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Microarrays play a determinant role in the detection and specification of biological molecules. The immobility of probe oligonucleotide with different sequences on the substrate surface is one of the main aims in designing of microarrays. In this regard, we select five different DNA single-strands to determine the best of probe single strand in the microarrays with a striped patterned double-layer graphene substrate. The results of the simulation illustrate that DNA single-strands on the substrate have distinct conformations related to each other. Thymine single strand has the maximum end to end distance and is more accessible for detecting target single strand in the microarrays. Also, the analysis of wettability results displays that the presence of a DNA single-strand in water drop decreases the amount of spreading of the droplets. Another important point is that the presence of a single strand increases the chance of water droplet pining on such surfaces.

Studying the structure and dynamics of nano-confined water inside carbon nanotubes has consistently attracted the wide-spread interest of researchers. In the present work, molecular dynamics simulations indicated internal nonwetting behavior for the central region of the long and narrow single-wall carbon nanotube (5,5) (SWNT) and showed that continuous single-file water molecules are not formed through it. Unlike the SWNT, by adding boron nitride nanotubes (6,6) as an outer wall to the SWNT, a continuously long single-file water chain is formed through the double-walled carbon and boron nitride hetero-nanotube (DWHNT) and thorough internal wetting of the DWHNT is observed. The position and the number of water molecules, electrostatic potential heatmap of the nanotube's wall, free energy profile of nano-confined water, and number of hydrogen bonds between them confirmed the aforementioned results and complete internal wetting of the DWHNT. After using the boron nitride nanotube (6,6) as the outer wall, an homogeneous electrostatic potential distribution in the DWHNT and increase in the hydrophilic characteristics of the nano-channel wall are observed, bringing about gradual trapping of more water molecules through it. Finally, water molecules occupied the central region of the DWHNT and a thorough single-file water chain is formed inside the nano-channel. Water dipole orientation inside the DWHNT and their radial distribution function asserted the occurrence of the liquid-solid quasi-phase transition of single-file water molecules confined inside the long and narrow carbon nanotube (5,5) under ambient conditions.

Due to their facile manipulation and transport property, carbon nanotubes (CNTs) are the best candidate for ions and water channels with high selectivity behaviors. In this work, water permeability and salt rejection in the water nanochannel made of CNT(12,12), CNT(13,13) and CNT(14,14) encapsulating fullerene were investigated with or without applying various hydrostatic pressures using molecular dynamics (MD) simulation. In addition to high water permeation, the water nanochannel reduced ion permeation. Based on the results, salt rejection in the channels made of CNT(12.12) and CNT(13.13) encapsulating fullerene was acquired 100%. In the water nanochannel made of CNT(14,14) encapsulating fullerene, a significant water permeability was achieved about 16.22 ± 0.85 × 10−13 cm3.s−1 which is more than the water permeability was reported for the natural water channels and a remarkable salt rejection (~91.62%) was obtained under 5 MPa hydrostatic pressure. It is elucidated that the value of water permeability in this channel was approximately doubled by increasing the hydrostatic pressure. Water and ion permeation, interaction energy of the fullerene with the carbon nanotube surface and the free energy profile for water molecules through the highly selective nanochannels were assessed. In order to study the operation of the water nanochannels, the movement pattern of the fullerene inside the CNT as well as the forces applied to the fullerene was investigated. The motion of the fullerene inside carbon nanotubes was affected by the exerted forces from water molecules on the fullerene and the interaction energy between CNT wall and fullerene. Therefore stronger interaction between fullerene and CNT wall prevents fullerene exiting the nanochannel. The CNT(14,14) encapsulating fullerene shows less energy barrier when water molecules cross the fullerene inside the nanochannel. The aforementioned results demonstrated that carbon nanotube encapsulating fullerene is a high-performance candidate water nanochannel with selective behavior to water molecules and tremendous salt rejection.

Microarray technology plays an important role in detecting the sequence of the genome. In the production of microarrays, the formation of a homogeneous and uniform spot due to biodroplet pining is of great importance. In this work, using the molecular dynamics simulation method, it is possible to create homogeneous spots on the surface of graphene-based surfaces. Hence, the behavior of five different types of DNA including homogeneous sequences of adenine, cytosine, guanine, and thymine as well as heterogeneous sequence of bases in the water droplets, was subjected to a double-layer graphene substrate with a pillar structure. The results showed that double layer graphene with pillar pattern are successful in pinning of biodroplet and this substrate leads to the differnet placement of Oligonucleotide probes. Also, the results of wettability demonstrated that the formation of hydrogen bond between a single strand and water molecules reduces the spreading and increases the contact angle and height of biodroplet containing oligonucleotides with respect to the water droplet without oligonucleotides on the surface of the double layer graphene in pillar pattern. The results of the simulation of single-stranded DNA after equilibration showed that single strand of adenine and heterogeneous single strands had the least folding compared to other single strands, and the single strand of adenine produced the most stable structure. Hence, single-stranded adenine is stretched more compared to other single strands, which is due to the lack of tendency of this single strand for internal hydrogen bonds and regular spiral structure resulting from a strong internal π-π stacking interaction. As a result, single strand of adenine is more accessible to detect target single strands for use in microarrays.

