Diode laser based detection of single molecules in solutions

Using a confocal microscope we studied bursts of fluorescence photons from single dye molecules that were excited at 632 nm with a CW diode laser or helium neon laser. The measurements were performed with new rhodamine derivatives in ethylene glycol solution. The potential of this method for future construction of a low-cost instrument for single-molecule detection is pointed out. To demonstrate the utility of our new dyes in bioanalytical applications we showed the single-molecule detection of labeled oligonucleotides in water.