Novel chemistry and applications of polythiazyl

Diverse investigations into the synthesis, formation, reactivity and stability of disulfur dinitride, S2N2, enabled through the fabrication of custom-made apparatus and tailored reaction conditions, are reported. The polymerisation process of the former to the (super)conductive polythiazyl material has also been explored by means of both single crystal X-ray diffraction and in situ reaction chemistry...

Polymerisation of S2N2 to (SN)(x) as a tool for the rapid imaging of fingerprints removed from metal surfaces

Polymerisation of S2N2 to (SN)x on metallic surfaces is induced by interaction with the minute corrosion signatures of removed (by washing) fingerprints; as vapour-phase S2N2 is employed, it follows that the process has the potential to rapidly screen large/convoluted metal pieces, such as explosive device fragments whose prints were wiped by the detonation

Finding evidence in the dark: utilization of inkjet-printed amino acids

© 2019, © 2019 Australian Academy of Forensic Sciences. Inkjet-printing amino acids has been suggested as a method to obtain pseudo latent fingermarks which are identical to each other and can therefore be used to compare different fingermark development techniques. This article outlines how this method of printing amino acids was utilized to obtain standardized fluorescent patterns that could be used to assess individual’s dark adaptation. Shapes, letters and patterns were printed in alanine using a standard inkjet printer, then developed using DFO to provide fluorescent images when viewed under green light and through a red filter. Images were also printed and developed using ninhydrin to obtain the resultant developed image in Ruhemann’s purple. The use of the fluorescent patterns to assess dark adaptation led to the confirmation that forensic examiners should dark adapt their eyes prior to looking for fluorescent evidence in the dark, as 16% more evidence was discoverable after waiting an average of 10 minutes in the dark prior to examination

The importance of dark adaptation for forensic examinations; an evaluation of the Crime-lite Eye™

Forensic practitioners are recommended to dark adapt their eyes prior to conducting evidential searches in the dark. The dark adaptation process remains poorly standardised across the discipline, with little quantified regarding the benefits of such preparative steps. Herein, we report the findings of a study that recruited 50 participants to assess the effectiveness of the Crime-lite Eye™ a darkness adaptation device developed to assist forensic practitioners both in the laboratory and in field. Participants were tasked with searching for the fluorescent signatures left by reaction of 1,8-diazafluoren-9-one (DFO) with amino acids, in a manner akin to the fluorogenic fingerprint treatment of porous evidence. Using an Epson Stylus Photo R265 inkjet printer, ink cartridges were filled with alanine solutions of various concentrations, allowing different motifs to be printed onto copy paper and subsequently developed using DFO. Participants searched for this ‘evidence’ both with and without dark adapted vision. On average, participants were able to locate and correctly recognise 16% more evidence once dark adapted using the Crime-lite Eye™. The increase in evidence located by participants once dark adapted suggests that crime scene officers should be dark adapting in order to visualise as much as possible. The time taken to dark adapt, 10 min on average during this study, is not excessively long, and should not significantly slow the investigation

Visualisation of latent fingermarks on polymer banknotes using copper vacuum metal deposition: a preliminary study

The UK's recent move to polymer banknotes has seen some of the currently used fingermark enhancement techniques for currency potentially become redundant, due to the surface characteristics of the polymer substrates. Possessing a non-porous surface with some semi-porous properties, alternate processes are required for polymer banknotes. This preliminary investigation explored the recovery of fingermarks from polymer notes via vacuum metal deposition using elemental copper. The study successfully demonstrated that fresh latent fingermarks, from an individual donor, could be clearly developed and imaged in the near infrared. By varying the deposition thickness of the copper, the contrast between the fingermark minutiae and the substrate could be readily optimised. Where the deposition thickness was thin enough to be visually indistinguishable, forensic gelatin lifters could be used to lift the fingermarks. These lifts could then be treated with rubeanic acid to produce a visually distinguishable mark. The technique has shown enough promise that it could be effectively utilised on other semi- and non-porous substrates

Non-invasive detection and chemical mapping of trace metal residues on the skin

Residual traces of the metals copper and lead on an individual's skin may be elucidated by reaction of rubeanic acid with a gelatine lift taken from the target area in question, yielding intensely coloured reaction products. This non-invasive technique has been shown to offer promise in chemically mapping the distribution of the minute metal residues across an individual's hand deposited through touching metal items, a technique with potential forensic significance

Fingerprint and inkjet-trace imaging using disulfur dinitride

Exposure of fingerprints to S2N2 vapour results in the prints being visually imaged by polymeric (SN)x on an unprecedented range of media; in addition, the polymer forms in response to the interaction of S2N2 with traces of inkjet inks, for example the minute amounts left by the contact between printed paper and an envelope

Rapid polymerisation of S2N2 within Na-ZSM-5 channels

Reaction of S2N2 vapour with Na-ZSM-5 results in rapid polymerisation and inclusion of the resulting (SN)x within the zeolite channels

A comparative evaluation of the disulfur dinitride process for the visualisation of fingermarks on metal surfaces

The disulfur dinitride process for fingermark visualisation was first reported a decade ago, with promising results obtained for a range of materials including metals. However, the friction sensitive nature of the material and difficulty of synthesis made routine use difficult. Many of these issues have since been addressed, making equipment and chemicals available to build an understanding of how the effectiveness of disulfur dinitride compares to other fingermark visualisation processes currently used on metal surfaces. This enables more informed advice to be given on selection of processes for treatment of metal items, an area of operational interest that encompasses weapons used in violent crime and the increasing incidence in metal theft. This paper reports a comparative study into the effectiveness of disulfur dinitride, cyanoacrylate fuming, vacuum metal deposition, gun blueing and wet powder suspensions on brass, bronze, copper and stainless steel. Experiments were conducted with the surfaces exposed to a range of environments including long term ageing, water/detergent washing, acetone washing and high temperature exposure. The results indicate that disulfur dinitride is an effective process for fingermark visualisation on metal surfaces, including those exposed to adverse environments, and may offer potential improvements over existing processes for those surfaces. Further work, including pseudo-operational trials, is recommended

The synthesis, full characterisation and utilisation of template-free silica sodalite, a novel polymorph of silica

Empty glass: Subjecting ethylene glycol silica sodalite to heat (680 °C) under a nitrogen atmosphere (i) successfully removes the templating agent to give cubic silica sodalite, which, upon consequent heating under an oxygen atmosphere (ii), transforms into a rhombohedral form of the empty sodalite, in effect a novel polymorph of silica