Current X-ray imaging technologies involving flat-panel detectors have difficulty in imaging three-dimensional (3D) objects because fabrication of large-area, flexible silicon-based photodetectors on highly curved surfaces remains a challenge 1-3 . Here we demonstrate ultralong-lived X-ray trapping for flat-panel-free, high-resolution 3D imaging using a series of solution-processable, lanthanide-doped nanoscintillators. Corroborated with quantum mechanical simulation, our experimental characterizations show that a thermally activated slow-hopping of trapped electrons, due to radiation-induced anionic migration in host lattices, induces more than 30 days of persistent radioluminescence. We further demonstrate X-ray luminescence extension imaging (Xr-LEI) with >20-lp/mm resolution and >15-day optical memory. These findings provide insight into mechanisms underlying X-ray energy conversion through enduring electron trapping and also offer a new paradigm to motivate future research in wearable X-ray detectors for patient-centered radiography and mammogram, imaging-guided therapeutics, high-energy physics, and deep learning in radiology.

We systematically provide an overview of X-ray-sensitive materials and the recent progress on X-ray-activated nanosystems for cancer-associated theranostic applications.

Suppression of carrier recombination is critically important in realizing high-efficiency polymer solar cells. Herein, it is demonstrated difluoro-substitution of thiophene conjugated side chain on donor polymer can suppress triplet formation for reducing carrier recombination. A new medium bandgap 2D-conjugated D-A copolymer J91 is designed and synthesized with bi(alkyl-difluorothienyl)-benzodithiophene as donor unit and fluorobenzotriazole as acceptor unit, for taking the advantages of the synergistic fluorination on the backbone and thiophene side chain. J91 demonstrates enhanced absorption, low-lying highest occupied molecular orbital energy level, and higher hole mobility, in comparison with its control polymer J52 without fluorination on the thiophene side chains. The transient absorption spectra indicate that J91 can suppress the triplet formation in its blend film with n-type organic semiconductor acceptor m-ITIC (3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(3-hexylphenyl)-dithieno[2,3-d:2,3'-d']-s-indaceno[1,2-b:5,6-b']-dithiophene). With these favorable properties, a higher power conversion efficiency of 11.63% with high V of 0.984 V and high J of 18.03 mA cm is obtained for the polymer solar cells based on J91/m-ITIC with thermal annealing. The improved photovoltaic performance by thermal annealing is explained from the morphology change upon thermal annealing as revealed by photoinduced force microscopy. The results indicate that side chain engineering can provide a new solution to suppress carrier recombination toward high efficiency, thus deserves further attention.

Although photodynamic therapy (PDT) has served as an important strategy for treatment of various diseases, it still experiences many challenges, such as shallow penetration of light, high‐dose light irradiation, and low therapy efficiency in deep tissue. Here, a low‐dose X‐ray‐activated persistent luminescence nanoparticle (PLNP)‐mediated PDT nanoplatform for depth‐independent and repeatable cancer treatment has been reported. In order to improve therapeutic efficiency, this study first synthesizes W(VI)‐doped ZnGa2O4:Cr PLNPs with stronger persistent luminescence intensity and longer persistent luminescence time than traditional ZnGa2O4:Cr PLNPs. The proposed PLNPs can serve as a persistent excitation light source for PDT, even after X‐ray irradiation has been removed. Both in vitro and in vivo experiments demonstrate that low‐dose (0.18 Gy) X‐ray irradiation is sufficient to activate the PDT nanoplatform and causes significant inhibitory effect on tumor progression. Therefore, such PDT nanoplatform will provide a promising depth‐independent treatment mode for clinical cancer therapy in the future.