The density functional theory method is utilized to verify the electronic structures of SiC nanotubes (SiCNTs) and SiC nanoribbons (SiCNRs) one-dimensional (1D) van der Waals homojunctions (vdWh) under an applied axial strain and an external electric field. According to the calculated results, the SiCNTs/SiCNRs 1D vdWhs are direct semiconductors with a type-II band alignment and robust electronic structures with different diameters or widths. Furthermore, the SiCNTs/SiCNRs 1D vdWhs are direct semiconductors with a type-I band alignment, respectively, in a range of[-0.3, -0.1] V/Å and[0.1, 0.3] V/Å and change into metal when the electric field intensity is equal to or higher than 0.4 V/Å. Interestingly, the SiCNTs/SiCNRs 1D vdWhs have robust electronic structures under axial strain. These findings demonstrate theoretically that the SiCNTs/SiCNRs 1D vdWhs can be employed in nanoelectronics devices. 相似文献
The authors describe a method for the determination of cobalt(II) ions based on the use of luminescent and water-soluble ZnO quantum dots capped with β-cyclodextrin (β-CD@ZnO QDs). The modified QDs display strong yellow-green fluorescence with a peak at 537 nm under 360 nm excitation. High-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, luminescence, and UV-visible absorption spectroscopy were used to characterize the β-CD@ZnO QDs. The fluorescence of the QDs is quenched by Co(II) ions. This finding was exploited to design a quenchometric assay designed for the detection of Co(II) in water solution. The detection limit is 0.34 μM (based on the 3σ/slope criterion), and the linear range extends from 1.0 to 10 μM. The method was applied to quantify Co(II) in spiked real samples. The quenching mechanism was studied, and this showed that aggregation-induced quenching causes the main effect.
Copper nanoclusters (Cu-NCs) were fabricated by chemical reduction of Cu(II) ions using formaldehyde as the reductant and poly(vinyl pyrrolidone) as the protecting agent. The resulting Cu-NCs were characterized by TEM, FT-IR, UV–vis and XPS and fluorescence spectroscopy. The Cu-NCs display a luminescence quantum yield of about 13 %, and the emission peaks shift from 398 to 457 nm on increasing the excitation wavelength from 310 to 390 nm. The Cu-NCs possess a storage stability of at least 2 months and are stable in the presence of high concentrations of salt. Their fluorescence is strongly quenched by hypochlorite, while other common cations, anions and hydrogen peroxide have minor (or no) effects on fluorescence. On this basis, a fluorometric hypochlorite assay was developed that has a 0.1 μM detection limit and a linear range that extends from 1 to 30 μM. The method was successfully used to the determination of hypochlorite in local tap water samples, and the results agreed well with those obtained by a colorimetric method.
We use an interpolation inequality on Besov spaces to show a logarithmically improved regularity criterion for the harmonic heat flow, the Landau-Lifshitz equations, and the Landau-Lifshitz-Maxwell system. 相似文献