Nanoparticles are building blocks for nanotechnology and have been widely exploited for various applications. Numerous methods have been studied for production of nanoparticles. Yet, a facile, economic and green synthesis is still to be developed to realize mass production with quality control. In recent years, my group has developed a general approach for synthesis of metallic and oxide nanoparticles. The approach combines chemical reduction with physical interaction and can be performed with generic chemicals in ambient conditions. In the seminar, I will first report the synthesis method and how we realized size selectivity and size distribution control of nanoparticles. I will then report simulation of nanoparticle growth in the synthesis system. Based on nucleation theory and kinetic aggregation and growth behavior, we developed a model using Monte Carlo stochastic algorithm to describe the growth of nanoparticles by particle-particle collision and subsequent coalescence, and performed numerical simulation of resulting average particle size and size distribution of the metallic nanoparticles produced in our designed system. The third topic will be about the application of nanoparticles used in hydrogen storage and solid-state power generator. We are developing synthesis of nanostructured porous hydride materials to achieve high capacity and fast kinetics. Some preliminary results on synthesis of nanocomposite metal hydride based on nanoparticles will be presented. Another application of nanoparticles is tunneling-thermionic nanostructures for waste heat recovery.