Controlled synthesis of monodisperse gold nanorods with a small diameter of around 10 nm and largest plasmon wavelength of 1200 nm

Gold nanorods have been widely used in various fields due to their tunable anisotropic localized surface plasmon resonance (SPR) property. The facile preparation of gold nanorods with a tunable SPR wavelength extending to a near-infrared window, and at the same time, a relatively small particle size for facilitating applications especially in the biomedical field is of great value yet highly challenging. In this work, a new reducing agent, 1,6-dihydroxynaphthalene, is proposed for the synthesis of gold nanorods. The results indicate that gold nanorods with good monodispersity, high shape yield, maximum SPR wavelength of 1200 nm, and especially small diameter of around 10 nm can be acquired simultaneously. In terms of spectral and size controls, by respectively varying the experimental parameters including the amount of silver ions, reducing agents, and gold seeds not only can a good linear correlation be acquired corresponding to a SPR wavelength ranging from around 600 nm to 1200 nm, but a regular change in the particle diameter from 10.5 nm to 7.5 nm could also be observed. The structural and morphological evolutions of the particle for each changed parameter were carefully studied, and insights were gained into the growth mechanism based on the detailed analysis of particle evolution at a specific stage of the growth process.