This work presents a molecular dynamics simulation study on the interfacial characterization of graphene/epoxy nanocomposites. In polymeric nanocomposites, the thermo-mechanical properties of a system strongly depend on the characteristics of the interphase region between the matrix and the inclusions. The first step in the characterization of this interphase is to distinguish its border limit (i.e., the interphase thickness). Here, we present a methodology to systematically quantify the interphase thickness based on analyzing the variation of the local mass density profile. To this end, three functions (average accumulated mass density, accumulated standard deviation (ASD) and its first derivative) are successively applied on the local mass density profile. Using this procedure, the interphase limit can be easily detected regardless of the oscillatory nature of the local mass density. The effect of the epoxy crosslinking density and number of graphene layers on the interphase thickness is then investigated, and the results are analyzed by studying the interaction energies, polymer dynamics and distribution quality of reacted and unreacted components, as well as conformational changes of the polymer chains in the interphase region. The results reveal that the crosslinking density is the most influential parameter on the interphase thickness: the higher the crosslinking degree, the thicker the interphase region. To a lower extent, the interaction energy has also an effect on the interphase thickness since there is an inverse relationship between the interaction energy and the crosslinking density in our case study. Overall, the reported findings highlight useful insights into the detection and properties of the interphase region in thermoset composites.

Evaporation of water nanodroplets on a hydrophilically adjusted graphene sheet was studied based on a molecular dynamics approach. Suspended graphene was used as a physically heterogeneous surface, and fixed graphene was considered as an ideally flat surface. State of the triple-phase contact line (TPCL) and shape evolution were addressed at four different temperatures on both substrates. Additionally, contact angle (CA) was studied during 3 and 22.5 ns simulations in both closed and opened conditions. The observed constant contact angle regime was predictable for the fixed graphene. However, it was not expected for the suspended system and was attributed to the oscillations of the substrate atoms. The size of the nanodroplet also affects the constant-contact-angle mode in both systems, when the number of water molecules decreases to less than 500. The oscillations created a surface on which physical heterogeneities were varying through time. Examination of the evaporation and condensation processes revealed higher rates for the fixed systems. Local mass fluxes were calculated to reveal the contribution of TPCL and meridian surface (MS) of the nanodroplet to evaporation and condensation. The obtained results indicate similar values for the mass flux ratio at the TPCL, which remains twice as large as the MS for both suspended and fixed graphene. The results confirm the assumption that a surface with varying heterogeneities can overwhelm the droplet and act as an ideally flat surface.

Recently, graphene oxide has been widely used for the extraction of hydrocarbon compounds. In the present work, the separation of water from a water-oil mixture by two-layer graphene oxide has been studied using molecular dynamics simulation. Several interlayer spacing of graphene oxide layers was considered, and for each gap in each layer of graphene oxide, several sizes were considered and it was determined the efficient interlayer distance as well as gap size which gives highest water-oil separation. The simulation results unveil that as the interlayer spacing and the size of the gap is reduced, the flux and permeability of the water molecules decrease, but the amount of water molecules separating from the oil increases. To study the number of layers’ impact for higher separation efficiency, a system containing a graphene oxide layer was also studied and the importance of the number of graphene layers was highlighted. Also, for the analysis of graphene oxide functional groups’ effect on separation, a system containing graphene layers was also investigated and the role of functional groups was revealed in hydrogen bond formation between graphene oxide and water molecules. By calculating PMF, the effect of functional groups on the repelling oil molecules from the graphene oxide’s gaps was investigated.

In this work, the behavior of a water nano-droplet on hydrophilic graphene oxide (GO) is studied at high temperatures using molecular dynamics simulation. The results showed that, with increasing temperature, spreading would overcome the evaporation of water molecules on the surface of GO. At high temperatures, the regime changes from partial to total wetting. After the spreading is complete and the surface is completely covered by water, evaporation of water occurs more rapidly. Simulation results revealed that as the system temperature rises, the number of hydrogen bonds between water molecules decreases. The water molecules reorient to the GO surface as the temperature increases and the number of possible H-bonds inside the bulk of the droplet decreases. However, the formation of H-bonds between water molecules and GO increases with temperature. The results obtained in terms of the contact angle and the density of the water molecules on the surface of the GO revealed that at different temperatures more water molecules spread on the surface of GO during simulation time. Increasing the temperature leads to increase in the number of evaporated water molecules from the surface of GO. Investigations of the dipolar momentum of water molecules in different layers of GO surface showed that water molecules in the initial layers tend to approach the surface with hydrogen atoms.

