Title: Multifunctional nanopore electrode array method for characterizing and manipulating single entities in attoliter-volume enclosures
Structurally regular nanopore arrays fabricated to contain independently controllable annular electrodes represent a new kind of architecture capable of electrochemically addressing small collections of matter—down to the single entity (molecule, particle, and biological cell) level. Furthermore, these nanopore electrode arrays (NEAs) can also be interrogated optically to achieve single entity spectroelectrochemistry. Larger entities such as nanoparticles and single bacterial cells are investigated by dark-field scattering and potential-controlled single-cell luminescence experiments, respectively, while NEA-confined molecules are probed by single molecule luminescence. By carrying out these experiments in arrays of identically constructed nanopores, massively parallel collections of single entities can be investigated simultaneously. The multilayer metal–insulator design of the NEAs enables highly efficient redox cycling experiments with large increases in analytical sensitivity for chemical sensing applications. NEAs may also be augmented with an additional orthogonally designed nanopore layer, such as a structured block copolymer, to achieve hierarchically organized multilayer structures with multiple stimulus-responsive transport control mechanisms. Finally, NEAs constructed with a transparent bottom layer permit optical access to the interior of the nanopore, which can result in the cutoff of far-field mode propagation, effectively trapping radiation in an ultrasmall volume inside the nanopore. The bottom metal layer may be used as both a working electrode and an optical cladding layer, thus, producing bifunctional electrochemical zero-mode waveguide architectures capable of carrying out spectroelectrochemical investigations down to the single molecule level. more »« less
Do, Hyein; Kwon, Seung-Ryong; Baek, Seol; Madukoma, Chinedu S.; Smiley, Marina K.; Dietrich, Lars E.; Shrout, Joshua D.; Bohn, Paul W.(
, The Analyst)
null
(Ed.)
The opportunistic pathogen Pseudomonas aeruginosa ( P. aeruginosa ) produces several redox-active phenazine metabolites, including pyocyanin (PYO) and phenazine-1-carboxamide (PCN), which are electron carrier molecules that also aid in virulence. In particular, PYO is an exclusive metabolite produced by P. aeruginosa , which acts as a virulence factor in hospital-acquired infections and is therefore a good biomarker for identifying early stage colonization by this pathogen. Here, we describe the use of nanopore electrode arrays (NEAs) exhibiting metal–insulator–metal ring electrode architectures for enhanced detection of these phenazine metabolites. The size of the nanopores allows phenazine metabolites to freely diffuse into the interior and access the working electrodes, while the bacteria are excluded. Consequently, highly efficient redox cycling reactions in the NEAs can be accessed by free diffusion unhindered by the presence of bacteria. This strategy yields low limits of detection, i.e. 10.5 and 20.7 nM for PYO and PCN, respectively, values far below single molecule pore occupancy, e.g. at 10.5 nM 〈 n pore 〉 ∼ 0.082 per nanopore – a limit which reflects the extraordinary signal amplification in the NEAs. Furthermore, experiments that compared results from minimal medium and rich medium show that P. aeruginosa produces the same types of phenazine metabolites even though growth rates and phenazine production patterns differ in these two media. The NEA measurement strategy developed here should be useful as a diagnostic for pathogens generally and for understanding metabolism in clinically important microbial communities.
Fu, Kaiyu; Han, Donghoon; Crouch, Garrison M.; Kwon, Seung‐Ryong; Bohn, Paul W.(
, Small)
Abstract
Single nanoparticle analysis can reveal how particle‐to‐particle heterogeneity affects ensemble properties derived from traditional bulk measurements. High‐bandwidth, low noise electrochemical measurements are needed to examine the fast heterogeneous electron‐transfer behavior of single nanoparticles with sufficient fidelity to resolve the behavior of individual nanoparticles. Herein, nanopore electrode arrays (NEAs) are fabricated in which each pore supports two vertically spaced, individually addressable electrodes. The top ring electrode serves as a particle gate to control the transport of silver nanoparticles (AgNPs) within individual attoliter volume NEAs nanopores, as shown by redox collisions of AgNPs collisions at the bottom disk electrode. The AgNP‐nanoporeis system has wide‐ranging technological applications as well as fundamental interest, since the transport of AgNPs within the NEA mimics the transport of ions through cell membranes via voltage‐gated ion channels. A voltage threshold is observed above which AgNPs are able to access the bottom electrode of the NEAs, i.e., a minimum potential at the gate electrode is required to switch between few and many observed collision events on the collector electrode. It is further shown that this threshold voltage is strongly dependent on the applied voltage at both electrodes as well as the size of AgNPs, as shown both experimentally and through finite‐element modeling. Overall, this study provides a precise method of monitoring nanoparticle transport and in situ redox reactions within nanoconfined spaces at the single particle level.
