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Akhtar A, Rashid U, Seth C, Kumar S, Broekmann P, Kaliginedi V. Modulating the charge transport in metal│molecule│metal junctions via electrochemical gating. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2021.138540] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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2
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Ai Y, Smida H, Ghilane J, Vilà N, Ghanbaja J, Walcarius A, Lacroix JC. Copper Nanowires through Oriented Mesoporous Silica: A Step towards Protected and Parallel Atomic Switches. Sci Rep 2017; 7:17752. [PMID: 29259182 PMCID: PMC5736686 DOI: 10.1038/s41598-017-17048-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 11/19/2017] [Indexed: 11/24/2022] Open
Abstract
The formation of copper atomic contacts has been investigated. Copper nanowires were grown by electrochemical deposition, in the scanning electrochemical microscopy (SECM) configuration, from a platinum microelectrode to an indium tin oxide (ITO) substrate. Self-termination leaves copper filaments between the two electrodes with an atomic point contact at the ITO electrode. Histogram analysis shows that the conductance of this contact is close to, or less than, 1 G0. Atomic contacts were also fabricated on ITO electrodes covered with vertically-aligned mesoporous silica films. Scanning Transmission Electron Microscopy images show that copper filaments occupy individual isolated nanopores. Contacts generated on bare ITO break down rapidly in sodium salicylate, whereas those generated in ITO/nanopores are unaffected; the nanopores protect the copper filaments. Finally, atomic switch behaviour was obtained using these ITO and ITO/nanopores electrodes.
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Affiliation(s)
- Yong Ai
- Université Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR 7086 CNRS, 15 rue Jean-Antoine de Baïf, F-75205, Paris, Cedex 13, France
| | - Hassiba Smida
- Université Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR 7086 CNRS, 15 rue Jean-Antoine de Baïf, F-75205, Paris, Cedex 13, France
| | - Jalal Ghilane
- Université Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR 7086 CNRS, 15 rue Jean-Antoine de Baïf, F-75205, Paris, Cedex 13, France.
| | - Neus Vilà
- Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564 CNRS and Université de Lorraine, 405 rue de Vandoeuvre, F-54600, Villers-lès-Nancy, France
| | - Jaafar Ghanbaja
- Institut Jean Lamour, UMR 7198 CNRS, Université de Lorraine, Parc de Saurupt, CS 50840, F-54011, Nancy, France
| | - Alain Walcarius
- Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564 CNRS and Université de Lorraine, 405 rue de Vandoeuvre, F-54600, Villers-lès-Nancy, France
| | - Jean Christophe Lacroix
- Université Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR 7086 CNRS, 15 rue Jean-Antoine de Baïf, F-75205, Paris, Cedex 13, France.
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3
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Hwang TW, Bohn PW. Potential-dependent restructuring and chemical noise at Au-Ag-Au atomic scale junctions. ACS NANO 2014; 8:1718-1727. [PMID: 24417308 DOI: 10.1021/nn406098u] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The effect of electrochemical potential on the behavior of electrochemically deposited Au-Ag-Au bimetallic atomic scale junctions (ASJs) is addressed here. A common strategy for ASJ production begins with overgrown nanojunctions and uses electromigration to back-thin the junction. Here, these steps are carried out with the entire junction under electrochemical potential control, and the relationship between junction stability and applied potential is characterized. The control of electrochemical potential provides a reliable method of regulating the size of nanojunctions. In general, more anodic potentials decrease junction stability and increase the rate at which conductance decays. Conductance behavior under these labile conditions is principally determined by Ag oxidation potential, electrochemical potential-induced surface stress, and the nature of the adsorbate. Junctions fabricated at more cathodic potentials experience only slight changes in conductance, likely due to surface atom diffusion and stress-induced structural rearrangement. Electrochemical potential also plays a significant role in determining adsorption-desorption kinetics of surface pyridine at steady state at Au-Ag-Au ASJs, as revealed through fluctuation spectroscopy. Average cutoff frequencies increase at more anodic potentials, as does the width of the cutoff frequency distribution measured over 80 independent runs. Three reversible reactions--pyridine adsorption, Ag atom desorption, and Ag-pyridine complex dissolution--can occur on the surface, and the combination of the three can explain the observed results.
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Affiliation(s)
- Tai-Wei Hwang
- Department of Chemical and Biomolecular Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States
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4
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Kundu P, Turner S, Van Aert S, Ravishankar N, Van Tendeloo G. Atomic structure of quantum gold nanowires: quantification of the lattice strain. ACS NANO 2014; 8:599-606. [PMID: 24289167 DOI: 10.1021/nn4052315] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Theoretical studies exist to compute the atomic arrangement in gold nanowires and the influence on their electronic behavior with decreasing diameter. Experimental studies, e.g., by transmission electron microscopy, on chemically synthesized ultrafine wires are however lacking owing to the unavailability of suitable protocols for sample preparation and the stability of the wires under electron beam irradiation. In this work, we present an atomic scale structural investigation on quantum single crystalline gold nanowires of 2 nm diameter, chemically prepared on a carbon film grid. Using low dose aberration-corrected high resolution (S)TEM, we observe an inhomogeneous strain distribution in the crystal, largely concentrated at the twin boundaries and the surface along with the presence of facets and surface steps leading to a noncircular cross section of the wires. These structural aspects are critical inputs needed to determine their unique electronic character and their potential as a suitable catalyst material. Furthermore, electron-beam-induced structural changes at the atomic scale, having implications on their mechanical behavior and their suitability as interconnects, are discussed.
