Self-assembly of nano/micro-structured Fe3O4 microspheres among 3D rGO/CNTs hierarchical networks with superior lithium storage performances.

Nano/micro-structured Fe3O4 microspheres among three-dimensional (3D) reduced graphene oxide (rGO)/carbon nanotubes (CNTs) hierarchical networks (the ternary composite is denoted as rGCFs) have been synthesized using a facile, self-assembled and one-pot hydrothermal approach. The rGCFs composite exhibits superior lithium storage performances: initial discharge and charge capacities of 1452 and 1036 mAh g(-1), respectively, remarkable rate capability at current densities from 100 mA g(-1) to 10 A g(-1) and outstanding cycling performance up to 200 cycles. The highly enhanced electrochemical performances of rGCFs depend heavily on the robust 3D rGO/CNTs hierarchical networks, the stable nano/microstructures of active Fe3O4 microspheres and the positive synergistic effects of building components. The systematic structure characterizations and electrochemical investigations provide insightful understanding towards the relationship between structure/morphology and lithium storage performances, which may pave the way for the rational design of composite materials with desirable goals.

Bis(2-meth-oxy-6-{[2-(methyl-ammonio)eth-yl]imino-meth-yl}phenolato)thio-cyanato-zinc(II) thio-cyanate hemihydrate.

The title mononuclear zinc(II) complex, [Zn(C(11)H(16)N(2)O(2))(2)(NCS)]NCS·0.5H(2)O, consists of a complex cation, a thio-cyanate anion, and half of a water mol-ecule. The Zn(II) atom in the cation is five-coordinated by two imine N and two phenolate O atoms from two bidentate Schiff base ligands, and by one N atom of a thio-cyanate ligand, forming a distorted trigonal-bipyramidal geometry. The ammonio H atoms are involved in hydrogen bonding with the ligand O atoms and the solvent water molecules (site occupation factor 0.5), which partially determines the conformation of the ligands.

N'-(2-Hydr-oxy-3,5-diiodo-benzyl-idene)-2-methoxy-benzohydrazide.

The title compound, C(15)H(12)I(2)N(2)O(3), was synthesized by the condensation of equimolar amounts of 3,5-diiodo-salicylaldehyde and 2-methoxy-benzohydrazide in a methanol solution. There are two independent mol-ecules, A and B, in the asymmetric unit. The dihedral angle between the two benzene rings is 30.2 (2)° for mol-ecule A and 21.7 (2)° for mol-ecule B. There are intra-molecular O-H⋯N and N-H⋯O hydrogen bonds in each mol-ecule. The crystal studied was an inversion twin with a 0.59 (3):0.41 (3) domain ratio.

3-Hydr-oxy-N'-(2-hydroxy-benzyl-idene)benzohydrazide.

The title compound, C(14)H(12)N(2)O(3), was synthesized by the condensation of salicylaldehyde with 3-hydroxy-benzo-hydrazide. The dihedral angle between the two benzene rings is 12.4 (2)°. The 2-hydr-oxy group forms an intra-molecular O-H⋯N hydrogen bond with the imide N atom. Mol-ecules are linked through inter-molecular O-H⋯O and N-H⋯O hydrogen bonds into a two-dimensional polymeric structure parallel to the ab plane.

N'-(5-Bromo-2-hydr-oxy-3-methoxy-benzyl-idene)isonicotinohydrazide.

The title compound, C(14)H(12)BrN(3)O(3), was prepared by reaction of 5-bromo-3-methoxy-salicylaldehyde and isonicotinohydrazide in methanol. The mol-ecule is not planar and adopts a trans configuration with respect to the C=N bond. There is an intra-molecular O-H⋯N hydrogen bond in the mol-ecule. The dihedral angle between the benzene and pyridine rings is 12.2 (2)°. In the crystal structure, mol-ecules are linked through inter-molecular N-H⋯N hydrogen bonds, forming chains running along the c-axis direction.

(E)-N'-(2-Hydr-oxy-4-methoxy-benzyl-idene)isonicotinohydrazide monohydrate.

The title compound, C(14)H(13)N(3)O(3)·H(2)O, was prepared by the reaction of 4-methoxy-salicylaldehyde and isonicotinohydrazide in ethanol. The Schiff base mol-ecule is not planar and has an E configuration with respect to the methyl-idene unit. The dihedral angle between the benzene and pyridine rings is 36.8 (2)°. In the mol-ecule there is an intra-molecular O-H⋯N hydrogen bond involving the hydroxyl substituent and the N atom of the 2-hydr-oxy-4-methoxy-benzyl-idene unit. In the crystal, the mol-ecules are linked through inter-molecular O-H⋯O, O-H⋯N and N-H⋯O hydrogen bonds, forming layers parallel to the bc plane.

High-sensitivity paracetamol sensor based on Pd/graphene oxide nanocomposite as an enhanced electrochemical sensing platform.

Well-dispersed Pd nanoparticles were facilely anchored on graphene oxide (Pd/GO) via a one-pot chemical reduction of the Pd(2+) precursor without any surfactants and templates. The morphology and composition of the Pd/GO nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and energy dispersive analysis of X-ray (EDX). The stepwise fabrication process of the Pd/GO modified electrode and its electrochemical sensing performance towards paracetamol was evaluated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The experimental results indicate that the as-synthesized Pd nanoparticles are relatively uniform in size (5-10 nm) without large aggregation and uniformly distributed in the carbon matrix with the overall Pd content of 28.77 wt% in Pd/GO. Compared with the GO modified electrode, the Pd/GO modified electrode shows a better electrocatalytic activity to the oxidation of paracetamol with lower oxidation potential and larger peak current, so the Pd/GO nanocomposite can be used as an enhanced sensing platform for the electrochemical determination of paracetamol. The kinetic parameters of the paracetamol electro-oxidation at Pd/GO electrode were studied in detail, and the determination conditions were optimized. Under the optimal conditions, the oxidation peak current is linear to the paracetamol concentration in the ranges of 0.005-0.5 µM and 0.5-80.0 µM with a detection limit of 2.2 nM. Based on the high sensitivity and good selectivity of the Pd/GO modified electrode, the proposed method was successfully applied to the determination of paracetamol in commercial tablets and human urines, and the satisfactory results confirm the applicability of this sensor in practical analysis.

Approach on quantitative structure-activity relationship for design of a pH neutral carrier containing tertiary amino group.

The quantitative structure-activity relationship (QSAR) for neutral carriers used to prepare hydrogen ion sensors has been studied. A series of synthesized carrier compounds were taken as the training set. Five molecular structure parameters of the compounds were calculated by using CNDO/2 algorithm and used as feature variables in constructing QSAR model. The lower and upper limits of the linear pH response range were taken as the activity measure. The corresponding model equations were derived from the stepwise regression procedure. With the established QSAR model, a new pH carrier, (4-hydroxybenzyl) didodecylamine (XIII) was proposed and synthesized. The PVC membrane pH electrode based on carrier XIII with a wide pH linear response range of 2.0-12.5 was prepared. Having a theoretical Nernstian response slope of 57.2+/-0.3 mV/pH (n=5 at 25 degrees C) without a super-Nernstian phenomenon, the sensor had low resistance, short response time, high selectivity and good reproducibility. Moreover, the sensor was successfully applied to detecting the pH value of serum samples.