Molecular layer-by-layer re-stacking of MoS-InSe by electrostatic means: assembly of a new layered photocatalyst

2D-layered transition metal chalcogenides are useful semiconductors for a wide range of opto-electronic applications. Their similarity as layered structures offers exciting possibility to modify their electronic properties by creating new heterojunction assemblies from layer-by-layer restacking of individual monolayer sheets, however, the lack of specific interaction between these layers could induce phase segregation. Here, we employed a chemical method using n -BuLi to exfoliate MoS 2 and In 2 Se 3 into their monolayer-containing colloids in solution. The bulky Se atoms can be selectively leached from In 2 Se 3 during Li treatment which gives positively charged surface monolayers in neutral pH whereas the strong polarization of Mo-S with moderate S leaching gives a negatively charged surface. Specific interlayer electrostatic attraction during their selective assembly gives a controllable atomic AB-type of layer stacking as supported by EXAFS, STEM with super-EDX mapping, TAS/TRPL and DFT calculations. Using this simple but inexpensive bottom-up solution method, a new photocatalyst assembled from layers for photo water splitting can be tailor-made with high activity. Selective assembly of monolayered MoS 2 (A) and In 2 Se 3 (B) in solution gives a controllable atomic AB-type layer stacking. A new class of photocatalysts can be tailor-made with high activity using this simple but inexpensive bottom-up solution method.