Synthetic conical nanochannels have gained attention for their ion rectification behavior, which can be used to mimic the functionalities of biological ion channels. Employing these nanochannels and inspired by biological synaptic dynamics, we herein demonstrate a new nanofluidic device as a memristor, the ion transport conductance of which depends on the history of its ion flow. The nanofluidic memristors show excellent repeatability, high ON/OFF ratios, and sufficiently long retention times, which are highly desirable for logic control and neuromorphic engineering applications in nanofluidic systems as well as for fundamental transport studies of ionic liquids on a nanoscale.

Nanochannel based devices have been widely used for single-molecule detection. The detection usually relies on the resistive-pulse model, where the change of the monitored current depends on the physical volumetric blocking of the nanochannel by the analyte. However, this mechanism requires that the nanochannel diameter should not be much larger than the analyte size, because, otherwise, the resultant current change would be too small to detect, and therefore poses particular challenges for the fabrication of nanochannels. To circumvent this issue, in this report, we propose a different mechanism of capacitive-pulse model, where the transport signals can be significantly magnified by the capacitive effect of the nanochannel. We experimentally demonstrate that current pulses with an averaged peak height of 0.87 nA can be achieved for transporting 60 nm nanoparticles through a conical nanochannel device, whereas the traditional resistive-pulse model only predicts one-order-of-magnitude lowered value. With further comprehensive simulation, the dependence of this effect on the nanochannel geometry as well as the surface charge density for both the nanochannel and the analyte is predicted, which would provide important guidance for better designing of the nanochannel-based sensors.

Density functional theory (DFT) calculation is employed to study the adsorption properties of Pb and Cu on recently synthesized two-dimensional materials MXenes, including Ti3C2, V2C1 and Ti2C1. The influence of surface decoration with functional groups such as H, OH and F have also been investigated. Most of these studied MXenes exhibit excellent capability to adsorb Pb and Cu, especially the adsorption capacity of Pb on Ti2C1 is as high as 2560 mg g−1. Both the binding energies and the adsorption capacities are sensitive to the functional groups attached to the MXenes' surface. Ab initio molecular dynamics (ab-init MD) simulation confirms that Ti2C1 remains stable at room temperature after adsorbing Pb atoms. Our calculations imply that these newly emerging two-dimensional MXenes are promising candidates for wastewater treatment and ion separation.

•Irradiation effects in 6H–SiC between neutron and C, Si ions were compared.•There is a good agreement in total disorder between neutron and ion irradiations.•The strain-to-dpa ratio induced by neutron is larger than that by ions.Irradiation effects of neutron and 3 MeV C+, Si+ in 6H–SiC were investigated by Raman spectroscopy and high-resolution XRD. The total disorder values of neutron irradiated SiC agree well with that of samples irradiated by ions at the same doses respectively. On the other hand, high-resolution XRD results shows that the lattice strain rate caused by neutron irradiation is 6.8%/dpa, while it is only 2.6%/dpa and 4.2%/dpa for Si+ and C+ irradiations respectively. Our results illustrate that the total disorder in neutron irradiated SiC can be accurately simulated by MeV Si+ or C+ irradiations at the same dose, but for the lattice strain and strain-related properties like surface hardness, the depth profile of irradiation damages induced by energetic ions must be considered. This research will contribute to a better understanding of the difference in irradiation effects between neutron and heavy ions.

MXenes, a series of two-dimensional (2D) layered early transition metal carbide, nitride, and carbonitride, have been prepared by exfoliating MAX phases recently. In addition to 2D planar MXene, one-dimensional tubular forms—MXene nanotubes—are also expected to form. Herein, we design atomic models for Ti2C as well as Ti2CO2 nanotubes in the 1–4 nm diameter range and investigate their basic properties through density functional theory (DFT). It is shown that though the strain energy of Ti2C nanotubes are always positive, Ti2CO2 nanotubes have negative strain energies when diameter beyond 2.5 nm, indicating that they could possibly folded from 2D Ti2CO2 nanosheets. Moreover, the band gap of Ti2CO2 nanotubes decrease with the growing diameter and the maximum band gap can reach up to 1.1 eV, over 3 times that of their planar form. Thus, tunable band gaps provide strong evidence for the effectiveness of nanostructuring on the electronic properties of Ti2CO2 nanotubes.

