Near-infrared organic scintillator material based on phosphorescent resonance energy transfer mechanism and preparation method thereof

Abstract

The invention belongs to the technical field of organic luminescent materials, and discloses a near-infrared organic scintillator material and a preparation method thereof. On the basis of a phosphorescent resonance energy transfer mechanism, an organic phosphorescent scintillator o-ITC crystal is used as an energy donor, and a near-infrared fluorescent illuminant RB or BBT-TPA is used as an energy receptor. The preparation method comprises the following steps: dissolving a near-infrared fluorescent illuminant material in an organic solvent, then adding an organic phosphorescent scintillator, and removing the solvent by using a vacuum rotary evaporator under specific conditions to finally obtain near-infrared organic scintillator materials: RB (at) o-ITC and BBT-TPA (at) o-ITC. The material effectively prolongs the light-emitting wavelength of an organic scintillator, the maximum radiation light-emitting wavelength of the BBT-TPA (at) o-ITC material reaches 920 nm, and the BBT-TPA (at) o-ITC material has wide application prospects in the fields of X-ray imaging, organic light-emitting diodes, biological imaging, advanced encryption and anti-counterfeiting, information memories and the like.

Description

Technical Field

[0001] The invention belongs to the field of organic luminescent materials, and in particular relates to near-infrared organic scintillator materials based on phosphorescence resonance energy transfer mechanism. Background Art

[0002] Scintillator materials are a type of material that can convert high-energy ionizing radiation energy of radioactive rays (X-rays) into low-energy visible photons. These materials are widely used in many fields such as medical diagnosis, industrial non-destructive testing, and safety inspection. During the radiographic imaging process, radioactive rays penetrate the imaging object and irradiate the scintillator screen. The scintillator material emits light and is detected by the detector, thereby displaying the structural or functional information of the detection object in the form of an image, providing technical means for diagnosis and detection of various observation objects.

[0003] In the prior art, CN112174941B discloses an organic compound containing halogen heavy atoms, which significantly improves the absorption efficiency of high-energy rays and the utilization efficiency of triplet excitons, thereby achieving a higher quantum yield, excellent luminescence performance and stability, while maintaining low biological toxicity. CN116693366A discloses an organic hot exciton scintillator material, product and performance testing method, and the prepared organic scintillator material has the advantages of short luminescence lifetime and high light yield.

[0004] However, the luminescence wavelengths of the organic scintillator materials mentioned above are mainly concentrated in the visible light range, which makes them susceptible to interference from ambient light or biological spontaneous luminescence, reduces imaging quality, and limits application scenarios. Especially in the fields of biomedicine and imaging technology, luminescence in the visible light range may cause serious background noise problems, affecting the resolution and accuracy of the final image. In addition, the number of currently available near-infrared organic scintillator materials is limited, and the synthesis process is usually complicated and difficult to prepare on a large scale, which poses a challenge to the practical application of the materials. Therefore, developing a simple and easy preparation method to obtain organic scintillator materials with near-infrared luminescence characteristics will not only help overcome the limitations of existing materials, but also have important economic value for expanding their application potential in biomedicine, imaging technology and other fields. Summary of the invention

[0005] In view of the problem that the luminescent wavelength of organic scintillator materials in the prior art is limited to the ultraviolet or visible light range, the present invention provides a near-infrared organic scintillator material based on the phosphorescence resonance energy transfer mechanism and a preparation method thereof, wherein pure organic phosphorescence scintillator material is used as an energy donor and near-infrared (NIR) fluorescent luminescent dye is used as an energy acceptor, and efficient energy transfer is achieved through phosphorescence resonance energy transfer (PRET), thereby preparing a near-infrared organic scintillator material. The material effectively extends the luminescent wavelength of the organic scintillator, has room temperature phosphorescence characteristics in the near-infrared range, can significantly reduce biological background light, and improve imaging resolution and penetration depth.

[0006] According to one aspect of the present invention, a near-infrared organic scintillator material is provided. The near-infrared organic scintillator material includes RB@o-ITC or BBT-TPA@o-ITC.