In this work, desalination by multilayer graphene membranes with a rippled structure has been considered by molecular dynamics simulation. The (6, 7.5 and 9) A distances between the graphene sheets in a layer (gap wide) are selected. Also, these mentioned distances are applied as an interlayer space (channel height). Results of simulation demonstrate that multilayer graphene membranes with a rippled structure are more efficient in water flux than multilayer graphene membranes with an unrippled structure. These differences are more significant for membranes with 9 A interlayer space. In this work, it is shown that water flux in 9 A rippled membrane is 20% more than 9 A unrippled one. According to the simulation results, multilayer membranes with a rippled and unrippled structure are different significantly in the case of water flux, but they do not show many differences with each other in rejection. Also, it is shown that the effect of channel is more important than gap; because ions lose more number of water molecules when flow through the channel as compared to flow through gap or pores. From calculation of density, the water flux, ions rejection and coordination number of ions, the results of investigation are obtained.

In this paper the adsorption behavior of a water droplet on the molybdenum disulfide and graphene surfaces were examined and compared. Results obtained from the calculation of the average of interaction energy between the water and the molybdenum disulfide surface and the graphene surfaces indicated that the van der Waals interaction plays an important role in the adsorption of water on these surfaces. The contour maps of the interaction energy between the water and the surfaces have revealed some different behaviors of the water droplet on these surfaces. The results showed that water sliding on the molybdenum disulfide surface and water pinning on the graphene surface is due to the difference in structural patterns of the surfaces. Molecular investigations of the water on the surfaces showed that the water molecules occupy continues positions on the molybdenum disulfide surface while they occupy discrete positions on the graphene surface. Two mechanisms for orientation and displacement of the water molecules on the surfaces were proposed. In addition, the effects of temperature and external field on movement of the water molecules on the surface were investigated. It was observed that the water - graphene system is more sensitive to the applied electric field than water-molybdenum disulfide system. In addition, the simulation results in the presence of the electric field showed that it is possible to take control of the water droplet on the graphite surface, so that the displacement of the water droplet can take place in a particular direction.

Nanotubes have extraordinary properties, which have attracted the attention of many researchers from diverse fields. The interaction between carbon nanotube (CNT) or boron nitride nanotube (BNNT) and polymer/copolymer/surfactant has shown potential improvement in properties and performance. This paper reviews the recent studies in this field obtained from molecular dynamics simulation calculations, focusing on the interaction energies between nanostructure and polymer, radial distribution function, diffusion and radius of gyration and some other physical chemistry properties. Recent studies show that the intermolecular interaction in mentioned systems is strongly influenced by the specific monomer structure of polymers. The high values of intermolecular interaction energy of such composites offer that an efficient load transfer exists at the interface between nanotube and polymer, which is of a key role in the composite reinforcement practical applications. Our study reviewed the possibility of wrapping CNT/BNNT/CNT bundles by polymers and also the effects of CNTs/CNT bundles’ length on the conformational behavior of polymer adsorbed on these nanostructures.

In this work, the melting/freezing point of confined water between two graphene sheets was calculated from the direct coexistence of the solid-liquid interface. Also, molecular dynamics simulation of confined liquid water-ice between two graphene sheets was applied. The phase transition temperature of the confined ice-water mixture was calculated as 240 K that was 29 K less than the non-confined ice-water system. In order to study the behavior of water molecules at different distances from the graphene sheets, 5 regions were provided using some imaginary planes, located between two graphene sheets. The obtained simulation results showed that water molecules located in the region near each graphene sheet with the thickness of 2 nm had a different behavior from other water molecules located in other regions. The results demonstrated that water molecules in the vicinity of graphene sheets had more mean square displacements than those in the middle regions.

This study provides a comprehensive investigation on the effect of epoxy crosslinking density and number of graphene layers on the interfacial mechanical behavior of graphene/epoxy nanocomposites. In particular, the graphene layers are detached in the normal and sliding directions within the framework of steered molecular dynamics, and the traction-separation curves are extracted for the whole separation process. The damage mechanism is also studied by analyzing the evolution of the local number density during pull-out tests. For better results interpretation, the variation of the interaction and adhesion energies, the number of pulled-out epoxy chains, and the distribution of crosslinked and uncrosslinked species are also investigated and discussed. Based on the results obtained, the crosslinking density has a significant effect on the interfacial properties between graphene and epoxy, especially in the normal mode. The damage behavior is also determined as the function of the epoxy crosslinking density so that at low crosslinking densities, the damage occurs in the polymer near the graphene, while the failure takes place in the interphase for higher crosslinking degrees. Increasing the number of graphene layers leads to a weaker interfacial strength, except for the double-layered graphene systems which have the highest traction peak among all samples.

