[ad_1]
NIST researchers have conducted simulations of a graphene membrane with pores lined with oxygen and immersed in a liquid solution of potassium ions (charged atoms), which can under certain conditions be trapped in the pores. A slight stretch of graphene greatly increases the flow of ions through the pores. Credit: NIST
Researchers at the National Institute of Standards and Technology (NIST) have conducted simulations suggesting that graphene, in addition to many other useful features, can be modified with special pores to serve as a filter or filter adjustable for ions (charged atoms) in liquid.
This concept, which could also work with other membrane materials, could have applications such as nanoscale mechanical sensors, drug delivery, water purification, and sieves or pumps for similar ionic mixtures. to the biological ion channels, essential for the functioning of living cells. The research is described in the November 26 issue of Nature Materials.
"Imagine something like a fine-mesh kitchen strainer with sugar crossing," said project manager Alex Smolyanitsky. "You stretch this strainer so that each hole of the mesh becomes larger by 1 to 2% .You would expect that the flow through this mesh increases substantially by the same amount." Well, here it increases by 1,000% I think it's pretty cool, with tons of apps. "
If it was possible to do this experimentally, this graphene sieve would be the first artificial ion channel to offer an exponential increase in ion flux under stretching, providing opportunities for rapid separation of ions or pumps or precise control of salinity. . Collaborators are planning laboratory studies on these systems, Smolyanitsky said.
Graphene is a layer of carbon atoms arranged in hexagons, similar in shape to the chicken wire, which conducts electricity. NIST molecular dynamics simulations focused on a graphite sheet of 5.5 on 6.4 nanometers (nm) with small holes aligned with oxygen atoms. These pores are crown ethers, electrically neutral circular molecules known to trap metal ions. A previous NIST simulation study had shown that this type of graphene membrane could be used for nanofluidic computation.
In the simulations, graphene was suspended in water containing potassium chloride, a salt that divides into potassium ions and chlorine. The pores of the crown ether can trap potassium ions, which have a positive charge. Trapping and release rates can be controlled electrically. An electric field of different forces has been applied to control the ion current flowing through the membrane.
The researchers then simulated tugging of the membrane with different degrees of force to dilate and dilate the pores, greatly increasing the flow of potassium ions across the membrane. Stretches in all directions had the greatest effect, but even shooting in one direction had a partial effect.
The researchers found that the unexpected increase in ion flux was due to the subtle interaction of a number of factors, including the fineness of graphene; interactions between ions and the surrounding liquid; and ion-pore interactions, which weaken when the pores are slightly stretched. There is a very sensitive balance between ions and their environment, said Smolyanitsky.
Explore further:
Researchers simulate a simple logic for nanofluidic computing
More information:
A. Fang, K. Kroenlein, D. Riccardi and A. Smolyanitsky. Highly mechanosensitive ion channels from crown ethers incorporated into graphene. Nature Materials. Posted online November 26, 2018.
Source link
