Here, we report a study of ion transport across graphene oxide （GO） membranes of various thicknesses, made by vacuum filtration of GO aqueous solutions. The diffusive transport rates of two charge-equivalent rutheni...Here, we report a study of ion transport across graphene oxide （GO） membranes of various thicknesses, made by vacuum filtration of GO aqueous solutions. The diffusive transport rates of two charge-equivalent ruthenium complex ions Ru（bpy）3^2＋ and Ru（phen）32% with a sub-angstrom size difference, are distinguishable through GO membranes and their ratio can be a unique tool for probing the transport-relevant pore structures. Pore and slit-dominant hindered diffusion models are presented and correlated to experimental results. Our analysis suggests that ion transport is mostly facilitated by large pores （larger than 1.75 nm in diameter） in the relatively thin GO membranes, while slits formed by GO stacking （less than 1.42 nm in width） become dominant only in thick membranes. By grafting PEG molecules to the lateral plane of GO sheets, membranes with enlarged interlayer spacing were engineered, which showed drastically increased ion transport rates and lower distinction among the two ruthenium complex ions, consistent with the prediction by the slit-dominant steric hindered diffusion model.展开更多
This paper studies the importance of corrections that account for the presence of walls on the forces act- ing on nanoparticles during their transport in microchannels.Theoretical and experimental investigations have ...This paper studies the importance of corrections that account for the presence of walls on the forces act- ing on nanoparticles during their transport in microchannels.Theoretical and experimental investigations have reported anisotropic and hindered motion of nanoparticles near a microchannel wall. To investigate the influence of the near-wall effects, various conditions were examined. In particular, computer simu- lations were performed with and without the near-wall correction of forces. The corresponding capture efficiency and the average penetration of the captured nanoparticles were compared, and the importance of the near-wall corrections was assessed. Effects were evaluated for the nanoparticle diameter, the chan- nel width, the channel length, and the pressure gradient. The results indicate that the inclusion of wall effects is crucial for the analysis of nanoparticle transport in microchannels.展开更多
文摘Here, we report a study of ion transport across graphene oxide （GO） membranes of various thicknesses, made by vacuum filtration of GO aqueous solutions. The diffusive transport rates of two charge-equivalent ruthenium complex ions Ru（bpy）3^2＋ and Ru（phen）32% with a sub-angstrom size difference, are distinguishable through GO membranes and their ratio can be a unique tool for probing the transport-relevant pore structures. Pore and slit-dominant hindered diffusion models are presented and correlated to experimental results. Our analysis suggests that ion transport is mostly facilitated by large pores （larger than 1.75 nm in diameter） in the relatively thin GO membranes, while slits formed by GO stacking （less than 1.42 nm in width） become dominant only in thick membranes. By grafting PEG molecules to the lateral plane of GO sheets, membranes with enlarged interlayer spacing were engineered, which showed drastically increased ion transport rates and lower distinction among the two ruthenium complex ions, consistent with the prediction by the slit-dominant steric hindered diffusion model.
文摘This paper studies the importance of corrections that account for the presence of walls on the forces act- ing on nanoparticles during their transport in microchannels.Theoretical and experimental investigations have reported anisotropic and hindered motion of nanoparticles near a microchannel wall. To investigate the influence of the near-wall effects, various conditions were examined. In particular, computer simu- lations were performed with and without the near-wall correction of forces. The corresponding capture efficiency and the average penetration of the captured nanoparticles were compared, and the importance of the near-wall corrections was assessed. Effects were evaluated for the nanoparticle diameter, the chan- nel width, the channel length, and the pressure gradient. The results indicate that the inclusion of wall effects is crucial for the analysis of nanoparticle transport in microchannels.
