A Super‐Bright and Temperature‐Inert Au Complex Scintillator With Thermally Stimulated Delayed Phosphorescence Characteristic

ABSTRACT

Scintillators serve as crucial core materials in high‐energy radiation sensors. Molecule‐based scintillators, one of the important kind of scintillators, have demonstrated outstanding advantages, such as high water‐oxygen stability, low cost, and low toxicity. However, limited exciton utilization and luminescence efficiency have an impact on the radioluminescence properties of materials, severely limiting the development of molecule‐based scintillators. In this work, the first thermally stimulated delayed phosphorescence (TSDP) molecule‐based scintillator (Au(TFPP)₃ ) was reported. Spin‐allowed reverse internal conversion (RIC) of triplet excitons occurs in the TSDP process, leading to efficient utilization of thermally sensitive triplet excitons and overcoming the significant temperature effect of scintillators. As a result, Au(TFPP)₃ not only has an ultrahigh photoluminescence quantum yield (PLQY) exceeding 99% but also has an excellent light yield (LY) as high as 99475 ± 275 photons MeV⁻¹. More importantly, all these luminescence properties are temperature independent over a very wide range from 100 to 370 K. The super‐bright and temperature‐inert characteristics render Au(TFPP)₃ highly suitable for ionising radiation detection, and Au(TFPP)₃ has been effectively applied in low‐dose x‐ray variable‐temperature imaging and α/β particle detection.

The first thermally stimulated delayed phosphorescence molecule‐based scintillator Au(TFPP)₃ achieves ultrahigh photoluminescence quantum yield and excellent light yield via efficient utilization of thermally sensitive triplet excitons, enabling low‐dose x‐ray variable‐temperature imaging and α/β particle detection.

1. Introduction

Scintillators are a type of high‐energy radiation‐sensing material capable of converting high‐energy radiation and particles into visible light and have exhibited extensive application value in areas such as bio‐diagnosis and therapy, nondestructive testing, and nuclear radiation protection [1, 2, 3, 4, 5, 6]. Compared with traditional inorganic scintillators, emerging molecule‐based scintillators have demonstrated outstanding advantages, such as high water‐oxygen stability, reduced cost, and lower toxicity, thereby establishing themselves as a focal research area within the field [7, 8, 9, 10, 11, 12, 13]. For a long time, the limited utilization of excitons has severely affected the radioluminescence performance of molecule‐based scintillators [14]. To address this problem, special luminescence processes such as thermally activated delayed fluorescence (TADF) and doublet luminescence have been introduced to the design of molecule‐based scintillators, endowing them with nearly 100% utilization of excitons [15, 16, 17]. To a certain extent, these strategies have contributed to enhancing the radioluminescence performance of molecule‐based scintillators. However, the spin‐forbidden reverse intersystem crossing (RISC) process in TADF scintillators leads to partial loss of thermosensitive triplet excitons, resulting in a nonradiative transition [18, 19]. For radical scintillators with doublet luminescence, the inherent aggregation‐induced quenching property limits their radioluminescence intensity [20, 21]. It is still a challenge to find an efficient emission mechanism to design high‐performance molecule‐based scintillators.

In 2018, YAM's team identified a novel phosphorescence emission mechanism in Au complexes, termed thermally stimulated delayed phosphorescence (TSDP) [22]. Unlike the spin‐forbidden RISC process, the TSDP mechanism can achieve efficient utilization of thermally sensitive triplet excitons via a more efficient and spin‐allowed reverse internal conversion (RIC) process (Figure 1a). Moreover, the thermally induced RIC process can effectively reduce the nonradiative transitions of the excited state caused by temperature, enabling luminescent materials with TSDP characteristics to maintain high luminescence quantum efficiency over a large temperature range.

FIGURE 1.

(a) The interaction between matter and high‐energy radiation, as well as the TADF and TSDP mechanisms of molecule‐based scintillators under high‐energy radiation excitation. (b) The synthesis method of Au(TFPP)₃.

This work is the first to introduce the TSDP mechanism into the design and development of molecule‐based scintillators, and an Au complex of Au(TFPP)₃ with outstanding radioluminescence properties has been prepared. Owing to its distinctive TSDP luminescence process, Au(TFPP)₃ exhibits an ultrahigh photoluminescence quantum yield (PLQY) exceeding 99%. Moreover, owing to its remarkable luminescence properties and the heavy‐atom effect of Au atoms, Au(TFPP)₃ demonstrates excellent radioluminescence characteristics toward ionizing radiation. On the one hand, Au(TFPP)₃ has outstanding x‐ray excited luminescence (XEL) intensity, with a relative light yield (LY) reaching 99475 ± 275 photons MeV⁻¹, and the detection limit for a low‐dose‐rate x‐ray response can reach 33.8 nGy s⁻¹. The scintillator screen fabricated by using Au(TFPP)₃ can achieve high‐resolution, low‐dose x‐ray imaging at different temperatures. On the other hand, Au(TFPP)₃ exhibits a sensitive radioluminescence signal when stimulated by α/β particles. A surface contamination monitor (SCM) was fabricated by integrating Au(TFPP)₃ with photomultiplier (PMT) and nuclear electronics components, which can perform real‐time detection of α/β particles in the environment. This work not only demonstrates the great application prospects of TSDP scintillators in the field of radiation sensing materials but also offers a new perspective for the construction of super‐bright and temperature‐inert molecule‐based scintillators.

2. Results and Discussion

Au(TFPP)₃ was synthesized via a one‐pot method with tris(4‐fluorophenyl)phosphane (TFPP) as the ligand and Au(TFPP)Cl as the precursor at room temperature (Figure 1b; Figures S1–S3). The detailed synthesis methods for centimeter‐sized crystals and powder microcrystals are described in the Methods section. The thermogravimetric (TG) data revealed that there was no weight loss within 120°C (Figure S4a). Powder x‐ray diffraction (PXRD) data indicate that even when Au(TFPP)₃ is immersed in water or exposed to air for 4 weeks, its crystalline phase purity remains remarkably stable (Figure S4b). As shown in Figure S5, Au(TFPP)₃ exhibits high hydrophobicity, as evidenced by a contact angle of 129.6° between its powdered sample and a water droplet. Moreover, the luminescence spectra of Au(TFPP)₃ barely changed after long‐term immersion in water or exposure to air, demonstrating outstanding water‐oxygen stability (Figures S6 and S7).

Au(TFPP)₃ exhibits bright blue‐green luminescence at room temperature, with the emission wavelength centered at 497 nm and a Stokes shift (Δλ) of 165 nm (Figure S8). Notably, the PLQY of Au(TFPP)₃ is as high as over 99% (Figure S9). To explore the intrinsic mechanism behind the ultrahigh luminescence intensity of Au(TFPP)₃ , the temperature‐dependent time‐resolved photoluminescence (TRPL) in the range of 10–360 K was investigated. As shown in Figure 2a, Figure S10, and Table S1, the PL lifetime of Au(TFPP)₃ exhibits an overall decreasing trend with increasing temperature in the range of 10–360 K. Notably, even when the temperature rises to 360 K, the fitted PL lifetime remains on the order of 8 µs. This relatively long emission lifetime indicates that the radiative transition process of the excited state of Au(TFPP)₃ likely originates from a long‐lived excited triplet state [23, 24, 25]. To confirm that the luminescence of Au(TFPP)₃ originates entirely from the triplet excited state, we characterized its luminescence dynamics via the femtosecond fluorescence upconversion (fs‐UCPL) technique. As shown in Figure S11, no discernible signal was observed in the fs‐UCPL spectrum within the 450–600 nm detection window, indicating that the S₁ state does not undergo detectable ns‐scale fluorescent radiative decay, thereby further ruling out the contribution of singlet states to luminescence. Subsequently, temperature‐dependent PL spectra and 3D‐TRPL of Au(TFPP)₃ were characterized. As shown in Figure 2b and Figures S12 and S13, the PL intensity gradually decreases between 10 and 100 K, whereas the emission wavelength remains nearly constant. In contrast, when the temperature exceeds 100 K, the emission intensity of Au(TFPP)₃ remains largely unchanged, whereas the emission wavelength slightly blueshifts to approximately 10 nm. The above experimental results indicate that Au(TFPP)₃ likely undergoes a thermally activated upconversion luminescence mechanism [26, 27, 28, 29]—specifically, a TSDP process—at temperatures above 100 K.

FIGURE 2.

(a) Temperature‐dependent PL lifetime decay curves of Au(TFPP)₃ in the range of 10 to 360 K (pulse laser Ex: 355 nm). Inset: PL lifetime variation curves of Au(TFPP)₃ at different temperatures. (b) Temperature‐dependent PL intensity of Au(TFPP)₃ in the range of 10–360 K. Inset: PL images of Au(TFPP)₃ at different temperatures. (c) fs‐TAS after excluding the PL‐contaminated spectral window, showing the intrinsic ESA dynamics in the 580–730 nm region (pump at 390 nm). (d) SOC constants and energy level diagram of Au(TFPP)₃ , calculated at the S₁ geometry. (e) Electron and hole distributions of Au(TFPP)₃ (isovalue = 0.2). (f) SOC constants and energy differences between the lowest five singlet and triplet excited states, calculated at the T₁ geometry. (g) Electrostatic potential of the Au(TFPP)₃ dimer. (h) Independent gradient model based on the Hirshfeld partition isosurface plot of the Au(TFPP)₃ dimer showing the H···F and F···F interactions.

