Synthesis of gemini surfactants with twelve symmetric fluorine atoms and one singlet F MR signal as novel F MRI agents

A family of fluorinated gemini surfactants derived from perfluoropinacol has been synthesized as novel ¹⁹F magnetic resonance imaging (¹⁹F MRI) agents. These fluorinated surfactants with 12 symmetric fluorine atoms and one singlet ¹⁹F MR peak can be conveniently prepared from perfluoropinacol and oligo(ethylene glycols) on multi-gram scales. Solubility, hydrophilicity (log P), and critical micelle concentration (CMC) measurements of these fluorinated surfactants indicated that high aqueous solubility can be achieved by introducing oligo(ethylene glycols) with appropriate length into perfluoropinacol, i.e., manipulating the fluorine content (F%). One of these fluorinated surfactants with high aqueous solubility and excellent ¹⁹F MR properties has been identified by ¹⁹F MRI phantom experiments as a promising ¹⁹F MRI agent.     

Electrochemical synthesis of amides: direct transformation of methyl ketones with formamides

A direct transformation from methyl ketones to secondary or tertiary amides has been developed through a novel electrochemical approach and a wide scope of formamides could be utilized as the amide sources. This transformation was promoted by in situ generated iodine through electrolysis of sodium iodide under mild, metal-free conditions. This electrochemical procedure could avoid the use of stoichiometric iodine and afforded the target products in good to excellent yields.     

Synthesis,Structures, Luminescent and Magnetic Properties of Heterometallic 5p‐4f Compounds with Ethylenediaminetetra­acetate

A series of heterometallic Ln^III–Sb^III edta‐containing compounds with the formulas [Sb₂(edta)₂Ln]NO₃ · nH₂O [edta = ethylenediaminetetraacetate; Ln = Eu, n = 7 ( 1 ); Gd, n = 7.5 ( 2 ) and Tb, n = 8 ( 3 )] were synthesized and characterized by elemental analyses (EA), powder X‐ray diffraction (PXDP), Fourier transform infrared spectroscopy (FT‐IR), and thermogravimetric analyses (TGA). Their fluorescence and magnetic properties were also studied. The thermal analysis demonstrates the compounds formation of the antimony, lanthanide ions, and edta^4– ligands. FT‐IR spectra reveal that the antimony and lanthanide ions are connected through the carboxylate bridges. The studies of luminescence properties show that compounds 1 and 3 exhibit typical luminescence in the visible region. Furthermore, magnetic properties reveal compounds 2 and 3 have weak ferromagnetic behavior.     

The band alignment at CdS/Cu2ZnSnSe4 heterojunction interface

Band alignment at CdS/Cu₂ZnSnSe₄ heterojunction interface is studied by X‐ray photoemission spectroscopy. The Cu₂ZnSnSe₄ thin films are prepared by selenization of electrodeposited Cu‐Zn‐Sn precursors. CdS overlayers with different thickness are sequentially grown on the Cu₂ZnSnSe₄ substrate by pulsed laser deposition process. Photoemission spectra are obtained before and after each growth to study the conduction and valence band offsets at the heterojunction interface. The determined conduction band offset of 0.34 eV indicates a spike‐like ‘type I’ band alignment at CdS/Cu₂ZnSnSe₄ interface. The spike will avoid interface recombination, and it is low enough that electron could transfer from the Cu₂ZnSnSe₄ layer to the buffer layer which is suitable for solar cell's fabrication. Copyright © 2012 John Wiley & Sons, Ltd.     

Multifractal analysis for Cu/Ti bilayer thin films

Two bilayer thin films with different stacking sequences, Cu/Ti/Si and Ti/Cu/Si, were deposited by DC magnetron sputtering technique. X‐ray diffraction technique was used to measure the crystallization structures, and scanning electron microscopy and atomic force microscopy were used to measured surface morphology. The multifractal spectra f(α)‐α was used to characterize the surface morphology. The result of |q|_max ≤ 53 is obtained by multifractal analysis. The shape of the multifractal spectra f(α) ? α is hook‐like for Cu/Ti/Si and bell jar‐like for Ti/Cu/Si. The spectrum width Δα = α_max ? α_min and Δf(=f(α_min) ? f(α_max)) of the multifractal spectra is able to quantitatively analyze the growth and surface roughness of the Cu/Ti bilayer thin films. The surface of Ti/Cu/Si thin film is more uniform and smoother than the film of Cu/Ti/Si. Copyright © 2013 John Wiley & Sons, Ltd.     

