Catalytic carbon dioxide hydrogenation to methane: A review of recent studies

Recently,various efforts have been put forward on the development of technologies for the synthesis of methane from CO₂ and H₂,since it can offer a solution for renewable H₂ storage and transportation.In parallel,this reaction is considered to be a critical step in reclaiming oxygen within a closed cycle.Over the years,extensive fundamental research works on CO₂ methanation have been investigated and reported in the literatures.In this updated review,we present a comprehensive overview of recent publications during the last 3 years.Various aspects on this reaction system are described in detail,such as thermodynamic considerations,catalyst innovations,the influence of reaction conditions,overall catalytic performance,and reaction mechanism.Finally,the future development of CO₂ methanation is discussed.     

A novel eudesmene sesquiterpenoid from <Emphasis Type="Italic">Schisandra sphenanthera</Emphasis> stems

Chemical investigation on the stems of Schisandra sphenanthera has afforded a novel eudesmene-type sesquiterpenoid, schisansphene A (1), and a known compound, alismol (2). Their structures and configurations were elucidated by spectroscopic methods, including 2D NMR techniques.     

An amide-containing metal-organic tetrahedron responding to a spin-trapping reaction in a fluorescent enhancement manner for biological imaging of NO in living cells

Metal-organic polyhedra represent a unique class of functional molecular containers that display interesting molecular recognition properties and fascinating reactivity reminiscent of the natural enzymes. By incorporating a triphenylamine moiety as a bright blue emitter, a robust cerium-based tetrahedron was developed as a luminescent detector of nitronyl nitroxide (PTIO), a specific spin-labeling nitric oxide (NO) trapper. The tetrahedron encapsulates molecules of NO and PTIO within the cavity to prompt the spin-trapping reaction and transforms the normal EPR responses into a more sensitively luminescent signaling system with the limit of detection improved to 5 nM. Twelve-fold amide groups are also functionalized within the tetrahedron to modify the hydrophilic/lipophilic environment, ensuring the successful application of biological imaging in living cells.     

Electronic and magnetic properties of early transition-metal substituted iron-cyclopentadienyl sandwich molecular wires: parity-dependent half-metallicity

Electronic and magnetic properties of early transition metals (V, Ti, Sc)-Fe(k)Cp(k + 1) sandwich molecular wires (SMWs) are investigated by means of ab initio calculations. It is found that all SMWs favor a ferromagnetic ground state. Significantly, V-Fe(k)Cp(k + 1) SMWs are either half-metallic or semiconducting, dependent upon the parity (even or odd) of the number (k) of Fe atoms in the unit cell of SMWs. This parity oscillation of conductive properties results from the combined effects of the band-folding and gap-opening at the Brillouin-zone boundary of one-dimensional materials. In contrast, Sc-Fe(k)Cp(k + 1) and Ti-Fe(k)Cp(k + 1) SMWs are always semiconducting. Our work may open up the way toward half metal/semiconductor heterostructures with perfect atomic interface.     

Nearly monodispersed core-shell structural Fe3O4@DFUR-LDH submicro particles for magnetically controlled drug delivery and release

Nearly monodispersed magnetic Fe(3)O(4)@DFUR-LDH submicro particles containing the anticancer agent DFUR were prepared via a coprecipitation-calcination-reconstruction strategy of LDH materials over the surface of Fe(3)O(4) particles, and present well-defined core-shell structure, strong magnetization and obvious magnetically controlled drug delivery and release properties.     

Enhanced ordering in gold nanoparticles self-assembly through excess free ligands

Self-assembly of nanometer-sized particles is an elegant and economical approach to achieve dense patterns over large areas beyond the resolution and throughput capabilities of electron-beam lithography. In this paper, we present results of self-assembly of oleylamine-capped gold nanoparticles with 8.0 ± 0.3 nm diameter into densely packed and well-ordered monolayers with center-to-center distance of ～11 nm. Self-assembly was done in a Langmuir-Blodgett trough and picked up onto Si substrates. The nanoparticles undesirably assembled within micrometer-sized "droplets" that were organic in nature. However, within these droplets, we observed that the addition of the excess ligand, oleylamine, drastically enhanced the self-assembly of the nanoparticles into monolayers with near-perfect ordering. This approach has the potential use in templated self-assembly of nanoparticles for rearranging poorly ordered assembly into a commensurate prepatterned substrate.     