Nanopore-based devices have recently become popular tools to detect biomolecules at the single-molecule level. Unlike the long-chain nucleic acids, protein molecules are still quite challenging to detect, since the protein molecules are much smaller in size and usually travel too fast through the nanopore with poor signal-to-noise ratio of the induced transport signals. In this work, we demonstrate a new type of nanopore device based on atomic layer deposition (ALD) Al2O3 modified track-etched conical nanochannels for protein sensing. These devices show very promising properties of high protein (bovine serum albumin) capture rate with well time-resolved transport signals and excellent signal-to-noise ratio for the transport events. Also, a special mechanism involving transient process of ion redistribution inside the nanochannel is proposed to explain the unusual biphasic waveshapes of the current change induced by the protein transport.

By employing both molecular dynamics (MD) simulations and ab initio calculations based on the density functional theory (DFT), we studied the efficiency of doping graphene with low energy Si ions implantation. Mainly two types of substitutional doping configurations resulting from Si ion implantation were found in graphene, namely perfect Si substitution at monovacancy (Si@MV), and Si interstitial defect at divacancy site (Si@DV). High efficiency for Si substitutions was obtained within a wide energy range varied between 30–150 eV. At the optimum energy of 70 eV, up to 59% of the incident Si ions would be incorporated in graphene by Si@MV. Moreover, the experimental doping efficiency should be higher than the above value of 59% because Si adatom on graphene surface can be eventually turned into a substitution atom via annihilating with a vacancy defect produced in the collision process. Such high doping efficiency makes ion implantation a powerful tool to dope graphene with Si and similar elements. Our results provide a theoretical clue for the property engineering of graphene by using ion irradiation technique, in particular for doping graphene with heavy ions.

Irradiation effects in Ni–17Mo–7Cr alloy have been systematically investigated by using 3 MeV Au ions at different fluences ranging from 8 × 1013 cm−2 to 2.3 × 1015 cm−2, corresponding to doses of 1–30 dpa. The results indicated that sample microstrain increased gradually from 0.14 to 0.22% as dose increased from 0 to 30 dpa. Besides, the nanohardness of Ni–17Mo–7Cr alloy increased with irradiation dose until 10 dpa, and then, softening effect became dominant while further increasing dose to 30 dpa. After being irradiated at room temperature, the swelling rate of Ni–17Mo–7Cr alloy was found to be around 0.04% per dpa. These data are helpful in estimating the irradiation resistance of this newly developed Ni–17Mo–7Cr alloy in nuclear energy systems.

•In this paper, we introduce a simple method for preparation of Janus nanowires by electrodeposition.•Using ion-track-etched PC polymer templates and commercial PC track-etched membrane templates, Ag/Cu Janus nanowires fabricated by this method all have uniform size. No matter how the holes array in the template, regular or not, the nanowires prepared by this method have similar properties.•By controlling the etching time, the size of the nanowires could be controlled easily and special shape nanowires also can be prepared by this template.•The polymer template is very easy to dissolve thoroughly and has no damage to nanowires almost. It is suitable for the preparation of nanowires suspension.•This method also has better applicability for polymer templates and can be seen as a simple convenient method for the preparation of Ag/Cu Janus nanowires.Bimetal (Janus) nanowire has been widely used as a promising nanoscale motor. In this paper we present a highly controllable method to fabricate Ag/Cu Janus nanowires using track-etched polymer templates. Ag/Cu Janus nanowires with uniform size and stabilized structure have been successfully fabricated by electrodepositing Ag nanowires, and subsequently Cu nanowires in track-etched polymer templates. The pore size of nanopores prepared by this template is uniform and continuously controlled, so aperture of achieved nanowires are uniform and can be regulated. This polymer template can dissolve inorganic solvents that do not react with the nanowires, making it is easy to release the nanowires into solution. The nanopore shape in the track-etched templates is adjustable (e.g. conical), nanowires with more special shapes could be fabricated. Thus, these features make this simple and inexpensive method very suitable for the preparation of Janus nanowire.

•Gas adsorption on MoS2 are investigated from first-principles calculations.•van der Waals interactions are considered in calculations.•NO and NO2 can bind strongly with MoS2 compared to other gas molecules.First-principles calculations within density functional theory have been carried out to investigate the adsorption of various gas molecules including CO, CO2, NH3, NO, NO2, CH4, H2O, N2, O2 and SO2 on MoS2 monolayer in order to fully exploit gas sensing capabilities of MoS2. By including van der Waals interactions between gas molecules and MoS2, we find that only NO and NO2 can bind strongly to MoS2 sheet compared to other gas molecules, in line with experimental observations. The charge transfer and variation of electronic structures are discussed in view of the density of states and molecular orbitals of gas molecules.

•Defect properties in Ti3SiC2 are investigated from first-principles calculations.•Si and C related defects are the most abundant defects in Ti3SiC2.•Si vacancies and Ti interstitials can decrease and increase the conductivity of Ti3SiC2, respectively.First-principles calculations have been carried out to investigate intrinsic defects including vacancies, interstitials, antisite defects, Frenkel and Schottky defects in the 312 MAX phase Ti3SiC2. The formation energies of defects are obtained according to the elemental chemical potentials which are determined by the phase stability conditions. The most stable self-interstitials are all found in the hexahedral position surrounded by two Ti(2) and three Si atoms. For the entire elemental chemical potential range considered, our results demonstrated that Si and C related defects, including vacancies, interstitials and Frenkel defects are the most dominant defects. Besides, the present calculations also reveal that the formation energies of C and Si Frenkel defects are much lower than those of all Schottky defects considered. In addition, the calculated profiles of densities of states for the defective Ti3SiC2 indicate that these defects should have great influence on its thermal and electrical properties.

With asymptotic and numerical analyses, we systematically study the influence of slip length and access Ohmic resistance (due to pore-end field focusing and concentration polarization) on the energy conversion efficiency of pressure-driven electrolyte flow through a charged nanopore. Hydrodynamic slip reduces the percent of energy dissipated by viscous dissipation but, through electro-osmotic convective current, can also reduce the electrical resistance of the nanopore. Since the nanopore resistance is in parallel to the load-access serial resistance, the latter effect can actually reduce useful current through the load. These two opposing effects of slip produce specific and finite optimum values of surface charge density and ionic strength. The optimization offers explicit analytical estimates for the realistic parameters and suggests an upper bound of 50% conversion efficiency at the slip length of 90 nm and 35% for measured electro-osmotic flow slip lengths of about 30 nm for charged channels.

We use Kinetic Monte Carlo (KMC) method to investigate the evolution of Helium-Vacancy clusters under different conditions with emphasizing the influence of system temperature. Our simulation results indicate that when initial helium concentration increases, the size and amount of the Helium-Vacancy cluster will increase dramatically. The Helium-Vacancy cluster will become larger accompanied with a decrease in its amount as the temperature increases. The results also indicate that irradiating He-contained sample produces less helium bubbles compared with other conditions, adding helium during irradiating the sample or adding helium atoms after the sample have been irradiated.

