ABSTRACT
Sulfur-doped graphdiyne at different sites has a tremendous impact on its electronic structure and properties. Due to the large number of S-doping sites, there is no comprehensive and systematic experimental and theoretical study regarding the identification of S-doped graphdiyne configurations. In this paper, X-ray photoelectron (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectra as well as geometries of 10 sulfur-doped graphdiyne molecules have been simulated at the density functional theory (DFT) level. Different types of carbon spectra were theoretically modeled to analyze the contribution of the spectra. Calculated results show that the NEXAFS spectra exhibit a clear dependence on the local structure. The theoretically simulated XPS spectra are in good agreement with the experimental spectra. The XPS spectra combined with the NEXAFS spectra can provide effective information for identifying the 10 S-doped conformations. Our research results provide further theoretical prediction and guidance for the experimental synthesis of S-doped graphdiyne, which solves the difficult problem of identification of S-doped carbon-based materials.
ABSTRACT
Our density functional theory calculations show that silicon doping in g-CN (SiC3N3) can improve the electrochemical performance of g-CN as an anode of alkali metal-ion batteries and solve the problems of too high adsorption ability and migration energy barrier commonly found in porous carbon nitride. The stability of SiC3N3 was verified by molecular dynamics simulations and phonon spectroscopy. Elastic constant calculations revealed that the Si doping in g-CN can improve its mechanical properties. Specifically, Li/Na/K has a suitable adsorption capability (-0.71/-0.52/-0.98 eV) and a lower migration barrier (0.73/0.43/0.21 eV) on SiC3N3, where the barrier of a single Li-ion is the lowest among the doped porous carbon nitride materials studied so far. Moreover, SiC3N3 exhibits a high theoretical capacity (253/1512/1512 mA h g-1) and a low open-circuit voltage (0.48/0.18/0.31 V) for Li/Na/K ion batteries. Compared with B-doped g-CN previously studied, Si doping can more effectively improve the electronic conductivity of g-CN owing to greater charge transfer between Si and g-CN; the migration energy barrier of alkali metal ions on SiC3N3 is reduced more significantly due to its puckered structure instead of a planar structure; and the capacity of SiC3N3 is nearly doubled for alkali metal ion batteries because it has more feasible adsorption sites for alkali metals. These results suggest that Si-doped g-CN can be a universal anode material for alkali metal ion batteries.
ABSTRACT
PURPOSE: The aim of this study was to explore elderly patients with end-stage renal disease (ESRD) white matter changes, the relationship between white matter (WM) abnormalities and emotional regulation strategies, coping styles in elderly ESRD patients. METHODS: Twenty-eight elderly ESRD patients and twenty-eight sex and age matched healthy controls (HC) were included in this study. Tract-based spatial statistic (TBSS) was used to investigate the microstructural changes of WM. Two questionnaires were used to measure emotional regulation strategies and coping styles. RESULTS: Neuroimaging analysis showed that the damage of WM structure was widespread in elderly ESRD patients. Psychological test results showed that there were differences in emotional regulation strategies and coping styles between elderly ESRD patients and HC. Furthermore, mediating analysis showed that the mean diffusivity (MD) of the significantly different brain regions played a complete mediating role between group and positive coping style. CONCLUSION: These results suggest that the integrity of WM, emotional regulation strategies and coping styles play an important role in ESRD patients. Our findings provide evidence that positive coping style may be fully mediated by MD. These results may help us develop new ways to treat and prevent physical and psychological problems in elderly ESRD hemodialysis patients.
