1,8-diazafluoren-9-imine (DFI) as a Novel Amino Acid Fingermark Enhancement Reagent

Abstract

1,8-diazafluoren-9-one (DFO) and 1,2-indanedione (IND) are well established latent fingermark enhancement reagents that develop fingermarks on porous surfaces. They produce fluorescent fingermarks that are easy to visualise on coloured or patterned substrates. 1,8-diazafluoren-9-imine (DFI) is a primary imine derivative of DFO, which has shown potential for fingermark enhancement. This research investigated whether DFI could be used as an effective amino acid enhancement reagent for latent fingermarks on porous surfaces. The research was aimed at improving the understanding of DFI, for characterisation of its behaviour in both suspension and solution, while also testing it on real world samples. Enhancement of fingermarks on thermally sensitive paper using suspensions of DFI or DFO in HFE-7100 without applied heat was investigated, and DFI was shown to be superior to DFO in this application. DFI was then compared to both DFO and IND for fingermark enhancement on a range of porous substrates typical of casework (copy paper, newsprint, envelopes) using optimal solvent systems containing Zn2+ and with post-treatment heating. All samples for both experiments were aged for either 1, 7, 31, or 61 days. The enhanced fingermarks were compared using split comparison analysis with a three series depletion, with analysis carried out using the University of Canberra (UC) grading scale. The comparisons showed that DFI was not a superior fingermark enhancement reagent compared to DFO or IND in the chosen solvent systems. These results indicate that the DFI suspension should be further investigated, and that it may be a useful method to develop fingermarks on difficult, thermally-sensitive substrates. The Zn2+-containing DFI working solution requires further optimisation, as it has been shown to work as an enhancement reagent but not to surpass DFO or IND.