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Electrochromic enhancement of latent fingerprints by poly(3,4-ethylenedioxythiophene)

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journal contribution
posted on 2014-05-20, 14:23 authored by Rachel Marie Sapstead (nee Brown), A. Robert Hillman
Spatially selective electrodeposition of poly-3,4-ethylenedioxythiophene (PEDOT) thin films on metallic surfaces is shown to be an effective means of visualizing latent fingerprints. The technique exploits the fingerprint deposit as an insulating mask, such that electrochemical processes (here, polymer deposition) may only take place on deposit-free areas of the surface between the ridges of the fingerprint deposit; the end result is a negative image of the fingermark. Use of a surfactant (sodium dodecylsulphate, SDS) to solubilise the EDOT monomer allows the use of an aqueous electrolyte. Electrochemical (coulometric) data provide a total assay of deposited material, yielding spatially averaged film thicknesses, which are commensurate with substantive filling of the trenches between fingerprint deposit ridges, but not overfilling to the extent that the ridge detail is covered. This is confirmed by optical microscopy and AFM images, which show continuous polymer deposition within the trenches and good definition at the ridge edges. Stainless steel substrates treated in this manner and transferred to background electrolyte (aqueous sulphuric acid) showed enhanced fingerprints when the contrast between the polymer background and fingerprint deposit was optimised using the electrochromic properties of the PEDOT films. The facility of the method to reveal fingerprints of various ages and subjected to plausible environmental histories was demonstrated. Comparison of this enhancement methodology with commonly used fingerprint enhancement methods (dusting with powder, application of wet powder suspensions and cyanoacrylate fuming) showed promising performance in selected scenarios of practical interest.

History

Citation

Physical Chemistry Chemical Physics, 2012,14, 8653-8661

Version

  • VoR (Version of Record)

Published in

Physical Chemistry Chemical Physics

Publisher

Royal Society of Chemistry

issn

1463-9076

eissn

1463-9084

Copyright date

2012

Available date

2014-05-20

Publisher version

http://pubs.rsc.org/en/Content/ArticleLanding/2012/CP/c2cp40733g#!divAbstract

Language

en

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