To further verify the upconversion process associated with the presence of the excited triplet state, femtosecond transient absorption spectroscopy (fs‐TAS) measurements were carried out under 390 nm excitation. As shown in Figure 2c and Figure S14, upon photoexcitation, Au(TFPP)₃ rapidly generates an excited‐state absorption (ESA) signal, which subsequently undergoes a multi‐step relaxation process. Further kinetic fitting was performed at the representative wavelengths of 650, 660, 700, and 720 nm, yielding four times constant components (the mean value obtained from the data of the four wavelengths): τ ₁ = 1.2 ps, τ ₂ = 32.3 ps, τ ₃ = 441.6 ps, and τ ₄ = 4.9 µs. The ps‐scale components can be attributed respectively to the ultrafast internal conversion (IC) and vibrational relaxation processes from the excited singlet state (τ ₁), the intersystem crossing (ISC) process from the S₁ state to the T_n states (τ ₂), and the mutual conversion and relaxation processes between the T₁ and T_n states (τ ₃); whereas the µs‐scale long‐lived component corresponds to the process of electron–hole recombination on triplet‐state (τ ₄).

To gain mechanistic insights into the TSDP behavior of the studied compound, we systematically investigated the excited‐state energetics and spin‐orbit coupling (SOC) interactions between the relevant singlet and triplet states. As shown in Figure 2d, the energy difference between the first singlet excited state (S₁) and the lowest triplet state (T₁) is 0.060 eV, with T₁ lying below S₁, suggesting a thermodynamically favorable ISC process. In addition, several higher‐lying triplet states—T₂, T₃, T₄, and T₅—are located within ±0.064 eV of S₁, with T₂ and T₃ slightly below (ΔE = 0.054 and 0.014 eV, respectively), and T₄ and T₅ slightly above (ΔE = −0.038 and −0.064 eV, respectively). This dense manifold triplet states near S₁ provides multiple ISC and RIC pathways, which are critical for enabling TSDP and TADF‐like behaviors [30, 31, 32, 33]. The calculated SOC values (based on S₁ geometry) between S₁ and the triplet manifold further support this interpretation. Because S₁ and T₁ have the same orbital component (n→π* of the HOMO to LUMO) (Figure 2e, Figure S15, and Table S2), the SOC interaction between S₁ and T₁ is relatively weak (2.62 cm⁻¹), implying that direct ISC from S₁ to T₁ is likely spin‐forbidden or inefficient. However, the higher triplet states (T₂, T₃, T₄, and T₅) involve different excited‐state configurations (π* character) and spatial distributions of the participating orbitals (from LUMO+1 to LUMO+10), which have significantly larger SOC values between S₁–T₂ (42.83 cm⁻¹), S₁–T₃ (43.65 cm⁻¹), S₁–T₄ (46.80 cm⁻¹), and S₁–T₅ (22.91 cm⁻¹) (Figure 2e; Figures S15 and S16). This indicates that ISC may preferentially proceed through these higher triplet states due to a stronger SOC effect, followed by rapid IC to T₁. This mechanism is particularly plausible for T₂/T₃, which lies 0.054/0.014 eV below S₁ and has a strong SOC effect (42.83/43.65 cm⁻¹), suggesting that ISC between S₁ and T₂/T₃ can occur efficiently even at or slightly above room temperature.

Moreover, the SOC (based on the T₁ geometry) between the ground state (S₀) and the triplet state also provides insight into the phosphorescence pathways (Figure 2f; Figure S17). The SOC values of 132.76 cm⁻¹ (T₁), 247.72 cm⁻¹ (T₂), and 192.12 cm⁻¹ (T₃) are notably large, indicating that radiative decay from these triplet states to S₀—that is, phosphorescence—is strongly allowed. Among these, T₂ stands out with both a very small ΔE (T₁–T₂) of 0.006 eV and the highest SOC with S₀, suggesting that it may serve as a key emissive triplet state in the TSDP process. This state is thermally accessible from T₁ via RIC and is also capable of strong phosphorescent emission to S₀. These findings collectively support a TSDP mechanism where excitation initially populates the S₁ state, followed by efficient ISC to high‐lying triplets (especially T₂ and T₃) and IC to T₁. Upon thermal activation, RIC to T₂ and phosphorescence are primarily mediated through T₁ and T₂ due to their substantial SOCs with S₀ (Figure S18). The presence of small T₁–T _n energy gaps, along with strong SOC‐mediated emissive pathways, creates a tunable and thermally resilient excited‐state landscape reminiscent of TSDP‐active compounds.

Owing to the highly efficient ISC process of Au(TFPP)₃ , its luminescence is predominantly derived from triplet excitons irrespective of excitation mode—whether via ionization or photoexcitation. Consequently, the luminescent behavior observed under these two excitation pathways should be highly consistent [34, 35, 36]. We constructed a temperature‐variable time‐resolved radioluminescence (TRRL) testing system by integrating a tungsten‐target pulsed x‐ray tube, a temperature‐control module, and a TCSPC unit (Figure S19a). As shown in Figure S19b–d, within 80–360 K, the radioluminescence lifetime of Au(TFPP)₃ is highly consistent with its PL lifetime in both temperature dependence trend and fitted lifetime values. The above results demonstrate that the RL process of Au(TFPP)₃ is analogous to its PL process, indicating that the TSDP mechanism also plays a dominant role in the RL process.