Bi2S3 nanomaterials: morphology manipulation and related properties

The Bi(2)S(3) nanomaterials with various morphologies such as nanorods, nanowires, nanowire bundles, urchin-like microspheres and urchin-like microspheres with cavities have been successfully synthesized through a simple hydrothermal method. Experimental results indicate that sulfur sources play crucial roles in determining the morphologies of Bi(2)S(3) products. Moreover, formation mechanisms of different Bi(2)S(3) nanostructures are discussed based on understanding of the growth habit of Bi(2)S(3) crystal. Finally, we also studied the morphologies-dependent electrochemical and optical properties of the as-synthesized Bi(2)S(3) nanomaterials.     

A density functional theory approach to mushroom-like platinum clusters on palladium-shell over Au core nanoparticles for high electrocatalytic activity

Recently, it was found that Pt clusters deposited on Pd shell over Au core nanoparticles (Au@Pd@Pt NPs) exhibit unusually high electrocatalytic activity for the electro-oxidation of formic acid (P. P. Fang, S. Duan, et al., Chem. Sci., 2011, 2, 531-539). In an attempt to offer an explanation, we used here carbon monoxide (CO) as probed molecules, and applied density functional theory (DFT) to simulate the surface Raman spectra of CO at this core-shell-cluster NPs with a two monolayer thickness of Pd shell and various Pt cluster coverage. Our DFT results show that the calculated Pt coverage dependent spectra fit the experimental ones well only if the Pt clusters adopt a mushroom-like structure, while currently the island-like structure is the widely accepted model, which follows the Volmer-Weber growth mode. This result infers that there should be a new growth mode, i.e., the mushroom growth mode as proposed in the present work, for Au@Pd@Pt NPs. We suggest that such a mushroom-like structure may offer novel active sites, which accounts for the observed high electrocatalytic activity of Au@Pd@Pt NPs.     

Speciation of mercury in water samples by dispersive liquid-liquid microextraction combined with high performance liquid chromatography-inductively coupled plasma mass spectrometry

The dispersive liquid-liquid microextraction (DLLME) combined with high performance liquid chromatography-inductively coupled plasma mass spectrometry for the speciation of mercury in water samples was described. Firstly methylmercury (MeHg⁺) and mercury (Hg²⁺) were complexed with sodium diethyldithiocarbamate, and then the complexes were extracted into carbon tetrachloride by using DLLME. Under the optimized conditions, the enrichment factors of 138 and 350 for MeHg⁺ and Hg²⁺ were obtained from only 5.00 mL sample solution. The detection limits of the analytes (as Hg) were 0.0076 ng mL⁻¹ for MeHg⁺ and 0.0014 ng mL⁻¹ for Hg²⁺, respectively. The relative standard deviations for ten replicate measurements of 0.5 ng mL⁻¹ MeHg⁺ and Hg²⁺ were 6.9% and 4.4%, respectively. Standard reference material of seawater (GBW(E)080042) was analyzed to verify the accuracy of the method and the results were in good agreement with the certified values. Finally, the developed method was successfully applied for the speciation of mercury in three environmental water samples.     

胆固醇分子印迹聚合物的制备及其选择性吸附

随着人们生活水平的逐步提高,因人体内胆固醇过高所产生的疾病呈逐年增加的趋势.近年来的研究表明,胆固醇分子印迹聚合物对胆固醇具有良好的选择性吸附能力.将胆固醇分子印迹聚合物作为胆固醇的识别剂,提取食品中的胆固醇和治疔胆固醇有关的疾病,展现出了良好的应用前景.本文分别从胆固醇分子印迹聚合物的制备方法、识别机理、提高选择性识别途径以及新的印迹方法等方面进行了综述.