Critical parameters in exfoliating graphite into graphene.

Dispersing graphite into few-layers graphene sheets (GS) in water is very appealing as an environmental-friendly, low-cost, low-energy method of obtaining graphene. Very high GS concentrations in water (0.7 mg mL(-1)) were obtained by optimizing the nature of dispersant and the type of ultra-sonic generator. We find that a multi-step sonication procedure involving both tip and bath sources considerably enhances the yield of exfoliated GS. Raman and transmission electron microscopy indicate few-layers graphene patches with typical size of ∼0.65 µm in one dimension and ∼0.35 µm in the other. These were further employed in combination with water-dispersed CNTs to fabricate conductive transparent electrodes for a molecularly-controlled solar-cell with an open-circuit voltage of 0.53 V.

Surprising Molecular Length Dependence in Conduction through a Hybrid Organic-Inorganic System.

A hybrid device made from gold nanoparticles connected by alkyldithiol molecules of different lengths was produced and its conduction properties were investigated for various lengths of the organic linker molecules. It was found that the conductivity increases with the length of the molecules. The surprising dependence of the conductivity on the molecules' length was explained by a model that takes into account the probability for forming continuous conductive paths for the different molecules.