Singlet fission sensitized photochemical long persistent luminescence system and application

Abstract

The present application relates to the technical field of light emitting, in particular to a kind of singlet fission sensitization type photochemical long afterglow system and application based on.The photochemical long afterglow system of the present application includes at least one sensitizer, at least one buffer and at least one luminophore;Wherein, the sensitizer has singlet fission property, and the absorption peak of the sensitizer and the emission peak of the luminophore peak position zero overlap.Due to the unique performance of the sensitizer singlet fission, singlet oxygen production efficiency is as high as 140%, directly breaks through the upper limit of the level of traditional photosensitizer.At the same time, the absorption of photosensitizer molecule and the emission of rare earth complex zero overlap, improve the upper limit of the optimal application concentration of photosensitizer.The integration of the two factors significantly enhances the light energy absorption conversion capacity of the system, directly realizes high-performance rare earth photochemical long afterglow luminescence in organic solution phase.

Description

Technical Field

[0001] This invention relates to the field of luminescent materials technology, and more particularly to a singlet-state splitting-sensitized photochemical long-afterglow system and its applications. Furthermore, this invention also relates to photochemical long-afterglow nanoparticles, photochemical long-afterglow nanoprobes, their preparation methods, and their applications. Background Technology

[0002] Long-afterglow luminescent materials have attracted much attention due to their unique ability to continue emitting photons after the excitation light is turned off. However, only in recent decades have rapid developments been made in the luminescence mechanism and material preparation of long-afterglow materials. Through continuous efforts by researchers, a wide variety of long-afterglow materials have been designed and synthesized, and their applications in displays, sensors, anti-counterfeiting, and security markings have been explored. Among them, inorganic long-afterglow powders exhibit the most outstanding performance in terms of luminescence duration and brightness. These are crystalline materials typically doped with rare earth elements or transition metals and are currently the most commonly used long-afterglow materials. For example, rare earth element-doped blue powder CaAl2O4:Eu 2+ ,Nd 3+ and green powder SrAl2O4:Eu 2+ ,Dy 3+ It has been widely used commercially and is especially common in daily life.

[0003] However, rare-earth-doped inorganic long-afterglow materials are also constrained by their crystal structure, facing a trade-off between size, morphology, and afterglow performance. For lanthanide-doped inorganic afterglow materials, the long-afterglow luminescence mechanism is usually associated with energy trapping and release within lattice traps. To obtain better afterglow performance, it is essential to increase the energy traps in the lattice through solid-state synthesis or high-temperature sintering. This inevitably limits these materials with ideal long-afterglow performance to a bulk crystalline matrix, making them incompatible with classic wet chemical synthesis routes. 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 for widespread application in biomedical fields such as diagnostics remains a challenge.

[0004] Since photochemical long-persistence mechanisms achieve long-persistence luminescence through a strategy of introducing photochemical reactions between light energy input and photon output, the organic integration of photochemistry and photophysics can overcome many limitations imposed by crystal matrices. Typically, photochemical long-persistence systems consist of three core functional components: photosensitizers, buffers, and luminescent agents, which primarily perform light energy absorption, photochemical energy buffering, and photon emission processes, respectively. Compared to photophysical energy level transitions, photochemical reactions proceed more slowly and are more readily induced, achieving long-persistence luminescence lifetimes without the need for stabilization in specific environments such as crystals, making them more compatible with biomedical applications in diagnostics and detection. However, compared to inorganic or organic long-persistence systems, reports on photochemical long-persistence systems are relatively few, and their system types and material properties require further research and development. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides a singlet-state splitting sensitized photochemical long-afterglow system and its applications. This invention introduces the unique properties of singlet-state splitting into the design of sensitizers for photochemical long-afterglow. When selectively excited by a light source, photosensitizer molecules can convert oxygen into singlet oxygen through type II sensitization. In this process, one singlet exciton in the sensitizer with singlet-state splitting properties can be converted into two triplet excitons, resulting in a theoretical upper limit of 200% for the triplet excited state. In contrast, the theoretical upper limit of the triplet excited state in classical photosensitizers is 100%. Therefore, by breaking through and increasing the upper limit of singlet oxygen yield, the luminescence performance of photochemical long-afterglow can be significantly improved.

[0006] In a first aspect of the invention, a singlet-state splitting sensitized photochemical long-afterglow system is provided. The photochemical long-afterglow system includes at least one sensitizer, at least one buffer, and at least one luminescent emitter; wherein the sensitizer possesses singlet-state splitting properties, and the absorption peak of the sensitizer and the emission peak of the luminescent emitter have zero overlap. Thus, in this photochemical long-afterglow system, the sensitizer, buffer, and luminescent emitter respectively undergo light energy absorption, photochemical energy buffering, and photon emission processes. For the photochemical long-afterglow system, the photosensitizer occupies a crucial position at the very beginning of light energy input, and is therefore an important component in triggering the photochemical reaction. Under excitation light irradiation, in the presence of the photosensitizer, singlet oxygen (…) can be continuously generated. 1The process involves converting input light energy (O2) into chemical energy stored in reactive oxygen species. Subsequently, singlet oxygen undergoes a photochemical reaction with a buffer, adding to the unsaturated olefin double bond of the buffer. As the intermediate product decomposes, excited-state energy centers are generated again, and this excited-state energy is transferred to the luminescent body and emitted as photons. According to the described photochemical long-afterglow luminescence process, the amount of singlet oxygen produced 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 high singlet oxygen yields are ideal choices for photochemical afterglow systems.

[0007] In some embodiments of the present invention, the sensitizer converts oxygen into singlet oxygen via type II sensitization under selective excitation by a light source. The type II sensitization mentioned here in the photosensitization reaction generally refers to an energy transfer mechanism in photochemistry, whereby 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 (S0) to an excited state (S1 or T1). Subsequently, the sensitizer transfers energy to the substrate molecule (such as O2) via a nonradiative transition, causing it to transition from the triplet state (S0, S1, T2). 3 O2) transitions to the singlet state ( 1 In the type II sensitization process (O2), only energy is transferred, no electron transfer occurs, and O2 is generated. 1 O2.

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

[0009]

[0010] In formula I-A, the R substituent can be a benzene ring. benzene ring derivatives Biphenyl and biphenyl derivatives Where n is between 1 and 6.

[0011] Among them, in formula I-B It can be a cycloalkane or a cycloalkane derivative, wherein the cycloalkane or cycloalkane derivative is similar to that in Formula I-B. The benzene rings in the main body, excluding the benzene rings, are fused together through shared chemical bonds.

[0012] Specifically, in Equation I-B It can be a cycloalkanes or cycloalkanes with 1-6 carbon atoms.

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

[0014] Compounds having the structure described in Formula I-A or Formula I-B are photosensitizer molecules with singlet-state splitting properties. These are benzobenzene molecules, and the molecule is composed of two tetrabenzobenzene bridging groups, which facilitates the generation of singlet-state splitting properties. Furthermore, the molecule is modified with multiple triisopropylsilyl groups, which can significantly increase the solubility of the photosensitizer component, thus benefiting research on photochemical long afterglow.

[0015] In some embodiments, the sensitizer has the following structure:

[0016]

[0017] Wherein, * represents a bonding site, and the * bonding site is located at any aromatic hydrogen atom of the benzene ring or its derivative;

[0018] R1 is selected from alkyl, alkoxy, or alkylamino groups having 1-8 carbon atoms;

[0019] The value of n ranges from 1 to 8.

