Photocatalytic activity of TiO2 prepared by microwave/sol–gel method

This study addresses the photodegradation efficiency of bisphenol A (4,4′-isopropylidenephenol, BPA) and the generation of hydroxyl radicals using the UV/TiO₂ system. Photocatalysts were formed by the microwave/sol–gel method and TiO₂ was prepared with anatase and rutile phases with a high surface area. The hydroxyl radicals generated by the preparation of TiO₂ by a microwave/sol–gel process, and its photoactivity, exceeded those of TiO₂ prepared using a sol–gel process.     

基于2013年8月中国中东部地区持续高温的延伸期稳定分量提取及改进研究

基于2013年8月中国中东部地区持续高温及其减弱过程, 利用美国国家环境预报中心/美国国家大气研究中心逐日平均的500 hPa高度场、风场再分析资料和美国国家海洋和大气管理局的海温重建扩展资料进行分析, 通过前期海温强迫相似年的选取方法以及带通滤波和经验正交函数分解等方法提取出10–30 d的稳定分量, 并通过对稳定分量的诊断分析探究了这次持续高温及其减弱过程的维持机制. 研究发现: 通过选取与个例前期海温强迫最相似的30年来代替常规的气候态30 年(1981–2010 年), 所提取的气候态稳定分量所占的比重变化不大, 稍有减弱, 而异常型稳定分量占的比重显著性提高, 且其所刻画的影响异常事件的天气系统强度及稳定性明显提高, 能够更加清晰地显示延伸期天气过程的维持机制. 这表明在提取稳定分量时考虑前期的海温强迫作用是非常有必要的. 同时, 通过对延伸期稳定分量的分析, 表明此次持续高温及减退过程主要受到北极涛动、亚洲大陆中高纬纬向环流形势和西太平洋副热带高压(西太副高)强度、位置的共同影响.     

Fabrication of positively charged catanionic vesicles from ion pair amphiphile with double-chained cationic surfactant

In this study, a pseudodouble-chained ion pair amphiphile, hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS), was prepared from a mixture of cationic surfactant, hexadecyltrimethylammonium bromide, and anionic surfactant, sodium dodecylsulfate. Positively charged catanionic vesicles were then successfully fabricated from HTMA-DS with the addition of cationic surfactants, dialkyldimethylammonium bromide (DXDAB), including ditetradecyldimethylammonium bromide (DTDAB), dihexadecyldimethylammonium bromide, and dioctadecyldimethylammonium bromide (DODAB), with a mechanical disruption approach. The control of charge characteristic and physical stability of the catanionic vesicles through the variations of DXDAB molar fraction and alkyl chain length was then explored by size, zeta potential, and Fourier transform infrared analyses. It was found that the molecular packing and/or molecular interaction of HTMA-DS with DXDAB rather than the electrostatic repulsion between the charged vesicles dominated the physical stability of the mixed HTMA-DS/DXDAB vesicles. The presence of DTDAB, which possesses short alkyl chains, could adjust the packing of the unmatched chains of HTMA⁺ and DS^? and promote the vesicle formation. However, the weak molecular interaction due to the short chains of DTDA⁺ could not maintain the vesicle structures in long-term storage. With increasing the alkyl chain length of DXDAB, it was possible to improve the vesicle physical stability through the enhanced molecular interaction in the vesicular bilayer. However, the long alkyl chains of DODAB unmatched with those of HTMA-DS, resulting in the vesicle disintegration in long-term storage. For the formation of stable charged catanionic vesicles of HTMA-DS/DXDAB, a good match in hydrophobic chains and strong molecular interaction were preferred for the vesicle-forming molecules.     

Determination of Carbon‐based Engineered Nanoparticles in Marketed Fish by Microwave‐assisted Extraction and Liquid Chromatography‐atmospheric Pressure Photoionization‐tandem Mass Spectrometry

An optimized method for the determination of two major carbon‐based engineered nanoparticles (C₆₀ and C₇₀) in marketed fish samples is described. The method involves the use of microwave‐assisted extraction (MAE) coupled with liquid chromatography ‐ tandem mass spectrometry with atmospheric pressure photoionization (LC‐APPI‐MS/MS). Factors affecting the extraction efficiency of the analytes from fish samples were optimized by a central composite design method. The optimal extraction temperature and time for MAE were found to be 233 °C for 22 min, and the extraction solution was composed of toluene and acetone in a ratio of 4.64:1. The limits of quantitation (LOQs) were 0.1 and 0.05 ng/g for C₆₀ and C₇₀, respectively. The precision for these analytes at two spiked levels, as indicated by relative standard deviations (RSDs), were less than 10% for both intra‐ and inter‐day analysis. Accuracy, expressed as the mean extraction recovery, was between 85 and 98%. The method was further validated based on EU Commission Decision 2002/657/EC, including a decision limit (CCα) and detection capability (CCβ) for marketed fish samples.     

