Gold nanorods: Electrochemical synthesis and optical properties

Aqueous solutions containing a high yield of suspended gold nanorods have been successfully synthesized via an electrochemical method. The control of preparing gold nanorods with different aspect ratios can be attained. Their absorption spectral features show a dominant surface plasma band corresponding to the longitudinal resonance, SP1, and its lambda(max) shifts markedly to the red as the aspect ratio is increased. Meanwhile, the dependence of lambda(max) for longitudinal resonance on the mean aspect ratio shows a deviation from the classical electrostatic model prediction at mean aspect ratios around 4 +/- 1, where it limits the validity of the classical electrostatic approximation.