s,2H),7.21(s,2H),7.16(s,2H),4.46(s,2H),1.49(s,3H).

[0058] BRSF:1H NMR(600MHz,Chloroform-d)δ8.17(d,J=14.9Hz,2H),7.22(d,J=4.0Hz,2H),7.13(d ,J=4.0Hz,2H),7.10(d,J=15.0Hz,2H),4.45(q,J=7.1Hz,2H),1.48(t,J=7.1Hz,3H).

[0059] BBSF:1H NMR(600MHz,Chloroform-d)δ8.39-8.32(m,4H),8.19(dd,J=6.7,2.0Hz,2H),7.89(d,J=8.3Hz,2H),7.84( dd,J=6.7,1.8Hz,2H),7.73(dd,J=8.4,1.4Hz,2H),7.56-7.49(m,6H),4.58(q,J=7.1Hz,2H),1.27(s,3H).

[0060] Example 2 Characterization of properties of curcumin compounds containing β-dicarbonyl fluoroborane skeleton

[0061] With CBP as the host molecule, BRSF as the guest molecule, and ultra-dry chlorobenzene as the solvent, a solution with a mass ratio of CBP:BRSF of 20:1 was prepared and stirred to ensure that the solution was completely uniform. BRSF / CBP thin films were prepared by spin coating. 200 μL of the solution was spin coated onto a clean glass substrate at a speed of 3500 rpm / min for 30 seconds. Then annealed on a hot stage at 80°C for 30 minutes to remove the residual trace solvent. Figure 3 a depicts the photoluminescence decay curve of the BRSF / CBP film at 700nm, showing a double exponential decay, and the lifetimes of the instantaneous and delayed components are 3.92ns and 21.8μs, respectively. In addition, the sensitivity of fluorescence decay to temperature is an important property of the TADF molecule, and the lifetime of the delayed component at 78K is significantly reduced to 9.86μs. Therefore, the emission peak at 700nm originates from TADF emission. Figure 3 As shown in (b), the instantaneous and delayed spectra of BRSF / CBP film are similar, indicating that they are from the same singlet excited state. Therefore, BRSF exhibits TADF properties.

[0062] Example 3 Preparation of host-guest doped nanoparticles

[0063] like Figure 4 As shown, this embodiment 3 provides a method for preparing host-guest doped nanoparticles. The curcumin compound with a host molecule β-dicarbonyl fluoroboron skeleton and the guest molecule are embedded in a high molecular polymer poloxamer F127 with good biocompatibility to form host-guest doped nanoparticles.

[0064] Step 1, weigh the host molecule, the guest molecule, poloxamer F127 and tetrahydrofuran solvent, place them in a beaker and stir until dissolved.

[0065] Step 2: The mixed solution is quickly injected into deionized water, and then ultrasonicated for a period of time and then allowed to stand at room temperature. The above system is repeatedly centrifuged and washed with deionized water to obtain a host-guest doped nanoparticle solution.

[0066] In step 1, the host molecules include but are not limited to BDFS, BRSF and BBSF, the guest molecules include but are not limited to 4,4'-di(9-carbazole)biphenyl (CBP), 1,3-dicarbazole-9-ylbenzene (mCP) and 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), the molar equivalent ratio of the host and guest molecules is 2 to 5:1, and 10 to 11 mg of poloxamer F127 is added to every 1 mL of tetrahydrofuran solvent.

[0067] In step 2, the volume ratio of the mixed solution to deionized water is 1:9-10, the ultrasonic time is 1-2 minutes, the frequency is 20-25 MHz, and the mixture is allowed to stand for 12-24 hours and then centrifuged at a speed of 9000-10000 rpm.

