Electrochemical development and enhancement of latent fingerprints on stainless steel via electrochromic effect of electrodeposited Co3O4 films

Abstract

Latent fingerprints are one of the most important trace evidences at crime scenes that can be used for individual recognition. The invisible nature of latent fingerprints gives rise to various kinds of development and imaging techniques, among which a number of electrochemical methods are receiving increasing attention. We report herein a new interfacial strategy based on spatially selective electrodeposition of Co3O4 films with electrochromic properties to develop and enhance latent fingerprints on stainless steel surfaces. During the development process by potentiostatical deposition of Co3O4 on the background, image contrast and development accuracy as two key factors that measure the effectiveness of fingerprint development are systemically evaluated from millimeter to microscopic scales. Three levels of morphological features in latent fingerprints can be well developed. Optical properties of deposited Co3O4 films can be reversibly adjusted by changing applied potential. This phenomenon is analyzed qualitatively through visual appraisal and determined quantitatively by using color channels. The results indicate that image enhancement of developed fingerprints can be easily accomplished by extracting the blue channel of captured images. Forensic DNA typing is also performed to reveal the impact of this method on DNA evidence in fingerprint residues. The ratio of detected loci reaches 80.9% after electrochemical process. This novel method has advantages including high development accuracy, adjustable image contrast, and relatively non-destructive to DNA analysis.