Visualization of level-3 latent fingerprints by surfactant-free CsPbBr3 MCs with Pb(OH)2 as a passivation layer and an anchored bridge

Abstract

The visualization of level 3 fingerprint features, such as pore size, spacing, and distribution, plays a crucial role in matching damaged latent fingerprints (LFPs). CsPbBr₃ microcrystals (MCs) show great potential for LFP visualization, but the use of organic surface passivation can deteriorate their fluorescence properties and reduce imaging quality. In this study, we developed CsPbBr₃ MCs with a Pb(OH)₂ passivation layer formed through a methylamine vapor phase transition, replacing the need for organic passivators. Thanks to the hydrophobic nature and hydrogen bonding properties of Pb(OH)₂, the CsPbBr₃ MCs demonstrate excellent structural and fluorescence properties, while also anchor effectively to amino acids. Beyond the pressure deficit mechanism, FT-IR analysis and theoretical calculations confirm that the –COOH groups in amino acids form hydrogen bonds with the OH groups of Pb(OH)₂, leading to the absorption of CsPbBr₃ MCs onto fingerprint ridges. This results in superior visualization of level 3 fingerprint details, offering new insights into the development of surfactant-free inorganic materials for fluorescence imaging.