CN113481008B

CN113481008B - Plasmon-enhanced up-conversion luminescent nanoparticles and preparation method and application thereof

Info

Publication number: CN113481008B
Application number: CN202110343702.XA
Authority: CN
Inventors: 殷金昌; 郑宏挺; 邵元智
Original assignee: Sun Yat Sen University
Current assignee: Sun Yat Sen University
Priority date: 2021-03-30
Filing date: 2021-03-30
Publication date: 2022-06-03
Anticipated expiration: 2041-03-30
Also published as: CN113481008A

Abstract

The invention discloses a plasmon enhanced up-conversion luminescent nanoparticle and a preparation method and application thereof. The plasmon enhanced upconversion luminescent nanoparticle comprises a gold nanoparticle group and Gd wrapping the gold nanoparticle group₂O₃A nanoparticle; the gold nanosphere group consists of 38-119 gold nanospheres, and the particle size of the gold nanospheres is 5-15 nm; the Gd₂O₃Nano particle doped with metal ion Yb³⁺And Ln³⁺. By Gd₂O₃:Yb³⁺/Ln³⁺The gold nanosphere group is wrapped by the nanoparticles, and under the condition that the gold nanospheres have a plasma resonance wavelength of 538nm, the gold nanosphere group can generate another two resonance peaks in a near-infrared region. The mutual synergy and competition effect of the excitation field enhancement effect, the Purcell effect and the quenching effect triggered by SPR are utilized, the up-conversion luminescence intensity is effectively enhanced, and the up-conversion luminescence efficiency is improved.

Description

Plasmon-enhanced up-conversion luminescent nanoparticles and preparation method and application thereof

Technical Field

The invention relates to the technical field of up-conversion materials, in particular to a plasmon enhanced up-conversion luminescent nanoparticle and a preparation method and application thereof.

Background

Upconversion luminescent materials are of great interest to researchers in the field of biomedical diagnostics due to their large stokes shift and optical imaging sensitivity. Wherein, Gd₂O₃:Yb³⁺/Ln³⁺(Ln ═ Er, Ho, Tm) nanoparticles have a large absorption cross section near 980nm and Gd³⁺The ions can be simultaneously used as a nuclear magnetic resonance contrast agent with high longitudinal relaxation rate to become one of the up-conversion luminescent materials with good medical imaging prospect. However, the poor efficiency of energy transfer between the sensitizer and the activator limits the resolution and resolution of the image.

By utilizing the principle that the Surface Plasmon Resonance (SPR) of noble metal enhances excitation and emission, the upconversion luminous efficiency can be improved to a certain degree, so that optical imaging with high definition and resolution ratio can be obtained. As one of the most common plasma materials, gold nanoparticles (aunps) have good chemical stability and biocompatibility and can be used as probes for photothermal photodynamic therapy, which is very suitable for biomedical applications.

However, AuNPs generally absorb emitted light for photothermal conversion and undergo fluorescence quenching, and the shape and size of AuNPs seriously affect the wavelength and spatial range of SPR enhancement. For this reason, there have been reports on Ilia et al (plasma-enhanced conversion: engineering enhancement and queuing at nano and macro scales [ J ]. Optical Materials Express,2018,8(12):3787-3804.) and Azza Hadj Youssef et al (hierarchy-induced variations of localized surface area response in top-enhanced Raman configuration, Opt.express 28,389565 (2020)). The large-size gold nanorods, gold nanoshells, gold nanosheets and the like have a double plasma mode, but the quenching area close to the metal surface is large, and the luminescent ions cannot be completely covered by the SPR enhancement area. The small-sized gold nanospheres (AuNS) and the gold nanostars with a large number of 'hot spots' only have one plasma resonance wavelength, and the enhancement effect on the up-conversion luminous efficiency is weak.

Therefore, it is required to develop a nanoparticle for effectively enhancing the upconversion luminescence efficiency using SPR.

