Near-infrared benzothiadiazole dye-sensitized upconversion luminescent probe and preparation method thereof

Abstract

The application discloses a kind of near-infrared benzothiadiazole dye sensitized rare earth upconversion luminescence nano-probes and preparation method thereof;Probe is composed of near-infrared benzothiadiazole dye and upconversion nanoparticle, benzothiadiazole dye is compounded with ligand-free lanthanide ion doped upconversion nanoparticle, and upconversion luminescence is enhanced.This application preparation method is simple, and it does not involve complex core-shell structure and energy migration process, benzothiadiazole dye is directly compounded with ligand-free rare earth nanoparticle, and upconversion luminescence nano-probe is formed, under the irradiation of 808nm laser, the emission spectrum of benzothiadiazole dye and the absorption spectrum of sensitizer ion in upconversion nanoparticle overlap, which can effectively enhance the upconversion luminescence intensity of nano-probe, and keep good light stability, keep more than 90% of initial luminescence intensity under the irradiation of 120 minutes excitation light.

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials, specifically relating to a near-infrared dye-sensitized upconversion luminescent probe. Background Technology

[0002] Lanthanide ion-doped upconversion nanoparticles are an important class of optical materials that absorb low-energy near-infrared light and emit high-energy visible or ultraviolet light. They possess characteristics such as narrow emission peaks, large anti-Stokes shift, long luminescence lifetime, and high photostability, making them promising for applications in bioluminescence imaging, photodynamic therapy, information storage, and optogenetics. However, realizing the practical application of upconversion nanoparticles still faces many challenges, primarily due to their weak luminescence. Lanthanide ions have small absorption cross-sections in the near-infrared region; for example, the commonly used sensitizer ion Yb... 3+ Its absorption range is 980-1023 nm, and its absorption cross-section is only ~10. -20 cm 2 Its efficiency is three to four orders of magnitude lower than that of organic dyes, which results in low upconversion luminescence efficiency and weak luminescence.

[0003] In recent years, sensitizing upconversion nanoparticles with organic dyes has been an effective method to enhance the intensity of upconversion luminescence. In 2012, Zou et al. first used IR-806 dye to sensitize the upconversion luminescence of NaYF4:Yb,Er nanoparticles, achieving luminescence intensities similar to those under irradiation at 808 nm (2 mW, corresponding to the dye's absorption band, where the upconversion nanoparticles show no absorption). In 2022, Liu et al. used indocyanine green (ICG) to sensitize multilayer core-shell upconversion nanoparticles, simultaneously enhancing both ultraviolet and near-infrared luminescence. However, commonly used organic dyes exhibit poor photostability, leading to luminescence quenching when irradiated for extended periods. Summary of the Invention

[0004] The technical problem solved by this invention is the poor photostability of near-infrared dye-sensitized rare-earth upconversion luminescent probes. This invention provides a near-infrared dye-sensitized rare-earth upconversion luminescent probe with high luminescence intensity and high photostability, along with its preparation method. This invention uses a near-infrared benzothiadiazole dye with a donor-acceptor-donor (DAD) structure to sensitize upconversion nanoparticles. The preparation method of this invention is simple, involving the direct reaction of the benzothiadiazole dye with lanthanide ions (Ln). 3+ The oscillating recombination of doped NaYF4-based upconversion nanoparticles avoids the use of complex core-shell structured upconversion nanoparticles. The emission spectrum of the benzothiadiazole dye overlaps well with the absorption spectrum of the sensitizer ions in the upconversion nanoparticles, achieving high luminescence intensity and high photostability under near-infrared light excitation.

[0005] The technical solution provided by this invention is as follows.

[0006] This invention provides a near-infrared benzothiadiazole dye-sensitized upconversion luminescent probe, wherein the upconversion nanoparticles are lanthanide ions (Ln). 3+ The doped NaYF4-based upconversion nanoparticles, with benzothiadiazole dyes possessing a DAD structure (where triphenylamine is the electron donor D and benzothiadiazole is the electron acceptor A), contain carboxylic acid groups that bind to lanthanide ions in the rare-earth upconversion luminescent particles. Their structure is as follows:

[0007] In the above structure, the lanthanide ion Ln 3+ The doped NaYF4-based upconversion nanoparticles, namely NaYF4:Yb,Ln, where Yb is the sensitizer and Ln is the activator, exhibit high-intensity luminescence when combined with benzothiadiazole dyes. Under near-infrared light excitation, energy transfer occurs via the pathway benzothiadiazole dye → Yb → Ln, avoiding the energy transfer mechanisms and complex synthesis processes found in core-shell structures. Furthermore, the benzothiadiazole dye molecules possess excellent stability, enabling sustained luminescence with high photostability.

