Scalable synthesis of semiconducting MoB₂ nanosheets for flexible and multifunctional UV–Vis photodetection

Two-dimensional (2D) materials hold great promise for next-generation optoelectronic devices, yet the scalable production of semiconducting 2D transition metal borides (MBenes) remains a major challenge. In this work, we developed a rapid solid-state exfoliation strategy to directly obtain wide bandgap semiconducting molybdenum boride (SMB) nanosheets from commercial MoB₂ powder. The exfoliation process by lithium borohydride (LiBH₄)-assisted lithiation and hydrolysis enables efficient exfoliation of bulk MoB₂ into few-layer SMB nanosheets of lateral dimensions within minutes, overcoming the intrinsic metallic limitations of conventional MBenes. The synthesized SMB nanosheets were deposited via spray coating onto a flexible polyethylene terephthalate (PET) substrate, followed by mask-assisted sputtering of Au contacts, and a low-power flexible broadband UV–visible (UV–vis) photodetector was fabricated. It exhibits excellent optoelectronic performance with a long-term stability, such as a high on-off ratio of 3.8 × 10³@0.1 V, an excellent responsivity (47 A W⁻¹), a high specific detectivity (7.9 × 10¹¹ Jones), and a rapid response/recovery (25 ms/48 ms). Beyond conventional photodetection, the flexible device enables real-time pulse monitoring, photoplethysmography (PPG), and imaging capabilities, underscoring its multifunctionality. This study presents a novel pathway for developing scalable, high-performance, and wearable optoelectronics devices based on 2D metal boride.