The effects of UV illumination on the electronic properties and gas sensing performance of ZnO are reported. It is found that UV light improves the sensitivity and the sensor response and recovery rate. By investigating the photoresponse behavior of ZnO, we observe that the electrons generated by UV light promote the adsorption of oxygen and form the photoinduced oxygen ions [O2−(hv)]. These ions [O2−(hv)] are responsible for the room-temperature gas sensing phenomena and promise enhanced sensor performance through further optimization.
A kind of interesting urchin-like selenium nanostructure consisting of Se nanorods with a diameter of ∼100 nm and a length of 4−5 μm was synthesized based on a facile dismutation reaction in a buffer system at ambient conditions. In the synthesis process, cetyltrimethylammonium bromide (CTAB) was used as a shape-directing agent. It is found that the reaction time, the buffer system, and the amount of ethanol have an important influence on the formation of this kind of morphology besides CTAB. The obtained samples were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), selected area electron diffraction (SAED), and transmission electron microscopy (TEM). The formation mechanism of the urchin-like Se nanostructure has been proposed.
Tree pruning is a very important work in forestry production, which plays an important role in the growth and lumber of trees. In the general environment of automatic production of machinery, the market urgently needs a robot that can realize pruning work to replace a large amount of manual labor and increase the economic benefits of forests. In this paper, a tree-climbing and pruning robot with simple operation and automatic climbing function suitable for trimming a variety of trees is designed. The climbing mechanism of the robot adopts an enveloping wheel climbing structure, and the wheels are installed obliquely to achieve spiral ascent. The pruning mechanism adopts a combination of a mechanical arm and a saw blade, which can change the pruning method according to actual work requirements.
The curtain wall cleaning robot suitable for special-shaped wall structure of buildings is designed, and the mechanical structure design and control system design of the curtain wall cleaning robot is completed in the paper.The curtain wall cleaning robot is composed of two parts with the same structure. The hinge mechanism is used to realize the turning action of irregular wall. The suction and movement of the cleaning robot are realized by vacuum adsorption of the sucker. And the motor controlled the rotation of the roller brush. The screw guide rail drives the roller brush up and down to realize cleaning. Based on the mechanical structure design, the control system of curtain wall cleaning robot is designed. And PLC control system is used to control the sequence of action of curtain wall cleaning robot.
The samples were analyzed and characterized by scanning electronic microscope (SEM) and X-ray diffraction (XRD).The XRD results showed that the diffraction peaks of PANI/ZnO nanocomposites agreed with the pure ZnO. The as-prepared nanocomposites with different amounts of PANI dopants exhibited different sensing properties. When the weight ratio of PANI is 5%, the photoelectric response of nanocomposites to UV light reaches maximum (1938). Compared with ZnO, the response shows 60 times improvement. Additionally, the probable photoelectric response mechanism was also proposed. Firstly, the existence of p-n heterojunctions formed between p-type PANI and n-type ZnO interfaces was confirmed by the IV characteristics. It is believed that the p-n heterojunctions can promote the charge separation and further increase the amount of absorbed negative oxygen ions. Secondly, the highly dispersed stated of PANI could suppress the formation of interfacial recombination centers and accelerate p-type hole transporting. The photocurrent of composites is improved significantly. And we hope this work can help for designing more photoelectric materials with the higher response.
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