Cost-effective synthesis of MIL-101(Cr) from recyclable wastes and composite with polyaniline as an ion-to-electron transducer for potentiometric Pb2+ sensing

Fabricating an ion-to-electron transducer (IET) from waste in the solid contact screen-printed ion-selective electrodes (SC-SP-ISEs) technique is challenging because its properties determine the potential stability and reproducibility of the designed sensors. Herein, we fabricated an IET substrate from recyclable wastes, and we applied it as an IET layer in an ISE-based sensor for fast and on-site detection of lead ions (Pb2+) in an environmental sample. First, MIL-101(Cr) was prepared based on a combination of PET and Cr+6 waste recycling (R-MIL-101(Cr)). Polyaniline (PANI) was polymerized over R-MIL-101(Cr) to prepare a conductive PANI@R-MIL-101(Cr) composite. Then, it was applied as an IET substrate in the construction of pb2+-ISE for the detection of Pb2+ ions in sediment samples collected from Lake Idku, Egypt. Three Pb2+ sensors were fabricated and abbreviated as sensors I, II, and III corresponded to PANI, R-MIL-101(Cr), and PANI@R-MIL-101(Cr) as IET substrates, respectively. The performance of the sensors was studied to be applied for fast and selective detection of Pb2+ at low concentration levels. Among the fabricated sensors, PANI@R-MIL-101(Cr) shows fast response (5 sec), low detection limit (1 × 10−7 mol/L), and long lifetime reaches 70 days with a potential drift of 0.9 mV h−1. The electrochemical characteristics prove the fast ion-to-electron transportation in the case of PANI@R-MIL-101(Cr) owing to its lower impedance and high capacitance. In-situ polymerization of PANI significantly enhanced the conductivity of the PANI@R-MIL-101(Cr) composite. The hydrophobic nature of PANI@R-MIL-101(Cr) ensures high stability by preventing the formation of water layers at the electrode/membrane interface. These results show the great potential of the IET-based PANI@R-MIL-101(Cr) layer for Pb2 + sensing in environmental samples with low detection limits and high stability for the future development of SC-ISEs.