Engineering topics
Ng, Fay
Publications and source records attributed to Ng, Fay.
Electrical conductivity in a non-covalent two-dimensional porous organic material with high crystallinity
Ultrathin porous films held together by non-covalent van der Waals interactions was obtained by a top-down approach, which is then utilized as channel material in a two-dimensional planar field-effect transistor device through easy stamp transfer.
Cumulene Wires Display Increasing Conductance with Increasing Length
One-dimensional sp-hybridized carbon wires, including cumulenes and polyynes, can be regarded as finite versions of carbynes. They are likely to be good candidates for molecular-scale conducting wires as they are predicted to have a high-conductance. In this study, we first characterize the single-molecule conductance of a series of cumulenes and polyynes with a backbone ranging in length from 4 to 8 carbon atoms, including [7]cumulene, the longest cumulenic carbon wire studied to date for molecular electronics. We observe different length dependence of conductance when comparing these two forms of carbon wires. Polyynes exhibit conductance decays with increasing molecular length, while cumulenes show a conductance increase with increasing molecular length. Their distinct conducting behaviors are attributed to their different bond length alternation, which is supported by theoretical calculations. Furthermore, this study confirms the long-standing theoretical predictions on sp-hybridized carbon wires and demonstrates that cumulenes can form highly conducting molecular wires.
The Structural Origins of Intense Circular Dichroism in a Waggling Helicene Nanoribbon
We report the synthesis of a new perylene-diimide-based helical nanoribbon, which exhibits the largest molar electronic circular dichroism in the visible range of any molecule. Here, this nanoribbon also displays a substantial increase in molar circular dichroism relative to a smaller helical analogue, even though they share a similar structure: both nanoribbons incorporate two conformationally dynamic double-[4]helicene termini and a rigid [6]helicene-based core within their helical superstructures. Using DFT and TDDFT calculations, we find that the double-[4]helicenes within both nanoribbons orient similarly in solution; as such, conformational differences do not account for the disparities in circular dichroism. Instead, our results implicate the configuration of the double-[6]helicene within the larger nanoribbon as the source of the observed chiroptical amplification.
Organic semiconductor compounds and methods of use
Organic perylene diimide-based compounds are provided. Methods of producing the organic compounds is also provided as well as methods of their use including, among other things, their use as organic semiconductor materials.