Gold nanoparticles and imaging mass spectrometry: double imaging of latent fingerprints

Latent fingerprint (LFP) detection is a top-priority task in forensic science. It is a simple and effective means for the identification of individuals. Development of nanomaterials which maximize the surface interaction with endogenous substances on the ridges to enhance the contrast of the fingerprints is an important application of nanotechnology in LFP detection. However, most developments in this area have mainly focused on the visualization of the physical pattern of the fingerprints and failed to explore the molecular information embedded in LFPs. Here, we have integrated certain distinctive properties of gold nanoparticles (AuNPs) with imaging mass spectrometry for both the visualization and molecular imaging of LFPs. Two contrasting colors (blue and pink), arising from different surface plasmon resonance (SPR) bands of the AuNPs, reveal the optical images of LFPs. The laser desorption/ionization property of the AuNPs allows the direct analysis of endogenous and exogenous compounds embedded in LFPs and imaging their distributions without disturbing the fingerprint patterns. The simultaneous visualization of LFP and the recording of its molecular images not only provide evidence on individual identity but also resolve overlapping fingerprints and detect hazardous substances.