Rapid identification of Sr on surfaces of metals, porous medium, transparent materials using single-shot laser-induced breakdown spectroscopy

Rapid threat analysis is essential in radiological terror scenes to protect workers and the public. Sr-90, a potential dirty bomb material, has been stolen multiple times. A conventional radiation detection is slow for detecting Sr-90 that only emits beta-ray. It rigorously interacts with matters and rarely reaches a detector. For fast analysis over large area after confirming the presence of radioactive Sr, laser-induced breakdown spectroscopy can be an attractive method. This study investigates the effect of different substrates on identifying Sr on their surface using single-shot. The thin layer of Sr on the forensic samples makes the single-shot analysis essential. The substrates include metallic (aluminium, stainless steels), porous (mortar, polyester), and transparent materials (poly(ethyl benzene-1, 4-dicarboxylate)). SrCO3, SrTiO3, and SrF2 are 3 target compounds selected based on historical theft cases. The limits of detection range over 1.09-19.06 mu g/cm(2). Stainless steel shows the lowest LOD at 407.77 nm for SrCO3 and SrF2. Higher standard error is explained by more heterogeneous Sr distribution. The transparent material shows the highest error. Additionally, potential ways to distinguish chemical compounds are suggested using Ti peaks and Sr-F vibration band. The applicability is discussed by comparing surface concentrations of Sr from terror and natural background.