Rational design of heterointerface between MoO2 and N-doped carbon with tunable electromagnetic interference shielding capacity.

Exploring highly efficient electromagnetic interference (EMI) shielding filler is urgently desired for next-generation wireless communication and integrated electronics. In this regard, a series of heterogeneous MoO2/N-doped carbon (MoO2/NC) nanorods with tunable conductivity have been successfully synthesized by regulating the pyrolysis temperature within 600, 700 and 800 °C. Profiting from the rational design of heterointerface and low-dimensional structure, the MoO2/NC powder achieves stronger EMI shielding capacity with the incremental temperature. It is found that the MoO2/NC-800 nanorods exhibit the optimal average EMI shielding effectiveness (SE) of 57.2 dB at a thickness of ∼0.3 mm in the X band. Meanwhile, the corresponding shielding mechanisms of MoO2/NC nanorods are also elaborately explained. More interestingly, the increase of sintering temperature makes an obvious effect on absorption loss but has little influence on reflection loss, demonstrating that adjusting the pyrolysis temperature is an effective strategy to strengthen the electromagnetic energy dissipation.

Construction of one-dimensional MoO2/NC heteronanowires for microwave absorption.

A combination of a special micro-nanostructure and multiple components has been proven as an effective strategy to strengthen the microwave attenuation capacity. In this work, one-dimensional MoO2/N-doped carbon (NC) nanowires with a heterostructure have been successfully prepared by utilizing mild in situ chemical oxidative polymerization and pyrolysis treatment. After compounding them with a thermoplastic polyurethane (TPU) matrix, the flexible composites exhibit tunable wave absorbing performance by modulating the filler loading of MoO2/NC heteronanowires. Experimental results demonstrate that the minimum reflection loss value of the MoO2/NC-TPU hybrid is up to -35.0 dB at 8.37 GHz under a thickness of only 2.3 mm with 40 wt% filler amounts. Moreover, the effective absorption bandwidth enables 3.26 GHz to be achieved (8.49-11.75 GHz) when the thickness changes to 2.0 mm, covering almost the whole X-band. Meanwhile, when the filler loading becomes 30 wt%, dual-absorption peaks appear. The relevant absorption mechanism is mainly attributed to the dielectric loss including strong dipolar/interfacial polarizations, Debye relaxation loss and multiple reflection and scattering.

Imidazole-modified C6 -chitosan derivatives used to extract ß-sitosterol from edible oil samples with a microwave-assisted solid phase extraction method.

ß-Sitosterol is a major bioactive constituent in plants with potent anticancer effects against many human cancer cells, but its bioavailability and therapeutic efficacy are limited by its poor solubility in water. In this study, C6 -imidazole chitosan, C6 -1-methylimidazole chitosan, C6 -1-ethylimidazole chitosan, C6 -1-vinylimidazole chitosan, C6 -1-allylimidazole chitosan, and C6 -1-butylimidazole chitosan were prepared to extract ß-sitosterol from edible oil samples via ultrasonic-assisted solid liquid extraction. The structures and properties of the newly synthesized products were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and elemental analysis. The extraction abilities of the derivatives were tested in the experiment with high-performance liquid chromatography (limit of detection 0.21 µg/g and limit of quantification 0.67 µg/g), and the % relative standard deviation (<3.25%) and recovery values of the prepared chitosan derivatives toward ß-sitosterol (average: 100.20%) were acceptable. The spiked interday and intraday recoveries of ß-sitosterol were 102.60 ± 2.78 and 103.90 ± 3.04%, respectively. The actual amounts of ß-sitosterol extracted from three real samples using C6 -imidazole chitosan according to the solid phase extraction method were 3302.40, 901.70, and 2045.60 mg/kg for corn oil, olive oil, and pea oil, respectively.

Application of amino-based chitosan cyclodextrin derivatives for the extraction of catechins in green tea with high-performance liquid chromatography.

Chitosan derivatives have been studied widely, but poor solubility in water restricts their applications. In this study, four types of amine-based chitosan derivatives were prepared and modified further with beta-cyclodextrin. The sequential microextraction of catechins ((+)-catechin and (-)-epigallocatechin gallate) from green tea powder by an optimized solid-phase extraction method using these four derivatives was investigated. The optimal conditions for the extraction of catechins were 60°C for a 40 min extraction period. The purity and amount of each catechin were determined by high-performance liquid chromatography. The different amines strengthened the extraction capacity of chitosan. Among the four types of amines, ethylene diamine grafted chitosan beta-cyclodextrin had the highest extraction capacity to catechins. Therefore, this material was used in the extraction assay, and the standard curves of (+)-catechin and (-)-epigallocatechin gallate were linear over the concentration range, 0.25-500 µg/mL, after assaying five data points in duplicate. Solid-phase extraction with the amino-based chitosan beta-cyclodextrin system is a new application of chitosan, which has potential applications in the extraction of bioactive compounds from plant materials or the removal of different impurities from specific extracts.

Application of Natural Deep Eutectic Solvents in the Extraction of Quercetin from Vegetables.

Quercetin is a phytochemical with disease prevention and health promotion activities that has attracted significant research attention. In this study, choline chloride and betaine-based natural deep eutectic solvents were prepared using a heating method. Their physical and chemical properties were also tested. Then, they were applied to extract quercetin from onion and broccoli with ultrasonic-assisted solid liquid method coupled with HPLC. Three factors (temperature, amount, and time) were considered for the optimization of the extraction assays. In the optimal conditions, the extraction recoveries were 88.91-98.99%, 88.45-99.01%, and 89.56-98.74% for quercetin, isorhamnetin, and kaempferol. Tailor-made natural deep eutectic solvents could be applied as sustainable and safe extraction media for biochemical applications.

Preparation of two-dimensional magnetic molecularly imprinted polymers based on boron nitride and a deep eutectic solvent for the selective recognition of flavonoids.

New types of two-dimensional (2D) boron nitride (BN) were developed as a 2D scaffold material. After modification with ternary deep eutectic solvents (DES, ChCl-caffeic acid-ethylene glycol), the processed BN was applied to the preparation of magnetic molecularly imprinted polymers (MMIPs). In the polymerization of MMIPs, DESs and hydrophobic Fe3O4 magnetite were applied as the functional monomer and magnetically susceptible component, respectively. A 2D ellipsoid material was formed successfully by polymerization on the surface of the processed BN. The proposed 2D-MMIPs were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and nitrogen sorption analysis techniques. The surface area of the 2D-MMIPs was increased using eco-friendly chemicals. The proposed 2D-MMIPs had a 2D oblate structure and a large surface area. The 2D-MMIPs were used for the preconcentration of flavonoids from Ginkgo biloba leaf extracts. High performance liquid chromatography-ultraviolet analysis revealed that the 2D-MMIPs have higher recoveries for the flavonoids (quercetin 96.8%, isorhamnetin 93.6% and kaempferol 94.8%) in Ginkgo biloba leaves than common MMIPs.

Evaluation of fatty acid/alcohol-based hydrophobic deep eutectic solvents as media for extracting antibiotics from environmental water.

Fatty acid/alcohol-based hydrophobic deep eutectic solvents (DESs) have been considered to be eco-friendly alternatives to replace conventional hydrophobic organic solvents (i.e., halogenated solvents). These novel eco-friendly solvents are applied in the extraction and determination of two antibiotics (levofloxacin, LOF; ciprofloxacin, COF) in environmental water by liquid-liquid microextraction (LLME). Two different families of hydrophobic DESs, one based on fatty acids and the other on fatty alcohols, were prepared and applied as a microextraction solvent. The study results showed that 1-octanol/ tricaprylylmethylammonium chloride-based DES (DES-14) had the best extraction efficiency. The vortex-assisted method exhibited better extraction efficiency than the heating, ultrasound, and microwave auxiliary methods in LLME. The main factors affecting the vortex-assisted LLME were optimized statistically using the Box-Behnken design (BBD) combined with response surface methodology (RSM). The optimal conditions for LOF and COF were as follows: 14:174 µL DES, 5.7 min vortex-assisted time, and 8.7% NaCl, w/v. Under these conditions, hydrophobic DES-based LLME was established for extraction and determination LOF and COF from environmental water, and the extraction recoveries of LOF and COF exceeded 94.8%. The proposed hydrophobic DES-based LLME method provides high precision, good linearity, acceptable limit of detection (LOD) and limit of quantification (LOQ), and satisfactory recoveries for the targets. These results support the potential of this method as a new type of extraction medium to replace conventional hydrophobic organic solvents in various applications.

Magnetic chitosan functionalized with ß-cyclodextrin as ultrasound-assisted extraction adsorbents for the removal of methyl orange in wastewater coupled with high-performance liquid chromatography.

Three types of choline chloride based deep eutectic solvents were prepared and used to modify magnetic chitosan. The adsorption capacity of the three deep-eutectic-solvent-modified magnetic chitosan/carboxymethyl-ß-cyclodextrin for removing methyl orange from wastewater was examined. The different deep eutectic solvents were used to strengthen the adsorption capacity of magnetic chitosan. Deep-eutectic-solvent-modified magnetic chitosan/carboxymethyl-ß-cyclodextrin materials were characterized by Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller surface area measurements. Among the three deep eutectic solvents, choline chloride/glycerol (1:2) modified magnetic chitosan/carboxymethyl-ß-cyclodextrin showed the highest adsorption capacity to methyl orange. Therefore, choline chloride/glycerol (1:3, 1:4, 1:5, 1:6) deep eutectic solvents were prepared for the assay, and choline chloride/glycerol-modified magnetic chitosan/carboxymethyl-ß-cyclodextrin prepared with choline chloride/glycerol (1:3) (volume: 40 µg, contact time: 30 min, and pH: 6) had the best adsorption capacity over the concentration range of 10-200 µg/mL.

Molecular imprinted polymers based on magnetic chitosan with different deep eutectic solvent monomers for the selective separation of catechins in black tea.

Two types of molecular-imprinted polymers-based magnetic chitosan with facile deep eutectic solvent-functional monomers (Fe3 O4 -CTS@DES-MIPs) were synthesized and applied as adsorbents in magnetic solid-phase extraction (MSPE) for the selective recognition and separation of (+)-catechin, (-)-epicatechin, and (-)-epigallocatechin gallate in black tea. The obtained Fe3 O4 -CTS@DES-MIPs were characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The selective recognition ability was examined by adsorption experiments. The actual amounts of (+)-catechin, (-)-epicatechin, and (-)-epigallocatechin gallate extracted from black tea using Fe3 O4 -CTS@DES-MIPs by the MSPE method were 13.10, 6.32, and 8.76 mg/g, respectively. In addition, the magnetic Fe3 O4 -CTS@DES-MIPs showed outstanding recognition and selectivity. Therefore, it can be used to separate bioactive compounds from black tea. The new-type of DES adopted as the functional monomer in this paper provides a new perspective for the recognition and separation of bioactive compounds.