Graphene-nanodiamond membranes for atomic-impact sensing: design and fluorescence readout limits.

Hybrid nanomaterial platforms that combine mechanically compliant two-dimensional membranes with optically active quantum emitters offer an attractive route towards ultrasensitive particle detection. Here, we investigate a sensor concept based on a graphene membrane suspended over a nanoscale aperture and functionalised with fluorescent nanodiamonds. The impact of an incoming atom transfers momentum to the membrane and excites an out-of-plane mechanical motion, which is transduced into an optical signal through the nanodiamond fluorescence. We develop a quantitative upper-bound model linking atomic momentum transfer, the mechanical response of the nanodiamond-loaded membrane, and the resulting optical transduction. Design maps for the mechanical resonance frequency and collision-induced oscillation amplitude reveal single-impact displacements in the femtometre-to-sub-picometre range for helium atoms. Even under favourable mechanical, collision, and optical conditions, the corresponding relative fluorescence modulation remains below 10