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Wang W.,CAS Lanzhou Institute of Chemical Physics | Wang W.,University of Chinese Academy of Sciences | Zheng A.,CAS Wuhan Center for Magnetic Resonance | Zhao P.,CAS Lanzhou Institute of Chemical Physics | And 3 more authors.
ACS Catalysis

The synthetic control and functions of porous organic polymers (POPs) with N-heterocyclic carbene gold(I) (Au-NHC@POPs) are described in this article. A series of Au-NHC@POPs with tunable physical properties such as surface area and pore size distribution were first synthesized via Sonogashira chemistry by differing monomer strut lengths and concentration during polymerization; a controllable transition from nonporous to microporous and the coexistence of micro- and mesoporous structures in the framework were realized by varying the monomer concentration. To explain this phenomenon, we put forward a model assumption of a branch-branch cross effect. Additionally, Au-NHC@POPs1 was found to have superior catalytic activity in alkyne hydration reactions, and the catalyst could be used six times with a slight loss of activity. © 2013 American Chemical Society. Source

Zhang Y.,Nanjing Southeast University | Zhang W.,Nanjing Southeast University | Li S.-H.,CAS Wuhan Center for Magnetic Resonance | Ye Q.,Nanjing Southeast University | And 4 more authors.
Journal of the American Chemical Society

A novel mononuclear metal-organic compound, [Cu(Hdabco)(H 2O)Cl 3] (1, dabco = 1,4-diazabicyclo[2.2.2]octane) in which the Cu II cation adopts a slightly distorted bipyramidal geometry where the three Cl anions constitute the equatorial plane and the Hdabco cation and H 2O molecule occupy the two axial positions, was synthesized. Its paraelectric-to-ferroelectric phase transition at 235 K (T c) and dynamic behaviors were characterized by single crystal X-ray diffraction analysis, thermal analysis, dielectric and ferroelectric measurements, second harmonic generation experiments, and solid-state nuclear magnetic resonance measurements. Compound 1 behaves as a molecular rotor above room temperature in which the (Hdabco) part rotates around the N•••N axis as a rotator and the [Cu(H 2O)Cl 3] part acts as a stator. In the temperature range 235-301 K, a twisting motion of the rotator is confirmed. Below the T c, the motions of the rotor are frozen and the molecules become ordered, corresponding to a ferroelectric phase. Origin of the ferroelectricity was ascribed to relative movements of the anions and cations from the equilibrium position, which is induced by the order-disorder transformation of the twisting motion of the molecule between the ferroelectric and paraelectric phases. Study of the deuterated analogue [Cu(Ddabco)(D 2O)Cl 3] (2) excludes the possibility of proton ordering as the origin of the ferroelectricity in 1. © 2012 American Chemical Society. Source

Liu C.,CAS Institute of Chemistry | Gao Z.,Jilin University | Zeng J.,CAS Institute of Chemistry | Hou Y.,CAS Institute of Chemistry | And 7 more authors.
ACS Nano

Detection of early malignant tumors remains clinically difficult; developing ultrasensitive imaging agents is therefore highly demanded. Owing to the unusual magnetic and optical properties associated with f-electrons, rare-earth elements are very suitable for creating functional materials potentially useful for tumor imaging. Nanometer-sized particles offer such a platform with which versatile unique properties of the rare-earth elements can be integrated. Yet the development of rare-earth nanoparticle-based tumor probes suitable for imaging tiny tumors in vivo remains difficult, which challenges not only the physical properties of the nanoparticles but also the rationality of the probe design. Here we report new approaches for size control synthesis of magnetic/upconversion fluorescent NaGdF4:Yb,Er nanocrystals and their applications for imaging tiny tumors in vivo. By independently varying F-:Ln3+ and Na+:Ln3+ ratios, the size and shape regulation mechanisms were investigated. By replacing the oleic acid ligand with PEG2000 bearing a maleimide group at one end and two phosphate groups at the other end, PEGylated NaGdF4:Yb,Er nanoparticles with optimized size and upconversion fluorescence were obtained. Accordingly, a dual-modality molecular tumor probe was prepared, as a proof of concept, by covalently attaching antitumor antibody to PEGylated NaGdF4:Yb,Er nanoparticles through a "click" reaction. Systematic investigations on tumor detections, through magnetic resonance imaging and upconversion fluorescence imaging, were carried out to image intraperitoneal tumors and subcutaneous tumors in vivo. Owing to the excellent properties of the molecular probes, tumors smaller than 2 mm was successfully imaged in vivo. In addition, pharmacokinetic studies on differently sized particles were performed to disclose the particle size dependent biodistributions and elimination pathways. © 2013 American Chemical Society. Source

Jiang B.,University of New Mexico | Liu R.,CAS Wuhan Center for Magnetic Resonance | Li J.,University of New Mexico | Xie D.,Nanjing University | And 2 more authors.
Chemical Science

Dissociative chemisorption of CH4 on transition-metal surfaces, representing the rate-limiting step in methane steam reforming, has been shown experimentally to be strongly mode selective. To understand the mode selectivity, a twelve-dimensional global potential energy surface is developed for CH4 interacting with a rigid Ni(111) surface based on a large number of density functional theory points. The reaction dynamics is investigated using an eight-dimensional quantum model, which includes representatives of all four vibrational modes of methane. After correcting for surface effects, key experimental observations, including the mode selectivity, are well reproduced. These theoretical results, along with mechanistic analysis, provide insights into this industrially important heterogeneous reaction. © 2013 The Royal Society of Chemistry. Source

Feng N.,CAS Wuhan Center for Magnetic Resonance | Wang Q.,CAS Wuhan Center for Magnetic Resonance | Zheng A.,CAS Wuhan Center for Magnetic Resonance | Zhang Z.,CAS Wuhan Center for Magnetic Resonance | And 4 more authors.
Journal of the American Chemical Society

The origin of the exceptionally high activity of (B, Ag)-codoped TiO 2 catalysts under solar-light irradiation has been investigated by XPS and 11B solid-state NMR spectroscopy in conjunction with density functional theory (DFT) calculations. XPS experimental results demonstrated that a portion of the dopant Ag (Ag3+) ions were implanted into the crystalline lattice of (B, Ag)-codoped TiO2 and were in close proximity to the interstitial B (Bint.) sites, forming [B int.-O-Ag] structural units. In situ XPS experiments were employed to follow the evolution of the chemical states of the B and Ag dopants during UV-vis irradiation. It was found that the [Bint.-O-Ag] units could trap the photoinduced electron to form a unique intermediate structure in the (B, Ag)-codoped TiO2 during the irradiation, which is responsible for the photoinduced shifts of the B 1s and Ag 3d peaks observed in the in situ XPS spectra. Solid-state NMR experiments including 11B triple-quantum and double-quantum magic angle spinning (MAS) NMR revealed that up to six different boron species were present in the catalysts and only the tricoordinated interstitial boron (T) species was in close proximity to the substitutional Ag species, leading to formation of [T-O-Ag] structural units. Furthermore, as demonstrated by DFT calculations, the [T-O-Ag] structural units were responsible for trapping the photoinduced electrons, which prolongs the life of the photoinduced charge carriers and eventually leads to a remarkable enhancement in the photocatalytic activity. All these unprecedented findings are expected to be crucial for understanding the roles of B and Ag dopants and their synergistic effect in numerous titania-mediated photocatalytic reactions. © 2013 American Chemical Society. Source

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