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Affiliation(s)
- Paromita Kundu
- Electron Microscopy for Materials Science (EMAT), University of Antwerp , Groenenborgerlaan 171, 2020 Antwerp, Belgium
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MacKenzie R, Fraschina C, Dielacher B, Sannomiya T, Dahlin AB, Vörös J. Simultaneous electrical and plasmonic monitoring of potential induced ion adsorption on metal nanowire arrays. NANOSCALE 2013; 5:4966-4975. [PMID: 23632884 DOI: 10.1039/c3nr34172k] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Simultaneous LSPR and electronic sensing of potential induced ion adsorption onto gold nanowire arrays is presented. The formation of a Stern layer upon applying an electrochemical potential generated a complex optical response. Simulation of a lossy atomic layer on the nanowire array using the Multiple Multipole Program (MMP) corresponded very well to the experimentally observed peak position, intensity, and radius of curvature changes. Additionally, a significant voltage-dependent change in the resistance of the gold nanowire array was observed during the controlled formation of the electrical double layer. The results demonstrated that an applied electrochemical potential induces measurable changes in the optical and electrical properties of the gold nanowire surface. This is the first demonstration of combined plasmonic and nanowire resistance-based sensing of a surface process in the literature.
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Affiliation(s)
- Robert MacKenzie
- ETH Zurich, Institute for Biomedical Engineering, Zurich, Switzerland
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6
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Hwang TW, Branagan SP, Bohn PW. Chemical Noise Produced by Equilibrium Adsorption/Desorption of Surface Pyridine at Au–Ag–Au Bimetallic Atom-Scale Junctions Studied by Fluctuation Spectroscopy. J Am Chem Soc 2013; 135:4522-8. [DOI: 10.1021/ja400567j] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tai-Wei Hwang
- Department
of Chemical and Biomolecular Engineering and ‡Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame,
Indiana 46556, United States
| | - Sean P. Branagan
- Department
of Chemical and Biomolecular Engineering and ‡Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame,
Indiana 46556, United States
| | - Paul W. Bohn
- Department
of Chemical and Biomolecular Engineering and ‡Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame,
Indiana 46556, United States
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7
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Scanning electrochemical microscopy for the fabrication of copper nanowires: Atomic contacts with quantized conductance, and molecular adsorption effect. Electrochim Acta 2012. [DOI: 10.1016/j.electacta.2012.07.115] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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8
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Dong X, Liu J, Zhang B, Xia Y. Surface structural analysis of electrochemically fabricated Ag quantum wire by its interactions with NH3 molecules in an aqueous environment. Electrochim Acta 2012. [DOI: 10.1016/j.electacta.2012.03.159] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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9
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Yang F, Donavan KC, Kung SC, Penner RM. The surface scattering-based detection of hydrogen in air using a platinum nanowire. NANO LETTERS 2012; 12:2924-30. [PMID: 22524464 DOI: 10.1021/nl300602m] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The performance of a single platinum (Pt) nanowire for detecting H(2) in air is reported. A Pt nanowire shows no resistance change upon exposure to H(2) in N(2), but H(2) exposure in air causes a reversible resistance decrease for H(2) concentrations above 10 ppm. The amplitude of the resistance change induced by H(2) exposure and the time rate of change of the nanowire resistance both increased with increasing temperature from 298 to 550 K. This resistance decrease of the Pt nanowire in the presence of H(2) results from reduced electron diffuse scattering at hydrogen-covered Pt surfaces as compared with oxygen-covered platinum surfaces, we hypothesize. The properties for the detection of H(2) in air of single Pt and Pd nanowires of similar size are compared in this study. Pt nanowires have a limit-of-detection for H(2) (LOD(H(2))) of 10 ppm; 3 orders of magnitude lower than for Pd nanowires of the same size, as well as a response time that is 1/100th of Pd for [H(2)] ≈ 1%.
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Affiliation(s)
- Fan Yang
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
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10
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Xing W, Hu J, Kung SC, Donavan KC, Yan W, Wu R, Penner RM. A chemically-responsive nanojunction within a silver nanowire. NANO LETTERS 2012; 12:1729-1735. [PMID: 22360286 DOI: 10.1021/nl300427w] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The formation of a nanometer-scale chemically responsive junction (CRJ) within a silver nanowire is described. A silver nanowire was first prepared on glass using the lithographically patterned nanowire electrodeposition method. A 1-5 nm gap was formed in this wire by electromigration. Finally, this gap was reconnected by applying a voltage ramp to the nanowire resulting in the formation of a resistive, ohmic CRJ. Exposure of this CRJ-containing nanowire to ammonia (NH(3)) induced a rapid (<30 s) and reversible resistance change that was as large as ΔR/R(0) = (+)138% in 7% NH(3) and observable down to 500 ppm NH(3). Exposure to water vapor produced a weaker resistance increase of ΔR/R(0,H(2)O) = (+)10-15% (for 2.3% water) while nitrogen dioxide (NO(2)) exposure induced a stronger concentration-normalized resistance decrease of ΔR/R(0,NO(2)) = (-)10-15% (for 500 ppm NO(2)). The proposed mechanism of the resistance response for a CRJ, supported by temperature-dependent measurements of the conductivity for CRJs and density functional theory calculations, is that semiconducting p-type Ag(x)O is formed within the CRJ and the binding of molecules to this Ag(x)O modulates its electrical resistance.
