Antioxidant properties of compounds isolated from wood vinegar by activity-guided and pH-gradient extraction

<p>The chemical profile of wood vinegar (WV) was studied by gas chromatography-mass spectrometry (GC/MS), and 48 organic compounds were identified, including phenols which accounted for 2.0%. Antioxidant compounds were isolated from WV by an activity-guided isolation method for further investigation. The dichloromethane extract from WV exhibited the highest total phenolic content and demonstrated more potent antioxidant activity than the other extracts. Then, the phenols were enriched by pH gradient extraction method from the dichloromethane extract. Seven phenols were isolated from the WV using a sequence of column chromatographic purification steps over silica gel and C18 column, followed by semi-preparative HPLC and their structures were identified by ¹H NMR and ¹³C NMR spectra. All the compounds showed potent antioxidant activities in the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline- 6-sulphonic acid (ABTS), and ferric-reducing antioxidant power (FRAP) assays. This study demonstrates that phenols isolated from WV have the potential to be used as antioxidant agents.</p

Strain Tunability of Perpendicular Magnetic Anisotropy in van der Waals Ferromagnets VI₃

Layered ferromagnets with strong magnetic anisotropy energy (MAE) have special applications in nanoscale memory elements in electronic circuits. Here, we report a strain tunability of perpendicular magnetic anisotropy in van der Waals (vdW) ferromagnets VI3 using magnetic circular dichroism measurements. For an unstrained flake, the M–H curve shows a rectangular-shaped hysteresis loop with a large coercivity (1.775 T at 10 K) and remanent magnetization. Furthermore, the coercivity can be enhanced to a maximum of 2.6 T under a 3.8% external in-plane tensile strain. Our DFT calculations show that the increased MAE under strain contributes to the enhancement of coercivity. Meanwhile, the strain tunability on the coercivity of CrI3, with a similar crystal structure, is limited. The main reason is the strong spin–orbit coupling in V3+ in VI6 octahedra in comparison with that in Cr3+. The strain tunability of coercivity in VI3 flakes highlights its potential for integration into vdW heterostructures