[0007] Preferably, the host compound of the RB@o-ITC is o-ITC crystal, and the guest compound of the RB@o-ITC is RB.

[0008] Preferably, the host compound of the BBT-TPA@o-ITC is o-ITC crystal, and the guest compound of the BBT-TPA@o-ITC is BBT-TPA.

[0009] The o-ITC crystal has the structural formula shown below:

[0010]

[0011] The RB has the structural formula shown below:

[0012]

[0013] The BBT-TPA has the structural formula shown below:

[0014]

[0015] According to another aspect of the present invention, a method for preparing a near-infrared organic scintillator material based on a phosphorescence resonance energy transfer mechanism is provided, wherein an organic phosphorescent scintillator o-ITC crystal is used as an energy donor, and a near-infrared fluorescent luminescent body RB or BBT-TPA is used as an energy acceptor.

[0016] Preferably, the method comprises the following steps:

[0017] Step 1: dissolving the near-infrared fluorescent luminescent body RB or BBT-TPA in an organic solvent;

[0018] Step 2: Add the organic phosphorescent scintillator material o-ITC crystal, and mix it thoroughly by ultrasonic treatment for 10 minutes. Then, remove the solvent by using a vacuum rotary evaporator at 30°C to obtain a near-infrared organic scintillator material.

[0019] Preferably, the organic solvent includes but is not limited to dichloromethane.

[0020] Preferably, the emission spectrum of the organic phosphorescent scintillator overlaps with the absorption spectrum of the near-infrared fluorescent light-emitting dye.

[0021] Preferably, the organic phosphorescent scintillator includes but is not limited to o-ITC crystal.

[0022] The energy donor of the present invention is an organic phosphorescent scintillator molecule. After the X-ray source excites the internal electrons of the heavy atom, a large number of electron-hole pairs are first generated, and a large number of singlet excitons and triplet excitons are generated by recombination. Through intersystem crossing and internal conversion processes, phosphorescence is finally emitted from the lowest excited state energy level (T1). Through phosphorescence resonance energy transfer, the phosphorescence can be used as an excitation light source to excite fluorescent dye molecules to emit fluorescence.

[0023] Preferably, the o-ITC crystal can be replaced by a scintillator material with an acceptor energy level match as the energy donor of the present invention.

[0024] Preferably, the near-infrared fluorescent light-emitting dye is an aggregated fluorescence quenching molecule, and the aggregated fluorescence quenching molecule includes but is not limited to RB and BBT-TPA.

[0025] In the present invention, fluorescent luminescent materials are used as energy acceptors, wherein RB and BBT-TPA are aggregate fluorescence quenching (ACQ) molecules.

[0026] Preferably, RB and BBT-TPA can be replaced by other luminophores whose acceptor energy levels are precisely matched to the energy donor organic phosphorescent scintillator molecules.

[0027] Specifically, when the aggregated fluorescence quenching molecule is RB, BRB must be prepared in advance with an organic solvent into a dilute RB solution with a concentration of 1 mg / mL, and then the RB solution is accurately pipetted with a pipette and added to a glass vial containing an organic phosphorescent scintillator. Ultrasonic treatment is performed for 10 minutes to allow it to be fully mixed. Thereafter, the solvent is removed using a vacuum rotary evaporator at 30°C to obtain a near-infrared organic scintillator material.

[0028] Specifically, when the aggregated fluorescence quenching molecule is BBT-TPA, BBT-TPA must be prepared in advance with an organic solvent into a dilute BBT-TPA solution with a concentration of 0.1 mg / mL, and then the BBT-TPA solution is accurately pipetted with a pipette and added to a glass vial containing an organic phosphorescent scintillator. Ultrasonic treatment is performed for 10 minutes to allow it to be fully mixed, and then the solvent is removed using a vacuum rotary evaporator at 30°C to obtain a near-infrared organic scintillator material.

[0029] Specifically, the material-liquid ratio of the organic phosphorescent scintillator to the fluorescent luminescent body dilution solution (RB dilute solution and BBT-TPA dilute solution) is 30 mg:(6-30) μL respectively; further, the optimal material-liquid ratio is 30 mg:18 μL.

