Microfluidics-based continuous flow formation of triangular silver nanoprisms with tuneable surface plasmon resonance

Controlled synthesis of nanoparticles with desired geometries can provide a direct approach for the formation of nanomaterials with tuneable size/shape-dependent characteristics, vastly expanding their range of applications in catalysis, electronics and optics, biology and medicine. In this report, we demonstrate the development of a microfluidics-based process for the direct synthesis (without seed-mediated growth) of silver nanoprisms in a continuous flow format using a flow focusing microreactor, coupled with UV-Vis-NIR spectroscopy for real time monitoring of optical properties of the produced nanoprisms. By adjusting microfluidic conditions, the nanomaterial's absorbance spectral position and peak broadness can be fine-tuned. TEM analysis of the produced nanoparticles quantitatively correlates the characteristics of absorbance spectra with the shape/geometry of nanoparticles. Furthermore, faster kinetics for the formation of nanoparticles has been observed in the microreactor compared to those in traditional batch reactors, and the microreactor's capability of synthesising homogenous nanoparticles over a prolonged operation time is demonstrated.