X-ray and γ-ray Sensing from Aqueous-Based Lead Sulfide Telluride Nanocomposites

Lead chalcogenides (PbS, PbSe, and PbTe) are exceptional semiconductors for a variety of applications that exploit their unique combination of heavy atomic mass and high charge mobility. For sensors of energetic quanta such as X-rays and γ-rays, the de-coupling of electronic and phononic modes can deliver high intrinsic energy resolution at room temperature. Thus far, the lack of a simple, effective fabrication procedure for making large-volume percolating networks has prevented the exploitation of these materials. Here, a synthesis strategy is reported that utilizes aqueous colloids of PbS_xTe_y nanoparticles that are grafted upon an aramid nanofiber scaffold, such that excellent charge transport is realized throughout the size-scalable solids. When sensing individual X-rays and γ-rays, the resulting nanoparticle-polymeric composite can exhibit an energy resolution equivalent to that of a commercial single-crystalline cadmium telluride detector (2.8 keV at 81 keV). Furthermore, the addition of interfaces and randomly distributed lattice planes within the solid results in enhanced stopping of the secondary electrons from the photonic interactions, a scattering effect that can result in either thin-film X-ray stopping layers or lightweight, flexible, charged-particle shielding.