Tiny pores in graphene could form a membrane

New membranes may filter water, separate biological samples, or deliver drugs
October 26, 2012

A scanning transmission electron microscope image taken at Oak Ridge National Laboratory showing a small hole in the graphene (small black region slightly below the center). The image is 8 nm by 8 nm, meaning that the hole is 0.5 nm in diameter. In this image, the honeycomb structure of graphene lattice is clearly seen. (Credit: Juan-Carlos Idrobo)

By assembling large membranes from single sheets of graphene grown by chemical vapor deposition, researchers from MIT, Oak Ridge National Laboratory (ORNL) and elsewhere have found that graphene has intrinsic defects, or holes, in its atom-sized armor.

In experiments, the researchers found that small molecules like salts passed easily through a graphene membrane’s tiny pores, while larger molecules were unable to penetrate.

The researchers found that pores ranged in size from about 1 to 12 nanometers — just wide enough to selectively let some small molecules through. A sheet of graphene is as thin as a single atom, but strong enough to let high volumes of fluids through without shredding apart.

According to Rohit Karnik, associate professor of mechanical engineering at MIT, applications for such membranes may include membranes that filter microscopic contaminants from water or separate specific types of molecules from biological samples; a portable sensor in which a layer of graphene could shield the sensor from the environment, letting through only a molecule or contaminant of interest; and drug delivery, with graphene, dotted with pores of a determined size, delivering therapies in a controlled release.

This work was funded by the King Fahd University of Petroleum and Minerals through the Center for Clean Water and Clean Energy at MIT and KFUPM, and was also supported by the ORNL ShaRE program.