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The conventional method for synthesizing gold nanobipyramids (AuNBPs) is well established. However, the cytotoxicity resulting from the conjugates between hexadecyltrimethylammonium bromide (CTAB) and gold limits their biomedical applications. This study introduces a dual surfactant approach with CTAB and sodium oleate (NaOL) in the seed‐mediated synthesis of the AuNBPs, which can significantly reduce the CTAB concentration to 10 mM. Additionally, optimal growth conditions are achieved by varying the volumes of seed solution, AgNO3, and HCl. Under low CTAB concentrations, AuNBPs with tunable sizes and localized surface plasmon resonances between 600 and 1200 nm are successfully synthesized, as characterized by UV–vis‐NIR spectroscopy, transmission electron microscopy (TEM), and finite‐difference time‐domain (FDTD) simulations. This work demonstrates a method for synthesizing AuNBPs at low CTAB concentrations using binary surfactants and provides a framework applicable to the synthesis of other metallic nanomaterials. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance of precious metal gold nanorods can be tuned by controlling the aspect ratio, and they find widespread applications in biotechnology, imaging, sensing, optoelectronics, photonics, and catalysis. Here, a method is proposed for the controlled etching of gold nanorods within mesoporous silica shells by using a certain concentration of H2O2 at room temperature. In the experiments, the amount of HCl is varied to adjust the acidity and/or change the amount of H2O2 to control the speed of corrosion, achieving controllable adjustment of the aspect ratio of the gold nanorods. The extinction spectra show that under the action of H2O2 and HCl, the longitudinal plasmonic resonance of the gold nanorods shifted to shorter wavelengths, and the intensity of the longitudinal plasmonic resonance decreased. The more hydrochloric acid or hydrogen peroxide added, the faster the corrosion rate of the gold nanorods, and the faster the blue shift of the longitudinal plasmonic resonance. In addition, the intensity of the extinction spectra at 320 nm increased linearly versus time, which can also be used to monitor the etching process. By corroding gold nanorods to control the plasmonic resonances, gold nanorods can find broader applications. [ABSTRACT FROM AUTHOR]