(458d) Continuous Millifluidic Synthesis of One-Dimensional Silver Nanostructures Using Tannic Acid As Reducing and Capping Agent: Parametric Study and Kinetic Behavior

The synthesis of nanomaterials in a continuous setting such as in microfluidic devices has been gaining significant attention due to their capability to enhance mass and heat transfer and ultimately lead to a better control over nanostructures’ size and morphology compared to that of the batch. However, microfluidic devices manufacturing is often costly and its use may be limited to small laboratory scale due to low throughput and as a result, may not be feasible for large-scale industrial production. Millifluidic reactors are able to maintain control over size and morphology, while also being cheaper to construct and are able to offer a higher throughput. This, however, depends on a number of factors such as the inner diameter of the reactor tubing/channel, tubing material, flowrate, residence time, and flow patterns arising from different geometrical configurations of the reactor. In this study, we were able to synthesize silver nanowires and nanorods in a helically-coiled millifluidic reactor in 96 minutes residence time by using merely tannic acid as both the reducing and capping agents. The synthesized silver nanostructures were characterized using Ultraviolet–visible Spectroscopy (UV-vis), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Energy Dispersive X-Ray (EDX). The silver nanowires synthesized in this process had a higher yield compared to that of the batch, which was done previously. We also investigated the effect of surfactant, light, various flow , and three different geometries of the reactor by changing the coil diameter. Additionally, the kinetic behavior was investigated by measuring the concentration of Ag⁺ ions in the millifluidic reactor at different residence times for three different coil diameters. The effect of coil diameter on the consumption of Ag⁺ ions, and subsequently the yield of silver nanowires, was analyzed and discussed. This study offers a versatile, inexpensive, and rapid approach towards the large-scale synthesis of silver nanowires in a continuous manner, without the need for using an external capping agent and hazardous reducing agents.