Vacuum metal deposition: visualisation of gold agglomerates using TEM imaging

Forensic Science International : Synergy
Xuejing DaiNaomi Speers

Abstract

Vacuum metal deposition (VMD) is a well-established technique that can be used for the development of latent fingermarks on a range of polymer surfaces, including polyethylene (PE) bags exposed to harsh environmental conditions. The technique has also proved to be effective on difficult semi-porous surfaces such as the polymer banknotes in circulation in Australia and in an increasing number of other countries. VMD is a two-stage technique. In the first stage, a small amount of gold is deposited under high vacuum onto the exhibit. This is then followed by the deposition, onto the gold layer, of a much thicker layer of zinc. Normal VMD development is characterised by zinc depositing all over the surface except on the fingermark ridges themselves. A phenomenon of reverse development (zinc on the ridges but not on the surface) has been reported by many authors. Recent studies indicated that this phenomenon might occur on low-density polyethylene (LDPE) when the amount of deposited gold is above an optimum quantity. The results suggested that the size of the gold agglomerates formed on the surface of the polymer plays a critical role. This preliminary study was aimed at visualising, by transmission electron microscopy (TEM), the fo...Continue Reading

Citations

Aug 14, 2013·Science & Justice : Journal of the Forensic Science Society·Susan KnightingDavid H Bremner
Nov 26, 2011·Forensic Science International : Synergy·A S Ramos, M T Vieira
Aug 20, 2010·Forensic Science International : Synergy·I-Heng YuJeh Shane Liao

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