Figure 2 displays fluorescence images for individual SWNTs before and after addition of DTT and Trolox, collected using wide-field epifluorescence microscopy (images for BME are provided in Figure S1, Supporting Information). Before addition of reducing agents, SWNTs appear as dim spots that are barely visible above the background, but the same SWNTs were brightened up to 10 times in the presence of DTT or Trolox (Table S1, Supporting Information). Indeed, some SWNTs that initially could not be observed became readily visible upon addition of the reducing agents. This brightening effect was reversible upon removal of the reducing agents (Figure S2, Supporting Information). Figure 2c presents histograms of individual SWNT fluorescence intensities before and after addition of Trolox.