Browsing by Subject "CHEMISTRY"

Now showing 1 - 3 of 3
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    ItemOpen Access
    Challenges encountered during development of Mn porphyrin-based, potent redox-active drug and superoxide dismutase mimic, MnTnBuOE-2-PyP5+, and its alkoxyalkyl analogues
    (JOURNAL OF INORGANIC BIOCHEMISTRY, 2017-04-01) Rajic, Zrinka; Tovmasyan, Artak; de Santana, Otávio L; Peixoto, Isabelle N; Spasojevic, Ivan; do Monte, Silmar A; Ventura, Elizete; Rebouças, Júlio S; Batinic-Haberle, Ines
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    ItemOpen 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.
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    ItemOpen Access
    Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance.
    (Nature communications, 2018-09-07) Hodgkins, Suzanne B; Richardson, Curtis J; Dommain, René; Wang, Hongjun; Glaser, Paul H; Verbeke, Brittany; Winkler, B Rose; Cobb, Alexander R; Rich, Virginia I; Missilmani, Malak; Flanagan, Neal; Ho, Mengchi; Hoyt, Alison M; Harvey, Charles F; Vining, S Rose; Hough, Moira A; Moore, Tim R; Richard, Pierre JH; De La Cruz, Florentino B; Toufaily, Joumana; Hamdan, Rasha; Cooper, William T; Chanton, Jeffrey P
    Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 °C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats.