CN111303879B

CN111303879B - Efficient single-spectrum band-up-conversion red light nanocrystalline material

Info

Publication number: CN111303879B
Application number: CN201910948779.2A
Authority: CN
Inventors: 雷磊; 张明洲; 徐时清
Original assignee: China Jiliang University
Current assignee: China Jiliang University
Priority date: 2019-10-08
Filing date: 2019-10-08
Publication date: 2022-11-22
Anticipated expiration: 2039-10-08
Also published as: CN111303879A

Abstract

The invention belongs to the field of inorganic luminescent materials. Efficient single-band up-conversion red light nanocrystalline material NaErF ₄ :Gd/Tm@NaYF ₄ Gd @ IR-806, the preparation method comprises the following steps in sequence: adding gadolinium acetate, erbium acetate, thulium acetate, oleic acid and octadecene into a three-necked bottle to obtain an anhydrous transparent solution A; naturally cooling the solution A to 50 ^o After C, dropwise adding a methanol solution of ammonium fluoride and sodium hydroxide into the solution A; after the methanol solution is completely volatilized, heating and preserving heat, and naturally cooling to room temperature; washing the solution with a mixed solution of ethanol and cyclohexane to obtain a core nanocrystal, and then preparing the core-shell nanocrystal by a layer-by-layer epitaxial growth method; removing oleic acid ligand on the surface of the core-shell nanocrystal by acid treatment to convert the core-shell nanocrystal into hydrophilic nanocrystal; preparing IR-806 organic dye by adopting a standard Schlenk technology, and then obtaining the core-shell nanocrystal coated by the organic dye through compounding. The method has the advantages of low preparation cost and high yield, and the product has the characteristics of showing high-efficiency single-band red light emission under the excitation condition of 800 nanometers.

Description

Efficient single-spectrum band-up-conversion red light nanocrystalline material

Technical Field

The invention belongs to the field of inorganic luminescent materials, and particularly relates to a single-band up-conversion red light nanocrystalline material.

Background

Upconversion luminescence refers to the conversion of low energy photons in the long wavelength region into high energy photons in the short wavelength region by absorption of two or more photons, a nonlinear optical process. The excitation source of the up-conversion luminescent nano material is usually near-infrared laser, has the characteristics of deep penetration depth, no spontaneous background fluorescence, excellent signal to noise ratio and the like in the cell imaging process, and can be used for preparing the up-conversion luminescent nano materialTo improve the sensitivity and spatial resolution of biological imaging. The main research system at present is rare earth ion doped fluoride nanocrystalline generating multiband emission under excitation of 980nm laser, which has many defects in the field of biological imaging, for example, firstly, although the excitation light source is positioned in the near infrared region, the excitation light source can realize larger penetration depth, and the up-conversion luminescence rare earth ion (Er) is commonly used ³⁺ ，Ho ³⁺ ，Tm ³⁺ ) The emission waveband of the light source is mainly green light (550 nm) or blue light (475 nm), and the red light and the near infrared light at the waveband of 600-1000nm are relatively weak, so that the emitted light is difficult to penetrate through deeper biological tissues, and the change of laser power, biological tissue depth and the like can generate different influences on different emission wavebands, thereby generating chromatic aberration and finally influencing the biological imaging effect; secondly, water molecules in the biological tissue have strong absorption near 980nm, so that the penetration depth of 980nm laser is greatly reduced, and the water molecules in the biological tissue absorb a large amount of photon energy with the wavelength of 980nm to generate local heat energy, so that the biological tissue is damaged; thirdly, since the photon absorption process of the trivalent rare earth ions is forbidden transition, the transition probability is very low, and the corresponding absorption band is very narrow, so that the up-conversion luminescence efficiency is very low, usually less than 1%. Therefore, the novel efficient single-spectrum band-up conversion red light nanocrystalline material is prepared by effectively regulating and controlling the material structure, and the development of the up conversion luminescence nanocrystalline material in the field of biological imaging is facilitated.