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Affiliation(s)
- Wendong Xing
- Department of Chemistry, University of California, Irvine, California 92697-2025, USA
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11
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Abstract
This paper reviews our work on the development of microwave carbon nanotube resonator sensors for gas detection. The sensor consists of a radio frequency resonator coated with a layer of carbon nanotubes. Upon exposure to gasses, the resonant frequency of the sensor shifts to indicate the presence of gasses. Our experimental results demonstrate that the microwave carbon nanotube resonator sensor achieves a sensitivity of 4000 Hz/ppm upon exposure to ammonia and the resonant frequency is recovered when ammonia is evacuated. The sensing mechanism is dependent on electron transfer from the ammonia to the nanotubes. This sensor platform has great potential for wireless sensing network applications.
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Affiliation(s)
- M. P. McGRATH
- Microwave Microsystems Laboratory, Dept. of Electrical and Computer Engineering, University of California at Davis, Davis, CA, USA
| | - A. PHAM
- Microwave Microsystems Laboratory, Dept. of Electrical and Computer Engineering, University of California at Davis, Davis, CA, USA
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12
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Hwang TW, Bohn PW. Robust Au-Ag-Au bimetallic atom-scale junctions fabricated by self-limited Ag electrodeposition at Au nanogaps. ACS NANO 2011; 5:8434-8441. [PMID: 21928783 DOI: 10.1021/nn203404k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Atom-scale junctions (ASJs) exhibit quantum conductance behavior and have potential both for fundamental studies of adsorbate-mediated conductance in mesoscopic conductors and as chemical sensors. Electrochemically fabricated ASJs, in particular, show the stability needed for molecular detection applications. However, achieving physically robust ASJs at high yield is a challenge because it is difficult to control the direction and kinetics of metal deposition. In this work, a novel electrochemical approach is reported, in which Au-Ag-Au bimetallic ASJs are reproducibly fabricated from an initially prepared Au nanogap by sequential overgrowth and self-limited thinning. Applying a potential across specially prepared Au nanoelectrodes in the presence of aqueous Ag(I) leads to preferential galvanic reactions resulting in the deposition of Ag and the formation of an atom-scale junction between the electrodes. An external resistor is added in series with the ASJ to control self-termination, and adjusting solution chemical potential (concentration) is used to mediate self-thinning of junctions. The result is long-lived, mechanically stable ASJs that, unlike previous constructions, are stable in flowing solution, as well as to changes in solution media. These bimetallic ASJs exhibit a number of behaviors characteristic of quantum structures, including long-lived fractional conductance states, that are interpreted to arise from two or more quantized ASJs in series.
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Affiliation(s)
- Tai-Wei Hwang
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
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13
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Duan BK, Zhang J, Bohn PW. Conductance-Based Chemical Sensing in Metallic Nanowires and Metal-Semiconductor Nanostructures. Anal Chem 2011; 84:2-8. [DOI: 10.1021/ac201240w] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Barrett K. Duan
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Jingying Zhang
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Paul W. Bohn
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
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14
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Soldano G, Santos E, Schmickler W. Intrinsic stability and hydrogen affinity of pure and bimetallic nanowires. J Chem Phys 2011; 134:174106. [PMID: 21548672 DOI: 10.1063/1.3585956] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A density functional theory study of the intrinsic stability of pure and bimetallic wires is presented. Several bimetallic combinations forming one-atom thick wires are studied. An explanation for the experimental instability of Cu wires in contrast to the stability of Au and Ag wires is given, which relies on the higher surface energy of the former. All the possible intercalations between Ni, Pd, Pt, Cu, Ag, and Au are studied. The bimetallic wires AuCu and AuAg were found to be the most stable ones. The reactivity of the latter two systems is also examined using hydrogen adsorption as a microscopic probe. It was found that at the inter-metal interface, up to second neighbors, Cu and Ag become more reactive and Au becomes more inert than the corresponding pure wires. These results are explained within the d-band model.
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Affiliation(s)
- G Soldano
- Institute of Theoretical Chemistry, Ulm University, Ulm, Germany.
