Morphology control of silver nanostructures via a chemical redox process by mixed amine ligands

Molecular recognition events that occur at the interface between inorganic surfaces and organic molecules play a critical role in a wide field of technologically and scientifically relevant processes including heterogeneous catalysis, crystal growth, and the development of sensor systems based on functional materials. Herein, we have developed a general and versatile method for the controlled synthesis of nanosized silver crystals with different shapes ranging from microspheres assembled with nanoparticles, nanocubes, nanocones to one-dimensional (1D) nanostructures including nanobelts and nanohelixes. These well-defined morphologies were obtained by controlling the relative growth rate of the crystal plates by selective use of capping ligand mixtures. The method involves the slow chemical reduction of the silver precursor by amine molecules. It is known that certain amines function as weak (and thus slow) reductants and as metal coordination ligands for metal complexes in solution. Both these properties should contribute to a slow rate of crystal growth and hence to the formation of special shapes under different solutions. We have used dodecylamine (DA) in combination with other amine ligands under selected solvents for the synthesis of the silver nanocrystals with different shapes. By changing the composition of the amine ligand mixture, nanosized crystals with different feature shapes and sizes can be obtained. Our results suggest a general strategy for the morphology controlled synthesis of metallic nanocrystals with different feather shapes: utilization of molecular recognition at the crystallographic planes under slow-growth conditions.