Nano-style sheets may aid health, shield ecosystem

Microscopically, ''nanomembrane'' sheets made from nylon resemble a tangled web. The tiny iron oxide particles on the fibre surfaces can help clean toxic chemicals from water, but if the particles get separated from the web, they can become hazards themselves.

In a new study, Cornell researchers examined these special nylon sheets – replete with applied nanoscale iron oxide particles – to see if the particles wash loose.

The particles work like magnets to capture bacteria and viruses, and to extract chemicals or dye molecules out of water. Membranes with these particles attached could be used in devices to detect water contamination or in filters to remove chemicals or dyes from industrial waste. However, to be effective and safe, the particles need to stay on the membrane. The study evaluated the nanoparticle treatment uniformity and particle retention of the nylon membranes as they were processed (or washed) in solutions of varying pH levels.

''It's critical to evaluate particle retention and stability on fibers to reduce human health and environmental concerns,'' said Nidia Trejo, a Cornell doctoral student in the field of fiber science. Trejo, who with Margaret Frey, professor of fibre science, authored the study, A comparative study on electrosprayed, layer-by-layer, and chemically grafted nanomembranes loaded with iron oxide nanoparticles, in the Journal of Applied Polymer Science, 14 July.

The nanomembrane sheet structure looks like a dryer sheet but is made from layers of tiny, randomly oriented fibres that only can be seen with electron microscopes. These nanomembranes have a high surface-to-volume ratio, which enhances the material's function.

Manufacturing methods vary depending on the liquid environments in which the membranes would be used. Adhering nanoparticles of iron oxide to nylon fibre is done in three ways - electrospraying, which facilitates uniform nanoparticle placement in the fibres; layer-by-layer assembly, where particles are coated on the fiber electrostatically; or chemical bonding.

''For the membrane, it's important to evaluate particle retention and stability,'' Trejo explained. ''You would want the nanoparticles to stay on the Nylon 6 membranes so the material can have function throughout the life use. If the material is used for wastewater treatment applications, you wouldn't want the particles themselves to become pollutants if are they releasing from the membranes and into the water.''

A range of state-of-the-art facilities on campus was used by the researchers. The Cornell Center for Materials Research (funded through the National Science Foundation's Materials Research Science and Engineering Center program) supported this study through its shared facilities. Additionally, Cornell's Nanobiotechnology Center and the Cornell Nutrient Analysis Laboratory supported this research.

(See: Can nanofibre save your life?)