Disclosure of Invention

In order to overcome the defect of weak up-conversion luminescence efficiency in the prior art, the invention provides the plasmon enhanced up-conversion luminescence nano-particle, and the nano-particle is Gd wrapped with a gold nano-sphere group (AuNSA)₂O₃:Yb³⁺/Ln³⁺The nanoparticles effectively enhance the up-conversion emission light intensity through mutual cooperation and competition of an excitation field enhancement effect, a Purcell effect and a quenching effect triggered by SPR.

The invention also aims to provide a preparation method of the plasmon-enhanced up-conversion luminescent nanoparticle.

The invention also aims to provide the application of the plasmon-enhanced up-conversion luminescent nanoparticles in biological optical imaging.

In order to solve the technical problems, the invention adopts the technical scheme that:

plasmon enhanced up-conversion luminescent nanoparticles (AuNSA @ Gd)₂O₃:Yb³⁺/Ln³⁺) Comprises gold nanosphere group (AuNSA) and Gd wrapping the AuNSA₂O₃A nanoparticle;

the AuNSA consists of 38-119 gold nanospheres, and the particle size of the gold nanospheres is 5-15 nm;

the Gd₂O₃Nano particle doped with metal ion Yb³⁺And Ln³⁺。

The inventor researches and discovers that although a small-sized gold nanosphere (AuNS) has only one plasmon resonance wavelength, when a plurality of AuNS are aggregated into an AuNSA, two other resonance peaks are generated in the near infrared region due to the interaction and action of the respective AuNS, namely, a strong resonance peak at a wavelength of 538nm and weaker resonance peaks at wavelengths of 773.5nm and 998 nm. Due to the existence of the resonance peak, the excitation field and the emission field can be enhanced simultaneously, and the SPR enhancement areas are mutually adjacent and can cover the whole luminescent particle. Compared with the nano-particles without coating AuNSA, the AuNSA @ Gd of the invention₂O₃:Yb³⁺/Ln³⁺The up-conversion luminous efficiency is improved by 46 to 96.1 times.

The Ln³⁺Is a lanthanide metal ion.

Preferably, said Ln³⁺Is Er³⁺、Ho³⁺Or Tm³⁺。

Through a large number of creative experiments and data theoretical analysis, the inventor believes that the AuNSA @ Gd of the application₂O₃:Yb³⁺/Ln³⁺The enhancement of the up-conversion luminescence efficiency is mainly caused by the mutual synergy and competition of the following three effects:

first, when the excitation light wavelength is close to the SPR resonance wavelength, a region in which the local electric field is significantly enhanced is formed around AuNSA, and Yb is in this region³⁺The strength and time of interaction with the excitation light are increased, resulting in Yb³⁺The excitation efficiency is improved, which is called an excitation field enhancement effect;

second, when the emitted light wavelength is close to the SPR resonance wavelength, due to the Purcell effect,Ln³⁺the spontaneous radiation transition probability of the corresponding excited state is improved, and the luminous efficiency of emitted light is directly enhanced;

third, although the emitted light is absorbed by AuNS resulting in fluorescence quenching, this quenching follows Ln³⁺The distance from the AuNS increases and the rapid decay, and the ions quenched are only a small proportion due to the larger size of the nanoparticles of the present application.

Thus, the AuNSA @ Gd of the present invention₂O₃:Yb³⁺/Ln³⁺The fluorescence quenching effect of the medium AuNP can be ignored, and the excitation field enhancement effect caused by SPR and the Purcell effect cause the enhancement of emitted light, so that the up-conversion luminescence efficiency is greatly improved.

Preferably, the particle size of the gold nanosphere is 7-11 nm.

The average particle size of the gold nanospheres is 9 nm.

Preferably, the AuNSA consists of AuNS with the number of 38-77.

Preferably, the AuNSA consists of AuNS with the number of 40-60.

Preferably, the average distance between AuNS is 8-26 nm.

Preferably, the Gd is₂O₃The particle size of the nanoparticles is 50-95 nm.

More preferably, the Gd₂O₃The particle size of the nano-particles is 70-85 nm.

