Electric field triggered release of gas from a quasi-one-dimensional hydrate in the carbon nanotube.

We systematically investigate the effects of an axial electric field on the formation and decomposition of quasi-one-dimensional nitrogen gas hydrates within a single-walled carbon nanotube (SWNT) by using molecular dynamics (MD) simulations. We find that the nitrogen hydrate in the SWNT undergoes a series of structure phase transitions with increasing electric field. Corresponding to the structure transition, the nitrogen gas releases from the carbon nanotube in the electric field range of 1 V nm-1 to 2 V nm-1. However, nitrogen molecules are trapped as guest molecules, forming a molecule wire, in the ice nanotube when the electric field is less than 1 V nm-1 or larger than 2 V nm-1. Our simulations indicate that the nanotube is an excellent tiny gas tank that can be used to trap gas molecules and control their release triggered sensitively by electric signals. The key to this phenomenon is the change in orientations of water dipoles induced by the electric field, which leads to the structural change in the hydrogen-bonding network and the change in the diffusion coefficient of the water molecules. Our findings here may help understanding the mechanism of the electrorelease of gas from hydrates confined in the nanoscale space.

Correction: Nanoporous two-dimensional MoS2 membranes for fast saline solution purification.

Correction for 'Nanoporous two-dimensional MoS2 membranes for fast saline solution purification' by Jianlong Kou et al., Phys. Chem. Chem. Phys., 2016, 18, 22210-22216.

Effect of aggregated gas molecules on dewetting transition of water between nanoscale hydrophobic plates.

Using molecular dynamics simulations, we have investigated the hydrophobic interactions and influence of nitrogen molecules on the critical distance of dewetting between the nanoscale hydrophobic plates. We show that dewetting transition is very sensitive to the distribution of nitrogen molecules. The nitrogen molecules prefer to aggregate in the vicinity of the two hydrophobic plates and exclude water molecules. Furthermore, our simulation results indicate that the effective range of hydrophobic attraction between the two nanoscale plates is enhanced by the aggregated nitrogen molecules. In particular, we find that the distribution patterns of nitrogen molecules are very different when the inter-plate region is filled with water or dewetted. These findings are helpful to understand the effects of gas molecules dissolved in water on hydrophobic interactions.

Phase transition-like behavior of the water monolayer close to the polarized surface of a nanotube.

By molecular dynamics simulations, we have investigated effects of temperature on the dynamical behavior of water layers at the charged surface of a nanotube. The behavior of the first water monolayer at the charged surface is very different from that of bulk water. There are three different temperature regions for the axial diffusion coefficient and they increase in different ways (linearly or exponentially) with temperature. The dipole distribution of water molecules was chosen as the order parameter to analyze the phase transition-like behavior. The simulation results indicate that the transition from ordered water to disordered water is continuous, which has not been found in the bulk counterpart. The mechanism behind the unexpected phenomenon was also investigated.

A controllable water signal transistor.

We performed molecular dynamics simulations to study the regulating ability of water chains confined in a Y-shaped nanochannel. It was shown that a signal at the molecular level could be controlled by two other charge-induced signals when the water chains were confined in a Y-shaped nanochannel, demonstrating promising applications as water signal transistors in nanosignal systems. The mechanism of a water signal transistor is similar to a signal logic device. This remarkable ability to control the water signal is attributed to the strong dipole-ordering of the water chains in the nanochannel. The controllable water signal process of the Y-shaped nanochannel provides opportunities for future application in the design of molecular-scale signal devices.

Nanoporous two-dimensional MoS2 membranes for fast saline solution purification.

Finding a membrane with both high permeability and high salt rejection is very important for saline solution purification. Here, we report the performance of molybdenum disulfide (MoS2) membranes with nanoscale pores for saline solution purification via all-atom molecular dynamics simulations. It was found that the nanoporous two-dimensional MoS2 membrane can impede salt ions, while allowing highly efficient permeation of water molecules. By engineering the appropriate sizes of the nanopores within two-dimensional MoS2 membranes, their water permeability can be tens of times as high as that of conventional reverse osmosis membranes, while still maintaining a high salt rejection rate. These remarkable water permeability and salt rejection properties of the nanoporous monolayer MoS2 membranes are attributed to the formation of single chain hydrogen bonds, which link the water molecules within the nanopores and those at the immediate exteriors of the nanopores, causing significant reduction in the resistance of water molecules passing through the nanopores, which are small enough for any salt ions to pass through. Therefore such nanoporous monolayer MoS2 membranes have great potential for saline solution purification.

