Soft X-ray charger (SXC) system for use with electrospray for mobility measurement of bioaerosols

Electrospray size spectrometry analysis (ESSA), a mobility-based aerosol technique to characterize the size and charge-state of nanoparticles, uses a neutralizer to bring multiply charged particles to an equilibrium charge-state. Typical ESSA setups incorporate a Po-210 neutralizer that has short half-life time and its radioactive nature leads to safety concerns. This work demonstrates that a soft X-ray charger (SXC) effectively neutralizes electrosprayed bioparticles. Calculations show that the SXC generates bipolar ions with number concentrations one and two orders of magnitude higher than conventional Po-210 and Kr-85 sources, respectively. Additionally, we established that an SXC may be safely implemented in ESSA.

► A soft X-ray charger (SXC) was applied to neutralize highly charged nanoparticles. ► Charged nanoparticles were aerosolized from two different electrospray systems. ► The neutralization efficacy of a SXC was compared to that of a Po-210 source. ► Nano-sized viruses and proteins were readily electrosprayed and size-characterized. ► In electrospray size spectrometry the SXC is equally effective as a Po-210 source.