Surfactant-free and controllable synthesis of hierarchical platinum nanostructures and their comparative studies in electrocatalysis, surface-enhanced Raman scattering and surface wettability

Via electroless metal deposition, hierarchical platinum nanostructures, consisting of pinecone-like, microspherical and flower-like (assembling with staggered nanosheets) structures, are successfully synthesized on silicon substrates without introducing any template or surfactant, by controlling the concentration of platinum salt and pH value. Based on the observations of morphological evolutions, the mechanism for formation of the three hierarchical Pt nanostructures is proposed by manipulating the growth kinetics. Their properties of electrocatalysis, surface-enhanced Raman scattering (SERS) and surface wettability are comparatively studied. The electrochemical surface area follows the order of microspherical structures > pinecone-like structures > flower-like structures, while the enhancement factor of SERS is in the order of flower-like structures > pinecone-like structures > microspherical structures. After modification with fluoroalkylsilane, the surfaces of flower-like structures and pinecone-like structures become superhydrophobic (165° and 158° of CA, respectively), whereas the CA is only 122° for microspherical structures.