Microfluidic-assisted synthesis of uniform polymer-stabilized silver colloids

Abstract

We report the controlled synthesis of polymer-stabilized silver nanoparticles (AgNPs) by using microfluidic devices. The microfluidic-based method enabled the preparation of sub-50 nm AgNPs which are much more homogenous compared to those produced in batch reactors where the control over flow and mixing conditions was not performed. The concentration of the silver precursor (silver nitrate - AgNO3) can be tuned to reach smaller or larger nanoparticles, although within a fairly narrow range. Regardless of the polymeric shell, the reducing agent concentration influences the size and polydispersity of the manufactured silver colloids, and relatively lower amounts allow for the manufacturing of more homogeneous nanoparticles. Notably, the use of the block copolymer PEO-b-P2VP as stabilizing agent leads to larger nanoparticles (23–51 nm) compared to those stabilized by PVP (7–14 nm) as possibly linked to different arrangements of the polymer chains at the interface between the precursor solutions. The produced AgNPs are highly uniform, with size distribution width influenced by the polymer concentration (FWHM < 100 nm were determined at higher concentrations), although this variable does not have a distinguished effect on the final size of the manufactured colloids. Overall, we provide relevant new knowledge within the framework of polymer-stabilized AgNPs since a variety of other polymer chains can be probed, possibly with different outcomes regarding the final particle size. The reported findings can thus guide to significant advances towards the manufacturing of highly homogeneous polymer-coated metallic colloids, particularly when a target size is required.