Fabrication of Predominantly Mn4+‐Doped TiO2 Nanoparticles under Equilibrium Conditions and Their Application as Visible‐Light Photocatalyts

The chemical state of a transition‐metal dopant in TiO₂ can intrinsically determine the performance of the doped material in applications such as photocatalysis and photovoltaics. In this study, manganese‐doped TiO₂ is fabricated by a near‐equilibrium process, in which the TiO₂ precursor powder precipitates from a hydrothermally obtained transparent mother solution. The doping level and subsequent thermal treatment influence the morphology and crystallization of the TiO₂ samples. FTIR spectroscopy and X‐ray photoelectron spectroscopy analyses indicate that the manganese dopant is substitutionally incorporated by replacing Ti⁴⁺ cations. The absorption band edge can be gradually shifted to 1.8 eV by increasing the nominal manganese content to 10 at %. Manganese atoms doped into the titanium lattice are associated with the dominant 4+ valence oxidation state, which introduces two curved, intermediate bands within the band gap and results in a significant enhancement in photoabsorption and the quantity of photogenerated hydroxyl radicals. Additionally, the high photocatalytic performance of manganese‐doped TiO₂ is also attributed to the low oxygen content, owing to the equilibrium fabrication conditions. This work provides an important strategy to control the chemical and defect states of dopants by using an equilibrium fabrication process.     

准聚轮烷的研究进展

准聚轮烷由于在刺激响应性材料、自修复材料、分子机器及荧光传感器等领域有着潜在的应用价值,近年来引起了研究人员极大的兴趣。根据准轮烷基团所处位置的不同,可将准聚轮烷分为三种类型：主链型、侧链型和其他类型 （如支化和网状准聚轮烷等）。本综述主要根据上述三种类型,基于冠醚、环糊精、杯芳烃、葫芦脲和柱芳烃这五种超分子主体分子所构筑的准聚轮烷的最新研究进展进行简要的综述,并对其未来的发展作了进一步的展望。     

吡啶并[2,3-d]嘧啶衍生物受体的合成及对阴离子识别研究

通过6-氨基嘧啶、取代苯甲醛与丙二腈的三组分反应合成了4种吡啶并[2,3-d]嘧啶受体分子,利用紫外-可见吸收光谱考察了其与F-,Cl-,Br-,AcO-,4HSO-,2 4H PO-等阴离子的作用.结果表明该类受体分子与阴离子形成氢键配合物,导致吡啶并[2,3-d]嘧啶受体的光谱发生变化.测定了配合物的结合比和稳定常数,发现受体化合物对AcO-离子具有良好的选择性,对其它多种阴离子无影响.Job曲线表明受体分子与阴离子间形成1∶1型的配合物.1H NMR滴定进一步证实了氢键作用的存在及参与类型.     

Naryl-substituted anthranilamides with intramolecular hydrogen bonds

Hydrogen bonding interaction as one type of non-covalent force has proven itself to be highly efficient for constructing structurally unique artificial secondary structures. Here, the structure of N_aryl-substituted anthranilamide in solution is demonstrated by various NMR technique, the intramolecular hydrogen bonds between amide attached to arylamine of the same ring is proposed, which is supported by its crystal structure in the solid phase. The substituent on the nitrogen atom of arylamine plays an important role in forming the presence of intramolecular hydrogen bonds. The chemical shift of the N_aryl-H downfield changes obviously, due to the formation of intramolecular hydrogen bonds and the deshielding effect of oxygen, and the neighboring C–H is activated and shows downfield protonic signal too. The presence of intramolecular hydrogen bonds probably provides the explanation for the transformation from N_aryl-substituted anthranilamide to imine, which could be converted into 2-aryl quinazolinone finally.     

A Rapid Method for Qualitative and Quantitative Analysis of Major Constituents in Dengzhanxixin Injection by LC-DAD-ESI–MSn

For the first time a rapid method for qualitative and quantitative analysis of constituents in Dengzhanxixin injection was established by liquid chromatography with electrospray ionization–tandem mass spectrometry. Eighteen compounds including flavonoids and phenolic acids were characterized or tentatively identified. Ten of these compounds, including 5-O-caffeoylquinic acid, caffeic acid, 1,3-O-dicaffeoylquinic acid, 6′-O-caffeoylerigeroside, scutellarin, 3,4-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid, erigoster B, apigenin-7-O-glucuronide and 4,5-O-dicaffeoylquinic acid, were further quantified as marker substances by LC-DAD using a C₁₈ column at 0.4 mL min^?1 within 37 min. The quantitative method was validated for ten interesting compounds, including linearity, accuracy, precisions, LOQ and LOD, which was proved to be sensitive, reproducible and accurate. The study might provide a comprehensive method for the quality assessment of dengzhanxixin injection.     

