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Cation Dependent Surface Charge Regulation in Gated Nanofluidic Devices.
Marie Fuest1, Kaushik K Rangharajan1, Caitlin Boone1
1Department of Mechanical and Aerospace Engineering, The Ohio State University , Columbus, Ohio 43210, United States.
Analytical Chemistry
|February 18, 2017
Summary
Surface charge significantly impacts nanoscale electrolyte transport. Divalent ions like Ca2+ and Mg2+ strongly interact with surfaces, reducing charge and influencing ion flow in nanofluidic devices.
Area of Science:
- Nanoscale science
- Physical chemistry
- Surface science
Background:
- Surface charge is a critical factor in aqueous electrolyte transport at the nanoscale.
- This phenomenon is relevant in both engineered systems and biological processes like ion transport.
Purpose of the Study:
- To investigate how surface charge density affects electrolyte transport in a gated nanofluidic channel.
- To compare the transport behavior of monovalent and divalent electrolytes, as well as mixtures.
Main Methods:
- Utilized a gated nanofluidic device with embedded electrodes to tune surface charge density.
- Systematically studied the transport of potassium chloride (KCl), sodium chloride (NaCl), magnesium chloride (MgCl2), calcium chloride (CaCl2), and KCl + CaCl2 mixtures.
- Employed nanochannel conductance measurements and numerical modeling.
Main Results:
- Divalent cations (Ca2+, Mg2+) significantly reduced native surface charge density (up to 4-5 times) compared to monovalent cations.
- In electrolyte mixtures, Ca2+ dominated, making nanochannel conductance independent of KCl concentration.
- Divalent ion-surface interactions limited the gate electrode's ability to modulate surface potential.
Conclusions:
- Cation-dependent interactions dictate nanoscale ion transport in nanofluidic devices.
- Surface charge modulation by external gates is influenced by specific ion-surface chemistries.
- Understanding these interactions is crucial for controlling ion transport in nanochannels.
