Laser Desorption Time-of-Flight Mass Spectrometer for Sub-Micrometer-Scale Mass Spectrometry Imaging Using Near-Field Optics Technique
LI Xiao-ping, YIN Zhi-bin, CHENG Xiao-ling, LIU Rong, HANG Wei*
Ministry of Education (MOE) Key Laboratory of Spectrochemical Analysis and Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
Abstract：Laser-based ionization time-of-flight mass spectrometry techniques, as an emerging mass spectrometry imaging technique, has been widely used in material, geology, environment, pharmacology, and especially life science. However, it is difficult to achieve sub-micrometer-scale imaging resolution due to the limits of diffraction limit of light, focusing distance and numerical aperture of focusing lens. The introduction of the near-field optics technique has overcome this limitation. By combining the near-field optics technique and laser ionization mass spectrometry, nanoscale crater on the solid surface could be achieved. In addition, traditional mass spectrometry imaging techniques usually neglect the topographical information of the irregular sample surface and cause unreal imaging. So it is important for multifunctional in-situ characterization to get the chemical and topographical information simultaneously. In this paper, a near-field nanometer aperture tip desorption postionization time-of-flight mass spectrometer was developed for sub-micrometer-scale chemical and topographical analysis. 532 and 355 nm laser were used as the desorption and postionizationlaser respectively. A tuning fork based AFM system was used to control the distance between the tip and sample. Copper phthalocyanine molecular layers was ablated to produce a series of nanoscale craters with the size from 550 to 850 nm, which indicated that the technique could achieve sub-micrometer-scale lateral resolution. Furthermore, a mass spectrometry imaging with high lateral resolution was carried out on a 7.5 μm×7.5 μm copper phthalocyanine grid pattern sample. As the results showed, the chemical imaging of the sample surface was achieved simultaneously with the topographical information, expanding the in-situ characterization ability of the mass spectrometry imaging techniques.
Key words：Nanometer aperture tip; Sub-micrometer-scale resolution; Mass spectrometry imaging; Topographical imaging; Time-of flight mass spectrometry
李晓萍，殷志斌，程肖玲，刘 蓉，杭 纬. 近场光学用于激光解吸飞行时间质谱的亚微米级空间分辨成像[J]. 光谱学与光谱分析, 2019, 39(05): 1354-1358.
LI Xiao-ping, YIN Zhi-bin, CHENG Xiao-ling, LIU Rong, HANG Wei. Laser Desorption Time-of-Flight Mass Spectrometer for Sub-Micrometer-Scale Mass Spectrometry Imaging Using Near-Field Optics Technique. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(05): 1354-1358.