Ba2Cd(B3O6)2: A Congruent‐Melting Compound with Isolated B3O6 Units

The single crystals of Ba₂Cd(B₃O₆)₂ were grown by the spontaneous crystallization method for the first time. They crystallize in the centrosymmetric trigonal space group R$\bar{3}$ with a = 7.143(3) Å, c = 17.405(16) Å, and Z = 3. The structure is characterized by isolated B₃O₆ units, and the Ba²⁺ and Cd²⁺ cations connect with B₃O₆ rings to form three dimensional structure. The TG/DSC and XRD results reveal that Ba₂Cd(B₃O₆)₂ melts congruently. First‐principles electronic structure calculation performed with the density functional theory (DFT) method shows that the calculated bandgaps are 4.66 eV, which is in good agreement with the UV/Vis/NIR experimental value 4.59 eV. The calculation shows that the Ba₂Cd(B₃O₆)₂ crystal has a large birefringence (Δn = 0.0875–0.0569 from 270 nm to 2600 nm), which demonstrates that Ba₂Cd(B₃O₆)₂ is a potential birefringence crystal.     

Synthesis,Structures, and Luminescent Properties of two 3, 5‐Dimethyl‐1‐H‐1, 2,4‐triazole‐Based Zinc Metal‐Organic Frameworks with Aromatic Carboxylate as Coligand

Two metal‐organic frameworks, [Zn(dmtrz)(btrc)_1/3]_n ( 1 ) and [Zn₂(dmtrz)₂(btec)(H₂O)₂]_n ( 2 ) (dmtrz = 3, 5‐dimethyl‐1‐H‐1, 2,4‐triazole, btrc = 1, 3,5‐benzenetricarboxylate, btec = 1, 2,4, 5‐benzenetetracarboxylate), were synthesized by hydrothermal reaction. The crystal structure analysis reveals that compound 1 is a dense 3D framework with Schläfli symbols of {4³}₂{4⁶ · 6⁶ · 8³}₃, which is a loh1 structure. Compound 2 is a 2D network. In addition, the photoluminescence of two compounds were studied in solid state at room temperature, together with their thermal analysis.     

Unsaturated polyester resins modified with phosphorus-containing groups: Effects on thermal properties and flammability

A novel reactive phosphorus-containing monomer [1-oxo-2,6,7-trioxa-1- phosphabicyclo-[2.2.2]octane-methyl diallyl phosphate, PDAP] was synthesized, and various amounts of PDAP were combined with unsaturated polyester by radical bulk polymerization. The resulting flame-retardant unsaturated polyester resin (FR-UPR) samples were investigated by thermogravimetric analysis (TGA), microscale combustion calorimetry (MCC), and limiting oxygen index (LOI) tests. Due to the relatively high phosphorus content of PDAP (18.2 wt%), incorporation of this monomer into unsaturated polyester resin (UPR) led to a marked decrease in the heat release capacity (HRC), the total heat release (THR), an increase in the LOI and the char yield upon combustion. In order to elaborate the interactions between the UPR and PDAP in degradation, differences between the experimental and theoretical mass losses of a FR-UPR sample were evaluated. Furthermore, thermogravimetry-Fourier transform infrared (TG-FTIR) and real-time Fourier transform infrared (RTIR) spectroscopy were employed to investigate the degradation behavior of UPRs, providing insight into the degradation mechanism.     

Identification of two polyamides (PA11 and PA1012) using pyrolysis-GC/MS and MALDI-TOF MS

The main goal of this work is to identify two polyamides (PA11 and PA1012) by mass spectrometry including pyrolysis-GC/MS and MALDI-TOF MS. PA11 and PA1012 have similar properties and cannot be distinguished by many other methods. Using pyrolysis-GC/MS, the pyrograms of PA11 and PA1012 at 600 °C were compared. Specific pyrolyzates for PA11 and PA1012 were obtained, 2-azacyclotridecanone for PA11 and 1,10-diaminodecane, 1,10-dicyanodecane for PA1012, respectively, which was the basis to distinguish them. Meanwhile, MALDI-TOF MS can give specific repeat unit for these two polyamides, dehydrated 11-aminoundecanoic acid (M = 183) for PA11, acetylate of dodecanedioic acid and diaminodecane (M = 366) for PA1012, which can be another means of identifying them.