Concentration-Polarization-Induced Precipitation and Ionic Current Oscillations with Tunable Frequency

Journal Article · Wed Jan 24 00:00:00 EST 2018 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.7b12265· OSTI ID:1470234

Acar, Elif Turker ^[1]; Hinkle, Preston ^[2]; Siwy, Zuzanna S.  ^[1]

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1. Univ. of California, Irvine, CA (United States); Istanbul Univ. (Turkey)
2. Univ. of California, Irvine, CA (United States)

At the nanoscale, charges present at the surfaces of liquid–solid interfaces greatly influence the properties of ions and molecules present in the solution, and can lead to nanoscale effects such as ion selectivity, ion current rectification, and modulation of local ionic concentrations. Concentration polarization is another nanoscale phenomenon whereby ion concentrations are enriched at one opening of an ion-selective nanopore and depleted at the other. We demonstrate that when a nanopore is in contact with a weakly soluble salt present at a concentration below its solubility product, concentration polarization can lead to locally enhanced ionic concentrations and precipitation of the salt. Formed precipitates partially or fully occlude the nanopore’s opening as indicated by a measured transient decrease of the nanopore’s conductance. We have confirmed experimental conditions at which the locally created precipitate is either pushed through or dissolved, clearing the pore entrance and allowing the precipitation reaction to occur again. The dynamic process of precipitate formation and dissolution is observed as ion current fluctuations and oscillations with frequencies reaching 200 Hz. The frequency of the system operation exceeds other nanopore-based oscillators by 2 orders of magnitude, which we believe stems from the 30 nm length of the pores examined here, versus ~10 μm long pores reported before.

• Research Organization: Univ. of Maryland, College Park, MD (United States). Energy Frontier Research Center (EFRC) Nanostructures for Electrical Energy Storage (NEES)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0001160
• OSTI ID: 1470234
• Journal Information: Journal of Physical Chemistry. C, Vol. 122, Issue 6; Related Information: NEES partners with University of Maryland (lead); University of California, Irvine; University of Florida; Los Alamos National Laboratory; Sandia National Laboratories; Yale University; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY