scholarly journals Calculated Terahertz Spectra of Glycine Oligopeptide Solutions Confined in Carbon Nanotubes

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 385 ◽  
Author(s):  
Dongxiong Ling ◽  
Mingkun Zhang ◽  
Jianxun Song ◽  
Dongshan Wei
Keyword(s):  
Carbon Nanotubes ◽  
Signal To Noise Ratio ◽  
Thz Spectroscopy ◽  
Water Molecules ◽  
Relaxation Dynamics ◽  
Confinement Effects ◽  
Nanofluidic Channels ◽  
Detection Of Biomolecules ◽  
Thz Absorption ◽  
Dynamics Simulations

To reduce the intense terahertz (THz) wave absorption of water and increase the signal-to-noise ratio, the THz spectroscopy detection of biomolecules usually operates using the nanofluidic channel technologies in practice. The effects of confinement due to the existence of nanofluidic channels on the conformation and dynamics of biomolecules are well known. However, studies of confinement effects on the THz spectra of biomolecules are still not clear. In this work, extensive all-atom molecular dynamics simulations are performed to investigate the THz spectra of the glycine oligopeptide solutions in free and confined environments. THz spectra of the oligopeptide solutions confined in carbon nanotubes (CNTs) with different radii are calculated and compared. Results indicate that with the increase of the degree of confinement (the reverse of the radius of CNT), the THz absorption coefficient decreases monotonically. By analyzing the diffusion coefficient and dielectric relaxation dynamics, the hydrogen bond life, and the vibration density of the state of the water molecules in free solution and in CNTs, we conclude that the confinement effects on the THz spectra of biomolecule solutions are mainly to slow down the dynamics of water molecules and hence to reduce the THz absorption of the whole solution in confined environments.

Carbon Nanotubes as Nano-Pumps: A Molecular Dynamics Investigation

2006 ◽  
Author(s):  
Soumik Banerjee ◽  
Sohail Murad ◽  
Ishwar K. Puri
Keyword(s):  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Material Processing ◽  
Drinking Water ◽  
Metal Ion ◽  
Surface Charge Density ◽  
Water Molecules ◽  
Ion Separation ◽  
Dynamics Simulations ◽  
Charged Ions

This paper focuses on the use of carbon nanotubes (CNT) for ion separation and encapsulation from a solution containing both positive and negatively charged ions. Metal ion separation from drinking water or during material processing applications can be an important issue. We use molecular dynamics simulations to demonstrate that a pair of carbon nanotubes with patterned positive and negative charges can form the basis of an effective device for the separation or encapsulation of ions. We consider three different charge patterns: i) Electrodes, where all the atoms of a CNT are charged with a finite surface charge density; ii) Alternate axial bands of positive and negative charges on each electrode; and iii) Alternate circumferential rings of positive and negative charges on the electrodes. The charge pattern determines the preferential intake of water and/or ions by a nanotube. As conventional electrodes they adsorb ions, but with an alternate band or ring charge pattern they adsorb the water molecules. Our simulations show that a charged CNT can be used as a nano-pump that provides purified water or ions from an impure solution.

Structure, dynamics and thermodynamics of single-file water under confinement: effects of polarizability of water molecules

RSC Advances ◽  
2015 ◽  
Vol 5 (3) ◽  
pp. 1893-1901 ◽  
Author(s):  
Hemant Kumar ◽  
Chandan Dasgupta ◽  
Prabal K. Maiti
Keyword(s):  
Carbon Nanotubes ◽  
Thermodynamic Properties ◽  
Single Wall Carbon Nanotubes ◽  
Water Molecules ◽  
Confinement Effects ◽  
Structural Dynamic ◽  
Single Wall Carbon ◽  
Structure Dynamics ◽  
Single File ◽  
Water Models

Various structural, dynamic and thermodynamic properties of water molecules confined in single-wall carbon nanotubes are investigated using both polarizable and non-polarizable water models.

