After ten years of discovering the amazing properties of pristine graphene and seeking its uses in electronics, photonics, and novel technologies, researchers are starting to add another layer to the beautifully complex world of graphene: chemically functionalized and nanostructured graphene.
The use of graphene for water desalination is back to the spotlight, after recent reports on controllable manufacture of nanopores in graphene films. Last April we wrote about a theoretical simulation, done at MIT, which showed that graphene with pores having a ~1 nanometer diameter would act as an excellent water filter, passing clean water while leaving behind any chemical residue. The news of MIT’s discovery was so big that the Smithsonian magazine, the publication of the famous Smithsonian Institution, named it one of the top 5 surprising scientific milestones of 2012 Nanometer-sized pores in graphene films are not only considered for water filtration, but also for rapid DNA sequencing, given that the lateral size of a DNA strand is about one nanometer.
Now, less than a year later, we are seeing first reports of sub-nanometer sized holes made controllably in graphene. At the beginning of February, we reported on our recent publication, together with Harvard University, the Lawrence Berkeley National Lab and FEI Corporation, in which we show movies of the creation of pores in a graphene film. The pores are catalyzed by residual silicon atoms and range in size from several angstroms to a few nanometers. The placement of the silicon atoms occurs randomly. Researchers at MIT have taken technology even further, showing that they can place nanopores at desired locations on the sheet. The nanopores are initiated by bombarding the sheet with gallium ions from a focused ion beam. The location of the bombardment target can be placed with nanometer accuracy, leading to graphene sheets with 5 trillion pores per square centimeter, each placed deterministically, all being of similar size.