Analytical Sciences

Imaging of Polycyclic Aromatic Hydrocarbons by Means of Sputtered Neutrals Mass Spectrometry Using a Diode-pumped Solid-State Laser

Kenji OHISHI,*1 Tetsuo SAKAMOTO,*1 Jiro SAIKAWA,*2 Naoya ISHIGAKI,*2 Koji TOJO,*2 Yutaka IDO,*2 Shun-ichi HAYASHI,*3 Shun-ichi ISHIUCHI,*4 Kentaro MISAWA,*4 and Masaaki FUJII*4

*1 Graduate School of Electrical and Electronics Engineering, Kogakuin University, 2665-1 Nakanomachi, Hachioji, Tokyo 192-0015, Japan
*2 Shimadzu Corporation, 2385-13 Iiyama, Atsugi, Kanagawa 243-0213, Japan
*3 Advanced Technology Research Laboratories, Nippon Steel & Sumitomo Metal Corporation, 20-1 Shintomi, Futtsu, Chiba 293-8511, Japan
*4 Chemical Resources Laboratory, Tokyo Institute of Technology, 4259, Nagatsuta, Midori, Yokohama, Kanagawa 226-8503, Japan

Laser post-ionization of sputtered molecules by pulsed Ga focused ion-beam (Ga-FIB) bombardment was examined for the detection and imaging of polycyclic aromatic hydrocarbons (PAHs) on particles. As model samples, pyrene and pelyrene adsorbed on TiO₂, blended regents of pyrene and n-heneicosan were used. The TiO₂ particle size was selected to be several micro-meters. Laser light and Ga-FIB were synchronized with each other. The repetition rate synchronized with Ga-FIB was 1 kHz for pyrene analysis and 2 kHz for perylene, respectively. The laser wavelength was set to 266 nm. The wavelength was a generated fourth harmonic of a Nd:YAG DPSS (diode-pumped solid-state) micro-chip laser (UV microchip laser). By using a UV microchip laser, laser-SNMS (laser post-ionized sputtered neutral mass spectrometry) analysis and imaging were performed. The imaging of pyrene (m/z = 202, C₁₆H₁₀) and perylene (m/z = 252, C₂₀H₁₂) has been successful. Both the scanning ion microscopy image of TiO₂ and the PAHs image in laser-SNMS analysis were well-fitted with each other.

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