RESUMO
Two-dimensional (2D) halide perovskite are appealing candidates for applications in optoelectronics and photovoltaics, but their energy conversion efficiency is severely limited by nonradiative electron-hole recombination. In most investigations, point defects with deep defect levels and deep charge-state transition levels in the band gap are treated as the carrier recombination centers. For the all-inorganic 2D Css 2PbI2Cl2, the IPb antisite defect is the most likely to form and cause nonradiative electron-hole recombination. By using density functional theory and ab initio nonradiative molecular dynamics calculations, we found that the IPb defect can introduce the deep acceptor and donor levels into the band gap. Because electron-phonon coupling gives rise to weak nonadiabatic coupling and rapid loss of electronic coherence, those levels lead to a reduction of the carrier loss and the prolongation of the excited-state carrier lifetime, thereby enhancing the photoelectric and defect tolerance properties of the Cs2PbI2Cl2 material. These results could deepen the understanding of the chemistry of defects and carrier dynamics in perovskite materials.
RESUMO
Thyroid cancer is the fastest increasing cancer in both men and women and is the most common endocrine cancer. Researchers have gradually intensified their research on the mechanism of thyroid cancer development. Within this realm, Oxidative stress is often believed to play a causal and contributory role in thyroid cancer development. NADPH oxidase is one of the important sources of reactive oxygen species for tumor cell growth and is involved in the biological processes of thyroid tumor cell proliferation, migration, invasion and epithelial-to-mesenchymal transition. However, the mechanism of NADPH oxidase in the pathogenesis of thyroid cancer is still not very clear at present. Clarifying the role and mechanism of NADPH oxidase in the pathogenesis of thyroid cancer will help to develop new strategies for the prevention and treatment of thyroid cancer as early as possible, and improve the survival rates of thyroid tumor patients. This article reviews the research progress on the mechanism of NADPH oxidase in thyroid cancer.
RESUMO
Surface defects are usually associated with the formation of other forms of expansion defects in crystals, which have an impact on the crystals' growth quality and optical properties. Thereby, the structure, stability, and electronic structure of the hydrogen and oxygen vacancy defects (VH and VO) on the (100) and (101) growth surfaces of KDP crystals were studied by using density functional theory. The effects of acidic and alkaline environments on the structure and properties of surface defects were also discussed. It has been found that the considered vacancy defects have different properties on the (100) and (101) surfaces, especially those that have been reported in the bulk KDP crystals. The (100) surface has a strong tolerance for surface VH and VO defects, while the VO defect causes a large lattice relaxation on the (101) surface and introduces a deep defect level in the band gap, which damages the optical properties of KDP crystals. In addition, the results show that the acidic environment is conducive to the repair of the VH defects on the surface and can eliminate the defect states introduced by the surface VO defects, which is conducive to improving the quality of the crystal surface and reducing the defect density. Our study opens up a new way to understand the structure and properties of surface defects in KDP crystals, which are different from the bulk phase, and also provides a theoretical basis for experimentally regulating the surface defects in KDP crystals through an acidic environment.
