306 research outputs found
Correction to Virus Bioresistor (VBR) for the Detection of the Bladder Cancer Marker DJ-1 in Urine at 10 pM in One Minute
No full textThe author list contained an error: Gregory A. Weiss was not identified as a corresponding author. Both of the corresponding authors, Gregory A. Weiss and Reginald M. Penner, are indicated in this Addition and Correction
From Proteins to Protons: Design of Nanoscopic Conductive Polymers Biosensors for Point-of-care Diagnostics
No full textConductive polymers are often used in biosensing architectures of many kinds. Their biocompatibility, electrical conductivity, and ease of polymerization allows many routes to fabricate innovative, nanoscale biosensors for point-of-care diagnostic purposes. The focus of this dissertation will be on two different types of nanoscale, conductive polymer biosensors that were fabricated since 2018 in the Penner Lab by myself and my associates. The first device is the Virus BioResistor (VBR). This device employs poly(3,4-ethylenedioxythiophene) (PEDOT) which is electropolymerized in the presence of virus particles which have been genetically engineered to bind a specific protein. A baselayer of PEDOT:PSS is used as a target for this electrodeposition. This event produces an electrically conductive bioaffinity layer, through which impedance measurements can be taken. In Chapter 2, advances are made to this device by increasing the PEDOT:PSS baselayer are discussed. The increase in the baselayer resistance causes a ~4x signal enhancement, without sacrificing signal-to-noise or specificity. The resulting device can detect deglycase 1 (DJ-1), a bladder cancer biomarker, at 10 pM in ~30 s. Chapter 3 discusses further enhancements made to the VBR through over-oxidation. The process of over-oxidation allows for the detection of larger proteins and antibodies, up to 150 kDa. Without this process, the VBR is insensitive to proteins larger than 66.5 kDa. This process has been shown to enable detection of multiple antibodies. Following this work, an effort was made to engineer a conductive polymer sensor that is nanoscopic in 3 dimensions, compared to the VBR which is only nanoscopic in 1 dimension. This device is discussed in Chapter 4 and is called a Nanojunction pH sensor (NJ-pH). The NJ-pH sensor relies on lithographically patterned nanowire electrodeposition to fabricated single gold nanowires onto which electrical contacts are evaporated. A nanogap is formed in this nanowire through electromigration, and the gap is then bridged through electropolymerization of poly(aniline) (PANI) which has a resistance that is pH sensitive. This device is shown to have impedances that range 5 orders of magnitude between pH 1 – 9, and can give a reliable pH measurement within 30 s. This device is completely nanoscopic and offers a new avenue for monitoring local pH on the nanoscale
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Exploring sub-micron, electrodeposition-enabled liquid- and gas-phase sensors
No full textChemical sensors and biosensors are important devices that are capable of providing real-time analytical information, widely applicable to problems ranging from point-of-care diagnostics to the detection of explosive or toxic gases. This dissertation will discuss a few different liquid- and gas-phase sensors developed during my time in the Penner Lab. Electrodeposition and electropolymerization have emerged as versatile tools for the fabrication of chemical sensors and biosensors. Electropolymerization allows for the ability to entrain receptors such as antibodies, engineered virus particles, and metal chelating agents into a conductive polymer sensing element and has proven to be a versatile method of preparing sensors for a variety of analyses. Meanwhile, electrodeposition has been utilized to fabricate nanostructured metal indicator microelectrodes as well as for rapid and sensitive hydrogen gas sensors. Chapter 2 will discuss the optimization of the Virus BioResistor (VBR) to allow for the detection of larger proteins. The VBR is a conductive polymer thin-film biosensor utilizing an electropolymerized virus-PEDOT composite bioaffinity layer, engineered specifically to bind proteins of interest. The VBR previously demonstrated fast and reproducible response to small proteins, but larger proteins, such as antibodies, exhibited minimal signal responses. An electrochemical overoxidation process to unlock the ability for the VBR to detect two different IgG antibodies is described and discussed. Chapter 3 details the fabrication of a nanojunction pH sensor, where a nanogap is fabricated within a single gold nanowire and is then subsequently bridged via the