Correlating Electron Injection Effects and Electron Storage Capacity in Plasmon Amplitude Modulation of Au Nanorods

The plasmon resonance peaks of Au nanorods (Au NRs) are highly sensitive to both their morphological parameters and their surrounding chemical environment. In this study, modulation of the plasmonic response was achieved by introducing reducing agents into the Au NRs solution. A rapid blueshift in the longitudinal plasmon resonance peak was observed upon the addition of reducing agents, with the degree of shift strongly dependent on the aspect ratio of the nanorods. In this process, a bigger blueshift of the plasmon resonance peak is observed when more NaBH4 solution is introduced. Furthermore, when a greater amount of NaOH solution is added, both the rate of the blueshift and the final extent of the shift increase. This phenomenon can be attributed to the change in the electron concentration within the Au NRs. The addition of more NaOH alters the electrical potential difference in the solution, leading to a higher electron concentration. Furthermore, the aspect ratio of the Au NRs exerts a more significant influence on the extent of the blueshift. Nanorods with higher aspect ratios can accommodate a larger number of electrons, thereby enabling a greater magnitude of shift. These results demonstrate an effective approach for tuning the plasmonic properties of Au NRs over a wide spectral range and establish a quantitative relationship among the plasmonic response, nanorod geometry, and reductive conditions in solution.