Colorimetric lab-on-a-tip based on a bimetallic nanoarchitecture

Mono- and multi-metal nanoparticles (MNPs), thanks to their unique and tunable features, still fascinate the analytical sciences, still tracing a witness major breakthrough in nanotechnology-based colorimetric sensing. Starting from the widespread use of colloidal MNPs in sensing and biosensing as nanoplasmonic tag or catalyst to finally end to the MNPs immobilization onto solid substrates. Here, ELISA microplates and micro-Tips decorated with adhesive and plasmonic-active polymeric films embodying gold/silver nanostructures will be presented. The support surfaces were initially modified with self-assembled gold nanoparticles on polydopamine films. Subsequently, the AuNPs-decored film was doped with catechin leading to the formation of a uniform silver plasmonic nano-network in the presence of Ag⁺. The bimetallic nanoarchitecture on ELISA microplate was exploited to assess oxidants and free radicals (H₂O₂, sodium hypochlorite, ABTS•⁺, etc.) using the LSPR decrease caused by silver nano-network etching as analytical signal. For the studied oxidants, the system allows differentiating the oxidants' ability with useful limits of detections, throughout a simple photometric/optical reading. Moreover, taking advantage of a similar strategy a nanodecored lab-on-a-tip was developed, the device speed-up the 4-nitrophenol reduction retaining the performances for more than 10 consecutive measures. In this case, the improved catalytic activity of the nanohybrid film (gold/silver) was demonstrated, resulting higher compared with the monometallic films also allowing a fast 4-nitrophenol colorimetric monitoring. In this presentation, a bimetallic adhesive robust and storable film able to modify different supports is proposed, the supports modified with such film result able to determine and monitor different molecules of analytical and biological interest without the needing of additional reagents. The film fabrication results versatile and potentially usable onto different supports and materials allowing tailor-nano decorations, proposing itself as a new and useful analytical read-out system.