Molecular Environmental Sciences
Dalton Abdala's webpage
Molecular Environmental Sciences
FEATURED BEAMLINES & TECHNIQUES AVAILABLE AT LNLS
sxs
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SOFT X-RAYS ABSORPTION SPECTROSCOPY
Opportunities
X-rays absorption spectroscopic techniques give information about the nature of the immediate chemical environment of an atom, i.e., identity and number of nearest neighboring atoms as well as the interatomic distance between neighboring atoms and the X-ray absorbing atom.
At beamline SXS, experimenters can have access to X-rays varying in energy from ~ 1.5 up to 5 keV, i.e., an energy range that encompasses the order of the binding energies of electrons in many geological structures and molecules in biological processes, thus enabling one to obtain detailed structural information of such materials at very small scales.
Among the techniques available at beamline SXS are X-ray Photoelectron Spectroscopy (XPS), X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopies. At these energies, one is able to collect information at the K-edge (Al, P, S, K and Ca, Mo, V, Ti) and L2,3-edge of several elements of environmental relevance.
nano-FTIR
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NANO-FOURIER TRANSFORM INFRA RED
Infra Red (IR) microscopy with FTIR spectroscopy enables chemical mapping of samples with a spatial resolution limited by diffraction (few μms). Near-field based approaches, such as scattering or aperture type scanning near-field optical microscopy (s-SNOM or a-SNOM), overcome this limitation. These systems are based on atomic force microscopy (AFM). The metallic probe in turn acts under optimized conditions as an antenna which confines the incident electric field around the tip-apex thus providing a nanoscale light source for high-resolution imaging. This very challenging experiment was done with a thermal (globar) source. Knowing that synchrotron radiation is about 500 times brighter than a globar, we decided to build a similar experiment at LNLS. At that time we were considering to build a “classical” IR beamline but these new possibilities were more exciting because among the 30 IR beamlines in the world, none had such possibility.
Topography (a) and optical signal (b) from a 40 nm thick SiO2 layer (center rectangle) on a Si substrate.
IMX
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X-RAY micro-TOMOGRAPHY
The full 3D information of a sample can be obtained by acquiring projection images along a number of different directions. Using the Radon transform and its inverse, these projections can be used as input for computerized tomographic reconstruction. In 2011, it was decided to build an imaging beamline on a bending magnet that could operate in either white or monochromatic beam.
The white beam energy spectrum ranges from 4 to 25 keV, with a photon flux at the sample of 10^15 ph/s. A monochromatic beam ranging between 6 keV and 14 keV is provided by either a double multilayer monochromator with a photon flux density of around 4 x 10^9 photons/s/mm2 (between 4 keV and 14 keV) or a double-crystal Silicon (Si111) monochromator with photon flux density of ~ 10^8 photons/s/mm2 (between 4 keV and 14 keV).
X-ray micro-tomography showing the porosity of soil microaggregates
The images were taken from soils formed from nearly same original materials. The picture on the left was, however, taken from a soil microaggregate collected under a forest, whereas the picture on the right is a soil microaggregate collected from an ant mound just beside the forest.
XAFS
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HARD X-RAYS ABSORPTION SPECTROSCOPY
Hard X-rays absorption spectroscopy provides molecular understanding on the reactivity and bioavailability of metals in soils and sediments. Spectroscopic techniques can verify the mechanisms by which metals interact with soils' consitutents, provide contaminant speciation and insights into their reactivity in the environment. Information obtained via XAFS techniques has been useful to substantiate proposed standard soils and sediment anaytical protocols as they provide a molecular basis for interpretation and extrapolation of research data.
At the XAFS beamlines (XAFS1, XAFS2 and DXAS), experimenters can have access to X-rays ranging from ~ 4 up to 20 keV. XANES and EXAFS data can be collected in fluorescence or transmission modes at the K-edge of metals and metaloids typically found in soil environments, such as Mn, Fe, Co, Ni, Cu, Zn, As, Se and Mo. At these energies, the L2,3-edge of a number of transition metals can also be probed, La, Sn, Ce, Au, Pt, Hg, Pb and others.
Research Highlights
Long-term manure application effects on soil P
Phosphorus surface complexation I
Phosphorus surface complexation II
Designing "smart fertilizers" more suited to tropical soils conditions
Ongoing Research
Designing "smart fertilizers"
Metal hypperaccumulating plants
Long-term application of organic residues in soils
MES Facts
MES statistics
Research Projects
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