Sub-micrometer-scale chemical analysis by nanosecond-laser-induced tip-enhanced ablation and ionization time-of-flight mass spectrometry

摘要

The tip-enhanced near-field technique has drawn great attention recently becauseit is a promising technique for nanoscale chemical analysis when combined withother spectroscopic methods. Furthermore, this integration can improve the spatialresolution of mass spectrometry. In this stud~ a nanosecond-laser （nsqaser）-inducedtip-enhanced ablation and ionization source was coupled to an in-house-builtlaser ionization time-of-flight mass spectrometer. Sub-micrometer-sized craters（with diameters of 200-300 nm） were observed on titanium （Ti） film coated ontoa gold （Au） substrate. The corresponding mass spectra were acquired, whichverified that sub-micrometer-sized ablation （and subsequently ionization） couldbe achieved by the ns-laser-induced tip-enhanced electromagnetic field. Inaddition, formation of the crater was studied with an increased number of laserpulses. Furthermore, a mass spectrometry imaging （MSI） experiment wasperformed with potassium chloride （KC1） residue dropped onto nano-patternedgold pillars, achieving 80-nm lateral resolution.