S1 Supporting Information Characterization of Proton Transport Across a Waveguide- Supported Lipid Bilayer Todd W. McBee, 1 Liying Wang, 1 Chenhao Ge, 1 Brooke M. Beam, 1 Ana L. Moore, 2 Devens Gust, 2 Thomas A. Moore, 2 Neal R. Armstrong, 1 and S. Scott Saavedra 1 1 Department of Chemistry, University of Arizona, Tucson, Arizona, 85721-0041 2 Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604 1. PANI structures and equilibria 2. Nernst expression for PANI At neutral pH, EB, ES, and LE are the dominant forms of PANI; the mole fractions of other forms of PANI are assumed to be negligible. K a is the diprotic dissociation constant of ES. (1) K a = [EB][H + ] [ES] 2 (2) DE cell = E o LE/ES - 0.0592 2 log [DLE] [DES] (3) DE cell = E o LE/ES - 0.0591 2 log [DLE]K a [DEB][DH + ] 2 (4) DE cell = E o LE/ES - 0.0296 log [DLE]K a [DEB] + 0.0296 log [DH + ] 2 (5) DE cell = E o LE/ES - 0.0296 log [DLE]K a [DEB] - 0.0592(DpH) Activities have been replaced with molarities by assuming that activity coefficients are unity. However, we recognize that the activity coefficients in a ITO/(PANI/PAA) 2 thin film are likely to be far less than unity. –(EB) n – –(ES 2+ ) n – 2H + –(LE) n – 2e - 2H + + 2e -