A Flexible Photoelectrochemical Sensor for Hexavalent Chromium Detection

This paper presents a photoelectrochemical (PEC) sensor using flexible polymer as the substrate for detection of hexavalent chromium (Cr(VI)) ions, showing a large sensing range from part per billion (ppb) level to part per million (ppm) level. This sensor utilizes layer-by-layer (LbL) self-assembled graphene intercalation to mediate the Schottky barrier formed between the metal electrodes (Au) and the photon-sensitive material (titanium dioxide, TiO 2 ), which enhances the photocurrent of the sensor more than three times. Additionally, graphene layer also improves the stability of the sensing signal (photocurrent) due to its role in facilitating the separation of photon-excited electrons and holes. Quercetin is used as the selective material in the sensing system, which can specifically interact with Cr(VI). The flexibility of metal electrode and nanomaterial films of the sensor allows the adoption of a flexible substrate, with great application potential in wearable or implantable sensors for animals and plants. The sensor shows a detection range from 14.9 to 3194.1 ppb in dissolved air, with a low detection limit of 9.5 ppb.