Lewis acid mediated cyclization: synthesis of 2 spirocyclohexylindolines.

Herein, we report the synthesis of 2-spirocyclohexylindolines based on a Lewis acid mediated cyclization. This diastereoselective procedure provides the target structures in a straightforward way via dual activation.

Doped graphene for metal-free catalysis.

Graphene has attracted increasing attention in different scientific fields including catalysis. Via modification with foreign metal-free elements such as nitrogen, its unique electronic and spin structure can be changed and these doped graphene sheets have been successfully employed in some catalytic reactions recently, showing them to be promising catalysts for a wide range of reactions. In this review, we summarize the recent advancements of these new and interesting catalysts, with an emphasis on the universal origin of their catalytic mechanisms. We are full of hope for future developments, such as more precisely controlled doping methods, atom-scale surface characterization technology, generating more active catalysts via doping, and finding wide applications in many different fields.

The influence of N-doped carbon materials on supported Pd: enhanced hydrogen storage and oxygen reduction performance.

N-doped graphene has become an important support for Pd in both hydrogen storage and catalytic reactions. The molecular orbitals of carbon materials (including graphene, fullerene, and small carbon clusters) and those of the supported Pd species will hybrid much stronger as N dopants are introduced, owing to the increased electrostatic attraction at the interface. This enhances the carbon substrates' catching force for the supported Pd, preventing its leaching and aggregation in many practical applications. The better dispersion and stabilization of Pd nanoparticles, which are induced by various carbon supports with N-doping, are pleasing to us and could increase their efficiency and facilitate their recycling during various reaction processes in several fields.

Improved performance of graphene doped with pyridinic N for Li-ion battery: a density functional theory model.

The performance of N-doped graphene on Li-ion battery has been investigated systematically by means of a density functional theory method. Pyridinic N doping, graphitic N atoms and 5-8-5 double vacancies have been selected as the functional defects to study their influence on Li storage compared to the pristine graphene. It has been confirmed that introducing pyridinic N atoms with p-type doping is a suitable method, especially for graphene doped with 4 pyridinic N atoms, whose structural distortion induced by Li intercalation is small and supplies strong force for Li adsorption. The diffusion barrier for this model is lower than for pristine graphene, both for the side and center diffusion routes, contributing to the high mobility. In addition, we point out that the strong catch force for Li will cause more Li to stay on the pyridinic N-doped graphene during the charge-discharge cycles, leading to a faster decrease of capacity compared to pristine graphene.

Synthesis of sulfonic acid-functionalized Fe3O4@C nanoparticles as magnetically recyclable solid acid catalysts for acetalization reaction.

The Fe3O4@C core-shell magnetic nanoparticles with an average size of about 190 nm were synthesized via a one-pot solvothermal process using ferrocene as a single reactant. The sulfonic acid-functionalized Fe3O4@C magnetic nanoparticles were obtained by grafting the sulfonic groups on the surface of Fe3O4@C nanoparticles to produce magnetically recyclable solid acid catalysts. The as-prepared products were characterized by X-ray diffraction and transmission electron microscopy. The catalytic performance of the as-prepared catalysts was examined through the condensation reaction of benzaldehyde and ethylene glycol. The results showed that the catalysts exhibited high catalytic activity with a conversion rate of 88.3% under mild conditions. Furthermore, catalysts with a magnetization saturation of 53.5 emu g(-1) at room temperature were easily separated from the reaction mixture by using a 0.2 T permanent magnet and were reused 8 times without any significant decrease in catalytic activity.

Yolk-type Au@Fe3O4@C nanospheres for drug delivery, MRI and two-photon fluorescence imaging.

Nearly monodispersed yolk-type Au@Fe3O4@C nanospheres with hollow cores of 50 nm in diameter were prepared through coating Au@SiO2 nanoparticles with Fe3O4@C double layers, followed by dissolving SiO2. The cytotoxicity of the nanospheres was evaluated by MTT assay, demonstrating a high biocompatibility. The yolk-type nanospheres show a high DOX loading content of 1237 mg g(-1). The coexistence of Fe3O4 and Au also makes the nanospheres as dual probes for MR imaging with a specific relaxivity (r2*) of 384.38 mM(-1) s(-1) and optical fluorescence imaging using a near-infrared (NIR) excitation.

Multifunctional Fe3O4@C@Ag hybrid nanoparticles as dual modal imaging probes and near-infrared light-responsive drug delivery platform.

Multifunctional nanocarriers based on Fe(3)O(4)@C@Ag hybrid nanoparticles with a diameter of 200 nm were fabricated by a facile method. Silver (Ag) nanoparticles were deposited onto the surface of Fe(3)O(4)@C nanospheres in dimethyl formamide (DMF) solution by reducing silver nitrate (AgNO(3)) with glucose. The nanocarriers of doxorubicin (DOX) with a high loading content of 997 mg/g and near-infrared (NIR) light-responsive drug delivery based on Ag nanoparticles were realized. Strong fluorescence can be observed in cell nucleus due to the presence of DOX after irradiated by NIR, and most cells were in the state of apoptosis, which indicates NIR-regulated drug release was realized. Moreover, measurements show that the nanocarriers could also be used as magnetic resonance imaging (MRI) contrast agents and fluorescent probes. The combination of synergistic NIR controlled drug release and dual modal imaging of MRI and two-photon fluorescence (TPF) imaging could lead to a potential multifunctional system for biomedical diagnosis and therapy.

Synthesis of carbon-coated, porous and water-dispersive Fe3O4 nanocapsules and their excellent performance for heavy metal removal applications.

Porous Fe(3)O(4)@C nanocapsules with a diameter of about 120 nm (about 50 nm cavity) were synthesized by combining a sacrificial template method with solvothermal treatment. The N(2) adsorption-desorption isotherms reveals their mesoporous structure and large BET surface area (159.8 m(2) g(-1)). The magnetic investigation indicates their superparamagnetic nature and high saturation magnetization (55.93 emu g(-1)). The nanocapsules also exhibit negative zeta potential (-27.59 mV) and possess carboxyl groups on the outer carbon layer, which keeps them highly dispersive in aqueous solution and provides a chelating function for metal ions. The heavy metals removal test demonstrates the excellent affinity of nanocapsules, the high efficiency for different metals (>90%), 79 mg g(-1) adsorption capacity for Pb(2+) and ultrafast removal process (Pb(2+), 99.57% within 1 minute). Protected by a porous carbon layer, the nanocapsules display excellent acidic resistance and adsorption properties even in an acidic solution (pH = 3). Moreover, the metal ions can be easily adsorbed and desorbed through manipulating the pH value for adsorbent regeneration and heavy metal recycling.