Wettability of water nanodroplet on graphene and graphene-coated metals in recent years have been the subject of interest. In the present work, the wettability of mono and three-layer graphene supported on underlying platinum was investigated using molecular dynamics simulation. Furthermore, the striped patterns were generated on the substrates by parallel grooves with different widths and depths. Wetting results showed that the Cassie-Baxter state converts into the Wenzel state by increasing the width of the grooves, which was confirmed by free energy results that obtained from free energy perturbation and potential of mean force methods. A chain of water molecules forms at interface by increasing the width of the grooves, which leads to higher hydrogen bond lifetime. Water-platinum interaction in the grooves and nanodroplet pinning cause anisotropy in the wetting and nanodroplet shape. This suggests that such artificial surfaces with anisotropic wetting properties can mimic water anisotropic behavior on some natural structures, which lead water to move in a specific direction.

Water and air pollutants have huge impacts on the entire living system. In addition, the newly emerging nanopollutants, increasing global warming, and consequent climate changes are posing major threats to the freshwater or fresh air availability. This has made it urgent to invent an appropriate water/air treatment technology that removes nanopollutants and also desalinates water to a significant extent. Carbon-based nanomaterials have generated marvelous interest in a wide range of research activities due to their high adsorption capacities. Carbon nanotubes, carbon nanotube bundles, and related materials have potential applications in gas/ion separation and water purification. Recently, gas/ion separation and water purification through carbon-based nanomaterials have received increasing attention. This review summarizes the properties of carbon nanotubes and carbon nanotube bundles related to gas separation, ion separation, and water purification using molecular dynamics simulations. Membranes-based carbon nanomaterials show promise of water purification and gas separation. These attractive properties of carbon nanotubes-based and carbon nanotube bundles-based nanomaterials make them proper candidates for gas separation, gas molecular-sieving processes, and desalination purposes in nanoscale dimensions.

In this study, the dispersion mechanism of aggregated carbon nanotubes (CNTs) using Triton X-100 surfactant under various concentrations is investigated with and without water molecules via molecular dynamics simulation. The obtained results showed that because of interaction between water molecules and hydrophilic segments of surfactant, water molecules play a significant role in the manner of adsorption of the surfactant on the CNT surface. In the presence of water molecules, the surfactant molecules are not able to wrap the CNTs, and they are located in the neighborhood of the CNTs. The results suggested that the creation of space between two CNTs in the absence of the surfactant is performed slowly, while, in the presence of the surfactant molecules, the creation of space between two CNTs which leads to the dispersion of the CNTs is remarkably rapid. The surfactant molecules cause to introduce more numbers of water molecules in the vicinity of and between the CNTs, and with the increasing radial distances between two CNTs, the number of water molecules is rapidly increased. The interfacial angle between two CNTs, surfactant gyration radius, and diagrams of radial distribution function between water molecules, the CNTs, and the surfactant molecules were calculated for a better description of dispersion mechanism of the CNTs by the surfactant and water molecules.

We present an investigation on the permeability and selectivity of graphene sheets with designed sub nanometer pores using molecular dynamics simulations. We show that nanoporous graphene can be used to separate water from a gaseous mixture of nitrogen, oxygen and water. The obtained results show that the separation is performed based on the absorption of water molecules on the nanoporous graphene surface. Pore size plays an important role in the possible formation of water clusters on the nanoporous graphene surface. In graphene sheets with large pores, the space between the neighboring graphene becomes smaller and water molecules form a cluster on the graphene surface quickly. Because the size of the water clusters is larger than that of the nanopore, they cannot pass through it, whereas nitrogen and oxygen molecules are able to pass through the nanoporous graphene. In this study, we propose a mechanism for the formation of water clusters on the nanoporous graphene surface. To illustrate the different steps of the proposed mechanism, several investigations were performed such as calculation of the distribution and accumulation of water molecules on the graphene surface, angle between the dipolar moment vector of water molecules and the graphene surface and formation and movement of multi-layer clusters. Moreover, a specific method to pass N2 and O2 molecules through nanoporous graphene is presented.