[0020] In some embodiments of the present invention, the structure of the sensitizer is shown below:

[0021]

[0022]

[0023] Wherein, the R2 substituent in formula A is

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

[0025]

[0026] In Formula II, the substituents R1, R2, and R3 may be the same or different. The substituent R1 in Formula II is selected from hydrogen, or alkyl, alkoxy, or alkylamino groups having 1 to 8 carbon atoms. The substituents R2 and R3 are each independently selected from alkyl, alkoxy, or alkylamino groups having 1 to 8 carbon atoms.

[0027] Specifically, the R1 substituent in Formula II is selected from hydrogen or from alkyl (C n H 2n+1More specifically, the substituents R1, R2, and R3 can be methyl (-CH3), ethyl (-C2H5), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), n-butyl (-CH2CH2CH2CH3), isobutyl (-CH2CH(CH3)2), sec-butyl (-CH(CH3)CH2CH3), tert-butyl (-C(CH3)3), n-pentyl (-CH2CH2CH2CH2CH3), isopentyl (-CH2CH2CH(CH3)2), neopentyl (-CH2C(CH3)3), sec-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH2CH(CH2CH3)2), etc., and their isomers.

[0028] Specifically, the substituents R1, R2, and R3 in Formula II can also be selected from alkoxy groups (C n H 2n+1 O-), more specifically, can be methoxy (-OCH3), ethoxy (-OC2H5), n-propoxy (-OCH2CH2CH3), isopropoxy (-OCH(CH3)2), n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, etc., and their isomers.

[0029] Specifically, the substituents R1, R2, and R3 in Formula II can also be selected from alkylamino (C n H 2n+1 NH-), for example, methylamino (-NHCH3), ethylamino (-NHC2H5), n-propylamino (-NHCH2CH2CH3), isopropylamino (-NHCH(CH3)2), n-butylamino, isobutylamino, sec-butylamino, tert-butylamino, etc. and their isomers.

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

[0031]

[0032] The structure shown in Formula II-A is a compound containing a special unsaturated alkene. The alkene double bond is located in a six-membered ring containing S and O, with a strong electron-donating group attached to the S end of the double bond. Due to this unique chemical structure, the electron cloud distribution is highly asymmetric. This double bond readily undergoes addition reactions with singlet oxygen and readily forms an excited state of ring-opening product through a coordinated decomposition mechanism.

[0033] In some embodiments of the present invention, the light emitter 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.

[0034] On the one hand, rare earth ions (such as Eu)3+ 、Tb 3 +、Dy 3+ The inner 4f electrons of rare earth ions are shielded by the outer electrons, resulting in long excited-state lifetimes (milliseconds to seconds), making them suitable for long afterglow applications. On the other hand, the ff transitions of rare earth ions are less affected by the crystal field, resulting in narrow emission spectral bandwidths (typically <10nm) and high color purity (e.g., Eu). 3+ red light, Tb 3 (+ green light), narrow-band emission reduces the reabsorption of energy inside the material, thus improving luminescence efficiency.

[0035] Preferably, the rare earth complex is a europium (Eu) complex. The Eu in the europium (Eu) complex... 3+ 5D0→ 7 The F2 transition produces sharp red emission (main peak at approximately 612 nm) with a full width at half maximum (FWHM) of only 5-10 nm, which is superior to other rare earth ions (such as Tb). 3 + green light, Dy 3+ (Blue / white light). Meanwhile, Eu 3+ The 4f electrons are shielded by the outer shell, and the coordination environment has little effect on their emission wavelength (Tb). 3 (The green light of the + is easily deflected by the ligand field). More importantly, the characteristics of narrowband red rare-earth emission avoid peak overlap between the photosensitizer and the emitting 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 as 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 material is 2.5-15 mM, and the concentration range of the sensitizer is 5-250 μM. The optimal range of each element in the long-afterglow system is essentially a balance between energy storage-release kinetics, material stability, and application requirements. By adjusting the type of luminescent material (energy level matching), buffer parameters (concentration), and concentration threshold, synergistic optimization of afterglow time, luminous efficiency, and environmental adaptability can be achieved, meeting diverse needs ranging from low-end luminescent materials to high-end biosensors and detection.

[0039] In a second aspect of the present invention, a photochemical long afterglow nanoparticle is provided, the photochemical long afterglow nanoparticle comprising the aforementioned sensitizer, buffer and luminescent body, wherein the sensitizer, buffer and luminescent body are encapsulated in a nanocarrier, the nanocarrier being polystyrene nanoparticles and polystyrene derivative nanoparticles.

[0040] In a third aspect of the present invention, a photochemical long-afterglow nanoprobe is provided, wherein the probe is formed by coupling modification of the surface of the aforementioned photochemical long-afterglow nanoparticles with protein substances.

[0041] In a fourth aspect of the invention, an application of a photochemical long-persistence nanoprobe is provided, the probe being used in the fields of bioimaging, immunochromatography, and homogeneous detection.

[0042] This invention provides a singlet-state splitting sensitized photochemical long-afterglow system, nanoparticles, and probes. Through innovative design of a singlet-state splitting sensitizer, a rare-earth-based photochemical persistent luminescence system with ultra-brightness characteristics has been successfully constructed. This system breaks through the technical bottleneck of traditional crystal-dependent long-afterglow materials. Based on the photochemical reaction energy storage and transfer (PCREST) ​​mechanism, it achieves, for the first time, a long-lasting luminescence phenomenon with a complete match to the ff transition spectrum of europium-based complexes in a liquid organic medium. The singlet-state splitting 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 sensitizer absorption band and the rare-earth luminescence peak. Furthermore, the nanoluminescent particles prepared based on this system exhibit a uniform and controllable nanoscale 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 in scenarios such as time-resolved fluorescence immunoassay, in vivo deep tissue imaging, homogeneous detection, and immunochromatography, where it has significant technical advantages. Attached Figure Description

[0043] Figure 1 A schematic diagram of a singlet splitting-sensitized photochemical afterglow system is shown.

[0044] Figure 2 The absorption spectrum of the photosensitizer TBPS in toluene solution is shown.

[0045] Figure 3 The fluorescence emission spectrum of the photosensitizer TBPS in toluene solution under 365 nm excitation is shown.

[0046] Figure 4 The emission spectrum of the luminescent material Eu(TTA)3(TPPO)2 under 365 nm excitation in toluene solution is shown.

[0047] Figure 5 The diagram shows the luminescence process of a singlet-state splitting sensitized photochemical afterglow system.

[0048] Figure 6 The long afterglow emission spectrum of the photochemical long afterglow system TBPS&SOMN&Eu(TTA)3(TPPO)2 in toluene solution is shown.

[0049] Figure 7 The decay curve of long-afterglow luminescence of the photochemical long-afterglow system TBPS&SOMN&Eu(TTA)3(TPPO)2 in toluene solution is shown.

[0050] Figure 8 The spectrum and photographs of a singlet-state splitting sensitized photochemical afterglow system are shown.

[0051] Figure 9 The trend of photochemical long afterglow luminescence intensity with component concentration is shown;

[0052] Figure 10 The trend of photochemical long afterglow luminescence intensity with the concentration of photosensitizer SiPc is shown.

