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Electron induced chemistry –applications from Astrochemistry to
cancer therapy
Nigel John Mason
Electron Induced Processes
Atmospheric physics and planetary atmospheres
Electron Induced Processes
Astrochemistry: Formation of molecules in Space
Electron Induced Processes
Semiconductor plasmas
Electron Induced Processes
Lighting industry
Electron Induced Processes
Radiation damage of DNA and cellular material
Electron Induced Processing
Nanotechnology and surface engineering
Electron Induced Chemistry;
In this presentation I will describe;
• The role of low energy electrons in electron driven chemistry
• Show how such research can be applied to study fundamental problems in natural and industrial world
In Europe this research has been developed through collaborative programme Funded by EU
2002 Framework V Network EPIC 2002-2005 Electron and Positron Induced Chemistry
EU COST Action P9 RADAM Radiation damage 2004-2007
ESF Programme Electron Induced Processing at the Molecular Level (EIPAM) 2004-2009
EU COST Action CM0601 Electron Controlled Chemical Lithography 2008-11
EU COST Action CM0805 Astrochemistry 2009 - 2013
Electron Based research in Europe
How do electrons trigger chemistry ?
By
• Exciting
• Dissociating or
• ionising molecules
with subsequent products being reactants in collisional chemistry
Electron Induced Chemistry; Chemical Control at the Molecular Level
Consider for example simple electron induced dissociation through an excited molecular electronic state.
e- + M M# X + R + e (1)
R + AB AR + B (2)
Example 1
Formation of glycine in the Interstellar medium
Electron Induced Chemistry; Chemical Control at the Molecular Level
Example: Glycine in the ISM ?
• Kuan et al 2003 – The Astrophysical Journal,
593:848–867, 2003
• Searched for interstellar conformer I glycine (NH2CH2COOH), the simplest amino acid, in the hot molecular cores Sgr B2(N-LMH), Orion KL
• ALMA will search/dectect for Glycine
Kleinman-Low (KL) Region of the Orion NebulaSubaru Telescope, NAOJ
To pumping station
Continuous flow cryostat Ion gauge
Cryogen inlet via transfer line
Temperaturecontroller
Sources
E-gun
Synchrotron
Ion Source
Resistive heater
ThermocouplesMgF2/ZnSe
substrate
Copper sample mount
Detectors
- UV-VIS / FTIR detector
- Photomultiplier Tube
Sources- UV-VIS / FTIR
spectrometer- Synchrotron
• Vacuum chamber to mimic empty space:
– P~10-8 - 10-10 mbar• Still > a million times higher
than ISM!
• Temperature very cold in space– Continuous flow LHe/LN2
cryostat• 12 K < T < 450 K
• Material to mimic grains
• Make ice Samples
• Use spectroscopy to see what you make
Experimental Procedure
• Ice sample was prepared at 10 K by depositing binary gas mixtures of methylamine (CH3NH2; and carbon dioxide (CO2) onto a cooled silver crystal.
• Ice thickness & column densities determined by Beer-Lambert Law
• Column densities of carbon dioxide and methylamine of
2.00.4 1016 cm-2 and 7.20.21017 cm-
2 respectively
5 keV Electron irradiation of methylammine and carbon
dioxide ice makes glycine simple amino acid
05th Jan 2006 Chemistry of Planets
Electron Induced Chemistry
• Some examples of laboratory study of electron induced synthesis of molecules under astrochemical conditions.
• Chemical synthesis in 1:1 Mixture of NH3:CO2 Ice with 1 keV electrons at 30 K
05th Jan 2006 Chemistry of Planets
Formation of ammonium carbamate
05th Jan 2006 Chemistry of Planets
Electron Induced Chemistry
• Some examples of laboratory study of electron induced synthesis of molecules under astrochemical conditions.
• Chemical synthesis in the Irradiation of 1:1 Mixture of NH3:CH3OH ice with 1 keV electrons at 20 K
05th Jan 2006 Chemistry of Planets
Formation of ethylene glycol in pure methanol ice
HOH2C-CH2OH
05th Jan 2006 Chemistry of Planets
Formation of methyl formate CH3OHCO
05th Jan 2006 Chemistry of Planets
Formation of formamide HCONH2
(Khanna, Lowenthal et al. 2002)
Electron Induced Chemistry; Chemical Control at the Molecular Level
These are examples of high energy electrons ‘Blasting’ molecules apart or release of secondary electrons !!
