Department of Physics, Indian Institute of Science, Bangalore 560012, India.
ACS Nano. 2010 Mar 23;4(3):1687-95. doi: 10.1021/nn901554h.
We report a nuclear magnetic resonance (NMR) study of confined water inside approximately 1.4 nm diameter single-walled carbon nanotubes (SWNTs). We show that the confined water does not freeze even up to 223 K. A pulse field gradient (PFG) NMR method is used to determine the mean squared displacement (MSD) of the water molecules inside the nanotubes at temperatures below 273 K, where the bulk water outside the nanotubes freezes and hence does not contribute to the proton NMR signal. We show that the mean squared displacement varies as the square root of time, predicted for single-file diffusion in a one-dimensional channel. We propose a qualitative understanding of our results based on available molecular dynamics simulations.
我们报告了一项关于受限在大约 1.4nm 直径单壁碳纳米管（SWNTs）内的水的核磁共振（NMR）研究。我们表明，即使在 223K 下，受限水也不会冻结。我们使用脉冲梯度（PFG）NMR 方法在低于 273K 的温度下确定纳米管内水分子的均方根位移（MSD），此时纳米管外的体相水冻结，因此不会对质子 NMR 信号产生贡献。我们表明，均方根位移随时间的平方根变化，这是一维通道中单分子扩散的预测。我们基于可用的分子动力学模拟提出了对我们结果的定性理解。
