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Determination of pK a of benzoic acid- and p-aminobenzoic acid-modified platinum surfaces by electrochemical and contact angle measurements |
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| Authors: | Secil Tekin-Celebi Ali Osman Solak Zafer Ustundag Serkan Demirci |
| Institution: | 1. Department of Chemistry, Faculty of Science, Ankara University, 06100, Ankarara, Turkey 2. Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA 3. Department of Chemical Engineering, Kyrgyzstan-Turkiye Manas University, 720044, Bishkek, Kyrgyzstan 4. Department of Chemistry, Faculty of Arts and Sciences, Dumlup?nar University, 43270, K??tahyara, Turkey 5. Department of Chemistry, Faculty of Arts and Sciences, Amasya University, 05100, Amasyara, Turkey |
| Abstract: | Acidity constant values of benzoic acid (BA)-modified platinum electrode (Pt-BA) and p-aminobenzoic acid (pABA)-modified platinum electrode (Pt-NHBA) surfaces were determined using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and contact angle measurements (CAM). Diazonium tetrafluoroborate salt reduction and pABA oxidation reactions were used to prepare (Pt-BA) and (Pt-NHBA) surfaces, respectively. Both surfaces exhibited pH dependence with Fe(CN)6]3?/4? redox probe solutions at different pH; this allowed us to estimate the surface pK a values. Acidity constants for Pt-BA surface were found to be pK a (3.09 ± 0.25), (4.89 ± 0.11), and (3.91 ± 0.54) by CV, EIS, and CAM techniques, respectively, while the values for Pt-NHBA surface were pK a (3.16 ± 0.45), (4.24 ± 0.40), and (5.64 ± 0.12). The Pt-BA surface pK a values were lower in CV and CAM measurements relative to the bulk solution of BA, while a higher value was observed in EIS for Pt-BA surface. The pK a values determined for Pt-NHBA surface via both CV and EIS were lower than the bulk value; however, the result obtained from CAM was one unit higher than pK a of bulk pABA. |
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