Taco grande: a dumbbell bis(crown ether)/paraquat [3](taco complex)

The first paraquat-based [3](taco complex) was successfully prepared from a linear bis(crown ether) host and paraquat as shown by proton NMR characterization and X-ray analysis. It has a dumbbell shape in the solid state. The two crown ether binding sites are independent of each other during their complexation in solution.     

Thermodynamic properties and viscosities of aqueous 1,1′-dimethyl-4,4′-dipyridinium dichloride solutions at 25°C

The densities, heat capacities, heats of dilution, and viscosities of aqueous 1,1-dimethyl-4,4-dipyridinium dichloride were measured below 1 m at 25°C. From the standard partial molal volumes and heat capacities and the B viscosity coefficients, this salt is shown to be a strong structure breaker. The excess enthalpies, entropies, volumes, and heat capacities all show negative deviations from the limiting Debye-Hückel law for 2:1 electrolytes. These excess functions cannot be explained through association or structural interactions and suggest that, at higher concentrations, this rigid bolaform electrolyte may behave more like a 1:1 electrolyte than a 2:1 electrolyte.     

H_3PW_(12)O_(40)/MCM-48的制备及其光催化降解农药(英文)

以介孔分子筛MCM-48为载体,采用水热法制备了负载磷钨酸H3PW12O40(HPW)的多金属氧酸盐催化剂HPW/MCM-48。利用傅里叶变换红外光谱(FT-IR)、小角度X射线粉末衍射(XRD)、氮气吸附检测和高分辨透射电子显微镜(HRTEM)对其结构进行了表征,并以农药吡虫啉和百草枯为对象,考察了所制备的HPW/MCM-48的光催化降解活性。结果表明,采用水热法制备的催化剂保持了MCM-48的介孔分子筛结构和HPW的Keggin结构,比表面积783.35m2·g-1,孔体积1.46cm3·g-1,平均孔径2.76nm,相比于母体HPW,HPW/MCM-48的比表面积大大增加;在365nm紫外光下反应14h后,20mg剂量HPW/MCM-48催化剂能使50mL,10mg·L-1吡虫啉和百草枯的降解率分别达57.38%和63.79%,而HPW对两种农药的降解率在25%左右,空白组降解率均低于5%,说明负载后HPW对两农药的降解活性显著增强。动力学考察表明,HPW/MCM-48对农药降解过程符合一级动力学方程,对吡虫啉和百草枯这两种农药的降解速率常数Ka分别为0.089和0.117h,半衰期t1/2为7.8和5.9h。     

A multicommuted flow system with solenoid micro-pumps for paraquat determination in natural waters

A flow system designed with solenoid micro-pumps is proposed for the determination of paraquat in natural waters. The procedure involves the reaction of paraquat with dehydroascorbic acid followed by spectrophotometric measurements. The proposed procedure minimizes the main drawbacks related to the standard chromatographic procedure and to flow analysis and manual methods with spectrophotometric detection based on the reaction with sodium dithionite, i.e. high solvent consumption and waste generation and low sampling rate for chromatography and high instability of the reagent in the spectrophotometric procedures. A home-made 10-cm optical-path flow cell was employed for improving sensitivity and detection limit. Linear response was observed for paraquat concentrations in the range 0.10–5.0 mg L⁻¹. The detection limit (99.7% confidence level), sampling rate and coefficient of variation (n = 10) were estimated as 22 μg L⁻¹, 63 measurements per hour and 1.0%, respectively. Results of determination of paraquat in natural water samples were in agreement with those achieved by the chromatographic reference procedure at the 95% confidence level.     

Water-insoluble cyclodextrin polymer crosslinked with citric acid for paraquat removal from water

The anionic water-insoluble cyclodextrin polymer (polyCTR-β-CD) was crosslinked between β-cyclodextrin (β-CD) and citric acid (CTR) at 180?°C during 30?minutes to eliminate paraquat (PQ) from water. The reaction yield was equal to 70.2%, the ionic exchange capacity corresponded to 3.29?mmol·g^?1 and the β-CD content was 0.29?mmol·g^?1. Then, samples were characterized by SEM, ATR-FTIR, TGA, BET and stereoscopic microscope. Adsorption experiments were investigated with different factors such as pH of the solution, contact time, initial concentration of paraquat and adsorption temperature. The relevant pH was equal to 6.5 and the optimal contact time was 120?minutes to attain adsorption equilibrium. At 30?°C, the adsorption capacity was increased (9.4, 17.4 and 20.8?mg·g^?1) when the initial concentration of paraquat was raised (25, 50 and 200?mg·L^?1 respectively). Adsorption kinetics was appropriated to the pseudo-second-order model and adsorption isotherm was fitted to the Langmuir model. For thermochemistry parameters at different temperatures, the negative ΔG° showed a spontaneous adsorption process, the negative ΔH° indicated an exothermic process and the positive ΔS° exhibited an increase disorder. Finally, the reusability of the insoluble polymer was reached 78.3% after four regeneration cycles in methanol.     

恒电压下百草枯和阿特拉津在纳米通道中迁移特性研究

采用化学沉积法将金沉积到聚碳酸酯膜内孔壁,制备了呈负电性的阵列金纳米通道.在外加恒电压作用下,阳离子型的百草枯选择性通过负电性的金纳米通道,阿特拉津为分子型化合物,不受电荷选择性和电泳作用影响,难以在金纳米通道内迁移.借此,可实现二者的分离.     

Water-soluble pillar[5]arenes: A new class of plant growth regulators

It is highly valuable to develop bifunctional chemical fertilizers that can both regulate plant growth and reduce the toxicity of pesticides. Here we report three water-soluble pillar[5]arenes WP5-1, WP5-2 and WP5-3 established as efficient plant growth regulators for wheat to efficiently improve the development of buds and roots in the seedling cultivation stage. Moreover, as macrocyclic hosts for the poisoning herbicide paraquat, WP5-2 and WP5-3 can also be employed to reduce its toxicity based on host–guest interactions, as confirmed by cell viability experiments towards HEK 293 and Raw 264.4 cell lines.     

Differential Pulse Voltammetric Determination of Paraquat Using a Bismuth‐Film Electrode

A bismuth‐film electrode (BiFE) ex situ electrochemically deposited onto a copper substrate has been presented for paraquat determination. The bismuth film was electrochemically deposited at an applied potential of ?0.18 V vs. Ag/AgCl (3.0 M KCl) for 200 s. The analytical curve was linear in the paraquat concentration range from 6.6×10^?7 M to 4.8×10^?5 M with a limit of detection of 9.3×10^?8 M. The method presented satisfactory results at a confidence level of 95% and the performance was evaluated in water samples.     

Rapid and sensitive detection of pesticides by surface-enhanced Raman spectroscopy technique based on glycidyl methacrylate-ethylene dimethacrylate (GMA-EDMA) porous material

A novelmethod of fast and sensitive SERS detection using GMA-EDMA porous material combined with a miniature device was reported in this study. A 100 μL solution containing sample, silver colloid and NaCl was evenly mixed to ensure the sample molecules would adsorb onto silver nanoparticles. Then the mixture was added onto the porous material surface slowly, so that the aggregation of silver colloid would stay on the surface while the liquid components would flow away. This technology can improve the sensitivity of SERS detection. By this method, two pesticides tricyclazole and paraquat were successfully detected at concentrations of 5×10-3 mg/L and 1×10-3 mg/L, respectively.