高荷电粒子动态去质子化/质子化的实验研究,The Journal of Physical Chemistry C

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高荷电粒子动态去质子化/质子化的实验研究
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2017-03-10 00:00:00 , DOI: 10.1021/acs.jpcc.7b01919
Yinghua Qiu ₁ , Anna Dawid _{1,

2} , Zuzanna S. Siwy _{1,

3,

4}

Affiliation

已发现单孔可用于检测和表征单个物体，例如细胞，颗粒，甚至单个分子。这种称为电阻脉冲技术的实验方法通常在对称的电解质条件下执行，以使通过物体的特性在测量和移位过程中保持恒定。在这里，我们报告了带高电荷的介电粒子穿过与pH梯度接触的孔隙的实验，并证明了这种设置可以探测粒子的质子化和去质子化。基于质子的快速扩散和亚毫秒级的羧基去质子化/质子化动力学，我们预计粒子将在几毫秒内改变其电离状态。然而，我们的结果表明，带高电荷的粒子的质子化和去质子化动力学非常慢，超过100毫秒。我们假设，在较高的pH值下，粒子上发生的平衡离子的缩合是导致质子化率提高的原因。减慢的去质子化归因于溶液中靠近高电荷表面的局部pH值的改变。此外，我们展示了中性粒子通过与pH梯度接触的孔的电渗流如何能够通过电压极性来探测孔的局部表面电荷性质的调制。减慢的去质子化归因于溶液中靠近高电荷表面的局部pH值的改变。此外，我们展示了中性粒子如何通过与pH梯度接触的孔隙进行电渗流，从而可以通过电压极性来探测孔隙的局部表面电荷性质的调制。减慢的去质子化归因于溶液中靠近高电荷表面的局部pH值的改变。此外，我们展示了中性粒子通过与pH梯度接触的孔的电渗流如何能够通过电压极性来探测孔的局部表面电荷性质的调制。

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Experimental Investigation of Dynamic Deprotonation/Protonation of Highly Charged Particles

Single pores have found application in detecting and characterizing individual objects such as cells, particles, and even individual molecules. The experimental approach, called resistive-pulse technique, is often performed at symmetric electrolyte conditions so that the properties of the passing object remain constant in the course of measurement and translocation. Here we report experiments with highly charged mesoparticles passing through pores placed in contact with a pH gradient and demonstrate that this setup allows probing protonation and deprotonation of the particles. On the basis of fast diffusion of protons and submillisecond deprotonation/protonation kinetics of carboxyl groups, we expected that the particles would change their ionization state within a few milliseconds. However, our results show that the kinetics of protonation and deprotonation of the highly charged particles is significantly slower and exceeds 100 ms. We hypothesize that condensation of counterions that occurs on the particles at higher pH is responsible for the modified rates of protonation. The slowed-down deprotonation is attributed to modified local pH of the solution next to a highly charged surface. In addition, we show how electroosmotic flow of neutral particles through a pore in contact with pH gradient can probe modulations of local surface charge properties of the pore by voltage polarity.

更新日期：2017-03-10

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