The step of improving {TAIL ~ the dispersion} of the particles in the washed suspension may be carried out by {HEAD ~ sonication} 
The step of improving { TAIL ~ the dispersion } of the particles in the washed suspension may be carried out by { HEAD ~ sonication }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD