Residue dissipation dynamics and dietary risk assessment of emamectin benzoate, chlorantraniliprole, chlorfenapyr, and lufenuron in cabbage.

Emamectin benzoate (EB), chlorantraniliprole (CTP), chlorfenapyr (CFP), and lufenuron (LFR) are widely used to control Spodoptera exigua on cabbage. This study is aimed at establishing a universal, sensitive, accurate, and efficient method for the determination of these pesticide residues in cabbage using QuEChERS pretreatment combined with ultra-performance liquid chromatography or gas chromatography-tandem mass spectrometry (UPLC‒MS/MS or GC‒MS/MS). The recoveries of these pesticides (containing metabolites) in cabbage detected by the optimized method ranged between 80.9% and 99.9%, with relative standard deviations (RSDs) of 0.164-12.5%. The limit of quantification (LOQ) of the four pesticides was determined to be 0.01 mg/kg. The standard curve, accuracy, precision, and LOQ of the analysis method all met the requirements of pesticide residue detection. The optimized method was used to detect the dissipation dynamics and terminal residues in 12 regions. The dissipation half-lives of CTP, CFP, and LFR were 3.35-7.01 d, 2.29-4.75 d, and 3.24-6.80 d, respectively. The terminal residues of all these pesticides were below the maximum residue limits (MRLs). The dietary risk assessment indicated that the dietary risk probabilities for EB, CTP, CFP, and LFR were all less than 1 and were within the acceptable range. This study provides a comprehensive assessment of the residues and dietary risks of EB, CTP, CFP, and LFR for the scientific use of pesticides.

Synthesis and properties of organoboron functionalized nanocellulose for crosslinking low polymer fracturing fluid system.

The traditional organoboron crosslinker used in the guar gum fracturing fluid has the disadvantages of a larger amount of guar gum and crosslinker and higher susceptibility to pH. Nanoparticles have special properties such as large specific surface area and many active groups, so the organic boron crosslinker and nanoparticles are combined to obtain nano crosslinkers. In this paper, rod-shaped nano-cellulose particles were prepared by acid hydrolysis, and a nanocellulose crosslinker was synthesized by combining with organic boron and KH550. Nanocellulose cross-linker has good temperature and salt resistance. It can meet the requirements of cross-linking guar gum fracturing fluid with a mass fraction of 0.3 wt% under neutral conditions. The residual viscosity is higher than 50 mPa s under shear at 170 s-1 and 110 °C for 60 minutes when the pH increases from 7 to 13, and NBC crosslinking can withstand a temperature of 160 °C under pH = 10. The crosslinking mechanism of the widely accepted nano-crosslinker is that the organoboron on the surface of the nanoparticle combines with the homeopathic ortho hydroxyl of the guar gum molecule to form a hydrogen bond and thereby form a complex network structure. This research shows that the hydrogen bonding between the nano-cellulose crosslinker and HPG molecules, and the resulting gel has a more complex network structure because of the formation of inter-chain cross-links.

High-performance electrocatalyst based on polyazine derived mesoporous nitrogen-doped carbon for oxygen reduction reaction.

Nitrogen-doped porous carbon materials have high potential in metal-free electrocatalysts, which is essential for several renewable energy conversion systems. Herein, we report a convenient and environment-friendly method to fabricate a nitrogen doped mesoporous carbon (NMC) using a nonionic surfactant of Pluronic F127 micelles as the template and a Schiff-base polymer (polyazine) as the precursor. The synthesized NMCs were of spheric morphology and mesoporous structures with surface area up to 1174 m2 g-1 and high level of nitrogen (2.9-19 at%) and oxygen (4.9-7.4 at%) simultaneously doped. The electrochemical data of NMCs were analyzed in the context of the BET and XPS information. A correlation between ORR activity and the pyridinic-N was found. The NMC-700 demonstrate the highest electrocatalytic activity for ORR among the studied materials, which can be ascribed to the reasonable surface area and mesoporous structure, as well as the most abundant touchable pyridinic-N, thus providing more effective active sites for the oxygen reduction. In comparsion to the control sample, the NMC-700 provides the ORR electrocatalytic activity approximate to that of commercial Pt/C catalyst with a highly long-term stability.

Synthesis and properties of a high-performance environment-friendly micro-nano filtration reducer.

In this research study, we modified hydroxyethyl cellulose to obtain hydrophobically associating hydroxyethyl cellulose, and grafted it onto the surface of nano-calcium carbonate to obtain a graft copolymer. The intramolecular or intermolecular associations between the macromolecular chains of the graft copolymers form different forms of supramolecular network structures, and they interact with nanoparticles to form stable structures to enhance their related properties. The structure of the obtained graft copolymer was characterized by Fourier transform infrared spectroscopy (FT-IR) and laser particle size analysis. Thermogravimetric analysis (TGA) showed the thermal stability of the graft copolymer, and the results showed that the graft copolymer obtained thermally decomposed after 370.86 °C, indicating that it has good thermal stability. Scanning electron microscopy (SEM) revealed the mechanism of the graft copolymers in drilling fluids. The fluid loss control performance and rheology of the filtration reducer were evaluated before and after hot rolling at 180 °C for 16 hours. The results showed that the graft copolymer has excellent fluid loss reduction performance, and it has good fluid loss reduction performance in fresh water, brine and saturated brine. The API fluid loss was only 6.4 mL after hot rolling at 180 °C for 16 h in the brine base slurry. Moreover, the obtained graft copolymer is easily biodegradable, has EC50 ≥ 30 000 and good environmental performance, and can be used in high temperature and high salt reservoir with high environmental protection requirements.

In Situ Formation of Ti47Cu38Zr7.5Fe2.5Sn2Si1Nb2 Amorphous Coating by Laser Surface Remelting.

In previous studies, Ti-based bulk metallic glasses (BMGs) free from Ni and Be were developed as promising biomaterials. Corresponding amorphous coatings might have low elastic modulus, remarkable wear resistance, good corrosion resistance, and biocompatibility. However, the amorphous coatings obtained by the common methods (high velocity oxygen fuel, laser cladding, etc.) have cracks, micro-pores, and unfused particles. In this work, a Ti-based Ti47Cu38Zr7.5Fe2.5Sn2Si1Nb2 amorphous coating with a maximum thickness of about 100 µm was obtained by laser surface remelting (LSR). The in-situ formation makes the coating dense and strongly bonded. It exhibited better corrosion resistance than the matrix and its corrosion mechanism was discussed. The effects of LSR on the microstructural evolution of Ti-based prefabricated alloy sheets were investigated. The nano-hardness in the heat affected zone (HAZ) was markedly increased by 51%, meanwhile the elastic modulus of the amorphous coating was decreased by 18%. This demonstrated that LSR could be an effective method to manufacture the high-quality amorphous coating. The in-situ amorphous coating free from Ni and Be had a low modulus, which might be a potential corrosion-resistant biomaterial.