[0068] Example 4 Morphological Characterization of Host-Guest Doped Nanoparticles

[0069] Taking BRSF@CBP nanoparticles as an example, 10 mg of poloxamer F127 was added to THF solutions of BDSF, BBSF, BRSF (0.00005 mmol) and CBP (0.0001 mmol) respectively. Then 1 mL of the mixed solution was quickly injected into 9 mL of deionized water under ultrasound. After standing at room temperature for 12 hours, the mixture was washed several times with deionized water and centrifuged to obtain three nanoparticle solutions. Figure 5 As shown, transmission electron microscopy images show that the nanoparticles of BDSF@CBP, BRSF@CBP and BBSF@CBP are uniform spherical in shape, with sizes of 50-70nm, 30-40nm and 40-50nm, respectively.

[0070] Example 5 Optical Characterization of Host-Guest Doped TADF Nanoparticles

[0071] like Figure 6As shown in a, the absorption peak of BRSF@CBP nanoparticles is located at 509nm, and it exhibits deep red light emission at a peak of 701nm with a large Stokes shift of 192nm. At the same time, the lifetime of BRSF@CBP nanoparticles is 8.28ns, showing a long TADF lifetime in solution ( Figure 6 b).

[0072] Example 6 STED properties of host-guest doped TADF nanoparticles

[0073] According to the peak positions of the absorption and emission spectra of BRSF@CBP nanoparticles, 470nm continuous wavelength light was selected as the excitation beam and 775nm continuous wavelength laser was selected as the STED beam. As the STED power increased, the fluorescence intensity of BRSF@CBP nanoparticles decreased significantly. When the STED power reached 435.75mW, the stimulated radiation loss efficiency of BRSF@CBP nanoparticles could reach 67% ( Figure 7 a). The saturation power of BRSF@CBP nanoparticles is 150.46 mW, which is lower than most STED nanoparticle probes reported so far, and can achieve STED imaging at low power. In addition, the optical stability of the probe is also an important factor in the super-resolution imaging process. Since the loss light power required for STED imaging is very high, it is easy to cause photobleaching of molecules, so the probe is required to have strong anti-photobleaching properties. In order to verify that the weakening of light intensity in the experiment is caused by light loss rather than photobleaching, by controlling the "on and off" of the loss wavelength and repeating it for 600 seconds, it was finally found that BRSF@CBP had only about 7% light loss in each cycle ( Figure 7 b), eliminating the decrease in fluorescence intensity caused by photobleaching, and also indicating that BRSF@CBP has excellent optical stability.

[0074] Example 7 STED imaging of host-guest doped TADF nanoparticles

[0075] In the confocal and STED images of BRSF@CBP nanoparticles ( Figure 8 a), the sample in confocal mode can only be displayed as a bright spot with a large luminous area, and the precise internal information of the spot cannot be resolved, so the achievable resolution is about 189.44nm. In STED mode, the large spot is actually a small luminous point, and the highest achievable resolution is about 122.50nm ( Figure 8 b).

[0076] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative work on the basis of the technical solution disclosed in the present invention should be included in the scope of protection of the present invention.

Claims

1. A curcumin compound containing a β-dicarbonyl fluoroborane skeleton, wherein the structure of formula I is as follows: in, R is selected from thiophene groups, preferably thiophene alkyl groups, more preferably 2-thiophene-methyl, 5-bromothiophene-2-methyl or dibenzothiophene-2-methyl.

2. The curcumin compound containing β-dicarbonyl fluorine boron skeleton according to claim 1, characterized in that: The specific structure of the compound represented by formula I is as follows:

3. A method for preparing a curcumin compound containing a β-dicarbonyl fluoroborane skeleton according to claim 1 or 2, characterized in that: The method comprises obtaining the compound shown in formula I according to the following reaction scheme: Step 1, adding ethyl acetate EtOAc to a mixture of ethyl diacetoacetate of compound 1 and boron trifluoride ether BF3·Et2O, and heating to perform a first contact reaction; Step 2, adding compound 2 and tri-tert-butyl borate B(n-OBu)3 to step 1, and then adding n-butylamine BuNH2 to carry out a second contact reaction; Step 3, cooling and purifying the crude product to obtain a curcumin compound with a β-dicarbonyl fluoroborane skeleton.

