Fig. 5. (A) Two-dimensional heat map measured by LIT of a sample with a concentration step, showing the strong difference in the signal between the two parts, with different concentrations (760 μg g⁻¹ and 250 μg g⁻¹, respectively) of gold nanoparticles. The numbers on the x and y axes are the lengths in meters. (B) Experimental (dashed lines) and simulated (continuous lines) LIT-measured profiles along the red line shown in (A) of a sample with a gold nanoparticle concentration gradient: 760 μg g⁻¹ for x < 0 and 250 μg g⁻¹ for x > 0.