Crystallographic analysis revealed the presence of distinct H···F and F···F interactions in Au(TFPP)₃ (Figures S20 and S21 and Table S3). Considering that specific molecular interactions such as hydrogen bonding and halogen bonding can constrain molecular vibrations, they are believed to enhance quantum effects by suppressing nonradiative decay pathways [37]. To verify this hypothesis, we carried out a detailed analysis of the weak interactions within the Au(TFPP)₃ dimer. As shown in Figure 2g, the electrostatic potential surfaces of the two Au(TFPP)₃ exhibit significant overlap and close spatial packing, indicating the presence of strong noncovalent interactions. Further insights from the independent gradient model based on Hirshfeld partitioning (IGMH) reveal that the dominant attractive forces arise primarily from H···F and F···F interactions (Figure 2h) [38, 39]. These results suggest that such weak, directional interactions play a key role in stabilizing the Au(TFPP)₃ dimer and possibly modulating its quantum yield.

Au(TFPP)₃ exhibited intense radioluminescence under x‐ray irradiation (Figure 3a). As shown in Figure 3b, under identical testing conditions, the XEL intensity of Au(TFPP)₃ is notably higher than that of the majority of commercial inorganic scintillators, such as LYSO:Ce, LuAG:Ce, YAP:Ce, and Bi₄Ge₃O₁₂ (BGO). Utilizing BGO as the standard, the relative LY of Au(TFPP)₃ was determined to be 99475 ± 275 photons MeV⁻¹ by means of the x‐ray attenuation efficiency and the integrated area of the XEL spectra under identical experimental conditions (Figure 3a,c, and Figures S22 and S23). This value is significantly higher than that of most molecule‐based scintillators reported in the literature (Table S4), indicating that Au(TFPP)₃ can efficiently convert high‐energy ionizing radiation into low‐energy visible photons [40, 41]. Moreover, the Au element in Au(TFPP)₃ endows it with good x‐ray absorption properties (Figure S24), ensuring it has intense radioluminescence [42].

FIGURE 3.

(a) XEL spectra of Au(TFPP)₃ and BGO under identical testing conditions. (b) Comparison of XEL intensity between Au(TFPP)₃ and commercial scintillators under identical testing conditions (parameters of the silver‐target x‐ray tube are voltage: 50 kV, beam energy: 23.8 keV, current: 80 µA, and dose rate: 763.2 µGy s⁻¹). (c) X‐ray attenuation efficiency for different sample thicknesses. (d) XEL intensity of Au(TFPP)₃ at different x‐ray dose rates (parameters of the silver‐target x‐ray tube are provided in Figure S41). (e,f) Radioluminescence signals of Au(TFPP)₃ and commercial scintillators to (e) an α radioactive source and (f) a β radioactive source. (g,h) Radiation hardness of Au(TFPP)₃ after long‐term (g) and more than 100 cycles of on–off (h) x‐ray irradiation (dose rate: 763.2 µGy s⁻¹).

As shown in Figure S25 and Figure 3d, the XEL intensity of Au(TFPP)₃ has an excellent linear correlation with the x‐ray dose rate. By employing the 3σ method, the limit of detection (LOD) of Au(TFPP)₃ for x‐ray was determined to be 33.8 nGy s⁻¹, which is approximately 1/160 of the requirements for medical detection [43]. In addition to x‐ray, Au(TFPP)₃ also exhibits a sensitive radioluminescence signal when stimulated by α/β particles (Figure S26). As shown in Figures S27 and S28, and Figure 3e,f, the detection frequencies of Au(TFPP)₃ for (activity: 0.8 µCi) and (activity: 0.2 µCi) can reach 2900 and 894 Hz, respectively, which are significantly superior to those of the traditional commercial inorganic scintillators LYSO:Ce, YAP:Ce, and BGO under the same detection conditions. More importantly, Au(TFPP)₃ has a high level of radiation hardness. Under conditions of continuous irradiation or cyclic irradiation with high‐dose‐rate x‐ray, Au(TFPP)₃ can maintain the stability of its XEL intensity (Figure 3g,h).

For x‐ray imaging materials, radioluminescence temperature stability and x‐ray imaging dose are two key indicators for assessing imaging performance [44, 45, 46, 47]. High radioluminescence temperature stability ensures that the imaging quality is not affected by the environmental temperature. Low‐dose x‐ray imaging not only significantly reduces the radiation dosage, minimizes the radiation exposure of relevant personnel, and enhances the safety of the imaging procedure but also mitigates the thermal damage inflicted on sensors by high‐energy operations, thus prolonging the service life of the equipment.

