銀蒸着法を用いた表面支援レーザー脱離イオン化イメージング質量分析の表面選択性について Surface sensitiveness of silver deposition surface-assisted laser desorption/ionization imaging mass spectrometry. 20/May/2016 Annual conference on mass spectrometry, Japan T. Satoh 1, H. Niimi 1, N. Kikuchi 1, M. Fujii 2, T. Seki 2, J. Matsuo 2, (JEOL Ltd. 1, Kyoto Univ. 2 )
Mission Improve the degree of recognition of Imaging mass spectrometry (IMS) using our MALDI-TOFMS, SpiralTOF, as a new tool for SURFACE ANALYSIS.
Comparison table of surface analytical tools Probe Detection Lateral Resolution Probing Depth Information EPMA Electron X-ray 1 μm < 1 μm Elements AES Electron Auger 10 nm < 10 nm Elements, Electron Chemical bonding Elements, XPS X-ray Electron 10 μm < 10 nm Chemical bonding Functional group TOF-SIMS Ion Ion < 1 μm < 10 nm Elements, Partial molecular structure MALDI-IMS UV laser Ion 10-100 μm???? nm Molecular structure The expected strengths of MALDI-IMS for surface analytical tools are Getting molecular structure information of the organic compounds Visualizing the localization of the organic compounds We have to investigate lateral resolution and probing depth in the point of surface analysis. 3
Surface sensitivity For IMS in industrial applications, the surface sensitivity and lateral resolution are crucial for understanding segregation, defects, and degradation on the surface. Compound B Compound A Compound A Minor Major Compound B Major
Solvent-free Ag-NP SALDI-IMS MALDI-IMS Laser 20μmφ In the conventional, MALDI-IMS preparation, matrix solution was applied to sample surface. Target compounds are delocalized in both lateral and depth direction Matrix crystals are about 20 um, which are comparable to laser diameter. Ag-NP SALDI-IMS Laser 20μmφ Ag-NP was deposited on sample surface for enhancement of ionization and also functioned as cationization agents. 5
Method
Two-layered samples Irganox1010/Irganox3114 and Irganox1010/PS 462 μm 1. Irganox3114 was deposited on Si wafer. (PS was spincoated) 2. 55lpi mesh was put on the Irganox3114 or PS layer. 3. Irganox 1010 was deposited on Irganox 3114 or PS layer. 4. 55 lpi mesh was removed from surface. 95 μm Irganox1010: 160nm Irganox3114 or PS:150 nm 1. Irganox3114 was deposited on Si wafer. (PS was spincoated) 2. 55lpi mesh was put on the Irganox3114 or PS layer. 3. Irganox 1010 was deposited on Irganox 3114 or PSlayer. 4. 55 lpi mesh was removed from surface. Irganox1010: 10, 50, 100 nm Irganox3114 150nm or PS 180 nm 7
Sample preparation SALDI-IMS preparation: Ag was deposited on sample surface to 10 nm thickness. MALDI-IMS preparation: DHB 40mg/mL and AgTFA 2mg/mL (both in THF) were mixed 1:1, v/v and sprayed using air brush 8
Features of JMS-S3000 SpiralTOF (Matrix assisted) Laser Desorption/Ionization Solid State Laser : Nd:YLF 349 nm ( < 5ns ) Laser irradiation diameter: 20 μm High mass resolution by adopting JEOL s patented ion optical system with spiral ion trajectory Total fight path length = 17m The flight path was five times longer than reflectron TOFMS. Isobaric peak separation is available. Chemical background ions reduction. Eliminating the post-source decay ions through electrostatic sectors. Advantage for observing minor components.
Results
Mass Images MALDI-IMS, Spray method Irganox1010 [M+Ag] + PS [M+Ag] + 100μm 11 In MALDI-IMS, the gird patterns of both mass images were obscured. The ions from the PS layer under the Irganox1010 were also observed. These results were caused by dissolving the layers when the solvent was sprayed on the surface.
Mass Images Ag-NP SALDI-IMS for Irganox1010/PS Irganox1010 [M+Ag] + PS [M+Ag] + (sum of (C 8 H 8 ) n C 4 H 10 Ag +, n=13-22) Line profile 100μm Line profile Complementary grid patterns were clearly observed. Ions from the PS layer under the Irganox1010 layer were not observed. These results indicated Ag-NP SALDI-IMS selectively enhanced the ionization efficiency near the sample surface. 12
Probing depth for Irganox1010/PS [Irganox-Ag] + [PS-Ag] + a) Irganox-10nm/PS Irganox1010 10, 50, 100nm b) Irganox-50nm/PS [PS-Ag] + [PS-Ag] + not observed!! c) Irganox-100nm/PS PS:180 nm The probing depth of 10-nm Ag-NP SALDI-IMS was considered to be 50-100 nm. 13
Mass Images Ag-NP SALDI-IMS for Irganox1010/Irganox3114 Irganox1010 [M+Ag] + Irganox3114 [M+Ag] + Ag 9 + Ag 7 + Ag 8 + Ag 11 +
Relative Intensity Probing depth for Irganox 1010/Irganox 3114 10nm 50nm 100nm Irganox 1010 Irganox 3114 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Line profile of Irganox3114 0 200 400 600 800 Distance (μm) Probing depth of the 10 nm-thickness Ag NP SALDI for Irganox 1010/Irganox 3114 was determined to 50-100 nm in 20 μm pixel IMS. a) 10nm 厚 b) 50nm 厚 c) 100nm 厚 15
Summary Solvent-free 10 nm-thick Ag-NP SALDI-IMS was developed for surface sensitive IMS. Solvent-free method was prevented delocalization at sample surface Lateral resolution(pixel size) : < 20 μm Proving depth: 50-100 nm. The probing depth of 10 nm Ag-NP SALDI was more than five times of their size. 50nm Future work: Study of the probing depth dependence on Ag-NP thickness. Application to depth profiling combined with a beam etching or a low angle cutting technique. Thank you for your attention!!! 16