5,442 research outputs found
Simple Phosphinate Ligands Access New Zinc Clusters Identified in the Synthesis of Zinc Oxide Nanoparticles
The bottom-up synthesis of ligand-stabilised functional nanoparticles from molecular precursors is widely applied but difficult to study mechanistically. Here, we use 31P NMR spectroscopy to follow the trajectory of phosphinate ligands during the synthesis of a range of new ligated zinc oxo clusters, containing 4, 6 and 11 zinc atoms. Using an organometallic route, the clusters interconvert rapidly, and self-assemble in solution based on thermodynamic equilibria, rather than nucleation kinetics. These clusters are also identified, in situ, during the synthesis of phosphinate-capped zinc oxide nanoparticles. Unexpectedly, the ligand is sequestered to a stable Zn11 cluster during the majority of the synthesis and only becomes coordinated to the nanoparticle surface, in the final step. As well as a versatile and accessible route to new (optionally doped) zinc clusters, the findings provide a new understanding of the role of well-defined molecular precursors during the synthesis of small (2-4 nm) nanoparticles
Vol. 7, No. 2
Contents:
Police and Fire Interest Arbitration in Illinois, by Thomas F. Sonneborn
Trends in Illinois Interest Arbitration, Carl S. Tominberg, Jane E. Shaffer
Recent Developments, by the Student Editorial Board
Further Referenceshttps://scholarship.kentlaw.iit.edu/iperr/1004/thumbnail.jp
Vol. 7, No. 2
Contents:
Police and Fire Interest Arbitration in Illinois, by Thomas F. Sonneborn
Trends in Illinois Interest Arbitration, Carl S. Tominberg, Jane E. Shaffer
Recent Developments, by the Student Editorial Board
Further Referenceshttps://scholarship.kentlaw.iit.edu/iperr/1004/thumbnail.jp
Safety, the Preface Paradox and Possible Worlds Semantics
This paper contains an argument to the effect that possible worlds semantics renders
semantic knowledge impossible, no matter what ontological interpretation is given
to possible worlds. The essential contention made is that possible worlds semantic
knowledge is unsafe and this is shown by a parallel with the preface paradox
The challenge of changing deeply-held student beliefs about the relativity of simultaneity
Previous research indicates that after standard instruction students at all
academic levels often construct a conceptual framework in which the ideas of
absolute simultaneity and the relativity of simultaneity co-exist. This article
describes the development and assessment of instructional materials intended to
improve student understanding of the concept of time in special relativity, the
relativity of simultaneity, and the role of observers in inertial reference
frames. Results from pretests and post-tests are presented to demonstrate the
effect of the curriculum in helping students deepen their understanding of
these topics. Excerpts from taped interviews and classroom interactions help
illustrate the intense cognitive conflict that students encounter as they are
led to confront the incompatibility of their deeply-held beliefs about
simultaneity with the results of special relativity.Comment: 17 pages, 6 figures, 2 tables, 27 references; Accepted for
publication in Physics Education Research Section, American Journal of
Physics (2001
Hierarchical carbon aerogel modified carbon fiber composites for structural power applications
The desire to reduce overall weight in devices is a key driver for perpetual material development; the ability to combine composites with energy storage functions/capabilities which simultaneously provide structural integrity has the potential to supersede monofunctional components. To achieve this ambition, the multifunctional structure must perform both mechanical and energy storage functions sufficiently, but often there is a trade off in performance which is a significant challenge to overcome. Carbon aerogels have been shown to contribute positively to (electro-chemical double layer) capacitive performance due to an increased surface area in multifunctional carbon fiber based composite electrodes, but have also been shown to reduce mechanical properties; the addition of nanoscale reinforcers, such as carbon nanotubes, graphene or alike, with their superlative electrical and mechanical properties are proposed to address these concerns and create a truly hierarchical structure suitable for structural power applications
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