An LC-MS-MS Method for the Determination of Perfluorinated Surfactants in Environmental Matrices

Recently, there has been increasing concern about perfluorinated surfactants, especially perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) due to their persistence and chronic toxicity in the aquatic environment. Solid phase extraction (SPE) followed by liquid chromatography coupled with tandem mass spectrometry (LC-MS-MS) are widely applied to quantitatively identify PFOS and PFOA. However, the application of this powerful analytical technique is limited by matrix susceptibility. The co-eluting matrix components in the SPE extracts affect the ionization efficiency and lead to erroneous results. An efficient sample clean-up method was developed in this study to significantly remove co-eluting matrix components by applying the SPE extracts onto a silica cartridge. It was shown that matrix effect (ME%) increased to >70% for both PFOS and PFOA in the analysis of raw sewage. Internal standardization was used to further compensate for the matrix effect, which also proved to improve the signal reproducibility. The clean-up method described in this study was applied to different water samples (surface water and wastewater) to evaluate the efficiency of silica clean-up and the influence of sample origin on the matrix effect. ME% and recovery efficiency (RE%) were in the range of 91.9–98.3% and 89.2–98.0%, respectively. Results showed that the developed method is robust and can be applied to analyze PFOS and PFOA in different environmental matrices.     

Determination of Trace Amounts of Chlorogenic Acid and Three of Its Metabolites Using Time-Resolved LPME and LC-UV Detection in Biological Specimens

Chlorogenic acid (CGA) is an effective antitumor, anti-inflammatory and antimicrobial agent. Since the absorption and metabolism of CGA remains controversial, time-resolved binary-solvent synergy liquid-phase microextraction (TRBSS-LPME) using hollow fiber was developed for the extraction of CGA and its metabolites: caffeic acid, p-hydroxycinnamic acid and ferulic acid, from biological specimens. In this technique, the target drugs were extracted into a binary-solvent immobilized in the wall pores of hollow fiber. The extraction occurred due to a pH gradient between the two sides of the fiber. After extraction, an aliquot was analyzed by LC. Under the optimal conditions, the CGA, caffeic acid, p-hydroxycinnamic acid and ferulic acid had good correlation of determination values (R > 0.97) and the detection limits (LODs) were 1.0, 1.0, 2.0, and 5.0 ng mL^?1 in plasma; and 1.0, 50, 10, and 50 ng mL^?1 in urine. The mean recoveries in plasma were 90.8–119.8% for CGA and its metabolites: caffeic acid, p-hydroxycinnamic acid and ferulic acid evaluated and the mean recoveries of caffeic acid and p-hydroxycinnamic acid in urine were 81.6–111.6%. Finally, TRBSS-LPME was successfully used for the determination of target drugs in biological specimens. It not only extended the linear range of CGA determination in biological samples and improved the sensitivity, but also eliminated interferences from complex constituents in the biological specimens and reduced the LOD.     

A highly efficient synthetic method for the preparation of 3,4-dimethylbenzaldehyde from o-xylene in aqueous media

In this study, 3,4-dimethylbenzaldehyde was obtained in 82.3% total yield by oxidation of 3,4-dimethylbenzyl chloride with NaNO₃/AcOH catalyzed by PEG-600 in aqueous media. The starting material 3,4-dimethylbenzyl chloride was prepared by chloromethylation of o-xylene in CTAB micellar catalytic system. Compared with other synthetic methods, this method not only enhanced the yield, but also afforded an efficient work-up procedure. The structures of the products were confirmed by Elemental analysis, ¹H NMR and ¹³C NMR or compared with authentic samples.     

Empirical line parameters of methane in the 1.63–1.48 μm transparency window by high sensitivity Cavity Ring Down Spectroscopy

The positions and intensities of methane in the 1.58 μm transparency window have been measured by high sensitivity Cavity Ring Down Spectroscopy at room temperature. The achieved sensitivity allowed measuring intensities as small as 3 × 10⁻²⁹ cm/molecule i.e. three orders of magnitude smaller than the intensity cut off of the HITRAN line list of methane. The complete list contains a total of 16,149 transitions between 6165 and 6750 cm⁻¹. Their intensity values vary over six orders of magnitude from 1.6 × 10⁻²⁹ to 2.5 × 10⁻²³ cm/molecule. Transitions due to CH₃D in “natural” abundance in our methane sample were identified using a new spectrum of CH₃D recorded separately with a Fourier Transform spectrometer. From simulations of the CH₃D and methane spectra at low resolution, the CH₃D isotopologue has be found to contribute by up to 30% of the absorption near 1.58 μm.