An official website of the United States government
Semiconducting conjugated polymers (CPs) have shown great potential in organic solar cells and organic field-effect transistors (OFETs), due to their tunable electronic and optical properties. In this study, we compare computational predictions of electronic and optical properties of ensembles of cis-polyacetylene (cis-PA) multiple oligomers in two different forms (a) undoped cis-PA and (b) cis- PA doped by phosphorous fluoride (PF6−) via density functional theory (DFT) with hybrid functionals. The comparison of undoped cis-PA under the constraint of injected charge carrier and cis-PA doped by PF6− shows that either doping or injection provides very similar features in electronic structure and optical properties. Doped and injected are similar to each other and different from the pristine, undoped PA. Computed results also indicate that the injection of charge carriers and adding p-type doping into the semiconducting CP model both greatly affect the conductivity. These observations provide a better understanding and practical use of the properties of polyacetylene films for flexible electronic applications.
more »
« less
New Insight into the “Fortuitous Error” that Led to the 2000 Nobel Prize in Chemistr
In 2000, the Nobel Prize in Chemistry was awarded to Hideki Shirakawa, Alan G. MacDiarmid, and Alan J. Heeger “for the discovery and development of electrically conductive polymers.” While this award was in reference to their collaborative efforts on conducting polyacetylene in the mid-to-late 1970s, the narrative leading up to these efforts began in 1967 with the production of polyacetylene plastic films via what has been called a “fortuitous error.” At the heart of this discovery were Shirakawa and a visiting Korean scientist, Hyung Chick Pyun. The current report provides background on Pyun and, for the first time, presents his version of the events leading to the discovery of polyacetylene films in order to provide new insight into this important historical event.
more »
« less
- Award ID(s):
- 2002877
- PAR ID:
- 10432325
- Date Published:
- Journal Name:
- Substantia
- Volume:
- 5
- Issue:
- 1
- ISSN:
- 2532-3997
- Page Range / eLocation ID:
- 91-97
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract AimArtificial light at night (ALAN) and roads are known threats to nocturnally migrating birds. How associations with ALAN and roads are defined in combination for these species at the population level across the full annual cycle has not been explored. LocationWestern Hemisphere. MethodsWe estimated range‐wide exposure, predictor importance and the prevalence of positive associations with ALAN and roads at a weekly temporal resolution for 166 nocturnally migrating bird species in three orders: Passeriformes (n = 104), Anseriformes (n = 27) and Charadriiformes (n = 35). We clustered Passeriformes based on the prevalence of positive associations. ResultsPositive associations with ALAN and roads were more prevalent for Passeriformes during migration when exposure and importance were highest. Positive associations with ALAN and roads were more prevalent for Anseriformes and Charadriiformes during the breeding season when exposure was lowest. Importance was uniform for Anseriformes and highest during migration for Charadriiformes. Our cluster analysis identified three groups of Passeriformes, each having similar associations with ALAN and roads. The first occurred in eastern North America during migration where exposure, prevalence, and importance were highest. The second wintered in Mexico and Central America where exposure, prevalence and importance were highest. The third occurred throughout North America where prevalence was low, and exposure and importance were uniform. The first and second were comprised of dense habitat specialists and long‐distance migrants. The third was comprised of open habitat specialists and short distance migrants. Main conclusionsOur findings suggest ALAN and roads pose the greatest risk during migration for Passeriformes and during the breeding season for Anseriformes and Charadriiformes. Our results emphasise the close relationship between ALAN and roads, the diversity of associations dictated by taxonomy, exposure, migration strategy and habitat and the need for more informed and comprehensive mitigation strategies where ALAN and roads are treated as interconnected threats.more » « less
-
Nelson, Karen E (Ed.)Abstract Artificial light at night (ALAN), an increasing anthropogenic driver, is widespread and shows rapid expansion with potential adverse impact on the terrestrial ecosystem. However, whether and to what extent does ALAN affect plant phenology, a critical factor influencing the timing of terrestrial ecosystem processes, remains unexplored due to limited ALAN observation. Here, we used the Black Marble ALAN product and phenology observations from USA National Phenology Network to investigate the impact of ALAN on deciduous woody plants phenology in the conterminous United States. We found that (1) ALAN significantly advanced the date of breaking leaf buds by 8.9 ± 6.9 days (mean ± SD) and delayed the coloring of leaves by 6.0 ± 11.9 days on average; (2) the magnitude of phenological changes was significantly correlated with the intensity of ALAN (P < 0.001); and (3) there was an interaction between ALAN and temperature on the coloring of leaves, but not on breaking leaf buds. We further showed that under future climate warming scenarios, ALAN will accelerate the advance in breaking leaf buds but exert a more complex effect on the coloring of leaves. This study suggests intensified ALAN may have far-reaching but underappreciated consequences in disrupting key ecosystem functions and services, which requires an interdisciplinary approach to investigate. Developing lighting strategies that minimize the impact of ALAN on ecosystems, especially those embedded and surrounding major cities, is challenging but must be pursued.more » « less
-
Abstract The discovery of ferroelectricity in AlN‐based thin films, including Al1‐xScxN and Al1‐xBxN, over the past few years has spurred great research interests worldwide. In this review, we carefully examined the latest developments for these ferroelectric films with respect to alloy composition, temperature, film thickness, deposition condition, and fatigue endurance by electric field cycling. Looking ahead, there is an urgent need to resolve the challenge of large current leakage faced by these films, which necessitates a combined efforts from both simulations and experiments to identify the root cause and eventually come up with engineering strategies to suppress such leakage. In addition, overcoming the thickness scaling challenge to push ferroelectric thin film down to a few nanometers for better device miniaturization will also be of great interest. Considering the somewhat unexpected discovery of AlN‐based thin films with potential ferroelectric application, we believe that it will be also rewarding to further explore other III‐V‐based semiconductor materials.more » « less
-
Abstract Artificial light at night (ALAN) is an increasingly important form of environmental disturbance as it alters Light:Dark cycles that regulate daily and seasonal changes in physiology and phenology. The Northern house mosquito (Culex pipiens) and the tiger mosquito (Aedes albopictus) enter an overwintering dormancy known as diapause that is cued by short days. These two species differ in diapause strategy:Cx. pipiensdiapause as adult females whileAe. albopictusenter a maternally-programmed, egg diapause. Previous studies found that ALAN inhibits diapause in both species, but the mechanism is unknown. As the circadian clock is implicated in the regulation of diapause in many insects, we examined whether exposure to ALAN altered the daily expression of core circadian cloc genes (cycle,Clock,period,timeless,cryptochrome 1,cryptochrome 2, andPar domain protein 1) in these two species when reared under short-day, diapause-inducing conditions. We found that exposure to ALAN altered the abundance of several clock genes in adult females of both species, but that clock gene rhythmicity was maintained for most genes. ALAN also had little effect on clock gene abundance in mature oocytes that were dissected from femaleAe. albopictusthat were reared under short day conditions. Our findings indicate that ALAN may inhibit diapause initiation through the circadian clock in two medically-important mosquitoes.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- The DOI is not currently available.
