Measuring and Controlling The Dimensions of Liquid-Exfoliated Nanosheets

Liquid phase exfoliation (LPE) has become an important production technique for colloidal dispersions and solution-processeable inks of a range of materials due to its versatility and applicability to a broad range of material classes. While mass production is possible, samples are inherently polydisperse and aspect ratios of lateral size/thickness are limited due to scission and delamination occurring simultaneously.[1]<br/>In this talk, I will first discuss our state-of-the-art in measuring nanosheet dimensions through atomic force microscopy, highlighting the challenges associated with this measurement. I will then present our recent in-depth analysis of nanosheet dimensions of WS₂ samples produced by tip sonication in both aqueous surfactant solution and the organic solvent N-methyl-2-pyrrolidone in conjunction with the effect of the liquid environment in centrifugation-based size selection. This data shows that the solvent not only has an impact on the outcome of the centrifugation, but also during sonication with aqueous surfactant based nanosheets having slightly higher length-thickness aspect ratios.<br/>In the second part of the talk, I will demonstrate that it is possible to derive and validate an accurate equation of motion of nanosheets in the centrifugal field accounting for nanosheet dimensionality by implementing length/thickness and length/width aspect ratios that are widely constant for a given material produced in LPE. We show that this equation allows us to predict the nanosheet dimensions in sediment and supernatant after centrifugation.<br/><br/><b>References </b><br/>[1] <i>ACS Nano</i> 2019, 13, 6, 7050–7061