Rapid synthesis of cypress-like CuO nanomaterials and CuO/MWCNTs composites for ultra-high sensitivity electrochemical sensing of nitrite

A highly efficient preparation method for cypress-like copper oxide (CuO) ink used in quick modification of screen-printed electrodes (SPE) is developed; the ink is used for the rapid detection of nitrite (NO2-). The cypress-like CuO nanomaterial is mixed with multi-walled carbon nanotubes (MWCNTs) to form an electronic ink and then evenly printed over SPE. The modified electrodes are used for enzyme-free detection of NO2-. The structure, morphology and composition and surface oxidation states of CuO is determined from X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of sensors utilizing the modified SPE is evaluated by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). Morphology of the prepared CuO is similar to that of cypress leaves, with a length of about 50 nm, and numerous cypress leaves with a length of 10 nm are vertically arranged on the surface. The electrode current response showed a linear dependence on the nitrite concentration and is in the range of 0.1-6500 mu M. An electrode sensitivity of 501 mu A.mM(-l).cm(-2) and a detection threshold of 0.039 mu M with a signal to noise ratio of 3 is observed. Therefore, CuO-MWCNTs modification of nitrite sensor electrodes enhances sensing selectivity, stability, and reliability.