A primary ion beam (commonly Ga+, Bi+, or inert cluster ions such as C60+) bombards the sample at keV-level energy, sputtering surface atoms and molecules out as secondary ions. The secondary ions enter the flight tube and achieve m/z separation in the field-free region by velocity differences - light ions are fast, heavy ions are slow, and the arrival time at the detector corresponds to their m/z.
Since each laser/ion pulse can acquire a complete m/z spectrum, TOF-SIMS features high mass resolution and high throughput; the introduction of cluster ion sources (such as C60+) significantly reduces sample damage caused by a single bombardment, making molecular information more stable under multiple scans.
The spatial resolution of TOF-SIMS is determined by the focusing capability of the primary ion beam; modern instruments can achieve sub-micrometer or even hundreds-of-nanometers pixel sizes, localizing molecular distributions at the scale of organelles and tissue micro-regions, making it one of the few mass spectrometry imaging methods capable of nanometer-scale resolution.
The cost of high resolution is that the single-pixel sampling amount is extremely small and signals are sparse, and the secondary ion yield decreases with accumulated bombardment (especially for organic molecules), so a trade-off must be made among resolution, sampling damage, and statistical signal-to-noise ratio.
TOF-SIMS can simultaneously obtain elemental, isotopic, and small-molecule fragment information, and is sensitive to lipids, drugs, additives, and inorganic distributions; however, its direct detection capability for intact macromolecules (such as proteins) is weak, often relying on characteristic fragments for inference. Matrix effects and charge states also complicate spectral interpretation.
It complements MALDI and DESI: MALDI/DESI excel at macromolecular and overall molecular imaging, while TOF-SIMS excels at high-resolution surface and elemental/small-molecule imaging. Multimodal combination can cover both resolution and molecular-species coverage on the same tissue.
TOF-SIMS is widely used for material surface contamination, drug tissue distribution, organelle lipid localization, and semiconductor interface analysis. It is usually paired with a dedicated vacuum chamber and cluster ion source; sample preparation emphasizes surface cleanliness and conductive treatment (such as conductive slides, metal evaporation).
For scenarios requiring ambient, matrix-free, or in-situ live sampling, TOF-SIMS is not suitable; such needs can be compared with Neo-Source LDPI, DPI, and other ambient matrix-free imaging sources, divided by sample state and resolution requirements.
To obtain detailed specifications, compatible models, or a quotation for the MSI LDPI / DPI full series imaging ion sources, visit the Neo-Source official website, or contact the official team for compatibility advice tailored to your mass spectrometer (Agilent / SCIEX / Thermo and other mainstream MS).