Open AccessCharge Regulation at a Nanoporous Two-Dimensional Interface
Author(s) -
Mandakranta Ghosh,
Moritz A. Junker,
Robert T. M. van Lent,
Lukas Madauß,
Marika Schleberger,
H. Lebius,
A. Benyagoub,
Jeffery A. Wood,
Rob G.H. Lammertink
Publication year - 2021
Publication title -
acs omega
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.779
H-Index - 40
ISSN - 2470-1343
DOI - 10.1021/acsomega.0c03958
Subject(s) - streaming current , nernst equation , membrane , zeta potential , membrane potential , donnan potential , surface charge , electric potential , analytical chemistry (journal) , chemistry , nanoporous , drop (telecommunication) , reversal potential , materials science , nanotechnology , chromatography , electrolyte , voltage , physics , telecommunications , biochemistry , receptor , patch clamp , nanoparticle , computer science , quantum mechanics , electrode
In this work, we have studied the pH-dependent surface charge nature of nanoporous graphene. This has been investigated by membrane potential and by streaming current measurements, both with varying pH. We observed a lowering of the membrane potential with decreasing pH for a fixed concentration gradient of potassium chloride (KCl) in the Donnan dominated regime. Interestingly, the potential reverses its sign close to pH 4. The fitted value of effective fixed ion concentration ( C̅ R ) in the membrane also follows the same trend. The streaming current measurements show a similar trend with sign reversal around pH 4.2. The zeta potential data from the streaming current measurement is further analyzed using a 1-pK model. The model is used to determine a representative pK (acid-base equilibrium constant) of 4.2 for the surface of these perforated graphene membranes. In addition, we have also theoretically investigated the effect of the PET support in our membrane potential measurement using numerical simulations. Our results indicate that the concentration drop inside the PET support can be a major contributor (up to 85%) for a significant deviation of the membrane potential from the ideal Nernst potential.