Gold Nanorod Enhanced Fluorescence Enables Single-Molecule Electrochemistry of Methylene Blue

Redox reactions are central to energy conversion and life metabolism. Herein we present electrochemical measurements with fluorescent readout of the redox-sensitive dye Methylene Blue (MB), at the single-molecule (SM) level. To overcome the low fluorescence quantum yield of MB we enhanced fluorescence by using individual gold nanorods to achieve the required sensitivity. By measuring the same molecule at different electrochemical potentials we determined the mid-point potential of each single molecule through its redox-induced fluorescence blinking dynamics.