Water dynamics in the hydration shell of hyper-branched poly-ethylenimine

Abstract

We performed THz and GHz dielectric relaxation spectroscopy to investigate the reorientational dynamics of water molecules in the hydration shell of amphiphilic hyper-branched poly-ethylenimine (HPEI).

Terahertz spectroscopy of water in nonionic reverse micelles

“…While there are some amphiphilic groups in reverse micelle solutions, the fast and bulk water will be affected by these groups (hydrophilic effects from hydroxy and ether groups and hydrophobic effect) via strong hydrogen bonds, and some of them transform slow hydration water with slower reorientation rotation. In this system, the dynamics of water from GHz to THz generally can be described as multiple Debye models [29,30] ,…”

“…3, the imaginary part is not equal to 0 and has the same order of magnitude as the complex permittivity of reverse micelle mixtures. In GHz and THz dielectric spectroscopy, compared with the permittivity of water, the permittivity of the background is too small and can be neglected [30] . While only in the THz region, the value of the permittivity of the reverse micelles is comparable with water in reverse micelles within a small nanopool.…”

“…where f is the proportion of Igepal and cyclohexane in the reverse micelle mixture, and εback ω represents the complex permittivity of the background in the third term. In order to restrict the number of free parameters, we reasonably fix τ fast and τ bulk for fast (0.1 ps) and bulk water (8.4 ps), respectively [30,31] . The measured complex permittivity and fitted lines of samples are shown in Fig.…”

“…S fast,pure and S bulk,pure are the relaxation strength of fast and bulk water in pure water, respectively, and c H 2 O 0 is the molar concentration of pure water, which is 55 mol/L. Here, we set S fast,pure = 3.5 and S bulk,pure = 72.2, which are calculated from the pure water in the GHz and THz regions with two Debye models [30] . We assume that the Kirkwood factor of fast water in pure water and overall reverse micelle mixture is equal to 1, which is the same as the bulk water in the overall calculations.…”

Facile preparation of a MXene–graphene oxide membrane and its voltage-gated ion transport behavior

“…[26][27][28][29][30][31] However, the disadvantages of Ti 3 C 2 T x , such as easy oxidation and agglomeration, limit its applications in water treatment. [32][33][34] Graphene oxide (GO) membranes have received considerable attention owing to their excellent ionic screening performance, 8,35,36 and they cannot achieve efficient water flux and ion transportation simultaneously by intelligently adjusting the ''off'' and ''on'' states of the channel.…”