[0053] Figure 11 The absorption spectrum of the photosensitizer SiPc in toluene is shown.

[0054] Figure 12 The changes in photochemical long afterglow luminescence intensity of photosensitizers TBPS and SiPc at different concentrations are shown.

[0055] Figure 13 The image shows photochemical long afterglow luminescence images using TBPS and SiPc as photosensitizers, respectively.

[0056] Figure 14 The emission spectra of different solution samples are shown;

[0057] Figure 15 The photochemical long afterglow luminescence spectra under different composition conditions are shown;

[0058] Figure 16 The long-afterglow emission spectra of the singlet-state splitting sensitized photochemical long-afterglow system are shown under different atmospheric conditions;

[0059] Figure 17 The absorption spectra of sensitizers TBPS and PdOEP in toluene are shown.

[0060] Figure 18 The performance of the singlet-state splitting sensitized photochemical long-afterglow system based on TBPS is compared with that of the ultra-bright long-afterglow system established using PdOEP as a photosensitizer.

[0061] Figure 19 A flowchart illustrating the preparation process of photochemical long afterglow nanoparticles (PA-NPs) is shown.

[0062] Figure 20 An aqueous solution of photochemical long afterglow nanoparticles (PA-NPs) and its scanning electron microscope image are shown.

[0063] Figure 21The long-afterglow luminescence properties of photochemical long-afterglow nanoparticles (PA-NPs) in aqueous solution are shown. Detailed Implementation

[0064] The following detailed description, in conjunction with specific embodiments, further illustrates the singlet-state splitting sensitized photochemical long afterglow system and its applications of the present invention. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection 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] The term "comprising" and its variations as used herein are open-ended inclusion, meaning "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". Definitions of other terms will be given in the description below.

[0066] The terms "photochemical long-afterglow system," "afterglow system," and "long-afterglow system" used in this article have the same meaning. They usually refer to a three-component system that includes a sensitizer, a buffer, and a luminescent body. In special cases, such as when a molecule has the functions of both a sensitizer and a buffer, or both a buffer and a luminescent body, it may also be a two-component system.

[0067] The terms "sensitizer," "photosensitizer," "photoactivator," and "photoabsorber" used in this article have similar meanings, and their main function is to absorb light energy when excited by a light source.

[0068] The term "singlet splitting" used in this article is typically a unique photophysical process, referring to the phenomenon where an excited singlet state (S1) formed after an organic molecule absorbs a photon spontaneously splits into two triplet excitons (T1) through a quantum mechanical mechanism. The core characteristic of this process is the conversion of a single high-energy exciton into two low-energy excitons, thereby breaking through the energy conversion efficiency limit of traditional photochemical systems.

[0069] In photochemical long-afterglow systems, three core functional components are mainly composed of photosensitizers, buffers, and luminescent agents, which respectively perform light energy absorption, photochemical energy buffering, and photon emission processes. For photochemical afterglow systems, the photosensitizer occupies a crucial position at the very beginning of light energy input, thus being an important component in triggering the photochemical reaction. Under excitation light irradiation, the presence of a photosensitizer allows for the continuous generation of singlet oxygen (…). 1The process involves converting input light energy (O2) into chemical energy stored in reactive oxygen species. Subsequently, singlet oxygen undergoes a photochemical reaction with a buffer, adding to the unsaturated olefin double bond of the buffer. As the intermediate product decomposes, excited-state energy centers are generated again, and this excited-state energy is transferred to the luminescent body and emitted as photons. According to the described photochemical long-afterglow luminescence process, the amount of singlet oxygen produced 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 high singlet oxygen yields are ideal choices for photochemical afterglow systems.

[0070] However, for conventionally established photochemical long-afterglow materials, photosensitizers are typically selected from porphyrins, phthalocyanines, and their complexes. For example, the most commonly used photosensitizer is a silicon phthalocyanine complex, known as a SiPc sensitizer. While these photosensitizers are indeed widely used, their singlet oxygen yield is limited by the maximum intersystem crossing (ISC) efficiency of the photosensitizer, and cannot exceed the upper limit of 100%. In practical applications, due to limitations imposed by the biological environment and experimental conditions, the singlet oxygen yield is often even lower. Therefore, to achieve superior photochemical long-afterglow performance and to enrich the photosensitizer composition for photochemical long-afterglow systems, it is urgent to develop more and more efficient photosensitizers and study their applications in photochemical long-afterglow systems.

[0071] To push the limits, this disclosure introduces the unique property of singlet state splitting into the design of sensitizers for photochemical long-afterglow. One singlet exciton in a singlet state split can be converted into two triplet excitons, resulting in a theoretical upper limit of 200% for the triplet excited state. In classical photosensitizers, the theoretical upper limit of the triplet excited state is 100%. Since oxygen requires energy transfer with the triplet excited state of the photosensitizer to produce singlet oxygen, theoretically, if a singlet-splitting molecule is used as a photosensitizer, absorbing the excitation energy of just one photon could potentially produce two singlet oxygen molecules, thus achieving a maximum singlet oxygen yield of 200%. Therefore, by breaking through and increasing the upper limit of singlet oxygen yield, the luminescence performance of photochemical long-afterglow can be significantly improved. Unfortunately, photosensitizers with singlet state splitting capabilities have not yet been reported in photochemical long-afterglow systems, and research on their sensitization properties for photochemical long-afterglow remains incomplete.

[0072] This disclosure discloses an ultrabright rare-earth luminescent long-persistence system developed based on a photochemical long-persistence construction strategy. This system directly exhibits the same emission curve as europium complexes, rare-earth ff-transition luminescent organisms, in organic solutions. The long-persistence luminescence is attributed to a photochemical energy storage and transfer (PCREST) ​​mechanism, which is relatively independent of traditional crystal structure-based theories, providing greater flexibility for long-persistence performance tuning and material design. To achieve efficient photochemical reactions and energy transfer processes, a photosensitizer with singlet-state splitting capability is designed and introduced into this long-persistence system, avoiding overlap with the wavefunction of the luminescent organism. Optimization and control of the long-persistence luminescence properties are performed in organic solutions, and high-quality long-persistence luminescent probes with uniform size and functional surfaces can be fabricated on demand using mature wet chemical synthesis methods, providing a possible pathway for exploring biomedical applications such as diagnostic detection.

[0073] It is worth noting that the photosensitizer component primarily performs the core function of excitation light energy absorption and photochemical energy conversion, and is key to regulating and controlling the light energy input process, affecting the absorption and conversion efficiency of excitation light as well as long-afterglow luminescence performance. The singlet-state splitting property enables the photosensitizer to achieve a singlet oxygen production efficiency exceeding 100%, which, compared to traditional photosensitizer photochemical systems, can fundamentally improve long-afterglow performance. The singlet oxygen generated by the singlet-state splitting photosensitizer undergoes a photochemical reaction with the buffer, briefly storing energy in chemical bonds and transferring it to the rare-earth complex luminescent body during bond breaking and recombination, thus forming a rare-earth photochemical long-afterglow phenomenon with a luminescence lifetime on the order of seconds. Simultaneously, the narrow-band red rare-earth emission characteristics avoid peak overlap between the photosensitizer and the luminescent body, and the minimized reabsorption effect with zero crosstalk helps maximize the emission of afterglow photons. Therefore, the singlet-state splitting sensitized photochemical long-afterglow system can directly achieve ultra-bright long-afterglow luminescence in organic phase solution, and high-quality long-afterglow luminescent nanoparticles can be prepared by wet chemical synthesis method, laying the foundation for related biomedical applications.

