Hydrocarbon contamination in angström-scale channels

Abstract

Air-borne hydrocarbon contamination is investigated for slit-like angstrom-channels made from 2D-materials, using gas flow measurements. Our results constitute a new way to monitor, assess and alleviate the hydrocarbon contamination in nanochannels.

Interfacial layering of hydrocarbons on pristine graphite surfaces immersed in water

“…The interactions of liquid water with graphite, graphene and, in general, hydrophobic 2D materials have many features in common, 16,17 therefore, these findings should be also applied to nanopore devices that involve 2D material-aqueous interfaces. 39 In summary, real-time and atomic-scale depth resolution images demonstrated that the interfacial water structure on pristine graphite surfaces transitioned from hydration to hydrocarbon layers. Free energy minimization drives the transfer of hydrocarbons, in particular, alkane-like molecules from the gas phase through water to adsorption on graphite surfaces.…”

“…The interactions of liquid water with graphite, graphene and, in general, hydrophobic 2D materials have many features in common, 16,17 therefore, these findings should be also applied to nanopore devices that involve 2D material-aqueous interfaces. 39…”

Clogging and Unclogging of Hydrocarbon-Contaminated Nanochannels

“…16 In fact, when nanochannels are reduced to angstrom sizes, clogging occurs from contamination adhering to them. 17 At the angstrom scale, the interaction between contaminants and the nanochannel wall becomes more significant. Adsorption of contaminants onto the wall of the nanochannel occurs as a result of this interaction, which hinders the permeation of fluid in the channel.…”

“…To gain deeper physical insight into the clogging mechanism and to be able to explain the recent experiment, 17 we calculated the energy barrier for the hydrocarbon to enter the nanochannel as a function of the width of the 2D channel. Once inside the channel, we obtained the diffusion barrier for the hydrocarbon to move inside the channel.…”

“…This is compatible with the experiment for ultraslim channels (0.4 nm), i.e., in which no clogging of the nanochannels is observed. 17 Accordingly, the energy barrier prevents any penetration of hydrocarbon and thus clogging of the nanochannel. Three regimes can be distinguished: (1) h < 0.64 nm when hydrocarbons (hexane) cannot enter the channel, (2) when h = 0.7 nm there is maximum binding of the hydrocarbons inside the channel, making unclogging almost impossible, and…”