Structures of Water Molecules in Carbon Nanotubes Induced with Electric Fields and its Application for Water-Methanol Separation

2016 ◽  
Vol 842 ◽  
pp. 453-456 ◽  
Author(s):  
Winarto ◽  
Daisuke Takaiwa ◽  
Eiji Yamamoto ◽  
Kenji Yasuoka
Keyword(s):  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Electric Field ◽  
Electric Fields ◽  
Electrostatic Interaction ◽  
Water Molecules ◽  
Ordered Structures ◽  
Separation Effect ◽  
Wide Range ◽  
Dynamics Simulations

Water confined in carbon nanotubes (CNTs) under the influence of an electric field has interesting properties that are potential for nanofluidic-based applications. With molecular dynamics simulations, this work shows that the electric field induces formation of ordered structures of water molecules in the CNTs. Formation of the ordered structures strengthens the electrostatic interaction between the water molecules. As a result, water strongly prefers to fill CNTs over methanol and it produces a separation effect. Interestingly, the separation effect with the electric field does not decrease for a wide range of CNT diameter.

Simulations of Pressurized Water Flow through Carbon Nanotubes

2010 ◽  
Vol 1258 ◽  
Author(s):  
Samantha Shaw ◽  
David Faux
Keyword(s):  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Water Molecules ◽  
Water Density ◽  
Pressurized Water ◽  
Molecular Arrangement ◽  
Flow Through ◽  
Dynamics Simulations ◽  
Maximum Occupancy

AbstractMolecular dynamics simulations of the flow of pressurised water through carbon nanotubes of chirality (9,0), (12,0), (15,0) and (18,0) have been undertaken at 298K with a water density of approximately 1240kg/m3. Results show that the rate of filling is least in the smallest diameter nanotube, but that there is less variation in the time taken to reach maximum occupancy. The water molecules are found to undergo restructuring due to their confinement, with detailed molecular arrangement dependent on CNT diameter. Enhanced rates of flow are shown for the (15,0) nanotube, highlighting the effect of nanotube diameter on confinement and thus on flow.

scholarly journals Electrical Breakdown Mechanism of Transformer Oil with Water Impurity: Molecular Dynamics Simulations and First-Principles Calculations

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 123
Author(s):  
Bin Cao ◽  
Ji-Wei Dong ◽  
Ming-He Chi
Keyword(s):  
Molecular Dynamics ◽  
Thermal Diffusion ◽  
First Principles ◽  
Electrical Breakdown ◽  
Transformer Oil ◽  
Water Molecules ◽  
Conducting Channel ◽  
Breakdown Mechanism ◽  
Water Impurity ◽  
Dynamics Simulations

Water impurity is the essential factor of reducing the insulation performance of transformer oil, which directly determines the operating safety and life of a transformer. Molecular dynamics simulations and first-principles electronic-structure calculations are employed to study the diffusion behavior of water molecules and the electrical breakdown mechanism of transformer oil containing water impurities. The molecular dynamics of an oil-water micro-system model demonstrates that the increase of aging acid concentration will exponentially expedite thermal diffusion of water molecules. Density of states (DOS) for a local region model of transformer oil containing water molecules indicates that water molecules can introduce unoccupied localized electron-states with energy levels close to the conduction band minimum of transformer oil, which makes water molecules capable of capturing electrons and transforming them into water ions during thermal diffusion. Subsequently, under a high electric field, water ions collide and impact on oil molecules to break the molecular chain of transformer oil, engendering carbonized components that introduce a conduction electronic-band in the band-gap of oil molecules as a manifestation of forming a conductive region in transformer oil. The conduction channel composed of carbonized components will be eventually formed, connecting two electrodes, with the carbonized components developing rapidly under the impact of water ions, based on which a large number of electron carriers will be produced similar to “avalanche” discharge, leading to an electrical breakdown of transformer oil insulation. The water impurity in oil, as the key factor for forming the carbonized conducting channel, initiates the electric breakdown process of transformer oil, which is dominated by thermal diffusion of water molecules. The increase of aging acid concentration will significantly promote the thermal diffusion of water impurities and the formation of an initial conducting channel, accounting for the degradation in dielectric strength of insulating oil containing water impurities after long-term operation of the transformer.

scholarly journals Temperature dependent poly(L-lactide) crystallization investigated by Fourier transform terahertz spectroscopy

2021 ◽  
Author(s):  
Seiichiro Ariyoshi ◽  
Satoshi Ohnishi ◽  
Hikaru Mikami ◽  
Hideto Tsuji ◽  
Yuki Arakawa ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Absorption Spectra ◽  
Terahertz Spectroscopy ◽  
Thz Spectroscopy ◽  
Frequency Range ◽  
Temperature Dependent ◽  
Thz Absorption

Poly(L-lactide) (PLLA) was investigated by Fourier transform terahertz (THz) spectroscopy over the frequency range of 1.0 – 8.5 THz. THz absorption spectra were acquired for PLLA samples isothermally crystallized at...

