ABSTRACT
Fipronil, a phenyl pyrazole insecticide, is extensively used in agriculture to control insect infestation. It has the potential to assimilate into the food chain, leading to serious health concerns. We report molecularly imprinted polymer (MIP)-based dispersive solid-phase microextraction for the targeted determination of fipronil in milk samples. Designing such a sorbent is of paramount importance for measuring the accurate amount of fipronil for monitoring its permissible limit. Response surface methodology based on a central composite design following a face-centered approach was used to optimize experimental conditions. The maximum binding capacity of 47 mg g-1 was achieved at optimal parameters of time (18 min), temperature (42 °C), pH (7), and analyte concentration (120 mg L-1). Under these conditions, a high percentage recovery of 94.6 ± 1.90% (n = 9) and a low limit of detection (LOD) and limit of quantitation (LOQ) (5.64 × 10-6 and 1.71 × 10-5 µg mL-1, respectively) were obtained. The MIP was well characterized through a scanning electron microscope (SEM) as well as Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) methods. Adsorption kinetics of the MIP followed the pseudo-first-order model (R 2 0.99 and χ2 0.96), suggesting the MIP-analyte interaction to be a physiosorptive process, while adsorption isotherms followed the Freundlich model (R 2 0.99). The real sample analysis through high-performance liquid chromatography (HPLC) confirmed the selective determination of fipronil from milk samples.
ABSTRACT
Refrigeration based on the electrocaloric effect can offer many advantages over conventional cooling technologies in terms of efficiency, size, weight, and power source. The discovery of ferroelectric and antiferroelectric properties in fluorite-based materials in 2011 has led to diverse applications related to memory (e.g., ferroelectric tunnel junctions, nonvolatile memory, and field-effect transistors) and energy fields (e.g., energy storage and harvesting, electrocaloric refrigeration, and infrared detection). Fluorite-based materials exhibit several properties not shared by most conventional materials (such as in terms of compatibility with complementary metal-oxide semiconductors and 3D nanostructures, deposition thickness at the nanometer scale, and simple composition). Here, the electrocaloric refrigeration properties of fluorite-based ferroelectric/antiferroelectric materials are reviewed by focusing on the advantages of ZrO2 - and HfO2 -based materials (e.g., relative to conventional perovskite- and polymer-based counterparts). Finally, the recent progress made in this research field are also discussed along with its future perspectives.
ABSTRACT
In this work, we prepared Cu2FeSnS4 (CFTS) microspheres via solvothermal method and studied their photocatalytic performance towards the degradation of organic pollutants. With increasing solvothermal temperature from 160 °C to 180 °C, the morphology of CFTS changes from irregular 2D to hierarchical 3D shapes. Hierarchical 3D CFTS microspheres packed with 2D nanosheets were successfully prepared at 180 °C. During the solvothermal process, octadecyl amine (ODA) acts as a capping agent to prevent the aggregation of particles, while L-cystine functions as an environmentally friendly sulfur source and complexing reagent. The large surface area and mesoporous structure of the as-prepared 3D hierarchical CFTS microspheres provide more active sites, enhance visible light absorption and promote charge separation and transfer, leading to the improved photodegradation performance for RhB and MB compared to the samples prepared at the temperature lower than 180 °C. This work provides a simple and low-cost method for the synthesis of 3D hierarchical CFTS towards photocatalytic applications.
