Scientists at Rice University (Houston, TX) and Ben-Gurion University of the Negev (BGU; Sede-Boqer, Israel) have discovered that laser-induced graphene (LIG) is a highly effective antifouling material and, when electrified, bacteria killer.1
LIG is a spongy version of graphene, the single-atom layer of carbon atoms. The Rice lab of chemist James Tour developed it three years ago by burning partway through a polyimide sheet with a laser, which turned the surface into a lattice of interconnected graphene sheets. The researchers have since suggested uses for the material in wearable electronics and fuel cells and for superhydrophobic or superhydrophilic surfaces.
The new research shows that LIG also protects surfaces from biofouling (the buildup of microorganisms, plants or other biological material on wet surfaces).
"This form of graphene is extremely resistant to biofilm formation, which has promise for places like water-treatment plants, oil-drilling operations, hospitals, and ocean applications like underwater pipes that are sensitive to fouling," Tour says.
When used as electrodes with a small applied voltage, LIG becomes the bacterial equivalent of a backyard electrical bug zapper. Tests with no charge confirmed what has long been known — that graphene-based nanoparticles have antibacterial properties. When 1.1 to 2.5 volts were applied, the highly conductive LIG electrodes "greatly enhanced" those properties.
Under the microscope, the researchers watched as fluorescently tagged Pseudomonas aeruginosa bacteria in a solution with LIG electrodes above 1.1 volts were drawn toward the anode. Above 1.5 volts, the cells began to disappear and vanished completely within 30 seconds. At 2.5 volts, bacteria disappeared almost completely from the surface after one second.
The Rice lab partnered with Professor Christopher Arnusch, a lecturer at the BGU Zuckerberg Institute for Water Research who specializes in water purification. Arnusch's lab tested LIG electrodes in a bacteria-laden solution with 10% secondary treated wastewater and found that after nine hours at 2.5 volts, 99.9% of the bacteria were killed.
1. Swatantra P. Singh et al., Applied Materials & Interfaces (2017); doi: 10.1021/acsami.7b04863