Stable radicals that are present in carbon substrates interact with paramagnetic oxygen through a Heisenberg spin exchange. This interaction can be significantly reduced under STP conditions by flowing a diamagnetic gas over the carbon system. This manuscript describes a simple method to characterize the nature of those radicals.
Green, U., Shenberger, Y., Aizenshtat, Z., Cohen, H., Ruthstein, S. Exploring the Radical Nature of a Carbon Surface by Electron Paramagnetic Resonance and a Calibrated Gas Flow. J. Vis. Exp. (86), e51548, doi:10.3791/51548 (2014).