electropolymerization of polyaniline (PANI), which is pH responsive. The nanogap is created in a facile manner via electromigration, and thefabricated nanojunction sensor is able to reliably detect a range of pH from 1 to 9 within 30 s via impedance. This serves as a first step towards fabricating a VBR that is on the nanometer scale in all three dimensions. Chapter 4 then explores chemiresistive gas sensing for the detection of ethylene gas utilizing a single platinum nanowire, fabricated using lithographically patterned nanowire electrodeposition (LPNE). Platinum nanowires exhibit a reversible decrease in resistance upon exposure to H2 due to the increase in the specularity of electron surface scattering by the formation of Pt – H. We test if this surface scattering modality is also observed to also occur in the presence of ethylene exposure. A simple platinum nanowire transducer capable of detecting ppm concentrations of ethylene in air is described and a mechanism involving the combustion of ethylene causing changes in electron surface scattering is proposed. Finally, Chapter 5 details a unique and collaborative urology project investigating the encrustation of ureteral stents. Stents are an indispensable tool in the medical field to relieve obstruction and preserve kidney function. However, these devices lose their efficacy over time as they become obstructed by encrustation. In this final chapter, I describe and compare the encrustation formation on 2-hydroxyethy methacrylate (HEMA)-coated Pellethane to that formed on commercially available polymer-based stents
Rational design approaches of two-dimensional metal oxides for chemiresistive gas sensors: A comprehensive review
No full textThe emergence of two-dimensional (2D) materials enables enormous progress in the development of high-performance chemical sensors facilitating exotic structural and material properties. In this review, we focus on the rational design and synthesis strategies of various 2D metal oxide-based for chemiresistive gas sensors. We first discuss various synthesis strategies for 2D metal oxides such as thin-film manufacturing, exfoliation of layered metal oxides, templating route using sacrificial layer, and template-free synthesis route to elucidate the basic design principles of metal oxide nanosheets both from the top-down and bottom-up perspectives and their efficacy toward gas sensing applications. Then, we discuss assembly strategies of 2D metal oxide nanosheets for hierarchical and hybrid nanostructures with increased design complexity in terms of morphology and/or composition, which boosted their sensing performances. Finally, we conclude by providing an outlook of development in 2D metal oxides for realizing practical gas sensing devices. Through this article, not only did we elucidate the representative synthesis strategies for 2D metal oxides for applications in gas sensors, but we also provided a rich insight into their fundamental design principles to help propel the future development of high-performance gas sensors.
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Lithographically Patterned Nanowires in Sensors and Transducers
No full textLithographically patterned metal nanowires were utilized in two studies on sensing and transduction. First, ultra-long (mm scale) polycrystalline gold nanowires were investigated for their ability to perform as thermophones, or thermoacoustic sound emitters. Arrays of ~4000 linear nanowires were fabricated at 5 um pitch on glass surfaces. Sound generation by the nanowires was evaluated as a function of acoustic frequency (from 5 - 120 kHz), angle from the plane of the nanowires, input power (from 0.30 - 2.5 W) and the width of the nanowires in the array (from 270 to 500 nm.) Classical theory based upon metal films accurately predicts the measured properties of these gold nanowire arrays. Angular "nodes" for the off-axis sound pressure level (SPL) versus frequency data, predicted by the directivity factor, were faithfully reproduced by these nanowire arrays. The maximum efficiency of these arrays (~10^{-10} at 25 kHz), the power dependence, and the frequency dependence were independent of the lateral dimensions of these wires over the range from 270 to 500 nm. Second, a PEDOT-deferoxamine nanojunction chemiresistor was developed for the rapid detection of Fe(III) at sub-nanomolar concentrations. The backbone of the sensor is a single lithographically patterned metal nanowire in which a nanogap is formed by focused ion beam (FIB). The nanowire is then electrochemically reconnected by the ionophore-doped polymer PEDOT-deferoxamine, creating a chemically responsive junction selective for Fe(III). Fabrication challenges, centered on the adhesion between the metal nanowire core and the PEDOT-DFA transduction layer, led to three design iterations of the sensor. Two of these nanojunctions were able to detect 10^{-11}-10^{-4} M Fe(III), demonstrating a dynamic range that is on par with ion selective electrodes and a limit of detection that is three order of magnitude better. However, these junctions fail to decrease the detection time and show a significant response to the control ion Zn(II)
