Near-infrared-light-mediated imaging of latent fingerprints based on molecular recognition

Photoluminescence is one of the most sensitive techniques for fingerprint detection, but it also suffers from background fluorescence and selectivity at the expense of generality. The method described herein integrates the advantages of near-infrared-light-mediated imaging and molecular recognition. In principle, upconversion nanoparticles (UCNPs) functionalized with a lysozyme-binding aptamer were used to detect fingerprints through recognizing lysozyme in the fingerprint ridges. UCNPs possess the ability to suppress background fluorescence and make it possible for fingerprint imaging on problematic surfaces. Lysozyme, a universal compound in fingerprints, was chosen as the target, thus simultaneously meeting the selectivity and generality criteria in photoluminescence approaches. Fingerprints on different surfaces and from different people were detected successfully. This strategy was used to detect fingerprints with cocaine powder by using UCNPs functionalized with a cocaine-binding aptamer.