Diapositive 1

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Chapter 1. Introduction, perspectives, and aims.
On the science of simulation and modelling.
Modelling at bulk, meso, and nano scale. (2
hours). Chapter 2. Experimental Techniques in
Nanotechnology. Theory and Experiment Two faces
of the same coin (2 hours). Chapter 3.
Introduction to Methods of the Classic and
Quantum Mechanics. Force Fields, Semiempirical,
Plane-Wave pseudopotential calculations. (2
hours) Chapter 4. Intoduction to Methods and
Techniques of Quantum Chemistry, Ab initio
methods, and Methods based on Density Functional
Theory (DFT). (4 hours) Chapter 5. Visualization
codes, algorithms and programs. GAUSSIAN,
CRYSTAL, and VASP. (6 hours).
.
2
.
Chapter 6. Calculation of physical and chemical
properties of nanomaterials. (2 hours). Chapter
7. Calculation of optical properties.
Photoluminescence. (3 hours). Chapter 8.
Modelization of the growth mechanism of
nanomaterials. Surface Energy and Wullf
architecture (3 hours) Chapter 9.
Heterostructures Modeling. Simple and complex
metal oxides. (2 hours) Chapter 10. Modelization
of chemical reaction at surfaces. Heterogeneous
catalysis. Towards an undertanding of the
Nanocatalysis. (4 hours)
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Chapter 2. Experimental Techniques in
Nanotechnology. Theory and Experiment Two faces
of the same coin
Juan Andrés y Lourdes Gracia Departamento de
Química-Física y Analítica Universitat Jaume
I Spain CMDCM, Sao Carlos Brazil
Sao Carlos, Novembro 2010
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Experiment and Theory
New strategies and methodologies
Simulation Oxford Dictionary Definition
produce a computer model of (a process)
5
Powerful and indispensable tools for
nanoscience/nanotechnology
SYNTHESIS Obtaining tiny slabs that serve as
precisely controlled mockups of the real world
catalysts.

1. Vapor Liquid Solid (VLS)
2. Chemical Vapor deposition (CVD)
3. Solid Vapor Deposition (SVD)
4. Single Source Chemical Vapor Deposition (SSCVD)
5. Litography
6. Laser Ablation
7. Sol-Gel
8. Template-Assisted Methods

6
M. L. Curri, R. Comparelli, M. Striccolia and A.
Agostiano Phys. Chem. Chem. Phys., 2010, 12, 1119
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Powerful and indispensable tools for
nanoscience/nanotechnology

• EXPERIMENTS
• Scanning Tunneling Microscopy (STM)
• Scanning Electron Microscopy (SEM)
• Energy-Dispersive X-ray Spectroscopy (EDX)
• Transmission Electron Microscopy (TEM)
• Selected Area Electron Diffraction (SAED)
• X-ray Photoelectron Spectroscopy (XPS)
• Powder X-ray Diffraction (XRD)
• Electron Energy Loss Spectroscopy (EELS)
• Raman Spectroscopy
• Photolumuniscence (PL)
• Cathodoluminiscence (CL)

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In the last 30 years, we have seen an
extraordinary experimental advance on the
techniques to produce, in a controlled way,
smaller and smaller structures, even in atomic
scale. Parallel to these achievements,
characterization techniques have also matured in
order to better understand the properties of
these materials. Altogether, these
factors are responsible for the rising of
nanoscience and nanotechnology. Schwartz, D.
A. Norberg, N. S. Nguyen, Q. P. Parker, J. M.
Gamelin, D. R. J. Am. Chem. Soc. 2003, 125,
13205. Peng, X. Manna, L. Yang, W. Wickham,
J. Scher, E. Kadavanich, A. Alivisatos, A. P.
Nature 2001, 404, 59. Shevchenko, E. V. Talapin,
D. V. Murray, C. B. OBrien, S. J. Am. Chem.
Soc. 2006, 128, 3620
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Powerful and indispensable tools for
nanoscience/nanotechnology

• Last but not least, theorists are employing ab
  initio schemes or density functional theory to
  calculate how molecules will stick to the
  nanoparticles and interact.

