Singlet splitting sensitization type photochemical long afterglow system and application

Abstract

The invention relates to the technical field of luminescence, in particular to a singlet splitting-based sensitization type photochemical long afterglow system and application of the singlet splitting-based sensitization type photochemical long afterglow system. The photochemical long afterglow system comprises at least one sensitizing agent, at least one buffering agent and at least one luminous body, wherein the sensitizer has a singlet state splitting property, and the absorption peak of the sensitizer and the emission peak of the luminous body are in zero peak position overlapping. The sensitizer has the unique performance of singlet splitting, so that the singlet oxygen generation efficiency reaches up to 140%, and the upper limit of the traditional photosensitizer level is directly broken through. Meanwhile, absorption of photosensitizer molecules and emission of the rare earth complex are zero-overlapped, and the upper limit of the optimal applicable concentration of the photosensitizer is increased. The integration of the two factors obviously enhances the light energy absorption and conversion capability of the system, and high-performance rare earth photochemical long afterglow luminescence is directly realized in an organic solution phase.

Description

Technical Field

[0001] The present invention relates to the technical field of luminescent materials, and particularly to a singlet fission sensitized type photochemical long afterglow system and applications thereof. In addition, the present invention also relates to photochemical long afterglow nanoparticles, photochemical long afterglow nanoprobes, and their preparation methods and applications. Background Art

[0002] Long afterglow luminescent materials have attracted much attention due to their unique ability to continuously emit photons after the excitation light is turned off. However, it was not until recent decades that the luminescence mechanism and material preparation of long afterglow have achieved rapid development. Through the continuous efforts of researchers, various long afterglow materials have now been designed and synthesized, and their applications in multiple fields such as display, sensing, anti-counterfeiting, and safety marking have been explored. Among them, inorganic long afterglow powders are the most prominent in terms of luminescence duration and brightness. This is a crystalline material usually doped with rare earth elements or transition metals, and is also the most commonly used long afterglow material at present. For example, the rare earth element doped blue powder CaAl 2 O 4 :Eu 2+ ,Nd 3+ and the green powder SrAl 2 O 4 :Eu 2+ ,Dy 3+ have been widely used commercially and are particularly common in life.

[0003] However, rare earth doped inorganic long afterglow materials are also restricted by their crystal structures and face the trade-off problem between size and morphology and afterglow performance. For lanthanide element doped inorganic afterglow materials, the long afterglow luminescence mechanism is usually associated with the energy capture and release in lattice traps. In order to obtain better afterglow performance, it is very necessary to increase the energy traps in the lattice through solid-phase synthesis or high-temperature sintering, resulting in these materials with ideal long afterglow performance being inevitably limited to the bulk crystalline matrix and being incompatible with the classical wet chemical synthesis route. Therefore, although long afterglow luminescence has the significant advantage of being free from excitation light and biological background interference, the construction of high-performance long afterglow luminescent materials with controllable size and surface morphology to achieve wide applications in biomedical fields such as diagnostic detection is still hindered.

[0004] Since the photochemical long afterglow mechanism realizes long afterglow luminescence by introducing a strategy of photochemical reaction between light energy input and photon output, the organic integration of photochemistry and photophysics can get rid of many limitations of the crystal matrix. Generally speaking, the photochemical long afterglow system consists of three core functional components: photosensitizer, energy buffer and emitter, which mainly carry out the processes of light energy absorption, photochemical energy buffering and photon emission respectively. Compared with the energy level transition of photophysics, the photochemical reaction proceeds more slowly and is more likely to occur. Without the stabilization of a specific environment such as a crystal, the luminescence lifetime can reach the long afterglow range, which is more compatible with the biomedical application environment of diagnostic detection. However, compared with inorganic long afterglow or organic long afterglow, there are relatively few reports on photochemical long afterglow, and its system types and material properties urgently need further research and development. Summary of the Invention

[0005] In view of the above-mentioned defects of the prior art, the present invention provides a singlet fission sensitized photochemical long afterglow system and application. The present invention introduces the unique property of singlet fission into the design of the photosensitizer for photochemical long afterglow. When selectively excited by a light source, the photosensitizer molecule can convert oxygen into singlet oxygen through type II sensitization. In this process, one singlet exciton of the photosensitizer with singlet fission property can be converted into two triplet excitons, so the theoretical yield limit of the triplet excited state is 200%. In a classical photosensitizer, the theoretical yield limit of the triplet excited state is 100%. Therefore, after breaking through and increasing the yield limit of singlet oxygen, the luminescence performance of photochemical long afterglow can be greatly improved.

[0006] In the first aspect of the present invention, there is provided a singlet fission sensitized photochemical long afterglow system, wherein the photochemical long afterglow system comprises at least one photosensitizer, at least one energy buffer and at least one emitter; wherein, the photosensitizer has the property of singlet fission, and the absorption peak of the photosensitizer has zero overlap with the emission peak of the emitter. Thus, in this photochemical long afterglow system, the photosensitizer, the energy buffer and the emitter respectively carry out the processes of light energy absorption, photochemical energy buffering and photon emission. For the photochemical afterglow system, the photosensitizer is in the most initial and crucial position of light energy input, so it is an important component to trigger the photochemical reaction. Under the irradiation of the excitation light, singlet oxygen ( 1 O 2) is equivalent to converting the input light energy into chemical energy and storing it in reactive oxygen species. Subsequently, singlet oxygen undergoes a photochemical reaction with the cache agent and adds to the double bond of the unsaturated olefin of the cache agent. With the decomposition of the intermediate product, an excited state energy center is generated again, and after transferring the excited state energy to the luminescent body, it is emitted in the form of photons. According to the described photochemical long afterglow luminescence process, the amount of singlet oxygen generated per unit time is generally positively correlated with the intensity of the series of photochemical reactions, and thus positively correlated with the intensity of the long afterglow luminescence. Therefore, a photosensitizer with a high singlet oxygen yield is an ideal choice for the photochemical afterglow system.

[0007] In some embodiments of the present invention, the sensitizer converts oxygen into singlet oxygen through type II sensitization under selective excitation by a light source. The type II sensitization mentioned here in the photosensitization reaction generally refers to the energy transfer mechanism in photochemistry. When a sensitizer (such as porphyrin, phthalocyanine, or certain dyes) is excited by light of a specific wavelength, it absorbs light energy and transitions from the ground state (S 0 ) to the excited state (S 1 or T 1 ). Subsequently, the sensitizer transfers the energy to the substrate molecule (such as O 2 ) through non-radiative transition, causing it to transition from the triplet state ( 3 O 2 ) to the singlet state ( 1 O 2 ). The type II sensitization process only transfers energy and does not involve electron transfer, generating 1 O 2 .

[0008] In some embodiments of the present invention, the structure of the sensitizer is shown in Formula I-A or Formula I-B:

[0009]

[0010] Among them, the R group substituent in Formula I-A can be a benzene ring a benzene ring derivative biphenyl and biphenyl derivatives where n is 1-6.

[0011] Among them, in Formula I-B, can be a cycloalkane or a cycloalkane derivative, and the cycloalkane or cycloalkane derivative is fused to the benzene ring of the main body part other than in Formula I-B through a shared chemical bond.

[0012] Specifically, in Formula I-B can be a cycloalkane or a cycloalkane derivative with 1-6 carbon atoms.

[0013] More specifically, the cycloalkane can be cyclopropane, cyclobutane, cyclopentane, cyclohexane, methylcyclopropane, 1,2-dimethylcyclohexane, etc.

[0014] The compound having the structure described by Formula I-A or Formula I-B is a photosensitizer molecule with singlet fission properties. This is a type of polyacene molecule, and it is bridged and connected by two tetracenes within the molecule, which is conducive to the generation of singlet fission properties. Additionally, multiple triisopropylsilyl groups are modified on this molecule, which can significantly increase the solubility of the photosensitizer component and is conducive to the related research of photochemical long afterglow.

[0015] In some embodiments, the structure of the sensitizer is as follows:

[0016]

[0017] Among them, * represents the bonding site, and the * bonding site is located at any aromatic hydrogen atom of the benzene ring or its derivatives;

[0018] Among them, R 1 is selected from alkyl, alkoxy, or alkylamino groups having 1 to 8 carbon atoms;

[0019] Among them, the value range of n is 1 to 8.

