A novel CNT@SnO2 core–sheath nanocomposite as a stabilizing support for catalysts of proton exchange membrane fuel cells

Mesoporous SnO₂ coated carbon nanotube (CNT) core–sheath nanocomposite, CNT@SnO₂, was prepared by a hydrothermal method and proposed as a catalyst support for proton exchange membrane fuel cells (PEMFCs). The CNT@SnO₂ and its supported Pt catalyst, Pt/(CNT@SnO₂), were characterized by TEM, XRD, cyclic voltammetry, and polarization curves. The CNT@SnO₂ composite showed a much lower anodic current than the CNT, especially at high potentials, indicating the CNT@SnO₂ was more corrosion resistant. The Pt/(CNT@SnO₂) catalyst was electrochemically active and exhibited comparable activity for the oxygen reduction reaction to the CNT supported catalyst (Pt/CNT). More importantly, the long-term stability of the Pt/(CNT@SnO₂) catalyst was significantly higher than that of the Pt/CNT catalyst, which might be mainly due to the fact that the CNT@SnO₂ was more corrosion resistant and mesoporous SnO₂ was beneficial to restrict the Pt migration and aggregation. Consequently, the CNT@SnO₂ would be a promising durable catalyst support for PEMFCs.     

The Antimony‐Based Type I Clathrate Compounds Cs8Cd18Sb28 and Cs8Zn18Sb28

In phase : The title compounds lie in a new region of phase space for such a structure, and have stoichiometries in accord with a classical Zintl phase formulation. The small semiconductor gaps indicated by DFT calculations are also supported by their diamagnetic susceptibilities.

     

New nor-oleanane triterpenoids from the fruits of Stauntonia brachyanthera with potential anti-inflammation activity

Abstract

The continuing studies on the fruits of Stauntonia brachyanthera led to the isolations of 6 normal and nor-oleanane triterpenoids, including two new compounds, brachyantheoraside B10 (1) and brachyantheraside C1 (2). Compounds 1–3 showed inhibitory activity on lipopolysaccharide (LPS)-induced nitric oxide production in RAW 264.7 macrophages with the IC₅₀ values of 27.04, 26.22, and 21.41?μM, respectively, which were all stronger than that of indomethacin. The study not only revealed a new type of nor-oleanane triterpenoids, but also confirmed the anti-inflammation abilities of three type nor-oleanane triterpenoids as the inhibitors of NO production.     

Adsorption property of congo red from aqueous solution by Cu-BTC/SiO 2 composite

The adsorption behavior of congo red from aqueous solution on Cu-BTC/SiO2 was investigated. Cu-BTC/SiO2 with mesoporous structure and large surface area was prepared by loading Cu-BTC into the mesoporous silica using in-situ synthesis method. The X-ray diffraction, scanning electron microscopy, and nitrogen adsorption–desorption analysis were used to characterize the structure and morphology of the prepared materials. The adsorption studies showed that the adsorption isotherm of congo red on Cu-BTC/SiO2 fitted well with Freundlich adsorption model and congo red is easy to be adsorbed by Cu-BTC/SiO2. The thermodynamic study showed that the adsorption behavior of congo red on Cu-BTC/SiO2 is an exothermic process at temperature under investigation.     

Morphological change of asymmetric oxyethylene/oxybutylene block copolymers induced by montmorillonite

Two oxyethylene/oxybutylene block copolymers (E(40)B(79) and E(47)B(62)), which exhibit body-centered cubic sphere (bcc) and hexagonally packed cylindrical (hex) melt morphologies in bulk, respectively, were blended with nanoclay of montmorillonite (MMT). The effects of MMT on the morphology and crystallization of E(40)B(79) and E(47)B(62) were studied with small-angle x-ray scattering, wide-angle x-ray diffraction, and differential scanning calorimeter. It is found that the E block in the block copolymers can intercalate into the galleries of MMT, leading to a larger layer spacing than that of neat MMT. The preferential absorption of the E block onto MMT plates induces the formation of a new lamellar structure, irrespectively of original morphology in the bulk. There is, however, coexistence of the new lamellar structure with regions retaining the melt morphology. The order-disorder transition temperature (T(ODT)) of the block copolymer is increased by MMT for E(40)B(79), but it remains unchanged for E(47)B(62). Crystallinity of the block copolymers is also greatly suppressed by the addition of MMT.     

