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Impermeable Graphenic Encasement of Bacteria

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posted on 09.03.2011, 00:00 by Nihar Mohanty, Monica Fahrenholtz, Ashvin Nagaraja, Daniel Boyle, Vikas Berry
Transmission electron microscopy (TEM) of hygroscopic, permeable, and electron-absorbing biological cells has been an important challenge due to the volumetric shrinkage, electrostatic charging, and structural degradation of cells under high vacuum and fixed electron beam.1−3 Here we show that bacterial cells can be encased within a graphenic chamber to preserve their dimensional and topological characteristics under high vacuum (10−5 Torr) and beam current (150 A/cm2). The strongly repelling π clouds in the interstitial sites of graphene’s lattice4 reduces the graphene-encased-cell’s permeability5 from 7.6−20 nm/s to 0 nm/s. The C−C bond flexibility5,6 enables conformal encasement of cells. Additionally, graphene’s high Young’s modulus6,7 retains cell’s structural integrity under TEM conditions, while its high electrical8 and thermal conductivity9 significantly abates electrostatic charging. We envision that the graphenic encasement approach will facilitate real-time TEM imaging of fluidic samples and potentially biochemical activity.