EURONanochem; Chemical Control at the Nanoscale

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EURONanochem Chemical Control at the Nanoscale
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EURONanochem

• Eurocore proposal co-ordinated by
• Professor G Dujardin
• Laboratoire de Photophysique Moléculaire,
  Université de ParisXI,FRANCE
• Professor G Gerber
• Fakultät für Physik und Astronomie, Universität
  Würzburg,GERMANY
• Professor F Gianturco
• Department of Chemistry Università di Roma "La
  Sapienza ITALY
• Professor Nigel J Mason (co-ordinator)
• Department of Physics Astronomy, Open
  University, UNITED KINGDOM
• Professor T D Maerk
• Institut Ionenphysik, University of Innsbruck,
  AUSTRIA

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EURONanochem

• Problem
• Conventional chemical reactions are mainly
  controlled
• based on conventional termodynamic variables.
• Aim
• To control chemical reactions through the ability
  to
• select the pathways of molecular dissociation.
• Methodology
• Control using photodissociation
• Control using electron induced fragmentation
• Provide spatial control through STM

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EURONanochem

• Brief description
• Chemical control with photons Using laser pulses
  with a duration of femtoseconds/picoseconds, the
  timescale on which the atoms in a molecule move,
  to manipulate molecular wavepackets and control
  dissociation pathways
• Chemical control using very low energy electrons
  to dissociate the molecular target at well
  defined reaction sites
• The application of STM technology to electron
  induced manipulation of single molecules on
  surfaces

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Bond Selectivity using photons Process of
coherent control.
Exploits the optical phase of coherent laser
light, coined coherent control. Such techniques
employ quantum mechanical interference between
the pathways leading to products of a chemical
reaction. One fs laser pulse can induce the
molecule only to bend, while a different light
pulse will cause it only to stretch. Hence can
select specific vibrations in molecules leading
to specific bond ruptures in turn opening
possibility of controlling chemical reactions.
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Optical control
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A laser-controlled molecule
Fully automated control
Science 282, 919 (1998) cited gt500?
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Optimal Control Experiments

• molecular gas phase photodissociation
• (selective bond-cleavage)
• selective excitation of complex molecules
• in the liquid phase
• photoisomerization of complex molecules
• in the liquid phase

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selectivity?
selectivity?
Bond Formation
Bond Cleavage
Femtosecond Laser-Assisted Catalytic Surface
Reactions of Syngas (COH2) and their
Optimization by Tailored Laser Pulses, Gerber et
al., Wuerzburg
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EURONanochem The programme

• Topic 1 Chemical Control using light Develop
  ultrafast femtosecond chemistry for selective
  bond by
• developing automated optimization of branching
  ratios of gas phase photodissociation reactions
• develop the technique of femtosecond polarization
  pulse shaping to study the attachment of
  functional groups to surfaces of materials such
  as semiconductors or molecular self-assembled
  monolayers
• extending present studies into the liquid phase
  to explore more biologically relevant chemical
  processes and
• complementing these experiments by theoretical
  studies.

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Bond Selectivity using Electrons Process of
Dissociative Electron Attachment (Low
electron energy!!!)
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Electron Induced Chemistry Chemical Control at
the Molecular Level
Selective C-Cl bond cleavage at 0 eV
Selective C-F bond cleavage at 3.2 eV
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Low-energy electrons induce single- and
double-strand breaks in DNA
An electron initially binds to DNA forming
transient molecular anion. This anion transforms
in a sequence of processes, leading to DNA strand
breaks.
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Example of Chemical surface transformations

• DEA produces products that subsequently react on
  the surface
• E.g. Irradiate film of NF3 and CH3Cl
• Form CH3F

e-
CH3Cl
e-
no ions
Cl-
(NF3)n(CH3Cl)m
e-
F-
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e-
Cl-
F-
CH3F
CH3Cl
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Control via e--induced chemistry developing
electron lithography
Basic e--molecule interactions Resonances E0
dependence
e--induced chemistry Cross sections Typical
reactions and products Reaction sequences
Surface functionalization Reactionsat the
interfaceof materials
Modification of materials properties -
structural- electrical - permeability - optical
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EURONanochem The programme

• Topic 2 Chemical Control using electrons
• to study intermolecular reactions leading to
  controlled coupling of a reactive fragment to
  another material
• to study the attachment of functional groups to
  surfaces of materials such as semiconductors or
  molecular self-assembled monolayers
• to explore the potential of these reactions for
  chemical lithography and e-beam techniques and
• to guide these experiments by theoretical
  studies, i.e. to predict which of different
  possible intermolecular reactions is
  energetically the most likely.

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Chemical control using STM
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STM induced chemistry
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Sloan and Palmer Nature 434, 367-371 Electron
excitation and dissociation of individual
oriented chlorobenzene molecules on a Si(111)-7 7
surface
The first electron interacts with the
chlorobenzene molecule the molecule is left
vibrationally excited (specifically, the C-Cl wag
mode is excited) the second electron interacts
with the molecule before the C-Cl wag mode has
fully relaxed, leading to dissociation of the
C-Cl bond by DEA
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EURONanochem The programme

• Topic 3 Chemical Control on the nanoscale
• STM experiments on prototype organic molecules
  adsorbed on surfaces with the aim of fabricating
  complex molecular architectures of any desired
  shape and size on the surface.
• Electron Simulated Desorption (ESD) and High
  Resolution Electron Energy Loss Spectroscopy
  (HREELS) experiments on to identify the ion
  resonances and the electronic transitions
  involved in the excitation mechanisms as well as
  the final products of the molecular reactions.
• Development of a comprehensive simulation of the
  coupled surface and STM tip system to model
  excitation and bond breaking of single molecules
  by STM-IET.
• Molecular dynamical calculations to unravel
  details of atomic and molecular manipulation at
  surfaces, leading to lateral motion, bond making
  or breaking, and desorption of the adsorbates.

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EURONanochem The programme

• Exploitation
• To explore how such fundamental techniques may be
  developed as a commercially viable technique.
• In developing such chemical control we also wish
  to exploit it in other modern technologies such
  as quantum information, nanotechnology and the
  biosciences.

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EURONanochem The programme

• Organisational
• Establishment of a European forum for discussion
  of challenges and opportunities in the
  development of chemical control.
• To further integration of European academic and
  industrial research communities in developing a
  common research framework in the utilisation of
  chemical control.
• To Encourage younger researchers and develop new
  groups (e.g in Central/Eastern Europe and the
  Balkans.
• To develop a coherent research programme that
  will allow methodologies for control of
  molecular dissociation pathways to be developed.
• To integrate researchers from femtosecond
  chemistry, electron chemistry, and scanning
  tunnel microscopy and share expertise and
  skills.

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EURONanochem The programme

• Hosting an annual Meeting in Europe (link to ESF
  EIPAM and COST ECCL)
• Develop international links ( USA Japan and
  Australia)
• Training -workshops and schools
• Industrial forums