[0030] Preferably, the organic solvent includes but is not limited to dichloromethane. Other organic solvents that can effectively dissolve fluorescent light emitters are also suitable for the present invention.

[0031] Preferably, the ultrasonic treatment time in step 2 is (8-12) min; further, the ultrasonic treatment time is 10 min.

[0032] According to the preparation method of the present invention, near-infrared organic scintillator materials RB@o-ITC and BBT-TPA@o-ITC are obtained, wherein the maximum wavelength of the radiation luminescence of the BBT-TPA@o-ITC material is located at 920nm.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention adopts the phosphorescence resonance energy transfer mechanism to prepare near-infrared organic scintillator materials, that is, utilizes phosphorescence energy resonance transfer, uses organic phosphorescence scintillator as energy donor, and near-infrared fluorescent light emitter as energy acceptor, to prepare near-infrared organic scintillator materials. The method of the present invention realizes the red shift of the scintillator emission wavelength to the near-infrared region under X-ray excitation. In the prepared organic scintillator materials, the maximum wavelength of the radiation luminescence of the BBT-TPA@o-ITC material is located at 920nm. The near-infrared organic scintillator materials obtained based on this invention are expected to be applied to X-ray imaging, organic light-emitting diodes, biological imaging, advanced encryption and anti-counterfeiting, information storage and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate the embodiments and together with the description are used to explain the principles of the present invention. Other embodiments and many expected advantages of the embodiments will be readily appreciated as they become better understood by reference to the following detailed description.

[0036] Figure 1 A schematic diagram of the luminescence process of an organic near-infrared scintillator based on the phosphorescence resonance energy transfer mechanism is shown;

[0037] Figure 2 The phosphorescence spectrum of o-ITC crystal and the absorption spectrum of RB and BBT-TPA dilute solutions are shown;

[0038] Figure 3 The photoluminescence spectra of the sample powder systems with different energy acceptor doping mass fractions are shown (a is RB / o-ITC; b is BBT-TPA / o-ITC);

[0039] Figure 4 The lifetime measurement results, energy transfer efficiency and photoluminescence quantum yield measurement results of sample powder systems with different RB doping mass fractions are shown;

[0040] Figure 5 The results of lifetime measurement, energy transfer efficiency and photoluminescence quantum yield measurement of sample powder systems with different BBT-TPA doping mass fractions are shown;

[0041] Figure 6 Powder XRD spectra of samples with different energy acceptor doping mass fractions are shown (a is RB / o-ITC; b is BBT-TPA / o-ITC);

[0042] Figure 7 shows a graph of the X-ray attenuation coefficient of a scintillator powder sample and an energy acceptor;

[0043] Figure 8 The X-ray irradiation luminescence spectra of the scintillator powder samples are shown (a is RB / o-ITC; b is BBT-TPA / o-ITC). DETAILED DESCRIPTION

[0044] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It will be appreciated that the specific embodiments described herein are only used to explain the relevant inventions, rather than to limit the inventions. It should also be noted that, for ease of description, only portions related to the relevant inventions are shown in the accompanying drawings. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0045] The experimental methods described in the following examples are all based on standard techniques unless otherwise specified. Similarly, the materials used in the examples are all standard items that can be obtained through ordinary commercial channels unless otherwise specified. Among them, o-ITC and BBT-TPA materials are non-commercial materials synthesized in this laboratory, and their preparation methods are shown in patent application publication numbers CN112174941B and CN111388448A, respectively.

[0046] The experimental principle of the present invention is as follows Figure 1 As shown in the figure, after the X-ray source excites the internal electrons of the heavy atoms, a large number of electron-hole pairs are first generated, which recombine to produce a large number of singlet excitons and triplet excitons, and finally emit phosphorescence from the lowest excited state energy level (T1) through intersystem crossing and internal conversion processes. Through phosphorescence resonance energy transfer, this phosphorescence can be used as an excitation light source to excite fluorescent dye molecules to emit fluorescence.