Preferably, the Gd is³⁺、Yb³⁺、Ln ³⁺The molar ratio of (1-2) to (5-25) to (94-73).

Preferably, the Gd³⁺、Yb³⁺、Ln ³⁺The molar ratio of (A) to (B) is 83: 15: 2.

Preferably, the molar ratio of Au to Gd is 1 to (2-15).

The invention also provides a preparation method of the plasmon-enhanced upconversion luminescent nanoparticle, which comprises the following steps:

dispersing a plurality of gold nanospheres in deionized water, and simultaneously adding urea and Gd³⁺、Yb³⁺、Ln ³⁺Heating and stirring uniformlyAnd (3) homogenizing, centrifuging to obtain a precursor, freeze-drying the precursor, heating at 650-950 ℃ for 2-8 h, cooling, and screening to obtain the plasmon enhanced up-conversion luminescent nanoparticles.

And screening to obtain the plasmon enhanced up-conversion luminescent nanoparticles with the number of the wrapped gold nanospheres of 38-119.

Preferably, the Gd is³⁺、Yb³⁺、Ln ³⁺Are respectively Gd³⁺、Yb³⁺、Ln ³⁺Nitrate, chloride or sulfate.

More preferably, the Gd³⁺、Yb³⁺、Ln ³⁺Are respectively Gd (NO)₃)₃、Yb(NO₃)₃、Ln(NO₃)₃。

Preferably, the heating and stirring are performed at 60-90 ℃.

Preferably, the freeze drying is drying for 6-12 h at the temperature of-40 to-20 ℃.

Preferably, the gold nanospheres are prepared by reducing chloroauric acid with trisodium citrate.

Optionally, the preparation method of the gold nanosphere comprises the following steps:

adding HAuCl₄And heating the solution to boiling, adding trisodium citrate, cooling to room temperature after the reaction solution becomes transparent orange red under the heating condition of 100-170 ℃, centrifuging, filtering and washing to obtain the gold nanospheres.

More preferably, the HAuCl₄The mass ratio of the sodium citrate to the trisodium citrate is 1: 5-10.

In HAuCl₄After trisodium citrate is added into the solution, the color of the reaction solution gradually changes from light blue to red, and the reaction solution can change into transparent orange-red under the continuous heating condition, so that the gold nanospheres are obtained.

The invention also protects the application of the plasmon enhanced up-conversion luminescent nano-particle in biological optical imaging.

Under the excitation of 980nm near infrared light, the AuNSA @ Gd of the invention₂O₃:Yb³⁺/Ln³⁺Can respectively emit red (661 nm), green (542 nm) and blue (484 nm) fluorescence, and can enable optical imaging to have higher sensitivity and definition when being applied to biological optical imaging.

Compared with the prior art, the invention has the beneficial effects that:

the invention develops a plasmon enhanced up-conversion luminescent nano particle which is prepared by Gd₂O₃:Yb³⁺/Ln³⁺The nanoparticles wrap AuNSA, and the AuNSA can generate two other resonance peaks in a near infrared region under the condition that AuNS has a 538nm plasma resonance wavelength. The mutual synergy and competition effect of the excitation field enhancement effect, the Purcell effect and the quenching effect triggered by SPR are utilized, the up-conversion luminescence intensity is effectively enhanced, and the up-conversion luminescence efficiency is improved. AuNSA @ Gd of the present invention₂O₃:Yb³⁺/Ln³⁺Under the excitation of 980nm near-infrared light, three kinds of fluorescence of red (-661 nm), green (-542 nm) and blue (-484 nm) can be respectively emitted, and the optical imaging has higher sensitivity and definition when being applied to biological optical imaging.

Drawings

FIG. 1 is a schematic diagram of a route for preparing plasmon-enhanced upconversion luminescent nanoparticles in example 1.

FIG. 2 is AuNSA @ Gd prepared in example 3₂O₃:Yb³⁺/Tm³⁺In which FIG. 2a is an inset of AuNSA @ Gd₂O₃:Yb³⁺/Tm³⁺The structure is schematic, and the inset of fig. 2b is the corresponding selected area electron diffraction pattern.

