Encapsulation of fluorescent carbon dots into mesoporous SiO2 colloidal spheres by surface functionalization-assisted cooperative assembly for high-contrast latent fingerprint development.

Exploiting solid powder fluorescence holds significant potential in diverse domains including medicine and forensics. Conventional fingerprint detection methods often fall short due to low contrast, sensitivity, and high toxicity. To addressing these challenges, we present a novel method for latent fingerprint detection using fluorescent carbon dots (CDs) encapsulated into conventional or mesoporous SiO₂ colloidal spheres (CD@SiO₂ or CDs@m-SiO₂) through a surface functionalization-assisted cooperative assembly process. The synthesized monodisperse CDs@SiO₂ and CDs@m-SiO₂ spheres, with tuning particle size, adjustable porosity and pore size, and highly dispersed CDs, exhibit improved fingerprint visibility and contrast on various substrates such as glass, stainless steel, and plastic. CDs located in SiO₂ with excellent affinity effectively avoids their solid-state self-quenching phenomenon, which, coupling with mesoporous SiO₂ shell, maximumly retains their fluorescence properties. Our method demonstrates a high contrast, selectivity, and sensitivity in fingerprint detection, offering an environmentally friendly and healthy alternative to conventional techniques, and showcasing a facile route to novel solid-state CDs-based fluorescent materials for forensic analysis.