[0047] Example 1: Preparation of RB@o-ITC organic scintillator material:

[0048] (1) Weigh 3 mg of RB solid powder and dissolve it in 3 mL of dichloromethane. Ultrasonicate for 3 minutes to fully dissolve it. Prepare a 1 mg / mL RB stock solution and seal it for later use.

[0049] (2) In a clean and dry small glass bottle, 30 mg of o-ITC crystals were placed, and 2 ml of dichloromethane was added to dissolve the crystals. Then, a corresponding volume of RB solution was transferred using a pipette and ultrasonically treated for 10 minutes to mix it thoroughly. Finally, a vacuum rotary evaporator was used to remove the solvent at 30°C to obtain the RB@o-ITC near-infrared organic scintillator material.

[0050] Example 2, preparation of BBT-TPA@o-ITC near-infrared organic scintillator material:

[0051] (1) Weigh 1.5 mg of BBT-TPA solid powder and dissolve it in 15 mL of dichloromethane. Ultrasonicate it for 3 minutes to fully dissolve it, and prepare a 0.1 mg / mL BBT-TPA mother solution, which is sealed and stored for later use;

[0052] (2) In a clean and dry small glass bottle, 30 mg of o-ITC crystals were placed, and 2 ml of dichloromethane was added to dissolve the crystals. Then, a corresponding volume of BBT-TPA solution was transferred using a pipette and ultrasonically treated for 10 minutes to mix it thoroughly. Finally, a vacuum rotary evaporator was used to remove the solvent at 30°C to obtain BBT-TPA@o-ITC near-infrared organic scintillator material.

[0053] Experimental Example 1: Factors affecting energy transfer efficiency:

[0054] (1) Energy level matching:

[0055] In order to determine the effect of energy level matching between the energy donor of organic phosphorescent scintillator material and the energy acceptor of near-infrared fluorescent dye on the energy transfer efficiency, the phosphorescence spectrum of o-ITC crystal, the fluorescence spectrum of RB and BBT-TPA dichloromethane solution and the ultraviolet absorption spectrum were characterized, and the photoluminescence spectrum and radioluminescence spectrum of RB@o-ITC and BBT-TPA@o-ITC near-infrared organic scintillator materials were measured. The instrument used for the determination of photoluminescence spectrum and luminescence lifetime was the steady-state transient fluorescence spectrometer Edinburgh FLS1000, and the excitation source was a xenon lamp light source. The instrument used for radioluminescence test was the spectrometer system (NOVA2S-EX) of Fuxiang Optics, and the excitation source was the X-ray source of Moxtek, model MAGPRO. The instrument used for the photoluminescence quantum yield test was the absolute PL quantum yield spectrometer produced by Hamamatsu, model C13534-12.

[0056] like Figure 2 As shown, the phosphorescence emission spectrum of the energy donor o-ITC overlaps with the ultraviolet absorption spectra of the energy acceptors RB and BBT-TPA to a large extent. The overlapping area between o-ITC and RB is 34.58, and the overlapping area with BBT-TPA is 29.23. It can be seen that the overlapping area of ​​the former is larger than that of the latter, so it is predicted that the energy transfer efficiency of RB is higher.

[0057] Figure 3 The energy transfer between RB, BBT-TPA and o-ITC is shown. The emission peak at 565nm is normalized. It can be seen that the emission intensity of RB@o-ITC in the 500-580nm band is significantly reduced, while the peak intensity near 700nm is significantly enhanced. This emission peak is slightly red-shifted compared to the emission of the dye itself. The above phenomenon shows that efficient energy transfer occurs between RB and o-ITC. In addition, Figure 4 As shown, the lifetime of the energy donor o-ITC at 550nm was tested, and the energy transfer efficiency between the energy donor o-ITC and the energy acceptor RB was calculated as follows:

[0058]

[0059] Among them, Φ ET is the energy transfer efficiency between the energy donor and the acceptor; τ D is the lifetime of the energy donor when the energy acceptor exists; τ0 is the lifetime of the energy donor when there is no energy acceptor.

[0060] The calculation results show that the energy transfer efficiency between o-ITC and RB is above 90%.