FIG. 3 is AuNSA @ Gd prepared in example 3₂O₃:Yb³⁺/Tm³⁺Energy spectrum analysis chart of (1).

FIG. 4 is AuNSA @ Gd prepared in example 1₂O₃:Yb³⁺/Er³⁺The absorption spectrum of the FDTD of (1) with the absorption spectrum experimentally measured using UV-3150.

FIG. 5 is AuNSA @ Gd prepared in example 1₂O₃:Yb³⁺/Er ³⁺Electric field intensity of FDTD simulation on plane with incident light wavelength of 980nm and Z ═ 0Graph (fig. 5a) and charge distribution graph (fig. 5 b).

FIG. 6 is AuNSA @ Gd prepared in example 1₂O₃:Yb³⁺/Er ³⁺FDTD simulated electric field intensity profile (fig. 6a) and charge distribution profile (fig. 6b) on the plane with incident light wavelength of 570nm and Z ═ 0.

FIG. 7 is AuNSA @ Gd prepared in example 1₂O₃:Yb³⁺/Er ³⁺A plot of FDTD simulated electric field strength (fig. 7a) and charge distribution (fig. 7b) on the plane with incident light wavelength of 710nm and Z ═ 0.

FIG. 8 shows AuNSA @ Gd prepared in examples 1 to 3₂O₃:Yb³⁺/Ln³⁺And SiO prepared in comparative examples 1 to 3₂@Gd₂O₃:Yb³⁺/Ln³⁺Emission spectra under excitation of 980nm laser, wherein fig. 8a is emission spectra of example 1 and comparative example 1, fig. 8b is emission spectra of example 2 and comparative example 2, and fig. 8c is emission spectra of example 3 and comparative example 3.

FIG. 9 is AuNSA @ Gd₂O₃:Yb³⁺/Ln³⁺CIE chromaticity diagram under 980nm laser excitation.

FIG. 10 is AuNSA @ Gd prepared in example 1₂O₃:Yb³⁺/Er³⁺10a, 10d, 10g are fluorescence images emitting red, green and blue light under 980nm laser irradiation, respectively; fig. 10b, 10e, and 10h are bright field images; fig. 10c, 10f, and 10i are superimposed images obtained by superimposing a fluorescence image and a corresponding bright field image.

Detailed Description

The present invention will be further described with reference to the following embodiments.

The raw materials in the examples and comparative examples are all commercially available;

reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Example 1

This example provides a plasmon enhanced upconversion luminescent nanoparticle, the preparation route is shown in fig. 1, and the preparation method is as follows:

100mL of 0.01% HAuCl₄Heating to boiling, rapidly adding 10mL of 1% trisodium citrate, gradually changing the solution from light blue to red, continuously heating until transparent orange red appears, naturally cooling to room temperature, centrifuging, filtering and washing to obtain the gold nanospheres, wherein the particle size of the gold nanospheres is 5-15 nm.

Dispersing several gold nanospheres in deionized water, and adding urea and Gd (NO)₃)₃·6H₂O、Yb(NO₃)₃·5H₂O、Er(NO₃)₃·6H₂O, wherein Gd (NO)₃)₃·6H₂O、Yb(NO₃)₃·5H₂O、Er(NO₃)₃·6H₂The molar ratio of O is 83: 15: 2, heating and stirring at 80 ℃ for 5h, centrifuging at 8000r/min for 8min to obtain a precursor, washing the precursor with deionized water and ethanol, freeze-drying at-40 ℃ for 6h, heating at 800 ℃ for 5h, naturally cooling, and screening the number of the coated gold nanospheres to obtain the plasmon enhanced up-conversion luminescent nanoparticle (AuNSA @ Gd @ nano-particle)₂O₃:Yb³⁺/Er ³⁺)。

Example 2

This example provides a plasmon enhanced upconversion luminescent nanoparticle (AuNSA @ Gd)₂O₃:Yb³⁺/Ho ³⁺) The preparation method differs from example 1 in that:

