Polyaniline functionalized CoAl-layered double hydroxide nanosheets as a platform for the electrochemical detection of carbaryl and isoprocarb.

The preparation of the polyaniline/CoAl-layered double hydroxide composite (PANI/CoAl-LDH) is presented by ultrasonic mixing the uniform PANI- and CoAl-LDH-building blocks, both of which are synthesized in a microemulsion system. Due to the improved surface area, increased adsorptive and catalytic sites, and enhanced conductivity, the PANI/CoAl-LDH-modified glassy carbon electrode (GCE) delivers rapid electron-transfer and mass-transfer between the substrate electrode and analytes. Consequently, PANI/CoAl-LDH/GCE demonstrates outstanding electrocatalytic activity toward carbaryl and isoprocarb with good selectivity, stability, and reproducibility. The amperometric sensor gives rise to a wide linear range of 0.1 ~ 150 µM for both carbaryl and isoprocarb at 0.19 and 0.39 V (vs. SCE), respectively. Their limits of detection are respectively 6.8 and 8.1 nM. This sensor is successfully used for the determination of carbaryl and isoprocarb pesticides in real vegetable samples with a relative standard deviation below 4%.

Amperometric sensing of catechol by using a nanocomposite prepared from Ag/Ag2O nanoparticles and N,S-doped carbon quantum dots.

This work describes the synthesis of a nanocomposite consisting of Ag2O, silver nanoparticles and N,S-doped carbon quantum dots (Ag2O/Ag@NS-CQD). The NS-CQD were prepared by hydrothermal treatment of p-aminobenzenesulfonic acid. They act as both the reducing and stabilizing agent for synthesis of Ag2O/Ag@NS-CQD. The composite was characterized by UV-vis spectroscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The glassy carbon electrode (GCE) was modified by coating it with Ag2O/Ag@NS-CQD. It exhibits excellent amperometric response to catechol, typically at a low working potential of around 0.25 V. Under the best experimental conditions, the sensor has a wide linear response (0.2 to 180 µM) and a low detection limit (13 nM; at S/N = 3). The method was applied to analysis of spiked water samples and gave satisfactory results. Graphical abstract Schematic representation of the preparation of the Ag/Ag2O@N,S-doped carbon quantum dots composite using p-aminobenzenesulfonic acid and silver nitrate as the starting materials. The corresponding modified glassy carbon electrode exhibits the excellent amperometric sensing performance toward catechol at pH 7.0 with low detection limit and good selectivity.

Human behavior-based particle swarm optimization.

Particle swarm optimization (PSO) has attracted many researchers interested in dealing with various optimization problems, owing to its easy implementation, few tuned parameters, and acceptable performance. However, the algorithm is easy to trap in the local optima because of rapid losing of the population diversity. Therefore, improving the performance of PSO and decreasing the dependence on parameters are two important research hot points. In this paper, we present a human behavior-based PSO, which is called HPSO. There are two remarkable differences between PSO and HPSO. First, the global worst particle was introduced into the velocity equation of PSO, which is endowed with random weight which obeys the standard normal distribution; this strategy is conducive to trade off exploration and exploitation ability of PSO. Second, we eliminate the two acceleration coefficients c 1 and c 2 in the standard PSO (SPSO) to reduce the parameters sensitivity of solved problems. Experimental results on 28 benchmark functions, which consist of unimodal, multimodal, rotated, and shifted high-dimensional functions, demonstrate the high performance of the proposed algorithm in terms of convergence accuracy and speed with lower computation cost.