In this work, we compared the structural and dynamical properties of water confined between two graphene oxide (GO) sheets with water confined between two graphene sheets through molecular dynamics simulations. Our results showed how the structure and dynamics of the water near the GO surfaces changes under confinement conditions. Different orientations of the water molecules to the GO sheets confirm the heterogeneous nature of the confined water. The density distribution of water near the GO sheets is different from the graphene surfaces due to the presence of hydrophilic functional groups of the GO sheets. Also, the hydrogen bonds between the water molecules are disturbed due to the presence of these groups on the GO surfaces. The results showed that as water molecules in areas which are close to the GO surfaces are isolated, and due to hydrogen bond formation between water molecules and the substituents of the GO, the water molecules have fewer hydrogen bonds with other water molecules around. In the middle region between two GO sheets, it has been seen that each water molecule is surrounded by more water molecules, and there are many more hydrogen bonds, so it is possible to consider a network structure of water in this region. There is a good quantitative agreement between experiments and the above mentioned results. These results were confirmed by the calculated coordination number, radial distribution functions and mean square displacements.

In this work, the liquid–solid phase transition temperature of water confined between two graphene oxide (GO) sheets is investigated using molecular dynamics simulations. The results demonstrate that, due to the presence of functional groups of the GO sheets, at temperatures below liquid–solid phase transition temperature, the water molecules near the confining sheets are not structured like ice and remained in the liquid form. The results also reveal the confinement effects on the melting and freezing rate of water molecules. The confining conditions delay the freezing process of the water molecules compared to the bulk water molecules. These results are confirmed by the calculated total energy, the density profile of water molecules confined between two GO sheets, the number of hydrogen bonding, radial distribution function, and mean square displacement. The liquid–solid phase transition temperature of water in the presence of GO sheets was calculated as 236 K, which was 34 K less than the temperature of the bulk water.

The positioning, adsorption, and movement of water on substrates is dependent upon the chemical nature and arrangement of the atoms of the surface. Therefore the behavior of water molecules on a substrate is a reflection of properties of the surface. Based on this premise, graphene and gold substrates were chosen to study this subject from a molecular perspective. In this work, the structural and dynamical behaviors of a water nanodroplet on Au (100) and the graphene interfaces have been studied by molecular dynamics simulation. The results have shown how the structural and dynamical behaviors of water molecules at the interface reflect the characteristics of these surfaces. The results have demonstrated that residence time and hydrogen bonds' lifetime at the water-Au (100) interface are bigger than at the water-graphene interface. Energy contour map analysis indicates a more uniform surface energy on graphene than on the gold surface. The obtained results illustrate that water clusters on gold and graphene form tetramer and hexamer structures, respectively. Furthermore, the water molecules are more ordered on the gold surface than on graphene. The study of hydrogen bonds showed that the order, stability, and the number of hydrogen bonds is higher on the gold surface. The positioning pattern of water molecules is also similar to the arrangement of gold atoms while no regularity was observed on graphene. The study of dynamical behavior of water molecules revealed that the movement of water on gold is much less than on graphene which is in agreement with the strong water-gold interaction in comparison to the water-graphene interaction.

During the past decade, the research on fluids in nanoconfined geometries has received considerable attention as a consequence of their wide applications in different fields. Several nanoconfined systems such as water and ionic liquids, together with an equally impressive array of nanoconfining media such as carbon nanotube, graphene and graphene oxide have received increasingly growing interest in the past years. Water is the first system that has been reviewed in this article, due to its important role in transport phenomena in environmental sciences. Water is often considered as a highly nanoconfined system, due to its reduction to a few layers of water molecules between the extended surface of large macromolecules. The second system discussed here is ionic liquids, which have been widely studied in the modern green chemistry movement. Considering the great importance of ionic liquids in industry, and also their oil/water counterpart, nanoconfined ionic liquid system has become an important area of research with many fascinating applications. Furthermore, the method of molecular dynamics simulation is one of the major tools in the theoretical study of water and ionic liquids in nanoconfinement, which increasingly has been joined with experimental procedures. In this way, the choice of water and ionic liquids in nanoconfinement is justified by applying molecular dynamics simulation approaches in this review article.

Using molecular dynamics (MDs) simulations, the adsorption of a nitrogen–oxygen mixture (representing air) on (8, 8), (10, 10), and (12, 12) single-walled carbon nanotube (SWCNT) bundles is investigated as a function of temperature, air loading and diameter of nanotubes at subcritical ( T = 100 K) and supercritical ( T = 200 and 300 K) temperatures of the air. In order to do this, heat of adsorption, diffusion coefficients, activation energy, and radial distribution functions (RDFs) were computed for further analysis of the adsorption process. The simulation of exposing air on nanotube bundles, show that the amount of adsorption, heat of adsorption, and diffusion coefficients are strongly influenced by the applied temperature, i.e., along with the temperature increase, the amount of adsorption would be reduced. Furthermore, the results show that oxygen is selectively adsorbed relative to nitrogen, so carbon nanotubes (CNTs) can be considered as promising gas-filtering systems in addition to their previous gas-storage capability.

