For a more quantitative evaluation, polar coordinates (r, θ) centered at the laser spot were applied to the averaged scattering images shown in Figs. 7a to -7, and these images were averaged over the θ direction. The resulting radial intensity profiles are presented in Fig. . The vertical axis represents the raw data in counts from the monochrome CMOS camera, with a range from 0 to 255. In principle, the concentration of PSNPs is considered to be linearly proportional to the scattering intensity. However, due to slight variations in the dark noise of the glass substrate across different locations, it was difficult to quantitatively convert this light intensity into concentration.