The mechanical properties of copper nanowires irradiated with energetic ions have been investigated by using molecular dynamics simulations. The Cu ions with energies ranging from 0.2 to 8.0 keV are used in our simulation, and both the elastic properties and yields under tension and compression are analyzed. The results show that two kinds of defects, namely point defects and stacking faults, appear in the irradiated nanowires depending on the incident ion energy. The Young modulus is significantly reduced by the ion irradiation, and the reduction magnitude depends on the vacancy number, which is determined by the ion energy. Moreover, the irradiated nanowires yield at a smaller strain, compared with the unirradiated nanowire. The mechanism for these changes are also discussed.

Track-etched polymer membranes are used to realize low-voltage electroosmotic (EO) pumps. The nanopores in polycarbonate (PC) and polyethylene terephthalate (PET) membranes were fabricated by the track-etching technique, the pore diameter was controlled in the range of 100 to 250 nm by adjusting the etching time. The results show that these EO pumps can provide high flow rates at low applied voltages (2–5 V). The maximum normalized flow rate is as high as 0.12 ml min−1 V−1 cm−2, which is comparable to the best values of previously demonstrated EO pumps. We attribute this high performance to the unique properties of the track-etched nanopores in the membranes.

Using molecular dynamics simulation with empirical potentials, we show that energetic cluster ion beam is a powerful tool to drill nanopores in graphene, which have been proved to possess the potential applications in nanopore-based single-molecule detection and analysis such as DNA sequencing. Two types of clusters are considered, and different cluster size and incident energies are used to simulate the impact events. Our results demonstrate that by choosing suitable cluster species and controlling its energy, a nanopore with expected size and quality could be created in a graphene sheet. Furthermore, suspended carbon chains could be formed at the edge of the nanopore via adjusting the ion energy, which provided a feasible way to decorate the nanopore with chemical methods such as adsorption of large molecules or foreign atoms for biosensing applications.

We present experimental investigations of electroosmotic (EO) pumping using polyethylene terephthalate (PET) track-etched membrane at a low applied voltage. An EO pump based on PET track-etched membrane has been designed and fabricated. Pumping performance of the device is experimentally studied in terms of flow rate as a function of applied voltage and KCl aqueous concentration. The PET track-etched membrane EO pump can generate flow rates on the order of 10 μl min−1 cm−2 at several applied volts. The measured flow rate tends to decrease with increasing KCl aqueous concentration. In addition, we study the EO flow in cylindrical nanopore with use of a continuum model, composed of Nernst Planck equations, Poisson equation and Navier Stokes equations.

The threshold displacement energies in silicon carbide under different pressures are determined with ab initio molecular dynamics. The results show that the threshold displacement energies change anisotropically in different crystallographic directions when high pressure is applied. However, the weighted average values for both the C and Si sublattice, which determine the defect production in a material under irradiation, are found to increase significantly with increasing external pressures. Besides, we have observed some new defect structures under high pressures which are not observed at ambient conditions. Our results show that irradiation under high pressures could decrease the production rate of point defects in SiC, thus greatly enhancing its resistivity against radiation damage. The combination of irradiation and high pressure technique hence provides a pathway to obtain new structure materials.

A method is reported here to tune the ionic current rectification behavior through a conical nanopore fabricated with the track-etching technique. In order to change the surface charge property of the pore wall, we added the cationic surfactant hexadecyl trimethylammonium bromide (CTAB) into the working electrolyte of 0.1 M KCl. By controlling the modified region and the concentration of CTAB, the ionic current rectification degree of the nanopore could be tuned over the wide range of 0.2–65 at the voltage of ±0.9 V. The mechanism of the changes in current rectification behavior was analyzed by numerically solving the Poison–Nernst–Planck (PNP) equations.