Zaino, Lawrence P.; Grismer, Dane A.; Han, Donghoon; Crouch, Garrison M.; Bohn, Paul W.(
, Faraday Discussions)
Zero-mode waveguides (ZMW) have the potential to be powerful confinement tools for studying electron transfer dynamics at single molecule occupancy conditions. Flavin mononucleotide contains an isoalloxazine chromophore, which is fluorescent in the oxidized state (FMN) while the reduced state (FMNH 2 ) exhibits dramatically lower light emission, i.e. a dark-state. This allows fluorescence emission to report the redox state of single FMN molecules, an observation that has been used previously to study single electron transfer events in surface-immobilized flavins and flavoenzymes, e.g. sarcosine oxidase, by direct wide-field imaging of ZMW arrays. Single molecule electron transfer dynamics have now been extended to the study of freely diffusing molecules using fluorescence measurements of Au ZMWs under single occupancy conditions. The Au in the ZMW serves both as an optical cladding layer and as the working electrode for potential control, thereby accessing single molecule electron transfer dynamics at μM concentrations. Consistent with expectations, the probability of observing single reduced molecules increases as the potential is scanned negative, E appl < E eq , and the probability of observing emitting oxidized molecules increases at E appl > E eq . Different single molecules exhibit different electron transfer properties as reflected in the position of E eq and the distribution of E eq among a population of FMN molecules. Two types of actively-controlled electroluminescence experiments were used: chronofluorometry experiments, in which the potential is alternately stepped between oxidizing and reducing potentials, and cyclic potential sweep fluorescence experiments, analogous to cyclic voltammetry, these latter experiments exhibiting a dramatic scan rate dependence with the slowest scan rates showing distinct intermediate states that are stable over a range of potentials. These states are assigned to flavosemiquinone species that are stabilized in the special environment of the ZMW nanopore.
Han, Donghoon; Crouch, Garrison M.; Fu, Kaiyu; Zaino III, Lawrence P.; Bohn, Paul W(
, Chemical Science)
null
(Ed.)
The ability of zero-mode waveguides (ZMW) to guide light into subwavelength-diameter nanoapertures has been exploited for studying electron transfer dynamics in zeptoliter-volume nanopores under single-molecule occupancy conditions. In this work, we report the spectroelectrochemical detection of individual molecules of the redox-active, fluorogenic molecule flavin mononucleotide (FMN) freely diffusing in solution. Our approach is based on an array of nanopore-confined recessed dual ring electrodes, wherein repeated reduction and oxidation of a single molecule at two closely spaced annular working electrodes yields amplified electrochemical signals. We have articulated these structures with an optically transparent bottom, so that the nanopores are bifunctional, exhibiting both nanophotonic and nanoelectrochemical behaviors allowing the coupling between electron transfer and fluorescence dynamics to be studied under redox cycling conditions. We also investigated the electric field intensity in electrochemical ZMWs (E-ZMW) through finite-element simulations, and the amplification of fluorescence by redox cycling agrees well with predictions based on optical confinement effects inside the E-ZMW. Proof-of-principle experiments are conducted showing that electrochemical and fluorescence signals may be correlated to reveal single molecule fluctuations in the array population. Cross-correlation of single molecule fluctuations in amperometric response and single photon emission provides unequivocal evidence of single molecule sensitivity.
The traditional von Neumann architecture limits the increase in computing efficiency and results in massive power consumption in modern computers due to the separation of storage and processing units. The novel neuromorphic computation system, an in-memory computing architecture with low power consumption, is aimed to break the bottleneck and meet the needs of the next generation of artificial intelligence (AI) systems. Thus, it is urgent to find a memory technology to implement the neuromorphic computing nanosystem. Nowadays, the silicon-based flash memory dominates non-volatile memory market, however, it is facing challenging issues to achieve the requirements of future data storage device development due to the drawbacks, such as scaling issue, relatively slow operation speed, and high voltage for program/erase operations. The emerging resistive random-access memory (RRAM) has prompted extensive research as its simple two-terminal structure, including top electrode (TE) layer, bottom electrode (BE) layer, and an intermediate resistive switching (RS) layer. It can utilize a temporary and reversible dielectric breakdown to cause the RS phenomenon between the high resistance state (HRS) and the low resistance state (LRS). RRAM is expected to outperform conventional memory device with the advantages, notably its low-voltage operation, short programming time, great cyclic stability, and good scalability. Among the materials for RS layer, indium gallium zinc oxide (IGZO) has shown attractive prospects in abundance and high atomic diffusion property of oxygen atoms, transparency. Additionally, its electrical properties can be easily modulated by controlling the stoichiometric ratio of indium and gallium as well as oxygen potential in the sputter gas. Moreover, since the IGZO can be applied to both the thin-film transistor (TFT) channel and RS layer, it has a great potential for fully integrated transparent electronics application. In this work, we proposed amorphous transparent IGZO-based