A near-infrared organic scintillator material based on phosphorescence resonance energy transfer mechanism and a preparation method thereof

Abstract

The application belongs to the technical field of organic luminescent materials, and discloses a near-infrared organic scintillator material and a preparation method thereof. Based on the phosphorescence resonance energy transfer mechanism, the application uses an organic phosphorescence scintillator o-ITC crystal as an energy donor, and a near-infrared fluorescent luminophore RB or BBT-TPA as an energy acceptor. The near-infrared fluorescent luminophore material is dissolved in an organic solvent, and then the organic phosphorescence scintillator is added. The solvent is removed under specific conditions using a vacuum rotary evaporator, and finally the near-infrared organic scintillator material RB@o-ITC and BBT-TPA@o-ITC is obtained. The material effectively prolongs the luminescence wavelength of the organic scintillator. The maximum radiation luminescence wavelength of the BBT-TPA@o-ITC material reaches 920 nm, and the material has a wide application prospect in the fields of X-ray imaging, organic light-emitting diodes, biological imaging, advanced encryption and anti-counterfeiting, information storage and the like.

Description

Technical Field

[0001] This invention belongs to the field of organic light-emitting materials, specifically relating to near-infrared organic scintillator materials based on phosphorescence resonance energy transfer mechanism. Background Technology

[0002] Scintillator materials are a class of materials capable of converting the high-energy ionizing radiation of radioactive rays (X-rays) into low-energy visible photons. These materials have wide applications in various fields such as medical diagnostics, industrial non-destructive testing, and security inspection. During X-ray imaging, radioactive rays penetrate the imaging object and illuminate the scintillator screen. The scintillator material emits light, which is detected by the detector, thus displaying the structural or functional information of the object in the form of an image, providing a technical means for the diagnosis and detection of various observed objects.

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

[0004] However, the emission wavelengths of the aforementioned organic scintillator materials are mainly concentrated in the visible light range, making them susceptible to interference from ambient light or bioluminescence, which reduces image quality and limits their application scenarios. Particularly in fields such as biomedicine and imaging technology, emission in the visible light range can cause severe background noise problems, affecting the resolution and accuracy of the final image. Furthermore, the number of currently available near-infrared organic scintillator materials is limited, and their synthesis processes are typically complex, making large-scale preparation difficult, which poses a challenge to the practical application of these materials. Therefore, developing a simple and feasible preparation method to obtain organic scintillator materials with near-infrared emission properties not only helps overcome the limitations of existing materials but also has significant economic value in expanding their application potential in fields such as biomedicine and imaging technology. Summary of the Invention

[0005] To address the limitation of emission wavelengths in existing organic scintillator materials to the ultraviolet or visible light range, this invention provides a near-infrared organic scintillator material based on a phosphorescence resonance energy transfer mechanism and its preparation method. Using a pure organic phosphorescent scintillator material as the energy donor and a near-infrared (NIR) fluorescent dye as the energy acceptor, efficient energy transfer is achieved through phosphorescence resonance energy transfer (PRET), resulting in a near-infrared organic scintillator material. This material effectively extends the emission wavelength of the organic scintillator, exhibits room-temperature phosphorescence properties in the near-infrared range, significantly reduces biological background light, and improves 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 comprising RB@o-ITC or BBT-TPA@o-ITC.

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

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

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

[0010]

[0011] The RB has the following structural formula:

[0012]

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

[0014]

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

[0016] Preferably, it includes the following steps:

[0017] Step 1: Dissolve the near-infrared phosphor RB or BBT-TPA in an organic solvent;

[0018] Step 2: Add o-ITC crystals of organic phosphorescent scintillator material, sonicate for 10 minutes to mix thoroughly, and then remove the solvent using a vacuum rotary evaporator at 30°C to obtain near-infrared organic scintillator material.

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

[0020] Preferably, the emission spectrum of the organophosphorescent scintillator overlaps with the absorption spectrum of the near-infrared fluorescent dye.

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

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

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

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

[0025] In this invention, fluorescent luminescent materials are used as energy acceptors, wherein RB and BBT-TPA belong to aggregated fluorescence quenching (ACQ) molecules.

[0026] Preferably, RB and BBT-TPA can be replaced by other photoluminescent organisms whose acceptor energy levels precisely match the energy donor organic phosphorescent scintillator molecules.

