This article explores the limits of conventional Raman spectroscopy for the analysis of colorant content of fabric and reports on the use of near-infrared excitation Raman spectroscopy for forensic analysis of colored fabric.
Forensic analysis of fabric is often critically important to establish a relationship between a suspect and a crime scene or demonstrate the absence of such connections. Most of commercially available fabric is colored with primarily organic colorants. These dye substances are highly fluorescent, which limits the use to conventional Raman spectroscopy for the analysis of the colorant content of fabric. At the same time, elucidation of the chemical composition of dyes in fabrics can be used to advance the importance of this physical piece of evidence for forensic research. The authors’ recent findings showed that near-infrared excitation Raman spectroscopy (NIeRS) could be used to overcome this limitation. However, they note that it remains unclear to what extent NIeRS could be used to identify the presence of several different colorants on fabric, as well as utilize for the analysis of dyes on fabric contaminated with paints. In this study, the authors utilized a hand-held NIeRS instrument to examine re-colored cotton fabric and cotton fabric with household paints applied on it. Their results indicate that NIeRS coupled with chemometrics highly accurately identify the presence of several colorants on cotton. The authors also found that the presence of paint fully obscures the ability of NIeRS to extract information about the dye content of the fabric. These results expand researchers’ understanding of the use of NIeRS in the forensic analysis of colored fabric. (Published Abstract Provided)