The Synthesis Of Nanosized Metal Sulfides By A Mild Biomolecule-assisted Hydrothermal/Solvothermal Method

Metal sulfides nanomaterials such as CdS, ZnS, NiS, Ag2S, MnS and PbS with narrowband gap and high light absorption coefficient show potential applications in light-emittingmaterials, sensors, solar cell and optoelectric devices, especially in photocatalysis. Thebiomolecules are considered to be one of the most ideal templates to prepare nanomaterialswith complexed structures due to their special structures and fascinating self-assemblyfunctions. Therefore, recently it becomes a hot topic to to synthesize nanomaterials withvarious morphologies by using biomolecules as template agent. This thesis focuses on thesynthesis of manganese sulfide and nickel sulfides by a mild biomolecule-assistedhydrothermal/solvothermal method. The correlation between phase transition and morphologyevolution of metal sulfides is also investigated. The main results and originality aresummarized as follows:（1） A facile biomolecule-assisted hydrothermal route has been demonstrated to growγ-MnS multipods consisting of hexagonal prism-like rods at130℃for10h in distilled waterwhen L-cystine was used as both the sulfur source and complexing agent. The influence ofsome experimental parameters, such as reactant molar ratio, reaction temperature, reactiontime, and the kind of surfactants on the formation of γ-MnS multipods was invesigated. Apossible formation mechanism for the γ-MnS multipods was also discussed based on thetime-dependent experiments. The room-temperature photoluminescence spectrum exhibits apeak centered at419nm corresponding to the band edge emission when the sample wasexcited with a wavelength of358nm（2） Based on the synthesis of γ-MnS, α-MnS solid nanospheres has been synthesized inwater-ethylenediamine mixed solvents in the presence of L-cystine as both the sulfur sourceand complexing agent at low temperature. It has greatly potential value of application in theenergy saving and environment protection.（3） A series of single-phase nickel sulfides, such as cubic NiS₂, hexagonal α-NiS andrhombohedral β-NiS, have been successfully synthesized in ethylene glycol through anacrylamide-assisted solvothermal process by using thiourea and nickel nitrate as the starting materials. The product was characterized by XRD and TEM. It was found that surfactantacrylamide played an important role in controlling the phase compositions and morphology ofnickel sulfides. The formation of β-NiS hollow nanospheres with cross-linked structure couldbe explained by the heterogeneous crystallization and rolling-up mechanism.