Optical properties and microstructure of Au nanorods via seed solution amount variation synthesized by seed-mediated growth method

•The results revealed that the rhombus-shaped nanoparticles were bimetallic.•The wavelength of TSPR peak appeared regardless of the amount of seed solution.•The wavelength of LPSR from 750 to 812 nm with the seed solution amount increases.•The AR increased from 3.47 to 4.13 when the seed solution amount increased.

The effect of seed solution amount variation on the aspect ratio and microstructure of gold nanorods (GNRs) using a seed-mediated method has been studied. The ultraviolet–visible (UV–Vis) absorption spectra for all samples shows that the wavelength of transverse surface plasmon resonance (TSPR) peak appeared at around 534 ± 10 nm regardless of the amount of seed solution used. The wavelength of longitudinal surface plasmon resonance (LSPR) of GNRs increased from 750 to 812 nm with seed solution amount being raised from 40 to 320 μl. Then, the wavelength of GNRs slightly decreased from 812 to 789 nm when the seed solution amount increased from 320 to 800 μl. The aspect ratio (AR) value measured from TEM images increased from 3.32 ± 0.07 to 4.03 ± 0.08 when the seed solution amount increased from 40 to 320 μl. Then, the AR value slightly decreased from 4.03 ± 0.08 to 3.95 ± 0.08 when the seed solution amount increased from 320 to 800 μl. The synthesized product of gold nanoparticles included spheres, nanorods and rhombus-shaped particles. The results of NBED and EDS revealed that the rhombus-shaped nanoparticles were bimetallic, containing gold and silver.