Researchers at Queen Mary University of London (London, United Kingdom) have published a study on the interaction of water molecules with bilayer graphene at various humidity levels. Thestudy, published by the scientific journal Physical Review B, determined that graphene properties change in humid conditions as waste penetrate between the layers. Changes in the properties of graphene depend on how the carbon layers interact with one another and when water permeates the layers.
A material consisting of two single atomic layers of carbon stacked on one another, bilayer graphene has several notable characteristics—including strength, conductivity, flexibility, and transparency—that make it a potentially valuable high-performance material. The purpose of the Queen Mary University study was to determine whether bilayer graphene reacted in the same manner to low humidity conditions as layered graphite, a similar carbon-based material. Graphite loses its lubricating ability in low-humidity conditions, a fact first discovered with airplanes flying at high altitudes during World War II.
After performing Raman measurements to identify the water molecules between graphene layers, the researchers observed that water forms an atomically thin layer at 22% relative humidity and separates graphene layers at over 50% relative humidity. “The critical points, 22% and 50% relative humidity, are very common conditions in daily life and these points can be easily crossed. Hence, many of the extraordinary properties of graphene could be modified by water in between graphene layers,” said Yiwei Sun, a postdoctoral research associate at Queen Mary's School of Engineering and Materials Science and lead author of the study.
Because some graphene-based devices may be fully operative in both dry and humid environments, Dr. Sun suggests that future experiments record relative humidity to determine its impact on other 2D-layered materials. In subsequent remarks, he added that his research focus is on the question of “how humidity can affect interlayer interaction between graphene layers.” In answering that question, he hopes his work can assist material scientists and engineers in finding or creating graphene-based products for real-life applications.
Source: Queen Mary University of London, www.qmul.ac.uk