Limits to non-fluorescent voltage sensitivity using surface and particle plasmons

Voltage sensitive fluorescent dyes have long been used to measure physiological voltages in live cell cultures. However dyes suffer from poor contrast and limited recording duration due to photobleaching. A photostable voltage sensitive cellular label, such as a noble metal nanoparticle, would potentially allow for indefinite recording from neural and other live cell cultures. Noble metals possess an inherent voltage sensitivity: their optical properties depend on their density of free electrons, which can be modulated in an aqueous environment by charging or discharging the double layer capacitance with an applied voltage. This manuscript contains a simple analysis of the expected voltage sensitivity using gold nanospheres and nanoshells in both darkfield and photothermal detection modalities and concludes that high bandwidth voltage measurement is fundamentally achievable.