Influence of Ag and Pd Contents on the Properties of PANI–Ag–Pd Nanocomposite Thin Films and Its Performance as Electrochemical Sensor for E. coli Detection

The use of Ag–Pd bimetallic nanoparticles was reported as an enhanced sensing material in electrochemical sensing application. The composite of bimetallic nanoparticles with conducting polymer has attracted an interest in microbial sensor. Ag–Pd bimetallic nanoparticles embedded in polyaniline (PANI) system was synthesized using sol–gel method and deposited on glass substrate by spin coating technique with various concentrations of Ag and Pd. The films properties were studied using XRD, TEM and AFM to analyze the internal structure and surface morphology. Sensor performance was carried out using current–voltage (I–V) measurement and electrochemical impedance spectroscopy (EIS) to monitor the presence of Escherichia coli bacteria in liquid medium. From XRD analysis, the face-centered cubic of Ag–Pd bimetallic crystal were found at lattice (1 1 1) and (2 0 0). The crystallite size and lattice parameter were found to be decrease as concentration of Pd increased. TEM analysis shows the particles of Ag–Pd bimetallic in spherical shape with 10–20 nm in diameter. AFM analysis show the surface roughness of PANI–Ag–Pd thin films decrease as the concentration of Pd increased. From I–V and EIS analysis, the prototype sensor of PANI–Ag–Pd nanocomposite thin films performed well with high sensitivity when Pd concentration is increasing.