We report on a fast, sensitive, label-free, and general dye-sensor platform for synthetic organic dyes detection by competitive adsorption on reduced graphene oxide (rGO) against a fluorescent dye (FD). Fluorescein (Fl) as fluorescence indicator and a cationic dye methylene blue (MB) as model analyte were employed to investigate the analytical feature of this assay platform. An anionic dye sunset yellow FCF (SY) was chosen as a comparison analyte to test the generality of this strategy. Results show that rGO can bind Fl and quench the fluorescence by fluorescence resonance energy transfer (FRET), while MB can displace Fl quickly from the Fl/rGO complex by competitive adsorption, inducing the fluorescence recovery which provides a quantitative readout for MB. Besides, this design was simply based on the competitive adsorption of rGO between dye and FD, and can be generally applied to other dyes for label-free detection. The fluorescence enhancement efficiency (FEE) is proportional to the dye concentration over the range of 7.60-420.00 ng mL(-1) MB and 7.28-400.25 ng mL(-1) SY, respectively. The linear regression equations were calculated as FEE(MB) = 0.0192c(MB)- 0.3103 for MB and FEE(SY) = 0.0142 c(SY)- 0.0427 for SY, with the detection limits of 1.03 and 1.15 ng mL(-1), respectively. The MB in waste water and SY in an orange-flavored sports drink sample were assayed with satisfactory results.
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