Chemical conversion synthesis of ZnS shell on ZnO nanowire arrays: morphology evolution and its effect on dye-sensitized solar cell.

Heterostructured ZnO/ZnS core/shell nanowire arrays have been successfully fabricated to serve as photoanode for the dye-sensitized solar cells (DSSCs) by a facile two-step approach, combining hydrothermal deposition and liquid-phase chemical conversion process. The morphology evolution of the ZnS coated on the ZnO nanowires and its effect on the performance of the DSSCs were systematically investigated by varying the reaction time during the chemical conversion process. The results show that the compact ZnS shell can effectively promote the photogenerated electrons transfer from the excited dye molecules to the conduction band of the ZnO, simultaneously suppress the recombination for the injected elelctrons from the dye and the redox electrolyte. As reaction time goes by, the surface of the nanowires becomes coarse because of the newly formed ZnS nanoparticles, which will enhance the dye loading, resulting in increment of the short-circuit current density (J(SC)) . Open-circuit photovoltage decay measurements also show that the electron lifetime (τ(n)) in the ZnO/ZnS core/shell nanostructures can be significantly prolonged because of the lower surface trap density in the ZnO after ZnS coating. For the ZnO/ZnS core/shell nanostructures, the J(SC) and η can reach a maximum of 8.38 mA/cm(2) and 1.92% after 6 h conversion time, corresponding to 12- and 16-fold increments of as-synthesized ZnO, respectively.

[Repetition of teaching contents between genetics and relative courses in agricultural and forestry colleges and approaches to solving the problem].

Genetics is one of the main courses in agricultural and forestry colleges. However, there is large repetition of teaching contents and joining problems between genetics and the relative courses. The negative effects of above problems are discussed in this paper. In order to relieve the conflict between the increase of genetics contents and the decrease of teaching hours in genetics teaching of undergraduates and provide reference for future textbook compilation, some approaches on solving repetition of teaching content and suggestions on joining problems are put forward.

Bud-like silica nanowires with self-assembled long segmented stems: a novel nanostructure and its growth mechanism.

A large quantity of bud-like silica nanowires with self-assembled long segmented stems were synthesized through thermal evaporation via using a piece of Si wafer and the mixture of Ga2O3 and carbon powder as source materials. The segmented stems were assembled from the bottom part of the bud-like silica nanowires with diameter of approximately 0.5 microm and length up to more than 20 microm. The bud-like silica nanowires could have one, two or three segmented stems. Some bud-like silica nanostrutures have a bowl-shaped cavity at their tips, others have a tail growing from their tips. The aligned silica nanowires were found extending from the thin silica shell coating the Ga ball, instead of nucleating and growing from the surface of the Ga ball directly. These interesting results could help us understand the diversity and versatility of the silica nanostructures which can be fabricated, and the knowledge of their growth mechanisms.

Self-assembled vapor-liquid-solid growth of aligned Cu-SiO2 core-shell nanocable arrays on Cu substrates.

The Cu-SiO2 core-shell nanocable arrays on the Cu wafers have been synthesized via a simple thermal evaporation of the SiO powder. The morphology and structure of the as-synthesized Cu-SiO2 core-shell nanocables are characterized by using scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray energy dispersive spectrometer. The growth of amorphous SiO2 shell follows a vapor-liquid-solid mechanism, and then molten metal Cu will be diffused into the SiO2 nanotubes, forming the Cu-SiO2 core-shell nanocable arrays. It is found that the aligned Cu-SiO2 core-shell nanocables prefer to grow along the grooves of the Cu substrate, and the density of the Cu-SiO2 core-shell nanocable arrays can be controlled by adjusting the growth temperature.