Synthesis And Properties Of Metal Oxide/sulfide Nanomaterials

In the past decades, a series of developments have been made in nanomaterials. Nowadays, exploiting more convenient, economical and large-scale synthetic strategies and achieving industrial applications of nanostructural materials are two key directions in nano field. This dissertation focuses on synthesis and applications of metal oxide/sulfide nanomaterials. On one hand, in order to overcome technical bottle-neck of nanosynthesis and achieve large-scale preparation of high quality nanocrystals, many efforts have been made to exploit new synthetic strategies. On the other hand, in order to achieve industrial applications of metal oxide/sulfide nanomaterials in many important areas such as catalysis and Li-ion batteries, valuable investigations have been carried out on the relationship between crystal structure, size and shape of nanomaterials and their properties.A simple synthetic method for metal and oxide nanocrystals has been developed based on thermal decomposition of metal nitrates. A system composed of a single component of octadecylamine (ODA) which served as both the solvent and the surfactant was designed and the decomposed regularities of three different kinds of metal nitrates in this system were investigated including silver nitrate, transition metal nitrates (manganese nitrate, cobalt nitrate, nickel nitrate, etc.) and rare-earth nitrates (cerium nitrate, lanthanum nitrate, yttrium nitrate, etc.). Controllable synthesis of monodisperse Ag nanoparticles and a series of transition metal oxide (Mn3O4, CoO, NiO, etc.) and rare-earth oxide (CeO2, La2O3, Y2O3, etc.) nanocrystals was achieved.A facile one-pot synthetic procedure for chalcogenide semiconductor nanocrystals (Ag2S, Bi2S3, CdS, MnS, Ag2Se, CdSe, etc.) has been developed. Nontoxic inorganic salts and inexpensive sulfur or selenium powder were employed as reagents while ODA was used as both the solvent and the surfactant. Control of shape and size of nanocrystals was achieved by adjusting the reaction conditions and semiconductors with one-dimensional (1D) nanostructures were obtained such as Ag2S nanowires and Bi2S3 nanotubes. This strategy was also suitable for preparation of high qualityâ… -â…¢-â…¥2 ternary semiconductors (AgInS2, CuInS2, AgInSe2, etc.).The assembly behavior of various kinds of monodisperse nanocrystals obtained via the above mentioned synthetic methods was investigated and a general strategy for mesoporous materials has been developed, namely, using monodisperse nanocrystals as uniform building blocks to construct mesoporous structures. The preparation of mesostructural materials including metal (Ag), metal oxides (CoO, NiO, MnO, etc.), and metal sulfides/selenides (Ag2S, Ag2Se) was achieved by this strategy.The applications of as-synthesized metal oxide/sulfide nanocrystals in many important areas such as catalysis and Li-ion batteries have been investigated. On one hand, the advantages of mesoporous metal oxides (CoO, NiO, MnO, etc.), mixed oxides (LiCoO2, LiNiO2, LiMn2O4, etc.), and metal sulfides (Bi2S3 nanotubes) as cathodes in Li-ion batteries were discussed. On the other hand, the influence of crystal morphology on catalytic performance of nanocatalysts (NiO) and supported nanocatalysts (CuO/MgO, Au/La2O3) was studied.