Preparation Of Inorganic Nanocrystals By A Two-Phase Approach

Ag2S has attracted a lot of attention in recent years due to its interesting properties. It is a direct, narrow band-gap (1.0 eV) semiconductor with good chemical stability and excellent optical limiting properties and has potential uses in photoconductors, photovoltaic cells, IR detectors, photography, and luminescent devices. Despite the important prospects and the number of studies involving Ag2S nanocrystals, few studies have addressed the near-IR optical properties of pure Ag2S nanocrystals.Silver sulfide nanocrystals have been synthesized by a number of methods. For example, Ag2S nanocrystals have been formed in micelles and from Ag(I)-glutathione complexes in aqueous solution. Solid-phase conversion of silver suspended in polymers and zeolites has produced supported Ag2S nanocrystals. In this work, we employed a two-phase approach which developed by Pan and his coworkers to synthesis Ag2S nanocrystals. The influence of the reaction conditions, Such as reaction time, species of sulfur sources and ligands on the formation of Ag2S nanocrystals in this reaction are studied. And we try to explore the near-IR optical properties of Ag2S nanocrystals. During this process, we found the emission peak of Ag2S nanocrystals shift slowly with the size variation of nanocrystals in the near-IR region.The size, shape, and microstructure of nanocrystalline materials strongly influence its properties. Thus, a fundamental understanding of the mechanisms of nanocrystal formation and growth is critical for achieving control over nanoparticle properties. Nanocrystal growth in solution typically involves two primary mechanisms: Ostwald ripening and aggregation. Oriented aggregation is a special case of aggregation whereby primary particles attach to one another in an irreversible and highly oriented fashion to produce secondary particles that are new single crystals or pseudocrystals.In this work, we employed ligands with short alkyl chain to assist the synthesis of ZrO2 and TiO2 nanocrystals in a two-phase approach. When we used acetic acid, butyl acid, and octyl acid as ligands, we found that the structure of the ZrO2 nanocrystals formed a three-dimensional structure, and the primary particles attached to one another in one-dimensional direction under the observance of high resolution TEM images. And the coexistence of both primary particles and secondary particles just give us the evidence of the mechanism of oriented aggregation.