Diffusion Reflection (DR) measurements of scattered light intensity as a function of distance from 4 different phantoms, each denoted by a different color: a water-only base (black), GNR690 (green), GNR760 (blue), and GNS (red). Each phantom was measured 2 times, as denoted by the marker shapes. The light source had wavelength 780nm, and the concentration of the particles in the phantoms was set so that they would contain a fluorophore concentration of 5μM. The legend depicts the slope ± standard error to the slope of a fitted line to the corresponding curve. As explained in Eq. (2), this slope is an indication of the spectral properties of the sample.