材料科学最新文献

Organic-inorganic hybrid scintillator PEA₂PbBr₄ has emerged as a promising fast scintillator for applications in ultrafast radiation imaging, transient diagnosis of pulsed radiation fields, and medical radiodiagnosis. However, its performance is limited by notably prolonged decay times under high-energy X-ray excitation due to inefficient radiative recombination of sparsely distributed bulk excitons. Furthermore, the difficulty in growing and processing high-quality, large-area single crystals hinders the development of scalable scintillation screens. Here, we report a general fabrication strategy for large-area uniform scintillation screens that synergistically enhances the decay time and imaging resolution under X-ray excitation by suppressing bulk exciton diffusion in PEA₂PbBr₄. By leveraging the spatial confinement of nano-porous templates, we reduce the dimensionality of PEA₂PbBr₄ from bulk single crystals to uniform 1D nanowires, leading to spatial localization of bulk excitons. This localization significantly shortens the radioluminescence decay time from 11.85 to 1.87 ns. Meanwhile, the regularly aligned periodic optical waveguide structure enables directional propagation of scintillation photons along the nanowires, yielding high spatial resolution imaging (57.1 lp/mm at MTF = 0.2). This work provides a viable approach for advancing the application of organic-inorganic hybrid scintillators in ultrafast radiation imaging.

S-scheme heterojunctions enable spatial separation of photogenerated carriers, but remain constrained by interfacial electron transfer efficiency. Herein, oxygen vacancy defects are locally formed by removing fluorine atoms from the highly oriented (001) crystal plane of TiO₂ with fluorine doping. These defects can introduce additional doping energy levels, serving as the bench for S-scheme interfacial electron transfer in CdS/TiO₂. As verified by femtosecond transient absorption spectra, in situ irradiated X-ray photoelectron spectra, and theoretical computational simulations, the defect energy levels trap the localized electrons, which participate in the S-scheme interfacial transfer upon photoexcitation. The electron trapping process effectively prolongs the lifetime of photogenerated carriers and retards the charge recombination within each component. Besides, the binding energy shifts and surface potential changes detected by emerging in situ irradiated soft X-ray absorption spectroscopy and in situ irradiated Kelvin probe force microscopy provide conclusive evidence for the CdS/TiO₂ S-scheme heterojunction. Benefitting from trap energy level-assisted S-scheme electron transfer mechanism, the optimal CdS/TiO₂ composite exhibits superb photocatalytic H₂ production performance.

Deep-seated tumors are difficult to treat because of their location, conventional treatment resistance, and limited light penetration during photothermal therapy (PTT). Interstitial PTT with "inside-out" laser irradiation using optical fibers (OFs) offers a promising solution. This study proposes a drug-device integrated platform assisted by a puncture needle combining stimuli-responsive hydrogels with a spherical-tip polymer OF (SPOF) to overcome dual challenges: Inadequate photothermal agent retention and insufficient optical penetration. The injectable thermosensitive hydrogel (SW8@Gel), composed of Pluronic F127 and aza-boron-dipyrromethene-derived SW8 nanoparticles, rapidly undergoes sol-gel transition at 38°C, facilitating localized and sustained delivery of the photothermal agent. The flexible low-bending-loss SPOF emits 360° divergent near-infrared II (1064 nm) light from its spherical tip, allowing single-fiber illumination of deep-seated tumors (penetration >10 cm) in complex biological environments. Integrating these components enables depth-adaptive tumor ablation. Compared to other methods, the SPOF/SW8@Gel combination demonstrates the lowest frequency and shortest duration for PTT of deep-seated tumors and achieves superior efficacy, with a 90% tumor regression rate in mice models and no off-target damage due to enhanced heating uniformity and reduced systemic toxicity. This platform offers a transformative clinically viable solution for precise ablation of deep malignancies, bridging advanced photonics and targeted oncotherapy.

Photochromic materials with rapid response and high stability are essential for progressive anti-counterfeiting and secure information encryption technologies. Herein, we report a Förster resonance energy transfer (FRET)-assisted strategy to boost the photochromic properties of highly crystalline C₃N₅ nanosheets (HC-C₃N₅) by integrating carbon dots (CDs). The incorporation of CDs significantly increased light absorption, fluorescence intensity, and energy transfer efficiency, leading to an ultrafast and reversible color transition from dark yellow to green under UV irradiation, with complete recovery within 180 s and excellent cycling stability. The transient photovoltage technique (TPV) test confirms a non-radiative energy transfer pathway between CDs and HC-C₃N₅, excluding the possibility of electron transfer. Building on the distinct photo response characteristics of bulk C₃N₅ (B-C₃N₅), HC-C₃N₅, and CDs/HC-C₃N₅, this study further explores their potential in multi-layered anti-counterfeiting labels and a time-resolved encryption system, enabling dynamic optical information encoding. This work not only reveals the key role of the FRET mechanism over CDs in modified photochromic materials, but also paves the way for next-generation anti-counterfeiting and secure data storage applications.