In single particle imaging experiments, beams of individual nanoparticles are exposed to intense pulses of x-rays from free-electron lasers to record diffraction patterns of single, isolated molecules. The reconstruction for structure determination relies on signal from many identical particles. Therefore, well-defined-sample delivery conditions are desired in order to achieve sample uniformity, including avoidance of charge polydispersity. We have observed charging of 220 nm polystyrene particles in an aerosol beam created by a gas-dynamic virtual nozzle focusing technique, without intentional charging of the nanoparticles. Here, we present a deflection method for detecting and characterizing the charge states of a beam of aerosolized nanoparticles. Our analysis of the observed charge-state distribution using optical light-sheet localization microscopy and quantitative particle trajectory simulations is consistent with previous descriptions of skewed charging probabilities of triboelectrically charged nanoparticles.
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