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Liquid phase exfoliation has become an important method for the production of large quantities of two-dimensional (2D) nanosheets. This method is versatile, having been used to produce dozens of different 2D materials in a range of stabilizing liquids. The resultant liquid-suspended nanosheets have been characterized in great detail and have been processed into a number of structures for a wide range of applications. This has led to a growing number of researchers adopting this method. As a result, best practice in terms of experimental procedure has evolved rapidly over recent years. As experimental complexity has increased, it has become more and more difficult to discuss the rational behind a chosen experimental procedure in full detail using standard "Methods" sections due to the frequent use of procedures developed in related prior reports. This can make it difficult to reproduce complex procedures and acts as a barrier to new researchers entering the field. To address this shortcoming, here we describe in detail the experimental methods and best practice used in our group when producing liquid exfoliated nanosheets. [ABSTRACT FROM AUTHOR]

In order to fulfill their potentialfor applications, it will benecessary to develop large-scale production methods for two-dimensional(2D) inorganic nanosheets. Here we demonstrate the large-scale shear-exfoliationof molybdenum disulfide nanosheets in aqueous surfactant solutionusing a kitchen blender. Using standard procedures, we measure howthe MoS2concentration and production rate scale with processingparameters. However, we also use recently developed methods basedon optical spectroscopy to simultaneously measure both nanosheet lateralsize and thickness, allowing us to also study the dependence of nanosheetdimensions on processing parameters. We found the nanosheet concentrationand production rates to depend sensitively on the mixing parameters(the MoS2concentration, Ci; the mixing time, t; the liquid volume, V; and the rotor speed, N). By optimizingmixing parameters, we achieved concentrations and production ratesas high as 0.4 mg/mL and 1.3 mg/min, respectively. Conversely, thenanosheet size and thickness were largely invariant with these parameters.The nanosheet concentration is also extremely sensitive to the surfactantconcentration. However, more interestingly the nanosheet lateral sizeand thickness also varied strongly with the surfactant concentration.This allows the mean nanosheet dimensions to be controlled duringshear exfoliation at least in the range ∼40–220 nm forlength and ∼2–12 layers for thickness. We demonstratethe importance of this by showing that the MoS2nanosheetsprepared using different surfactant concentrations, and so displayingdifferent nanosheets sizes, perform differently when used as hydrogenevolution catalysts. We find the nanosheets produced using high surfactantconcentrations, which gives smaller flake sizes, perform significantlybetter, consistent with catalysis occurring at nanosheet edges. Finally,we also demonstrate that shear exfoliation using a kitchen blenderis not limited to MoS2but can also be achieved for boronnitride and tungsten disulfide. [ABSTRACT FROM AUTHOR]

Here,we demonstrate a simple method to exfoliate layered molybdenumtrioxide (MoO3) crystallites to give multilayer MoO3nanosheets dispersed in solvents. Exfoliation is achievedby sonicating MoO3powder in the presence of suitable solventsfollowed by centrifugation to remove undispersed material. This procedureworks well in a range of solvents with Hildebrand solubility parametersclose to 21 MPa1/2and is consistent with the predictionsof classical solubility theory. We have fully optimized this processand demonstrated methods to separate the resultant nanosheets by size.Raman spectroscopy suggests the exfoliation process does not damagethe MoO3. This is supported by measurements showing thatthe reaggregated nanosheets display very similar photoluminescenceto bulk MoO3. However, the dispersed nanosheets had distinctlydifferent photoluminescence, indicating a decoupling of the monolayerson exfoliation. We have used liquid-exfoliated MoO3toprepare supercapacitor electrodes that have relatively low capacitance(∼2 F/g at 10 mV/s) because of the low electrical conductivityof the MoO3. However, addition of carbon nanotubes beyondthe percolation threshold yielded a 100-fold increase in capacitance.Some MoO3/nanotube composites displayed a capacitance ashigh as 540 F/g at 0.1 mV/s. This is the first example of solventexfoliation of a layered metal oxide. We believe this work opens theway to liquid exfoliation of a wide range of layered compounds, leadingto an array of new solution-processed 2D materials. [ABSTRACT FROM AUTHOR]