Oxidative Etching of Hexagonal Boron Nitride Toward Nanosheets with Defined Edges and Holes.

Yunlong Liao,Zhongfang Chen,Xiaogang Han,Kaixiong Tu,John W Connell,Yi Lin,Liangbing Hu

doi:10.1038/srep14510

Abstract

Lateral surface etching of two-dimensional (2D) nanosheets results in holey 2D nanosheets that have abundant edge atoms. Recent reports on holey graphene showed that holey 2D nanosheets can outperform their intact counterparts in many potential applications such as energy storage, catalysis, sensing, transistors, and molecular transport/separation. From both fundamental and application perspectives, it is desirable to obtain holey 2D nanosheets with defined hole morphology and hole edge structures. This remains a great challenge for graphene and is little explored for other 2D nanomaterials. Here, a facile, controllable, and scalable method is reported to carve geometrically defined pit/hole shapes and edges on hexagonal boron nitride (h-BN) basal plane surfaces via oxidative etching in air using silver nanoparticles as catalysts. The etched h-BN was further purified and exfoliated into nanosheets that inherited the hole/edge structural motifs and, under certain conditions, possess altered optical bandgap properties likely induced by the enriched zigzag edge atoms. This method opens up an exciting approach to further explore the physical and chemical properties of hole- and edge-enriched boron nitride and other 2D nanosheets, paving the way toward applications that can take advantage of their unique structures and performance characteristics.

Highlights

Ideal two-dimensional (2D) nanosheets are infinite, those in the real world are of limited size bounded by peripheral edge atoms
Metallic Ag nanoparticles were used as the etching catalyst and were grown on both basal plane surfaces and peripheral edges of hexagonal boron nitride (h-BN) platelets using a facile and scalable solvent-free process previously developed by the authors[25]
The as-obtained Ag-decorated h-BN (Ag-BN; Ag:BN ~ 1:5 mol/mol) sample was subjected to heating in static air using an open-ended tube furnace at an elevated temperature

Summary

Introduction

Ideal two-dimensional (2D) nanosheets are infinite, those in the real world are of limited size bounded by peripheral edge atoms. One such example that has received significant attention recently is “holey graphene”[5,6,7], sometimes called “graphene nanomesh” or, in computation models, “graphene antidot”[8] For these 2D materials, in addition to peripheral sheet edges, they possess edges around the high density vacancies/holes which can have a pronounced impact on the properties of nanosheets, making these materials perform differently from their intact counterparts. The epitaxial growth of in-plane seamless graphene-boron nitride heterojunctions has been achieved starting from basal plane-etched graphene[17,18,19] Such in-plane hybrid nanosheets are expected to have unique electronic properties, further highlighting the importance of controlling the shape, concentration and chemistry of edge structures in 2D nanomaterials. The oxidized BNNS exhibited elongated and randomly oriented etched pits and paths on the nanosheet surfaces[24]

Methods

Results

Conclusion