A fluorometric aptasensor for bisphenol a based on the inner filter effect of gold nanoparticles on the fluorescence of nitrogen-doped carbon dots

An aptamer-based fluorometric assay is described for the determination of bisphenol A (BPA). The aptamer against BPA is first attached to the surface of the red AuNPs, and this prevents the AuNPs from salt-induced formation of a blue-colored aggregate. Hence, the blue fluorescence of added nitrogen-doped carbon dots (NCDots) is quenched via an inner filter effect (IFE) caused by the red AuNPs. After addition of BPA, the BPA/aptamer complex is formed, and the AuNPs are no longer stabilized agains aggregation. This weakens the IFE and results in the recovery of the fluorescence of the NCDots which is measured best at excitation/emission wavelengths of 300/420nm. The recovered fluorescence increases linearly in the 10 to 250nM and 250 to 900nM BPA concentration ranges, and the detection limit is 3.3nM. The method was successfully applied to the determination of BPA in spiked environmental tap water samples.