Perylene Monolayer Protected Gold Nanorods: Unique Optical, Electronic Properties and Self-Assemblies

Here we report the synthesis and characterization of organosoluble perylene monolayer protected gold nanorods. From H-1 NMR, FT-IR, and differential scanning calorimetry experiments, the successful thiol exchange and stacking of perylene molecules on gold nanorods were confirmed. The resulting gold nanorods encapsulated with perylene thiol molecules via strong covalent Au-S linkages showed unique optical and electronic properties compared to the initial free perylene molecules and gold nanorods, indicating there were strong interactions between perylene chromophores and gold nanorods. When attached on gold nanorods, the perylene chromophores did not exhibit any typical UV-vis absorption or fluorescence emission signal, originating from the charge transfer from gold nanorods to perylene chromophores. However, the missing signals reappeared upon the addition of iodine, which detached the perylene molecules from gold nanorods. For the hybrid gold nanorods, particular electronic properties were also investigated by cyclic voltammetry and electron diffraction. Furthermore, with strong pi-pi intermolecular interactions, the perylene thiol monolayer protected gold nanorods were able to aggregate. When drying from highly diluted solution, gold nanorods formed well-organized side-by-side self-assembly arrays.