Current inversions induced by resonant coupling to surface waves in a nanosized water pump.

We conducted a molecular dynamics simulation to investigate current inversions in a nanosized water pump based on a single-walled carbon nanotube powered by mechanical vibration. It was found that the water current depended sensitively on the frequency of mechanical vibration. Especially in the resonance region, the nanoscale pump underwent reversals of the water current. This phenomenon was attributed to the dynamics competition of the water molecules in the two sections (the left and right parts) divided by the vibrating atom and the differences in phase and decay between the two mechanical waves generated by mechanical vibration and propagating in opposite directions toward the two ends of the carbon nanotube. Our findings provide an insight into water transportation through nanosized pumps and have potential in the design of high-flux nanofluidic systems and nanoscale energy converters.

A transition between bistable ice when coupling electric field and nanoconfinement.

The effects of an electric field on the phase behavior of water confined inside a nanoscale space were studied using molecular dynamics simulations. It was found that the diffusion coefficient of water reaches its maximum when value of the surfaces' charge is at the threshold, qc = 0.5e. This unexpected phenomenon was attributed to the intermediate state between two stable ice states induced by nanoconfinement and the electric field generated by charged surfaces, respectively. Our finding is helpful to understand electromelting and electrofreezing of water under nanoconfinement with the electric field.

Electromanipulating water flow in nanochannels.

In sharp contrast to the prevailing view that a stationary charge outside a nanochannel impedes water permeation across the nanochannel, molecular dynamics simulations show that a vibrational charge outside the nanochannel can promote water flux. In the vibrational charge system, a decrease in the distance between the charge and the nanochannel leads to an increase in the water net flux, which is contrary to that of the fixed-charge system. The increase in net water flux is the result of the vibrational charge-induced disruption of hydrogen bonds when the net water flux is strongly affected by the vibrational frequency of the charge. In particular, the net flux is reaches a maximum when the vibrational frequency matches the inherent frequency of hydrogen bond inside the nanochannel. This electromanipulating transport phenomenon provides an important new mechanism of water transport confined in nanochannels.

Electricity resonance-induced fast transport of water through nanochannels.

We performed molecular dynamics simulations to study water permeation through a single-walled carbon nanotube with electrical interference. It was found that the water net flux across the nanochannel is greatly affected by the external electrical interference, with the maximal net flux occurred at an electrical interference frequency of 16670 GHz being about nine times as high as the net flux at the low or high frequency range of (<1000 GHz or >80,000 GHz). The above phenomena can be attributed to the breakage of hydrogen bonds as the electrical interference frequency approaches to the inherent resonant frequency of hydrogen bonds. The new mechanism of regulating water flux across nanochannels revealed in this study provides an insight into the water transportation through biological water channels and has tremendous potential in the design of high-flux nanofluidic systems.

Graphyne as the membrane for water desalination.

Permeation through membrane with pores is important in the choice of materials for filtration and separation techniques. Here, we report by the molecular dynamics simulations that a single-layer graphyne membrane can be impermeable to salt ions, while it allows the permeation of water molecules. The salt rejection and water permeability of graphyne are closely related to the hydrostatic pressure, type of graphyne membrane, and the salt concentration of solution, respectively. By analyzing hydration shell structure, we found that the average coordination number of ions plays a key role in water purification. Our calculation showed that the salt rejection of the graphyne-3 membrane is the best and it can keep an ideal rate of 100% in consideration cases. In comprehensive evaluation of both salt rejection and permeability, the graphyne-4 is a perfect purification membrane. To sum up, our results indicated that the graphynes (graphyne-3 and -4) not only have higher salt rejection but also possess higher water permeability which is several orders of magnitude higher than conventional reverse osmosis membranes. The single-layer graphyne membrane may have a great potential application as a membrane for water purification.

Vibrating-charge-driven water pump controlled by the deformation of the carbon nanotube.

