Sofronov Oleksandr O, Bakker Huib J
AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands.
ACS Cent Sci. 2020 Jul 22;6(7):1150-1158. doi: 10.1021/acscentsci.0c00340. Epub 2020 Jun 3.
The transport of protons in nanoconfined environments, such as in nanochannels of biological or artificial proton conductive membranes, is essential to chemistry, biology, and nanotechnology. In water, proton diffusion occurs by hopping of protons between water molecules. This process involves the rearrangement of many hydrogen bonds and as such can be strongly affected by nanoconfinement. We study the vibrational and structural dynamics of hydrated protons in water nanodroplets stabilized by a cationic surfactant using polarization-resolved femtosecond infrared transient absorption spectroscopy. We determine the time scale of proton hopping in the center of the water nanodroplets from the dynamics of the anisotropy of the transient absorption signals. We find that in small nanodroplets with a diameter <4 nm, proton hopping is more than 10 times slower than in bulk water. Even in relatively large nanodroplets with a diameter of ∼7 nm, we find that the rate of proton hopping is slowed by ∼4 times compared with bulk water.
质子在纳米受限环境中的传输，比如在生物或人工质子传导膜的纳米通道中，对于化学、生物学和纳米技术而言至关重要。在水中，质子通过在水分子之间跳跃来扩散。这个过程涉及许多氢键的重排，因此会受到纳米限域的强烈影响。我们使用偏振分辨飞秒红外瞬态吸收光谱法研究了由阳离子表面活性剂稳定的水纳米液滴中水合质子的振动和结构动力学。我们从瞬态吸收信号各向异性的动力学中确定了水纳米液滴中心质子跳跃的时间尺度。我们发现，在直径小于4纳米的小纳米液滴中，质子跳跃比在体相水中慢1０倍以上。即使在直径约为7纳米的相对较大的纳米液滴中，我们也发现质子跳跃速率与体相水相比减慢了约4倍。