THEORY
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History (1) All of Chemistry revolves
around swapping electrons, and theoretical and
computational methods and techniques forecasting
how atoms and molecules will rearrange themselves
and bond as the electrons they share shift to
minimize energy.
11
History (2) G.Whitesides What Will
Chemistry Do in the Next Twenty Years? Angew.
Chem Int. Ed. Engl., 29, 1209 (1990)
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The path of Chemistry in the future will be
determined by its generation of new ideas through
four basic research Areas
.Materials Chemistry .Biological
Chemistry .Computational Chemistry .Chemistry
exploring the limits of size and speed in
chemical phenomena
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Somorjai, G. A. Levine, R. D. The Changing
Landscape of Physical Chemistry at the Beginning
of the 21st Century J. Phys. Chem. B 109, 9853
(2005).
Now enter the nanosciences, which again are also
driven by the needs of technologies, which
provide challenges to learn the manipulation of
matter on the nanoscale connecting molecules and
studying their self-assembly, optical, chemical,
electronic, magnetic, and mechanical properties.
The centralizing themes of physical chemistry
again become dominant at the start of the 21st
century, just as they were dominant in the early
decades of the 20th century.
There are major changes occurring in the way
research is performed in physical chemistry. This
is in part due to our success in providing an
ever-increasing science component to existing and
emerging technologies that accelerates their need
for even more. Our ability to study the science
of chemical complexity permitted us to target
major scientific and societal problems that
require an interdisciplinary approach
These include environmental chemistry, problems
of size reduction in microelectronics that led to
the rise of nanoscience and nanotechnologies, and
the design of drugs and implant devices that
extend human life span and sustain the health of
the human body.
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THE ROYAL SWEDISH ACADEMY OF SCIENCES
The discovery of carbon atoms bound in the form
of a ball is rewarded
Nanostructures 1996
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THE ROYAL SWEDISH ACADEMY OF SCIENCES
Development of computational methods in chemistry
awarded
Quantum Chemistry 1998
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THE ROYAL SWEDISH ACADEMY OF SCIENCES
Femtochemistry 1999
For showing that it is possible with rapid laser
technique to see how atoms in a molecule move
during a chemical reaction.
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Chemistry is not solely an experimental science
anymore
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Nobel Prize in Physics 2010
Andre Geim and Konstantin Novoselov for their
"groundbreaking experiments regarding the
two-dimensional material graphene
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M. Pumera, Chem. Soc. Rev., 2010, 39, 41464157
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Nobel Prize in Chemistry 2010

• Richard F. Heck, Ei-ichi Negishi, and Akira
  Suzuki

winners for "developing new, more efficient ways
of linking carbon atoms together to build the
complex molecules that are improving our everyday
lives."
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This was a reaction that was possible with
other metals, but it did not work very well. With
palladium it worked much better.
One of the main features of the reactions
is that they are catalytic processes that allow
synthetic chemists to do things which they could
not previously do - to join carbon atoms together
in a new way,'
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• To illustrate the diversity and importance of the
  palladium-catalysed cross coupling reactions
• - Total synthesis of the anticancer drug Taxol
  (paclitaxel)
• The Heck reaction is also used to make a
  strategic bond in a synthesis of morphine.
• - Negishi coupling was key to the laboratory
  synthesis of the natural product hennoxazole A, a
  marine antiviral compound.
• - Suzuki coupling is used to prepare the
  antiviral bromoindole alkaloid dragmacidin.
• These are merely a handful of examples of
  palladium-catalysed cross coupling, which has
  been used - and continues to be used - in the
  synthesis of thousands of important compounds,
  from the most complex natural products to
  tonne-scale industrial intermediates.

