Trionic all-optical biological voltage sensing via quantum statistics

Quantum confinement in monolayer semiconductors results in optical properties intricately linked to electrons, which can be manipulated by external electric fields. These optoelectronic features offer untapped potential for studying biological electrical activity. In addition to their relatively high quantum yields, picosecond level emission lifetimes make these materials particularly promising for monitoring biological voltages with high spatiotemporal resolution. Here we investigate exciton-to-trion conversion in & aring;ngstr & ouml;m-thick semiconductors to experimentally demonstrate label-free, dual-polarity, all-optical detection of electrical activity, via changes in photoluminescence, in cardiomyocyte cultures with ultrahigh temporal resolution. We devise a physical model to demonstrate that this conversion process is inherently governed by the quantum statistics of the background electrons induced by biological activity. We show that the monolayer MoS2 enables completely bias-free tetherless operation due to its substantial trion density originating from intrinsic sulfur vacancies introduced during chemical vapour deposition. Our work opens up an unexplored avenue of opportunities for label-free all-optical voltage sensing using & aring;ngstr & ouml;m-thick semiconductor materials whose applications have been elusive in the biological domain. This line of thinking at the intersection of biology and quantum science could lead to the discovery of non-ubiquitous quantum materials for detection of biological electrical activity.