Chemistry of extracting high-contrast invisible fingerprints from transparent and colored substrates using a novel phosphorescent labelElectronic supplementary information (ESI) available: TEM images and fluorescence confocal images of the as-prepared nanophosphor and its preparation. See DOI: 10.1039/c7ay02713c

Traditionally used fluorescent powders for developing invisible (latent) fingerprints involve complicated operation and show characteristics of auto-fluorescence interference and high toxicity. To overcome these serious drawbacks we report a novel application and facile methodology to extract high contrast fingerprints on non-porous and porous substrates using a chemically inert, visible light excitable, and nanosized SrAl 2 O 4 :Eu 2+ ,Dy 3+ phosphorescent label in the dark. The chemistry of non-covalent physisorption interaction between the long afterglow phosphor powder and sweat residue in fingerprints has been discussed in detail. Real-time fingerprint development on porous and non-porous substrates has also been performed. Conventional fluorescent powders for developing latent fingerprints show characteristics of complicated operation, auto-fluorescence interference and high toxicity. To overcome these issues, we report a facile methodology to extract high contrast fingerprints on non-porous and porous substrates using a phosphorescent label.