[0061] Similarly, if Figure 4 As shown, the emission intensity of BBT-TPA@o-ITC in the 500-580nm band is significantly reduced, and a new emission peak appears near 920nm, which is very consistent with the emission peak of BBT-TPA itself, indicating that BBT-TPA and o-ITC have efficient energy transfer. The energy transfer efficiency between the energy donor o-ITC and the energy acceptor BBT-TPA was calculated according to the energy transfer efficiency calculation formula. The calculation results show that the energy transfer efficiency between o-ITC and BBT-TPA is less than 90%.

[0062] It can be seen from this that resonance energy transfer can only occur when the emission spectrum of the energy donor overlaps with the absorption spectrum of the energy acceptor, and the more the spectrum overlaps, the higher the energy transfer efficiency.

[0063] (2) Doping mass fraction of energy acceptor:

[0064] In order to determine the effect of the doping mass fraction of the dye energy acceptor on the energy transfer efficiency, according to the preparation method of Example 1 and Example 2, five mass fraction gradients of 0.02%, 0.04%, 0.06%, 0.08% and 0.1% were set for the fluorescent light emitter, and the emission lifetime changes of the energy donor o-ITC at the 550nm phosphorescence peak of various RB@o-ITC materials and BBT-TPA@o-ITC materials were measured.

[0065] like Figure 5 As shown in the figure, with the increase of the RB doping mass fraction, the emission lifetime of the energy donor o-ITC of the RB@o-ITC material at the 550nm phosphorescence peak shows a shortening trend in the range of 0%-0.1%, and the calculated energy transfer efficiency between the energy donor and the energy acceptor also shows a gradually increasing trend, which is in line with the changing law of phosphorescence resonance energy transfer. The photoluminescence quantum yield of the doped material system was tested. The measurement results show that with the increase of the RB doping mass fraction, the photoluminescence quantum yield of the doped material also shows a trend of first increasing and then decreasing, and the photoluminescence quantum yield has a maximum value when the RB doping mass fraction is 0.06%.

[0066] Similarly, if Figure 6As shown in the figure, with the increase of the doping mass fraction of the near-infrared dye BBT-TPA, the emission lifetime of the energy donor o-ITC of the BBT-TPA@o-ITC material at the 550nm phosphorescence peak shows a shortening trend in the range of 0%-0.1%, and the calculated energy transfer efficiency between the energy donor and the energy acceptor also shows a gradually increasing trend. The photoluminescence quantum yield of the doped material system was tested. The measurement results show that with the increase of the doping mass fraction of BBT-TPA, the photoluminescence quantum yield of the doped material also shows a trend of first increasing and then decreasing, and reaches a maximum value of 14.52% when the BBT-TPA doping mass fraction is 0.04%.

[0067] The energy transfer efficiency between the energy donor o-ITC and the energy acceptors RB and BBT-TPA gradually increases with the increase of the doping mass fraction, but the photoluminescence quantum yield decreases. This is mainly because RB and BBT-TPA are both aggregation quenching (ACQ) type dyes, and their luminescence is weakened when the doping mass fraction is too high. Therefore, the optimal doping mass fraction of the dye RB in the present invention is 0.06%; and the optimal doping mass fraction of BBT-TPA is 0.04%.

[0068] Experimental Example 2: X-ray irradiation luminescence wavelength of RB@o-ITC and BBT-TPA@o-ITC materials:

[0069] The instrument used for the X-ray radiation luminescence test of the system is a spectrometer system (NOVA2S-EX) of Fuxiang Optics, and the excitation source is an X-ray source of Moxtek, model MAGPRO.

[0070] In order to explore the effect of the introduction of the guest on the host crystal phase, the doped powder was subjected to Figure 7 As shown, the RB@o-ITC material and the BBT-TPA@o-ITC material obtained through the above-mentioned treatment process have a good crystal phase, and the introduction of the dye luminescent body does not destroy the crystal structure of the energy donor.