But at low energies electrons can do surprising things !
Electron Induced Chemistry; Chemical Control at the Molecular Level
At low energies electrons can do surprising things !
• They can ‘stick’ to the molecule • To form a negative ion or ‘resonance’ • But only for a very short period of time (10-14 s)
• Then the electron detaches • Leaving molecule excited or not (elastic scattering)• But this process can also lead to the dissociation of the molecule
This is the process of Dissociative Electron Attachment (DEA)
Bond Selectivity using Electrons
Process of Dissociative Electron Attachment
Electron Induced Chemistry; Chemical Control at the Molecular Level
Dissociative electron attachment therefore
provides a method for breaking up molecules
at low energies
Energies lower than the chemical bond energy !!!
Hence electrons can initiate chemistry
Electron Induced chemistry
• Electrons used to ‘tune’ the products of a reaction
• Through selective bond dissociation different energy different pathways
Electron Induced Chemistry; Chemical Control at the Molecular Level
Electron Induced Chemistry; Chemical Control at the Molecular Level
Selective C-Cl bondcleavage at 0 eV
Selective C-F bondcleavage at 3.2 eV
Illenberger et al Berlin
Nucleophilic Displacement (SN2) Reaction
e.g. : F- + CH3Cl CH3F + Cl-
e- + CH3Cl CH3 + Cl-
< 10-23 cm2 (unmeasurably small)
fromimpurity
SN2 Reaction
Illenberger et al Berlin
(NF3)n•(CH3Cl)m
CH3Cle-
e-
e-
no ions
F-
Cl-
• Chemical surface transformations using electron induced reactions/
• DEA produces products that subsequently react on the surface
• E.g. Irradiate film of NF3 and CH3Cl
• Form CH3F
e-
F-
CH3Cl CH3F
Cl-
R. Balog and E. Illenberger
Phys. Rev. Letters 91 213201-1
• Complete chemical
Transformation
of thin films
e + C2F4Cl2 → C2F4 + Cl2
C2F4 desorbs
So surface transformation
to 100% Cl2 film !!Cl2
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
Functionalization of H-diamond
CH3CN / H-diamond at 35 K, E0 = 2 eV
0 100 200 300 400 500
(d)
(c)
(b)
(1a)
Inte
nsi
ty (
a.u
.)
Energy Loss (meV)
C. Jäggle
Cooperation:R.Azria and A.Lafosse
e-(E0)
CH3CNH HH HH H
H HH HH H
HCH
2C
N
HH HNC
CH
2
DEA and biomolecules
• DEA is a universal process
• So DEA will occur in biomolecules including those constituents of DNA
• So can DEA induced fragmentation lead to DNA damage ?
In many molecules DEA leads to H atom loss
• This is most dominant process in DEA to organic acids
• E.g. acetic, formic and …
Relative cross sections of H Relative cross sections of H channel channel for Carboxylic acidsfor Carboxylic acids
0 2 4 6 8 10 12 14 16 18
0 2 4 6 8 10 12 14 16 18 0 2 4 6 8 10 12 14 16 18
0 2 4 6 8 10 12 14 16 18
8.6eV
6.5eVWater
6.6eV9.1eV
7.3eVFormic Acid
9.1eV
7.7eV
6.7 eVAcetic Acid
6.7eV 9.1eV
7.7eVPropionic Acid
Electron energy (eV)
Ion
cu
rren
t
O
HCC
H
H
OH
O
HCC
H
H
OD
CHCH33COODCOOD
0 2 4 6 8 10 12 14 16 180 2 4 6 8 10 12 14 16 18
Electron energy (eV)
H/ CH3COOH
H/ CH3COOD
D/ CH3COOD
Electron energy (eV)
H/ CH3COOH
CHCH33COOHCOOH
Prabhudesai et al. PRL (2005)
Is this unique for carboxylic Is this unique for carboxylic acids?acids?
