The vessel attracts, trapping the organic molecules that often contaminate the nano’s surface
(Nanowerk News) Rice University engineers have created a vessel that can prevent volatile organic compounds (VOCs) from accumulating on the surface of deposited nanomaterials.
The low-cost, portable storage technology addresses a ubiquitous problem in nanomanufacturing and materials science labs and is described in a paper published in the journal of the American Chemical Society. Nano Letters (“Reducing Contamination with Nano Structure Activated Ultraclean Storage”).
“VOCs are in the air that surrounds us every day,” said study corresponding author Daniel Preston, an assistant professor in Rice’s Department of Mechanical Engineering. “They stick to surfaces and form a layer, mainly of carbon. You can’t see these layers with the naked eye, but they form, often within minutes, on nearly any surface exposed to air.”
VOCs are carbon-based molecules emitted from many common products, including cleaning fluids, paints, and office and craft supplies. They accumulate indoors in very high concentrations, and the thin layer of carbon gunk they deposit on surfaces can hamper industrial nano-fabrication processes, limit the accuracy of microfluidic assay kits and create confusion for scientists doing fundamental research on surfaces.
To solve the problem, Ph.D. student and lead author of the study Zhen Liu, along with Preston and others from his lab, developed a new type of storage container that keeps things clean. Experiments show that his approach effectively prevents surface contamination for at least six weeks and can even clear VOC deposited films from previously contaminated surfaces.
This technology relies on ultraclean walls inside the container. The surface of the inner wall is reinforced with small projections and divots ranging in size from one millionth to one millionth of a meter. Microscopic and nanoscopic imperfections increase the surface area of the walls, making more of their metal atoms available to airborne VOCs present in the container when sealed.
“Texture allows the internal container walls to act as a ‘sacrificial’ material,” says Liu. “VOC is drawn to the surface of the container walls, which allows other items stored inside to stay clean.”
He said the idea of using large, pre-cleaned surfaces to accumulate pollutants was proposed 50 years ago but had largely gone unnoticed. He and his colleagues refined the idea with modern cleaning methods and nanotexturing surfaces. They demonstrated, through a series of experiments, that their approach did a better job of preventing VOCs from coating the surfaces of deposited materials than other approaches, including sealed petri dishes and state-of-the-art vacuum desiccators.
Preston’s group built on their experiment, developing a theoretical model that accurately characterized what was happening inside the container. Preston said this model would allow them to refine the design and optimize system performance in the future.
