Preparation and Evaluation of Metal Nanopowders for the Detection of Fingermarks on Nonporous Surfaces

• NCJ Number: 215687
• Journal: Journal of Forensic Identification Volume: 56 Issue: 5 Dated: September-October 2006 Pages: 756-768
• Author(s): Mi Jung Choi; Andrew M. McDonagh; Philip J. Maynard; Richard Wuhrer; Chris Lennard; Claude Roux
• Date Published: September 2006
• Length: 13 pages
• Publication Format: Article
• Publication Type: Report (Study/Research)
• Language: English
• Country: United States of America

Annotation

This study compared gold and silver nanoparticles that use oleylamine as a stabilizer with conventional powders for developing latent fingermarks on nonporous surfaces.

Abstract

Generally, the pale-colored silver nanopowder provided significantly less contrast than the gold powder. Both powders gave similar development of ridge detail; however, because the preparation of silver nanopowder requires more steps and is more time-consuming, comparisons with conventional powders were conducted with only the gold nanopowder. Gold powder development yielded superior ridge detail on glass and painted wood compared to normal black powder. Fingermarks of reasonable quality were obtained with the gold powder even after 3 weeks, with almost no background staining. Only on plastic surfaces was any background staining observed with the gold powder, but it was significantly less than with normal black powder. For aged fingermarks, black magnetic powder showed better performance than normal black powder or gold nanopowder, especially for aged fingermarks on plastic; however, the fingermarks developed by black magnetic powder were always accompanied by significantly strong background staining, which decreased the contrasts and blurred ridges. Gold nanopowder and aluminum powder yielded similar results on each of the nonporous surfaces tested; the aluminum powder produced gray ridges, with some instances of background staining. White powder produced satisfactory ridge detail, but fingermarks developed by gold powder or aluminum powder were superior. Treatment with physical developer after powdering with gold or silver nanopowders resulted in enhanced ridge and valley contrast. This effect was not achieved when normal powders were used. This paper describes the materials and methods used, including the preparation of gold and silver nanopowders, as well as fingermark imaging and recording. 7 figures, 1 table, and 9 references