{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,3]],"date-time":"2026-09-03T14:20:10Z","timestamp":1788445210463,"version":"build-2803163510"},"reference-count":42,"publisher":"American Chemical Society (ACS)","issue":"3","license":[{"start":{"date-parts":[[2015,1,14]],"date-time":"2015-01-14T00:00:00Z","timestamp":1421193600000},"content-version":"vor","delay-in-days":366,"URL":"https:\/\/pubs.acs.org\/page\/policy\/authorchoice_termsofuse.html"}],"funder":[{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["0814194"],"award-info":[{"award-number":["0814194"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001677","name":"National institute of Health and Medical Research","doi-asserted-by":"publisher","award":["RR022864"],"award-info":[{"award-number":["RR022864"]}],"id":[{"id":"10.13039\/501100001677","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2014,2,4]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>An optical impedance spectroscopy (OIS) technique based on a single-mode electro-active-integrated optical waveguide (EA-IOW) was developed to investigate electron-transfer processes of redox adsorbates. A highly sensitive single-mode EA-IOW device was used to optically follow the time-dependent faradaic current originated from a submonolayer of cytochrome c undergoing redox exchanges driven by a harmonic modulation of the electric potential at several dc bias potentials and at several frequencies. To properly retrieve the faradaic current density from the ac-modulated optical signal, we introduce here a mathematical formalism that (i) accounts for intrinsic changes that invariably occur in the optical baseline of the EA-IOW device during potential modulation and (ii) provides accurate results for the electro-chemical parameters. We are able to optically reconstruct the faradaic current density profile against the dc bias potential in the working electrode, identify the formal potential, and determine the energy-width of the electron-transfer process. In addition, by combining the optically reconstructed faradaic signal with simple electrical measurements of impedance across the whole electrochemical cell and the capacitance of the electric double-layer, we are able to determine the time-constant connected to the redox reaction of the adsorbed protein assembly. For cytochrome c directly immobilized onto the indium tin oxide (ITO) surface, we measured a reaction rate constant of 26.5 s\u20131. Finally, we calculate the charge-transfer resistance and pseudocapacitance associated with the electron-transfer process and show that the frequency dependence of the redox reaction of the protein submonolayer follows as expected the electrical equivalent of an RC-series admittance diagram. Above all, we show here that OIS with single-mode EA-IOW\u2019s provide strong analytical signals that can be readily monitored even for small surface-densities of species involved in the redox process (e.g., fmol\/cm2, 0.1% of a full protein monolayer). This experimental approach, when combined with the analytical formalism described here, brings additional sensitivity, accuracy, and simplicity to electro-chemical analysis and is expected to become a useful tool in investigations of redox processes.<\/jats:p>","DOI":"10.1021\/ac4030736","type":"journal-article","created":{"date-parts":[[2014,1,13]],"date-time":"2014-01-13T12:29:20Z","timestamp":1389616160000},"page":"1468-1477","source":"Crossref","is-referenced-by-count":16,"title":["Optical Impedance Spectroscopy with Single-Mode Electro-Active-Integrated\nOptical Waveguides"],"prefix":"10.1021","volume":"86","author":[{"given":"Xue","family":"Han","sequence":"first","affiliation":[{"name":"University of Louisville , , , ,","place":["Louisville, Kentucky, United States, 40292"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sergio B.","family":"Mendes","sequence":"additional","affiliation":[{"name":"University of Louisville , , , ,","place":["Louisville, Kentucky, United States, 40292"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2014,1,13]]},"reference":[{"issue":"2","key":"2026090310044163400_cit1a","doi-asserted-by":"crossref","first-page":"99","DOI":"10.1002\/1521-4095(20020116)14:2<99::AID-ADMA99>3.0.CO;2-9","volume":"14","author":"Dimitrakopoulos","year":"2002","journal-title":"Adv. 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