[0020] In some embodiments of the present invention, the structure of the sensitizer is as follows:

[0021]

[0022]

[0023] Among them, R in Formula A 2 The substituent is

[0024] In some embodiments of the present invention, the structure of the cache agent is as shown in Formula II:

[0025]

[0026] Among them, R in Formula II 1 , R 2 , R 3 The substituents can be the same or different, and the R 1 substituent in Formula II is selected from hydrogen, or alkyl, alkoxy, or alkylamino groups having 1 to 8 carbon atoms; R 2 , R 3 substituents are each independently selected from alkyl, alkoxy, or alkylamino groups having 1 to 8 carbon atoms.

[0027] Specifically, R in Formula II 1The substituent is selected from hydrogen or from alkyl groups (C n H 2n+1- ), and more specifically, R 1 , R 2 , R 3 The substituent can be methyl (-CH 3 ), ethyl (-C 2 H 5 ), n-propyl (-CH 2 CH 2 CH 3 ), isopropyl (-CH(CH 3 ) 2 ), n-butyl (-CH 2 CH 2 CH 2 CH 3 ), isobutyl (-CH 2 CH(CH 3 ) 2 ), sec-butyl (-CH(CH 3 )CH 2 CH 3 ), tert-butyl (-C(CH 3 ) 3 ), n-pentyl (-CH 2 CH 2 CH 2 CH 2 CH 3 ), isopentyl (-CH 2 CH 2 CH(CH 3 ) 2 ), neopentyl (-CH 2 C(CH 3 ) 3 ), sec-pentyl (-CH(CH 3 )CH 2 CH 2 CH 3 ), 3-pentyl (-CH 2 CH(CH 2 CH 3 ) 2 ) and their isomers.

[0028] Specifically, R 1 , R 2 , R 3 The substituent in formula II can also be selected from alkoxy groups (C n H 2n+1 O-), and more specifically, it can be methoxy (-OCH 3 ), ethoxy (-OC 2 H 5)、n - propoxy (-OCH 2 CH 2 CH 3 )、isopropoxy (-OCH(CH 3 ) 2 ), n - butoxy, isobutoxy, sec - butoxy, tert - butoxy, etc. and their isomers.

[0029] Specifically, R 1 , R 2 , R 3 substituents can also be selected from alkylamino (C n H 2n+1 NH-), for example, methylamino (-NHCH 3 ), ethylamino (-NHC 2 H 5 ), n - propylamino (-NHCH 2 CH 2 CH 3 ), isopropylamino (-NHCH(CH 3 )) 2 ), n - butylamino, isobutylamino, sec - butylamino, tert - butylamino, etc. and their isomers.

[0030] In some embodiments of the present invention, the structure of the cache agent is shown in Formula II - A:

[0031]

[0032] The structure shown in Formula II - A is a compound containing a special unsaturated olefin. The olefinic double bond is located in a six - membered ring containing S and O, and a strong electron - donating group is connected to the S - end side of the double bond. Due to this unique chemical structure, the electron cloud distribution is very asymmetric. This double bond is prone to addition reaction with singlet oxygen and is prone to form an excited state of the ring - opening product through a concerted decomposition mechanism.

[0033] In some embodiments of the present invention, the luminescent body is selected from one of rare - earth complexes, and the central atom of the rare - earth complex is preferably Eu, Tb, Sm, Yb, Nd, Dy, Er, Ho, Pr.

[0034] On the one hand, the inner - layer 4f electrons of rare - earth ions (such as Eu 3+ , Tb 3+ , Dy 3+ etc.) are shielded by outer - layer electrons, and the excited - state lifetime is long (milliseconds to seconds), which is suitable for long - afterglow applications. On the other hand, the f - f transition of rare - earth ions is less affected by the crystal field, and the emission spectrum bandwidth is narrow (usually <10nm), and the color purity is high (such as the red light of Eu 3+ , the green light of Tb 3+The green light) reduces the internal energy reabsorption of the material with narrow-band emission and improves the luminescence efficiency.

[0035] Preferably, the rare earth complex is a rare earth europium (Eu) complex. Eu in the rare earth europium (Eu) complex 3+ of 5 D 0 → 7 F 2 transition generates sharp red light emission (main peak at about 612 nm), and the full width at half maximum is only 5 - 10 nm, which is superior to other rare earth ions (such as Tb 3+ green light, Dy 3+ blue / white light). At the same time, the 4f electrons of Eu 3+ are shielded by the outer layer, and the coordination environment has little influence on its emission wavelength (the green light of Tb 3+ is easily shifted by the ligand field). More importantly, the characteristics of narrow-band red light rare earth emission avoid the peak overlap between the photosensitizer and the luminescent body, and the minimized reabsorption effect with zero crosstalk helps to maximize the emission of afterglow photons.

[0036] More preferably, the structure of the rare earth complex is shown in Formula III:

[0037]

[0038] In some embodiments of the present invention, the concentration range of the buffer in the photochemical long afterglow system is 0.5 - 10 mM, the concentration range of the luminescent body is 2.5 - 15 mM, and the concentration range of the sensitizer is 5 - 250 μM. The preferred ranges of each element in the long afterglow system are essentially a balance among energy storage - release kinetics, material stability, and application requirements. By regulating the type of luminescent body (energy level matching), buffer parameters (concentration), and concentration thresholds, the synergistic optimization of afterglow time, luminescence efficiency, and environmental adaptability can be achieved to meet the diverse requirements from low-end luminous materials to high-end biosensors and detections.

[0039] In the second aspect of the present invention, there is provided a photochemical long afterglow nanoparticle, which includes the sensitizer, buffer, and luminescent body described above, and the sensitizer, buffer, and luminescent body are encapsulated into a nanocarrier, and the nanocarrier is a polystyrene nanoparticle and a polystyrene derivative nanoparticle.

[0040] In the third aspect of the present invention, there is provided a photochemical long afterglow nanoprobe, which is formed by conjugating and modifying the surface of the photochemical long afterglow nanoparticle described above with a protein substance.

[0041] In the fourth aspect of the present invention, there is provided an application of the photochemical long afterglow nanoprobe, and the probe is applied to the fields of bioimaging, immunochromatography, and homogeneous detection.

[0042] The singlet fission sensitized type photochemical long afterglow system, nanoparticles and probes provided by the present invention successfully construct a rare earth-based photochemical persistent luminescence system with super brightness characteristics by innovatively designing a singlet fission type sensitizer. This system breaks through the technical bottleneck of traditional crystallization-dependent long afterglow materials. Based on the mechanism of photochemical reaction energy storage and transfer (PCREST), for the first time, a long-lasting luminescence phenomenon that perfectly matches the f-f transition spectrum of europium complexes is realized in a liquid organic medium. The singlet fission characteristics of the novel sensitizer enable its singlet oxygen quantum yield to reach a breakthrough level of 140%, significantly exceeding the theoretical limit of traditional photosensitizers; the unique spectral design achieves zero overlap between the absorption band of the sensitizer and the rare earth luminescence peak. In addition, the prepared nano-luminescent particles based on this system exhibit a uniform and controllable nano-scale particle size distribution and persistent visible afterglow intensity. The successful development of this photochemical persistent luminescence system provides a new paradigm for the design of high-brightness long afterglow materials. It shows broad application prospects in the field of biomedical detection, especially having significant technical advantages in scenarios such as time-resolved fluorescence immunoassay, in vivo deep tissue imaging, homogeneous detection, and immunochromatography. Brief Description of the Drawings

[0043] Figure 1 Showing a schematic diagram of the singlet fission sensitized type photochemical afterglow system;

[0044] Figure 2 Showing the absorption spectrum of the photosensitizer TBPS in toluene solution;

[0045] Figure 3 Showing the fluorescence emission spectrum of the photosensitizer TBPS in toluene solution under 365 nm excitation;

[0046] Figure 4 Showing the emitter Eu(TTA) 3 (TPPO) 2 Emission spectrum under 365 nm excitation in toluene solution;

[0047] Figure 5 Showing the luminescence process diagram of the singlet fission sensitized type photochemical afterglow system;

[0048] Figure 6 Showing the photochemical long afterglow system TBPS&SOMN&Eu(TTA) 3 (TPPO) 2 Long afterglow emission spectrum in toluene solution;

[0049] Figure 7 Showing the photochemical long afterglow system TBPS&SOMN&Eu(TTA) 3 (TPPO) 2Long afterglow luminescence decay curve in toluene solution;

[0050] Figure 8 Showing the spectra and photos of singlet fission sensitized type photochemical long afterglow system;

[0051] Figure 9 Showing the variation trend of photochemical long afterglow luminescence intensity with component concentration;

