A molecular beacon and graphene oxide-based fluorescent biosensor for Cu2+ detection

In this work, we report a “turn-on” fluorescent strategy for the direct detection of Cu2+ in solutions using molecular beacons (MBs) and graphene oxide (GO). MBs are special single-stranded DNA and carry fluorescence sources. GO is a new nanomaterial having remarkable physical properties. In the sensing system, GO was used as an efficient fluorescence quencher upon the adsorption of MBs, which reduced the background signal and made the detection method highly sensitive. In the presence of Cu2+, the MBs were cut into short pieces and released by the GO, leading to fluorescence restoration. The detection limit of the sensing strategy was ∼50 nM, which is sufficiently sensitive for practical applications. The sensing method also exhibited high selectivity in testing samples containing other metal ions. The application of the method for drinking water is demonstrated.

► For the first time, molecular beacons are employed for the detection of copper ions.
► Graphene oxide is used in the sensing system to reduce the background signal and improve the detection sensitivity.
► The detection limit was experimentally determined as 53.3 nM, which is sufficiently low for practical applications.
► The sensing system is simple and exhibits high selectivity over other metal ions.