Synthesis And Giant Magnetoresistance/optical Properties Of Silver Chalcogenides Nanomaterials

Non-stoichiometric silver chalcogenides have aroused wide attention because of their outstanding linear magnetoresistance effect, and their linear magnetoresistance effect has not yet reached saturation in the super magnetic field up to 55 T, similar to colossal magnetoresistance materials. On the other hand, the physical and chemical properties of nanomaterials are different from bulk materials. Surface effect, quantum size effect and macroscopic quantum tunnel effect of nanomaterials result in a special optical, mechanical, magnetic, electrical, superconducting, and other special performance. In the thesis, synthesize of non-stoichiometric compound silver chalcogenide nano-materials, growth mechanism and physical properties is mainly studied. Their giant magnetoresistance and optical absorption properties are different from counterpart bulk non-stoichiometric silver chalcogenide materials. Here giant resistances of our samples (non-stoichiometric silver chalcogenide nanostructures) are nonlinear, associated with the magnetic field. In the thesis, our work has been as follow as:1. Different size Ag_2+δSe microspheres are synthesized by using ammonia, PEG (800), high purity selenium powder, AgNO₃ and different proportions of water as a solvent mixture. In the meanwhile, different reaction times and reaction temperatures are studied, which affect morphologies of samples. In the end, the TEM, SEM, XRD, UV-VIS, PPMS are used for characterizing morphology, structure, optical properties, and giant magnetoresistance.2. We have directly synthesized the Ag_2+δTe nanorods by using the hydrothermal approach with the reaction flux to AgNO₃ and Na2TeO₃. In the meanwhile, as mentioned above, we have still researched phases and morphologies of Ag_2+δTe nanorods under different conditions, including reaction times and reaction temperatures. In the end, the TEM, SEM, XRD, UV-VIS, PPMS, etc. are used for characterizing morphology, structure and giant magnetoresistance.3. In this thesis, Ag_2+δS nanospheres were synthesized by hydrothermal method after thiourea was used as both surfactant and the sulfur source and AgNO₃ solution was served as solvent. Simultaneously, different reaction time and different concentrations of thiourea are studied, which affect this morphology of Ag_2+δS nanospheres. In the end, the TEM, SEM, XRD, UV-VIS, etc. are used for characterizing morphology, structure, as well as optical and optoelectrical properties.