Enzyme-free colorimetric assay for mercury(II) using DNA conjugated to gold nanoparticles and strand displacement amplification

The authors describe a colorimetric method for the determination of Hg(II) ion. It is based on the color change from red to colorless as displayed by gold nanoparticle (AuNP) modified with thymine - rich DNA. Signal amplification is accomplished by free strand displacement recycling. In this strategy, Hg(II) unfolds the arch-trigger duplex due to the high affinity between Hg(II) and the thymines to form T-Hg(II)-T structures, thereby causing the release of trigger. The liberated trigger unfolds the hairpin structure of H1, and unfolded H1 further unfolds with H2. As a result, the H2 hairpin displaces trigger, and the released trigger unfolds another H1. This results in strong and enzyme-free strand displacement recycling amplification. The aggregation of DNA-AuNPs occurs in the presence of the duplex formed by hairpins H2 and H1. This results in a color change from red to colorless that can be visually observed. Under optimal conditions, the assay has a detection range over 4 orders of magnitude and a 3.4 nM detection limit. The assay is selective, sensitive, rapid and cost-effective. In our perception, it represents a useful platform for determination of Hg(II).

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Graphical abstract Schematic presentation of the  simple, rapid, low cost colorimetric detection of mercury(II) based on enzyme-free strand displacement amplification along with DNA-labeled AuNP.

     

Isothermal and nonisothermal crystallization kinetics of novel biobased poly(ethylene succinate-<Emphasis Type="Italic">co</Emphasis>-ethylene sebacate) copolymers from the amorphous state

In this work, the isothermal and nonisothermal crystallization kinetics of three novel biobased poly(ethylene succinate-co-ethylene sebacate) (PESSe) copolymers was systematically investigated with differential scanning calorimetry under different crystallization conditions from the amorphous state. For the isothermal cold crystallization kinetics study, the Avrami equation could well describe the crystallization process of PESSe at various crystallization temperatures. All three PESSe copolymers crystallized through the same crystallization mechanism; moreover, the overall isothermal cold crystallization rate of PESSe decreased with increasing ethylene sebacate (ESe) comonomer content. The nonisothermal cold crystallization kinetics of PESSe was also studied at different heating rates. With increasing ESe content or heating rate, the nonisothermal cold crystallization exotherm of PESSe copolymers shifted to high temperature range. Both the crystallization rate parameter and crystallization rate coefficient of PESSe copolymers decreased with increasing ESe content, indicating that PESSe copolymer with higher ESe content crystallized more slowly than that with lower ESe content. The Ozawa equation was used to analyze the nonisothermal cold crystallization kinetics of PESSe copolymers, which was found to fit the crystallization process very well.     

Enhanced Photocatalytic Degradation of Methylene Blue over Hexagonal WO<Subscript>3</Subscript>/Graphene under Visible-Light Irradiation

A series of composites containing hexagonal tungsten trioxide (h-WO₃) and reduced graphene oxide (rGO) sheets are synthesized via a modified one-step hydrothermal route without assisted additive. The composites are characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and UV-vis absorption spectroscopy. The new procedure made it possible to increase the reduction degree of GO. Based on the evidence presented hexagonal WO₃ grows on the surface of graphene through chemical interactions with the surface. The visible-light photocatalytic degradation of methylene blue shows that the h-WO₃/rGO composites exhibit superior photocatalytic performance of 96% with a maximum degradation rate achieved under visible-light irradiation for 6 h. The speculations concerning the mechanism of photocatalytic reactions are discussed. The improved photocatalytic activity can be accounted for by the increased adsorption toward chemical species, the enhanced light absorption and an efficient separation of photogenerated electron-hole pairs and transfer of charge carriers.     

Copolyphenylenes with pendant benzimidazolyl and diethanolaminohexyloxy groups: Synthesis and electron‐transporting application in PLEDs

Two new electron‐transporting copolyphenylenes P1NH and P2NH possessing balanced charges crucial to emission efficiency of polymer light‐emitting diodes (PLEDs) have been synthesized and applied as an electron‐transporting layer (ETL). The main chain structure is all para‐linkage for P1NH and both para‐ and meta‐linkage for P2NH , with the same pendant electron‐withdrawing benzimidazolyl and polar diethanolaminohexyloxy groups. Both copolymers possess excellent thermal stability (T _d > 300 °C, T _g > 100 °C) due to their rigid backbones. In addition, the pendant groups effectively lower LUMO (～ ?2.70 eV) and HOMO (～ ?5.70 eV) levels, resulting in improved electron‐transporting and hole‐blocking capabilities. Multilayer yellow‐emitting PLEDs with a configuration of ITO/PEDOT:PSS/SY/ETL/LiF/Al were successfully fabricated by the spin‐coating process. The maximum luminance and maximum current efficiency of the P1NH ‐based device were 12,881 cd/m² and 10.94 cd/A, respectively, superior to the performance of P2NH ‐based device (4938 cd/m², 3.70 cd/A) and the device without ETL (8690 cd/m², 2.78 cd/A). Current results indicate that P1NH is highly effective in enhancing electron transport and device performance. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2494–2505     

超高效液相色谱-三重四极杆质谱法测定食品中34种非法添加减肥类化合物

建立了超高效液相色谱-三重四极杆质谱测定食品(含保健食品)中34种减肥类非法添加化合物的方法。采用Waters CORTECS T3色谱柱(100 mm×2.1 mm,2.7μm),以0.1%(v/v)甲酸水溶液-含0.1%(v/v)甲酸的乙腈溶液为流动相,梯度洗脱,在电喷雾离子源、正离子或负离子模式下以多反应监测(MRM)方式检测。西布曲明等29种化合物在0.5~10μg/L范围内、氯噻嗪等5种化合物在2.5~50μg/L范围内均呈良好的线性关系,相关系数(r)均大于0.99;西布曲明等29种化合物在5、10和20μg/kg添加水平下的平均加标回收率为49.2%~136.2%,相对标准偏差(RSD)为0.7%~15.0%(n=6),氯噻嗪等5种化合物在25、50和100μg/kg添加水平下的平均加标回收率为51.5%~130.9%,RSD为0.8%~14.0%(n=6);西布曲明等29种化合物的检出限为5μg/kg,定量限为10μg/kg,氯噻嗪等5种化合物的检出限为25μg/kg,定量限为50μg/kg。本方法已应用于实际样品的测定,共检出了12种化合物,有效打击了非法添加行为。     

Determination of Rosiglitazone by Direct Analysis in Real-Time Mass Spectrometry

The determination of rosiglitazone in dietary supplements by direct analysis in real-time mass spectrometry normally provides low repeatability. The [M+H]⁺ signal sharply decreased in the presence of strong-base and weak-acid ionic compounds because rosiglitazone decomposition occurred due to the hydrolysis of strong-base and weak-acid anions. The repeatability was improved and the influence of ionic compounds was minimized by the use of pioglitazone as an internal standard. Orbitrap mass spectrometry was used to provide high resolution in which isotopic interferences from M?+?1 of pioglitazone upon M of rosiglitazone were eliminated. This approach was used to determine rosiglitazone in tablet and dietary supplements in 1?min per sample.