Zinc Oxide Nanostructures: From Chestnut Husk-Like Structures to Hollow Nanocages, Synthesis and Structure

Domenica Scarano,Adriano Zecchina,Serena Bertarione,Federico Cesano

doi:10.3390/cryst8040153

Domenica Scarano, Adriano Zecchina + Show 2 more

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https://doi.org/10.3390/cryst8040153

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Abstract

Tailor-made nanostructured ZnO cages have been catalytically grown on Au and Pt films covering silicon substrates, by a controlled evaporation process, which means an accurate choice of temperatures, times, gas flows (He in the heating, He/air during the synthesis), and Au/Pt film thickness. The effect of the process parameters affecting the morphology and the structure of the obtained materials has been investigated by XRD analysis, scanning electron microscopy (SEM) and atomic force microscopy (AFM) microscopies, and FTIR spectroscopies. In particular, the role of the synthesis temperature in affecting the size and shape of the obtained ZnO cages has been highlighted. It will be shown that by adopting higher temperatures, the protruding nanowhiskers several microns in length, covering the cages and exhibiting both basal and prismatic faces, change into very thin and narrow structures, with extended prismatic faces, prevailing with respect to the basal ones. At an even higher process temperature, the building up of Au particles aggregates inside and/or anchored to the walls of the hollow cages, without any evidence of elongated ZnO nanostructures will be highlighted. From FTIR spectra information on lattice modes of the investigated ZnO, materials have been obtained.

Highlights

Nanocrystalline materials have attracted an increasing interest, because of their interesting properties and wide applications in many fields of science
Table S1), the intensity of the polar basal planes is slightly prevailing when compared to the one of the (10-10) and (10-11) prismatic faces, which means that (0002) basal planes have the main role in delimiting the ZnO cages
ZnO nanostructures that were surrounded by nanowhiskers, exposing the more stable elongated prismatic ZnO surfaces, has been observed after high temperatures processes

Summary

Introduction

Nanocrystalline materials have attracted an increasing interest, because of their interesting properties and wide applications in many fields of science. Many studies have been focused on both the synthesis [1] and the morphological-structural characterization of new functional materials to use in post-synthesis treatments (deposition on substrates, blending with polymers, building up of two-dimensional (2D)/three-dimensional (3D) lattices with control of the properties at nanoscopic level) [2,3,4,5]. The control of the sizes, shape, and orientation together with the porosity and the surface area of nano/microcrystallites, grown as three-dimensionally organized systems on different types of substrates, represent the main task to design the new generations of smart and functional materials, with specific properties [9,10,11,12].

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