A green and facile route for constructing flower-shaped TiO2 nanocrystals assembled on graphene oxide sheets for enhanced photocatalytic activity.

We have demonstrated an environmentally friendly in situ assembly method for the preparation of novel three-dimensional TiO2/graphene oxide (TiO2/GO) nanostructures with favorable flower-shaped architectures. Very little information on such a morphology of TiO2/GO nanostructures is available in the literature. The as-synthesized sample was characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption-desorption measurements and Raman spectroscopy. Also the TiO2/GO composites exhibited enhanced photocatalytic properties.

Environment-friendly biomimetic synthesis of TiO2 nanomaterials for photocatalytic application.

We have demonstrated an environment-friendly biomimetic synthesis method for the preparation of TiO(2) nanomaterials with different crystal phases and morphologies. This is the first time that it has been found that the crystal phase of TiO(2) can be controlled just by using different biotemplates, and cannot be changed by calcination up to 750 °C. In our experiment, anatase TiO(2) was obtained by using yeast and albumen templates, while rutile TiO(2) was formed by using dandelion pollen as the template.

Diffusion and kinetics of solvent-free reaction between molecular crystals by time-resolved powder UV-Vis reflection spectrum.

Traditionally, chemical reaction between solids has been considered to typically occur on a geological time scale without the benefit of high temperature, due to diffusion block in the solids. However, recent advancements have revealed that many solvent-free reactions between molecular crystals can quickly occur at room or near-room temperature. These reactions have raised a novel scientific question as to how the reactive species can overcome the diffusion-controlled kinetic limitations under such moderate conditions. From time-resolved powder UV-vis reflection spectra and optical micrographs with the reaction between dimethylglyoxime and Ni(Ac) 2.4H 2O and the reaction between hexamethylenetetramine and CoCl 2.6H 2O as models, we found that the solvent-free reaction really occurs at an intermediate state between the solid state and the liquid state. Formation of the liquid phase provides a convenient approach to diffusion of reactive species, whereas formation of a solid product layer hampered the transfer of reactive species. Both factors led to a broad reactive rate band in the long reaction region. The results have explained the diffusion mechanism of the fast reaction between the molecular crystals under moderate conditions.

Sulfonated graphene oxide as an adsorbent for removal of Pb2+ and methylene blue.

One of the major challenges encountered in some conventional nano-structured adsorbents such as graphene oxide (GO) and graphene is the structural limits including serious aggregation and hydrophilic surface in water. And the sulfanilic acid functionalized graphene oxide (SGO) can powerfully attract positively charged pollutants. Therefore, the SGO served as an adsorbent to remove dyes and toxic metal ions from aqueous solution were intensively investigated. At the same time the reduced sulfonated graphene oxide (rSGO), reduced graphene oxide (rGO), and graphene oxide (GO) were performed as the comparative samples. The results showed that the maximum adsorption capacities of SGO were 2530 mg/g for methylene blue and 415 mg/g for Pb2+, which was much higher than that of the contrast samples and adsorbents reported in literatures. The adsorption of SGO was investigated systematically including the saturated adsorption capacities, isotherm, and kinetic adsorption process. The SGO displayed high adsorption efficiency and superior adsorption capacity toward metal ions and dyes, which is mainly attribute to the good dispersibility and the multiple adsorption sites of SGO. These results are promising not only providing effective adsorbing heavy metal ions and organic dyes, but also gaining insights into adsorption mechanism of graphene materials.

Cobalt and cobalt oxides N-codoped porous carbon derived from metal-organic framework as bifunctional catalyst for oxygen reduction and oxygen evolution reactions.

Metal-organic framework (MOF)-derived transition metal/metal oxide-carbon hybrids are promising cost-effective electrocatalysts to replace noble metal catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, Co@CoO@Co3O4-N/C was prepared by two-step thermal treatment of Co-MOF ([Co(INA)2]·0.5EtOH) (INA: isonicotinic acid). Firstly, Co-MOF, as precursor, was pyrolyzed at different temperatures in N2 atmosphere to obtain Co-N/C-T (T = 700, 800, 900 °C) materials among which Co-N/C-800 shows remarkably high ORR activity. After oxidation treatment, Co-N/C-800 is transformed into Co@CoO@Co3O4-N/C which exhibits enhanced electrocatalytic activities for both ORR and OER. The as-obtained Co@CoO@Co3O4-N/C has more positive onset potential (-0.136 V vs. Ag/AgCl) and higher limit current density (4.9 mA cm-2) than Co-N/C-800 (-0.143 V vs. Ag/AgCl and 3.9 mA cm-2), as well as better tolerance to methanol and stability (80.0%) than those of Pt/C (63.2%) for ORR. Co@CoO@Co3O4-N/C also displays outstanding OER performances, with lower overpotential (450 mV) than that of Co-N/C-800 (492 mV) at a current density of 10 mA cm-2. The excellent electrochemical performance of Co@CoO@Co3O4-N/C can be ascribed to uniformly dispersed Co-Nx active sites, strong synergistic effects between N-doped carbon support and Co@CoO@Co3O4 as well as ordered mesoporous structure, boosting mass transfer and accelerating electrocatalytic reaction.

Lgf-YL-9 induces apoptosis in human epidermoid carcinoma KB cells and multidrug resistant KBv200 cells via reactive oxygen species-independent mitochondrial pathway.

