Highly sensitive X-ray responsive molecular switches.

Li, Jiangang; Wei, Kuanjian; Liu, Xiangmei; Zhou, Zijian; Dai, Peiling; Shen, Jiacheng; Xu, Xiuwen; Zhu, Mingye et al. · Nat Commun · 2026

basic_science · Level V

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Abstract

X-ray-triggered molecular switching promises remote control behind physical barriers, yet existing radioswitches typically require multi-gray doses to reach a photostationary state. Here we route X-ray energy through triplet excitons to enable low-dose switching. An efficient scintillator acts as a triplet sensitizer, transferring energy to a photoswitch with lower triplet energy via triplet-triplet energy transfer (TTET). Flexible films combining a Cu<sub>2</sub>I<sub>2</sub>(POP)<sub>2</sub> scintillator with hydrazone switch 1-I reach a photostationary state at ~0.18 Gy and show a detection limit near 0.01 mGy, about two orders of magnitude lower than previous systems. HPLC quantification, radical-scavenger tests, and time-resolved spectroscopy support a TTET-dominated mechanism and establish a design rule based on triplet-level matching. Isomerization quenches fluorescence, enabling optical readout for high-resolution radiography (3251 dpi) with pattern retention for at least two months. In this work, we show that penetrating X-rays enable practical control of molecular functions in previously inaccessible complex environments.