Fig. 1: The photoelectron transfer and charge injection process of ZnAuPN for neuromodulation.

A The design of a bimetallic zinc and gold porphyrins self-assembled nanoelectrode array brings an optimal photoelectrical performance with high-efficient photoelectron transfer and charge injection in neurons. The 2D ZnAuPN prefers to tightly adhere to the outer membrane of neurons, and upon laser illumination, the excited electron will ultrafast transfer over porphyrin rings to accumulate near the undercoordinated Au-atom centers which serve as stimulating electrodes, forming the electron-rich Au points to allow for the robust charge injection at ZnAuPN/neuron interface. The Au atom as the reactive center causes the photoelectrochemical redox from oxidation (Ox) to reduction (Red) solution for Faradaic current injection in solution (Faradaic process). B ZnAuPN with enhanced nonlinear optical sensitivity can be excited by both visible one-photon and near-infrared two-photon. The ultrafast photoelectron transfer process is shown including both the intermolecular charge transfer (CT) (~2.7 ps) and energy transfer (ET) (~66 ps) from ZnP to the adjacent AuP⁺, and the intramolecular CT (~0.5 ps) in single AuP⁺, with the total transfer efficiency up to 97%. All these effects afford the high-efficient current injection for optical control on a single neuron at ms temporal resolution. C TEM image of ZnAuPN. D AFM image of ZnAuPN with the height profile in the insert figure. E HAADF-STEM image of ZnAuPN. Single Au atoms are indicated by red circles. Data are representative of at least three independent experiments with similar results.