Dual-mode detection of dopamine based on 0D/2D/2D CuInS2/ZnS quantum dot-black phosphorous nanosheet-TiO2 nanosheet nanocomposites.

In this work, we designed new dual-mode "turn-on" electrochemical (EC) and photoelectrochemical (PEC) sensors for the detection of dopamine (DA) based on 0D/2D/2D CuInS2/ZnS quantum dot (QD)-black phosphorous nanosheet (BPNS)-TiO2 nanosheet (TiO2NS) nanocomposites. QDs can not only improve the photocurrent of the developed PEC sensors, but also provide the electrochemical signal in the EC detection. BPNSs as p-type semiconductor with high conductive properties work as electron acceptors and are utilized to improve the sensitivity of the DA PEC and EC sensors. Under irradiation of visible light or the applied voltage, DA is both excited and releases electrons, realizing "turn-on" detection. The PEC sensors have a linear range of 0.1-100 μM with a lower detection limit of 0.028 μM. For the EC detection, BPNSs can accelerate electron transfer which attribute to its excellent conductivity. In the range of 1-200 μM, the working curve of DA detection by the EC sensors was established and the detection limit is 0.88 μM. Comparing the two methods, the PEC sensors have a lower detection limit, and the EC sensors have a wider monitoring range. The dual-mode sensors of EC and PEC pave an effective way for the detection in biological and medical fields.