Disclosure of Invention

The invention discloses a novel efficient single-band up-conversion red light nano material, which is prepared by firstly preparing NaErF by adopting a coprecipitation method ₄ Gd/Tm nuclear nanocrystalline, adopts layer upon layer epitaxial growth method to prepare NaErF ₄ :Gd/Tm@NaYF ₄ Gd nucleocapsid nanometer crystal, then changing the nucleocapsid nanometer crystal from hydrophobic to hydrophilic by acid treatment, preparing IR-806 organic dye by utilizing standard Schlenk technology, obtaining the nucleocapsid nanometer crystal coated by the organic dye by compounding, because the absorption of the organic dye near 800 nanometers is far higher than that of Er ³⁺ Ions and photons absorbed by the organic dye can be effectively transferred to Er ³⁺ Ion at 800nmUnder the excitation condition of a rice laser, bright single-band up-conversion red light emission is generated.

In order to realize the purpose, the technical scheme adopted by the invention is as follows:

the efficient single-band up-conversion red light nanocrystalline material adopting the technical scheme has a chemical formula of NaErF ₄ :Gd/Tm@NaYF ₄ Gd @ IR-806. Gd in the nucleus ³⁺ Ion substituted Er ³⁺ Ions, while enhancing the absorption of the nano-crystal to incident light, weaken Er ³⁺ Obtaining the best Er by the radiationless cross relaxation probability between ions ³⁺ Ion doping concentration; tm in the nucleus ³⁺ Ion for promoting Er ³⁺ : ⁴ I _11/2 → ⁴ I _13/2 The red-green ratio is improved by the radiationless relaxation process; gd ions in the shell layer are used for enhancing the interaction between IR-806 molecules; IR-806 is used to greatly enhance the nanoparticle's absorption cross section for incident photons. Under this condition, a high efficiency single band red light emission of 800nm excitation is achieved. The preparation method adopts a layer-by-layer epitaxial growth method to prepare the core-shell nano material and further compound the IR-806 organic dye, and has the advantages of low cost, high yield, good product dispersibility, uniform shape and high-efficiency single-band red light emission excited by 800 nanometers. The single-band red-light nanocrystalline material designed by the patent has the characteristics of deeper penetration depth and high resolution in the biological imaging process, and can greatly promote the development of the up-conversion luminescent nanomaterial in the biological imaging field.

Drawings

FIG. 1: core-shell nanocrystalline NaErF ₄ :Gd/Tm@NaYF ₄ X-ray diffraction pattern of Gd;

FIG. 2: nuclear nanocrystal NaErF ₄ Transmission electron micrographs of Gd/Tm;

FIG. 3: core-shell nanocrystalline NaErF ₄ :Gd/Tm@NaYF ₄ Transmission electron micrographs of Gd;

FIG. 4: (a) Comparative example NaErF ₄ :Gd/Tm@NaYF ₄ Gd and (b) in the examples NaErF ₄ :Gd/Tm@NaYF ₄ Gd @ IR806 upconverted luminescence spectra under the excitation condition of 800nm laser.

Detailed Description

This patent is further described below in conjunction with fig. 1-4.

