Strongly fluorescent graphene quantum dots (GQDs) have been prepared by one-step solvothermal method with PL quantum yield as high as 11.4%. The GQDs have high stability and can be dissolved in most polar solvents. Because of fine biocompatibility and low toxicity, GQDs are demonstrated to be excellent bioimaging agents.

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The recent boom in multifunction portable electronic equipments requires the development of compact and miniaturized electronic circuits with high efficiencies, low costs and long lasting time. For the operation of most line-powered electronics, alternating current (ac) line-filters are used to attenuate the leftover ac ripples on direct current (dc) voltage busses. Today, aluminum electrolytic capacitors (AECs) are widely applied for this purpose. However, they are usually the largest components in electronic circuits. Replacing AECs by more compact capacitors will have an immense impact on future electronic devices. Here, we report a double-layer capacitor based on three-dimensional (3D) interpenetrating graphene electrodes fabricated by electrochemical reduction of graphene oxide (ErGO-DLC). At 120-hertz, the ErGO-DLC exhibited a phase angle of −84 degrees, a specific capacitance of 283 microfaradays per centimeter square and a resistor-capacitor (RC) time constant of 1.35 milliseconds, making it capable of replacing AECs for the application of 120-hertz filtering.

Catalysts for oxygen reduction reaction (ORR) are crucial in fuel cells. Developing metal-free catalyst with high activity at low-cost and high-volume production remains a great challenge. Here, we report a novel type of nitrogen-doped nanoporous carbon nanosheets derived from a conveniently available and accessible plant, Typha orientalis. The nanosheets have high surface area (the highest surface area can be 898 m 2 g À1 ), abundant micropores and high content of nitrogen (highest content of 9.1 at.%). The typical product exhibits an unexpected, surprisingly high ORR activity. In alkaline media, it exhibits similar catalytic activity but superior tolerance to methanol as compared to commercial 20% Pt/C. In acidic media as well, it shows excellent catalytic ability, stability and tolerance to methanol. This low-cost, simple and readily scalable approach provides a straightforward route to synthesize excellent electrocatalysts directly from biomass, which may find broad applications in the fields of supercapacitors, sensors, and gas uptake. Broader contextElectrocatalysts for the oxygen reduction reaction (ORR) are crucial in fuel cells and other electrochemical devices. It is highly challenging but extremely desirable to develop inexpensive metal-free catalysts, with high activity and with the capability of high-volume production of high yields for fuel cells. In this work, we have reported a novel type of nitrogen-doped nanoporous carbon nanosheets, which has been derived for the rst time from a conveniently available and accessible plant Typha orientalis. The materials have a high surface area, abundant micropores and a high content of nitrogen. A typical product exhibits an unexpected, surprisingly high ORR activity. In alkaline media, it exhibits similar catalytic activity but superior tolerance to methanol than commercial 20% Pt/C. The high activities can be ascribed to the large surface area with abundant micropores, the high content of pyridine and pyrrolic-like nitrogen atoms within the materials and the 3D interpenetrated network structure produced by numerous carbon nanosheets. The products were prepared using the plant Typha orientalis as carbon source and without using any organic solvent. The synthesis strategy is simple, low-cost, and can be easily scaled up for production.

Graphene has a unique atom-thick two-dimensional structure and excellent properties, making it attractive for a variety of electrochemical applications, including electrosynthesis, electrochemical sensors or electrocatalysis, and energy conversion and storage. However, the electrochemistry of single-layer graphene has not yet been well understood, possibly due to the technical difficulties in handling individual graphene sheet. Here, we report the electrochemical behavior at single-layer graphene-based electrodes, comparing the basal plane of graphene to its edge. The graphene edge showed 4 orders of magnitude higher specific capacitance, much faster electron transfer rate and stronger electrocatalytic activity than those of graphene basal plane. A convergent diffusion effect was observed at the sub-nanometer thick graphene edge-electrode to accelerate the electrochemical reactions. Coupling with the high conductivity of a high-quality graphene basal plane, graphene edge is an ideal electrode for electrocatalysis and for the storage of capacitive charges.

Covalently grafting reduced graphene oxide (rGO) sheets with sulfophenyl or ethylenediamine groups can produce chemically modified graphene (CMG) for fabricating high-performance gas sensors. The NO(2) sensors based on these CMGs exhibit sensitivities 4 to 16 times higher than that of a sensor based on rGO. They also show excellent selectivity and repeatability without the aid of UV-light or thermal treatment.

Ni–Fe layered double hydroxide nanoplates loaded on a three-dimensional electrochemically reduced graphene oxide electrode for efficient water oxidation, exhibiting higher activity, kinetics, and stability than those of the IrO2catalyst.

A fibre-shaped solid electrochemical capacitor based on electrochemically reduced graphene oxide has been fabricated, exhibiting high specific capacitance and rate capability, long cycling life and attractive flexibility.