Hexadentate ß-Dicarbonyl(bis-catecholamine) Ligands for Efficient Uranyl Cation Decorporation: Thermodynamic and Antioxidant Activity Studies.

The special linear dioxo cation structure of the uranyl cation, which relegates ligand coordination to an equatorial plane perpendicular to the O═U═O vector, poses an unusual challenge for the rational design of efficient chelating agents. Therefore, the planar hexadentate ligand rational design employed in this work incorporates two bidentate catecholamine (CAM) chelating moieties and a flexible linker with a ß-dicarbonyl chelating moiety (ß-dicarbonyl(CAM)2 ligands). The solution thermodynamics of ß-dicarbonyl(CAM)2 with a uranyl cation was investigated by potentiometric and spectrophotometric titrations. The results demonstrated that the pUO22+ values are significantly higher than for the previously reported TMA(2Li-1,2-HOPO)2, and efficient chelation of the uranyl cation was realized by the planar hexadentate ß-dicarbonyl(CAM)2. The efficient chelating ability of ß-dicarbonyl(CAM)2 was attributed to the presence of the more flexible ß-dicarbonyl chelating linker and planar hexadentate structure, which favors the geometric arrangement between ligand and uranyl coordinative preference. Meanwhile, ß-dicarbonyl(CAM)2 also exhibits higher antiradical efficiency in comparison to butylated hydroxyanisole. These results indicated that ß-dicarbonyl(CAM)2 has potential application prospects as a chelating agent for efficient chelation of a uranyl cation.

Ultrasmall Abundant Metal-Based Clusters as Oxygen-Evolving Catalysts.

The oxygen evolution reaction is a crucial step in water electrolysis to develop clean and renewable energy. Although noble metal-based catalysts have demonstrated high activity for the oxygen evolution reaction, their application is limited by their high cost and low availability. Here we report the use of a molecule-to-cluster strategy for preparing ultrasmall trimetallic clusters by using the polyoxometalate molecule as a precursor. Ultrafine (0.8 nm) transition-metal clusters with controllable chemical composition are obtained. The transition-metal clusters enable highly efficient oxygen evolution through water electrolysis in alkaline media, manifested by an overpotential of 192 mV at 10 mA cm-2, a low Tafel slope of 36 mV dec-1, and long-term stability for 30 h of electrolysis. We note, however, that besides the excellent performance as an oxygen evolution catalyst, our molecule-to-cluster strategy provides a means to achieve well-defined transition-metal clusters in the subnanometer regime, which potentially can have an impact on several other applications.

New tris(dopamine) derivative as an iron chelator. Synthesis, solution thermodynamic stability, and antioxidant research.

A new tris(dopamine) derivative, containing three dopamine chelate moieties which were attached to a trimesic acid molecular scaffold, has been prepared and fully characterized by NMR, FTIR and HRMS. The solution thermodynamic stability of the chelator with Fe(III), Mg(II), Zn(II) and Fe(II) ions was investigated. Results demonstrated that the chelator exhibited effective binding ability and improved selectivity to Fe(III) ion. The chelator possessed affinity similar to that of diethylenetriaminepentaacetic acid chelator for Fe(III) ion. The high affinity could be attributed to the favorable geometric arrangement between the chelator and Fe(III) ion coordination preference. The chelator also exhibited high antioxidant activity and nontoxicity to neuron-like rat pheochromocytoma cells. Hence, the chelator could be used as chelating agent for iron overload situations without depleting essential metal ions, such as Mg(II) and Zn(II) ions.

Arbitrary-Shaped Graphene-Based Planar Sandwich Supercapacitors on One Substrate with Enhanced Flexibility and Integration.

The emerging smart power source-unitized electronics represent an utmost innovative paradigm requiring dramatic alteration from materials to device assembly and integration. However, traditional power sources with huge bottlenecks on the design and performance cannot keep pace with the revolutionized progress of shape-confirmable integrated circuits. Here, we demonstrate a versatile printable technology to fabricate arbitrary-shaped, printable graphene-based planar sandwich supercapacitors based on the layer-structured film of electrochemically exfoliated graphene as two electrodes and nanosized graphene oxide (lateral size of 100 nm) as a separator on one substrate. These monolithic planar supercapacitors not only possess arbitrary shapes, e.g., rectangle, hollow-square, "A" letter, "1" and "2" numbers, circle, and junction-wire shape, but also exhibit outstanding performance (∼280 F cm-3), excellent flexibility (no capacitance degradation under different bending states), and applicable scalability, which are far beyond those achieved by conventional technologies. More notably, such planar supercapacitors with superior integration can be readily interconnected in parallel and series, without use of metal interconnects and contacts, to modulate the output current and voltage of modular power sources for designable integrated circuits in various shapes and sizes.

A multiple gadolinium complex decorated fullerene as a highly sensitive T(1) contrast agent.

We report a simple strategy to construct a multiple gadolinium complex decorated fullerene (CGDn) as an enhanced T1 contrast agent. The CGDn exhibits much higher T1 relaxivity (∼49.7 mM(-1) s(-1)) than individual Gd-DOTA, and shows excellent T1 contrast enhancement ability both in vitro and in vivo.

Ultra-bright alkylated graphene quantum dots.

Highly efficient and stable photoluminescence (PL) are urgently desired for graphene quantum dots (GQDs) to facilitate their prospective applications as optical materials. Here, we report the facile and straightforward synthesis of alkylated graphene quantum dots (AGQDs) via the solvothermal reaction of propagatively alkylated graphene sheets (PAGenes). In contrast to most GQDs reported so far, the synthesized AGQDs process pH-independent and ultra-bright PL with a relative quantum yield of up to 65%. Structural and chemical composition characterization demonstrated that the synthesized AGQDs are nearly oxygen-defect-free with alkyl groups decorated on edges and basal plane, which may contribute to their greatly improved pH tolerance and high quantum efficiency. The photocatalytic performance of AGQDs-P25 nanocomposites was evaluated by the degradation of Rhodamine B under visible light. The photocatalytic rate is ca. 5.9 times higher than that of pure P25, indicating that AGQDs could harness the visible spectrum of sunlight for energy conversion or environmental therapy.