Quantum Tunneling Currents in a Nanoengineered Electrochemical System

5 years ago

Quantum Tunneling Currents in a Nanoengineered Electrochemical System

Chaitanya Gupta, Roger T. Howe, Matthew Seal, Boris Murmann, Shuai Chang, Ross M. Walker, Sean R. Fischer

We develop an equivalent circuit model for charge transfer across a nanoscale electrochemical interface and apply it to tune the interface parameters so that tunneling electrons transduce information about the vibronic structure of the interface. Model predictions are broadly consistent with cyclic voltammograms acquired using a custom, low-noise potentiostat on a 50 nm diameter Pt(80%)–Ir(20%) electrode functionalized with 10 nm diameter gold nanoparticles and immersed in a phosphate buffer with a redox couple. Conductance–voltage sweeps for 1 μM 2-d-leucine have shifted vibronic peaks from those for 1 μM leucine, indicating promise for label-free sensing. The model is based on two interdependent lengths that describe the interaction strengths between the participant electronic states in the electrolyte and the participant reaction coordinates, and between the latter and the surrounding bath modes. These lengths translate into capacitive elements which are positioned in parallel to the classical capacitance defined by the interface geometry. We identify an optimal charge-transfer regime, defined by a specific interface geometry, in which the energy transferred between the transitioning electron and a specific reaction coordinate mode is dissipated exactly by the interaction of the recipient mode with the surrounding bath. The perturbative effect of coupling external potentiostatic instrumentation to the nanoelectrochemical interface for measuring charge transfer is defined by an equivalent interface “temperature”.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b04350

DOI: 10.1021/acs.jpcc.7b04350