Green luminescent, graphene quantum dots (GQDs) with a uniform size of 3, 5, and 8.2(±0.3) nm in diameter were prepared electrochemically from MWCNTs in propylene carbonate by using LiClO(4) at 90 °C, whereas similar particles of 23(±2) nm were obtained at 30 °C under identical conditions. Both these sets of GQDs displayed a remarkable quantum efficiency of 6.3 and 5.1%, respectively. This method offers a novel strategy to synthesise size-tunable GQDs as evidenced by multiple characterisation techniques like transmission and scanning electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray diffraction (XRD). Photoluminescence of these GQDs can be tailored by size variation through a systematic change in key process parameters, like diameter of carbon nanotube, electric field, concentration of supporting electrolyte and temperature. GQDs are promising candidates for a variety of applications, such as biomarkers, nanoelectronic devices and chemosensors due to their unique features, like high photostability, biocompatibility, nontoxicity and tunable solubility in water.

Size-controlled synthesis of luminescent quantum dots of MoS2 (≤2 layers) with narrow size distribution, ranging from 2.5 to 6 nm, from their bulk material using a unique electrochemical etching of bulk MoS2 is demonstrated. Excitation-dependent photoluminescence emission is observed in the MoS2 QDs. "As-synthesized" MoS2 QDs also exhibit excellent electrocatalytic activity towards hydrogen evolution reactions.

Polymer electrolyte membrane fuel cells (PEMFCs) continue to receive extensive attention because of their utility as a clean energy source for automotive, stationary, and portable applications.[1] The proton conductivity of the polymer electrolyte membrane (PEM) is one of the key factors limiting the performance of PEMFCs, which depends on the relative humidity, and controls the cost and durability. [2] Consequently, an improvement in the proton conductivity of the electrolyte membrane even by an order of magnitude could change the performance of fuel cells dramatically. [3] Currently, Nafion-based membranes are widely used as the PEM in fuel cells that operate from 60 to 80 8C. Although these membranes show good proton conductivities from 0.1 to 0.01 S cm À1 in a humid environment, they have many limitations, such as: 1) dependence on water for conductivity; 2) high methanol permeability; 3) a tendency to disintegrate in the presence of hydroxyl radicals, an intermediate in the cathode reaction; and 4) moderate mechanical and chemical stability.To improve the performance of electrolytes used in PEMFCs, two different approaches have been adopted. First is the synthesis of alternative membranes that could operate at higher temperatures without the need for humidification. The phosphoric acid doped polybenzimidazole membrane is a widely exploited example in this category. [4,5]