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15
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Shi P, Zhang J, Lin HY, Bohn PW. Effect of molecular adsorption on the electrical conductance of single au nanowires fabricated by electron-beam lithography and focused ion beam etching. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2010; 6:2598-603. [PMID: 20957763 DOI: 10.1002/smll.201001295] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Metal nanowires are one of the potential candidates for nanostructured sensing elements used in future portable devices for chemical detection; however, the optimal methods for fabrication have yet to be fully explored. Two routes to nanowire fabrication, electron-beam lithography (EBL) and focused ion beam (FIB) etching, are studied, and their electrical and chemical sensing properties are compared. Although nanowires fabricated by both techniques exhibit ohmic conductance, I-V characterization indicates that nanowires fabricated by FIB etching exhibit abnormally high resistivity. In addition, the resistivity of nanowires fabricated by FIB etching shows very low sensitivity toward molecular adsorption, while those fabricated by EBL exhibit sensitive resistance change upon exposure to solution-phase adsorbates. The mean grain sizes of nanowires prepared by FIB etching are much smaller than those fabricated by EBL, so their resistance is dominated by grain-boundary scattering. As a result, these nanowires are much less sensitive to molecular adsorption, which mediates nanowire conduction through surface scattering. The much reduced mean grain sizes of these nanowires correlate with Ga ion damage caused during the ion milling process. Thus, even though the nanowires prepared by FIB etching can be smaller than their EBL counterparts, their reduced sensitivity to adsorption suggests that nanowires produced by EBL are preferred for chemical and biochemical sensing applications.
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Affiliation(s)
- Ping Shi
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
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16
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Dean SL, Stapleton JJ, Keating CD. Organically modified silicas on metal nanowires. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:14861-70. [PMID: 20715881 PMCID: PMC2938830 DOI: 10.1021/la102070c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 07/30/2010] [Indexed: 05/16/2023]
Abstract
Organically modified silica coatings were prepared on metal nanowires using a variety of silicon alkoxides with different functional groups (i.e., carboxyl groups, polyethylene oxide, cyano, dihydroimidazole, and hexyl linkers). Organically modified silicas were deposited onto the surface of 6-μm-long, ∼300-nm-wide, cylindrical metal nanowires in suspension by the hydrolysis and polycondensation of silicon alkoxides. Syntheses were performed at several ratios of tetraethoxysilane to an organically modified silicon alkoxide to incorporate desired functional groups into thin organosilica shells on the nanowires. These coatings were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. All of the organically modified silicas prepared here were sufficiently porous to allow the removal of the metal nanowire cores by acid etching to form organically modified silica nanotubes. Additional functionality provided to the modified silicas as compared to unmodified silica prepared using only tetraethoxysilane precursors was demonstrated by chromate adsorption on imidazole-containing silicas and resistance to protein adsorption on polyethyleneoxide-containing silicas. Organically modified silica coatings on nanowires and other nano- and microparticles have potential application in fields such as biosensing or nanoscale therapeutics due to the enhanced properties of the silica coatings, for example, the prevention of biofouling.
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Ramgir NS, Yang Y, Zacharias M. Nanowire-based sensors. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2010; 6:1705-1722. [PMID: 20712030 DOI: 10.1002/smll.201000972] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Nanowires are important potential candidates for the realization of the next generation of sensors. They offer many advantages such as high surface-to-volume ratios, Debye lengths comparable to the target molecule, minimum power consumption, and they can be relatively easily incorporated into microelectronic devices. Accordingly, there has been an intensified search for novel nanowire materials and corresponding platforms for realizing single-molecule detection with superior sensing performance. In this work, progress made towards the use of nanowires for achieving better sensing performance is critically reviewed. In particular, various nanowires types (metallic, semiconducting, and insulating) and their employment either as a sensor material or as a template material are discussed. Major obstacles and future steps towards the ultimate nanosensors based on nanowires are addressed.
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Affiliation(s)
- Niranjan S Ramgir
- Nanotechnology Institute of Microsystems Engineering (IMTEK) Georges-Köhler-Allee 103 Freiburg, D 79110, Germany
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18
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Shi P, Bohn PW. Electrochemical control of stability and restructuring dynamics in Au-Ag-Au and Au-Cu-Au bimetallic atom-scale junctions. ACS NANO 2010; 4:2946-2954. [PMID: 20394406 DOI: 10.1021/nn1003716] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Metallic atom-scale junctions (ASJs) are interesting fundamentally because they support ballistic transport, characterized by conduction quantized in units of G(0) = 2e(2)/h. They are also of potential practical interest since ASJ conductance is extraordinarily sensitive to molecular adsorption. Monometallic Au ASJs were previously fabricated electrochemically using an I(-)/I(3)(-) medium and a unique open working electrode configuration to produce slow electrodeposition or electrodissolution, resulting in reproducible ASJs with limiting conductance <5 G(0). Here, bimetallic Au-Cu-Au and Au-Ag-Au ASJ structures are obtained by electrochemical deposition/dissolution of Cu and Ag in K(2)SO(4) supporting electrolyte. The ASJs are fabricated in Si(3)N(4)-protected Au nanogaps obtained by focused ion beam milling, a protocol which yields repeatable and reproducible Au-Cu-Au or Au-Ag-Au ASJs without damaging the Au nanogap substrates. While Au-Ag-Au ASJs are relatively stable (hours) at open circuit potential in the supporting electrolyte, Au-Cu-Au ASJs exhibit spontaneous restructuring dynamics, characterized by monotonic, stepwise decreases in conductance under the same conditions. However, the Au-Cu-Au ASJs can be stabilized by applying sufficiently negative potentials. Hydrogen adsorption and shifts in the Fermi level are possible reasons for the enhanced stability of Au-Cu-Au structures at large negative overpotentials. In light of these observations, it is possible to integrate ASJs in microfluidic devices as renewable, nanostructured sensing elements for chemical detection.
