Paper-Based Nanoplatforms for Multifunctional Applications

M L Matias,R Martins,D Nunes,S H Ferreira,M P Duarte,R Borda D’Agua,E Fortunato,A Pimentel

doi:10.1155/2019/6501923

Abstract

In this work, zinc oxide (ZnO) and titanium dioxide (TiO2) nanostructures were grown on different cellulose paper substrates, namely, Whatman, office, and commercial hospital papers, using a hydrothermal method assisted by microwave irradiation. Pure ZnO and TiO2 nanostructures were synthesized; however, the growth of TiO2 above ZnO was also investigated to produce a uniform heterostructure. Continuous ZnO nanorod arrays were grown on Whatman and hospital papers; however, on office paper, the formation of nanoplates originating nanoflower structures could be observed. TiO2 nanoparticles homogeneously covered all the substrates, in some conditions forming uniform TiO2 films. Structural characterization was carried out by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Raman spectroscopy. The optical characterization of all the materials was carried out. The produced materials were investigated for multifunctional applications, like photocatalyst agents, bacterial inactivators, and ultraviolet (UV) sensors. To evaluate the photocatalytic activity under UV and solar radiations, rhodamine B was the model-test contaminant indicator and the best photocatalytic activity was achieved with Whatman paper. Hospital paper with TiO2 nanoparticles showed significant antibacterial properties against Staphylococcus aureus. ZnO-based UV sensors demonstrated a responsivity of 0.61 μA W-1.

Highlights

zinc oxide (ZnO) and TiO2 nanostructuresZinc oxide is a n-type semiconductor with a direct and wide bandgap of 3.37 eV and has a large free exciton energy of around 60 meV [5]
ZnO and TiO2 nanostructures, as well as ZnO/TiO2 heterostructures were successfully synthesized under microwave irradiation using cellulose-based substrates at low temperatures and fast synthesis times
Hospital paper was selected for the antibacterial activity experiments in a way to avoid growth and proliferation of microorganisms commonly found in the hospital environment, and besides it is a disposable paper

Summary

Introduction

ZnO and TiO2 nanostructuresZinc oxide is a n-type semiconductor with a direct and wide bandgap of 3.37 eV and has a large free exciton energy of around 60 meV (at room temperature) [5]. ZnO is used in a variety of applications, for instance in thin film transistors [20,21], solar cells [22,23], UV/ozone and glucose sensors [5,24,25], photocatalytic agent [24,26,27] and as an antibacterial and antifungal agent [5,28]. It has three polymorphs: wurtzite, rock-salt and zinc-blende structures, at room temperature, the stable phase of ZnO is hexagonal wurtzite [29]. ZnO chemical and physical properties are highly influenced by its size, shape, morphology, crystallinity, as well as the solvents and precursors used to achieve the desired nanostructure [5]

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Conclusion