Browsing by Subject "Chemistry, Multidisciplinary"

Now showing 1 - 4 of 4

Open Access
BigSMILES: A Structurally-Based Line Notation for Describing Macromolecules.
(ACS central science, 2019-09-12) Lin, Tzyy-Shyang; Coley, Connor W; Mochigase, Hidenobu; Beech, Haley K; Wang, Wencong; Wang, Zi; Woods, Eliot; Craig, Stephen L; Johnson, Jeremiah A; Kalow, Julia A; Jensen, Klavs F; Olsen, Bradley D
Having a compact yet robust structurally based identifier or representation system is a key enabling factor for efficient sharing and dissemination of research results within the chemistry community, and such systems lay down the essential foundations for future informatics and data-driven research. While substantial advances have been made for small molecules, the polymer community has struggled in coming up with an efficient representation system. This is because, unlike other disciplines in chemistry, the basic premise that each distinct chemical species corresponds to a well-defined chemical structure does not hold for polymers. Polymers are intrinsically stochastic molecules that are often ensembles with a distribution of chemical structures. This difficulty limits the applicability of all deterministic representations developed for small molecules. In this work, a new representation system that is capable of handling the stochastic nature of polymers is proposed. The new system is based on the popular "simplified molecular-input line-entry system" (SMILES), and it aims to provide representations that can be used as indexing identifiers for entries in polymer databases. As a pilot test, the entries of the standard data set of the glass transition temperature of linear polymers (Bicerano, 2002) were converted into the new BigSMILES language. Furthermore, it is hoped that the proposed system will provide a more effective language for communication within the polymer community and increase cohesion between the researchers within the community.
Open Access
Carrier Dynamics Engineering for High-Performance Electron-Transport-Layer-free Perovskite Photovoltaics
(CHEM, 2018-10-11) Han, Q; Ding, J; Bai, Y; Li, T; Ma, JY; Chen, YX; Zhou, Y; Liu, J; Ge, QQ; Chen, J; Glass, JT; Therien, MJ; Liu, J; Mitzi, DB; Hu, JS
Open Access
Importance of diameter control on selective synthesis of semiconducting single-walled carbon nanotubes.
(ACS nano, 2014-08-11) Li, Jinghua; Ke, Chung-Ting; Liu, Kaihui; Li, Pan; Liang, Sihang; Finkelstein, Gleb; Wang, Feng; Liu, Jie
The coexistence of semiconducting and metallic single-walled carbon nanotubes (SWNTs) during synthesis is one of the major bottlenecks that prevent their broad application for the next-generation nanoelectronics. Herein, we present more understanding and demonstration of the growth of highly enriched semiconducting SWNTs (s-SWNTs) with a narrow diameter distribution. An important fact discovered in our experiments is that the selective elimination of metallic SWNTs (m-SWNTs) from the mixed arrays grown on quartz is diameter-dependent. Our method emphasizes controlling the diameter distribution of SWNTs in a narrow range where m-SWNTs can be effectively and selectively etched during growth. In order to achieve narrow diameter distribution, uniform and stable Fe-W nanoclusters were used as the catalyst precursors. About 90% of as-prepared SWNTs fall into the diameter range 2.0-3.2 nm. Electrical measurement results on individual SWNTs confirm that the selectivity of s-SWNTs is ∼95%. The present study provides an effective strategy for increasing the purity of s-SWNTs via controlling the diameter distribution of SWNTs and adjusting the etchant concentration. Furthermore, by carefully comparing the chirality distributions of Fe-W-catalyzed and Fe-catalyzed SWNTs under different water vapor concentrations, the relationship between the diameter-dependent and electronic-type-dependent etching mechanisms was investigated.
Open Access
"on course" for supporting expanded participation and improving scientific reasoning in undergraduate thesis writing
(Journal of Chemical Education, 2015-01-01) Dowd, JE; Roy, CP; Thompson, RJ; Reynolds, JA
© 2014 The American Chemical Society and Division of Chemical Education, Inc. The Department of Chemistry at Duke University has endeavored to expand participation in undergraduate honors thesis research while maintaining the quality of the learning experience. Accomplishing this goal has been constrained by limited departmental resources (including faculty time) and increased diversity in students' preparation to engage in the research and writing processes. Here we assessed the relationship between iterative changes in pedagogical and mentoring support of honors research that efficiently employed departmental resources (including the chemistry thesis assessment protocol, ChemTAP) and students' scientific reasoning and writing skills reflected in their undergraduate theses. We found that, although we cannot disentangle some gradual changes over time from specific interventions, students exhibited the strongest performance when they participated in a course with structured scaffolding and used assessment tools explicitly designed to enhance the scientific reasoning in writing. Furthermore, less prepared students exhibited more positive changes.