[0027] Specifically, when the aggregation fluorescence quenching molecule is RB, BRB needs to be prepared into a dilute RB solution with a concentration of 1 mg / mL using an organic solvent beforehand. Then, the RB solution is precisely transferred into a glass vial containing the organic phosphorescent scintillator using a pipette. The vial is ultrasonicated for 10 minutes to ensure thorough mixing. Afterward, the solvent is removed using a vacuum rotary evaporator at 30°C to obtain the near-infrared organic scintillator material.

[0028] Specifically, when the aggregation fluorescence quenching molecule is BBT-TPA, it is necessary to prepare a dilute BBT-TPA solution with a concentration of 0.1 mg / mL using an organic solvent beforehand. Then, the BBT-TPA solution is precisely transferred using a pipette and added to a glass vial containing an organic phosphorescent scintillator. The vial is ultrasonicated for 10 minutes to ensure thorough mixing. Afterward, the solvent is removed using a vacuum rotary evaporator at 30°C to obtain the near-infrared organic scintillator material.

[0029] Specifically, the ratio of the organic phosphor scintillator to the phosphor diluent (RB dilute solution and BBT-TPA dilute solution) is 30 mg:(6-30) μL; further, the optimal 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 applicable to this invention.

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

[0032] Near-infrared organic scintillator materials RB@o-ITC and BBT-TPA@o-ITC were obtained according to the preparation method of the present invention. Among them, the maximum wavelength of radiative emission of BBT-TPA@o-ITC material is located at 920 nm.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] This invention employs a phosphorescence resonance energy transfer mechanism to prepare near-infrared organic scintillator materials. Specifically, it utilizes phosphorescence energy resonance transfer, employing an organic phosphorescent scintillator as the energy donor and a near-infrared fluorescent emitter as the energy acceptor, to prepare near-infrared organic scintillator materials. This method achieves a redshift of the scintillator emission wavelength to the near-infrared region under X-ray excitation. Among the prepared organic scintillator materials, the maximum radiative emission wavelength of the BBT-TPA@o-ITC material is located at 920 nm. Based on this, the near-infrared organic scintillator materials obtained by this invention hold promise for applications in X-ray imaging, organic light-emitting diodes, bioimaging, advanced encryption and anti-counterfeiting, and information storage. Attached Figure Description

[0035] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the description, serve to explain the principles of the invention. Other embodiments and many anticipated advantages of the embodiments will be readily recognized as they become better understood through reference to the following detailed description.

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

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

[0038] Figure 3 The photoluminescence spectra of 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, energy transfer efficiency, and photoluminescence quantum yield of the sample powder systems with different RB doping mass fractions are shown.

[0040] Figure 5 The lifetime, energy transfer efficiency, and photoluminescence quantum yield of the 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 The X-ray attenuation coefficient curves of the scintillator powder sample and the energy acceptor are shown.

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

[0044] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. The present application will now be described in detail with reference to the accompanying drawings and embodiments.

[0045] Unless otherwise expressly stated, the experimental methods described in the following examples all employ standard techniques. Similarly, the materials used in the examples are 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 our laboratory, and their preparation methods can be found in patent application publication numbers CN112174941B and CN111388448A, respectively.

[0046] The experimental principle of this invention is as follows: Figure 1 As shown, after the internal electrons of heavy atoms are excited by an X-ray source, a large number of electron-hole pairs are first generated, which recombine to produce a large number of singlet and triplet excitons. Through intersystem crossing and internal conversion processes, phosphorescence is finally emitted from the lowest excited state energy level (T1). Through phosphorescence resonance energy transfer, this phosphorescence can be used as an excitation 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. Sonicate the solution for 3 minutes to ensure complete dissolution and prepare a 1 mg / mL RB stock solution. Seal and store for later use.

[0049] (2) In a clean and dry small glass bottle, add 30 mg of o-ITC crystals and 2 ml of dichloromethane to dissolve the crystals. Then, use a pipette to transfer the corresponding volume of RB solution and sonicate for 10 minutes to mix it thoroughly. Finally, use a vacuum rotary evaporator at 30°C to remove the solvent to obtain 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. Sonicate the solution for 3 minutes to ensure complete dissolution and prepare a 0.1 mg / mL BBT-TPA stock solution. Seal and store for later use.

