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Qian Miao

Publications and source records attributed to Qian Miao.

8 recordsLinked to original sources
PubMed2006

Hexathiapentacene: structure, molecular packing, and thin-film transistors.

In this communication we report the electrical characteristics of hexathiapentacene (HTP) and emphasize the unusual chemical structure and molecular packing. We report field-effect mobilities as high as 0.04 cm2 V-1 s-1 and current on/off ratios of >105. With crystallographic evidence of unusually long S-S bonds compared to normal S-S bonds, we have suggested a unique resonance structure similar to trithiapentalene, which well explains the bonding characteristics of HTP. This work appears to be the first to determine its molecular structure/packing mode and to study its application in organic transistors.

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PubMed2006

Chemical complementarity in the contacts for nanoscale organic field-effect transistors.

This study describes the effect of covalent derivatization of source and drain electrodes with monolayers of organic semiconductors. These monolayers form a template on the metal surface and provide better electronic coupling between the electrode and the semiconductor. We see a large improvement in nanoscale (40-100 nm) transistors only when the monolayer presents functionality that is complementary to the chemical and electronic structure of the molecular semiconductor.

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PubMed2006

Organization of acenes with a cruciform assembly motif.

This study explores the assembly in the crystalline state of a class of pentacenes that are substituted along their long edges with aromatic rings forming rigid, cruciform molecules. The crystals were grown from the gas phase, and their structures were compared with DFT-optimized geometries. Both crystallographic and computed structures show that a planar acene core is the exception rather than the rule. In the assembly of these molecules, the phenyl groups block the herringbone motif and further guide the arrangement of the acene core into higher order structures. The packing for the phenyl-substituted derivatives is dictated by close contacts between the C-H's of the pendant aromatic rings and the carbons at the fusions in the acene backbone. Using thiophene substituents instead of phenyls creates cofacially stacked acenes. In thin films, the thiophene-substituted derivative forms devices with good electrical properties: relatively high mobility, high ON/OFF ratios, and low threshold voltage for device activation. An unusual result is obtained for the decaphenyl pentacene when devices are fabricated on its crystalline surface. Although its acene cores are well isolated from each other, this material still exhibits good electrical properties.

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PubMed2005

A recyclable electrochemical allylation in water.

To develop environmentally benign processes for C-C bond formation, electrochemistry is applied in a tin-mediated allylation reaction in water. In this electrochemical process, the corresponding homoallylic alcohols are prepared in excellent yields, while both tin salt and water can be recycled and electrode materials are not consumed.

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PubMed2004

Attaching organic semiconductors to gate oxides: in situ assembly of monolayer field effect transistors.

This study unveils a new tetracene derivative that forms dense, upright monolayers on the surface of aluminum oxide. These monolayers spontaneously self-organize into the active layer in nanoscale field-effect transistor devices when aluminum oxide is used as the dielectric layer. This method gives high yields of working devices that have source-drain distances that are less than 60 nm, thereby providing a method to electrically probe the monolayer assemblies formed from approximately 10 zeptomoles of material (approximately 104 molecules). Moreover, this study delineates a new avenue for research in thin-film organic transistors where the active molecules are linked to the dielectric surface to form a monolayer transistor.

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PubMed2004

Poly[[bis[aqua(1,10-phenanthroline)lanthanum(III)]-mu-aqua-di-mu-5-sulfonatoisophthalato] monohydrate] and poly[[[triaqualanthanum(III)]-mu-5-sulfonatoisophthalato] monohydrate].

In the two related polymeric title compounds, [[La2(sip)2(phen)2(H2O)3].H2O]n [sip is the 5-sulfonatoisophthalate trianion (C8H3O7S3-) and phen is 1,10-phenanthroline (C12H8N2)], (I), and [[La(sip)(H2O)3].H2O]n, (II), the lanthanum(III) ions are nine-coordinate, with similar distorted monocapped square-antiprism coordination geometry. The two crystal structures are very different. In (I), the sip anion acts as a pentadentate ligand, one of the coordinated water molecules lies on a twofold axis and further inversion, n-glide and translation operations generate a two-dimensional framework. In (II), the sip anion functions as a hexadentate ligand and a three-dimensional network with trinuclear 24-membered rings is developed via inversion, n-glide, twofold-screw and translation operations. Both structures also have extensive O-H...O hydrogen-bonded networks and pi-pi interactions.

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PubMed2003

Synthesis, assembly, and thin film transistors of dihydrodiazapentacene: an isostructural motif for pentacene.

The study below details the synthesis, assembly, and thin film transistors from dihydrodiazapentacenes. These molecules have the same molecular shape as pentacene but are much easier to prepare and have much greater environmental stability. Thin films made from the dihydrodiazapentacene behave as field effect transistors with mobilities and on/off ratios high enough to be useful in certain applications. X-ray diffraction and AFM experiments on these films show that the molecules stack in layers with their long axis upright from the surface. Some of the derivatives synthesized for this study have unexpectedly high solubility in polar solvents such as DMF and DMSO. The crystal structure from DMF reveals self-assembled channels with each of the aniline functionalities forming a hydrogen bond with solvent. In more nonpolar solvents, the solid-state assembly switches to a herringbone motif characteristic of the linear acenes.

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