Studies on the synthesis and use of rare earth doped nanophosphors for application on latent fingerprints

Abstract

Nanotechnology has been increasingly employed in forensic science for the detection of latent fingerprints, using multiple techniques from new aluminium nanomaterials for dusting to quantum dot dispersions, to try to increase and enhance areas where prints are likely to be found at scenes of crime. Different substrates use a diverse range of methods to develop prints when they are found and each method has its own drawbacks. It is not viable to use many of these techniques in conditions other than in a laboratory due to the harmful environmental effects they can cause over long term use. With this in mind a new easier to use technique that can be used on any substrate from wood to glass to paper was looked into. A range of nano-sized rare earth phosphor precursors were synthesised using homogeneous precipitation and solid state methods which were then converted to phosphors by firing at 980oC. Eu3+ and Tb3+ doped Y2O3, YVO4 and Y2O2S were chosen for their luminescent intensity. Analysis of each of the phosphors was carried out using multiple techniques and a single host lattice chosen for continuation. Y2O3:Eu3+ and Y2O3:Tb3+ were coated using a modified Stöber process to try and decrease the agglomeration of particles as well as allowing for surface modification to take place. Modifications of the surface were prepared and analysed, and these particles were then used in multiple fingerprint examinations to examine the adherence on fingerprints of different ages. The surface modifications manifested great adherence to the fingerprint residue even after two weeks elapsed and showed great promise after a two year period.