Classification of Pre-dyed Textile Fibers Exposed to Weathering and Photodegradation by Non-destructive Excitation-Emission Fluorescence Spectroscopy Paired With Discriminant Unfolded-Partial Least Squares

• NCJ Number: 253955
• Journal: Forensic Chemistry Volume: 12 Dated: March 2019 Pages: 25-32
• Author(s): Nirvani Mujumdar; Arsenio Munoz de la Pena; Andres D. Campiglia
• Date Published: March 2019
• Length: 8 pages
• Grant Number(s): 2011-DN-BX-K553
• Agencies: NIJ-Sponsored
• Publication Type: Research (Applied/Empirical); Report (Study/Research); Report (Grant Sponsored); Program/Project Description
• Award: Comparison of Microspectrophotometry and Room-Temperature Fluorescence Excitation-Emission Matrix Spectroscopy for Non-Destructive Forensic Fiber Examination

Annotation

In this study, undyed textile fabrics - such as Acrylic 864, Nylon 361 and Cotton 400 - were pre-dyed with Basic Green 4 (BG4), Acid Yellow 17 (AY17), and Direct Blue 1 (DB1) dyes, respectively; and they were then exposed to two extremely diverse weather conditions in the United States, i.e., desert and humid environmental settings in Arizona (AZ) and Florida (FL) respectively, for different time intervals of exposure, which included 0, 3, 6, 9 and 12 months.

Abstract

After every interval of a 3-month period, 10 fibers were uniformly sampled from each cloth piece, and fluorescence microscopy was used to collect two-dimensional excitation and fluorescence spectra (2-D spectra) and three-dimensional (3D) excitation-emission matrices (EEMs). A significant loss of fluorescence intensity was observed upon fiber exposure to outdoor weathering conditions. For a comprehensive statistical data analysis and to be able to discriminate between any two single fibers weathered under different conditions, a multiway calibration algorithm known as discriminant unfolded partial least-squares (DU-PLS) method was applied to the exposed fibers. Results indicate that fluorescence spectroscopy combined with DU-PLS has the ability to appropriately classify and differentiate between any two pairs of dyed cotton or nylon fibers (acrylic in some cases) exposed to dry versus humid weather environments under different time intervals of exposure. These results provide the foundation for future studies that can contribute to a non-destructive approach capable of providing information on the weathering history of the fiber. (publisher abstract modified)