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Affiliation(s)
- Ping Shi
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA
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19
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Jiang DE, Nobusada K, Luo W, Whetten RL. Thiolated gold nanowires: metallic versus semiconducting. ACS NANO 2009; 3:2351-2357. [PMID: 19603760 DOI: 10.1021/nn900498c] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Tremendous research efforts have been spent on thiolated gold nanoparticles and self-assembled monolayers of thiolate (RS-) on gold, but thiolated gold nanowires have received almost no attention. Here we computationally design two such one-dimensional nanosystems by creating a linear chain of Au icosahedra, fused together by either vertex sharing or face sharing. Then neighboring Au icosahedra are bridged by five thiolate groups for the vertex-sharing model and three RS-Au-SR motifs for the face-sharing model. We show that the vertex-sharing thiolated gold nanowire can be made either semiconducting or metallic by tuning the charge, while the face-sharing one is always metallic. We explain this difference between the two nanowires by examining their band structures and invoking a previously proposed electron-count rule. Implications of our findings for previous experimentation of gold nanowires are discussed, and a potential way to make thiolated gold nanowires is proposed.
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Affiliation(s)
- De-en Jiang
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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20
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Daneshgar P, Norouzi P, Moosavi-Movahedi AA, Ganjali MR, Haghshenas E, Dousty F, Farhadi M. Fabrication of carbon nanotube and dysprosium nanowire modified electrodes as a sensor for determination of curcumin. J APPL ELECTROCHEM 2009. [DOI: 10.1007/s10800-009-9908-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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21
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Bohn PW. Nanoscale control and manipulation of molecular transport in chemical analysis. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2009; 2:279-296. [PMID: 20636063 DOI: 10.1146/annurev-anchem-060908-155130] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The ability to understand and control molecular transport is critical to numerous chemical measurement strategies, especially as they apply to mass-limited samples in nanometer-scale structures. The characteristics of nanoscale structures and devices highlighted in the examples discussed in this article include enhanced mass transport, accessing novel physical behavior, large surface-to-volume ratio, diminished background signals, and the fact that molecular characteristics can dominate the behavior of the structure. The control of nanoscale transport is physically embodied in different structures and experiments. Those structures and experiments highlighted here are featured because of their centrality (nanochannels and nanopores), their connection to more familiar macroscale phenomena (nanoelectrodes), and/or their ability to introduce control (stimulus-responsive materials) or because they represent especially interesting possibilities (stochastic sensing structures).
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Affiliation(s)
- Paul W Bohn
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.
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22
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Shi P, Bohn PW. Stable atom-scale junctions on silicon fabricated by kinetically controlled electrochemical deposition and dissolution. ACS NANO 2008; 2:1581-1588. [PMID: 19206360 DOI: 10.1021/nn8002955] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Metallic atom-scale junctions (ASJs) constitute the natural limit of nanowires, in which the limiting region of conduction is only a few atoms wide. They are of interest because they exhibit ballistic conduction and their conductance is extraordinarily sensitive to molecular adsorption. However, identifying robust and regenerable mechanisms for their production is a challenge. Gold ASJs have been fabricated electrochemically on silicon using an iodide-containing medium to control the kinetics. Extremely slow electrodeposition or electrodissolution rates were achieved and used to reliably produce ASJs with limiting conductance <5 G(0). Starting from a photolithographically fabricated, Si(3)N(4)-protected micrometer-scale Au bridge between two contact electrodes, a nanometer-scale gap was prepared by focused ion beam milling. The opposing Au faces of this construct were then used in an open-circuit working electrode configuration to produce Au ASJs, either directly or by first overgrowing a thicker Au nanowire and electrothinning it back to an ASJ. Gold ASJs produced by either approach exhibit good stabilityin some cases being stable over hours at 300 Kand quantized conductance properties. The influence of deposition/dissolution potential and supporting electrolyte on the stability of ASJs are considered.
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Affiliation(s)
- Ping Shi
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA
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Frank S, Hartnig C, Gross A, Schmickler W. Spiral adsorbate structures on monoatomic nanowire electrodes. Chemphyschem 2008; 9:1371-4. [PMID: 18551694 DOI: 10.1002/cphc.200700822] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Stefan Frank
- Zentrum für Sonnenenergie- und Wasserstoff-Forschung, Baden-Württemberg 89081 Ulm, Germany
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24
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Allen M, Sabio EM, Qi X, Nwengela B, Islam MS, Osterloh FE. Metallic LiMo3Se3 nanowire film sensors for electrical detection of metal ions in water. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:7031-7. [PMID: 18507421 DOI: 10.1021/la8004085] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
LiMo 3Se 3 nanowire film sensors were fabricated by drop-coating a 0.05% (mass) aqueous nanowire solution onto microfabricated indium tin oxide electrode pairs. According to scanning electron microscopy (SEM) and atomic force microscopy (AFM), the films are made of a dense network of 3-7 nm thick nanowire bundles. Immersion of the films in 1.0 M aqueous solutions of group 1 or 2 element halides or of Zn(II), Mn(II), Fe(II), or Co(II) chlorides results in an increase of the electrical resistance of the films. The resistance change is always positive and reaches up to 9% of the base resistance of the films. It occurs over the course of 30-240 s, and it is reversible for monovalent ions and partially reversible for divalent ions. The signal depends on the concentration of the electrolyte and on the size and charge of the metal cation. Anions do not play a significant role, presumably, because they are repelled by the negatively charged nanowire strands. The magnitude of the electrical response and its sign suggest that it is due to analyte-induced scattering of conduction electrons in the nanowires. An ion-induced field effect can be excluded based on gated conductance measurements of the nanowire films.
