Size, shape and surface structure of gold snowflake-like particles tailored by the addition of monovalent and divalent inorganic salts

Gold nanostructures are known for their unique electro-optical behavior called surface plasmon resonance. Their chemically stable and biocompatible properties are being utilized in a vast area of applications. Within this work, gold snowflake-like particles (Au SFLPs) were prepared via chemical reduction in an aqueous bulk phase assisted by monovalent and divalent inorganic salts. The addition of inorganic salts in combination with a particular concentration ratio between chemical reduction precursors plays a key role in the Au SFLPs size, surface morphology and shape evolution. The reaction parameters, such as reaction temperature, pH, stirring speed, concentrations of reactants and their types, influencing shape development of Au SFLPs, were systematically tested and described. The theory of growth and aggregation of gold seeds and the diffusion within the electric double layer - surrounding the particles, is used to propose a controlled mechanism, explaining the organization of gold atoms into Au SFLPs. A novel efficient trapping method was developed to efficiently collect individual Au SFLPs without surface structure destruction. Enhanced electro-optical behavior of the Au SFLPs, resulting from the nanostructured surface, was confirmed by the detection of 5,10,15,20-Tetrakis(1-methyl-4-pyridinio) porphyrin via surface-enhanced Raman spectroscopy (SERS).