25
Over the last years, first-principles
calculations have become recognized as an
outstanding tool so as to elucidate the
electronic structure of crystalline materials
26
Theory and experimentation combine today in the
search for understanding of the inner structure
of matter
W. Kohn, Rev. Mod. Phys, 1999, 71, 1253 (Nobel
Lecture) Electronic structure of matter-wave
functions and density functionals
.....for his development of the
density-functional theory.....
J. A. Pople, Rev. Mod. Phys, 1999, 71, 1267
(Nobel Lecture) Quantum chemical models
.....for his development of computational
methods in quantum chemistry.....
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Basic Challenges Since chemistry concerns the
study of properties of substances or molecular
systems in terms of atoms, the basic challenge
facing computational chemistry is to describe or
even predict.
1. the structure and stability of a molecular
system. concerns prediction of which
state of system has the lowest energy.
2. the (free) energy of different states of a
molecular system. involves prediction of the
relative (free)energy of different states.
3. reaction processes within molecular systems
in terms of interactions at the atomic
level. involves prediction of the dynamic
process of change of states.
1 lt 2 lt 3 Increasing difficulty
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Theory vs. Experiment
Modern research in the chemical sciences
seeks not only to make useful molecules and
materials but to understand, design, and control
their properties. Theory is at the very center of
this effort, providing the framework for an
atomic and molecular level description of
chemical structure and reactivity that forms the
basis for interpreting experimental data and
provides guidance toward new experimental
directions. Theoretical and computational
chemistry has developed into an important tool in
almost all areas of chemistry. Their methods and
techniques have found its way into the everyday
work of many experimental chemists. Calculations
can predict the outcome of chemical reactions,
afford insight into reaction mechanisms, and be
used to interpret structure and bonding in
molecules. Thus, contemporary theory offers
tremendous opportunities in experimental chemical
research.
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Theory vs. Experiment
Combined experimental and computational
studies of chemical reactivity can yield
remarkable insight into reaction mechanisms and
kinetics. This is particularly true for chemical
reaction taking place in very tight places,
involving unusual mechanistic features.
Physics-based simulations complement experiments
in building a molecular-level understanding they
can test hypotheses and interpret and analyse
experimental data in terms of interactions at the
atomic level not available experimentally.
The joint use of both theoretical and
experimental results also suggests additional
experiments and simulations that can further
increase our knowledge. The insights
gained from simulation are synergistic with those
that arise from new experiments, and sometimes
they lead the way on problems where experiments
are not available.
30
Feymann, R. P. Eng. Sci. 23, 22 (1960).
The principle of Physics as far as I can see, do
not speak against the possibility of maneuvering
things atom by atom .
Quantum Mechanics
Theoretical and Computational Chemistry
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THEORETICAL AND COMPUTATIONAL CHEMISTRY
32
Classification of Molecular Systems
33
Points 1. 2. 3. allows us to say we can
actually start to observe phenomena at the atomic
scale under realistic conditions.
The dream of Richard P. Feynman (in 1960s)
is fulfilled!
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Methods Techniques of Theoretical and
Computational Chemistry

• Prediction

• Interpretation

• Characterization

• Understanding physical and chemical properties at
  atomic level

35
Computational and Theoretical Chemistry
- Energy (DE, DG, DH and DS) - Ionization
potential (IP) - Electron affinity (EA) -
Geometry (bond distance, bond angle and dihedral
angle) - Electronic properties (molecular
orbitals, density of states, band gap) -
Vibrational Frequencies, IR (analysis of
stationary points R, P, I and TS structures) -
Analysis of Potential Energy Surfaces (crossing
points, valley ridge inflexion points, conical
intersections) - Electron density (topological
analysis AIM, ELF)
36
Computational and Theoretical Chemistry
Software GAUSSIAN (2009) CRYSTAL (2009)
VASP GAMESS MOLCAS ADF XcrysDen TopMo
d
Hardware Silicon Graphics MIPS R14k
400MHz PC/Linux Cluster, AMD 2200MP
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Theoretical work
Experimental work
complementary tools
The cooperation between both worlds is mandatory
38
Interaction between Experiments, Analytical
Theories, and ComputationR. A. Marcus, J. Phys.
Chem. C 2009, 113, 1459814608

• We all recognize that one of the main goals in
  research is to capture the physical essence of a
  phenomenon and use it not only to interpret but
  also to predict the results of new experiments.
  One view of theory, demonstrated in the present
  article, is that experiments are primary, often
  the source of new theory, and that the
  interaction of theory and experiment is
  paramount, each stimulating the other.
• Nevertheless, discerning basic theoretical
  problems in the wealth of available experimental
  and computational results can be a major hurdle
  and sometimes the development of the theory can
  be relatively rapid once the existence of an
  experimental puzzle is known. The writer
  continues to be impressed with this exciting
  interplay of experiment and theory and with many
  experimental puzzles that exist and that continue
  to arise in new experiments, when one keeps an
  eye out for them. For the theoretically oriented
  students it is perhaps a truism to add that the
  broader ones background is in physics, chemistry
  and mathematics, and the more one is familiar
  with the new results and the potential and
  limitations of new techniques, the larger the
  range of interesting problems that one can
  address.

