Competitive photoelectrochemical aptamer sensor based on a Z-scheme Fe2O3/g-C3N4 heterojunction for sensitive detection of lead ions

Lead ion (Pb2+) is one of the heavy metal contaminants within the environment, which can seriously affect biological health. Thus, it is very important to detect lead ions, especially exceeding the standard concentration (100 ng/mL). In this work, we have developed a photoelectrochemical (PEC) aptamer sensor with Z-scheme Fe2O3/g-C3N4 heterojunction as a substrate material for sensitive detection of Pb2+. Specifically, Fe2O3/g-C3N4 is employed as a substrate with a powerful and stable photocurrent response. Au and DNA-1 connected to the substrate material via the Au-S bond and increased the electron conduction. Marking DNA-2 with ZnO effectively reduced the light absorption intensity resulting in a lower photocurrent response. Surprisingly, the Pb2+ PEC sensor showed good linearity in the detection range of 62 pg/mL to 1 μg/mL with a detection limit as low as 7.9 pg/mL (S/N = 3). The sensor showed stable recovery and low relative standard deviation in real sample detection. Additionally, the sensor exhibited excellent stability, selectivity, and reproducibility. The reproducibility of the electrodes was evaluated, and the accuracy of the individual electrode current values was calculated to range from 0.5% to 2.71% with an RSD of 1.74%. Such PEC sensor guarantees to supply a brand-new approach to the detection of Pb2+.