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EM study of Mesoporous Crystals, Hollow Spheres and Intergrowth Tungsten Bronzes
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Research subject
Structural Chemistry
URN: urn:nbn:se:su:diva-36942OAI: diva2:291288
2010-02-01, K247, Svante Arrheniusväg 16c, Stockholm, 14:00 (English)
Available from: 2010-06-29 Created: 2010-02-01 Last updated: 2010-06-29Bibliographically approved
List of papers
1. An Appraisal of High Resolution Scanning Electron Microscopy Applied To Porous Materials
Open this publication in new window or tab >>An Appraisal of High Resolution Scanning Electron Microscopy Applied To Porous Materials
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2009 (English)In: JEOL News, Vol. 44, no 1, 17-22 p.Article in journal (Refereed) Published
Abstract [en]

Nanoporous materials such as zeolites and mesoporous silica crystals have attracted a lot of attention in recent years. In particular, the incorporation of various materials such as organic molecules, or metal nanoparticles and other inorganic compounds within their pores which give rise to fascinating new functions. For such materials, it is essential to determine their structure, composition and mechanisms of growth in order to maximize their utility in future applications.

Recent progress in the performance of SEM is enormous, especially in low energy imaging where we can now directly observe fine surface structures of porous materials even those that are electrical insulators. Furthermore, by precise filtration and detection of emitted electrons by their energy, we can selectively obtain different types of information such as material composition, location of particles inside or outside the pores etc. The physical processes and technologies behind this precise tuning of landing and detection energies for both impact and emitted electrons, respectively, are explained and illustrated using a number of porous materials including zeolite LTA, SBA-15, SBA-16, zeolite LTL, FDU-16 and Au@TiO2 ' rattle spheres,' along with comparisons with other techniques such as atomic force microscopy (AFM) and transmission electron microscopy (TEM). We conclude that, by using extremely low landing energies, advanced sample preparation techniques and through a thorough understanding of the physical processes involved, HRSEM is providing new and unique information and perspectives on these industrially important materials.

National Category
Chemical Sciences
Research subject
Inorganic Chemistry; Structural Chemistry
urn:nbn:se:su:diva-36800 (URN)

Totalt antal författare 17 st.

Available from: 2010-01-27 Created: 2010-01-26 Last updated: 2012-11-20Bibliographically approved
2. Ordered Mesoporous Pd/Silica-Carbon as a Highly Active Heterogeneous Catalyst for Coupling Reaction of Chlorobenzene in Aqueous Media
Open this publication in new window or tab >>Ordered Mesoporous Pd/Silica-Carbon as a Highly Active Heterogeneous Catalyst for Coupling Reaction of Chlorobenzene in Aqueous Media
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2009 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, no 12, 4541-4550 p.Article in journal (Refereed) Published
Abstract [en]

Heterogeneous palladium catalysts, which are supported on ordered mesoporous silica-carbon nanocomposites, have been applied in water-mediated coupling reactions of chlorobenzene without assistance of any phase-transfer catalysts. Characterization by XRD, TEM, N2 sorption, FT-IR, TG, XPS, and H2 chemisorption techniques reveals the highly ordered mesostructure, high surface areas (?345 m2/ g), large pore volumes (?0.46 cm3/g), uniform mesopore sizes (?6.3 nm), hybrid silicate and carbonaceous compositions, and a high dispersion of palladium nanoparticles (about 3 nm) in the mesopores. The catalyst exhibits a high yield for trans-stilbene (?60%) in the Heck coupling reaction of chlorobenzene and styrene at 100 ‹C and for biphenyl (46%) in the Ullmann coupling reaction of chlorobenzene at 30 ‹C, using water as a solvent. When substituted aryl chlorides (hydroxyl, methoxyl, and methyl) are involved in the Ullmann reaction, the yields of symmetrical substituted biphenyl are also higher than 44% (this value reaches 86% for the coupling reaction of 4-chlorophenol) at a low temperature of 30 ‹C. This heterogeneous catalyst is stable, which shows negligible metal leaching, and can be reused more than 20 times. For comparison, the catalytic activities for Pd catalysts supported on pure mesoporous polymeric, carbonaceous, and silicate frameworks are also investigated. The results clearly indicate that the pore wall nature shows great influence on the dispersion of metallic Pd species and, in turn, the catalytic performance.


National Category
Natural Sciences
urn:nbn:se:su:diva-36709 (URN)10.1021/ja808481g (DOI)000264792900067 ()
Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2011-12-09Bibliographically approved

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