Comparison of One-Focus and Two-Foci Setup in Single-Molecule Detection Experiments

Abstract

Single molecule detection in fluid flow has become a widely used technique in ultrasensitive fluorescence detection. The detection of a single molecule in a fluid flow at room temperature is limited by effects such as background signals from the surrounding liquid and possible contamination in it, photobleaching effects which restrict the overall number of detectable photons from one molecule, and diffusion can cause the molecule to miss the exciting laser beam when flowing along the capillary. A method for enhancing the single molecule detection efficiency is the use of multiple excitation-detection regions along the capillary and the application of an analysis for correlating the photon detection data from the different regions. In this note we demonstrate that, at a constant laser power, no improvement results using time-correlated detection from multiple-foci regions. (AIP) {copyright} {ital 1997} {ital Society for Applied Spectroscopy}