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Affiliation(s)
- Mark Allen
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
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25
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Lin HY, Chen HA, Lin HN. Fabrication of a Single Metal Nanowire Connected with Dissimilar Metal Electrodes and Its Application to Chemical Sensing. Anal Chem 2008; 80:1937-41. [DOI: 10.1021/ac701911j] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hsin-Yu Lin
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Hsiang-An Chen
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Heh-Nan Lin
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
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26
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Lou P, Lee JY. An atomistic model and key parameters for devising single molecular nanowire sensors. Phys Chem Chem Phys 2008; 10:828-33. [DOI: 10.1039/b714307a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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27
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Dong X, Xia Y, Zhu G, Zhang B. Molecular sensing with the tunnel junction of an Au nanogap in solution. NANOTECHNOLOGY 2007; 18:395502. [PMID: 21730417 DOI: 10.1088/0957-4484/18/39/395502] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The tunnel junction of a gold nanogap was fabricated electrochemically for a molecular sensing device in solution. The tunnel junction was sensitive enough to detect the variation of a potential barrier within the nanogap, such as the chemical adsorption of molecules. By monitoring the variation of the tunneling current, which represents the change of a potential barrier due to molecular adsorption, the molecules could be detected.
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Affiliation(s)
- Xiaodong Dong
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Graduate University of the Chinese Academy of Sciences, Changchun, Jilin 130022, People's Republic of China
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28
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Cross CE, Hemminger JC, Penner RM. Physical vapor deposition of one-dimensional nanoparticle arrays on graphite: seeding the electrodeposition of gold nanowires. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:10372-9. [PMID: 17715955 DOI: 10.1021/la7016209] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
One-dimensional (1D) ensembles of 2-15 nm diameter gold nanoparticles were prepared using physical vapor deposition (PVD) on highly oriented pyrolytic graphite (HOPG) basal plane surfaces. These 1D Au nanoparticle ensembles (NPEs) were prepared by depositing gold (0.2-0.6 nm/s) at an equivalent thickness of 3-4 nm onto HOPG surfaces at 670-690 K. Under these conditions, vapor-deposited gold nucleated selectively at the linear step edge defects present on these HOPG surfaces with virtually no nucleation of gold particles on terraces. The number density of 2-15 nm diameter gold particles at step edges was 30-40 microm-1. These 1D NPEs were up to a millimeter in length and organized into parallel arrays on the HOPG surface, following the organization of step edges. Surprisingly, the deposition of more gold by PVD did not lead to the formation of continuous gold nanowires at step edges under the range of sample temperature or deposition flux we have investigated. Instead, these 1D Au NPEs were used as nucleation templates for the preparation by electrodeposition of gold nanowires. The electrodeposition of gold occurred selectively on PVD gold nanoparticles over the potential range from 700-640 mV vs SCE, and after optimization of the electrodeposition parameters continuous gold nanowires as small as 80-90 nm in diameter and several micrometers in length were obtained.
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Affiliation(s)
- C E Cross
- Department of Chemistry and Institute for Surface and Interface Science, University of California, Irvine, California 92697-2025, USA
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29
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Mieszawska AJ, Jalilian R, Sumanasekera GU, Zamborini FP. The synthesis and fabrication of one-dimensional nanoscale heterojunctions. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2007; 3:722-56. [PMID: 17444570 DOI: 10.1002/smll.200600727] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
There are a variety of methods for synthesizing or fabricating one-dimensional (1D) nanostructures containing heterojunctions between different materials. Here we review recent developments in the synthesis and fabrication of heterojunctions formed between different materials within the same 1D nanostructure or between different 1D nanostructures composed of different materials. Structures containing 1D nanoscale heterojunctions exhibit interesting chemistry as well as size, shape, and material-dependent properties that are unique when compared to single-component materials. This leads to new or enhanced properties or multifunctionality useful for a variety of applications in electronics, photonics, catalysis, and sensing, for example. This review separates the methods into vapor-phase synthesis, solution-phase synthesis, template-based synthesis, and other approaches, such as lithography, electrospinning, and assembly. These methods are used to form a variety of heterojunctions, including segmented, core/shell, branched, or crossed, from different combinations of semiconductor, metal, carbon, and polymeric materials.
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Affiliation(s)
- Aneta J Mieszawska
- Department of Chemistry, University of Louisville, Louisville, KY 40292, USA
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30
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Kwapiński T. Conductance oscillations of a quantum wire disturbed by an adatom. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:176218. [PMID: 21690963 DOI: 10.1088/0953-8984/19/17/176218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The conductance through a quantum wire with a side-attached atom (adatom) is investigated using the tight-binding Hamiltonian and Green function method. The adatom can be coupled with one or more atoms and it disturbs the electron transport through the wire. Analytical formulae for the transmittance are obtained for the most probable connections. Also, conductance oscillations as a function of the wire length are studied for a disturbed wire. It is shown that the period of these oscillations remains unchanged in the presence of the adatom but the value of the conductance strongly depends on the adatom-wire couplings and the kind of connections of the adatom to the wire.