0 2 4 6 8 10 12 14 16 180 2 4 6 8 10 12 14 16 18
0 2 4 6 8 10 12 14 16 18
9.6eV
6.3eVEthanol
10.1eV7.9eV
6.4eVMethanol
8.6eV
6.5eV Water
CH3OH CH3CH2OH
H H from Amine from AmineH / CH4
H / NH3
0 2 4 6 8 10 12 14 16 18Electron energy (eV)
n-Propyl amine
CH3CH2CH2NH2
or X e-
<20 eV
Single and double strand breaks may be induced by secondary
species: a large number of secondary electron with kinetic energies
below about 20 eV, are produced along the radiation track
Damage of the genom in living cell by ionising
radiation is about 1/3 a direct and 2/3 an indirect
processes.
Radiation damage to DNA
Can electrons damage DNACan electrons damage DNA??
super coiled DNA
single strand break SSB
double strand breakDSB
DNA damage - strand breaks
Mechanisms for ssb and dsb induction at low-energies
• Boudaiffa et al. (Leon Sanche, Sherbrooke Canada) demonstrated that there apperas tpo be a corrrelation between patterns of ssb and dsb induced in DNA and DEA of constituent molecules
Resonant Formation of DNA Strand Breaks by Low-Energy (3 to 20eV) Electrons. Science 287, 1658-1660 (2000). B. Boudaiffa, P. Cloutier, D. Hunting, M.A. Huels et L. Sanche.
L. Sanche et al. Science, 287 (2000) 1659 and PRL (2004)
Strand breaks of DNA
10
0 5 10 15 20
0
5
10
SSB DSB
Electron Energy (eV)
DN
A b
reak
s pe
r 10
4 in
cide
nt e
lect
rons
L. Sanche et al. Science, 287 (2000) 1659 and PRL (2004)
Strand breaks of DNA
10
0 5 10 15 20
0
5
10
SSB DSB
Electron Energy (eV)
DN
A b
reak
s pe
r 10
4 in
cide
nt e
lect
rons
e- + DNA → DNA-* → fragments
DNA – deoxyribonucleoside acid
ion beam
neutral beam
electron beamFWHM ~ 100 meVIe ~ few nA
Hemispherical electron monochromator
oven
quadrupole mass spectrometer
channeltron
~ 150°C~ 10-7 mbar
Experimental setup – gas phase Innsbruck
Thymine + e- → TNI-* →electron attachment
C5H6N2O2-
e-dissociative electron attachment
(T-H)- + H(T-2H)- + neutral(s)
C4H5N2O- + neutral(s)
C2H3N2O- + neutral(s)
C3H2NO- + neutral(s)
CN- + neutral(s)
O- + neutral(s)H- + neutral(s)
OCN- + neutral(s)
→→→
→→
→C3H4N- + neutral(s)
→
→
→
→
Dissociative Electron Attachment
126 amu
125 amu
124 amu
1 amu
16 amu
26 amu
42 amu
54 amu
68 amu
99 amu
73 amu
0 1 2 3 40
2
4
6
8
10
12
Cro
ss s
ectio
n (1
0-20 m
2)
Electron energy (eV)
H loss
e-
Electron Attachment to Thymine
(M-H)-
125 amu
0.4
0
0.7
Δ#,1
1.4
binding energies of C-H and N-H bonds
electron affinities of various (U-H) isomers
1.3
0.9
1.6
Emin
2.3
1
3
5
6
#
1
23 4
5
6
4.3 eV 5.0 eV
4.5 eV
5.8 eV-4.5 eV
-3.4 eV
-2.9 eV
-2.7 eV
C
C
C
CO
N
O
N
C
C
C
C
CO
N
O
N
C
e-
Quantum Chemical Calculations
Thymine-methyl-d3-6-d
5-methyluracil
1-methylthymine Uracil 3-methyluracil
Thymine
Carbon
Nitrogen
Oxygen
Hydrogen
Deuterium
Thymine-methyl-d3-6-d
5-methyluracil
1-methylthymine Uracil 3-methyluracil
Isotope and site labelling thymine
0 1 2 3
0
20
40
60
80
100
Io
n s
ign
al (
arb
. un
its
)
Electron energy (eV)
(M-H)-
m1T
m3U
1
3
Site and bond selectivity in DEA
129 amu
GCAT
GCAT
G+C+A+TG+C+A+T
EA - electron affinityEA(CN)= 3.82 eVEA(CNO)= 3.61 eV
DEA to oligomers
O
PO-
NH2
N N
NNHO O
O
O
NH2
O
N
N
P
OO OO-
O
O NH2
N
N
N
N
NN
O
O
O
OO
O
O-
O
OH
G
C
A
Toligomertetramer
(1172 amu)
P
CN- CNO-Gas phase
Condensed phase
Does DEA explain effectiveness of some radiosensitizers ?