[0071] like Figure 8 As shown in the figure, under X-ray irradiation, the emission peaks of RB@o-ITC material and BBT-TPA@o-ITC material are located at 620nm (RB) for deep red afterglow luminescence and 920nm (BBT-TPA) for near-infrared luminescence. Among them, under the condition of the same sample mass, for RB@o-ITC scintillator materials with different RB doping mass fractions, the RB@o-ITC scintillator material with RB doping mass fraction of 0.06% has the highest irradiation luminescence intensity, which is consistent with the previous research results.

[0072] Similarly, under the condition of the same sample mass, the energy donor radiation luminescence intensity of the BBT-TPA@o-ITC scintillator material shows a trend of first increasing and then decreasing with the increase of the BBT-TPA doping mass fraction, reaching the minimum value at 0.04%, which is consistent with the previous research results. After the above experimental research, the optimal doping mass fraction of the dye RB in the present invention is 0.06%; the optimal doping mass fraction of BBT-TPA is 0.04%.

[0073] From the above analysis, it can be seen that the near-infrared organic scintillator based on the phosphorescence resonance energy transfer mechanism prepared by the present invention has a radiation luminescence wavelength of up to 920nm, which is the longest luminescence wavelength among the organic scintillator materials reported so far. It is expected to be applied in X-ray imaging, organic light-emitting diodes, biological imaging, advanced encryption and anti-counterfeiting, information storage and other fields.

[0074] The above describes the specific implementation and experimental methods of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with the technical field can easily think of any form of change, adjustment, replacement or derivation within the technical scope disclosed in the present application, which should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application shall be based on the scope of protection of the claims. The simple fact that certain measures are recorded in different dependent claims does not mean that the combination of these measures cannot be used for improvement. Any reference symbols in the claims should not be interpreted as limiting the scope.

Claims

1. A near-infrared organic scintillator material, characterized in that: The near-infrared organic scintillator material includes RB@o-ITC or BBT-TPA@o-ITC.

2. The near-infrared organic scintillator material according to claim 1, characterized in that: The host compound of the RB@o-ITC is o-ITC crystal, and the guest compound of the RB@o-ITC is RB.

3. The near-infrared organic scintillator material according to claim 1, characterized in that: The host compound of the BBT-TPA@o-ITC is o-ITC crystal, and the guest compound of the BBT-TPA@o-ITC is BBT-TPA.

4. The near-infrared organic scintillator material according to claim 2 or 3, characterized in that: The molecular structure of the o-ITC crystal is:

5. The near-infrared organic scintillator material according to claim 2, characterized in that: The molecular structure of the RB is:

6. The near-infrared organic scintillator material according to claim 3, characterized in that: The molecular structural formula of the BBT-TPA is:

7. A method for preparing a near-infrared organic scintillator material, characterized in that: The near-infrared organic scintillator material is prepared based on phosphorescence resonance energy transfer, using organic phosphorescent scintillator o-ITC crystal as energy donor and near-infrared fluorescent luminescent body RB or BBT-TPA as energy acceptor.

8. The preparation method according to claim 7, characterized in that: The method comprises the following preparation steps: S1, dissolving the near-infrared fluorescent luminescent body RB or BBT-TPA in an organic solvent; S2, adding the organic phosphorescent scintillator o-ITC crystal, treating with ultrasound for 10 minutes, and removing the solvent using a vacuum rotary evaporator at 30° C. to obtain a near-infrared organic scintillator material.

9. The preparation method according to claim 8, characterized in that: The phosphorescence emission spectrum of the organic phosphorescent scintillator overlaps with the absorption spectrum of the near-infrared fluorescent light emitter.

10. The preparation method according to claim 8, characterized in that: When the near-infrared fluorescent luminescent body is RB, a dilute RB solution with a concentration of 0.1 mg / mL is prepared in advance using an organic solvent, and then a proper amount of the solution is removed using a pipette and added to the organic phosphorescent scintillator solution to prepare the near-infrared organic scintillator material.

11. The preparation method according to claim 8, characterized in that: When the near-infrared fluorescent luminescent body is BBT-TPA, a dilute BBT-TPA solution with a concentration of 0.1 mg / mL needs to be prepared in advance with an organic solvent, and then a proper amount of the solution is transferred using a pipette and added to the organic phosphorescent scintillator solution to prepare the near-infrared organic scintillator material.

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