The directed transport of water molecules in a single-walled carbon nanotube (SWNT) based on a ratchet effect is investigated by molecular dynamics simulations. The system is driven far away from thermal equilibrium by an additional deterministic perturbation of a vibrating charge, and the spatial inversion symmetry is broken by the continuous deformations of the SWNT. It is well-known that the water flux across a circular channel decreases when the channel is narrowed or deformed. However, our simulation results show that the water flux almost increases linearly within a deformation of 1.9 Å. There exists an optimized value of deformation at which the pumping capacity takes its maximum value. Moreover, the direction of transport even exhibits a change of sign with narrowing the carbon nanotube.

Water permeation through single-layer graphyne membrane.

We report the molecular dynamics simulations of spontaneous and continuous permeation of water molecules through a single-layer graphyne-3 membrane. We found that the graphyne-3 membrane is more permeable to water molecules than (5, 5) carbon nanotube membranes of similar pore diameter. The remarkable hydraulic permeability of the single-layer graphyne-3 membrane is attributed to the hydrogen bond formation, which connects the water molecules on both sides of the monolayer graphyne-3 membrane and aids to overcome the resistance of the nanopores, and to the relatively lower energy barrier at the pore entrance. Consequently, the single-layer graphyne-3 membrane has a great potential for application as membranes for desalination of sea water, filtration of polluted water, etc.

The ice-like water monolayer near the wall makes inner water shells diffuse faster inside a charged nanotube.

Using molecular dynamics simulations, we have investigated the impact of the ice-like water monolayer inside the tube and nearest to the tube wall on the diffusion properties of other inner water shells confined within a charged nanotube. We find that the axial diffusion coefficient of the first water monolayer near the wall monotonously decreases with the charge size on the nanotube, indicating a tighter control of the first monolayer from the larger sized charge. However, for the other water shells, the diffusion coefficients increase when the charge is larger than a critical value qc (~1.0 e). This unexpected phenomenon is attributed to the decreased number of hydrogen bonds between the first monolayer and other inner water shells caused by the very unique hydrogen-bond network patterns in the first ice-like monolayer, which makes it behave like a "hydrophobic water layer." Our findings may have implications for water treatment, non-fouling surfaces, catalysis engine, and biological sensor.

Capability of charge signal conversion and transmission by water chains confined inside Y-shaped carbon nanotubes.

The molecular scale signal conversion, transmission, and amplification by a single external charge through a water-mediated Y-shaped nanotube have been studied using molecular dynamics simulations. Our results show that the signal converting capability is highly sensitive to the magnitude of the charge, while the signal transmitting capability is independent of the charge signal. There is a sharp two-state-like transition in the signal converting capacity for both positive and negative charges. When the charge magnitude is above a threshold (|q| ≥ ~0.7 e), the water dipole orientations in the main tube can be effectively controlled by the signaling charge (i.e., signal conversion), and then be transmitted and amplified through the Y-junction, despite the thermal noises and interferences between branch signals. On the other hand, the signal transmitting capability, characterized by the correlation between the two water dipole orientations in the two branches, is found to be always larger than 0.6, independent of charge signals, indicating that the water-mediated Y-tube is an excellent signal transmitter. These findings may provide useful insights for the future design of molecular scale signal processing devices based on Y-shaped nanotubes.

Unidirectional motion of a water nanodroplet subjected to a surface energy gradient.

We perform molecular dynamics simulations to demonstrate that when a nanodroplet is confined inside a carbon nanotube (CNT), unidirectional motion can be created by a nonzero surface energy gradient. It is found that the water nanodroplet moves along the direction of increasing surface energy. The transportation efficiency of the water nanodroplet is found to be dependent on the surface energy gradient; environmental temperature; and the flexibility, diameter, and defectiveness of the CNT. It is shown that higher surface energy gradient, the smaller diameter of the CNT, and fewer defects promote higher transportation efficiency. However, when the temperature is too high or too low, the water transport across the CNT is impeded. Except for the initial stage at the relatively low environmental temperature, higher flexibility of the CNT wall reduces the transportation efficiency. It is also found that the hydrogen bonds of water molecules play a role in the dynamic acceleration process with a wavelike feature. The present work provides insight for the development of CNT devices for applications such as drug delivery, nanopumps, chemical process control, and molecular medicine.

[Detection of hematopoietic chimera by real-time fluorescent quantitative PCR with erythrocyte Kidd blood group gene].

