Preparation, Characterization, Self-assembly And Related Properties Studies Of Monodisperse Nanocrystals

Nanocrystals,Because of their small makeups and high specific surface areas,show novel mechanical,optical,magnetic and electronic properties.In this thesis,we synthesized several kinds of nanocryatals by this method,and related properties,such as optical and electrochemical properties,were also investigated.The content and innovation of this thesis are as follows:1.Using Cu(acac)2 as single-precursor and oleylamine as solvent and surfactant,CuO,Cu₂O and Cu nanoparticles were synthesized through controlling the growth temperature.CuO and Cu₂O nanoparticles have nanoporous structural configurations composed of a large number of primary particles.According to the difference between the crystal planes and the reaction temperature,we proposed the possible growth mechanisms of CuO,Cu₂O and Cu nanoparticles.Selective adsorption of oleylamine on various crystal planes may play an important role in the growth process.The process of CuO,Cu₂O and Cu nanoparticle producing is a gradual reduction approach.2.Metal(Cd,Cu and Ni)sulfides nanocrystals have been synthesized by a single-source molecular precursor method.The size of the nanocrystals can be well controlled by adjusting the ration of the oleylamine and precursors.This synthesis may represent a general approach towards metal-sulfide nanocrystals,which may promise both adequate academic and practical interest in the development of synthetic methodologies for inorganic nanocrystals,and in the expansion of their potential applications.As-prepared nanoparticles have an organic layer on its which can induce the nanoparticle forming an orderly layer on the substrate.3.Based on the former work,the size of the synthesized CdS nanocrystals could be easily controlled by adjusting the ratio of reaction sources under inert atmosphere.The studies on the optical properties reveal that as-synthesized nanocrystals have an obvious size-dependent photoluminescence characteristic,where as-prepared CdS nanocrystals only show a band edge emission and no trap state emission,because the structural defects in the nanocrystals may be improved completely during the long time of annealing process which is the virtue of this method.4.The colloidal,highly crystalline,and size-controlled ZnS nanorods have been prepared through a thermal decomposition of single-source-precursor approach in oleylamine solution.The length and width of nanorods can be controlled simply by varying the molar ratio of Zinc 2-Mercaptobenzothiazole complex and oleylamine or prolonging the anneal duration.Optical and electrochemical properties of different sizes ZnS nanorods are discussed and size-dependent optical and electrochemical band gap are observed evidently,which show a direct correlation between the electronic spectra and electrochemical band gap.5.Quasi-monodispersed Ag nanoparticles were prepared in a large scale through a single-source molecular precursor route.The synthesized Ag nanocrystals were assembled into superstructures by using a small molecular assistant.Based on the IR spectra,the formation mechanism of Ag nanoparticles superstructures was discussed.The tautomery of small molecules urged them react with each other through intermolecular hydrogen bond and constructer'a long chain molecule',which act as a template for the formation of Ag superstructures.The assembly method might exploit a new route to the ordered nanostructures,which may be useful for the fabrication of other ordered one-,two- or three-dimensional nanosuperstructures.