Using molecular dynamics (MD) simulations, we demonstrated that charged carbon nanotubes (CNTs) can be applied as nanoelectrodes for separation of Na + and Cl − ions from NaCl solution and subsequent desalination in a typical nanoscale lab-on-a-chip system. Three different surface charge densities (σ = 0.84, 1.68 and 3.36 C/m 2 ) were exerted on nanotubes. Our results show that under such electrical external field, positive ions (Na + ) are transported to negatively charged CNT and vice versa. This external field leads to ion pair break-up and consequent desalination; although, the amount of separation depends on the magnitude of applied charge. Interestingly, applying electrical charges on CNTs induces hydrophilic nature in them which is entirely contrary to their previous hydrophobic nature. Moreover, depending on the type of applied charge, positive or negative, water molecules orient differently relative to CNT electrodes. Extra investigations on Na + ions reveal a basic disruption in their hydration shell which occurs upon the presence of external field. This study provides us the potential application of CNTs as efficient nanomaterials for desalination purposes in nanoscale dimensions.

In this work, a molecular dynamic (MD) simulation method was employed to study the interfacial binding between the single-walled carbon nanotubes (SWCNTs) and some polymers and copolymers. The polymers studied include poly(vinyl pyrrolidone) as hydrophilic and poly(vinyl acetate) as hydrophobic polymers and also copolymers consisting of a series of vinyl pyrrolidone and vinyl acetate copolymers with different homogeneities in the backbone. The copolymers investigated have different structures and include alternative, diblock and triblock copolymers. This study has computed the intermolecular interaction energies between SWCNTs and polymers/copolymers in order to assess the effects of compositional heterogeneity on the interfacial binding between SWCNTs and polymers/copolymers. Also, the morphology of polymers/copolymers adsorbed to the surface of nanotubes has been studied. The obtained results showed that the intermolecular interactions in the simulated systems are strongly influenced by the monomer sequence distribution of hydrophilic and hydrophobic monomers in copolymers. The different values of intermolecular interaction energy for copolymers with identical numbers of hydrophilic and hydrophobic monomers but with different distributions suggest that an efficient load transfer through the interface between nanotube and copolymers is highly dependent on compositional heterogeneity of copolymers. Furthermore, we obtained the plots of the radial distribution function and the radius of gyration in order to study the effects of compositional heterogeneity on behavior of the studied nanocomposites. The results of the radial distribution function and the radius of gyration are in agreement with the findings of interfacial binding between SWCNTs and polymers/copolymers.

Adsorption and separation of binary mixtures of noble gases including Argon (Ar), Krypton (Kr), and Xenon (Xe) on (10,10) single-walled carbon nanotube (SWCNT) bundles is simulated by extensive equilibrium molecular dynamics (MD). Adsorption energies, diffusion coefficients, activation energies, and radial distribution functions (RDFs) were calculated to address the thermodynamics, transport and structural properties of adsorption process. The simulation results of exposing Ar–Kr, Ar–Xe, and Kr–Xe mixtures on (10,10) SWCNT bundles at temperatures of 75, 150, and 300 K, show that amount of adsorption is strongly influenced by the applied temperature. On the other hand, RDF plots show obviously that separation of binary gaseous mixture is occurred, where the heavier noble gas is adsorbed more than the lighter one in a selective manner by bundle. It is seen that the increase in the applied temperature results in more separation. These findings provide us a possible application of carbon nanotubes (CNTs) as efficient nanomaterials for separation and storage of gas mixtures.

In this work the behavior of the (8,2) single walled carbon nanotubes (CNTs) and functionalized carbon nanotubes (FCNTs) with four functional groups in water were studied using molecular dynamic (MD) simulation method. Glutamine as a long chain functional group and carboxyl as a short chain functional group have been used as functional groups in FCNTs. Four functional groups in each FCNT were localized at two positions: (i) all four functional groups were in the sidewalls of nanotube, (ii) two functional groups were at the ends and two functional groups were in the sidewalls of nanotube. The intermolecular interaction energies between CNTs or FCNTs and water molecules, the plots of radial distribution function and the diffusion coefficients of CNTs and FCNTs in water were computed for investigating the effects of type and position of functional groups on the behavior of FCNTs in water. The obtained results from three methods are consistent with each others. Results showed that the position of the functional groups in FCNTs has an important role in the interaction of hydrophilic groups of FCNTs with water molecules. Furthermore we also investigated the behavior of FCNTs with sixteen carboxyl functional groups in water. The presence of these large numbers of carboxyl functional groups on the carbon nanotubes prevents water molecules from moving towards hydrophilic carboxyl functional groups. This demonstrates the advantage of using lower number of functional groups each containing many hydrophilic groups like glutamine functional group.

