ZnAl2O4-based luminescent marker for gunshot residue identification and ammunition traceability

Lanthanide-doped ZnAl2O4 spinel was used as a luminescent marker for gunshot residue (GSR). GSR was visually identified on shooters' hands, as well as on firearms and the firing range. After the shot, GSR was collected and analyzed by several techniques, including FTIR, Raman and emission spectroscopies and SEM-EDS. It was observed that markers provide an optically and structurally unique signature for GSR, allowing their identification by the tested techniques. SEM-EDS shows that lanthanide ions act as a chemical taggant. FTIR and Raman spectra provided a chemical signature of GSR, as well as emission spectra. Thus, it was possible to unequivocally identify GSR, even when lead-free ammunition was used. By employing different emitting centers, it was also possible to distinguish between two types of ammunition, opening a new perspective for traceability.