Patterned Bi Nanoparticles on a Layer-by-Layer MXene Film for Highly Improved Photodetection

To improve the photodetction performance of MXene titanium carbide (Ti3C2), a MXene film assembled by two-dimensional (2D) MXene Ti3C2Tx nanosheets (NSs) via a layer-by-layer technique is employed to facilely pattern zero-dimensional (0D) bismuth nanoparticles (Bi NPs), abbreviated as patterned Bi NP@MXene Ti3C2Tx NS, for the construction of a prototypical photoelectrochemical (PEC)-type photodetector. Compared to individual 2D MXene Ti3C2Tx NSs and 0D Bi NPs, the patterned Bi NP@MXene Ti3C2Tx NS displays remarkably better PEC performance, including photocurrent density, photoresponsivity, and detectivity under the same conditions. A theoretical investigation demonstrates that monolayer Bi shows a semiconducting property on the MXene Ti3C2 that usually yields a strict bandgap match with an incident light, while multilayer (≥2) Bi tends to be conductive, which not only facilitates electron transport but also promotes the generation of photoinduced current by overcoming the work function. The intriguing experimental and theoretical results indicate that 2D MXene Ti3C2Tx NSs can be employed as building blocks to construct many promising hydrides for various photoelectronic devices, further greatly widening the application prospects of 2D MXenes.