Using molecular dynamics (MD) simulations, neon adsorption on an open-ended (10,10) single-walled carbon nanotube (SWCNT) was investigated at supercritical temperatures of neon, i.e. T=50, 70, and 90 K. Adsorption isotherms, heat of adsorption, self-diffusion coefficients, activation energy, and structural properties of neon gas were computed and analyzed in detail. All adsorption isotherms are predicted to be of Langmuir shape type І at this range of temperature. The results show that temperature is in a direct correlation with adsorption capacity, i.e. increase in temperature causes lower adsorption of neon gas by SWCNT. All aforementioned quantities confirm this fact and are in good agreement with previous experimental and theoretical works.

In the present work, the effect of temperature gradient on the behavior of a water nano-droplet resting on a suspended graphene was studied based on a non-equilibrium molecular dynamics simulation. The acquired results indicate that the applied temperature gradient to the suspended graphene drives the water nano-droplet to the colder region. The droplet accelerates its motion toward the cold reservoir as the temperature gradient is increased. In addition to the translational motion of the nano-droplet, the vortical motion of the water molecules was also observed. Contact angle analysis was also utilized to describe the directional motion of the nano-droplet. The translational motion of the droplet leads to the estimation of contact angle hysteresis through advancing and receding contact angles while the rotational motion resulted in the advancing and receding fronts being switched with one another through the simulation. The average displacement vector of the water molecules shows that parts of the droplet seem to stagnate while other parts rotate around them. The reason behind this particular behavior was studied based on interaction energy contours between a water molecule and the suspended graphene. The obtained data indicate that the rotational motion is in agreement with the migration of the water molecules to low interaction energy regions in order to avoid high interaction energy areas.In the present work, the effect of temperature gradient on the behavior of a water nano-droplet resting on a suspended graphene was studied based on a non-equilibrium molecular dynamics simulation. The acquired results indicate that the applied temperature gradient to the suspended graphene drives the water nano-droplet to the colder region. The droplet accelerates its motion toward the cold reservoir as the temperature gradient is increased. In addition to the translational motion of the nano-droplet, the vortical motion of the water molecules was also observed. Contact angle analysis was also utilized to describe the directional motion of the nano-droplet. The translational motion of the droplet leads to the estimation of contact angle hysteresis through advancing and receding contact angles while the rotational motion resulted in the advancing and receding fronts being switched with one another through the simulation. The average displacement vector of the water molecules shows that parts of the drople...

Molecular dynamics (MD) simulations were performed to investigate the interfacial binding between the single-walled carbon nanotubes (SWCNTs) and conjugated polymers including polythiophene (PT), polypyrrole (PP), poly(2,6-pyridinylenevinylene-co-2,5-dioctyloxy-p-phenylenevinylene) (PPyPV), and poly(m-phenylenevinylene-co-2,5-dioctyloxy-p-phenylenevinylene) (PmPV). The intermolecular interaction energy between SWCNTs and polymer molecules was computed, and the morphology of polymers physisorbed to the surface of nanotubes was investigated by the radius of gyration (R(g)) and the alignment angle (theta). The influence of nanotube radius and temperature on the interfacial adhesion of nanotube-polymer and R(g) of polymers was explored more. Our simulation results showed that the strongest interaction between the SWCNTs and these conjugated polymers was observed, first for PT, then PPy and PmPV, and finally PPyPV. Furthermore, we compared our results to the work by Yang and his co-workers (J. Phys. Chem. B 2005, 109, 10009). Our results show that the intermolecular interaction in our systems is strongly influenced by the specific monomer structure of polymer and nanotube radius, but the influence of temperature could be negligible. The high values of intermolecular interaction energy of such composites suggest to us that an efficient load transfer will exist in the interface between nanotube and heterocyclic conjugated polymer, which is of a key role in the composite reinforcement practical applications.

The effect of temperature on the (liquid + liquid) equilibrium of the aqueous solution of surfactant polyoxyethylene cetylether (with abbreviation name Brij 58) and diammonium hydrogen phosphate has been investigated at T = (303.15, 313.15, 323.15, and 333.15) K. The Flory–Huggins equation with two electrostatic terms (Debye–Huckle and Pitzer–Debye–Huckle equations) was used to correlate the phase behavior of this system. Good agreement has been found between experimental and calculated data from both models. The results indicated that the enlargement of the two-phase region upon increasing the temperature. Additionally temperature dependency of the parameters of the Flory–Huggins model has been calculated.

