| Black phosphorus(BP),a new two-dimensional semiconductor with adjustable direct band gap structure,high carrier mobility and other unique properties have potential applications in the fields of electronics and optoelectronics.However,BP is unstable and degrades readily upon exposure to ambient conditions with reaction with water and oxygen.This thesis aims to search highly efficient and environmentally friendly dispersion systems and produce stable single-or few-layer black phosphorus with high yield.The content of this paper is divided into the following three parts:(1)We have shown that BP can be exfoliated by ultrasonication in polyvinylpyrrolidone/ethanol.The rate of BP degradation was suppressed by coating with a polymer to shield the nanosheets from reaction with water and air.We obtained high quality BP flakes consisting of a high level of 51%crystalline single-layer that are free from oxidation.We presented a simple kinetic model and illuminated a possible mechanism of BP exfoliation.We reduced the content of PVP by a successive centrifugation and re-dispersion process.We prepared Cu/BP nanocomposites with superior HER performance.(2)We demonstrated a new molecule,N,N'-dimethylpropyleneurea(DMPU),for effective exfoliation and dispersion of two-dimensional BP nanosheets.A very high exfoliation efficiency of up to 16%was achieved in DMPU,significantly surpassing other good solvents.The solvation shell appears to protect the nanosheets from reacting with water and air.Exfoliated flakes are free from structural disorder or oxidation.(3)We studied the biological antibacterial properties of black phosphorus by plate counting.We demonstrated that our exfoliated BP nanosheets exhibit excellent antimicrobial activities against both Escherichia coli and Staphylococcus aureus,outperforming other common two-dimensional materials of graphene and MoS2.Exfoliated BP nanosheets showed minimal cytotoxicity,with good biocompatibility,suggesting promise in antibacterial application. |
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