[Todos] VIERNES 30/11 - 13.00 hs - Seminarios DQIAQF - INQUIMAE

[andrea en qi.fcen.uba.ar]

Seminarios DQIAQF - INQUIMAE, VIERNES 30 de noviembre - 13 hs.

Aula de Seminarios INQUIMAE - DQIAQF
Facultad de Ciencias Exactas y Naturales
Ciudad Universitaria - Pab. 2  -  Piso 3

Seminario doble! Primer seminario:

Functional Nanosheets of Oxides and Hydroxides
Prof. Takayoshi Sasaki

International Center for Materials Nanoarchitectonics, National Institute
for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
We have synthesized a variety of oxide and hydroxide nanosheets via total
exfoliation of their precursory layered compounds into colloidal single
layers1), which is triggered by intercalation of bulky organic ions or by
solvation with organic solvents. The resulting nanosheets are characterized
by their very high two-dimensional anisotropy; a molecular-level thickness
of 1-3 nm versus a bulk lateral size in a micrometer range, and thus can be
taken as “ceramics graphene”. The nanosheets exhibit a range of
intriguingproperties based
on their composition and structure. Typical nanosheets of Ti1-dO24d- and Ca2
Nb3O10- are wide-gap semiconductors, while those of MnO20.4- and
Cs4W11O362-are redox active.
These nanosheets are useful as a building block to fabricate various
nanostructured materials such as nanocomposites and nanofilms. Because they
are charged macromolecular moieties monodispersed in solvents, various
wet-process synthetic approaches involving self-assembly can be applied to
organize and combine them with various species including polyions,
complexes, and clusters. We have demonstrated that selection of nanosheets
and their counterparts as well as precise control over their
nanoarchitectures leads to a range of functionalities such as high photo
chemical activities, superior dielectric properties even at a nanometer
scale thickness, and so forth.

References:
1 R. Ma and T. Sasaki, *Adv. Mater*. *22*, 5082 (2010).


Segundo Seminario:
General Applicability of Alkali-Metal Ion Extraction and Phase
Transformation Reactions at Mid-Temperature Utilizing PTFE Powder
Tadashi C. Ozawa, TaKayoshi sasaki

Soft Chemistry Group, International Center for Materials Nanoarchitectonics
(WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki,
Tsukuba, Ibaraki 305-0044, Japan
Email: OZAWA.Tadashi en nims.go.jp
 **

A new approach to extract alkali-metal ions from layered compounds using
polytetrafluoroethylene (AEP reaction) has been explored. We have
discovered that when K0.8(Li0.27Ti1.73)O4 (KLTO) was reacted with
polytetrafluoroethylene at 400 °C in flowing Ar, alkali-metal ions were
extracted from KLTO and the remaining alkali-metal ion extracted KLTO
transformed into brookite, which is a metastable phase [1]. The driving
force of this AEP reaction is attributed to the strong ionic interaction
between alkali-metal ions in KLTO and F in polytetrafluoroethylene,
and the simultaneous
transformation of the alkali-metal ion extracted layered compound
intermediate to the metastable phase product is assisted by the
mid-temperature reaction environment. This AEP reaction is likely
applicable to various kinds of layered compounds other than KLTO to produce
many interesting compounds, including metastable ones, which are not
possible or difficult to prepare by other synthetic routes. In order to
clarify such general applicability of this AEP process, we have also
investigated the AEP reactions of other kinds of alkali-metal ion
containing layered compounds. Based on the structural similarities among
those layered compound precursors and their AEP reaction products, a
retrosynthetic utilization of the AEP process is proposed.

   References* ***
[1] Ozawa, T. C.; Sasaki, T. *Inorg. Chem.* 49 (2010) 3044.
[2] Ozawa, T. C.; Sasaki, T. *Inorg. Chem.* 51 (2012) 7317.
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