Zn2+ Induced Self-Assembled Growth of Octapodal CuxO-ZnO Microcrystals: Multifunctional Applications in Reductive Degradation of Organic Pollutants and Nonenzymatic Electrochemical Sensing of Glucose

Abstract

Development of solution based synthetic methodology for the controlled growth of hyperbranched oxide nanomaterials is important for practical applications in nanotechnology. A binary metal oxide nanocomposite CuxO-ZnO with octapod microstructures was fabricated in a one pot hydrothermal method using a water-polyethylene glycol mixture as a solvent. The highly oriented growth of the microstructures emerged from controlled mixing of the precursor metal salts without any involvement of external shape-directing agents. An investigation into the organized conformation and geometric architectural evolution revealed that the reaction temperature and concentration ratio of the precursor metal salts played critical roles on the morphology of the composite structure. The obtained octapod architecture was characterized by various spectroscopic as well as microscopic techniques. A time dependent study demonstrated the evolution of octapod morphology from self-assembled cubic seeds in a template-free pathway. The hyperbranched mixed metal oxide composite showed effective catalytic activity for the reduction of 4-nitrophenol with a rate constant (kapp) of 2.1 × 10-2 s-1 and an activity factor (K) of 2100 s-1 g-1. Additionally, the composite oxide material showed high efficiency toward the reduction of common organic dye pollutants under ambient condition. Moreover, the CuxO-ZnO octapodal microcrystals showed excellent activity toward electrocatalytic glucose oxidation with a sensitivity of 2091 μA/mmol/cm2 when a potential of 0.6 V was applied. The high efficiency of the microparticles in these catalytic applications could be attributed to the coexistance of CuxO and ZnO phases in the matrix and the synergistic electronic effect owing to the formation of heterojunctions, which allowed efficient movement of holes and free electrons. The template-free structural evolution of the CuxO-ZnO materials into octapodal geometry through a simple hydrothermal pathway might encourage promising applications for sensing and organic decontamination. Copyright © 2018 American Chemical Society.