Pyrazolon derivatives were reported to have cytotoxicity to some tumour cells. In the present study, we investigated the effect of Lgf-YL-9 on cytotoxicity and cell apoptosis in human epidermoid carcinoma drug-sensitive parental KB cells and multidrug resistant (MDR) KBv200 cells. Lgf-YL-9 exhibited potent cytotoxicity not only to KB cells but also to KBv200 cells, and the IC(50) were 3.81 and 3.45 microg/mL in KB cells and KBv200 cells, respectively. Importantly, Lgf-YL-9 effectively inhibited tumour growth of KB cell xenografts in nude mice. Lgf-YL-9-induced cell apoptosis was confirmed by chromatin condensation, DNA fragmentation, Annexin-V and propidium iodide (PI) double-staining assay and poly(ADP-ribose) polymerase (PARP) cleavage. Furthermore, Lgf-YL-9-mediated apoptosis in KB cells and KBv200 cells was accompanied by the loss of mitochondrial membrane potential (DeltaPsi(m)), the release of cytochrome c, and the activation of caspases-3, -7, and -9, but not by intercalating to DNA. Although Lgf-YL-9-induced apoptosis was associated with the decrease of DeltaPsi(m), reactive oxygen species (ROS) reduction was interestingly observed in both cell lines. The data suggest that Lgf-YL-9 has similar cytotoxicity to drug-sensitive parental KB cells and MDR KBv200 cells. Lgf-YL-9-induced apoptosis is involved in a new ROS-independent mitochondrial dysfunction pathway, but not in intercalating to DNA.

Interaction between nitrogen and sulfur in co-doped graphene and synergetic effect in supercapacitor.

The co-doping of graphene with nitrogen and sulfur was investigated aiming at understanding their interactions with the presence of oxygen in graphene. The co-doped graphene (NS-G) was synthesized via a one-pot hydrothermal route using graphene oxide as starting material and L-cysteine, an amino acid containing both N and S, as the doping agent. The obtained NS-G with a three-dimensional hierarchical structure containing both macropores and mesopores exhibited excellent mechanical stabilities under both wet and dry conditions. As compared to N or S singly doped graphene, the co-doped sample contains significantly higher concentrations of N and S species especially pyrollic N groups. The co-doped sample considerably outperformed the singly doped samples when used as free-standing electrode in supercapacitors due to enhanced pseudocapacitance. The simultaneous incorporation of S and N species with the presence of oxygen significantly modified the surface chemistry of carbon leading to considerably higher doping levels, although directly bonding between N and S is neither likely nor detected. Hence, the synergetic effect between N and S occurred through carbon atoms in neighboring hexagonal rings in a graphene sheet.

Syntheses, structure diversity and properties of complexes with 4-acyl pyrazolone salicylidene hydrazide derivatives.

Five new complexes [Zn(HL(1))(OAc)(CH(3)CH(2)OH)] (1), [Cd(2)(HL(1))(2)(OAc)(2)(CH(3)CH(2)OH)(2)] (2), [Cu(6)(L(1))(6)] (3) (H(2)L(1) = N-(1-phenyl-3-phenmethyl-4-phenylethylene-pyrazolone-5)-salicylidene hydrazide, OAc = acetate anion), {[Zn(L(2))(CH(3)OH)]·(CH(3)OH)}(n) (4) (H(2)L(2) = N-(1-phenyl-3-phenmethyl-4-ethylene-pyrazolone-5)-salicylidene hydrazine), [Cu(L(3))](n) (5) (H(2)L(3) = N-(1-phenyl-3-phenmethyl-4-benzylidene-pyrazolone-5)-salicylidene hydrazide) have been synthesized and characterized by chemical and spectroscopic techniques. Complexes 1-3 feature mononuclear, dinuclear and rare hexanuclear structures, respectively. The different molecular structures and different coordination modes of H(2)L(1) in complexes 1-3 indicate that the coordination geometry of the metal atoms have a remarkable impact on the structure of these complexes. Complexes 4 and 5 have 1D chain structures. Comparing complexes 4 and 1 or 5 and 3, it can be concluded that the substituents at the 4-position of the ligands have a significant effect on the structure of the resulting complexes. It is worth noting that N(2) atoms of the pyrazolyl ring play an important role in building the two-dimensional networks for 1 and 2 by hydrogen bonds, a novel hexanuclear unit for 3, and the 1D polymer chain for 4 and 5 by bridging bonds. Complexes 1, 2 and 4 show strong fluorescent behavior in the solid state. The magnetic property of complex 3 shows the presence of intramolecular antiferromagnetic exchange (J = -8.63 cm(-1)).

Tuning size and magnetic thermal hysteresis in a new near room temperature spin crossover compound.

A mononuclear spin crossover compound Fe(AP-Mesal)2, which exhibits spin transitions near room temperature and light induced excited spin state trapping (LIESST) effects at low temperature, was synthesized and substructured in the form of micro- and nanoscaled particles. A thermal hysteresis loop was detected with particle size reduction to microscale and nanoscale.

Ab initio/DFT and AIM studies on dual hydrogen-bonded complexes of 2-hydroxypyridine/2-pyridone tautomerism.

The second-order Møller-Plesset (MP2) and density functional theory (DFT) calculations have been carried out to investigate the structures and stabilities of hydrogen (H-) bonded 2-hydroxypyridine (2HP)/2-pyridone (2PY) dimeric forms as well as 2HP-2PY complexes. The results on single-point counterpoise (CP) correction of these complexes were compared against CP-optimized correction. The nature of the intermolecular contacts in the sense of normal H-bond or blue-shifting H-bond was determined on the basis of harmonic vibrational, atom-in-molecule (AIM), and natural bond orbital (NBO) analysis. A blue-shifting C-H...N H-bond was found and NBO analysis revealed a slight decrease in the population of the contacting sigmaC-H* antibonding orbital as the primary reason of the C-H contraction. Good correlations have been established between the interaction energies and the H-bond distances versus other characteristic H-bond parameters.