Investigation Of In Situ Synthesis Of Highly Monodispersed Silver Nano-Colloids And Nanocomposites

Metal nanoparticles own the nanometer-level size or structure, high specific surface area, unique physical and chemical properties. Its performance depends on its particle size, dispersibility, particle morphology, crystallinity, structural characteristics and the external environment. Silver nano-colloids are the most common metal nanoparticles, and scientists’study of silver nano-colloids is gradual deepening. Currently, highly dispersed and small-sized silver nano-colloids result in the promising potential applications including novel chemical and biological sensors, single-electron transistors, supercapacitors, and data storage devices. Therefore, preparation of silver nanoparticles which own highly dispersed, narrow distribution, small particle size, and neat morphology becomes the focus of research.In this article, highly monodispersed (3.0-4.2nm) nonaqueous small-sized (3.7±0.1nm) silver nano-colloids were successfully synthesized by in situ synthesis. Firstly, silver nano-colloids were obtained using silver dodecanate as organic precursor,3,3,5-trimethylcyclohexyl methacrylate (TMCHMA) as UV-curable monomer, and triethylamine (Et3N) as promoter. The nano-colloids and its formation mechanism were studied by UV-vis absorption spectroscopy (UV-vis), thermal gravity analysis (TG), transmission electron microscope (TEM), X-ray diffraction (XRD), etc. The possible forming mechanism of the silver nano-colloids was proposed. Silver dodecanate dissolved in UV-curable monomer, and heating was conducive to the formation of the micelle structure. When the temperature reached to120℃, thermal decomposition reaction of silver dodecanate occurred, resulting in generation of silver atoms and dodecanoic acid. Dodecanoic acid was coated on the surface of silver nanoparticles by chemical adsorption, forming core-shell structure, and it played an important role in controlling particle size and stability. Moreover, the addition of Et3N could promote the formation of silver nanoparticles.Meanwhile, the particle size and distribution, morphology and dispersion of silver nano-colloids were adjusted by changing the proportion of precursor and monomers, Et3N dropping speed and reaction temperature. For highly monodispersed small-sized silver nanoparticles, the ratio of TMCHMA and silver dodecanoate should not below5:0.1, while the input rate of Et3N is better to less than0.04mL/min, and140℃is considered to be the optimal temperature. Silver nanoparticles were charactered by HRTEM, XRD, TG, etc, indicating high crystalline nature of the resulted silver nanoparticles with the face-centered-cubic (FCC) crystal structure. The average size of the particles is3.7nm, and silver nanoparticles is speculated to have core-shell structure, in which silver crystal acted as core and other organic soft matters, such as dodecanoic acid and TMCHMA were in the shell.Finally, polymer based nanocomposite was synthesized by UV irradiation on the silver nano-colloids. By scanning electron microscope (SEM) and thermal gravity analysis(TG), the nanocomposites was demonstrated to have excellent nano-structure and excellent thermal performance, providing a green and fast method to prepare polymer based nanocomposites.