| 1. |
- Zhang, Fengling, et al.
(författare)
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Ordered mesoporous Ag-TiO2-KIT-6 heterostructure: synthesis, characterization and photocatalysis
- 2009
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428. ; 19:18, s. 2771-2777
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Tidskriftsartikel (refereegranskat)abstract
- Ordered mesoporous Ag-TiO2-KIT-6 heterostructured nanocrystals were successfully synthesized by a template-based method, where a layer of TiO2 and Ag2O nanoparticles were deposited on cubic (Ia3d) silica (KIT-6) in an orderly manner; at the same time, the formed Ag2O nanoparticles were photolyzed to metallic Ag nanoparticles. Our results show that Ag-TiO2-KIT-6 is an ordered mesoporous composite material, which is composed of Ag-TiO2 heterostructures and the amorphous KIT-6 template. In addition, Ag-TiO2-KIT-6 possesses the highest photocatalytic activity among the as-synthesized photocatalysts, which can be attributed to the Ag-TiO2 heterojunctions and the excellent texture: (1) Ag-TiO2 heterojunctions improve the separation of photogenerated electron-hole pairs due to the potential energy differences between Ag and TiO2 nanocrystals, thus enhancing the photocatalytic activity; (2) the Ag-TiO2-KIT-6 sample possesses a high BET surface area and a large number of ordered pore channels, which facilitate adsorption and transportation of dye molecules, also leading to higher photocatalytic activity. It was also found that the Ag-TiO2 heterostructure plays a more important role in enhancing the photocatalytic activity than high BET surface area.
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| 2. |
- Lui, A. T. Y., et al.
(författare)
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Cluster observation of plasma flow reversal in the magnetotail during a substorm
- 2006
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Ingår i: Annales Geophysicae. - 0992-7689 .- 1432-0576. ; 24:7, s. 2005-2013
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Tidskriftsartikel (refereegranskat)abstract
- We investigate in detail a reversal of plasma flow from tailward to earthward detected by Cluster at the downstream distance of similar to 19 RE in the midnight sector of the magnetotail on 22 August 2001. This flow reversal was accompanied by a sign reversal of the B-z component and occurred during the late substorm expansion phase as revealed by simultaneous global view of auroral activity from IMAGE. We examine the associated Hall current system signature, current density, electric field, Lorentz force, and current dissipation/dynamo term, the last two parameters being new features that have not been studied previously for plasma flow reversals. It is found that (1) there was no clear quadrupole Hall current system signature organized by the flow reversal time, (2) the x-component of the Lorentz force did not change sign while the other two did, (3) the timing sequence of flow reversal from the Cluster configuration did not match tailward motion of a single plasma flow source, (4) the electric field was occasionally dawnward, producing a dynamo effect, and (5) the electric field was occasionally larger at the high-latitude plasma sheet than near the neutral sheet. These observations are consistent with the current disruption model for substorms in which these disturbances are due to shifting dominance of multiple current disruption sites and turbulence at the observing location.
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| 3. |
- Lui, A. T. Y., et al.
(författare)
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Prelude to THEMIS tail conjunction study
- 2007
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Ingår i: Annales Geophysicae. - 0992-7689 .- 1432-0576. ; 25:4, s. 1001-1009
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Tidskriftsartikel (refereegranskat)abstract
- A close conjunction of several satellites (LANL, GOES. Polar. Geotail, and Cluster) distributed from the geostationary altitude to about 16 R-E downstream in the tail occurred during substorm activity as indicated by global auroral imaging and ground-based magnetometer data. This constellation of satellites resembles what is planned for the THEMIS (Time History of Events and Macroscopic Interactions during Substorms) mission to resolve the substorm controversy on the location of the substorm expansion onset region. In this article, we show in detail the dipolarization and dynamic changes seen by these satellites associated with two onsets of substorm intensification activity. In particular, we find that dipolarization at similar to 16 R-E downstream in the tail can occur with dawnward electric field and without plasma flow, just like some near-Earth dipolarization events reported previously. The spreading of substorm disturbances in the tail coupled with complementary ground observations indicates that the observed time sequence on the onsets of substorm disturbances favors initiation in the near-Earth region for this THEMIS-like conjunction.
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