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Electrochemical reactions at nanoscale structures possess unique characteristics, e.g. fast mass transport, high signal-to-noise ratio at low concentration, and insignificant ohmic losses even at low electrolyte concentrations. These properties motivate the fabrication of high density, laterally ordered arrays of nanopores, embedding vertically stacked metal–insulator–metal electrode structures and exhibiting precisely controlled pore size and interpore spacing for use in redox cycling. These nanoscale recessed ring-disk electrode (RRDE) arrays exhibit current amplification factors, AF RC , as large as 55-fold with Ru(NH 3 ) 6 2/3+ , indicative of capture efficiencies at the top and bottom electrodes, Φ t,b , exceeding 99%. Finite element simulations performed to investigate the concentration distribution of redox species and to assess operating characteristics are in excellent agreement with experiment. AF RC increases as the pore diameter, at constant pore spacing, increases in the range 200–500 nm and as the pore spacing, at constant pore diameter, decreases in the range 1000–460 nm. Optimized nanoscale RRDE arrays exhibit a linear current response with concentration ranging from 0.1 μM to 10 mM and a small capacitive current with scan rate up to 100 V s −1 . At the lowest concentrations, the average pore occupancy is 〈 n 〉 ∼ 0.13 molecule establishing productive electrochemical signals at occupancies at and below the single molecule level in these nanoscale RRDE arrays.
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Assessment of 1/ f noise associated with nanopores fabricated through chemically tuned controlled dielectric breakdown
Abstract Recently, we developed a fabrication method—chemically‐tuned controlled dielectric breakdown (CT‐CDB)—that produces nanopores (through thin silicon nitride membranes) surpassing legacy drawbacks associated with solid‐state nanopores (SSNs). However, the noise characteristics of CT‐CDB nanopores are largely unexplored. In this work, we investigated the 1/fnoise of CT‐CDB nanopores of varying solution pH, electrolyte type, electrolyte concentration, applied voltage, and pore diameter. Our findings indicate that the bulk Hooge parameter (αb) is about an order of magnitude greater than SSNs fabricated by transmission electron microscopy (TEM) while the surface Hooge parameter (αs) is ∼3 order magnitude greater. Theαsof CT‐CDB nanopores was ∼5 orders of magnitude greater than theirαb, which suggests that the surface contribution plays a dominant role in 1/fnoise. Experiments with DNA exhibited increasing capture rates with pH up to pH ∼8 followed by a drop at pH ∼9 perhaps due to the onset of electroosmotic force acting against the electrophoretic force. The1/fnoise was also measured for several electrolytes and LiCl was found to outperform NaCl, KCl, RbCl, and CsCl. The 1/fnoise was found to increase with the increasing electrolyte concentration and pore diameter. Taken together, the findings of this work suggest the pH approximate 7–8 range to be optimal for DNA sensing with CT‐CDB nanopores.
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- PAR ID:
- 10452154
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ELECTROPHORESIS
- Volume:
- 42
- Issue:
- 7-8
- ISSN:
- 0173-0835
- Format(s):
- Medium: X Size: p. 899-909
- Size(s):
- p. 899-909
- Sponsoring Org:
- National Science Foundation
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