Continuous synthesis of metal and metal oxide nanoparticles in microwave reactor

The aim of the study is to elaborate a universal method for obtaining metal (Ag and Cu) and metal oxide (CuO and SnO) nanoparticles (NPs) in a microwave flow reactor. The combination of microwave radiation energy with the flow-through process allows us to efficiently obtain NPs with accurate size control. The metal and metal oxide NPs synthesised by the microwave-assisted continuous method are characterised by ultraviolet-visible spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and dynamic light scattering. The results show the formation of spherical Ag, Cu and SnO NPs and CuO nanowires. In order to optimise the size of the NPs, the effects of reaction conditions, such as the concentration of stabiliser, irradiation time, pH of the solution and irradiation power of NP synthesis are studied. Under the most favourable reaction conditions, NPs with average diameters of 20 and 45 nm for Ag and Cu NPs, and 25 and 7 nm for SnO and CuO NPs, respectively, are obtained. The efficiency of the processes is 0.3-0.6 g/h for metal NP synthesis and 2.5-8.7 g/h for metal oxide NP synthesis.