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1. Improved Spatial Resolution of Electroencephalogram Using Tripolar Concentric Ring Electrode Sensors

   https://doi.org/10.1155/2020/6269394  

   Liu, Xiang; Makeyev, Oleksandr; Besio, Walter (June 2020, Journal of Sensors)

   The electroencephalogram (EEG) is broadly used for research of brain activities and diagnosis of brain diseases and disorders. Although EEG provides good temporal resolution of millisecond or less, it does not provide good spatial resolution. There are two main reasons for the poor spatial resolution: the blurring effects of the head volume conductor and poor signal-to-noise ratio. We have developed a tripolar concentric ring electrode (TCRE) Laplacian sensor and now report on computer simulations comparing spatial resolution between conventional EEG disc electrode sensors and TCRE Laplacian sensors. We also performed visual evoked stimulus experiments and acquired visual evoked potentials (VEPs) from healthy human subjects. From the simulations, we found that TCRE Laplacian sensors can provide approximately a tenfold improvement in spatial resolution and pass signals from specific volumes. Placing TCRE sensors near the brain region of interest will allow passage of the wanted signals and rejection of distant interference signals. We were also able to detect VEPs on the scalp surface and show that TCREs separated VEP sources better than conventional disc electrodes. 

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2. Redox Cycling in Nanopore-Confined Recessed Dual-Ring Electrode Arrays

   https://doi.org/10.1021/acs.jpcc.6b01287  

   Han, Donghoon; Zaino, Lawrence P.; Fu, Kaiyu; Bohn, Paul W. (September 2016, The Journal of Physical Chemistry C)
3. A rotating ring disc electrode study of photo(electro)catalyst for nitrogen fixation

   https://doi.org/10.1039/D2FD00168C  

   Liu, Yu-Hsuan; Huang, Po-Wei; Hatzell, Marta C. (January 2023, Faraday Discussions)

   There are numerous reports of photo(electro)catalysts demonstrating activity for nitrogen reduction to ammonia and a few reports of photo(electro)catalysts demonstrating activity for nitrogen oxidation to nitric acid. However, progress in advancing solar-to-fertilizer applications is slow, due in part to the pace of catalyst screening. Most evaluations of photo(electro)catalysts activity occur using batch reactors. This is because common product analyses require accumulation of ammonia or nitric acid in the reactor to overcome instrument detection limits. The primary aim here is to examine the use of an electroanalytical method, rotating ring disk electrode voltammetry (RRDE), to detect ammonia produced by a nitrogen fixing photo(electro)catalyst. To examine the potential for RRDE, we investigated a photo(electro)catalyst known to reduce nitrogen to ammonia (titania), while varying the applied electrochemical potential and degree of illumination on the disk. We show that the observed ammonia oxidation at the ring electrode corresponds strongly with ammonia measurements obtained from the bulk electrolyte. Indicating that RRDE may be effective for catalyst screening. The chief limitation of this approach is the need for an alkaline electrolyte. In addition, this approach does not rule out the presence of adventitious ammonia. 

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4. Electrochemistry at single molecule occupancy in nanopore-confined recessed ring-disk electrode arrays

   https://doi.org/10.1039/C6FD00062B  

   Fu, Kaiyu; Han, Donghoon; Ma, Chaoxiong; Bohn, Paul W. (January 2016, Faraday Discuss.)

   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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5. Redox Cycling in Nanoscale-Recessed Ring-Disk Electrode Arrays for Enhanced Electrochemical Sensitivity

   https://doi.org/10.1021/nn401542x  

   Ma, Chaoxiong; Contento, Nicholas M.; Gibson, Larry R.; Bohn, Paul W. (May 2013, ACS Nano)