[0052] Figure 10 Showing the variation trend of photochemical long afterglow luminescence intensity with the concentration of photosensitizer SiPc;

[0053] Figure 11 Showing the absorption spectrum of photosensitizer SiPc in toluene;

[0054] Figure 12 Showing the change of photochemical long afterglow luminescence intensity of photosensitizers TBPS and SiPc at different concentrations;

[0055] Figure 13 Showing the photochemical long afterglow luminescence images with TBPS and SiPc as photosensitizers respectively;

[0056] Figure 14 Showing the luminescence spectra of different solution samples;

[0057] Figure 15 Showing the photochemical long afterglow luminescence spectra under different component conditions;

[0058] Figure 16 Showing the long afterglow luminescence spectra of singlet fission sensitized type photochemical long afterglow system under different atmosphere conditions;

[0059] Figure 17 Showing the absorption spectra of sensitizers TBPS and PdOEP in toluene;

[0060] Figure 18 Showing the performance comparison between the singlet fission sensitized type photochemical long afterglow system based on TBPS and the ultra-bright long afterglow system established with PdOEP as photosensitizer;

[0061] Figure 19 Showing the preparation flow chart of photochemical long afterglow nanoparticles (PA-NPs);

[0062] Figure 20 Showing the aqueous solution of photochemical long afterglow nanoparticles (PA-NPs) and its scanning electron microscope image;

[0063] Figure 21 Showing the long afterglow luminescence performance of photochemical long afterglow nanoparticles (PA-NPs) in aqueous solution. Detailed implementation manners

[0064] The following will further elaborate in detail on the multi-parameter condition optimization method and application based on homogeneous immunoassay of the present invention in combination with specific embodiments. It should be understood that the following embodiments are only for illustrative explanation of the present invention and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0065] As used herein, the term "comprising" and its variants are open-ended, that is, "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The relevant definitions of other terms will be given in the following description.

[0066] As used herein, "photochemical persistent luminescence system", "persistent luminescence system" and "long persistent luminescence system" have the same meaning, and generally refer to a three-component system including a sensitizer, a buffer and a luminescent body. In special cases, for example, when a molecule has both the functions of a sensitizer and a buffer, or both the functions of a buffer and a luminescent body, it may also be a two-component system.

[0067] As used herein, "sensitizer", "photosensitizer", "photoactivator", "light absorber" and the like have similar meanings, and their main function is to absorb light energy under the excitation of a light source.

[0068] As used herein, "singlet fission" is usually a unique photophysical process, which refers to the phenomenon that the excited singlet state (S 1 ) formed by an organic molecule absorbing a photon spontaneously splits into two triplet excitons (T 1 ) through a quantum mechanical mechanism. The core feature of this process is to convert a single high-energy exciton into two low-energy excitons, thereby breaking through the energy conversion efficiency limit of traditional photochemical systems.

[0069] In a photochemical persistent luminescence system, it is mainly composed of three core functional components: a photosensitizer, a buffer and a luminescent body, which respectively carry out the processes of light energy absorption, photochemical energy buffering and photon emission. For a photochemical persistent luminescence system, the photosensitizer is in the most crucial initial position of light energy input, so it is an important component for triggering a photochemical reaction. In the presence of a photosensitizer under the irradiation of excitation light, singlet oxygen ( 1 O 2) is equivalent to converting the input light energy into chemical energy and storing it in reactive oxygen species. Subsequently, singlet oxygen undergoes a photochemical reaction with the cache agent and adds to the unsaturated olefin double bond of the cache agent. With the decomposition of the intermediate product, an excited-state energy center is generated again, and after transferring the excited-state energy to the luminescent body, it is emitted in the form of photons. According to the described photochemical long-afterglow luminescence process, the amount of singlet oxygen generated per unit time is generally positively correlated with the intensity of the series of photochemical reactions, and thus positively correlated with the intensity of the long-afterglow luminescence. Therefore, photosensitizers with a high singlet oxygen yield are very ideal choices for photochemical afterglow systems.

[0070] However, for conventional established photochemical long-afterglow materials, photosensitizers are usually selected from porphyrins, phthalocyanines and their complexes. For example, the most commonly used photosensitizer is the silicon phthalocyanine complex, called the SiPc sensitizer. These photosensitizers are indeed widely used, but their singlet oxygen yield is restricted by the maximum intersystem crossing (ISC) efficiency of the photosensitizer and cannot exceed the upper limit of 100%. In practical applications, due to the influence of biological environments and experimental conditions, etc., the singlet oxygen yield is often lower. Therefore, in order to achieve more excellent photochemical long-afterglow performance and also to enrich the photosensitizer components of photochemical long-afterglow, it is urgent to develop more and more efficient photosensitizers and study their applications in photochemical long-afterglow systems.

[0071] To break through the limit, the present disclosure introduces the unique property of singlet fission into the design of sensitizers for photochemical long-afterglow. In singlet fission, one singlet exciton can be converted into two triplet excitons, so the theoretical yield upper limit of the triplet excited state is 200%. While in classical photosensitizers, the theoretical yield upper limit of the triplet excited state is 100%. Since oxygen needs to undergo an energy transfer process with the triplet excited state of the photosensitizer to generate singlet oxygen. Theoretically, if a molecule with singlet fission is used as a photosensitizer, it is possible to generate two singlet oxygens by only absorbing the excitation light energy of one photon, thus achieving a maximum singlet oxygen yield of 200%. Thus, after breaking through and increasing the upper limit of the singlet oxygen yield, the luminescence performance of photochemical long-afterglow can be greatly improved. Unfortunately, however, photosensitizers with singlet fission ability have not been reported in photochemical long-afterglow systems, and the research on their sensitization properties for photochemical long-afterglow is still in a blank state.

[0072] In the embodiments of the present disclosure, a super-bright rare-earth luminescent persistent afterglow system has been developed based on a construction strategy of photochemical persistent afterglow. This system directly exhibits the same emission curve as the europium complex, a rare-earth f-f transition type luminescent material, in an organic solution. The persistent afterglow luminescence is attributed to the mechanism of photochemical energy storage and transfer (PCREST), which is relatively independent of the traditional theory based on crystal structures, providing a greater space for the regulation of persistent afterglow performance and the free design of materials. To achieve effective photochemical reactions and energy transfer processes, a photosensitizer with singlet fission ability is designed and introduced into this persistent afterglow system, and the wave function overlap with the luminescent material is avoided. The persistent afterglow luminescence properties are optimized and regulated in an organic solution, and then high-quality persistent afterglow luminescent probes with uniform size and functional surfaces can be fabricated as needed by using mature wet chemical synthesis methods, providing a possible approach for exploring biomedical applications such as diagnostic detection.

[0073] It should be noted that the photosensitizer component mainly performs the core functions of absorbing excitation light energy and photochemical energy conversion. It is the key to regulating and restricting the light energy input link, affecting the absorption, conversion and utilization efficiency of excitation light and the persistent afterglow luminescence performance. The property of singlet fission enables the photosensitizer to have a singlet oxygen production efficiency of more than 100%, which can improve the persistent afterglow performance from the source compared with the photochemical systems of traditional photosensitizers. The singlet oxygen generated by the singlet fission photosensitizer undergoes a photochemical reaction with the quencher, stores the energy in chemical bonds briefly, and transfers it to the rare-earth complex luminescent material during the bond-breaking and recombination process, thus forming a rare-earth photochemical persistent afterglow phenomenon with a luminescence lifetime up to the second level. At the same time, the characteristic of narrow-band red light rare-earth emission avoids the peak overlap between the photosensitizer and the luminescent material, and the minimized reabsorption effect with zero crosstalk helps to maximize the emission of afterglow photons. Therefore, the singlet fission sensitized photochemical persistent afterglow system can directly achieve super-bright persistent afterglow luminescence in an organic phase solution, and then high-quality persistent afterglow luminescent nanoparticles can be prepared by wet chemical synthesis methods, laying a foundation for related biomedical applications.

[0074] Specifically, referring to Figure 1 , Figure 1 shows a schematic diagram of the singlet fission sensitized photochemical afterglow system in the embodiments of the present invention. Among them, Figure 1 (a) is a schematic diagram of the luminescence path of photochemical persistent afterglow, involving the combined action of photochemical and photophysical processes among the photosensitizer, quencher and luminescent material. The persistent afterglow luminescence mechanism is energy storage and transfer based on photochemical reactions; Figure 1 (b) are the three functional molecules and their chemical structures included in the photochemical persistent afterglow system. Among them, TBPS is a singlet fission type photosensitizer, SOMN is a quencher, and the rare-earth complex Eu(TTA) 3 (TPPO) 2 is the luminescent material.

