Multilayered MoAlB@MBene structures using mild microwave-assisted etching and their optical properties

MBenes, a novel class of transition metal borides, represent an exciting advancement in two-dimensional (2D) materials. This study introduces a novel and mild microwave-assisted hydrothermal method. A multilayered (ML) MoAlB@MBene structure is achieved when a mixture of hydrochloric acid (HCl) and hydrogen peroxide (H₂O₂) is used in combination with acid (0.1 M HCl) or base (0.1 M NaOH) pre-treatment. This method differs from reported etching techniques, which require long reaction times and highly concentrated acids (or bases). Also, they demonstrated that instead of selectively etching, the MAB phases dissolve, incompletely etch, or even oxidize. Achieving a multilayer structure within 4 hours was previously challenging. The current process allows for ML MBene formation and controlled oxidation in 4 hours. This leads to a distinct bandgap opening in ML MoAlB@MBene, with energy levels of 3.54, 3.58, 3.65, and 3.88 eV. The study also explores the optical absorption characteristics and time-resolved photoluminescence (TRPL) behavior of ML MoAlB@MBene. This demonstrates its tunable optical properties and significant potential for applications in high-performance light-emitting diodes, photovoltaics, photocatalysts, laser diodes, and more.