[0074] Specifically, see Figure 1 , Figure 1 A schematic diagram of a singlet splitting-sensitized photochemical afterglow system according to an embodiment of the present invention is shown, wherein, Figure 1 (a) is a schematic diagram of the photochemical long-afterglow luminescence pathway, involving the combined effects of photochemical and photophysical processes between photosensitizers, buffers and luminescent bodies. The long-afterglow luminescence mechanism is based on energy storage and transfer through photochemical reactions. Figure 1 (b) shows the three functional molecules and their chemical structures contained in the photochemical long afterglow system. Among them, TBPS is a singlet splitting photosensitizer, SOMN is a buffer, and the rare earth complex Eu(TTA)3(TPPO)2 is the luminescent agent.

[0075] The following are specific embodiments, which make the principles and performance advantages of this disclosure more apparent.

[0076] Example 1: Synthesis of photosensitizer compound TBPS

[0077] Compound A (100 mg), compound B (15 mg), PdCl2 (20 mg), and K2CO3 (300 mg) were added to 20 mL of a mixture of THF and H2O (10:1, v:v). The mixture was then stirred at 70 °C for 24 hours. After cooling to room temperature, the solvent was removed by evaporation. Finally, the product was purified to obtain approximately 30 mg of TBPS red powder.

[0078] Specifically, the synthetic route of the TBPS photosensitizer is shown below:

[0079]

[0080] The results show that compound TBPS is a photosensitizer molecule with singlet-state splitting properties. It belongs to the benzobenzene class of molecules, and its internal structure is composed of two tetrabenzobenzenes bridged together, which facilitates the generation of singlet-state splitting properties. Furthermore, the molecule is modified with multiple triisopropylsilyl groups, which significantly increases the solubility of the photosensitizer components, thus benefiting research on photochemical long afterglow.

[0081] First, the UV-Vis absorption spectroscopy of the photosensitizer TBPS molecule was performed. (Refer to...) Figure 2 , Figure 2 This is the absorption spectrum of the photosensitizer TBPS in toluene solution. The absorption spectral data of TBPS shows significant absorption in the green region, and its main peak matches well with a commonly used 532 nm laser, laying the foundation for subsequent excitation of photochemical long-afterglow systems. Quantitative calculations show that the molar extinction coefficient of TBPS molecules at 532 nm is as high as 3.2 × 10⁻⁶. 4 L mol -1 ·cm -1 Furthermore, TBPS exhibits a broad absorption peak in the green light region, enabling efficient photon absorption even in broadband green LEDs, thus reducing the stringency required for light source selection. Notably, TBPS molecules show no absorption peak in the red light region, allowing for effective combination with red-emitting emitters as a photosensitizer for long-afterglow photochemical lighting, thereby preventing self-absorption within the system. Therefore, the synthesized TBPS molecules possess desirable light absorption properties and hold promise for application as a photosensitizer in long-afterglow photochemical systems.

[0082] Furthermore, the emission spectra of TBPS molecules were characterized. For example... Figure 3 As shown, Figure 3 The image shows the fluorescence emission spectrum of the photosensitizer TBPS in toluene solution excited at 365 nm. Under 365 nm ultraviolet light excitation, the fluorescence emission data of TBPS indicates that its emission is in the yellow and red light regions. It is noteworthy that due to the singlet splitting property of this molecule, its fluorescence emission is significantly weaker compared to other benzo[a]benzene fluorescent dyes. Benzen[a]benzene fluorescent dyes typically possess excellent fluorescence emission properties; for example, 9,10-diphenylanthracene (DPA) and rubrene are commonly used as emitters in organic upconversion systems. However, as a photosensitizer, TBPS primarily functions to absorb incident photons and generate singlet oxygen, so its poor fluorescence emission is not necessarily detrimental. In photochemical long-afterglow systems, it is difficult for a single component to simultaneously function as both a photosensitizer and a luminescent agent, and this often hinders energy utilization and transfer processes. This is mainly because the two functional properties required by photosensitizers and luminescent agents are mutually exclusive. Theoretically, molecules with strong singlet oxygen sensitization have weakened luminescence, and conversely, molecules with strong luminescence have weakened singlet oxygen sensitization. To some extent, poor fluorescence emission properties may be more advantageous as photosensitizers, thus better matching the functional settings of each component in a photochemical long-persistence system.

[0083] When selectively excited by a light source, TBPS photosensitizer molecules can convert oxygen into singlet oxygen through type II sensitization. Studies have shown that the singlet oxygen yield of TBPS molecules is as high as 140%, significantly higher than that of photosensitizers used in traditional photochemical long-persistence systems, greatly increasing the feasibility of designing singlet splitting sensitized photochemical long-persistence systems.

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

[0085] The synthetic route of the Eu(TTA)3(TPPO)2 luminescent compound is shown below:

[0086]

[0087] The rare earth complex Eu(TTA)3(TPPO)2 luminescent material was synthesized according to the indicated route. Specifically, EuCl3·6H2O (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 was stirred to pH 5–6 and refluxed in an oil bath for 8 h. After cooling to ambient temperature, the crude precipitate was washed three times with water and ethanol. The residue was dried to obtain approximately 400 mg of the europium complex.

[0088] Europium complex Eu(TTA)3(TPPO)2 is a commonly used rare-earth luminescent material. Due to its unique ff transition, it typically produces sharp red light emission at 615 nm. Theoretically, the TBPS photosensitizer has no absorption peak at the emission point of europium complex Eu(TTA)3(TPPO)2, which can eliminate the self-absorption effect and ensure maximum photon emission, thus improving long-afterglow luminescence performance. Under 365 nm ultraviolet light excitation, europium complex Eu(TTA)3(TPPO)2 emits bright red light. Characterization of its emission spectrum reveals that the main peak is located at 615 nm (e.g., ...). Figure 4 As shown, Figure 4 This is the emission spectrum of the luminescent Eu(TTA)3(TPPO)2 in toluene solution under 365 nm excitation. This is the emission spectrum of the europium(III) ion corresponding to... 5 D0→ 7 The characteristic emission peak of the F2 transition has a very narrow emission peak due to the characteristics of the ff transition, with a half-width at half-maximum (FWHM) of only ~5 nm. This rare earth complex exhibits sharp emission in the red light region, which is advantageous for biomedical applications such as diagnostic testing, as it can reduce the influence of blood samples on luminescence absorption to a certain extent.

[0089] Example 3 Synthesis of the caching compound SOMN

[0090] The synthetic route for the SOMN caching compound is shown below:

[0091]

[0092] First, in a 100 mL three-necked flask, 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 added sequentially. The mixture was refluxed under argon protection for 4 h, and then cooled to room temperature. Next, saturated NaHCO3 solution was slowly added dropwise, and the mixture was separated. The organic phase was collected and washed three times with saturated NaHCO3 solution, followed by rotary evaporation to remove the organic solvent. Using dichloromethane and petroleum ether as eluents, the final product was purified by column chromatography to obtain a white solid in 40% yield.

