The Ion Sensitivity of Surface Conductive Single Crystalline Diamond

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• 作者：Andreas Hä ; rtl ; Jose A. Garrido ; Stefan Nowy ; Ralf Zimmermann ; Carsten Werner ; Dominik Horinek ; Roland Netz ; Martin Stutzmann
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：February 7, 2007
• 年：2007
• 卷：129
• 期：5
• 页码：1287 - 1292
• 全文大小：142K
• 年卷期：v.129,no.5(February 7, 2007)
• ISSN：1520-5126

文摘

Charge build-up at the solid/aqueous interface is a ubiquitous phenomenon that determines theproperties of interfacial electrical double layers. Due to its unique properties, the surface of diamond offersan attractive platform to investigate charging mechanisms in aqueous solutions. We investigate the surfacecharge by studying the ion sensitivity of H-terminated single crystalline diamond surface conductive layers.The effect of monovalent and divalent salts has been probed at different pH values. For a pH above 3.5,increasing the ionic strength results in a decrease of the surface conductivity, in contrast to the resultsobtained for pH below 3.5. Electrokinetic experiments are in good agreement with the surface conductivitymeasurements, showing an isoelectric point at pH 3.5 for the H-terminated diamond surface. We discussthe results in terms of the Coulombic screening by electrolyte ions of the surface potential, which is inducedby a pH-dependent surface charge. The origin of this surface charge is discussed in terms of chargeregulation by amphoteric hydroxyl surface groups and unsymmetrical adsorption of hydroxide and hydroniumions induced by the hydrophobic nature of the H-terminated diamond surface. This surface charge canhave important consequences for processes governed by the diamond/aqueous interface, such as electrontransfer to charged redox molecules, adsorption of charged molecules and proteins, and ion sensitivity.