Zilin Ruan,Jianchen Lu,Baijin Li,Qizan Chen,Zhenliang Hao,Lei Gao,Jinming Cai
Structural defects in two-dimensional materials offer an effective way to engineer their functionalities. In-situ local measurements to build the structure-function relationship are crucial for future device technology. Here, we present a comprehensive study of intrinsic defects in single-layer WS 2 grown by chemical vapor deposition using a combination of scanning tunneling microscopy/spectroscopy, non-contact atomic force microscopy and density functional theory calculations. We probed the rarely observed positively charged defects and the intersection of adjacent charging rings at sufficiently high bias caused by subsurface defects. We also directly identified and visualized the widely observed negatively charged defects as chalcogen vacancies-related defects. The results reported here will guide future efforts of targeted defect engineering and doping of the single-layer transition metal dichalcogenides .
Xuliang Lin,Xueqing Qiu,Duming Zhu,Zihao Li,Ningxin Zhan,Jieyi Zheng,Hongming Lou,Mingsong Zhou,Dongjie Yang
Effect of the molecular structure of lignin-based polyoxyethylene ether (EHL–PEG) on enzymatic hydrolysis of Avicel and corn stover was investigated. With the increase of PEG contents and molecular weight of EHL–PEG, glucose yield of corn stover increased. EHL–PEG enhanced enzymatic hydrolysis of corn stover significantly at buffer pH 4.8–5.5. Glucose yield of corn stover at 20% solid content increased from 32.8% to 63.8% by adding EHL–PEG, while that with PEG4600 was 54.2%. Effect of EHL–PEG on enzymatic hydrolysis kinetics of cellulose film was studied by quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). An enhancing mechanism of EHL–PEG on enzymatic hydrolysis kinetics of cellulose was proposed. Cellulase aggregates dispersed by EHL–PEG excavated extensive cavities into the surface of cellulose film, making the film become more loose and exposed. After the maximum enzymatic hydrolysis rate, the film was mainly peeled off layer by layer until equilibrium.
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