Deciphering the biphasic pulse signals based on nanoparticles translocated through nanopores

Solid-state nanopores, as a high-throughput and label-free single-molecule detection technology, have been extensively employed in biomolecular analysis. This study investigates the translocation of gold nanoparticles through silicon nitride solid-state nanopores, systematically examining the influence of applied voltage and nanopore diameter on translocation signatures under low-salt conditions. Theoretical simulations and experimental results demonstrate that under low-salt conditions, the translocation signals of gold nanoparticles exhibit biphasic pulse characteristics due to the synergistic interplay of volume exclusion and surface charge interactions. As the applied positive voltage increases, the signal waveform of current enhancement shifts to a biphasic pulse pattern with a typical feature of an initial current increase followed by a subsequent reduction. Furthermore, the biphasic signal profile also demonstrates a dependence on the pore size. Enhanced current signals mostly occur in smaller nanopores, while blocked current is dominant in larger pores. These findings provide experimental evidence for optimizing nanopore dimensions in gold nanoparticle detection and promote nanopore-based single-particle sensing applications.