Within the framework of the macroscopic dielectric continuum model and Loudon＇s uniaxial crystal model, the phonon modes of a wurtzite/zinc-blende one-dimensional （1D） cylindrical nanowire （NW） are derived and st...Within the framework of the macroscopic dielectric continuum model and Loudon＇s uniaxial crystal model, the phonon modes of a wurtzite/zinc-blende one-dimensional （1D） cylindrical nanowire （NW） are derived and studied. The analytical phonon states of phonon modes are given. It is found that there exist two types of polar phonon modes, i.e. interface optical （IO） phonon modes and the quasi-confined （QC） phonon modes existing in 1D wurtzite/zinc-blende NWs. Via the standard procedure of field quantization, the Fr6hlich electron-phonon interaction Hamiltonians are obtained. Numerical calculations of dispersive behavior of these phonon modes on a wurtzite/zinc-blende ZnO/MgO NW are performed. The frequency ranges of the IO and QC phonon modes of the ZnO/MgO NWs are analyzed and discussed. It is found that the IO modes only exist in one frequency range, while QC modes may appear in three frequency ranges. The dispersive properties of the IO and QC modes on the free wave-number kz and the azimuthal quantum number m are discussed. The analytical Hamiltonians of electron-phonon interaction obtained here are quite useful for further investigating phonon influence on optoelectronics properties of wurtzite/zinc-blende 1D NW structures.展开更多
Toxicity of MgO and ZnO nanoparticles at concentrations of 250, 500 or 1 000 mg/L for Citrus maxima seedlings was investigated to evaluate the potentiality of their use as nano-fertilizers. Uptake and translocation of...Toxicity of MgO and ZnO nanoparticles at concentrations of 250, 500 or 1 000 mg/L for Citrus maxima seedlings was investigated to evaluate the potentiality of their use as nano-fertilizers. Uptake and translocation of metal oxide nanoparticles and lipid peroxidation were measured and compared with those of plants exposed to the highest equivalent concentrations of Mg^(2+) and Zn^(2+). MgO nanoparticles were translocated from roots to shoots, while translocation of ZnO nanoparticles was low. Exposure to Mg^(2+) and MgO at all concentrations entailed severe toxicity and strong oxidative stress. ZnO nanoparticles showed only mild toxicity, while Zn^(2+) caused leaf vein chlorosis and strong oxidative stress to plant shoots. In conclusion, the toxicity of MgO nanoparticles to the plant resulted from the dissolved Mg^(2+) concentration, while that of ZnO nanoparticles was not correlated with the dissolved Zn^(2+) concentration. Our findings are significant for development and application of MgO and ZnO nanoparticles as nano-fertilizers in agriculture.展开更多
基金Supported by National Natural Science Foundation of China under Grant No.60906042by the National Basic Research Program of China under Grant No.2006CB921607
文摘Within the framework of the macroscopic dielectric continuum model and Loudon＇s uniaxial crystal model, the phonon modes of a wurtzite/zinc-blende one-dimensional （1D） cylindrical nanowire （NW） are derived and studied. The analytical phonon states of phonon modes are given. It is found that there exist two types of polar phonon modes, i.e. interface optical （IO） phonon modes and the quasi-confined （QC） phonon modes existing in 1D wurtzite/zinc-blende NWs. Via the standard procedure of field quantization, the Fr6hlich electron-phonon interaction Hamiltonians are obtained. Numerical calculations of dispersive behavior of these phonon modes on a wurtzite/zinc-blende ZnO/MgO NW are performed. The frequency ranges of the IO and QC phonon modes of the ZnO/MgO NWs are analyzed and discussed. It is found that the IO modes only exist in one frequency range, while QC modes may appear in three frequency ranges. The dispersive properties of the IO and QC modes on the free wave-number kz and the azimuthal quantum number m are discussed. The analytical Hamiltonians of electron-phonon interaction obtained here are quite useful for further investigating phonon influence on optoelectronics properties of wurtzite/zinc-blende 1D NW structures.
基金Funded by the National Natural Science Foundation of China(No.31301735)the Fundamental Research Funds for the Central Universities(Nos.WUT2017IB006,WUT2018IB021,WUT2018IB023)
文摘Toxicity of MgO and ZnO nanoparticles at concentrations of 250, 500 or 1 000 mg/L for Citrus maxima seedlings was investigated to evaluate the potentiality of their use as nano-fertilizers. Uptake and translocation of metal oxide nanoparticles and lipid peroxidation were measured and compared with those of plants exposed to the highest equivalent concentrations of Mg^(2+) and Zn^(2+). MgO nanoparticles were translocated from roots to shoots, while translocation of ZnO nanoparticles was low. Exposure to Mg^(2+) and MgO at all concentrations entailed severe toxicity and strong oxidative stress. ZnO nanoparticles showed only mild toxicity, while Zn^(2+) caused leaf vein chlorosis and strong oxidative stress to plant shoots. In conclusion, the toxicity of MgO nanoparticles to the plant resulted from the dissolved Mg^(2+) concentration, while that of ZnO nanoparticles was not correlated with the dissolved Zn^(2+) concentration. Our findings are significant for development and application of MgO and ZnO nanoparticles as nano-fertilizers in agriculture.
