I suspect that the objective is to disperse the PbO rather than dissolve it. Dissolution is easy (hydrochloric acid) but then you end up with Pb2+ and Cl- ions. Dispersion is not possible to nanosize (< 100 nm) for a powder - indeed 'nanopowder' is an oxymoron. The 3 steps are wetting, separation, stabilization with the separation step being the critical one. People will use enormous amounts of ultrasonic energy - actually milling the material and introducing contamination from the ultrasound tip as it slowly destroys itself through cavitation.