Novel upconverting nanoparticles for fingermark detection

Abstract This paper reports the synthesis of high-quality upconverter nanoparticles (UCNPs) – sodium yttrium tetrafluoride doped with ytterbium and erbium (NaYF4:Yb,Er) with a silica shell and capped with carboxyl functional groups. The effect of different synthesis methods on the silica capping has been studied in detail. The main goal of this research was to design tailor-made UCNPs for fingermark detection and to validate a NP-based detection technique that is user-friendly, cost-effective and can be implemented in routine practice by law enforcement agencies. UCNP powders and solutions were used as a proof-of-concept to detect latent fingermarks on an aluminium foil substrate. This study not only highlights the potential use of UCNPs as a fingermark detection method but also identifies a number of shortfalls in its application that need to be addressed before such an approach could be implemented as a valid detection technique.