Negative Result: Assessing tropolone and its derivatives as chemical fingermark developers on paper surfaces

Tropolone reacts with amino acids to form adducts that generate contrast on highly fluorescent paper surfaces upon UV irradiation. Furthermore, the conjugated seven-membered ring of tropolone enables secondary chemical treatments; demonstrated here using two diazonium salts, 4-methoxybenzenediazonium tetrafluoroborate (4MBD) and 4-nitrobenzenediazonium tetrafluoroborate (4NBD). These produce yellow and red dyed fingermarks, respectively. While tropolone treatment is rapid to effect and compatible with ninhydrin in a detection sequence, the methodology proved less effective than current chemical visualisation treatments. Nevertheless, this work unambiguously demonstrates the reactivity of tropolone towards fingermark residues and may inspire future generations of non-benzenoid chemical visualisation treatments.