[0008] In this invention, the preparation method of the near-infrared benzothiadiazole dye-sensitized rare-earth upconversion luminescent probe is as follows: A. Synthesis of benzothiadiazole dyes; B. Preparation of Ln by thermal coprecipitation 3+ Doped NaYF4-based upconversion nanoparticles NaYF4:Yb,Ln; C. Acid treatment method to remove oleic acid ligands from the surface of upconversion nanoparticles; D. Combining ligandless upconversion nanoparticles with near-infrared organic dyes by oscillation.

[0009] The beneficial effects of this invention are as follows:

[0010] (1) This invention provides a novel near-infrared benzothiadiazole dye-sensitized upconversion luminescence probe, which achieves enhanced dye-sensitized luminescence by complexing a benzothiadiazole dye onto the surface of ligand-free rare-earth upconversion nanoparticles, at 197 W / cm². 2 The 808nm excitation source can achieve an upconversion emission spectrum enhancement factor of 42 times;

[0011] (2) The rare earth upconversion nanoparticles used in this method do not involve core-shell structures, the synthesis process is simple, and the composite method with benzothiadiazole dyes is simple.

[0012] (3) Compared with cyanine dyes, the benzothiadiazole dyes of the present invention exhibit high photostability. Attached Figure Description

[0013] The accompanying drawings are intended to provide a further understanding of the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0014] In the attached diagram:

[0015] Figure 1 This is a transmission electron microscope image of the NaYF4:Yb,Er (20:2mol%) nanoparticles in Example 2.

[0016] Figure 2 The image shows the X-ray diffraction pattern of the NaYF4:Yb,Er (20:2mol%) nanoparticles in Example 3.

[0017] Figure 3 This is a transmission electron microscope image of the ligand-free NaYF4:Yb,Er (20:2mol%) nanoparticles in Example 4.

[0018] Figure 4 The ultraviolet absorption spectrum and emission spectrum under 808nm laser excitation of the near-infrared dye CH1055 used in Example 4 are shown.

[0019] Figure 5 The Fourier transform infrared spectrum is shown for the material obtained by combining the near-infrared dye CH1055 with ligandless NaYF4:Yb,Er (20:2mol%) nanoparticles in Example 4.

[0020] Figure 6 The emission spectrum of the near-infrared dye CH1055 after being combined with ligandless NaYF4:Yb,Er (20:2mol%) nanoparticles in Example 4 is shown. The excitation light was an 808nm laser.

[0021] Figure 7 The emission spectra and luminescence enhancement factors of near-infrared dye CH1055 and ligandless NaYF4:Yb,Er (20:2mol%) nanoparticles in Example 4 were measured after oscillation for different times. The excitation light was an 808nm laser.

[0022] Figure 8 In Example 4, different volumes of near-infrared dye CH1055 were added and ligand-free NaYF4:Yb,Er (20:2 mol%) nanoparticles were oscillated and mixed. The emission spectrum and luminescence enhancement factor were then measured. The excitation light was an 808 nm laser.

[0023] Figure 9In Example 4, 40 μL of near-infrared dye CH1055 (0.5 mg / mL DMF solution) and ligandless NaYF4:Yb,Er (20:2 mol%) nanoparticles were added and shaken for 2040 minutes. The change in upconversion luminescence intensity with light irradiation time was observed, and the excitation light was an 808 nm laser. Detailed Implementation

[0024] The specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0025] This invention utilizes near-infrared benzothiadiazole dyes (CH1055) to sensitize lanthanide ion-doped upconversion nanoparticles. Example 1 prepared benzothiadiazole dyes; Example 2 prepared NaYF4:Yb,Er (20:2 mol%) nanoparticles; Example 3 prepared ligand-free upconversion nanoparticles; and Example 4 prepared benzothiadiazole dye (CH1055)-sensitized upconversion luminescent probes.

