物联网在设施蔬菜大棚种植上的应用

物联网是互联网技术的扩展和延伸,其与互联网进行连接,可以实现信息的即时通讯和交换,开展智能化管理、监控、追踪、定位以及识别。随着我国农业科技化和现代化的发展,蔬菜大棚种植也逐渐引入物联网技术,对促进种植效率和质量的提升具有积极意义。主要针对物联网在设施蔬菜大棚种植上的应用进行分析和阐述,希望给予我国农业领域以参考和借鉴。

High performance room temperature gas sensor based on novel morphology of zinc oxide nanostructures

Zinc oxide uniform nanostructures with novel morphologies were synthesized through simple and fast ammonia based controlled precipitation method in aqueous media and in the absence of any additive. Selected batches of the synthesized solids were characterized by SEM, XRD, FTIR and TG/DTA. FTIR analysis revealed that the morphology of nanostructures had little effect on their IR spectral profile of the synthesized material. The as-prepared, calcined and commercial ZnO nanostructures (ZnO-AP, ZnO-Cal and ZnO-Com) were then employed as gas sensors for the detection of ammonia, acetone and ethanol. ZnO-AP and ZnO-Cal based sensors showed superior and reproducible performance towards 1×10^-6 ammonia with gas response of 63.79% and 66.87% and response/recovery time of 13 and 3 s, respectively, at room temperature (29℃). This was attributed to the unique morphology and remarkable uniformity in shape and size of the synthesized nanostructures. In contrast, the ZnO-Com based sensor did not respond to ammonia concentration less than 200×10^-6. In addition, ZnO-Cal showed high selectivity to ammonia as compared to acetone and ethanol at room temperature. Moreover, the lowest detection limit was 1×10^-6, which demonstrates excellent ammonia sensing characteristics of the synthesized ZnO.

Effect of Screw-Dislocation on Electrical Properties of Spiral-Type Bi2Se3 Nanoplates

We systematically investigated the electrical nanoplates through field effect transistor and properties of spiral-type and smooth Bi2Se3 conductive atomic force microscopy （CAFM） measurement. It is observed that both nanoplates possess high conductivity and show metallic-like behavior. Compared to the smooth nanoplate, the spiral-type one exhibits the higher carrier concentration and lower mobility. CAFM characterization reveals that the conductance at the screw-dislocation edge is even higher than that on the terrace, implying that the dislocation can supply excess carriers to compensate the low mobility and achieve high conductivity. The unique structure and electrical properties make the spiral-type Bi2 Se3 nanoplates a good candidate for catalysts and gas sensors.

Fabrication of single-walled carbon nanotube-based highly sensitive gas sensors

A highly sensitive single-walled carbon nanotube(SWCNT)-based ammonia(NH3) gas detector is manufactured by orderly assembling SWCNT using the dielectrophoretical(DEP) technology.Atom force microscopy(AFM) and scanning electron microscopy(SEM) images revealed that SWCNTs were assembled between the microelectrodes.SWCNTs were affected by the electrophoretic force which was carried out by the related theoretical analysis in a nonuniform electric field.The SWCNT field effect transistors geometry was obtained.The electrical performance of NH3 gas sensor with the SWCNT field effect transistors geometry was tested before and after the adoption of NH3 at room temperature.Experimental results indicated that the efficient assembly of SWCNT was obtained by the applied alternating current voltage with frequency of 2 MHz and amplitude of 10 V.The SWCNTs-based gas sensor had high sensitivity to NH3,and the electrical conductance of NH3 gas sensor reduced two times after interaction with NH3.The SWCNTs surface gas molecules were removed by means of ultraviolet ray irradiation for 10 min.Hence,the fabricated NH3 gas sensor could be reversible.There is a clear evidence that the adsorption of NH3 on the SWCNT channel is easy to be realized.Our theoretical results are consistent with recent experiments.

Preparation of bilayer/three-layer PEO-carbon nanotube composite thin films and their toluene-sensing application

The bilayer poly(ethylene oxide)/multiple-walled carbon nanotubes(PEO/MWCNTs) and three-layer PEO/MWCNTs/PEO composite thin films were fabricated with the spraying process on the interdigitated transducers(IDTs) as gas sensors for toluene-sensing application.Compared with the bilayer thin film sensor,the sensor with three-layer thin films exhibited higher response values and better recovery property.The microstructures of sensing films were characterized by scanning electron microscopy(SEM) to indicate that the better sensing response of three-layer thin films might be ascribed to the sufficient adsorption of toluene molecules on the surfaces of upper and bottom PEO films.The selectivity of the three-layer film sensor was further investigated by comparing responses upon exposure to different interference vapors with the response to toluene exposure,and much higher response was observed in the case of toluene.Good repeatability of the three-layer film sensor was also observed.