Benefiting from the TSDP process, Au(TFPP)₃ exhibits excellent temperature‐inert radioluminescence properties, with its intense XEL remaining largely unaffected by temperature variations. As shown in Figure 4a and Figures S29 and S30, when the temperature is increased from 100 to 370 K, the XEL intensity of commercial scintillators decreases sharply, whereas that of Au(TFPP)₃ remains greater than 95% the initial value. In addition, the radiation hardness of Au(TFPP)₃ under high temperature has been systematically characterized. As shown in Figure S31, under conditions of continuous or cyclic irradiation with high‐dose‐rate x‐ray, the XEL intensity of Au(TFPP)₃ at 370 K exhibited no significant attenuation, demonstrating its excellent radiation hardness. As shown in Figure S32, the PXRD pattern of Au(TFPP)₃ at 370 K is consistent with that at room temperature, indicating that it maintains excellent phase purity and structural stability under this temperature condition. Combining excellent temperature‐independent radioluminescence with its high XEL intensity, Au(TFPP)₃ has great application potential in low‐dose x‐ray variable‐temperature imaging. For this purpose, a flexible scintillation screen was fabricated with Au(TFPP)₃ microcrystals via the vacuum filtration method (Figure S33). Even after 500 cycles of bending, its XEL intensity remains unaltered (Figure S34).

FIGURE 4.

(a) Variation in the XEL intensity of Au(TFPP)₃ at different temperatures (parameters of the silver‐target x‐ray tube are voltage: 50 kV, beam energy: 23.8 keV, current: 80 µA, and dose rate: 763.2 µGy s⁻¹). (b) X‐ray imaging photographs of the pencil, memory cards, Bluetooth headphones, and dried fish using scintillator screens at a dose of 0.1018 mGy. (c–e) X‐ray imaging photographs and gray value curve of the standard line‐pair mask under (c) 293 K, (d) 323 K, and (e) 373 K at a dose of 0.1018 mGy.

A simple x‐ray imaging system was subsequently constructed to investigate the imaging performance of the Au(TFPP)₃ ‐based scintillation screen under low‐dose x‐ray irradiation (Figure S35). As shown in Figures S36 and S37, even at an ultralow dose of 0.0232 mGy, the metal spring within the capsule can be clearly visualized through the Au(TFPP)₃ ‐based scintillation screen (the gray value reaches 20); when the x‐ray dose is greater than 0.1018 mGy, the imaging resolution has reached saturation (the gray value is stable at 150). According to the edge method and modulation transfer function (MTF) calculation, the spatial resolution of the Au(TFPP)₃ ‐based scintillation screen can reach 34.4 LP mm⁻¹ at a low dose of 0.1018 mGy (Figure S38). Subsequently, we employed the Au(TFPP)₃ ‐based scintillation screen to carry out low‐dose x‐ray imaging of actual objects in daily life. As shown in Figure 4b, under an x‐ray dose of 0.1018 mGy, the built‐in circuits of the memory card, the internal structure of the bluetooth headset, the fish bones in the dried fish, and the pencil core can all be clearly presented on the scintillation screen. In addition, considering the high‐temperature stability of the XEL performance of Au(TFPP)₃ , x‐ray variable‐temperature imaging was performed with the Au(TFPP)₃ ‐based scintillation screen under a low x‐ray dose of 0.1018 mGy. As shown in Figure 4c–e, when the temperature was increased from room temperature to 370 K, the resolution was almost unchanged, demonstrating excellent x‐ray variable‐temperature imaging capability.

Environmental radiation detection involves the measurement of radioactive levels within the environment [48, 49]. The objective is to monitor environmental ionizing radiation, issue early warnings, guarantee the safety of radiation‐related operations, and provide essential safeguards for emergency responses during nuclear accidents [50].

To realize highly sensitive and accurate environmental radiation detection, the scintillator should exhibit not only high radioluminescence intensity but also weak afterglow emission [51, 52]. As shown in Figure 5a,b, the thermoluminescence (TL) spectra and afterglow spectra demonstrate that, in contrast to commercial inorganic scintillators, Au(TFPP)₃ does not exhibit any TL or afterglow emission. This property can ensure the reliability of α/β particle detection. Thus, an SCM was fabricated with an Au(TFPP)₃ crystal, PMT, and nuclear electronics devices. Specifically, the PMT can amplify the signal of scintillation photons through the multiplication effect into an electrical signal, which is then passed to the nuclear electronics for processing and analysis, forming a complete chain for signal processing (Figure S39) [53, 54].

FIGURE 5.

(a,b) TL spectra (a) and afterglow decay curves (b) of Au(TFPP)₃ and commercial inorganic scintillators after x‐ray irradiation (exposed to x‐ray irradiation at a dose rate of 763.2 µGy s⁻¹ for 120 s, total dose: 91.58 mGy). (c,d) Internal design (c) and physical diagram (d) of the SCM. (e) Detection performance of the SCM on a clean desktop and a desktop with radioactive sources, where the α‐radioactive source is and the β‐radioactive source is .

The internal structure of the scintillator detector is shown in detail in Figure 5c,d. As shown in Figure 5e, when the detection background is a clean desktop, the count on the SCM display screen is approximately four counts per second (CPS). This background signal is due to the detector's response to cosmic rays in the air. When the α/β radioactive source is present on the desktop, the SCM can yield a sensitive response signal to the α/β particles generated in the environment (Videos S1–S3). Consequently, the count on the display screen will increase promptly. Specifically, an α radioactive source () gives rise to a count of approximately 2300 CPS, whereas a β radioactive source () generates a count of approximately 600 CPS (Figure S40).

