Generally speaking, you are supposed to use the POA for the benefit of the person for whom it is intended: paying bills, etc.  If Mom retained personal contents  - which she probably did - and is requesting that you donate it to the home (and I would have her sign something as long as she is competant) - then your brother can say nothing.  But if you are considered to be "dissipating" her assets then he has a legitimate gripe.  Good luck.