Novel double layer lanthanide metal-organic networks for sensing applications.

A trifunctional aromatic building block (H2L) containing three different types of functional groups (carboxyl C([double bond, length as m-dash]O)OH, aldehyde C([double bond, length as m-dash]O)H, and O-ether) was applied for the hydrothermal synthesis of two novel lanthanide 2D coordination polymers [Ln(µ-HL)(µ3-L)(phen)]n {Ln = Tb (1) and Eu (2); H2L = 5-methoxy-(4-benzaldehyde)-1,3-benzene dicarboxylic acid; phen = 1,10-phenanthroline}. Both compounds 1 and 2 are isostructural and reveal very complicated 2D metal-organic double layers with the 3,4L27 topology. The presence of free aldehyde groups positioned outside of the double layers opens up a possibility of using them as functional groups toward sensing amines and small organic molecules. The fluorescence measurements for the Tb derivative 1 reveal that it acts as an efficient fluorescence sensor for p-phenylenediamine, benzidine and acetone molecules via a luminescence quenching effect. A similar sensing behavior was observed for the Eu compound 2. Moreover, thin-films of 1-PEG on glass (1-PEG-glass thin-film material) were fabricated and investigated for the detection of amine vapors.

Few-Layered Mo(1-x)WxS2 Hollow Nanospheres on Ni3S2 Nanorod Heterostructure as Robust Electrocatalysts for Overall Water Splitting.

Owing to unique optical, electronic, and catalytic properties, MoS2 have received increasing interest in electrochemical water splitting. Herein, few-layered Mo(1-x)WxS2 hollow nanospheres-modified Ni3S2 heterostructures are prepared through a facile hydrothermal method to further enhance the electrocatalytic performance of MoS2. The doping of W element optimizes the electronic structure of MoS2@Ni3S2 thus improving the conductivity and charge-transfer ability of MoS2@Ni3S2. In addition, benefitting from the few-layered hollow structure of Mo(1-x)WxS2, the strong electronic interactions between Mo(1-x)WxS2 and Ni3S2 and the hierarchical structure of one-dimensional nanorods and three-dimensional Ni foam, massive active sites and fast ion and charge transportation are obtained. As a result, the optimized Mo(1-x)WxS2@Ni3S2 heterostructure (Mo-W-S-2@Ni3S2) achieves an extremely low overpotential of 98 mV for hydrogen evolution reaction and 285 mV for oxygen evolution reaction at 10 mA cm-2 in alkaline electrolyte. Particularly, using Mo-W-S-2@Ni3S2 heterostructure as a bifunctional electrocatalyst, a cell voltage of 1.62 V is required to deliver a 10 mA cm-2 water splitting current density. In addition, the electrode can be maintained at 10 mA cm-2 for at least 50 h, indicating the excellent stability of Mo-W-S-2@Ni3S2 heterostructure. Therefore, this development demonstrates an effective and feasible strategy to prepare highly efficient bifunctional electrocatalysts for overall water splitting.

A highly sensitive non-enzymatic glucose sensor based on bimetallic Cu-Ag superstructures.

Bimetallic Cu-Ag superstructures were successfully fabricated for the first time by using the natural leaves as reducing agent through a facile one-step hydrothermal process. Morphology, structure and composition of the Cu-Ag superstructures were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES), respectively. The results reveal that the Cu-Ag superstructure is bimetallic nanocomposite constructed by nanoparticles with low Ag content and shows a rough surface and porous flexural algae-like microstructure. By using a three-dimensional nickel foam as the scaffold, a novel non-enzymatic glucose sensor based on Cu-Ag nanocomposites has been fabricated and applied to non-enzymatic glucose detection. The as-prepared Cu-Ag nanocomposites based glucose sensor displays distinctly enhanced electrocatalytic activity compared to those obtained with pure Cu nanomaterials prepared with a similar procedure, revealing a synergistic effect of the matrix Cu and the doped Ag. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy indicate that the Cu-Ag superstructures based glucose sensor displays a fascinating sensitivity up to 7745.7 µA mM(-1) cm(-2), outstanding detection limit of 0.08 µM and fast amperometric response (<2 s) for glucose detection. Furthermore, the sensor also exhibits significant selectivity, excellent stability and reproducibility, as well as attractive feasibility for real sample analysis. Because of its excellent electrochemical performance, low cost and easy preparation, this novel electrode material is a promising candidate in the development of non-enzymatic glucose sensor.