[0026] Example 1

[0027] Synthesis of benzothiadiazole dyes (CH1055, 1a)

[0028] 6.7 g (13 mmol) of compound (2a), 3.84 g (10 mmol) of compound (3), 0.5246 g (2 mmol) of triphenylphosphine, and 2.12 g (20 mmol) of sodium carbonate were added to a 50 mL round-bottom flask. Under nitrogen protection, 30 mL of toluene / water mixture (v / v, 8:2) was added. Nitrogen gas was bubbled into the reaction solution to purge oxygen for 20 minutes, and then 1.1556 g (1 mmol) of tetrakis(triphenylphosphine)palladium was added. Nitrogen gas was bubbled into the reaction solution for another 10 minutes. The reaction was heated under reflux for 2-4 h under nitrogen protection. After the reaction was complete, ethyl acetate (EA) (15 mL × 3) was added for extraction three times. The organic phases were combined and washed twice with water (10 mL × 2). The organic phase was dried over anhydrous magnesium sulfate for 1 h, filtered, and the filtrate was evaporated to dryness and passed through a silica gel column to obtain reaction intermediate (4a).

[0029] 6.7 g (13 mmol) of compound (2a), 6.94 g (10 mmol) of reaction intermediate (4a), 0.5246 g (2 mmol) of triphenylphosphine, and 2.12 g (20 mmol) of sodium carbonate were added to a 50 mL round-bottom flask. Under nitrogen protection, 30 mL of toluene / water mixture (v / v, 8:2) was added. Nitrogen gas was bubbled into the reaction solution for 20 minutes to purge oxygen, and then 1.1556 g (1 mmol) of tetrakis(triphenylphosphine)palladium was added. Nitrogen gas was bubbled into the reaction solution for another 10 minutes. The nitrogen gas was removed, and the mixture was heated under reflux for 36 h. After the reaction was completed, ethyl acetate (15 mL × 3) was added for extraction three times. The organic phases were combined and washed twice with water (10 mL × 2). The organic phase was dried over anhydrous magnesium sulfate for 1 h, filtered, and the filtrate was evaporated to dryness and passed through a silica gel column to obtain reaction intermediate (6a).

[0030] 10.03 g (10 mmol) of reaction intermediate (6a) and 6.72 g (120 mmol) of reduced iron powder were added to a 50 mL round-bottom flask. Under nitrogen protection, 20 mL of glacial acetic acid was added, and the mixture was reacted at 100 °C for 5 h with mechanical stirring. After the reaction was completed, sodium carbonate was added to adjust the pH to 8, and ethyl acetate (25 mL × 3) was added for extraction three times. The organic phases were combined and washed twice with water (15 mL × 2). The organic phase was dried over anhydrous magnesium sulfate for 2 h, filtered, and the filtrate was evaporated to dryness. 12 mL of anhydrous pyridine was added to the concentrated filtrate, and the reaction system was protected with argon. 5.568 g (40 mmol) of N-sulfinylaniline was then added and stirred until homogeneous. The reaction was carried out at 80 °C for 5 min, then allowed to return to room temperature. Under argon protection, 100 mmol of trimethylchlorosilane was added to the reaction system. The mixture was stirred until homogeneous, and the reaction was carried out at 80 °C for 5 h under argon protection. After the reaction was completed, the reaction solution was evaporated to dryness under reduced pressure, and then dissolved in 30 mL of dichloromethane. The dichloromethane phase was washed sequentially with 20 mL of 1 N hydrochloric acid solution, 20 mL of 1 M sodium bicarbonate solution, and 20 mL of water. The washed dichloromethane phase was then dried with anhydrous magnesium sulfate for 2 hours. Finally, it was filtered, concentrated under reduced pressure, and passed through a silica gel column to obtain a benzothiadiazine dye (CH1055), i.e., 1a. 1 H NMR (400MHz, DMSO) δ8.10(d,J=7.9Hz,4H), 7.24(d,J=7.6Hz,8H), 7.08(d,J=7.8Hz,12H), 2.83(t,J=7.1Hz,8H), 2.56(t,J=7.4Hz,8H); 13 C NMR (101MHz, DMSO) δ174.26, 152.44, 145.17, 138.81, 137.03, 136.39, 133.37, 130.01, 128.41, 125.45, 120.81, 35.62, 30.27.

[0031] Example 2

[0032] Preparation of NaYF4:Yb,Er (20:2 mol%) nanoparticles

[0033] 1.56 mL of yttrium acetate aqueous solution (Y(Ac)3, 0.2 mol / L), 0.4 mL of ytterbium acetate aqueous solution (Yb(Ac)3, 0.2 mol / L), 0.04 mL of thulium acetate aqueous solution (Er(Ac)3, 0.2 mol / L), and 3 mL of oleic acid were added to a 50 mL double-necked round-bottom flask. The flask was then placed in a silicone oil bath, and heating was started at 130 °C with stirring at 300 rpm for 30 minutes. The oil bath temperature was then increased to 150 °C, and stirring was continued at 300 rpm for 30 minutes. After 30 minutes, 7 mL of 1-octadecene was added, and stirring was continued at 300 rpm for 30 minutes. Heating was then turned off, stirring continued, and the mixture was cooled to room temperature to obtain the precursor solution.

