The Investigation On The Modification Of Semiconductor Nanomaterials By Gamma Ray Irradiation

With the development of economy and society, we have more and more put ourattention on the environment. So, we need more energy-efficient, environmentallyfriendly and green way to synthesize materials. For a long time, gamma ray irradiationhas been used in the polymerization of polymer materials, modification and foodpreservation and sterilization and so on. In this thesis, gamma ray irradiation was usedto modify semiconductor nanomaterials, the principle is the using of high-energygamma-rays (1.17and1.33MeV) energy chemical synthesis and chemical bondswithin the material and methods of fracture defect growth.This thesis is elaborated from the following aspects:(1) Gamma ray irradiation may reduce Ag2SnO3and cause Ag nanoparticlesin-situ growing. Here, the pristine and irradiated products (0to500kGy) wereemployed to photodegrade Congo Red. At the dose of400kGy, the photocatalyticactivity reached the maximum with enhancement of3.7folds. The experiment may beexplained that gamma ray irradiation can lead to the Ag/Ag2SnO3heterojunction,which reinforced the combination between Congo Red and Ag2SnO3due to the Lewisacid-base interaction, and thus improved the photocatalytic efficiency. By the time, wehave found that Ag2SnO3is a thermally unstable materials. Then we study the productsafter heating Ag2SnO3. The results show that we could abtain Ag/SnO2heterostructurematerial via directly decomposing single-source precursor Ag2SnO3at temperature of400°C, owing to the in-situ growth from the decomposition. This kind ofheterogeneous structure was helpful to improve the photocatalysis efficiency. WhenAg/SnO2heterogeneous material was employed as photocatalysts in the degradation ofConco Red, its catalytic efficiency is3-fold that of the mixture of Ag and SnO2powders. (2) Gas sensing of semiconductor is an important field in the material science.Here, Ag2SnO3was synthesized and irradiated with different doses of gamma rayranging from0to500kGy. The irradiated products were employed to detect tworeducing gases (alcohol and nitromethane) and one oxidizing gas (acetic acid). At thedose of400kGy, the gas-sensing response of the three detected gas reached themaximum with enhancements of9,6.3and10.6folds compared with the unirradiatedproducts. Also, the gas-sensors has a selectivity to different gases. The experimentmay be explained by the in-situ growth of silver (Ag) from the decomposition ofAg2SnO3under gamma ray, which accelerated the electron transference in thegas-sensing processes and improved the corresponding activity.(3) The effect of gamma irradiation on silicon nanowires was investigated. Here,an additional defect emerged in the gamma-ray-irradiated silicon nanowires andconfirmed with electron spin resonance spectra.29Si nuclear magnetic resonancespectroscopy showed that irradiation doses had influence on the Q4unit structure. Thisphenomenon indicated that the unique core/shell structure of silicon nanowires mightbring out metastable defects under gamma ray irradiation, which served as a satisfiedmodel to investigate defects on the interface of Si/SiOx.(4) The emission of commercial available graphene quantum dots (GQDs) wasdemonstrated to tune in the range of505-550nm with irradiation doses ranging from0to500kGy. Their photoluminescence was also obviously improved at the optimal doseof100kGy: the peak intensity and fluorescence quantum efficiency were2.1and1.97times of the pristine GQDs, while the peak width shrank by12%. In addition, based ontheir low cytotoxicity and good biocompatibility, the pristine and100kGy irradiatedGQDs were utilized as bioimaging probes of4T1cancer cells. The results showed theirradiated GQDs were more efficient bioimaging probes than the pristine ones.(5) Silicon nanowires are important semiconductor with core/shell structure. In thiswork, the piezoelectric material alpha-quartz was grown in the interface of siliconnanowires by thermal treatment at600oC for half an hour. These nanowires wereemployed as starting materials to fabricate piezoelectric nanogenerators, which couldconvert kinetic energy into electrical one, exhibiting the output voltage of36.5V and the response current of1.4μA under a free-falling object of300g at the height of30cm. By the time, we have found that gamma ray irradiation could also induceelectrostatic charge on silicon nanowires.