Figure 7.
Ultrabright fluorescent particles having complex spectra excited with a single wavelength. (a) Fluorescent confocal image of multiplexing micro-UMSPs excited at 488 nm containing varying amounts of coumarin 504, rhodamine 560, rhodamine 6G, and rhodamine 640. The scale bar is 10 μm. The particles with different fluorescent spectra are physically mixed in this image. (b) Sequential FRET can be used to transfer the excitation energy from one dye to the next. The absorbance and fluorescence spectra of five dyes in sequence are shown. Because the efficiency of FRET can be controlled by changing the distance between the dye molecules, the resulting spectrum can have a mix of fluorescence of all encapsulated dyes. [Reproduced from Ref. 32 with permission from RCS, copyright 2017].