[0075] The following are specific embodiments, through which the principles and performance advantages of the present disclosure become more obvious.

[0076] Example 1 Synthesis of Photosensitizer Compound TBPS

[0077] Compound A (100 mg), compound B (15 mg), PdCl 2 (20 mg) and K 2 CO 3 (300 mg) were added to a mixed solution of 20 mL of THF and H 2 O (10:1, v:v). Then, the mixture was stirred at 70 °C for 24 hours. After cooling to room temperature, the solvent was removed by evaporation. Finally, the obtained product was purified to obtain approximately 30 mg of red powder of TBPS.

[0078] Specifically, the synthesis route of the photosensitizer TBPS compound is as follows:

[0079]

[0080] The results show that the compound TBPS is a photosensitizer molecule with singlet fission properties. This is a type of acene molecule, and it is bridged by two tetracenes within the molecule, which is beneficial to the generation of singlet fission properties. In addition, this molecule is modified with multiple triisopropylsilyl groups, which can significantly increase the solubility of the photosensitizer component and is beneficial to the related research of photochemical long afterglow.

[0081] First, the ultraviolet-visible absorption spectrum of the photosensitizer TBPS molecule was measured. Referring to Figure 2 , Figure 2 is the absorption spectrum of the photosensitizer TBPS in toluene solution. The absorption spectrum data of TBPS show that it has obvious absorption in the green light region, and its main peak can well match the commonly used 532 nm laser, laying a foundation for the light source excitation of the subsequent photochemical long afterglow system. Through quantitative calculation, it shows that the molar extinction coefficient of the TBPS molecule at 532 nm is as high as 3.2×10 4 L mol -1 ·cm -1In addition, the absorption peak of TBPS in the green light region is relatively wide, and it can also achieve efficient photon absorption for wide-spectrum green LED lights, so the choice of light source does not have to be very demanding. It is worth noting that the TBPS molecule has no absorption peak in the red light region at all. When used as a photosensitizer for photochemical long afterglow, it can be combined with a light emitter that emits red light very well, thus avoiding the occurrence of self-absorption in the system. Therefore, the synthesized TBPS molecule has relatively ideal light absorption properties and is expected to be used as a photosensitizer in the photochemical long afterglow system.

[0082] Furthermore, the emission spectrum of the TBPS molecule was characterized. As Figure 3 shown, Figure 3 Figure 1 is the fluorescence emission spectrum of the photosensitizer TBPS in toluene solution excited by 365 nm. Under the excitation of 365 nm ultraviolet light, the fluorescence emission spectrum data of TBPS show that its emission is in the yellow and red light regions. It is worth noting that due to the influence of the singlet fission property of this molecule, its fluorescence emission is significantly weaker than that of other acene-based fluorescent dyes. For acene-based fluorescent dyes, they usually have excellent fluorescence emission properties. For example, 9,10-diphenylanthracene (DPA) and rubrene are often used as emitters in organic upconversion systems. However, as a photosensitizer, the main function of TBPS should be the absorption of incident photons and the generation of singlet oxygen, so the poor fluorescence emission ability has no adverse effect. In the photochemical long afterglow system, it is relatively difficult for a component to perform the functions of both a photosensitizer and a light emitter at the same time, and it is often not conducive to the energy utilization and transfer process. This is mainly because there is a trade-off between the two functional properties required for the photosensitizer and the light emitter. Theoretically, the luminescence ability of a molecule with strong singlet oxygen sensitization is weakened, and vice versa, the singlet oxygen sensitization of a molecule with strong luminescence ability will also be weakened. To a certain extent, the poor fluorescence emission property may be more beneficial for it to be used as a photosensitizer, so as to better match the component function settings of each performing its own duties in the photochemical long afterglow system.

[0083] When selectively exciting with a light source, the TBPS photosensitizer molecule can convert oxygen into singlet oxygen through type II sensitization. Research shows that the singlet oxygen yield of the TBPS molecule is as high as 140%, which is significantly higher than that of the photosensitizers used in traditional photochemical long afterglow systems, greatly increasing the feasibility of designing a singlet fission sensitized photochemical long afterglow system.

[0084] Example 2 Synthesis of the luminescent compound Eu(TTA) 3 (TPPO) 2 Synthesis

[0085] The synthetic route of the compound Eu(TTA) 3 (TPPO) 2 is as follows:

[0086]

[0087] Rare earth complex Eu(TTA) 3 (TPPO) 2 The luminescent material was synthesized according to the route shown. Specifically, EuCl 3 ·6H 2 O (120 mg, dissolved in 1.25 mL of water) was added to a solution of TPPO ligand (190 mg) and TTA ligand (220 mg) in 10 mL of ethanol. The mixture with the pH adjusted to 5 - 6 was stirred and heated under reflux in an oil bath for 8 h. After cooling to ambient temperature, the crude precipitate was washed 3 times with water and ethanol. The residue was dried to finally obtain approximately 400 mg of the europium complex.

[0088] Generally speaking, the europium complex Eu(TTA) 3 (TPPO) 2 is a commonly used rare earth luminescent material, and due to its unique f-f transition, it usually produces a sharp red light emission at 615 nm. Theoretically, the TBPS photosensitizer has no absorption peak at the emission of the europium complex Eu(TTA) 3 (TPPO) 2 , which can eliminate the self-absorption effect and thus ensure the maximum emission of photons, being beneficial to the improvement of the long afterglow luminescence performance. Under the excitation of 365 nm ultraviolet light, the europium complex Eu(TTA) 3 (TPPO) 2 emits bright red light. Through characterization by the emission spectrum, it is found that the main peak is located at 615 nm (as Figure 4 shown, Figure 4 is the emission spectrum diagram of the luminescent material Eu(TTA) 3 (TPPO) 2 in toluene solution under 365 nm excitation). This is the characteristic emission peak corresponding to the 5 D 0 → 7 F 2 transition of europium(III) ions. Due to the characteristics of the f-f transition, its emission peak is very narrow, and the full width at half maximum (FWHM) is only ~5 nm. The sharp emission of this rare earth complex in the red light region is beneficial for biomedical applications such as diagnostic detection, and can weaken the absorption effect of blood samples on luminescence to a certain extent.

[0089] Example 3 Synthesis of the buffer compound SOMN

[0090] The synthesis route of the compound SOMN buffer is as follows:

[0091]

[0092] First, 2.6 g of benzoin raw material (10 mmol), 40 mL of toluene, 2.1 mL of 2-mercaptoethanol (0.03 mol), and 2.5 mL of trimethylchlorosilane (0.02 mol) were successively added to a 100 mL three-necked flask. The mixed solution was refluxed for 4 h under argon protection and then cooled to room temperature. Then, saturated NaHCO 3 solution was slowly added dropwise, and liquid separation operation was carried out. The organic phase layer was collected and washed three times with saturated NaHCO 3 solution, and then the organic solvent was removed by rotary evaporation. Using dichloromethane and petroleum ether as eluents, the final product of white solid was obtained after column chromatography separation and purification, and the yield was 40%.

