SPECIAL TOPICS IN ION BEAM ANALYSIS PART 1 THE MeV SIMS (or, can - PowerPoint PPT Presentation

SPECIAL TOPICS IN ION BEAM ANALYSIS – PART 1 THE MeV SIMS (or, can we analize molecules?) Milko Jakšić Laboratory for Ion Beam Interactions, Experimental physics division Ruđer Bošković Institute Zagreb, Croatia

OUTLINE • Ion microprobe – focusing the ion beam • Interaction of heavy ions and matter & Ion Beam Analysis • SIMS (Secondary Ion Mass Spectroscopy) ‐ history and basics • SIMS with MeV ions at the Ruđer Bošković Institute – The setup – Cultural heritage studies application – Applications in forensics • SIMS setup with STIM detector as a START trigger – Application to molecular imaging of cells • Capillary SIMS & increasing mass resolution • Conclusions • Transnational access to accelerator facilities 2

Ion beam focusing Demagnifications: Dx = x/X Dy = y/Y Horizontal plane Ion microprobe basics: - Solenoid lenses (used in electron microscopy) can not focus MeV ions (unless superconductive magnets are used) - Systems of magnetic or electrostatic quadrupoles have to be used - The main parameter that determines microbeam spot size of the MeV ion microprobe systems is demagnification ! - Many possible sources of unwanted influences on final microbeam size: ion source brightness, ion beam current, focusing element aberrations, vibrations, misalignments, working Vertical plane distances, collimation, vacuum levels, ion mass and energy,….

Ion beam focusing RBI microprobe setup: - High excitation triplet (Oxford) for low rigidity ions (up to 8 MeV protons) - Classical doublet is used for high rigidity ions (only two first quads are connected) and using longer working distance. - Magnetic beam scanning is used - Working distance is 11 cm for triplet, 26 cm for doublet From: F. Watt , G.W. Grime (Eds.), Principles and Applications of High Energy Ion Microbeams, Adam Hilger , Bristol (1987).

Imaging using focused ion beam focus focus quadrupole doublet proton focusing lens beam object slits sample pixe pixe x-ray Y X scan detector scan scan amplifier generator X-ray Y X energy spectrum Fe Ca elemental Pb S maps Elemental images

Interaction of fast (MeV) ions with matter a) Ionization of atoms (scattering with electrons) b) Scattering with atomic nuclei c) Nuclear reactions ionization scattering Every process lead to one or more analytical techniques: ION BEAM ANALYSIS

IBA and interactions of ion beam with matter Are there any process that can result in analysis of molecules? Yes, mass spectrometry ! 7

keV ions and SIMS Nuclear stopping Sputtering process !

keV ions and SIMS ‐ Secondary ion mass spectrometry SIMS spectra are dominated by molecular fragments !!! 9

What about the MeV ions? 100000 100000 Cu I Electronic 10000 10000 Si -1 stopping is 1000 Number of charge pairs (ion*nm) 1000 C much higher !! -1 100 100 Vacancies (ion*nm) protons 10 10 1 1 I 0,1 0,1 Si Cu 0,01 0,01 C 1E-3 1E-3 protons E ions = 1 MeV/amu 1E-4 1E-4 1E-5 1E-5 1E-6 1E-6 500 1000 500 1000 Depth (nm) Depth (nm) 10

What about the MeV ions?

Secondary Ion Mass Spectrometry (SIMS) The history – PDMS ! • 1974 first papers on desorption of molecular ions using fission fragments from 252 Cf source (plasma desorption mass spectrometry – PDMS) appeared • Later PDMS was abandoned and replaced by other mass spectrometry techniques like electron spray ionisation (ESI), matrix‐assisted laser desorption/ionization MALDI and SIMS using ions of keV energies. • In 2008, group of prof. J. Matsuo from Kyoto University started to use a MeV ions for desorption (same principle as PDMS, but MeV ions are produced by ion beam accelerator) • Today, 5‐6 laboratories in the world are performing SIMS measurements with MeV ions 12

Secondary Ion Mass Spectrometry (SIMS) The history – the use of MeV accelerator Kyoto University - Jiro Matsuo et al, Nucl. Instr. Meth., 267 (2009) 2144 Imaging mass spectrometry with nuclear microprobes for biological applications MeV SIMS Heavy ions of aprox. 1 MeV per nucleon 13

Linear TOF telescope for MeV SIMS providing a trigger (START signal)!! START ‐beam chopper STOP ‐MCP detector Pulse duration 2 ns Time between two pulses 100 μ s

Linear TOF telescope for MeV SIMS providing a trigger (START signal)!! START ‐beam chopper STOP ‐MCP detector Pulse duration 2 ns Time between two pulses 100 μ s 0.020 0.025 0.030 0.035 0.040 0.045 0.050 T im e (  s) 100 pA = 620 ions in 1  s, or 1.22 ion in 2 ns

Linear TOF telescope for MeV SIMS Target Einzel lens Grid MCP positive fragments Anode L≈400 mm 0 ‐2 kV 0 +5 kV 0 0‐3 kV MeV ions (chopped beam)

