| In the recent years, a great deal of researchers made efforts towards the development of miniaturized gas-sensing devices, particularly for toxic gas and for pollution monitoring. These researches mainly concluded the development and the breakout of new materials, new technologies, and new principles. As a new type of application materials, nanomaterials are particularly suitable for gas-sensing field. Nano-materials have many characteristics, such as small size, high surface area and special morphology. Especially, hierarchical and hollow nanomaterials have higher sensitivities for different gaseous species. Tin oxide (SnO2) is a common n-type semiconductor (Eg=3.6eV at300K) which can be made into different morphologies. When used as gas sensor, it has high sensitivity, response and recovery of good performance characteristics and a very broad application prospects. In this paper, several simple classification and principles of the sensors, overview of the hierarchical and hollow nanomaterials application in gas sensor, and the current situation and future direction of development of SnO2gas sensor materials are concerned.Dye-sensitized solar cells (DSSCs)have great promise for converting solar-energy to electricity due to low cost, easy productive process and relatively high conversion efficiency. Now the primary photovoltaic(PV) materials TiO2,which conversion efficiency is more than11%.Comparatively speaking, other metal oxide conductors, such as zinc and tin oxides which have comparable band gap widths and photoelectric properties have less concerned than titanium dioxide. The electron mobility of ZnO ranges from205to1000cm2V-1s-1,which is higher than TiO2(0.1-4cm2V-1s-1).So we use ZnO as electrode in DSSCs enabling electrons’ diffusion transport. Moreover, ZnO can be processed into different nanostructures, such as nanoparticles, nanowires, nanotubes and so on, providing more options for modifying the electrode morphology to improve the charge collection. However, the conversion efficiency of ZnO-based DSSCs still is lower than TiO2, leaving much space for us to improve the efficiency through modifying the morphology of the electrode.This topic is mainly about simple and effective method of preparation of the hierarchical and hollow Tin oxide and its application in gas sensor. The traditional SnO2nanomaterials often have the defects of the uneven size distribution, dispersed unevenly agglomeration, resulting in decreased sensitivity and slow response and recovery speed. The pollen-templated hierarchical Tin Oxide nanomaterials are fine ellipsoids of uniform diameter of about9μm, with open pores’ networks surrounding entirely and evenly dispersed nanoparticles of diameter of a few nanometers inside favor for the connective structures. So the samples have the characteristics of high surface area (135.98m2g-1) and good conductivity, which are favorable for both gas molecule transports and sensing reactions.The hierarchical and hollow Tin oxide is made into ethanol gas sensor, and the ethanol-sensing tests showed that the hierarchical and hollow Tin oxide sensor has following characteristics: The detection limit of the sensor is especially low under20ppm ethanol at300℃, reaching the industry standard. The gas sensor exhibits high responses to ethanol (9to ethanol of200ppm,1.34to ethanol of20ppm).Another work is mostly about hierarchical and hollow zinc oxide and its application in DSSCs. ZnO with this kind nanostructure exhibits large internal surface area (105.6m2g-1) and strong lighting scattering property, having an advantage in photoanode in DSSCs, exhibiting5.52mA cm-2in Jsc,441mV in Voc,0.51in FF and1.29%in photoelectric conversion efficiency(η)。... |
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