Improving the quality of nanoparticle production by using a new biphasic synthesis in a slug flow microreactor

Abstract The use of laboratory scaled batch reactors is one of the most common methods to produce nanomaterials. However, a fast and reproducible screening of the synthesis parameters on short time scales as well as the transfer to large scaled production volumes is difficult. An innovative biphasic micro tube reactor is presented in this study that allows a continuous, fast and reproducible production of nanomaterials at high temperatures without the known drawback of reactor fouling or clogging. By transferring the synthesis of silver nanoparticles from a simple laboratory batch reactor to the micro tube reactor, we were able to accelerate the formation speed of the particles by a factor of 4 and narrow the size distribution from 33% down to 12% relative standard deviation. Due to the precise heating and cooling sector in this system, particles could be generated with a very narrow residence time distribution on short time scales (30–150 s) with diameters ranging from 7 nm to 120 nm. In addition, we describe how the relevant growth regimes – nutrient-mediated growth and Ostwald ripening – change with increasing temperature and explain the problems arising from too slow or a too fast reaction rates in the polyol synthesis. Based on the presented formalism, the optimal parameters for the production of silver nanoparticles in the micro tube reactor are analysed.