Umar Hasan Khan

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If they could be easily exfoliated, layered materials would become a diverse source of two-dimensional crystals whose properties would be useful in applications ranging from electronics to energy storage. We show that layered compounds such as MoS(2), WS(2), MoSe(2), MoTe(2), TaSe(2), NbSe(2), NiTe(2), BN, and Bi(2)Te(3) can be efficiently dispersed in(More)
We have developed methods to exfoliate MoS 2 in large quantities in surfactant-water solutions. This method can be extended to a range of other layered compounds. The layered material tends to be exfoliated as relatively defect free flakes with lateral sizes of 100s of nm. in layered crystals and can be metals, semiconductors or insulators. [1] In addition,(More)
To progress from the laboratory to commercial applications, it will be necessary to develop industrially scalable methods to produce large quantities of defect-free graphene. Here we show that high-shear mixing of graphite in suitable stabilizing liquids results in large-scale exfoliation to give dispersions of graphene nanosheets. X-ray photoelectron(More)
Solvent exfoliation of inorganic layered compounds is likely to be important for a range of applications. However, this method generally gives dispersions of small nanosheets at low concentrations. Here we describe methods, based on sonication of powdered MoS 2 in the solvent N-methyl-pyrrolidone, to prepare dispersions with significantly increased lateral(More)
We have prepared composites of polyvinyl acetate (PVAc) reinforced with solution exfoliated graphene. We observe a 50% increase in stiffness and a 100% increase in tensile strength on addition of 0.1 vol % graphene compared to the pristine polymer. As PVAc is commonly used commercially as a glue, we have tested such composites as adhesives. The adhesive(More)
Monitoring of human bodily motion requires wearable sensors that can detect position, velocity and acceleration. They should be cheap, lightweight, mechanically compliant and display reasonable sensitivity at high strains and strain rates. No reported material has simultaneously demonstrated all the above requirements. Here we describe a simple method to(More)
In this work we have used melt-processing to mix liquid-exfoliated boron-nitride nanosheets with PET to produce composites for gas barrier applications. Sonication of h-BN powder, followed by centrifugation-based size-selection, was used to prepare suspensions of nanosheets with aspect ratio >1000. The solvent was removed to give a weakly aggregated powder(More)
Advances in lithium ion batteries would facilitate technological developments in areas from electrical vehicles to mobile communications. While two-dimensional systems like MoS2 are promising electrode materials due to their potentially high capacity, their poor rate capability and low cycle stability are severe handicaps. Here, we study the electrical,(More)
While liquid phase exfoliation can be used to produce nanosheets stabilized in polymer solutions, very little is known about the resultant nanosheet size, thickness or monolayer content. Here we use semi-quantitative spectroscopic metrics based on extinction, Raman and photoluminescence (PL) spectroscopy to investigate these parameters for WS2 nanosheets(More)