Nanometer-Sized MIL-101(Cr) Loaded with Metal Ions for Applications as a Nitrite Sensor with Enhanced Electrochemical Properties

In this work, iron ions, copper ions, and cobalt ions were introduced into the nanometer-sized Material of Institute Lavoisier (MIL)-101(Cr) using a simple impregnation technique to improve the electrochemical sensing performance for nitrite. The characterization results of scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) confirmed the successful preparation of octahedral MIL-101(Cr) and metal-ion-loaded MIL-101(Cr) with the size of about 300 nm. Electrochemical characterization unequivocally demonstrated that the electrochemical properties of the loaded nanometer-sized MIL-101(Cr) surpassed those of the original MIL-101(Cr). Notably, introducing iron ions into MIL-101(Cr) significantly enhanced the electrochemical properties. Consequently, a nitrite electrochemical sensor was constructed utilizing the superior electrochemical properties of the nanometer-sized MIL-101(Cr) loaded with iron ions. The proposed nitrite sensor exhibits a linear detection range from 2.5 μM to 11.4 mM, with a sensitivity of 179.9 μA mM–1 cm–2 and a detection limit of 0.21 μM. Additionally, the proposed nitrite sensor demonstrates exceptional anti-interference capability, repeatability, reproducibility, and stability and can also be applied to determine the nitrite content in sausage samples, further proving its efficacy and reliability for practical applications.