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