Assessment of detection limits for dyed and mounted textile fibers using Raman spectroscopy

Area of Science:

• Forensic Science
• Analytical Chemistry
• Materials Science

Background:

• Textile fibers are crucial trace evidence linking objects and locations in investigations.
• Raman spectroscopy is a validated method for analyzing pigments, paints, inks, and dyes.

Purpose of the Study:

• To evaluate the efficacy of Raman spectroscopy in identifying diverse dye classes and colors on multiple textile fiber types.
• To determine the detection limits of Raman spectroscopy for various dyes on different fibers under varied conditions.

Main Methods:

• Examined four dye categories (reactive, disperse, acid, direct) on five fiber types (cotton, polyester, nylon, wool, rayon).
• Tested four colors (black, blue, red, yellow) at concentrations from 4% down to 0.05%.
• Utilized two laser excitation sources (532 nm and 780 nm) and three mounting conditions (Permount™, Entellan® new, unmounted).

Main Results:

• Raman spectroscopy successfully detected some dyes at low concentrations (0.5% and 0.05%), even when mounted.
• Detection capability was influenced by excitation source, dye class, concentration, fiber type, and mounting method.
• The technique demonstrated potential for identifying dyes under challenging forensic conditions.

Conclusions:

• Raman spectroscopy shows promise as a valuable tool for forensic fiber dye analysis.
• Optimization of parameters such as laser source and mounting is key for maximizing detection.
• Further research is warranted to fully establish Raman spectroscopy's role in forensic investigations involving textile fibers.