Surface studies of developed fingerprints have aided in the elimination of criminal cases before moving to the court. The combination of X-ray photoelectron spectroscopy (XPS) with the aryldiazonium gold(III), 4-O 2 NC 6 H 4 N 2 + AuCl 4 -, surface modifier has shown to be a novel approach in latent fingerprint detection and development for the quantification of film elements.The robust gold-aryl film was developed on the reducing chemicals excreted in the sebaceous fingerprints without the need for external stimuli, and at lesser extent after contacting the free metal surface. The concurrent reduction of the diazonium functional group and gold(III) from[AuCl 4 ]developed a robust gold-aryl film which showed increasing gold(0) quantity in the time range 30 to 120 min over copper coins and model flat sheets. SEM and XRD support the presence of reduced gold on the top of the latent fingerprints and the presence of CuO resulting from the reaction of the diazonium salt with copper metal. This research combines the quantification of deposits using XPS, the surface sensitive technique for chemical analysis, in addition to the surface imaging.

Surface modifiers through redox routes emerged as the most preferred in forensic science. Aryldiazonium salts stabilized with tetrachloroaurate (III) are excellent redox modifiers in the development of latent fingerprints on nickel surfaces. Nickel coins were fingerprinted and developed with a stable diazonium salt [O 2 N-4-C 6 H 4 N≡N] AuCl 4 . The developed surfaces were studied using XPS that showed the presence of the characteristic gold and organic modifier peaks. Also, imaging analysis using SEM showed clusters of gold. EDS quantitative analysis estimated a good amount of gold presence on the fingerprinted compared with the non-fingerprinted area. Our results are important in the analysis of nickel coins using a spontaneous route by simply depositing diazonium salt solution drops on the nickel surface without any additional reducing agent. This work brings strong supporting evidence for the efficient combination of diazonium surface chemistry and high-performance surface analytical tools (XPS, SEM-EDS) in the fast, spontaneous development of fingerprints and their morphological and chemical composition assessments.