Why MeV SIMS? Tissue Living cell Bacteria 10 5 Molecular weight Protein 10 4 Lipid 10 3 Drag 10 2 1000 100 10 1 0.1 0.01 Spatial resolution (μm) Microbeam setup for MeV SIMS (Q triplet) • Molecular mapping of tissue • Pulsed ion beam (repetition rate 100 μs) • Detected masses: ~ 1000 Da • Object slit opening : 100 μm x 100 μm • High efficiency: >1% secondary ion yield • Collimator slit opening: 2 mm x 2 mm 10 3 higher yield for heavy molecules • • Beam dimension: ~ 5 μm (+ beam halo) than keV SIMS • Average pulsed current: ~ 1 fA • < 5ns pulse duration 17

MeV SIMS spectra and beam resolution test • 5 MeV O +3 • scan size 270×270 μm 2 • MeV SIMS image of Leucine • 0.1 mol solution of evaporated on Si substrate Leucine‐ C 6 H 13 NO 2 through Precision Electroformed Mash, 200 line/inch (space 112.3 μm, wire 14.7 μm) • prepared by Keisuke Wakamoto, Kyoto University • lateral beam resolution: x = (2.6 ± 1.2) μm y = (5.3 ± 2.0) μm 18

MeV SIMS – Imaging in forensics Molecular imaging of the ink intersections Pen 2 under Pen 3 Pen 3 under Pen 2 Green: m/z=611 Blue: m/z=576 Red: m/z=105 Identification of pigments (variations of blue phthalocyanines and alkyd binder)

MeV SIMS – Imaging in forensics Beam: 8 MeV Si 4+ Image size: 1×1 mm 2 Sample: Fingerprint on Si m/Z=23 30000 20000 Counts 10000 0 m/Z=365 0 50 100 150 200 250 300 350 400 m/Z

Cultural heritage studies using MeV SIMS “Study of modern paint materials and their stability using MeV SIMS and other analytical techniques” • Project with the Academy of Fine Arts Vienna • The most used binding media in artistic field, especially acrylic, vinyl and alkyds • Behavior of those materials, their interaction with other materials as well as their degradation with time is not well understood 21

Analysis of the colour pigment Table 1: description of the pigments used for the mock‐ups preparation, with relative molecular mass values 22

Identification of different blue phthalocyanine pigments in alkyd paints: 5 MeV Si 4+ Cu‐PC Metal free PC chlorinated Cu‐PC Binding medium Phthalocyanine 23

• 2 component mock‐ups were prepared at the Academy of Fine Arts • Commercial paints Griffin • Artificial ageing using increased temperature, (UV) light • UV1 + T1 ‐ 2 months ageing UV+T, T1 only temperature T • UV2 + T2 ‐ 4 months ageing UV+T, T2 only temperature T 24

5 MeV Si 4+ PB15:3 • Alkyd: • m/z= 76,104, 148 phthalic anhydride • m/z=191 ‐ polyol alkyd component Trimethylolpropane • m/z=284 ‐ drying oil alkyd component (stearic acid) 25

SIMS setup with STIM detector used as trigger Microbeam setup for MeV SIMS (Q triplet) • Continuous beam • Object slit opening :5 μmx5 μm • Collimator slit opening: 50 µmx50 µm • Beam dimension: <400 nm (Low beam halo) • Average current: ~ 1 fA (~10 kHz) • ~2 ns START pulse width • Molecular mapping of single cell • Detected masses: ~ 1000 Da • High efficiency: ~ 0.1 secondary ion yield • In addition, STIM image of the sample is recorded Requirements: • thin samples (transparent for the primary ions being used) Cell thickness is ~ 5 µm ☑ • Tissues sections ~5 µm ☑ • • Samples are mounted on the thin (100 nm) Si 3 N 4 windows 26

Beam resolution test • Beam: 9 MeV O 4+ • STIM measurements on a Ni‐plated grid • Smallest grid bars are = 400 nm • Scan (map) size= 27x27 µm 2 • Lateral resolution: FWHM (x)=(300±60) nm FWHM (y)=(500±100) nm (due to 45° orientation) 27

Molecular imaging of red onion cells Single layer of onion cells mounted on the 1x1 mm 2 window • Cryofixation (plunge freezing in LN2) • Freeze dried (24 h, 80°C at 10 ‐3 mbar) • SIMS measurements were performed by 9 MeV O 4+ ions Single cell size width ~ 50 µm 28

Molecular maps of the single onion cell Scan size=200x200 µm 2 (≈800 nm/pixel) 20000 600 Positive ions Negative ions 16000 400 12000 Counts Counts 8000 200 4000 0 0 0 100 200 300 400 500 600 700 800 900 0 100 200 300 400 500 600 700 800 900 1000 m/z m/z 29

Molecular maps of the single onion cell Scan size=200x200 µm 2 (≈800 nm/pixel) 30

Molecular imaging of single cancer cell Cell line preparation: • CaCo‐2 cells were derived from a human colorectal adenocarcinoma • Grown on 100 nm thin Si 3 N 4 window (with 5 nm Au layer) • Washed in ammonium formate (NH 4 HCOO) • Cryofixation (plunge freezing in LN 2 ) Freeze dried (24 h, 80°C at 10 ‐3 mbar) • 31