[0052] (2) In a clean and dry small glass bottle, add 30 mg of o-ITC crystals and 2 mL of dichloromethane to dissolve the crystals. Then, use a pipette to transfer the corresponding volume of BBT-TPA solution and sonicate for 10 minutes to mix it thoroughly. Finally, use a vacuum rotary evaporator at 30°C to remove the solvent 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] To determine the effect of energy level matching between the energy donor and the energy acceptor of the near-infrared fluorescent dye in organophosphorescent scintillator materials on energy transfer efficiency, the phosphorescence spectrum of o-ITC crystals, the fluorescence spectrum of RB and BBT-TPA dichloromethane solutions, and the ultraviolet absorption spectrum were characterized. The photoluminescence and radiative emission spectra of RB@o-ITC and BBT-TPA@o-ITC near-infrared organic scintillator materials were also measured. The photoluminescence spectroscopy and luminescence lifetime measurements were performed using an Edinburgh FLS1000 steady-state transient fluorescence spectrometer with a xenon lamp as the excitation source. The radiative emission measurements were performed using a NOVA2S-EX spectrometer system from Fuhsing Optics with a Moxtek MAGPRO X-ray source as the excitation source. The photoluminescence quantum yield measurements were performed using an absolute PL quantum yield spectrometer, model C13534-12, manufactured by Hamamatsu Optics.

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

[0057] Figure 3 The energy transfer between RB, BBT-TPA, and o-ITC is shown. Normalizing the emission peak at 565 nm reveals that the emission intensity of RB@o-ITC significantly decreases in the 500-580 nm band, while the peak intensity near 700 nm is significantly enhanced. This emission peak shows a slight redshift compared to the emission of the dye itself. These phenomena indicate that efficient energy transfer occurs between RB and o-ITC. Furthermore, as... Figure 4 As shown, the lifetime of the energy donor o-ITC at 550 nm was tested, and the energy transfer efficiency between the energy donor o-ITC and the energy acceptor RB was calculated using the following formula:

[0058]

[0059] Where, Φ ET The efficiency of energy transfer between energy donors and acceptors; τ D τ0 represents the lifetime of the energy donor when the energy acceptor is present; τ0 represents the lifetime of the energy donor when the energy acceptor is absent.

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

[0061] Similarly, such as Figure 4 As shown, the emission intensity of BBT-TPA@o-ITC decreases significantly in the 500-580nm band, while a new emission peak appears near 920nm. This peak closely matches the emission peak of BBT-TPA itself, indicating that efficient energy transfer occurs between BBT-TPA and o-ITC. The energy transfer efficiency between the energy donor o-ITC and the energy acceptor BBT-TPA was calculated using the energy transfer efficiency formula. The results show that the energy transfer efficiency between o-ITC and BBT-TPA is below 90%.

[0062] Therefore, resonance energy transfer can only occur when the emission spectrum of the energy donor and the absorption spectrum of the energy acceptor overlap, and the greater the spectral overlap, the higher the energy transfer efficiency.

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

[0064] To determine the effect of the doping mass fraction of the dye energy acceptor on the energy transfer efficiency, five mass fraction gradients of 0.02%, 0.04%, 0.06%, 0.08%, and 0.1% were set for the phosphors according to the preparation methods of Examples 1 and 2. The emission lifetime of the energy donor o-ITC of various RB@o-ITC materials and BBT-TPA@o-ITC materials at the phosphorescence peak of 550 nm was measured.

[0065] like Figure 5 As shown, with the increase of the RB doping mass fraction, the emission lifetime of the energy donor o-ITC in the 550 nm phosphorescence peak of the RB@o-ITC material shows a shortening trend in the range of 0%-0.1%, and the calculated energy transfer efficiency between the energy donor and energy acceptor also shows a gradual increasing trend, which is consistent with the variation law of phosphorescent 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, such as Figure 6As shown, with the increase of the near-infrared dye BBT-TPA doping mass fraction, the emission lifetime of the energy donor o-ITC in the 550 nm phosphorescence peak of the BBT-TPA@o-ITC material shows a shortening trend in the range of 0%-0.1%, and the calculated energy transfer efficiency between the energy donor and energy acceptor also shows a gradual increasing trend. The photoluminescence quantum yield of the doped material system was tested. The measurement results show that with the increase of the BBT-TPA doping mass fraction, the photoluminescence quantum yield of the doped material also shows a trend of first increasing and then decreasing, and has 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 increasing doping mass fraction, but the photoluminescence quantum yield decreases. This is mainly because RB and BBT-TPA are both aggregation quenching (ACQ) type dyes; if the doping mass fraction is too high, their luminescence weakens. Therefore, the optimal doping mass fraction for dye RB in this invention is 0.06%, while the optimal doping mass fraction for BBT-TPA is 0.04%.

