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Abstract：
The grafting density of probes at sensor interface plays a critical role in the performance of biochemical sensors. However, compared with macroscopic interface, the effects of probe grafting density at nanometric confinement are rarely studied due to the limitation of precise grafting density regulation and characterization at the nanoscale. Here, we investigate the effect from the grafting density of DNA probes on ionic signal for nucleic acid detection in a cylindrical nanochannel array (with diameter of 25 nm) by combing experiments and theories. We set up a theoretical model of charge distribution from close to inner wall of nanochannels at low probe grafting density to spreading in whole space at high probe grafting density. The theoretical results fit well with the experimental results. A reverse of ionic output from signal-off to signal-on occurs with increasing probe grafting density. Low probe grafting density offers a high current change ratio that is further enhanced using long-chain DNA probes or the electrolyte with a low salt concentration. This work develops an approach to enhance performance of nanochannel-based sensors and explore physicochemical properties in nanometric confines.
摘要：
探针在传感器界面的接枝密度对生化传感器的性能起着至关重要的作用。然而,与宏观界面相比，由于纳米尺度上精确的接枝密度调节和表征的限制，很少研究纳米尺度下探针接枝密度的影响。这里,我们通过结合实验和理论，研究了DNA探针的接枝密度对圆柱形纳米通道阵列（直径为25nm）中核酸检测的离子信号的影响。我们建立了从低探针接枝密度下纳米通道内壁附近到高探针接枝密度下整个空间扩散的电荷分布的理论模型。理论结果与实验结果吻合良好。随着探针接枝密度的增加，离子输出从信号关闭到信号开启的反向发生。低探针接枝密度提供高电流变化率,其使用长链DNA探针或具有低盐浓度的电解质进一步增强。这项工作开发了一种方法来增强基于纳米通道的传感器的性能，并探索纳米范围内的物理化学性质。
