Molecular Wires from Contorted Aromatic Compounds

Xiao, Shengxiong; Myers, Matthew; Miao, Qian; Sanaur, Sébastien; Pang, Keliang; Steigerwald, Michael L.; Nuckolls, Colin

doi:10.1002/anie.200502142

Cited by 312 publications

(199 citation statements)

References 44 publications

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“…There is a broad tail on the emission and significant red-shifting when the monolayer spectrum is compared with that from solution. This type of shift is a hallmark of aggregation in disk-shaped molecules due to delocalization of the excited state (19).…”

Section: Resultsmentioning

confidence: 99%

“…We used the contorted hexabenzocoronenes (Fig. 1B) because we have shown previously that compound 1A, which is surrounded by four alkyl groups, self-organizes into molecular stacks with exceptional semiconducting properties (19). Moreover, these molecules are extremely stable in ambient conditions.…”

Section: Resultsmentioning

confidence: 99%

“…Because the diameter of these self-assembled columns (Ϸ2.8 nm for 1C with its side chains fully extended) is larger than the diameter of a typical SWNT (Ϸ1-2 nm), the maximum number of columns that these nanotube electrodes can contact is two, even considering significant fringing fields near the electrodes. Given the size of the gap and the volume of the molecules assembled in this gap, we can estimate that the collective properties of Ϸ4-12 molecules are being probed (assuming that the molecule pack is Ϸ0.5 nm, face-to-face, and is Ϸ2.5 nm in diameter) (19). To further understand the importance of the contact material and geometry, we fabricated devices with gaps between platinum electrodes.…”

Section: Resultsmentioning

confidence: 99%

“…For this process, we used the columnar mesogen 1A to bridge the nanogaps between SWNTs. We have previously shown that 1A forms efficacious thin film transistors when cast from solution (19). A small volume of solution of 1A was drop cast so that it covered the junction in the SWNT but did not span the gold contact pads, shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Compounds 1B and 1C were synthesized by a procedure that is similar to the one developed for 1A (19). Full characterization is provided in Supporting Materials and Methods, which is published as supporting information on the PNAS web site.…”

Section: Methodsmentioning

confidence: 99%

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Chemoresponsive monolayer transistors

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This work details a method to make efficacious field-effect transistors from monolayers of polycyclic aromatic hydrocarbons that are able to sense and respond to their chemical environment. The molecules used in this study are functionalized so that they assemble laterally into columns and attach themselves to the silicon oxide surface of a silicon wafer. To measure the electrical properties of these monolayers, we use ultrasmall point contacts that are separated by only a few nanometers as the source and drain electrodes. These contacts are formed through an oxidative cutting of an individual metallic single-walled carbon nanotube that is held between macroscopic metal leads. The molecules assemble in the gap and form transistors with large current modulation and high gate efficiency. Because these devices are formed from an individual stack of molecules, their electrical properties change significantly when exposed to electron-deficient molecules such as tetracyanoquinodimethane (TCNQ), forming the basis for new types of environmental and molecular sensors.chemistry ͉ electronic materials ͉ nanoscience ͉ self-assembly T his work details a method to make chemoresponsive transistors by making devices out of a monolayer of polycyclic aromatic hydrocarbons that are chemically attached to surfaces. The devices are formed through a self-assembly process of organic semiconductors on the oxide surface of a silicon wafer (Fig. 1A) (1, 2). Previous studies on organic field-effect transistors (OFETs) (3, 4) have shown that the path for electrical current is through at most the first few layers of molecules at the oxide interface (5-7). In general, when the semiconducting layers of typical OFETs are scaled down to a monolayer, their properties become poor, presumably due to discontinuities or defects in the films (8-11). The strategy used here circumvents this problem by a chemical functionalization of the molecular semiconductors ( Fig. 1B) so that they both assemble laterally and chemically attach themselves to the substrate (Fig. 1C). The important result is that when ultrasmall point contacts separated by molecular length-scales are used as the source and drain (S͞D) electrodes, transistors can be made that have high gate efficiency and large ON͞OFF ratios from only a monolayer of molecules. The electrical properties of these monolayers are responsive to electron acceptors such as tetracyanoquinodimethane (TCNQ). Results and DiscussionDevice Fabrication. We first describe the devices used to measure the properties of the monolayers and then the structural and electrical characterization of these monolayers. Fig. 2 shows a schematic and micrograph of the devices used. Au (50 nm) on Cr (5 nm) pads, which are separated by 20 m, form the contact to an individual single-walled carbon nanotube (SWNT). The nanotubes were grown by a chemical vapor deposition (CVD) process described elsewhere (12, 13). The nanotube is then oxidatively cut by using an ultrafine lithographic process that produces a very small gap between the nan...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Liquid Crystals

