A Fluorescent Chemosensor for Al3+ Based on CO Isomerization Derivated from Curcumin

A simple and nontoxic fluorescent chemosensor of di‐O‐methyl curcumin has been prepared from curcumin. The sensor exhibited selective and sensitive fluorescent responses toward Al³⁺ over a wide range of metal ions, such as Mn²⁺, Ce³⁺, Pt²⁺, Sn⁴⁺, Hg⁺, Sb³⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Cu²⁺, Ni²⁺, Na⁺, NH₄⁺, Ag⁺, Pb²⁺, Zn²⁺, Fe²⁺, Fe³⁺, Hg²⁺ and Cr³⁺ in ethanol/water. The free ligand showed quite weak fluorescence emission due to the isomerization of C?O double bond in the excited state, however, after addition of Al³⁺, fluorescence emission results in a prominent fluorescence enhancement.     

Effect of epoxy resin on rheology of polycarbonate/clay nanocomposites

Polycarbonate/clay nanocomposites (PCNs) were prepared by melt intercalation using epoxy resin as a compatibilizer. The intercalated structure of PCNs was investigated using XRD and TEM. The linear and nonlinear dynamic rheological properties of PCNs were measured by the use of a parallel plate rheometer. The results reveal that the presence of epoxy influences rheological behavior of PCNs significantly. Addition of epoxy can improve dispersion of clay, enhancing the low-frequency viscoelastic responses; while high loadings of epoxy lead to a severe degradation of PC matrix, decreasing the high-frequency responses together with the plasticizing effect of excessive epoxy. Both of these two effects result in invalidity of time-temperature superposition. Moreover, all samples show high sensitivity to both the quiescent and large amplitude oscillatory shear (LAOS) deformation, despite enhanced percolation of tactoids due to the compatibilization of epoxy.     

Rapid Detection of Irreversible Acetylcholineasterase Inhibitor by Mass Spectrometry Assay

Here we developed a rapid method to detect acetylcholinesterase (AChE) activity by matrix‐assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI‐FTMS) for screening irreversible AChE inhibitors. Due to its good salt‐tolerance and low sample consumption, MALDI‐FTMS could facilitate rapid detection, especially detection in real application. AChE activity was determined through calculating abundance of substrate and product in mass spectrometry. By this approach, we investigated the relation of organophosphorous (OP) concentrations and AChE inhibition. Shown in different inhibition curves from different OP pesticides, enzyme inhibitions still kept good correlation with concentration of OPs. Finally, this AChE‐inhibited method was applied to screen whole bloods of four decedents and discuss their death reason. In contrast to healthy persons, three of decedents showed low AChE activity, and probably died for irreversible AChE inhibitors. Through the following detecting in GC‐MS/MS, the possible death reason of these three decedents was confirmed, and another decedent actually died for sumicidin, a non‐AChE inhibitor. It demonstrated that screening irreversible AChE inhibitors by detecting enzyme activity in MALDI‐FTMS provided fast and accurate analysis results and excluded another toxicants not functioning on AChE. This method offered alternative choices for indicating the existence of enzyme inhibitors.     

4‐Phosphatephenyl Covalently Modified Glassy Carbon Electrode for Real‐Time Electrochemical Monitoring of Paracetamol Release from Electrospun Nanofibers

A glassy carbon electrode (GCE) was covalently modified by 4‐phosphatephenyl (4‐PP). Sensing paracetamol (PCT) via linear sweep voltammetry in sulfuric buffer solution of pH 1.02 at 36.8 °C, the 4‐PP‐modified GCE showed high electrochemical sensitivity and long reusability. PCT‐loaded poly(vinyl alcohol) (PVA) nanofibers were prepared by electrospinning. Based on the calibration curve of PCT on the 4‐PP‐modified GCE, the PCT release process from the nanofibers was electrochemically monitored in real time via two routes. The results showed that the covalently modified GCE can be repeatedly used as real‐time electrochemical monitoring platform for drug release from drug‐loaded nanofibers in the long term.     

Allylation and alkylation of oxindoleketimines via imine umpolung strategy

When treated with an alkoxide base like t-BuOK in aprotic solvent, N-diphenylmethyl imino oxindoles, made conveniently through condensation of corresponding isatins with N-diphenylmethyl amine, are deprotonated to form azaallyl anions. Allylation and alkylation of this type of intermediates proceed smoothly with diverse C-electrophiles. Acidic work up finishes 3-amino-3-allyl/alkyl oxindoles. The overall transformation equals to an umpolung process at the C3 of isatins.     

Periodic Mesoporous Organosilicas as Efficient Nanoreactors in Cascade Reactions Preparing Cyclopropanic Derivatives

In this work, three organosilica precursors functionalized with carbamate moieties were synthesized by condensing of 3‐isocyanatopropyltriethoxysilane and coupling regents of either hydroquinone (HQ), bisphenol A (BPA), or 1,1′‐bi‐2‐naphthol (BN). These organosilica precursors were covalently bonded in the framework of periodic mesoporous organosilicas by co‐condensation and hydrolysis with tetraethyl orthosilicate (TEOS) under hydrothermal treatment. The compositions and physical properties were characterized with FTIR, XRD, thermogravimetric/differential thermal analysis (TG/DTA), ²⁹Si NMR, ¹³C NMR spectroscopies, SEM, TEM, and BET technologies. These characterizations suggest that three different structures were formed as the result of different sizes and compositions of the organosilica precursors. The three mesoporous organosilicas were applied as heterogeneous catalysts in the one‐pot cascade Knoevenagel and Michael cyclopropanic reactions for the synthesis of cyclopropanic derivatives and showed excellent activity and selectivity. The highest conversion was obtained with mesoporous catalyst (MC)‐HQ owing to its ordered mesostructure, highest surface area, and weakest stereo effect of the organic linking groups compared with MC‐BAP and MC‐BN. This methodology employed cheaper and more easily obtainable raw materials as reagents over the traditional alkene additive system and these heterogeneous catalysts exhibit superior performance and recyclability than typical homogeneous organic catalysts.     

微波快速合成α—巯基—β—（4—甲氧基）苯基丙烯酸

１引言α－巯基－β－（４－甲氧基）苯基丙烯酸是一种高灵敏度、高选择性的显色剂,可用于痕量镍的测定［１］,也是一种重要的有机合成中间体。本文报道在微波辐射条件下由对甲氧基苯甲醛和绕丹宁快速缩合成对甲氧基苯亚甲基绕丹宁,然后对甲氧基苯亚甲基绕丹宁在氢氧化...     

Rheological properties and crystallization behavior of multi‐walled carbon nanotube/poly(ε‐caprolactone) composites

Multi‐walled carbon nanotube/poly(ε‐caprolactone) composites (PCLCNs) were prepared by melt compounding. The rheology, nonisothermal crystallization behavior, and thermal stability of PCLCNs were, respectively, investigated by the parallel‐plate rheometer, differential scanning calorimeter, and TGA. Cole–Cole plots were employed successfully to detect the rheological percolation of PCLCNs under small amplitude oscillatory shear. PCLCNs present a low percolation threshold of about 2–3 wt % in contrast to that of clay‐based nanocomposites. The percolated nanotube network is very sensitive to the steady shear deformation, and is also to the temperature, which makes the principle of time‐temperature superposition be invalid on those percolated PCLCNs. Small addition of nanotube cannot improve the thermal stability of PCL but can increase crystallization temperature remarkably due to the nucleating effect. As the nanotube is much enough to be percolated, however, the impeding effect becomes the dominant role on the crystallization, and the thermal stability increases to some extent. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3137–3147, 2007