The study of voltage-dependent ion current fluctuation phenomena in synthetic nanopores is important as it is helpful to investigate the mechanism of mass transport in nanoscale systems, which have similarities with natural ion channels in the biological cell membrane. Moreover, we could fabricate some high-performance nanofluidic devices through clearly understanding ion current fluctuation behavior. In this paper, we report a nanofluidic pulser induced by formation and dissolution of weakly soluble salts in conical nanopores. The current fluctuation signals are easily controllable in 1 M KCl electrolyte. Amplitude, frequency, and waveform of ion fluctuation current of the nanofluidic pulser could be controlled by changing the applied negative voltage, and the time ratio of pore opening/closing could be simply manipulated by the concentration of the bivalent cation. A high-quality square wave of ion current signal is found, especially when the negative voltage is below 300 mV. Additionally, we developed a new model about the formation and dissolution process of precipitation. Our work is helpful for the design of nanoscale ion current waveform generators in the future.

In this letter, we report a method to modify the surface charge property of single track-etched nanopores with a cationic surfactant (CTAB). The dependence of surface charge density on the surfactant concentration was investigated by measuring the streaming current when the nanopore was immersed in 0.01 M KCl solution with different CTAB concentrations. The results showed that, when the concentration of CTAB was increased gradually, the surface charge of the nanopore was inverted from negative to positive. Our calculation indicated that the surface charge density changed from −9 to 8 mC/m2. We utilized this method to modify the surface property of single conical track-etched nanopores. Its current rectification properties (both the direction and magnitude) were successfully tuned by adjusting the CTAB concentration in the solutions.

The damage production induced by MeV highly charged ions (HCI) irradiations in graphene supported on a SiO2SiO2 substrate is investigated using molecular dynamics method. We get results in agreement with our recent experiments. We find that the electronic energy loss and potential energy deposition have similar effects on the defects creation in SiO2SiO2 substrate-supported graphene and both mechanisms of energy deposition seem to contribute in an additive way. The influences of the energy deposition depth and radius are studied. Only the energy deposited below the surface within 2.5 nm will induce the damage in graphene. Hence, the HCI can be a powerful tool to induce defects in graphene without causing deep damage of the substrate. When charge of incident Xeq+Xeq+ is above 30, a nanopore is formed and the size of nanopore in graphene can be controlled by changing the incident charge state.

Density functional theory (DFT) calculation is employed to study the adsorption properties of Pb and Cu on recently synthesized two-dimensional materials MXenes, including Ti3C2, V2C1 and Ti2C1. The influence of surface decoration with functional groups such as H, OH and F have also been investigated. Most of these studied MXenes exhibit excellent capability to adsorb Pb and Cu, especially the adsorption capacity of Pb on Ti2C1 is as high as 2560 mg g−1. Both the binding energies and the adsorption capacities are sensitive to the functional groups attached to the MXenes' surface. Ab initio molecular dynamics (ab-init MD) simulation confirms that Ti2C1 remains stable at room temperature after adsorbing Pb atoms. Our calculations imply that these newly emerging two-dimensional MXenes are promising candidates for wastewater treatment and ion separation.

A method is reported here to tune the ionic current rectification behavior through a conical nanopore fabricated with the track-etching technique. In order to change the surface charge property of the pore wall, we added the cationic surfactant hexadecyl trimethylammonium bromide (CTAB) into the working electrolyte of 0.1 M KCl. By controlling the modified region and the concentration of CTAB, the ionic current rectification degree of the nanopore could be tuned over the wide range of 0.2–65 at the voltage of ±0.9 V. The mechanism of the changes in current rectification behavior was analyzed by numerically solving the Poison–Nernst–Planck (PNP) equations.

Synthetic conical nanochannels have gained attention for their ion rectification behavior, which can be used to mimic the functionalities of biological ion channels. Employing these nanochannels and inspired by biological synaptic dynamics, we herein demonstrate a new nanofluidic device as a memristor, the ion transport conductance of which depends on the history of its ion flow. The nanofluidic memristors show excellent repeatability, high ON/OFF ratios, and sufficiently long retention times, which are highly desirable for logic control and neuromorphic engineering applications in nanofluidic systems as well as for fundamental transport studies of ionic liquids on a nanoscale.