Optical methods for modulating cellular behavior are promising for both fundamental and clinical applications. However, most available methods are either mechanically invasive, require genetic manipulation of target cells, or cannot provide sub-cellular specificity. Here, we address all these issues by showing optical neuromodulation with free-standing coaxial p-type/intrinsic/n-type silicon nanowires (PIN-SiNWs). We revealed the presence of atomic gold on the nanowire surfaces, likely due to gold diffusion during the material growth. To evaluate how surface gold impacts the photoelectrochemical properties of single PIN-SiNWs, we used modified quartz pipettes from a patch clamp and recorded sustained cathodic photocurrents from single PIN-SiNWs. We show that these currents can elicit action potentials in primary rat dorsal root ganglion neurons through a primarily atomic gold-enhanced photoelectrochemical process. This work shows that wireless and non-genetic photoelectrochemical neuromodulation with single nanostructures is possible, and has implications for both basic research and photo-responsive therapies for neurodegenerative diseases.