Tryptophan Molecular Moiré Superlattices with Visible Fluorescence

Moiré superlattices of molecules may give birth to a new field of chemistry. For example, when crystalline nanoscale 2D sheets of a molecule are stacked with lattice planes twisted at low angles of each other, the interactions at the interfaces - that differs from the supramolecular interactions within the crystalline nanosheet and can be termed as hypermolecular interactions - may bring about new physical and chemical properties. Herein, we report for the first time the chemical synthesis of moiré superlattices of L or D tryptophan (trp) molecules formed in situ through twisted stacking of trp crystalline nanosheets. Transmission emission microscopy (TEM) measurements supported the formation of moiré superlattices of the crystalline 2D nanosheets. The resulting films were stable under alkaline conditions and exhibited strong photoluminescence emission peak at 452 nm and an additional peak at 500 nm due to the formation of a new energy state.