Dynamic visualization level 3 details of latent fingerprints by fluorescence imaging and photoluminescent macromolecules functionalized with spiropyran photoswitch

Abstract

Detecting latent fingerprints (LFPs) poses a considerable challenge for individual identification in the case of the criminal scene because detecting more details about three levels of identification patterns at a fast rate and by conventional instruments is very important for investigators. This research involved creating nanoparticles made of a copolymer containing tertiary amine-functionalized methacrylate through emulsion copolymerization, and then modifying them with a spiropyran derivative. The concentration of tertiary amine groups significantly influenced the optical properties, with samples containing more than 10 wt% exhibiting negative photochromism, leading to the absence of dynamic emission and reversible photochromism. The study of the kinetics of isomerization from spiropyran to merocyanine using solid-state fluorescence spectroscopy highlighted the important role of negative photochromism in the photoswitching of spiropyran. The resulting dynamic photoluminescent polymer powders were effectively utilized for LFP visualization through powder dusting, fluorescence imaging, optical security tag production, and the development of innovative OLEDs. The study confirmed the efficiency of these polymer powders in visualizing LFPs, enabling the identification of intricate details and patterns at three distinct levels. The observed LFPs emitted fluorescence in a range of colors, displaying high contrast, resolution, maximum intensity, and brightness. Three levels of identification details were detected for an unknown LFP that remained on the surface of the glass bottle as a real sample in the criminal scene. Successful identification of the unknown offender indicates the potential application of samples for time-dependent visualization of LFPs in criminal scenes.