[0093] Using TBPS molecules from Example 1 as the sensitizer, Eu(TTA)3(TPPO)2 from Example 2 as the luminescent agent, and SOMN from this example as the buffer, a photochemical long-afterglow system was constructed, referring to... Figure 5 , Figure 5Shows the luminescence process of a singlet-splitting sensitized type photochemical afterglow system. Based on the photochemical energy storage and transfer (PCREST) strategy, the indirect excitation of the europium complex lumophore is achieved, enabling the intrinsic luminescence of this 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 forming 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 quencher and singlet oxygen plays an important role. This photochemical reaction (>s level) is slower and more likely 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 are usually completed at the ms level, and due to the significantly slower photochemical reaction of the quencher SOMN, it becomes the rate-determining step of the entire path. Based on this design, when the photosensitizer is excited by a light source, through the photochemical energy storage and transfer (PCREST) mechanism, the long afterglow luminescence of rare earth complexes is ultimately 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 after adding three functional components, namely the photosensitizer TBPS, the quencher SOMN, and the lumophore Eu(TTA)3(TPPO)2 complex, to the organic phase solution, the photosensitizer TBPS successfully triggers the photochemical reaction, and red long afterglow luminescence is observed in the organic solution. Subsequently, a fiber optic spectrometer is 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 to irradiate the mixed solution with a 532 nm light source for 2 s and collect the signal peak after turning off the light source. The results show that the main peak of the long afterglow spectrum of TBPS&SOMN&Eu(TTA)3(TPPO)2 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 D0→ 7 F2 transition of europium (III) ions, and its characteristic of having a narrow emission peak due to f-f transition is completely retained.

[0094] Studies on achieving long-afterglow luminescence in organic solvents for long-afterglow materials are rarely reported, especially for the intrinsic narrow-band long-afterglow emission of rare earth elements. Traditional rare earth complexes can also achieve long-afterglow luminescence through photochemical long-afterglow mechanisms. Given the extensive and well-studied nature of rare earth complexes, this research holds promise for greatly expanding and enriching the range of rare earth long-afterglow luminescent materials. In photochemical long-afterglow systems, when the long-afterglow luminescence is consistent with the emission of the luminescent material and can be directly carried out in organic solutions, the luminescent properties of the material can be more easily designed and adjusted. The fact that luminescence can still be observed with the naked eye after the light source is turned off provides an intuitive indication that it falls within the category of long-afterglow luminescence. To more accurately and quantitatively describe the continuous luminescence phenomenon, the luminescence lifetime of the three-component mixed system was subsequently tested. Figure 7 As shown, Figure 7 The decay curves of the long-persistence photochemical system TBPS&SOMN&Eu(TTA)3(TPPO)2 in toluene solution are presented. The testing method involved irradiating the mixed solution with a 532 nm light source for 2 seconds, then turning off the excitation source and collecting the signal intensity at 615 nm and its decay over 60 seconds. The results show that the intensity of the emitted photons decays continuously over time, and fitting reveals a long-persistence lifetime of 3 seconds. Therefore, the luminescence lifetime of the rare-earth complex is extended from ~1 millisecond to as long as 3 seconds, an extension exceeding three orders of magnitude. The luminescence lifetime of rare-earth complexes is typically difficult to control over a wide range; the photochemical long-persistence mechanism provides a new pathway for lifetime extension, overcoming the limitation of short luminescence lifetimes inherent in the luminescent material itself.

[0095] In photochemical long-persistence systems, the photochemical reaction of the caching agent is significantly slower, becoming the rate-determining step in the entire luminescence pathway; thus, the luminescence lifetime is mainly determined by the caching agent. The photochemical reaction of the caching agent SOMN is shown below, mainly involving the addition reaction of singlet oxygen and the decomposition and ring-opening reaction of the generated intermediate.

[0096]

[0097] After the photochemical reaction, the buffer SOMN generates an excited state but does not emit light directly, mainly due to its very low fluorescence quantum yield (<0.1%). Furthermore, the absorption peaks of SOMN and its decomposition products are located in the ultraviolet region, showing no significant absorption of green light in the visible region. Therefore, the core function of SOMN is to first briefly buffer energy in chemical bonds for later use, and then decompose to form an excited state to transfer energy to the luminescent material. The buffer establishes an energy connection channel between the photosensitizer and the luminescent material, organically integrating the photochemical and photophysical processes. This allows for the maintenance of photon input and photon output (i.e., photoluminescence mode) while overcoming limitations such as energy matching between the photosensitizer and the luminescent material, significantly broadening the design possibilities for the wavelength and lifetime properties of luminescent materials.

[0098] Building upon the achievement of 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 agent, the photosensitizer TBPS is highly suitable for pairing with it to construct the photochemical long-afterglow system. For example... Figure 8 As shown, Figure 8 The image shows the spectrum and photograph of a singlet splitting sensitized photochemical afterglow system, where J(λ) is the overlap integral of the absorption peak of the photosensitizer TBPS and the emission peak of the luminescent material Eu(TTA)3(TPPO)2. Besides its excellent singlet oxygen generation capability, the absorption peak of the photosensitizer TBPS and the emission peak of the luminescent material Eu(TTA)3(TPPO)2 are far apart and do not overlap. Calculations show that the Stokes shift between the absorption peak of the photosensitizer TBPS and the emission peak of the luminescent material Eu(TTA)3(TPPO)2 is as high as 2100 cm⁻¹. -1 In terms of quantitative evaluation of spectral overlap, the overlap integral J(λ) between the main absorption peak of the photosensitizer TBPS and the main emission peak of the luminescent agent Eu(TTA)3(TPPO)2 can be calculated. 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 while the luminescent agent is mainly responsible for light emission. The absorption peak of the photosensitizer and the emission peak of the luminescent agent have zero overlap, and the mutual interference is small, thus avoiding the adverse effects of long-afterglow emission being absorbed and filtered by the system. Intuitively, the color of the long-afterglow solution under bright field conditions is red. Usually, red solutions also have weak absorption of red light because only photons in the red light band of the solution that are not absorbed can be transmitted to the naked eye or camera and appear red. Under dark field conditions, the color of long-afterglow emission in the dark is also red, consistent with the color in a bright environment (e.g., Figure 8 (As shown in the illustration).

[0099] Based on the design principle that each component in a photochemical long-afterglow system performs its specific function, the combination of photosensitizer, buffer, and luminescent agent is suitable. When the interference between them is small, the performance of long-afterglow luminescence can be more easily optimized by adjusting the concentration of each component. Firstly, the concentrations of the buffer SOMN and the luminescent agent Eu(TTA)3(TPPO)2 complex were optimized in the photochemical long-afterglow system, such as... Figure 9 As shown, Figure 9To investigate the variation of photochemical long-afterglow luminescence intensity with component concentration, the method involved fixing the photosensitizer concentration in a toluene solution. The concentrations of either the buffer (a) or the luminescent material (b) were adjusted, and the solution was irradiated with a 532 nm laser for 2 seconds, after which the laser was turned off. The changes in the photochemical long-afterglow luminescence intensity at 615 nm were recorded. The results showed that initially, the long-afterglow luminescence intensity gradually increased with increasing SOMN buffer concentration, mainly due to the enhanced capture level of singlet oxygen generated by photosensitization resulting from increased buffer molecules. However, when the SOMN buffer concentration exceeded 3 mM, further increases in buffer concentration led to a gradual decrease in long-afterglow luminescence intensity, primarily due to insufficient energy transfer caused by excessive buffer molecules. For the luminescent material Eu(TTA)3(TPPO)2, long-afterglow luminescence continuously increased with increasing luminescent material concentration; even at a relatively high concentration of 10 mM, no decreasing trend in long-afterglow intensity was observed. Based on the above experimental results and analysis, the preferred concentration of the buffer SOMN was determined to be 3 mM, and the preferred concentration of the luminescent Eu(TTA)3(TPPO)2 complex was determined to be 10 mM, which were used in the study of photochemical long afterglow.