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Affiliation(s)
- T Kwapiński
- Institute of Physics, M Curie-Skłodowska University, 20-031 Lublin, Poland
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Qi X, Osterloh FE, Giacomo JA, Chiang S. Effect of additives on LiMo3Se3 nanowire film chemical sensors. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:8253-6. [PMID: 16952270 DOI: 10.1021/la0614278] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Here we investigate the effect of lithium iodide and cetyltrimethylammonium (CTA) bromide additives on the ability of LiMo(3)Se(3) nanowire film sensors to bind and detect organic solvents electrically. Both additives decrease the electrical conductivity of the films. Lithium iodide increases the response of the films to both polar and nonpolar analytes. CTA increases the response of the films to nonpolar analytes but reduces the response to polar analytes. Quartz crystal microbalance measurements show that the modified electrical sensitivities of the films are due to altered analyte adsorption abilities of the films. These results show that the Li(+) ions are involved in analyte binding in native LiMo(3)Se(3) films and that a programming of LiMo(3)Se(3) nanowire film sensors is possible by replacing lithium cations with other receptors.
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Affiliation(s)
- Xiubin Qi
- Departments of Chemistry and Physics, University of California, 1 Shields Avenue, Davis, California 95616, USA
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32
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Qi X, Osterloh FE, Barriga SA, Giacomo JA, Chiang S. Molecular Adsorption to LiMo3Se3 Nanowire Film Chemiresistors. Anal Chem 2005; 78:1306-11. [PMID: 16478126 DOI: 10.1021/ac051701n] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Thin films of metallic nanowire bundles derived from the Chevrel compound LiMo3Se3 undergo reversible increases of their electrical resistance (up to 70%) upon exposure to vapors of organic solvents (Qi, X. B.; Osterloh, F. E. J. Am. Chem. Soc. 2005, 127 (21), 7666-7667). Using quartz crystal microbalance measurements with four analytes, we demonstrate here that the temporal and steady-state resistance changes of the films depend on the time following the adsorption and on the number of molecules that adsorb to the nanowire films at a given pressure. The adsorption ability of the films and the corresponding film resistance increase in the row: hexane < THF < ethanol < DMSO, closely following the polarities of the solvents. On average, approximately 10(5) analyte molecules per LiMo3Se3 unit are required to produce a measurable electrical response. Atomic force microscopy scans on nanowire films reveal that analytes deposit on top of the nanowire bundles and cause the films to swell by approximately 6% in volume. The temporal and steady-state resistance data of the LiMo3Se3 chemiresistors can be explained by assuming that coating of the nanowire bundles with analyte molecules reduces the interwire charge transport in the films.
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Affiliation(s)
- Xiubin Qi
- Department of Chemistry and Department of Physics, University of California, 1 Shields Avenue, Davis, CA 95616, USA
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33
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Murray BJ, Newberg JT, Walter EC, Li Q, Hemminger JC, Penner RM. Reversible Resistance Modulation in Mesoscopic Silver Wires Induced by Exposure to Amine Vapor. Anal Chem 2005; 77:5205-14. [PMID: 16097760 DOI: 10.1021/ac050636e] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ensembles of silver nanowires (AgNEs) with diameters ranging from 200 nm to 1.0 microm have been prepared by electrochemical step edge decoration. These AgNEs showed a rapid (< 5 s), reversible increase in resistance upon exposure to the vapor of ammonia, trimethylamine, and pyridine. The amplitude of the resistance change was up to +3000% (DeltaR/Ro)-more than 2 orders of magnitude larger than can be explained based on boundary layer scattering effects. We experimentally probe the mechanism for this resistance modulation in the case of ammonia, and we propose a model to describe it. Conductive tip atomic force microscopy was used to probe individual sections of nanowires in AgNEs; these data revealed that the resistance change caused by NH(3) exposure was concentrated within a minority (approximately 10%) of the 5-microm wire segments that were probed--not uniformly distributed along each nanowire. All AgNEs showed a temperature dependence of their resistance, alpha, that was smaller than expected for silver metal. Highly sensitive AgNEs sometimes showed a negative alpha, characteristic of semiconductors, but negative alpha values were never observed for AgNEs with a low sensitivity to NH3. AgNEs did not respond to hydrocarbons, O2, H2O, N2, CO, or Ar, but a large (DeltaR/Ro > |-50%|) irreversible decrease in resistance was seen upon exposures to acids including HCl, HNO3, and H2SO4. Based on these and other data, we propose a model in which oxidized constrictions in silver nanowires limit the conductivity of the wire and provide a means for "gating" conduction based on the protonation state of the oxide surface.
