Organic Crystals with Methyl Lock Effect for High-Efficiency X-Ray Scintillation and Advanced Anti-Counterfeiting.

Organic crystal scintillators that convert X-rays to visible photons have broad application prospects in medical radiography and security screening as sustainable materials. Although molecules with high photoluminescence properties under UV excitation are usually transplanted as scintillators for X-ray detection, the development of scintillant materials is still far behind that of photoluminescent counterparts. Here, a hypothesis is proposed that chemical bond inversion induced by high-energy radiation is a key factor responsible for the suppression of scintillation in organic materials. A "methyl lock" strategy is presented to limit this inversion and successfully liberate its radioluminescence ability. As a result, 1,4-bis(2-methylstyryl)benzene (bis-MSB) crystals with "methyl lock" exhibit an 8.9-fold increase in relative light output compared to 1,4-distyrylbenzene (DSB) without "methyl lock," achieving a remarkably low minimum detectable dose rate of 14.9 nGy s-1. The detector, based on bis-MSB crystal scintillators, offers exceptional resolution (50 lp mm-1), enabling precise X-ray imaging and computed tomography scanning. The distinct photo- and radio-luminescence behaviors of bis-MSB and DSB molecules make them promising materials for applications in information security and smart, multi-level anti-counterfeiting measures.