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Visualising Supramolecular Assembly by <br/>preparative Mass Spectrometry

Final Report Summary - VISUAL-MS (Visualising Supramolecular Assembly by preparative Mass Spectrometry)

An image is worth a thousand words – this well-known aphorism is not only true in everyday life but also in science and, even more, in nano-science and technology. Scanning tunnelling microscopy (STM) has achieved extraordinary results in the last two decades in the visualisation of individual adsorbed molecules, from simple aromatic compounds, to DNA bases, amino acids and a vast library of synthetic molecules. Unfortunately, these remarkable analytical capabilities are achieved only under ultrahigh vacuum (UHV) conditions and therefore cannot be directly applied to more interesting systems composed of functional (bio)-molecules or complex synthetic compounds. In fact, thermal sublimation is the strategy of choice for transferring molecules onto surfaces in UHV but large, complex molecular systems are not compatible with this process.
The main goal of VISUAL-MS was to overcome these limitations by designing and building a novel instrument capable of transferring large and fragile macromolecules into vacuum, to soft-land them intact onto atomically flat and clean surfaces, and to image them in-situ by high-resolution STM. This goal was very successfully achieved, resulting in a new experimental set-up, the only instrument of this type in the UK, one of the very few worldwide, and probably the most compact, efficient and cost effective. A number of innovative solutions have been developed during the planning and realisation of this equipment, from novel methods to evaluate realistic ion trajectories in simulation software to highly efficient ion transport devices with close to 100% transmission.
The underlying principle of VISUAL-MS – i.e. coupling intact surface deposition of functional molecules with their imaging at high spatial resolution – has been applied to a number of systems, ranging from small biomolecules to (opto)-electronically active molecules. In all cases, a deep understanding of molecule-surface interactions has been achieved, that will serve as a reference in the formulation of future rationale protocols for the fabrication of (bio)molecular functionalised substrates. Moreover, the same method has been employed to solve a major problem in polymer science: how to precisely and reliably characterise the microstructure of a polymeric macromolecule. In particular, VISUAL-MS demonstrated the capability of imaging the structure of conjugated polymers used in organic electronics and photovoltaics with sub-monomer resolution. This breakthrough opens the door to a possible revolution in polymer analytics and bears the potential of a huge impact on a number of industrial sectors including electronics, energy, medicine, and healthcare.