[0093] The TBPS molecule in Example 1 was selected as the sensitizer, and Eu(TTA) 3 (TPPO) 2 in Example 2 was selected as the luminescent body, and the SOMN in this example was used as the buffer agent to construct a photochemical long afterglow system. Referring to Figure 5 , Figure 5 shows the luminescence process of the singlet fission sensitized photochemical afterglow system. Based on the photochemical energy storage and transfer (PCREST) strategy, indirect excitation of the europium complex luminescent body is achieved, enabling the intrinsic luminescence of the complex to reach an ultra-long luminescence lifetime of up to several seconds. Since the SOMN molecule is a compound containing special unsaturated olefins, the olefinic double bond is located in a six-membered ring containing S and O, and a strong electron-donating group is connected to the S end side of the double bond. Based on this unique chemical structure, the electron cloud distribution is very asymmetric, and this double bond is prone to addition reaction with singlet oxygen and is prone to form an excited state of the ring-opening product through a concerted decomposition mechanism. The photochemical long afterglow luminescence process is theoretically caused by a series of photochemical reactions, and the photochemical reaction between the buffer agent and singlet oxygen plays an important role. This photochemical reaction (>s level) is slower and easier to occur compared to the photophysical energy level transition (<ms level), and does not require special stabilization such as a crystalline environment. The photosensitization process and the luminescence process of rare earth complexes can usually be completed at the ms level. Since the photochemical reaction of the buffer agent SOMN is significantly slower, it becomes the rate-determining step of the whole path. Based on this design, under the excitation of a light source by the photosensitizer, through the photochemical energy storage and transfer (PCREST) mechanism, the long afterglow luminescence of rare earth complexes is finally achieved. In fact, this is similar to the category of photoluminescence (photon excitation → photon emission). The difference is that the organic integration of photochemistry and photophysics makes the luminescence process reach the long afterglow category, and it is called photochemical long afterglow due to the unique properties of photochemistry. The above phenomena indicate that adding the photosensitizer TBPS, the buffer agent SOMN, and the luminescent body Eu(TTA) to the organic phase solution3 (TPPO) 2 After the three functional components of the complex, the photosensitizer TBPS successfully triggered the photochemical reaction, and red long-afterglow luminescence was observed in the organic solution. Subsequently, the optical fiber spectrometer was used to collect and characterize the spectrum of the long-afterglow luminescence. As Figure 6 shown, Figure 6 is the long-afterglow emission spectrum of the photochemical long-afterglow system TBPS&SOMN&Eu(TTA) 3 (TPPO) 2 in toluene solution. The test method is that the mixed solution is irradiated with a 532 nm light source for 2 s, and the signal peak is collected after the light source is turned off. The results show that TBPS&SOMN&Eu(TTA) 3 (TPPO) 2 The main peak of the long-afterglow spectrum in toluene solution is located at 615 nm, and it has the same emission spectral curve as the Eu(TTA) 3 (TPPO) 2 complex itself. The main peak of the long-afterglow is still the characteristic emission peak corresponding to the 5 D 0 → 7 F 2 transition of europium(III) ions, and its characteristic of narrow emission peak due to f-f transition is completely retained.

[0094] For long-afterglow materials, the research on realizing long-afterglow luminescence in organic solvents has rarely been reported, especially the narrow-band long-afterglow emission of rare earths themselves. Through the luminescence mechanism of photochemical long-afterglow, traditional rare earth complexes can also achieve long-afterglow luminescence. Since the research on rare earth complexes is very sufficient and extensive, it is expected to greatly expand and enrich rare earth long-afterglow luminescent materials. In the photochemical long-afterglow system, when the long-afterglow luminescence is consistent with the emission of the luminescent body and can be directly carried out in the organic solution, it is more convenient to design and adjust the luminescence properties of the material. The luminescence can still be observed by the naked eye after the light source is turned off, which intuitively judges that it belongs to the category of long-afterglow luminescence. In order to more accurately quantitatively describe the persistent luminescence phenomenon, the luminescence lifetime of the three-component mixed system was tested next. As Figure 7 shown, Figure 7 is the photochemical long-afterglow system TBPS&SOMN&Eu(TTA) 3 (TPPO) 2The long afterglow luminescence decay curve in toluene solution was measured by irradiating the mixed solution with a 532 nm light source for 2 s and collecting the signal intensity at 615 nm and its decay changes within 60 s after turning off the excitation light source. The results showed that the intensity value of the emitted photons continuously decayed over time. After fitting, the long afterglow luminescence lifetime of the system was revealed to be 3 s. Therefore, the luminescence lifetime of the rare earth complex was extended from ~1 millisecond to as long as 3 s, with an extension amplitude exceeding three orders of magnitude. The luminescence lifetime of rare earth complexes is usually difficult to regulate over a large range. The photochemical long afterglow mechanism provides a new path for lifetime extension, breaking through the limitation of the short luminescence lifetime of the luminescent material itself.

[0095] In the photochemical long afterglow system, the photoreaction of the cache agent is significantly slower and becomes the rate-determining step of the entire luminescence path. Therefore, the luminescence lifetime is mainly determined by the cache agent. The photoreaction of the cache agent SOMN is as follows, mainly including the addition reaction of singlet oxygen and the decomposition and ring-opening reaction of the generated intermediate product.

[0096]

[0097] After the photoreaction of the cache agent SOMN, an excited state is generated but it does not emit light directly, mainly because the fluorescence quantum yield is very low (<0.1%). In addition, the absorption peaks of the cache agent SOMN and its decomposition products are all in the ultraviolet region and have no obvious absorption effect on the green light in the visible region. Therefore, the core role of the cache agent SOMN is to first temporarily cache the energy in the chemical bond for later use, and then decompose to form an excited state and transfer the energy to the luminescent body. The cache agent establishes an energy connection channel between the photosensitizer and the luminescent body, organically integrating the photochemical process and the photophysical process. Thus, while maintaining the input and output of energy in the form of photons (i.e., the photoluminescence mode), it breaks the limitations such as the energy matching between the photosensitizer and the luminescent body, greatly broadening the design of the wavelength and lifetime properties of the luminescent material.

[0098] On the basis of achieving photochemical long afterglow luminescence, the system was further optimized to obtain a high-brightness photochemical long afterglow organic solution system. When the rare earth europium complex Eu(TTA) 3 (TPPO) 2 is used as the luminescent body, the photosensitizer TBPS is very suitable to be paired with it to jointly construct a photochemical long afterglow system. As Figure 8 shown, Figure 8 is the spectrum and photo of the singlet fission sensitized photochemical afterglow system. Among them, J(λ) is the overlap integral of the absorption peak of the photosensitizer TBPS and the emission peak of the luminescent body Eu(TTA) 3 (TPPO) 2 In addition to its excellent singlet oxygen generation ability, the absorption peak of the photosensitizer TBPS overlaps with that of the luminescent body Eu(TTA)3 (TPPO) 2 The emission peaks are far apart and do not overlap. Calculations show that the main absorption peak of the photosensitizer TBPS and the emitter Eu(TTA) 3 (TPPO) 2 have a Stokes shift as high as 2100 cm -1 between their main emission peaks. In terms of the quantitative evaluation of spectral overlap, the overlap integral J(λ) of the main absorption peak of the photosensitizer TBPS and the main emission peak of the emitter Eu(TTA) 3 (TPPO) 2 can be obtained by calculation. The results show that the spectral overlap integral of absorption and emission is zero. In the photochemical long afterglow system, the photosensitizer is mainly responsible for light absorption and the emitter is mainly responsible for light emission. The absorption peak of the photosensitizer and the emission peak of the emitter have zero overlap, and the interference between them is small, thus avoiding the adverse effect of the long afterglow luminescence being absorbed and internally filtered by the system. Intuitively, the color of the long afterglow solution under bright field conditions is red. Usually, the absorption of red light by the red solution is also weak because the photons not absorbed in the red light band of the solution can be transmitted to the naked eye or the camera and present red. Under dark field conditions, the color of the long afterglow luminescence in the dark is also red, consistent with the color in the bright environment (as shown in the inset of Figure 8 ).

[0099] According to the design concept that each component in the photochemical long afterglow system performs its own function, the combination of the photosensitizer, the buffer and the emitter is appropriate. When the interference between them is small, the performance of the long afterglow luminescence can be more conveniently optimized by adjusting the concentrations of each component. First, in the photochemical long afterglow system, the concentrations of the buffer SOMN and the emitter Eu(TTA) 3 (TPPO) 2 complex were optimized. As shown in Figure 9 , Figure 9 is the variation trend of the photochemical long afterglow luminescence intensity with the component concentration. The test method is to fix the concentration of the photosensitizer in toluene solution, adjust the concentration of the buffer (a) or the emitter (b), irradiate with a 532 nm laser for 2 s and then turn off the laser, and record the change of the photochemical long afterglow luminescence intensity at 615 nm. The research results show that at first, as the concentration of the buffer SOMN increases, the long afterglow luminescence intensity gradually increases, mainly due to the enhanced capture level of the singlet oxygen generated by photosensitization after the increase of the buffer molecules. When the concentration of the buffer SOMN exceeds 3 mM, further increasing the concentration of the buffer, the intensity of the long afterglow luminescence will gradually decrease, mainly because too many buffer molecules lead to insufficient energy transfer. For the emitter Eu(TTA) 3 (TPPO) 2For long afterglow luminescence, it continuously enhances with the increase in the concentration of the luminescent material. Even when the concentration of the luminescent material reaches a relatively high level of 10 mM, no downward trend in the long afterglow intensity is observed. Based on the above experimental results and analysis, the optimal concentration of the buffer SOMN is determined to be 3 mM, and the 3 (TPPO) 2 optimal concentration of the Eu(TTA)

