Cucurbit[7]uril Induces Superior Probe Performance for Single-Molecule Detection

The photophysics of a complex between cucurbit[7]uril (CB7) and rhodamine 6G (R6G) was investigated using single-molecule spectroscopy. On the basis of the distribution of fluorescence intensity, two stable conformations of the CB7/R6G complex were identified. Both exhibit enhanced fluorescence relative to R6G alone. The two conformations are attributed to a flexible inclusion complex of R6G in CB7. Our single-molecule measurements also indicate that the photostability of R6G upon complex formation improves by 13× as opposed to 1.5× reported from ensemble measurements. The simplicity of using CB7 to enhance the fluorescence performance of a fluorophore makes it a promising strategy to deliver better probes for single-molecule spectroscopy in physical and life sciences research.