Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets

Abstract

Two-dimensional (2D) transition metal oxide systems present exotic electronic properties and high specific surface areas, and also demonstrate promising applications ranging from electronics to energy storage. Yet, in contrast to other types of nanostructures, the question as to whether we could assemble 2D nanomaterials with an atomic thickness from molecules in a general way, which may give them some interesting properties such as those of graphene, still remains unresolved. Herein, we report a generalized and fundamental approach to molecular self-assembly synthesis of ultrathin 2D nanosheets of transition metal oxides by rationally employing lamellar reverse micelles. It is worth emphasizing that the synthesized crystallized ultrathin transition metal oxide nanosheets possess confined thickness, high specific surface area and chemically reactive facets, so that they could have promising applications in nanostructured electronics, photonics, sensors, and energy conversion and storage devices.

Ultraviolet Sensors Based on Two-Dimensional Zinc Oxide Structures

“…[45], the 2D ZnO structures can be obtained using conductive glass substrates, such as indium-doped ZnO and indium tin oxide (ITO). This was supported by several published works [27,39,42].…”

“…The XRD patterns reveal the polycrystalline nature and can be indexed as hexagonal wurtzite structures of ZnO. Several published research studies showed the preferred orientation along the c-axis orientation of the (0001) plane [9,27,36,39,42,55]. No significant difference in the XRD pattern was noticed for different morphologies of the prepared 2D ZnO.…”

“…Several structures have been produced using this method, such as nanosheets [39], flake-like nanostructures [40], ZnO plate structures [27,41], and ZnO nanowalls [42]. In this method, two or three electrodes are used; they are the working electrode, typically using conductive glass, such as indium tin oxide (ITO), and the second electrode is usually platinum (Pt), which serves as a counter electrode.…”

“…The cell is usually heated up to a temperature ranging between 70 and 85°C. The size of the 2D ZnO sheet-like structures was increased through adjusting the electrodeposition time [39]. The growth mechanism of the 2D ZnO nanostructures produced through the electrodeposition method might be summarised as follows.…”

“…Different ZnO structures were studied for the UV applications, such as nanowires [67,68], nanorods [69,70] and nanobelts [71]; however, few results were published on 2D ZnO structures, and they focused on one type of device structure. The MSM type photoconductive UV based on 2D ZnO structures was explored by several groups [27,39,55]. Here, we review the application of 2D ZnO for UV sensors application.…”