Highly Sensitive Detection of CB [7] Based on Fluorescence Resonance Energy Transfer between RhB and Gold Nanoparticles

Background: Cucurbit[n]uril (CB[n], n=5, 6, 7, 8 and 10#137;is a type of macrocyclic compounds formed by n glycerol units and 2n methylene. The different sizes of the cavity lead to the different chemical characteristics of CB[n]. Therefore, it is very important to distinguish and detect CB[n]. Methods: At room temperature, Rhodamine B was added to a gold nanoparticles solution. The above mixture was respectively mixed with different concentrations of Cucurbituril[n] or β-cyclodextrin solutions. The fluorescence spectra and ultraviolet-visible spectra of samples were determined. Results: It was found that 1.2nM gold nanoparticles could quench the fluorescence of 1μM Rhodamine B completely. After adding a certain amount of Cucurbituril[7], the fluorescence intensity of Rhodamine B was restored. Compared with other macrocyclic compounds, such as Cucurbituril[5], Cucurbituril[6] and β-cyclodextrin, we found that this method had unique selectivity for Cucurbituril[ 7]. Under the optimal conditions, the fluorescence recovery efficiency was linearly proportional to the concentration of Cucurbituril[7] in the range of 0.8-8 μg·mL^-1. The detection limit was 0.21 μg·mL^-1. Conclusion: The research established an effective and practical FRET-based detection method for CB[7] with RhB as a donor and the gold nanoparticles as the acceptor. The system had unique and extensive selectivity for CB[7].