AVS 60th International Symposium and Exhibition
    Applied Surface Science Tuesday Sessions
       Session AS+BI-TuA

Paper AS+BI-TuA4
Forensic XPS Characterization of Surface-Modified Textile Fibers

Tuesday, October 29, 2013, 3:00 pm, Room 204

Session: Forensic Science, Art and Archaeology (2:00-3:20 pm)/Quasicrystals and Complex Metal Alloys (4:00-6:00 pm)
Presenter: B. Strohmeier, Thermo Fisher Scientific
Authors: B. Strohmeier, Thermo Fisher Scientific
C. Deeks, Thermo Fisher Scientific, UK
R. Blackledge, Forensic Chemist Consultant
Correspondent: Click to Email
Despite its many advantages and unique capabilities as a surface analytical technique, X-ray photoelectron spectroscopy (XPS) has not been widely used in forensic science for the examination of specimens gathered at the scene of a crime. Reasons for the lack of forensic XPS studies in the past include: 1) the absence of standard forensic XPS methods and standard reference materials for comparison to real world samples; and 2) the historical long analysis times (e.g., hours per sample), relatively large analysis areas (e.g., several square millimeters), and the relative high cost of XPS instrumentation compared to more common forensic analytical tools such as scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM/EDS), Fourier transform infrared (FT-IR) microscopy, and Raman microscopy. Advances in XPS instrumentation over the last few decades, however, have improved typical analysis times to minutes per sample and analysis areas down to the range of tens to hundreds of micrometers. In addition, recently developed argon cluster ion sources now allow depth profiling of organic species with minimal ion beam damage, thus preserving the chemical information available from XPS. Therefore, XPS has increased potential for new applications in forensic science. One such area is the forensic surface characterization of textile fibers. White cotton fibers are so common and have so few visual distinguishing features that they are largely ignored by forensic scientists at crime scenes. However, most fabrics today have received one or more types of organic-based surface-modification treatments to provide stain resistance, permanent press characteristics, and/or waterproof properties. This presentation will discuss a proof of concept study on the use of XPS to differentiate individual textile fibers based on their surface chemistry. Materials examined in this study included swatches, threads, and individual fibers from a variety of different cotton and polyester/rayon fabrics before and after receiving one of several different commercial textile surface-treatments. Results indicated that small spot XPS combined with argon cluster ion depth profiling can: 1) distinguish among various untreated textile materials based on differences in surface chemistry resulting from their specific manufacturing process; and 2) distinguish between otherwise identical appearing fibers by differences in the textile surface treatment applied. These results demonstrate that XPS has the potential for identifying and distinguishing textile fibers found at crime scenes.