Er(NO₃)₃·6H₂substitution of equimolar amounts of O with Ho (NO)₃)₃·6H₂O。

Example 3

This example provides a plasmon enhanced upconversion luminescent nanoparticle (AuNSA @ Gd)₂O₃:Yb³⁺/Tm ³⁺) The preparation method differs from example 1 in that:

Er(NO₃)₃·6H₂substitution of equimolar amounts of O for Tm (NO)₃)₃·6H₂O。

Example 4

This example is a plasmon enhanced upconversion luminescent nanoparticle, and the preparation method is different from example 1 in that:

Gd³⁺、Yb³⁺、Ln ³⁺the molar ratio of (A) to (B) is 94: 5: 1.

Example 5

Gd³⁺、Yb³⁺、Ln ³⁺in a molar ratio of 73: 25: 2.

Example 6

Gd³⁺、Yb³⁺、Ln ³⁺are respectively Gd³⁺、Yb³⁺、Ln ³⁺Sulfate salt of (a).

Example 7

washing the precursor with deionized water and ethanol, freeze-drying, heating at 950 ℃ for 2h, and naturally cooling to obtain the plasmon enhanced up-conversion luminescent nanoparticles.

Example 8

This example is a plasmon enhanced upconversion luminescent nanoparticle, and the preparation method differs from example 1 in that:

washing the precursor with deionized water and ethanol, freeze-drying, heating at 650 ℃ for 5h, and naturally cooling to obtain the plasmon enhanced up-conversion luminescent nanoparticles.

Comparative example 1

This comparative example provides a nanoparticle (SiO)₂@Gd₂O₃:Yb³⁺/Er ³⁺) The up-conversion luminescent nano-particles have SiO₂Nucleus, Gd₂O₃:Yb³⁺/Er ³Core-shell of shellThe structure and the preparation method are as follows:

mixing SiO₂Dispersing the nanoparticles in deionized water, and adding urea and Gd (NO)₃)₃·6H₂O、Yb(NO₃)₃·5H₂O、Er(NO₃)₃·6H₂O, wherein Gd (NO)₃)₃·6H₂O、Yb(NO₃)₃·5H₂O、Er(NO₃)₃·6H₂The molar ratio of O is 83: 15: 2, heating and stirring at 80 ℃ for 5h, centrifuging at 8000r/min for 8min to obtain a precursor, washing the precursor with deionized water and ethanol, freeze-drying at-40 ℃ for 6h, heating at 800 ℃ for 5h, and naturally cooling to obtain SiO₂@Gd₂O₃:Yb³⁺/Er ³⁺。

Comparative example 2

This comparative example provides a nanoparticle (SiO)₂@Gd₂O₃:Yb³⁺/Ho³⁺) The preparation method differs from comparative example 1 in that:

Comparative example 3

This comparative example provides a nanoparticle (SiO)₂@Gd₂O₃:Yb³⁺/Tm³⁺) The preparation method differs from comparative example 1 in that:

Comparative example 4

This comparative example provides a nanoparticle (Gd)₂O₃:Yb³⁺/Er ³⁺) The preparation method comprises the following steps:

adding urea and Gd (NO) into 100mL of deionized water₃)₃·6H₂O、Yb(NO₃)₃·5H₂O、Er(NO₃)₃·6H₂O, wherein Gd (NO)₃)₃·6H₂O、Yb(NO₃)₃·5H₂O、Er(NO₃)₃·6H₂The molar ratio of O is 83: 15: 2, heating and stirring at 80 ℃ for 5h, centrifuging at 8000r/min and 8min to obtain a precursor, washing the precursor with deionized water and ethanol, freeze-drying at-40 ℃ for 6h, heating at 800 ℃ for 5h, and naturally cooling to obtain Gd₂O₃:Ln³⁺/Er³⁺)。

Comparative example 5

This comparative example provides a nanoparticle, the preparation method differing from example 1 in that:

the particle size of the gold nanospheres is 25-35 nm, and the preparation method of the gold nanospheres comprises the following steps:

100mL of 0.01% HAuCl₄Heating to boiling, rapidly adding 2mL of 1% trisodium citrate, gradually changing the solution from light blue to red, continuously heating until transparent orange red appears, naturally cooling to room temperature, centrifuging, filtering and washing to obtain the gold nanospheres, wherein the particle size of the gold nanospheres is 25-35 nm.

