Visible light photoelectrochemical sensor for ultrasensitive determination of dopamine based on synergistic effect of graphene quantum dots and TiO2 nanoparticles

•The GQDs–TiO2 could prevent GQDs assembling and achieve the immobilization of GQDs.•The GQDs–TiO2 showed synergistic amplification on the PEC in the visible region.•The PEC sensor for sensitive and selective detection of dopamine was constructed.•The sensor showed wide linear response and low detection limit for dopamine detection.

We have demonstrated a facile approach for fabricating graphene quantum dots–TiO2 (GQDs–TiO2) nanocomposites by a simple physical adsorption method. Compared with pure GQDs and TiO2 nanoparticles (NPs), the as-prepared GQDs–TiO2 nanocomposites showed enhanced photoelectrochemical (PEC) signal under visible-light irradiation. The photocurrent of GQDs–TiO2/GCE was nearly 30-fold and 12-fold enhancement than that of GQDs/GCE and TiO2/GCE, respectively, which was attributed to the synergistic amplification between TiO2 NPs and GQDs. More interestingly, the photocurrent of GQDs–TiO2 nanocomposites was selectively sensitized by dopamine (DA), and enhanced with the increasing of DA concentration. Further, a new PEC methodology for ultrasensitive determination of DA was developed, which showed linearly enhanced photocurrent by increasing the DA concentration from 0.02 to 105 μM with a detection limit of 6.7 nM (S/N = 3) under optimized conditions. This strategy opens up a new avenue for the application of GQDs-based nanocomposites in the field of PEC sensing and monitoring.

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