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Liquid crystals (LCs) represent a state of matter which is characterized by a unique combination of order and mobility on molecular, supramolecular and macroscopic levels. This is a true thermodynamic stable state of matter and has been recognized and accepted as the fourth state of matter after solid, liquid, and gas (1-18). They have developed from a mere scientific curiosity in the beginning to one of the foundations of mobile information technology devices today (19)(20)(21)(22)(23)(24)(25). LCs are presently common topics in academic books and also in our daily life. Terms such as LCD, ie, LC display, and Kevlar have become familiar consumer products. The unusual feature which makes this state of matter unique among the others is the combination of orientational (and, sometimes, positional) order and dynamics, giving rise to materials with anisotropic physical properties that are switchable under the influence of small external stimuli. LCs have been regarded as unique functional soft materials from both scientific and technological point of view. The unique combination of counterintuitive properties, ie, order and fluidity, is not only an essential requirement for living matter, but also it is the foundation of the numerous technological applications of LC materials. Simultaneous exhibition of order and dynamics is the basic principle for self-organization and structure formation in living systems. Accordingly, LCs play a crucial role in living systems and in biology (18). For example, no life would be possible without the ordered and dynamic self-assembly of lipids into bilayers within the cell membrane. Several biological molecules such as lipids, carbohydrates, proteins, and nucleic acids have been found to exist in various liquid crystalline phases (26-34). The appearance of mesomorphism in DNAs has been related to the significant role that LCs would have played in the evolution of biological information in the pre-biotic world (35-38). LCs self-assemble into various structures with the help of many different types of molecular interactions such as van der Waals, dipolar and quadrupolar interaction, charge transfer, p-p interaction, metal coordination, and hydrogen bonding. Thus, LCs can be considered as prototype supramolecular systems which furnish well-defined self-assembled architectures using noncovalent secondary interactions (39). Scientifically, the LC field is a fertile ground to study supramolecular self-assembly of matter and soft materials. Moreover, LCs persuasively demonstrate the powerful organization principle of matter by maximizing the interaction energy and minimizing the excluded volume.Overall, LCs have developed into a fascinating and prosperous field, reaching out into different areas of science by providing basic knowledge of the fundamental rules governing self-assembly from simple to complex modes. The domains of LCs span across multiple disciplines of pure and applied science including optics, materials science, bioscience, nanoscience etc. Their science and technology are tru...

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Self‐Assembly of Supramolecular Wires

Weiss

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2012

Supramolecular Chemistry

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This review focuses on the strategies available for the construction of persistent linear species from monomers. The scope is mostly restricted to wires, but also includes some selected examples illustrating the fast developing area of fibers and tubular structures, given that their linearity is governed by supramolecular interactions. Strategies are primarily limited to those that are based on noncovalent assembly obtained by iterative interactions that range from coordination bonds to π‐interactions and hydrogen bonding. Each approach is illustrated by a selection of either pioneering or recent examples. The use of supramolecular templates to assemble molecules into linear wires, whose structures are sometimes covalently locked, is also briefly presented.

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Molecular Wires from Contorted Aromatic Compounds

Cited by 312 publications

References 44 publications

Chemoresponsive monolayer transistors

Chemoresponsive monolayer transistors

Liquid Crystals

Self‐Assembly of Supramolecular Wires

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