Photoinduced Electronic Modulation in a Thorium Cluster: Enabling Dual Radiation Sensing and Photothermal Conversion

Understanding the fundamental properties of actinide-based materials is essential for expanding their applications in optical switching, radiation sensing, and integrated energy conversion. Herein, a thorium-based cluster (Th-106) is reported as an actinide system exhibiting pronounced irradiation-induced electronic modulation, where charge redistribution and ligand radical generation within the framework give rise to distinct photochromic, radiochromic, and photothermal responses. UV and X-ray irradiation induces the formation of radical species, resulting in visible photochromic and radiochromic transitions accompanied by enhanced visible-near-infrared absorption and improved photothermal conversion efficiency. In contrast, X-ray irradiation induces a distinctly different color evolution through a reversible radiochromic process, enabling direct visual detection of ionizing radiation. The differentiated chromic responses under UV and X-ray excitation highlight the involvement of irradiation-induced electronic modulation in regulating light absorption, charge redistribution, and nonradiative relaxation pathways within the thorium cluster framework. By integrating photochromism, radiochromism, radiation sensing, and photothermal conversion within a single material, Th-106 provides a promising actinide-based platform for exploring irradiation-responsive photophysical processes and developing multifunctional radiation-responsive materials.