[0034] The flask containing the precursor was fixed to a heating mantle and stirred steadily. A mixture of 2 mmol ammonium fluoride-methanol solution and 1 mmol sodium hydroxide-methanol solution was poured into the flask, and the mixture was stirred at 45°C for 30 minutes. After 30 minutes, the temperature was increased to 100°C. Vacuum was then applied until no more bubbles appeared, at which point nitrogen gas was introduced. Vacuuming was repeated until no more bubbles appeared in the flask (the entire process took approximately 10 minutes). Nitrogen gas was then introduced, and the reaction temperature was set to 290°C for 2 hours. The heating was then turned off while stirring continued. After cooling to room temperature, anhydrous ethanol was added as a precipitant, and the mixture was centrifuged at 6000 rpm for 5 minutes. The precipitate was washed twice with cyclohexane and anhydrous ethanol to obtain NaYF4:Yb,Er (20:2 mol%) nanoparticles, which were dispersed in 4 mL of cyclohexane.

[0035] Example 3

[0036] Preparation of ligand-free NaYF4:Yb,Er (20:0.2 mol%) nanoparticles

[0037] Take 0.8 mL of the nanoparticles obtained in Example 2 into a centrifuge tube, add 0.8 mL of anhydrous ethanol, shake well, and centrifuge at 16000 rpm for 5 minutes. Take the precipitate, sonicate it in 0.8 mL of anhydrous ethanol, add 0.8 mL of dilute hydrochloric acid (0.1 mol / L), sonicate again for 10 seconds, shake well, and centrifuge at 16000 rpm for 5 minutes. After centrifugation, discard the supernatant, disperse the precipitate in 0.8 mL of anhydrous ethanol, add 0.2 mL of dilute hydrochloric acid (0.1 mol / L), shake well, and centrifuge at 16000 rpm for 5 minutes. Disperse the precipitate in 1 mL of N,N-dimethylformamide (DMF) to obtain a ligand-free upconversion nanoparticle-DMF solution for subsequent experiments.

[0038] Take a 1mL glass bottle, place it in a 70℃ drying oven and heat for 30 minutes. Then remove it, cool it to room temperature, and weigh it, recording the mass as m1. Take 0.1mL of the ligandless upconversion nanoparticle solution from Example 2 into the above glass bottle, place it in a 120℃ drying oven and heat for 8 hours. Then remove it, cool it to room temperature, and weigh it, recording the mass as m2. Calculate the mass concentration of the ligandless upconversion nanoparticle-DMF solution from Example 2 based on m1 and m2.

[0039] Example 4

[0040] Preparation of benzothiadiazole dye (CH1055) sensitized upconversion luminescent probe

[0041] Preparation of a 1 mg / mL ligand-free upconversion nanoparticle-DMF solution: Take 2 mg of the ligand-free upconversion nanoparticle-DMF solution obtained in Example 2, and add DMF to a final volume of 2 mL. Preparation of a 0.516 mmol / L near-infrared benzothiadiazole dye (CH1055)-DMF solution: Weigh 0.5 mg of CH1055 and pour it into a 5 mL brown glass bottle, add 1 mL of DMF, shake for 10 minutes, and store at 4°C. The relative molecular mass of CH1055 is 968.4 g / mol, and the molar concentration of the CH1055-DMF solution is calculated to be 0.516 mmol / L.

[0042] Add 2 mL of ligand-free upconversion nanoparticle-DMF solution (1 mg / mL) to a brown glass bottle, then add 0.01 mL of CH1055-DMF solution (0.516 mmol / L). After shaking for different times, obtain a benzothiadiazole dye (CH1055) sensitized upconversion luminescent probe. After centrifugation and drying, measure the infrared spectrum, as shown in the attached figure. Figure 5 As shown, the successful composite of benzothiadiazole dye (CH1055) and upconversion nanoparticles is demonstrated.

