Synthesis And Properties Investigations Of Sn, Sb-Chalcogenide Semiconductors

The objective of this dissertation is to explore how to highly efficiently synthesize ofseveral inorganic semiconductor nanocrystal materials. Based on those semiconductingmaterials, photoelectric detectors, gas sensors, and so on have been fabricated. We havealso investigated the performances of the semiconductor nanomaterials, madebreakthroughs in some of the performance, enhanced the understanding of gas sensingmechanism and the mechanism of optoelectronic devices, and developed a number of newtype photocatalysts with visible light absorption. The main contents are as follows:1. By using a facile polyol refluxing process, we reported the successful synthesis ofporous SnS and SnS2architectures on a large scale at constant pressure. The morphologiesand chemical component have been analysed in details, and the electronic structures of SnSand SnS2were further investigated by band structure calculations.. A new photodetector hasbeen fabricated by configuring the samples as photoelectrochemical cell, exhibitingexcellent photosensitivity with the features of rapid response and recover time to0.5second,with greatly enhanced Ion/offas high as1.4×103, three orders of magnitude higher thanprevious work. Photocatalytic properties of both samples were investigated byphotodegradation of MB and RhB under visible light irradiation. The results indicate thepotential application of the SnSxnanostructures in visible-light-driven photocatalysts. Welayed stress on using as little as possible materials to achieve maximum photocatalyticeffect, realized the purpose on dye adsorption and degradation using trace materials withina short time.2. We report here the synthesis of two types of porous SnO₂nanoflowers by in-situoxidization of SnS and SnS2precursors with similar morphologies. As-synthesized SnO₂products were characterized with morphology, crystallinity and band-gap and so on.Configured as resistor-type chemical sensors, the as-synthesized SnO₂products exhibitedexcellent sensitivity and fast response/recover time towards different gases includingethanol, methanol, methanal and acetone. At the optimal sensing temperature of270oC, theporous SnO₂samples derived from the SnS precursor exhibit high sensitivities to ethanolfor43.23. In addition, we can see that the sensor device susceptible to other three gases andthe lowest detection limit was0.5ppm. It was found that the sensitivity toward ethanol dramatically increased by2.4times and the working temperature decreased to120oC whennovel metal Pt nanoparticles were loaded onto the surface of the SnO₂flowers. Theenhanced gas sensing performances can be attributed to the synergistic effects of thePt-loaded SnO₂products. And we also found its sensitivity can be reach to40.64at90oC,which approached to the previous level before loaded. At last, the gas sensing properties ofthe porous SnO₂sample derived from the SnS2precursor were also investigated and thecorresponding results are demonstrated, indicating good sensing properties too. In a word,at optimal sensing temperature, the porous SnO₂samples exhibited high sensitivities toseveral volatile organic gases, especially to ethanol. It was found that the optimaltemperature decreased and the sensitivity toward ethanol dramatically increased afterloaded Pt, which will pay the new way for the application of SnO₂gas sensors at lowoptimal temperature.3. In recent years, extensive attention has been paid to the fabrication ofone-dimensional nanostructured semiconductors for constructing electronic andoptoelectronic devices with improved performances. Tin sulphide nanoribbons weresynthesized via a facile polyol refluxing process. The photoconductive properties of theSnS nanoribbons were tested by assembling the samples into photoelectrochemical cells,exhibiting excellent photosensitivity with the features of rapid response and recover time,and stable on/off cycle performance to the stimulated sunlight. The photocurrent density isthe highest one among all reported SnS photoelectrode. Using it as a new photodetector, theratio of the photocurrent to the dark current is about336, and the response and recoverytime were all found to be0.1second. Flexible photodetectors were then fabricated on PETsubstrate, showing high flexible, fast response to visible light with different intensities. TheIon/Ioffis calculated to be about22, and the response and recovery time are5.4s and1.8srespectively. Photocatalytic properties of the as-synthesized SnS nanoribbons were alsostudied by photocatalytic degradation of methylene blue （MB）. Almost all of MB wasdecomposed within2h, indicating the SnS nanoribbons are good candidates for highperformance photocatalysts.4. Needle-like and flower-like antimony sulfide products were successfullysynthesized. The antimony sulfide photodetectors based not only on rigid FTO but also onflexible PET substrates are proposed, and the flower-like antimony sulfide photodetector exhibited excellent photoconductive performance in terms of high sensitivity to the visiblelight, excellent stability and reproducibility, and fast response and recovery time. The rigidSb₂S₃nanoflowers photodetector has high photoresponse characteristic, its response timeand decay time were found relatively fast to be6ms and10ms respectively, the Ion/Ioffisabout38. The linear photocurrent characteristics demonstrate the good Ohmic contactsbetween the Sb₂S₃nanoflowers materials and the electrodes. In addition to good sensitivityto light intensity, the Sb₂S₃nanoflowers photodetector also exhibits perfect wavelengthselectivity. The flexible Sb₂S₃nanoflowers photodetector based on PET substrate were alsofabricated. The ratio of the photocurrent to the dark current is about5, the response andrecovery time were found to be around0.09s and0.27s. Above all, the device exhibitedexcellent photoconductive performance to visible light, such as high flexible, light-weight,high stability and adequate bendability and fast response and recovery time..