Ultrastable radicals in naphthalenediimide-based materials and their stimulus-boosting near-infrared photothermal conversion

Abstract

Persistent stable radical-doped characteristic of naphthalenediimide-based crystalline materials under ambient conditions, even bearing 300 °C high temperature treatment, was studied by UV-Vis-NIR absorption spectroscopy, electron paramagnetic resonance (EPR) spectroscopy and powder X-ray diffraction (PXRD) analyses. On exposure to additional visible light or after-heat treatments, more ultrastable organic radicals can be sharply formed due to the strong and intrinsic electron transfer interactions in the crystalline materials. The significant near-infrared photothermal conversion was directly achieved in these radical-doped crystalline materials without extra chemical modification or photochemical means; furthermore, it can be effectively enhanced by further photo-induction and thermal-activation processes.