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Affiliation(s)
- B J Murray
- Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
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34
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Davis JJ, Morgan DA, Wrathmell CL, Axford DN, Zhao J, Wang N. Molecular bioelectronics. ACTA ACUST UNITED AC 2005. [DOI: 10.1039/b417712f] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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36
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Ashley K. Developments in electrochemical sensors for occupational and environmental health applications. JOURNAL OF HAZARDOUS MATERIALS 2003; 102:1-12. [PMID: 12963279 DOI: 10.1016/s0304-3894(03)00198-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
This paper provides an overview of recent advances in electrochemical sensors for industrial hygiene monitoring applications. Currently available instrument technologies as well as new devices under development are both exemplified. Progress in ruggedization and miniaturization of electroanalytical devices has led to significant improvements for on-site monitoring applications, e.g. in harsh environments and in biological monitoring. Sensor arrays and modified electrodes offer considerable promise for improved electrochemical sensing, i.e. through multi-species detection and enhanced selectivity. On-site electroanalytical detection and measurement in the field may become more widely used for applications in occupational health monitoring.
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Affiliation(s)
- Kevin Ashley
- US Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Cincinnati, OH 45226-1998, USA.
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37
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The orientation of 2,2′-bipyridine adsorbed at a SERS-active Au(111) electrode surface. J Electroanal Chem (Lausanne) 2003. [DOI: 10.1016/s0022-0728(03)00215-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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38
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Walter EC, Zach MP, Favier F, Murray BJ, Inazu K, Hemminger JC, Penner RM. Metal nanowire arrays by electrodeposition. Chemphyschem 2003; 4:131-8. [PMID: 12619411 DOI: 10.1002/cphc.200390022] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We describe two related methods for preparing arrays of nanowires composed of molybdenum, copper, nickel, gold, and palladium. Nanowires were obtained by selectively electrodepositing either a metal oxide or a metal at the step edges present on the basal plane of highly oriented pyrolytic graphite (HOPG) electrodes. If a metal oxide was electrodeposited, then nanowires of the parent metal were obtained by reduction at elevated temperature in hydrogen. The resulting nanowires were organized in parallel arrays of 100-1000 wires. These nanowires were long (some > 500 microns), polycrystalline, and approximately hemicylindrical in cross-section. The nanowire arrays prepared by electrodeposition were also "portable": After embedding the nanowires in a polymer or cyanoacrylate film, arrays of nanowires could be lifted off the graphite surface thereby facilitating the incorporation of metal nanowire arrays into devices such as sensors.
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Affiliation(s)
- Erich C Walter
- Department of Chemistry, University of California-Irvine, Irvine, CA 92697-2025, USA
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39
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Xu B, He H, Tao NJ. Controlling the conductance of atomically thin metal wires with electrochemical potential. J Am Chem Soc 2002; 124:13568-75. [PMID: 12418912 DOI: 10.1021/ja027810q] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report on the study of quantum transport in atomically thin Au wires suspended between two Au electrodes by modulating the electrochemical potential of the wires in various electrolytes. The potential modulation induces a conductance modulation with a phase shift that is always approximately 180 degrees, meaning that an increase in the potential always causes a decrease in the conductance. The amplitude of the induced conductance modulation, however, depends on several parameters. First, it depends on the atomic configurations of the individual wires. Second, the relative amplitude, defined as the ratio of the conductance modulation amplitude to the conductance, decreases as the diameter of the wire increases. Third, it depends on whether anion adsorption is present. In the absence of anion adsorption, it is approximately 0.55G(0) (G(0) = 2e(2)/h) per V of potential modulation, for a wire with conductance quantized near 1G(0). This double layer charging-induced conductance modulation can be attributed to a change in the effective diameter of the wire. In the presence of anion adsorption, the amplitude is much larger (e.g., approximately 1.6G(0)/V when I(-) adsorption takes place) and correlates well with the strength of the adsorption, which is due to the scattering of conduction electrons by the adsorbed anions.
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Affiliation(s)
- Bingqian Xu
- Department of Electrical Engineering and The Center for Solid State Electronics Research, Arizona State University, Tempe 85287, USA
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40
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He H, Boussaad S, Xu B, Li C, Tao N. Electrochemical fabrication of atomically thin metallic wires and electrodes separated with molecular-scale gaps. J Electroanal Chem (Lausanne) 2002. [DOI: 10.1016/s0022-0728(02)00692-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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41
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Adsorbate effect on the mechanical stability of atomically thin metallic wires. J Electroanal Chem (Lausanne) 2002. [DOI: 10.1016/s0022-0728(01)00714-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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42
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Favier F, Walter EC, Zach MP, Benter T, Penner RM. Hydrogen sensors and switches from electrodeposited palladium mesowire arrays. Science 2001; 293:2227-31. [PMID: 11567132 DOI: 10.1126/science.1063189] [Citation(s) in RCA: 1208] [Impact Index Per Article: 52.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Hydrogen sensors and hydrogen-activated switches were fabricated from arrays of mesoscopic palladium wires. These palladium "mesowire" arrays were prepared by electrodeposition onto graphite surfaces and were transferred onto a cyanoacrylate film. Exposure to hydrogen gas caused a rapid (less than 75 milliseconds) reversible decrease in the resistance of the array that correlated with the hydrogen concentration over a range from 2 to 10%. The sensor response appears to involve the closing of nanoscopic gaps or "break junctions" in wires caused by the dilation of palladium grains undergoing hydrogen absorption. Wire arrays in which all wires possessed nanoscopic gaps reverted to open circuits in the absence of hydrogen gas.
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Affiliation(s)
- F Favier
- UMR 5072 CNRS-Université Montpellier II, 34095 Montpellier, France
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