Comparative example 6

The comparative example provides a nanoparticle, the preparation method is as follows:

dispersing a plurality of gold nanospheres with the particle size of 5-15 nm in deionized water according to the molar ratio of Au to Gd of 1: 20, and adding urea and Gd (NO)₃)₃·6H₂O、Yb(NO₃)₃·5H₂O、Er(NO₃)₃·6H₂O, wherein Gd (NO)₃)₃·6H₂O、Yb(NO₃)₃·5H₂O、Er(NO₃)₃·6H₂The molar ratio of O is 83: 15: 2, heating and stirring at 80 ℃ for 5h, centrifuging at 8000r/min for 8min to obtain a precursor, washing the precursor by deionized water and ethanol, freeze-drying at-40 ℃ for 6h, heating at 800 ℃ for 5h, naturally cooling, and screening to obtain the nanoparticles, wherein the number of the coated gold nanospheres is 5-20.

Test method

(1) Topography and Structure testing

By being equipped with 300kV field emission gunDetection of AuNSA @ Gd by Transmission Electron microscope (TEM, FEI Tecnai-G2F 30)₂O₃:Yb³⁺/Ln³⁺Obtaining a TEM image and a SAED pattern;

observation of AuNSA @ Gd by energy dispersive X-ray Spectroscopy (EDX)₂O₃:Yb³⁺/Ln³⁺Obtaining a spectrum analysis chart.

(2) Test for luminescent Property

AuNSA @ Gd was determined by an ultraviolet-visible-near infrared spectrophotometer (UV-3150)₂O₃:Yb³⁺/Ln³⁺Absorption spectra in a 1cm quartz cell;

simulation of AuNSA @ Gd prepared in example 1 by Finite Difference Time Domain (FDTD)₂O₃:Yb³⁺Er³⁺Absorption curve, electric field strength and charge distribution;

measuring the fluorescence emission spectrogram of the nano particles by an Edinburgh spectrophotometer (FLS920) with a 980nm diode laser as an excitation source;

(3) tumor cell optical imaging test

Inoculating HeLa cells of cervical cancer on 24-well culture plate at 37 deg.C and 5% CO₂The cells were cultured in Dulbecco's Modified Eagle's Media (DMEM) containing 10% fetal bovine serum, penicillin (100 units/mL) and streptomycin (100mg/mL) under ambient conditions. After the growth to logarithmic growth phase, cells were washed with Phosphate Buffered Saline (PBS) and incubated in a medium containing 20. mu.g/mLAuNSA @ Gd₂O₃:Yb³⁺/Ln³⁺Under the same conditions for another 2 hours. The medium containing excess sample was removed, and the PBS-washed cells were fixed and imaged using a confocal laser scanning microscope (Leica TCS SP8X), setting the emission wavelength for fluorescence imaging to 980nm, and optionally using a band-pass filter to obtain live cell fluorescence images.

Test results

AuNSA @ Gd prepared in example 3 was added₂O₃:Yb³⁺/Tm³⁺The appearance of the sample was observed under a transmission electron microscope with a 300kV field emission gun, and the result is shown in FIG. 2; examples3 AuNSA @ Gd₂O₃:Yb³⁺/Tm³⁺Energy spectrum analysis chart, as shown in fig. 3.

AuNSA @ Gd can be seen from FIG. 2₂O₃:Yb³⁺/Tm³⁺Has good crystallinity in Gd₂O₃There are some dark small particles of varying sizes in the nanoparticles. The results of the energy spectrum analysis chart of FIG. 3 show that the prepared nanoparticles contain gold element, confirming that Gd₂O₃The small particles in the gold nanoparticle groups are gold nanosphere groups, and the molar ratio of Au to Gd is 1: 2-15. Because the precursor is annealed at 800 ℃ during experimental preparation to cause the gold to be molten, the gold nanospheres present irregular spherical shapes.

