Solution-Based, Template-Assisted Realization of Large-Scale Graphitic ZnO

Abstract

With a honeycomb single-atomic-layer structure similar to those of graphene and hexagonal boron nitride (hBN), the graphitic phase of ZnO (gZnO) have been predicted to offer many advantages for engineering, including high-temperature stability in ambient conditions and great potential in heterostructure applications. However, there is little experimental data about this hexagonal phase due to the difficulty of synthesizing large-area gZnO for characterization and applications. In this work, we demonstrate a solution-based approach to realize gZnO nanoflakes with thicknesses down to a monolayer and sizes up to 20 μm. X-ray photoelectron spectroscopy, X-ray absorption near-edge spectroscopy, photoluminescence, atomic force microscopy, and electron microscopy characterizations are conducted on synthesized gZnO samples. Measurements show significant changes to the electronic band structure compared to its bulk phase, including an increase of the band gap to 4.8 eV. The gZnO nanosheets also exhibit excellent stability at temperatures as high as 800 °C in ambient environment. This wide band gap layered material provides us with a platform for harsh environment electronic devices, deep ultraviolet optical applications, and a practical alternative for hBN. Our synthesis method may also be applied to achieve other types of 2D oxides.

Progress in the Utilization Efficiency Improvement of Hot Carriers in Plasmon-Mediated Heterostructure Photocatalysis

“…The distinguishing of non-thermal effects (HCs effects) and thermal effects, which allows us to quantify each contribution for the enhancement of the process of photocatalysis, is also of great importance for designing specific structures with different purposes [136][137][138]. Second, in the past years, although numerable technologies on the optimization and design of the rational employment of PMH have emerged [139][140][141][142][143], the crystal growth mechanisms and hetero-assembly techniques still need to be revealed clearly. Furthermore, the optical characteristics of PMH are studied mainly on a macroscopic level; for example, the absorption and reflection in self-assembly films, and the optical phenomena we observed, are integrated effects with millions of nanostructures.…”

Tuning Photocatalytic Performance of Multilayer ZnO for Water Splitting by Biaxial Strain Composites

“…In the case of ZnO, for instance, due to surface depolarization, ZnO films that are only a few atomic layers thick favor a stable graphite-like multilayer structure. Furthermore, when the number of layers increases, ZnO films begin transforming into the bulk structure at a certain critical thickness [21][22][23][24][25]. Theoretically, some previous first-principles calculation studies predicted the existence of graphite-like multilayer ZnO [9,26].…”

Green-Lighting the Sub-Band Gap Excitation in Two-Dimensional Zinc Oxide

“…The gZnO flakes appear as micron-sized faint bluish-white patches on Si/SiO 2 substrate when observed using an optical microscope, with low visibility being a result of close refractive index values for SiO 2 and ZnO (Figure 1a). 1 The height profile of these bluish patches conducted via atomic force microscopy (AFM) shows that the patches actually comprise fragmented micron-sized flakes of average thickness <6 nm (Figure 1b). The granularity of film in height profile AFM image can be attributed to the formation of ZnO NPs in the wrinkled folds of GO during the annealing process; ZnO NPs so formed rest as isolated islands over gZnO layers.…”

“…Graphitic zinc oxide (gZnO) belongs to rare breed of planar thermally stable two-dimensional materials that cover the energy spectrum in between hBN and narrow band gap 2D semiconductors like transition metal dichalcogenides (TMDs). − However, taming the necessary evil of wide band gap in 2D semiconductors like gZnO to harness ultraviolet and visible light is a different challenge altogether. There are no experimental reports that show photoexcitation of gZnO at visible wavelengths despite theoretical studies predicting amenability of gZnO to band gap engineering via routes such as doping and structural modifications. − …”

“…Graphitic zinc oxide (gZnO) is synthesized using a graphene oxide (GO) template method. , Annealing the gZnO-GO composite in air results in decomposition of GO, leaving behind gZnO layers on the substrate. The gZnO flakes appear as micron-sized faint bluish-white patches on Si/SiO 2 substrate when observed using an optical microscope, with low visibility being a result of close refractive index values for SiO 2 and ZnO (Figure a) . The height profile of these bluish patches conducted via atomic force microscopy (AFM) shows that the patches actually comprise fragmented micron-sized flakes of average thickness <6 nm (Figure b).…”