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