Browsing by Author "Lin, Shih-Chieh"

Now showing 1 - 3 of 3

Hierarchical Superstructures with Control of Helicity from the Self-Assembly of Chiral Bent-Core Molecules
(2012-07-01)
Lin, Shih-Chieh
;
Ho, Rong-Ming
;
Chang, Chin-Yen
;
Hsu, Chain-Shu
;
應用化學系
"Herein, two asymmetric chiral bent-core molecules, 3-[(4-{[4-(heptyloxy)benzoyl]oxy}benzoyl)oxy]-phenyl-4-[(4-{[(1R)-1-methylheptyl]oxy}benzoyl)oxy] benzoate (BC7R) and 3-[(4-{[4-(heptyloxy)benzoyl]oxy}benzoyl)oxy]-phenyl-4-[(4-{[(1S)-1-methylheptyl]oxy}benzoyl)oxy] benzoate (BC7S), were synthesized to demonstrate control of the helicity of their self-assembled hierarchical superstructures. Mirror-imaged CD spectra showed a split-type Cotton effect after the formation of self-assembled aggregates of BC7R and BC7S, thereby suggesting the formation of intermolecular exciton couplets with opposite optical activities. Both twisted and helical ribbons with preferential helicity that corresponded to the twisting character of the intermolecular exciton couplet were found in the aggregates. The formation of helical ribbons was attributed to the merging of twisted ribbons through an increase in width to improve morphological stability. As a result, control of the helicity of hierarchical superstructures from the self-assembly of bent-core molecules could be achieved by taking advantage of the transfer of chiral information from the molecular level onto the hierarchical scale."
Hierarchical Superstructures with Helical Sense in Self-Assembled Achiral Banana-Shaped Liquid Crystalline Molecules
(2008-11-10)
Lin, Shih-Chieh
;
Lin, Tz-Feng
;
Ho, Rong-Ming
;
Chang, Chin-Yen
;
Hsu, Chain-Shu
The self-assembly of 1,3-phenylene bis[4-(4-n-heptyloxybenzoyloxy)-benzoates] (BC7) is studied to examine the formation of helical morphologies from achiral banana-shaped liquid crystal molecules at different self-assembling levels. Various hierarchical superstructures including flat-elongated lamellar crystal, left- and right-handed helical ribbons, and tubular texture are observed while the BC7 molecules self-assemble in THF/H(2)O solution. By contrast, only plate-like morphology is observed in the self-assembly of achiral linear shaped 1,4-phenylene bis[4-(4-n-heptyloxybenzoyloxy)-benzoates] (LC7) molecules, indicating that the chirality of the self-assembled texture is strongly dependent upon the molecular geometry of the achiral molecules. The formation of the helical superstructures, namely hierarchical chirality, is attributed to the conformational chirality from the achiral banana-shaped liquid crystalline molecules, as evidenced by significant optical activity in time-resolved circular dichroism experiments. Selective area electron diffraction is performed to examine the structural packing of the hierarchical superstructures. As observed, the molecular disposition of the lamellar crystal is identical to that of the helical superstructure. Also, the diffraction patterns of the helical superstructures appeared arc-like patterns consisting of a series of reflections, suggesting that the helical morphology resulted from the curving of the lamellar crystals through a twisting and bending mechanism. Consequently, the model of molecular disposition in the self-assembled helical superstructures from the achiral banana-shaped molecules is proposed. The morphological evolution in this study may provide further understanding with respect to the chiral information transfer mechanism from specific molecular geometry to hierarchical chirality in the achiral banana-shaped molecules.
Solution-Processed Vertical Organic Transistors Fabricated by Nanoimprint Lithography
(2013-02-01)
Wu, Yang-Kai
;
Huang, Jian-Hao
;
Tsai, Wu-Wei
;
Chen, Yung-Pin
;
Lin, Shih-Chieh
In this letter, we demonstrate the first vertical-channel organic transistor using nanoimprint technology to produce a base electrode with high-density nanometer pores to well control the channel current vertically flowing through the pores. The aspect ratios of nanopores, which determine the switching performance of the vertical transistor, are greatly enhanced by transferring the nanostructure to the underlying layers. Without pore accumulation, a low leakage current can be achieved. The vertical transistor delivers an ON current of 0.35 mA/cm(2) and an ON/OFF current ratio of around 3000 at 1.8 V. The results prove the feasibility to produce low-voltage organic transistors over a large area with potentially low production cost.