Time-Resolved In-Line UV/VIS/NIR Spectroscopy: A Customized Setup for the Investigation of the Flow-Synthesis of Plasmonic Patchy Particles

Kinetic measurements can play an important supporting role in the development of plasmonic nanoparticle synthesis. Specifically, they provide crucial insights into the reaction dynamics, and nucleation and growth phenomena that ultimately influence particle morphology and properties. Here we present an innovative in-line monitoring system developed to investigate the flow synthesis of silver patches on silica core particles. Our custom-built setup comprises a 3D-printed T-mixer directly connected to a glass tube. Using a computer controlled linear stage, the position of a fiber-coupled UV-VIS-NIR spectrometer along the glass tube can be arbitrarily set in order to obtain an extinction spectrum at early reaction times. Moreover, a second glass tube, connected to the first with an arbitrary long spacer tube enables later reaction times to be probed. We give details of the determination of characteristic mixing time of the T-mixer-tube combination and show how raw spectral data from growing silver patches can be processed and analysed. This leads to the acquisition of valuable data concerning the patch formation kinetics. Our work offers fresh insights into the potential of in-line spectroscopic monitoring systems for application to similar nanoparticle systems with strong dependency of the optical properties on morphology.
The authors gratefully acknowledge the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) for funding of the Collaborative Research Centre 1411 "Design of Particulate Products" (Project-ID 416229255).