Preparation and application of a polythiophene solid‐phase microextraction fiber for the determination of endocrine‐disruptor pesticides in well waters

A robust solid‐phase microextraction fiber was fabricated by electropolymerization of thiophene on a stainless steel wire. This fiber was applied for the determination of endocrine‐disruptor pesticides, namely, chlorpyrifos, penconazole, procymidone, bromopropylate, and λ‐cyhalothrin in well waters by a headspace solid‐phase microextraction procedure. Operational parameters, namely, pH, sample volume, adsorption temperature and time, desorption temperature, stirring rate, and salt amount were optimized as 7.0, 8 mL, 70°C and 20 min, 250°C, 600 rpm, and 0.3 g/mL, respectively. The separation power of GC was coupled with the excellent sensitivity of the developed fiber enabling us to determine pesticide mixtures simultaneously in a ng/mL range. The LOD was in the range of 0.02–0.64 ng/mL. The method was successfully applied for the selective and sensitive determination of target pesticides in well water samples with acceptable recovery values (92–110%). The polythiophene fiber gives satisfactory results compared with commercial fibers. Commonly used pesticides with different polarities were chosen as representative compounds to search the applicability of the fiber for well water analysis collected from vineyards.     

Synthesis of Star Poly(N‐isopropylacrylamide) with a Core of Cucurbit[6]uril via ATRP and Controlled Thermoresponsivity

A series of CB[6]‐based macroinitiators with “n” bromo‐initiation sites on the “equator” of CB[6] is developed for the synthesis of CB[6]‐star poly(N‐isopropylacrylamide) (CB[6]‐star PNIPAM) by atom transfer radical polymerization. By taking advantage of the exceptional binding affinity of the CB[6] core, CB[6]‐star PNIPAM is used as a host macromolecule to construct large compound vesicles in the presence of protonated n‐butylamine at pH 5.63. The deprotonated n‐butylamine is detached from the CB[6] core at pH 11.1, which destructs the vesicular structures. For CB[6]‐star PNIPAM, the thermoresponsive properties can be adjusted by simply changing the formation and destruction of the inclusion complexes of the CB[6] core with n‐butylamine. These results suggest that the prepared CB[6]‐star PNIPAM shows pH and temperature responsiveness, which has great potential for the design of a dual response smart material.

     

Nanoscopically resolved dynamic charge‐carrier distribution in operating interband cascade lasers

Dynamic charge carriers play a vital role in active photonic quantum/nanodevices, such as electrically pumped semiconductor lasers. Here we present a systematic experimental study of gain‐providing charge‐carrier distribution in a lasing interband cascade laser. The unique charge‐carrier distribution profile in the quantum‐well active region is quantitatively measured at nanometer scales by using a noninvasive scanning voltage microscopy technique. Experimental results clearly confirm the accumulation and spatial segregation of holes and electrons in the beating heart of the device. The measurement also shows that the charge‐carrier density is essentially clamped in the presence of stimulated emission at low temperatures. The threshold charge‐carrier density exhibits a linear but fairly weak temperature dependence, in contrast to the exponential temperature dependence of the threshold current. The experimental approach will lead to a deeper understanding of fundamental processes that govern the operation and performance of nanoelectronic devices, quantum devices and optoelectronic devices.

     

An inorganic–organic hybrid material based on ZnO nanoparticles anchored to a composite made from polythiophene and hexagonally ordered silica for use in solid-phase fiber microextraction of PAHs

We report on an inorganic–organic hybrid nanocomposite that represents a novel kind of fiber coating for solid-phase microextraction (SPME) of polycyclic aromatic hydrocarbons (PAHs). The material is composed of ZnO nanoparticles, polythiophene and hexagonally ordered silica, and displays good extraction capability due to its nanostructure. The nanocomposite was synthesized by an in-situ polymerization technique, and the ZnO nanoparticles were anchored to the pores in the walls. The ZnO/polythiophene/hexagonally ordered silica (ZnO/PT/SBA-15) nanocomposite was then deposited on a stainless steel wire to obtain the fiber for SPME of PAHs. Optimum conditions include an extraction temperature of 85 °C (for 30 min only), a desorption temperature of 260 °C (for 2 min), and a salt concentration (NaCl) of 20 % (w/v). The detection limits are between 8.2 and 20 pg mL^?1, and the linear responses extend from 0.1 to 10 ng mL^?1. The repeatability for one fiber (for n?=?5), expressed as relative standard deviation, is between 4.3 and 9.1 %. The method offers the advantage of being simple to use, rapid, and low-cost (in terms of equipment). The thermal stability of the fiber and high relative recovery (compared to conventional methods) represent additional attractive features.

One-Pot Synthesis of Mannich Bases Under Solvent-Free Conditions

A mild and practically convenient one-pot procedure for the Mannich reaction via condensation of amines, aldehydes and malonates, β-ketoesters, or β-dicarbonyl compounds has been carried out without using any organic solvent, metallic catalyst, or Lewis acids or bases at room temperature. The present protocol offers several advantages, such as goods yields, simple procedure with easy workup, and the absence of any volatile, hazardous organic solvents and metallic catalyst.     

Paal–Knorr Pyrrole Synthesis in Water

Water was a suitable medium for Paal–Knorr pyrrole cyclocondensation. Hexa-2,5-dione was reacted with several aliphatic and aromatic primary amines, affording N-substituted 2,5-dimethyl pyrrole derivatives in good to excellent yields. An efficient, green method using water either as environmentally friendly solvent or catalyst was presented.     

Feasibility of tetracycline,a common antibiotic,as chelating agent for spectrophotometric determination of UO2 2+ after cloud point extraction

A cloud point extraction (CPE) procedure was presented for the preconcentration of UO₂ ²⁺ ion in different water samples. Tetracycline (TC) is the second most widely used antibiotics in the world and is used as chelating agent. To the best of our knowledge, this is the first work that an antibiotic is used as a chelating agent for CPE of UO₂ ²⁺. Besides, the use of TC as complexing agent provides excellent chelating features. TC molecule has large numbers of functional groups (adjacent hydroxyl oxygen atoms and cyclohexanone oxygen atoms, amide groups) which can form stable complex with UO₂ ²⁺. After complexation with TC, UO₂ ²⁺ ions were quantitatively recovered in Triton X-100 after cooling in the ice bath. 3.0 mL of acetate buffer was added to the surfactant-rich phase prior to its analysis by UV–Vis spectrophotometer. The influence of analytical parameters including pH, buffer volume, TC, Triton X-100 concentrations, bath temperature, incubation time were optimized. The effect of the matrix ions on the recovery of UO₂ ²⁺ ions was investigated. The limit of detection was 0.0746 μg mL^?1 along with enrichment factor of 14.3 with a R.S.D. of 3.6 %. The proposed procedure was applied to the analysis of various environmental water samples. On the other hand, the electronic distribution of TC molecule is investigated with their frontier molecular orbital density distributions.