CuO–ZnO p–n junction enhanced oxygen sensing property of polypyrrole nanocomposite at room temperature

In this paper, CuO–ZnO and Polypyrrole (PPy) nanocomposites are synthesized by one pot sol–gel method and chemical polymerization of pyrrole respectively. Polypyrrole loaded p–n junction is formed by adding different weight percentage (10 wt%, 30 wt% and 50 wt%) of CuO–ZnO nanocomposite with PPy and then coated on a substrate using spin coating method. Elemental analysis is done by X-ray Photoelectron Spectroscopy. The morphological studies by High Resolution Transmission Electron Microscopy and Field Emission Scanning Electron Microscopy show the coating of CuO–ZnO nanocomposite on polypyrrole with various weight ratios. The crystal structure and chemical composition of the nanocomposites are characterized by X-ray Diffraction and Fourier Transform Infrared Spectroscopy respectively. From the UV–visible Spectroscopy, the band gap energy of the Polypyrrole is calculated as 3.05 eV. The electrodes are investigated for sensing towards Oxygen, Hydrogen and LPG at room temperature. It reveals that the fabricated electrodes can selectively sense the oxygen gas with improved sensitivity, response time and recovery time. The nanocomposite containing 50 wt% of CuO–ZnO have high response with low response time and recovery time towards oxygen gas in the range of 40–200 parts per million (ppm) at room temperature (30 °C). The sensitivity of the electrodes is highly stable for the period of 50 days.