The detection of gunshot residue is one of the many essential applications of inorganic chemistry employed by forensic scientists to assist the criminal justice system. Inorganic gunshot residue particles originate from the primer mixture of the ammunition with lead styphnate being commonly used as an initiator. The visualisation of lead residues is a valuable investigative tool, enabling detection of bullet impact sites and the determination of shooting distance. Colourimetric reagents are applied to trace evidence and will react positively in the presence of the target compound by producing a colour change, enabling the trace to be visualised. They have an advantage over instrumental techniques by being cost-effective, efficient, accessible, and easy to apply. Sodium rhodizonate is a colourimetric reagent commonly used for the detection of lead in gunshot residue analysis, reacting with lead traces to form a red complex. However, this technique suffers from poor contrast on dark and red coloured surfaces, consequently requiring transfer of the gunshot residue to an alternative substrate that reduces the technique’s sensitivity.
Perovskite semiconductors have extensive applications ranging from solar cells to LEDs. Utilising the fluorescence of lead perovskites, gunshot residue traces can be visualised on dark coloured surfaces, simplifying evidence treatment and mitigating a loss of sensitivity in the transfer process. This work showcases the application of perovskites in improving gunshot residue visualisation with fluorescent lead detection and optimisation for use under ambient conditions.