The scope of this study is a new procedure for visualizing dactyloscopic traces on an absorbent surface using a solution based on aggregates of 1,8-diazafluoren-9-one (DFO) in a polyvinylpyrrolidone polymer (PVP). An absorbent surface is defined as a plain or thermal paper, which is considered to be a difficult surface due to its varying chemical composition. In the case of the thermal paper surface, the procedure can be further improved by the addition of Au/Ag nanoparticles, which cause an enhancement of the fluorescence phenomenon from the surface of the fingerprint. The procedure requires the use of forensic illuminators and filters to reveal traces at the crime scene. Regarding the visualization of fingerprint prints in the forensic laboratory, the use of a stereo fluorescence microscope provides higher-resolution images when analyzing single patterns in the form of minutiae. The presented procedure is competitive with known, highly toxic current methods for revealing dactyloscopic traces using the DFO molecule. It also represents a key contribution to the development of methods for visualizing traces on thermal paper using fluorescent dyes and suitable control of their spectroscopic properties.