This study was aimed to establish the real-time fluorescent quantitative PCR (RT-qPCR) with erythrocyte Kidd blood group gene for detecting the hematopoietic chimera and to investigate the feasibility of this method. The TaqMan MGB probes and special primers were designed on basis of difference of erythrocyte Kidd blood group alleles, the hematopoietic chimerism was detected by RT-qPCR, the DNA chimerism was simulated by means of dilution of multiple proportions, and the sensitivity analysis was performed. The results showed that the RT-qPCR with erythrocyte Kidd blood group gene could effectively distinguish JK*A and JK*B alleles. There was no significant difference between the theoretic value and the practical measured value by this method (P > 0.05). As 156 donor's cells could be discriminated from 10(4) chimeric cells, this method may effectively detect donor's cells with correlation coefficient 0.998. It is concluded that the established RT-qPCR with erythrocyte Kidd blood group gene shows the feasibility for quantitative detection of hematopoietic chimera, and may be used to quantitatively detect chimera in a certain range.

[Rare blood group screening by serological and molecular methods in Zhejiang Han population].

This study was aimed to investigate the distribution of rare blood group in Zhejiang Han population. The H(-) (H system), GPA(-) and s(-) (MNS), Rhnull, Rhmod, D--, CCDEE, CCdEE (variations of Rh), GPC(-) (Gerbich), i(+) (I), Lu(b-) (Lutheran), Js(b-) and k(-) (Kell), Fy(a-) (Duffy), Ok(a-) (Ok), Di(b-) (Diego) phenotypes were screened by serological or molecular methods. Jk (a-b-) phenotype was detected by urea hemolytic test. The results showed that one Di (a+b-) individual was found in 1618 blood donors, three Fy (a-b+) individuals in 1007 donors and one CCdEE individual in 633 Rh negative donors. No Jk (a-b-), H(-), GPA(-), s(-), GPC(-), i(+) (adult), Lu(b-), k(-), Js(b-), Lu(b-) and Ok(a-) phenotypes were found in this large scale survey. It is concluded that Di (a+b-), Fy (a-b+), CCdEE phenotypes are confirmed in the blood donors and this study provides the distribution data of erythrocyte rare blood group in Zhejiang Han population.

Controllable transport of water through nanochannel by rachet-like mechanism.

By using molecular dynamics simulation, we have investigated systematically the feasibility of continuous unidirectional water flux across a deformed single-walled carbon nanotube (SWNT) driven by an oscillating charge outside without osmotic pressure or hydrostatic drop. Simulation results indicate that the flux is dependent sensitively on the oscillating frequency of the charge, the distance of the charge from the SWNT, and the asymmetry of the water-SWNT system. A resonance-like phenomenon is found that the water flux is enhanced significantly when the period of the oscillation is close to twice the average hopping time of water molecules inside the SWNT. These findings are helpful in developing a novel design of efficient functional nanofluidic devices.

[Discrimination of alleles in HLA-C*07:01:01G and HLA-C*07:02:01G groups through detection sequences in exons 1 to 7 of HLA-C locus by using polymerase chain reaction sequence-based typing].

This study was aimed to discriminate the alleles in the HLA-C*07:01:01G and HLA-C*07:02:01G groups and analyze their associations with HLA-B locus. Samples previously typed as HLA-C*07:01:01G and HLA-C*07:02:01G were collected. The nucleotide sequences in exons 1 to 7 of the HLA-C locus were sequenced by polymerase chain reaction sequence-based typing (PCR-SBT) and HLA-B genotyping was also preformed by PCR-SBT in these samples. The results showed that 4 samples (30.8%) were confirmed as HLA-C*07:01:01 and 9 samples (69.2%) were HLA-C*07:06 among 13 samples previously typed as HLA-C*07:01:01G. Linkage disequilibrium (LD) analysis showed that HLA-C*07:06 allele was strongly related with HLA-B*44:03. All samples were typed as C*07:02:01 among 102 individuals previously typed as C*07:02:01G. LD analysis showed that C*07:02:01 was strongly related with HLA-B*51:01, B*46:01, B*39:01, B*40:01, B*38:02, B*15:02 alleles. It is concluded that HLA-C*07:01:01 and HLA-C*07:06 alleles are confirmed in the HLA-C*07:01:01G group and HLA-C*07:02:01 is a preferred allele in the HLA-C*07:02:01G.