Yerba mate tea mediated synthesis of nanoscale zero valent iron particles and their application in detection of Pb ions in water

• Published in: Sensing and Bio-Sensing Research 2025-02, Vol.47, p.100728, Article 100728
• Main Authors: Mampane, L., Moothi, K., Ntwampe, O., Moloto, N., Ndlovu, G., Jijana, A., Tetyana, P., Mphuthi, N., Ngqalakwezi, A., Shumbula, P., Ntsendwana, B., Sikhwivhilu, L.
• Format: Article
• Language: English
• Subjects: Electrochemical sensor; Gold screen printed electrodes (AuSPE); Pb2+ ions; Zero-valent Iron
• ISSN: 2214-1804; 2214-1804
• DOI: 10.1016/j.sbsr.2024.100728

Yerba-mate tea extracts were used to successfully synthesise nanoscale zero-valent iron (NZVI) particles. The tea extracts acted as both the reducing and capping agents. The morphological, optical and structural properties were characterized using Transmission Electron Microscope (TEM), X-ray Diffraction (XRD), UV–vis absorption spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy, respectively. The XRD and FTIR confirmed a complete reduction of Fe ions forming nanoparticles with an average size of 3 to 3.5 nm synthesized at 25 °C as shown by TEM images, indicating enhanced electrocatalytic sites. The as-synthesized NZVI particles were immobilized on AuSPE and evaluated on the electrocatalytic behaviour using ferri/ferrocyanide as a redox probe. Thus, they were modified on the screen-printed carbon electrodes to fabricate an electrochemical sensor for Pb2+ detection. The sensor was optimised to detect traces of Pb ions from 5 to 9 parts per billion concentrations. The surface concentration of the adsorbed electro-active film on the reduction half of AuSPE/NZVI modified electrodes was determined and estimated to be 1.32 × 10−10 mol cm−2. Moreover, the charge transfer coefficient of AuSPE/NZVI particles was estimated to be 5.43 × 10−17 cm2s−1. The sensor gave a relatively low limit of detection 2.56 ppb for Pb2+ ions. This was lower than most commercially available heavy metal detectors with a detection limit of 3.5 ppb. •The nano Zero Valent Iron (NZVI) particles were successfully using yeba mate tea extract as reducing agents.•The NZVI modified AuSPE exhibited enhanced rapid electron and charge transfer kinetics towards ferri/ferro cyanide redox probe.•The NZVI based sensor demonstrated excellent limits of detection for Pb 2+ ions in water•High selectivity in the presence of competing ions.