Quartz Nanopores Research Articles

Lattice Boltzmann simulation of liquid flow in nanoporous media

In this paper, a multi-relaxation-time lattice Boltzmann (LB) model for nanoscale liquid flow is established to investigate the liquid flow characteristics in nanoporous media. The slip length and effective viscosity obtained by molecular dynamics (MD) simulations are adopted to account for the nanoscale effect. First, the LB model for water flow in nanopores is built and water flow characteristics in nanoporous media are investigated. The fluid-solid interaction force shows significant influence on water flow in nanoporous media. The water flux through nanoporous media increases with the decrease of fluid-solid interaction force. In hydrophobic nanoporous media, the nanoscale effect can decrease the gap between water flow resistance in large pores and that in small pores, making the velocity distribution more uniform. In addition, the end effect caused by the bending of streamlines can induce significant additional flow resistance. Neglecting the end effect can greatly overestimate water flow ability. The pore structure also has significant influence on water flow in nanoporous media. With the increase of specific interfacial length, the nanoscale effect increases. Finally, the LB model for oil (octane) flow in quartz nanopores is also established by incorporating the MD simulation results. Oil flow simulation in quartz nanoporous media shows that the conclusions obtained for water flow are also applicable for oil flow.

Translocation frequency of double-stranded DNA through a solid-state nanopore.

Solid-state nanopores are single-molecule sensors that measure changes in ionic current as charged polymers such as DNA pass through. Here, we present comprehensive experiments on the length, voltage, and salt dependence of the frequency of double-stranded DNA translocations through conical quartz nanopores with mean opening diameter 15 nm. We observe an entropic barrier-limited, length-dependent translocation frequency at 4M LiCl salt concentration and a drift-dominated, length-independent translocation frequency at 1M KCl salt concentration. These observations are described by a unifying convection-diffusion equation, which includes the contribution of an entropic barrier for polymer entry.

Molecular dynamics simulations of oil transport through inorganic nanopores in shale

Understanding the transport of liquid hydrocarbon through nanopores of inorganic minerals is crucial not only to develop liquid-rich shale reservoirs, but also to grasp oil migration from deeply buried extremely low permeability source rocks. We report a molecular study of liquid hydrocarbon (octane) flow through inorganic (quartz) nanopores ranging in size from 1.7 to 11.2nm. Through equilibrium molecular dynamics (EMD), we observe the layering structure of confined octane and conclude that in the center of slits having apertures greater than 3.6nm, the octane properties, e.g., density, self-diffusion coefficient, and viscosity, tend to be bulk-liquid-like. Near the solid–liquid interface, octane molecules diffuse more slowly. Then we use nonequilibrium molecular dynamics (NEMD) to study the pressure-driven flow of octane in quartz slits and present two methods to characterize the behavior: (1) slip length coupled with effective viscosity and (2) apparent viscosity. The Navier–Stokes equation can reasonably describe the flow in quartz nanopores larger than 1.7nm; however, a slip boundary condition or viscosity correction is essential. Although the slip length (∼0.9nm) is small, significant error can be caused in the estimation of overall flux if it is neglected. The variations in slip length and apparent viscosity with driving force, pore size, and temperature can be described by empirical exponential functions. These results can be readily incorporated into existing techniques to estimate apparent liquid permeability of shale—the most fundamental property required for shale exploitation.

Molecular simulation of methane adsorption in slit-like quartz pores

The GCMC and MD methods were used to investigate the structural properties and adsorption behaviors of methane in quartz nanopores.

Adsorption properties of CH4 and CO2 in quartz nanopores studied by molecular simulation

Competitive adsorption isotherms and adsorption density distributions of binary mixtures containing CH4 and CO2 in nanopores with 100% and 60% surface hydroxylation at 323 K.

Nanopore analysis of amyloid fibrils formed by lysozyme aggregation.

The measurement of single particle size distributions of amyloid fibrils is crucial for determining mechanisms of growth and toxicity. Nanopore sensing is an attractive solution for this problem since it gives information on aggregates' shapes with relatively high throughput for a single particle technology. In this paper we study the translocation of lysozyme fibrils through quartz glass nanopores. We demonstrate that, under appropriate salt and pH conditions, lysozyme fibrils translocate through bare quartz nanopores without causing significant clogging. This enables us to measure statistics on tens of thousands of translocations of lysozyme fibrils with the same nanopore and track their development over a time course of aggregation spanning 24 h. Analysis of our events shows that the statistics are consistent with a simple bulk conductivity model for the passage of rods with a fixed cross sectional area through a conical glass nanopore.

Structure of sodium sulphate aqueous solution/quartz interface: a molecular dynamics simulation

The molecular dynamics simulation was used to investigate the aqueous sodium sulphate solutions within quartz nanopores. Simulation was conducted for 13 ns to obtain the equilibrium distribution of water molecules, sulphate and sodium ions (Na+ and ) within the pores. The results clearly show an adsorption of sodium sulphate solution onto the quartz surface. However, Na+ shows a stronger attachment to the fully hydroxylated surface than due to size effects. The majority of Na+ ions appear within the primary and secondary water adsorption sites from the quartz surface. A special orientation of water molecules has been found in these layers, where one of the O–H bonds was parallel to the normal direction of the quartz surface. These observations illustrate the effect of quartz surface on the diffusion and precipitation of aqueous salt solutions under confinement, thus providing the mechanism of salt destruction on mural paintings.