Up-conversion properties of lanthanide-organic frameworks and how to track ammunitions using these materials

This manuscript reports the first example of up-conversion properties involving Yb3+ and Tb3+ ions in five isostructural Lanthanide-Organic Frameworks (LnOFs), herein designated as UCMarker-1 to UCMarker-5, respectively, and their application as optical probes for the identification of gunshot residues (GSRs) and the ammunition encryption procedure. The excitation of the Yb3+ 2F7/2 ↔ 2F5/2 transition (980 nm) at room temperature leads to visible up-conversion (UC) emission of Tb3+ 5D4 → 7FJ. The GSR and lead-free primer residues are easily identified upon UV radiation (λ = 254 nm). These results prove that the exploration of LnOFs to identify GSR is attractive for the identification of ammunition origins or caliber recognition.