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

[0069] The X-ray radiation luminescence test of the system was performed using a NOVA2S-EX spectrometer system from Fuxiang Optics, with a MAGPRO X-ray source from Moxtek as the excitation source.

[0070] To investigate the effect of the introduction of a guest phase on the host crystalline phase, the doped powder was subjected to the following tests: Figure 7 As shown, the RB@o-ITC material and BBT-TPA@o-ITC material obtained through the above processing have good crystal phases, and the introduction of the dye luminescent material does not destroy the crystal structure of the energy donor.

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

[0072] Similarly, under the same sample mass conditions, the energy donor radiative luminescence intensity of the BBT-TPA@o-ITC scintillator material first increases and then decreases with increasing BBT-TPA doping mass fraction, reaching a minimum at 0.04%, which is consistent with the previous findings. Based on the above experimental investigations, the optimal doping mass fraction of dye RB in this invention is 0.06%; the optimal doping mass fraction of BBT-TPA is 0.04%.

[0073] As can be seen from the above analysis, the near-infrared organic scintillator prepared by this invention has a radiation emission wavelength of up to 920 nm, which is the longest emission wavelength reported among organic scintillator materials to date. It is expected to be applied in fields such as X-ray imaging, organic light-emitting diodes, bio-imaging, advanced encryption and anti-counterfeiting, and information storage.

[0074] The specific implementation and experimental methods of this application have been described above, but the scope of protection of this application is not limited thereto. Any changes, adjustments, substitutions, or derivatives that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims. The simple fact that certain measures are recited in mutually different dependent claims does not indicate that combinations of these measures cannot be used for improvement. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A near-infrared organic scintillator material, characterized by, The near-infrared organic scintillator material comprises RB@o-ITC or BBT-TPA@o-ITC; The host compound of the RB@o-ITC is an o-ITC crystal, and the guest compound of the RB@o-ITC is RB; The host compound of the BBT-TPA@o-ITC is an o-ITC crystal, and the guest compound of the BBT-TPA@o-ITC is BBT-TPA; The molecular structural formula of the o-ITC crystal is as follows: ； The molecular structural formula of the RB is as follows: ； The molecular structural formula of the BBT-TPA is as follows: 。 2. A method of preparing a near-infrared organic scintillator material, characterized by, The near-infrared organic scintillator material is prepared based on phosphorescence resonance energy transfer, with the organic phosphorescent scintillator o-ITC crystal as an energy donor and the near-infrared fluorescent luminophore RB or BBT-TPA as an energy acceptor. The preparation process comprises the following steps: S1, dissolving the near-infrared fluorescent luminophore RB or BBT-TPA in an organic solvent; S2, adding the organic phosphorescent scintillator o-ITC crystal, treating for 10 minutes through ultrasonic, removing the solvent at an environment of 30 DEG C by using a vacuum rotary evaporator, and obtaining the near-infrared organic scintillator material.

3. The preparation method according to claim 2, characterized in that, The phosphorescence emission spectrum of the organic phosphorescent scintillator overlaps with the absorption spectrum of the near-infrared fluorescent luminophore.

4. The preparation method according to claim 2, characterized in that, When the near-infrared fluorescent luminophore is RB, a RB dilute solution with a concentration of 0.1 mg / mL is prepared in advance by using an organic solvent, and then an appropriate amount of solution is taken by using a pipette gun and added into the organic phosphorescent scintillator solution for preparation of the near-infrared organic scintillator material.

5. The preparation method according to claim 2, characterized in that, When the near-infrared fluorescent luminophore is BBT-TPA, a BBT-TPA dilute solution with a concentration of 0.1 mg / mL is prepared in advance by using an organic solvent, and then an appropriate amount of solution is taken by using a pipette gun and added into the organic phosphorescent scintillator solution for preparation of the near-infrared organic scintillator material.

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