Performing morphology and structure tests on the plasmon-enhanced upconversion luminescent nanoparticles prepared in examples 1 to 3, wherein the particle size of the gold nanospheres is 5 to 15nm, preferably 7 to 11nm, and the average particle size of the gold nanospheres is 9.0nm according to pictures under all electron microscopes; gd (Gd)₂O₃The particle diameter of the nano-particles is 50-95 nm, preferably 70-85 nm, Gd₂O₃The average particle size of the nanoparticles was 79.5 nm; single Gd particle₂O₃The number of the nano gold balls wrapped by the nano particles is 38-119, preferably 38-77, and more preferably 40-60.

FIG. 4 is AuNSA @ Gd prepared in example 1₂O₃:Yb³⁺Er ³⁺FDTD simulated absorption curve in the range of 400-1200 nm, and AuNSA @ Gd experimentally measured by using UV-3150₂O₃:Yb³⁺/Er³⁺The absorption spectrum of (1). It can be seen that the absorption curve of the FDTD simulation shows AuNSA @ Gd₂O₃:Yb³⁺/Er³⁺Respectively has strong resonance peak at 570nm wavelength and weaker resonance peak near 710nm and 1005 nm; the absorption spectrum obtained by the experiment shows that AuNSA @ Gd₂O₃:Yb³⁺/Er³⁺The resonance peak is strong at 538nm, and weak at 773.5nm and 998 nm. Because the position, size, spacing and other factors of the gold nanospheres simulated by FDTD are not completely consistent with those of the experimental sample, the gold nanospheres and the experimental sample are considered to tend to fall within the error rangeThe potential aspect is more consistent.

According to the electric field intensity diagrams and the charge distribution diagrams of the FDTD simulation in FIGS. 5 to 7, the electric field around the gold nanosphere group can be seen to be enhanced. Besides one resonance peak at the resonance wavelength of the gold nanospheres, two resonance peaks also exist in a near infrared region due to the aggregation and mutual influence of the gold nanospheres. Because Ln³⁺The wavelength of the ion up-conversion emission light (about 542-661 nm) is near the visible light formant, and the excitation light wavelength is 980nm and is also included in the near infrared formant, so Ln³⁺The up-conversion luminous efficiency of the ions is affected by the nearby gold nanospheres.

AuNSA @ Gd prepared in examples 1 to 3 were detected respectively₂O₃:Yb³⁺/Ln³⁺And SiO prepared in comparative examples 1 to 3₂@Gd₂O₃:Yb³⁺/Ln³⁺The emission spectrum under excitation of 980nm laser is shown in FIG. 8. It can be seen that in the same Ln³⁺Under the condition of AuNSA @ Gd₂O₃:Yb³⁺/Ln³⁺Emission intensity of (2) and SiO₂@Gd₂O₃:Yb³⁺/Ln³⁺The improvement is remarkable. Specifically, AuNSA @ Gd₂O₃:Yb³⁺/Er³⁺Photoluminescence at 562nm and 661nm with SiO₂@Gd₂O₃:Yb³⁺/Er³⁺Compared with the AuNSA @ Gd which is respectively improved by 54.5 times and 46.1 times₂O₃:Yb³⁺/Ho³⁺Photoluminescence at 542nm and 655nm is respectively improved by 54.3 and 47.1 times, AuNSA @ Gd₂O₃:Yb³⁺/Tm³⁺Photoluminescence Enhancement factors (Enhancement Factor) at 484nm and 798nm were 54.1 and 96.1 times. In addition, AuNSA @ Gd prepared in example 1 compares to the nanoparticles prepared in comparative examples 4, 5, 6₂O₃:Yb³⁺/Er³⁺The photoluminescence intensity at 562nm and 661nm was also significantly higher. This indicates that the gold nanospheres are too large in particle size, do not contain gold nanospheres, or Gd₂O₃The number of gold nanospheres wrapped by the nanoparticles is too small, so that excellent photoluminescence performance cannot be achieved.

