(a) Extinction spectra of the star solutions (~0.1 nM) in DI. (b) The corresponding calculated absorption spectra of nanostars embedded in water. The data points (±1 SD) were interpolated with a spline fit. (c) The scatter plots of polarization-averaged absorption against aspect ratio (AR) tuned by varying branch height while keeping the base width, core and tip diameters, and branch number, constant. Their corresponding 3D geometry is on top, where the blue one is the original model for S30 nanostars. (Inset) The linear relationship between the plasmon peak position and AR, which is tuned by varying branch height (red, R2 = 0.997) or base width (blue, R2 = 0.987) while keeping all other parameters constant.