Seedless Synthesis of High‐Quality Gold Nanorods with a Widely Controllable Plasmon Wavelength Range

The ever‐increasing demand for convenient and rapid preparation of size‐ and spectral‐tunable gold nanorods underscores the significance of the seedless synthetic method, yet elucidating the intricate underlying mechanism that sets it apart from the seed‐mediated growth route continues to pose a formidable challenge. In this study, we introduce a seedless technique that utilizes m‐phenylenediamine as a reducing agent to facilitate the synthesis of monodisperse gold nanorods. These nanorods exhibit a high shape yield, a minimal diameter of approximately 9.9 nm, and a precisely tunable longitudinal surface plasmon resonance wavelength ranging from 658 to 1028 nm. Furthermore, a pivotal observation has arisen, emphasizing the critical role played by the distinct kinetics of seed formation and the precise quantity of gold seed particles throughout the growth process. Notably, the variations in these parameters between seed‐mediated and seedless synthetic routes exert a profound influence on the diameter, shape yield, and monodispersity of the synthesized gold nanorods. This insight provides crucial comprehension into the intricate synthetic mechanisms unique to the seedless approach for fabricating these nanoparticles.