Tris(Znsalen) cryptand minimizes Znsalen aggregation arising from intermolecular Zn…O interaction

Exploring the factors to control Znsalen aggregation is of importance to design functional materials in catalysis, optical materials and biological imaging. In this work, we synthesized and characterized four cryptand type triZnsalen complexes and found that cryptand structure could efficiently minimize intermolecular Zn···O interaction. More importantly, encapsulated by PLGA nanoparticles, cryptand triZnsalen 1 displayed visible intracellular fluorescence whereas monomeric Znsalen 5 could not. These results provide a new access to design new luminescent materials with the potential application in optics and biological studies.     

纳米二氧化钛-氧化锌/硅溶胶/导电胶复合材料固定联吡啶钌制备磷酸可待因电化学发光传感器

利用硅溶胶的成膜性、纳米二氧化钛-氧化锌大的比表面积及导电胶的粘结性,制备了纳米二氧化钛-氧化锌/硅溶胶/导电胶复合材料,基于此复合材料将联吡啶钌固定到金电极表面,制备了磷酸可待因电化学发光(ECL)传感器.在优化的实验条件(800 V负高压、扫描速度100 mV/s,磷酸盐缓冲体系(pH 6.5))下,可待因浓度在1.0×10-7～1.0×10-4 mol/L范围内与电化学发光强度呈良好的线性关系(r2=0.9973),检出限为2.56×10-8 mol/L (S/N=3).传感器表现出良好的重现性与稳定性,连续平行测定1.28×10-5 mol/L可待因溶液10次,发光强度的相对标准偏差(RSD)为2.7％;室温下保存10天后,发光强度为初始值的92％以上.测定可待因药物实际样品的加标回收率在99.3％ ～ 102.5％之间.     

Catalysis and inhibition of benzimidazole units on thermal imidization of poly(amic acid) via hydrogen bonding interactions

The effect of benzimidazole units on thermal imidizaiton was studied when they were introduced into the main chain of poly(amic acid)(PAA). The thermal imidization process of PAA-PABZ synthesized by 3,3',4,4'-biphenyltetracarboxylic dianhydride(BPDA) and 2-(4-aminophenyl)-5(6)-aminobenzimidazole(PABZ) was studied by TGA, DSC, DMA, FTIR and in situ FTIR. The results of FTIR and in situ FTIR indicate benzimidazole units act as an "in situ" catalyst to accelerate thermal imidization of PAA to polyimide(PI) when the temperature is lower than 170 °C. FTIR and 1H-NMR results demonstrate that in situ catalysis is caused by the hydrogen bonding interactions between C=N of benzimidazole and ―NH― in ―CONH― of PAA and the semi-ionization of the H in imidazole ring of benzimidazole. However, when the imidization temperature is higher than 170 °C, the thermal imidization process is inhibited. DMA and in situ FTIR results illustrate that the decreased mobility of PI-PABZ macromolecular chains and the reduced reactive ability of anhydride formed during the intramolecular breakdown of polymer chains lead to the inhibition of thermal imidization process.     

Dipolar Rotors Orderly Aligned in Mesoporous Fluorinated Organosilica Architectures

New mesoporous covalent frameworks, based on hybrid fluorinated organosilicas, were prepared to realize a periodic architecture of fast molecular rotors containing dynamic dipoles in their structure. The mobile elements, designed on the basis of fluorinated p‐divinylbenzene moieties, were integrated into the robust covalent structure through siloxane bonds, and showed not only the rapid dynamics of the aromatic rings (ca. 10⁸ Hz at 325 K), as detected by solid‐state NMR spectroscopy, but also a dielectric response typical of a fast dipole reorientation under the stimuli of an applied electric field. Furthermore, the mesochannels are open and accessible to diffusing in gas molecules, and rotor mobility could be individually regulated by I₂ vapors. The iodine enters the channels of the periodic structure and reacts with the pivotal double bonds of the divinyl‐fluoro‐phenylene rotors, affecting their motion and the dielectric properties.     

A consensus successive projections algorithm – multiple linear regression method for analyzing near infrared spectra

The successive projections algorithm (SPA) is widely used to select variables for multiple linear regression (MLR) modeling. However, SPA used only once may not obtain all the useful information of the full spectra, because the number of selected variables cannot exceed the number of calibration samples in the SPA algorithm. Therefore, the SPA-MLR method risks the loss of useful information. To make a full use of the useful information in the spectra, a new method named “consensus SPA-MLR” (C-SPA-MLR) is proposed herein. This method is the combination of consensus strategy and SPA-MLR method. In the C-SPA-MLR method, SPA-MLR is used to construct member models with different subsets of variables, which are selected from the remaining variables iteratively. A consensus prediction is obtained by combining the predictions of the member models. The proposed method is evaluated by analyzing the near infrared (NIR) spectra of corn and diesel. The results of C-SPA-MLR method showed a better prediction performance compared with the SPA-MLR and full-spectra PLS methods. Moreover, these results could serve as a reference for combination the consensus strategy and other variable selection methods when analyzing NIR spectra and other spectroscopic techniques.     

Iron(III)‐Selective Chelation‐Enhanced Fluorescence Sensing for In Vivo Imaging Applications

A “turn‐on” pattern Fe³⁺‐selective fluorescent sensor was synthesized and characterized that showed high fluorescence discrimination of Fe³⁺ over Fe²⁺ and other tested ions. With a 62‐fold fluorescence enhancement towards Fe³⁺, the probe was employed to detect Fe³⁺ in vivo in HeLa cells and Caenorhabditis elegans, and it was also successfully used to elucidate Fe³⁺ enrichment and exchange infected by innexin3 (Inx3) in hemichannel‐closed Sf9 cells.     

Tris(pentafluoroethyl)silanol Derivatives and the Lewis Amphoteric Tris(pentafluoroethyl)silanolate Anion, [Si(C2F5)3O]−

While alkyl-substituted siloxanes are widely known, virtually nothing is known about perfluoroalkyl siloxanes and their congener species, the silanols and silanolates. We recently reported on the tris(pentafluoroethyl)silanide ion, [Si(C₂F₅)₃]⁻, which features Lewis amphoteric character deriving from the pentafluoroethyl substituents and their strong electron-withdrawing properties. Transferring this knowledge, we investigated the Lewis amphoteric behavior of the tris(pentafluoroethyl)silanolate, [Si(C₂F₅)₃O]⁻. In order to examine such Lewis amphoteric behavior, we first developed a strategy for the synthesis of the corresponding silanol Si(C₂F₅)₃OH, which readily condenses at room temperature to the hexakis(pentafluoroethyl)disiloxane, (C₂F₅)₃SiOSi(C₂F₅)₃. Deprotonation of Si(C₂F₅)₃OH employing a sterically demanding phosphazene base allows the characterization of the first example of a dimeric triorganosilanolate: the dianionic hexakis(pentafluoroethyl)disilanolate, [{Si(C₂F₅)₃O}₂]²⁻, implies Lewis amphoteric character of the monomeric [Si(C₂F₅)₃O]⁻ anion.     

指导本科生课外科研实践活动*——“我爱实验室”有感

由南开大学化学学院科技创新协会面向低年级本科生举办的“我爱实验室”活动,旨在拓宽学生的专业知识领域、使学生深入了解科研前沿方向、培养学生科研素养等。基于实验室的研究方向,学生自主调研文献选题、设计实验过程、参与组会沟通、交流并解决实验中遇到的问题。课外科研实践活动的开展不仅提高了学生的实验技能,而且拓宽了学生的知识领域,更重要的是培养和提高学生进行科学研究的素养和能力。