Ultra-Fast Responding and Recovering Hydrogen Sensors: Metal-Organic Framework Layer on Pd Nanowires
No full textIon transport in thin polypyrrole films
No full textTypescript (photocopy).Fundamental and applied aspects of ion transport in polypyrrole films are investigated. In this context, three objectives have been accomplished: i) Composites of polypyrrole and a porous host membrane have been prepared which possess superior mechanical properties to the homogeneous polymer, but which retain its desirable electrochemical characteristics. ii) Two new electrochemical methods for quantitating ion transport in polypyrrole films are demonstrated. The small amplitude nature of both experiments minimizes the perturbation of the polymer redox state. These techniques circumvent many of the problems associated with the determination of diffusion coefficients in conducting polymers with conventional large amplitude electrochemical methods. iii) A technique for synthesizing polypyrrole films possessing a well defined "fibrillar-microporous" (F/MP) morphology which facilitates ion transport is developed. Controlled morphology films prepared using this new method are electrochemically characterized. The generality of this electrochemical method for preparing highly structured surfaces is demonstrated by depositing platinum structures with the same well-defined F/MP geometry. A modification of this procedure is used to prepare ultramicroelectrode ensembles (UME). UME's have electroanalytical applications since the signal-to-noise ratios for such electrodes are enhanced relative to those obtained at electrodes with conventional dimensions
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Understanding degradation in low-dimensional transition metal chalcogenide electrodes
No full textWith the increasingly widespread adoption of electronics into everyday objects with the introduction of the Internet of Things, the need for smaller, more efficient, and more robust energy storage devices is greater than ever. In this dissertation I discuss the development of a method of fabrication of nanoscopic thin films of niobium (V) oxide, Nb2O5, an intercalation material for Li-ion supercapacitors and batteries. Electrophoretic deposition from a colloidal solution of amorphous NbOx nanoparticles followed by calcination resulted in crystalline thin films of orthorhombic T-Nb2O5 with an inherent mesoporosity imparted by the electrophoretic deposition process. These films were evaluated electrochemically and were determined to have extraordinarily high energy storage metrics, however with repeated cycling these favorable metrics diminished. The high performance of Nb2O5 for Li-ion supercapacitors prompted an investigation of the mechanisms of capacity degradation over tens of thousands of charge/discharge cycles using electron microscopy, x-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and other methods. The result of these studies illustrated that there were two parallel causes of capacity degradation in Nb2O5 thin films: delamination of the active material from the current collector, and the progressive loss of crystalline structure associated with repeated insertion and extraction of Li-ions from the T-Nb2O5 lattice. After completing the degradation study of Nb¬2O5 I turned my attention to understanding the electrochemical performance of manganese (II) sulfide, MnS, a conversion material for Na-ion energy storage. To do this I standardized a procedure for the electrodeposition of MnS thin films using the electrochemical quartz crystal microbalance technique. I then developed a method for the fabrication of core@shell Au@MnS nanowires. Comparison of the electrochemical performance of the thin film and nanowire samples with equivalent thicknesses show that the nanowire morphology imparts enhanced rate capability and improved energy storage metrics relative to thin films for high power applications
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Rapid and Ultrasensitive Hydrogen Sensing: From Single Nanowires to Carbon Nanotubes
