Phase-dependent ion-to-electron transducing efficiency of WS2 nanosheets for an all-solid-state potentiometric calcium sensor.

Ultrathin metallic WS2 (M-WS2) nanosheets and semiconductive WS2 (S-WS2) nanosheets were exfoliated and for the first time employed as ion-to-electron transducing layer to construct an all-solid-state ion-selective electrode. Importantly, we found that the transducing efficiency of WS2 nanosheet-based solid-contact layer is phase-dependent. The M-WS2 nanosheets with larger content of 1 T-phase structure exhibit higher transducing efficiency than S-WS2 nanosheets, which can be ascribed to the remarkable conductivity of M-WS2 nanosheets. In order to demonstrate the excellent properties of the M-WS2 nanosheet-based tranducing layer, an all-solid-state calcium ion potentiometric sensor was constructed as the model. As expected, a Nernstian response (27.41 mV per decade, R2 = 0.9998) with a wide linear range of 1.0 × 10-5.0 to 1.0 × 10-2.0 M and a limit of detection of 2.0 μM was obtained. The developed all-solid-state potentiometric sensor using M-WS2 nanosheets as ion-to-electron transducing layer is expected to bring new progress for routine detection in various fields. Graphical Abstract Schematic illustration of the introduction of WS2 nanosheets with different phase structures as a new-generation solid-contact ion-to-electron transducing layer for all-solid-state potentiometric sensors.