3. Conclusion

In conclusion, the TSDP mechanism was introduced for the development of a molecule‐based scintillator for the first time. The resulting Au complex of Au(TFPP)₃ exhibits super‐bright and temperature‐inert scintillation properties, making it suitable for low‐dose x‐ray variable‐temperature imaging and environmental radiation (α/β particle) detection. Mechanistic investigations revealed that the outstanding scintillation properties of Au(TFPP)₃ stem from the fact that the TSDP mechanism can efficiently utilize radiation‐induced thermosensitive triplet excitons through a highly efficient and spin‐allowed RIC process. This work demonstrates the broad application prospects of TSDP scintillators in the field of radiation sensing and provides a new strategy for the development of high‐performance molecule‐based scintillators.

4. Experimental Section

4.1. Synthesis of Precursor Au(TFPP)Cl

The synthesis method of precursor Au(TFPP)Cl was referred to the relevant literature [55]. TFPP (1.76 g, 5.6 mmol) was dissolved in 24 mL of anhydrous ethanol. Subsequently, H[AuCl₄] (1.00 g, 2.8 mmol) was dissolved in 20 mL of anhydrous ethanol and then slowly added dropwise to the above TFPP solution. The reaction mixture was stirred under dark conditions for 2∼3 h. Upon completion of the reaction, the resulting precipitate was subjected to suction filtration and thoroughly washed with anhydrous ethanol. Eventually, a white solid product, Au(TFPP)Cl (0.96 g, 1.75 mmol), was obtained, with a yield of 63%.

4.2. Synthesis of Au(TFPP)₃

Au(TFPP)Cl (360 mg, 0.65 mmol) was dissolved in 30 mL of dichloromethane. Subsequently, TFPP (616 mg, 1.95 mmol) was dissolved in 10 mL of anhydrous ethanol and then added dropwise to the above solution. The reaction mixture was transferred into a conical flask and allowed to stand at room temperature to enable the slow evaporation of the solvent. After a few days, large‐sized Au(TFPP)₃ crystals (605 mg, 0.51 mmol) (Figure 1b) were successfully isolated, with a yield of 79%. Mechanical grinding of large‐sized Au(TFPP)₃ crystals yields Au(TFPP)₃ powder crystals (Figure S41).

4.3. Preparation of the Scintillation Film

The Au(TFPP)₃ crystals (100 mg) were dispersed in 0.5 mL of pure water, and three small steel balls were added. Then, mechanical grinding treatment was carried out at a frequency of 45 Hz (each run lasted for 45 s with a 15 s interval, which was repeated 30 times). After processing, a milky white, uniform microcrystalline suspension was obtained. Under vacuum suction filtration, the Au(TFPP)₃ microcrystal suspension was filtered onto a commercial PVDF filtration membrane (diameter: 50 mm; thickness: 0.1 mm; pore size: 0.43 µm). Consequently, an Au(TFPP)₃ microcrystal film with an approximate area of 20 cm² was fabricated.

4.4. Crystallographic Analysis

SCXRD measurements were performed on a Bruker D8 VENTURE diffractometer with Mo‐Kα radiation (λ = 0.71073 Å) at 300 K. Data collection and reduction were performed via the program APEX3 software package. The structure was solved with intrinsic phasing methods (SHELXT‐2015) [56] and refined by full‐matrix least‐squares on F ² via OLEX2 [57], which utilized the SHELXL‐2015 module [58]. All the atoms were refined anisotropically, and the hydrogen atoms were placed in their calculated positions with idealized geometries and assigned fixed isotropic displacement parameters. The detailed crystal data and structural refinements of Au(TFPP)₃ can be found in Table S3.

4.5. Measurement of PL and TRPL

HORIBA FluoroLog‐3 fluorescence spectrometer with an integrating sphere (BaSO₄) and temperature control system (PHYSIKE PHY‐ACRYO‐4K‐101‐HT) was used to determine the PLQY and temperature‐dependent PL spectra. All PL emission spectra were measured with an excitation wavelength of 375 nm. During the measurement, the grating slit width of the fluorescence spectrometer was set to 1 nm, and the photomultiplier tube voltage was adjusted to 950 V. TRPL spectra were acquired using a HORIBA FluoroLog‐3 fluorescence spectrometer integrated with a 355 nm pulsed laser, TCSPC module (FL‐1054), and temperature control system (PHYSIKE PHY‐ACRYO‐4K‐101‐HT).

4.6. Measurement of XEL and TRRL

XEL spectra at different temperatures were recorded by an Edinburgh FS5 fiber optic fluorescence spectrometer with a temperature control system (NSTEC HCS621GXY) and a miniature silver‐target x‐ray tube (Moxtek Inc.). TRRL spectra were acquired using a custom‐built setup (picoX 5084) integrated with a tungsten‐target pulsed x‐ray tube (Hamamatsu N16432), TCSPC module (picoquant TimeHarp 260), and temperature control system (FERMI OP101). During the TRRL measurement, the tungsten‐target pulsed x‐ray tube operated at a tube voltage of 30 kV and a tube current of 2 µA.

