光操作技術を用いた金ナノ粒子の電気検出における光吸収の影響

抄録

To improve the throughput of nanopore sequencers, a novel approach using optical tweezers has been proposed to efficiently transport nanoparticles to the detection area based on the well-known Coulter principle. This method successfully achieved the electrical detection of gold nanoparticles (AuNPs) and polystyrene nanoparticles. However, the current response of AuNPs displayed a conductive pulse rather than a resistive pulse. This phenomenon highlights the need for further investigation into the effect of AuNP’s optical absorption on ionic current responses. In this study, AuNPs with an average diameter of 200 nm were brought to and passed through the detection area using optical tweezers in 13.7 mM and 27.4 mM NaCl dispersions. Additionally, in a 13.7 mM NaCl dispersion, AuNPs with average diameters of 200 nm and 150 nm were similarly transported and passed through the detection area. The results demonstrated that for particles with the same average diameter, the larger conductive pulses were obtained in the lower electrolyte concentrations. Similarly, for the same electrolyte concentration, smaller particles led to larger conductive pulses. These findings suggest that in the ionic current detection of optically trapped AuNPs, the influence of electrically polarized fields generated by surface plasmons dominates over the excluded volume effect described by Coulter’s principle. Furthermore, this method allows for flexible adjustment of the measurement time for individual particles, indicating the potential for achieving high-precision single-particle identification.