Shape-Controlled Synthesis and Photo-Thermal Conversion of Gold and Silver Nanostuctures.

Gold and silver nanostructures (such as Au nanorods, Ag nanoplates, nanocubes and so on) exhibit strong and tunable surface plasmon resonance in the near-infrared region (NIR). Under a certain NIR laser irradiation, noble metal nanostructrues achieve a high photo-thermal effect, which would be useful in the therapy. Au nanorods with longitudinal surface plasmon resonance (SPR_L) shifting in the region of 650-1 100 nm are synthesized by a "seed" method. Ag nanoplates and nanocubes with SPR located in the region of 650-850 nm are produced by a hydrothermal method. Through adjusting laser power and irradiating time, the changes of colloids are studied under NIR laser irradiation, and then the changes are compared with that of water. Under low power laser irradiation (808 nm, <1 W), temperature of Au nanorods colloid increases to about 57 °C. While Au nanorods undergo deformation from rod to spherical particle under irradiation of high power (1 064 nm, 8 W), resulting in the disappearance of SPR_L. Under 808 nm NIR laser irradiation, morphology evolutions and photo-thermal conversion of Ag nanostructures are also studied with change of power and irradiation time. Ag nanostructures have a lower photo-thermal conversion compared with that of Au nanorods colloid. Snipping and dendrite can be observed for Ag nanoplates after irradiating, while Ag nanocubes have no obvious shape change. [ABSTRACT FROM AUTHOR]