Electric fields as actuators in unimolecular contacts

Single-molecule detection is essential for investigating individual molecules and (electro)chemical processes at the molecular level. Often, interrogation of individual molecules is achieved by fixating them in nanogaps to minimise the masking effect of surrounding molecular ensembles common to bulk analysis. Electrical detection methods are reliable options for single-molecule studies as they are label-free and provide a robust real-time readout easy to monitor. Here we review how the electric field generated in the nanogap between two electrodes can be employed to achieve active control over the target molecule beyond simple molecular sensing. First, we describe the use of electric fields to build the interelectrode nanogap, to orient the molecular contact, to steer molecule- electrode interaction, and to promote reactivity of the trapped molecule. Second, we focus on the use of the electric field as a contact stabilising agent, to address the main drawbacks of single-molecule sensing, such as detection rate and timescales.