39
Experiment and Theory in Harmony
Mark A. Johnson at Yale University discusses how
the two sides of physical chemistry have
necessarily developed together, and looks at how
their synergy dictates the direction of
contemporary research.
Equations such as Schrödingers famous
contribution to quantum mechanics underpin much
of physical chemistry.
Nature Chemistry, 1, 8 (2009)
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Experiment and Theory in Harmony
Physical chemists seek to anchor the empirical
rules of chemistry to the laws of physics, and
thus provide secure concepts to explain the
trends seen in reactivity and molecular
structure.
A recurrent theme in contemporary physical
chemistry is a convergence of experimental and
theoretical methods towards sufficiently complex
model systems. By this I mean systems that not
only reproduce real chemical processes but also
do so in a fashion that reveals molecular level,
quantum-mechanically consistent pictures that are
not greatly obscured by either thermal or
ensemble averaging.
Nature Chemistry, 1, 8 (2009)
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Controlling the properties of nanostructures
requires a detailed understanding of structure,
microstructure, and chemistry at
ever-decreasinglength scales. The modern day
transmission electron microscope has thus become
an indispensable tool in the study of
nanostructures. In this Perspective,we present a
brief account of the capabilities of the TEM with
some typical examples for characterizing
nanostructures. The modern-day TEM has moved from
a simple characterization tool to a nanoscale
laboratory enabling in situ observation of
several fundamental processes at unprecedented
resolution levels.
N. Ravishankar, J. Phys. Chem. Letters, 2010, 1,
12121220
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technique (spatial resolution) information
imaging mass thickness contrast (gt1 nm) diffraction contrast (1 nm) bright field/dark field imaging phase contrast (lt0.1 nm) high resolution imaging Z-contrast (lt0.1 nm) high-angle annular dark field imaging distinguishing particles with large difference in average Z phases, defects, orientation relationship, growth direction, morphology atomic structure of defect-free and defect-containing crystals atomic level distribution of high Z elements
diffraction selected area diffraction (500 nm) microdiffraction/nanobeam diffraction (1-10 nm) convergent beam electron diffraction (1-10 nm) orientation, crystal structure orientation, local structure point group/space group information
spectroscopy X-ray energy-dispersive spectroscopy (10 nm) electron energy loss spectroscopy (lt1 nm) composition, elemental mapping elemental mapping (including light elements),
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The future of nanotechnology rests upon
approaches to making new, useful nanomaterials
and testing them in complex systems. Currently,
the advance from discovery to application is
constrained in nanomaterials relative to a mature
market, as seen in molecular and bulk matter. To
reap the benefits of nanotechnology, improvements
in characterization are needed to increase
throughput as creativity outpaces our ability to
confirm results. The considerations of research,
commerce, and regulation are part of a larger
feedback loop that illustrates a mutual need for
rapid, easy, and standardized characterization of
a large property matrix. Now, we have an
opportunity and a need to strike a new balance
that drives higher quality research, simplifies
commercial exploitation, and allows reasoned
regulatory approaches.
Erik K. Richman and James E. Hutchison VOL. 3 ?
NO. 9 ? 24412446 ? 2009
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Techniques for nanoscale structure determination
Surface science techniques are
characterized by their ability to provide
sensitivity to a slice of material with nanoscale
thicknesson top of a single-crystal substrate.
The blossoming of nanoscience and
nanotechnology requires adapting or developing
appropriate techniques of characterization with
additional nanoscale resolution in one or two of
the other dimensions. The challenge of
detailed atomic-level structure (bond lengths and
bond angles) in such nanomaterials is even more
formidable, especially if we wish to keep a
three-dimensional spatial resolution in a single
nanoparticle.
51
Techniques for nanoscale structure determination
A recent overview of the issues involved
is available in a recent review article 4, so
we will only discuss the most promising
techniques here, with special focus on STM and
LEED since these methods are not covered in any
detail in that review. At present, it
appears that mainly STM, XRD (x-ray diffraction)
and high-energy electron diffraction are ready
for the task of detailed nanostructure
determination, while XAFS may provide such
information in conjunction with other techniques
no other technique can at this stage, to my
knowledge, find the atomic positions in an
individual nanostructure with an accuracy of the
order of 0.1 Å 0.01 nm.
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Techniques for nanoscale structure determination
Scanning tunneling microscopy (STM) STM
unquestionably dominates the field of structural
analysis of nanostructures 5. However, a visual
inspection of STM images is not sufficient to
extract bond lengths and angles, except those
parallel to an extended surface that provides
some reference yardstick such as known bulk
lattice constants. In fact, even in a
qualitative sense, a visual inspection of an STM
image is known to often give incorrect answers
to equate bumps in topographic images with
atoms or even electronic orbitals has been shown
in many cases to lead to gross errors of
interpretation. For example, oxygen atoms
often appear as dips when one expects to see
bumps, as happens when they are adsorbed on
various metal surfaces this and other examples
are discussed in Ref. 6. It is safe to assume
that a substantial fraction of published visual
interpretations of STM images are simply wrong in
some atomic-scale conclusions.
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Techniques for nanoscale structure determination