scholarly journals Origin and control of ionic hydration patterns in nanopores

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Miraslau L. Barabash ◽  
William A. T. Gibby ◽  
Carlo Guardiani ◽  
Alex Smolyanitsky ◽  
Dmitry G. Luchinsky ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Distribution Functions ◽  
Water Molecules ◽  
Surrounding Water ◽  
Ionic Hydration ◽  
Hydration Shells ◽  
Water Layers ◽  
Dynamics Simulations ◽  
And Control

AbstractIn order to permeate a nanopore, an ion must overcome a dehydration energy barrier caused by the redistribution of surrounding water molecules. The redistribution is inhomogeneous, anisotropic and strongly position-dependent, resulting in complex patterns that are routinely observed in molecular dynamics simulations. Here, we study the physical origin of these patterns and of how they can be predicted and controlled. We introduce an analytic model able to predict the patterns in a graphene nanopore in terms of experimentally accessible radial distribution functions, giving results that agree well with molecular dynamics simulations. The patterns are attributable to a complex interplay of ionic hydration shells with water layers adjacent to the graphene membrane and with the hydration cloud of the nanopore rim atoms, and we discuss ways of controlling them. Our findings pave the way to designing required transport properties into nanoionic devices by optimising the structure of the hydration patterns.

scholarly journals Optimal Relabeling of Water Molecules and Single-Molecule Entropy Estimation

Biophysica ◽  
2021 ◽  
Vol 1 (3) ◽  
pp. 279-296
Author(s):  
Federico Fogolari ◽  
Gennaro Esposito
Keyword(s):  
Single Molecule ◽  
Degrees Of Freedom ◽  
Water Molecules ◽  
Maximum Information ◽  
Nearest Neighbours ◽  
Biomolecular Simulations ◽  
Solvent Molecules ◽  
Solvation Entropy ◽  
Dynamics Simulations ◽  
Internal Degrees Of Freedom

Estimation of solvent entropy from equilibrium molecular dynamics simulations is a long-standing problem in statistical mechanics. In recent years, methods that estimate entropy using k-th nearest neighbours (kNN) have been applied to internal degrees of freedom in biomolecular simulations, and for the rigorous computation of positional-orientational entropy of one and two molecules. The mutual information expansion (MIE) and the maximum information spanning tree (MIST) methods were proposed and used to deal with a large number of non-independent degrees of freedom, providing estimates or bounds on the global entropy, thus complementing the kNN method. The application of the combination of such methods to solvent molecules appears problematic because of the indistinguishability of molecules and of their symmetric parts. All indistiguishable molecules span the same global conformational volume, making application of MIE and MIST methods difficult. Here, we address the problem of indistinguishability by relabeling water molecules in such a way that each water molecule spans only a local region throughout the simulation. Then, we work out approximations and show how to compute the single-molecule entropy for the system of relabeled molecules. The results suggest that relabeling water molecules is promising for computation of solvation entropy.

Activation of Nanoflows for Fuel Cells

2012 ◽  
Vol 3 (2) ◽  
Author(s):  
Z. Insepov ◽  
R. J. Miller
Keyword(s):  
Carbon Nanotubes ◽  
Fuel Cells ◽  
Surface Waves ◽  
Traveling Waves ◽  
Gas Flow ◽  
Atomic Mass ◽  
Flow Rates ◽  
Selective Filter ◽  
Phase Velocities ◽  
Dynamics Simulations

Propagation of Rayleigh traveling waves from a gas on a nanotube surface activates a macroscopic flow of the gas (or gases) that depends critically on the atomic mass of the gas. Our molecular dynamics simulations show that the surface waves are capable of actuating significant macroscopic flows of atomic and molecular hydrogen, helium, and a mixture of both gases both inside and outside carbon nanotubes (CNT). In addition, our simulations predict a new “nanoseparation” effect when a nanotube is filled with a mixture of two gases with different masses or placed inside a volume filled with a mixture of several gases with different masses. The mass selectivity of the nanopumping can be used to develop a highly selective filter for various gases. Gas flow rates, pumping, and separation efficiencies were calculated at various wave frequencies and phase velocities of the surface waves. The nanopumping effect was analyzed for its applicability to actuate nanofluids into fuel cells through carbon nanotubes.

Sign in / Sign up

Export Citation Format

Share Document