Au/Lum/RhB@Ag-DMcT ICP-Based Double-Ratio Colorimetric and Fluorometric Dual Mode Assay and Multi-Responsive Coffee Ring Chips for Point-of-Use Analysis of Phosphate Ions

In this work, by fully exploring the stimulus response of the guest-functionalized infinite coordination polymers (ICPs), a double-ratio colorimetric and fluorometric dual mode assay and multi-responsive coffee ring chips for point-of-use analysis of phosphate ions (Pi) were proposed. First, the complex host-guest interactions were rationally designed to obtain Au/ Lum/RhB@Ag-DMcT ICPs. The composite ICPs exhibited a purple-blue color resulted from the modulated localized surface plasmon resonance (LSPR) of the Au core, and a blue fluorescence color stemmed from the unique aggregation-induced-emission (AIE) of Luminol (Lum) and the aggregation-caused-quenching (ACQ) of rhodamine B (RhB). With the presence of Pi, the host- guest interactions of the shell within Au/Lum/RhB@Ag-DMcT ICPs were interrupted to release Au core, Lum, and RhB in a dispersed state. Consequently, the color of the solution changed to purple-red (the mixed color of the Au core and RhB guest), and the fluorescence color turned to orange-red (AIE of Lum decreased, while the ACQ of RhB recovered). This constituted the sensing mechanism for dual-mode Pi assay with the double ratiometric response. Second, during the stimulus response, the surface wettability/size/amount of Au/Lum/RhB@Ag-DMcT ICPs simultaneously altered. These changes were reflected in the form of the coffee ring deposition pattern variances on the glass substrate and served as signal readouts for the exploration of multi-responsive coffee ring chips for the first time. Quantitative Pi detection with high accuracy and reliability in real samples was thereby realized, which offered an opportunity for the point-of-use analysis of Pi in resources-limited areas in a high-throughput fashion.