[0100] complex is determined to be 10 mM and is used in the study of photochemical long afterglow. The concentration optimization of the photosensitizer is also necessary for photochemical long afterglow, but the optimization of the upper limit of the photosensitizer concentration is often very limited. According to traditional reports on photochemical long afterglow research, the optimal dosage of the photosensitizer is usually at a level below 10 μM. Although a larger photosensitizer concentration can have a stronger light absorption ability, thereby increasing the total amount of input photons at the source. To more clearly reveal the limitations of the photosensitizer concentration regulation, first, silicon phthalocyanine (SiPc) is selected as the photosensitizer for experimental research. This molecule is one of the most commonly used photosensitizers in the photochemical long afterglow system. The variation trend of the photochemical long afterglow luminescence intensity with the concentration of the photosensitizer SiPc is as Figure 10 shown. The test method is to fix the concentrations of the buffer and the luminescent material in a toluene solution, adjust the concentration of the photosensitizer, irradiate with a 680 nm laser for 2 s and then turn off the laser, and record the change in the 615 nm luminescence intensity of the photochemical long afterglow, where the concentration of the buffer SOMN is 3 mM, and the concentration of the Eu(TTA) 3 (TPPO) 2 complex is 10 mM. The results show that at first, the long afterglow luminescence intensity gradually increases with the increase in the concentration of the photosensitizer SiPc, mainly due to the increase in the amount of singlet oxygen generated by photosensitization after the increase in the number of photosensitizer molecules. However, when the concentration of the photosensitizer SiPc exceeds 5 μM, further increasing the concentration of the photosensitizer will significantly reduce the intensity of the long afterglow luminescence. Based on this experimental result, the optimal concentration of the photosensitizer SiPc in the photochemical long afterglow system is preferably 5 μM, which is consistent with previous studies.

[0101] Furthermore, the above-mentioned concentration quenching problem caused by the traditional photosensitizer SiPc is studied and analyzed. By testing the absorption spectrum of SiPc, it is found that the main absorption peak of this classic phthalocyanine photosensitizer SiPc is near 680 nm, and obvious absorption exists in the spectral range from 600 nm to 700 nm (as Figure 11 shown). It is not difficult to find that the luminescent material Eu(TTA) 3 (TPPO) 2The emission peaks of the complex also fall within this range, and there is an overlap problem between the absorption peak of the photosensitizer SiPc and the emission peak of the luminescent substance. This problem is obviously unfavorable for long afterglow luminescence because it will cause self-absorption inner filter effect inside the system, resulting in luminescence quenching. Therefore, in the photochemical long afterglow system, the optimal concentration of the photosensitizer SiPc is only at a relatively low level of 5 μM, which greatly limits the input and absorption ability of the excitation photon energy, equivalent to restricting the source of energy.

[0102] Compared with the significant concentration quenching of the traditional photosensitizer SiPc, the photosensitizer TBPS designed in this disclosure can obtain better long afterglow luminescence performance at high concentrations (as Figure 12 shown). As the concentration of the photosensitizer TBPS increases, the long afterglow luminescence intensity gradually increases, and no trend of decreasing long afterglow intensity is observed even when the dosage of the photosensitizer TBPS at a high concentration of 200 μM is used. This is still mainly attributed to the increase in the amount of singlet oxygen generated by photosensitization after the increase in the number of photosensitizer molecules. The zero-overlap characteristic between the photosensitizer TBPS and the luminescent Eu(TTA) 3 (TPPO) 2 complex enables the TBPS sensitizer to reach an extremely high applicable concentration without having an adverse inner filter effect on the long afterglow signal of rare earth luminescence. Based on this, the concentration of the photosensitizer TBPS in the photochemical long afterglow system is preferably at a relatively high level of 200 μM. The experimental results also illustrate from another aspect that the energy input source in the system with 5 μM low-concentration SiPc as the photosensitizer is far from reaching the optimal or saturated level. The effective input amount of photon energy is a bottleneck for the improvement of photochemical long afterglow performance, and this bottleneck severely restricts the photochemical long afterglow performance of rare earths involving the above SiPc photosensitizer. Therefore, the design, development, and application of the singlet fission type photosensitizer TBPS break through the bottleneck, improve the absorption ability through high concentration, and achieve the effect of expanding the source of photon energy input and then improving the photochemical long afterglow luminescence performance.

[0103] The design introduction of the singlet fission type photosensitizer TBPS brings new opportunities for photochemical long afterglow, especially for the photochemical long afterglow system using rare earth europium complexes as luminescent substances, and has great potential to construct high-brightness rare earth photochemical long afterglow luminescent materials. When performing long afterglow luminescence experiments using a laser with a low excitation power (2.5 mW cm -2 ), the solution with the new TBPS molecule as the photosensitizer can still emit bright visible red long afterglow, while no obvious long afterglow emission is observed in the solution with the traditional and commonly used SiPc molecule as the photosensitizer. The photochemical long afterglow luminescence images with TBPS and SiPc as photosensitizers respectively are as Figure 13As shown, the concentrations of photosensitizer TBPS and SiPc are respectively optimized at 200 μM and 5 μM, and the concentrations of buffer SOMN and emitter Eu(TTA) 3 (TPPO) 2 are 3 mM and 10 mM respectively. The solution sample containing TBPS (right) is excited by a 532 nm laser, while the solution sample containing SiPc (left) is excited by a 680 nm laser, and the power density of both lasers is 2.5 mW cm -2 at a relatively low level. With the same buffer and emitter components, such a large performance improvement can be achieved when the photosensitizer component is changed from the traditional SiPc photosensitizer to the singlet fission type TBPS photosensitizer. Fundamentally, the improvement mainly benefits from two factors: (1) The photosensitizer TBPS molecule has the unique property of singlet fission, enabling a singlet oxygen generation efficiency as high as 140%, directly breaking through the upper limit of the traditional photosensitizer level; (2) The absorption of the photosensitizer TBPS molecule has zero overlap with the emission of the rare earth complex, increasing the upper limit of the optimal applicable concentration of the photosensitizer. These two factors greatly enhance the light energy absorption and conversion ability of the photosensitizer component, and the advantages of the singlet fission type photosensitizer TBPS in the study of photochemical long afterglow are intuitively reflected, directly achieving high-performance rare earth photochemical long afterglow luminescence in the organic solution phase.

[0104] Subsequently, by preparing a series of solution samples and analyzing the emission spectra, a verification study on the mechanism of the above photochemical long afterglow luminescence was carried out. Theoretically, for the TBPS&SOMN&Eu(TTA) 3 (TPPO) 2 ternary mixed solution, only the matching photosensitizer TBPS component can be excited under the irradiation of light with a wavelength of 532 nm. After exciting the ternary mixed solution with 532 nm, only the characteristic emission peak of the emitter Eu(TTA) 3 (TPPO) 2 was observed in the delayed afterglow spectrum (as shown by the red line in Figure 14 ). For the SOMN&Eu(TTA) 3 (TPPO) 2 binary mixed solution and the Eu(TTA) 3 (TPPO) 2 single-component solution, in the absence of the photosensitizer TBPS, no obvious rare earth complex emission peak was detected in the steady-state spectrum after excitation with 532 nm (as shown by the blue and black lines in Figure 14 ), indicating that Eu(TTA) 3 (TPPO) 2It cannot be directly excited by 532-nm photons. In fact, 532-nm photons have a selective excitation effect on the photosensitizer TBPS component. Under the condition that the excited state efficiently sensitizes oxygen to generate singlet oxygen continuously in the photosensitizer TBPS, the buffer agent SOMN component serves as an energy bridge connecting chemical energy and light energy through the photochemical reaction it participates in, and also extends the luminescence duration to the long afterglow luminescence range at the second level. Therefore, the luminescence of the rare earth europium complex here conforms to the photochemical long afterglow mechanism of photochemical energy storage and transfer, which is different from the traditional dye-sensitized or energy transfer mechanisms. It should be noted here that Figure 14 are the luminescence spectra of different solution samples, where the photosensitizer TBPS, the buffer agent SOMN, and the luminescent body Eu(TTA) 3 (TPPO) 2 The concentrations of the three components are 200 μM, 3 mM, and 10 mM respectively, and the samples are excited by a 532-nm light source. Among them, the samples of the three components are tested in the long afterglow spectrum mode, and the other two samples are tested in the fluorescence spectrum mode.