[0100] Optimizing the concentration of photosensitizers is essential for photochemical long afterglow, but the upper limit of photosensitizer concentration is often very limited. According to traditional reports on photochemical long afterglow research, the optimal amount of photosensitizer is usually below 10 μM, although higher concentrations can result in stronger light absorption, thus increasing the total number of input photons at the source. To more clearly reveal the limitations of photosensitizer concentration adjustment, we first selected phthalocyanine (SiPc) as the photosensitizer for experimental research. This molecule is one of the most commonly used photosensitizers in photochemical long afterglow systems. The trend of photochemical long afterglow luminescence intensity with SiPc concentration is shown below. Figure 10 As shown, the test method involved fixing the concentrations of the buffer and the luminescent agent in a toluene solution. By adjusting the concentration of the photosensitizer, the solution was irradiated with a 680 nm laser for 2 seconds, and then the laser was turned off. The change in the photochemical long-afterglow luminescence intensity at 615 nm was recorded. The concentration of the buffer SOMN was 3 mM, and the concentration of the luminescent agent Eu(TTA)3(TPPO)2 complex was 10 mM. The results showed that initially, the long-afterglow luminescence intensity gradually increased with the increase of the photosensitizer SiPc concentration, mainly due to the increase in the amount of singlet oxygen generated by photosensitization after the increase of photosensitizer molecules. However, when the photosensitizer SiPc concentration exceeded 5 μM, further increasing the photosensitizer concentration significantly reduced the intensity of the long-afterglow luminescence. Based on these experimental results, the optimal concentration of the photosensitizer SiPc in the photochemical long-afterglow system is 5 μM, which is consistent with previous studies.

[0101] Furthermore, the concentration quenching problem caused by the traditional photosensitizer SiPc was investigated and analyzed. By testing the absorption spectrum of SiPc, it was found that the main absorption peak of this classic phthalocyanine photosensitizer SiPc is around 680 nm, and significant absorption is also present in the spectral range of 600 nm to 700 nm (e.g., Figure 11 (As shown). It is not difficult to find that the emission peak of the luminescent Eu(TTA)3(TPPO)2 complex is also distributed in this range, and there is an overlap between the absorption peak of the photosensitizer SiPc and the emission peak of the luminescent material. This problem is obviously detrimental to long-persistence luminescence because it will cause the self-absorption internal filtering effect within the system, leading to luminescence quenching. Therefore, the optimal concentration of the photosensitizer SiPc in the photochemical long-persistence system is only a low level of 5 μM, which greatly limits the input and absorption capacity of excitation photon energy, which is equivalent to limiting the energy source.

[0102] Compared to the significant concentration quenching of traditional photosensitizer SiPc, the photosensitizer TBPS designed in this disclosure can achieve superior long-afterglow luminescence performance at high concentrations (e.g., Figure 12 (As shown). With increasing TBPS concentration, the long-afterglow luminescence intensity gradually increased. Even at a high concentration of 200 μM TBPS, no decrease in long-afterglow intensity was observed, primarily due to the increased singlet oxygen generated by photosensitization after increasing the number of photosensitizer molecules. The zero-overlap characteristic between the TBPS photosensitizer and the Eu(TTA)3(TPPO)2 luminescent complex allows the TBPS sensitizer to reach an extremely high usable concentration without adversely affecting the long-afterglow signal of rare-earth luminescence. Based on this, a high concentration of 200 μM TBPS is preferred in the photochemical long-afterglow system. Experimental results also indicate that in a system using a low concentration of 5 μM SiPc as the photosensitizer, the energy input source is far from optimal or saturated. The effective input of photon energy is a bottleneck for improving photochemical long-afterglow performance, severely limiting the performance of rare-earth photochemical long-afterglow systems involving SiPc photosensitizers. Therefore, the design, development and application of the singlet split photosensitizer TBPS has broken through the bottleneck. By increasing the absorption capacity through high concentration, it can achieve the effect of expanding the open source of photon energy input and thus improving the photochemical long afterglow luminescence performance.

[0103] The design and introduction of the singlet-state splitting photosensitizer TBPS has brought new opportunities for photochemical long afterglow, especially for photochemical long afterglow systems using rare-earth europium complexes as luminescent agents, which have great potential to construct high-brightness rare-earth photochemical long afterglow luminescent materials. When using low excitation power (2.5 mW cm⁻¹), -2When conducting long-afterglow luminescence experiments with a laser, the solution using the novel TBPS molecule as a photosensitizer still emitted a bright and visible red long-afterglow emission, while the solution using the commonly used SiPc molecule as a photosensitizer did not show obvious long-afterglow emission. The photochemical long-afterglow luminescence images using TBPS and SiPc as photosensitizers are shown below. Figure 13 As shown, the optimal concentrations of photosensitizer TBPS and SiPc are 200 μM and 5 μM, respectively, while the concentrations of buffer SOMN and luminescent material Eu(TTA)3(TPPO)2 are 3 mM and 10 mM, respectively. The solution sample containing TBPS (right) was excited by a 532 nm laser, while the solution sample containing SiPc (left) was excited by a 680 nm laser. Both lasers had a power density of 2.5 mW / cm². -2 The same buffer and luminescent components, when the photosensitizer component is changed from the traditional SiPc photosensitizer to the singlet-state splitting TBPS photosensitizer, such a large performance improvement can be obtained. In essence, the improvement is mainly due to two factors: (1) The photosensitizer TBPS molecule has the unique property of singlet-state splitting, which makes the 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 and the emission of rare earth complex have zero overlap, which improves 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-state splitting photosensitizer TBPS in the study of photochemical long afterglow are intuitively reflected, directly realizing high-performance rare earth photochemical long afterglow luminescence in the organic solution phase.

