Fig. 1From: pH-responsive theranostic nanocomposites as synergistically enhancing positive and negative magnetic resonance imaging contrast agentsTEM images for nanoparticles: a OA-Fe3O4 NPs, b Fe3O4@nSiO2 NPs, c Fe3O4@nSiO2@mSiO2 NPs, d Fe3O4@SiO2@PAA-cRGD NPs. The scale bars are 50 nmBack to article page