Polyurea dendrimer-perylene nanoshells are found to accurately discriminate structurally closely related nitroaromatics. Both studied systems, PUREG1-PER6 and PUREG4-PER48, present high sensitivity (detection limits between 5 x 10(-6) and 20 x 10(-6) M) and selectivity for 2,4,6-trinitrotoluene (TNT) collected from a powdered military grenade and picric acid. The selectivity is highly dependent on the dendrimer generation. A conformationally restricted 3D arrangement in PUREG4-PER48, which is favored by shell pi-pi stacking and core urea-assisted hydrogen bonding, supports the formation of self-imprinted channels with molecular recognition for picric acid and TNT in complex mixtures of nitroaromatics.