Two-dimensional cuse nanosheets with microscale lateral size: Synthesis and template-assisted phase transformation

Semiconducting nanosheets with microscale lateral size are attractive building blocks for the fabrication of electronic and optoelectronic devices. The phase-controlled chemical synthesis of semiconducting nanosheets is of particular interest, because their intriguing properties are not only related to their size and shape, but also phase-dependent. Herein, a facile method for the synthesis of phase-pure, microsized, two-dimensional (2D) CuSe nanosheets with an average thickness of approximately 5nm is demonstrated. These hexagonal-phased CuSe nanosheets were transformed into cubic-phased Cu _2-xSe nanosheets with the same morphology simply by treatment with heat in the presence of Cu^I cations. The phase transformation, proposed to be a template-assisted process, can be extended to other systems, such as CuS and Cu_1.97S nanoplates. Our study offers a new method for the phase-controlled preparation of 2D nanomaterials, which are not readily accessible by conventional wet-chemical methods. Not fazed by change: A facile solution-based strategy was used for the preparation of microsized CuSe nanosheets. As-prepared CuSe with a hexagonal phase was transformed into Cu _2-xSe with a cubic phase through simple treatment with heat without damaging the shape of the original 2D nanosheets (see picture). The two kinds of nanosheets show different optical properties and are both promising building blocks for the construction of various devices.