We have used aqueous dispersions of silver nanowires to prepare thin, flexible, transparent, conducting films. The nanowires are of length and diameter close to 6.5 µm and 85 nm respectively. At low thickness, the films consist of networks but appear to become bulk-like for mean film thicknesses above ~160 nm. These films can be very transparent with optical transmittance reaching as high as 92% for low thickness. The transmittance (550 nm) decreases with increasing thickness, consistent with an optical conductivity of 6472 S/m. The films are also very uniform; the transmittance varies spatially by typically <2%. The sheet resistance decreases with increasing thickness, falling below 1 Ω/ for thicknesses above 300 nm. The DC conductivity increases from 2×10 5 S/m for very thin films before saturating at 5×10 6 S/m for thicker films.Similarly, the ratio of DC to optical conductivity increases with increasing thickness from 25 for the thinnest films, saturating at ~500 for thicknesses above ~160 nm. We believe this is the highest conductivity ratio ever observed for nanostructured films and is matched only by doped metal oxide films. These nanowire films are electromechanically very robust, with all but the thinnest films showing no change in sheet resistance when flexed over >1000 cycles. Such results make these films ideal as replacements for indium tin oxide as transparent electrodes. We have prepared films with optical transmittance and sheet resistance of 85% and 13 Ω/ respectively. This is very close to that displayed by commercially available indium tin oxide.

Liquid phase exfoliation has become an important method for the production of large quantities of 2-dimensional nanosheets. This method is versatile, having been used to produce dozens of different 2D materials in a range of stabilizing liquids. The resultant liquidsuspended 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 practise 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:Here we demonstrate a simple method to exfoliate layered molybdenum trioxide (MoO3) crystallites to give multi-layer MoO3 nanosheets dispersed in solvents. Exfoliation is achieved by sonicating MoO3 powder in the presence of suitable solvents followed by centrifugation to remove undispersed material. This procedure works well in a range of solvents with Hildebrand solubility parameters close to 21 MPa 1/2 , and is consistent with the predictions of classical solubility theory. We have fully optimised this process and demonstrated methods to separate the resultant nanosheets by size. Raman spectroscopy suggests the exfoliation process does not damage the MoO3. This is supported by measurements which show reaggregated nanosheets to display very similar photoluminescence to bulk MoO3. However, the dispersed nanosheets had distinctly different photoluminescence indicating a decoupling of the monolayers on exfoliation. We have used liquid exfoliated MoO3 to prepare supercapacitor electrodes which had relatively low capacitance (~2 F/g at 10 mV/s), due to the low electrical conductivity of the MoO3.However, addition of carbon nanotubes beyond the percolation threshold yielded a 100-fold increase in capacitance. Some MoO3/nanotube composites displayed capacitances as high as 540 F/g at 0.1 mV/s. This is the first example of solvent exfoliation of a layered metal oxide.We believe this work opens the way to liquid exfoliation of a wide range of layered compounds leading to an array of new solution processed 2D materials.