Nanocomposites of nitrogen-doped carbon dots/hydrotalcite with enhanced solid-state fluorescence for the recognition of latent fingerprints

Abstract

In this work, a green emissive nanocomposite was synthesized by embedding nitrogen-doped carbon dots into hydrotalcite (N-CD/hydrotalcite) via a hydrothermal process for the recognition of latent fingerprints (LFPs). Good dispersion of the nano-sized N-CD on the surface of hydrotalcite overcomes the fluorescence quenching of N-CD in the solid state and can enhance solid-state fluorescence. N-CD/hydrotalcite emits stable strong green fluorescence even at different excitation wavelengths and exhibits good selectivity and sensitivity for the visualization of LFPs on various substrates such as glass slides, tiles, leather, aluminum foil, printing paper, colored surfaces of plastic packing, copper foil, planks, leaves, currencies, and bar codes. The high-level details of the ridge patterns of both fresh and aged LFPs can be clearly identified with good clarity and high contrast without background interferences under the excitation of a 450 nm light source. There is no significant difference in the LFP image visualized by N-CD/hydrotalcite and commercial fluorescent powders, indicating that the effectiveness of N-CD/hydrotalcite for the visualization of LFPs is equivalent to that of commercial fluorescent powders. These observations illustrate that N-CD/hydrotalcite has great potential in the recognition of LFPs.