Scintillating Metal Organic Frameworks: A New Class of Radiation Detection Materials

摘要

The detection and identification of subatomic particles is an important scientific problem withimplications for medical devices, radiography, biochemical analysis, particle physics, and astrophysics.In addition, the development of efficient detectors of neutrons generated by fissile material is apressing need for nuclear nonproliferation and counterterrorism efforts. A critical objective in the fieldof radiation detection is to develop the physical insight necessary to rationally design new scintillationmaterials for specific applications. However, none of the material types currently used in has sufficientsynthetic versatility to exert systematic control over the factors controlling the light output and itsdynamics. Here we describe a spectroscopic investigation of two stilbene-based metal-organicframeworks (MOFs) we synthesized, demonstrating that they emit light in response to ionizingradiation, creating the first completely new class of scintillation materials since the advent of plasticscintillators in 1950. This highly novel and unexpected property of MOFs opens a new route to rationaldesign of radiation detection materials, since the spectroscopy shows that both the luminescencespectrum and its timing can be varied by altering the local environment of the chromophore within theMOF. Therefore, the inherent synthetic flexibility of MOFs, which enables both the chromophorestructure and its local environment to be systematically varied, suggests that this class of materials canserve as a controlled "nanolaboratory" for probing a broad range of photophysical and radiationdetection phenomena. In this presentation we report on the time-dependent fluorescence andradioluminescence of these MOFs and related structures. Multiple decay characteristics have beenobserved for some materials under study, including fast (ns) exponential and slow (microsecond) non-exponential components. We interpret the results in terms of the electronic states, crystal structures,intermolecular interactions, and transport effects mediating the luminescence. The potential forparticle discrimination schemes and large scale production of MOFs and will be discussed.