Desen Su,Yunyun Zheng,Minmin Huang,Ziqiang Chen,Lisong Chen,Meizhen Chen,Qinghua Yao
Depending on the manufacturing process, Tieguanyin tea (TGY) is classified into three main groups, light flavor type (LFT), heavy flavor type (HFT), and stale flavor type (SFT). However, the compositions and contents of volatile compounds among TGY types were still unclear. This study aimed to develop an efficient method for the nonselective determination of volatile compounds in teas via direct-headspace injection coupled with gas chromatography mass spectrometry (DHI-GC-MS), and to perform a comprehensive comparison among these teas. One hundred and twelve volatile compounds belonging to 9 classes were identified. Among them, 33 common volatiles from 4 categories (aldehydes, alcohols, ketones, and acids) were the dominant volatiles and accounted for 71.5%, 73.0%, and 71.8% of the total amount in LFT, HFT, and SFT, respectively. E-Nerolidol, ethanol, acetic acid, and some volatiles with five and six-carbon chains were the key chemicals to distinguish three different TGY teas. With PLS-DA analysis, distinct differences among different groups were observed. The results generated from this study may offer valuable insights for better grading of TGY teas.
Lei Li,Shan Li,Hao Wang,Zongmin Zhu,Xianze Yin,Jiawei Mao
In this work, a DOPO-based imidazolone derivative named DHI was synthesized using DOPO, 5-amino-2-benzimidazolinone and 4-hydroxybenzaldehyde as raw materials. The chemical structure of DHI was characterized by 1 H-NMR, 31 P-NMR and Fourier transform infrared spectra (FTIR). Then, a series of different flame-retardant epoxy resin (EP) thermosets were prepared by mixing flame retardant DHI. The thermal properties of the cured EPs was investigated by thermogravimetry analysis (TGA) and differential scanning calorimeter (DSC), and the results showed the thermal stability and glass transition temperature ( T g ) of the cured EP modified with DHI declined slightly compared with that of neat EP. The limited oxygen index (LOI) and UL94 test results exhibited DHI imparted good flame retardancy to EP. The EP-4 (phosphorus content of 1.25%) possessed a LOI value of 36.5% and achieved a V-0 rating. Furthermore, the peak of heat release rate (PHRR) and total heat release rate (THR) of EP-4 decreased by 38.7% and 24.5%, respectively. Excitedly, the total smoke production (TSP) of EP-4 sample declined by 62.5%, which meant DHI also made EP obtain excellent smoke suppression property. Moreover, the flame-retardant mechanism was studied by scanning electron microscopy (SEM) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). It was reasonable inferred that DHI could not only promote EP to form dense char layer in condensed phase, but also restrain combustion in gaseous phase through catching the free radicals sourced from the degradation of EP.
Wanjie Bai,Haotian Li,Huijie Liu,Xianheng Wang,Zhipeng Gu,Ye Yang,Yiwen Li
Black color is the most typical feature of natural and synthetic melanins, which results from the complex packing and chemical disorder of the molecular structure within melanins. From nature and beyond nature, breaking through the black color boundary, expanding the scope of inherent functions, and establishing clearer structure-function relationship of melanin is necessary but hard due to the inherent chaos structure caused by random covalent coupling and supramolecular assembly. Herein, starting from melanin-inspired monomers, we chose and assembled typical organic acceptor molecules (TCNB/TCNQ) with melanin-inspired donor molecules to prepare a series of colorful melanin-inspired pigments through the co-crystallization strategy. The resulting colorful melanin-inspired pigments exhibited multiple colors and different rod-like morphologies compared with many melanin-like polymers. Particularly, green DHI/TCNQ powder presented excellent photothermal efficiency (∼69.8%) for antibacterial application. This work would provide new structure-function tailoring strategy toward the design of melanin-like polymers with highly ordered structures and desirable properties.
危险品化学品经营许可证（带存储）