The utilization of methane, which is the main constituent of natural gas, coal-bed gas, shale gas, and the vast gas hydrate resources, for the production of chemicals is one of the most important research targets in catalysis. The current technology for chemical utilization of methane involves high-temperature steam reforming to produce syngas, and the subsequent conversion of syngas to methanol, followed by methanol transformation. However, steam reforming of methane is an energy-and cost-intensive process. The direct transformation of methane to valuable chemicals would be the most desirable route, however, despite many efforts it remains difficult to achieve.[1] The development of novel catalytic routes for the transformation of methane is of high significance from both practical and fundamental points of view.Monohalogenomethanes (CH 3 Cl or CH 3 Br) could be alternative platform molecules for the conversion of CH 4 to chemicals. Olah et al. reported the catalytic monohalogenation of CH 4 by Cl 2 or Br 2 over supported superacids or noble metals, followed by hydrolysis of methyl halides to methanol and dimethyl ether.[2] Zhou et al. disclosed the conversion of CH 4 or C 2 H 6 to alkyl bromides by using Br 2 , and the subsequent conversion to oxygenates through stoichiometric reactions with metal oxides.[3] GRT, Inc. developed a technology for the transformation of CH 4 to various products, particularly liquid hydrocarbon fuels, through the reaction with Br 2 via methyl bromides, and claimed that this is a costeffective route.[4] In these processes, the generated HCl, HBr, or metal bromides must be oxidized to Cl 2 or Br 2 to complete the catalytic cycle. HBr was demonstrated to be useful for the oxidative bromination of CH 4 in the presence of O 2 instead of Br 2 over supported Ru or Rh catalysts, [5] but the high cost and limited availability of noble metals may hinder the large-scale application of this system. Zn-MCM-48-supported hydrated dibromo(dioxo)molybdenum(VI), which might generate Br 2 during reaction, catalyzed the oxidation of CH 4 to methanol and dimethyl ether, but the long-term stability of this system was not confirmed.[6] SiO 2 -supported FePO 4 was stable for the oxidative bromination of CH 4 , which provided CH 3 Br with a selectivity of approximately 50 %.[7] Only a few studies have been devoted to the oxidative chlorination of CH 4 to CH 3 Cl, although HCl is cheaper than HBr. Lercher and co-workers found that LaCl 3 was a superior catalyst for this reaction, which provided CH 3 Cl with a selectivity of around 55 % at a CH 4 conversion of 12 % at 748 K.[8]Herein, we present a novel catalytic route for the conversion of CH 4 to propylene via monohalogenomethane. Propylene is one of the most important bulk chemicals, and currently, it is mainly produced as a coproduct of ethylene through the cracking of naphtha. However, the demand for propylene is growing much faster than the demand for ethylene.[9] The development of novel routes for the production of propylene, for example, dehydrogenat...

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The preparation of a series of novel homopolymers and copolymers containing bisazobenzene chromophores with side‐on structure in the side chains via atom transfer radical polymerization (ATRP) were presented. UV–vis spectra of the thin films of these polymers under irradiation of 488 nm Ar+ laser suggested that the photoisomerization of the bisazobenzene chromophores happened mainly on one of the two azo groups in the bisazobenzene chromophores with similar probability due to their side‐on structure. Good photoalignment behaviors of these polymers were proved by photoinduced birefringence measurements because side‐on structure permitted the two azo groups in the bisazobenzene chromophores both participated in the trans–cis–trans photoisomerization cycles equally to induce the whole chromophore reorientation. Furthermore, the reorientation axis located at the middle of chromophore decreased the sweep volume during photoalignment. The impetus for this study was to evaluate the photoisomerization and photoalignment process of side‐on bisazobenzene‐containing polymers and to find possible applications in the photosensitive devices. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3460–3472, 2007

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Nitroxide radicals, such as 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and its derivatives, have recently been used as contrast agents for magnetic resonance imaging (MRI) and electron paramagnetic resonance imaging (EPRI). However, their rapid one-electron bioreduction to diamagnetic N-hydroxy species when administered intravenously has limited their use in in vivo applications. In this article, a new approach of silica coating for carrying stable radicals was proposed. A 4-carboxyl-TEMPO nitroxide radical was covalently linked with 3-aminopropyl-trimethoxysilane to produce a silanizing TEMPO radical. Utilizing a facile reaction based on the copolymerization of silanizing TEMPO radicals with tetraethyl orthosilicate in reverse microemulsion, a TEMPO radicals doped SiO2 nanostructure was synthesized and coated on the surface of NaYF4:Yb,Er/NaYF4 upconversion nanoparticles (UCNPs) to generate a novel multifunctional nanoprobe, PEGylated UCNP@TEMPO@SiO2 for upconversion luminescence (UCL) and magnetic resonance dual-modality imaging. The electron spin resonance (ESR) signals generated by the TEMPO@SiO2 show an enhanced reduction resistance property for a period of time of up to 1 h, even in the presence of 5 mM ascorbic acid. The longitudinal relaxivity of PEGylated UCNPs@TEMPO@SiO2 nanocomposites is about 10 times stronger than that for free TEMPO radicals. The core-shell NaYF4:Yb,Er/NaYF4 UCNPs synthesized by this modified user-friendly one-pot solvothermal strategy show a significant enhancement of UCL emission of up to 60 times more than the core NaYF4:Yb,Er. Furthermore, the PEGylated UCNP@TEMPO@SiO2 nanocomposites were further used as multifunctional nanoprobes to explore their performance in the UCL imaging of living cells and T1-weighted MRI in vitro and in vivo.