• Observation of correlation between carcinogens and DEA rates ?
• Effectiveness of halogenated compounds as radiosensitizers
Uracil Thymine Bromouracil (Radiosensitizer)
(UCl)-
(UCl-HCl)-
0
2
4
6
8
10
0 1 2 3 40
100
200
300
400
500
Electron energy (eV)
0
50
100
150
200
250
Cro
ss s
ecti
on
(Å
2 )
(Cl)-
Ratios: X-/(U-yl)- = 1.3, 40, 490 (X=Cl,Br,I) Present: Cl-/(U-yl)- =0.47
Halo-uracils measured by Illenberger et al Berlin.UCl + eUCl + e-- anionsanions
+ Br
.
≈ 600 Å2
Freie University Berlin
New techniques for electron scattering!
The Method of Scanning Tunnel Microscopy
Electron current from fine metal tip interacts with (metal) substrate
Electron Induced Chemistry; Nanotechnology
Electron Induced Chemistry; Nanotechnology
www.eng.yale.edu/.../ spm/stm-operation.gif
STM
M
e-
Single Molecule Engineering
• Changing environment like temp., pressure or catalyst
• Coherent pulse sequence – (Potter et.al. Nature 355, 66 (1998))
• Optimal control by shaping of fast pulses – (Levis et.al. Science 292, 709 (2001))
• Addressing single molecule using STM – (Pascual et al. Nature 2003, Sloan and Palmer,
Nature 2005)
Optimal control using laser pulse shapingOptimal control using laser pulse shapingActive control of chemical reactions
Nature, 2003
Making new molecules
Hla et al (Berlin)
C12H10
Electron Induced Chemistry; Nanotechnology
Electron Induced Chemistry; Nanotechnology
Chemical Control at the Molecular Level
Nature 434, 367-371
Two-electron dissociation of single molecules by atomic manipulation at room temperature
Electron Induced Chemistry; Nanotechnology
Chemical Control at the Molecular Level
Electron excitation and dissociation of individual oriented chlorobenzene molecules on a Si(111)-7 7 surface at room temperature by a two-electron mechanism that couples vibrational excitation and dissociative electron attachment steps.
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;
Electron Induced Chemistry; Nanotechnology
Chemical Control at the Molecular Level
Focussed Electron and Ion Beam Deposition
Focussed Electron and Ion Beam Deposition
Focussed Electron and Ion Beam Deposition
Focussed Electron and Ion Beam Deposition
Focussed Electron and Ion Beam Deposition
So What Next ?????
• Plans for 2011-14 (in Europe)
1.Negative ions in plasmas. Use to tune fragmentation pathways in semiconductor plasmas.
2.Anions may be used to form radicals for surface chemistry.
Electron Induced Chemistry;
• Plan for 2011-14 (in Europe)
1. Tune fragmentation pathways in semiconductor plasmas. Negative ions in plasmas programme Europe with Japan.
2. DEA as a process for nanolithography (electron/positron and photoelectron processing). Surface engineering using STM to manipulate molecules EU programme
Electron Induced Chemistry;
• Plan for 2011-14 (in Europe)
1. Tune fragmentation pathways in semiconductor plasmas. Negative ions in plasmas programme Europe with Japan.
2. DEA as a process for nanolithography (electron/positron and photoelectron processing). Surface engineering using STM to manipulate molecules
3. Electron damage of biomolecules and DNA (electron transport in DNA nanowires).NEW COST IBCT Action
Electron Induced Chemistry;
Plan for 2010-14 (in Europe)
1. Tune fragmentation pathways in semiconductor plasmas. Negative ions in plasmas programme Europe with Japan.
2. DEA as a process for nanolithography (electron/positron and photoelectron processing). Surface engineering using STM to manipulate molecules EU programme (with Australia).
