Solvothermal Synthesis And Characterization Of Monodisperse Nanoparticles

Nanoparticle materials often exhibit very interesting electronic, optical, magnetic, and chemical properties, which are unachievable for their bulk counterparts. Most of these applications require particles of uniform shape and narrow size distribution, therefore many efforts have been devoted to the synthesis and study of monodisperse nanocrystals and considerable progress has been made. Herein, we describe the solvothermal method to synthesize monodisperse nanoparticlesFirst, solvothermal method with PVP as surfactant and ethanol as solvent and reductant was used to synthesize silver monodisperse nanoparticles. The shapes of silver nanoparticles have been successfully tuned among quasi-spherical, right triangle and right hexagon by changing the molar ratio between the repeating unit of PVP and AgNO₃, and the aging temperature and time, which also changed the size of the nanoparticles. When the reaction temperature and aging time were 180℃and 20h respectively, the shapes of final particles would change from quasi-spherical to right hexagon to right triangle as the molar ratio between the repeating unit of PVP and AgNO₃ changed from 0.1875 to 0.375 to 1.875. And when other conditions were fixed, the size of the final particles would change from 66.7nm to 100nm as the reaction temperature were incresed from 100℃to 180℃.Second, monodisperse ZnS and CdS nanoparticles were synthesized by the solvent-thermal method. The effects of preparation parameters on ZnS and CdS particles such as reaction temperature, aging time, surfactant and the mol ratio of precursor between surfactant were discussed in details. Effects of solvent thermal treatment on structure and morphology of the particles were also investigated. In addition, the particles with better crystalline are obtained with reaction temperature and aging time increased. With PVP as surfactant, 100nm monodisperse ZnS nanoparticles and 50nm monodisperse CdS nanoparticles were abtained. With the increase of the reaction temperature from 150℃to 200℃, the crystalline structure of both ZnS and CdS would change from faced-cube to hexagon.Third, highly monodisperse hexagonal phase Zn_7.23Cd_2.77S₁₀ nanoparticles with diameters of 20nm have been synthesized by the liquid-solid-solution transiting reaction, and the succedent diffusion growth under heat-treatment. Using zinc acetate, cadmium chloride and sodium sulfide as precursor and sodium oleate and oleic acid as the surfactant and ligand, the process is reproducible and leads, with high application to monodisperse nanoparticles. In principle, this method could be modified to prepare other monodisperse binary and ternary II-VI group semiconductor monodisperse nanocrystals.