This work was aimed to investigate the behavior, morphology, structure, and dynamical properties of pure ionic liquid (IL) 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4]) confined between two parallel and flat graphene sheets at different interwall distances, H. Thus, molecular dynamic (MD) simulations were performed for different interwall distances including (10, 14, 16, 20, 23, and 28) A at seven temperatures from 278 to 308 K. These results showed that the distribution and orientation of cations and anions on the graphene sheets depended on H. At the shortest H, a dense monolayer of the anions and cations was formed between two graphene sheets. The number of these layers increased as H increased. The potential energy diagram as a function of H demonstrated a minimum potential energy at H = 16 A. Also, there was a minimum overlap between the density profiles of the cations and anions at H = 16 A. Diffusion coefficients of the cations and anions increased as temperature and H increased. Moreover, slope of the plot of the diffusion coefficients of the cations and anions versus H significantly changed at H = 16 A. Orientation functions revealed that most of the cations oriented parallel to the graphene sheets.

In this work, the two mixtures of ionic liquid 1-n-propyl-4-amino-1,2,4-triazolium bromide and each type of the aggregated single-walled carbon nanotubes (SWCNTs), i.e. bundled SWCNTs and non-bundled, were investigated using molecular dynamics (MD) simulations. The structural characteristics of a SWCNT in the ionic liquid (IL) were examined by analyzing the radial distribution functions and the results show that the nearest IL cations to the SWCNT surface can approach it from three different positions. Also, the possibility of the dispersion of the bundled SWCNTs containing three and seven carbon nanotubes was investigated. The obtained results showed that under the investigated conditions, the IL cannot disperse the bundled SWCNTs, but it can disperse six and seven aggregated non-bundled ones. Moreover, we investigated the underlying dispersion mechanism of the aggregated SWCNTs in the IL, using MD simulations. The self diffusion coefficients and transport numbers of the cations and anions were computed in the systems containing pure IL, the mixtures of IL and one, six and seven non-bundled SWCNTs and the systems containing IL and bundled SWCNTs with three and seven carbon nanotubes. The obtained results showed that the diffusion coefficients and the transport numbers of the cations are more than anions in all mentioned systems.

Carbon nanotubes (CNTs) hold the promise of delivering exceptional mechanical properties and multifunctional characteristics due to their unique physiochemical properties and prospective applications in various nanotechnologies. However, current techniques of CNTs fabrication cannot produce homogenous CNTs, and this prevents the widespread use of CNTs. Ever-increasing interest in applying CNTs in many different fields has led to continued efforts to develop dispersion and functionalization techniques. Techniques for separating bundles of CNTs into homogeneous dispersion are still under development. The preparation of effective dispersions of CNTs presents a major impediment to the extension and utilization of CNTs. CNTs intrinsically tend to bundle and/or aggregate. The prevention of such behavior has been explored by testing various techniques to improve the dispersibility of CNTs in a variety of solvents. There are mainly two approaches to obtain a good quality dispersion; chemical functionalization and physical interactions. The chemical functionalization technique has been found effective, but deteriorates the intrinsic properties of CNTs through the introduction of defects in the wall. Physical blending approaches with the ultrasound and high speed shearing have been proven capable of debundling CNTs and stabilizing individual CNTs while maintaining their integrity and intrinsic properties. Contemporary methods for dispersion of CNTs in aqueous media are discussed and most attention is paid to molecular dynamics simulation techniques and other physical techniques, as well as to the use of various surfactants and polymers.

Ionic liquids (ILs) with interesting and useful properties are usually organic salts which have an asymmetric organic cation and a wide assortment of anions. Mixing ILs and some materials like nano structures adjusts their properties positively. This paper reviews the recent computational molecular dynamics studies about mixture of ILs and some materials including carbon nanotubes (CNT), gases and water. Below we mention some reported results in this review. In the case of ILs–CNT systems, we review the behavior of ILs in the CNT dispersing. The results show that ILs cannot disperse the bundled single-walled CNTs, but it can disperse some aggregated non-bundled ones. In the case of confined water/IL mixtures, the obtained results show that the most interaction energy value is observed in pure water and pure IL systems. It was shown in the case of absorption of gases such as SO2 by ILs systems, that the diffusion coefficient of cation in the pure ILs and IL/SO2 gas mixtures was greater than that of the anions and much less than that of the SO2 molecules. In addition, in comparison with pure ILs, the presence of SO2 leads to an increase in the diffusion coefficients, conductivity, density and heat capacity of the ionic species of the IL/SO2 gas mixtures.