3. Electron damage of biomolecules and DNA ( electron transport in DNA nanowires) EU Programme.
4. Astrochemistry; low temperature electron processing of ices to probe molecular formation in space;
Electron Induced Chemistry;
Collaborative programmes (Europe)
ESF/COST Electron Controlled Chemical Lithography 2007-10
ESF/COST The Chemical Cosmos 2009-2013
ESF/COST IBCT 2010-14
EU Research Infrastructure Europlanet 2009 -2012
EU Initial Training Network LASSIE 2010-14
VAMDC atomic and molecular database 2009-2012
COST is supported by the EU RTD Framework Programme
ESF provides the COST Office through an EC contract
VAMDC
• A database of Atomic and molecular data for applications including astronomy.
• Http://www.vamdc.org/
Role for Quantemol
• This range of applications requires a lot of data !
Data overload ?Data overload ?
DatabasesDatabases Assembly, Assembly,
intercomparisointercomparison, n, error/sensitiviterror/sensitivity analysisy analysis
Quantemol NQuantemol N
Calculate cross sections ! But low Calculate cross sections ! But low energy so..energy so..
Combine with higher energy (India, Combine with higher energy (India, Vinodkumar. Joshipure, Antony) Vinodkumar. Joshipure, Antony)
Zero to 1000s eVZero to 1000s eV
COST is supported by the EU RTD Framework Programme
ESF provides the COST Office through an EC contract
0.1 1 10 100 10000
10
20
30
40
50
60
TC
S2إ) )
Ei(eV)
Present Qmol Present SCOP Zecca Soeoka Garcia Ariyasinghe szmytkowski Alle Liu ADR Liu SEF Munjal Gianturco
e - NH3
COST is supported by the EU RTD Framework Programme
ESF provides the COST Office through an EC contract
0.1 1 10 100 1000
0
10
20
30
40
50
60
70
TC
Sإ)
2)
Ei(eV)
Present Qmol Present SCOP Szmytkowski Munjal Bettega J ain
e - PH3
Quantemol Quantemol
Ca n estiamte cross sections for Ca n estiamte cross sections for targets experimrntalists don’t want targets experimrntalists don’t want to touch ! Or cant do to touch ! Or cant do
Radicals ( CFRadicals ( CFxx SiH SiHxx OH CCCH etc) OH CCCH etc)
But challenge for larger systems But challenge for larger systems DyIDyI33
The team – with thanks UCL and OU • Sarah Barnett, Julia Davies, • Jon Gingell, Andy Birrell,• Nykola Jones, Petra Tegeder• Paulo Vieira, Samuel Eden, • Paul Kendall, Anita Dawes• Philip Holtom, Robin Mukerji,• Dagmar Jaksch, Mike Davis, • Sarah Webb, Liz Drage, • Eva Vasekova, Gosia Smialek, • Bhala Sivaraman, Sohan Jeetha• Patrick Cahillane, William
Stevens.
Sylwia Ptasinska, Sam Eden, Jimena Gorfinkiel, Radmila Panajatovic
And finally to all my colleagues– with thanks
• Tilmann Märk, Paul Scheier et al , Universität Innsbruck, Austria• David Field, Nykola Jones,Soren Hoffmann University Aarhus,
Denmark • Eugen Illenberger and group Frei University Berli• Stefan Matejcik, Jan D. Skalny, Comenius University, Bratislava• Gustavo Garcia, Madrid, Spain• Paulo Vieira Lisbon. Portugal• Marie Jeanne Hubin Franskin, Jacques Delwishe, Liege, Belgium • K Joshipura and M Vinodkumar Sarad Patel university India• B Raja Sekhar CAT Indore and BARC India• H Tanaka Sophia Univeristy Tokyo and Y Itikawa , Japan
• And all those others in our EU Collaborations