Metal-free and ecofriendly photoluminescent nanoparticles for visualization of latent fingerprints, anticounterfeiting, and information encryption

Visualization of latent fingerprints (LFPs) on different substrates is a significant challenge for security forces in crime scene, which the highly fluorescent materials with maximum brightness and contrast for rapid detection by simple instruments are essential for this propose. In this study, the multi-color photoluminescent functional polymer nanoparticles based on oxazolidine (as fluorescent dye with concentration of 1 wt%) and a copolymer of methyl methacrylate (MMA)/2-(dimethylamino)ethyl methacrylate (DMAEMA) as matrix were synthesized by emulsion copolymerization and physical post-polymerization modification methods. After investigation of physicochemical and optical properties, the multi-color photoluminescent polymer powders were used for printing of security tags and visualization of LFPs by means of powder dusting strategy. The printed encoded security tags as quick responsive (QR) codes are highly fluorescent with maximum brightness and resolution in different colors. The photoluminescent polymer powders were used for fast and facile visualization of LFPs by powder dusting and fluorescence imaging using of smart phone camera under UV irradiation (365 nm). Results of fluorescence imaging indicated that the unique and personal details of fingerprints patterns are detectable by naked eye. Therefore, developed highly photoluminescent polymer powders for powder dusting and fluorescence imaging can provide reliable evidence to recognition of individual identity in a short time and by the least facilities.

Automated summary

In this study, multi-color photoluminescent polymer nanoparticles were synthesized and used for printing security tags and visualizing latent fingerprints. The fluorescent polymer powders enabled fast and easy detection of individual fingerprint details through powder dusting and fluorescence imaging under UV illumination.