Electrospray synthesis and in-situ sizing of nanoparticulate CsH₂PO₄

Nanometer-sized particles of the solid acid electrolyte material CsH₂PO₄ have been prepared by electrospray synthesis. Using a differential mobility analyzer to provide real-time particle-size information, the role of electrospray parameters, such as precursor solution composition, surface tension, and conductivity, sheath gas temperature and flow rate, and solution flow rate, were evaluated. The results are compared with particle sizes calculated using well-established scaling laws. The much smaller sizes of the detected particles in comparison to the sizes expected from the predicted initial droplet sizes suggests that droplets undergo fission along the path toward deposition. In flight fission events may also explain the observed counterintuitive result that aerosol particle size decreases with increasing solute concentration. The in situ feedback provided by this system enabled rapid identification of solution and process parameters that result in mean particle sizes of ∼15 nm, substantially smaller than any prior results.