Latent fingermark detection and enhancement using carboxyl-functionalised silicon oxide nanoparticles doped with a ruthenium complex

Abstract

The utilisation of nanoparticles (NPs) for latent fingermark detection and enhancement is not foreign to fingerprint researchers. NPs bear three distinctive and desirable advantages for latent fingermark development. First of all, the average spherical diameter of NPs is less than 100 nm; the small size of NPs is beneficial to produce enhanced fingermark ridges with high resolution. In addition, the surface of NPs can be modified using various functional groups to selectively interact with fingermark residues. Finally, the core of a range of NPs can be integrated with luminescent dye molecules; such luminescent NPs are advantageous for fingermark development on substrates with complex backgrounds. By combining the above three favourable features for latent fingermark detection, NPs have the potential to develop latent fingermarks with improved selectivity and sensitivity compared to current benchmark methods (two areas in which improvements are arguably necessary with current fingermark detection techniques). However, there is only a limited number of NPs that can simultaneously fulfill the three aforementioned characteristics. Silicon oxide nanoparticles (SiO2 NPs) are a type of NP that can be exploited for a combination of the three desirable NP characteristics. In particular, carboxyl- functionalised SiO2 NPs doped with a ruthenium complex (RuBpy-doped CES-SiO2 NPs) have been shown, in a preliminary study, to have the potential to be a promising fingermark detection reagent. The aim of this research was to investigate RuBpy-doped CES-SiO2 NPs for latent fingermark detection and enhancement on non-porous surfaces. Using the NPs as a colloidal dispersion bath for fingermark treatment, various detection parameters were evaluated and optimised (e.g., NP concentration in the colloidal dispersion, treatment time and treatment bath temperature). The overall optimisation of detection parameters was successful in comparison to results from the preliminary study. Superior fingermark detection effectiveness was obtained with a lower NP concentration used in the colloidal dispersion. A relatively short treatment time (5 min in comparison to 60 min) was also implemented with fingermark treatment conducted using a bath temperature of 40°C. Through a fingermark comparison study against the preliminary method, the optimised detection parameters were concluded to offer improved fingermark detection effectiveness and enhanced practicality. This research has demonstrated the use of SiO2-based NPs for latent fingermark detection and enhancement on non-porous substrates. The apparent benefits that can be achieved from exploring functionalised NPs for the advancement of latent fingermark detection techniques have been confirmed and further studies into their use for this application are encouraged.

Date of Thesis submission	2020
Original language	English
Supervisor	Chris Lennard (Supervisor), Claude Roux (Supervisor), Sébastien Moret (Supervisor), Val Spikmans (Supervisor) & Xanthe Spindler (Supervisor)