Light Entrapment by Plasmonic Chiral Lock for Enhancement of 2D Flakes Catalytic Activity

Plasmon-based triggering leads to an effective increase of material catalytic activity in a number of relevant photoelectrochemical transformations, including nitrogen reduction for the production of ammonia. The efficiency of the plasmon assistance can be significantly increased through the rational design of hybrid photoelectrodes, e.g., by placing a redox-active material at plasmonic hot spots that may arise between two coupled nanostructures. In this work, we describe the creation and utilization of chiral plasmon-active hybrid structures (based on the so-called gold helicoids) coupled with redox-active 2H-MoS₂. The chiral plasmon-active gold nanoparticles (with the same or opposite chirality) were spatially separated by thin two-dimensional (2D) flakes to reach mutual plasmon coupling between them. Using numerical simulations and SERS measurements, the dependence of the local enhancement of the electric field (EF) inside the created plasmon-active diastereomer consisting of Au helicoid-2D MoS₂-Au helicoid "sandwich structure", on the mutual chirality of the nanoparticles is demonstrated. It is found that the plasmon energy is more efficiently "concentrated" in the MoS₂ space using the "chiral trap" of light energy (i.e., chiral plasmonic lock), even in the case where the chiral handedness of Au nanoparticles is matching. The created hybrid structures were subsequently used for nitrogen reduction and ammonia production proceeding on the MoS₂ surface. A clear dependence of the catalytic activity of MoS₂ on the matching or mismatching of Au helicoid chiralities (and related local value of EF) is observed. In particular, a two-time increase in the ammonia yield is obtained in the case of matching chirality, compared to that in the case of mismatched configuration or the control experiments performed with nonchiral Au nanocubes. Hence, the utilization of chiral plasmonic nanoparticles and their dimers (or multimers) provides an additional opportunity for even more effective photosensibilization of redox-active materials.