Open-Air Plasma Treatment to Enhance Nanoparticle Adhesion on Nylon- and Cotton-Based Fabrics for Chemical Protection

Nylon- and cotton-based fabrics, particularly a 50:50 nylon-cotton blend ("NYCO"), are commonly used for military and workforce garments. Developing high-throughput methods to attach reactive or sorptive metal oxide or metal-organic framework (MOF) nanoparticles (NPs) is important for chemical protection. Open-air plasma treatment has been used to activate cotton, nylon, and NYCO such that they covalently bond to ca. 20 nm zinc oxide and UiO-66-NH₂ MOF particles. For cotton, X-ray photoelectron spectroscopy (XPS) shows that plasma treatment partially oxidizes cellulose, with transformation of aliphatic carbons to hydroxyl and carbonyl groups. For nylon, XPS indicates the formation of additional hydroxyl groups and transformation of some amide groups to hydroxyamides. Plasma-treated fabrics and untreated controls were spray-coated with ethanolic suspensions of ZnO or UiO-66-NH₂ particles, ultrasonicated in ethanol, and air-dried. In some cases, particle-covered fabrics were machine-washed to assess durability. For all three fabrics, scanning electron microscopy (SEM) and XPS demonstrated that plasma treatment significantly enhances the surface concentration of ZnO NPs that remain after ultrasonication. However, machine washing removes most of the ZnO NPs, with minimal differences between untreated and plasma-treated fabrics. In the case of UiO-66-NH₂, particle sizes of ca. 200 and 500 nm were evaluated, and adhesion was significantly better on NYCO for the smaller particles due to more attachment sites per unit mass; a significant surface concentration of the smaller MOF remains on NYCO even after five wash cycles. To demonstrate the efficacy of the process for treating fabrics to impart chemical protection, permeation times of the nerve agent simulant dimethyl methylphosphonate were compared for bare and MOF-functionalized NYCO. The functionalized fabric exhibited a permeation time that was almost three times greater than for bare, plasma-treated fabric. These results demonstrate the practicality of the process for high-throughput preparation of metal oxide and UiO-66-NH₂ functionalized NYCO for chemical protection.