Water and Organic Solvent Dispersible Gold Nanorods that are pH Responsive

摘要

Shape-controlled gold nanorods are prepared in the presence of a capping agent, cetyltrimethylammonium bromide (CTAB), which controls their morphology and dispersibility in water. To control their dispersibility between water and another organic solvent, a pH-responsive amphiphile C18AA was introduced on gold nanorods instead of CTAB. The C18AA-capped gold nano- rods were dispersed in both water and chloroform. These gold nanorods were pH-responsive depending on the extent of C18AA deprotonation observed: deprotonation of the terminal amine above pH 9.5 increases the hydrophobicity of the nano- rods, resulting in them being more soluble in chloroform than in water. C18AA-capped gold nanorods can transfer from the water phase to the organic phase by changing the pH from 9.0 to 12.5. The morphology of the nanorods did not change as a result of ligand-exchange, or phase transfer, due to the stabiliz- ing effect of the C18AA capping molecule. C18AA-capped gold nanorods can also be transferred to the water phase by evapo- rating the chloroform.