Author
David B. Holt
Bio: David B. Holt is an academic researcher from United States Naval Research Laboratory. The author has contributed to research in topics: Molecular electronics & Molecular wire. The author has an hindex of 9, co-authored 9 publications receiving 879 citations.
Papers
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TL;DR: It is demonstrated that oligo(phenylene ethynylene), a conjugated organic molecule, acts like a molecular wire under symmetric contact conditions, but exhibits characteristics of a molecular diode when the connections are asymmetric.
Abstract: Charge transport studies across molecular length scales under symmetric and asymmetric metal-molecule contact conditions using a simple crossed-wire tunnel junction technique are presented. It is demonstrated that oligo(phenylene ethynylene), a conjugated organic molecule, acts like a molecular wire under symmetric contact conditions, but exhibits characteristics of a molecular diode when the connections are asymmetric. To understand this behavior, we have calculated current-voltage (I-V) characteristics using extended Huckel theory coupled with a Green's function approach. The experimentally observed I-V characteristics are in excellent qualitative agreement with the theory.
353 citations
TL;DR: Junction conductance as a function of molecular structure is consistent with I-V characteristics calculated from extended Hückel theory coupled with a Green's function approach, and can be understood on the basis of bond-length alternation.
Abstract: Current-voltage (I-V) characteristics for metal-molecule-metal junctions formed from three classes of molecules measured with a simple crossed-wire molecular electronics test-bed are reported. Junction conductance as a function of molecular structure is consistent with I-V characteristics calculated from extended Huckel theory coupled with a Green's function approach, and can be understood on the basis of bond-length alternation.
290 citations
TL;DR: Optical and x-ray scattering studies of a chiral, organosiloxane smectic-A liquid crystal indicate a large field induced optical tilt of up to 31 degrees accompanied by a very small contraction of thesmectic layers, suggesting that the molecules have a nonzero tilt even with no applied field.
Abstract: Optical and x-ray scattering studies of a chiral, organosiloxane smectic-A liquid crystal indicate a large field induced optical tilt of up to 31 degrees accompanied by a very small contraction of the smectic layers. This result suggests that the molecules have a nonzero tilt even with no applied field, and that the primary effect of the field is to induce long range order in the direction of the molecular tilt.
87 citations
TL;DR: An experimentally simple crossed‐wire tunnel junction is used to interrogate how factors such as metal‐molecule coupling, molecular structure, and the choice of metal electrode influence the current‐voltage characteristics of a molecular junction.
Abstract: For molecular electronics to become a viable technology the factors that control charge transport across a metal-molecule-metal junction need to be elucidated. We use an experimentally simple crossed-wire tunnel junction to interrogate how factors such as metal-molecule coupling, molecular structure, and the choice of metal electrode influence the current-voltage characteristics of a molecular junction.
50 citations
TL;DR: A method for fabricating capillary-based immunosensors in a coupon milled from an inexpensive, commodity plastic (PMMA, plexiglass) is demonstrated and the key feature of the technique is the use of sol-gel technology to deposit a glass-like film on surfaces of the plastic capillary channels to facilitate antibody immobilization.
42 citations
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7,711 citations
TL;DR: Molecular conductance junctions are structures in which single molecules or small groups of molecules conduct electrical current between two electrodes and there is still limited correspondence between experimental and theoretical studies of these systems.
Abstract: Molecular conductance junctions are structures in which single molecules or small groups of molecules conduct electrical current between two electrodes. In such junctions, the connection between the molecule and the electrodes greatly affects the current-voltage characteristics. Despite several experimental and theoretical advances, including the understanding of simple systems, there is still limited correspondence between experimental and theoretical studies of these systems.
2,195 citations
TL;DR: The nature of the molecule-gold interface, whose chemistry and structure remain elusive, the self-assembly process on planar and irregular surfaces, and on nanometre-sized objects, and the chemical reactivity and thermal stability of these systems in ambient and aqueous solutions are reviewed.
Abstract: Self-assembled monolayers (SAMs) of alkanethiols and dialkanethiols on gold are key elements for building many systems and devices with applications in the wide field of nanotechnology. Despite the progress made in the knowledge of these fascinating two-dimensional molecular systems, there are still several “hot topics” that deserve special attention in order to understand and to control their physical and chemistry properties at the molecular level. This critical review focuses on some of these topics, including the nature of the molecule–gold interface, whose chemistry and structure remain elusive, the self-assembly process on planar and irregular surfaces, and on nanometre-sized objects, and the chemical reactivity and thermal stability of these systems in ambient and aqueous solutions, an issue which seriously limits their technological applications (375 references).
1,177 citations
TL;DR: The role of polymers as gas sensors, pH sensors, ion-selective sensors, humidity sensors, biosensor devices, etc., are reviewed and discussed in this article, and current trends in sensor research and also challenges in future sensor research are discussed.
1,126 citations
TL;DR: This Review covers the major advances with the most general applicability and emphasizes new insights into the development of efficient platform methodologies for building reliable molecular electronic devices with desired functionalities through the combination of programmed bottom-up self-assembly and sophisticated top-down device fabrication.
Abstract: Creating functional electrical circuits using individual or ensemble molecules, often termed as “molecular-scale electronics”, not only meets the increasing technical demands of the miniaturization of traditional Si-based electronic devices, but also provides an ideal window of exploring the intrinsic properties of materials at the molecular level. This Review covers the major advances with the most general applicability and emphasizes new insights into the development of efficient platform methodologies for building reliable molecular electronic devices with desired functionalities through the combination of programmed bottom-up self-assembly and sophisticated top-down device fabrication. First, we summarize a number of different approaches of forming molecular-scale junctions and discuss various experimental techniques for examining these nanoscale circuits in details. We then give a full introduction of characterization techniques and theoretical simulations for molecular electronics. Third, we highlig...
949 citations