EURONanochem; Chemical Control at the Nanoscale

Eurocore proposal co-ordinated by

Professor G Dujardin Laboratoire de Photophysique Moléculaire, Université de ParisXI,FRANCE

Professor G GerberFakultät für Physik und Astronomie, Universität Würzburg,GERMANY

Professor F GianturcoDepartment 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

EURONanochem

Problem: Conventional chemical reactions are mainly controlledbased on conventional termodynamic variables.

Aim:

To control chemical reactions through the ability toselect the pathways of molecular dissociation.

Methodology;• Control using photodissociation;• Control using electron induced fragmentation;• Provide spatial control through STM

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

EURONanochem

Bond Selectivity using photonsProcess 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.

Optical control

Electric control field E(t)

A laser-controlled molecule

Fully automated control Science 282, 919 (1998)cited >500

- molecular gas phase photodissociation

(selective bond-cleavage)

- selective excitation of complex molecules in the liquid phase

- photoisomerization of complex molecules in the liquid phase

Optimal Control Experiments

selective bond-forming reactions

Femtosecond Laser-Assisted Catalytic Surface Reactions of Syngas (CO+H2) and their Optimization by Tailored Laser Pulses,

Gerber et al., Wuerzburg

Bond Cleavage Bond Formation

selectivity? selectivity?

Topic 1; Chemical Control using light Develop ultrafast femtosecond chemistry for selective bond by

(a) developing automated optimization of branching ratios of gas phase photodissociation reactions

(b) 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;

(c) extending present studies into the liquid phase to explore more biologically relevant chemical processes and

(d) complementing these experiments by theoretical studies.

EURONanochem: The programme

Bond Selectivity using Electrons

Process of Dissociative Electron Attachment (Low electron

energy!!!)

Electron Induced Chemistry; Chemical Control at the Molecular Level

Selective C-Cl bondcleavage at 0 eV

Selective C-F bondcleavage at 3.2 eV

An electron initially binds to DNA forming transient molecular anion. This anion transforms in a sequence of processes, leading to DNA strand breaks.

Low-energy electrons induce single- and double-strand breaks in DNA

• DEA produces products that subsequently react on the surface

• E.g. Irradiate film of NF3 and CH3Cl• Form CH3F

Example of Chemical surface transformations

(NF3)n•(CH3Cl)m

CH3Cle-

e-

e-

no ions

F-

Cl-

e-

F-

CH3ClCH3F

Cl-

Basice--moleculeinteractions

Resonances

E0 dependence

Control via e--induced chemistry developing electron lithography

e--induced chemistry

Cross sections

Typical reactions and products

Reaction sequences

Surface functionalization

Reactionsat the interface

of materials

Modification of materials properties

- structural- electrical- permeability- optical

Topic 2; Chemical Control using electronsa) to study intermolecular reactions leading to controlled

coupling of a reactive fragment to another material b) to study the attachment of functional groups to

surfaces of materials such as semiconductors or molecular self-assembled monolayers;

c) to explore the potential of these reactions for chemical lithography and e-beam techniques and

d) to guide these experiments by theoretical studies, i.e. to predict which of different possible intermolecular reactions is energetically the most likely.

EURONanochem: The programme

Chemical control using STM

Nature, 2003

STM induced chemistry

Figure 2: Schematic drawing of the sequence of steps by which an STM probe can (a) dissociate a C6H5I molecule on a terrace; (b and c) draw the iodine atom away; (d) pull one C6H5 (phenyl) molecule toward another; (e) weld them together; (f) pull one phenyl to confirm the association. Hla et al, Physical Review Letters 85 2777 (2000).

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;

Topic 3; Chemical Control on the nanoscale(a) 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.

(b) 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.

(c) 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.

(d) 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.

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.

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.

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

EURONanochem: The programme