In the recent times the field of metallic nanoparticle synthesis has gained a wide popularity. The size effects and quantum confinement leading to enhancement of physical and chemical properties of metallic nanoparticles are widely exploited in the field of medicine, catalysis and electronics. Synthesis of metallic nanoparticles through chemical reduction method is a popular method owing to its simplicity and economic viability. In this method, the morphology of these nanoparticles is dependent on the thermodynamics and kinetics of the reaction and is easily controlled by reactant concentration, temperature, mixing. Controlling these parameters in a batch reactor is challenging. This can be addressed by utilizing millifluidc reactors. The work analyses the nanoparticle shape control by manipulating the thermodynamics and kinetics of particle growth through reactant ratios and mixing. Different shapes of silver nanoparticles (rod-like, bent, triangular) were synthesized in curved, straight millifluidic reactors. Further, the synthesis bimetallic nanoparticles, which offer better properties compared to pure metal nanoparticles, were explored for the copper-silver bimetallic system. The thermodynamics of the metal mixing was studied and applied in the structure control of these bimetallic nanoparticles. The structure control (core-shell, Janus like) was achieved by changing the sequence of addition of the reactants. This work also proposes a novel nanoparticle synthesis and separation method via interfacial trapping in an environmentally benign aqueous two-phase system. We show that this method can be applied for large scale synthesis and recycling of unreacted solutions.