Open Linear Polymer Host-Guest Interactions Sensed by Luminescent Silver Nanodots

The selectivity of the linear polymer chain toward itsbindingmoieties has been considered negligible; thus, a clear demonstrationshowing the best-fit binding of a linear polymer to its guest counterpartis still unknown. Luminescent poly(acrylic acid) (PAA)-stabilizedsilver nanodots (PAA-AgNDs) have been applied as a turn-on sensorto monitor the interaction between the PAA chain and its binding cations.The binding of cations ions to the PAA chain may cross-link the linearPAA chain via coordination with carboxylate, which increases the rigidityof the polymer chain, retards the nonradiative decay of PAA-AgNDs,and consequently enhances the emission of silver nanodots while inducinga blue-shift of its emission spectrum. For the first time, we havedemonstrated that a linear polymer chain can act as an open host toselectively bind to its best-matching cations. Specifically, amongGroup 2 cations (Mg2+, Ca2+, Sr2+, Ba2+), calcium ions show the strongest bonding to thePAA polymer chain. Our research suggests that, with extra rigidity,the polymer improves its chemical stability as calcium ions cross-linkedthe linear polymer. Meanwhile, it has also been demonstrated thatluminescent silver nanodots can be excellent probes for the detectionof polymer activities with straightforward and simple visualizationmethods.

Automated summary

This study utilizes luminescent poly(acrylic acid) (PAA)-stabilized silver nanodots (PAA-AgNDs) as a turn-on sensor to monitor the interaction between the PAA chain and its binding cations. The binding of cations cross-links the linear PAA chain, enhances the emission of silver nanodots, and induces a blue-shift of its emission spectrum. Calcium ions show the strongest bonding to the PAA polymer chain among Group 2 cations. The research also demonstrates that luminescent silver nanodots can be excellent probes for the detection of polymer activities with straightforward visualization methods.