Gas Phase Single Nanoparticle Characterisation

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Nanoparticle samples suffer from physical as well as chemical heterogeneity. This leads to a reduced performance in technological applications. Performance optimisation requires obtaining insights into the intrinsic properties of individual nanoparticles and how they contribute to the properties of the ensemble. Most single nanoparticle techniques, however, probe deposited particles, whose properties are perturbed, either by the support or neighbouring particles. Probing truly inherent properties requires isolating nanoparticles in the gas phase. Here, I propose to develop groundbreaking, ultrasensitive mass spectrometric and laser spectroscopic tools to study single nanoparticles isolated in the gas phase. Charged metal, semiconductor and insulator nanoparticles in the size range from 5 to 100 nm will be trapped in a buffer-gas filled, temperature-controlled (10-300 K) cryogenic quadrupole ion-trap optimised for spectroscopy. The absolute mass and absolute charge of single, trapped nanoparticles will be determined non-destructively and quasi-continuously by optical means. Temperature-programmed desorption mass spectrometry, UV/Vis action spectroscopy and dispersed fluorescence spectroscopy will be used to accurately determine the temperature and characterise the optical properties of single semiconductor nanocrystals, to study plasmonic excitations in bare and coated metal nanoparticles, and to monitor the temporal evolution of energy conversion in fluorescent nanodiamonds. The overarching goal is to establish a novel single nanoparticle characterisation tool set that allows dissecting nanoparticle heterogeneity in order to improve the performance of nanoparticle applications across all disciplines, e.g., the sensitivity of nanosensors, the selectivity of nanocatalysts or the efficiency of drug nanocarriers.