Low-frequency flicker noise in stochastic ionic transport across atomically thin graphene nanopores

Atomically thin 2D nanopores have emerged as promising platforms from nanofluidics research to practical applications. Low-frequency flicker noise in 2D nanopores limits detection accuracy and performance of nanopore sensors. However, the physical mechanisms of low-frequency noise are still under debate and achieving its control in 2D nanopores remains challenging. Here, we report multivalent-cations-modulated low-frequency noise in graphene nanopores and demonstrate that low-frequency noise originates from surface charge fluctuations induced by reversible adsorption-desorption of ions. Unexpectedly, its amplitude can be greatly controlled up to about 3 orders of magnitude by a trace of multivalent cations (at least 0.1% of concentration in mixture solutions). Moreover, low-frequency noise can be suppressed by 2 orders of magnitude via adding organic solvents with a high dielectric constant based on suppressing interactions between surface charge and ions. Our findings will facilitate understanding of low-frequency noise in nanofluidics and design of related applications including ultrasensitive nanofluidic devices.