A rapid detection impedimetric sensor based on magnetic alloy-doped polyaniline thin-film for E. coli identification in water

Purpose This study aims to investigate the integration of magnetic alloy-doped polyaniline (PANI) thin films for enhanced electrochemical detection of Escherichia coli O157:H7 in water. Silver-based magnetic alloys, namely, Ag-Fe, Ag-Co and Ag-Ni nanoparticles, were incorporated into the PANI matrix to improve conductivity and sensitivity of the sensing platform. Design/methodology/approach Magnetic alloys doped PANI nanocomposite thin films were synthesized via an aqueous sol–gel method. Structural, morphological and optical characterizations were performed using X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM) and UV-visible spectroscopy. The sensing performance toward E. coli was evaluated using electrochemical impedance spectroscopy (EIS) by comparing impedance responses before and after bacterial incubation in water samples. Findings XRD patterns revealed the characteristic broad amorphous band of PANI alongside distinct diffraction peaks corresponding to Ag and magnetic alloy nanoparticles at the (111) and (200) Miller indices. AFM analysis demonstrated variations in surface roughness and grain size among all films. TEM images confirmed spherical-shaped nanoparticles with nanoscale particle sizes. UV–Visible spectra exhibited absorption maxima in the range of 370–470 nm, attributed to surface plasmon resonance effects. EIS results indicated that the presence of E. coli increased the conductivity of the nanocomposite films. Among the films, PANI-Ag-Fe demonstrated the highest sensitivity, while PANI-Ag exhibited the lowest sensitivity. Originality/value This work demonstrates the synergistic effect of incorporating silver-based magnetic alloys into PANI matrices to simultaneously enhance electrical conductivity and sensing sensitivity, highlighting PANI-Ag-Fe nanocomposite thin films as a promising platform for bacterial biosensing applications.