Fluorescence imaging of surface-versatile latent fingerprints at the second and third level using double ESIPT-based AIE fluorophore

Abstract

Latent fingerprints (LFPs) identification is of paramount importance for national security and criminal investigations. We designed and synthesized fluorescent organic molecule HPBI for the rapid fluorescence imaging of latent fingerprints on various surfaces such as aluminium foil, currency paper, brick, and glass, which did not require any post treatment. The HPBI exhibits a combination of ESIPT and AIE properties and forms green fluorescent nano-aggregates in CH₃CN–H₂O (1 : 1) mixture, as evaluated by DFT, SEM, TEM, and fluorescent microscopic studies. Spraying the solution of spherical HPBI nanoaggregates (50–100 nm size) on various surfaces resulted in fluorescence display of LFPs in <2 minutes. LFPs clearly revealed level-2 (ridge ending, islands, bifurcation) and level-3 (ridges path deviation, edge contours, sweat pores) details with high contrast and no background interference. The relocation of fluorescent fingerprints on cello tape provides an efficient and clean method for carrying fingerprints to the forensic laboratory.