Scanning tunneling microscopy (STM) Many
theoretical models of STM have been developed
since the early work of Tersoff and Hamann 7,8.
Most of the basic principles governing the
current or topographic contrast recorded in an
STM image are now well understood in terms of the
electronic and atomic structures of both the tip
and surface being probed, together with their
interactions 9. In particular, the STM
tip has to be treated on an equal footing with
the sample to be probed the geometry and
electronic structure of the tip can affect the
image as much as the samples properties. This
becomes particularly important for nanostructures
with corners and edges, which can look like tips
from the point of view of the STM tip.
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Techniques for nanoscale structure determination
Scanning tunneling microscopy (STM)
A theory which has revealed itself to be
computationally fast, convenient and remarkably
realistic for calculating STM images is the
elastic-scattering quantum chemistry (ESQC)
method 1012, in spite of the use of the simple
Extended Hückel Theory (EHT) to describe the
electronic structure. It has been
successfully applied to a variety of surfaces,
although rarely to fit unknown atomic positions
to experimental images. One example of structural
determination by such fitting is the case of S
atoms adsorbed on Mo(100), for which the S height
above the Mo substrate was obtained 13,14.
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Techniques for nanoscale structure determination
Scanning tunneling microscopy (STM)
More recently, ab initio based formalisms
relying on Bardeens approximation to the
electron current have been successfully applied
to semiconductor and metal surfaces 8,15.
Such codes, however, involve large computer
resources and become inefficient when dealing
with complex systems for which many possible
structural configurations need to be explored,
especially when there is a need to simulate
entire images rather than just a few scan lines.
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Techniques for nanoscale structure determination
Scanning tunneling microscopy (STM)
While most STM computer codes are set up
for periodic twodimensional surfaces, their
application to non-periodic systems such as
nanostructures is feasible to some degree through
the subterfuge of periodic boundary conditions
(i.e. repeating tip-nanostructure units), thanks
to the relative locality of STM tunneling.
Converting periodic codes to non-periodic ones is
also an option, even though this may require more
computing resources.
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Techniques for nanoscale structure determination
X-ray diffraction (XRD)
X-ray diffraction has recently started to
be applied to nanoparticles 1621. Several of
these studies obtain the particle shape and/or
average lattice parameters, without determining
localatom-by-atom deviations from such average
lattice constants. The challenge with XRD
is to obtain a measurable signal, usually
requiring enough identical nanoparticles, thus
also demanding sufficient uniformity of size and
orientation.
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Techniques for nanoscale structure determination
X-ray diffraction (XRD)
A very successful example is the structure
determination of 102-atom gold clusters, each
coated in a layer of p-mercaptobenzoic acid
molecules and then crystallized 18.
Their analysis revealed an unexpected chiral
structure with 5-fold axial symmetry the Au core
can be viewed as five twinned face-centered cubic
crystallites.
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Techniques for nanoscale structure determination
X-ray diffraction (XRD)
Another example concerns Co nano-islands on
Cu(001) 21, for which the so-called mesoscopic
misfit was investigated. The authors observe that
small Co islands (12 nm in diameter) deposited
on Cu(001) at 170 K (the total coverage is in the
0.10.5 ML range) show significant static
disorder, i.e. many Co atoms are positioned
somewhat away from the ideal hollow sites.
This is due to the fact that the CoCo distance
is observed to be sharply reduced (by up to 10)
in these islands as compared to the bulk.
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Techniques for nanoscale structure determination
X-ray absorption spectroscopy (XAS)
A natural technique for investigating
nanoparticles is x-ray absorption spectroscopy
(XAS), including in particular extended x-ray
absorption fine structure (EXAFS), and x-ray
absorption near-edge structure (XANES, also
called near-edge x-ray absorption fine structure
or NEXAFS) this technique inherently focuses
on structure around a central atom 22,23, and
is thus less dependent on periodic ordering than
XRD or LEED.
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Techniques for nanoscale structure determination
X-ray absorption spectroscopy (XAS)
One example is provided by the study of
carbon-supported Pt nanoparticles in the 26 nm
diameter range 22. An fcc packing of the Pt
atoms and a hemispherical cluster shape were in
this case suggested by STEM (scanning
transmission electron microscopy) and supported
by the EXAFS data. Using
temperature-dependent EXAFS data, it is possible
to distinguish static disorder (in this case
atomic relaxations from bulk-like positions) from
thermal disorder (random displacements due to
thermal vibrations).
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Techniques for nanoscale structure determination
X-ray absorption spectroscopy (XAS)
This provides a distribution of interatomic
distances in the nanoparticles. However, it is
difficult to assign specific displacements to
specific atoms, so that a relatively simple model
must be fit to the available data. For
the smallest nanoparticles (2 nm), one model
yielded an average first-nearest-neighbor
distance reduced by 0.002 nm or 0.7 relative to
bulk Pt and largest individual reductions about 6
times larger.
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Techniques for nanoscale structure determination
Low-energy electron diffraction and NanoLEED
LEED was developed over the last half
century to measure the atomic structure of an
