Ultrafast scintillating metal-organic frameworks films

Abstract

Compositionally engineered metal-organic frameworks (MOFs) have been designed and used to fabricate ultrafast scintillating films with emission in both the UV and visible regions. The inclusion of hafnium (Hf) ions in the nodes of the MOF increases the interaction cross-section with ionizing radiation, partially compensating for the low density of the porous material and dramatically increasing the system scintillation yield. The high diffusivity of bimolecular excitons within the framed conjugated ligands allows bimolecular annihilation processes between excited states that partially quench the MOF luminescence, resulting in ultrafast scintillation pulses under X-ray excitation with kinetics in the hundreds of picoseconds time scale. Despite the quenching, the gain in scintillation yield achieved by incorporating Hf ions is large enough to maintain the light yield of the films above 104 ph/MeV under soft X-rays. These unprecedented high efficiencies and simultaneous ultrafast emission kinetics obtained at room temperature in a technologically attractive solid-state configuration, together with the versatility of its composition allowing for further application-specific modifications, place the MOF platform in a prominent position for the realization of the next generation of ultrafast scintillation counters for high-energy physics studies and medical imaging applications.