Researchers from the City University of New York, Fitzpatrick Institute of Photonics at Duke University, the New York Police Department Crime Lab, and the Metropolitan Museum of Art constituted a multidisciplinary collaborative for the purpose of furthering the application of Raman spectroscopy and nondestructive surface enhanced Raman scattering (SERS) analysis techniques as applied to the evaluation of trace evidence and the examination of questioned documents.
The work in Phase I of the project, which is covered in this report, successfully demonstrated that SERS can be used to identify organic colorants present in inks, paints, and textile fibers. The techniques developed are particularly suited for handling microscopic samples; textile dyes were successfully identified from samples as small as a 1-millimeter section of a single silk fibril of 50-micometer diameter, as well as from textiles severely degraded by burial. SERS was also effective for trace analysis of pharmaceuticals and drugs of abuse. Analytical procedures for SERS of a number of representative dyes were developed; the core of a high-quality spectral database was assembled as a proof-of-concept experiment; and innovative nondestructive approaches were investigated. To date, the colorants database includes approximately 50 natural and synthetic dyes. Raman spectroscopy is characterized by very high spectral resolution, leading to effective discrimination among various species, and it has the added advantage of allowing nondestructive, in-situ detection. The low intensity of normal Raman scattering has prevented its wide application as a sensitive spectroscopic probe, and interference from fluorescence often obscures the much weaker Raman signal. SERS has been found useful in overcoming these restrictions. Based on the success of Phase I, funding for Phase II is currently being requested. Tables, figures, and references