[0104] Subsequently, the mechanism of the aforementioned photochemical long-afterglow luminescence was verified by preparing a series of solution samples and analyzing their emission spectra. Theoretically, for a three-component mixed solution of TBPS, SOMN, and Eu(TTA)3(TPPO)2, only the photosensitizer TBPS component, which is matched with it, can be excited under 532 nm light irradiation. After exciting the three-component mixed solution with 532 nm light, only the characteristic emission peak of the luminescent Eu(TTA)3(TPPO)2 was observed in the delayed afterglow spectrum (e.g.,...). Figure 14 (As shown by the red line). For both the two-component mixed solution of SOMN and Eu(TTA)3(TPPO)2 and the single-component solution of Eu(TTA)3(TPPO)2, in the absence of the photosensitizer TBPS, no obvious rare earth complex emission peaks were detected in the steady-state spectrum after excitation at 532 nm (as shown by the red line). Figure 14As shown by the blue and black lines, Eu(TTA)3(TPPO)2 cannot be directly excited by 532nm photons. In fact, 532nm photons selectively excite the photosensitizer TBPS component. The excited state efficiently converts to singlet oxygen under the condition that TBPS continuously sensitizes oxygen, while the buffer SOMN component acts as an energy bridge connecting chemical and light energy through its participation in the photochemical reaction. This also extends the luminescence duration to a long afterglow luminescence range on the order of seconds. Therefore, the luminescence of the rare-earth europium complex here conforms to the photochemical energy storage and transfer mechanism of long afterglow, which is different from the traditional dye sensitization or energy transfer mechanism. It should be noted here that... Figure 14 The emission spectra of different solution samples are shown. The concentrations of the three components—photosensitizer TBPS, buffer SOMN, and luminescent agent Eu(TTA)3(TPPO)2—are 200 μM, 3 mM, and 10 mM, respectively. The samples were excited using a 532 nm light source. The three-component sample was tested using long-persistence spectroscopy mode, while the other two samples were tested using fluorescence spectroscopy mode.

[0105] Through a controlled experiment using long-afterglow spectroscopy, it was found that the red long-afterglow emission signal of Eu(TTA)3(TPPO)2 could only be detected when both the photosensitizer TBPS and the buffer SOMN were added to the solution. Figure 15 As shown, Figure 15 The images show photochemical long-persistence emission spectra under different component conditions. The red line represents the long-persistence emission spectrum when all three components—the photosensitizer TBPS, the buffer SOMN, and the luminescent agent Eu(TTA)3(TPPO)2—are present. The black lines represent the long-persistence emission spectra without the photosensitizer TBPS and without the buffer SOMN, respectively. When the photosensitizer TBPS is absent, as... Figure 15 As shown by the black line in (a), or when the cache SOMN is missing, such as Figure 15 (b) As shown by the black line, 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 synergistic mechanism of the functions of each component in the photochemical long-afterglow system. The photochemical long-afterglow ultimately manifests as the emission peak of the luminescent body, i.e., the intrinsic ff transition luminescence of the rare earth complex. Therefore, through the combined design of three functional units, a rare earth photochemical long-afterglow luminescence system was established, enabling direct regulation and optimization of long-afterglow luminescence in the organic phase, ultimately obtaining a high-brightness rare earth long-afterglow luminescent solution.

[0106] Furthermore, photochemical long-afterglow luminescence can occur in ordinary organic solutions without the need for additional protective measures or additives, such as deoxygenation or the addition of antioxidants. In fact, when the solution is placed in a nitrogen-filled glove box, the long-afterglow luminescence becomes too weak to be detected. Figure 16 As shown, Figure 16 The long-afterglow emission spectra of a singlet-state splitting sensitized photochemical long-afterglow system under different atmospheric conditions were obtained. The concentrations of the photosensitizer TBPS, the buffer SOMN, and the luminescent material Eu(TTA)3(TPPO)2 were 200 μM, 3 mM, and 10 mM, respectively. The samples were excited using a 532 nm light source, and the long-afterglow spectra were collected after the excitation light was turned off. Since normal environments and atmospheres typically contain abundant oxygen, eliminating the need to eliminate oxygen interference greatly simplifies application design, thus rare-earth photochemical long-afterglow luminescent materials possess high feasibility and practicality.

[0107] Finally, the long-afterglow brightness of the constructed organic-phase photochemical long-afterglow luminescent material was evaluated. The study primarily employed a comparative approach, evaluating the material by comparing it with a previously established ultra-bright long-afterglow system using the porphyrin complex PdOEP as a photosensitizer. Figure 17 As shown, Figure 17 The absorption spectra of sensitizers TBPS and PdOEP in toluene are shown, with TBPS at a concentration of 20 μM and PdOEP at a concentration of 2.5 μM. Both TBPS and PdOEP exhibit absorption peaks in the green light region, and PdOEP is frequently used in optical studies with 532 nm excitation light. Furthermore, PdOEP exhibits a high singlet oxygen yield of 90%, which, while lower than TBPS's 140%, is still considered high among traditional photosensitizers. Analysis of the absorption spectra shows that the molar extinction coefficients of TBPS and PdOEP at 532 nm are 3.2 × 10⁻⁶. 4 L mol -1 cm -1 and 8.1×10 3 L mol -1 cm -1 The results showed that this value of the photosensitizer TBPS was approximately four times that of the photosensitizer PdOEP. Therefore, compared to the photosensitizer PdOEP, the photosensitizer TBPS can more fully absorb the commonly used 532nm excitation light energy.

[0108] Using a 532nm laser at a low power density (2.5mW cm⁻¹) -2 When the sample was irradiated, a higher brightness red long-persistence luminescence was observed in the photochemical long-persistence system based on the photosensitizer TBPS, such as... Figure 18 As shown, Figure 18 To compare the performance of a TBPS-based singlet-state splitting sensitized photochemical long-afterglow system with an ultra-bright long-afterglow system established using PdOEP as a photosensitizer, both tests were conducted using 532 nm laser excitation. This phenomenon is attributed to the more efficient absorption and utilization of 532 nm excitation light energy by the TBPS photosensitizer molecules, mainly reflected in the significant improvement in molar extinction coefficient and singlet oxygen yield. The comparative results demonstrate the advantage of the singlet-state splitting photosensitizer TBPS in improving long-afterglow luminescence performance. Based on this, an ultra-bright rare-earth photochemical long-afterglow luminescence solution system was successfully constructed.

[0109] Example 4 Synthesis of Photochemical Long Afterglow Nanoparticles PA-NPs

[0110] Based on the previously constructed ultrabright photochemical long-afterglow organic phase solution, a bottom-up method for preparing long-afterglow nanoparticles was designed using a wet chemical synthesis process. This method enables the on-demand fabrication of long-afterglow nanomaterials; for example, size, morphology, and functional surfaces can all be designed and selected as needed. Wet chemical synthesis is the most commonly used method for manufacturing new materials, and a wide variety of functional materials can be easily obtained through various mature solution processing techniques. To obtain high-quality long-afterglow nanoparticles with uniform size and functionalized surfaces, carboxylated polystyrene microspheres and an ultrabright photochemical long-afterglow molecular system were selected as building blocks. Preparation can be achieved through a one-step wet chemical synthesis in solution. See details below. Figure 19 , Figure 19 This is a flowchart of the preparation process of photochemical long afterglow nanoparticles (PA-NPs), in which carboxylated polystyrene microspheres and ultrabright photochemical long afterglow molecular systems are used as building blocks, and the preparation is carried out by a bottom-up wet chemical synthesis method.

