Synthesis of Au Nanorods by Using Gamma-ray Irradiation

To synthesize Au nanorods without the use of seed crystals, we applied gamma-ray irradiation from Co-60 radioactive source to reduce aqueous solution containing Au ions. The total dose was fixed to 6.0 kGy with various dose rates from 0.4 to 13.6 kGy/h. After the irradiation, two surface plasmon bands in the range around 530nm and above 700nm were observed in UV/vis spectra. We observed by a transmission electron microscopy (TEM) that rod-shaped Au nanoparticles with the length of 20-25 nm, and the width of about 7-15nm were produced as well as a small amount of spherical particles. The size and the aspect ratio of the Au nanorods are well correlated with gamma-ray irradiation dose rate; with increasing the dose rate, their size decreases and the aspect ratio increases. (C) 2012 The Japan Society of Applied Physics