The effect of ionic strength on the sensing performance of liquid-gated biosensors

We experimentally demonstrated that the effect of ionic strength of electrolyte on the electrical signal of liquid-gated graphene field-effect transistors (G-FETs) in sensing of E. coli. Phosphate buffered saline (PBS) with different concentrations, which affects the ionic strength, was employed as the electrolyte for biosensor operation. The results showed that larger response (4.16%) was obtained by using the PBS with smaller ionic strength (1.627 mM). When the ionic strength is too low (0.1627 mM), it causes negative effect on the antibody-E. coli interaction, resulting in a smaller response (2.98%). This study provides a simple method to optimize the operation conditions of graphene biosensors, which enables the optimization of the electrical response.