Photoelectrochemical sensor based on zinc phthalocyanine semiconducting polymer dots for ultrasensitive detection of dopamine

Developing materials with excellent photoelectric activity is critical to improving the sensitivity of photoelectrochemical (PEC) sensors. Herein, we reported a convenience method to synthesize phthalocyanine polymer dots (Pdots), which dope zinc phthalocyanine (ZnPc) into a conjugated polymer poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo{2,1,3}thiadia-zol-4,8-diyl)] (P8BT). The synthesized materials were characterized by energy dispersive spectrometry (EDS), electrochemical impedance spectroscopy (EIS), fluorescence (FL) spectroscopy, transmission electron microscopy (TEM), ultraviolet-visible diffuse reflectance spectroscopy (UV–vis DRS), and dynamic light scattering (DLS). Then, ZnPc-P8BT-Pdots were modified on an indium tin oxide (ITO) electrode by repeated immersion to develop an ultrasensitive PEC sensor for dopamine (DA) detection. Semiconducting polymers in ZnPc-doped forms exhibit a typical photocurrent reduction in comparison with the original polymers. As the photocurrent was weakened, energy was transferred from the conjugated polymers to ZnPc. The photocurrent intensity of ZnPc-P8BT-Pdots/ITO increases as the concentration of DA increases under blue light irradiation. Under the best experimental conditions, the PEC sensor realized the detection of DA (2.5 nM-125 μM) with a limit of detection (LOD) of 1.69 nM (S/N = 3). Moreover, the ZnPc-P8BT-Pdots/ITO sensor for the detection of DA exhibited superior PEC performance, high sensitivity, rapid response, and favorable stability. This study indicated that ZnPc-P8BT-Pdots possess the promising potential to construct PEC sensors for pharmaceutical analysis.