Comparative example

800nm excited single-band red light nano material NaErF ₄ :Gd/Tm@NaYF ₄ Gd comprises the following steps in sequence: (a) Adding 0.75 mmol of erbium acetate, 0.05 mmol of thulium acetate, 0.2 mmol of gadolinium acetate, 25 mmol of oleic acid and 30 mmol of octadecene into a three-neck bottle, and preserving the temperature at 160 ℃ for 50 minutes under the protection of argon to obtain an anhydrous transparent solution A; (b) After the solution A is naturally cooled to room temperature, 8 ml of methanol solution containing 4 mmol of ammonium fluoride and 2 mmol of sodium hydroxide is dropwise added into the solution A, and then the temperature is kept at 80 ℃ for half an hour; (c) After the methanol solution is completely volatilized, heating to 300 ℃, preserving the heat for 90 minutes at the temperature, and naturally cooling to room temperature; (d) Washing the nanocrystalline obtained in the step (c) by using a mixed solution of ethanol and cyclohexane, and then storing the core nanocrystalline in 4 ml of cyclohexane for later use; (e) Adding 0.3 mmol of gadolinium acetate, 0.7 mmol of yttrium acetate, 25 mmol of oleic acid and 30 mmol of octadecene into a three-neck bottle, and preserving the temperature at 160 ℃ for 60 minutes under the protection of argon gas to obtain an anhydrous transparent solution B; (f) After the solution B is naturally cooled to 60 ℃, the core nanocrystals in the step (d) are dropwise added into the solution B, and then the temperature is maintained at 100 ℃ for 40 minutes; (g) After the solution is naturally cooled to room temperature, 8 ml of methanol solution containing 4 mmol of ammonium fluoride and 2 mmol of sodium hydroxide is added dropwise, and then the temperature is kept for half an hour at 80 ℃; (h) After the methanol solution is completely volatilized, heating to 290 ℃, preserving the heat for 90 minutes at the temperature, and naturally cooling to room temperature; (i) Washing the obtained nano-crystal with a mixed solution of ethanol and cyclohexane, and finally drying at 30-60 ℃ to obtain a final product.

NaErF prepared by the above method ₄ :Gd/Tm@NaYF ₄ Gd nanocrystals, powder X-ray diffraction analysis shows that the synthesized product is pure hexagonal phase (figure 1); transmission electron microscope observation shows that the core nanocrystal is monodisperse uniform nanoparticles with the size of about 50 nanometers (figure 2), and the shape of the core shell is a single componentDispersed uniform nanoparticles, approximately 75nm in size (fig. 3); almost no Er was observed under the irradiation of 800nm laser ³⁺ In the red wavelength band (fig. 4 a).

Examples

An efficient single-band up-conversion red light nanocrystalline material with a chemical formula of NaErF ₄ :Gd/Tm@NaYF ₄ :Gd@IR806。

NaErF ₄ :Gd/Tm@NaYF ₄ The preparation method of Gd @ IR806 sequentially comprises the following steps: (1) Adding 0.75 mmol of erbium acetate, 0.05 mmol of thulium acetate, 0.2 mmol of gadolinium acetate, 25 mmol of oleic acid and 30 mmol of octadecene into a three-neck flask, and preserving the temperature at 160 ℃ for 50 minutes under the protection of argon to obtain an anhydrous transparent solution A; (2) After the solution A is naturally cooled to room temperature, 8 ml of methanol solution containing 4 mmol of ammonium fluoride and 2 mmol of sodium hydroxide is dropwise added into the solution A, and then the solution A is kept at 80 ℃ for half an hour; (3) After the methanol solution is completely volatilized, heating to 300 ℃, preserving the heat for 90 minutes at the temperature, and naturally cooling to room temperature; (4) Washing the core nanocrystal obtained in the step (3) by using a mixed solution of ethanol and cyclohexane to obtain a nanocrystal core, and storing the nanocrystal core in 4 ml of cyclohexane for later use; (5) Adding 0.3 mmol of gadolinium acetate, 0.7 mmol of yttrium acetate, 25 mmol of oleic acid and 30 mmol of octadecene into a three-necked bottle, and preserving the temperature at 160 ℃ for 60 minutes under the protection of argon to obtain an anhydrous transparent solution B; (6) After the solution B is naturally cooled to 60 ℃, dropwise adding the core nanocrystals obtained in the step (d) into the solution B, and then preserving the heat at 100 ℃ for 40 minutes; (7) After the solution is naturally cooled to room temperature, 8 ml of methanol solution containing 4 mmol of ammonium fluoride and 2 mmol of sodium hydroxide is added dropwise, and then the temperature is kept for half an hour at 80 ℃; (8) After the methanol solution is completely volatilized, heating to 290 ℃, preserving the heat for 90 minutes at the temperature, and naturally cooling to room temperature; (9) Washing and centrifuging by using mixed solution of ethanol and cyclohexane to obtain core-shell nanocrystals, and then storing the obtained core-shell nanocrystals in 4 ml of cyclohexane for later use; (10) Performing ultrasonic treatment on the core-shell nanocrystal obtained in the step (9) for 5 minutes by using a mixed solution of 1 ml of ethanol and 1 ml of hydrochloric acid, wherein the concentration of the hydrochloric acid is 0.2 mol/L,then washing with a mixed solution of ethanol and deionized water, and storing for later use; (11) Dissolving 1 mmol of IR-780 iodide and 2.5 mmol of p-mercaptobenzoic acid in 10 ml of dimethylformamide, stirring at room temperature for 15 hours, and filtering with a 0.45-micron needle filter to obtain a product IR-806; (12) And (3) dissolving 100 mg of the core-shell nanocrystal obtained in the step (10) and IR-8062 mg obtained in the step (11) in 3 ml of trichloromethane solution, stirring for 2 hours under the condition of nitrogen protection and room temperature, and finally centrifuging to obtain the high-efficiency single-band converted red light nanocrystal material.

