Practical SERS method for assessment of the washing durability of textiles containing silver nanoparticles

The popular use of silver nanoparticles (Ag NPs) in the production of commercial odor-control and antibacterial textile products has raised questions about their washing durability. Poor durability not only deteriorates product performance but also results in unknown amounts of Ag NPs leaching into sewage- and water-treatment systems. Therefore, it is necessary to have a quick and easy method for detecting Ag NPs in washing solutions for assessment of washing durability. In this study, we have developed a practical surface-enhanced Raman spectroscopy (SERS) method for measuring the concentrations of Ag NPs in water and a detergent solution. To improve the sensitivity and reproducibility of SERS signals from the complexation of an indicator molecule (ferric dimethyl-dithiocarbamate, in this study) with NPs, the coffee ring effect was utilized. The active SERS hot spots in the aggregated NPs along the coffee ring effectively intensified the signature SERS response, even with NPs of about 10 nm in diameter and a concentration as low as 0.01 mg L-1. The linear relationships between SERS intensity and Ag NP concentration (R-2 > 0.99) successfully quantified the amount of Ag NPs released from Ag NP-treated cotton fabrics during washing as well as other Ag speciation formed in a detergent solution.