extended surface of about a millimeter in size to
a depth of about a nanometer, as given by the
cross-section of the typical LEED beam and by the
electron mean-free path, respectively 24.
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Techniques for nanoscale structure determination
Low-energy electron diffraction and NanoLEED
In that well-tested and successful
implementation, LEED has solved some 1000 surface
structures of great variety 25. This
implementation also allows determining the
structure of some nanostructures, for example C60
buckyballs adsorbed in a periodic (4 x 4) lattice
on an extended Cu(111) surface 26 as long as
the nanostructure is periodic with a unit cell
that is not too large, a conventional LEED
analysis is possible.
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Techniques for nanoscale structure determination
Low-energy electron diffraction and NanoLEED
A different approach for LEED would be to
sample a single and thus non-periodic
nanostructure, for instance a single nanodot,
nanotube or nanowire (attached to a surface or
hanging from supports). This could be
achieved experimentally by narrow or focused LEED
beams two approaches have already been proposed,
as discussed next.
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Techniques for nanoscale structure determination
Low-energy electron diffraction and NanoLEED
It should be possible to focus the incident
LEED beam onto a small area, as can currently be
done in low-energy electron microscopy (LEEM) on
the scale of 250 nm, including in future onto
smaller areas. Diffraction from single
objects as small as a few nanometers is
conceivable. Electron beams have in fact been
focusedto dimensions in the 50 nm range in
various applications 27. Then the
diffracted pattern can be recorded, either as
angular dependent intensity data or as
energy-dependent data (IV curves).
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Techniques for nanoscale structure determination
Low-energy electron diffraction and NanoLEED
This idea has been proposed theoretically
in the form of convergent- beam LEED (CBLEED)
28. The angular spread of the converging beam
then implies a corresponding broadening of the
diffraction pattern. In the case of an
ordered structure, the sharp spots of normal LEED
would be replaced by disks delimited by the
angular spread of the convergent beam these
disks contain angle- dependent intensities that
provide additional structural information not
present in sharp spots.
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Techniques for nanoscale structure determination
Low-energy electron diffraction and NanoLEED
Even for a diffuse LEED pattern (without
sharp spots due to absence of long-range
periodicity) this would still be valuable if this
spread is taken into account in the calculation
through convolution (as is already commonly done,
for example, in photoelectron diffraction to
reflect the angular aperture of the detector
29).
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Techniques for nanoscale structure determination
Low-energy electron diffraction and NanoLEED
Another approach is to use as electron
source an STM tip located tens or hundreds of
nanometers from the nanostructure this tip
serves to emit a very narrow beam with angular
spread of only about 5º 30. Such an
experiment has already produced LEED patterns
from areas as small as 400 lmacross, with areas
smaller than 50 nm across being possible.
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Techniques for nanoscale structure determination
Low-energy electron diffraction and NanoLEED
On the theoretical side, two new features
must be addressed to analyze measured LEED
intensities a convergent incident beam and the
greater structural complexity of a nanostructure
compared with typical periodic unit cells on an
extended surface. These challenges are
met in a new method, called NanoLEED, that we
have implemented in recent years 3134.
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Techniques for nanoscale structure determination
High-energy electron diffraction
Transmission electron microscopy (TEM) and
high-resolution electron microscopy (HREM) can
certainly image nanostructure at the atomic
scale, including for single nanostructures, but
do not provide three- imensional structure.
However, a closely related approach, under the
name coherent electron diffraction (CED), has
very recently been used to determine relaxations
of the surface of single Au nanocrystals
(supported by graphene) of diameter 3-5 nm 46.
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Techniques for nanoscale structure determination
High-energy electron diffraction
Thus, the 200 kV electron diffraction
pattern of a single 4 nm nanocrystal was fit with
simple models of atomic relaxation, giving radial
bond length contractions up to 8 relative to the
interior of the particle the larger values occur
for atoms that have lower coordination, as
expected.
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The Chemical Structure of a Molecule Resolved by
Atomic Force Microscopy
Resolving individual atoms has always been the
ultimate goal of surface microscopy. The scanning
tunneling microscope images atomic-scale features
on surfaces, but resolving single atoms within an
adsorbed molecule remains a great challenge
because the tunneling current is primarily
sensitive to the local electron density of states
close to the Fermi level. We demonstrate imaging
of molecules with unprecedented atomic resolution
by probing the short-range chemical forces with
use of noncontact atomic force microscopy. The
key step is functionalizing the microscopes tip
apex with suitable, atomically well-defined
terminations, such as CO molecules. Our
experimental findings are corroborated by ab
initio density functional theory calculations.
Comparison with theory shows that Pauli repulsion
is the source of the atomic resolution, whereas
van der Waals and electrostatic forces only add a
diffuse attractive.
Leo Gross, Fabian Mohn, Nikolaj Moll, Peter
Liljeroth, Gerhard Meyer SCIENCE 325 1110 (2009)
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Top Catal (2010) 53832847