NaErF prepared by the above method ₄ :Gd/Tm@NaYF ₄ Gd @ IR806 nanocrystalline shows Er under 808 nanometer laser irradiation ³⁺ Bright single-band red emission around 650nm (fig. 4 b). Compared with the comparative example, the organic dye IR806 is used for preparing the nano-crystalline NaErF with the core-shell ₄ :Gd/Tm@NaYF ₄ Gd is effectively compounded, because IR806 has a very large absorption cross section near 800nm, and absorbed energy can be effectively transferred to Er ³⁺ Ions, and thus a bright single band up-converted red emission. Compared with the comparative example, the up-conversion luminescence intensity in the example is improved by more than three orders of magnitude.

The invention adopts a coprecipitation method to prepare NaErF firstly ₄ Gd/Tm nuclear nanocrystalline, and then adopts epitaxial growth method to prepare NaErF ₄ :Gd/Tm@NaYF ₄ Gd core-shell nanocrystalline is treated by acid to remove oleic acid ligand on the surface of the core-shell nanocrystalline, so that the Gd core-shell nanocrystalline is converted into hydrophilic nanocrystalline, IR-806 organic dye is prepared by adopting a standard Schlenk technology, and then the core-shell nanocrystalline coated by the organic dye is obtained by compounding. The organic dye can efficiently absorb 800 nanometer photons to obtain bright single-band up-conversion red light emission. The invention is characterized in that the NaErF coated with the organic dye IR-806 is obtained by surface modification ₄ :Gd/Tm@NaYF ₄ Gd core-shell nanocrystals, IR-806 used to greatly enhance the nanoparticle absorption cross section to incident photons, gd ions in the shell layer used to greatly enhance the IR-806 intermolecular interaction, and further achieve 800nm excited high-efficiency single-band up-conversion red light emission.

Claims

1. An efficient single-band up-conversion red light nanocrystalline material is characterized in that the chemical formula is as follows: naErF4: gd/Tm @ NaYF4: gd @ IR-806.

2. The efficient single band up-conversion red light nanocrystal material of claim 1, wherein the nanocrystal material is an 800nm excited single band up-conversion red light nanocrystal material.

3. The efficient single-spectrum band-pass conversion red light nanocrystalline material of claim 1, characterized in that NaErF4: gd/Tm core nanocrystalline is prepared by a coprecipitation method, then NaErF4: gd/Tm @ NaYF4: gd core shell is prepared by an epitaxial growth method, and finally organic dye IR-806 is coated.