Anal. Chem. 2010, 82, 801–807
Articles C60+ Secondary Ion Microscopy Using a Delay Line Detector Leendert A. Klerk,† Nicholas P. Lockyer,‡ Andriy Kharchenko,† Luke MacAleese,† Patricia Y. W. Dankers,§ John C. Vickerman,‡ and Ron M. A. Heeren*,† FOM Institute for Atomic and Molecular Physics, Science Park 104, 1098 XG, Amsterdam, Netherlands, Surface Analysis Research Centre, Manchester Interdisciplinary Biocentre, CEAS, The University of Manchester, Manchester M1 7DN, United Kingdom, and Department of Pathology and Medical Biology, University Medical Center Groningen, Hanzeplein 1, 9713 GZ, Groningen, The Netherlands Buckminsterfullerene (C60) as a primary ion for secondary ion mass spectrometry (SIMS) has shown many benefits over classical SIMS sources in the analysis of large organic molecules including many of biological significance. One constraint has been the limited focusing capabilities of the C60+ beam. Although this could be circumvented by using beam size limiting apertures at the cost of beam current, high-resolution imaging using conventional time-of-flight (TOF) instruments has been challenging and time-consuming. We present a method in which we combine the use of an unfocused C60+ beam with an ion optical microscope. A delay line detector is used to obtain fully resolved hyperspectral data sets that contain both the full mass spectral and the localization information. The obtained image resolving power is 4 µm at a pixel size of 250 nm. Microscope mode C60+ imaging was shown to resolve micrometer-scale features in a combined polymer-tissue sample. Our new approach demonstrates high-quality SIMS imaging using the full C60+ beam current. This results in equal or better resolving power at reduced acquisition speed. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a powerful tool for the chemical analysis of surfaces. It offers high-resolution imaging and mass spectral information about the molecular composition of biological and synthetic samples.1 In SIMS, secondary ions are generated under the impact of highenergy primary ions (Ga+, Aun+, Bin+, C60+, etc.) in a process known as sputtering. The sputter yield is the number of sputtered molecules, atoms, or ions per primary ion impact. In order to solve biological questions at the cellular length scale using SIMS imaging, there is a tendency toward higher spatial * To whom correspondence should be addressed. Phone: +31 20 7547100. Fax: +31 20 7547290. E-mail:
[email protected]. † FOM Institute for Atomic and Molecular Physics. ‡ The University of Manchester. § University Medical Center Groningen. (1) Vickerman, J. C.; Briggs, D. ToF-SIMS: Surface Analysis by Mass Spectrometry; IM Publications and SurfaceSpectra Ltd.: Charlton, U.K., 2001. 10.1021/ac902587g 2010 American Chemical Society Published on Web 12/31/2009
resolution. Although matrix-assisted laser desorption and ionization (MALDI) MS can be used for mass spectral imaging analysis,2,3 SIMS is the favored technique in certain cases, especially when studying lipids and small molecules (