[0105] Through the control variable long afterglow spectrum test control experiment, it is found that only when the photosensitizer TBPS and the buffer agent SOMN are added to the solution at the same time, can the red long afterglow luminescence signal of Eu(TTA) 3 (TPPO) 2 be detected, as shown in Figure 15 shown, Figure 15 is the photochemical long afterglow luminescence spectrogram under different component conditions. The red line is the long afterglow luminescence spectrum when all three components of the photosensitizer TBPS, the buffer agent SOMN, and the luminescent body Eu(TTA) 3 (TPPO) 2 exist. The black lines are the long afterglow luminescence spectra lacking the photosensitizer TBPS and lacking the buffer agent (SOMN) respectively. When the photosensitizer TBPS is missing, as shown by the black line in Figure 15 (a), or when the buffer agent SOMN is missing, as shown by the black line in Figure 15 (b), the photochemical long afterglow system is incomplete, and the long afterglow luminescence process based on photochemical energy storage and transfer cannot proceed, resulting in the disappearance of the long afterglow luminescence signal. The above experimental results further verify the action mechanism of the functional synergy of each component in the photochemical long afterglow system. The photochemical long afterglow is finally manifested as the emission peak of the luminescent body, that is, the intrinsic f-f transition luminescence of the rare earth complex. Therefore, through the combined design of three functional units, a rare earth photochemical long afterglow luminescence system is established, and the regulation and optimization of long afterglow luminescence are directly realized in the organic phase, and finally a rare earth long afterglow luminescence solution with high brightness is obtained.

[0106] In addition, photochemical long afterglow luminescence can occur in ordinary organic solutions without the need for additional protective measures or additives, such as deoxygenation or addition of antioxidants. In fact, when the solution is placed in a glove box filled with nitrogen, the long afterglow luminescence becomes too weak to be detected, as Figure 16 shown Figure 16 is the long afterglow luminescence spectrum of the singlet fission sensitized type photochemical long afterglow system under different atmosphere conditions. Among them, the concentrations of the photosensitizer TBPS, the buffer SOMN, and the luminescent Eu(TTA) 3 (TPPO) 2 are 200 μM, 3 mM, and 10 mM respectively. The sample is excited by a 532 nm light source, and the long afterglow spectrum is collected after turning off the excitation light. Since normal environments and the atmosphere usually contain abundant oxygen, the ability to not need to eliminate the influence of oxygen can greatly simplify the application design. Therefore, rare earth photochemical long afterglow luminescent materials have high feasibility and practicality.

[0107] Finally, the long afterglow brightness of the constructed organic phase photochemical long afterglow luminescent material is evaluated. The research is mainly carried out by the method of reference comparison, and the evaluation is carried out by comparing with the ultra-bright long afterglow system established with the porphyrin complex PdOEP as the photosensitizer before. As Figure 17 shown Figure 17 is the absorption spectra of the sensitizer TBPS and PdOEP in toluene. Among them, the concentration of TBPS in toluene is 20 μM, and the concentration of PdOEP in toluene is 2.5 μM. Both the photosensitizer TBPS and the photosensitizer PdOEP have absorption peaks in the green light region, and the photosensitizer PdOEP is also often used with a 532 nm excitation light for optical research. In addition, the singlet oxygen yield of the photosensitizer PdOEP is as high as 90%, although it is inferior to 140% of the photosensitizer TBPS, it is still at a relatively high level among traditional photosensitizers. By analyzing and calculating the absorption spectra of the photosensitizers, the molar extinction coefficients of the photosensitizer TBPS and the photosensitizer PdOEP at 532 nm are 3.2×10 4 L mol -1 cm -1 and 8.1×10 3 L mol -1 cm -1 respectively. The results show that this value of the photosensitizer TBPS is about 4 times that of the photosensitizer PdOEP. Therefore, compared with the photosensitizer PdOEP, the photosensitizer TBPS can absorb the energy of the commonly used 532 nm excitation light more fully.

[0108] When using a 532 nm laser at a low power density (2.5 mW cm -2)When irradiating the sample, a red persistent luminescence with higher brightness was observed in the photochemical persistent luminescence system based on the photosensitizer TBPS, as Figure 18 shown, Figure 18 Figure 4 shows the performance comparison between the singlet fission sensitized photochemical persistent luminescence system based on TBPS and the ultra-bright persistent luminescence system established with PdOEP as the photosensitizer. The test conditions were both using 532 nm laser excitation. This phenomenon is attributed to the more efficient absorption and utilization of the 532 nm excitation light energy by the TBPS molecule of the photosensitizer, which is mainly reflected in the significant increase in the molar extinction coefficient and singlet oxygen yield. The comparison results show the advantages of the singlet fission type photosensitizer TBPS in improving the persistent luminescence performance. Based on this, an ultra-bright rare earth photochemical persistent luminescence solution system was successfully constructed.

[0109] Example 4 Synthesis of Photochemical Persistent Luminescence Nanoparticles PA-NPs

[0110] Based on the constructed ultra-bright photochemical persistent luminescence organic phase solution, a bottom-up preparation method for persistent luminescence nanoparticles was designed using a wet chemical synthesis process. This method can fabricate persistent luminescence nanomaterials on demand, for example, the size, morphology, functional surface, etc. can all be designed and selected according to requirements. Wet chemical synthesis is the most commonly used means to manufacture new material substances, and a variety of mature solution processing technologies can easily obtain rich functional materials. In order to obtain high-quality persistent luminescence nanoparticles with uniform size and functionalized surface, carboxylated polystyrene microspheres and an ultra-bright photochemical persistent luminescence molecular system were selected as the building components, and they can be prepared through a one-step wet chemical synthesis in solution. For details, see Figure 19 , Figure 19 Figure 5 is the preparation flow chart of the photochemical persistent luminescence nanoparticles (PA-NPs), where carboxylated polystyrene microspheres and an ultra-bright photochemical persistent luminescence molecular system were used as the building components, and a bottom-up wet chemical synthesis method was adopted for preparation.

[0111] To synthesize the photochemical persistent luminescence nanoparticles PA-NPs, a solution containing a photosensitizer (TBPS, 200 uM), a buffer agent (SOMN, 3 mM), and a luminescent agent (Eu-complex, 10 mM) dissolved in tetrahydrofuran (THF, as a swelling agent) was prepared. Cross-linked carboxylated polystyrene nanoparticles were used as the blank nanocarriers, and the carboxyl groups can provide hydrophilic groups and functional sites for antibody conjugation. Subsequently, hydrophobic functional molecules (sensitizer, buffer agent, luminescent agent) were encapsulated into the nanocarriers to obtain a mixture solution. The mixture was stirred in the dark for 4 h, and then the nanoparticles were washed 3 times with water and ethanol. Finally, the nanoparticles were dispersed in water for further use.

[0112] According to the design, the photochemical long afterglow nanoparticles are mainly composed of two parts: a nanocarrier and a photochemical long afterglow molecule. The nanocarrier is associated with two key features: size and morphology, and a functional surface, while the photochemical long afterglow molecule is associated with the key feature of long afterglow luminescence performance. Cross-linked carboxylated polystyrene nanoparticles are used as the nanocarrier. The nanocarriers have a uniform size, and the carboxyl groups distributed on the surface can provide hydrophilicity while providing coupling sites for further biological applications. A super-bright photochemical long afterglow molecular system is loaded into the nanocarrier. The loading method is simple, mild, and controllable, which helps to prepare high-quality photochemical long afterglow nanoparticles. After wet chemical synthesis, the photosensitizer TBPS & the buffer SOMN & the luminescent Eu(TTA) 3 (TPPO) 2 Three hydrophobic molecules are encapsulated in the nanocarrier, and the prepared photochemical long afterglow nanoparticles (named PA-NPs) are obtained after centrifugation and washing. The photochemical long afterglow nanoparticles are well-dispersed in water, forming a pink aqueous solution (as Figure 20 shown). Characterization by field emission scanning electron microscope images shows that the prepared PA-NPs have a diameter of ~180 nm. The nanoparticle size is uniform, and the coefficient of variation CV < 5%.

