Shape-controllable synthesis of silica coated core/shell upconversion nanomaterials and rapid imaging of latent fingerprints

Upconversion nanomaterials with complex morphologies have attracted considerable interests due to morphology-dependent properties. In this work, silica coated-NaYF 4 upconversion nanomaterials (NaYF 4 @SiO 2 ) of various shapes – nanorods, nanodumbbell and nanowire – were synthesized through controlling the ratio of NaYF 4 nanorods to silica. The nanodumbbell and nanowire morphologies showed much higher fluorescence efficiency than that of nanorod. These upconversion nanoparticles (UCNPs) exhibited a high signal-to-noise ratio, effectively circumvent luminescence quenching and excellent photo-stability under 980 nm excitation. In particular, the as-prepared nanodumbbells were successfully applied to rapid latent fingerprint imaging, showing advantages over commercial fluorescence reagents. Such nanoparticles with further modification are expected to have a great potential in forensic and biological sciences.