Highly sensitive electrochemical detection of E. coli O157:H7 using conductive carbon dot/ZnO nanorod/PANI composite electrode

A selective electrochemical sensor based on carbon dot (CD)/ZnO nanoroad/PANI nanoassembly has been developed towards the detection of cadmium (II) present in the environmental samples. In this work, a conductive nanocomposite electrode, CDs/ZnO/PANI, was successfully fabricated by polymerizing aniline (PANI) in the presence of carbon dot and Zinc oxide nanorod and followed by coating onto printed carbon sheet. These CDs were nearly spherical with good size distribution and excellent monodispersity, and the average size of CD were around 3–5 nm as evidence from Transmission electron microscope (TEM). ZnO nanorod having average length of 20 nm has been synthesized and characterized by TEM. The nanocomposite CDs/ZnO/PANI was characterized by Fourier transforms infrared spectroscopy, UV–Vis spectroscopy, Scanning Electron Microscopy (SEM) and electrochemical analyzer. SEM investigation confirms that the CD and ZnO are uniformly dispersed in PANI matrix. In addition, the outstanding electrical conductivity of CD/ZnO/PANI was found to increase the sensitivity for the detection of E.Coli. The developed electrochemical biosensor also showed good selectivity and was successfully detected E. coli O157:H7 with a detection limit of 1.3×10−18M, in water samples.