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nomad-lab
AreaB-AppDef
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6ee6443d
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6ee6443d
authored
3 years ago
by
Tamas Haraszti
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added more about the nanoscale description and a section about crystal structures.
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microstructure/readme.md
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@@ -27,10 +27,72 @@ of composition.
Especially for porous solid samples (solid / gas interface) one may detect the
specific surface area as an intergral characteristic of the sample.
## nano to microscale
The lowest scale we can reach in analysing the sample is to understand the quantum state
of atoms and molecules within the sample. Especially for samples containing macromolecules
or colloidal nanoparticles, the common classification originally used for proteins
is a good starting point.
Here the
[
structure
](
https://en.wikipedia.org/wiki/Protein_structure
)
is then built up as:
-
primary structure: the spatial sequence of chemical elements as they form the chain
of chemical bonds
-
secondary structure: the direct aggregates of such groups, forming beta sheets and
alpha helixes for proteins
-
tertiary structure: how the actual conformation of the primary and secondary level
folds up
-
quarternary structure: the direct aggregation of the individual molecules
And from this level, further supramolecular structure formation spans up to the microscale.
## crystal structures
For crystal growth, this problem is most often investigated from top to down, because
an ideal crystal shows a nanoscale periodicity spanning up to macroscopic scales. In such
systems the actual structure elements of interest are those deviating from the ideal
structure. Defects form from atomic level point defects up to micro- and macroscopic
dislocations. And these defects play crucial roles in the physical- chemical properties of
the resulted material.
Thus, they must be analyzed and described together with the ideal crystal structure.
# Experimental methods applied
## Microscopy
Microscopic imaging is available using a large number of various tools and spans length
scales from a few nm to micrometers. Such methods include:
-
optical microscopy (bright field, dark field, polarization, fluorescence, etc.)
-
electron microscopy (transmission, scanning, etc.)
-
X-ray microscopy
The here mentioned methods typically provide a projected image of the sample, from
which image processing tools can extraxt size and shape information of a small
population of samples.
### tomography and holography
Other imaging tools may provide three dimensional information usually with a lower
resolution than the projection systems. Both tomography and holography require extensize
data processing and several model assumptions to extract spatial information abou the
sample.
### spectral imaging
Further possibility is to combine point spectroscopy or other elementary analysis
tools with imaging to obtain the (usually) 2 dimensional composition pattern of a sample.
-
EDX
-
Raman imaging (microscopy, CARS)
## Scattering and diffraction
Scattering techniques collect information in the spatial Fourier space thus require
extensive modeling of the sample to obtain characteristic size and shape information.
These models often also produce some parameters about the size distribution of the sample.
## Adsorption isotherms
Adsorption measurements indirectly identify the specific surface area of the sample based
on assumptions how the molecules bind to the surface.
(We also obtain some reaction kinetics parameters of the process along the area / binding
capacity.)
## spectroscopy
Spectroscopic methods provide information about the molecular composition and the quantum
state of the atoms or atom groups within the material. With modelling the data, we can gain
insight the nanoscale organization of the molecules within the sample.
-
NMR
-
APRES / XPS
-
mass spectrometry
-
absorption and fluorescence spectroscopies (UV/VIS, IR, X-ray...)
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