4. The method for preparing a curcumin compound containing a β-dicarbonyl fluorine boron skeleton according to claim 3, wherein: In the step 2, compound 2 is selected from any one of the following groups: 2-thiophenecarboxaldehyde, 5-bromothiophene-2-methyl and dibenzothiophene-2-carboxaldehyde.

5. The method for preparing a curcumin compound containing a β-dicarbonyl fluorine boron skeleton according to claim 3, wherein: In the step 1, the conditions of the first contact reaction include: reaction time of 0.5 to 1 h; reaction temperature of 50 to 60 ° C; preferably, the reaction time is 0.5 h and the reaction temperature is 55 ° C; more preferably, compound 1 and boron trifluoride ether BF3·Et2O are weighed in a branch tube reactor, ethyl acetate is added as a solvent, and the reaction is heated in an oil bath at 55 ° C for 0.5 hours; and / or The conditions for the second contact reaction include: reaction time of 8 to 12 hours; reaction temperature of 50 to 60°C; preferably, the reaction time is 12 hours and the reaction temperature is 55°C; more preferably, compound 2 and tri-tert-butyl borate B(n-OBu)3 are added to the reaction solution, and n-butylamine BuNH2 is added to the reaction system after 0.5 to 1 hour, and n-butylamine BuNH2 is added to the reaction system again after 5 to 7 hours.

6. The method for preparing a curcumin compound containing a β-dicarbonyl fluoroborane skeleton according to claim 3, wherein: The molar equivalent ratio of compound 1 ethyl diacetoacetate, boron trifluoride ether BF3·Et2O, compound 2, tri-tert-butyl borate B(n-OBu)3 and n-butylamine BuNH2 in the reaction system is 1-1.2:1.1-1.3:2.5-3:2.5-3:0.6-0.

8.

7. The method for preparing a curcumin derivative containing a β-dicarbonyl fluoroborane skeleton according to claim 3, wherein: In the step 3, a silica gel column is used for purification; preferably, the elution reagent for purification is petroleum ether / V: dichloromethane / V=1-1.2:1; more preferably, the product is dark red, and the yield is 50-60%.

8. A method for preparing host-guest doped TADF nanoparticles using the curcumin derivative containing a β-dicarbonyl fluoroboron skeleton as claimed in claim 1 or 2, comprising the following steps: Step a, using the curcumin derivative containing a β-dicarbonyl fluoroborane skeleton as claimed in claim 1 or 2 as a host molecule, and dissolving a guest molecule, poloxamer F127 and tetrahydrofuran solvent to obtain a mixed solution; Step b, rapidly injecting the mixed solution into deionized water, and allowing to stand at room temperature after ultrasonication; repeatedly centrifuging the system and washing it with deionized water to obtain a host-guest doped TADF nanoparticle solution. In step a, the host molecule is selected from any one of the following groups: BDSF, BRSF and BBSF; The guest molecule is selected from any one of the following groups: 4,4'-di(9-carbazole)biphenyl (CBP), 1,3-dicarbazole-9-ylbenzene (mCP), and 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi); The molar equivalent ratio of the host molecule to the guest molecule is 2 to 5:1, and 10 to 11 mg of poloxamer F127 is added to every 1 mL of tetrahydrofuran solvent; In the step b, the volume ratio of the mixed solution to deionized water is 1:9-10, the ultrasonic time is 1-2 minutes, the frequency is 20-25 MHz, and after standing for 12-24 hours, centrifugation is performed at a speed of 9000-10000 rpm.

9. A low-power host-guest doped TADF nanoparticle as claimed in claim 8.

10. Use of the low-power host-guest doped TADF nanoparticles according to claim 9 in STED imaging.

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