[0113] Subsequently, the long afterglow luminescence properties of the photochemical long afterglow nanoparticles PA-NPs were tested. When PA-NPs are dispersed in water and irradiated with a 532 nm laser and the excitation light is turned off, bright red long afterglow luminescence can be observed from the aqueous solution. The long afterglow luminescence brightness exceeds 100 mcd m -2 level, which is much higher than the visible level of 0.32 mcd m -2 brightness level. Furthermore, spectral characterization tests show that the characteristic emission peaks attributed to the rare earth complex Eu(TTA) 3 (TPPO) 2 appear in the afterglow spectrum, as Figure 21 shown, Figure 21 is the long afterglow luminescence performance of the photochemical long afterglow nanoparticles (PA-NPs) in aqueous solution. The test conditions are irradiation with a 532 nm laser for 2 s and then turning off, and then collecting the long afterglow luminescence spectrum. The inset is the bright field and long afterglow luminescence photos of the photochemical long afterglow nanoparticles. Therefore, rare earth photochemical long afterglow luminescent nanoparticles are successfully prepared and still maintain high-brightness rare earth long afterglow luminescence in aqueous solution.

[0114] In potential biophotonics and biomedical applications, the stability of long-afterglow nanoparticles in aqueous phase is an important indicator. A long-term stability study was conducted on the photochemical long-afterglow nanoparticles. The results showed that the prepared PA-NPs had good dispersion stability in water. Dynamic light scattering measurements indicated that their hydrodynamic diameter did not change significantly during the 3-month long-term storage. The aqueous solution of PA-NPs was stored away from light, and the results showed that the long-afterglow luminescence intensity did not change significantly within 3 months. Therefore, the prepared photochemical long-afterglow luminescent nanoparticles PA-NPs have good long-term stability and can meet the requirements of a wide range of application scenarios.

[0115] The above-prepared high-quality long-afterglow luminescent nanoparticles have ideal properties such as a uniform particle size at the nanoscale, surface groups that can be bioconjugated and modified, high-brightness long-afterglow luminescence, narrow-band emission characteristic of rare earths, and excellent long-term stability. Thanks to the unique luminescence mechanism of photochemical long afterglow, after breaking through the limitations of crystal structure and specific environment, a super-bright photochemical long-afterglow solution system compatible with wet chemical synthesis was obtained, laying a foundation for the preparation of high-quality long-afterglow nanomaterials. Designed on demand according to the target, through a bottom-up wet chemical synthesis method, high-performance long-afterglow luminescent nanoparticles with uniform size and functionalized surface were finally successfully prepared. The preparation method of the long-afterglow nanoparticles is simple and the conditions are mild, providing a photochemical research path for the development of long-afterglow luminescence detection-related probes.

[0116] Example 5 Synthesis of Sensitized Microspheres and Luminescent Microspheres

[0117] The synthesis of nanoparticles for homogeneous immunoassay was carried out with reference to Example 4. The photosensitizer was encapsulated in a separate nanocarrier to obtain sensitized microspheres, and the quencher and emitter were encapsulated into another separate nanocarrier to obtain luminescent microspheres. The nanoparticles of sensitized microspheres and luminescent microspheres were stored in two containers for further use.

[0118] For the above-constructed high-performance photochemical long-afterglow nanomaterials, the carboxyl groups on their surfaces can be further conjugated and modified to form long-afterglow luminescent probes with detection functions. Utilizing the characteristic of collecting signals after the excitation light is turned off for long-afterglow luminescence, it is possible to avoid excitation light and biological background interference and establish application advantages in biomedical aspects such as imaging detection. For example, after activating some of the carboxyl groups on the surface of the photochemical long-afterglow nanomaterial, they can react and conjugate with the amino groups of protein substances such as antibodies, and long-afterglow luminescent detection probes for biomarkers such as antigens can be formed through this modification. Therefore, the research on long-afterglow luminescence detection probes based on photochemical long afterglow has broad application prospects. For example, immunochromatography, homogeneous detection, etc.

[0119] In summary, through the design of singlet fission type photosensitizers, the present disclosure has developed a photochemical long afterglow material system with ultra-bright rare earth luminescence characteristics. The rare earth long afterglow luminescence is based on the energy storage and transfer (PCREST) mechanism of photochemical reactions, breaking away from the limitations associated with traditional crystallization mechanisms. As a result, long afterglow luminescence with the same emission curve as the f-f transition of europium complexes was directly observed in organic solutions. Due to the unique property of singlet fission of the photosensitizer molecules, the singlet oxygen generation efficiency is as high as 140%, directly breaking through the upper limit of the traditional photosensitizer level. At the same time, the absorption of the photosensitizer molecules and the emission of the rare earth complexes have zero overlap, increasing the upper limit of the optimal applicable concentration of the photosensitizer. The integration of these two factors significantly enhances the light energy absorption and conversion ability of the system, directly achieving high-performance rare earth photochemical long afterglow luminescence in the organic solution phase. Based on this, high-quality long afterglow luminescent nanoparticles were prepared, which have properties such as a uniform particle size at the nanoscale, surface groups that can be bio-conjugated and modified, high-brightness long afterglow luminescence, narrow-band emission characteristic of rare earths, and excellent long-term stability. This work has established a singlet fission sensitized photochemical long afterglow system, providing a new path for the design and preparation of high-brightness long afterglow luminescent materials, and having broad application prospects in biomedical fields such as long afterglow detection.

Claims

1. A singlet splitting sensitized photochemical long afterglow system, characterized in that: The photochemical long afterglow system includes at least one sensitizer, at least one buffer and at least one luminophore; wherein the sensitizer has a singlet splitting property, and the absorption peak of the sensitizer overlaps with the emission peak of the luminophore at zero peak position.

2. The photochemical long afterglow system according to claim 1, characterized in that: The sensitizer converts oxygen into singlet oxygen through type II sensitization under selective excitation of a light source.

3. The photochemical long afterglow system according to claim 2, characterized in that: The structure of the sensitizer is shown in Formula Ⅰ-A or Formula Ⅰ-B: Wherein, the R substituent in formula Ⅰ-A is selected from the group consisting of a benzene ring Benzene ring derivatives Bridged cycloalkanes, biphenyls and biphenyl derivatives Where n is 1-6; Among them, in formula I-B is selected from cycloalkanes or cycloalkanes derivatives having 1 to 6 carbon atoms, wherein the cycloalkanes or cycloalkanes derivatives are the same as the cycloalkanes in formula I-B. The benzene rings in the main body other than the above are fused by a shared chemical bond.

4. The photochemical long afterglow system according to claim 3, characterized in that: The structure of the sensitizer is shown below: Wherein, * represents a bonding site, and the *bonding site is located at any aromatic hydrogen atom of a benzene ring or its derivatives; Wherein, R1 is selected from an alkyl group, an alkoxy group or an alkylamino group having 1 to 8 carbon atoms; The value range of n is 1-8.

5. The photochemical long afterglow system according to claim 3, characterized in that: The structure of the sensitizer is shown below: Wherein, the R2 substituent in formula A is 6. The photochemical long afterglow system according to claim 1, characterized in that: The structure of the buffer is shown in Formula II: Wherein, the R1, R2, and R3 substituents in formula II may be the same or different, and the R1 substituent in formula II is selected from hydrogen, or an alkyl, alkoxy, or alkylamino group having 1 to 8 carbon atoms; the R2 and R3 substituents are each independently selected from an alkyl, alkoxy, or alkylamino group having 1 to 8 carbon atoms.

7. The photochemical long afterglow system according to claim 6, characterized in that: The structure of the cache agent is shown in Formula II-A:

8. The photochemical long afterglow system according to claim 1, characterized in that: The luminophore is selected from a rare earth complex, and the central atom of the rare earth complex is preferably Eu, Tb, Sm, Yb, Nd, Dy, Er, Ho, or Pr.

9. The photochemical long afterglow system according to claim 8, characterized in that: The structure of the rare earth complex is shown in Formula III:

10. The photochemical long afterglow system according to claim 1, characterized in that: In the photochemical long afterglow system, the concentration range of the buffer is 0.5-10 mM, the concentration range of the luminophore is 2.5-15 mM, and the concentration range of the sensitizer is 5-250 μM.

11. A photochemical long afterglow nanoparticle, characterized in that: The photochemical long afterglow nanoparticles include the sensitizer, buffer and luminophore according to any one of claims 1 to 10. The sensitizer, buffer and luminophore are encapsulated into a nanocarrier, and the nanocarrier is a polystyrene nanoparticle and a polystyrene derivative nanoparticle.

12. A photochemical long afterglow nanoprobe, characterized in that: The probe is formed by coupling and modifying the surface of the photochemical long afterglow nanoparticles described in claim 11 with protein substances.

13. The photochemical long afterglow nanoprobe according to claim 12, characterized in that: The probe is used in the fields of biological imaging, immunochromatography and homogeneous detection.

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