As now there is no methodology to use nanotechnology for weed control. We have to develop. If I will find methods I will tell you. Use the following links, you may get some ideas.
i think you are using sea weed samples first of all u mixed the sample with aqueous solution.crushed weed mixeing with water this is the control.after that how much amount of nanoparticle added noted.stored in dark room.every 24hrs u measured the sample with ur control after that using ur analtical studies