Synthesis of various gold hierarchical architectures assisted by functionalized ionic liquids in aqueous solutions and their efficient SERS responses

Developing a simple and green route for the controlled synthesis of hierarchical nanomaterials with anisotropic particles as subunits is highly desirable and technically important. Here, a functionalized ionic liquid (FIL) assisted strategy is developed for the preparation of hierarchical Au nanomaterials at room temperature. Various morphologies of Au products, including nanoplate-built flowers, nanobar-built flowers and nanourchins, have been well achieved using the current route in aqueous solutions of imidazolium ILs with different functional groups, such as 1-carboxymethy-3-methylimidazolium chloride ([CMmim]Cl), 1-hydroxylethyl- 3-methylimidazolium chloride ([HEmim]Cl), and 1-(3-aminopropyl)-3- methylimidazolium chloride ([APmim]Cl). The influence of these FILs on the morphology of Au products and their growth process has been studied systematically. It is shown that the functionalized ILs play important roles in the construction of these interesting Au hierarchies. The seed, IL concentration (within a certain range), reaction temperature have negligible influence, but stirring and anions of the ILs have important influences, on the product morphologies. Based on these results, the possible growth mechanism is proposed for the formation of different Au hierarchies. In addition, all the Au samples prepared with the assistance of the functionalized ILs, especially the nanoplate-built flowers, exhibit striking SERS sensitivity and high reproducibility.