Evaluation of thermodynamic and photophysical properties of tricarbocyanine near-IR dyes in organized media using single-molecule monitoring

Detection of single NIR fluorescent dye molecules in the organized media sodium dodecyl sulfate (SDS) and triton X-100 surfactnts above their critical micelle concentrations was used to determine partition coefficients and photophysical properties of dye molecules resident within the micelle aggregate. Inspection of the filtered data showed evidence of large amplitude photon bursts arising from single molecular events in these organized media. In pure H2O containing dye, no bursts were observed. The results indicate that only molecules resident within the hydrophobic core of the micelle were detected. From the number of events observed and the number of events expected, partition coefficients (Kp) for IR-132 in SDS and triton X-100 solutions were calculated. In addition, the photon yield per molecule associated with only those molecules resident within the hydrophobic cavity of the micelle was determined.