FIG. 9 is a CIE chromaticity diagram showing AuNSA @ Gd prepared according to the present invention₂O₃:Yb³⁺/Ln³⁺Luminescent color of (2), Er³⁺、Ho³ ⁺And Tm³⁺The emitted light of (a) is red (x-0.5378, y-0.4538), green (x-0.2975, y-0.6877) and blue (x-0.1513, y-0.2024), respectively.

According to the test result in fig. 10, imaging the pretreated cervical cancer HeLa cells by using a confocal laser scanning microscope with an excitation wavelength of 980nm can observe obvious fluorescence in red, green and blue cells, and the emission wavelengths are respectively over 600nm, within the ranges of 500-570 nm and 450-500 nm. By comparing the fluorescence image with the corresponding superimposed image, the AuNSA @ Gd of the present invention can be seen₂O₃:Yb³⁺/Ln³⁺Can be effectively taken up by HeLa cells and keeps the inherent remarkable fluorescence property; the superimposed images show that the fluorescence is mainly distributed in the cytoplasm. Thus, AuNSA @ Gd of the present invention was verified₂O₃:Yb³⁺/Ln³⁺Has good cell compatibility and endocytosis, and can realize clear and sensitive biological optical imaging under the excitation wavelength of 980 nm.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. The plasmon-enhanced upconversion luminescent nanoparticle is characterized by comprising a gold nanoparticle group and Gd wrapping the gold nanoparticle group₂O₃A nanoparticle;

the gold nanosphere group consists of 38-119 gold nanospheres, and the particle size of each gold nanosphere is 5-15 nm;

the Gd₂O₃Nano particle doped with metal ion Yb³⁺And Ln³⁺Said Ln³⁺Is Er³⁺、Ho³⁺Or Tm³⁺；

The plasmon enhanced up-conversion luminescent nanoparticle is prepared by the following method:

dispersing a plurality of gold nanospheres in deionized water, and simultaneously adding urea and Gd³⁺、Yb³⁺、Ln³⁺And heating and stirring the nitrate, chloride or sulfate uniformly, centrifuging to obtain a precursor, freeze-drying the precursor, heating at 650-950 ℃ for 2-8 h, cooling, and screening to obtain the plasmon-enhanced up-conversion luminescent nanoparticles.

2. The plasmon-enhanced upconversion luminescent nanoparticle according to claim 1, wherein the gold nanosphere has a particle size of 7 to 11 nm.

3. The plasmon-enhanced upconversion luminescent nanoparticle of claim 1, wherein Gd is present₂O₃The particle size of the nanoparticles is 50-95 nm.

4. The plasmon-enhanced upconversion luminescent nanoparticle of claim 1, wherein Gd is present³⁺、Yb³⁺、Ln³⁺The molar ratio of (1-2) to (5-25) to (94-73).

5. The plasmon-enhanced upconversion luminescent nanoparticle according to claim 1, wherein the molar ratio of Au to Gd is 1: 2-15.

6. The method for preparing plasmon-enhanced upconversion luminescent nanoparticles according to any of claims 1 to 5, comprising the steps of:

dispersing a plurality of gold nanospheres in deionized water, and simultaneously adding urea and Gd³⁺、Yb³⁺、Ln³⁺Heating and stirringUniformly mixing, centrifuging to obtain a precursor, freeze-drying the precursor, heating at 650-950 ℃ for 2-8 h, cooling, and screening to obtain the plasmon enhanced up-conversion luminescent nanoparticles;

the Gd³⁺、Yb³⁺、Ln³⁺Are respectively Gd³⁺、Yb³⁺、Ln³⁺Nitrate, chloride or sulfate.

7. The preparation method of claim 6, wherein the gold nanospheres are prepared by reducing chloroauric acid with trisodium citrate.

8. Use of the plasmon-enhanced upconversion luminescent nanoparticles according to any of claims 1 to 5 in bio-optical imaging.