• Ex-situ characterization
• Transmission electron microscopy (TEM)
• X-ray diffraction (XRD)
• Diffuse reflectance UVVis spectroscopy X-ray
  photoelectron spectroscopy (XPS)
• Scanning electron microscopy (SEM)
• Chemisorption, physisorptionSmall angle X-ray
  scattering (SAXS)
• Energy dispersive X-ray analysis (EDX)
• Thermogravimetric analysis (TGA)
• Temperature programmed oxidation (TPO)
• Inductively coupled plasmaoptical emission
  spectroscopy (ICPOES)

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Top Catal (2010) 53832847

• Spectroscopies and microscopy for in situ
  characterization
• High-pressure scanning tunneling microscopy
  (HP-STM)
• Sum frequency generation spectroscopy (SFG)
• Ambient-pressure X-ray photoelectron
  spectroscopy (APXPS)
• Diffuse reflectance infrared spectroscopy
  (DRIFTS)
• UV-Raman and surface enhanced raman spectroscopy
  (SERS)
• Transmission electron microscopy (TEM)
• Tapered element oscillating microbalance (TEOM)
• Thermogravimetric analysis (TGA)
• UVVis diffuse reflectance spectroscopy
• X-ray diffraction (XRD)
• Small-angle/wide-angle X-ray scattering
  (SAXS-WAXS)
• Near-edge X-ray absorption fine structure
  (NEXAFS)
• Extended X-ray absorption fine structure (EXAFS)

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