Precision at the nanoscale: an 'ionic' view of composition, structure and properties

The study of matter at the nanoscale has traditionally relied on electron microscopy and optical spectroscopy to relate particle size with emerging properties. Mass spectrometry (MS), although a century-old analytical technique, has emerged in recent decades as a central tool for investigating atomically precise clusters (APCs). The introduction of soft ionisation methods, such as electrospray ionisation (ESI) and matrix-assisted laser desorption/ionisation (MALDI), has enabled the detailed analysis of cluster composition, fragmentation pathways, and structural features of APCs. The integration of ion mobility spectrometry with MS has further allowed direct correlations among their molecular formula, structure, and stability. At the same time, new developments such as charge-detection MS, ultraviolet photodissociation, and mass photometry have expanded the analytical range to larger and more complex systems. Beyond fundamental characterisation, MS is increasingly being applied to probe intrinsic properties such as ionisation potentials and support material applications through cluster deposition and related approaches. This review highlights the expanding role of MS in APC research and the impact of mass spectrometry-based techniques in materials science.