The unique properties of nanoparticles mainly depend on their size and morphology; thus, it is of the utmost importance to synthesize them monodispersely to be useful in an application. Micro uidic reactors enable a monodisperse nanoparticle synthesis through a precise control over the reaction conditions such as temperature, residence time, and reactant concentrations. Droplet-based microreactors facilitate the rapid mixing of reactants with a reduced diffusion length, while maintaining a uniform residence time because of the circulating ow profile in contrast to the parabolic ow profile in continuous ow microreactors. In this thesis, a droplet-based silicon microreactor was fabricated and used for silica nanoparticle synthesis. Silica nanoparticles were obtained with a size range of 25:0 2:7 nm. Considering the shorter processing time and the decreased amount of materials used alongside the comparable size range and monodispersity, this method was later implemented to be used for silica coating of quantum dot semiconductors. Silica coating of quantum dots maintain their photostability and preserve their optical properties. This thesis is the first attempt to coat CdSe/CdS core/shell quantum dots with a silica layer inside a microreactor. The accurate control over the reaction could enable the adjustable size and size distribution of the synthesized nanoparticles. The initial results are presented as part of this thesis.