Our laboratory has been interested in how 2D electronic materials such as graphene form out of plane chemical bonds mediated by electron transfer. This presentation will highlight several examples of how Raman spectroscopy and the correlation of specific phonon modes can be used to map the spatial heterogeneity Fermi level variances for specific applications. As an example, bilayer graphene is increasingly attractive for electronic applications because of its electric field tunable band structure and band gap. The chemical functionalization of monolayer graphene has been widely explored to date, but there is much less known for bilayer graphene. Of particular interest in bilayer graphene is the use of chemical functionalization to generate an external electric field to open a bandgap. The covalent and non-covalent functionalization are studied of bilayer graphene using an electrochemical process with aryl diazonium salts, and we use Raman spectroscopic mapping and conductive atomic force microscopy (cAFM) to study the resulting changes in the physical and electronic structures. Distinct changes observed in the Raman spectra and AFM images as a function of degree of functionalization can be used as a guide for further studies of the chemistry of bilayer graphene. In another example, a significant advantage of graphene as a biosensor is its potential to display a continuum of independent and aligned sensors at a specific interface. Here, we demonstrate a nanoscale version of a micro-physiometer � a device that measures cellular metabolic activity from the local acidification rate. Graphene can function as an array of independent pH sensors enabling subcellular and spatiotemporal detection of single biological cells. Raman spectroscopy shows that aqueous protons (H+) p-dope graphene � in agreement with established doping trajectories, and that graphene displays two distinct pKa values (2.9 and 14.2).

Use of doping trajectories and Raman spectroscopy in the understanding of graphene chemistry

246th National Meeting (2013)

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