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

[0112] According to the design, photochemical long-afterglow nanoparticles are mainly composed of two parts: a nanocarrier and photochemical long-afterglow molecules. The nanocarrier is associated with two key characteristics: size, morphology, and functional surface, while the photochemical long-afterglow molecules are associated with the key characteristic of long-afterglow luminescence performance. Cross-linked carboxylated polystyrene nanoparticles are used as the nanocarrier. The nanocarrier has uniform size, and the carboxyl groups distributed on its surface provide hydrophilicity and can provide coupling sites for further biological applications. The ultra-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. Through wet chemical synthesis, three hydrophobic molecules—the photosensitizer TBPS, the buffer SOMN, and the luminescent material Eu(TTA)3(TPPO)2—are encapsulated in the nanocarrier. After centrifugation and washing, the prepared photochemical long-afterglow nanoparticles (named PA-NPs) are obtained. The photochemical long-afterglow nanoparticles disperse well in water, forming a pink aqueous solution (e.g., ...). Figure 20 (As shown). Characterization by field emission scanning electron microscopy (FEM) images revealed that the prepared PA-NPs had a diameter of ~180 nm. The nanoparticles were uniform in size, with a coefficient of variation (CV) <5%.

[0113] Subsequently, the long-afterglow luminescence properties of photochemical long-afterglow nanoparticles (PA-NPs) were tested. When PA-NPs were dispersed in water, bright red long-afterglow luminescence was observed from the aqueous solution after irradiation with a 532 nm laser and subsequent shutdown of the excitation light. The brightness of the long-afterglow luminescence exceeded 100 mcd / m². -2 The level is far higher than the 0.32 mcd m visible to the naked eye. -2 Brightness level. Furthermore, spectral characterization tests showed that the characteristic emission peaks attributed to the luminescent Eu(TTA)3(TPPO)2 rare-earth complex appeared in the afterglow spectrum, such as... Figure 21 As shown, Figure 21 To demonstrate the long-persistent luminescence performance of photochemical long-persistent luminescence nanoparticles (PA-NPs) in aqueous solution, the testing conditions involved irradiation with a 532 nm laser for 2 seconds followed by laser shutdown, and then acquisition of the long-persistent luminescence spectrum. The inset shows bright-field and long-persistent luminescence images of the photochemical long-persistent luminescence nanoparticles. Therefore, rare-earth photochemical long-persistent luminescent nanoparticles were successfully prepared, maintaining high-brightness rare-earth long-persistent luminescence even in aqueous solution.

[0114] In potential biophotonics and biomedical applications, the stability of long-persistent luminescent nanoparticles (PA-NPs) in aqueous phase is an important indicator. This study investigated the long-term stability of photochemical long-persistent luminescent nanoparticles. Results showed that the prepared PA-NPs exhibited good dispersion stability in water, and dynamic light scattering measurements indicated no significant change in their hydrated particle size during 3 months of storage. Storage of the PA-NPs aqueous solution in the dark also showed no significant change in the long-persistent luminescence intensity over 3 months. Therefore, the prepared photochemical long-persistent luminescent nanoparticles (PA-NPs) possess excellent long-term stability and can meet the needs of a wide range of applications.

[0115] The high-quality long-persistent luminescent nanoparticles prepared above possess ideal properties such as uniform nanoscale particle size, bio-conjugable surface groups, high-brightness long-persistent luminescence, narrow-band emission characteristic of rare earth elements, and excellent long-term stability. Benefiting from the unique luminescence mechanism of photochemical long-persistent luminescence, and after overcoming the limitations of crystal structure and specific environments, an ultra-bright photochemical long-persistent solution system compatible with wet chemical synthesis was obtained, laying the foundation for the preparation of high-quality long-persistent nanomaterials. Based on target-oriented design, and through a bottom-up wet chemical synthesis method, high-performance long-persistent luminescent nanoparticles with uniform size and functionalized surfaces were successfully prepared. The preparation method of these long-persistent nanoparticles is simple and under mild conditions, providing a photochemical research path for the development of probes related to long-persistent luminescence detection.

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

[0117] The synthesis of the nanoparticles used for homogeneous immunoassay was performed according to Example 4. A photosensitizer was encapsulated in a separate nanocarrier to obtain sensitized microspheres, and a buffer and luminescent agent were encapsulated in another separate nanocarrier to obtain luminescent microspheres. The sensitized and luminescent microspheres were stored in two separate containers for further use.

[0118] The high-performance photochemical long-persistence nanomaterials constructed above can have their surface carboxyl groups further coupled and modified to form long-persistence luminescent probes with detection capabilities. Utilizing the characteristic of long-persistence luminescence—collecting signals after the excitation light is turned off—interference from excitation light and biological background can be avoided, establishing advantages in biomedical applications such as imaging detection. For example, after activating some of the carboxyl groups on the surface of the photochemical long-persistence nanomaterials, they can react and couple with the amino groups of proteins such as antibodies, thus forming long-persistence luminescent detection probes for biomarkers such as antigens. Therefore, research on luminescent detection probes based on photochemical long-persistence has broad application prospects, such as immunochromatography and homogeneous detection.

[0119] In summary, this disclosure develops a photochemical long-afterglow material system with ultra-bright rare-earth luminescence properties by introducing a singlet-state splitting photosensitizer. Rare-earth long-afterglow luminescence is based on the photochemical energy storage and transfer (PCREST) ​​mechanism, overcoming the limitations associated with traditional crystallization mechanisms. Thus, long-afterglow luminescence with the same emission curve as the europium complex's ff transition is directly observed in organic solutions. Due to the unique singlet-state splitting property of the photosensitizer molecule, the singlet oxygen generation efficiency reaches as high as 140%, directly breaking through the upper limit of traditional photosensitizer levels. Simultaneously, the zero overlap between the photosensitizer molecule's absorption and the rare-earth complex's emission increases the upper limit of the optimal applicable concentration of the photosensitizer. The integration of these two factors significantly enhances the system's light energy absorption and conversion capability, 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, possessing uniform nanoscale particle size, bioconjugable surface groups, high-brightness long-afterglow luminescence, narrow-band emission characteristic of rare-earth elements, and excellent long-term stability. This work establishes a singlet-state splitting sensitized photochemical long-afterglow system, providing a new pathway for the design and preparation of high-brightness long-afterglow luminescent materials, and has broad application prospects in biomedical fields such as long-afterglow detection.

Claims

1. A singlet-state splitting sensitized photochemical long afterglow system, characterized in that, The photochemical long afterglow system includes The invention comprises a sensitizer, a buffer, and a luminescent material; wherein the sensitizer exhibits singlet state splitting properties, and the absorption peak of the sensitizer has zero overlap with the emission peak of the luminescent material; the sensitizer, under selective excitation by a light source, converts oxygen into singlet oxygen through type II sensitization. The structure of the sensitizer is as follows: ； The structure of the buffer is shown in Formula II-A: Formula II-A; The structure of the light-emitting body is shown in Formula III: Formula III; In the photochemical long afterglow system, the concentration range of the buffer is 0.5-10 mM, the concentration range of the luminescent material is 2.5-15 mM, and the concentration range of the sensitizer is 5-250 μM.

2. A photochemical long afterglow nanoparticle, characterized in that, The photochemical long-afterglow nanoparticles include the photochemical long-afterglow system of claim 1, wherein the photochemical long-afterglow system is encapsulated in a nanocarrier, and the nanocarrier is cross-linked carboxylated polystyrene nanoparticles.

3. A photochemical long afterglow nanoprobe, characterized in that, The probe is prepared by coupling and modifying the surface of the photochemical long afterglow nanoparticles described in claim 2 with protein substances.

4. The photochemical long afterglow nanoprobe according to claim 3, characterized in that, The probe is used in the fields of bioimaging, immunochromatography, and homogeneous detection.

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