A disposable photoelectrochemical sensor based on magnetic photocatalyst BiOI/NiFe@N-CNTs for the assay of hexavalent chromium

Chromium is widely used in different industries and can be found in wastewater. Hexavalent chromium (Cr(VI)) is considered life-threatening pollutant and shows adverse effects on environment and human health. Therefore, an effective method is demanded for reliable detection of Cr(VI). In this work, a magnetic photocatalyst (BiOI/NiFe@N-CNTs) composed of bismuth oxyiodide (BiOI) and magnetic bamboo-like carbon nanotubes capsulated with nickel-iron (NiFe) particles (FeNi@N-CNTs) was prepared by one-step hydrothermal method. Various characterization techniques revealed that BiOI/NiFe@N-CNTs possessed abundant pores and larger surface area because of its interlaced nanotubes morphology. It showed excellent cathodic photoelectrochemical (PEC) activity and good photoelectron transfer capacity with [Fe(CN) ₆ ] ³⁻ . Based on these features, a disposable magnetic PEC sensor for Cr(VI) assay was constructed by modifying screen-printed electrode (SPE) with BiOI/NiFe@N-CNTs via magnetic control. The PEC sensor presented a broad detection range of 0.2 nM−10.0 µM and a low detection limit (LOD) of 65 pM (S/N = 3). The practical application of the sensor in real water samples obtained acceptable results. The low cost, low consumption volume in samples, and disposability make the magnetic PEC sensor a potential tool for monitoring Cr(VI).