No full textNanoscale devices take many advantages, including low power consumption for energy sav- ing, highly miniaturized structures for portable equipment and tiny amount of materials needed for manufacturing purposes, particularly considering rare metals. Nano-devices have exhibited significant potentials for wide industrial applications, for example, chemical and biological sensing, nano-electronics, environment and health monitoring etc. In this disser- tation, two types of H2 sensors are discussed, they are based on single metal nanowires and metal nanoparticles-decorated carbon nanotube (CNT) ropes respectively.Single nanowire H2 sensors are fabricated by applying the methods of lithographically patterned nanowire electrodepositon (LPNE). Single palladium (Pd) nanowires with the dimension of 40 nm (height) × 100 nm (width) × 50 μm (length) are electrodeposited within LPNE templates and electrically isolated by metal contacts. Then platinum (Pt) layers are electrodeposited onto single Pd nanowires (Pd@Pt nanowires) to catalytically enhance the H2 sensing performance. The Pt layer coverage thickness is altered as average 0.1 monolayer (ML), 1 ML and 10 ML. For each coverage, the Pd@Pt nanowire sensors are evaluated at five different working temperatures, Pd@Pt sensors exhibited lowest detection at 500 ppm H2 exposure. Both response and recovery behaviors of Pd@Pt sensors are accelerated at higher temperature, yet the drawback is deterioration of sensitivity and detection limit.A type of more advanced H2 sensors based on semiconducting CNT ropes are developed, in order to enhance the H2 sensing performance for rapid response/ recovery and wider detec- tion range. CNT ropes deposition are achieved by applying processes of dielectrophoresis in aqueous solution containing suspended CNTs. Single CNT ropes are electrical isolated at the length of 50 μm, and employed as the electrode for electrodepositing Pd nanoparticles of four coulombic loadings. Bare CNT ropes show no response to H2/ air exposures, however the sensitivity to H2 is very strongly enhanced. Pd–CNT sensors are capable of detecting H2 mixture in a very wide range between 10 ppm to 4 vol% at room temperature. The influence of Pd nanoparticle diameter to H2 sensing is also evaluated
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Energy Storage in Niobium(V) Oxide Nanostructures: Fabrication, Conductivity and Degradation
No full textEnergy storage has been the biggest obstacle in the widespread adoption of renewable energy resources. The work presented in this thesis is aimed at developing and understanding the behavior of Niobium Pentoxide (Nb2O5) electrochemical energy storage devices. Nb2O5 is a Li+ intercalation metal oxide that is of current interest for lithium ion battery electrodes. In the first part of this thesis, electrophoretic deposition (ED) of Nb2O5 thin- films from aqueous NbOx colloidal solutions is described, which exhibits unusually high specific capacities for Li+ -based energy storage as a consequence of 70% porosity. The excellent energy storage metrics are attributed to augmentation of the faradaic capacity by high double-layer capacities enabled by the mesoporous structure of these films. In the second part of this thesis, the effect of Li+ intercalation on the conductivity of Nb2O5 has been explored. The electrical conductivity, σ, of battery and capacitor electrode materials is a factor determining the energy storage performance of these materials, but it is difficult to directly measure in-situ particularly for electrodeposited materials. Our approach exploits an array of nanoribbon of Nb2O5, fabricated using lithographically patterned nanoribbon electrodeposition (LPNE). σ of Nb2O5 nanoribbons is measured in-situ in a battery electrolyte as a function of the equilibrium potential and, separately, during repetitive lithiation/delithiation cycling. σ in the non-lithiated Nb2O5 is characteristic of semiconducting metal oxides, but it increases dramatically with lithiation. The last part of the thesis is aimed at uncovering the mechanism of capacity upon repetitive cycling for Nb2O5 based energy storage devices. Microscopy, spectroscopy and electrochemical characterization tools have been employed to gain insight into the electronic, structural, compositional and morphological evolution of Nb2O5 thin films as it undergoes thousands of cycles of charge-discharge. Overall, the work in this thesis elucidates a strategy towards fabrication of energy storage devices from materials that are difficult to electrodeposit using conventional redox reactions. Furthermore, it illustrates an approach to combine electrochemical and microscopy-based methods, to gain insights into the interactions between Li+ ions and the active material, during repetitive charge discharge cycling
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