Synthesis and Preparation of Mono-layer h-BN Nanopowders by Using a Combination of CVD Method with Isopropanol-Assisted Exfoliation Process

Abstract

An experimental study is performed to introduce a new procedure for producing single-layer hexagonal-boron nitride (h-BN) nanopowders. In our modified procedure, synthesis and exfoliation processes are employed to achieve a two-dimensional (2D) h-BN. In the first stage, h-BN nanosheets are successfully synthesized through reacting of boric anhydride (B₂O₃) with guanidine hydrochloride (CH₅N₃ • HCl) in nitrogen/hydrogen (N₂/H₂ = 90/10, v/v) atmosphere in the chemical vapor deposition (CVD) furnace. This process results in efficient synthesis of multi-layer h-BN. In fact, the product is significantly cost-effective and applicable for various purposes, such as subsequent exfoliation to obtain single-layer h-BN. In the next step, the prepared h-BN is characterized by using various methods: X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR), and micro-Raman spectroscopy. Finally, the formed multi-layer h-BN nanosheets are converted into single-layer 2D h-BN through a series of solvent-assisted exfoliation experiments. According to our experimental results, the distance between h-BN layers expands through intercalating isopropanol (IP) molecules among them under ultrasonic treatment. As a result of this process, the platelets are completely separated and single-layer h-BN nanosheets are produced. Therefore, this process is recommended for the straight forward production of 2D h-BN.