Halide ions can trigger the oxidative etching of gold nanorods with the iodide ions being the most efficient

Gold nanorods (Au NRs) have been used as the nanoprobes for detecting various targets based on the oxidative etching by hydrogen peroxide. Halide ions such as chlorine and bromine are reported to have obvious effects on the shape-controlled syntheses and tuning the plasmonic wavelength of gold or silver nanoparticles. However, the influence of the halide ions on the oxidative etching of Au NRs especially the Au NRs stabilized with different surface agents remains unknown. Here, we study the effect of halide ions on oxidative etching of CTAB- and CTAC-Au NRs. The results show that halide ions have triggered the etching of Au NRs and are essential to the occurrence of the oxidation reaction. However, the efficiency of the three types of halide ions on the etching is distinctive, performing in the order: Cl⁻ < Br⁻ < I⁻. The possible reason is discussed and attributed to the redox potential of the various gold halides and the binding strength between Au and halide ions. The systematic results are believed to offer new insights into the reaction mechanism occurring in the relevant oxidative etching of noble nanoparticles, which can be important for improving the plasmon-assisted sensing based on anisotropic shortening of Au NRs.