Carboxylated carbon nanotubes can serve as pathways for molecules in sandwich-like two-phase organic-water systems

Ion Separation Together with Water Purification via a New Type of Nanotube: A Molecular Dynamics Study

We propose a CNT-based concentric twin tube (CTT) as nanochannels for both water purification and ion separation at the nanoscale. In the model, a source reservoir dealing with the solution connects three containers via the CTT that has three subchannels for mass transfer. Before entering the three subchannels, the solution in the separating zone will form three layers (the aqua cations, water, and the aqua anions, respectively) by applying a charged capacitor with the two electrodes parallel to the flow direction of the solution. Under an electric field with moderate intensity, the three subchannels in the CTT have stable configurations for mass transfer. Since the water and the two types of aqua ions are collected by three different containers, the present model can realize both ion separation and water purification. The mass transfer in the subchannels will be sped up by an external pressure exerted on the solution in the source reservoir. The physical properties of the model, e.g., water purification speed, are analyzed with respect to the effects of the electric field, the size of CTT, and the concentration of solute, such as NaCl.

Toward a quasiphase transition in the single-file chain of water molecules: Simple lattice model

Recently, Ma et al. [Phys. Rev. Lett. 118, 027402 (2017)] have suggested that water molecules encapsulated in (6,5) single-wall carbon nanotube experience a temperature-induced quasiphase transition around 150 K interpreted as changes in the water dipoles orientation. We discuss further this temperature-driven quasiphase transition performing quantum chemical calculations and molecular dynamics simulations and, most importantly, suggesting a simple lattice model to reproduce the properties of the one-dimensional confined finite arrays of water molecules. The lattice model takes into account not only the short-range and long-range interactions but also the rotations in a narrow tube, and both ingredients provide an explanation for a temperature-driven orientational ordering of the water molecules, which persists within a relatively wide temperature range.

A Hybrid Nanomaterial Based on Single Walled Carbon Nanotubes Cross-Linked via Axially Substituted Silicon (IV) Phthalocyanine for Chemiresistive Sensors

In this work, the novel hybrid nanomaterial SWCNT/SiPc made of single walled carbon nanotubes (SWCNT) cross-linked via axially substituted silicon (IV) phthalocyanine (SiPc) was studied as the active layer of chemiresistive layers for the detection of ammonia and hydrogen. SWCNT/SiPc is the first example of a carbon-based nanomaterial in which an axially substituted phthalocyanine derivative is used as a linker. The prepared hybrid material was characterized by spectroscopic methods, thermogravimetry, scanning and transmission electron microscopies. The layers of the prepared hybrid were tested as sensors toward ammonia and hydrogen by a chemiresistive method at different temperatures and relative humidity as well as in the presence of interfering gases like carbon dioxide, hydrogen sulfide and volatile organic vapors. The hybrid layers exhibited the completely reversible sensor response to both gases at room temperature; the recovery time was 100-200 s for NH3 and 50-120 s in the case of H2 depending on the gas concentrations. At the relative humidity (RH) of 20%, the sensor response was almost the same as that measured at RH 5%, whereas the further increase of RH led to its 2-3 fold decrease. It was demonstrated that the SWCNT/SiPc layers can be successfully used for the detection of both NH3 and H2 in the presence of CO2. On the contrary, H2S was found to be an interfering gas for the NH3 detection.