RRAMs and investigated switching behaviors of the memory cells prepared with different top electrodes. First, ITO was choosing to serve as both TE and BE to achieve high transmittance. A multi-target magnetron sputtering system was employed to deposit all three layers (TE, RS, BE layers) on glass substrate. I-V characteristics were evaluated by a semiconductor parameter analyzer, and the bipolar RS feature of our RRAM devices was demonstrated by typical butterfly curves. The optical transmission analysis was carried out via a UV-Vis spectrometer and the average transmittance was around 80% out of entire devices in the visible-light wavelength range, implying high transparency. We adjusted the oxygen partial pressure during the sputtering of IGZO to optimize the property because the oxygen vacancy concentration governs the RS performance. Electrode selection is crucial and can impact the performance of the whole device. Thus, Cu TE was chosen for our second type of device because the diffusion of Cu ions can be beneficial for the formation of the conductive filament (CF). A ~5 nm SiO 2 barrier layer was employed between TE and RS layers to confine the diffusion of Cu into the RS layer. At the same time, this SiO 2 inserting layer can provide an additional interfacial series resistance in the device to lower the off current, consequently, improve the on/off ratio and whole performance. Finally, an oxygen affinity metal Ti was selected as the TE for our third type of device because the concentration of the oxygen atoms can be shifted towards the Ti electrode, which provides an oxygengettering activity near the Ti metal. This process may in turn lead to the formation of a sub-stoichiometric region in the neighboring oxide that is believed to be the origin of better performance. In conclusion, the transparent amorphous IGZO-based RRAMs were established. To tune the property of RS layer, the sputtering conditions of RS were varied. To investigate the influence of TE selections on switching performance of RRAMs, we integrated a set of TE materials, and a barrier layer on IGZO-based RRAM and compared the switch characteristics. Our encouraging results clearly demonstrate that IGZO is a promising material in RRAM applications and breaking the bottleneck of current memory technologies.
Baek, Seol, Cutri, Allison R., Han, Donghoon, Kwon, Seung-Ryong, Reitemeier, Julius, Sundaresan, Vignesh, and Bohn, Paul W. Multifunctional nanopore electrode array method for characterizing and manipulating single entities in attoliter-volume enclosures. Retrieved from https://par.nsf.gov/biblio/10382066. Journal of Applied Physics 132.17 Web. doi:10.1063/5.0101693.
Baek, Seol, Cutri, Allison R., Han, Donghoon, Kwon, Seung-Ryong, Reitemeier, Julius, Sundaresan, Vignesh, & Bohn, Paul W. Multifunctional nanopore electrode array method for characterizing and manipulating single entities in attoliter-volume enclosures. Journal of Applied Physics, 132 (17). Retrieved from https://par.nsf.gov/biblio/10382066. https://doi.org/10.1063/5.0101693
Baek, Seol, Cutri, Allison R., Han, Donghoon, Kwon, Seung-Ryong, Reitemeier, Julius, Sundaresan, Vignesh, and Bohn, Paul W.
"Multifunctional nanopore electrode array method for characterizing and manipulating single entities in attoliter-volume enclosures". Journal of Applied Physics 132 (17). Country unknown/Code not available. https://doi.org/10.1063/5.0101693.https://par.nsf.gov/biblio/10382066.
@article{osti_10382066,
place = {Country unknown/Code not available},
title = {Multifunctional nanopore electrode array method for characterizing and manipulating single entities in attoliter-volume enclosures},
url = {https://par.nsf.gov/biblio/10382066},
DOI = {10.1063/5.0101693},
abstractNote = {Structurally regular nanopore arrays fabricated to contain independently controllable annular electrodes represent a new kind of architecture capable of electrochemically addressing small collections of matter—down to the single entity (molecule, particle, and biological cell) level. Furthermore, these nanopore electrode arrays (NEAs) can also be interrogated optically to achieve single entity spectroelectrochemistry. Larger entities such as nanoparticles and single bacterial cells are investigated by dark-field scattering and potential-controlled single-cell luminescence experiments, respectively, while NEA-confined molecules are probed by single molecule luminescence. By carrying out these experiments in arrays of identically constructed nanopores, massively parallel collections of single entities can be investigated simultaneously. The multilayer metal–insulator design of the NEAs enables highly efficient redox cycling experiments with large increases in analytical sensitivity for chemical sensing applications. NEAs may also be augmented with an additional orthogonally designed nanopore layer, such as a structured block copolymer, to achieve hierarchically organized multilayer structures with multiple stimulus-responsive transport control mechanisms. Finally, NEAs constructed with a transparent bottom layer permit optical access to the interior of the nanopore, which can result in the cutoff of far-field mode propagation, effectively trapping radiation in an ultrasmall volume inside the nanopore. The bottom metal layer may be used as both a working electrode and an optical cladding layer, thus, producing bifunctional electrochemical zero-mode waveguide architectures capable of carrying out spectroelectrochemical investigations down to the single molecule level.},
journal = {Journal of Applied Physics},
volume = {132},
number = {17},
author = {Baek, Seol and Cutri, Allison R. and Han, Donghoon and Kwon, Seung-Ryong and Reitemeier, Julius and Sundaresan, Vignesh and Bohn, Paul W.},
}
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