Figure 2.

Thermochromic calibration of particle-bound and free dye. (a) A diagram of the calibration setup is shown. For each individual ferrofluid sample, a calibration was obtained by monitoring the change in fluorescence intensity of each dye in response to temperature cycling in a custom temperature-controlled cuvette holder. (b-c) A representative of calibration curves from a ferrofluid containing Dylight 550-labeled 12-nm iron oxide nanoparticles (b) and free DY-521XL solution (c) is shown. Fluorescence at five temperatures were measured three times in a randomly permuted sweep. The points represent the average of each measurement. The error bars represent mean ± standard error of the mean (SEM) and are not shown if smaller than the plotted symbols. To see this figure in color, go online.