[0043] 2 mL of ligand-free upconversion nanoparticle-DMF solution (1 mg / mL) was added to a brown glass bottle, followed by 0.04 mL of CH1055-DMF solution (0.516 mmol / L). After shaking for different times, a benzothiadiazole dye (CH1055)-sensitized upconversion luminescent probe was obtained. Its emission spectrum was measured at shaking times of 25, 35, 630, 720, 1020, 1320, 2040, and 2160 minutes, with an excitation light of 197 W / cm². 2 The 808nm laser. (Attached) Figure 6 The emission spectra of the luminescent probe and the dye-free upconversion nanoparticles after oscillation for 2040 minutes are shown in the attached figure. Figure 7 The results showed that sufficient oscillation allowed the dye to fully recombine with the upconversion nanoparticles, and the luminescence intensity was highest at 2040 minutes of oscillation.

[0044] 2 mL of ligand-free upconversion nanoparticle-DMF solution (1 mg / mL) was added to a brown glass bottle. Different volumes of CH1055-DMF solution (0.516 mmol / L) were then added (0.005, 0.01, 0.015, 0.02, 0.04, and 0.08 mL, respectively). After shaking for 20-40 minutes, a benzothiadiazole dye (CH1055)-sensitized upconversion luminescent probe was obtained. Its emission spectrum was measured; the excitation light was 197 W / cm². 2 The 808nm laser. (Attached) Figure 8 The results show that the luminescence intensity is highest when the volume of CH1055-DMF solution (0.516 mmol / L) is 0.04 mL, and the upconversion luminescence spectrum enhancement factor can reach 42 times compared with the upconversion nanoparticles without composite dye.

[0045] 2 mL of ligand-free upconversion nanoparticle-DMF solution (1 mg / mL) was added to a brown glass bottle, followed by CH1055-DMF solution (0.516 mmol / L), bringing the volume to 0.04 mL. After shaking for 20-40 minutes, a benzothiadiazole dye (CH1055) sensitized the upconversion luminescent probe. The change in upconversion luminescence intensity with light irradiation time was tested, with an excitation light intensity of 197 W / cm². 2 The 808nm laser. (Attached) Figure 9 The results showed that after 120 minutes of continuous irradiation, the luminescence intensity was 90% of the initial luminescence intensity, maintaining good luminescence stability.

[0046] Example 5

[0047] By replacing Er with Tm in Examples 2, 3, and 4, while keeping all other steps unchanged, a CH1055-NaYF4:Yb,Tm upconversion luminescent probe with high luminescence intensity and high photostability was obtained. Compared with unsensitized NaYF4:Yb,Tm (20:0.2mol%) upconversion nanoparticles, the upconversion luminescence spectrum enhancement factor can reach 40 times. (Using 197 W / cm²) 2 After irradiation with an 808nm laser for 120 minutes, its luminous intensity remained at 92% of the initial luminous intensity.

[0048] Example 6

[0049] By replacing Er with Ho in Examples 2, 3, and 4, while keeping all other steps unchanged, a CH1055-NaYF4:Yb,Ho upconversion luminescent probe with high luminescence intensity and high photostability was obtained. Compared with unsensitized NaYF4:Yb,Ho (20:0.2 mol%) upconversion nanoparticles, the upconversion luminescence spectrum enhancement factor can reach 42 times, using 197 W / cm². 2After irradiation with an 808nm laser for 120 minutes, its luminous intensity remained at 91% of the initial luminous intensity.

Claims

1. A near-infrared benzothiadiazole dye-sensitized upconversion luminescent probe, characterized in that, It consists of benzothiadiazole dyes and upconversion nanoparticles. The benzothiadiazole dyes are combined with ligand-free lanthanide ion-doped upconversion nanoparticles to achieve enhanced upconversion luminescence. Among them, the lanthanide ion-doped upconversion nanoparticles are NaYF4:Yb,Ln, and the structural formula of the near-infrared benzothiadiazole dyes is as follows:

2. The near-infrared benzothiadiazole dye-sensitized upconversion luminescent probe according to claim 1, characterized in that, In lanthanide ion-doped upconversion nanoparticles NaYF4:Yb,Ln, Ln is Er, Tm, or Ho.

3. The near-infrared benzothiadiazole dye-sensitized upconversion luminescent probe according to claim 1, characterized in that, In the lanthanide ion-doped upconversion nanoparticles NaYF4:Yb,Ln, Ln is represented by Er.

4. A method for preparing a near-infrared benzothiadiazole dye-sensitized rare-earth upconversion luminescent probe according to claim 1, characterized in that, This includes the synthesis of benzothiadiazole molecules, the synthesis of lanthanide ion-doped upconversion nanoparticles, the removal of oleic acid ligands from the surface of upconversion nanoparticles by acid treatment, and the formation of luminescent probes by oscillation of ligand-free upconversion nanoparticles with near-infrared benzothiadiazole dyes.

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