[Todos] SEMINARIO EXTRAORDINARIO GCIA.INV.yAPLICACIONES-TANDAR-26/ENERO 11:00 hs

[Graciela Mastrogiacomo]

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                                       SEMINARIOS 2010
            Gerencia Investigacion y Aplicaciones - TANDAR - CNEA
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Martes 26 de enero, 11:00 Hs.
Aula Nivel 0, TANDAR


"Synchrotron X-rays and DFT to Unveil Molecules in Action:
1) Relaxed Final State DFT Simulations of Sulfur K-edge XANES and
MicroXANES for Catalysis;
2)Applications of XANES to Biology, Medicine (Cancer) and Chemistry"


                                Dra. Ana 
MIJOVILOVICH  [1]
Inorganic Chemistry and Catalysis, University of Utrecht, The 
Netherlands.
On leave to: The Canadian Light Source, Saskatoon, Canada


X-ray Near Edge Structure (XANES) and the space-resolved microXANES 
can
provide qualitative and quantitative information on the fate of 
Sulfur in
diverse environments. The DFT used in the works presented here [1], 
allows
calculating the experimental spectrum, that is, with the excited core 
hole
(after the excitation of the 1s electron during the "X-ray 
absorption"
process) and the subsequent relaxation and with the calculation of 
the
transition matrix, instead of extrapolating the XANES from the 
densities
of states in the ground state. It has proven to be very successful in
solutions and amino acids [2].  Here examples are shown for the 
analysis
of the differences between aliphatic and thiophenic sulfur compounds,
usually found in oils and coals [3]. The questions that can be 
answered
range from identification and quantification of sulfur compounds for
speciation analysis, to the analysis of the electronic structure of 
the
sulfur, like the sulfur hybridization, protonation of the compound, 
as
well as differentiation of aliphatic and aromatic sulfur. The 
advantages
and limitations of the techniques are explained.

Study cases:
1) Understanding Sulfur compounds speciation in detail: a) Thiophenic 
and
aliphatic sulfur [3]; b) Sulfide-disulfide [4]. DFT simulations 
treating
the core hole as "half core hole" give the best approximation to the
XANES. Including the relaxation of the first excited states and 
taking the
non-orthogonal transition moments gives almost a perfect match many 
eV
above the edge. This unusual result is due to the use of the diffuse 
basis
set, which allows  a good description of both the delocalized states 
as
well as bound states, in the near edge region. The first LUMO 
transitions
and their relation to the spectral features are discussed.

2) Theory in action: microspectroscopy of the oligomerization 
reactions on
zeolite crystals [5]. We focus on XANES simulations to understand the 
fate
of thiophene deposited on zeolite crystals, termally treated.

3) Microspectroscopy with spatial resolution to study the fate of 
metals
in cancer tissues and cells and the binding of anticancer 
metallo-drugs
(Ga and Pt),  and studies of the metal accumulation in 
hyperaccumulator
plants.
_______________________________________________________

[1]  E-mail: ana_mijo en yahoo.com
http://www.anorg.chem.uu.nl/peopleOld/postdoctoralfellows/Ana%20Mijovilovich/index.htm


Quedan todos cordialmente invitados !


11:00 hs - Aula Nivel 0, TANDAR
CNEA - Centro Atomico Constituyentes
Av. Gral. Paz y Constituyentes
6772-7065 / 7007
Coordinadores:
Dres. Andres Arazi: < mailto: arazi en tandar.cnea.gov.ar  y
Daniel L. Hojman: < mailto: hojman en tandar.cnea.gov.ar
Secretaria: Graciela Mastrogiacomo:
mailto:gmastro en tandar.cnea.gov.ar
http://www.tandar.cnea.gov.ar/eventos/seminariosUAF/
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