Solid State and Structural Chemistry Unit, Indian Institute of Science Bengaluru, Karnataka, India.
J Chem Phys. 2020 Jun 14;152(22):224707. doi: 10.1063/5.0010613.
We unravel the combined effects of confinement and surface interactions by studying the position dependent, time-resolved dynamic response functions in nano-containers of different shapes. Spectroscopic signatures are additionally studied through solvation dynamics by placing ionic and dipolar probes at varying distances from the enclosing surface. We find that the confined water molecules exhibit exotic dynamical features and stark differences from that in the bulk liquid. We employ atomistic molecular dynamics simulation to obtain the solvation time correlation function, non-Gaussian parameter, and non-linear response function that reveal the existence of heterogeneous and non-exponential dynamics with a strong sensitivity to both the size and the shape of the enclosure. Importantly, the slower long-time decay constant exhibits a non-monotonic spatial dependence. The initial ultrafast component is reminiscent of the same in the bulk, but it is found to have a different origin in the present systems. We perform shell-wise analyses to understand the microscopic origin of these observations and the range of the propagation of the surface induced effects.
我们通过研究不同形状纳米容器中位置相关的、时变的动态响应函数,揭示了受限环境和表面相互作用的综合效应。我们还通过在不同距离处放置离子和偶极探针来研究溶剂化动力学,从而获得光谱特征。我们发现,受限水分子表现出奇特的动力学特征,与体相液体有明显的区别。我们采用原子分子动力学模拟获得溶剂化时间相关函数、非高斯参数和非线性响应函数,这些函数揭示了存在不均匀和非指数动力学,并且对封装的大小和形状非常敏感。重要的是,较慢的长时间衰减常数表现出非单调的空间依赖性。初始超快分量类似于体相中的相同分量,但在本系统中发现其具有不同的起源。我们进行壳层分析,以理解这些观察结果的微观起源和表面诱导效应的传播范围。