Shape-Controlled Synthesis of Silver Nature-Like Spiky Particles for Piezoresistive Sensor Applications

Silver particles with spiky nanostructured morphologies have been obtained by two different wet-synthesis approaches. A detailed investigation was carried out into the synthesis parameters to tune the shape of the sample into desert-rose- and succulent-like particles. The first synthetic route was based on the reduction of silver nitrate by iron sulfate in the presence of maleic acid as anisotropic agent, whereas in the second method ascorbic acid was used as the reducing agent and citric acid as the anisotropic agent. A nucleation model is proposed to explain the growth mechanism and the effect of each parameter on the particle morphology. These Ag nanostructured spiky particles have been used as conductive fillers in polymeric piezoresistive composites, the working principle of which is based on the tunneling conduction mechanism. Composite samples were thus prepared and characterized, demonstrating the enhancing effect of the sharp protrusions on the tunneling phenomena upon a mechanical compressive strain.