Rescuing fluorescence with steric hindrance: Perylene diimide based powder for latent fingerprint imaging

We reported sterically crowded perylene diimide for rescuing its solid-state fluorescence through functionalization with bulkier hydroxyphenyl benzothiazole (PH2). The PH2 has (i) lambda max.at 620 nm; (ii) 28.8 % solid-state quantum yield and (iii) 100 % red colour purity calculated from CIE plot. PH2 adsorbed on silica nanoparticles was utilized as a fluorescent powder for the visualization of latent fingerprints on different porous, non-porous and curved surfaces using powder-dusting methods. The LFPs were subjected to laboratory conditions simulating those in the field such as aging, temperature, UV light and humidity and we successfully demonstrated the applicability of PH2-SiO2 powder for the development and visualization of ridge pattern from these degraded LFPs. We also aimed to recover LFPs from physical evidence by developing the LFPs with PH2-SiO2 followed by lifting of fingerprints using adhesive tape.