A metal-decorated nickel foam-inducing regulatable manganese dioxide nanosheet array architecture for high-performance supercapacitor applications.

Three dimensional manganese dioxide/Pt/nickel foam (shortened to MnPtNF) hybrid electrodes were prepared by double-pulse polarization and potentiostatic deposition technologies for supercapacitor applications. The decoration of Pt nanoparticles onto nickel foam varies the nucleation mechanism of the manganese dioxide species, inducing the formation of manganese dioxide nanosheets. Additionally, controlling the size of the Pt nanoparticles leads to modulated nanosheet architecture and electrochemical properties of the manganese dioxide electrode, as revealed by XRD, Raman spectra, SEM, TEM, cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The nanosheet architecture of the MnPtNF electrode favors the transportation of electrons and ions, which results in the enhanced electrochemical properties. Importantly, the optimized MnPtNF electrode obtains a maximum specific capacitance of 1222 F g(-1) at 5 A g(-1) (89% of the theoretical specific capacitance of MnO2) and 600 F g(-1) at 100 A g(-1). Moreover, the presence of Pt nanoparticles in the MnO2 electrode effectively improves its cycling stability, which is confirmed by the increase of the specific capacitance retention from 14.7% to 90% after 600 cycles.

Synthesis and Magnetic Properties of Nearly Monodisperse CoFe2O4Nanoparticles Through a Simple Hydrothermal Condition.

Nearly monodisperse cobalt ferrite (CoFe2O4) nanoparticles without any size-selection process have been prepared through an alluring method in an oleylamine/ethanol/water system. Well-defined nanospheres with an average size of 5.5 nm have been synthesized using metal chloride as the law materials and oleic amine as the capping agent, through a general liquid-solid-solution (LSS) process. Magnetic measurement indicates that the particles exhibit a very high coercivity at 10 K and perform superparamagnetism at room temperature which is further illuminated by ZFC/FC curves. These superparamagnetic cobalt ferrite nanomaterials are considered to have potential application in the fields of biomedicine. The synthesis method is possible to be a general approach for the preparation of other pure binary and ternary compounds.

Electrodeposited nickel hydroxide on nickel foam with ultrahigh capacitance.

Electrodeposited Ni(OH)(2) on nickel foam with porous and 3D nanostructures has ultrahigh capacitance in the potential range -0.05-0.45 V, and a maximum specific capacitance as high as 3152 F g(-1) can be achieved in 3% KOH solution at a charge/discharge current density of 4 A g(-1).

Effects of annealing temperature on magnetic property and structure of amorphous Co49Pt51 alloy nanowire arrays prepared by direct-current electrodeposition.

Co49Pt51 nanowire arrays with an average diameter of 35 nm and lengths up to several micrometers were grown in an ordered porous anodic aluminum oxide (AAO) template using direct-current electrodeposition. The as-deposited samples were annealed at 100, 200, 300, 400, 500, 600, and 700 degrees C, respectively. The temperature dependence of the magnetic property of the Co49Pt51 nanowire arrays associated with the microstructure was analyzed by X-ray diffraction and a vibrating sample magnetometer. Magnetic measurements show that the samples both as-prepared and annealed at low temperatures have excellent perpendicular anisotropy. The perpendicular coercivity (Hc(perpendicular)) of Co49Pt51 alloy nanowire arrays increases dramatically as the annealing temperature (T(A)) rises, reaches a maximum(Hc(perpendicular) = 2770 Oe) at 400 degrees C, and then decreases sharply as T(A) rises further. This phenomenon should be attributed to the special structure of the nanowire arrays/AAO, and the microstructure factors significantly change during the annealing process.