Effects of the temperature and beam parameters on depth profiles in X-ray photoelectron spectrometry and secondary ion mass spectrometry under C60–Ar cosputtering

Polymethylmethacrylate (PMMA) is widely used in various fields, including the semiconductor, biomaterial and microelectronic fields. Obtaining the correct depth profiles of PMMA is essential, especially when it is used as a thin-film. There have been many studies that have used earlier generation of cluster ion (SF₅⁺) as the sputtering source to profile PMMA films, but few reports have discussed the use of the more recently developed C₆₀⁺ in the PMMA sputtering process. In this study, X-ray photoelectron spectroscopy (XPS) and dynamic secondary ion mass spectroscopy (D-SIMS) were used concurrently to monitor the depth profiles of PMMA under C₆₀⁺ bombardment. Additionally, the cosputtering technique (C₆₀⁺ sputtering with auxiliary, low-kinetic-energy Ar⁺) was introduced to improve the analytical results. The proper cosputtering conditions could eliminate the signal enhancement near the interface that occurred with C₆₀⁺ sputtering and enhance the sputtering yield of the characteristic signals. Atomic force microscopy (AFM) was also used to measure the ion-induced topography. Furthermore, the effect of the specimen temperature on the PMMA depth profile was also examined. At higher temperatures (+120 °C), the depolymerization reaction that corresponded to main-chain scission dominated the sputtering process. At lower temperatures (−120 °C), the cross-linking mechanism was retarded significantly due to the immobilization of free radicals. Both the higher and lower sample temperatures were found to further improve the resulting depth profiles.     

Thermal‐ and Photo‐Induced Phase‐Transition Behaviors of a Tapered Dendritic Liquid Crystal with Photochromic Azobenzene Mesogens and a Bicyclic Chiral Center

A ribbon‐shaped chiral liquid crystalline (LC) dendrimer with photochromic azobenzene mesogens and an isosorbide chiral center (abbreviated as AZ₃DLC) was successfully synthesized and its major phase transitions were studied by using differential scanning calorimetry (DSC) and linear polarized optical microscopy (POM). Its ordered structures at different temperatures were further identified through structure‐sensitive diffraction techniques. Based on the experimental results, it was found that the AZ₃DLC molecule exhibited the low‐ordered chiral smectic (Sm*) LC phase with 6.31 nm periodicity at a high‐temperature phase region. AZ₃DLC showed the reversible photoisomerization in both organic solvents and nematic (N) LC media. As a chiral‐inducing agent, it exhibited a good solubility, a high helical‐twisting power, and a large change in the helical‐twisting power due to its photochemical isomerization in the commercially available N LC hosts. Therefore, we were able to reversibly “remote‐control” the colors in the whole visible region by finely tuning the helical pitch of the spontaneously formed helical superstructures.     

para‐Quinodimethane‐Bridged Perylene Dimers and Pericondensed Quaterrylenes: The Effect of the Fusion Mode on the Ground States and Physical Properties

Polycyclic hydrocarbon compounds with a singlet biradical ground state show unique physical properties and promising material applications; therefore, it is important to understand the fundamental structure/biradical character/physical properties relationships. In this study, para‐quinodimethane (p‐QDM)‐bridged quinoidal perylene dimers 4 and 5 with different fusion modes and their corresponding aromatic counterparts, the pericondensed quaterrylenes 6 and 7 , were synthesized. Their ground‐state electronic structures and physical properties were studied by using various experiments assisted with DFT calculations. The proaromatic p‐QDM‐bridged perylene monoimide dimer 4 has a singlet biradical ground state with a small singlet/triplet energy gap (?2.97 kcal mol^?1), whereas the antiaromatic s‐indacene‐bridged N‐annulated perylene dimer 5 exists as a closed‐shell quinoid with an obvious intramolecular charge‐transfer character. Both of these dimers showed shorter singlet excited‐state lifetimes, larger two‐photon‐absorption cross sections, and smaller energy gaps than the corresponding aromatic quaterrylene derivatives 6 and 7 , respectively. Our studies revealed how the fusion mode and aromaticity affect the ground state and, consequently, the photophysical properties and electronic properties of a series of extended polycyclic hydrocarbon compounds.     

Synthesis and Characterization of NiIIIN3S2 Complexes as Active Site Models for the Oxidized Form of Nickel Superoxide Dismutase

Nickel complexes, [Ni(H₂BA^RTPP)](ClO₄)₂ (R=Ph for 1 or iPr for 2 ), supported by a pentadentate ligand H₂BA^RTPP were synthesized and oxidized to form Ni^III species having a N3S2 coordination environment to mimic the active site of the oxidized form of nickel superoxide dismutase (NiSODox). The Ni^III species 2 ⁺ exhibited a rhombic signal with g values at 2.15, 2.12 and 2.02 similar to that of NiSODox. DFT calculations revealed that 2 ⁺ has an unpaired electron primarily located in the d orbital of the Ni^III center, which strongly overlaps with the p_z orbital of the axial pyridine nitrogen of H₂BA^PrTPP.     

Chirality Control of Quadruple Helixes of Metal Strings by Peripheral Chiral Ligands

Chirality control of helixes with the Δ (P) or Λ (M) form is interesting in various fields such as extended metal atom chains (EMACs), in which the metal backbones are helically wrapped by four ligands. Herein, we report two EMACs, Δ‐[Ni₅((?)camnpda)₄] and Λ‐[Ni₅((+)camnpda)₄], whose chiralities are controlled by chiral ligands with naphthyridine and camphorsulfonyl groups. There is a large energy difference (108 kcal mol^?1) between the two helical structures with one chiral ligand. Furthermore, the electron communication between [Ni₂]³⁺ units is more pronounced than in [Ni₅(bna)₄Cl₂]²⁺ (bna=binaphthyridylamido). The results demonstrate control of small‐scale helical structure and set the stage for future development of chiral controlled base and nanoelectronic devices.