Size-Controlled Synthesis of Gold Nanostars and Their Characterizations and Plasmon Resonances

Gold nanostar particles were synthesized using seed-mediated method. Au-seed was synthesized with the diameter of approximately 3 nm and a considerably low STDEV of less than 1 nm. Then, different amount of Au seed was introduced into the growth solution of nanostars and the influence of the changes in concentration of Au seed on the growth process was investigated. The size of gold nanostars increased with decreasing the concentration of Au seeds. We further extended this method to enable size-control of gold nanostars from approximately 70 nm to 140 nm in size. Also the longer branch length caused red shifting of resonant plasmonic peaks in the absorption spectra of the sample with the lower amount of Au seed. Thanks to this method, we could control size, and spikes of gold nanostars and the obtained results broaden the concept of the formation and morphology of gold nanostars. The plasmon band shift was attributed to variations in branch numbers, and overall star size.