A ratiometric nanosensor based on conjugated polyelectrolyte-stabilized AgNPs for ultrasensitive fluorescent and colorimetric sensing of melamine.

A new ratiometric nanosensor is developed for selective and ultrasensitive detection of melamine based on conjugated polyelectrolyte (CPE)-stabilized silver nanoparticles (P1-AgNPs) by perfectly combining the advantages of CPE and AgNPs. P1 featuring a π -delocalized backbone bearing pyridinyl groups can act as an excellent dual-emission fluorescent probe as well as a polymer localizer for AgNPs. In the presence of melamine, the fluorescence intensity at 386 nm increases owing to the turn-on of the fluorescence of P1, whereas FL intensity at 488 nm decreases due to the melamine-induced aggregation and subsequent aggregation-enhanced emission quenching of P1-AgNPs, therefore leading to the ratiometric fluorescent sensing of analyte. Moreover, analyte-induced aggregation of P1-AgNPs also allows the ratiometric colorimetric measurement of melamine. Under the optimum conditions, this facile ratiometric nanosensor favors the fluorescent and colorimetric determination of melamine in liquid milk products with the detection limit as low as 0.1 and 0.45 nM, respectively. [ABSTRACT FROM AUTHOR]