4.7. Measurement of fs‐TAS

The fs‐TAS measurements were carried out on a commercial pump‐probe spectrometer equipped with a microscope‐coupled optical configuration (Ultrafast Systems LLC), driven by a Ti:sapphire regenerative amplifier (Astrella, Coherent). The amplifier delivered laser pulses centered at ∼800 nm with a pulse duration of < 100 fs, a repetition rate of 1 kHz, and a pulse energy of ∼7 mJ. A portion of the 800 nm output was directed into an optical parametric amplifier to generate 390 nm pump pulses. For femtosecond micro‐transient absorption measurements (Helios system), the probe white‐light continuum pulses were generated by focusing a small fraction of the 800 nm beam onto a sapphire crystal, covering the spectral region of approximately 450–730 nm. The pump and probe beams were spatially overlapped and focused on selected microcrystalline regions of the sample through the microscope optical path. The pump‐probe delay in the fs time window was controlled by a mechanical optical delay line, covering a delay range from ∼100 fs to 7 ns. For nanosecond transient absorption measurements (EOS system), the pump beam was generated in the same manner as described above. The probe beams were provided by an additional supercontinuum source covering 450–730 nm with a pulse duration of ∼0.5 ns and a repetition rate of 2 kHz. The pump‐probe delay in the nanosecond to microsecond time window was electronically controlled, covering a delay range from 1 ns to 25 µs. The transient kinetic traces at selected probe wavelengths were fitted with multi‐exponential functions to extract the characteristic time constants.

Owing to the high PLQY of Au(TFPP)₃ , pump‐induced emission signals inevitably propagate into the detection channel and overlap with the authentic transient absorption signal, leading to significant interference with the apparent ΔA signal in the short‐wavelength region. Notably, within the range of 450–600 nm, where strong spectral overlap with the emission band of Au(TFPP)₃ occurs, the measured transient absorption signal is substantially suppressed by the emission signal, rendering it unsuitable for direct analysis of the genuine excited‐state absorption (ESA) or ground‐state bleaching (GSB) processes (Figure S14a). To avoid misinterpretation in kinetic analysis caused by the luminescent background, the short‐wavelength region strongly affected by luminescence signals was excluded during subsequent data processing, with only the relatively reliable positive ESA signals within the range of 580–730 nm remaining for analysis.

4.8. Calculation of Relative LY

For molecule‐based scintillators, the LY is typically calculated via the relative method [34]. First, the photon cross‐section of the sample under x‐ray irradiation is obtained based on the photon cross‐section database, and then it is converted into the x‐ray attenuation coefficient in combination with the crystal density parameters (Figure S23). Through calculations via relevant formulas, the x‐ray attenuation coefficient of the sample is subsequently converted into a thickness‐dependent x‐ray attenuation efficiency. The x‐ray attenuation efficiency of the sample at a thickness of 0.5 mm was further determined (Figure 3c). Commercial scintillators with known LY (BGO) were selected as standard samples. Under the same test conditions (parameters of the silver‐target x‐ray tube are voltage: 50 kV, current: 80 µA), XEL spectra of a sample with a thickness of 0.5 mm and the corresponding standard sample were obtained (Figure 3a). Finally, based on the x‐ray attenuation efficiency and the integral area ratio of the XEL spectra, the relative LY of the sample was calculated. LY measurements were repeated three times under identical experimental conditions, and the corresponding standard deviation was calculated (Equation 1).

$$\mathrm{SD}=\sqrt{\frac{{\sum }_{\mathrm{i}=1}^{\mathrm{n}}{\left({\mathrm{x}}_{\mathrm{i}}-\overline{\mathrm{x}}\right)}^2}{\mathrm{n}-1}}$$ (1)

where SD is the overall standard deviation, n is the sample size, $\overline{x}$ is the sample mean, and x _i is the i‐th data value. Details of the specific calculation method can be found in previously reported work [59].

4.9. Measurement of the LOD

To ensure the accuracy of the test data, the dose rate of the silver‐target x‐ray tube should be calibrated by TL dosimetry before the LOD of the sample is calculated. The specific calibration method can be found in previous work [59]. The silver‐target x‐ray tube and XEL testing equipment used in this study are presented in Figure S42a,b. The calibration results of the dose rate of the silver‐target x‐ray tube are shown in Figure S42c. XEL spectra of the samples under x‐ray irradiation at various dose rates were subsequently acquired. The LOD of the sample's response to x‐ray was calculated via the 3σ method.

4.10. Detection Method for α/β Particles

As shown in Figure S26, the α/β particle detection system consists of a nuclear instrument module (NIM) chassis, a high‐voltage power supply, a PMT, a spectrum amplifier, an oscilloscope, and a sample chamber. The α radioactive source being detected is , with an activity of 0.2 µCi, and its decay scheme is shown in Figure S43. The β radioactive source being detected is , with an activity of 0.2 µCi, and its decay scheme is shown in Figures S44‐S45.