Mechanism of surfactant micelle formation

The mechanism of micelle formation of surfactants sodium dodecyl sulfate (SDS), n-hexyldecyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) in heavy water solutions was studied by 1H NMR (chemical shift and line shape) and NMR self-diffusion experiments. 1H NMR and self-diffusion experiments of these three surfactants show that their chemical shifts (delta) begin to change and resonance peaks begins to broaden with the increase in concentration significantly below their critical micelle concentrations (cmc's). At the same time, self-diffusion coefficients ( D) of the surfactant molecules decrease simultaneously as their concentrations increase. These indicate that when the concentrations are near and lower than their cmc's, there are oligomers (premicelles) formed in these three surfactant systems. Carefully examining the dependence of chemical shift and self-diffusion coefficient on concentration in the region just slightly above their cmc's, one finds that the pseudophase transition model is not applicable to the variation of physical properties (chemical shift and self-diffusion coefficient) with concentration of these systems. This indicates that premicelles still exist in this concentration region along with the formation of micelles. The curved dependence of chemical shift and self-diffusion coefficient on the increase in concentration suggests that the premicelles grow as the concentration increases until a definite value when the size of the premicelle reaches that of the micelle, i.e., the system is likely dominated by the monomers and micelles. Additionally, the approximate values of premicelle coming forth concentration (pmc) and cmc were obtained by again fitting chemical shifts to reciprocals of concentrations at a different perspective, and are in good accordant with experimental results and literature values and prove the former conclusion.     

Electrocatalytic activity of horseradish peroxidase/chitosan/carbon microsphere microbiocomposites to hydrogen peroxide

Colloidal carbon microspheres (CMS) are dispersed in chitosan (CHIT) solution to form an organic-inorganic hybrid with excellent micro-environment for the immobilization of biomolecules. A novel amperometric biosensor for the determination of hydrogen peroxide (H(2)O(2)) has been constructed by entrapping horseradish peroxidase (HRP) in as-synthesized CMS/CHIT hybrid. The modification of glassy carbon electrode is made by a simple solution-evaporation method. The electrochemical properties of the biosensor are characterized in electrochemical methods. The proposed biosensor shows high sensitive determination and fast response to H(2)O(2) at -0.15 V. The constructed HRP/CHIT/CMS/GC electrode also exhibits a fine linear correlation with H(2)O(2) concentration. The calculated value of the apparent Michaelis-Menten constant, 2.33 mM, suggests that the HRP in CMS/CHIT hybrid keeps its native bioactivity and has high affinity for H(2)O(2).     

Synthesis of Clicked Imidazolium‐Containing Biosourced Copolymers and Application in Carbon Nanotube Dispersion

New polyesters incorporating a variable quantity of imidazolium rings along the backbone are synthesized by Huisgen 1,3‐dipolar cycloaddition (“click” reaction). Subsequently, the imidazolium‐grafted copolymers reveal an efficient dispersing ability toward the carbon nanotubes (CNTs) through supramolecular interactions in organic media. Interestingly, these compounds offer a simple and reliable strategy to control the quantity of dispersed CNTs as a function of imidazolium content. This approach is particularly suitable for the elaboration of biosourced and biodegradable materials based on poly(butylene succinate) with high‐performance properties.     

CdS nanocrystallites sensitized ZnO nanorods with plasmon enhanced photoelectrochemical performance

A sandwiched structure of CdS/Ag/ZnO nanorod photoanode exhibits greatly enhanced photoelectrochemical activity for solar hydrogen generation, due to synergistic effect of CdS nanocrystallites and plasmonic Ag nanoparticles for the enhanced optical absorption and the promoted charge carrier separation.     

催化动力学极谱法测定痕量钼

在稀Ｈ２ＳＯ４介质中，钼（Ⅵ）对硫酸联氨还原乙基橙的反应有强烈的催化作用。建立了催化动力学极谱法测定痕量钼的新体系，方法线性范围为２０－３００ｎｇ／ｍＬ，检出限为３．５４ｎｇ／ｍＬ。方法应用于尿中中钼的测定，结果满意。