Unravelling the Role of Synthesis Conditions on the Structure of Zinc Oxide-Reduced Graphene Oxide Nanofillers.

Zélia Alves,Paula Ferreira,Cláudia Nunes

doi:10.3390/nano11082149

Abstract

The diversity of zinc oxide (ZnO) particles and derived composites applications is highly dependent on their structure, size, morphology, defect amounts, and/or presence of dopant molecules. In this work, ZnO nanostructures are grown in situ on graphene oxide (GO) sheets by an easily implementable solvothermal method with simultaneous reduction of GO. The effect of two zinc precursors (zinc acetate (ZA) and zinc acetate dihydrate (ZAD)), NaOH concentration (0.5, 1 or 2 M), and concentration (1 and 12.5 mg/mL) and pH (pH = 1, 4, 8, and 12) of GO suspension were evaluated. While the ZnO particle morphology shows to be precursor dependent, the average particle size length decreases with lower NaOH concentration, as well as with the addition of a higher basicity and concentration of GO suspension. A lowered band gap and a higher specific surface area are obtained from the ZnO composites with higher amounts of GO suspension. Otherwise, the low concentration and the higher pH of GO suspension induce more lattice defects on the ZnO crystal structure. The role of the different condition parameters on the ZnO nanostructures and their interaction with graphene sheets was observed to tune the ZnO–rGO nanofiller properties for photocatalytic and antimicrobial activities.

Highlights

The synthesis of zinc oxide (ZnO) structures was previously described to be very susceptible to different conditions, from the type of zinc precursor to the pH of solution and to the presence of different molecules in the medium such as the graphene oxide (GO) [34,35,38]
For a clearer comprehensive look, the results and discussion are sectioned in three parts: (i) effect of zinc precursor, NaOH concentration and GO addition on ZnO structures; (ii) effect of GO concentration on ZnO structures; and (iii) effect of pH
ZnO–reduced graphene oxide (rGO) particles were mainly characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and RAMAN, and some of them by UV-vis diffuse reflectance spectroscopy (DRS)

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Nanofillers have become interesting structures to enhance the performance properties of eco-friendly biopolymer-based materials and further enhance its functionality [1,2]. Among the type of nanofillers, inorganic and carbon-based structures, zinc oxide (ZnO) nanoparticles [3] and reduced graphene oxide (rGO) [4] have been explored

Methods

Results

Conclusion