During the detection process, a tableting machine was used to fabricate the sample into a semi‐transparent disc with a thickness of 0.2 mm and a diameter of 10 mm. Then, the radioactive source and the sample were placed together in the sample chamber, ensuring that the sample was directly above the radioactive source. The response signal of the sample to the radioactive source was subsequently recorded through the oscilloscope.

4.11. Measurement of TL and Afterglow

Before the TL measurement, the samples were first exposed to x‐ray irradiation at a dose rate of 763.2 µGy s⁻¹ for 120 s (total dose: 91.58 mGy). The x‐ray was generated by a silver‐target x‐ray tube, with operating parameters configured as follows: tube current of 80 µA and tube voltage of 50 kV. TL spectra were recorded by an LTTL‐3DS TL spectrometer. During the TL signal collection, a constant heating rate of 3 K s⁻¹ was adopted. The temperature scanning range was set differently based on the thermal stability of each sample: 300–420 K for Au(TFPP)₃ and CsI:Tl, 300–500 K for LYSO:Ce, LuAG:Ce, YAP:Ce, and BGO. Prior to afterglow measurements, the total x‐ray irradiation dose applied to the samples was identical to that employed in the preceding TL measurements. The afterglow decay curves were acquired at room temperature using an LTTL‐3DS TL spectrometer.

4.12. X‐Ray Imaging

The X‐ray imaging system consists of a calibrated silver‐target x‐ray tube, a scintillation screen, an imaging sample, and a digital camera (Figure S35). In the process of x‐ray imaging, the dose rate was regulated by adjusting the current and voltage of the silver‐target x‐ray tube. Moreover, the distance between the scintillation screen and the silver‐target x‐ray tube was set at a fixed value of 50 mm. The exposure time of the digital camera was set to 2 s. The x‐ray dose during the imaging process can be obtained by multiplying the dose rate of the silver‐target x‐ray tube by the exposure time of the camera. During the high‐temperature imaging experiments, the scintillation screen was closely adhered to the surface of a thin glass dish filled with hot glycerol to mimic high‐temperature environmental conditions.

The resolution of x‐ray imaging is computed via the slanted‐edge method [60]. A mould with a sharp edge is placed close to the scintillation screen to acquire x‐ray images of its edge profile. Depending on the acquired x‐ray image of the slanted edge, the MTF curve is calculated via the ImageJ software.

4.13. Preparation of the SCM

The internal core structure of the SCM mainly consists of a scintillator probe and PMT components (Figure S39). Among them, the scintillator probe is a scintillator array composed of Au(TFPP)₃ crystals, and the aluminum film covering the periphery is used to ensure that the scintillator is not contaminated by the radioactive source during the detection process. The PMT is connected to the nuclear electronics module embedded in the housing and the counting display screen through data connection lines.

4.14. Theoretical Calculations

The ground states, the lowest singlet excited states, and the lowest five triplet excited states of Au(TFPP)₃ were calculated via a two‐layer ONIOM approach to accurately assess the electronic structures in the crystal matrix (Figure S46 and Tables S5–S10). In this framework, a select cluster at the crystal's core was treated as the “QM layer,” employing the PBE0/def2‐SVP method within the Gaussian 16 software suite [61]. The surrounding molecules were classified as the “MM layer” and assessed via the Universal Force Field (UFF). This was complemented by an electronic embedding technique that integrated the MM region's partial charges directly into the QM Hamiltonian [62].

To account for scalar relativistic effects, the second‐order Douglas–Kroll–Hess (DKH2) method was employed by the ORCA 6.1.0 program [63]. The spin‐orbit coupling between the lowest singlet excited state and triplet excited states was simulated via the PBE0 functional, along with the large scalar‐relativistically recontracted DKH‐def2‐TZVP basis set and the corresponding SARC/J auxiliary basis set. To accelerate the computations of the Coulomb and Hartree–Fock exchange integrals within these hybrid functionals, the RIJCOSX algorithm was also applied. Additionally, IGMH analysis was conducted, with the results visualized via the VMD and Multiwfn programs [64].

Author Contributions

Q.C.P., Y.S.H., J.W.Y., Y.B.S., K.L., and S.Q.Z. conceived this study. Q.C.P., Y.S.H., J.W.Y., K.L., and S.Q.Z. designed the experiments. Q.C.P., Y.S.H., J.W.Y., J.C.Z., Q.Y., Y.C.H., Z.Y.G., Y.B.S., Q.T., and K.L. carried out the experiments and data analysis. S.Q.Z. supervised the research. All the authors interpreted the results, and Q.C.P., K.L., Y.B.S., and S.Q.Z. cowrote the manuscript with input from all the authors.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Supporting File 1: adma74246‐sup‐0001‐SuppMat.docx.

Supporting File 2: adma74246‐sup‐0002‐MovieS1.avi.

Supporting File 3: adma74246‐sup‐0003‐MovieS2.avi.

Supporting File 4: adma74246‐sup‐0004‐MovieS3.avi.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.