Cu²⁺ Ion Doping-Induced Self-Assembled ZnO-Cu_xO Nanostructures for Electrochemical Sensing of Hydrogen Peroxide and p-Nitrophenol

The development of functional oxide nanostructures with a controlled size and morphology is crucial for fine-tuning of the properties and their applications in diverse areas. Herein, a simple and facile, template-free synthetic approach has been adopted for the fabrication of hybrid ZnO-CuxO nanostructures with a flower-like morphology through a hydrothermal pathway using a polyethylene glycol–water mixture as a reaction medium in a single step. The ZnO-CuxO nanoflowers thus obtained were characterized using a variety of spectroscopic and electron microscopic techniques. The formation of flower-like superstructures with diameters in the range of 8–10 μm could be confirmed from the electron microscopic studies. A detailed analysis indicates the critical role of metal counterions as well as the amount of water in the reaction medium during the shape-controlled evolution of the flower-like structures. The nanoflowers could be successfully utilized for the electrochemical detection of p-nitrophenol as well as H2O2. The limits of detection for p-nitrophenol and H2O2 were calculated to be 15.7 and 7.3 μM, respectively. The excellent detection ability can be attributed to the synergistic effect between ZnO and CuxO in the hybrid composite. The template-free synthesis of ZnO-CuxO nanostructures might provide a simple method for the development of other mixed oxide nanostructures with application potential in sensing of environmental hazards.